| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Steven Rostedt | 16816 | 75.20% | 216 | 61.89% |
| Vincent Donnefort | 1670 | 7.47% | 4 | 1.15% |
| Vaibhav Nagarnaik | 1286 | 5.75% | 11 | 3.15% |
| Tzvetomir Stoyanov (VMware) | 635 | 2.84% | 5 | 1.43% |
| Tom Zanussi | 377 | 1.69% | 4 | 1.15% |
| Robert Richter | 217 | 0.97% | 4 | 1.15% |
| Nicholas Piggin | 179 | 0.80% | 1 | 0.29% |
| Zheng Yejian | 178 | 0.80% | 6 | 1.72% |
| Lai Jiangshan | 117 | 0.52% | 7 | 2.01% |
| Slava Pestov | 63 | 0.28% | 1 | 0.29% |
| David Sharp | 62 | 0.28% | 3 | 0.86% |
| Uros Bizjak | 60 | 0.27% | 5 | 1.43% |
| Rusty Russell | 56 | 0.25% | 3 | 0.86% |
| Sebastian Andrzej Siewior | 55 | 0.25% | 3 | 0.86% |
| Chen Lin | 54 | 0.24% | 1 | 0.29% |
| Mukesh Ojha | 51 | 0.23% | 1 | 0.29% |
| David S. Miller | 46 | 0.21% | 1 | 0.29% |
| Gaurav Kohli | 34 | 0.15% | 1 | 0.29% |
| Tze-nan Wu | 29 | 0.13% | 1 | 0.29% |
| Petr Pavlu | 28 | 0.13% | 2 | 0.57% |
| Jia-Ju Bai | 28 | 0.13% | 1 | 0.29% |
| Haoran Luo | 27 | 0.12% | 1 | 0.29% |
| Peter Zijlstra | 25 | 0.11% | 2 | 0.57% |
| Qiujun Huang | 24 | 0.11% | 5 | 1.43% |
| Masami Hiramatsu | 23 | 0.10% | 1 | 0.29% |
| Thomas Gleixner | 22 | 0.10% | 4 | 1.15% |
| Johannes Berg | 20 | 0.09% | 1 | 0.29% |
| Ingo Molnar | 15 | 0.07% | 4 | 1.15% |
| Linus Torvalds | 11 | 0.05% | 4 | 1.15% |
| Wei Yongjun | 11 | 0.05% | 1 | 0.29% |
| Andrea Righi | 11 | 0.05% | 1 | 0.29% |
| Huang Ying | 10 | 0.04% | 1 | 0.29% |
| Vegard Nossum | 9 | 0.04% | 2 | 0.57% |
| Rabin Vincent | 9 | 0.04% | 1 | 0.29% |
| Yaowei Bai | 8 | 0.04% | 3 | 0.86% |
| Eric Dumazet | 7 | 0.03% | 1 | 0.29% |
| Jovi Zhangwei | 7 | 0.03% | 2 | 0.57% |
| Paul E. McKenney | 6 | 0.03% | 1 | 0.29% |
| Andrew Morton | 6 | 0.03% | 1 | 0.29% |
| Daniil Tatianin | 5 | 0.02% | 1 | 0.29% |
| Jiri Olsa | 4 | 0.02% | 3 | 0.86% |
| Doug Anderson | 4 | 0.02% | 1 | 0.29% |
| Josef Bacik | 4 | 0.02% | 1 | 0.29% |
| James Hogan | 4 | 0.02% | 1 | 0.29% |
| Cui GaoSheng | 3 | 0.01% | 1 | 0.29% |
| Wan Jiabing | 3 | 0.01% | 1 | 0.29% |
| Matthew Garrett | 3 | 0.01% | 1 | 0.29% |
| linke li | 3 | 0.01% | 1 | 0.29% |
| Frédéric Weisbecker | 3 | 0.01% | 1 | 0.29% |
| caihuoqing | 3 | 0.01% | 1 | 0.29% |
| Fabian Frederick | 3 | 0.01% | 1 | 0.29% |
| Wang Tianhong | 2 | 0.01% | 1 | 0.29% |
| Corey Minyard | 2 | 0.01% | 1 | 0.29% |
| Linus Torvalds (pre-git) | 2 | 0.01% | 1 | 0.29% |
| Wenji Huang | 2 | 0.01% | 1 | 0.29% |
| Adam Buchbinder | 2 | 0.01% | 1 | 0.29% |
| Yoshihiro Yunomae | 2 | 0.01% | 1 | 0.29% |
| Jiapeng Chong | 2 | 0.01% | 1 | 0.29% |
| Mathieu Desnoyers | 2 | 0.01% | 1 | 0.29% |
| Lucas De Marchi | 2 | 0.01% | 1 | 0.29% |
| Wei Ming Chen | 2 | 0.01% | 1 | 0.29% |
| Jesper Juhl | 1 | 0.00% | 1 | 0.29% |
| Stephen Rothwell | 1 | 0.00% | 1 | 0.29% |
| Al Viro | 1 | 0.00% | 1 | 0.29% |
| Chris Wilson | 1 | 0.00% | 1 | 0.29% |
| Ross Zwisler | 1 | 0.00% | 1 | 0.29% |
| Breno Leitão | 1 | 0.00% | 1 | 0.29% |
| Mark Rutland | 1 | 0.00% | 1 | 0.29% |
| Richard Kennedy | 1 | 0.00% | 1 | 0.29% |
| Total | 22362 | 349 |
// SPDX-License-Identifier: GPL-2.0 /* * Generic ring buffer * * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> */ #include <linux/trace_recursion.h> #include <linux/trace_events.h> #include <linux/ring_buffer.h> #include <linux/trace_clock.h> #include <linux/sched/clock.h> #include <linux/cacheflush.h> #include <linux/trace_seq.h> #include <linux/spinlock.h> #include <linux/irq_work.h> #include <linux/security.h> #include <linux/uaccess.h> #include <linux/hardirq.h> #include <linux/kthread.h> /* for self test */ #include <linux/module.h> #include <linux/percpu.h> #include <linux/mutex.h> #include <linux/delay.h> #include <linux/slab.h> #include <linux/init.h> #include <linux/hash.h> #include <linux/list.h> #include <linux/cpu.h> #include <linux/oom.h> #include <linux/mm.h> #include <asm/local64.h> #include <asm/local.h> /* * The "absolute" timestamp in the buffer is only 59 bits. * If a clock has the 5 MSBs set, it needs to be saved and * reinserted. */ #define TS_MSB (0xf8ULL << 56) #define ABS_TS_MASK (~TS_MSB) static void update_pages_handler(struct work_struct *work); /* * The ring buffer header is special. We must manually up keep it. */ int ring_buffer_print_entry_header(struct trace_seq *s) { trace_seq_puts(s, "# compressed entry header\n"); trace_seq_puts(s, "\ttype_len : 5 bits\n"); trace_seq_puts(s, "\ttime_delta : 27 bits\n"); trace_seq_puts(s, "\tarray : 32 bits\n"); trace_seq_putc(s, '\n'); trace_seq_printf(s, "\tpadding : type == %d\n", RINGBUF_TYPE_PADDING); trace_seq_printf(s, "\ttime_extend : type == %d\n", RINGBUF_TYPE_TIME_EXTEND); trace_seq_printf(s, "\ttime_stamp : type == %d\n", RINGBUF_TYPE_TIME_STAMP); trace_seq_printf(s, "\tdata max type_len == %d\n", RINGBUF_TYPE_DATA_TYPE_LEN_MAX); return !trace_seq_has_overflowed(s); } /* * The ring buffer is made up of a list of pages. A separate list of pages is * allocated for each CPU. A writer may only write to a buffer that is * associated with the CPU it is currently executing on. A reader may read * from any per cpu buffer. * * The reader is special. For each per cpu buffer, the reader has its own * reader page. When a reader has read the entire reader page, this reader * page is swapped with another page in the ring buffer. * * Now, as long as the writer is off the reader page, the reader can do what * ever it wants with that page. The writer will never write to that page * again (as long as it is out of the ring buffer). * * Here's some silly ASCII art. * * +------+ * |reader| RING BUFFER * |page | * +------+ +---+ +---+ +---+ * | |-->| |-->| | * +---+ +---+ +---+ * ^ | * | | * +---------------+ * * * +------+ * |reader| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * | |-->| |-->| | * +---+ +---+ +---+ * ^ | * | | * +---------------+ * * * +------+ * |reader| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * ^ | |-->| |-->| | * | +---+ +---+ +---+ * | | * | | * +------------------------------+ * * * +------+ * |buffer| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * ^ | | | |-->| | * | New +---+ +---+ +---+ * | Reader------^ | * | page | * +------------------------------+ * * * After we make this swap, the reader can hand this page off to the splice * code and be done with it. It can even allocate a new page if it needs to * and swap that into the ring buffer. * * We will be using cmpxchg soon to make all this lockless. * */ /* Used for individual buffers (after the counter) */ #define RB_BUFFER_OFF (1 << 20) #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) #define RB_ALIGNMENT 4U #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS # define RB_FORCE_8BYTE_ALIGNMENT 0 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT #else # define RB_FORCE_8BYTE_ALIGNMENT 1 # define RB_ARCH_ALIGNMENT 8U #endif #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT) /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX enum { RB_LEN_TIME_EXTEND = 8, RB_LEN_TIME_STAMP = 8, }; #define skip_time_extend(event) \ ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) #define extended_time(event) \ (event->type_len >= RINGBUF_TYPE_TIME_EXTEND) static inline bool rb_null_event(struct ring_buffer_event *event) { return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; } static void rb_event_set_padding(struct ring_buffer_event *event) { /* padding has a NULL time_delta */ event->type_len = RINGBUF_TYPE_PADDING; event->time_delta = 0; } static unsigned rb_event_data_length(struct ring_buffer_event *event) { unsigned length; if (event->type_len) length = event->type_len * RB_ALIGNMENT; else length = event->array[0]; return length + RB_EVNT_HDR_SIZE; } /* * Return the length of the given event. Will return * the length of the time extend if the event is a * time extend. */ static inline unsigned rb_event_length(struct ring_buffer_event *event) { switch (event->type_len) { case RINGBUF_TYPE_PADDING: if (rb_null_event(event)) /* undefined */ return -1; return event->array[0] + RB_EVNT_HDR_SIZE; case RINGBUF_TYPE_TIME_EXTEND: return RB_LEN_TIME_EXTEND; case RINGBUF_TYPE_TIME_STAMP: return RB_LEN_TIME_STAMP; case RINGBUF_TYPE_DATA: return rb_event_data_length(event); default: WARN_ON_ONCE(1); } /* not hit */ return 0; } /* * Return total length of time extend and data, * or just the event length for all other events. */ static inline unsigned rb_event_ts_length(struct ring_buffer_event *event) { unsigned len = 0; if (extended_time(event)) { /* time extends include the data event after it */ len = RB_LEN_TIME_EXTEND; event = skip_time_extend(event); } return len + rb_event_length(event); } /** * ring_buffer_event_length - return the length of the event * @event: the event to get the length of * * Returns the size of the data load of a data event. * If the event is something other than a data event, it * returns the size of the event itself. With the exception * of a TIME EXTEND, where it still returns the size of the * data load of the data event after it. */ unsigned ring_buffer_event_length(struct ring_buffer_event *event) { unsigned length; if (extended_time(event)) event = skip_time_extend(event); length = rb_event_length(event); if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) return length; length -= RB_EVNT_HDR_SIZE; if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) length -= sizeof(event->array[0]); return length; } EXPORT_SYMBOL_GPL(ring_buffer_event_length); /* inline for ring buffer fast paths */ static __always_inline void * rb_event_data(struct ring_buffer_event *event) { if (extended_time(event)) event = skip_time_extend(event); WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); /* If length is in len field, then array[0] has the data */ if (event->type_len) return (void *)&event->array[0]; /* Otherwise length is in array[0] and array[1] has the data */ return (void *)&event->array[1]; } /** * ring_buffer_event_data - return the data of the event * @event: the event to get the data from */ void *ring_buffer_event_data(struct ring_buffer_event *event) { return rb_event_data(event); } EXPORT_SYMBOL_GPL(ring_buffer_event_data); #define for_each_buffer_cpu(buffer, cpu) \ for_each_cpu(cpu, buffer->cpumask) #define for_each_online_buffer_cpu(buffer, cpu) \ for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask) #define TS_SHIFT 27 #define TS_MASK ((1ULL << TS_SHIFT) - 1) #define TS_DELTA_TEST (~TS_MASK) static u64 rb_event_time_stamp(struct ring_buffer_event *event) { u64 ts; ts = event->array[0]; ts <<= TS_SHIFT; ts += event->time_delta; return ts; } /* Flag when events were overwritten */ #define RB_MISSED_EVENTS (1 << 31) /* Missed count stored at end */ #define RB_MISSED_STORED (1 << 30) #define RB_MISSED_MASK (3 << 30) struct buffer_data_page { u64 time_stamp; /* page time stamp */ local_t commit; /* write committed index */ unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */ }; struct buffer_data_read_page { unsigned order; /* order of the page */ struct buffer_data_page *data; /* actual data, stored in this page */ }; /* * Note, the buffer_page list must be first. The buffer pages * are allocated in cache lines, which means that each buffer * page will be at the beginning of a cache line, and thus * the least significant bits will be zero. We use this to * add flags in the list struct pointers, to make the ring buffer * lockless. */ struct buffer_page { struct list_head list; /* list of buffer pages */ local_t write; /* index for next write */ unsigned read; /* index for next read */ local_t entries; /* entries on this page */ unsigned long real_end; /* real end of data */ unsigned order; /* order of the page */ u32 id; /* ID for external mapping */ struct buffer_data_page *page; /* Actual data page */ }; /* * The buffer page counters, write and entries, must be reset * atomically when crossing page boundaries. To synchronize this * update, two counters are inserted into the number. One is * the actual counter for the write position or count on the page. * * The other is a counter of updaters. Before an update happens * the update partition of the counter is incremented. This will * allow the updater to update the counter atomically. * * The counter is 20 bits, and the state data is 12. */ #define RB_WRITE_MASK 0xfffff #define RB_WRITE_INTCNT (1 << 20) static void rb_init_page(struct buffer_data_page *bpage) { local_set(&bpage->commit, 0); } static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage) { return local_read(&bpage->page->commit); } static void free_buffer_page(struct buffer_page *bpage) { free_pages((unsigned long)bpage->page, bpage->order); kfree(bpage); } /* * We need to fit the time_stamp delta into 27 bits. */ static inline bool test_time_stamp(u64 delta) { return !!(delta & TS_DELTA_TEST); } struct rb_irq_work { struct irq_work work; wait_queue_head_t waiters; wait_queue_head_t full_waiters; atomic_t seq; bool waiters_pending; bool full_waiters_pending; bool wakeup_full; }; /* * Structure to hold event state and handle nested events. */ struct rb_event_info { u64 ts; u64 delta; u64 before; u64 after; unsigned long length; struct buffer_page *tail_page; int add_timestamp; }; /* * Used for the add_timestamp * NONE * EXTEND - wants a time extend * ABSOLUTE - the buffer requests all events to have absolute time stamps * FORCE - force a full time stamp. */ enum { RB_ADD_STAMP_NONE = 0, RB_ADD_STAMP_EXTEND = BIT(1), RB_ADD_STAMP_ABSOLUTE = BIT(2), RB_ADD_STAMP_FORCE = BIT(3) }; /* * Used for which event context the event is in. * TRANSITION = 0 * NMI = 1 * IRQ = 2 * SOFTIRQ = 3 * NORMAL = 4 * * See trace_recursive_lock() comment below for more details. */ enum { RB_CTX_TRANSITION, RB_CTX_NMI, RB_CTX_IRQ, RB_CTX_SOFTIRQ, RB_CTX_NORMAL, RB_CTX_MAX }; struct rb_time_struct { local64_t time; }; typedef struct rb_time_struct rb_time_t; #define MAX_NEST 5 /* * head_page == tail_page && head == tail then buffer is empty. */ struct ring_buffer_per_cpu { int cpu; atomic_t record_disabled; atomic_t resize_disabled; struct trace_buffer *buffer; raw_spinlock_t reader_lock; /* serialize readers */ arch_spinlock_t lock; struct lock_class_key lock_key; struct buffer_data_page *free_page; unsigned long nr_pages; unsigned int current_context; struct list_head *pages; struct buffer_page *head_page; /* read from head */ struct buffer_page *tail_page; /* write to tail */ struct buffer_page *commit_page; /* committed pages */ struct buffer_page *reader_page; unsigned long lost_events; unsigned long last_overrun; unsigned long nest; local_t entries_bytes; local_t entries; local_t overrun; local_t commit_overrun; local_t dropped_events; local_t committing; local_t commits; local_t pages_touched; local_t pages_lost; local_t pages_read; long last_pages_touch; size_t shortest_full; unsigned long read; unsigned long read_bytes; rb_time_t write_stamp; rb_time_t before_stamp; u64 event_stamp[MAX_NEST]; u64 read_stamp; /* pages removed since last reset */ unsigned long pages_removed; unsigned int mapped; struct mutex mapping_lock; unsigned long *subbuf_ids; /* ID to subbuf VA */ struct trace_buffer_meta *meta_page; /* ring buffer pages to update, > 0 to add, < 0 to remove */ long nr_pages_to_update; struct list_head new_pages; /* new pages to add */ struct work_struct update_pages_work; struct completion update_done; struct rb_irq_work irq_work; }; struct trace_buffer { unsigned flags; int cpus; atomic_t record_disabled; atomic_t resizing; cpumask_var_t cpumask; struct lock_class_key *reader_lock_key; struct mutex mutex; struct ring_buffer_per_cpu **buffers; struct hlist_node node; u64 (*clock)(void); struct rb_irq_work irq_work; bool time_stamp_abs; unsigned int subbuf_size; unsigned int subbuf_order; unsigned int max_data_size; }; struct ring_buffer_iter { struct ring_buffer_per_cpu *cpu_buffer; unsigned long head; unsigned long next_event; struct buffer_page *head_page; struct buffer_page *cache_reader_page; unsigned long cache_read; unsigned long cache_pages_removed; u64 read_stamp; u64 page_stamp; struct ring_buffer_event *event; size_t event_size; int missed_events; }; int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s) { struct buffer_data_page field; trace_seq_printf(s, "\tfield: u64 timestamp;\t" "offset:0;\tsize:%u;\tsigned:%u;\n", (unsigned int)sizeof(field.time_stamp), (unsigned int)is_signed_type(u64)); trace_seq_printf(s, "\tfield: local_t commit;\t" "offset:%u;\tsize:%u;\tsigned:%u;\n", (unsigned int)offsetof(typeof(field), commit), (unsigned int)sizeof(field.commit), (unsigned int)is_signed_type(long)); trace_seq_printf(s, "\tfield: int overwrite;\t" "offset:%u;\tsize:%u;\tsigned:%u;\n", (unsigned int)offsetof(typeof(field), commit), 1, (unsigned int)is_signed_type(long)); trace_seq_printf(s, "\tfield: char data;\t" "offset:%u;\tsize:%u;\tsigned:%u;\n", (unsigned int)offsetof(typeof(field), data), (unsigned int)buffer->subbuf_size, (unsigned int)is_signed_type(char)); return !trace_seq_has_overflowed(s); } static inline void rb_time_read(rb_time_t *t, u64 *ret) { *ret = local64_read(&t->time); } static void rb_time_set(rb_time_t *t, u64 val) { local64_set(&t->time, val); } /* * Enable this to make sure that the event passed to * ring_buffer_event_time_stamp() is not committed and also * is on the buffer that it passed in. */ //#define RB_VERIFY_EVENT #ifdef RB_VERIFY_EVENT static struct list_head *rb_list_head(struct list_head *list); static void verify_event(struct ring_buffer_per_cpu *cpu_buffer, void *event) { struct buffer_page *page = cpu_buffer->commit_page; struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page); struct list_head *next; long commit, write; unsigned long addr = (unsigned long)event; bool done = false; int stop = 0; /* Make sure the event exists and is not committed yet */ do { if (page == tail_page || WARN_ON_ONCE(stop++ > 100)) done = true; commit = local_read(&page->page->commit); write = local_read(&page->write); if (addr >= (unsigned long)&page->page->data[commit] && addr < (unsigned long)&page->page->data[write]) return; next = rb_list_head(page->list.next); page = list_entry(next, struct buffer_page, list); } while (!done); WARN_ON_ONCE(1); } #else static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer, void *event) { } #endif /* * The absolute time stamp drops the 5 MSBs and some clocks may * require them. The rb_fix_abs_ts() will take a previous full * time stamp, and add the 5 MSB of that time stamp on to the * saved absolute time stamp. Then they are compared in case of * the unlikely event that the latest time stamp incremented * the 5 MSB. */ static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts) { if (save_ts & TS_MSB) { abs |= save_ts & TS_MSB; /* Check for overflow */ if (unlikely(abs < save_ts)) abs += 1ULL << 59; } return abs; } static inline u64 rb_time_stamp(struct trace_buffer *buffer); /** * ring_buffer_event_time_stamp - return the event's current time stamp * @buffer: The buffer that the event is on * @event: the event to get the time stamp of * * Note, this must be called after @event is reserved, and before it is * committed to the ring buffer. And must be called from the same * context where the event was reserved (normal, softirq, irq, etc). * * Returns the time stamp associated with the current event. * If the event has an extended time stamp, then that is used as * the time stamp to return. * In the highly unlikely case that the event was nested more than * the max nesting, then the write_stamp of the buffer is returned, * otherwise current time is returned, but that really neither of * the last two cases should ever happen. */ u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer, struct ring_buffer_event *event) { struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()]; unsigned int nest; u64 ts; /* If the event includes an absolute time, then just use that */ if (event->type_len == RINGBUF_TYPE_TIME_STAMP) { ts = rb_event_time_stamp(event); return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp); } nest = local_read(&cpu_buffer->committing); verify_event(cpu_buffer, event); if (WARN_ON_ONCE(!nest)) goto fail; /* Read the current saved nesting level time stamp */ if (likely(--nest < MAX_NEST)) return cpu_buffer->event_stamp[nest]; /* Shouldn't happen, warn if it does */ WARN_ONCE(1, "nest (%d) greater than max", nest); fail: rb_time_read(&cpu_buffer->write_stamp, &ts); return ts; } /** * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer * @buffer: The ring_buffer to get the number of pages from * @cpu: The cpu of the ring_buffer to get the number of pages from * * Returns the number of pages that have content in the ring buffer. */ size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu) { size_t read; size_t lost; size_t cnt; read = local_read(&buffer->buffers[cpu]->pages_read); lost = local_read(&buffer->buffers[cpu]->pages_lost); cnt = local_read(&buffer->buffers[cpu]->pages_touched); if (WARN_ON_ONCE(cnt < lost)) return 0; cnt -= lost; /* The reader can read an empty page, but not more than that */ if (cnt < read) { WARN_ON_ONCE(read > cnt + 1); return 0; } return cnt - read; } static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full) { struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; size_t nr_pages; size_t dirty; nr_pages = cpu_buffer->nr_pages; if (!nr_pages || !full) return true; /* * Add one as dirty will never equal nr_pages, as the sub-buffer * that the writer is on is not counted as dirty. * This is needed if "buffer_percent" is set to 100. */ dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1; return (dirty * 100) >= (full * nr_pages); } /* * rb_wake_up_waiters - wake up tasks waiting for ring buffer input * * Schedules a delayed work to wake up any task that is blocked on the * ring buffer waiters queue. */ static void rb_wake_up_waiters(struct irq_work *work) { struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); /* For waiters waiting for the first wake up */ (void)atomic_fetch_inc_release(&rbwork->seq); wake_up_all(&rbwork->waiters); if (rbwork->full_waiters_pending || rbwork->wakeup_full) { /* Only cpu_buffer sets the above flags */ struct ring_buffer_per_cpu *cpu_buffer = container_of(rbwork, struct ring_buffer_per_cpu, irq_work); /* Called from interrupt context */ raw_spin_lock(&cpu_buffer->reader_lock); rbwork->wakeup_full = false; rbwork->full_waiters_pending = false; /* Waking up all waiters, they will reset the shortest full */ cpu_buffer->shortest_full = 0; raw_spin_unlock(&cpu_buffer->reader_lock); wake_up_all(&rbwork->full_waiters); } } /** * ring_buffer_wake_waiters - wake up any waiters on this ring buffer * @buffer: The ring buffer to wake waiters on * @cpu: The CPU buffer to wake waiters on * * In the case of a file that represents a ring buffer is closing, * it is prudent to wake up any waiters that are on this. */ void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; struct rb_irq_work *rbwork; if (!buffer) return; if (cpu == RING_BUFFER_ALL_CPUS) { /* Wake up individual ones too. One level recursion */ for_each_buffer_cpu(buffer, cpu) ring_buffer_wake_waiters(buffer, cpu); rbwork = &buffer->irq_work; } else { if (WARN_ON_ONCE(!buffer->buffers)) return; if (WARN_ON_ONCE(cpu >= nr_cpu_ids)) return; cpu_buffer = buffer->buffers[cpu]; /* The CPU buffer may not have been initialized yet */ if (!cpu_buffer) return; rbwork = &cpu_buffer->irq_work; } /* This can be called in any context */ irq_work_queue(&rbwork->work); } static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full) { struct ring_buffer_per_cpu *cpu_buffer; bool ret = false; /* Reads of all CPUs always waits for any data */ if (cpu == RING_BUFFER_ALL_CPUS) return !ring_buffer_empty(buffer); cpu_buffer = buffer->buffers[cpu]; if (!ring_buffer_empty_cpu(buffer, cpu)) { unsigned long flags; bool pagebusy; if (!full) return true; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; ret = !pagebusy && full_hit(buffer, cpu, full); if (!ret && (!cpu_buffer->shortest_full || cpu_buffer->shortest_full > full)) { cpu_buffer->shortest_full = full; } raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } return ret; } static inline bool rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer, int cpu, int full, ring_buffer_cond_fn cond, void *data) { if (rb_watermark_hit(buffer, cpu, full)) return true; if (cond(data)) return true; /* * The events can happen in critical sections where * checking a work queue can cause deadlocks. * After adding a task to the queue, this flag is set * only to notify events to try to wake up the queue * using irq_work. * * We don't clear it even if the buffer is no longer * empty. The flag only causes the next event to run * irq_work to do the work queue wake up. The worse * that can happen if we race with !trace_empty() is that * an event will cause an irq_work to try to wake up * an empty queue. * * There's no reason to protect this flag either, as * the work queue and irq_work logic will do the necessary * synchronization for the wake ups. The only thing * that is necessary is that the wake up happens after * a task has been queued. It's OK for spurious wake ups. */ if (full) rbwork->full_waiters_pending = true; else rbwork->waiters_pending = true; return false; } struct rb_wait_data { struct rb_irq_work *irq_work; int seq; }; /* * The default wait condition for ring_buffer_wait() is to just to exit the * wait loop the first time it is woken up. */ static bool rb_wait_once(void *data) { struct rb_wait_data *rdata = data; struct rb_irq_work *rbwork = rdata->irq_work; return atomic_read_acquire(&rbwork->seq) != rdata->seq; } /** * ring_buffer_wait - wait for input to the ring buffer * @buffer: buffer to wait on * @cpu: the cpu buffer to wait on * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS * @cond: condition function to break out of wait (NULL to run once) * @data: the data to pass to @cond. * * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon * as data is added to any of the @buffer's cpu buffers. Otherwise * it will wait for data to be added to a specific cpu buffer. */ int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full, ring_buffer_cond_fn cond, void *data) { struct ring_buffer_per_cpu *cpu_buffer; struct wait_queue_head *waitq; struct rb_irq_work *rbwork; struct rb_wait_data rdata; int ret = 0; /* * Depending on what the caller is waiting for, either any * data in any cpu buffer, or a specific buffer, put the * caller on the appropriate wait queue. */ if (cpu == RING_BUFFER_ALL_CPUS) { rbwork = &buffer->irq_work; /* Full only makes sense on per cpu reads */ full = 0; } else { if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -ENODEV; cpu_buffer = buffer->buffers[cpu]; rbwork = &cpu_buffer->irq_work; } if (full) waitq = &rbwork->full_waiters; else waitq = &rbwork->waiters; /* Set up to exit loop as soon as it is woken */ if (!cond) { cond = rb_wait_once; rdata.irq_work = rbwork; rdata.seq = atomic_read_acquire(&rbwork->seq); data = &rdata; } ret = wait_event_interruptible((*waitq), rb_wait_cond(rbwork, buffer, cpu, full, cond, data)); return ret; } /** * ring_buffer_poll_wait - poll on buffer input * @buffer: buffer to wait on * @cpu: the cpu buffer to wait on * @filp: the file descriptor * @poll_table: The poll descriptor * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS * * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon * as data is added to any of the @buffer's cpu buffers. Otherwise * it will wait for data to be added to a specific cpu buffer. * * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers, * zero otherwise. */ __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu, struct file *filp, poll_table *poll_table, int full) { struct ring_buffer_per_cpu *cpu_buffer; struct rb_irq_work *rbwork; if (cpu == RING_BUFFER_ALL_CPUS) { rbwork = &buffer->irq_work; full = 0; } else { if (!cpumask_test_cpu(cpu, buffer->cpumask)) return EPOLLERR; cpu_buffer = buffer->buffers[cpu]; rbwork = &cpu_buffer->irq_work; } if (full) { poll_wait(filp, &rbwork->full_waiters, poll_table); if (rb_watermark_hit(buffer, cpu, full)) return EPOLLIN | EPOLLRDNORM; /* * Only allow full_waiters_pending update to be seen after * the shortest_full is set (in rb_watermark_hit). If the * writer sees the full_waiters_pending flag set, it will * compare the amount in the ring buffer to shortest_full. * If the amount in the ring buffer is greater than the * shortest_full percent, it will call the irq_work handler * to wake up this list. The irq_handler will reset shortest_full * back to zero. That's done under the reader_lock, but * the below smp_mb() makes sure that the update to * full_waiters_pending doesn't leak up into the above. */ smp_mb(); rbwork->full_waiters_pending = true; return 0; } poll_wait(filp, &rbwork->waiters, poll_table); rbwork->waiters_pending = true; /* * There's a tight race between setting the waiters_pending and * checking if the ring buffer is empty. Once the waiters_pending bit * is set, the next event will wake the task up, but we can get stuck * if there's only a single event in. * * FIXME: Ideally, we need a memory barrier on the writer side as well, * but adding a memory barrier to all events will cause too much of a * performance hit in the fast path. We only need a memory barrier when * the buffer goes from empty to having content. But as this race is * extremely small, and it's not a problem if another event comes in, we * will fix it later. */ smp_mb(); if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) return EPOLLIN | EPOLLRDNORM; return 0; } /* buffer may be either ring_buffer or ring_buffer_per_cpu */ #define RB_WARN_ON(b, cond) \ ({ \ int _____ret = unlikely(cond); \ if (_____ret) { \ if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ struct ring_buffer_per_cpu *__b = \ (void *)b; \ atomic_inc(&__b->buffer->record_disabled); \ } else \ atomic_inc(&b->record_disabled); \ WARN_ON(1); \ } \ _____ret; \ }) /* Up this if you want to test the TIME_EXTENTS and normalization */ #define DEBUG_SHIFT 0 static inline u64 rb_time_stamp(struct trace_buffer *buffer) { u64 ts; /* Skip retpolines :-( */ if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local)) ts = trace_clock_local(); else ts = buffer->clock(); /* shift to debug/test normalization and TIME_EXTENTS */ return ts << DEBUG_SHIFT; } u64 ring_buffer_time_stamp(struct trace_buffer *buffer) { u64 time; preempt_disable_notrace(); time = rb_time_stamp(buffer); preempt_enable_notrace(); return time; } EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer, int cpu, u64 *ts) { /* Just stupid testing the normalize function and deltas */ *ts >>= DEBUG_SHIFT; } EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); /* * Making the ring buffer lockless makes things tricky. * Although writes only happen on the CPU that they are on, * and they only need to worry about interrupts. Reads can * happen on any CPU. * * The reader page is always off the ring buffer, but when the * reader finishes with a page, it needs to swap its page with * a new one from the buffer. The reader needs to take from * the head (writes go to the tail). But if a writer is in overwrite * mode and wraps, it must push the head page forward. * * Here lies the problem. * * The reader must be careful to replace only the head page, and * not another one. As described at the top of the file in the * ASCII art, the reader sets its old page to point to the next * page after head. It then sets the page after head to point to * the old reader page. But if the writer moves the head page * during this operation, the reader could end up with the tail. * * We use cmpxchg to help prevent this race. We also do something * special with the page before head. We set the LSB to 1. * * When the writer must push the page forward, it will clear the * bit that points to the head page, move the head, and then set * the bit that points to the new head page. * * We also don't want an interrupt coming in and moving the head * page on another writer. Thus we use the second LSB to catch * that too. Thus: * * head->list->prev->next bit 1 bit 0 * ------- ------- * Normal page 0 0 * Points to head page 0 1 * New head page 1 0 * * Note we can not trust the prev pointer of the head page, because: * * +----+ +-----+ +-----+ * | |------>| T |---X--->| N | * | |<------| | | | * +----+ +-----+ +-----+ * ^ ^ | * | +-----+ | | * +----------| R |----------+ | * | |<-----------+ * +-----+ * * Key: ---X--> HEAD flag set in pointer * T Tail page * R Reader page * N Next page * * (see __rb_reserve_next() to see where this happens) * * What the above shows is that the reader just swapped out * the reader page with a page in the buffer, but before it * could make the new header point back to the new page added * it was preempted by a writer. The writer moved forward onto * the new page added by the reader and is about to move forward * again. * * You can see, it is legitimate for the previous pointer of * the head (or any page) not to point back to itself. But only * temporarily. */ #define RB_PAGE_NORMAL 0UL #define RB_PAGE_HEAD 1UL #define RB_PAGE_UPDATE 2UL #define RB_FLAG_MASK 3UL /* PAGE_MOVED is not part of the mask */ #define RB_PAGE_MOVED 4UL /* * rb_list_head - remove any bit */ static struct list_head *rb_list_head(struct list_head *list) { unsigned long val = (unsigned long)list; return (struct list_head *)(val & ~RB_FLAG_MASK); } /* * rb_is_head_page - test if the given page is the head page * * Because the reader may move the head_page pointer, we can * not trust what the head page is (it may be pointing to * the reader page). But if the next page is a header page, * its flags will be non zero. */ static inline int rb_is_head_page(struct buffer_page *page, struct list_head *list) { unsigned long val; val = (unsigned long)list->next; if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) return RB_PAGE_MOVED; return val & RB_FLAG_MASK; } /* * rb_is_reader_page * * The unique thing about the reader page, is that, if the * writer is ever on it, the previous pointer never points * back to the reader page. */ static bool rb_is_reader_page(struct buffer_page *page) { struct list_head *list = page->list.prev; return rb_list_head(list->next) != &page->list; } /* * rb_set_list_to_head - set a list_head to be pointing to head. */ static void rb_set_list_to_head(struct list_head *list) { unsigned long *ptr; ptr = (unsigned long *)&list->next; *ptr |= RB_PAGE_HEAD; *ptr &= ~RB_PAGE_UPDATE; } /* * rb_head_page_activate - sets up head page */ static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) { struct buffer_page *head; head = cpu_buffer->head_page; if (!head) return; /* * Set the previous list pointer to have the HEAD flag. */ rb_set_list_to_head(head->list.prev); } static void rb_list_head_clear(struct list_head *list) { unsigned long *ptr = (unsigned long *)&list->next; *ptr &= ~RB_FLAG_MASK; } /* * rb_head_page_deactivate - clears head page ptr (for free list) */ static void rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) { struct list_head *hd; /* Go through the whole list and clear any pointers found. */ rb_list_head_clear(cpu_buffer->pages); list_for_each(hd, cpu_buffer->pages) rb_list_head_clear(hd); } static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *head, struct buffer_page *prev, int old_flag, int new_flag) { struct list_head *list; unsigned long val = (unsigned long)&head->list; unsigned long ret; list = &prev->list; val &= ~RB_FLAG_MASK; ret = cmpxchg((unsigned long *)&list->next, val | old_flag, val | new_flag); /* check if the reader took the page */ if ((ret & ~RB_FLAG_MASK) != val) return RB_PAGE_MOVED; return ret & RB_FLAG_MASK; } static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *head, struct buffer_page *prev, int old_flag) { return rb_head_page_set(cpu_buffer, head, prev, old_flag, RB_PAGE_UPDATE); } static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *head, struct buffer_page *prev, int old_flag) { return rb_head_page_set(cpu_buffer, head, prev, old_flag, RB_PAGE_HEAD); } static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *head, struct buffer_page *prev, int old_flag) { return rb_head_page_set(cpu_buffer, head, prev, old_flag, RB_PAGE_NORMAL); } static inline void rb_inc_page(struct buffer_page **bpage) { struct list_head *p = rb_list_head((*bpage)->list.next); *bpage = list_entry(p, struct buffer_page, list); } static struct buffer_page * rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) { struct buffer_page *head; struct buffer_page *page; struct list_head *list; int i; if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) return NULL; /* sanity check */ list = cpu_buffer->pages; if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) return NULL; page = head = cpu_buffer->head_page; /* * It is possible that the writer moves the header behind * where we started, and we miss in one loop. * A second loop should grab the header, but we'll do * three loops just because I'm paranoid. */ for (i = 0; i < 3; i++) { do { if (rb_is_head_page(page, page->list.prev)) { cpu_buffer->head_page = page; return page; } rb_inc_page(&page); } while (page != head); } RB_WARN_ON(cpu_buffer, 1); return NULL; } static bool rb_head_page_replace(struct buffer_page *old, struct buffer_page *new) { unsigned long *ptr = (unsigned long *)&old->list.prev->next; unsigned long val; val = *ptr & ~RB_FLAG_MASK; val |= RB_PAGE_HEAD; return try_cmpxchg(ptr, &val, (unsigned long)&new->list); } /* * rb_tail_page_update - move the tail page forward */ static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *tail_page, struct buffer_page *next_page) { unsigned long old_entries; unsigned long old_write; /* * The tail page now needs to be moved forward. * * We need to reset the tail page, but without messing * with possible erasing of data brought in by interrupts * that have moved the tail page and are currently on it. * * We add a counter to the write field to denote this. */ old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); /* * Just make sure we have seen our old_write and synchronize * with any interrupts that come in. */ barrier(); /* * If the tail page is still the same as what we think * it is, then it is up to us to update the tail * pointer. */ if (tail_page == READ_ONCE(cpu_buffer->tail_page)) { /* Zero the write counter */ unsigned long val = old_write & ~RB_WRITE_MASK; unsigned long eval = old_entries & ~RB_WRITE_MASK; /* * This will only succeed if an interrupt did * not come in and change it. In which case, we * do not want to modify it. * * We add (void) to let the compiler know that we do not care * about the return value of these functions. We use the * cmpxchg to only update if an interrupt did not already * do it for us. If the cmpxchg fails, we don't care. */ (void)local_cmpxchg(&next_page->write, old_write, val); (void)local_cmpxchg(&next_page->entries, old_entries, eval); /* * No need to worry about races with clearing out the commit. * it only can increment when a commit takes place. But that * only happens in the outer most nested commit. */ local_set(&next_page->page->commit, 0); /* Either we update tail_page or an interrupt does */ if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page)) local_inc(&cpu_buffer->pages_touched); } } static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *bpage) { unsigned long val = (unsigned long)bpage; RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK); } /** * rb_check_pages - integrity check of buffer pages * @cpu_buffer: CPU buffer with pages to test * * As a safety measure we check to make sure the data pages have not * been corrupted. * * Callers of this function need to guarantee that the list of pages doesn't get * modified during the check. In particular, if it's possible that the function * is invoked with concurrent readers which can swap in a new reader page then * the caller should take cpu_buffer->reader_lock. */ static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) { struct list_head *head = rb_list_head(cpu_buffer->pages); struct list_head *tmp; if (RB_WARN_ON(cpu_buffer, rb_list_head(rb_list_head(head->next)->prev) != head)) return; if (RB_WARN_ON(cpu_buffer, rb_list_head(rb_list_head(head->prev)->next) != head)) return; for (tmp = rb_list_head(head->next); tmp != head; tmp = rb_list_head(tmp->next)) { if (RB_WARN_ON(cpu_buffer, rb_list_head(rb_list_head(tmp->next)->prev) != tmp)) return; if (RB_WARN_ON(cpu_buffer, rb_list_head(rb_list_head(tmp->prev)->next) != tmp)) return; } } static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, long nr_pages, struct list_head *pages) { struct buffer_page *bpage, *tmp; bool user_thread = current->mm != NULL; gfp_t mflags; long i; /* * Check if the available memory is there first. * Note, si_mem_available() only gives us a rough estimate of available * memory. It may not be accurate. But we don't care, we just want * to prevent doing any allocation when it is obvious that it is * not going to succeed. */ i = si_mem_available(); if (i < nr_pages) return -ENOMEM; /* * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails * gracefully without invoking oom-killer and the system is not * destabilized. */ mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL; /* * If a user thread allocates too much, and si_mem_available() * reports there's enough memory, even though there is not. * Make sure the OOM killer kills this thread. This can happen * even with RETRY_MAYFAIL because another task may be doing * an allocation after this task has taken all memory. * This is the task the OOM killer needs to take out during this * loop, even if it was triggered by an allocation somewhere else. */ if (user_thread) set_current_oom_origin(); for (i = 0; i < nr_pages; i++) { struct page *page; bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), mflags, cpu_to_node(cpu_buffer->cpu)); if (!bpage) goto free_pages; rb_check_bpage(cpu_buffer, bpage); list_add(&bpage->list, pages); page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags | __GFP_COMP | __GFP_ZERO, cpu_buffer->buffer->subbuf_order); if (!page) goto free_pages; bpage->page = page_address(page); bpage->order = cpu_buffer->buffer->subbuf_order; rb_init_page(bpage->page); if (user_thread && fatal_signal_pending(current)) goto free_pages; } if (user_thread) clear_current_oom_origin(); return 0; free_pages: list_for_each_entry_safe(bpage, tmp, pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } if (user_thread) clear_current_oom_origin(); return -ENOMEM; } static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages) { LIST_HEAD(pages); WARN_ON(!nr_pages); if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages)) return -ENOMEM; /* * The ring buffer page list is a circular list that does not * start and end with a list head. All page list items point to * other pages. */ cpu_buffer->pages = pages.next; list_del(&pages); cpu_buffer->nr_pages = nr_pages; rb_check_pages(cpu_buffer); return 0; } static struct ring_buffer_per_cpu * rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage; struct page *page; int ret; cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); if (!cpu_buffer) return NULL; cpu_buffer->cpu = cpu; cpu_buffer->buffer = buffer; raw_spin_lock_init(&cpu_buffer->reader_lock); lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); init_completion(&cpu_buffer->update_done); init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); init_waitqueue_head(&cpu_buffer->irq_work.waiters); init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); mutex_init(&cpu_buffer->mapping_lock); bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); if (!bpage) goto fail_free_buffer; rb_check_bpage(cpu_buffer, bpage); cpu_buffer->reader_page = bpage; page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_COMP | __GFP_ZERO, cpu_buffer->buffer->subbuf_order); if (!page) goto fail_free_reader; bpage->page = page_address(page); rb_init_page(bpage->page); INIT_LIST_HEAD(&cpu_buffer->reader_page->list); INIT_LIST_HEAD(&cpu_buffer->new_pages); ret = rb_allocate_pages(cpu_buffer, nr_pages); if (ret < 0) goto fail_free_reader; cpu_buffer->head_page = list_entry(cpu_buffer->pages, struct buffer_page, list); cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; rb_head_page_activate(cpu_buffer); return cpu_buffer; fail_free_reader: free_buffer_page(cpu_buffer->reader_page); fail_free_buffer: kfree(cpu_buffer); return NULL; } static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) { struct list_head *head = cpu_buffer->pages; struct buffer_page *bpage, *tmp; irq_work_sync(&cpu_buffer->irq_work.work); free_buffer_page(cpu_buffer->reader_page); if (head) { rb_head_page_deactivate(cpu_buffer); list_for_each_entry_safe(bpage, tmp, head, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } bpage = list_entry(head, struct buffer_page, list); free_buffer_page(bpage); } free_page((unsigned long)cpu_buffer->free_page); kfree(cpu_buffer); } /** * __ring_buffer_alloc - allocate a new ring_buffer * @size: the size in bytes per cpu that is needed. * @flags: attributes to set for the ring buffer. * @key: ring buffer reader_lock_key. * * Currently the only flag that is available is the RB_FL_OVERWRITE * flag. This flag means that the buffer will overwrite old data * when the buffer wraps. If this flag is not set, the buffer will * drop data when the tail hits the head. */ struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *key) { struct trace_buffer *buffer; long nr_pages; int bsize; int cpu; int ret; /* keep it in its own cache line */ buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), GFP_KERNEL); if (!buffer) return NULL; if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) goto fail_free_buffer; /* Default buffer page size - one system page */ buffer->subbuf_order = 0; buffer->subbuf_size = PAGE_SIZE - BUF_PAGE_HDR_SIZE; /* Max payload is buffer page size - header (8bytes) */ buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2); nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size); buffer->flags = flags; buffer->clock = trace_clock_local; buffer->reader_lock_key = key; init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); init_waitqueue_head(&buffer->irq_work.waiters); /* need at least two pages */ if (nr_pages < 2) nr_pages = 2; buffer->cpus = nr_cpu_ids; bsize = sizeof(void *) * nr_cpu_ids; buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), GFP_KERNEL); if (!buffer->buffers) goto fail_free_cpumask; cpu = raw_smp_processor_id(); cpumask_set_cpu(cpu, buffer->cpumask); buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); if (!buffer->buffers[cpu]) goto fail_free_buffers; ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); if (ret < 0) goto fail_free_buffers; mutex_init(&buffer->mutex); return buffer; fail_free_buffers: for_each_buffer_cpu(buffer, cpu) { if (buffer->buffers[cpu]) rb_free_cpu_buffer(buffer->buffers[cpu]); } kfree(buffer->buffers); fail_free_cpumask: free_cpumask_var(buffer->cpumask); fail_free_buffer: kfree(buffer); return NULL; } EXPORT_SYMBOL_GPL(__ring_buffer_alloc); /** * ring_buffer_free - free a ring buffer. * @buffer: the buffer to free. */ void ring_buffer_free(struct trace_buffer *buffer) { int cpu; cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); irq_work_sync(&buffer->irq_work.work); for_each_buffer_cpu(buffer, cpu) rb_free_cpu_buffer(buffer->buffers[cpu]); kfree(buffer->buffers); free_cpumask_var(buffer->cpumask); kfree(buffer); } EXPORT_SYMBOL_GPL(ring_buffer_free); void ring_buffer_set_clock(struct trace_buffer *buffer, u64 (*clock)(void)) { buffer->clock = clock; } void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs) { buffer->time_stamp_abs = abs; } bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer) { return buffer->time_stamp_abs; } static inline unsigned long rb_page_entries(struct buffer_page *bpage) { return local_read(&bpage->entries) & RB_WRITE_MASK; } static inline unsigned long rb_page_write(struct buffer_page *bpage) { return local_read(&bpage->write) & RB_WRITE_MASK; } static bool rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages) { struct list_head *tail_page, *to_remove, *next_page; struct buffer_page *to_remove_page, *tmp_iter_page; struct buffer_page *last_page, *first_page; unsigned long nr_removed; unsigned long head_bit; int page_entries; head_bit = 0; raw_spin_lock_irq(&cpu_buffer->reader_lock); atomic_inc(&cpu_buffer->record_disabled); /* * We don't race with the readers since we have acquired the reader * lock. We also don't race with writers after disabling recording. * This makes it easy to figure out the first and the last page to be * removed from the list. We unlink all the pages in between including * the first and last pages. This is done in a busy loop so that we * lose the least number of traces. * The pages are freed after we restart recording and unlock readers. */ tail_page = &cpu_buffer->tail_page->list; /* * tail page might be on reader page, we remove the next page * from the ring buffer */ if (cpu_buffer->tail_page == cpu_buffer->reader_page) tail_page = rb_list_head(tail_page->next); to_remove = tail_page; /* start of pages to remove */ first_page = list_entry(rb_list_head(to_remove->next), struct buffer_page, list); for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { to_remove = rb_list_head(to_remove)->next; head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; } /* Read iterators need to reset themselves when some pages removed */ cpu_buffer->pages_removed += nr_removed; next_page = rb_list_head(to_remove)->next; /* * Now we remove all pages between tail_page and next_page. * Make sure that we have head_bit value preserved for the * next page */ tail_page->next = (struct list_head *)((unsigned long)next_page | head_bit); next_page = rb_list_head(next_page); next_page->prev = tail_page; /* make sure pages points to a valid page in the ring buffer */ cpu_buffer->pages = next_page; /* update head page */ if (head_bit) cpu_buffer->head_page = list_entry(next_page, struct buffer_page, list); /* pages are removed, resume tracing and then free the pages */ atomic_dec(&cpu_buffer->record_disabled); raw_spin_unlock_irq(&cpu_buffer->reader_lock); RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)); /* last buffer page to remove */ last_page = list_entry(rb_list_head(to_remove), struct buffer_page, list); tmp_iter_page = first_page; do { cond_resched(); to_remove_page = tmp_iter_page; rb_inc_page(&tmp_iter_page); /* update the counters */ page_entries = rb_page_entries(to_remove_page); if (page_entries) { /* * If something was added to this page, it was full * since it is not the tail page. So we deduct the * bytes consumed in ring buffer from here. * Increment overrun to account for the lost events. */ local_add(page_entries, &cpu_buffer->overrun); local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes); local_inc(&cpu_buffer->pages_lost); } /* * We have already removed references to this list item, just * free up the buffer_page and its page */ free_buffer_page(to_remove_page); nr_removed--; } while (to_remove_page != last_page); RB_WARN_ON(cpu_buffer, nr_removed); return nr_removed == 0; } static bool rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) { struct list_head *pages = &cpu_buffer->new_pages; unsigned long flags; bool success; int retries; /* Can be called at early boot up, where interrupts must not been enabled */ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); /* * We are holding the reader lock, so the reader page won't be swapped * in the ring buffer. Now we are racing with the writer trying to * move head page and the tail page. * We are going to adapt the reader page update process where: * 1. We first splice the start and end of list of new pages between * the head page and its previous page. * 2. We cmpxchg the prev_page->next to point from head page to the * start of new pages list. * 3. Finally, we update the head->prev to the end of new list. * * We will try this process 10 times, to make sure that we don't keep * spinning. */ retries = 10; success = false; while (retries--) { struct list_head *head_page, *prev_page; struct list_head *last_page, *first_page; struct list_head *head_page_with_bit; struct buffer_page *hpage = rb_set_head_page(cpu_buffer); if (!hpage) break; head_page = &hpage->list; prev_page = head_page->prev; first_page = pages->next; last_page = pages->prev; head_page_with_bit = (struct list_head *) ((unsigned long)head_page | RB_PAGE_HEAD); last_page->next = head_page_with_bit; first_page->prev = prev_page; /* caution: head_page_with_bit gets updated on cmpxchg failure */ if (try_cmpxchg(&prev_page->next, &head_page_with_bit, first_page)) { /* * yay, we replaced the page pointer to our new list, * now, we just have to update to head page's prev * pointer to point to end of list */ head_page->prev = last_page; success = true; break; } } if (success) INIT_LIST_HEAD(pages); /* * If we weren't successful in adding in new pages, warn and stop * tracing */ RB_WARN_ON(cpu_buffer, !success); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); /* free pages if they weren't inserted */ if (!success) { struct buffer_page *bpage, *tmp; list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } } return success; } static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer) { bool success; if (cpu_buffer->nr_pages_to_update > 0) success = rb_insert_pages(cpu_buffer); else success = rb_remove_pages(cpu_buffer, -cpu_buffer->nr_pages_to_update); if (success) cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update; } static void update_pages_handler(struct work_struct *work) { struct ring_buffer_per_cpu *cpu_buffer = container_of(work, struct ring_buffer_per_cpu, update_pages_work); rb_update_pages(cpu_buffer); complete(&cpu_buffer->update_done); } /** * ring_buffer_resize - resize the ring buffer * @buffer: the buffer to resize. * @size: the new size. * @cpu_id: the cpu buffer to resize * * Minimum size is 2 * buffer->subbuf_size. * * Returns 0 on success and < 0 on failure. */ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size, int cpu_id) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long nr_pages; int cpu, err; /* * Always succeed at resizing a non-existent buffer: */ if (!buffer) return 0; /* Make sure the requested buffer exists */ if (cpu_id != RING_BUFFER_ALL_CPUS && !cpumask_test_cpu(cpu_id, buffer->cpumask)) return 0; nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size); /* we need a minimum of two pages */ if (nr_pages < 2) nr_pages = 2; /* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex); atomic_inc(&buffer->resizing); if (cpu_id == RING_BUFFER_ALL_CPUS) { /* * Don't succeed if resizing is disabled, as a reader might be * manipulating the ring buffer and is expecting a sane state while * this is true. */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; if (atomic_read(&cpu_buffer->resize_disabled)) { err = -EBUSY; goto out_err_unlock; } } /* calculate the pages to update */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; cpu_buffer->nr_pages_to_update = nr_pages - cpu_buffer->nr_pages; /* * nothing more to do for removing pages or no update */ if (cpu_buffer->nr_pages_to_update <= 0) continue; /* * to add pages, make sure all new pages can be * allocated without receiving ENOMEM */ INIT_LIST_HEAD(&cpu_buffer->new_pages); if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update, &cpu_buffer->new_pages)) { /* not enough memory for new pages */ err = -ENOMEM; goto out_err; } cond_resched(); } cpus_read_lock(); /* * Fire off all the required work handlers * We can't schedule on offline CPUs, but it's not necessary * since we can change their buffer sizes without any race. */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; if (!cpu_buffer->nr_pages_to_update) continue; /* Can't run something on an offline CPU. */ if (!cpu_online(cpu)) { rb_update_pages(cpu_buffer); cpu_buffer->nr_pages_to_update = 0; } else { /* Run directly if possible. */ migrate_disable(); if (cpu != smp_processor_id()) { migrate_enable(); schedule_work_on(cpu, &cpu_buffer->update_pages_work); } else { update_pages_handler(&cpu_buffer->update_pages_work); migrate_enable(); } } } /* wait for all the updates to complete */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; if (!cpu_buffer->nr_pages_to_update) continue; if (cpu_online(cpu)) wait_for_completion(&cpu_buffer->update_done); cpu_buffer->nr_pages_to_update = 0; } cpus_read_unlock(); } else { cpu_buffer = buffer->buffers[cpu_id]; if (nr_pages == cpu_buffer->nr_pages) goto out; /* * Don't succeed if resizing is disabled, as a reader might be * manipulating the ring buffer and is expecting a sane state while * this is true. */ if (atomic_read(&cpu_buffer->resize_disabled)) { err = -EBUSY; goto out_err_unlock; } cpu_buffer->nr_pages_to_update = nr_pages - cpu_buffer->nr_pages; INIT_LIST_HEAD(&cpu_buffer->new_pages); if (cpu_buffer->nr_pages_to_update > 0 && __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update, &cpu_buffer->new_pages)) { err = -ENOMEM; goto out_err; } cpus_read_lock(); /* Can't run something on an offline CPU. */ if (!cpu_online(cpu_id)) rb_update_pages(cpu_buffer); else { /* Run directly if possible. */ migrate_disable(); if (cpu_id == smp_processor_id()) { rb_update_pages(cpu_buffer); migrate_enable(); } else { migrate_enable(); schedule_work_on(cpu_id, &cpu_buffer->update_pages_work); wait_for_completion(&cpu_buffer->update_done); } } cpu_buffer->nr_pages_to_update = 0; cpus_read_unlock(); } out: /* * The ring buffer resize can happen with the ring buffer * enabled, so that the update disturbs the tracing as little * as possible. But if the buffer is disabled, we do not need * to worry about that, and we can take the time to verify * that the buffer is not corrupt. */ if (atomic_read(&buffer->record_disabled)) { atomic_inc(&buffer->record_disabled); /* * Even though the buffer was disabled, we must make sure * that it is truly disabled before calling rb_check_pages. * There could have been a race between checking * record_disable and incrementing it. */ synchronize_rcu(); for_each_buffer_cpu(buffer, cpu) { unsigned long flags; cpu_buffer = buffer->buffers[cpu]; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_check_pages(cpu_buffer); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } atomic_dec(&buffer->record_disabled); } atomic_dec(&buffer->resizing); mutex_unlock(&buffer->mutex); return 0; out_err: for_each_buffer_cpu(buffer, cpu) { struct buffer_page *bpage, *tmp; cpu_buffer = buffer->buffers[cpu]; cpu_buffer->nr_pages_to_update = 0; if (list_empty(&cpu_buffer->new_pages)) continue; list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } } out_err_unlock: atomic_dec(&buffer->resizing); mutex_unlock(&buffer->mutex); return err; } EXPORT_SYMBOL_GPL(ring_buffer_resize); void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val) { mutex_lock(&buffer->mutex); if (val) buffer->flags |= RB_FL_OVERWRITE; else buffer->flags &= ~RB_FL_OVERWRITE; mutex_unlock(&buffer->mutex); } EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) { return bpage->page->data + index; } static __always_inline struct ring_buffer_event * rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) { return __rb_page_index(cpu_buffer->reader_page, cpu_buffer->reader_page->read); } static struct ring_buffer_event * rb_iter_head_event(struct ring_buffer_iter *iter) { struct ring_buffer_event *event; struct buffer_page *iter_head_page = iter->head_page; unsigned long commit; unsigned length; if (iter->head != iter->next_event) return iter->event; /* * When the writer goes across pages, it issues a cmpxchg which * is a mb(), which will synchronize with the rmb here. * (see rb_tail_page_update() and __rb_reserve_next()) */ commit = rb_page_commit(iter_head_page); smp_rmb(); /* An event needs to be at least 8 bytes in size */ if (iter->head > commit - 8) goto reset; event = __rb_page_index(iter_head_page, iter->head); length = rb_event_length(event); /* * READ_ONCE() doesn't work on functions and we don't want the * compiler doing any crazy optimizations with length. */ barrier(); if ((iter->head + length) > commit || length > iter->event_size) /* Writer corrupted the read? */ goto reset; memcpy(iter->event, event, length); /* * If the page stamp is still the same after this rmb() then the * event was safely copied without the writer entering the page. */ smp_rmb(); /* Make sure the page didn't change since we read this */ if (iter->page_stamp != iter_head_page->page->time_stamp || commit > rb_page_commit(iter_head_page)) goto reset; iter->next_event = iter->head + length; return iter->event; reset: /* Reset to the beginning */ iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; iter->head = 0; iter->next_event = 0; iter->missed_events = 1; return NULL; } /* Size is determined by what has been committed */ static __always_inline unsigned rb_page_size(struct buffer_page *bpage) { return rb_page_commit(bpage) & ~RB_MISSED_MASK; } static __always_inline unsigned rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) { return rb_page_commit(cpu_buffer->commit_page); } static __always_inline unsigned rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event) { unsigned long addr = (unsigned long)event; addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1; return addr - BUF_PAGE_HDR_SIZE; } static void rb_inc_iter(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; /* * The iterator could be on the reader page (it starts there). * But the head could have moved, since the reader was * found. Check for this case and assign the iterator * to the head page instead of next. */ if (iter->head_page == cpu_buffer->reader_page) iter->head_page = rb_set_head_page(cpu_buffer); else rb_inc_page(&iter->head_page); iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; iter->head = 0; iter->next_event = 0; } /* * rb_handle_head_page - writer hit the head page * * Returns: +1 to retry page * 0 to continue * -1 on error */ static int rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *tail_page, struct buffer_page *next_page) { struct buffer_page *new_head; int entries; int type; int ret; entries = rb_page_entries(next_page); /* * The hard part is here. We need to move the head * forward, and protect against both readers on * other CPUs and writers coming in via interrupts. */ type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, RB_PAGE_HEAD); /* * type can be one of four: * NORMAL - an interrupt already moved it for us * HEAD - we are the first to get here. * UPDATE - we are the interrupt interrupting * a current move. * MOVED - a reader on another CPU moved the next * pointer to its reader page. Give up * and try again. */ switch (type) { case RB_PAGE_HEAD: /* * We changed the head to UPDATE, thus * it is our responsibility to update * the counters. */ local_add(entries, &cpu_buffer->overrun); local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes); local_inc(&cpu_buffer->pages_lost); /* * The entries will be zeroed out when we move the * tail page. */ /* still more to do */ break; case RB_PAGE_UPDATE: /* * This is an interrupt that interrupt the * previous update. Still more to do. */ break; case RB_PAGE_NORMAL: /* * An interrupt came in before the update * and processed this for us. * Nothing left to do. */ return 1; case RB_PAGE_MOVED: /* * The reader is on another CPU and just did * a swap with our next_page. * Try again. */ return 1; default: RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ return -1; } /* * Now that we are here, the old head pointer is * set to UPDATE. This will keep the reader from * swapping the head page with the reader page. * The reader (on another CPU) will spin till * we are finished. * * We just need to protect against interrupts * doing the job. We will set the next pointer * to HEAD. After that, we set the old pointer * to NORMAL, but only if it was HEAD before. * otherwise we are an interrupt, and only * want the outer most commit to reset it. */ new_head = next_page; rb_inc_page(&new_head); ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, RB_PAGE_NORMAL); /* * Valid returns are: * HEAD - an interrupt came in and already set it. * NORMAL - One of two things: * 1) We really set it. * 2) A bunch of interrupts came in and moved * the page forward again. */ switch (ret) { case RB_PAGE_HEAD: case RB_PAGE_NORMAL: /* OK */ break; default: RB_WARN_ON(cpu_buffer, 1); return -1; } /* * It is possible that an interrupt came in, * set the head up, then more interrupts came in * and moved it again. When we get back here, * the page would have been set to NORMAL but we * just set it back to HEAD. * * How do you detect this? Well, if that happened * the tail page would have moved. */ if (ret == RB_PAGE_NORMAL) { struct buffer_page *buffer_tail_page; buffer_tail_page = READ_ONCE(cpu_buffer->tail_page); /* * If the tail had moved passed next, then we need * to reset the pointer. */ if (buffer_tail_page != tail_page && buffer_tail_page != next_page) rb_head_page_set_normal(cpu_buffer, new_head, next_page, RB_PAGE_HEAD); } /* * If this was the outer most commit (the one that * changed the original pointer from HEAD to UPDATE), * then it is up to us to reset it to NORMAL. */ if (type == RB_PAGE_HEAD) { ret = rb_head_page_set_normal(cpu_buffer, next_page, tail_page, RB_PAGE_UPDATE); if (RB_WARN_ON(cpu_buffer, ret != RB_PAGE_UPDATE)) return -1; } return 0; } static inline void rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, unsigned long tail, struct rb_event_info *info) { unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size); struct buffer_page *tail_page = info->tail_page; struct ring_buffer_event *event; unsigned long length = info->length; /* * Only the event that crossed the page boundary * must fill the old tail_page with padding. */ if (tail >= bsize) { /* * If the page was filled, then we still need * to update the real_end. Reset it to zero * and the reader will ignore it. */ if (tail == bsize) tail_page->real_end = 0; local_sub(length, &tail_page->write); return; } event = __rb_page_index(tail_page, tail); /* * Save the original length to the meta data. * This will be used by the reader to add lost event * counter. */ tail_page->real_end = tail; /* * If this event is bigger than the minimum size, then * we need to be careful that we don't subtract the * write counter enough to allow another writer to slip * in on this page. * We put in a discarded commit instead, to make sure * that this space is not used again, and this space will * not be accounted into 'entries_bytes'. * * If we are less than the minimum size, we don't need to * worry about it. */ if (tail > (bsize - RB_EVNT_MIN_SIZE)) { /* No room for any events */ /* Mark the rest of the page with padding */ rb_event_set_padding(event); /* Make sure the padding is visible before the write update */ smp_wmb(); /* Set the write back to the previous setting */ local_sub(length, &tail_page->write); return; } /* Put in a discarded event */ event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE; event->type_len = RINGBUF_TYPE_PADDING; /* time delta must be non zero */ event->time_delta = 1; /* account for padding bytes */ local_add(bsize - tail, &cpu_buffer->entries_bytes); /* Make sure the padding is visible before the tail_page->write update */ smp_wmb(); /* Set write to end of buffer */ length = (tail + length) - bsize; local_sub(length, &tail_page->write); } static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer); /* * This is the slow path, force gcc not to inline it. */ static noinline struct ring_buffer_event * rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, unsigned long tail, struct rb_event_info *info) { struct buffer_page *tail_page = info->tail_page; struct buffer_page *commit_page = cpu_buffer->commit_page; struct trace_buffer *buffer = cpu_buffer->buffer; struct buffer_page *next_page; int ret; next_page = tail_page; rb_inc_page(&next_page); /* * If for some reason, we had an interrupt storm that made * it all the way around the buffer, bail, and warn * about it. */ if (unlikely(next_page == commit_page)) { local_inc(&cpu_buffer->commit_overrun); goto out_reset; } /* * This is where the fun begins! * * We are fighting against races between a reader that * could be on another CPU trying to swap its reader * page with the buffer head. * * We are also fighting against interrupts coming in and * moving the head or tail on us as well. * * If the next page is the head page then we have filled * the buffer, unless the commit page is still on the * reader page. */ if (rb_is_head_page(next_page, &tail_page->list)) { /* * If the commit is not on the reader page, then * move the header page. */ if (!rb_is_reader_page(cpu_buffer->commit_page)) { /* * If we are not in overwrite mode, * this is easy, just stop here. */ if (!(buffer->flags & RB_FL_OVERWRITE)) { local_inc(&cpu_buffer->dropped_events); goto out_reset; } ret = rb_handle_head_page(cpu_buffer, tail_page, next_page); if (ret < 0) goto out_reset; if (ret) goto out_again; } else { /* * We need to be careful here too. The * commit page could still be on the reader * page. We could have a small buffer, and * have filled up the buffer with events * from interrupts and such, and wrapped. * * Note, if the tail page is also on the * reader_page, we let it move out. */ if (unlikely((cpu_buffer->commit_page != cpu_buffer->tail_page) && (cpu_buffer->commit_page == cpu_buffer->reader_page))) { local_inc(&cpu_buffer->commit_overrun); goto out_reset; } } } rb_tail_page_update(cpu_buffer, tail_page, next_page); out_again: rb_reset_tail(cpu_buffer, tail, info); /* Commit what we have for now. */ rb_end_commit(cpu_buffer); /* rb_end_commit() decs committing */ local_inc(&cpu_buffer->committing); /* fail and let the caller try again */ return ERR_PTR(-EAGAIN); out_reset: /* reset write */ rb_reset_tail(cpu_buffer, tail, info); return NULL; } /* Slow path */ static struct ring_buffer_event * rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event, u64 delta, bool abs) { if (abs) event->type_len = RINGBUF_TYPE_TIME_STAMP; else event->type_len = RINGBUF_TYPE_TIME_EXTEND; /* Not the first event on the page, or not delta? */ if (abs || rb_event_index(cpu_buffer, event)) { event->time_delta = delta & TS_MASK; event->array[0] = delta >> TS_SHIFT; } else { /* nope, just zero it */ event->time_delta = 0; event->array[0] = 0; } return skip_time_extend(event); } #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK static inline bool sched_clock_stable(void) { return true; } #endif static void rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer, struct rb_event_info *info) { u64 write_stamp; WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s", (unsigned long long)info->delta, (unsigned long long)info->ts, (unsigned long long)info->before, (unsigned long long)info->after, (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}), sched_clock_stable() ? "" : "If you just came from a suspend/resume,\n" "please switch to the trace global clock:\n" " echo global > /sys/kernel/tracing/trace_clock\n" "or add trace_clock=global to the kernel command line\n"); } static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event **event, struct rb_event_info *info, u64 *delta, unsigned int *length) { bool abs = info->add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE); if (unlikely(info->delta > (1ULL << 59))) { /* * Some timers can use more than 59 bits, and when a timestamp * is added to the buffer, it will lose those bits. */ if (abs && (info->ts & TS_MSB)) { info->delta &= ABS_TS_MASK; /* did the clock go backwards */ } else if (info->before == info->after && info->before > info->ts) { /* not interrupted */ static int once; /* * This is possible with a recalibrating of the TSC. * Do not produce a call stack, but just report it. */ if (!once) { once++; pr_warn("Ring buffer clock went backwards: %llu -> %llu\n", info->before, info->ts); } } else rb_check_timestamp(cpu_buffer, info); if (!abs) info->delta = 0; } *event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs); *length -= RB_LEN_TIME_EXTEND; *delta = 0; } /** * rb_update_event - update event type and data * @cpu_buffer: The per cpu buffer of the @event * @event: the event to update * @info: The info to update the @event with (contains length and delta) * * Update the type and data fields of the @event. The length * is the actual size that is written to the ring buffer, * and with this, we can determine what to place into the * data field. */ static void rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event, struct rb_event_info *info) { unsigned length = info->length; u64 delta = info->delta; unsigned int nest = local_read(&cpu_buffer->committing) - 1; if (!WARN_ON_ONCE(nest >= MAX_NEST)) cpu_buffer->event_stamp[nest] = info->ts; /* * If we need to add a timestamp, then we * add it to the start of the reserved space. */ if (unlikely(info->add_timestamp)) rb_add_timestamp(cpu_buffer, &event, info, &delta, &length); event->time_delta = delta; length -= RB_EVNT_HDR_SIZE; if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) { event->type_len = 0; event->array[0] = length; } else event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); } static unsigned rb_calculate_event_length(unsigned length) { struct ring_buffer_event event; /* Used only for sizeof array */ /* zero length can cause confusions */ if (!length) length++; if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) length += sizeof(event.array[0]); length += RB_EVNT_HDR_SIZE; length = ALIGN(length, RB_ARCH_ALIGNMENT); /* * In case the time delta is larger than the 27 bits for it * in the header, we need to add a timestamp. If another * event comes in when trying to discard this one to increase * the length, then the timestamp will be added in the allocated * space of this event. If length is bigger than the size needed * for the TIME_EXTEND, then padding has to be used. The events * length must be either RB_LEN_TIME_EXTEND, or greater than or equal * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding. * As length is a multiple of 4, we only need to worry if it * is 12 (RB_LEN_TIME_EXTEND + 4). */ if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT) length += RB_ALIGNMENT; return length; } static inline bool rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event) { unsigned long new_index, old_index; struct buffer_page *bpage; unsigned long addr; new_index = rb_event_index(cpu_buffer, event); old_index = new_index + rb_event_ts_length(event); addr = (unsigned long)event; addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1); bpage = READ_ONCE(cpu_buffer->tail_page); /* * Make sure the tail_page is still the same and * the next write location is the end of this event */ if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { unsigned long write_mask = local_read(&bpage->write) & ~RB_WRITE_MASK; unsigned long event_length = rb_event_length(event); /* * For the before_stamp to be different than the write_stamp * to make sure that the next event adds an absolute * value and does not rely on the saved write stamp, which * is now going to be bogus. * * By setting the before_stamp to zero, the next event * is not going to use the write_stamp and will instead * create an absolute timestamp. This means there's no * reason to update the wirte_stamp! */ rb_time_set(&cpu_buffer->before_stamp, 0); /* * If an event were to come in now, it would see that the * write_stamp and the before_stamp are different, and assume * that this event just added itself before updating * the write stamp. The interrupting event will fix the * write stamp for us, and use an absolute timestamp. */ /* * This is on the tail page. It is possible that * a write could come in and move the tail page * and write to the next page. That is fine * because we just shorten what is on this page. */ old_index += write_mask; new_index += write_mask; /* caution: old_index gets updated on cmpxchg failure */ if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) { /* update counters */ local_sub(event_length, &cpu_buffer->entries_bytes); return true; } } /* could not discard */ return false; } static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) { local_inc(&cpu_buffer->committing); local_inc(&cpu_buffer->commits); } static __always_inline void rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) { unsigned long max_count; /* * We only race with interrupts and NMIs on this CPU. * If we own the commit event, then we can commit * all others that interrupted us, since the interruptions * are in stack format (they finish before they come * back to us). This allows us to do a simple loop to * assign the commit to the tail. */ again: max_count = cpu_buffer->nr_pages * 100; while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) { if (RB_WARN_ON(cpu_buffer, !(--max_count))) return; if (RB_WARN_ON(cpu_buffer, rb_is_reader_page(cpu_buffer->tail_page))) return; /* * No need for a memory barrier here, as the update * of the tail_page did it for this page. */ local_set(&cpu_buffer->commit_page->page->commit, rb_page_write(cpu_buffer->commit_page)); rb_inc_page(&cpu_buffer->commit_page); /* add barrier to keep gcc from optimizing too much */ barrier(); } while (rb_commit_index(cpu_buffer) != rb_page_write(cpu_buffer->commit_page)) { /* Make sure the readers see the content of what is committed. */ smp_wmb(); local_set(&cpu_buffer->commit_page->page->commit, rb_page_write(cpu_buffer->commit_page)); RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->commit_page->page->commit) & ~RB_WRITE_MASK); barrier(); } /* again, keep gcc from optimizing */ barrier(); /* * If an interrupt came in just after the first while loop * and pushed the tail page forward, we will be left with * a dangling commit that will never go forward. */ if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page))) goto again; } static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) { unsigned long commits; if (RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing))) return; again: commits = local_read(&cpu_buffer->commits); /* synchronize with interrupts */ barrier(); if (local_read(&cpu_buffer->committing) == 1) rb_set_commit_to_write(cpu_buffer); local_dec(&cpu_buffer->committing); /* synchronize with interrupts */ barrier(); /* * Need to account for interrupts coming in between the * updating of the commit page and the clearing of the * committing counter. */ if (unlikely(local_read(&cpu_buffer->commits) != commits) && !local_read(&cpu_buffer->committing)) { local_inc(&cpu_buffer->committing); goto again; } } static inline void rb_event_discard(struct ring_buffer_event *event) { if (extended_time(event)) event = skip_time_extend(event); /* array[0] holds the actual length for the discarded event */ event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; event->type_len = RINGBUF_TYPE_PADDING; /* time delta must be non zero */ if (!event->time_delta) event->time_delta = 1; } static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer) { local_inc(&cpu_buffer->entries); rb_end_commit(cpu_buffer); } static __always_inline void rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) { if (buffer->irq_work.waiters_pending) { buffer->irq_work.waiters_pending = false; /* irq_work_queue() supplies it's own memory barriers */ irq_work_queue(&buffer->irq_work.work); } if (cpu_buffer->irq_work.waiters_pending) { cpu_buffer->irq_work.waiters_pending = false; /* irq_work_queue() supplies it's own memory barriers */ irq_work_queue(&cpu_buffer->irq_work.work); } if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched)) return; if (cpu_buffer->reader_page == cpu_buffer->commit_page) return; if (!cpu_buffer->irq_work.full_waiters_pending) return; cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched); if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full)) return; cpu_buffer->irq_work.wakeup_full = true; cpu_buffer->irq_work.full_waiters_pending = false; /* irq_work_queue() supplies it's own memory barriers */ irq_work_queue(&cpu_buffer->irq_work.work); } #ifdef CONFIG_RING_BUFFER_RECORD_RECURSION # define do_ring_buffer_record_recursion() \ do_ftrace_record_recursion(_THIS_IP_, _RET_IP_) #else # define do_ring_buffer_record_recursion() do { } while (0) #endif /* * The lock and unlock are done within a preempt disable section. * The current_context per_cpu variable can only be modified * by the current task between lock and unlock. But it can * be modified more than once via an interrupt. To pass this * information from the lock to the unlock without having to * access the 'in_interrupt()' functions again (which do show * a bit of overhead in something as critical as function tracing, * we use a bitmask trick. * * bit 1 = NMI context * bit 2 = IRQ context * bit 3 = SoftIRQ context * bit 4 = normal context. * * This works because this is the order of contexts that can * preempt other contexts. A SoftIRQ never preempts an IRQ * context. * * When the context is determined, the corresponding bit is * checked and set (if it was set, then a recursion of that context * happened). * * On unlock, we need to clear this bit. To do so, just subtract * 1 from the current_context and AND it to itself. * * (binary) * 101 - 1 = 100 * 101 & 100 = 100 (clearing bit zero) * * 1010 - 1 = 1001 * 1010 & 1001 = 1000 (clearing bit 1) * * The least significant bit can be cleared this way, and it * just so happens that it is the same bit corresponding to * the current context. * * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit * is set when a recursion is detected at the current context, and if * the TRANSITION bit is already set, it will fail the recursion. * This is needed because there's a lag between the changing of * interrupt context and updating the preempt count. In this case, * a false positive will be found. To handle this, one extra recursion * is allowed, and this is done by the TRANSITION bit. If the TRANSITION * bit is already set, then it is considered a recursion and the function * ends. Otherwise, the TRANSITION bit is set, and that bit is returned. * * On the trace_recursive_unlock(), the TRANSITION bit will be the first * to be cleared. Even if it wasn't the context that set it. That is, * if an interrupt comes in while NORMAL bit is set and the ring buffer * is called before preempt_count() is updated, since the check will * be on the NORMAL bit, the TRANSITION bit will then be set. If an * NMI then comes in, it will set the NMI bit, but when the NMI code * does the trace_recursive_unlock() it will clear the TRANSITION bit * and leave the NMI bit set. But this is fine, because the interrupt * code that set the TRANSITION bit will then clear the NMI bit when it * calls trace_recursive_unlock(). If another NMI comes in, it will * set the TRANSITION bit and continue. * * Note: The TRANSITION bit only handles a single transition between context. */ static __always_inline bool trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) { unsigned int val = cpu_buffer->current_context; int bit = interrupt_context_level(); bit = RB_CTX_NORMAL - bit; if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) { /* * It is possible that this was called by transitioning * between interrupt context, and preempt_count() has not * been updated yet. In this case, use the TRANSITION bit. */ bit = RB_CTX_TRANSITION; if (val & (1 << (bit + cpu_buffer->nest))) { do_ring_buffer_record_recursion(); return true; } } val |= (1 << (bit + cpu_buffer->nest)); cpu_buffer->current_context = val; return false; } static __always_inline void trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) { cpu_buffer->current_context &= cpu_buffer->current_context - (1 << cpu_buffer->nest); } /* The recursive locking above uses 5 bits */ #define NESTED_BITS 5 /** * ring_buffer_nest_start - Allow to trace while nested * @buffer: The ring buffer to modify * * The ring buffer has a safety mechanism to prevent recursion. * But there may be a case where a trace needs to be done while * tracing something else. In this case, calling this function * will allow this function to nest within a currently active * ring_buffer_lock_reserve(). * * Call this function before calling another ring_buffer_lock_reserve() and * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit(). */ void ring_buffer_nest_start(struct trace_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; int cpu; /* Enabled by ring_buffer_nest_end() */ preempt_disable_notrace(); cpu = raw_smp_processor_id(); cpu_buffer = buffer->buffers[cpu]; /* This is the shift value for the above recursive locking */ cpu_buffer->nest += NESTED_BITS; } /** * ring_buffer_nest_end - Allow to trace while nested * @buffer: The ring buffer to modify * * Must be called after ring_buffer_nest_start() and after the * ring_buffer_unlock_commit(). */ void ring_buffer_nest_end(struct trace_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; int cpu; /* disabled by ring_buffer_nest_start() */ cpu = raw_smp_processor_id(); cpu_buffer = buffer->buffers[cpu]; /* This is the shift value for the above recursive locking */ cpu_buffer->nest -= NESTED_BITS; preempt_enable_notrace(); } /** * ring_buffer_unlock_commit - commit a reserved * @buffer: The buffer to commit to * * This commits the data to the ring buffer, and releases any locks held. * * Must be paired with ring_buffer_lock_reserve. */ int ring_buffer_unlock_commit(struct trace_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; int cpu = raw_smp_processor_id(); cpu_buffer = buffer->buffers[cpu]; rb_commit(cpu_buffer); rb_wakeups(buffer, cpu_buffer); trace_recursive_unlock(cpu_buffer); preempt_enable_notrace(); return 0; } EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); /* Special value to validate all deltas on a page. */ #define CHECK_FULL_PAGE 1L #ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS static const char *show_irq_str(int bits) { const char *type[] = { ".", // 0 "s", // 1 "h", // 2 "Hs", // 3 "n", // 4 "Ns", // 5 "Nh", // 6 "NHs", // 7 }; return type[bits]; } /* Assume this is an trace event */ static const char *show_flags(struct ring_buffer_event *event) { struct trace_entry *entry; int bits = 0; if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry)) return "X"; entry = ring_buffer_event_data(event); if (entry->flags & TRACE_FLAG_SOFTIRQ) bits |= 1; if (entry->flags & TRACE_FLAG_HARDIRQ) bits |= 2; if (entry->flags & TRACE_FLAG_NMI) bits |= 4; return show_irq_str(bits); } static const char *show_irq(struct ring_buffer_event *event) { struct trace_entry *entry; if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry)) return ""; entry = ring_buffer_event_data(event); if (entry->flags & TRACE_FLAG_IRQS_OFF) return "d"; return ""; } static const char *show_interrupt_level(void) { unsigned long pc = preempt_count(); unsigned char level = 0; if (pc & SOFTIRQ_OFFSET) level |= 1; if (pc & HARDIRQ_MASK) level |= 2; if (pc & NMI_MASK) level |= 4; return show_irq_str(level); } static void dump_buffer_page(struct buffer_data_page *bpage, struct rb_event_info *info, unsigned long tail) { struct ring_buffer_event *event; u64 ts, delta; int e; ts = bpage->time_stamp; pr_warn(" [%lld] PAGE TIME STAMP\n", ts); for (e = 0; e < tail; e += rb_event_length(event)) { event = (struct ring_buffer_event *)(bpage->data + e); switch (event->type_len) { case RINGBUF_TYPE_TIME_EXTEND: delta = rb_event_time_stamp(event); ts += delta; pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n", e, ts, delta); break; case RINGBUF_TYPE_TIME_STAMP: delta = rb_event_time_stamp(event); ts = rb_fix_abs_ts(delta, ts); pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n", e, ts, delta); break; case RINGBUF_TYPE_PADDING: ts += event->time_delta; pr_warn(" 0x%x: [%lld] delta:%d PADDING\n", e, ts, event->time_delta); break; case RINGBUF_TYPE_DATA: ts += event->time_delta; pr_warn(" 0x%x: [%lld] delta:%d %s%s\n", e, ts, event->time_delta, show_flags(event), show_irq(event)); break; default: break; } } pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e); } static DEFINE_PER_CPU(atomic_t, checking); static atomic_t ts_dump; #define buffer_warn_return(fmt, ...) \ do { \ /* If another report is happening, ignore this one */ \ if (atomic_inc_return(&ts_dump) != 1) { \ atomic_dec(&ts_dump); \ goto out; \ } \ atomic_inc(&cpu_buffer->record_disabled); \ pr_warn(fmt, ##__VA_ARGS__); \ dump_buffer_page(bpage, info, tail); \ atomic_dec(&ts_dump); \ /* There's some cases in boot up that this can happen */ \ if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \ /* Do not re-enable checking */ \ return; \ } while (0) /* * Check if the current event time stamp matches the deltas on * the buffer page. */ static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer, struct rb_event_info *info, unsigned long tail) { struct ring_buffer_event *event; struct buffer_data_page *bpage; u64 ts, delta; bool full = false; int e; bpage = info->tail_page->page; if (tail == CHECK_FULL_PAGE) { full = true; tail = local_read(&bpage->commit); } else if (info->add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) { /* Ignore events with absolute time stamps */ return; } /* * Do not check the first event (skip possible extends too). * Also do not check if previous events have not been committed. */ if (tail <= 8 || tail > local_read(&bpage->commit)) return; /* * If this interrupted another event, */ if (atomic_inc_return(this_cpu_ptr(&checking)) != 1) goto out; ts = bpage->time_stamp; for (e = 0; e < tail; e += rb_event_length(event)) { event = (struct ring_buffer_event *)(bpage->data + e); switch (event->type_len) { case RINGBUF_TYPE_TIME_EXTEND: delta = rb_event_time_stamp(event); ts += delta; break; case RINGBUF_TYPE_TIME_STAMP: delta = rb_event_time_stamp(event); delta = rb_fix_abs_ts(delta, ts); if (delta < ts) { buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n", cpu_buffer->cpu, ts, delta); } ts = delta; break; case RINGBUF_TYPE_PADDING: if (event->time_delta == 1) break; fallthrough; case RINGBUF_TYPE_DATA: ts += event->time_delta; break; default: RB_WARN_ON(cpu_buffer, 1); } } if ((full && ts > info->ts) || (!full && ts + info->delta != info->ts)) { buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n", cpu_buffer->cpu, ts + info->delta, info->ts, info->delta, info->before, info->after, full ? " (full)" : "", show_interrupt_level()); } out: atomic_dec(this_cpu_ptr(&checking)); } #else static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer, struct rb_event_info *info, unsigned long tail) { } #endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */ static struct ring_buffer_event * __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, struct rb_event_info *info) { struct ring_buffer_event *event; struct buffer_page *tail_page; unsigned long tail, write, w; /* Don't let the compiler play games with cpu_buffer->tail_page */ tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page); /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK; barrier(); rb_time_read(&cpu_buffer->before_stamp, &info->before); rb_time_read(&cpu_buffer->write_stamp, &info->after); barrier(); info->ts = rb_time_stamp(cpu_buffer->buffer); if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) { info->delta = info->ts; } else { /* * If interrupting an event time update, we may need an * absolute timestamp. * Don't bother if this is the start of a new page (w == 0). */ if (!w) { /* Use the sub-buffer timestamp */ info->delta = 0; } else if (unlikely(info->before != info->after)) { info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND; info->length += RB_LEN_TIME_EXTEND; } else { info->delta = info->ts - info->after; if (unlikely(test_time_stamp(info->delta))) { info->add_timestamp |= RB_ADD_STAMP_EXTEND; info->length += RB_LEN_TIME_EXTEND; } } } /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts); /*C*/ write = local_add_return(info->length, &tail_page->write); /* set write to only the index of the write */ write &= RB_WRITE_MASK; tail = write - info->length; /* See if we shot pass the end of this buffer page */ if (unlikely(write > cpu_buffer->buffer->subbuf_size)) { check_buffer(cpu_buffer, info, CHECK_FULL_PAGE); return rb_move_tail(cpu_buffer, tail, info); } if (likely(tail == w)) { /* Nothing interrupted us between A and C */ /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts); /* * If something came in between C and D, the write stamp * may now not be in sync. But that's fine as the before_stamp * will be different and then next event will just be forced * to use an absolute timestamp. */ if (likely(!(info->add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)))) /* This did not interrupt any time update */ info->delta = info->ts - info->after; else /* Just use full timestamp for interrupting event */ info->delta = info->ts; check_buffer(cpu_buffer, info, tail); } else { u64 ts; /* SLOW PATH - Interrupted between A and C */ /* Save the old before_stamp */ rb_time_read(&cpu_buffer->before_stamp, &info->before); /* * Read a new timestamp and update the before_stamp to make * the next event after this one force using an absolute * timestamp. This is in case an interrupt were to come in * between E and F. */ ts = rb_time_stamp(cpu_buffer->buffer); rb_time_set(&cpu_buffer->before_stamp, ts); barrier(); /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after); barrier(); /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) && info->after == info->before && info->after < ts) { /* * Nothing came after this event between C and F, it is * safe to use info->after for the delta as it * matched info->before and is still valid. */ info->delta = ts - info->after; } else { /* * Interrupted between C and F: * Lost the previous events time stamp. Just set the * delta to zero, and this will be the same time as * the event this event interrupted. And the events that * came after this will still be correct (as they would * have built their delta on the previous event. */ info->delta = 0; } info->ts = ts; info->add_timestamp &= ~RB_ADD_STAMP_FORCE; } /* * If this is the first commit on the page, then it has the same * timestamp as the page itself. */ if (unlikely(!tail && !(info->add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)))) info->delta = 0; /* We reserved something on the buffer */ event = __rb_page_index(tail_page, tail); rb_update_event(cpu_buffer, event, info); local_inc(&tail_page->entries); /* * If this is the first commit on the page, then update * its timestamp. */ if (unlikely(!tail)) tail_page->page->time_stamp = info->ts; /* account for these added bytes */ local_add(info->length, &cpu_buffer->entries_bytes); return event; } static __always_inline struct ring_buffer_event * rb_reserve_next_event(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer, unsigned long length) { struct ring_buffer_event *event; struct rb_event_info info; int nr_loops = 0; int add_ts_default; /* ring buffer does cmpxchg, make sure it is safe in NMI context */ if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) && (unlikely(in_nmi()))) { return NULL; } rb_start_commit(cpu_buffer); /* The commit page can not change after this */ #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP /* * Due to the ability to swap a cpu buffer from a buffer * it is possible it was swapped before we committed. * (committing stops a swap). We check for it here and * if it happened, we have to fail the write. */ barrier(); if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { local_dec(&cpu_buffer->committing); local_dec(&cpu_buffer->commits); return NULL; } #endif info.length = rb_calculate_event_length(length); if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) { add_ts_default = RB_ADD_STAMP_ABSOLUTE; info.length += RB_LEN_TIME_EXTEND; if (info.length > cpu_buffer->buffer->max_data_size) goto out_fail; } else { add_ts_default = RB_ADD_STAMP_NONE; } again: info.add_timestamp = add_ts_default; info.delta = 0; /* * We allow for interrupts to reenter here and do a trace. * If one does, it will cause this original code to loop * back here. Even with heavy interrupts happening, this * should only happen a few times in a row. If this happens * 1000 times in a row, there must be either an interrupt * storm or we have something buggy. * Bail! */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) goto out_fail; event = __rb_reserve_next(cpu_buffer, &info); if (unlikely(PTR_ERR(event) == -EAGAIN)) { if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND)) info.length -= RB_LEN_TIME_EXTEND; goto again; } if (likely(event)) return event; out_fail: rb_end_commit(cpu_buffer); return NULL; } /** * ring_buffer_lock_reserve - reserve a part of the buffer * @buffer: the ring buffer to reserve from * @length: the length of the data to reserve (excluding event header) * * Returns a reserved event on the ring buffer to copy directly to. * The user of this interface will need to get the body to write into * and can use the ring_buffer_event_data() interface. * * The length is the length of the data needed, not the event length * which also includes the event header. * * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. * If NULL is returned, then nothing has been allocated or locked. */ struct ring_buffer_event * ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; int cpu; /* If we are tracing schedule, we don't want to recurse */ preempt_disable_notrace(); if (unlikely(atomic_read(&buffer->record_disabled))) goto out; cpu = raw_smp_processor_id(); if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) goto out; cpu_buffer = buffer->buffers[cpu]; if (unlikely(atomic_read(&cpu_buffer->record_disabled))) goto out; if (unlikely(length > buffer->max_data_size)) goto out; if (unlikely(trace_recursive_lock(cpu_buffer))) goto out; event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) goto out_unlock; return event; out_unlock: trace_recursive_unlock(cpu_buffer); out: preempt_enable_notrace(); return NULL; } EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); /* * Decrement the entries to the page that an event is on. * The event does not even need to exist, only the pointer * to the page it is on. This may only be called before the commit * takes place. */ static inline void rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event) { unsigned long addr = (unsigned long)event; struct buffer_page *bpage = cpu_buffer->commit_page; struct buffer_page *start; addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1); /* Do the likely case first */ if (likely(bpage->page == (void *)addr)) { local_dec(&bpage->entries); return; } /* * Because the commit page may be on the reader page we * start with the next page and check the end loop there. */ rb_inc_page(&bpage); start = bpage; do { if (bpage->page == (void *)addr) { local_dec(&bpage->entries); return; } rb_inc_page(&bpage); } while (bpage != start); /* commit not part of this buffer?? */ RB_WARN_ON(cpu_buffer, 1); } /** * ring_buffer_discard_commit - discard an event that has not been committed * @buffer: the ring buffer * @event: non committed event to discard * * Sometimes an event that is in the ring buffer needs to be ignored. * This function lets the user discard an event in the ring buffer * and then that event will not be read later. * * This function only works if it is called before the item has been * committed. It will try to free the event from the ring buffer * if another event has not been added behind it. * * If another event has been added behind it, it will set the event * up as discarded, and perform the commit. * * If this function is called, do not call ring_buffer_unlock_commit on * the event. */ void ring_buffer_discard_commit(struct trace_buffer *buffer, struct ring_buffer_event *event) { struct ring_buffer_per_cpu *cpu_buffer; int cpu; /* The event is discarded regardless */ rb_event_discard(event); cpu = smp_processor_id(); cpu_buffer = buffer->buffers[cpu]; /* * This must only be called if the event has not been * committed yet. Thus we can assume that preemption * is still disabled. */ RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); rb_decrement_entry(cpu_buffer, event); if (rb_try_to_discard(cpu_buffer, event)) goto out; out: rb_end_commit(cpu_buffer); trace_recursive_unlock(cpu_buffer); preempt_enable_notrace(); } EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); /** * ring_buffer_write - write data to the buffer without reserving * @buffer: The ring buffer to write to. * @length: The length of the data being written (excluding the event header) * @data: The data to write to the buffer. * * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as * one function. If you already have the data to write to the buffer, it * may be easier to simply call this function. * * Note, like ring_buffer_lock_reserve, the length is the length of the data * and not the length of the event which would hold the header. */ int ring_buffer_write(struct trace_buffer *buffer, unsigned long length, void *data) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; void *body; int ret = -EBUSY; int cpu; preempt_disable_notrace(); if (atomic_read(&buffer->record_disabled)) goto out; cpu = raw_smp_processor_id(); if (!cpumask_test_cpu(cpu, buffer->cpumask)) goto out; cpu_buffer = buffer->buffers[cpu]; if (atomic_read(&cpu_buffer->record_disabled)) goto out; if (length > buffer->max_data_size) goto out; if (unlikely(trace_recursive_lock(cpu_buffer))) goto out; event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) goto out_unlock; body = rb_event_data(event); memcpy(body, data, length); rb_commit(cpu_buffer); rb_wakeups(buffer, cpu_buffer); ret = 0; out_unlock: trace_recursive_unlock(cpu_buffer); out: preempt_enable_notrace(); return ret; } EXPORT_SYMBOL_GPL(ring_buffer_write); static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) { struct buffer_page *reader = cpu_buffer->reader_page; struct buffer_page *head = rb_set_head_page(cpu_buffer); struct buffer_page *commit = cpu_buffer->commit_page; /* In case of error, head will be NULL */ if (unlikely(!head)) return true; /* Reader should exhaust content in reader page */ if (reader->read != rb_page_size(reader)) return false; /* * If writers are committing on the reader page, knowing all * committed content has been read, the ring buffer is empty. */ if (commit == reader) return true; /* * If writers are committing on a page other than reader page * and head page, there should always be content to read. */ if (commit != head) return false; /* * Writers are committing on the head page, we just need * to care about there're committed data, and the reader will * swap reader page with head page when it is to read data. */ return rb_page_commit(commit) == 0; } /** * ring_buffer_record_disable - stop all writes into the buffer * @buffer: The ring buffer to stop writes to. * * This prevents all writes to the buffer. Any attempt to write * to the buffer after this will fail and return NULL. * * The caller should call synchronize_rcu() after this. */ void ring_buffer_record_disable(struct trace_buffer *buffer) { atomic_inc(&buffer->record_disabled); } EXPORT_SYMBOL_GPL(ring_buffer_record_disable); /** * ring_buffer_record_enable - enable writes to the buffer * @buffer: The ring buffer to enable writes * * Note, multiple disables will need the same number of enables * to truly enable the writing (much like preempt_disable). */ void ring_buffer_record_enable(struct trace_buffer *buffer) { atomic_dec(&buffer->record_disabled); } EXPORT_SYMBOL_GPL(ring_buffer_record_enable); /** * ring_buffer_record_off - stop all writes into the buffer * @buffer: The ring buffer to stop writes to. * * This prevents all writes to the buffer. Any attempt to write * to the buffer after this will fail and return NULL. * * This is different than ring_buffer_record_disable() as * it works like an on/off switch, where as the disable() version * must be paired with a enable(). */ void ring_buffer_record_off(struct trace_buffer *buffer) { unsigned int rd; unsigned int new_rd; rd = atomic_read(&buffer->record_disabled); do { new_rd = rd | RB_BUFFER_OFF; } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd)); } EXPORT_SYMBOL_GPL(ring_buffer_record_off); /** * ring_buffer_record_on - restart writes into the buffer * @buffer: The ring buffer to start writes to. * * This enables all writes to the buffer that was disabled by * ring_buffer_record_off(). * * This is different than ring_buffer_record_enable() as * it works like an on/off switch, where as the enable() version * must be paired with a disable(). */ void ring_buffer_record_on(struct trace_buffer *buffer) { unsigned int rd; unsigned int new_rd; rd = atomic_read(&buffer->record_disabled); do { new_rd = rd & ~RB_BUFFER_OFF; } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd)); } EXPORT_SYMBOL_GPL(ring_buffer_record_on); /** * ring_buffer_record_is_on - return true if the ring buffer can write * @buffer: The ring buffer to see if write is enabled * * Returns true if the ring buffer is in a state that it accepts writes. */ bool ring_buffer_record_is_on(struct trace_buffer *buffer) { return !atomic_read(&buffer->record_disabled); } /** * ring_buffer_record_is_set_on - return true if the ring buffer is set writable * @buffer: The ring buffer to see if write is set enabled * * Returns true if the ring buffer is set writable by ring_buffer_record_on(). * Note that this does NOT mean it is in a writable state. * * It may return true when the ring buffer has been disabled by * ring_buffer_record_disable(), as that is a temporary disabling of * the ring buffer. */ bool ring_buffer_record_is_set_on(struct trace_buffer *buffer) { return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); } /** * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer * @buffer: The ring buffer to stop writes to. * @cpu: The CPU buffer to stop * * This prevents all writes to the buffer. Any attempt to write * to the buffer after this will fail and return NULL. * * The caller should call synchronize_rcu() after this. */ void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return; cpu_buffer = buffer->buffers[cpu]; atomic_inc(&cpu_buffer->record_disabled); } EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); /** * ring_buffer_record_enable_cpu - enable writes to the buffer * @buffer: The ring buffer to enable writes * @cpu: The CPU to enable. * * Note, multiple disables will need the same number of enables * to truly enable the writing (much like preempt_disable). */ void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return; cpu_buffer = buffer->buffers[cpu]; atomic_dec(&cpu_buffer->record_disabled); } EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); /* * The total entries in the ring buffer is the running counter * of entries entered into the ring buffer, minus the sum of * the entries read from the ring buffer and the number of * entries that were overwritten. */ static inline unsigned long rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) { return local_read(&cpu_buffer->entries) - (local_read(&cpu_buffer->overrun) + cpu_buffer->read); } /** * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer * @buffer: The ring buffer * @cpu: The per CPU buffer to read from. */ u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu) { unsigned long flags; struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage; u64 ret = 0; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); /* * if the tail is on reader_page, oldest time stamp is on the reader * page */ if (cpu_buffer->tail_page == cpu_buffer->reader_page) bpage = cpu_buffer->reader_page; else bpage = rb_set_head_page(cpu_buffer); if (bpage) ret = bpage->page->time_stamp; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); return ret; } EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts); /** * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer * @buffer: The ring buffer * @cpu: The per CPU buffer to read from. */ unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes; return ret; } EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu); /** * ring_buffer_entries_cpu - get the number of entries in a cpu buffer * @buffer: The ring buffer * @cpu: The per CPU buffer to get the entries from. */ unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; return rb_num_of_entries(cpu_buffer); } EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); /** * ring_buffer_overrun_cpu - get the number of overruns caused by the ring * buffer wrapping around (only if RB_FL_OVERWRITE is on). * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */ unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; ret = local_read(&cpu_buffer->overrun); return ret; } EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); /** * ring_buffer_commit_overrun_cpu - get the number of overruns caused by * commits failing due to the buffer wrapping around while there are uncommitted * events, such as during an interrupt storm. * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */ unsigned long ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; ret = local_read(&cpu_buffer->commit_overrun); return ret; } EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); /** * ring_buffer_dropped_events_cpu - get the number of dropped events caused by * the ring buffer filling up (only if RB_FL_OVERWRITE is off). * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */ unsigned long ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; ret = local_read(&cpu_buffer->dropped_events); return ret; } EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu); /** * ring_buffer_read_events_cpu - get the number of events successfully read * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of events read */ unsigned long ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; return cpu_buffer->read; } EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu); /** * ring_buffer_entries - get the number of entries in a buffer * @buffer: The ring buffer * * Returns the total number of entries in the ring buffer * (all CPU entries) */ unsigned long ring_buffer_entries(struct trace_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long entries = 0; int cpu; /* if you care about this being correct, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; entries += rb_num_of_entries(cpu_buffer); } return entries; } EXPORT_SYMBOL_GPL(ring_buffer_entries); /** * ring_buffer_overruns - get the number of overruns in buffer * @buffer: The ring buffer * * Returns the total number of overruns in the ring buffer * (all CPU entries) */ unsigned long ring_buffer_overruns(struct trace_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long overruns = 0; int cpu; /* if you care about this being correct, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; overruns += local_read(&cpu_buffer->overrun); } return overruns; } EXPORT_SYMBOL_GPL(ring_buffer_overruns); static void rb_iter_reset(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; /* Iterator usage is expected to have record disabled */ iter->head_page = cpu_buffer->reader_page; iter->head = cpu_buffer->reader_page->read; iter->next_event = iter->head; iter->cache_reader_page = iter->head_page; iter->cache_read = cpu_buffer->read; iter->cache_pages_removed = cpu_buffer->pages_removed; if (iter->head) { iter->read_stamp = cpu_buffer->read_stamp; iter->page_stamp = cpu_buffer->reader_page->page->time_stamp; } else { iter->read_stamp = iter->head_page->page->time_stamp; iter->page_stamp = iter->read_stamp; } } /** * ring_buffer_iter_reset - reset an iterator * @iter: The iterator to reset * * Resets the iterator, so that it will start from the beginning * again. */ void ring_buffer_iter_reset(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; if (!iter) return; cpu_buffer = iter->cpu_buffer; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_iter_reset(iter); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); /** * ring_buffer_iter_empty - check if an iterator has no more to read * @iter: The iterator to check */ int ring_buffer_iter_empty(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *reader; struct buffer_page *head_page; struct buffer_page *commit_page; struct buffer_page *curr_commit_page; unsigned commit; u64 curr_commit_ts; u64 commit_ts; cpu_buffer = iter->cpu_buffer; reader = cpu_buffer->reader_page; head_page = cpu_buffer->head_page; commit_page = READ_ONCE(cpu_buffer->commit_page); commit_ts = commit_page->page->time_stamp; /* * When the writer goes across pages, it issues a cmpxchg which * is a mb(), which will synchronize with the rmb here. * (see rb_tail_page_update()) */ smp_rmb(); commit = rb_page_commit(commit_page); /* We want to make sure that the commit page doesn't change */ smp_rmb(); /* Make sure commit page didn't change */ curr_commit_page = READ_ONCE(cpu_buffer->commit_page); curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp); /* If the commit page changed, then there's more data */ if (curr_commit_page != commit_page || curr_commit_ts != commit_ts) return 0; /* Still racy, as it may return a false positive, but that's OK */ return ((iter->head_page == commit_page && iter->head >= commit) || (iter->head_page == reader && commit_page == head_page && head_page->read == commit && iter->head == rb_page_size(cpu_buffer->reader_page))); } EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); static void rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event) { u64 delta; switch (event->type_len) { case RINGBUF_TYPE_PADDING: return; case RINGBUF_TYPE_TIME_EXTEND: delta = rb_event_time_stamp(event); cpu_buffer->read_stamp += delta; return; case RINGBUF_TYPE_TIME_STAMP: delta = rb_event_time_stamp(event); delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp); cpu_buffer->read_stamp = delta; return; case RINGBUF_TYPE_DATA: cpu_buffer->read_stamp += event->time_delta; return; default: RB_WARN_ON(cpu_buffer, 1); } } static void rb_update_iter_read_stamp(struct ring_buffer_iter *iter, struct ring_buffer_event *event) { u64 delta; switch (event->type_len) { case RINGBUF_TYPE_PADDING: return; case RINGBUF_TYPE_TIME_EXTEND: delta = rb_event_time_stamp(event); iter->read_stamp += delta; return; case RINGBUF_TYPE_TIME_STAMP: delta = rb_event_time_stamp(event); delta = rb_fix_abs_ts(delta, iter->read_stamp); iter->read_stamp = delta; return; case RINGBUF_TYPE_DATA: iter->read_stamp += event->time_delta; return; default: RB_WARN_ON(iter->cpu_buffer, 1); } } static struct buffer_page * rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) { struct buffer_page *reader = NULL; unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size); unsigned long overwrite; unsigned long flags; int nr_loops = 0; bool ret; local_irq_save(flags); arch_spin_lock(&cpu_buffer->lock); again: /* * This should normally only loop twice. But because the * start of the reader inserts an empty page, it causes * a case where we will loop three times. There should be no * reason to loop four times (that I know of). */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { reader = NULL; goto out; } reader = cpu_buffer->reader_page; /* If there's more to read, return this page */ if (cpu_buffer->reader_page->read < rb_page_size(reader)) goto out; /* Never should we have an index greater than the size */ if (RB_WARN_ON(cpu_buffer, cpu_buffer->reader_page->read > rb_page_size(reader))) goto out; /* check if we caught up to the tail */ reader = NULL; if (cpu_buffer->commit_page == cpu_buffer->reader_page) goto out; /* Don't bother swapping if the ring buffer is empty */ if (rb_num_of_entries(cpu_buffer) == 0) goto out; /* * Reset the reader page to size zero. */ local_set(&cpu_buffer->reader_page->write, 0); local_set(&cpu_buffer->reader_page->entries, 0); local_set(&cpu_buffer->reader_page->page->commit, 0); cpu_buffer->reader_page->real_end = 0; spin: /* * Splice the empty reader page into the list around the head. */ reader = rb_set_head_page(cpu_buffer); if (!reader) goto out; cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); cpu_buffer->reader_page->list.prev = reader->list.prev; /* * cpu_buffer->pages just needs to point to the buffer, it * has no specific buffer page to point to. Lets move it out * of our way so we don't accidentally swap it. */ cpu_buffer->pages = reader->list.prev; /* The reader page will be pointing to the new head */ rb_set_list_to_head(&cpu_buffer->reader_page->list); /* * We want to make sure we read the overruns after we set up our * pointers to the next object. The writer side does a * cmpxchg to cross pages which acts as the mb on the writer * side. Note, the reader will constantly fail the swap * while the writer is updating the pointers, so this * guarantees that the overwrite recorded here is the one we * want to compare with the last_overrun. */ smp_mb(); overwrite = local_read(&(cpu_buffer->overrun)); /* * Here's the tricky part. * * We need to move the pointer past the header page. * But we can only do that if a writer is not currently * moving it. The page before the header page has the * flag bit '1' set if it is pointing to the page we want. * but if the writer is in the process of moving it * than it will be '2' or already moved '0'. */ ret = rb_head_page_replace(reader, cpu_buffer->reader_page); /* * If we did not convert it, then we must try again. */ if (!ret) goto spin; /* * Yay! We succeeded in replacing the page. * * Now make the new head point back to the reader page. */ rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; rb_inc_page(&cpu_buffer->head_page); local_inc(&cpu_buffer->pages_read); /* Finally update the reader page to the new head */ cpu_buffer->reader_page = reader; cpu_buffer->reader_page->read = 0; if (overwrite != cpu_buffer->last_overrun) { cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; cpu_buffer->last_overrun = overwrite; } goto again; out: /* Update the read_stamp on the first event */ if (reader && reader->read == 0) cpu_buffer->read_stamp = reader->page->time_stamp; arch_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags); /* * The writer has preempt disable, wait for it. But not forever * Although, 1 second is pretty much "forever" */ #define USECS_WAIT 1000000 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) { /* If the write is past the end of page, a writer is still updating it */ if (likely(!reader || rb_page_write(reader) <= bsize)) break; udelay(1); /* Get the latest version of the reader write value */ smp_rmb(); } /* The writer is not moving forward? Something is wrong */ if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT)) reader = NULL; /* * Make sure we see any padding after the write update * (see rb_reset_tail()). * * In addition, a writer may be writing on the reader page * if the page has not been fully filled, so the read barrier * is also needed to make sure we see the content of what is * committed by the writer (see rb_set_commit_to_write()). */ smp_rmb(); return reader; } static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) { struct ring_buffer_event *event; struct buffer_page *reader; unsigned length; reader = rb_get_reader_page(cpu_buffer); /* This function should not be called when buffer is empty */ if (RB_WARN_ON(cpu_buffer, !reader)) return; event = rb_reader_event(cpu_buffer); if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) cpu_buffer->read++; rb_update_read_stamp(cpu_buffer, event); length = rb_event_length(event); cpu_buffer->reader_page->read += length; cpu_buffer->read_bytes += length; } static void rb_advance_iter(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer; cpu_buffer = iter->cpu_buffer; /* If head == next_event then we need to jump to the next event */ if (iter->head == iter->next_event) { /* If the event gets overwritten again, there's nothing to do */ if (rb_iter_head_event(iter) == NULL) return; } iter->head = iter->next_event; /* * Check if we are at the end of the buffer. */ if (iter->next_event >= rb_page_size(iter->head_page)) { /* discarded commits can make the page empty */ if (iter->head_page == cpu_buffer->commit_page) return; rb_inc_iter(iter); return; } rb_update_iter_read_stamp(iter, iter->event); } static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) { return cpu_buffer->lost_events; } static struct ring_buffer_event * rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, unsigned long *lost_events) { struct ring_buffer_event *event; struct buffer_page *reader; int nr_loops = 0; if (ts) *ts = 0; again: /* * We repeat when a time extend is encountered. * Since the time extend is always attached to a data event, * we should never loop more than once. * (We never hit the following condition more than twice). */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) return NULL; reader = rb_get_reader_page(cpu_buffer); if (!reader) return NULL; event = rb_reader_event(cpu_buffer); switch (event->type_len) { case RINGBUF_TYPE_PADDING: if (rb_null_event(event)) RB_WARN_ON(cpu_buffer, 1); /* * Because the writer could be discarding every * event it creates (which would probably be bad) * if we were to go back to "again" then we may never * catch up, and will trigger the warn on, or lock * the box. Return the padding, and we will release * the current locks, and try again. */ return event; case RINGBUF_TYPE_TIME_EXTEND: /* Internal data, OK to advance */ rb_advance_reader(cpu_buffer); goto again; case RINGBUF_TYPE_TIME_STAMP: if (ts) { *ts = rb_event_time_stamp(event); *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp); ring_buffer_normalize_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu, ts); } /* Internal data, OK to advance */ rb_advance_reader(cpu_buffer); goto again; case RINGBUF_TYPE_DATA: if (ts && !(*ts)) { *ts = cpu_buffer->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu, ts); } if (lost_events) *lost_events = rb_lost_events(cpu_buffer); return event; default: RB_WARN_ON(cpu_buffer, 1); } return NULL; } EXPORT_SYMBOL_GPL(ring_buffer_peek); static struct ring_buffer_event * rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) { struct trace_buffer *buffer; struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; int nr_loops = 0; if (ts) *ts = 0; cpu_buffer = iter->cpu_buffer; buffer = cpu_buffer->buffer; /* * Check if someone performed a consuming read to the buffer * or removed some pages from the buffer. In these cases, * iterator was invalidated and we need to reset it. */ if (unlikely(iter->cache_read != cpu_buffer->read || iter->cache_reader_page != cpu_buffer->reader_page || iter->cache_pages_removed != cpu_buffer->pages_removed)) rb_iter_reset(iter); again: if (ring_buffer_iter_empty(iter)) return NULL; /* * As the writer can mess with what the iterator is trying * to read, just give up if we fail to get an event after * three tries. The iterator is not as reliable when reading * the ring buffer with an active write as the consumer is. * Do not warn if the three failures is reached. */ if (++nr_loops > 3) return NULL; if (rb_per_cpu_empty(cpu_buffer)) return NULL; if (iter->head >= rb_page_size(iter->head_page)) { rb_inc_iter(iter); goto again; } event = rb_iter_head_event(iter); if (!event) goto again; switch (event->type_len) { case RINGBUF_TYPE_PADDING: if (rb_null_event(event)) { rb_inc_iter(iter); goto again; } rb_advance_iter(iter); return event; case RINGBUF_TYPE_TIME_EXTEND: /* Internal data, OK to advance */ rb_advance_iter(iter); goto again; case RINGBUF_TYPE_TIME_STAMP: if (ts) { *ts = rb_event_time_stamp(event); *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp); ring_buffer_normalize_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu, ts); } /* Internal data, OK to advance */ rb_advance_iter(iter); goto again; case RINGBUF_TYPE_DATA: if (ts && !(*ts)) { *ts = iter->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(buffer, cpu_buffer->cpu, ts); } return event; default: RB_WARN_ON(cpu_buffer, 1); } return NULL; } EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer) { if (likely(!in_nmi())) { raw_spin_lock(&cpu_buffer->reader_lock); return true; } /* * If an NMI die dumps out the content of the ring buffer * trylock must be used to prevent a deadlock if the NMI * preempted a task that holds the ring buffer locks. If * we get the lock then all is fine, if not, then continue * to do the read, but this can corrupt the ring buffer, * so it must be permanently disabled from future writes. * Reading from NMI is a oneshot deal. */ if (raw_spin_trylock(&cpu_buffer->reader_lock)) return true; /* Continue without locking, but disable the ring buffer */ atomic_inc(&cpu_buffer->record_disabled); return false; } static inline void rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked) { if (likely(locked)) raw_spin_unlock(&cpu_buffer->reader_lock); } /** * ring_buffer_peek - peek at the next event to be read * @buffer: The ring buffer to read * @cpu: The cpu to peak at * @ts: The timestamp counter of this event. * @lost_events: a variable to store if events were lost (may be NULL) * * This will return the event that will be read next, but does * not consume the data. */ struct ring_buffer_event * ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts, unsigned long *lost_events) { struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; struct ring_buffer_event *event; unsigned long flags; bool dolock; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return NULL; again: local_irq_save(flags); dolock = rb_reader_lock(cpu_buffer); event = rb_buffer_peek(cpu_buffer, ts, lost_events); if (event && event->type_len == RINGBUF_TYPE_PADDING) rb_advance_reader(cpu_buffer); rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags); if (event && event->type_len == RINGBUF_TYPE_PADDING) goto again; return event; } /** ring_buffer_iter_dropped - report if there are dropped events * @iter: The ring buffer iterator * * Returns true if there was dropped events since the last peek. */ bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter) { bool ret = iter->missed_events != 0; iter->missed_events = 0; return ret; } EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped); /** * ring_buffer_iter_peek - peek at the next event to be read * @iter: The ring buffer iterator * @ts: The timestamp counter of this event. * * This will return the event that will be read next, but does * not increment the iterator. */ struct ring_buffer_event * ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; struct ring_buffer_event *event; unsigned long flags; again: raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); event = rb_iter_peek(iter, ts); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); if (event && event->type_len == RINGBUF_TYPE_PADDING) goto again; return event; } /** * ring_buffer_consume - return an event and consume it * @buffer: The ring buffer to get the next event from * @cpu: the cpu to read the buffer from * @ts: a variable to store the timestamp (may be NULL) * @lost_events: a variable to store if events were lost (may be NULL) * * Returns the next event in the ring buffer, and that event is consumed. * Meaning, that sequential reads will keep returning a different event, * and eventually empty the ring buffer if the producer is slower. */ struct ring_buffer_event * ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts, unsigned long *lost_events) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event = NULL; unsigned long flags; bool dolock; again: /* might be called in atomic */ preempt_disable(); if (!cpumask_test_cpu(cpu, buffer->cpumask)) goto out; cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); dolock = rb_reader_lock(cpu_buffer); event = rb_buffer_peek(cpu_buffer, ts, lost_events); if (event) { cpu_buffer->lost_events = 0; rb_advance_reader(cpu_buffer); } rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags); out: preempt_enable(); if (event && event->type_len == RINGBUF_TYPE_PADDING) goto again; return event; } EXPORT_SYMBOL_GPL(ring_buffer_consume); /** * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer * @buffer: The ring buffer to read from * @cpu: The cpu buffer to iterate over * @flags: gfp flags to use for memory allocation * * This performs the initial preparations necessary to iterate * through the buffer. Memory is allocated, buffer resizing * is disabled, and the iterator pointer is returned to the caller. * * After a sequence of ring_buffer_read_prepare calls, the user is * expected to make at least one call to ring_buffer_read_prepare_sync. * Afterwards, ring_buffer_read_start is invoked to get things going * for real. * * This overall must be paired with ring_buffer_read_finish. */ struct ring_buffer_iter * ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_iter *iter; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return NULL; iter = kzalloc(sizeof(*iter), flags); if (!iter) return NULL; /* Holds the entire event: data and meta data */ iter->event_size = buffer->subbuf_size; iter->event = kmalloc(iter->event_size, flags); if (!iter->event) { kfree(iter); return NULL; } cpu_buffer = buffer->buffers[cpu]; iter->cpu_buffer = cpu_buffer; atomic_inc(&cpu_buffer->resize_disabled); return iter; } EXPORT_SYMBOL_GPL(ring_buffer_read_prepare); /** * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls * * All previously invoked ring_buffer_read_prepare calls to prepare * iterators will be synchronized. Afterwards, read_buffer_read_start * calls on those iterators are allowed. */ void ring_buffer_read_prepare_sync(void) { synchronize_rcu(); } EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync); /** * ring_buffer_read_start - start a non consuming read of the buffer * @iter: The iterator returned by ring_buffer_read_prepare * * This finalizes the startup of an iteration through the buffer. * The iterator comes from a call to ring_buffer_read_prepare and * an intervening ring_buffer_read_prepare_sync must have been * performed. * * Must be paired with ring_buffer_read_finish. */ void ring_buffer_read_start(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; if (!iter) return; cpu_buffer = iter->cpu_buffer; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); arch_spin_lock(&cpu_buffer->lock); rb_iter_reset(iter); arch_spin_unlock(&cpu_buffer->lock); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } EXPORT_SYMBOL_GPL(ring_buffer_read_start); /** * ring_buffer_read_finish - finish reading the iterator of the buffer * @iter: The iterator retrieved by ring_buffer_start * * This re-enables resizing of the buffer, and frees the iterator. */ void ring_buffer_read_finish(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; unsigned long flags; /* Use this opportunity to check the integrity of the ring buffer. */ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_check_pages(cpu_buffer); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); atomic_dec(&cpu_buffer->resize_disabled); kfree(iter->event); kfree(iter); } EXPORT_SYMBOL_GPL(ring_buffer_read_finish); /** * ring_buffer_iter_advance - advance the iterator to the next location * @iter: The ring buffer iterator * * Move the location of the iterator such that the next read will * be the next location of the iterator. */ void ring_buffer_iter_advance(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; unsigned long flags; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_advance_iter(iter); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } EXPORT_SYMBOL_GPL(ring_buffer_iter_advance); /** * ring_buffer_size - return the size of the ring buffer (in bytes) * @buffer: The ring buffer. * @cpu: The CPU to get ring buffer size from. */ unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu) { if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages; } EXPORT_SYMBOL_GPL(ring_buffer_size); /** * ring_buffer_max_event_size - return the max data size of an event * @buffer: The ring buffer. * * Returns the maximum size an event can be. */ unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer) { /* If abs timestamp is requested, events have a timestamp too */ if (ring_buffer_time_stamp_abs(buffer)) return buffer->max_data_size - RB_LEN_TIME_EXTEND; return buffer->max_data_size; } EXPORT_SYMBOL_GPL(ring_buffer_max_event_size); static void rb_clear_buffer_page(struct buffer_page *page) { local_set(&page->write, 0); local_set(&page->entries, 0); rb_init_page(page->page); page->read = 0; } static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer) { struct trace_buffer_meta *meta = cpu_buffer->meta_page; meta->reader.read = cpu_buffer->reader_page->read; meta->reader.id = cpu_buffer->reader_page->id; meta->reader.lost_events = cpu_buffer->lost_events; meta->entries = local_read(&cpu_buffer->entries); meta->overrun = local_read(&cpu_buffer->overrun); meta->read = cpu_buffer->read; /* Some archs do not have data cache coherency between kernel and user-space */ flush_dcache_folio(virt_to_folio(cpu_buffer->meta_page)); } static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) { struct buffer_page *page; rb_head_page_deactivate(cpu_buffer); cpu_buffer->head_page = list_entry(cpu_buffer->pages, struct buffer_page, list); rb_clear_buffer_page(cpu_buffer->head_page); list_for_each_entry(page, cpu_buffer->pages, list) { rb_clear_buffer_page(page); } cpu_buffer->tail_page = cpu_buffer->head_page; cpu_buffer->commit_page = cpu_buffer->head_page; INIT_LIST_HEAD(&cpu_buffer->reader_page->list); INIT_LIST_HEAD(&cpu_buffer->new_pages); rb_clear_buffer_page(cpu_buffer->reader_page); local_set(&cpu_buffer->entries_bytes, 0); local_set(&cpu_buffer->overrun, 0); local_set(&cpu_buffer->commit_overrun, 0); local_set(&cpu_buffer->dropped_events, 0); local_set(&cpu_buffer->entries, 0); local_set(&cpu_buffer->committing, 0); local_set(&cpu_buffer->commits, 0); local_set(&cpu_buffer->pages_touched, 0); local_set(&cpu_buffer->pages_lost, 0); local_set(&cpu_buffer->pages_read, 0); cpu_buffer->last_pages_touch = 0; cpu_buffer->shortest_full = 0; cpu_buffer->read = 0; cpu_buffer->read_bytes = 0; rb_time_set(&cpu_buffer->write_stamp, 0); rb_time_set(&cpu_buffer->before_stamp, 0); memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp)); cpu_buffer->lost_events = 0; cpu_buffer->last_overrun = 0; if (cpu_buffer->mapped) rb_update_meta_page(cpu_buffer); rb_head_page_activate(cpu_buffer); cpu_buffer->pages_removed = 0; } /* Must have disabled the cpu buffer then done a synchronize_rcu */ static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) { unsigned long flags; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) goto out; arch_spin_lock(&cpu_buffer->lock); rb_reset_cpu(cpu_buffer); arch_spin_unlock(&cpu_buffer->lock); out: raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } /** * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer * @buffer: The ring buffer to reset a per cpu buffer of * @cpu: The CPU buffer to be reset */ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return; /* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex); atomic_inc(&cpu_buffer->resize_disabled); atomic_inc(&cpu_buffer->record_disabled); /* Make sure all commits have finished */ synchronize_rcu(); reset_disabled_cpu_buffer(cpu_buffer); atomic_dec(&cpu_buffer->record_disabled); atomic_dec(&cpu_buffer->resize_disabled); mutex_unlock(&buffer->mutex); } EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); /* Flag to ensure proper resetting of atomic variables */ #define RESET_BIT (1 << 30) /** * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer * @buffer: The ring buffer to reset a per cpu buffer of */ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; int cpu; /* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex); for_each_online_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; atomic_add(RESET_BIT, &cpu_buffer->resize_disabled); atomic_inc(&cpu_buffer->record_disabled); } /* Make sure all commits have finished */ synchronize_rcu(); for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; /* * If a CPU came online during the synchronize_rcu(), then * ignore it. */ if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT)) continue; reset_disabled_cpu_buffer(cpu_buffer); atomic_dec(&cpu_buffer->record_disabled); atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled); } mutex_unlock(&buffer->mutex); } /** * ring_buffer_reset - reset a ring buffer * @buffer: The ring buffer to reset all cpu buffers */ void ring_buffer_reset(struct trace_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; int cpu; /* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex); for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; atomic_inc(&cpu_buffer->resize_disabled); atomic_inc(&cpu_buffer->record_disabled); } /* Make sure all commits have finished */ synchronize_rcu(); for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; reset_disabled_cpu_buffer(cpu_buffer); atomic_dec(&cpu_buffer->record_disabled); atomic_dec(&cpu_buffer->resize_disabled); } mutex_unlock(&buffer->mutex); } EXPORT_SYMBOL_GPL(ring_buffer_reset); /** * ring_buffer_empty - is the ring buffer empty? * @buffer: The ring buffer to test */ bool ring_buffer_empty(struct trace_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; bool dolock; bool ret; int cpu; /* yes this is racy, but if you don't like the race, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); dolock = rb_reader_lock(cpu_buffer); ret = rb_per_cpu_empty(cpu_buffer); rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags); if (!ret) return false; } return true; } EXPORT_SYMBOL_GPL(ring_buffer_empty); /** * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? * @buffer: The ring buffer * @cpu: The CPU buffer to test */ bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; bool dolock; bool ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return true; cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); dolock = rb_reader_lock(cpu_buffer); ret = rb_per_cpu_empty(cpu_buffer); rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags); return ret; } EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP /** * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers * @buffer_a: One buffer to swap with * @buffer_b: The other buffer to swap with * @cpu: the CPU of the buffers to swap * * This function is useful for tracers that want to take a "snapshot" * of a CPU buffer and has another back up buffer lying around. * it is expected that the tracer handles the cpu buffer not being * used at the moment. */ int ring_buffer_swap_cpu(struct trace_buffer *buffer_a, struct trace_buffer *buffer_b, int cpu) { struct ring_buffer_per_cpu *cpu_buffer_a; struct ring_buffer_per_cpu *cpu_buffer_b; int ret = -EINVAL; if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || !cpumask_test_cpu(cpu, buffer_b->cpumask)) goto out; cpu_buffer_a = buffer_a->buffers[cpu]; cpu_buffer_b = buffer_b->buffers[cpu]; /* It's up to the callers to not try to swap mapped buffers */ if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) { ret = -EBUSY; goto out; } /* At least make sure the two buffers are somewhat the same */ if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages) goto out; if (buffer_a->subbuf_order != buffer_b->subbuf_order) goto out; ret = -EAGAIN; if (atomic_read(&buffer_a->record_disabled)) goto out; if (atomic_read(&buffer_b->record_disabled)) goto out; if (atomic_read(&cpu_buffer_a->record_disabled)) goto out; if (atomic_read(&cpu_buffer_b->record_disabled)) goto out; /* * We can't do a synchronize_rcu here because this * function can be called in atomic context. * Normally this will be called from the same CPU as cpu. * If not it's up to the caller to protect this. */ atomic_inc(&cpu_buffer_a->record_disabled); atomic_inc(&cpu_buffer_b->record_disabled); ret = -EBUSY; if (local_read(&cpu_buffer_a->committing)) goto out_dec; if (local_read(&cpu_buffer_b->committing)) goto out_dec; /* * When resize is in progress, we cannot swap it because * it will mess the state of the cpu buffer. */ if (atomic_read(&buffer_a->resizing)) goto out_dec; if (atomic_read(&buffer_b->resizing)) goto out_dec; buffer_a->buffers[cpu] = cpu_buffer_b; buffer_b->buffers[cpu] = cpu_buffer_a; cpu_buffer_b->buffer = buffer_a; cpu_buffer_a->buffer = buffer_b; ret = 0; out_dec: atomic_dec(&cpu_buffer_a->record_disabled); atomic_dec(&cpu_buffer_b->record_disabled); out: return ret; } EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */ /** * ring_buffer_alloc_read_page - allocate a page to read from buffer * @buffer: the buffer to allocate for. * @cpu: the cpu buffer to allocate. * * This function is used in conjunction with ring_buffer_read_page. * When reading a full page from the ring buffer, these functions * can be used to speed up the process. The calling function should * allocate a few pages first with this function. Then when it * needs to get pages from the ring buffer, it passes the result * of this function into ring_buffer_read_page, which will swap * the page that was allocated, with the read page of the buffer. * * Returns: * The page allocated, or ERR_PTR */ struct buffer_data_read_page * ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; struct buffer_data_read_page *bpage = NULL; unsigned long flags; struct page *page; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return ERR_PTR(-ENODEV); bpage = kzalloc(sizeof(*bpage), GFP_KERNEL); if (!bpage) return ERR_PTR(-ENOMEM); bpage->order = buffer->subbuf_order; cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); arch_spin_lock(&cpu_buffer->lock); if (cpu_buffer->free_page) { bpage->data = cpu_buffer->free_page; cpu_buffer->free_page = NULL; } arch_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags); if (bpage->data) goto out; page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_NORETRY | __GFP_COMP | __GFP_ZERO, cpu_buffer->buffer->subbuf_order); if (!page) { kfree(bpage); return ERR_PTR(-ENOMEM); } bpage->data = page_address(page); out: rb_init_page(bpage->data); return bpage; } EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); /** * ring_buffer_free_read_page - free an allocated read page * @buffer: the buffer the page was allocate for * @cpu: the cpu buffer the page came from * @data_page: the page to free * * Free a page allocated from ring_buffer_alloc_read_page. */ void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, struct buffer_data_read_page *data_page) { struct ring_buffer_per_cpu *cpu_buffer; struct buffer_data_page *bpage = data_page->data; struct page *page = virt_to_page(bpage); unsigned long flags; if (!buffer || !buffer->buffers || !buffer->buffers[cpu]) return; cpu_buffer = buffer->buffers[cpu]; /* * If the page is still in use someplace else, or order of the page * is different from the subbuffer order of the buffer - * we can't reuse it */ if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order) goto out; local_irq_save(flags); arch_spin_lock(&cpu_buffer->lock); if (!cpu_buffer->free_page) { cpu_buffer->free_page = bpage; bpage = NULL; } arch_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags); out: free_pages((unsigned long)bpage, data_page->order); kfree(data_page); } EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); /** * ring_buffer_read_page - extract a page from the ring buffer * @buffer: buffer to extract from * @data_page: the page to use allocated from ring_buffer_alloc_read_page * @len: amount to extract * @cpu: the cpu of the buffer to extract * @full: should the extraction only happen when the page is full. * * This function will pull out a page from the ring buffer and consume it. * @data_page must be the address of the variable that was returned * from ring_buffer_alloc_read_page. This is because the page might be used * to swap with a page in the ring buffer. * * for example: * rpage = ring_buffer_alloc_read_page(buffer, cpu); * if (IS_ERR(rpage)) * return PTR_ERR(rpage); * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0); * if (ret >= 0) * process_page(ring_buffer_read_page_data(rpage), ret); * ring_buffer_free_read_page(buffer, cpu, rpage); * * When @full is set, the function will not return true unless * the writer is off the reader page. * * Note: it is up to the calling functions to handle sleeps and wakeups. * The ring buffer can be used anywhere in the kernel and can not * blindly call wake_up. The layer that uses the ring buffer must be * responsible for that. * * Returns: * >=0 if data has been transferred, returns the offset of consumed data. * <0 if no data has been transferred. */ int ring_buffer_read_page(struct trace_buffer *buffer, struct buffer_data_read_page *data_page, size_t len, int cpu, int full) { struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; struct ring_buffer_event *event; struct buffer_data_page *bpage; struct buffer_page *reader; unsigned long missed_events; unsigned long flags; unsigned int commit; unsigned int read; u64 save_timestamp; int ret = -1; if (!cpumask_test_cpu(cpu, buffer->cpumask)) goto out; /* * If len is not big enough to hold the page header, then * we can not copy anything. */ if (len <= BUF_PAGE_HDR_SIZE) goto out; len -= BUF_PAGE_HDR_SIZE; if (!data_page || !data_page->data) goto out; if (data_page->order != buffer->subbuf_order) goto out; bpage = data_page->data; if (!bpage) goto out; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); reader = rb_get_reader_page(cpu_buffer); if (!reader) goto out_unlock; event = rb_reader_event(cpu_buffer); read = reader->read; commit = rb_page_size(reader); /* Check if any events were dropped */ missed_events = cpu_buffer->lost_events; /* * If this page has been partially read or * if len is not big enough to read the rest of the page or * a writer is still on the page, then * we must copy the data from the page to the buffer. * Otherwise, we can simply swap the page with the one passed in. */ if (read || (len < (commit - read)) || cpu_buffer->reader_page == cpu_buffer->commit_page || cpu_buffer->mapped) { struct buffer_data_page *rpage = cpu_buffer->reader_page->page; unsigned int rpos = read; unsigned int pos = 0; unsigned int size; /* * If a full page is expected, this can still be returned * if there's been a previous partial read and the * rest of the page can be read and the commit page is off * the reader page. */ if (full && (!read || (len < (commit - read)) || cpu_buffer->reader_page == cpu_buffer->commit_page)) goto out_unlock; if (len > (commit - read)) len = (commit - read); /* Always keep the time extend and data together */ size = rb_event_ts_length(event); if (len < size) goto out_unlock; /* save the current timestamp, since the user will need it */ save_timestamp = cpu_buffer->read_stamp; /* Need to copy one event at a time */ do { /* We need the size of one event, because * rb_advance_reader only advances by one event, * whereas rb_event_ts_length may include the size of * one or two events. * We have already ensured there's enough space if this * is a time extend. */ size = rb_event_length(event); memcpy(bpage->data + pos, rpage->data + rpos, size); len -= size; rb_advance_reader(cpu_buffer); rpos = reader->read; pos += size; if (rpos >= commit) break; event = rb_reader_event(cpu_buffer); /* Always keep the time extend and data together */ size = rb_event_ts_length(event); } while (len >= size); /* update bpage */ local_set(&bpage->commit, pos); bpage->time_stamp = save_timestamp; /* we copied everything to the beginning */ read = 0; } else { /* update the entry counter */ cpu_buffer->read += rb_page_entries(reader); cpu_buffer->read_bytes += rb_page_size(reader); /* swap the pages */ rb_init_page(bpage); bpage = reader->page; reader->page = data_page->data; local_set(&reader->write, 0); local_set(&reader->entries, 0); reader->read = 0; data_page->data = bpage; /* * Use the real_end for the data size, * This gives us a chance to store the lost events * on the page. */ if (reader->real_end) local_set(&bpage->commit, reader->real_end); } ret = read; cpu_buffer->lost_events = 0; commit = local_read(&bpage->commit); /* * Set a flag in the commit field if we lost events */ if (missed_events) { /* If there is room at the end of the page to save the * missed events, then record it there. */ if (buffer->subbuf_size - commit >= sizeof(missed_events)) { memcpy(&bpage->data[commit], &missed_events, sizeof(missed_events)); local_add(RB_MISSED_STORED, &bpage->commit); commit += sizeof(missed_events); } local_add(RB_MISSED_EVENTS, &bpage->commit); } /* * This page may be off to user land. Zero it out here. */ if (commit < buffer->subbuf_size) memset(&bpage->data[commit], 0, buffer->subbuf_size - commit); out_unlock: raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); out: return ret; } EXPORT_SYMBOL_GPL(ring_buffer_read_page); /** * ring_buffer_read_page_data - get pointer to the data in the page. * @page: the page to get the data from * * Returns pointer to the actual data in this page. */ void *ring_buffer_read_page_data(struct buffer_data_read_page *page) { return page->data; } EXPORT_SYMBOL_GPL(ring_buffer_read_page_data); /** * ring_buffer_subbuf_size_get - get size of the sub buffer. * @buffer: the buffer to get the sub buffer size from * * Returns size of the sub buffer, in bytes. */ int ring_buffer_subbuf_size_get(struct trace_buffer *buffer) { return buffer->subbuf_size + BUF_PAGE_HDR_SIZE; } EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get); /** * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page. * @buffer: The ring_buffer to get the system sub page order from * * By default, one ring buffer sub page equals to one system page. This parameter * is configurable, per ring buffer. The size of the ring buffer sub page can be * extended, but must be an order of system page size. * * Returns the order of buffer sub page size, in system pages: * 0 means the sub buffer size is 1 system page and so forth. * In case of an error < 0 is returned. */ int ring_buffer_subbuf_order_get(struct trace_buffer *buffer) { if (!buffer) return -EINVAL; return buffer->subbuf_order; } EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get); /** * ring_buffer_subbuf_order_set - set the size of ring buffer sub page. * @buffer: The ring_buffer to set the new page size. * @order: Order of the system pages in one sub buffer page * * By default, one ring buffer pages equals to one system page. This API can be * used to set new size of the ring buffer page. The size must be order of * system page size, that's why the input parameter @order is the order of * system pages that are allocated for one ring buffer page: * 0 - 1 system page * 1 - 2 system pages * 3 - 4 system pages * ... * * Returns 0 on success or < 0 in case of an error. */ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) { struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage, *tmp; int old_order, old_size; int nr_pages; int psize; int err; int cpu; if (!buffer || order < 0) return -EINVAL; if (buffer->subbuf_order == order) return 0; psize = (1 << order) * PAGE_SIZE; if (psize <= BUF_PAGE_HDR_SIZE) return -EINVAL; /* Size of a subbuf cannot be greater than the write counter */ if (psize > RB_WRITE_MASK + 1) return -EINVAL; old_order = buffer->subbuf_order; old_size = buffer->subbuf_size; /* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex); atomic_inc(&buffer->record_disabled); /* Make sure all commits have finished */ synchronize_rcu(); buffer->subbuf_order = order; buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE; /* Make sure all new buffers are allocated, before deleting the old ones */ for_each_buffer_cpu(buffer, cpu) { if (!cpumask_test_cpu(cpu, buffer->cpumask)) continue; cpu_buffer = buffer->buffers[cpu]; if (cpu_buffer->mapped) { err = -EBUSY; goto error; } /* Update the number of pages to match the new size */ nr_pages = old_size * buffer->buffers[cpu]->nr_pages; nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size); /* we need a minimum of two pages */ if (nr_pages < 2) nr_pages = 2; cpu_buffer->nr_pages_to_update = nr_pages; /* Include the reader page */ nr_pages++; /* Allocate the new size buffer */ INIT_LIST_HEAD(&cpu_buffer->new_pages); if (__rb_allocate_pages(cpu_buffer, nr_pages, &cpu_buffer->new_pages)) { /* not enough memory for new pages */ err = -ENOMEM; goto error; } } for_each_buffer_cpu(buffer, cpu) { if (!cpumask_test_cpu(cpu, buffer->cpumask)) continue; cpu_buffer = buffer->buffers[cpu]; /* Clear the head bit to make the link list normal to read */ rb_head_page_deactivate(cpu_buffer); /* Now walk the list and free all the old sub buffers */ list_for_each_entry_safe(bpage, tmp, cpu_buffer->pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } /* The above loop stopped an the last page needing to be freed */ bpage = list_entry(cpu_buffer->pages, struct buffer_page, list); free_buffer_page(bpage); /* Free the current reader page */ free_buffer_page(cpu_buffer->reader_page); /* One page was allocated for the reader page */ cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next, struct buffer_page, list); list_del_init(&cpu_buffer->reader_page->list); /* The cpu_buffer pages are a link list with no head */ cpu_buffer->pages = cpu_buffer->new_pages.next; cpu_buffer->new_pages.next->prev = cpu_buffer->new_pages.prev; cpu_buffer->new_pages.prev->next = cpu_buffer->new_pages.next; /* Clear the new_pages list */ INIT_LIST_HEAD(&cpu_buffer->new_pages); cpu_buffer->head_page = list_entry(cpu_buffer->pages, struct buffer_page, list); cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update; cpu_buffer->nr_pages_to_update = 0; free_pages((unsigned long)cpu_buffer->free_page, old_order); cpu_buffer->free_page = NULL; rb_head_page_activate(cpu_buffer); rb_check_pages(cpu_buffer); } atomic_dec(&buffer->record_disabled); mutex_unlock(&buffer->mutex); return 0; error: buffer->subbuf_order = old_order; buffer->subbuf_size = old_size; atomic_dec(&buffer->record_disabled); mutex_unlock(&buffer->mutex); for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; if (!cpu_buffer->nr_pages_to_update) continue; list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } } return err; } EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set); static int rb_alloc_meta_page(struct ring_buffer_per_cpu *cpu_buffer) { struct page *page; if (cpu_buffer->meta_page) return 0; page = alloc_page(GFP_USER | __GFP_ZERO); if (!page) return -ENOMEM; cpu_buffer->meta_page = page_to_virt(page); return 0; } static void rb_free_meta_page(struct ring_buffer_per_cpu *cpu_buffer) { unsigned long addr = (unsigned long)cpu_buffer->meta_page; free_page(addr); cpu_buffer->meta_page = NULL; } static void rb_setup_ids_meta_page(struct ring_buffer_per_cpu *cpu_buffer, unsigned long *subbuf_ids) { struct trace_buffer_meta *meta = cpu_buffer->meta_page; unsigned int nr_subbufs = cpu_buffer->nr_pages + 1; struct buffer_page *first_subbuf, *subbuf; int id = 0; subbuf_ids[id] = (unsigned long)cpu_buffer->reader_page->page; cpu_buffer->reader_page->id = id++; first_subbuf = subbuf = rb_set_head_page(cpu_buffer); do { if (WARN_ON(id >= nr_subbufs)) break; subbuf_ids[id] = (unsigned long)subbuf->page; subbuf->id = id; rb_inc_page(&subbuf); id++; } while (subbuf != first_subbuf); /* install subbuf ID to kern VA translation */ cpu_buffer->subbuf_ids = subbuf_ids; meta->meta_page_size = PAGE_SIZE; meta->meta_struct_len = sizeof(*meta); meta->nr_subbufs = nr_subbufs; meta->subbuf_size = cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE; rb_update_meta_page(cpu_buffer); } static struct ring_buffer_per_cpu * rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return ERR_PTR(-EINVAL); cpu_buffer = buffer->buffers[cpu]; mutex_lock(&cpu_buffer->mapping_lock); if (!cpu_buffer->mapped) { mutex_unlock(&cpu_buffer->mapping_lock); return ERR_PTR(-ENODEV); } return cpu_buffer; } static void rb_put_mapped_buffer(struct ring_buffer_per_cpu *cpu_buffer) { mutex_unlock(&cpu_buffer->mapping_lock); } /* * Fast-path for rb_buffer_(un)map(). Called whenever the meta-page doesn't need * to be set-up or torn-down. */ static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer, bool inc) { unsigned long flags; lockdep_assert_held(&cpu_buffer->mapping_lock); if (inc && cpu_buffer->mapped == UINT_MAX) return -EBUSY; if (WARN_ON(!inc && cpu_buffer->mapped == 0)) return -EINVAL; mutex_lock(&cpu_buffer->buffer->mutex); raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); if (inc) cpu_buffer->mapped++; else cpu_buffer->mapped--; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); mutex_unlock(&cpu_buffer->buffer->mutex); return 0; } /* * +--------------+ pgoff == 0 * | meta page | * +--------------+ pgoff == 1 * | subbuffer 0 | * | | * +--------------+ pgoff == (1 + (1 << subbuf_order)) * | subbuffer 1 | * | | * ... */ #ifdef CONFIG_MMU static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer, struct vm_area_struct *vma) { unsigned long nr_subbufs, nr_pages, vma_pages, pgoff = vma->vm_pgoff; unsigned int subbuf_pages, subbuf_order; struct page **pages; int p = 0, s = 0; int err; /* Refuse MP_PRIVATE or writable mappings */ if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC || !(vma->vm_flags & VM_MAYSHARE)) return -EPERM; /* * Make sure the mapping cannot become writable later. Also tell the VM * to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND). */ vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP, VM_MAYWRITE); lockdep_assert_held(&cpu_buffer->mapping_lock); subbuf_order = cpu_buffer->buffer->subbuf_order; subbuf_pages = 1 << subbuf_order; nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */ nr_pages = ((nr_subbufs) << subbuf_order) - pgoff + 1; /* + meta-page */ vma_pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; if (!vma_pages || vma_pages > nr_pages) return -EINVAL; nr_pages = vma_pages; pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL); if (!pages) return -ENOMEM; if (!pgoff) { pages[p++] = virt_to_page(cpu_buffer->meta_page); /* * TODO: Align sub-buffers on their size, once * vm_insert_pages() supports the zero-page. */ } else { /* Skip the meta-page */ pgoff--; if (pgoff % subbuf_pages) { err = -EINVAL; goto out; } s += pgoff / subbuf_pages; } while (p < nr_pages) { struct page *page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]); int off = 0; if (WARN_ON_ONCE(s >= nr_subbufs)) { err = -EINVAL; goto out; } for (; off < (1 << (subbuf_order)); off++, page++) { if (p >= nr_pages) break; pages[p++] = page; } s++; } err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages); out: kfree(pages); return err; } #else static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer, struct vm_area_struct *vma) { return -EOPNOTSUPP; } #endif int ring_buffer_map(struct trace_buffer *buffer, int cpu, struct vm_area_struct *vma) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags, *subbuf_ids; int err = 0; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -EINVAL; cpu_buffer = buffer->buffers[cpu]; mutex_lock(&cpu_buffer->mapping_lock); if (cpu_buffer->mapped) { err = __rb_map_vma(cpu_buffer, vma); if (!err) err = __rb_inc_dec_mapped(cpu_buffer, true); mutex_unlock(&cpu_buffer->mapping_lock); return err; } /* prevent another thread from changing buffer/sub-buffer sizes */ mutex_lock(&buffer->mutex); err = rb_alloc_meta_page(cpu_buffer); if (err) goto unlock; /* subbuf_ids include the reader while nr_pages does not */ subbuf_ids = kcalloc(cpu_buffer->nr_pages + 1, sizeof(*subbuf_ids), GFP_KERNEL); if (!subbuf_ids) { rb_free_meta_page(cpu_buffer); err = -ENOMEM; goto unlock; } atomic_inc(&cpu_buffer->resize_disabled); /* * Lock all readers to block any subbuf swap until the subbuf IDs are * assigned. */ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_setup_ids_meta_page(cpu_buffer, subbuf_ids); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); err = __rb_map_vma(cpu_buffer, vma); if (!err) { raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); cpu_buffer->mapped = 1; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } else { kfree(cpu_buffer->subbuf_ids); cpu_buffer->subbuf_ids = NULL; rb_free_meta_page(cpu_buffer); } unlock: mutex_unlock(&buffer->mutex); mutex_unlock(&cpu_buffer->mapping_lock); return err; } int ring_buffer_unmap(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; int err = 0; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -EINVAL; cpu_buffer = buffer->buffers[cpu]; mutex_lock(&cpu_buffer->mapping_lock); if (!cpu_buffer->mapped) { err = -ENODEV; goto out; } else if (cpu_buffer->mapped > 1) { __rb_inc_dec_mapped(cpu_buffer, false); goto out; } mutex_lock(&buffer->mutex); raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); cpu_buffer->mapped = 0; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); kfree(cpu_buffer->subbuf_ids); cpu_buffer->subbuf_ids = NULL; rb_free_meta_page(cpu_buffer); atomic_dec(&cpu_buffer->resize_disabled); mutex_unlock(&buffer->mutex); out: mutex_unlock(&cpu_buffer->mapping_lock); return err; } int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *reader; unsigned long missed_events; unsigned long reader_size; unsigned long flags; cpu_buffer = rb_get_mapped_buffer(buffer, cpu); if (IS_ERR(cpu_buffer)) return (int)PTR_ERR(cpu_buffer); raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); consume: if (rb_per_cpu_empty(cpu_buffer)) goto out; reader_size = rb_page_size(cpu_buffer->reader_page); /* * There are data to be read on the current reader page, we can * return to the caller. But before that, we assume the latter will read * everything. Let's update the kernel reader accordingly. */ if (cpu_buffer->reader_page->read < reader_size) { while (cpu_buffer->reader_page->read < reader_size) rb_advance_reader(cpu_buffer); goto out; } reader = rb_get_reader_page(cpu_buffer); if (WARN_ON(!reader)) goto out; /* Check if any events were dropped */ missed_events = cpu_buffer->lost_events; if (cpu_buffer->reader_page != cpu_buffer->commit_page) { if (missed_events) { struct buffer_data_page *bpage = reader->page; unsigned int commit; /* * Use the real_end for the data size, * This gives us a chance to store the lost events * on the page. */ if (reader->real_end) local_set(&bpage->commit, reader->real_end); /* * If there is room at the end of the page to save the * missed events, then record it there. */ commit = rb_page_size(reader); if (buffer->subbuf_size - commit >= sizeof(missed_events)) { memcpy(&bpage->data[commit], &missed_events, sizeof(missed_events)); local_add(RB_MISSED_STORED, &bpage->commit); } local_add(RB_MISSED_EVENTS, &bpage->commit); } } else { /* * There really shouldn't be any missed events if the commit * is on the reader page. */ WARN_ON_ONCE(missed_events); } cpu_buffer->lost_events = 0; goto consume; out: /* Some archs do not have data cache coherency between kernel and user-space */ flush_dcache_folio(virt_to_folio(cpu_buffer->reader_page->page)); rb_update_meta_page(cpu_buffer); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); rb_put_mapped_buffer(cpu_buffer); return 0; } /* * We only allocate new buffers, never free them if the CPU goes down. * If we were to free the buffer, then the user would lose any trace that was in * the buffer. */ int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node) { struct trace_buffer *buffer; long nr_pages_same; int cpu_i; unsigned long nr_pages; buffer = container_of(node, struct trace_buffer, node); if (cpumask_test_cpu(cpu, buffer->cpumask)) return 0; nr_pages = 0; nr_pages_same = 1; /* check if all cpu sizes are same */ for_each_buffer_cpu(buffer, cpu_i) { /* fill in the size from first enabled cpu */ if (nr_pages == 0) nr_pages = buffer->buffers[cpu_i]->nr_pages; if (nr_pages != buffer->buffers[cpu_i]->nr_pages) { nr_pages_same = 0; break; } } /* allocate minimum pages, user can later expand it */ if (!nr_pages_same) nr_pages = 2; buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); if (!buffer->buffers[cpu]) { WARN(1, "failed to allocate ring buffer on CPU %u\n", cpu); return -ENOMEM; } smp_wmb(); cpumask_set_cpu(cpu, buffer->cpumask); return 0; } #ifdef CONFIG_RING_BUFFER_STARTUP_TEST /* * This is a basic integrity check of the ring buffer. * Late in the boot cycle this test will run when configured in. * It will kick off a thread per CPU that will go into a loop * writing to the per cpu ring buffer various sizes of data. * Some of the data will be large items, some small. * * Another thread is created that goes into a spin, sending out * IPIs to the other CPUs to also write into the ring buffer. * this is to test the nesting ability of the buffer. * * Basic stats are recorded and reported. If something in the * ring buffer should happen that's not expected, a big warning * is displayed and all ring buffers are disabled. */ static struct task_struct *rb_threads[NR_CPUS] __initdata; struct rb_test_data { struct trace_buffer *buffer; unsigned long events; unsigned long bytes_written; unsigned long bytes_alloc; unsigned long bytes_dropped; unsigned long events_nested; unsigned long bytes_written_nested; unsigned long bytes_alloc_nested; unsigned long bytes_dropped_nested; int min_size_nested; int max_size_nested; int max_size; int min_size; int cpu; int cnt; }; static struct rb_test_data rb_data[NR_CPUS] __initdata; /* 1 meg per cpu */ #define RB_TEST_BUFFER_SIZE 1048576 static char rb_string[] __initdata = "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\" "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890" "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv"; static bool rb_test_started __initdata; struct rb_item { int size; char str[]; }; static __init int rb_write_something(struct rb_test_data *data, bool nested) { struct ring_buffer_event *event; struct rb_item *item; bool started; int event_len; int size; int len; int cnt; /* Have nested writes different that what is written */ cnt = data->cnt + (nested ? 27 : 0); /* Multiply cnt by ~e, to make some unique increment */ size = (cnt * 68 / 25) % (sizeof(rb_string) - 1); len = size + sizeof(struct rb_item); started = rb_test_started; /* read rb_test_started before checking buffer enabled */ smp_rmb(); event = ring_buffer_lock_reserve(data->buffer, len); if (!event) { /* Ignore dropped events before test starts. */ if (started) { if (nested) data->bytes_dropped += len; else data->bytes_dropped_nested += len; } return len; } event_len = ring_buffer_event_length(event); if (RB_WARN_ON(data->buffer, event_len < len)) goto out; item = ring_buffer_event_data(event); item->size = size; memcpy(item->str, rb_string, size); if (nested) { data->bytes_alloc_nested += event_len; data->bytes_written_nested += len; data->events_nested++; if (!data->min_size_nested || len < data->min_size_nested) data->min_size_nested = len; if (len > data->max_size_nested) data->max_size_nested = len; } else { data->bytes_alloc += event_len; data->bytes_written += len; data->events++; if (!data->min_size || len < data->min_size) data->max_size = len; if (len > data->max_size) data->max_size = len; } out: ring_buffer_unlock_commit(data->buffer); return 0; } static __init int rb_test(void *arg) { struct rb_test_data *data = arg; while (!kthread_should_stop()) { rb_write_something(data, false); data->cnt++; set_current_state(TASK_INTERRUPTIBLE); /* Now sleep between a min of 100-300us and a max of 1ms */ usleep_range(((data->cnt % 3) + 1) * 100, 1000); } return 0; } static __init void rb_ipi(void *ignore) { struct rb_test_data *data; int cpu = smp_processor_id(); data = &rb_data[cpu]; rb_write_something(data, true); } static __init int rb_hammer_test(void *arg) { while (!kthread_should_stop()) { /* Send an IPI to all cpus to write data! */ smp_call_function(rb_ipi, NULL, 1); /* No sleep, but for non preempt, let others run */ schedule(); } return 0; } static __init int test_ringbuffer(void) { struct task_struct *rb_hammer; struct trace_buffer *buffer; int cpu; int ret = 0; if (security_locked_down(LOCKDOWN_TRACEFS)) { pr_warn("Lockdown is enabled, skipping ring buffer tests\n"); return 0; } pr_info("Running ring buffer tests...\n"); buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE); if (WARN_ON(!buffer)) return 0; /* Disable buffer so that threads can't write to it yet */ ring_buffer_record_off(buffer); for_each_online_cpu(cpu) { rb_data[cpu].buffer = buffer; rb_data[cpu].cpu = cpu; rb_data[cpu].cnt = cpu; rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu], cpu, "rbtester/%u"); if (WARN_ON(IS_ERR(rb_threads[cpu]))) { pr_cont("FAILED\n"); ret = PTR_ERR(rb_threads[cpu]); goto out_free; } } /* Now create the rb hammer! */ rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer"); if (WARN_ON(IS_ERR(rb_hammer))) { pr_cont("FAILED\n"); ret = PTR_ERR(rb_hammer); goto out_free; } ring_buffer_record_on(buffer); /* * Show buffer is enabled before setting rb_test_started. * Yes there's a small race window where events could be * dropped and the thread wont catch it. But when a ring * buffer gets enabled, there will always be some kind of * delay before other CPUs see it. Thus, we don't care about * those dropped events. We care about events dropped after * the threads see that the buffer is active. */ smp_wmb(); rb_test_started = true; set_current_state(TASK_INTERRUPTIBLE); /* Just run for 10 seconds */; schedule_timeout(10 * HZ); kthread_stop(rb_hammer); out_free: for_each_online_cpu(cpu) { if (!rb_threads[cpu]) break; kthread_stop(rb_threads[cpu]); } if (ret) { ring_buffer_free(buffer); return ret; } /* Report! */ pr_info("finished\n"); for_each_online_cpu(cpu) { struct ring_buffer_event *event; struct rb_test_data *data = &rb_data[cpu]; struct rb_item *item; unsigned long total_events; unsigned long total_dropped; unsigned long total_written; unsigned long total_alloc; unsigned long total_read = 0; unsigned long total_size = 0; unsigned long total_len = 0; unsigned long total_lost = 0; unsigned long lost; int big_event_size; int small_event_size; ret = -1; total_events = data->events + data->events_nested; total_written = data->bytes_written + data->bytes_written_nested; total_alloc = data->bytes_alloc + data->bytes_alloc_nested; total_dropped = data->bytes_dropped + data->bytes_dropped_nested; big_event_size = data->max_size + data->max_size_nested; small_event_size = data->min_size + data->min_size_nested; pr_info("CPU %d:\n", cpu); pr_info(" events: %ld\n", total_events); pr_info(" dropped bytes: %ld\n", total_dropped); pr_info(" alloced bytes: %ld\n", total_alloc); pr_info(" written bytes: %ld\n", total_written); pr_info(" biggest event: %d\n", big_event_size); pr_info(" smallest event: %d\n", small_event_size); if (RB_WARN_ON(buffer, total_dropped)) break; ret = 0; while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) { total_lost += lost; item = ring_buffer_event_data(event); total_len += ring_buffer_event_length(event); total_size += item->size + sizeof(struct rb_item); if (memcmp(&item->str[0], rb_string, item->size) != 0) { pr_info("FAILED!\n"); pr_info("buffer had: %.*s\n", item->size, item->str); pr_info("expected: %.*s\n", item->size, rb_string); RB_WARN_ON(buffer, 1); ret = -1; break; } total_read++; } if (ret) break; ret = -1; pr_info(" read events: %ld\n", total_read); pr_info(" lost events: %ld\n", total_lost); pr_info(" total events: %ld\n", total_lost + total_read); pr_info(" recorded len bytes: %ld\n", total_len); pr_info(" recorded size bytes: %ld\n", total_size); if (total_lost) { pr_info(" With dropped events, record len and size may not match\n" " alloced and written from above\n"); } else { if (RB_WARN_ON(buffer, total_len != total_alloc || total_size != total_written)) break; } if (RB_WARN_ON(buffer, total_lost + total_read != total_events)) break; ret = 0; } if (!ret) pr_info("Ring buffer PASSED!\n"); ring_buffer_free(buffer); return 0; } late_initcall(test_ringbuffer); #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
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