| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Kay Sievers | 3536 | 32.80% | 19 | 6.44% |
| Petr Mladek | 964 | 8.94% | 19 | 6.44% |
| Tejun Heo | 879 | 8.15% | 4 | 1.36% |
| Linus Torvalds (pre-git) | 477 | 4.42% | 26 | 8.81% |
| Borislav Petkov | 460 | 4.27% | 2 | 0.68% |
| Linus Torvalds | 433 | 4.02% | 17 | 5.76% |
| Sergey Senozhatsky | 392 | 3.64% | 17 | 5.76% |
| Simon Kågström | 221 | 2.05% | 1 | 0.34% |
| John Z. Bohach | 207 | 1.92% | 1 | 0.34% |
| Tetsuo Handa | 205 | 1.90% | 3 | 1.02% |
| Robin Getz | 167 | 1.55% | 4 | 1.36% |
| Kees Cook | 158 | 1.47% | 4 | 1.36% |
| Joe Perches | 156 | 1.45% | 10 | 3.39% |
| Samuel Thibault | 154 | 1.43% | 1 | 0.34% |
| Andrew Morton | 144 | 1.34% | 11 | 3.73% |
| Luis R. Rodriguez | 123 | 1.14% | 3 | 1.02% |
| Frédéric Weisbecker | 123 | 1.14% | 2 | 0.68% |
| Russell King | 109 | 1.01% | 2 | 0.68% |
| Randy Dunlap | 92 | 0.85% | 5 | 1.69% |
| Anton Vorontsov | 86 | 0.80% | 1 | 0.34% |
| Steven Rostedt | 85 | 0.79% | 4 | 1.36% |
| Jan Kara | 71 | 0.66% | 2 | 0.68% |
| Thomas Gleixner | 61 | 0.57% | 5 | 1.69% |
| Andrew Cooks | 60 | 0.56% | 1 | 0.34% |
| Yang Ruirui | 58 | 0.54% | 2 | 0.68% |
| He Zhe | 57 | 0.53% | 4 | 1.36% |
| Peter Zijlstra | 52 | 0.48% | 4 | 1.36% |
| Peter Hurley | 50 | 0.46% | 2 | 0.68% |
| Jan Beulich | 50 | 0.46% | 1 | 0.34% |
| Benjamin Herrenschmidt | 44 | 0.41% | 3 | 1.02% |
| Andres Salomon | 44 | 0.41% | 1 | 0.34% |
| Alex Elder | 42 | 0.39% | 5 | 1.69% |
| Sebastian Andrzej Siewior | 40 | 0.37% | 1 | 0.34% |
| Matt Mackall | 39 | 0.36% | 2 | 0.68% |
| Gerd Hoffmann | 37 | 0.34% | 1 | 0.34% |
| Fabio Massimo Di Nitto | 37 | 0.34% | 1 | 0.34% |
| Mathias Krause | 33 | 0.31% | 1 | 0.34% |
| Nico Pitre | 32 | 0.30% | 1 | 0.34% |
| Ingo Molnar | 30 | 0.28% | 10 | 3.39% |
| Greg Edwards | 29 | 0.27% | 1 | 0.34% |
| Kevin Cernekee | 28 | 0.26% | 1 | 0.34% |
| Nikitas Angelinas | 28 | 0.26% | 1 | 0.34% |
| Andreas Bießmann | 28 | 0.26% | 1 | 0.34% |
| Vivek Goyal | 28 | 0.26% | 1 | 0.34% |
| Mike Travis | 27 | 0.25% | 1 | 0.34% |
| Ivan Delalande | 27 | 0.25% | 1 | 0.34% |
| Torben Hohn | 26 | 0.24% | 1 | 0.34% |
| Abderrahmane Benbachir | 25 | 0.23% | 1 | 0.34% |
| Will Deacon | 24 | 0.22% | 1 | 0.34% |
| Vasant Hegde | 23 | 0.21% | 1 | 0.34% |
| Vasily Averin | 22 | 0.20% | 2 | 0.68% |
| Yinghai Lu | 21 | 0.19% | 2 | 0.68% |
| Geert Uytterhoeven | 21 | 0.19% | 1 | 0.34% |
| Yanmin Zhang | 21 | 0.19% | 1 | 0.34% |
| Aleksey Makarov | 19 | 0.18% | 2 | 0.68% |
| Daniel Vetter | 18 | 0.17% | 2 | 0.68% |
| Matt Redfearn | 18 | 0.17% | 1 | 0.34% |
| Thierry Reding | 15 | 0.14% | 1 | 0.34% |
| Arve Hjönnevåg | 14 | 0.13% | 1 | 0.34% |
| Thomas Zimmermann | 14 | 0.13% | 1 | 0.34% |
| Feng Tang | 14 | 0.13% | 1 | 0.34% |
| Ard Biesheuvel | 14 | 0.13% | 1 | 0.34% |
| Frans Pop | 13 | 0.12% | 1 | 0.34% |
| Markus Armbruster | 12 | 0.11% | 1 | 0.34% |
| Matthew Garrett | 12 | 0.11% | 1 | 0.34% |
| Jan Kiszka | 11 | 0.10% | 1 | 0.34% |
| Jason Wessel | 11 | 0.10% | 2 | 0.68% |
| Namit Gupta | 10 | 0.09% | 1 | 0.34% |
| Andrey Ryabinin | 10 | 0.09% | 1 | 0.34% |
| Matthew Wilcox | 9 | 0.08% | 1 | 0.34% |
| Martin Schwidefsky | 9 | 0.08% | 1 | 0.34% |
| Christian Bornträger | 9 | 0.08% | 1 | 0.34% |
| Al Viro | 9 | 0.08% | 3 | 1.02% |
| Huang Ying | 8 | 0.07% | 1 | 0.34% |
| Stephen Warren | 8 | 0.07% | 1 | 0.34% |
| Johannes Berg | 7 | 0.06% | 1 | 0.34% |
| Stephen Chivers | 7 | 0.06% | 1 | 0.34% |
| Stephen D. Smalley | 7 | 0.06% | 1 | 0.34% |
| Nick Andrew | 7 | 0.06% | 1 | 0.34% |
| Christoph Hellwig | 6 | 0.06% | 3 | 1.02% |
| Keith M. Wesolowski | 6 | 0.06% | 1 | 0.34% |
| Yuanhan Liu | 6 | 0.06% | 1 | 0.34% |
| Hans de Goede | 5 | 0.05% | 1 | 0.34% |
| Dan Rosenberg | 5 | 0.05% | 1 | 0.34% |
| Guillaume Knispel | 5 | 0.05% | 1 | 0.34% |
| Jesper Juhl | 5 | 0.05% | 1 | 0.34% |
| Maciej W. Rozycki | 5 | 0.05% | 1 | 0.34% |
| Tim Bird | 5 | 0.05% | 2 | 0.68% |
| James Simmons | 5 | 0.05% | 1 | 0.34% |
| Rafael J. Wysocki | 3 | 0.03% | 1 | 0.34% |
| Hari Bathini | 3 | 0.03% | 1 | 0.34% |
| Neil Zhang | 3 | 0.03% | 1 | 0.34% |
| Heiko Carstens | 3 | 0.03% | 1 | 0.34% |
| Arnd Bergmann | 3 | 0.03% | 1 | 0.34% |
| Jan Engelhardt | 3 | 0.03% | 1 | 0.34% |
| Dave Young | 3 | 0.03% | 1 | 0.34% |
| Neil Horman | 2 | 0.02% | 1 | 0.34% |
| Jane Li | 2 | 0.02% | 1 | 0.34% |
| Daniel R Thompson | 2 | 0.02% | 1 | 0.34% |
| Mike Rapoport | 2 | 0.02% | 1 | 0.34% |
| John Stultz | 2 | 0.02% | 1 | 0.34% |
| Michael Ellerman | 2 | 0.02% | 1 | 0.34% |
| Christoph Lameter | 2 | 0.02% | 1 | 0.34% |
| Nadia Yvette Chambers | 2 | 0.02% | 1 | 0.34% |
| Santosh Shilimkar | 2 | 0.02% | 1 | 0.34% |
| Werner Almesberger | 2 | 0.02% | 1 | 0.34% |
| Gustavo Padovan | 2 | 0.02% | 1 | 0.34% |
| Sonic Zhang | 1 | 0.01% | 1 | 0.34% |
| Martin Waitz | 1 | 0.01% | 1 | 0.34% |
| Eric Paris | 1 | 0.01% | 1 | 0.34% |
| Antonio Ospite | 1 | 0.01% | 1 | 0.34% |
| Nicolas Kaiser | 1 | 0.01% | 1 | 0.34% |
| Dirk Gouders | 1 | 0.01% | 1 | 0.34% |
| Uwe Kleine-König | 1 | 0.01% | 1 | 0.34% |
| Nishanth Aravamudan | 1 | 0.01% | 1 | 0.34% |
| Patrick Pletscher | 1 | 0.01% | 1 | 0.34% |
| Francois Cami | 1 | 0.01% | 1 | 0.34% |
| Tomeu Vizoso | 1 | 0.01% | 1 | 0.34% |
| Pavel Machek | 1 | 0.01% | 1 | 0.34% |
| Rusty Russell | 1 | 0.01% | 1 | 0.34% |
| Alan Stern | 1 | 0.01% | 1 | 0.34% |
| Total | 10781 | 295 |
/* * linux/kernel/printk.c * * Copyright (C) 1991, 1992 Linus Torvalds * * Modified to make sys_syslog() more flexible: added commands to * return the last 4k of kernel messages, regardless of whether * they've been read or not. Added option to suppress kernel printk's * to the console. Added hook for sending the console messages * elsewhere, in preparation for a serial line console (someday). * Ted Ts'o, 2/11/93. * Modified for sysctl support, 1/8/97, Chris Horn. * Fixed SMP synchronization, 08/08/99, Manfred Spraul * manfred@colorfullife.com * Rewrote bits to get rid of console_lock * 01Mar01 Andrew Morton */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/kernel.h> #include <linux/mm.h> #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/console.h> #include <linux/init.h> #include <linux/jiffies.h> #include <linux/nmi.h> #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/delay.h> #include <linux/smp.h> #include <linux/security.h> #include <linux/memblock.h> #include <linux/syscalls.h> #include <linux/crash_core.h> #include <linux/kdb.h> #include <linux/ratelimit.h> #include <linux/kmsg_dump.h> #include <linux/syslog.h> #include <linux/cpu.h> #include <linux/rculist.h> #include <linux/poll.h> #include <linux/irq_work.h> #include <linux/ctype.h> #include <linux/uio.h> #include <linux/sched/clock.h> #include <linux/sched/debug.h> #include <linux/sched/task_stack.h> #include <linux/uaccess.h> #include <asm/sections.h> #include <trace/events/initcall.h> #define CREATE_TRACE_POINTS #include <trace/events/printk.h> #include "console_cmdline.h" #include "braille.h" #include "internal.h" int console_printk[4] = { CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */ MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */ CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */ CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */ }; atomic_t ignore_console_lock_warning __read_mostly = ATOMIC_INIT(0); EXPORT_SYMBOL(ignore_console_lock_warning); /* * Low level drivers may need that to know if they can schedule in * their unblank() callback or not. So let's export it. */ int oops_in_progress; EXPORT_SYMBOL(oops_in_progress); /* * console_sem protects the console_drivers list, and also * provides serialisation for access to the entire console * driver system. */ static DEFINE_SEMAPHORE(console_sem); struct console *console_drivers; EXPORT_SYMBOL_GPL(console_drivers); #ifdef CONFIG_LOCKDEP static struct lockdep_map console_lock_dep_map = { .name = "console_lock" }; #endif enum devkmsg_log_bits { __DEVKMSG_LOG_BIT_ON = 0, __DEVKMSG_LOG_BIT_OFF, __DEVKMSG_LOG_BIT_LOCK, }; enum devkmsg_log_masks { DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON), DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF), DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK), }; /* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */ #define DEVKMSG_LOG_MASK_DEFAULT 0 static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT; static int __control_devkmsg(char *str) { if (!str) return -EINVAL; if (!strncmp(str, "on", 2)) { devkmsg_log = DEVKMSG_LOG_MASK_ON; return 2; } else if (!strncmp(str, "off", 3)) { devkmsg_log = DEVKMSG_LOG_MASK_OFF; return 3; } else if (!strncmp(str, "ratelimit", 9)) { devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT; return 9; } return -EINVAL; } static int __init control_devkmsg(char *str) { if (__control_devkmsg(str) < 0) return 1; /* * Set sysctl string accordingly: */ if (devkmsg_log == DEVKMSG_LOG_MASK_ON) strcpy(devkmsg_log_str, "on"); else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) strcpy(devkmsg_log_str, "off"); /* else "ratelimit" which is set by default. */ /* * Sysctl cannot change it anymore. The kernel command line setting of * this parameter is to force the setting to be permanent throughout the * runtime of the system. This is a precation measure against userspace * trying to be a smarta** and attempting to change it up on us. */ devkmsg_log |= DEVKMSG_LOG_MASK_LOCK; return 0; } __setup("printk.devkmsg=", control_devkmsg); char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit"; int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { char old_str[DEVKMSG_STR_MAX_SIZE]; unsigned int old; int err; if (write) { if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK) return -EINVAL; old = devkmsg_log; strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE); } err = proc_dostring(table, write, buffer, lenp, ppos); if (err) return err; if (write) { err = __control_devkmsg(devkmsg_log_str); /* * Do not accept an unknown string OR a known string with * trailing crap... */ if (err < 0 || (err + 1 != *lenp)) { /* ... and restore old setting. */ devkmsg_log = old; strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE); return -EINVAL; } } return 0; } /* Number of registered extended console drivers. */ static int nr_ext_console_drivers; /* * Helper macros to handle lockdep when locking/unlocking console_sem. We use * macros instead of functions so that _RET_IP_ contains useful information. */ #define down_console_sem() do { \ down(&console_sem);\ mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\ } while (0) static int __down_trylock_console_sem(unsigned long ip) { int lock_failed; unsigned long flags; /* * Here and in __up_console_sem() we need to be in safe mode, * because spindump/WARN/etc from under console ->lock will * deadlock in printk()->down_trylock_console_sem() otherwise. */ printk_safe_enter_irqsave(flags); lock_failed = down_trylock(&console_sem); printk_safe_exit_irqrestore(flags); if (lock_failed) return 1; mutex_acquire(&console_lock_dep_map, 0, 1, ip); return 0; } #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_) static void __up_console_sem(unsigned long ip) { unsigned long flags; mutex_release(&console_lock_dep_map, 1, ip); printk_safe_enter_irqsave(flags); up(&console_sem); printk_safe_exit_irqrestore(flags); } #define up_console_sem() __up_console_sem(_RET_IP_) /* * This is used for debugging the mess that is the VT code by * keeping track if we have the console semaphore held. It's * definitely not the perfect debug tool (we don't know if _WE_ * hold it and are racing, but it helps tracking those weird code * paths in the console code where we end up in places I want * locked without the console sempahore held). */ static int console_locked, console_suspended; /* * If exclusive_console is non-NULL then only this console is to be printed to. */ static struct console *exclusive_console; /* * Array of consoles built from command line options (console=) */ #define MAX_CMDLINECONSOLES 8 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; static int preferred_console = -1; int console_set_on_cmdline; EXPORT_SYMBOL(console_set_on_cmdline); /* Flag: console code may call schedule() */ static int console_may_schedule; enum con_msg_format_flags { MSG_FORMAT_DEFAULT = 0, MSG_FORMAT_SYSLOG = (1 << 0), }; static int console_msg_format = MSG_FORMAT_DEFAULT; /* * The printk log buffer consists of a chain of concatenated variable * length records. Every record starts with a record header, containing * the overall length of the record. * * The heads to the first and last entry in the buffer, as well as the * sequence numbers of these entries are maintained when messages are * stored. * * If the heads indicate available messages, the length in the header * tells the start next message. A length == 0 for the next message * indicates a wrap-around to the beginning of the buffer. * * Every record carries the monotonic timestamp in microseconds, as well as * the standard userspace syslog level and syslog facility. The usual * kernel messages use LOG_KERN; userspace-injected messages always carry * a matching syslog facility, by default LOG_USER. The origin of every * message can be reliably determined that way. * * The human readable log message directly follows the message header. The * length of the message text is stored in the header, the stored message * is not terminated. * * Optionally, a message can carry a dictionary of properties (key/value pairs), * to provide userspace with a machine-readable message context. * * Examples for well-defined, commonly used property names are: * DEVICE=b12:8 device identifier * b12:8 block dev_t * c127:3 char dev_t * n8 netdev ifindex * +sound:card0 subsystem:devname * SUBSYSTEM=pci driver-core subsystem name * * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value * follows directly after a '=' character. Every property is terminated by * a '\0' character. The last property is not terminated. * * Example of a message structure: * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec * 0008 34 00 record is 52 bytes long * 000a 0b 00 text is 11 bytes long * 000c 1f 00 dictionary is 23 bytes long * 000e 03 00 LOG_KERN (facility) LOG_ERR (level) * 0010 69 74 27 73 20 61 20 6c "it's a l" * 69 6e 65 "ine" * 001b 44 45 56 49 43 "DEVIC" * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D" * 52 49 56 45 52 3d 62 75 "RIVER=bu" * 67 "g" * 0032 00 00 00 padding to next message header * * The 'struct printk_log' buffer header must never be directly exported to * userspace, it is a kernel-private implementation detail that might * need to be changed in the future, when the requirements change. * * /dev/kmsg exports the structured data in the following line format: * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n" * * Users of the export format should ignore possible additional values * separated by ',', and find the message after the ';' character. * * The optional key/value pairs are attached as continuation lines starting * with a space character and terminated by a newline. All possible * non-prinatable characters are escaped in the "\xff" notation. */ enum log_flags { LOG_NEWLINE = 2, /* text ended with a newline */ LOG_PREFIX = 4, /* text started with a prefix */ LOG_CONT = 8, /* text is a fragment of a continuation line */ }; struct printk_log { u64 ts_nsec; /* timestamp in nanoseconds */ u16 len; /* length of entire record */ u16 text_len; /* length of text buffer */ u16 dict_len; /* length of dictionary buffer */ u8 facility; /* syslog facility */ u8 flags:5; /* internal record flags */ u8 level:3; /* syslog level */ } #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS __packed __aligned(4) #endif ; /* * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken * within the scheduler's rq lock. It must be released before calling * console_unlock() or anything else that might wake up a process. */ DEFINE_RAW_SPINLOCK(logbuf_lock); /* * Helper macros to lock/unlock logbuf_lock and switch between * printk-safe/unsafe modes. */ #define logbuf_lock_irq() \ do { \ printk_safe_enter_irq(); \ raw_spin_lock(&logbuf_lock); \ } while (0) #define logbuf_unlock_irq() \ do { \ raw_spin_unlock(&logbuf_lock); \ printk_safe_exit_irq(); \ } while (0) #define logbuf_lock_irqsave(flags) \ do { \ printk_safe_enter_irqsave(flags); \ raw_spin_lock(&logbuf_lock); \ } while (0) #define logbuf_unlock_irqrestore(flags) \ do { \ raw_spin_unlock(&logbuf_lock); \ printk_safe_exit_irqrestore(flags); \ } while (0) #ifdef CONFIG_PRINTK DECLARE_WAIT_QUEUE_HEAD(log_wait); /* the next printk record to read by syslog(READ) or /proc/kmsg */ static u64 syslog_seq; static u32 syslog_idx; static size_t syslog_partial; static bool syslog_time; /* index and sequence number of the first record stored in the buffer */ static u64 log_first_seq; static u32 log_first_idx; /* index and sequence number of the next record to store in the buffer */ static u64 log_next_seq; static u32 log_next_idx; /* the next printk record to write to the console */ static u64 console_seq; static u32 console_idx; static u64 exclusive_console_stop_seq; /* the next printk record to read after the last 'clear' command */ static u64 clear_seq; static u32 clear_idx; #define PREFIX_MAX 32 #define LOG_LINE_MAX (1024 - PREFIX_MAX) #define LOG_LEVEL(v) ((v) & 0x07) #define LOG_FACILITY(v) ((v) >> 3 & 0xff) /* record buffer */ #define LOG_ALIGN __alignof__(struct printk_log) #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) #define LOG_BUF_LEN_MAX (u32)(1 << 31) static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN); static char *log_buf = __log_buf; static u32 log_buf_len = __LOG_BUF_LEN; /* Return log buffer address */ char *log_buf_addr_get(void) { return log_buf; } /* Return log buffer size */ u32 log_buf_len_get(void) { return log_buf_len; } /* human readable text of the record */ static char *log_text(const struct printk_log *msg) { return (char *)msg + sizeof(struct printk_log); } /* optional key/value pair dictionary attached to the record */ static char *log_dict(const struct printk_log *msg) { return (char *)msg + sizeof(struct printk_log) + msg->text_len; } /* get record by index; idx must point to valid msg */ static struct printk_log *log_from_idx(u32 idx) { struct printk_log *msg = (struct printk_log *)(log_buf + idx); /* * A length == 0 record is the end of buffer marker. Wrap around and * read the message at the start of the buffer. */ if (!msg->len) return (struct printk_log *)log_buf; return msg; } /* get next record; idx must point to valid msg */ static u32 log_next(u32 idx) { struct printk_log *msg = (struct printk_log *)(log_buf + idx); /* length == 0 indicates the end of the buffer; wrap */ /* * A length == 0 record is the end of buffer marker. Wrap around and * read the message at the start of the buffer as *this* one, and * return the one after that. */ if (!msg->len) { msg = (struct printk_log *)log_buf; return msg->len; } return idx + msg->len; } /* * Check whether there is enough free space for the given message. * * The same values of first_idx and next_idx mean that the buffer * is either empty or full. * * If the buffer is empty, we must respect the position of the indexes. * They cannot be reset to the beginning of the buffer. */ static int logbuf_has_space(u32 msg_size, bool empty) { u32 free; if (log_next_idx > log_first_idx || empty) free = max(log_buf_len - log_next_idx, log_first_idx); else free = log_first_idx - log_next_idx; /* * We need space also for an empty header that signalizes wrapping * of the buffer. */ return free >= msg_size + sizeof(struct printk_log); } static int log_make_free_space(u32 msg_size) { while (log_first_seq < log_next_seq && !logbuf_has_space(msg_size, false)) { /* drop old messages until we have enough contiguous space */ log_first_idx = log_next(log_first_idx); log_first_seq++; } if (clear_seq < log_first_seq) { clear_seq = log_first_seq; clear_idx = log_first_idx; } /* sequence numbers are equal, so the log buffer is empty */ if (logbuf_has_space(msg_size, log_first_seq == log_next_seq)) return 0; return -ENOMEM; } /* compute the message size including the padding bytes */ static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len) { u32 size; size = sizeof(struct printk_log) + text_len + dict_len; *pad_len = (-size) & (LOG_ALIGN - 1); size += *pad_len; return size; } /* * Define how much of the log buffer we could take at maximum. The value * must be greater than two. Note that only half of the buffer is available * when the index points to the middle. */ #define MAX_LOG_TAKE_PART 4 static const char trunc_msg[] = "<truncated>"; static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len, u16 *dict_len, u32 *pad_len) { /* * The message should not take the whole buffer. Otherwise, it might * get removed too soon. */ u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART; if (*text_len > max_text_len) *text_len = max_text_len; /* enable the warning message */ *trunc_msg_len = strlen(trunc_msg); /* disable the "dict" completely */ *dict_len = 0; /* compute the size again, count also the warning message */ return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len); } /* insert record into the buffer, discard old ones, update heads */ static int log_store(int facility, int level, enum log_flags flags, u64 ts_nsec, const char *dict, u16 dict_len, const char *text, u16 text_len) { struct printk_log *msg; u32 size, pad_len; u16 trunc_msg_len = 0; /* number of '\0' padding bytes to next message */ size = msg_used_size(text_len, dict_len, &pad_len); if (log_make_free_space(size)) { /* truncate the message if it is too long for empty buffer */ size = truncate_msg(&text_len, &trunc_msg_len, &dict_len, &pad_len); /* survive when the log buffer is too small for trunc_msg */ if (log_make_free_space(size)) return 0; } if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) { /* * This message + an additional empty header does not fit * at the end of the buffer. Add an empty header with len == 0 * to signify a wrap around. */ memset(log_buf + log_next_idx, 0, sizeof(struct printk_log)); log_next_idx = 0; } /* fill message */ msg = (struct printk_log *)(log_buf + log_next_idx); memcpy(log_text(msg), text, text_len); msg->text_len = text_len; if (trunc_msg_len) { memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len); msg->text_len += trunc_msg_len; } memcpy(log_dict(msg), dict, dict_len); msg->dict_len = dict_len; msg->facility = facility; msg->level = level & 7; msg->flags = flags & 0x1f; if (ts_nsec > 0) msg->ts_nsec = ts_nsec; else msg->ts_nsec = local_clock(); memset(log_dict(msg) + dict_len, 0, pad_len); msg->len = size; /* insert message */ log_next_idx += msg->len; log_next_seq++; return msg->text_len; } int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT); static int syslog_action_restricted(int type) { if (dmesg_restrict) return 1; /* * Unless restricted, we allow "read all" and "get buffer size" * for everybody. */ return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER; } static int check_syslog_permissions(int type, int source) { /* * If this is from /proc/kmsg and we've already opened it, then we've * already done the capabilities checks at open time. */ if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN) goto ok; if (syslog_action_restricted(type)) { if (capable(CAP_SYSLOG)) goto ok; /* * For historical reasons, accept CAP_SYS_ADMIN too, with * a warning. */ if (capable(CAP_SYS_ADMIN)) { pr_warn_once("%s (%d): Attempt to access syslog with " "CAP_SYS_ADMIN but no CAP_SYSLOG " "(deprecated).\n", current->comm, task_pid_nr(current)); goto ok; } return -EPERM; } ok: return security_syslog(type); } static void append_char(char **pp, char *e, char c) { if (*pp < e) *(*pp)++ = c; } static ssize_t msg_print_ext_header(char *buf, size_t size, struct printk_log *msg, u64 seq) { u64 ts_usec = msg->ts_nsec; do_div(ts_usec, 1000); return scnprintf(buf, size, "%u,%llu,%llu,%c;", (msg->facility << 3) | msg->level, seq, ts_usec, msg->flags & LOG_CONT ? 'c' : '-'); } static ssize_t msg_print_ext_body(char *buf, size_t size, char *dict, size_t dict_len, char *text, size_t text_len) { char *p = buf, *e = buf + size; size_t i; /* escape non-printable characters */ for (i = 0; i < text_len; i++) { unsigned char c = text[i]; if (c < ' ' || c >= 127 || c == '\\') p += scnprintf(p, e - p, "\\x%02x", c); else append_char(&p, e, c); } append_char(&p, e, '\n'); if (dict_len) { bool line = true; for (i = 0; i < dict_len; i++) { unsigned char c = dict[i]; if (line) { append_char(&p, e, ' '); line = false; } if (c == '\0') { append_char(&p, e, '\n'); line = true; continue; } if (c < ' ' || c >= 127 || c == '\\') { p += scnprintf(p, e - p, "\\x%02x", c); continue; } append_char(&p, e, c); } append_char(&p, e, '\n'); } return p - buf; } /* /dev/kmsg - userspace message inject/listen interface */ struct devkmsg_user { u64 seq; u32 idx; struct ratelimit_state rs; struct mutex lock; char buf[CONSOLE_EXT_LOG_MAX]; }; static __printf(3, 4) __cold int devkmsg_emit(int facility, int level, const char *fmt, ...) { va_list args; int r; va_start(args, fmt); r = vprintk_emit(facility, level, NULL, 0, fmt, args); va_end(args); return r; } static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) { char *buf, *line; int level = default_message_loglevel; int facility = 1; /* LOG_USER */ struct file *file = iocb->ki_filp; struct devkmsg_user *user = file->private_data; size_t len = iov_iter_count(from); ssize_t ret = len; if (!user || len > LOG_LINE_MAX) return -EINVAL; /* Ignore when user logging is disabled. */ if (devkmsg_log & DEVKMSG_LOG_MASK_OFF) return len; /* Ratelimit when not explicitly enabled. */ if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) { if (!___ratelimit(&user->rs, current->comm)) return ret; } buf = kmalloc(len+1, GFP_KERNEL); if (buf == NULL) return -ENOMEM; buf[len] = '\0'; if (!copy_from_iter_full(buf, len, from)) { kfree(buf); return -EFAULT; } /* * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace * the decimal value represents 32bit, the lower 3 bit are the log * level, the rest are the log facility. * * If no prefix or no userspace facility is specified, we * enforce LOG_USER, to be able to reliably distinguish * kernel-generated messages from userspace-injected ones. */ line = buf; if (line[0] == '<') { char *endp = NULL; unsigned int u; u = simple_strtoul(line + 1, &endp, 10); if (endp && endp[0] == '>') { level = LOG_LEVEL(u); if (LOG_FACILITY(u) != 0) facility = LOG_FACILITY(u); endp++; len -= endp - line; line = endp; } } devkmsg_emit(facility, level, "%s", line); kfree(buf); return ret; } static ssize_t devkmsg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct devkmsg_user *user = file->private_data; struct printk_log *msg; size_t len; ssize_t ret; if (!user) return -EBADF; ret = mutex_lock_interruptible(&user->lock); if (ret) return ret; logbuf_lock_irq(); while (user->seq == log_next_seq) { if (file->f_flags & O_NONBLOCK) { ret = -EAGAIN; logbuf_unlock_irq(); goto out; } logbuf_unlock_irq(); ret = wait_event_interruptible(log_wait, user->seq != log_next_seq); if (ret) goto out; logbuf_lock_irq(); } if (user->seq < log_first_seq) { /* our last seen message is gone, return error and reset */ user->idx = log_first_idx; user->seq = log_first_seq; ret = -EPIPE; logbuf_unlock_irq(); goto out; } msg = log_from_idx(user->idx); len = msg_print_ext_header(user->buf, sizeof(user->buf), msg, user->seq); len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len, log_dict(msg), msg->dict_len, log_text(msg), msg->text_len); user->idx = log_next(user->idx); user->seq++; logbuf_unlock_irq(); if (len > count) { ret = -EINVAL; goto out; } if (copy_to_user(buf, user->buf, len)) { ret = -EFAULT; goto out; } ret = len; out: mutex_unlock(&user->lock); return ret; } static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) { struct devkmsg_user *user = file->private_data; loff_t ret = 0; if (!user) return -EBADF; if (offset) return -ESPIPE; logbuf_lock_irq(); switch (whence) { case SEEK_SET: /* the first record */ user->idx = log_first_idx; user->seq = log_first_seq; break; case SEEK_DATA: /* * The first record after the last SYSLOG_ACTION_CLEAR, * like issued by 'dmesg -c'. Reading /dev/kmsg itself * changes no global state, and does not clear anything. */ user->idx = clear_idx; user->seq = clear_seq; break; case SEEK_END: /* after the last record */ user->idx = log_next_idx; user->seq = log_next_seq; break; default: ret = -EINVAL; } logbuf_unlock_irq(); return ret; } static __poll_t devkmsg_poll(struct file *file, poll_table *wait) { struct devkmsg_user *user = file->private_data; __poll_t ret = 0; if (!user) return EPOLLERR|EPOLLNVAL; poll_wait(file, &log_wait, wait); logbuf_lock_irq(); if (user->seq < log_next_seq) { /* return error when data has vanished underneath us */ if (user->seq < log_first_seq) ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI; else ret = EPOLLIN|EPOLLRDNORM; } logbuf_unlock_irq(); return ret; } static int devkmsg_open(struct inode *inode, struct file *file) { struct devkmsg_user *user; int err; if (devkmsg_log & DEVKMSG_LOG_MASK_OFF) return -EPERM; /* write-only does not need any file context */ if ((file->f_flags & O_ACCMODE) != O_WRONLY) { err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL, SYSLOG_FROM_READER); if (err) return err; } user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL); if (!user) return -ENOMEM; ratelimit_default_init(&user->rs); ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE); mutex_init(&user->lock); logbuf_lock_irq(); user->idx = log_first_idx; user->seq = log_first_seq; logbuf_unlock_irq(); file->private_data = user; return 0; } static int devkmsg_release(struct inode *inode, struct file *file) { struct devkmsg_user *user = file->private_data; if (!user) return 0; ratelimit_state_exit(&user->rs); mutex_destroy(&user->lock); kfree(user); return 0; } const struct file_operations kmsg_fops = { .open = devkmsg_open, .read = devkmsg_read, .write_iter = devkmsg_write, .llseek = devkmsg_llseek, .poll = devkmsg_poll, .release = devkmsg_release, }; #ifdef CONFIG_CRASH_CORE /* * This appends the listed symbols to /proc/vmcore * * /proc/vmcore is used by various utilities, like crash and makedumpfile to * obtain access to symbols that are otherwise very difficult to locate. These * symbols are specifically used so that utilities can access and extract the * dmesg log from a vmcore file after a crash. */ void log_buf_vmcoreinfo_setup(void) { VMCOREINFO_SYMBOL(log_buf); VMCOREINFO_SYMBOL(log_buf_len); VMCOREINFO_SYMBOL(log_first_idx); VMCOREINFO_SYMBOL(clear_idx); VMCOREINFO_SYMBOL(log_next_idx); /* * Export struct printk_log size and field offsets. User space tools can * parse it and detect any changes to structure down the line. */ VMCOREINFO_STRUCT_SIZE(printk_log); VMCOREINFO_OFFSET(printk_log, ts_nsec); VMCOREINFO_OFFSET(printk_log, len); VMCOREINFO_OFFSET(printk_log, text_len); VMCOREINFO_OFFSET(printk_log, dict_len); } #endif /* requested log_buf_len from kernel cmdline */ static unsigned long __initdata new_log_buf_len; /* we practice scaling the ring buffer by powers of 2 */ static void __init log_buf_len_update(u64 size) { if (size > (u64)LOG_BUF_LEN_MAX) { size = (u64)LOG_BUF_LEN_MAX; pr_err("log_buf over 2G is not supported.\n"); } if (size) size = roundup_pow_of_two(size); if (size > log_buf_len) new_log_buf_len = (unsigned long)size; } /* save requested log_buf_len since it's too early to process it */ static int __init log_buf_len_setup(char *str) { u64 size; if (!str) return -EINVAL; size = memparse(str, &str); log_buf_len_update(size); return 0; } early_param("log_buf_len", log_buf_len_setup); #ifdef CONFIG_SMP #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT) static void __init log_buf_add_cpu(void) { unsigned int cpu_extra; /* * archs should set up cpu_possible_bits properly with * set_cpu_possible() after setup_arch() but just in * case lets ensure this is valid. */ if (num_possible_cpus() == 1) return; cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN; /* by default this will only continue through for large > 64 CPUs */ if (cpu_extra <= __LOG_BUF_LEN / 2) return; pr_info("log_buf_len individual max cpu contribution: %d bytes\n", __LOG_CPU_MAX_BUF_LEN); pr_info("log_buf_len total cpu_extra contributions: %d bytes\n", cpu_extra); pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN); log_buf_len_update(cpu_extra + __LOG_BUF_LEN); } #else /* !CONFIG_SMP */ static inline void log_buf_add_cpu(void) {} #endif /* CONFIG_SMP */ void __init setup_log_buf(int early) { unsigned long flags; char *new_log_buf; unsigned int free; if (log_buf != __log_buf) return; if (!early && !new_log_buf_len) log_buf_add_cpu(); if (!new_log_buf_len) return; if (early) { new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN); } else { new_log_buf = memblock_alloc_nopanic(new_log_buf_len, LOG_ALIGN); } if (unlikely(!new_log_buf)) { pr_err("log_buf_len: %lu bytes not available\n", new_log_buf_len); return; } logbuf_lock_irqsave(flags); log_buf_len = new_log_buf_len; log_buf = new_log_buf; new_log_buf_len = 0; free = __LOG_BUF_LEN - log_next_idx; memcpy(log_buf, __log_buf, __LOG_BUF_LEN); logbuf_unlock_irqrestore(flags); pr_info("log_buf_len: %u bytes\n", log_buf_len); pr_info("early log buf free: %u(%u%%)\n", free, (free * 100) / __LOG_BUF_LEN); } static bool __read_mostly ignore_loglevel; static int __init ignore_loglevel_setup(char *str) { ignore_loglevel = true; pr_info("debug: ignoring loglevel setting.\n"); return 0; } early_param("ignore_loglevel", ignore_loglevel_setup); module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR); MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting (prints all kernel messages to the console)"); static bool suppress_message_printing(int level) { return (level >= console_loglevel && !ignore_loglevel); } #ifdef CONFIG_BOOT_PRINTK_DELAY static int boot_delay; /* msecs delay after each printk during bootup */ static unsigned long long loops_per_msec; /* based on boot_delay */ static int __init boot_delay_setup(char *str) { unsigned long lpj; lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ loops_per_msec = (unsigned long long)lpj / 1000 * HZ; get_option(&str, &boot_delay); if (boot_delay > 10 * 1000) boot_delay = 0; pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, " "HZ: %d, loops_per_msec: %llu\n", boot_delay, preset_lpj, lpj, HZ, loops_per_msec); return 0; } early_param("boot_delay", boot_delay_setup); static void boot_delay_msec(int level) { unsigned long long k; unsigned long timeout; if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING) || suppress_message_printing(level)) { return; } k = (unsigned long long)loops_per_msec * boot_delay; timeout = jiffies + msecs_to_jiffies(boot_delay); while (k) { k--; cpu_relax(); /* * use (volatile) jiffies to prevent * compiler reduction; loop termination via jiffies * is secondary and may or may not happen. */ if (time_after(jiffies, timeout)) break; touch_nmi_watchdog(); } } #else static inline void boot_delay_msec(int level) { } #endif static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME); module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); static size_t print_syslog(unsigned int level, char *buf) { return sprintf(buf, "<%u>", level); } static size_t print_time(u64 ts, char *buf) { unsigned long rem_nsec = do_div(ts, 1000000000); return sprintf(buf, "[%5lu.%06lu] ", (unsigned long)ts, rem_nsec / 1000); } static size_t print_prefix(const struct printk_log *msg, bool syslog, bool time, char *buf) { size_t len = 0; if (syslog) len = print_syslog((msg->facility << 3) | msg->level, buf); if (time) len += print_time(msg->ts_nsec, buf + len); return len; } static size_t msg_print_text(const struct printk_log *msg, bool syslog, bool time, char *buf, size_t size) { const char *text = log_text(msg); size_t text_size = msg->text_len; size_t len = 0; char prefix[PREFIX_MAX]; const size_t prefix_len = print_prefix(msg, syslog, time, prefix); do { const char *next = memchr(text, '\n', text_size); size_t text_len; if (next) { text_len = next - text; next++; text_size -= next - text; } else { text_len = text_size; } if (buf) { if (prefix_len + text_len + 1 >= size - len) break; memcpy(buf + len, prefix, prefix_len); len += prefix_len; memcpy(buf + len, text, text_len); len += text_len; buf[len++] = '\n'; } else { /* SYSLOG_ACTION_* buffer size only calculation */ len += prefix_len + text_len + 1; } text = next; } while (text); return len; } static int syslog_print(char __user *buf, int size) { char *text; struct printk_log *msg; int len = 0; text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); if (!text) return -ENOMEM; while (size > 0) { size_t n; size_t skip; logbuf_lock_irq(); if (syslog_seq < log_first_seq) { /* messages are gone, move to first one */ syslog_seq = log_first_seq; syslog_idx = log_first_idx; syslog_partial = 0; } if (syslog_seq == log_next_seq) { logbuf_unlock_irq(); break; } /* * To keep reading/counting partial line consistent, * use printk_time value as of the beginning of a line. */ if (!syslog_partial) syslog_time = printk_time; skip = syslog_partial; msg = log_from_idx(syslog_idx); n = msg_print_text(msg, true, syslog_time, text, LOG_LINE_MAX + PREFIX_MAX); if (n - syslog_partial <= size) { /* message fits into buffer, move forward */ syslog_idx = log_next(syslog_idx); syslog_seq++; n -= syslog_partial; syslog_partial = 0; } else if (!len){ /* partial read(), remember position */ n = size; syslog_partial += n; } else n = 0; logbuf_unlock_irq(); if (!n) break; if (copy_to_user(buf, text + skip, n)) { if (!len) len = -EFAULT; break; } len += n; size -= n; buf += n; } kfree(text); return len; } static int syslog_print_all(char __user *buf, int size, bool clear) { char *text; int len = 0; u64 next_seq; u64 seq; u32 idx; bool time; text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); if (!text) return -ENOMEM; time = printk_time; logbuf_lock_irq(); /* * Find first record that fits, including all following records, * into the user-provided buffer for this dump. */ seq = clear_seq; idx = clear_idx; while (seq < log_next_seq) { struct printk_log *msg = log_from_idx(idx); len += msg_print_text(msg, true, time, NULL, 0); idx = log_next(idx); seq++; } /* move first record forward until length fits into the buffer */ seq = clear_seq; idx = clear_idx; while (len > size && seq < log_next_seq) { struct printk_log *msg = log_from_idx(idx); len -= msg_print_text(msg, true, time, NULL, 0); idx = log_next(idx); seq++; } /* last message fitting into this dump */ next_seq = log_next_seq; len = 0; while (len >= 0 && seq < next_seq) { struct printk_log *msg = log_from_idx(idx); int textlen = msg_print_text(msg, true, time, text, LOG_LINE_MAX + PREFIX_MAX); idx = log_next(idx); seq++; logbuf_unlock_irq(); if (copy_to_user(buf + len, text, textlen)) len = -EFAULT; else len += textlen; logbuf_lock_irq(); if (seq < log_first_seq) { /* messages are gone, move to next one */ seq = log_first_seq; idx = log_first_idx; } } if (clear) { clear_seq = log_next_seq; clear_idx = log_next_idx; } logbuf_unlock_irq(); kfree(text); return len; } static void syslog_clear(void) { logbuf_lock_irq(); clear_seq = log_next_seq; clear_idx = log_next_idx; logbuf_unlock_irq(); } int do_syslog(int type, char __user *buf, int len, int source) { bool clear = false; static int saved_console_loglevel = LOGLEVEL_DEFAULT; int error; error = check_syslog_permissions(type, source); if (error) return error; switch (type) { case SYSLOG_ACTION_CLOSE: /* Close log */ break; case SYSLOG_ACTION_OPEN: /* Open log */ break; case SYSLOG_ACTION_READ: /* Read from log */ if (!buf || len < 0) return -EINVAL; if (!len) return 0; if (!access_ok(buf, len)) return -EFAULT; error = wait_event_interruptible(log_wait, syslog_seq != log_next_seq); if (error) return error; error = syslog_print(buf, len); break; /* Read/clear last kernel messages */ case SYSLOG_ACTION_READ_CLEAR: clear = true; /* FALL THRU */ /* Read last kernel messages */ case SYSLOG_ACTION_READ_ALL: if (!buf || len < 0) return -EINVAL; if (!len) return 0; if (!access_ok(buf, len)) return -EFAULT; error = syslog_print_all(buf, len, clear); break; /* Clear ring buffer */ case SYSLOG_ACTION_CLEAR: syslog_clear(); break; /* Disable logging to console */ case SYSLOG_ACTION_CONSOLE_OFF: if (saved_console_loglevel == LOGLEVEL_DEFAULT) saved_console_loglevel = console_loglevel; console_loglevel = minimum_console_loglevel; break; /* Enable logging to console */ case SYSLOG_ACTION_CONSOLE_ON: if (saved_console_loglevel != LOGLEVEL_DEFAULT) { console_loglevel = saved_console_loglevel; saved_console_loglevel = LOGLEVEL_DEFAULT; } break; /* Set level of messages printed to console */ case SYSLOG_ACTION_CONSOLE_LEVEL: if (len < 1 || len > 8) return -EINVAL; if (len < minimum_console_loglevel) len = minimum_console_loglevel; console_loglevel = len; /* Implicitly re-enable logging to console */ saved_console_loglevel = LOGLEVEL_DEFAULT; break; /* Number of chars in the log buffer */ case SYSLOG_ACTION_SIZE_UNREAD: logbuf_lock_irq(); if (syslog_seq < log_first_seq) { /* messages are gone, move to first one */ syslog_seq = log_first_seq; syslog_idx = log_first_idx; syslog_partial = 0; } if (source == SYSLOG_FROM_PROC) { /* * Short-cut for poll(/"proc/kmsg") which simply checks * for pending data, not the size; return the count of * records, not the length. */ error = log_next_seq - syslog_seq; } else { u64 seq = syslog_seq; u32 idx = syslog_idx; bool time = syslog_partial ? syslog_time : printk_time; while (seq < log_next_seq) { struct printk_log *msg = log_from_idx(idx); error += msg_print_text(msg, true, time, NULL, 0); time = printk_time; idx = log_next(idx); seq++; } error -= syslog_partial; } logbuf_unlock_irq(); break; /* Size of the log buffer */ case SYSLOG_ACTION_SIZE_BUFFER: error = log_buf_len; break; default: error = -EINVAL; break; } return error; } SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) { return do_syslog(type, buf, len, SYSLOG_FROM_READER); } /* * Special console_lock variants that help to reduce the risk of soft-lockups. * They allow to pass console_lock to another printk() call using a busy wait. */ #ifdef CONFIG_LOCKDEP static struct lockdep_map console_owner_dep_map = { .name = "console_owner" }; #endif static DEFINE_RAW_SPINLOCK(console_owner_lock); static struct task_struct *console_owner; static bool console_waiter; /** * console_lock_spinning_enable - mark beginning of code where another * thread might safely busy wait * * This basically converts console_lock into a spinlock. This marks * the section where the console_lock owner can not sleep, because * there may be a waiter spinning (like a spinlock). Also it must be * ready to hand over the lock at the end of the section. */ static void console_lock_spinning_enable(void) { raw_spin_lock(&console_owner_lock); console_owner = current; raw_spin_unlock(&console_owner_lock); /* The waiter may spin on us after setting console_owner */ spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); } /** * console_lock_spinning_disable_and_check - mark end of code where another * thread was able to busy wait and check if there is a waiter * * This is called at the end of the section where spinning is allowed. * It has two functions. First, it is a signal that it is no longer * safe to start busy waiting for the lock. Second, it checks if * there is a busy waiter and passes the lock rights to her. * * Important: Callers lose the lock if there was a busy waiter. * They must not touch items synchronized by console_lock * in this case. * * Return: 1 if the lock rights were passed, 0 otherwise. */ static int console_lock_spinning_disable_and_check(void) { int waiter; raw_spin_lock(&console_owner_lock); waiter = READ_ONCE(console_waiter); console_owner = NULL; raw_spin_unlock(&console_owner_lock); if (!waiter) { spin_release(&console_owner_dep_map, 1, _THIS_IP_); return 0; } /* The waiter is now free to continue */ WRITE_ONCE(console_waiter, false); spin_release(&console_owner_dep_map, 1, _THIS_IP_); /* * Hand off console_lock to waiter. The waiter will perform * the up(). After this, the waiter is the console_lock owner. */ mutex_release(&console_lock_dep_map, 1, _THIS_IP_); return 1; } /** * console_trylock_spinning - try to get console_lock by busy waiting * * This allows to busy wait for the console_lock when the current * owner is running in specially marked sections. It means that * the current owner is running and cannot reschedule until it * is ready to lose the lock. * * Return: 1 if we got the lock, 0 othrewise */ static int console_trylock_spinning(void) { struct task_struct *owner = NULL; bool waiter; bool spin = false; unsigned long flags; if (console_trylock()) return 1; printk_safe_enter_irqsave(flags); raw_spin_lock(&console_owner_lock); owner = READ_ONCE(console_owner); waiter = READ_ONCE(console_waiter); if (!waiter && owner && owner != current) { WRITE_ONCE(console_waiter, true); spin = true; } raw_spin_unlock(&console_owner_lock); /* * If there is an active printk() writing to the * consoles, instead of having it write our data too, * see if we can offload that load from the active * printer, and do some printing ourselves. * Go into a spin only if there isn't already a waiter * spinning, and there is an active printer, and * that active printer isn't us (recursive printk?). */ if (!spin) { printk_safe_exit_irqrestore(flags); return 0; } /* We spin waiting for the owner to release us */ spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); /* Owner will clear console_waiter on hand off */ while (READ_ONCE(console_waiter)) cpu_relax(); spin_release(&console_owner_dep_map, 1, _THIS_IP_); printk_safe_exit_irqrestore(flags); /* * The owner passed the console lock to us. * Since we did not spin on console lock, annotate * this as a trylock. Otherwise lockdep will * complain. */ mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_); return 1; } /* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. * The console_lock must be held. */ static void call_console_drivers(const char *ext_text, size_t ext_len, const char *text, size_t len) { struct console *con; trace_console_rcuidle(text, len); if (!console_drivers) return; for_each_console(con) { if (exclusive_console && con != exclusive_console) continue; if (!(con->flags & CON_ENABLED)) continue; if (!con->write) continue; if (!cpu_online(smp_processor_id()) && !(con->flags & CON_ANYTIME)) continue; if (con->flags & CON_EXTENDED) con->write(con, ext_text, ext_len); else con->write(con, text, len); } } int printk_delay_msec __read_mostly; static inline void printk_delay(void) { if (unlikely(printk_delay_msec)) { int m = printk_delay_msec; while (m--) { mdelay(1); touch_nmi_watchdog(); } } } /* * Continuation lines are buffered, and not committed to the record buffer * until the line is complete, or a race forces it. The line fragments * though, are printed immediately to the consoles to ensure everything has * reached the console in case of a kernel crash. */ static struct cont { char buf[LOG_LINE_MAX]; size_t len; /* length == 0 means unused buffer */ struct task_struct *owner; /* task of first print*/ u64 ts_nsec; /* time of first print */ u8 level; /* log level of first message */ u8 facility; /* log facility of first message */ enum log_flags flags; /* prefix, newline flags */ } cont; static void cont_flush(void) { if (cont.len == 0) return; log_store(cont.facility, cont.level, cont.flags, cont.ts_nsec, NULL, 0, cont.buf, cont.len); cont.len = 0; } static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len) { /* If the line gets too long, split it up in separate records. */ if (cont.len + len > sizeof(cont.buf)) { cont_flush(); return false; } if (!cont.len) { cont.facility = facility; cont.level = level; cont.owner = current; cont.ts_nsec = local_clock(); cont.flags = flags; } memcpy(cont.buf + cont.len, text, len); cont.len += len; // The original flags come from the first line, // but later continuations can add a newline. if (flags & LOG_NEWLINE) { cont.flags |= LOG_NEWLINE; cont_flush(); } return true; } static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len) { /* * If an earlier line was buffered, and we're a continuation * write from the same process, try to add it to the buffer. */ if (cont.len) { if (cont.owner == current && (lflags & LOG_CONT)) { if (cont_add(facility, level, lflags, text, text_len)) return text_len; } /* Otherwise, make sure it's flushed */ cont_flush(); } /* Skip empty continuation lines that couldn't be added - they just flush */ if (!text_len && (lflags & LOG_CONT)) return 0; /* If it doesn't end in a newline, try to buffer the current line */ if (!(lflags & LOG_NEWLINE)) { if (cont_add(facility, level, lflags, text, text_len)) return text_len; } /* Store it in the record log */ return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len); } /* Must be called under logbuf_lock. */ int vprintk_store(int facility, int level, const char *dict, size_t dictlen, const char *fmt, va_list args) { static char textbuf[LOG_LINE_MAX]; char *text = textbuf; size_t text_len; enum log_flags lflags = 0; /* * The printf needs to come first; we need the syslog * prefix which might be passed-in as a parameter. */ text_len = vscnprintf(text, sizeof(textbuf), fmt, args); /* mark and strip a trailing newline */ if (text_len && text[text_len-1] == '\n') { text_len--; lflags |= LOG_NEWLINE; } /* strip kernel syslog prefix and extract log level or control flags */ if (facility == 0) { int kern_level; while ((kern_level = printk_get_level(text)) != 0) { switch (kern_level) { case '0' ... '7': if (level == LOGLEVEL_DEFAULT) level = kern_level - '0'; /* fallthrough */ case 'd': /* KERN_DEFAULT */ lflags |= LOG_PREFIX; break; case 'c': /* KERN_CONT */ lflags |= LOG_CONT; } text_len -= 2; text += 2; } } if (level == LOGLEVEL_DEFAULT) level = default_message_loglevel; if (dict) lflags |= LOG_PREFIX|LOG_NEWLINE; return log_output(facility, level, lflags, dict, dictlen, text, text_len); } asmlinkage int vprintk_emit(int facility, int level, const char *dict, size_t dictlen, const char *fmt, va_list args) { int printed_len; bool in_sched = false, pending_output; unsigned long flags; u64 curr_log_seq; if (level == LOGLEVEL_SCHED) { level = LOGLEVEL_DEFAULT; in_sched = true; } boot_delay_msec(level); printk_delay(); /* This stops the holder of console_sem just where we want him */ logbuf_lock_irqsave(flags); curr_log_seq = log_next_seq; printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args); pending_output = (curr_log_seq != log_next_seq); logbuf_unlock_irqrestore(flags); /* If called from the scheduler, we can not call up(). */ if (!in_sched && pending_output) { /* * Disable preemption to avoid being preempted while holding * console_sem which would prevent anyone from printing to * console */ preempt_disable(); /* * Try to acquire and then immediately release the console * semaphore. The release will print out buffers and wake up * /dev/kmsg and syslog() users. */ if (console_trylock_spinning()) console_unlock(); preempt_enable(); } if (pending_output) wake_up_klogd(); return printed_len; } EXPORT_SYMBOL(vprintk_emit); asmlinkage int vprintk(const char *fmt, va_list args) { return vprintk_func(fmt, args); } EXPORT_SYMBOL(vprintk); int vprintk_default(const char *fmt, va_list args) { int r; #ifdef CONFIG_KGDB_KDB /* Allow to pass printk() to kdb but avoid a recursion. */ if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) { r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args); return r; } #endif r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args); return r; } EXPORT_SYMBOL_GPL(vprintk_default); /** * printk - print a kernel message * @fmt: format string * * This is printk(). It can be called from any context. We want it to work. * * We try to grab the console_lock. If we succeed, it's easy - we log the * output and call the console drivers. If we fail to get the semaphore, we * place the output into the log buffer and return. The current holder of * the console_sem will notice the new output in console_unlock(); and will * send it to the consoles before releasing the lock. * * One effect of this deferred printing is that code which calls printk() and * then changes console_loglevel may break. This is because console_loglevel * is inspected when the actual printing occurs. * * See also: * printf(3) * * See the vsnprintf() documentation for format string extensions over C99. */ asmlinkage __visible int printk(const char *fmt, ...) { va_list args; int r; va_start(args, fmt); r = vprintk_func(fmt, args); va_end(args); return r; } EXPORT_SYMBOL(printk); #else /* CONFIG_PRINTK */ #define LOG_LINE_MAX 0 #define PREFIX_MAX 0 #define printk_time false static u64 syslog_seq; static u32 syslog_idx; static u64 console_seq; static u32 console_idx; static u64 exclusive_console_stop_seq; static u64 log_first_seq; static u32 log_first_idx; static u64 log_next_seq; static char *log_text(const struct printk_log *msg) { return NULL; } static char *log_dict(const struct printk_log *msg) { return NULL; } static struct printk_log *log_from_idx(u32 idx) { return NULL; } static u32 log_next(u32 idx) { return 0; } static ssize_t msg_print_ext_header(char *buf, size_t size, struct printk_log *msg, u64 seq) { return 0; } static ssize_t msg_print_ext_body(char *buf, size_t size, char *dict, size_t dict_len, char *text, size_t text_len) { return 0; } static void console_lock_spinning_enable(void) { } static int console_lock_spinning_disable_and_check(void) { return 0; } static void call_console_drivers(const char *ext_text, size_t ext_len, const char *text, size_t len) {} static size_t msg_print_text(const struct printk_log *msg, bool syslog, bool time, char *buf, size_t size) { return 0; } static bool suppress_message_printing(int level) { return false; } #endif /* CONFIG_PRINTK */ #ifdef CONFIG_EARLY_PRINTK struct console *early_console; asmlinkage __visible void early_printk(const char *fmt, ...) { va_list ap; char buf[512]; int n; if (!early_console) return; va_start(ap, fmt); n = vscnprintf(buf, sizeof(buf), fmt, ap); va_end(ap); early_console->write(early_console, buf, n); } #endif static int __add_preferred_console(char *name, int idx, char *options, char *brl_options) { struct console_cmdline *c; int i; /* * See if this tty is not yet registered, and * if we have a slot free. */ for (i = 0, c = console_cmdline; i < MAX_CMDLINECONSOLES && c->name[0]; i++, c++) { if (strcmp(c->name, name) == 0 && c->index == idx) { if (!brl_options) preferred_console = i; return 0; } } if (i == MAX_CMDLINECONSOLES) return -E2BIG; if (!brl_options) preferred_console = i; strlcpy(c->name, name, sizeof(c->name)); c->options = options; braille_set_options(c, brl_options); c->index = idx; return 0; } static int __init console_msg_format_setup(char *str) { if (!strcmp(str, "syslog")) console_msg_format = MSG_FORMAT_SYSLOG; if (!strcmp(str, "default")) console_msg_format = MSG_FORMAT_DEFAULT; return 1; } __setup("console_msg_format=", console_msg_format_setup); /* * Set up a console. Called via do_early_param() in init/main.c * for each "console=" parameter in the boot command line. */ static int __init console_setup(char *str) { char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */ char *s, *options, *brl_options = NULL; int idx; if (_braille_console_setup(&str, &brl_options)) return 1; /* * Decode str into name, index, options. */ if (str[0] >= '0' && str[0] <= '9') { strcpy(buf, "ttyS"); strncpy(buf + 4, str, sizeof(buf) - 5); } else { strncpy(buf, str, sizeof(buf) - 1); } buf[sizeof(buf) - 1] = 0; options = strchr(str, ','); if (options) *(options++) = 0; #ifdef __sparc__ if (!strcmp(str, "ttya")) strcpy(buf, "ttyS0"); if (!strcmp(str, "ttyb")) strcpy(buf, "ttyS1"); #endif for (s = buf; *s; s++) if (isdigit(*s) || *s == ',') break; idx = simple_strtoul(s, NULL, 10); *s = 0; __add_preferred_console(buf, idx, options, brl_options); console_set_on_cmdline = 1; return 1; } __setup("console=", console_setup); /** * add_preferred_console - add a device to the list of preferred consoles. * @name: device name * @idx: device index * @options: options for this console * * The last preferred console added will be used for kernel messages * and stdin/out/err for init. Normally this is used by console_setup * above to handle user-supplied console arguments; however it can also * be used by arch-specific code either to override the user or more * commonly to provide a default console (ie from PROM variables) when * the user has not supplied one. */ int add_preferred_console(char *name, int idx, char *options) { return __add_preferred_console(name, idx, options, NULL); } bool console_suspend_enabled = true; EXPORT_SYMBOL(console_suspend_enabled); static int __init console_suspend_disable(char *str) { console_suspend_enabled = false; return 1; } __setup("no_console_suspend", console_suspend_disable); module_param_named(console_suspend, console_suspend_enabled, bool, S_IRUGO | S_IWUSR); MODULE_PARM_DESC(console_suspend, "suspend console during suspend" " and hibernate operations"); /** * suspend_console - suspend the console subsystem * * This disables printk() while we go into suspend states */ void suspend_console(void) { if (!console_suspend_enabled) return; pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); console_lock(); console_suspended = 1; up_console_sem(); } void resume_console(void) { if (!console_suspend_enabled) return; down_console_sem(); console_suspended = 0; console_unlock(); } /** * console_cpu_notify - print deferred console messages after CPU hotplug * @cpu: unused * * If printk() is called from a CPU that is not online yet, the messages * will be printed on the console only if there are CON_ANYTIME consoles. * This function is called when a new CPU comes online (or fails to come * up) or goes offline. */ static int console_cpu_notify(unsigned int cpu) { if (!cpuhp_tasks_frozen) { /* If trylock fails, someone else is doing the printing */ if (console_trylock()) console_unlock(); } return 0; } /** * console_lock - lock the console system for exclusive use. * * Acquires a lock which guarantees that the caller has * exclusive access to the console system and the console_drivers list. * * Can sleep, returns nothing. */ void console_lock(void) { might_sleep(); down_console_sem(); if (console_suspended) return; console_locked = 1; console_may_schedule = 1; } EXPORT_SYMBOL(console_lock); /** * console_trylock - try to lock the console system for exclusive use. * * Try to acquire a lock which guarantees that the caller has exclusive * access to the console system and the console_drivers list. * * returns 1 on success, and 0 on failure to acquire the lock. */ int console_trylock(void) { if (down_trylock_console_sem()) return 0; if (console_suspended) { up_console_sem(); return 0; } console_locked = 1; console_may_schedule = 0; return 1; } EXPORT_SYMBOL(console_trylock); int is_console_locked(void) { return console_locked; } EXPORT_SYMBOL(is_console_locked); /* * Check if we have any console that is capable of printing while cpu is * booting or shutting down. Requires console_sem. */ static int have_callable_console(void) { struct console *con; for_each_console(con) if ((con->flags & CON_ENABLED) && (con->flags & CON_ANYTIME)) return 1; return 0; } /* * Can we actually use the console at this time on this cpu? * * Console drivers may assume that per-cpu resources have been allocated. So * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't * call them until this CPU is officially up. */ static inline int can_use_console(void) { return cpu_online(raw_smp_processor_id()) || have_callable_console(); } /** * console_unlock - unlock the console system * * Releases the console_lock which the caller holds on the console system * and the console driver list. * * While the console_lock was held, console output may have been buffered * by printk(). If this is the case, console_unlock(); emits * the output prior to releasing the lock. * * If there is output waiting, we wake /dev/kmsg and syslog() users. * * console_unlock(); may be called from any context. */ void console_unlock(void) { static char ext_text[CONSOLE_EXT_LOG_MAX]; static char text[LOG_LINE_MAX + PREFIX_MAX]; unsigned long flags; bool do_cond_resched, retry; if (console_suspended) { up_console_sem(); return; } /* * Console drivers are called with interrupts disabled, so * @console_may_schedule should be cleared before; however, we may * end up dumping a lot of lines, for example, if called from * console registration path, and should invoke cond_resched() * between lines if allowable. Not doing so can cause a very long * scheduling stall on a slow console leading to RCU stall and * softlockup warnings which exacerbate the issue with more * messages practically incapacitating the system. * * console_trylock() is not able to detect the preemptive * context reliably. Therefore the value must be stored before * and cleared after the the "again" goto label. */ do_cond_resched = console_may_schedule; again: console_may_schedule = 0; /* * We released the console_sem lock, so we need to recheck if * cpu is online and (if not) is there at least one CON_ANYTIME * console. */ if (!can_use_console()) { console_locked = 0; up_console_sem(); return; } for (;;) { struct printk_log *msg; size_t ext_len = 0; size_t len; printk_safe_enter_irqsave(flags); raw_spin_lock(&logbuf_lock); if (console_seq < log_first_seq) { len = sprintf(text, "** %llu printk messages dropped **\n", log_first_seq - console_seq); /* messages are gone, move to first one */ console_seq = log_first_seq; console_idx = log_first_idx; } else { len = 0; } skip: if (console_seq == log_next_seq) break; msg = log_from_idx(console_idx); if (suppress_message_printing(msg->level)) { /* * Skip record we have buffered and already printed * directly to the console when we received it, and * record that has level above the console loglevel. */ console_idx = log_next(console_idx); console_seq++; goto skip; } /* Output to all consoles once old messages replayed. */ if (unlikely(exclusive_console && console_seq >= exclusive_console_stop_seq)) { exclusive_console = NULL; } len += msg_print_text(msg, console_msg_format & MSG_FORMAT_SYSLOG, printk_time, text + len, sizeof(text) - len); if (nr_ext_console_drivers) { ext_len = msg_print_ext_header(ext_text, sizeof(ext_text), msg, console_seq); ext_len += msg_print_ext_body(ext_text + ext_len, sizeof(ext_text) - ext_len, log_dict(msg), msg->dict_len, log_text(msg), msg->text_len); } console_idx = log_next(console_idx); console_seq++; raw_spin_unlock(&logbuf_lock); /* * While actively printing out messages, if another printk() * were to occur on another CPU, it may wait for this one to * finish. This task can not be preempted if there is a * waiter waiting to take over. */ console_lock_spinning_enable(); stop_critical_timings(); /* don't trace print latency */ call_console_drivers(ext_text, ext_len, text, len); start_critical_timings(); if (console_lock_spinning_disable_and_check()) { printk_safe_exit_irqrestore(flags); return; } printk_safe_exit_irqrestore(flags); if (do_cond_resched) cond_resched(); } console_locked = 0; raw_spin_unlock(&logbuf_lock); up_console_sem(); /* * Someone could have filled up the buffer again, so re-check if there's * something to flush. In case we cannot trylock the console_sem again, * there's a new owner and the console_unlock() from them will do the * flush, no worries. */ raw_spin_lock(&logbuf_lock); retry = console_seq != log_next_seq; raw_spin_unlock(&logbuf_lock); printk_safe_exit_irqrestore(flags); if (retry && console_trylock()) goto again; } EXPORT_SYMBOL(console_unlock); /** * console_conditional_schedule - yield the CPU if required * * If the console code is currently allowed to sleep, and * if this CPU should yield the CPU to another task, do * so here. * * Must be called within console_lock();. */ void __sched console_conditional_schedule(void) { if (console_may_schedule) cond_resched(); } EXPORT_SYMBOL(console_conditional_schedule); void console_unblank(void) { struct console *c; /* * console_unblank can no longer be called in interrupt context unless * oops_in_progress is set to 1.. */ if (oops_in_progress) { if (down_trylock_console_sem() != 0) return; } else console_lock(); console_locked = 1; console_may_schedule = 0; for_each_console(c) if ((c->flags & CON_ENABLED) && c->unblank) c->unblank(); console_unlock(); } /** * console_flush_on_panic - flush console content on panic * * Immediately output all pending messages no matter what. */ void console_flush_on_panic(void) { /* * If someone else is holding the console lock, trylock will fail * and may_schedule may be set. Ignore and proceed to unlock so * that messages are flushed out. As this can be called from any * context and we don't want to get preempted while flushing, * ensure may_schedule is cleared. */ console_trylock(); console_may_schedule = 0; console_unlock(); } /* * Return the console tty driver structure and its associated index */ struct tty_driver *console_device(int *index) { struct console *c; struct tty_driver *driver = NULL; console_lock(); for_each_console(c) { if (!c->device) continue; driver = c->device(c, index); if (driver) break; } console_unlock(); return driver; } /* * Prevent further output on the passed console device so that (for example) * serial drivers can disable console output before suspending a port, and can * re-enable output afterwards. */ void console_stop(struct console *console) { console_lock(); console->flags &= ~CON_ENABLED; console_unlock(); } EXPORT_SYMBOL(console_stop); void console_start(struct console *console) { console_lock(); console->flags |= CON_ENABLED; console_unlock(); } EXPORT_SYMBOL(console_start); static int __read_mostly keep_bootcon; static int __init keep_bootcon_setup(char *str) { keep_bootcon = 1; pr_info("debug: skip boot console de-registration.\n"); return 0; } early_param("keep_bootcon", keep_bootcon_setup); /* * The console driver calls this routine during kernel initialization * to register the console printing procedure with printk() and to * print any messages that were printed by the kernel before the * console driver was initialized. * * This can happen pretty early during the boot process (because of * early_printk) - sometimes before setup_arch() completes - be careful * of what kernel features are used - they may not be initialised yet. * * There are two types of consoles - bootconsoles (early_printk) and * "real" consoles (everything which is not a bootconsole) which are * handled differently. * - Any number of bootconsoles can be registered at any time. * - As soon as a "real" console is registered, all bootconsoles * will be unregistered automatically. * - Once a "real" console is registered, any attempt to register a * bootconsoles will be rejected */ void register_console(struct console *newcon) { int i; unsigned long flags; struct console *bcon = NULL; struct console_cmdline *c; static bool has_preferred; if (console_drivers) for_each_console(bcon) if (WARN(bcon == newcon, "console '%s%d' already registered\n", bcon->name, bcon->index)) return; /* * before we register a new CON_BOOT console, make sure we don't * already have a valid console */ if (console_drivers && newcon->flags & CON_BOOT) { /* find the last or real console */ for_each_console(bcon) { if (!(bcon->flags & CON_BOOT)) { pr_info("Too late to register bootconsole %s%d\n", newcon->name, newcon->index); return; } } } if (console_drivers && console_drivers->flags & CON_BOOT) bcon = console_drivers; if (!has_preferred || bcon || !console_drivers) has_preferred = preferred_console >= 0; /* * See if we want to use this console driver. If we * didn't select a console we take the first one * that registers here. */ if (!has_preferred) { if (newcon->index < 0) newcon->index = 0; if (newcon->setup == NULL || newcon->setup(newcon, NULL) == 0) { newcon->flags |= CON_ENABLED; if (newcon->device) { newcon->flags |= CON_CONSDEV; has_preferred = true; } } } /* * See if this console matches one we selected on * the command line. */ for (i = 0, c = console_cmdline; i < MAX_CMDLINECONSOLES && c->name[0]; i++, c++) { if (!newcon->match || newcon->match(newcon, c->name, c->index, c->options) != 0) { /* default matching */ BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name)); if (strcmp(c->name, newcon->name) != 0) continue; if (newcon->index >= 0 && newcon->index != c->index) continue; if (newcon->index < 0) newcon->index = c->index; if (_braille_register_console(newcon, c)) return; if (newcon->setup && newcon->setup(newcon, c->options) != 0) break; } newcon->flags |= CON_ENABLED; if (i == preferred_console) { newcon->flags |= CON_CONSDEV; has_preferred = true; } break; } if (!(newcon->flags & CON_ENABLED)) return; /* * If we have a bootconsole, and are switching to a real console, * don't print everything out again, since when the boot console, and * the real console are the same physical device, it's annoying to * see the beginning boot messages twice */ if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) newcon->flags &= ~CON_PRINTBUFFER; /* * Put this console in the list - keep the * preferred driver at the head of the list. */ console_lock(); if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) { newcon->next = console_drivers; console_drivers = newcon; if (newcon->next) newcon->next->flags &= ~CON_CONSDEV; } else { newcon->next = console_drivers->next; console_drivers->next = newcon; } if (newcon->flags & CON_EXTENDED) nr_ext_console_drivers++; if (newcon->flags & CON_PRINTBUFFER) { /* * console_unlock(); will print out the buffered messages * for us. */ logbuf_lock_irqsave(flags); console_seq = syslog_seq; console_idx = syslog_idx; /* * We're about to replay the log buffer. Only do this to the * just-registered console to avoid excessive message spam to * the already-registered consoles. * * Set exclusive_console with disabled interrupts to reduce * race window with eventual console_flush_on_panic() that * ignores console_lock. */ exclusive_console = newcon; exclusive_console_stop_seq = console_seq; logbuf_unlock_irqrestore(flags); } console_unlock(); console_sysfs_notify(); /* * By unregistering the bootconsoles after we enable the real console * we get the "console xxx enabled" message on all the consoles - * boot consoles, real consoles, etc - this is to ensure that end * users know there might be something in the kernel's log buffer that * went to the bootconsole (that they do not see on the real console) */ pr_info("%sconsole [%s%d] enabled\n", (newcon->flags & CON_BOOT) ? "boot" : "" , newcon->name, newcon->index); if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) && !keep_bootcon) { /* We need to iterate through all boot consoles, to make * sure we print everything out, before we unregister them. */ for_each_console(bcon) if (bcon->flags & CON_BOOT) unregister_console(bcon); } } EXPORT_SYMBOL(register_console); int unregister_console(struct console *console) { struct console *a, *b; int res; pr_info("%sconsole [%s%d] disabled\n", (console->flags & CON_BOOT) ? "boot" : "" , console->name, console->index); res = _braille_unregister_console(console); if (res) return res; res = 1; console_lock(); if (console_drivers == console) { console_drivers=console->next; res = 0; } else if (console_drivers) { for (a=console_drivers->next, b=console_drivers ; a; b=a, a=b->next) { if (a == console) { b->next = a->next; res = 0; break; } } } if (!res && (console->flags & CON_EXTENDED)) nr_ext_console_drivers--; /* * If this isn't the last console and it has CON_CONSDEV set, we * need to set it on the next preferred console. */ if (console_drivers != NULL && console->flags & CON_CONSDEV) console_drivers->flags |= CON_CONSDEV; console->flags &= ~CON_ENABLED; console_unlock(); console_sysfs_notify(); return res; } EXPORT_SYMBOL(unregister_console); /* * Initialize the console device. This is called *early*, so * we can't necessarily depend on lots of kernel help here. * Just do some early initializations, and do the complex setup * later. */ void __init console_init(void) { int ret; initcall_t call; initcall_entry_t *ce; /* Setup the default TTY line discipline. */ n_tty_init(); /* * set up the console device so that later boot sequences can * inform about problems etc.. */ ce = __con_initcall_start; trace_initcall_level("console"); while (ce < __con_initcall_end) { call = initcall_from_entry(ce); trace_initcall_start(call); ret = call(); trace_initcall_finish(call, ret); ce++; } } /* * Some boot consoles access data that is in the init section and which will * be discarded after the initcalls have been run. To make sure that no code * will access this data, unregister the boot consoles in a late initcall. * * If for some reason, such as deferred probe or the driver being a loadable * module, the real console hasn't registered yet at this point, there will * be a brief interval in which no messages are logged to the console, which * makes it difficult to diagnose problems that occur during this time. * * To mitigate this problem somewhat, only unregister consoles whose memory * intersects with the init section. Note that all other boot consoles will * get unregistred when the real preferred console is registered. */ static int __init printk_late_init(void) { struct console *con; int ret; for_each_console(con) { if (!(con->flags & CON_BOOT)) continue; /* Check addresses that might be used for enabled consoles. */ if (init_section_intersects(con, sizeof(*con)) || init_section_contains(con->write, 0) || init_section_contains(con->read, 0) || init_section_contains(con->device, 0) || init_section_contains(con->unblank, 0) || init_section_contains(con->data, 0)) { /* * Please, consider moving the reported consoles out * of the init section. */ pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n", con->name, con->index); unregister_console(con); } } ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL, console_cpu_notify); WARN_ON(ret < 0); ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online", console_cpu_notify, NULL); WARN_ON(ret < 0); return 0; } late_initcall(printk_late_init); #if defined CONFIG_PRINTK /* * Delayed printk version, for scheduler-internal messages: */ #define PRINTK_PENDING_WAKEUP 0x01 #define PRINTK_PENDING_OUTPUT 0x02 static DEFINE_PER_CPU(int, printk_pending); static void wake_up_klogd_work_func(struct irq_work *irq_work) { int pending = __this_cpu_xchg(printk_pending, 0); if (pending & PRINTK_PENDING_OUTPUT) { /* If trylock fails, someone else is doing the printing */ if (console_trylock()) console_unlock(); } if (pending & PRINTK_PENDING_WAKEUP) wake_up_interruptible(&log_wait); } static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = { .func = wake_up_klogd_work_func, .flags = IRQ_WORK_LAZY, }; void wake_up_klogd(void) { preempt_disable(); if (waitqueue_active(&log_wait)) { this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP); irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); } preempt_enable(); } void defer_console_output(void) { preempt_disable(); __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT); irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); preempt_enable(); } int vprintk_deferred(const char *fmt, va_list args) { int r; r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args); defer_console_output(); return r; } int printk_deferred(const char *fmt, ...) { va_list args; int r; va_start(args, fmt); r = vprintk_deferred(fmt, args); va_end(args); return r; } /* * printk rate limiting, lifted from the networking subsystem. * * This enforces a rate limit: not more than 10 kernel messages * every 5s to make a denial-of-service attack impossible. */ DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10); int __printk_ratelimit(const char *func) { return ___ratelimit(&printk_ratelimit_state, func); } EXPORT_SYMBOL(__printk_ratelimit); /** * printk_timed_ratelimit - caller-controlled printk ratelimiting * @caller_jiffies: pointer to caller's state * @interval_msecs: minimum interval between prints * * printk_timed_ratelimit() returns true if more than @interval_msecs * milliseconds have elapsed since the last time printk_timed_ratelimit() * returned true. */ bool printk_timed_ratelimit(unsigned long *caller_jiffies, unsigned int interval_msecs) { unsigned long elapsed = jiffies - *caller_jiffies; if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs)) return false; *caller_jiffies = jiffies; return true; } EXPORT_SYMBOL(printk_timed_ratelimit); static DEFINE_SPINLOCK(dump_list_lock); static LIST_HEAD(dump_list); /** * kmsg_dump_register - register a kernel log dumper. * @dumper: pointer to the kmsg_dumper structure * * Adds a kernel log dumper to the system. The dump callback in the * structure will be called when the kernel oopses or panics and must be * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise. */ int kmsg_dump_register(struct kmsg_dumper *dumper) { unsigned long flags; int err = -EBUSY; /* The dump callback needs to be set */ if (!dumper->dump) return -EINVAL; spin_lock_irqsave(&dump_list_lock, flags); /* Don't allow registering multiple times */ if (!dumper->registered) { dumper->registered = 1; list_add_tail_rcu(&dumper->list, &dump_list); err = 0; } spin_unlock_irqrestore(&dump_list_lock, flags); return err; } EXPORT_SYMBOL_GPL(kmsg_dump_register); /** * kmsg_dump_unregister - unregister a kmsg dumper. * @dumper: pointer to the kmsg_dumper structure * * Removes a dump device from the system. Returns zero on success and * %-EINVAL otherwise. */ int kmsg_dump_unregister(struct kmsg_dumper *dumper) { unsigned long flags; int err = -EINVAL; spin_lock_irqsave(&dump_list_lock, flags); if (dumper->registered) { dumper->registered = 0; list_del_rcu(&dumper->list); err = 0; } spin_unlock_irqrestore(&dump_list_lock, flags); synchronize_rcu(); return err; } EXPORT_SYMBOL_GPL(kmsg_dump_unregister); static bool always_kmsg_dump; module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR); /** * kmsg_dump - dump kernel log to kernel message dumpers. * @reason: the reason (oops, panic etc) for dumping * * Call each of the registered dumper's dump() callback, which can * retrieve the kmsg records with kmsg_dump_get_line() or * kmsg_dump_get_buffer(). */ void kmsg_dump(enum kmsg_dump_reason reason) { struct kmsg_dumper *dumper; unsigned long flags; if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump) return; rcu_read_lock(); list_for_each_entry_rcu(dumper, &dump_list, list) { if (dumper->max_reason && reason > dumper->max_reason) continue; /* initialize iterator with data about the stored records */ dumper->active = true; logbuf_lock_irqsave(flags); dumper->cur_seq = clear_seq; dumper->cur_idx = clear_idx; dumper->next_seq = log_next_seq; dumper->next_idx = log_next_idx; logbuf_unlock_irqrestore(flags); /* invoke dumper which will iterate over records */ dumper->dump(dumper, reason); /* reset iterator */ dumper->active = false; } rcu_read_unlock(); } /** * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version) * @dumper: registered kmsg dumper * @syslog: include the "<4>" prefixes * @line: buffer to copy the line to * @size: maximum size of the buffer * @len: length of line placed into buffer * * Start at the beginning of the kmsg buffer, with the oldest kmsg * record, and copy one record into the provided buffer. * * Consecutive calls will return the next available record moving * towards the end of the buffer with the youngest messages. * * A return value of FALSE indicates that there are no more records to * read. * * The function is similar to kmsg_dump_get_line(), but grabs no locks. */ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog, char *line, size_t size, size_t *len) { struct printk_log *msg; size_t l = 0; bool ret = false; if (!dumper->active) goto out; if (dumper->cur_seq < log_first_seq) { /* messages are gone, move to first available one */ dumper->cur_seq = log_first_seq; dumper->cur_idx = log_first_idx; } /* last entry */ if (dumper->cur_seq >= log_next_seq) goto out; msg = log_from_idx(dumper->cur_idx); l = msg_print_text(msg, syslog, printk_time, line, size); dumper->cur_idx = log_next(dumper->cur_idx); dumper->cur_seq++; ret = true; out: if (len) *len = l; return ret; } /** * kmsg_dump_get_line - retrieve one kmsg log line * @dumper: registered kmsg dumper * @syslog: include the "<4>" prefixes * @line: buffer to copy the line to * @size: maximum size of the buffer * @len: length of line placed into buffer * * Start at the beginning of the kmsg buffer, with the oldest kmsg * record, and copy one record into the provided buffer. * * Consecutive calls will return the next available record moving * towards the end of the buffer with the youngest messages. * * A return value of FALSE indicates that there are no more records to * read. */ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog, char *line, size_t size, size_t *len) { unsigned long flags; bool ret; logbuf_lock_irqsave(flags); ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len); logbuf_unlock_irqrestore(flags); return ret; } EXPORT_SYMBOL_GPL(kmsg_dump_get_line); /** * kmsg_dump_get_buffer - copy kmsg log lines * @dumper: registered kmsg dumper * @syslog: include the "<4>" prefixes * @buf: buffer to copy the line to * @size: maximum size of the buffer * @len: length of line placed into buffer * * Start at the end of the kmsg buffer and fill the provided buffer * with as many of the the *youngest* kmsg records that fit into it. * If the buffer is large enough, all available kmsg records will be * copied with a single call. * * Consecutive calls will fill the buffer with the next block of * available older records, not including the earlier retrieved ones. * * A return value of FALSE indicates that there are no more records to * read. */ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, char *buf, size_t size, size_t *len) { unsigned long flags; u64 seq; u32 idx; u64 next_seq; u32 next_idx; size_t l = 0; bool ret = false; bool time = printk_time; if (!dumper->active) goto out; logbuf_lock_irqsave(flags); if (dumper->cur_seq < log_first_seq) { /* messages are gone, move to first available one */ dumper->cur_seq = log_first_seq; dumper->cur_idx = log_first_idx; } /* last entry */ if (dumper->cur_seq >= dumper->next_seq) { logbuf_unlock_irqrestore(flags); goto out; } /* calculate length of entire buffer */ seq = dumper->cur_seq; idx = dumper->cur_idx; while (seq < dumper->next_seq) { struct printk_log *msg = log_from_idx(idx); l += msg_print_text(msg, true, time, NULL, 0); idx = log_next(idx); seq++; } /* move first record forward until length fits into the buffer */ seq = dumper->cur_seq; idx = dumper->cur_idx; while (l > size && seq < dumper->next_seq) { struct printk_log *msg = log_from_idx(idx); l -= msg_print_text(msg, true, time, NULL, 0); idx = log_next(idx); seq++; } /* last message in next interation */ next_seq = seq; next_idx = idx; l = 0; while (seq < dumper->next_seq) { struct printk_log *msg = log_from_idx(idx); l += msg_print_text(msg, syslog, time, buf + l, size - l); idx = log_next(idx); seq++; } dumper->next_seq = next_seq; dumper->next_idx = next_idx; ret = true; logbuf_unlock_irqrestore(flags); out: if (len) *len = l; return ret; } EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); /** * kmsg_dump_rewind_nolock - reset the interator (unlocked version) * @dumper: registered kmsg dumper * * Reset the dumper's iterator so that kmsg_dump_get_line() and * kmsg_dump_get_buffer() can be called again and used multiple * times within the same dumper.dump() callback. * * The function is similar to kmsg_dump_rewind(), but grabs no locks. */ void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper) { dumper->cur_seq = clear_seq; dumper->cur_idx = clear_idx; dumper->next_seq = log_next_seq; dumper->next_idx = log_next_idx; } /** * kmsg_dump_rewind - reset the interator * @dumper: registered kmsg dumper * * Reset the dumper's iterator so that kmsg_dump_get_line() and * kmsg_dump_get_buffer() can be called again and used multiple * times within the same dumper.dump() callback. */ void kmsg_dump_rewind(struct kmsg_dumper *dumper) { unsigned long flags; logbuf_lock_irqsave(flags); kmsg_dump_rewind_nolock(dumper); logbuf_unlock_irqrestore(flags); } EXPORT_SYMBOL_GPL(kmsg_dump_rewind); #endif
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