| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Pekka Paalanen | 1621 | 74.49% | 12 | 35.29% |
| Karol Herbst | 212 | 9.74% | 2 | 5.88% |
| Stuart Bennett | 201 | 9.24% | 7 | 20.59% |
| Marcin Ślusarz | 37 | 1.70% | 1 | 2.94% |
| Andi Kleen | 34 | 1.56% | 1 | 2.94% |
| Joe Perches | 23 | 1.06% | 1 | 2.94% |
| Luca Barbieri | 22 | 1.01% | 1 | 2.94% |
| Ingo Molnar | 9 | 0.41% | 2 | 5.88% |
| K.Prasad | 8 | 0.37% | 1 | 2.94% |
| Tejun Heo | 3 | 0.14% | 1 | 2.94% |
| André Goddard Rosa | 2 | 0.09% | 1 | 2.94% |
| Shaun Patterson | 1 | 0.05% | 1 | 2.94% |
| Andrew Lutomirski | 1 | 0.05% | 1 | 2.94% |
| Greg Kroah-Hartman | 1 | 0.05% | 1 | 2.94% |
| Paul Gortmaker | 1 | 0.05% | 1 | 2.94% |
| Total | 2176 | 34 |
// SPDX-License-Identifier: GPL-2.0 /* Support for MMIO probes. * Benfit many code from kprobes * (C) 2002 Louis Zhuang <louis.zhuang@intel.com>. * 2007 Alexander Eichner * 2008 Pekka Paalanen <pq@iki.fi> */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/list.h> #include <linux/rculist.h> #include <linux/spinlock.h> #include <linux/hash.h> #include <linux/export.h> #include <linux/kernel.h> #include <linux/uaccess.h> #include <linux/ptrace.h> #include <linux/preempt.h> #include <linux/percpu.h> #include <linux/kdebug.h> #include <linux/mutex.h> #include <linux/io.h> #include <linux/slab.h> #include <asm/cacheflush.h> #include <asm/tlbflush.h> #include <linux/errno.h> #include <asm/debugreg.h> #include <linux/mmiotrace.h> #define KMMIO_PAGE_HASH_BITS 4 #define KMMIO_PAGE_TABLE_SIZE (1 << KMMIO_PAGE_HASH_BITS) struct kmmio_fault_page { struct list_head list; struct kmmio_fault_page *release_next; unsigned long addr; /* the requested address */ pteval_t old_presence; /* page presence prior to arming */ bool armed; /* * Number of times this page has been registered as a part * of a probe. If zero, page is disarmed and this may be freed. * Used only by writers (RCU) and post_kmmio_handler(). * Protected by kmmio_lock, when linked into kmmio_page_table. */ int count; bool scheduled_for_release; }; struct kmmio_delayed_release { struct rcu_head rcu; struct kmmio_fault_page *release_list; }; struct kmmio_context { struct kmmio_fault_page *fpage; struct kmmio_probe *probe; unsigned long saved_flags; unsigned long addr; int active; }; static DEFINE_SPINLOCK(kmmio_lock); /* Protected by kmmio_lock */ unsigned int kmmio_count; /* Read-protected by RCU, write-protected by kmmio_lock. */ static struct list_head kmmio_page_table[KMMIO_PAGE_TABLE_SIZE]; static LIST_HEAD(kmmio_probes); static struct list_head *kmmio_page_list(unsigned long addr) { unsigned int l; pte_t *pte = lookup_address(addr, &l); if (!pte) return NULL; addr &= page_level_mask(l); return &kmmio_page_table[hash_long(addr, KMMIO_PAGE_HASH_BITS)]; } /* Accessed per-cpu */ static DEFINE_PER_CPU(struct kmmio_context, kmmio_ctx); /* * this is basically a dynamic stabbing problem: * Could use the existing prio tree code or * Possible better implementations: * The Interval Skip List: A Data Structure for Finding All Intervals That * Overlap a Point (might be simple) * Space Efficient Dynamic Stabbing with Fast Queries - Mikkel Thorup */ /* Get the kmmio at this addr (if any). You must be holding RCU read lock. */ static struct kmmio_probe *get_kmmio_probe(unsigned long addr) { struct kmmio_probe *p; list_for_each_entry_rcu(p, &kmmio_probes, list) { if (addr >= p->addr && addr < (p->addr + p->len)) return p; } return NULL; } /* You must be holding RCU read lock. */ static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long addr) { struct list_head *head; struct kmmio_fault_page *f; unsigned int l; pte_t *pte = lookup_address(addr, &l); if (!pte) return NULL; addr &= page_level_mask(l); head = kmmio_page_list(addr); list_for_each_entry_rcu(f, head, list) { if (f->addr == addr) return f; } return NULL; } static void clear_pmd_presence(pmd_t *pmd, bool clear, pmdval_t *old) { pmd_t new_pmd; pmdval_t v = pmd_val(*pmd); if (clear) { *old = v; new_pmd = pmd_mknotpresent(*pmd); } else { /* Presume this has been called with clear==true previously */ new_pmd = __pmd(*old); } set_pmd(pmd, new_pmd); } static void clear_pte_presence(pte_t *pte, bool clear, pteval_t *old) { pteval_t v = pte_val(*pte); if (clear) { *old = v; /* Nothing should care about address */ pte_clear(&init_mm, 0, pte); } else { /* Presume this has been called with clear==true previously */ set_pte_atomic(pte, __pte(*old)); } } static int clear_page_presence(struct kmmio_fault_page *f, bool clear) { unsigned int level; pte_t *pte = lookup_address(f->addr, &level); if (!pte) { pr_err("no pte for addr 0x%08lx\n", f->addr); return -1; } switch (level) { case PG_LEVEL_2M: clear_pmd_presence((pmd_t *)pte, clear, &f->old_presence); break; case PG_LEVEL_4K: clear_pte_presence(pte, clear, &f->old_presence); break; default: pr_err("unexpected page level 0x%x.\n", level); return -1; } __flush_tlb_one_kernel(f->addr); return 0; } /* * Mark the given page as not present. Access to it will trigger a fault. * * Struct kmmio_fault_page is protected by RCU and kmmio_lock, but the * protection is ignored here. RCU read lock is assumed held, so the struct * will not disappear unexpectedly. Furthermore, the caller must guarantee, * that double arming the same virtual address (page) cannot occur. * * Double disarming on the other hand is allowed, and may occur when a fault * and mmiotrace shutdown happen simultaneously. */ static int arm_kmmio_fault_page(struct kmmio_fault_page *f) { int ret; WARN_ONCE(f->armed, KERN_ERR pr_fmt("kmmio page already armed.\n")); if (f->armed) { pr_warning("double-arm: addr 0x%08lx, ref %d, old %d\n", f->addr, f->count, !!f->old_presence); } ret = clear_page_presence(f, true); WARN_ONCE(ret < 0, KERN_ERR pr_fmt("arming at 0x%08lx failed.\n"), f->addr); f->armed = true; return ret; } /** Restore the given page to saved presence state. */ static void disarm_kmmio_fault_page(struct kmmio_fault_page *f) { int ret = clear_page_presence(f, false); WARN_ONCE(ret < 0, KERN_ERR "kmmio disarming at 0x%08lx failed.\n", f->addr); f->armed = false; } /* * This is being called from do_page_fault(). * * We may be in an interrupt or a critical section. Also prefecthing may * trigger a page fault. We may be in the middle of process switch. * We cannot take any locks, because we could be executing especially * within a kmmio critical section. * * Local interrupts are disabled, so preemption cannot happen. * Do not enable interrupts, do not sleep, and watch out for other CPUs. */ /* * Interrupts are disabled on entry as trap3 is an interrupt gate * and they remain disabled throughout this function. */ int kmmio_handler(struct pt_regs *regs, unsigned long addr) { struct kmmio_context *ctx; struct kmmio_fault_page *faultpage; int ret = 0; /* default to fault not handled */ unsigned long page_base = addr; unsigned int l; pte_t *pte = lookup_address(addr, &l); if (!pte) return -EINVAL; page_base &= page_level_mask(l); /* * Preemption is now disabled to prevent process switch during * single stepping. We can only handle one active kmmio trace * per cpu, so ensure that we finish it before something else * gets to run. We also hold the RCU read lock over single * stepping to avoid looking up the probe and kmmio_fault_page * again. */ preempt_disable(); rcu_read_lock(); faultpage = get_kmmio_fault_page(page_base); if (!faultpage) { /* * Either this page fault is not caused by kmmio, or * another CPU just pulled the kmmio probe from under * our feet. The latter case should not be possible. */ goto no_kmmio; } ctx = &get_cpu_var(kmmio_ctx); if (ctx->active) { if (page_base == ctx->addr) { /* * A second fault on the same page means some other * condition needs handling by do_page_fault(), the * page really not being present is the most common. */ pr_debug("secondary hit for 0x%08lx CPU %d.\n", addr, smp_processor_id()); if (!faultpage->old_presence) pr_info("unexpected secondary hit for address 0x%08lx on CPU %d.\n", addr, smp_processor_id()); } else { /* * Prevent overwriting already in-flight context. * This should not happen, let's hope disarming at * least prevents a panic. */ pr_emerg("recursive probe hit on CPU %d, for address 0x%08lx. Ignoring.\n", smp_processor_id(), addr); pr_emerg("previous hit was at 0x%08lx.\n", ctx->addr); disarm_kmmio_fault_page(faultpage); } goto no_kmmio_ctx; } ctx->active++; ctx->fpage = faultpage; ctx->probe = get_kmmio_probe(page_base); ctx->saved_flags = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF)); ctx->addr = page_base; if (ctx->probe && ctx->probe->pre_handler) ctx->probe->pre_handler(ctx->probe, regs, addr); /* * Enable single-stepping and disable interrupts for the faulting * context. Local interrupts must not get enabled during stepping. */ regs->flags |= X86_EFLAGS_TF; regs->flags &= ~X86_EFLAGS_IF; /* Now we set present bit in PTE and single step. */ disarm_kmmio_fault_page(ctx->fpage); /* * If another cpu accesses the same page while we are stepping, * the access will not be caught. It will simply succeed and the * only downside is we lose the event. If this becomes a problem, * the user should drop to single cpu before tracing. */ put_cpu_var(kmmio_ctx); return 1; /* fault handled */ no_kmmio_ctx: put_cpu_var(kmmio_ctx); no_kmmio: rcu_read_unlock(); preempt_enable_no_resched(); return ret; } /* * Interrupts are disabled on entry as trap1 is an interrupt gate * and they remain disabled throughout this function. * This must always get called as the pair to kmmio_handler(). */ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs) { int ret = 0; struct kmmio_context *ctx = &get_cpu_var(kmmio_ctx); if (!ctx->active) { /* * debug traps without an active context are due to either * something external causing them (f.e. using a debugger while * mmio tracing enabled), or erroneous behaviour */ pr_warning("unexpected debug trap on CPU %d.\n", smp_processor_id()); goto out; } if (ctx->probe && ctx->probe->post_handler) ctx->probe->post_handler(ctx->probe, condition, regs); /* Prevent racing against release_kmmio_fault_page(). */ spin_lock(&kmmio_lock); if (ctx->fpage->count) arm_kmmio_fault_page(ctx->fpage); spin_unlock(&kmmio_lock); regs->flags &= ~X86_EFLAGS_TF; regs->flags |= ctx->saved_flags; /* These were acquired in kmmio_handler(). */ ctx->active--; BUG_ON(ctx->active); rcu_read_unlock(); preempt_enable_no_resched(); /* * if somebody else is singlestepping across a probe point, flags * will have TF set, in which case, continue the remaining processing * of do_debug, as if this is not a probe hit. */ if (!(regs->flags & X86_EFLAGS_TF)) ret = 1; out: put_cpu_var(kmmio_ctx); return ret; } /* You must be holding kmmio_lock. */ static int add_kmmio_fault_page(unsigned long addr) { struct kmmio_fault_page *f; f = get_kmmio_fault_page(addr); if (f) { if (!f->count) arm_kmmio_fault_page(f); f->count++; return 0; } f = kzalloc(sizeof(*f), GFP_ATOMIC); if (!f) return -1; f->count = 1; f->addr = addr; if (arm_kmmio_fault_page(f)) { kfree(f); return -1; } list_add_rcu(&f->list, kmmio_page_list(f->addr)); return 0; } /* You must be holding kmmio_lock. */ static void release_kmmio_fault_page(unsigned long addr, struct kmmio_fault_page **release_list) { struct kmmio_fault_page *f; f = get_kmmio_fault_page(addr); if (!f) return; f->count--; BUG_ON(f->count < 0); if (!f->count) { disarm_kmmio_fault_page(f); if (!f->scheduled_for_release) { f->release_next = *release_list; *release_list = f; f->scheduled_for_release = true; } } } /* * With page-unaligned ioremaps, one or two armed pages may contain * addresses from outside the intended mapping. Events for these addresses * are currently silently dropped. The events may result only from programming * mistakes by accessing addresses before the beginning or past the end of a * mapping. */ int register_kmmio_probe(struct kmmio_probe *p) { unsigned long flags; int ret = 0; unsigned long size = 0; unsigned long addr = p->addr & PAGE_MASK; const unsigned long size_lim = p->len + (p->addr & ~PAGE_MASK); unsigned int l; pte_t *pte; spin_lock_irqsave(&kmmio_lock, flags); if (get_kmmio_probe(addr)) { ret = -EEXIST; goto out; } pte = lookup_address(addr, &l); if (!pte) { ret = -EINVAL; goto out; } kmmio_count++; list_add_rcu(&p->list, &kmmio_probes); while (size < size_lim) { if (add_kmmio_fault_page(addr + size)) pr_err("Unable to set page fault.\n"); size += page_level_size(l); } out: spin_unlock_irqrestore(&kmmio_lock, flags); /* * XXX: What should I do here? * Here was a call to global_flush_tlb(), but it does not exist * anymore. It seems it's not needed after all. */ return ret; } EXPORT_SYMBOL(register_kmmio_probe); static void rcu_free_kmmio_fault_pages(struct rcu_head *head) { struct kmmio_delayed_release *dr = container_of( head, struct kmmio_delayed_release, rcu); struct kmmio_fault_page *f = dr->release_list; while (f) { struct kmmio_fault_page *next = f->release_next; BUG_ON(f->count); kfree(f); f = next; } kfree(dr); } static void remove_kmmio_fault_pages(struct rcu_head *head) { struct kmmio_delayed_release *dr = container_of(head, struct kmmio_delayed_release, rcu); struct kmmio_fault_page *f = dr->release_list; struct kmmio_fault_page **prevp = &dr->release_list; unsigned long flags; spin_lock_irqsave(&kmmio_lock, flags); while (f) { if (!f->count) { list_del_rcu(&f->list); prevp = &f->release_next; } else { *prevp = f->release_next; f->release_next = NULL; f->scheduled_for_release = false; } f = *prevp; } spin_unlock_irqrestore(&kmmio_lock, flags); /* This is the real RCU destroy call. */ call_rcu(&dr->rcu, rcu_free_kmmio_fault_pages); } /* * Remove a kmmio probe. You have to synchronize_rcu() before you can be * sure that the callbacks will not be called anymore. Only after that * you may actually release your struct kmmio_probe. * * Unregistering a kmmio fault page has three steps: * 1. release_kmmio_fault_page() * Disarm the page, wait a grace period to let all faults finish. * 2. remove_kmmio_fault_pages() * Remove the pages from kmmio_page_table. * 3. rcu_free_kmmio_fault_pages() * Actually free the kmmio_fault_page structs as with RCU. */ void unregister_kmmio_probe(struct kmmio_probe *p) { unsigned long flags; unsigned long size = 0; unsigned long addr = p->addr & PAGE_MASK; const unsigned long size_lim = p->len + (p->addr & ~PAGE_MASK); struct kmmio_fault_page *release_list = NULL; struct kmmio_delayed_release *drelease; unsigned int l; pte_t *pte; pte = lookup_address(addr, &l); if (!pte) return; spin_lock_irqsave(&kmmio_lock, flags); while (size < size_lim) { release_kmmio_fault_page(addr + size, &release_list); size += page_level_size(l); } list_del_rcu(&p->list); kmmio_count--; spin_unlock_irqrestore(&kmmio_lock, flags); if (!release_list) return; drelease = kmalloc(sizeof(*drelease), GFP_ATOMIC); if (!drelease) { pr_crit("leaking kmmio_fault_page objects.\n"); return; } drelease->release_list = release_list; /* * This is not really RCU here. We have just disarmed a set of * pages so that they cannot trigger page faults anymore. However, * we cannot remove the pages from kmmio_page_table, * because a probe hit might be in flight on another CPU. The * pages are collected into a list, and they will be removed from * kmmio_page_table when it is certain that no probe hit related to * these pages can be in flight. RCU grace period sounds like a * good choice. * * If we removed the pages too early, kmmio page fault handler might * not find the respective kmmio_fault_page and determine it's not * a kmmio fault, when it actually is. This would lead to madness. */ call_rcu(&drelease->rcu, remove_kmmio_fault_pages); } EXPORT_SYMBOL(unregister_kmmio_probe); static int kmmio_die_notifier(struct notifier_block *nb, unsigned long val, void *args) { struct die_args *arg = args; unsigned long* dr6_p = (unsigned long *)ERR_PTR(arg->err); if (val == DIE_DEBUG && (*dr6_p & DR_STEP)) if (post_kmmio_handler(*dr6_p, arg->regs) == 1) { /* * Reset the BS bit in dr6 (pointed by args->err) to * denote completion of processing */ *dr6_p &= ~DR_STEP; return NOTIFY_STOP; } return NOTIFY_DONE; } static struct notifier_block nb_die = { .notifier_call = kmmio_die_notifier }; int kmmio_init(void) { int i; for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++) INIT_LIST_HEAD(&kmmio_page_table[i]); return register_die_notifier(&nb_die); } void kmmio_cleanup(void) { int i; unregister_die_notifier(&nb_die); for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++) { WARN_ONCE(!list_empty(&kmmio_page_table[i]), KERN_ERR "kmmio_page_table not empty at cleanup, any further tracing will leak memory.\n"); } }
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