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| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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| #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; |
| <------>pteval_t old_presence; |
| <------>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); |
| |
| |
| unsigned int kmmio_count; |
| |
| |
| 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)]; |
| } |
| |
| |
| static DEFINE_PER_CPU(struct kmmio_context, kmmio_ctx); |
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| 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; |
| } |
| |
| |
| 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_mkinvalid(*pmd); |
| <------>} else { |
| <------><------> |
| <------><------>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; |
| <------><------> |
| <------><------>pte_clear(&init_mm, 0, pte); |
| <------>} else { |
| <------><------> |
| <------><------>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; |
| } |
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| 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_warn("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; |
| } |
| |
| |
| 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; |
| } |
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| int kmmio_handler(struct pt_regs *regs, unsigned long addr) |
| { |
| <------>struct kmmio_context *ctx; |
| <------>struct kmmio_fault_page *faultpage; |
| <------>int ret = 0; |
| <------>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 = this_cpu_ptr(&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->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; |
| |
| <------> |
| <------>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. |
| <------> */ |
| |
| <------>return 1; |
| |
| no_kmmio: |
| <------>rcu_read_unlock(); |
| <------>preempt_enable_no_resched(); |
| <------>return ret; |
| } |
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| static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs) |
| { |
| <------>int ret = 0; |
| <------>struct kmmio_context *ctx = this_cpu_ptr(&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_warn("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); |
| |
| <------> |
| <------>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; |
| |
| <------> |
| <------>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: |
| <------>return ret; |
| } |
| |
| |
| 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; |
| } |
| |
| |
| 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; |
| <------><------>} |
| <------>} |
| } |
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| 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); |
| |
| <------> |
| <------>call_rcu(&dr->rcu, rcu_free_kmmio_fault_pages); |
| } |
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| 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"); |
| <------>} |
| } |
| |