/* * Kernel Probes (KProbes) * kernel/kprobes.c * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * Copyright (C) IBM Corporation, 2002, 2004 * * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel * Probes initial implementation (includes suggestions from * Rusty Russell). * 2004-Aug Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with * hlists and exceptions notifier as suggested by Andi Kleen. * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes * interface to access function arguments. * 2004-Sep Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes * exceptions notifier to be first on the priority list. * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi * <prasanna@in.ibm.com> added function-return probes. */ #include <linux/kprobes.h> #include <linux/hash.h> #include <linux/init.h> #include <linux/slab.h> #include <linux/module.h> #include <linux/moduleloader.h> #include <linux/kallsyms.h> #include <linux/freezer.h> #include <asm-generic/sections.h> #include <asm/cacheflush.h> #include <asm/errno.h> #include <asm/kdebug.h> #define KPROBE_HASH_BITS 6 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) /* * Some oddball architectures like 64bit powerpc have function descriptors * so this must be overridable. */ #ifndef kprobe_lookup_name #define kprobe_lookup_name(name, addr) \ addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name))) #endif static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE]; static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE]; static atomic_t kprobe_count; DEFINE_MUTEX(kprobe_mutex); /* Protects kprobe_table */ DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */ static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL; static struct notifier_block kprobe_page_fault_nb = { .notifier_call = kprobe_exceptions_notify, .priority = 0x7fffffff /* we need to notified first */ }; #ifdef __ARCH_WANT_KPROBES_INSN_SLOT /* * kprobe->ainsn.insn points to the copy of the instruction to be * single-stepped. x86_64, POWER4 and above have no-exec support and * stepping on the instruction on a vmalloced/kmalloced/data page * is a recipe for disaster */ #define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t))) struct kprobe_insn_page { struct hlist_node hlist; kprobe_opcode_t *insns; /* Page of instruction slots */ char slot_used[INSNS_PER_PAGE]; int nused; int ngarbage; }; static struct hlist_head kprobe_insn_pages; static int kprobe_garbage_slots; static int collect_garbage_slots(void); static int __kprobes check_safety(void) { int ret = 0; #if defined(CONFIG_PREEMPT) && defined(CONFIG_PM) ret = freeze_processes(); if (ret == 0) { struct task_struct *p, *q; do_each_thread(p, q) { if (p != current && p->state == TASK_RUNNING && p->pid != 0) { printk("Check failed: %s is running\n",p->comm); ret = -1; goto loop_end; } } while_each_thread(p, q); } loop_end: thaw_processes(); #else synchronize_sched(); #endif return ret; } /** * get_insn_slot() - Find a slot on an executable page for an instruction. * We allocate an executable page if there's no room on existing ones. */ kprobe_opcode_t __kprobes *get_insn_slot(void) { struct kprobe_insn_page *kip; struct hlist_node *pos; retry: hlist_for_each(pos, &kprobe_insn_pages) { kip = hlist_entry(pos, struct kprobe_insn_page, hlist); if (kip->nused < INSNS_PER_PAGE) { int i; for (i = 0; i < INSNS_PER_PAGE; i++) { if (!kip->slot_used[i]) { kip->slot_used[i] = 1; kip->nused++; return kip->insns + (i * MAX_INSN_SIZE); } } /* Surprise! No unused slots. Fix kip->nused. */ kip->nused = INSNS_PER_PAGE; } } /* If there are any garbage slots, collect it and try again. */ if (kprobe_garbage_slots && collect_garbage_slots() == 0) { goto retry; } /* All out of space. Need to allocate a new page. Use slot 0. */ kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL); if (!kip) { return NULL; } /* * Use module_alloc so this page is within +/- 2GB of where the * kernel image and loaded module images reside. This is required * so x86_64 can correctly handle the %rip-relative fixups. */ kip->insns = module_alloc(PAGE_SIZE); if (!kip->insns) { kfree(kip); return NULL; } INIT_HLIST_NODE(&kip->hlist); hlist_add_head(&kip->hlist, &kprobe_insn_pages); memset(kip->slot_used, 0, INSNS_PER_PAGE); kip->slot_used[0] = 1; kip->nused = 1; kip->ngarbage = 0; return kip->insns; } /* Return 1 if all garbages are collected, otherwise 0. */ static int __kprobes collect_one_slot(struct kprobe_insn_page *kip, int idx) { kip->slot_used[idx] = 0; kip->nused--; if (kip->nused == 0) { /* * Page is no longer in use. Free it unless * it's the last one. We keep the last one * so as not to have to set it up again the * next time somebody inserts a probe. */ hlist_del(&kip->hlist); if (hlist_empty(&kprobe_insn_pages)) { INIT_HLIST_NODE(&kip->hlist); hlist_add_head(&kip->hlist, &kprobe_insn_pages); } else { module_free(NULL, kip->insns); kfree(kip); } return 1; } return 0; } static int __kprobes collect_garbage_slots(void) { struct kprobe_insn_page *kip; struct hlist_node *pos, *next; /* Ensure no-one is preepmted on the garbages */ if (check_safety() != 0) return -EAGAIN; hlist_for_each_safe(pos, next, &kprobe_insn_pages) { int i; kip = hlist_entry(pos, struct kprobe_insn_page, hlist); if (kip->ngarbage == 0) continue; kip->ngarbage = 0; /* we will collect all garbages */ for (i = 0; i < INSNS_PER_PAGE; i++) { if (kip->slot_used[i] == -1 && collect_one_slot(kip, i)) break; } } kprobe_garbage_slots = 0; return 0; } void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty) { struct kprobe_insn_page *kip; struct hlist_node *pos; hlist_for_each(pos, &kprobe_insn_pages) { kip = hlist_entry(pos, struct kprobe_insn_page, hlist); if (kip->insns <= slot && slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) { int i = (slot - kip->insns) / MAX_INSN_SIZE; if (dirty) { kip->slot_used[i] = -1; kip->ngarbage++; } else { collect_one_slot(kip, i); } break; } } if (dirty && (++kprobe_garbage_slots > INSNS_PER_PAGE)) { collect_garbage_slots(); } } #endif /* We have preemption disabled.. so it is safe to use __ versions */ static inline void set_kprobe_instance(struct kprobe *kp) { __get_cpu_var(kprobe_instance) = kp; } static inline void reset_kprobe_instance(void) { __get_cpu_var(kprobe_instance) = NULL; } /* * This routine is called either: * - under the kprobe_mutex - during kprobe_[un]register() * OR * - with preemption disabled - from arch/xxx/kernel/kprobes.c */ struct kprobe __kprobes *get_kprobe(void *addr) { struct hlist_head *head; struct hlist_node *node; struct kprobe *p; head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)]; hlist_for_each_entry_rcu(p, node, head, hlist) { if (p->addr == addr) return p; } return NULL; } /* * Aggregate handlers for multiple kprobes support - these handlers * take care of invoking the individual kprobe handlers on p->list */ static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe *kp; list_for_each_entry_rcu(kp, &p->list, list) { if (kp->pre_handler) { set_kprobe_instance(kp); if (kp->pre_handler(kp, regs)) return 1; } reset_kprobe_instance(); } return 0; } static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs, unsigned long flags) { struct kprobe *kp; list_for_each_entry_rcu(kp, &p->list, list) { if (kp->post_handler) { set_kprobe_instance(kp); kp->post_handler(kp, regs, flags); reset_kprobe_instance(); } } return; } static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, int trapnr) { struct kprobe *cur = __get_cpu_var(kprobe_instance); /* * if we faulted "during" the execution of a user specified * probe handler, invoke just that probe's fault handler */ if (cur && cur->fault_handler) { if (cur->fault_handler(cur, regs, trapnr)) return 1; } return 0; } static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe *cur = __get_cpu_var(kprobe_instance); int ret = 0; if (cur && cur->break_handler) { if (cur->break_handler(cur, regs)) ret = 1; } reset_kprobe_instance(); return ret; } /* Walks the list and increments nmissed count for multiprobe case */ void __kprobes kprobes_inc_nmissed_count(struct kprobe *p) { struct kprobe *kp; if (p->pre_handler != aggr_pre_handler) { p->nmissed++; } else { list_for_each_entry_rcu(kp, &p->list, list) kp->nmissed++; } return; } /* Called with kretprobe_lock held */ struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp) { struct hlist_node *node; struct kretprobe_instance *ri; hlist_for_each_entry(ri, node, &rp->free_instances, uflist) return ri; return NULL; } /* Called with kretprobe_lock held */ static struct kretprobe_instance __kprobes *get_used_rp_inst(struct kretprobe *rp) { struct hlist_node *node; struct kretprobe_instance *ri; hlist_for_each_entry(ri, node, &rp->used_instances, uflist) return ri; return NULL; } /* Called with kretprobe_lock held */ void __kprobes add_rp_inst(struct kretprobe_instance *ri) { /* * Remove rp inst off the free list - * Add it back when probed function returns */ hlist_del(&ri->uflist); /* Add rp inst onto table */ INIT_HLIST_NODE(&ri->hlist); hlist_add_head(&ri->hlist, &kretprobe_inst_table[hash_ptr(ri->task, KPROBE_HASH_BITS)]); /* Also add this rp inst to the used list. */ INIT_HLIST_NODE(&ri->uflist); hlist_add_head(&ri->uflist, &ri->rp->used_instances); } /* Called with kretprobe_lock held */ void __kprobes recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head) { /* remove rp inst off the rprobe_inst_table */ hlist_del(&ri->hlist); if (ri->rp) { /* remove rp inst off the used list */ hlist_del(&ri->uflist); /* put rp inst back onto the free list */ INIT_HLIST_NODE(&ri->uflist); hlist_add_head(&ri->uflist, &ri->rp->free_instances); } else /* Unregistering */ hlist_add_head(&ri->hlist, head); } struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk) { return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)]; } /* * This function is called from finish_task_switch when task tk becomes dead, * so that we can recycle any function-return probe instances associated * with this task. These left over instances represent probed functions * that have been called but will never return. */ void __kprobes kprobe_flush_task(struct task_struct *tk) { struct kretprobe_instance *ri; struct hlist_head *head, empty_rp; struct hlist_node *node, *tmp; unsigned long flags = 0; INIT_HLIST_HEAD(&empty_rp); spin_lock_irqsave(&kretprobe_lock, flags); head = kretprobe_inst_table_head(tk); hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { if (ri->task == tk) recycle_rp_inst(ri, &empty_rp); } spin_unlock_irqrestore(&kretprobe_lock, flags); hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { hlist_del(&ri->hlist); kfree(ri); } } static inline void free_rp_inst(struct kretprobe *rp) { struct kretprobe_instance *ri; while ((ri = get_free_rp_inst(rp)) != NULL) { hlist_del(&ri->uflist); kfree(ri); } } /* * Keep all fields in the kprobe consistent */ static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p) { memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t)); memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn)); } /* * Add the new probe to old_p->list. Fail if this is the * second jprobe at the address - two jprobes can't coexist */ static int __kprobes add_new_kprobe(struct kprobe *old_p, struct kprobe *p) { if (p->break_handler) { if (old_p->break_handler) return -EEXIST; list_add_tail_rcu(&p->list, &old_p->list); old_p->break_handler = aggr_break_handler; } else list_add_rcu(&p->list, &old_p->list); if (p->post_handler && !old_p->post_handler) old_p->post_handler = aggr_post_handler; return 0; } /* * Fill in the required fields of the "manager kprobe". Replace the * earlier kprobe in the hlist with the manager kprobe */ static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p) { copy_kprobe(p, ap); flush_insn_slot(ap); ap->addr = p->addr; ap->pre_handler = aggr_pre_handler; ap->fault_handler = aggr_fault_handler; if (p->post_handler) ap->post_handler = aggr_post_handler; if (p->break_handler) ap->break_handler = aggr_break_handler; INIT_LIST_HEAD(&ap->list); list_add_rcu(&p->list, &ap->list); hlist_replace_rcu(&p->hlist, &ap->hlist); } /* * This is the second or subsequent kprobe at the address - handle * the intricacies */ static int __kprobes register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p) { int ret = 0; struct kprobe *ap; if (old_p->pre_handler == aggr_pre_handler) { copy_kprobe(old_p, p); ret = add_new_kprobe(old_p, p); } else { ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL); if (!ap) return -ENOMEM; add_aggr_kprobe(ap, old_p); copy_kprobe(ap, p); ret = add_new_kprobe(ap, p); } return ret; } static int __kprobes in_kprobes_functions(unsigned long addr) { if (addr >= (unsigned long)__kprobes_text_start && addr < (unsigned long)__kprobes_text_end) return -EINVAL; return 0; } static int __kprobes __register_kprobe(struct kprobe *p, unsigned long called_from) { int ret = 0; struct kprobe *old_p; struct module *probed_mod; /* * If we have a symbol_name argument look it up, * and add it to the address. That way the addr * field can either be global or relative to a symbol. */ if (p->symbol_name) { if (p->addr) return -EINVAL; kprobe_lookup_name(p->symbol_name, p->addr); } if (!p->addr) return -EINVAL; p->addr = (kprobe_opcode_t *)(((char *)p->addr)+ p->offset); if ((!kernel_text_address((unsigned long) p->addr)) || in_kprobes_functions((unsigned long) p->addr)) return -EINVAL; p->mod_refcounted = 0; /* Check are we probing a module */ if ((probed_mod = module_text_address((unsigned long) p->addr))) { struct module *calling_mod = module_text_address(called_from); /* We must allow modules to probe themself and * in this case avoid incrementing the module refcount, * so as to allow unloading of self probing modules. */ if (calling_mod && (calling_mod != probed_mod)) { if (unlikely(!try_module_get(probed_mod))) return -EINVAL; p->mod_refcounted = 1; } else probed_mod = NULL; } p->nmissed = 0; mutex_lock(&kprobe_mutex); old_p = get_kprobe(p->addr); if (old_p) { ret = register_aggr_kprobe(old_p, p); if (!ret) atomic_inc(&kprobe_count); goto out; } if ((ret = arch_prepare_kprobe(p)) != 0) goto out; INIT_HLIST_NODE(&p->hlist); hlist_add_head_rcu(&p->hlist, &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]); if (atomic_add_return(1, &kprobe_count) == \ (ARCH_INACTIVE_KPROBE_COUNT + 1)) register_page_fault_notifier(&kprobe_page_fault_nb); arch_arm_kprobe(p); out: mutex_unlock(&kprobe_mutex); if (ret && probed_mod) module_put(probed_mod); return ret; } int __kprobes register_kprobe(struct kprobe *p) { return __register_kprobe(p, (unsigned long)__builtin_return_address(0)); } void __kprobes unregister_kprobe(struct kprobe *p) { struct module *mod; struct kprobe *old_p, *list_p; int cleanup_p; mutex_lock(&kprobe_mutex); old_p = get_kprobe(p->addr); if (unlikely(!old_p)) { mutex_unlock(&kprobe_mutex); return; } if (p != old_p) { list_for_each_entry_rcu(list_p, &old_p->list, list) if (list_p == p) /* kprobe p is a valid probe */ goto valid_p; mutex_unlock(&kprobe_mutex); return; } valid_p: if ((old_p == p) || ((old_p->pre_handler == aggr_pre_handler) && (p->list.next == &old_p->list) && (p->list.prev == &old_p->list))) { /* Only probe on the hash list */ arch_disarm_kprobe(p); hlist_del_rcu(&old_p->hlist); cleanup_p = 1; } else { list_del_rcu(&p->list); cleanup_p = 0; } mutex_unlock(&kprobe_mutex); synchronize_sched(); if (p->mod_refcounted && (mod = module_text_address((unsigned long)p->addr))) module_put(mod); if (cleanup_p) { if (p != old_p) { list_del_rcu(&p->list); kfree(old_p); } arch_remove_kprobe(p); } else { mutex_lock(&kprobe_mutex); if (p->break_handler) old_p->break_handler = NULL; if (p->post_handler){ list_for_each_entry_rcu(list_p, &old_p->list, list){ if (list_p->post_handler){ cleanup_p = 2; break; } } if (cleanup_p == 0) old_p->post_handler = NULL; } mutex_unlock(&kprobe_mutex); } /* Call unregister_page_fault_notifier() * if no probes are active */ mutex_lock(&kprobe_mutex); if (atomic_add_return(-1, &kprobe_count) == \ ARCH_INACTIVE_KPROBE_COUNT) unregister_page_fault_notifier(&kprobe_page_fault_nb); mutex_unlock(&kprobe_mutex); return; } static struct notifier_block kprobe_exceptions_nb = { .notifier_call = kprobe_exceptions_notify, .priority = 0x7fffffff /* we need to be notified first */ }; int __kprobes register_jprobe(struct jprobe *jp) { /* Todo: Verify probepoint is a function entry point */ jp->kp.pre_handler = setjmp_pre_handler; jp->kp.break_handler = longjmp_break_handler; return __register_kprobe(&jp->kp, (unsigned long)__builtin_return_address(0)); } void __kprobes unregister_jprobe(struct jprobe *jp) { unregister_kprobe(&jp->kp); } #ifdef ARCH_SUPPORTS_KRETPROBES /* * This kprobe pre_handler is registered with every kretprobe. When probe * hits it will set up the return probe. */ static int __kprobes pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) { struct kretprobe *rp = container_of(p, struct kretprobe, kp); unsigned long flags = 0; /*TODO: consider to only swap the RA after the last pre_handler fired */ spin_lock_irqsave(&kretprobe_lock, flags); arch_prepare_kretprobe(rp, regs); spin_unlock_irqrestore(&kretprobe_lock, flags); return 0; } int __kprobes register_kretprobe(struct kretprobe *rp) { int ret = 0; struct kretprobe_instance *inst; int i; rp->kp.pre_handler = pre_handler_kretprobe; rp->kp.post_handler = NULL; rp->kp.fault_handler = NULL; rp->kp.break_handler = NULL; /* Pre-allocate memory for max kretprobe instances */ if (rp->maxactive <= 0) { #ifdef CONFIG_PREEMPT rp->maxactive = max(10, 2 * NR_CPUS); #else rp->maxactive = NR_CPUS; #endif } INIT_HLIST_HEAD(&rp->used_instances); INIT_HLIST_HEAD(&rp->free_instances); for (i = 0; i < rp->maxactive; i++) { inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL); if (inst == NULL) { free_rp_inst(rp); return -ENOMEM; } INIT_HLIST_NODE(&inst->uflist); hlist_add_head(&inst->uflist, &rp->free_instances); } rp->nmissed = 0; /* Establish function entry probe point */ if ((ret = __register_kprobe(&rp->kp, (unsigned long)__builtin_return_address(0))) != 0) free_rp_inst(rp); return ret; } #else /* ARCH_SUPPORTS_KRETPROBES */ int __kprobes register_kretprobe(struct kretprobe *rp) { return -ENOSYS; } #endif /* ARCH_SUPPORTS_KRETPROBES */ void __kprobes unregister_kretprobe(struct kretprobe *rp) { unsigned long flags; struct kretprobe_instance *ri; unregister_kprobe(&rp->kp); /* No race here */ spin_lock_irqsave(&kretprobe_lock, flags); while ((ri = get_used_rp_inst(rp)) != NULL) { ri->rp = NULL; hlist_del(&ri->uflist); } spin_unlock_irqrestore(&kretprobe_lock, flags); free_rp_inst(rp); } static int __init init_kprobes(void) { int i, err = 0; /* FIXME allocate the probe table, currently defined statically */ /* initialize all list heads */ for (i = 0; i < KPROBE_TABLE_SIZE; i++) { INIT_HLIST_HEAD(&kprobe_table[i]); INIT_HLIST_HEAD(&kretprobe_inst_table[i]); } atomic_set(&kprobe_count, 0); err = arch_init_kprobes(); if (!err) err = register_die_notifier(&kprobe_exceptions_nb); return err; } __initcall(init_kprobes); EXPORT_SYMBOL_GPL(register_kprobe); EXPORT_SYMBOL_GPL(unregister_kprobe); EXPORT_SYMBOL_GPL(register_jprobe); EXPORT_SYMBOL_GPL(unregister_jprobe); EXPORT_SYMBOL_GPL(jprobe_return); EXPORT_SYMBOL_GPL(register_kretprobe); EXPORT_SYMBOL_GPL(unregister_kretprobe);