| /* |
| * 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 <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) |
| |
| static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE]; |
| static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE]; |
| |
| static DECLARE_MUTEX(kprobe_mutex); /* Protects kprobe_table */ |
| DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */ |
| static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL; |
| |
| #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; |
| }; |
| |
| static struct hlist_head kprobe_insn_pages; |
| |
| /** |
| * 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; |
| |
| 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; |
| } |
| } |
| |
| /* 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; |
| return kip->insns; |
| } |
| |
| void __kprobes free_insn_slot(kprobe_opcode_t *slot) |
| { |
| 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; |
| kip->slot_used[i] = 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; |
| } |
| } |
| } |
| #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) |
| { |
| /* 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 */ |
| kfree(ri); |
| } |
| |
| 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 exit_thread or flush_thread when task tk's |
| * stack is being recycled 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; |
| struct hlist_node *node, *tmp; |
| unsigned long flags = 0; |
| |
| spin_lock_irqsave(&kretprobe_lock, flags); |
| head = kretprobe_inst_table_head(current); |
| hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { |
| if (ri->task == tk) |
| recycle_rp_inst(ri); |
| } |
| spin_unlock_irqrestore(&kretprobe_lock, flags); |
| } |
| |
| /* |
| * 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; |
| } |
| |
| 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) |
| { |
| struct kprobe *kp; |
| |
| if (p->break_handler) { |
| list_for_each_entry_rcu(kp, &old_p->list, list) { |
| if (kp->break_handler) |
| return -EEXIST; |
| } |
| list_add_tail_rcu(&p->list, &old_p->list); |
| } else |
| list_add_rcu(&p->list, &old_p->list); |
| 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); |
| ap->addr = p->addr; |
| ap->pre_handler = aggr_pre_handler; |
| ap->post_handler = aggr_post_handler; |
| ap->fault_handler = aggr_fault_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 = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC); |
| 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; |
| } |
| |
| int __kprobes register_kprobe(struct kprobe *p) |
| { |
| int ret = 0; |
| struct kprobe *old_p; |
| struct module *mod; |
| |
| if ((!kernel_text_address((unsigned long) p->addr)) || |
| in_kprobes_functions((unsigned long) p->addr)) |
| return -EINVAL; |
| |
| if ((mod = module_text_address((unsigned long) p->addr)) && |
| (unlikely(!try_module_get(mod)))) |
| return -EINVAL; |
| |
| p->nmissed = 0; |
| down(&kprobe_mutex); |
| old_p = get_kprobe(p->addr); |
| if (old_p) { |
| ret = register_aggr_kprobe(old_p, p); |
| 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)]); |
| |
| arch_arm_kprobe(p); |
| |
| out: |
| up(&kprobe_mutex); |
| |
| if (ret && mod) |
| module_put(mod); |
| return ret; |
| } |
| |
| void __kprobes unregister_kprobe(struct kprobe *p) |
| { |
| struct module *mod; |
| struct kprobe *old_p, *cleanup_p; |
| |
| down(&kprobe_mutex); |
| old_p = get_kprobe(p->addr); |
| if (unlikely(!old_p)) { |
| up(&kprobe_mutex); |
| return; |
| } |
| |
| if ((old_p->pre_handler == aggr_pre_handler) && |
| (p->list.next == &old_p->list) && |
| (p->list.prev == &old_p->list)) { |
| /* Only one element in the aggregate list */ |
| arch_disarm_kprobe(p); |
| hlist_del_rcu(&old_p->hlist); |
| cleanup_p = old_p; |
| } else if (old_p == p) { |
| /* Only one kprobe element in the hash list */ |
| arch_disarm_kprobe(p); |
| hlist_del_rcu(&p->hlist); |
| cleanup_p = p; |
| } else { |
| list_del_rcu(&p->list); |
| cleanup_p = NULL; |
| } |
| |
| up(&kprobe_mutex); |
| |
| synchronize_sched(); |
| if ((mod = module_text_address((unsigned long)p->addr))) |
| module_put(mod); |
| |
| if (cleanup_p) { |
| if (cleanup_p->pre_handler == aggr_pre_handler) { |
| list_del_rcu(&p->list); |
| kfree(old_p); |
| } |
| down(&kprobe_mutex); |
| arch_remove_kprobe(p); |
| up(&kprobe_mutex); |
| } |
| } |
| |
| static struct notifier_block kprobe_exceptions_nb = { |
| .notifier_call = kprobe_exceptions_notify, |
| .priority = 0x7fffffff /* we need to 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); |
| } |
| |
| void __kprobes unregister_jprobe(struct jprobe *jp) |
| { |
| unregister_kprobe(&jp->kp); |
| } |
| |
| #ifdef ARCH_SUPPORTS_KRETPROBES |
| |
| int __kprobes register_kretprobe(struct kretprobe *rp) |
| { |
| int ret = 0; |
| struct kretprobe_instance *inst; |
| int i; |
| |
| rp->kp.pre_handler = pre_handler_kretprobe; |
| |
| /* 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)) != 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); |
| free_rp_inst(rp); |
| while ((ri = get_used_rp_inst(rp)) != NULL) { |
| ri->rp = NULL; |
| hlist_del(&ri->uflist); |
| } |
| spin_unlock_irqrestore(&kretprobe_lock, flags); |
| } |
| |
| 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]); |
| } |
| |
| 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); |
| |