diff options
Diffstat (limited to 'kernel/kprobes.c')
-rw-r--r-- | kernel/kprobes.c | 360 |
1 files changed, 337 insertions, 23 deletions
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 037142b7..90c0e82 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -27,12 +27,16 @@ * 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/spinlock.h> #include <linux/hash.h> #include <linux/init.h> #include <linux/module.h> +#include <linux/moduleloader.h> #include <asm/cacheflush.h> #include <asm/errno.h> #include <asm/kdebug.h> @@ -41,11 +45,112 @@ #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]; unsigned int kprobe_cpu = NR_CPUS; static DEFINE_SPINLOCK(kprobe_lock); static struct kprobe *curr_kprobe; +/* + * 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 *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 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; + } + } +} + /* Locks kprobe: irqs must be disabled */ void lock_kprobes(void) { @@ -78,22 +183,23 @@ struct kprobe *get_kprobe(void *addr) * Aggregate handlers for multiple kprobes support - these handlers * take care of invoking the individual kprobe handlers on p->list */ -int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs) +static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe *kp; list_for_each_entry(kp, &p->list, list) { if (kp->pre_handler) { curr_kprobe = kp; - kp->pre_handler(kp, regs); - curr_kprobe = NULL; + if (kp->pre_handler(kp, regs)) + return 1; } + curr_kprobe = NULL; } return 0; } -void aggr_post_handler(struct kprobe *p, struct pt_regs *regs, - unsigned long flags) +static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs, + unsigned long flags) { struct kprobe *kp; @@ -107,7 +213,8 @@ void aggr_post_handler(struct kprobe *p, struct pt_regs *regs, return; } -int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, int trapnr) +static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, + int trapnr) { /* * if we faulted "during" the execution of a user specified @@ -120,19 +227,159 @@ int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, int trapnr) return 0; } +static int aggr_break_handler(struct kprobe *p, struct pt_regs *regs) +{ + struct kprobe *kp = curr_kprobe; + if (curr_kprobe && kp->break_handler) { + if (kp->break_handler(kp, regs)) { + curr_kprobe = NULL; + return 1; + } + } + curr_kprobe = NULL; + return 0; +} + +struct kretprobe_instance *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; +} + +static struct kretprobe_instance *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; +} + +void 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); +} + +void 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 * 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 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(&kprobe_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(&kprobe_lock, flags); +} + +/* + * This kprobe pre_handler is registered with every kretprobe. When probe + * hits it will set up the return probe. + */ +static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) +{ + struct kretprobe *rp = container_of(p, struct kretprobe, kp); + + /*TODO: consider to only swap the RA after the last pre_handler fired */ + arch_prepare_kretprobe(rp, regs); + 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 add_new_kprobe(struct kprobe *old_p, struct kprobe *p) +{ + struct kprobe *kp; + + if (p->break_handler) { + list_for_each_entry(kp, &old_p->list, list) { + if (kp->break_handler) + return -EEXIST; + } + list_add_tail(&p->list, &old_p->list); + } else + list_add(&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->opcode = p->opcode; - memcpy(&ap->ainsn, &p->ainsn, sizeof(struct arch_specific_insn)); - 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(&p->list, &ap->list); @@ -153,16 +400,16 @@ static int register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p) int ret = 0; struct kprobe *ap; - if (old_p->break_handler || p->break_handler) { - ret = -EEXIST; /* kprobe and jprobe can't (yet) coexist */ - } else if (old_p->pre_handler == aggr_pre_handler) { - list_add(&p->list, &old_p->list); + 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); - list_add(&p->list, &ap->list); + copy_kprobe(ap, p); + ret = add_new_kprobe(ap, p); } return ret; } @@ -170,10 +417,8 @@ static int register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p) /* kprobe removal house-keeping routines */ static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags) { - *p->addr = p->opcode; + arch_disarm_kprobe(p); hlist_del(&p->hlist); - flush_icache_range((unsigned long) p->addr, - (unsigned long) p->addr + sizeof(kprobe_opcode_t)); spin_unlock_irqrestore(&kprobe_lock, flags); arch_remove_kprobe(p); } @@ -200,6 +445,7 @@ int register_kprobe(struct kprobe *p) } spin_lock_irqsave(&kprobe_lock, flags); old_p = get_kprobe(p->addr); + p->nmissed = 0; if (old_p) { ret = register_aggr_kprobe(old_p, p); goto out; @@ -210,10 +456,8 @@ int register_kprobe(struct kprobe *p) hlist_add_head(&p->hlist, &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]); - p->opcode = *p->addr; - *p->addr = BREAKPOINT_INSTRUCTION; - flush_icache_range((unsigned long) p->addr, - (unsigned long) p->addr + sizeof(kprobe_opcode_t)); + arch_arm_kprobe(p); + out: spin_unlock_irqrestore(&kprobe_lock, flags); rm_kprobe: @@ -257,16 +501,83 @@ void unregister_jprobe(struct jprobe *jp) unregister_kprobe(&jp->kp); } +#ifdef ARCH_SUPPORTS_KRETPROBES + +int 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 register_kretprobe(struct kretprobe *rp) +{ + return -ENOSYS; +} + +#endif /* ARCH_SUPPORTS_KRETPROBES */ + +void unregister_kretprobe(struct kretprobe *rp) +{ + unsigned long flags; + struct kretprobe_instance *ri; + + unregister_kprobe(&rp->kp); + /* No race here */ + spin_lock_irqsave(&kprobe_lock, flags); + free_rp_inst(rp); + while ((ri = get_used_rp_inst(rp)) != NULL) { + ri->rp = NULL; + hlist_del(&ri->uflist); + } + spin_unlock_irqrestore(&kprobe_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++) + for (i = 0; i < KPROBE_TABLE_SIZE; i++) { INIT_HLIST_HEAD(&kprobe_table[i]); + INIT_HLIST_HEAD(&kretprobe_inst_table[i]); + } + + err = arch_init(); + if (!err) + err = register_die_notifier(&kprobe_exceptions_nb); - err = register_die_notifier(&kprobe_exceptions_nb); return err; } @@ -277,3 +588,6 @@ 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); + |