From b4c6c34a530b4d1c626f4ac0a884e0a9b849378c Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Wed, 6 Dec 2006 20:38:11 -0800 Subject: [PATCH] [PATCH] kprobes: enable booster on the preemptible kernel When we are unregistering a kprobe-booster, we can't release its instruction buffer immediately on the preemptive kernel, because some processes might be preempted on the buffer. The freeze_processes() and thaw_processes() functions can clean most of processes up from the buffer. There are still some non-frozen threads who have the PF_NOFREEZE flag. If those threads are sleeping (not preempted) at the known place outside the buffer, we can ensure safety of freeing. However, the processing of this check routine takes a long time. So, this patch introduces the garbage collection mechanism of insn_slot. It also introduces the "dirty" flag to free_insn_slot because of efficiency. The "clean" instruction slots (dirty flag is cleared) are released immediately. But the "dirty" slots which are used by boosted kprobes, are marked as garbages. collect_garbage_slots() will be invoked to release "dirty" slots if there are more than INSNS_PER_PAGE garbage slots or if there are no unused slots. Cc: "Keshavamurthy, Anil S" Cc: Ananth N Mavinakayanahalli Cc: "bibo,mao" Cc: Prasanna S Panchamukhi Cc: Yumiko Sugita Cc: Satoshi Oshima Cc: Hideo Aoki Signed-off-by: Masami Hiramatsu Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/kprobes.c | 4 +- arch/ia64/kernel/kprobes.c | 2 +- arch/powerpc/kernel/kprobes.c | 2 +- arch/s390/kernel/kprobes.c | 2 +- arch/x86_64/kernel/kprobes.c | 2 +- include/linux/kprobes.h | 2 +- kernel/kprobes.c | 117 ++++++++++++++++++++++++++++------ 7 files changed, 103 insertions(+), 28 deletions(-) diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c index fc79e1e859c4..af1d53344993 100644 --- a/arch/i386/kernel/kprobes.c +++ b/arch/i386/kernel/kprobes.c @@ -184,7 +184,7 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p) void __kprobes arch_remove_kprobe(struct kprobe *p) { mutex_lock(&kprobe_mutex); - free_insn_slot(p->ainsn.insn); + free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1)); mutex_unlock(&kprobe_mutex); } @@ -333,7 +333,7 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) return 1; ss_probe: -#ifndef CONFIG_PREEMPT +#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM) if (p->ainsn.boostable == 1 && !p->post_handler){ /* Boost up -- we can execute copied instructions directly */ reset_current_kprobe(); diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c index 51217d63285e..4d592ee9300b 100644 --- a/arch/ia64/kernel/kprobes.c +++ b/arch/ia64/kernel/kprobes.c @@ -481,7 +481,7 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p) void __kprobes arch_remove_kprobe(struct kprobe *p) { mutex_lock(&kprobe_mutex); - free_insn_slot(p->ainsn.insn); + free_insn_slot(p->ainsn.insn, 0); mutex_unlock(&kprobe_mutex); } /* diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c index 7b8d12b9026c..4657563f8813 100644 --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -85,7 +85,7 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p) void __kprobes arch_remove_kprobe(struct kprobe *p) { mutex_lock(&kprobe_mutex); - free_insn_slot(p->ainsn.insn); + free_insn_slot(p->ainsn.insn, 0); mutex_unlock(&kprobe_mutex); } diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c index 67914fe7f317..576368c4f605 100644 --- a/arch/s390/kernel/kprobes.c +++ b/arch/s390/kernel/kprobes.c @@ -200,7 +200,7 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p) void __kprobes arch_remove_kprobe(struct kprobe *p) { mutex_lock(&kprobe_mutex); - free_insn_slot(p->ainsn.insn); + free_insn_slot(p->ainsn.insn, 0); mutex_unlock(&kprobe_mutex); } diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c index ac241567e682..209c8c0bec71 100644 --- a/arch/x86_64/kernel/kprobes.c +++ b/arch/x86_64/kernel/kprobes.c @@ -224,7 +224,7 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p) void __kprobes arch_remove_kprobe(struct kprobe *p) { mutex_lock(&kprobe_mutex); - free_insn_slot(p->ainsn.insn); + free_insn_slot(p->ainsn.insn, 0); mutex_unlock(&kprobe_mutex); } diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h index ac4c0559f751..769be39b9681 100644 --- a/include/linux/kprobes.h +++ b/include/linux/kprobes.h @@ -165,7 +165,7 @@ extern void arch_disarm_kprobe(struct kprobe *p); extern int arch_init_kprobes(void); extern void show_registers(struct pt_regs *regs); extern kprobe_opcode_t *get_insn_slot(void); -extern void free_insn_slot(kprobe_opcode_t *slot); +extern void free_insn_slot(kprobe_opcode_t *slot, int dirty); extern void kprobes_inc_nmissed_count(struct kprobe *p); /* Get the kprobe at this addr (if any) - called with preemption disabled */ diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 610c837ad9e0..17ec4afb0994 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -38,6 +38,7 @@ #include #include #include +#include #include #include #include @@ -83,9 +84,36 @@ struct kprobe_insn_page { 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. @@ -96,6 +124,7 @@ 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) { @@ -112,7 +141,11 @@ kprobe_opcode_t __kprobes *get_insn_slot(void) } } - /* All out of space. Need to allocate a new page. Use slot 0.*/ + /* 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; @@ -133,10 +166,62 @@ kprobe_opcode_t __kprobes *get_insn_slot(void) memset(kip->slot_used, 0, INSNS_PER_PAGE); kip->slot_used[0] = 1; kip->nused = 1; + kip->ngarbage = 0; return kip->insns; } -void __kprobes free_insn_slot(kprobe_opcode_t *slot) +/* 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; @@ -146,28 +231,18 @@ void __kprobes free_insn_slot(kprobe_opcode_t *slot) 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); - } + if (dirty) { + kip->slot_used[i] = -1; + kip->ngarbage++; + } else { + collect_one_slot(kip, i); } - return; + break; } } + if (dirty && (++kprobe_garbage_slots > INSNS_PER_PAGE)) { + collect_garbage_slots(); + } } #endif