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[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" <anil.s.keshavamurthy@intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "bibo,mao" <bibo.mao@intel.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Yumiko Sugita <yumiko.sugita.yf@hitachi.com>
Cc: Satoshi Oshima <soshima@redhat.com>
Cc: Hideo Aoki <haoki@redhat.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Masami Hiramatsu 2006-12-06 20:38:11 -08:00 committed by Linus Torvalds
parent c15bb29640
commit b4c6c34a53
7 changed files with 103 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/i386/kernel/kprobes.c
View File

@ -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();

2
arch/ia64/kernel/kprobes.c
View File

@ -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);
}
/*

2
arch/powerpc/kernel/kprobes.c
View File

@ -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);
}

2
arch/s390/kernel/kprobes.c
View File

@ -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);
}

2
arch/x86_64/kernel/kprobes.c
View File

@ -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);
}

2
include/linux/kprobes.h
View File

@ -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 */

117
kernel/kprobes.c
View File

@ -38,6 +38,7 @@
#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>
@ -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