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kprobes: Support delayed unoptimizing

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Unoptimization occurs when a probe is unregistered or disabled,
and is heavy because it recovers instructions by using
stop_machine(). This patch delays unoptimization operations and
unoptimize several probes at once by using
text_poke_smp_batch(). This can avoid unexpected system slowdown
coming from stop_machine().

Changes in v5:
- Split this patch into several cleanup patches and this patch.
- Fix some text_mutex lock miss.
- Use bool instead of int for behavior flags.
- Add additional comment for (un)optimizing path.

Changes in v2:
- Use dynamic allocated buffers and params.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: 2nddept-manager@sdl.hitachi.co.jp
LKML-Reference: <20101203095409.2961.82733.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Masami Hiramatsu 2010-12-03 18:54:09 +09:00 committed by Ingo Molnar
parent 61f4e13ffd
commit 6274de4984
2 changed files with 237 additions and 77 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
arch/x86/kernel/kprobes.c
View file

@ -1184,6 +1184,10 @@ static void __kprobes optimized_callback(struct optimized_kprobe *op,
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
/* This is possible if op is under delayed unoptimizing */
if (kprobe_disabled(&op->kp))
return;
preempt_disable();
if (kprobe_running()) {
kprobes_inc_nmissed_count(&op->kp);

310
kernel/kprobes.c
View file

@ -354,6 +354,13 @@ static inline int kprobe_aggrprobe(struct kprobe *p)
return p->pre_handler == aggr_pre_handler;
}
/* Return true(!0) if the kprobe is unused */
static inline int kprobe_unused(struct kprobe *p)
{
return kprobe_aggrprobe(p) && kprobe_disabled(p) &&
list_empty(&p->list);
}
/*
* Keep all fields in the kprobe consistent
*/
@ -384,6 +391,17 @@ void __kprobes opt_pre_handler(struct kprobe *p, struct pt_regs *regs)
}
}
/* Free optimized instructions and optimized_kprobe */
static __kprobes void free_aggr_kprobe(struct kprobe *p)
{
struct optimized_kprobe *op;
op = container_of(p, struct optimized_kprobe, kp);
arch_remove_optimized_kprobe(op);
arch_remove_kprobe(p);
kfree(op);
}
/* Return true(!0) if the kprobe is ready for optimization. */
static inline int kprobe_optready(struct kprobe *p)
{
@ -397,6 +415,33 @@ static inline int kprobe_optready(struct kprobe *p)
return 0;
}
/* Return true(!0) if the kprobe is disarmed. Note: p must be on hash list */
static inline int kprobe_disarmed(struct kprobe *p)
{
struct optimized_kprobe *op;
/* If kprobe is not aggr/opt probe, just return kprobe is disabled */
if (!kprobe_aggrprobe(p))
return kprobe_disabled(p);
op = container_of(p, struct optimized_kprobe, kp);
return kprobe_disabled(p) && list_empty(&op->list);
}
/* Return true(!0) if the probe is queued on (un)optimizing lists */
static int __kprobes kprobe_queued(struct kprobe *p)
{
struct optimized_kprobe *op;
if (kprobe_aggrprobe(p)) {
op = container_of(p, struct optimized_kprobe, kp);
if (!list_empty(&op->list))
return 1;
}
return 0;
}
/*
* Return an optimized kprobe whose optimizing code replaces
* instructions including addr (exclude breakpoint).
@ -422,9 +467,11 @@ static struct kprobe *__kprobes get_optimized_kprobe(unsigned long addr)
/* Optimization staging list, protected by kprobe_mutex */
static LIST_HEAD(optimizing_list);
static LIST_HEAD(unoptimizing_list);
static void kprobe_optimizer(struct work_struct *work);
static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
static DECLARE_COMPLETION(optimizer_comp);
#define OPTIMIZE_DELAY 5
/*
@ -435,6 +482,11 @@ static __kprobes void do_optimize_kprobes(void)
{
struct optimized_kprobe *op, *tmp;
/* Optimization never be done when disarmed */
if (kprobes_all_disarmed || !kprobes_allow_optimization ||
list_empty(&optimizing_list))
return;
/*
* The optimization/unoptimization refers online_cpus via
* stop_machine() and cpu-hotplug modifies online_cpus.
@ -457,17 +509,79 @@ static __kprobes void do_optimize_kprobes(void)
put_online_cpus();
}
/*
* Unoptimize (replace a jump with a breakpoint and remove the breakpoint
* if need) kprobes listed on unoptimizing_list.
*/
static __kprobes void do_unoptimize_kprobes(struct list_head *free_list)
{
struct optimized_kprobe *op, *tmp;
/* Unoptimization must be done anytime */
if (list_empty(&unoptimizing_list))
return;
/* Ditto to do_optimize_kprobes */
get_online_cpus();
mutex_lock(&text_mutex);
list_for_each_entry_safe(op, tmp, &unoptimizing_list, list) {
/* Unoptimize kprobes */
arch_unoptimize_kprobe(op);
/* Disarm probes if marked disabled */
if (kprobe_disabled(&op->kp))
arch_disarm_kprobe(&op->kp);
if (kprobe_unused(&op->kp)) {
/*
* Remove unused probes from hash list. After waiting
* for synchronization, these probes are reclaimed.
* (reclaiming is done by do_free_cleaned_kprobes.)
*/
hlist_del_rcu(&op->kp.hlist);
/* Move only unused probes on free_list */
list_move(&op->list, free_list);
} else
list_del_init(&op->list);
}
mutex_unlock(&text_mutex);
put_online_cpus();
}
/* Reclaim all kprobes on the free_list */
static __kprobes void do_free_cleaned_kprobes(struct list_head *free_list)
{
struct optimized_kprobe *op, *tmp;
list_for_each_entry_safe(op, tmp, free_list, list) {
BUG_ON(!kprobe_unused(&op->kp));
list_del_init(&op->list);
free_aggr_kprobe(&op->kp);
}
}
/* Start optimizer after OPTIMIZE_DELAY passed */
static __kprobes void kick_kprobe_optimizer(void)
{
if (!delayed_work_pending(&optimizing_work))
schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
}
/* Kprobe jump optimizer */
static __kprobes void kprobe_optimizer(struct work_struct *work)
{
LIST_HEAD(free_list);
/* Lock modules while optimizing kprobes */
mutex_lock(&module_mutex);
mutex_lock(&kprobe_mutex);
if (kprobes_all_disarmed || !kprobes_allow_optimization)
goto end;
/*
* Wait for quiesence period to ensure all running interrupts
* Step 1: Unoptimize kprobes and collect cleaned (unused and disarmed)
* kprobes before waiting for quiesence period.
*/
do_unoptimize_kprobes(&free_list);
/*
* Step 2: Wait for quiesence period to ensure all running interrupts
* are done. Because optprobe may modify multiple instructions
* there is a chance that Nth instruction is interrupted. In that
* case, running interrupt can return to 2nd-Nth byte of jump
@ -475,10 +589,24 @@ static __kprobes void kprobe_optimizer(struct work_struct *work)
*/
synchronize_sched();
/* Step 3: Optimize kprobes after quiesence period */
do_optimize_kprobes();
end:
/* Step 4: Free cleaned kprobes after quiesence period */
do_free_cleaned_kprobes(&free_list);
mutex_unlock(&kprobe_mutex);
mutex_unlock(&module_mutex);
/* Wake up all waiters */
complete_all(&optimizer_comp);
}
/* Wait for completing optimization and unoptimization */
static __kprobes void wait_for_kprobe_optimizer(void)
{
if (delayed_work_pending(&optimizing_work))
wait_for_completion(&optimizer_comp);
}
/* Optimize kprobe if p is ready to be optimized */
@ -504,27 +632,63 @@ static __kprobes void optimize_kprobe(struct kprobe *p)
/* Check if it is already optimized. */
if (op->kp.flags & KPROBE_FLAG_OPTIMIZED)
return;
op->kp.flags |= KPROBE_FLAG_OPTIMIZED;
list_add(&op->list, &optimizing_list);
if (!delayed_work_pending(&optimizing_work))
schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
if (!list_empty(&op->list))
/* This is under unoptimizing. Just dequeue the probe */
list_del_init(&op->list);
else {
list_add(&op->list, &optimizing_list);
kick_kprobe_optimizer();
}
}
/* Short cut to direct unoptimizing */
static __kprobes void force_unoptimize_kprobe(struct optimized_kprobe *op)
{
get_online_cpus();
arch_unoptimize_kprobe(op);
put_online_cpus();
if (kprobe_disabled(&op->kp))
arch_disarm_kprobe(&op->kp);
}
/* Unoptimize a kprobe if p is optimized */
static __kprobes void unoptimize_kprobe(struct kprobe *p)
static __kprobes void unoptimize_kprobe(struct kprobe *p, bool force)
{
struct optimized_kprobe *op;
if ((p->flags & KPROBE_FLAG_OPTIMIZED) && kprobe_aggrprobe(p)) {
op = container_of(p, struct optimized_kprobe, kp);
if (!list_empty(&op->list))
/* Dequeue from the optimization queue */
if (!kprobe_aggrprobe(p) || kprobe_disarmed(p))
return; /* This is not an optprobe nor optimized */
op = container_of(p, struct optimized_kprobe, kp);
if (!kprobe_optimized(p)) {
/* Unoptimized or unoptimizing case */
if (force && !list_empty(&op->list)) {
/*
* Only if this is unoptimizing kprobe and forced,
* forcibly unoptimize it. (No need to unoptimize
* unoptimized kprobe again :)
*/
list_del_init(&op->list);
else
/* Replace jump with break */
arch_unoptimize_kprobe(op);
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
force_unoptimize_kprobe(op);
}
return;
}
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
if (!list_empty(&op->list)) {
/* Dequeue from the optimization queue */
list_del_init(&op->list);
return;
}
/* Optimized kprobe case */
if (force)
/* Forcibly update the code: this is a special case */
force_unoptimize_kprobe(op);
else {
list_add(&op->list, &unoptimizing_list);
kick_kprobe_optimizer();
}
}
@ -534,12 +698,12 @@ static void __kprobes kill_optimized_kprobe(struct kprobe *p)
struct optimized_kprobe *op;
op = container_of(p, struct optimized_kprobe, kp);
if (!list_empty(&op->list)) {
/* Dequeue from the optimization queue */
if (!list_empty(&op->list))
/* Dequeue from the (un)optimization queue */
list_del_init(&op->list);
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
}
/* Don't unoptimize, because the target code will be freed. */
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
/* Don't touch the code, because it is already freed. */
arch_remove_optimized_kprobe(op);
}
@ -552,16 +716,6 @@ static __kprobes void prepare_optimized_kprobe(struct kprobe *p)
arch_prepare_optimized_kprobe(op);
}
/* Free optimized instructions and optimized_kprobe */
static __kprobes void free_aggr_kprobe(struct kprobe *p)
{
struct optimized_kprobe *op;
op = container_of(p, struct optimized_kprobe, kp);
arch_remove_optimized_kprobe(op);
kfree(op);
}
/* Allocate new optimized_kprobe and try to prepare optimized instructions */
static __kprobes struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
{
@ -596,7 +750,8 @@ static __kprobes void try_to_optimize_kprobe(struct kprobe *p)
op = container_of(ap, struct optimized_kprobe, kp);
if (!arch_prepared_optinsn(&op->optinsn)) {
/* If failed to setup optimizing, fallback to kprobe */
free_aggr_kprobe(ap);
arch_remove_optimized_kprobe(op);
kfree(op);
return;
}
@ -640,21 +795,16 @@ static void __kprobes unoptimize_all_kprobes(void)
return;
kprobes_allow_optimization = false;
printk(KERN_INFO "Kprobes globally unoptimized\n");
get_online_cpus(); /* For avoiding text_mutex deadlock */
mutex_lock(&text_mutex);
for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
head = &kprobe_table[i];
hlist_for_each_entry_rcu(p, node, head, hlist) {
if (!kprobe_disabled(p))
unoptimize_kprobe(p);
unoptimize_kprobe(p, false);
}
}
mutex_unlock(&text_mutex);
put_online_cpus();
/* Allow all currently running kprobes to complete */
synchronize_sched();
/* Wait for unoptimizing completion */
wait_for_kprobe_optimizer();
printk(KERN_INFO "Kprobes globally unoptimized\n");
}
int sysctl_kprobes_optimization;
@ -678,6 +828,7 @@ int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
}
#endif /* CONFIG_SYSCTL */
/* Put a breakpoint for a probe. Must be called with text_mutex locked */
static void __kprobes __arm_kprobe(struct kprobe *p)
{
struct kprobe *_p;
@ -685,37 +836,45 @@ static void __kprobes __arm_kprobe(struct kprobe *p)
/* Check collision with other optimized kprobes */
_p = get_optimized_kprobe((unsigned long)p->addr);
if (unlikely(_p))
unoptimize_kprobe(_p); /* Fallback to unoptimized kprobe */
/* Fallback to unoptimized kprobe */
unoptimize_kprobe(_p, true);
arch_arm_kprobe(p);
optimize_kprobe(p); /* Try to optimize (add kprobe to a list) */
}
static void __kprobes __disarm_kprobe(struct kprobe *p)
/* Remove the breakpoint of a probe. Must be called with text_mutex locked */
static void __kprobes __disarm_kprobe(struct kprobe *p, bool reopt)
{
struct kprobe *_p;
unoptimize_kprobe(p); /* Try to unoptimize */
arch_disarm_kprobe(p);
unoptimize_kprobe(p, false); /* Try to unoptimize */
/* If another kprobe was blocked, optimize it. */
_p = get_optimized_kprobe((unsigned long)p->addr);
if (unlikely(_p))
optimize_kprobe(_p);
if (!kprobe_queued(p)) {
arch_disarm_kprobe(p);
/* If another kprobe was blocked, optimize it. */
_p = get_optimized_kprobe((unsigned long)p->addr);
if (unlikely(_p) && reopt)
optimize_kprobe(_p);
}
/* TODO: reoptimize others after unoptimized this probe */
}
#else /* !CONFIG_OPTPROBES */
#define optimize_kprobe(p) do {} while (0)
#define unoptimize_kprobe(p) do {} while (0)
#define unoptimize_kprobe(p, f) do {} while (0)
#define kill_optimized_kprobe(p) do {} while (0)
#define prepare_optimized_kprobe(p) do {} while (0)
#define try_to_optimize_kprobe(p) do {} while (0)
#define __arm_kprobe(p) arch_arm_kprobe(p)
#define __disarm_kprobe(p) arch_disarm_kprobe(p)
#define __disarm_kprobe(p, o) arch_disarm_kprobe(p)
#define kprobe_disarmed(p) kprobe_disabled(p)
#define wait_for_kprobe_optimizer() do {} while (0)
static __kprobes void free_aggr_kprobe(struct kprobe *p)
{
arch_remove_kprobe(p);
kfree(p);
}
@ -741,11 +900,10 @@ static void __kprobes arm_kprobe(struct kprobe *kp)
/* Disarm a kprobe with text_mutex */
static void __kprobes disarm_kprobe(struct kprobe *kp)
{
get_online_cpus(); /* For avoiding text_mutex deadlock */
/* Ditto */
mutex_lock(&text_mutex);
__disarm_kprobe(kp);
__disarm_kprobe(kp, true);
mutex_unlock(&text_mutex);
put_online_cpus();
}
/*
@ -951,7 +1109,7 @@ static int __kprobes add_new_kprobe(struct kprobe *ap, struct kprobe *p)
BUG_ON(kprobe_gone(ap) || kprobe_gone(p));
if (p->break_handler || p->post_handler)
unoptimize_kprobe(ap); /* Fall back to normal kprobe */
unoptimize_kprobe(ap, true); /* Fall back to normal kprobe */
if (p->break_handler) {
if (ap->break_handler)
@ -1014,7 +1172,9 @@ static int __kprobes register_aggr_kprobe(struct kprobe *orig_p,
if (!ap)
return -ENOMEM;
init_aggr_kprobe(ap, orig_p);
}
} else if (kprobe_unused(ap))
/* Busy to die */
return -EBUSY;
if (kprobe_gone(ap)) {
/*
@ -1283,8 +1443,11 @@ static int __kprobes __unregister_kprobe_top(struct kprobe *p)
/* Following process expects this probe is an aggrprobe */
WARN_ON(!kprobe_aggrprobe(ap));
if (list_is_singular(&ap->list))
/* This probe is the last child of aggrprobe */
if (list_is_singular(&ap->list) && kprobe_disarmed(ap))
/*
* !disarmed could be happen if the probe is under delayed
* unoptimizing.
*/
goto disarmed;
else {
/* If disabling probe has special handlers, update aggrprobe */
@ -1313,6 +1476,7 @@ static int __kprobes __unregister_kprobe_top(struct kprobe *p)
return 0;
disarmed:
BUG_ON(!kprobe_disarmed(ap));
hlist_del_rcu(&ap->hlist);
return 0;
}
@ -1322,14 +1486,15 @@ static void __kprobes __unregister_kprobe_bottom(struct kprobe *p)
struct kprobe *ap;
if (list_empty(&p->list))
/* This is an independent kprobe */
arch_remove_kprobe(p);
else if (list_is_singular(&p->list)) {
/* "p" is the last child of an aggr_kprobe */
/* This is the last child of an aggrprobe */
ap = list_entry(p->list.next, struct kprobe, list);
list_del(&p->list);
arch_remove_kprobe(ap);
free_aggr_kprobe(ap);
}
/* Otherwise, do nothing. */
}
int __kprobes register_kprobes(struct kprobe **kps, int num)
@ -1951,36 +2116,27 @@ static void __kprobes disarm_all_kprobes(void)
mutex_lock(&kprobe_mutex);
/* If kprobes are already disarmed, just return */
if (kprobes_all_disarmed)
goto already_disabled;
if (kprobes_all_disarmed) {
mutex_unlock(&kprobe_mutex);
return;
}
kprobes_all_disarmed = true;
printk(KERN_INFO "Kprobes globally disabled\n");
/*
* Here we call get_online_cpus() for avoiding text_mutex deadlock,
* because disarming may also unoptimize kprobes.
*/
get_online_cpus();
mutex_lock(&text_mutex);
for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
head = &kprobe_table[i];
hlist_for_each_entry_rcu(p, node, head, hlist) {
if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p))
__disarm_kprobe(p);
__disarm_kprobe(p, false);
}
}
mutex_unlock(&text_mutex);
put_online_cpus();
mutex_unlock(&kprobe_mutex);
/* Allow all currently running kprobes to complete */
synchronize_sched();
return;
already_disabled:
mutex_unlock(&kprobe_mutex);
return;
/* Wait for disarming all kprobes by optimizer */
wait_for_kprobe_optimizer();
}
/*