kprobes: Support delayed unoptimizing
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>
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1f4f9b9..ba4d4c0 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -354,6 +354,13 @@
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 @@
}
}
+/* 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 @@
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 @@
/* 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 @@
{
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 @@
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 @@
*/
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 @@
/* 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 @@
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 @@
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 @@
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 @@
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 @@
}
#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 @@
/* 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 @@
/* 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 @@
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 @@
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 @@
/* 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 @@
return 0;
disarmed:
+ BUG_ON(!kprobe_disarmed(ap));
hlist_del_rcu(&ap->hlist);
return 0;
}
@@ -1322,14 +1486,15 @@
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 @@
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();
}
/*
