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Subject[PATCH -tip v8 3/9] kprobes: Introduce kprobes jump optimization
Date
Introduce kprobes jump optimization arch-independent parts.
Kprobes uses breakpoint instruction for interrupting execution flow, on
some architectures, it can be replaced by a jump instruction and
interruption emulation code. This gains kprobs' performance drastically.

To enable this feature, set CONFIG_OPTPROBES=y (default y if the arch
supports OPTPROBE).

Changes in v6:
- Cleanup coding style for readability.
- Add comments around get/put_online_cpus().

Changes in v5:
- Use get_online_cpus()/put_online_cpus() for avoiding text_mutex
deadlock.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Anders Kaseorg <andersk@ksplice.com>
Cc: Tim Abbott <tabbott@ksplice.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
---
arch/Kconfig | 13 +
include/linux/kprobes.h | 36 ++++
kernel/kprobes.c | 439 ++++++++++++++++++++++++++++++++++++++++++-----
3 files changed, 442 insertions(+), 46 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 32e8b68..2622a9d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -57,6 +57,17 @@ config KPROBES
for kernel debugging, non-intrusive instrumentation and testing.
If in doubt, say "N".

+config OPTPROBES
+ bool "Kprobes jump optimization support (EXPERIMENTAL)"
+ default y
+ depends on KPROBES
+ depends on !PREEMPT
+ depends on HAVE_OPTPROBES
+ select KALLSYMS_ALL
+ help
+ This option will allow kprobes to optimize breakpoint to
+ a jump for reducing its overhead.
+
config HAVE_EFFICIENT_UNALIGNED_ACCESS
bool
help
@@ -99,6 +110,8 @@ config HAVE_KPROBES
config HAVE_KRETPROBES
bool

+config HAVE_OPTPROBES
+ bool
#
# An arch should select this if it provides all these things:
#
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 1b672f7..aed1f95 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -122,6 +122,11 @@ struct kprobe {
/* Kprobe status flags */
#define KPROBE_FLAG_GONE 1 /* breakpoint has already gone */
#define KPROBE_FLAG_DISABLED 2 /* probe is temporarily disabled */
+#define KPROBE_FLAG_OPTIMIZED 4 /*
+ * probe is really optimized.
+ * NOTE:
+ * this flag is only for optimized_kprobe.
+ */

/* Has this kprobe gone ? */
static inline int kprobe_gone(struct kprobe *p)
@@ -134,6 +139,12 @@ static inline int kprobe_disabled(struct kprobe *p)
{
return p->flags & (KPROBE_FLAG_DISABLED | KPROBE_FLAG_GONE);
}
+
+/* Is this kprobe really running optimized path ? */
+static inline int kprobe_optimized(struct kprobe *p)
+{
+ return p->flags & KPROBE_FLAG_OPTIMIZED;
+}
/*
* Special probe type that uses setjmp-longjmp type tricks to resume
* execution at a specified entry with a matching prototype corresponding
@@ -249,6 +260,31 @@ extern kprobe_opcode_t *get_insn_slot(void);
extern void free_insn_slot(kprobe_opcode_t *slot, int dirty);
extern void kprobes_inc_nmissed_count(struct kprobe *p);

+#ifdef CONFIG_OPTPROBES
+/*
+ * Internal structure for direct jump optimized probe
+ */
+struct optimized_kprobe {
+ struct kprobe kp;
+ struct list_head list; /* list for optimizing queue */
+ struct arch_optimized_insn optinsn;
+};
+
+/* Architecture dependent functions for direct jump optimization */
+extern int arch_prepared_optinsn(struct arch_optimized_insn *optinsn);
+extern int arch_check_optimized_kprobe(struct optimized_kprobe *op);
+extern int arch_prepare_optimized_kprobe(struct optimized_kprobe *op);
+extern void arch_remove_optimized_kprobe(struct optimized_kprobe *op);
+extern int arch_optimize_kprobe(struct optimized_kprobe *op);
+extern void arch_unoptimize_kprobe(struct optimized_kprobe *op);
+extern kprobe_opcode_t *get_optinsn_slot(void);
+extern void free_optinsn_slot(kprobe_opcode_t *slot, int dirty);
+extern int arch_within_optimized_kprobe(struct optimized_kprobe *op,
+ unsigned long addr);
+
+extern void opt_pre_handler(struct kprobe *p, struct pt_regs *regs);
+#endif /* CONFIG_OPTPROBES */
+
/* Get the kprobe at this addr (if any) - called with preemption disabled */
struct kprobe *get_kprobe(void *addr);
void kretprobe_hash_lock(struct task_struct *tsk,
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 57a2a23..759bb8e 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -44,6 +44,7 @@
#include <linux/debugfs.h>
#include <linux/kdebug.h>
#include <linux/memory.h>
+#include <linux/cpu.h>

#include <asm-generic/sections.h>
#include <asm/cacheflush.h>
@@ -303,6 +304,33 @@ void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty)
__free_insn_slot(&kprobe_insn_slots, slot, dirty);
mutex_unlock(&kprobe_insn_mutex);
}
+#ifdef CONFIG_OPTPROBES
+/* For optimized_kprobe buffer */
+static DEFINE_MUTEX(kprobe_optinsn_mutex); /* Protects kprobe_optinsn_slots */
+static struct kprobe_insn_cache kprobe_optinsn_slots = {
+ .pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
+ /* .insn_size is initialized later */
+ .nr_garbage = 0,
+};
+/* Get a slot for optimized_kprobe buffer */
+kprobe_opcode_t __kprobes *get_optinsn_slot(void)
+{
+ kprobe_opcode_t *ret = NULL;
+
+ mutex_lock(&kprobe_optinsn_mutex);
+ ret = __get_insn_slot(&kprobe_optinsn_slots);
+ mutex_unlock(&kprobe_optinsn_mutex);
+
+ return ret;
+}
+
+void __kprobes free_optinsn_slot(kprobe_opcode_t * slot, int dirty)
+{
+ mutex_lock(&kprobe_optinsn_mutex);
+ __free_insn_slot(&kprobe_optinsn_slots, slot, dirty);
+ mutex_unlock(&kprobe_optinsn_mutex);
+}
+#endif
#endif

/* We have preemption disabled.. so it is safe to use __ versions */
@@ -333,23 +361,303 @@ struct kprobe __kprobes *get_kprobe(void *addr)
if (p->addr == addr)
return p;
}
+
+ return NULL;
+}
+
+static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs);
+
+/* Return true if the kprobe is an aggregator */
+static inline int kprobe_aggrprobe(struct kprobe *p)
+{
+ return p->pre_handler == aggr_pre_handler;
+}
+
+/*
+ * 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));
+}
+
+#ifdef CONFIG_OPTPROBES
+/*
+ * Call all pre_handler on the list, but ignores its return value.
+ * This must be called from arch-dep optimized caller.
+ */
+void __kprobes opt_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ struct kprobe *kp;
+
+ list_for_each_entry_rcu(kp, &p->list, list) {
+ if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
+ set_kprobe_instance(kp);
+ kp->pre_handler(kp, regs);
+ }
+ reset_kprobe_instance();
+ }
+}
+
+/* Return true(!0) if the kprobe is ready for optimization. */
+static inline int kprobe_optready(struct kprobe *p)
+{
+ struct optimized_kprobe *op;
+
+ if (kprobe_aggrprobe(p)) {
+ op = container_of(p, struct optimized_kprobe, kp);
+ return arch_prepared_optinsn(&op->optinsn);
+ }
+
+ return 0;
+}
+
+/* Return an optimized kprobe which replaces instructions including addr. */
+struct kprobe *__kprobes get_optimized_kprobe(unsigned long addr)
+{
+ int i;
+ struct kprobe *p = NULL;
+ struct optimized_kprobe *op;
+
+ for (i = 0; !p && i < MAX_OPTIMIZED_LENGTH; i++)
+ p = get_kprobe((void *)(addr - i));
+
+ if (p && kprobe_optready(p)) {
+ op = container_of(p, struct optimized_kprobe, kp);
+ if (arch_within_optimized_kprobe(op, addr))
+ return p;
+ }
+
return NULL;
}

+/* Optimization staging list, protected by kprobe_mutex */
+static LIST_HEAD(optimizing_list);
+
+static void kprobe_optimizer(struct work_struct *work);
+static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
+#define OPTIMIZE_DELAY 5
+
+/* Kprobe jump optimizer */
+static __kprobes void kprobe_optimizer(struct work_struct *work)
+{
+ struct optimized_kprobe *op, *tmp;
+
+ /* Lock modules while optimizing kprobes */
+ mutex_lock(&module_mutex);
+ mutex_lock(&kprobe_mutex);
+ if (kprobes_all_disarmed)
+ goto end;
+
+ /*
+ * 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
+ * instruction. This wait is for avoiding it.
+ */
+ synchronize_sched();
+
+ /*
+ * The optimization/unoptimization refers online_cpus via
+ * stop_machine() and cpu-hotplug modifies online_cpus.
+ * And same time, text_mutex will be held in cpu-hotplug and here.
+ * This combination can cause a deadlock (cpu-hotplug try to lock
+ * text_mutex but stop_machine can not be done because online_cpus
+ * has been changed)
+ * To avoid this deadlock, we need to call get_online_cpus()
+ * for preventing cpu-hotplug outside of text_mutex locking.
+ */
+ get_online_cpus();
+ mutex_lock(&text_mutex);
+ list_for_each_entry_safe(op, tmp, &optimizing_list, list) {
+ WARN_ON(kprobe_disabled(&op->kp));
+ if (arch_optimize_kprobe(op) < 0)
+ op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
+ list_del_init(&op->list);
+ }
+ mutex_unlock(&text_mutex);
+ put_online_cpus();
+end:
+ mutex_unlock(&kprobe_mutex);
+ mutex_unlock(&module_mutex);
+}
+
+/* Optimize kprobe if p is ready to be optimized */
+static __kprobes void optimize_kprobe(struct kprobe *p)
+{
+ struct optimized_kprobe *op;
+
+ /* Check if the kprobe is disabled or not ready for optimization. */
+ if (!kprobe_optready(p) ||
+ (kprobe_disabled(p) || kprobes_all_disarmed))
+ return;
+
+ /* Both of break_handler and post_handler are not supported. */
+ if (p->break_handler || p->post_handler)
+ return;
+
+ op = container_of(p, struct optimized_kprobe, kp);
+
+ /* Check there is no other kprobes at the optimized instructions */
+ if (arch_check_optimized_kprobe(op) < 0)
+ return;
+
+ /* 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);
+}
+
+/* Unoptimize a kprobe if p is optimized */
+static __kprobes void unoptimize_kprobe(struct kprobe *p)
+{
+ 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 */
+ list_del_init(&op->list);
+ else
+ /* Replace jump with break */
+ arch_unoptimize_kprobe(op);
+ op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
+ }
+}
+
+/* Remove optimized instructions */
+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 */
+ list_del_init(&op->list);
+ op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
+ }
+ /* Don't unoptimize, because the target code will be freed. */
+ arch_remove_optimized_kprobe(op);
+}
+
+/* Try to prepare optimized instructions */
+static __kprobes void prepare_optimized_kprobe(struct kprobe *p)
+{
+ struct optimized_kprobe *op;
+
+ op = container_of(p, struct optimized_kprobe, kp);
+ 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)
+{
+ struct optimized_kprobe *op;
+
+ op = kzalloc(sizeof(struct optimized_kprobe), GFP_KERNEL);
+ if (!op)
+ return NULL;
+
+ INIT_LIST_HEAD(&op->list);
+ op->kp.addr = p->addr;
+ arch_prepare_optimized_kprobe(op);
+
+ return &op->kp;
+}
+
+static void __kprobes init_aggr_kprobe(struct kprobe *ap, struct kprobe *p);
+
+/*
+ * Prepare an optimized_kprobe and optimize it
+ * NOTE: p must be a normal registered kprobe
+ */
+static __kprobes void try_to_optimize_kprobe(struct kprobe *p)
+{
+ struct kprobe *ap;
+ struct optimized_kprobe *op;
+
+ ap = alloc_aggr_kprobe(p);
+ if (!ap)
+ return;
+
+ 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);
+ return;
+ }
+
+ init_aggr_kprobe(ap, p);
+ optimize_kprobe(ap);
+}
+#else /* !CONFIG_OPTPROBES */
+#define get_optimized_kprobe(addr) (NULL)
+#define optimize_kprobe(p) do {} while (0)
+#define unoptimize_kprobe(p) 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)
+
+static __kprobes void free_aggr_kprobe(struct kprobe *p)
+{
+ kfree(p);
+}
+
+static __kprobes struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
+{
+ return kzalloc(sizeof(struct kprobe), GFP_KERNEL);
+}
+#endif /* CONFIG_OPTPROBES */
+
+static void __kprobes __arm_kprobe(struct kprobe *kp)
+{
+ arch_arm_kprobe(kp);
+ optimize_kprobe(kp); /* Try to optimize (add kprobe to a list) */
+}
+
+static void __kprobes __disarm_kprobe(struct kprobe *kp)
+{
+ unoptimize_kprobe(kp); /* Try to unoptimize */
+ arch_disarm_kprobe(kp);
+}
+
/* Arm a kprobe with text_mutex */
static void __kprobes arm_kprobe(struct kprobe *kp)
{
+ /*
+ * Here, since __arm_kprobe() doesn't use stop_machine(),
+ * this doesn't cause deadlock on text_mutex. So, we don't
+ * need get_online_cpus().
+ */
mutex_lock(&text_mutex);
- arch_arm_kprobe(kp);
+ __arm_kprobe(kp);
mutex_unlock(&text_mutex);
}

/* Disarm a kprobe with text_mutex */
static void __kprobes disarm_kprobe(struct kprobe *kp)
{
+ get_online_cpus(); /* For avoiding text_mutex deadlock */
mutex_lock(&text_mutex);
- arch_disarm_kprobe(kp);
+ __disarm_kprobe(kp);
mutex_unlock(&text_mutex);
+ put_online_cpus();
}

/*
@@ -418,7 +726,7 @@ static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
{
struct kprobe *kp;
- if (p->pre_handler != aggr_pre_handler) {
+ if (!kprobe_aggrprobe(p)) {
p->nmissed++;
} else {
list_for_each_entry_rcu(kp, &p->list, list)
@@ -542,21 +850,16 @@ static void __kprobes cleanup_rp_inst(struct kretprobe *rp)
}

/*
- * 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 ap->list. Fail if this is the
* second jprobe at the address - two jprobes can't coexist
*/
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 */
+
if (p->break_handler) {
if (ap->break_handler)
return -EEXIST;
@@ -571,7 +874,7 @@ static int __kprobes add_new_kprobe(struct kprobe *ap, struct kprobe *p)
ap->flags &= ~KPROBE_FLAG_DISABLED;
if (!kprobes_all_disarmed)
/* Arm the breakpoint again. */
- arm_kprobe(ap);
+ __arm_kprobe(ap);
}
return 0;
}
@@ -580,12 +883,13 @@ static int __kprobes add_new_kprobe(struct kprobe *ap, struct kprobe *p)
* 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)
+static void __kprobes init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
{
+ /* Copy p's insn slot to ap */
copy_kprobe(p, ap);
flush_insn_slot(ap);
ap->addr = p->addr;
- ap->flags = p->flags;
+ ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED;
ap->pre_handler = aggr_pre_handler;
ap->fault_handler = aggr_fault_handler;
/* We don't care the kprobe which has gone. */
@@ -595,8 +899,9 @@ static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
ap->break_handler = aggr_break_handler;

INIT_LIST_HEAD(&ap->list);
- list_add_rcu(&p->list, &ap->list);
+ INIT_HLIST_NODE(&ap->hlist);

+ list_add_rcu(&p->list, &ap->list);
hlist_replace_rcu(&p->hlist, &ap->hlist);
}

@@ -610,12 +915,12 @@ static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
int ret = 0;
struct kprobe *ap = old_p;

- if (old_p->pre_handler != aggr_pre_handler) {
- /* If old_p is not an aggr_probe, create new aggr_kprobe. */
- ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
+ if (!kprobe_aggrprobe(old_p)) {
+ /* If old_p is not an aggr_kprobe, create new aggr_kprobe. */
+ ap = alloc_aggr_kprobe(old_p);
if (!ap)
return -ENOMEM;
- add_aggr_kprobe(ap, old_p);
+ init_aggr_kprobe(ap, old_p);
}

if (kprobe_gone(ap)) {
@@ -634,6 +939,9 @@ static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
*/
return ret;

+ /* Prepare optimized instructions if possible. */
+ prepare_optimized_kprobe(ap);
+
/*
* Clear gone flag to prevent allocating new slot again, and
* set disabled flag because it is not armed yet.
@@ -642,6 +950,7 @@ static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
| KPROBE_FLAG_DISABLED;
}

+ /* Copy ap's insn slot to p */
copy_kprobe(ap, p);
return add_new_kprobe(ap, p);
}
@@ -791,16 +1100,25 @@ int __kprobes register_kprobe(struct kprobe *p)
p->nmissed = 0;
INIT_LIST_HEAD(&p->list);
mutex_lock(&kprobe_mutex);
+
+ get_online_cpus(); /* For avoiding text_mutex deadlock. */
+ mutex_lock(&text_mutex);
+
old_p = get_kprobe(p->addr);
if (old_p) {
+ /* Since this may unoptimize old_p, locking text_mutex. */
ret = register_aggr_kprobe(old_p, p);
goto out;
}

- mutex_lock(&text_mutex);
+ /* Check collision with other optimized kprobes */
+ old_p = get_optimized_kprobe((unsigned long)p->addr);
+ if (unlikely(old_p))
+ unoptimize_kprobe(old_p); /* Fallback to unoptimized kprobe */
+
ret = arch_prepare_kprobe(p);
if (ret)
- goto out_unlock_text;
+ goto out;

INIT_HLIST_NODE(&p->hlist);
hlist_add_head_rcu(&p->hlist,
@@ -809,9 +1127,12 @@ int __kprobes register_kprobe(struct kprobe *p)
if (!kprobes_all_disarmed && !kprobe_disabled(p))
arch_arm_kprobe(p);

-out_unlock_text:
- mutex_unlock(&text_mutex);
+ /* Try to optimize kprobe */
+ try_to_optimize_kprobe(p);
+
out:
+ mutex_unlock(&text_mutex);
+ put_online_cpus();
mutex_unlock(&kprobe_mutex);

if (probed_mod)
@@ -833,7 +1154,7 @@ static int __kprobes __unregister_kprobe_top(struct kprobe *p)
return -EINVAL;

if (old_p == p ||
- (old_p->pre_handler == aggr_pre_handler &&
+ (kprobe_aggrprobe(old_p) &&
list_is_singular(&old_p->list))) {
/*
* Only probe on the hash list. Disarm only if kprobes are
@@ -841,8 +1162,13 @@ static int __kprobes __unregister_kprobe_top(struct kprobe *p)
* already have been removed. We save on flushing icache.
*/
if (!kprobes_all_disarmed && !kprobe_disabled(old_p))
- disarm_kprobe(p);
+ disarm_kprobe(old_p);
hlist_del_rcu(&old_p->hlist);
+
+ /* If another kprobe was blocked, optimize it. */
+ old_p = get_optimized_kprobe((unsigned long)p->addr);
+ if (unlikely(old_p))
+ optimize_kprobe(old_p);
} else {
if (p->break_handler && !kprobe_gone(p))
old_p->break_handler = NULL;
@@ -857,8 +1183,13 @@ noclean:
list_del_rcu(&p->list);
if (!kprobe_disabled(old_p)) {
try_to_disable_aggr_kprobe(old_p);
- if (!kprobes_all_disarmed && kprobe_disabled(old_p))
- disarm_kprobe(old_p);
+ if (!kprobes_all_disarmed) {
+ if (kprobe_disabled(old_p))
+ disarm_kprobe(old_p);
+ else
+ /* Try to optimize this probe again */
+ optimize_kprobe(old_p);
+ }
}
}
return 0;
@@ -875,7 +1206,7 @@ static void __kprobes __unregister_kprobe_bottom(struct kprobe *p)
old_p = list_entry(p->list.next, struct kprobe, list);
list_del(&p->list);
arch_remove_kprobe(old_p);
- kfree(old_p);
+ free_aggr_kprobe(old_p);
}
}

@@ -1171,7 +1502,7 @@ static void __kprobes kill_kprobe(struct kprobe *p)
struct kprobe *kp;

p->flags |= KPROBE_FLAG_GONE;
- if (p->pre_handler == aggr_pre_handler) {
+ if (kprobe_aggrprobe(p)) {
/*
* If this is an aggr_kprobe, we have to list all the
* chained probes and mark them GONE.
@@ -1180,6 +1511,7 @@ static void __kprobes kill_kprobe(struct kprobe *p)
kp->flags |= KPROBE_FLAG_GONE;
p->post_handler = NULL;
p->break_handler = NULL;
+ kill_optimized_kprobe(p);
}
/*
* Here, we can remove insn_slot safely, because no thread calls
@@ -1289,6 +1621,11 @@ static int __init init_kprobes(void)
}
}

+#if defined(CONFIG_OPTPROBES) && defined(__ARCH_WANT_KPROBES_INSN_SLOT)
+ /* Init kprobe_optinsn_slots */
+ kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
+#endif
+
/* By default, kprobes are armed */
kprobes_all_disarmed = false;

@@ -1307,7 +1644,7 @@ static int __init init_kprobes(void)

#ifdef CONFIG_DEBUG_FS
static void __kprobes report_probe(struct seq_file *pi, struct kprobe *p,
- const char *sym, int offset,char *modname)
+ const char *sym, int offset, char *modname, struct kprobe *pp)
{
char *kprobe_type;

@@ -1317,19 +1654,21 @@ static void __kprobes report_probe(struct seq_file *pi, struct kprobe *p,
kprobe_type = "j";
else
kprobe_type = "k";
+
if (sym)
- seq_printf(pi, "%p %s %s+0x%x %s %s%s\n",
+ seq_printf(pi, "%p %s %s+0x%x %s ",
p->addr, kprobe_type, sym, offset,
- (modname ? modname : " "),
- (kprobe_gone(p) ? "[GONE]" : ""),
- ((kprobe_disabled(p) && !kprobe_gone(p)) ?
- "[DISABLED]" : ""));
+ (modname ? modname : " "));
else
- seq_printf(pi, "%p %s %p %s%s\n",
- p->addr, kprobe_type, p->addr,
- (kprobe_gone(p) ? "[GONE]" : ""),
- ((kprobe_disabled(p) && !kprobe_gone(p)) ?
- "[DISABLED]" : ""));
+ seq_printf(pi, "%p %s %p ",
+ p->addr, kprobe_type, p->addr);
+
+ if (!pp)
+ pp = p;
+ seq_printf(pi, "%s%s%s\n",
+ (kprobe_gone(p) ? "[GONE]" : ""),
+ ((kprobe_disabled(p) && !kprobe_gone(p)) ? "[DISABLED]" : ""),
+ (kprobe_optimized(pp) ? "[OPTIMIZED]" : ""));
}

static void __kprobes *kprobe_seq_start(struct seq_file *f, loff_t *pos)
@@ -1365,11 +1704,11 @@ static int __kprobes show_kprobe_addr(struct seq_file *pi, void *v)
hlist_for_each_entry_rcu(p, node, head, hlist) {
sym = kallsyms_lookup((unsigned long)p->addr, NULL,
&offset, &modname, namebuf);
- if (p->pre_handler == aggr_pre_handler) {
+ if (kprobe_aggrprobe(p)) {
list_for_each_entry_rcu(kp, &p->list, list)
- report_probe(pi, kp, sym, offset, modname);
+ report_probe(pi, kp, sym, offset, modname, p);
} else
- report_probe(pi, p, sym, offset, modname);
+ report_probe(pi, p, sym, offset, modname, NULL);
}
preempt_enable();
return 0;
@@ -1472,12 +1811,13 @@ static void __kprobes arm_all_kprobes(void)
if (!kprobes_all_disarmed)
goto already_enabled;

+ /* Arming kprobes doesn't optimize kprobe itself */
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))
- arch_arm_kprobe(p);
+ __arm_kprobe(p);
}
mutex_unlock(&text_mutex);

@@ -1504,16 +1844,23 @@ static void __kprobes disarm_all_kprobes(void)

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))
- arch_disarm_kprobe(p);
+ __disarm_kprobe(p);
}
}

mutex_unlock(&text_mutex);
+ put_online_cpus();
mutex_unlock(&kprobe_mutex);
/* Allow all currently running kprobes to complete */
synchronize_sched();

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com


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