kprobes: support per-kprobe disabling
Add disable_kprobe() and enable_kprobe() to disable/enable kprobes
temporarily.
disable_kprobe() asynchronously disables probe handlers of specified
kprobe. So, after calling it, some handlers can be called at a while.
enable_kprobe() enables specified kprobe.
aggr_pre_handler and aggr_post_handler check disabled probes. On the
other hand aggr_break_handler and aggr_fault_handler don't check it
because these handlers will be called while executing pre or post handlers
and usually those help error handling.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index 48b3de9..f609af2 100644
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -212,7 +212,9 @@
is single-stepped, Kprobe calls kp->post_handler. If a fault
occurs during execution of kp->pre_handler or kp->post_handler,
or during single-stepping of the probed instruction, Kprobes calls
-kp->fault_handler. Any or all handlers can be NULL.
+kp->fault_handler. Any or all handlers can be NULL. If kp->flags
+is set KPROBE_FLAG_DISABLED, that kp will be registered but disabled,
+so, it's handlers aren't hit until calling enable_kprobe(kp).
NOTE:
1. With the introduction of the "symbol_name" field to struct kprobe,
@@ -363,6 +365,22 @@
incorrect probes. However, other probes in the array are
unregistered correctly.
+4.7 disable_kprobe
+
+#include <linux/kprobes.h>
+int disable_kprobe(struct kprobe *kp);
+
+Temporarily disables the specified kprobe. You can enable it again by using
+enable_kprobe(). You must specify the kprobe which has been registered.
+
+4.8 enable_kprobe
+
+#include <linux/kprobes.h>
+int enable_kprobe(struct kprobe *kp);
+
+Enables kprobe which has been disabled by disable_kprobe(). You must specify
+the kprobe which has been registered.
+
5. Kprobes Features and Limitations
Kprobes allows multiple probes at the same address. Currently,
@@ -500,10 +518,14 @@
is also specified. Following columns show probe status. If the probe is on
a virtual address that is no longer valid (module init sections, module
virtual addresses that correspond to modules that've been unloaded),
-such probes are marked with [GONE].
+such probes are marked with [GONE]. If the probe is temporarily disabled,
+such probes are marked with [DISABLED].
-/debug/kprobes/enabled: Turn kprobes ON/OFF
+/debug/kprobes/enabled: Turn kprobes ON/OFF forcibly.
-Provides a knob to globally turn registered kprobes ON or OFF. By default,
-all kprobes are enabled. By echoing "0" to this file, all registered probes
-will be disarmed, till such time a "1" is echoed to this file.
+Provides a knob to globally and forcibly turn registered kprobes ON or OFF.
+By default, all kprobes are enabled. By echoing "0" to this file, all
+registered probes will be disarmed, till such time a "1" is echoed to this
+file. Note that this knob just disarms and arms all kprobes and doesn't
+change each probe's disabling state. This means that disabled kprobes (marked
+[DISABLED]) will be not enabled if you turn ON all kprobes by this knob.
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 39826a6..1071cfd 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -112,18 +112,28 @@
/* copy of the original instruction */
struct arch_specific_insn ainsn;
- /* Indicates various status flags. Protected by kprobe_mutex. */
+ /*
+ * Indicates various status flags.
+ * Protected by kprobe_mutex after this kprobe is registered.
+ */
u32 flags;
};
/* Kprobe status flags */
#define KPROBE_FLAG_GONE 1 /* breakpoint has already gone */
+#define KPROBE_FLAG_DISABLED 2 /* probe is temporarily disabled */
+/* Has this kprobe gone ? */
static inline int kprobe_gone(struct kprobe *p)
{
return p->flags & KPROBE_FLAG_GONE;
}
+/* Is this kprobe disabled ? */
+static inline int kprobe_disabled(struct kprobe *p)
+{
+ return p->flags & (KPROBE_FLAG_DISABLED | KPROBE_FLAG_GONE);
+}
/*
* Special probe type that uses setjmp-longjmp type tricks to resume
* execution at a specified entry with a matching prototype corresponding
@@ -283,6 +293,9 @@
void kprobe_flush_task(struct task_struct *tk);
void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
+int disable_kprobe(struct kprobe *kp);
+int enable_kprobe(struct kprobe *kp);
+
#else /* !CONFIG_KPROBES: */
static inline int kprobes_built_in(void)
@@ -349,5 +362,13 @@
static inline void kprobe_flush_task(struct task_struct *tk)
{
}
+static inline int disable_kprobe(struct kprobe *kp)
+{
+ return -ENOSYS;
+}
+static inline int enable_kprobe(struct kprobe *kp)
+{
+ return -ENOSYS;
+}
#endif /* CONFIG_KPROBES */
#endif /* _LINUX_KPROBES_H */
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index dae198b..a5e74dd 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -328,7 +328,7 @@
struct kprobe *kp;
list_for_each_entry_rcu(kp, &p->list, list) {
- if (kp->pre_handler && !kprobe_gone(kp)) {
+ if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
set_kprobe_instance(kp);
if (kp->pre_handler(kp, regs))
return 1;
@@ -344,7 +344,7 @@
struct kprobe *kp;
list_for_each_entry_rcu(kp, &p->list, list) {
- if (kp->post_handler && !kprobe_gone(kp)) {
+ if (kp->post_handler && likely(!kprobe_disabled(kp))) {
set_kprobe_instance(kp);
kp->post_handler(kp, regs, flags);
reset_kprobe_instance();
@@ -523,6 +523,7 @@
*/
static int __kprobes add_new_kprobe(struct kprobe *ap, struct kprobe *p)
{
+ BUG_ON(kprobe_gone(ap) || kprobe_gone(p));
if (p->break_handler) {
if (ap->break_handler)
return -EEXIST;
@@ -532,6 +533,13 @@
list_add_rcu(&p->list, &ap->list);
if (p->post_handler && !ap->post_handler)
ap->post_handler = aggr_post_handler;
+
+ if (kprobe_disabled(ap) && !kprobe_disabled(p)) {
+ ap->flags &= ~KPROBE_FLAG_DISABLED;
+ if (!kprobes_all_disarmed)
+ /* Arm the breakpoint again. */
+ arch_arm_kprobe(ap);
+ }
return 0;
}
@@ -592,20 +600,36 @@
* freed by unregister_kprobe.
*/
return ret;
- /* Clear gone flag to prevent allocating new slot again. */
- ap->flags &= ~KPROBE_FLAG_GONE;
+
/*
- * If the old_p has gone, its breakpoint has been disarmed.
- * We have to arm it again after preparing real kprobes.
+ * Clear gone flag to prevent allocating new slot again, and
+ * set disabled flag because it is not armed yet.
*/
- if (!kprobes_all_disarmed)
- arch_arm_kprobe(ap);
+ ap->flags = (ap->flags & ~KPROBE_FLAG_GONE)
+ | KPROBE_FLAG_DISABLED;
}
copy_kprobe(ap, p);
return add_new_kprobe(ap, p);
}
+/* Try to disable aggr_kprobe, and return 1 if succeeded.*/
+static int __kprobes try_to_disable_aggr_kprobe(struct kprobe *p)
+{
+ struct kprobe *kp;
+
+ list_for_each_entry_rcu(kp, &p->list, list) {
+ if (!kprobe_disabled(kp))
+ /*
+ * There is an active probe on the list.
+ * We can't disable aggr_kprobe.
+ */
+ return 0;
+ }
+ p->flags |= KPROBE_FLAG_DISABLED;
+ return 1;
+}
+
static int __kprobes in_kprobes_functions(unsigned long addr)
{
struct kprobe_blackpoint *kb;
@@ -664,7 +688,9 @@
return -EINVAL;
}
- p->flags = 0;
+ /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
+ p->flags &= KPROBE_FLAG_DISABLED;
+
/*
* Check if are we probing a module.
*/
@@ -709,7 +735,7 @@
hlist_add_head_rcu(&p->hlist,
&kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
- if (!kprobes_all_disarmed)
+ if (!kprobes_all_disarmed && !kprobe_disabled(p))
arch_arm_kprobe(p);
out_unlock_text:
@@ -724,6 +750,26 @@
}
EXPORT_SYMBOL_GPL(register_kprobe);
+/* Check passed kprobe is valid and return kprobe in kprobe_table. */
+static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p)
+{
+ struct kprobe *old_p, *list_p;
+
+ old_p = get_kprobe(p->addr);
+ if (unlikely(!old_p))
+ return NULL;
+
+ if (p != old_p) {
+ list_for_each_entry_rcu(list_p, &old_p->list, list)
+ if (list_p == p)
+ /* kprobe p is a valid probe */
+ goto valid;
+ return NULL;
+ }
+valid:
+ return old_p;
+}
+
/*
* Unregister a kprobe without a scheduler synchronization.
*/
@@ -731,18 +777,10 @@
{
struct kprobe *old_p, *list_p;
- old_p = get_kprobe(p->addr);
- if (unlikely(!old_p))
+ old_p = __get_valid_kprobe(p);
+ if (old_p == NULL)
return -EINVAL;
- if (p != old_p) {
- list_for_each_entry_rcu(list_p, &old_p->list, list)
- if (list_p == p)
- /* kprobe p is a valid probe */
- goto valid_p;
- return -EINVAL;
- }
-valid_p:
if (old_p == p ||
(old_p->pre_handler == aggr_pre_handler &&
list_is_singular(&old_p->list))) {
@@ -751,7 +789,7 @@
* enabled and not gone - otherwise, the breakpoint would
* already have been removed. We save on flushing icache.
*/
- if (!kprobes_all_disarmed && !kprobe_gone(old_p)) {
+ if (!kprobes_all_disarmed && !kprobe_disabled(old_p)) {
mutex_lock(&text_mutex);
arch_disarm_kprobe(p);
mutex_unlock(&text_mutex);
@@ -769,6 +807,11 @@
}
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))
+ arch_disarm_kprobe(old_p);
+ }
}
return 0;
}
@@ -1078,6 +1121,7 @@
static void __kprobes kill_kprobe(struct kprobe *p)
{
struct kprobe *kp;
+
p->flags |= KPROBE_FLAG_GONE;
if (p->pre_handler == aggr_pre_handler) {
/*
@@ -1219,12 +1263,18 @@
else
kprobe_type = "k";
if (sym)
- seq_printf(pi, "%p %s %s+0x%x %s %s\n", p->addr, kprobe_type,
- sym, offset, (modname ? modname : " "),
- (kprobe_gone(p) ? "[GONE]" : ""));
+ seq_printf(pi, "%p %s %s+0x%x %s %s%s\n",
+ p->addr, kprobe_type, sym, offset,
+ (modname ? modname : " "),
+ (kprobe_gone(p) ? "[GONE]" : ""),
+ ((kprobe_disabled(p) && !kprobe_gone(p)) ?
+ "[DISABLED]" : ""));
else
- seq_printf(pi, "%p %s %p %s\n", p->addr, kprobe_type, p->addr,
- (kprobe_gone(p) ? "[GONE]" : ""));
+ 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]" : ""));
}
static void __kprobes *kprobe_seq_start(struct seq_file *f, loff_t *pos)
@@ -1289,6 +1339,71 @@
.release = seq_release,
};
+/* Disable one kprobe */
+int __kprobes disable_kprobe(struct kprobe *kp)
+{
+ int ret = 0;
+ struct kprobe *p;
+
+ mutex_lock(&kprobe_mutex);
+
+ /* Check whether specified probe is valid. */
+ p = __get_valid_kprobe(kp);
+ if (unlikely(p == NULL)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ /* If the probe is already disabled (or gone), just return */
+ if (kprobe_disabled(kp))
+ goto out;
+
+ kp->flags |= KPROBE_FLAG_DISABLED;
+ if (p != kp)
+ /* When kp != p, p is always enabled. */
+ try_to_disable_aggr_kprobe(p);
+
+ if (!kprobes_all_disarmed && kprobe_disabled(p))
+ arch_disarm_kprobe(p);
+out:
+ mutex_unlock(&kprobe_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(disable_kprobe);
+
+/* Enable one kprobe */
+int __kprobes enable_kprobe(struct kprobe *kp)
+{
+ int ret = 0;
+ struct kprobe *p;
+
+ mutex_lock(&kprobe_mutex);
+
+ /* Check whether specified probe is valid. */
+ p = __get_valid_kprobe(kp);
+ if (unlikely(p == NULL)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (kprobe_gone(kp)) {
+ /* This kprobe has gone, we couldn't enable it. */
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (!kprobes_all_disarmed && kprobe_disabled(p))
+ arch_arm_kprobe(p);
+
+ p->flags &= ~KPROBE_FLAG_DISABLED;
+ if (p != kp)
+ kp->flags &= ~KPROBE_FLAG_DISABLED;
+out:
+ mutex_unlock(&kprobe_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(enable_kprobe);
+
static void __kprobes arm_all_kprobes(void)
{
struct hlist_head *head;
@@ -1306,7 +1421,7 @@
for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
head = &kprobe_table[i];
hlist_for_each_entry_rcu(p, node, head, hlist)
- if (!kprobe_gone(p))
+ if (!kprobe_disabled(p))
arch_arm_kprobe(p);
}
mutex_unlock(&text_mutex);
@@ -1338,7 +1453,7 @@
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_gone(p))
+ if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p))
arch_disarm_kprobe(p);
}
}