Commit de5bd88d authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Linus Torvalds

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: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Acked-by: default avatarAnanth 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e579abeb
......@@ -212,7 +212,9 @@ hit, Kprobes calls kp->pre_handler. After the probed instruction
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 @@ probes) in the specified array, they clear the addr field of those
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 @@ the probe. If the probed function belongs to a module, the module name
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.
......@@ -112,18 +112,28 @@ struct kprobe {
/* 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 unregister_kretprobes(struct kretprobe **rps, int num);
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 unregister_kretprobes(struct kretprobe **rps, int num)
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 */
......@@ -328,7 +328,7 @@ static int __kprobes aggr_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 && !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 @@ static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
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 inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
*/
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 @@ static int __kprobes add_new_kprobe(struct kprobe *ap, struct kprobe *p)
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 @@ static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
* 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 @@ int __kprobes register_kprobe(struct kprobe *p)
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 @@ int __kprobes register_kprobe(struct kprobe *p)
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:
......@@ -724,25 +750,37 @@ int __kprobes register_kprobe(struct kprobe *p)
}
EXPORT_SYMBOL_GPL(register_kprobe);
/*
* Unregister a kprobe without a scheduler synchronization.
*/
static int __kprobes __unregister_kprobe_top(struct kprobe *p)
/* 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 -EINVAL;
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_p;
return -EINVAL;
goto valid;
return NULL;
}
valid_p:
valid:
return old_p;
}
/*
* Unregister a kprobe without a scheduler synchronization.
*/
static int __kprobes __unregister_kprobe_top(struct kprobe *p)
{
struct kprobe *old_p, *list_p;
old_p = __get_valid_kprobe(p);
if (old_p == NULL)
return -EINVAL;
if (old_p == p ||
(old_p->pre_handler == aggr_pre_handler &&
list_is_singular(&old_p->list))) {
......@@ -751,7 +789,7 @@ static int __kprobes __unregister_kprobe_top(struct kprobe *p)
* 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 @@ static int __kprobes __unregister_kprobe_top(struct kprobe *p)
}
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 int __kprobes pre_handler_kretprobe(struct kprobe *p,
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 @@ static void __kprobes report_probe(struct seq_file *pi, struct kprobe *p,
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 @@ static struct file_operations debugfs_kprobes_operations = {
.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 @@ static void __kprobes arm_all_kprobes(void)
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 @@ static void __kprobes disarm_all_kprobes(void)
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);
}
}
......
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