Commit df019b1d authored by Keshavamurthy Anil S's avatar Keshavamurthy Anil S Committed by Linus Torvalds
Browse files

[PATCH] kprobes: fix unloading of self probed module

When a kprobes modules is written in such a way that probes are inserted on
itself, then unload of that moudle was not possible due to reference
couning on the same module.

The below patch makes a check and incrementes the module refcount only if
it is not a self probed module.

We need to allow modules to probe themself for kprobes performance

This patch has been tested on several x86_64, ppc64 and IA64 architectures.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent ef43bc4f
......@@ -68,6 +68,9 @@ struct kprobe {
/* list of kprobes for multi-handler support */
struct list_head list;
/* Indicates that the corresponding module has been ref counted */
unsigned int mod_refcounted;
/*count the number of times this probe was temporarily disarmed */
unsigned long nmissed;
......@@ -449,19 +449,32 @@ static int __kprobes in_kprobes_functions(unsigned long addr)
return 0;
int __kprobes register_kprobe(struct kprobe *p)
static int __kprobes __register_kprobe(struct kprobe *p,
unsigned long called_from)
int ret = 0;
struct kprobe *old_p;
struct module *mod;
struct module *probed_mod;
if ((!kernel_text_address((unsigned long) p->addr)) ||
in_kprobes_functions((unsigned long) p->addr))
return -EINVAL;
if ((mod = module_text_address((unsigned long) p->addr)) &&
p->mod_refcounted = 0;
/* Check are we probing a module */
if ((probed_mod = module_text_address((unsigned long) p->addr))) {
struct module *calling_mod = module_text_address(called_from);
/* We must allow modules to probe themself and
* in this case avoid incrementing the module refcount,
* so as to allow unloading of self probing modules.
if (calling_mod && (calling_mod != probed_mod)) {
if (unlikely(!try_module_get(probed_mod)))
return -EINVAL;
p->mod_refcounted = 1;
} else
probed_mod = NULL;
p->nmissed = 0;
......@@ -483,11 +496,17 @@ int __kprobes register_kprobe(struct kprobe *p)
if (ret && mod)
if (ret && probed_mod)
return ret;
int __kprobes register_kprobe(struct kprobe *p)
return __register_kprobe(p,
(unsigned long)__builtin_return_address(0));
void __kprobes unregister_kprobe(struct kprobe *p)
struct module *mod;
......@@ -524,7 +543,8 @@ valid_p:
if ((mod = module_text_address((unsigned long)p->addr)))
if (p->mod_refcounted &&
(mod = module_text_address((unsigned long)p->addr)))
if (cleanup_p) {
......@@ -547,7 +567,8 @@ int __kprobes register_jprobe(struct jprobe *jp)
jp->kp.pre_handler = setjmp_pre_handler;
jp->kp.break_handler = longjmp_break_handler;
return register_kprobe(&jp->kp);
return __register_kprobe(&jp->kp,
(unsigned long)__builtin_return_address(0));
void __kprobes unregister_jprobe(struct jprobe *jp)
......@@ -587,7 +608,8 @@ int __kprobes register_kretprobe(struct kretprobe *rp)
rp->nmissed = 0;
/* Establish function entry probe point */
if ((ret = register_kprobe(&rp->kp)) != 0)
if ((ret = __register_kprobe(&rp->kp,
(unsigned long)__builtin_return_address(0))) != 0)
return ret;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment