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authorKeshavamurthy Anil S <anil.s.keshavamurthy@intel.com>2006-01-11 12:17:41 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-11 18:42:12 -0800
commitdf019b1d8b893d0f0ee5a9b0f71486f0892561ae (patch)
tree9d2ced14291502af1ca687b5d854d8394cbfb84d
parentef43bc4fc32bec8fda7bae8948b774616dc9e496 (diff)
[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 measurements 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: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--include/linux/kprobes.h3
-rw-r--r--kernel/kprobes.c42
2 files changed, 35 insertions, 10 deletions
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 10005bc92a3..669756bc20a 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -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;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 34a885bb82e..3ea6325228d 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -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)) &&
- (unlikely(!try_module_get(mod))))
- return -EINVAL;
+ 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;
down(&kprobe_mutex);
@@ -483,11 +496,17 @@ int __kprobes register_kprobe(struct kprobe *p)
out:
up(&kprobe_mutex);
- if (ret && mod)
- module_put(mod);
+ if (ret && probed_mod)
+ module_put(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:
up(&kprobe_mutex);
synchronize_sched();
- if ((mod = module_text_address((unsigned long)p->addr)))
+ if (p->mod_refcounted &&
+ (mod = module_text_address((unsigned long)p->addr)))
module_put(mod);
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)
free_rp_inst(rp);
return ret;
}