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Subject[PATCH 15/19] kprobes: cleanup to separate probe-able check
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Separate probe-able address checking code from
register_kprobe().

Link: http://lkml.kernel.org/r/20120605102820.27845.90133.stgit@localhost.localdomain

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/kprobes.c | 82 ++++++++++++++++++++++++++++++------------------------
1 file changed, 45 insertions(+), 37 deletions(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 7a8a122..6137fe3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1313,67 +1313,80 @@ static inline int check_kprobe_rereg(struct kprobe *p)
return ret;
}

-int __kprobes register_kprobe(struct kprobe *p)
+static __kprobes int check_kprobe_address_safe(struct kprobe *p,
+ struct module **probed_mod)
{
int ret = 0;
- struct kprobe *old_p;
- struct module *probed_mod;
- kprobe_opcode_t *addr;
-
- addr = kprobe_addr(p);
- if (IS_ERR(addr))
- return PTR_ERR(addr);
- p->addr = addr;
-
- ret = check_kprobe_rereg(p);
- if (ret)
- return ret;

jump_label_lock();
preempt_disable();
+
+ /* Ensure it is not in reserved area nor out of text */
if (!kernel_text_address((unsigned long) p->addr) ||
in_kprobes_functions((unsigned long) p->addr) ||
ftrace_text_reserved(p->addr, p->addr) ||
jump_label_text_reserved(p->addr, p->addr)) {
ret = -EINVAL;
- goto cannot_probe;
+ goto out;
}

- /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
- p->flags &= KPROBE_FLAG_DISABLED;
-
- /*
- * Check if are we probing a module.
- */
- probed_mod = __module_text_address((unsigned long) p->addr);
- if (probed_mod) {
- /* Return -ENOENT if fail. */
- ret = -ENOENT;
+ /* Check if are we probing a module */
+ *probed_mod = __module_text_address((unsigned long) p->addr);
+ if (*probed_mod) {
/*
* We must hold a refcount of the probed module while updating
* its code to prohibit unexpected unloading.
*/
- if (unlikely(!try_module_get(probed_mod)))
- goto cannot_probe;
+ if (unlikely(!try_module_get(*probed_mod))) {
+ ret = -ENOENT;
+ goto out;
+ }

/*
* If the module freed .init.text, we couldn't insert
* kprobes in there.
*/
- if (within_module_init((unsigned long)p->addr, probed_mod) &&
- probed_mod->state != MODULE_STATE_COMING) {
- module_put(probed_mod);
- goto cannot_probe;
+ if (within_module_init((unsigned long)p->addr, *probed_mod) &&
+ (*probed_mod)->state != MODULE_STATE_COMING) {
+ module_put(*probed_mod);
+ *probed_mod = NULL;
+ ret = -ENOENT;
}
- /* ret will be updated by following code */
}
+out:
preempt_enable();
jump_label_unlock();

+ return ret;
+}
+
+int __kprobes register_kprobe(struct kprobe *p)
+{
+ int ret;
+ struct kprobe *old_p;
+ struct module *probed_mod;
+ kprobe_opcode_t *addr;
+
+ /* Adjust probe address from symbol */
+ addr = kprobe_addr(p);
+ if (IS_ERR(addr))
+ return PTR_ERR(addr);
+ p->addr = addr;
+
+ ret = check_kprobe_rereg(p);
+ if (ret)
+ return ret;
+
+ /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
+ p->flags &= KPROBE_FLAG_DISABLED;
p->nmissed = 0;
INIT_LIST_HEAD(&p->list);
- mutex_lock(&kprobe_mutex);

+ ret = check_kprobe_address_safe(p, &probed_mod);
+ if (ret)
+ return ret;
+
+ mutex_lock(&kprobe_mutex);
jump_label_lock(); /* needed to call jump_label_text_reserved() */

get_online_cpus(); /* For avoiding text_mutex deadlock. */
@@ -1410,11 +1423,6 @@ out:
module_put(probed_mod);

return ret;
-
-cannot_probe:
- preempt_enable();
- jump_label_unlock();
- return ret;
}
EXPORT_SYMBOL_GPL(register_kprobe);

--
1.7.10.4

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