kprobes: support probing module __init function
Masami Hiramatsu [Tue, 6 Jan 2009 22:41:55 +0000 (14:41 -0800)]
Allow kprobes to probe module __init routines.  When __init functions are
freed, kprobes which probe those functions are set to "Gone" flag.  These
"Gone" probes are disarmed from the code and never be enabled.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kprobes.c

index ddefb9f..1b9cbdc 100644 (file)
@@ -677,6 +677,16 @@ int __kprobes register_kprobe(struct kprobe *p)
                        preempt_enable();
                        return -EINVAL;
                }
+               /*
+                * 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);
+                       preempt_enable();
+                       return -EINVAL;
+               }
        }
        preempt_enable();
 
@@ -1073,19 +1083,24 @@ static int __kprobes kprobes_module_callback(struct notifier_block *nb,
        struct hlist_node *node;
        struct kprobe *p;
        unsigned int i;
+       int checkcore = (val == MODULE_STATE_GOING);
 
-       if (val != MODULE_STATE_GOING)
+       if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
                return NOTIFY_DONE;
 
        /*
-        * module .text section will be freed. We need to
-        * disable kprobes which have been inserted in the section.
+        * When MODULE_STATE_GOING was notified, both of module .text and
+        * .init.text sections would be freed. When MODULE_STATE_LIVE was
+        * notified, only .init.text section would be freed. We need to
+        * disable kprobes which have been inserted in the sections.
         */
        mutex_lock(&kprobe_mutex);
        for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
                head = &kprobe_table[i];
                hlist_for_each_entry_rcu(p, node, head, hlist)
-                       if (within_module_core((unsigned long)p->addr, mod)) {
+                       if (within_module_init((unsigned long)p->addr, mod) ||
+                           (checkcore &&
+                            within_module_core((unsigned long)p->addr, mod))) {
                                /*
                                 * The vaddr this probe is installed will soon
                                 * be vfreed buy not synced to disk. Hence,