kprobes: cleanup to separate probe-able check

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>

1 files changed, 45 insertions, 37 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 7a8a1222c7b1..6137fe32b4b8 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);