kprobes: set kprobes_all_disarmed earlier to enable re-optimization.

In original code, the probed instruction doesn't get optimized after

echo 0 > /sys/kernel/debug/kprobes/enabled
echo 1 > /sys/kernel/debug/kprobes/enabled

This is because original code checks kprobes_all_disarmed in
optimize_kprobe(), but this flag is turned off after calling that
function.  Therefore, optimize_kprobe() will see kprobes_all_disarmed ==
true and doesn't do the optimization.

This patch simply turns off kprobes_all_disarmed earlier to enable
optimization.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2ca272f8f62e..c39790001854 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2320,6 +2320,12 @@ static void arm_all_kprobes(void)
         if (!kprobes_all_disarmed)
                 goto already_enabled;
 
+        /*
+         * optimize_kprobe() called by arm_kprobe() checks
+         * kprobes_all_disarmed, so set kprobes_all_disarmed before
+         * arm_kprobe.
+         */
+        kprobes_all_disarmed = false;
         /* Arming kprobes doesn't optimize kprobe itself */
         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
                 head = &kprobe_table[i];
@@ -2328,7 +2334,6 @@ static void arm_all_kprobes(void)
                                 arm_kprobe(p);
         }
 
-        kprobes_all_disarmed = false;
         printk(KERN_INFO "Kprobes globally enabled\n");
 
 already_enabled: