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Subject[PATCH] kprobes: bugfix: set kprobes_all_disarmed earlier to enable re-optimization.
Date
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>
---
kernel/kprobes.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index bad4e95..b185464 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:
--
1.8.4


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