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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2017-05-16 20:58:35 +0200 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2017-05-18 03:55:58 +0200 |
| commit | 545a028190dae4437aac4f86da7c8ab20857647c (patch) | |
| tree | b0c28f76813590769ca2bdedf85071f97dc59023 | |
| parent | selftests/ftrace: Add test to remove instance with active event triggers (diff) | |
| download | linux-545a028190dae4437aac4f86da7c8ab20857647c.tar.xz linux-545a028190dae4437aac4f86da7c8ab20857647c.zip | |
kprobes: Document how optimized kprobes are removed from module unload
Thomas discovered a bug where the kprobe trace tests had a race
condition where the kprobe_optimizer called from a delayed work queue
that does the optimizing and "unoptimizing" of a kprobe, can try to
modify the text after it has been freed by the init code.
The kprobe trace selftest is a special case, and Thomas and myself
investigated to see if there's a chance that this could also be a bug
with module unloading, as the code is not obvious to how it handles
this. After adding lots of printks, I figured it out. Thomas suggested
that this should be commented so that others will not have to go
through this exercise again.
Link: http://lkml.kernel.org/r/20170516145835.3827d3aa@gandalf.local.home
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/kprobes.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 199243bba554..2d2d3a568e4e 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -2183,6 +2183,12 @@ static int kprobes_module_callback(struct notifier_block *nb, * The vaddr this probe is installed will soon * be vfreed buy not synced to disk. Hence, * disarming the breakpoint isn't needed. + * + * Note, this will also move any optimized probes + * that are pending to be removed from their + * corresponding lists to the freeing_list and + * will not be touched by the delayed + * kprobe_optimizer work handler. */ kill_kprobe(p); } |