From: Steven Rostedt (VMware) Date: Fri, 6 Nov 2020 02:32:41 +0000 (-0500) Subject: livepatch/ftrace: Add recursion protection to the ftrace callback X-Git-Tag: accepted/tizen/unified/20230118.172025~8229^2~27 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=13f3ea9a2c829f28610bb8772a8b9c328412930e;p=platform%2Fkernel%2Flinux-rpi.git livepatch/ftrace: Add recursion protection to the ftrace callback If a ftrace callback does not supply its own recursion protection and does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will make a helper trampoline to do so before calling the callback instead of just calling the callback directly. The default for ftrace_ops is going to change. It will expect that handlers provide their own recursion protection, unless its ftrace_ops states otherwise. Link: https://lkml.kernel.org/r/20201028115613.291169246@goodmis.org Link: https://lkml.kernel.org/r/20201106023547.122802424@goodmis.org Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Masami Hiramatsu Cc: Andrew Morton Cc: Josh Poimboeuf Cc: Jiri Kosina Cc: Joe Lawrence Cc: live-patching@vger.kernel.org Reviewed-by: Petr Mladek Acked-by: Miroslav Benes Signed-off-by: Steven Rostedt (VMware) --- diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c index b552cf2..6c0164d 100644 --- a/kernel/livepatch/patch.c +++ b/kernel/livepatch/patch.c @@ -45,9 +45,13 @@ static void notrace klp_ftrace_handler(unsigned long ip, struct klp_ops *ops; struct klp_func *func; int patch_state; + int bit; ops = container_of(fops, struct klp_ops, fops); + bit = ftrace_test_recursion_trylock(); + if (bit < 0) + return; /* * A variant of synchronize_rcu() is used to allow patching functions * where RCU is not watching, see klp_synchronize_transition(). @@ -117,6 +121,7 @@ static void notrace klp_ftrace_handler(unsigned long ip, unlock: preempt_enable_notrace(); + ftrace_test_recursion_unlock(bit); } /*