From: "Steven Rostedt (VMware)" <rost...@goodmis.org> 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/20201028115612.990886...@goodmis.org Link: https://lkml.kernel.org/r/20201106023546.720372...@goodmis.org Cc: Peter Zijlstra <pet...@infradead.org> Cc: Ingo Molnar <mi...@kernel.org> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Jiri Kosina <ji...@kernel.org> Cc: Miroslav Benes <mbe...@suse.cz> Cc: Petr Mladek <pmla...@suse.com> Cc: Masami Hiramatsu <mhira...@kernel.org> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Thomas Meyer <tho...@m3y3r.de> Reviewed-by: Kees Cook <keesc...@chromium.org> Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> --- fs/pstore/ftrace.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c index 5c0450701293..816210fc5d3a 100644 --- a/fs/pstore/ftrace.c +++ b/fs/pstore/ftrace.c @@ -28,6 +28,7 @@ static void notrace pstore_ftrace_call(unsigned long ip, struct ftrace_ops *op, struct pt_regs *regs) { + int bit; unsigned long flags; struct pstore_ftrace_record rec = {}; struct pstore_record record = { @@ -40,6 +41,10 @@ static void notrace pstore_ftrace_call(unsigned long ip, if (unlikely(oops_in_progress)) return; + bit = ftrace_test_recursion_trylock(); + if (bit < 0) + return; + local_irq_save(flags); rec.ip = ip; @@ -49,6 +54,7 @@ static void notrace pstore_ftrace_call(unsigned long ip, psinfo->write(&record); local_irq_restore(flags); + ftrace_test_recursion_unlock(bit); } static struct ftrace_ops pstore_ftrace_ops __read_mostly = { -- 2.28.0
