Re: [PATCH] ftrace: return first found result in lookup_rec()
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2020-03-06 17:12:49
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On Fri, 6 Mar 2020 09:10:35 +0100 Artem Savkov [off-list ref] wrote:
quoted hunk ↗ jump to hunk
It appears that ip ranges can overlap so. In that case lookup_rec() returns whatever results it got last even if it found nothing in last searched page. This breaks an obscure livepatch late module patching usecase: - load livepatch - load the patched module - unload livepatch - try to load livepatch again To fix this return from lookup_rec() as soon as it found the record containing searched-for ip. This used to be this way prior lookup_rec() introduction. Fixes: 7e16f581a817 ("ftrace: Separate out functionality from ftrace_location_range()") Signed-off-by: Artem Savkov <redacted> --- kernel/trace/ftrace.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 3f7ee102868a..b0f5ee1fd6e4 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c@@ -1547,8 +1547,10 @@ static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end) rec = bsearch(&key, pg->records, pg->index, sizeof(struct dyn_ftrace), ftrace_cmp_recs);
how about just adding: if (rec) break; as that will do the same thing without adding two returns. -- Steve
+ if (rec) + return rec; } - return rec; + return NULL; } /**