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From: Steven Rostedt <>
To: Linus Torvalds <>
Cc: LKML <>,
	Ingo Molnar <>,
	Andrew Morton <>,
	Artem Savkov <>
Subject: [GIT PULL] ftrace: Return the first found result in lookup_rec()
Date: Wed, 11 Mar 2020 10:45:36 -0400	[thread overview]
Message-ID: <20200311104536.59de3c5a@gandalf.local.home> (raw)


Have ftrace lookup_rec() return a consistent record otherwise it
can break live patching.

Please pull the latest trace-v5.6-rc4 tree, which can be found at:


Tag SHA1: 3bedd0c3802cdffacf9fd6a4cac9f3fa6a4da477
Head SHA1: d9815bff6b379ff46981bea9dfeb146081eab314

Artem Savkov (1):
      ftrace: Return the first found result in lookup_rec()

 kernel/trace/ftrace.c | 2 ++
 1 file changed, 2 insertions(+)
commit d9815bff6b379ff46981bea9dfeb146081eab314
Author: Artem Savkov <>
Date:   Fri Mar 6 18:43:17 2020 +0100

    ftrace: Return the first found result in lookup_rec()
    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()
    Fixes: 7e16f581a817 ("ftrace: Separate out functionality from ftrace_location_range()")
    Signed-off-by: Artem Savkov <>
    Signed-off-by: Steven Rostedt (VMware) <>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 3f7ee102868a..fd81c7de77a7 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1547,6 +1547,8 @@ static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end)
 		rec = bsearch(&key, pg->records, pg->index,
 			      sizeof(struct dyn_ftrace),
+		if (rec)
+			break;
 	return rec;

             reply	other threads:[~2020-03-11 14:45 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11 14:45 Steven Rostedt [this message]
2020-03-11 20:45 ` [GIT PULL] ftrace: Return the first found result in lookup_rec() pr-tracker-bot

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