From: Steven Rostedt <rostedt@goodmis.org>
To: Artem Savkov <asavkov@redhat.com>
Cc: linux-kernel@vger.kernel.org, live-patching@vger.kernel.org
Subject: Re: [PATCH] ftrace: return first found result in lookup_rec()
Date: Fri, 6 Mar 2020 12:12:46 -0500 [thread overview]
Message-ID: <20200306121246.5dac2573@gandalf.local.home> (raw)
In-Reply-To: <20200306081035.21213-1-asavkov@redhat.com>
On Fri, 6 Mar 2020 09:10:35 +0100
Artem Savkov <asavkov@redhat.com> wrote:
> 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 <asavkov@redhat.com>
> ---
> 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;
> }
>
> /**
next prev parent reply other threads:[~2020-03-06 17:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-06 8:10 [PATCH] ftrace: return first found result in lookup_rec() Artem Savkov
2020-03-06 17:12 ` Steven Rostedt [this message]
2020-03-06 17:43 ` [PATCH v2] " Artem Savkov
2020-03-10 19:38 ` Steven Rostedt
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