On Fri, 6 Mar 2020 18:43:17 +0100
Artem Savkov <asavkov@xxxxxxxxxx> 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.
>
> v2: break instead of two returns
Thanks Artem, I applied your patch. But just an FYI, it's best to place the
"v2" statement below the three dashes "---" so that it doesn't get pulled
into the git commit when this patch is applied via a script.
-- Steve
>
> Fixes: 7e16f581a817 ("ftrace: Separate out functionality from ftrace_location_range()")
> Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
> ---
> kernel/trace/ftrace.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> 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),
> ftrace_cmp_recs);
> + if (rec)
> + break;
> }
> return rec;
> }
