linux-kernel - Re: [PATCH 09/24] perf tools: Add check for existing link in buildid dir

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Message-ID: <20201118091124.GA1414446@krava>
Date:   Wed, 18 Nov 2020 10:11:24 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Song Liu <songliubraving@...com>,
        Stephane Eranian <eranian@...gle.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 09/24] perf tools: Add check for existing link in buildid
 dir

On Tue, Nov 17, 2020 at 01:23:09PM -0800, Ian Rogers wrote:
> On Tue, Nov 17, 2020 at 3:01 AM Jiri Olsa <jolsa@...nel.org> wrote:
> 
> > When adding new build id link we fail if the link is already
> > there. Adding check for existing link and output debug message
> > that the build id is already linked.
> >
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > ---
> >  tools/perf/util/build-id.c | 15 ++++++++++++++-
> >  1 file changed, 14 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> > index 7d9ecc37849c..ef9a31b54ba2 100644
> > --- a/tools/perf/util/build-id.c
> > +++ b/tools/perf/util/build-id.c
> > @@ -754,8 +754,21 @@ int build_id_cache__add_s(const char *sbuild_id,
> > const char *name,
> >         tmp = dir_name + strlen(buildid_dir) - 5;
> >         memcpy(tmp, "../..", 5);
> >
> > -       if (symlink(tmp, linkname) == 0)
> > +       if (symlink(tmp, linkname) == 0) {
> >                 err = 0;
> > +       } else if (errno == EEXIST) {
> > +               char path[PATH_MAX];
> > +
> > +               if (readlink(linkname, path, sizeof(path)) == -1) {
> > +                       pr_err("Cant read link: %s\n", linkname);
> > +                       goto out_free;
> > +               }
> >
> 
> readlink needs null termination, such as:
> https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/util/build-id.c?h=perf/core#n212

will fix, thanks

jirka

> 
> Thanks,
> Ian
> 
> +               if (strcmp(tmp, path)) {
> > +                       pr_debug("build <%s> already linked to %s\n",
> > +                                sbuild_id, linkname);
> > +               }
> > +               err = 0;
> > +       }
> >
> >         /* Update SDT cache : error is just warned */
> >         if (realname &&
> > --
> > 2.26.2
> >
> >