Re: [PATCH v3 1/3] perf annotate: Fix a bug reading link name from a build-id file

[Taeung Song]

On 03/28/2017 03:01 AM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 27, 2017 at 04:10:36PM +0900, Taeung Song escreveu:
> > It is wrong way to read link name from a build-id file.
> > Because a build-id file is not symbolic link
> > but build-id directory of it is symbolic link, so fix it.
>
> Ok, applied, in the past it was always a symlink, but the following cset
> changed that, so I added:
>
>     Fixes: 01412261d994 ("perf buildid-cache: Use path/to/bin/buildid/elf instead of path/to/bin/buildid")
>
> Thanks,
>
> - Arnaldo

Thank you!

- Taeung

> > For example, if build-id file name gotten from
> > dso__build_id_filename() is as below,
> >
> >   /root/.debug/.build-id/4f/75c7d197c951659d1c1b8b5fd49bcdf8f3f8b1/elf
> >
> > To correctly read link name of build-id,
> > use the build-id dir path that is a symbolic link,
> > instead of the above build-id file name like below.
> >
> >   /root/.debug/.build-id/4f/75c7d197c951659d1c1b8b5fd49bcdf8f3f8b1
> >
> > Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> > Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Signed-off-by: Taeung Song <treeze.taeung@xxxxxxxxx>
> > ---
> >  tools/perf/util/annotate.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> > index 3d0263e..6dc9148 100644
> > --- a/tools/perf/util/annotate.c
> > +++ b/tools/perf/util/annotate.c
> > @@ -1307,6 +1307,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
> >  {
> >  	char linkname[PATH_MAX];
> >  	char *build_id_filename;
> > +	char *build_id_path = NULL;
> >
> >  	if (dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS &&
> >  	    !dso__is_kcore(dso))
> > @@ -1322,8 +1323,14 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
> >  		goto fallback;
> >  	}
> >
> > +	build_id_path = strdup(filename);
> > +	if (!build_id_path)
> > +		return -1;
> > +
> > +	dirname(build_id_path);
> > +
> >  	if (dso__is_kcore(dso) ||
> > -	    readlink(filename, linkname, sizeof(linkname)) < 0 ||
> > +	    readlink(build_id_path, linkname, sizeof(linkname)) < 0 ||
> >  	    strstr(linkname, DSO__NAME_KALLSYMS) ||
> >  	    access(filename, R_OK)) {
> >  fallback:
> > @@ -1335,6 +1342,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
> >  		__symbol__join_symfs(filename, filename_size, dso->long_name);
> >  	}
> >
> > +	free(build_id_path);
> >  	return 0;
> >  }
> >
> > --
> > 2.7.4