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

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Date:   Tue, 28 Mar 2017 20:54:28 +0900
From:   Taeung Song <treeze.taeung@...il.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Wang Nan <wangnan0@...wei.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH v3 1/3] perf annotate: Fix a bug reading link name from a
 build-id file



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@...nel.org>
>> Cc: Jiri Olsa <jolsa@...hat.com>
>> Signed-off-by: Taeung Song <treeze.taeung@...il.com>
>> ---
>>  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