linux-kernel - Re: [PATCH 1/4] perf buildid-cache: Don't skip 16-byte build-ids

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Date:   Tue, 16 Feb 2021 11:35:06 -0500
From:   Nicholas Fraser <nfraser@...eweavers.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        "Frank Ch. Eigler" <fche@...hat.com>,
        Song Liu <songliubraving@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kim Phillips <kim.phillips@....com>,
        Tommi Rantala <tommi.t.rantala@...ia.com>,
        Remi Bernon <rbernon@...eweavers.com>,
        linux-kernel@...r.kernel.org,
        Ulrich Czekalla <uczekalla@...eweavers.com>,
        Huw Davies <huw@...eweavers.com>
Subject: Re: [PATCH 1/4] perf buildid-cache: Don't skip 16-byte build-ids

No problem, I've added a call to "perf buildid-cache -l" in check() to make
sure the added IDs are reported. The MD5 test fails without the previous
patch to allow 16-byte build-ids.

Do you also want PE files tested by this test script? This would make the
script depend on a number of things:

- We'd need to change "readelf" to something that can read the build-id of
  PE files;

- We'd need MinGW installed to build them on the fly the same as the ELF
  test cases, although we could use tests/pe-file.exe instead which is
  already included;

- We'd need Wine to actually run it under perf record, which I'm sure you
  don't want to depend on;

- We'd need to detect whether perf was built with libbfd support. Easily
  done by calling perf version --build-options but by this point the test
  case is getting pretty out of hand for what it's supposed to test.

I'll send patches for this test without PE support. It still tests 16-byte
build-ids because it tests an MD5 ELF file. Let me know if you also want me
to add PE support to this script. We can make it optionally perform PE
tests if all of the necessary tools are installed but it would take some
pretty large changes to the script.

Nick


On 2021-02-15 9:31 a.m., Jiri Olsa wrote:
> On Wed, Feb 10, 2021 at 02:17:25PM -0500, Nicholas Fraser wrote:
>> lsdir_bid_tail_filter() ignored any build-id that wasn't exactly 20
>> bytes. This worked only for SHA-1 build-ids. The build-id for a PE file
>> is always a 16-byte GUID and ELF files can also have MD5 or UUID
>> build-ids.
>>
>> This fix changes the filter to allow build-ids between 16 and 20 bytes.
> 
> hi,
> there's tests/shell/buildid.sh test for this, please add
> testcase for this.. looks like perf buildid-cacle -l will
> end up calling this function
> 
> thanks,
> jirka
> 
>>
>> Signed-off-by: Nicholas Fraser <nfraser@...eweavers.com>
>> ---
>>  tools/perf/util/build-id.c | 5 +++--
>>  tools/perf/util/build-id.h | 4 +++-
>>  2 files changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
>> index 02df36b30ac5..e32e8f2ff3bd 100644
>> --- a/tools/perf/util/build-id.c
>> +++ b/tools/perf/util/build-id.c
>> @@ -448,7 +448,8 @@ static bool lsdir_bid_tail_filter(const char *name __maybe_unused,
>>  	int i = 0;
>>  	while (isxdigit(d->d_name[i]) && i < SBUILD_ID_SIZE - 3)
>>  		i++;
>> -	return (i == SBUILD_ID_SIZE - 3) && (d->d_name[i] == '\0');
>> +	return (i >= SBUILD_ID_MIN_SIZE - 3) && (i <= SBUILD_ID_SIZE - 3) &&
>> +		(d->d_name[i] == '\0');
>>  }
>>  
>>  struct strlist *build_id_cache__list_all(bool validonly)
>> @@ -490,7 +491,7 @@ struct strlist *build_id_cache__list_all(bool validonly)
>>  		}
>>  		strlist__for_each_entry(nd2, linklist) {
>>  			if (snprintf(sbuild_id, SBUILD_ID_SIZE, "%s%s",
>> -				     nd->s, nd2->s) != SBUILD_ID_SIZE - 1)
>> +				     nd->s, nd2->s) > SBUILD_ID_SIZE - 1)
>>  				goto err_out;
>>  			if (validonly && !build_id_cache__valid_id(sbuild_id))
>>  				continue;
>> diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
>> index 02613f4b2c29..c19617151670 100644
>> --- a/tools/perf/util/build-id.h
>> +++ b/tools/perf/util/build-id.h
>> @@ -2,8 +2,10 @@
>>  #ifndef PERF_BUILD_ID_H_
>>  #define PERF_BUILD_ID_H_ 1
>>  
>> -#define BUILD_ID_SIZE	20
>> +#define BUILD_ID_SIZE	20 /* SHA-1 length in bytes */
>> +#define BUILD_ID_MIN_SIZE	16 /* MD5/UUID/GUID length in bytes */
>>  #define SBUILD_ID_SIZE	(BUILD_ID_SIZE * 2 + 1)
>> +#define SBUILD_ID_MIN_SIZE	(BUILD_ID_MIN_SIZE * 2 + 1)
>>  
>>  #include "machine.h"
>>  #include "tool.h"
>> -- 
>> 2.30.0
>>
>