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

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Date:   Wed, 17 Feb 2021 20:54:00 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Nicholas Fraser <nfraser@...eweavers.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

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.
> 
> Signed-off-by: Nicholas Fraser <nfraser@...eweavers.com>

Acked-by: Jiri Olsa <jolsa@...hat.com>

thanks,
jirka

> ---
>  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
>