linux-kernel - Re: [PATCH 8/9] perf tools: Add size to struct perf_record_header_build

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Date:   Wed, 30 Sep 2020 22:31:47 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     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>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 8/9] perf tools: Add size to struct perf_record_header_build_id

On Wed, Sep 30, 2020 at 10:15 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> We do not store size with build ids in perf data,
> but there's enough space to do it. Adding misc bit
> PERF_RECORD_MISC_BUILD_ID_SIZE to mark build id event
> with size.
>
> With this fix the dso with md5 build id will have correct
> build id data and will be usable for debuginfod processing
> if needed (coming in following patches).
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

Acked-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/lib/perf/include/perf/event.h | 12 +++++++++++-
>  tools/perf/util/build-id.c          |  8 +++++---
>  tools/perf/util/header.c            | 10 +++++++---
>  3 files changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
> index a6dbba6b9073..988c539bedb6 100644
> --- a/tools/lib/perf/include/perf/event.h
> +++ b/tools/lib/perf/include/perf/event.h
> @@ -201,10 +201,20 @@ struct perf_record_header_tracing_data {
>         __u32                    size;
>  };
>
> +#define PERF_RECORD_MISC_BUILD_ID_SIZE (1 << 15)
> +
>  struct perf_record_header_build_id {
>         struct perf_event_header header;
>         pid_t                    pid;
> -       __u8                     build_id[24];
> +       union {
> +               __u8             build_id[24];
> +               struct {
> +                       __u8     data[20];
> +                       __u8     size;
> +                       __u8     reserved1__;
> +                       __u16    reserved2__;
> +               };
> +       };
>         char                     filename[];
>  };
>
> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> index b5648735f01f..8763772f1095 100644
> --- a/tools/perf/util/build-id.c
> +++ b/tools/perf/util/build-id.c
> @@ -296,7 +296,7 @@ char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size,
>                         continue;               \
>                 else
>
> -static int write_buildid(const char *name, size_t name_len, u8 *build_id,
> +static int write_buildid(const char *name, size_t name_len, struct build_id *bid,
>                          pid_t pid, u16 misc, struct feat_fd *fd)
>  {
>         int err;
> @@ -307,7 +307,9 @@ static int write_buildid(const char *name, size_t name_len, u8 *build_id,
>         len = PERF_ALIGN(len, NAME_ALIGN);
>
>         memset(&b, 0, sizeof(b));
> -       memcpy(&b.build_id, build_id, BUILD_ID_SIZE);
> +       memcpy(&b.data, bid->data, bid->size);
> +       b.size = (u8) bid->size;
> +       misc |= PERF_RECORD_MISC_BUILD_ID_SIZE;
>         b.pid = pid;
>         b.header.misc = misc;
>         b.header.size = sizeof(b) + len;
> @@ -354,7 +356,7 @@ static int machine__write_buildid_table(struct machine *machine,
>                 in_kernel = pos->kernel ||
>                                 is_kernel_module(name,
>                                         PERF_RECORD_MISC_CPUMODE_UNKNOWN);
> -               err = write_buildid(name, name_len, pos->bid.data, machine->pid,
> +               err = write_buildid(name, name_len, &pos->bid, machine->pid,
>                                     in_kernel ? kmisc : umisc, fd);
>                 if (err)
>                         break;
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 21243adbb9fd..8da3886f10a8 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -2083,8 +2083,12 @@ static int __event_process_build_id(struct perf_record_header_build_id *bev,
>         if (dso != NULL) {
>                 char sbuild_id[SBUILD_ID_SIZE];
>                 struct build_id bid;
> +               size_t size = BUILD_ID_SIZE;
>
> -               build_id__init(&bid, bev->build_id, BUILD_ID_SIZE);
> +               if (bev->header.misc & PERF_RECORD_MISC_BUILD_ID_SIZE)
> +                       size = bev->size;
> +
> +               build_id__init(&bid, bev->data, size);
>                 dso__set_build_id(dso, &bid);
>
>                 if (dso_space != DSO_SPACE__USER) {
> @@ -2098,8 +2102,8 @@ static int __event_process_build_id(struct perf_record_header_build_id *bev,
>                 }
>
>                 build_id__sprintf(&dso->bid, sbuild_id);
> -               pr_debug("build id event received for %s: %s\n",
> -                        dso->long_name, sbuild_id);
> +               pr_debug("build id event received for %s: %s [%lu]\n",
> +                        dso->long_name, sbuild_id, size);
>                 dso__put(dso);
>         }
>
> --
> 2.26.2
>