linux-kernel - Re: [PATCH] perf inject: Keep build-ID data if no option is used

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Message-ID: <CAP-5=fXShAb9Ez-j64fY8c_XDpRUp33Z1Z75jS9=+UaTKa68HQ@mail.gmail.com>
Date: Wed, 17 Dec 2025 10:57:01 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, James Clark <james.clark@...aro.org>, 
	Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org, 
	Gabriel Marin <gmx@...gle.com>
Subject: Re: [PATCH] perf inject: Keep build-ID data if no option is used

On Wed, Dec 17, 2025 at 10:39 AM Namhyung Kim <namhyung@...nel.org> wrote:
>
> The keep_feat() determines which header features will be kept or
> discarded.  Usually perf inject will add build-IDs based on -b, -B or
> other related options.  But it lose build-ID when none of those options
> are used.  This is meaningful only when --buildid-mmap is not used.
>
> The following example shows the impact of this change.
>
>   $ perf record --no-buildid-mmap true
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Captured and wrote 0.037 MB perf.data (5 samples) ]
>
>   $ perf inject -i perf.data -o perf.data.inject
>
>   $ perf buildid-list -i perf.data
>   08cccc2a9388d5247ccb3e864f3063b975b0a15d /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
>   fd5c4d5673256cd6bda51725dba048dabb0f854e [kernel.kallsyms]
>   97a36ce1140071be5c36b147fa0bed173e05a602 [vdso]
>
>   $ perf buildid-list -i perf.data.inject
>   97a36ce1140071be5c36b147fa0bed173e05a602 [vdso]
>
> With this change, perf.data.inject would show the same list (of course,
> you need to run perf inject again).
>
> Reported-by: Gabriel Marin <gmx@...gle.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>

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

Thanks,
Ian

> ---
>  tools/perf/builtin-inject.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index aa7be4fb5838fb99..6080afec537d2178 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -2022,7 +2022,7 @@ static int save_section_info(struct perf_inject *inject)
>         return perf_header__process_sections(header, fd, inject, save_section_info_cb);
>  }
>
> -static bool keep_feat(int feat)
> +static bool keep_feat(struct perf_inject *inject, int feat)
>  {
>         switch (feat) {
>         /* Keep original information that describes the machine or software */
> @@ -2050,6 +2050,7 @@ static bool keep_feat(int feat)
>                 return true;
>         /* Information that can be updated */
>         case HEADER_BUILD_ID:
> +               return inject->build_id_style == BID_RWS__NONE;
>         case HEADER_CMDLINE:
>         case HEADER_EVENT_DESC:
>         case HEADER_BRANCH_STACK:
> @@ -2108,7 +2109,7 @@ static int feat_copy_cb(struct feat_copier *fc, int feat, struct feat_writer *fw
>         int ret;
>
>         if (!inject->secs[feat].offset ||
> -           !keep_feat(feat))
> +           !keep_feat(inject, feat))
>                 return 0;
>
>         ret = feat_copy(inject, feat, fw);
> --
> 2.52.0.313.g674ac2bdf7-goog
>