linux-kernel - Re: [PATCH 2/2] perf symbols: Fix HAVE_LIBBFD_BUILDID

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Message-ID: <CAP-5=fWHGFBaCgiRcj8zVy196OE07F8jnSUbjvsO_HerdqeyTg@mail.gmail.com>
Date: Wed, 3 Sep 2025 09:07:29 -0700
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>, Sam James <sam@...too.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Leo Yan <leo.yan@....com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] perf symbols: Fix HAVE_LIBBFD_BUILDID_SUPPORT build

On Wed, Sep 3, 2025 at 8:15 AM James Clark <james.clark@...aro.org> wrote:
>
> read_build_id() now has a blocking argument, but libbfd uses fopen()
> internally which doesn't support O_NONBLOCK. Fix the build by adding the
> argument and ignoring it:
>
>   util/symbol-elf.c:964:8: error: too many arguments to function ‘read_build_id’
>     964 |  err = read_build_id(filename, bid, block);
>
> Fixes: 2c369d91d093 ("perf symbol: Add blocking argument to filename__read_build_id")
> Signed-off-by: James Clark <james.clark@...aro.org>

Libbfd should go away:
https://lore.kernel.org/lkml/20250823003216.733941-14-irogers@google.com/
but I can imagine that currently this is hit in a build test - sorry
for missing that and thanks for the fix!

We should probably honor the blocking argument (use fdopen) as the
probe perf tests will invoke perf record system wide with data pages
and predictably hang on this for files like mmap-ed in sound devices.
That said, maybe this hanging will serve as an indication not to use
the deprecated libbfd code. From the sounds of things this will break
gentoo :-(
https://lore.kernel.org/lkml/87ldnacz33.fsf@gentoo.org/

Thanks,
Ian

> ---
>  tools/perf/util/symbol-elf.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index 033c79231a54..e0d6ff7d0acf 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -873,7 +873,8 @@ static int elf_read_build_id(Elf *elf, void *bf, size_t size)
>
>  #ifdef HAVE_LIBBFD_BUILDID_SUPPORT
>
> -static int read_build_id(const char *filename, struct build_id *bid)
> +static int read_build_id(const char *filename, struct build_id *bid,
> +                        bool block __maybe_unused)
>  {
>         size_t size = sizeof(bid->data);
>         int err = -1;
>
> --
> 2.34.1
>