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

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Message-ID: <549d3812-a606-4981-83f5-0a99b0ff9f6a@linaro.org>
Date: Thu, 4 Sep 2025 15:18:46 +0100
From: James Clark <james.clark@...aro.org>
To: Rémi Bernon <rbernon@...eweavers.com>,
 Ian Rogers <irogers@...gle.com>, 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 04/09/2025 9:27 am, Rémi Bernon wrote:
> Hi!
> 
> On 9/4/25 10:13, James Clark wrote:
>>
>>
>> On 03/09/2025 5:07 pm, Ian Rogers wrote:
>>> 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@...gle.com/
>>> but I can imagine that currently this is hit in a build test - sorry
>>> for missing that and thanks for the fix!
>>>
>>
>> Yeah just one of the build tests, I'm not actually using it.
>>
>> Remi are you still using this? To be fair the addition for PE support 
>> is fairly recent and even includes a binary for testing it so I'm not 
>> sure if we should be so quick to remove it.
>>
> Yes, I'm still using it occasionally, and I think it's generally useful 
> for Wine profiling purposes and I would rather prefer that it's not 
> removed.
> 
> I know it's not built by default because of license conflicts. I didn't 
> realize that was an issue when contributing the changes, and it is quite 
> unfortunate (and silly IMO).
> 
> Then I'm not particularly attached to libbfd and any other option that 
> would let perf read PE files would be alright, as long as PE support is 
> kept.
> 
> Cheers,

It looks like libLLVM might work. Looking at the doxygen there are vague 
references to PE binaries around the getBuildID() function. But as 
mentioned in the linked thread, it's huge at 100+ MB.

WRT that thread, I think maybe re-writing some of this in Perf wouldn't 
be so bad. Surely getting the buildID is trivial. For PE binaries it's 
hard to tell what's supported currently, what's being used and what's 
being done by what library or tool. addr2line, libbfd, symbols, 
disassembly etc.

James