Re: Fix build ID parsing logic in stable trees

Omar Sandoval
2024-11-07T20:04:08Z

On Wed, Nov 06, 2024 at 12:57:34PM +0100, Jiri Olsa wrote:
> On Wed, Nov 06, 2024 at 07:12:05AM +0100, Greg KH wrote:
> > On Tue, Nov 05, 2024 at 10:15:04AM +0100, Jiri Olsa wrote:
> > > On Tue, Nov 05, 2024 at 07:54:48AM +0100, Greg KH wrote:
> > > > On Mon, Nov 04, 2024 at 06:52:52PM +0100, Jiri Olsa wrote:
> > > > > hi,
> > > > > sending fix for buildid parsing that affects only stable trees
> > > > > after merging upstream fix [1].
> > > > >
> > > > > Upstream then factored out the whole buildid parsing code, so it
> > > > > does not have the problem.
> > > >
> > > > Why not just take those patches instead?
> > >
> > > I guess we could, but I thought it's too big for stable
> > >
> > > we'd need following 2 changes to fix the issue:
> > > de3ec364c3c3 lib/buildid: add single folio-based file reader abstraction
> > > 60c845b4896b lib/buildid: take into account e_phoff when fetching program headers
> > >
> > > and there's also few other follow ups:
> > > 5ac9b4e935df lib/buildid: Handle memfd_secret() files in build_id_parse()
> > > cdbb44f9a74f lib/buildid: don't limit .note.gnu.build-id to the first page in ELF
> > > ad41251c290d lib/buildid: implement sleepable build_id_parse() API
> > > 45b8fc309654 lib/buildid: rename build_id_parse() into build_id_parse_nofault()
> > > 4e9d360c4cdf lib/buildid: remove single-page limit for PHDR search
> > >
> > > which I guess are not strictly needed
> >
> > Can you verify what exact ones are needed here? We'll be glad to take
> > them if you can verify that they work properly.
>
> ok, will check

Hello,

I noticed that the BUILD-ID field in vmcoreinfo is broken on
stable/longterm kernels and found this thread. Can we please get this
fixed soon?

I tried cherry-picking the patches mentioned above ("lib/buildid: add
single folio-based file reader abstraction" and "lib/buildid: take into
account e_phoff when fetching program headers"), but they don't apply
cleanly before 6.11, and they'd need to be reworked for 5.15, which was
before folios were introduced. Jiri's minimal fix works for me and seems
like a much safer option.

Tested-by: Omar Sandoval <osandov@fb.com>

Thanks,
Omar