From: Jiri Olsa <jolsa@redhat.com>
To: Yonghong Song <yhs@fb.com>
Cc: Jiri Olsa <jolsa@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Song Liu <songliubraving@fb.com>,
lkml <linux-kernel@vger.kernel.org>,
bpf@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
Ingo Molnar <mingo@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Namhyung Kim <namhyung@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Michael Petlan <mpetlan@redhat.com>,
Ian Rogers <irogers@google.com>,
Stephane Eranian <eranian@google.com>,
Alexei Budankov <abudankov@huawei.com>,
Andi Kleen <ak@linux.intel.com>,
Adrian Hunter <adrian.hunter@intel.com>
Subject: Re: [PATCH bpf-next 2/3] bpf: Add size arg to build_id_parse function
Date: Thu, 14 Jan 2021 23:02:34 +0100 [thread overview]
Message-ID: <20210114220234.GA1456269@krava> (raw)
In-Reply-To: <d90fd73f-b9a6-c436-f8ae-0833ce3926ef@fb.com>
On Thu, Jan 14, 2021 at 01:05:33PM -0800, Yonghong Song wrote:
>
>
> On 1/14/21 12:01 PM, Jiri Olsa wrote:
> > On Thu, Jan 14, 2021 at 10:56:33AM -0800, Yonghong Song wrote:
> > >
> > >
> > > On 1/14/21 5:40 AM, Jiri Olsa wrote:
> > > > It's possible to have other build id types (other than default SHA1).
> > > > Currently there's also ld support for MD5 build id.
> > >
> > > Currently, bpf build_id based stackmap does not returns the size of
> > > the build_id. Did you see an issue here? I guess user space can check
> > > the length of non-zero bits of the build id to decide what kind of
> > > type it is, right?
> >
> > you can have zero bytes in the build id hash, so you need to get the size
> >
> > I never saw MD5 being used in practise just SHA1, but we added the
> > size to be complete and make sure we'll fit with build id, because
> > there's only limited space in mmap2 event
>
> I am asking to check whether we should extend uapi struct
> bpf_stack_build_id to include build_id_size as well. I guess
> we can delay this until a real use case.
right, we can try make some MD5 build id binaries and check if it
explodes with some bcc tools, but I don't expect that.. I'll try
to find some time for that
perf tool uses build ids in .debug cache as file links, and we had
few isues there
jirka
next prev parent reply other threads:[~2021-01-14 22:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 13:40 [PATCHv7 bpf-next 0/3] perf: Add mmap2 build id support Jiri Olsa
2021-01-14 13:40 ` [PATCH bpf-next 1/3] bpf: Move stack_map_get_build_id into lib Jiri Olsa
2021-01-14 13:40 ` [PATCH bpf-next 2/3] bpf: Add size arg to build_id_parse function Jiri Olsa
2021-01-14 18:56 ` Yonghong Song
2021-01-14 20:01 ` Jiri Olsa
2021-01-14 21:05 ` Yonghong Song
2021-01-14 22:02 ` Jiri Olsa [this message]
2021-01-14 23:43 ` Yonghong Song
2021-01-15 3:47 ` Alexei Starovoitov
2021-01-26 20:52 ` Jiri Olsa
2021-01-26 21:00 ` Yonghong Song
2021-01-14 13:40 ` [PATCH bpf-next 3/3] perf: Add build id data in mmap2 event Jiri Olsa
2021-01-15 3:50 ` [PATCHv7 bpf-next 0/3] perf: Add mmap2 build id support patchwork-bot+netdevbpf
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