Re: [PATCH 2/2] bpf_encoder: Translate SHN_XINDEX in symbol's st_shndx values

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andriin@fb.com>,
	dwarves@vger.kernel.org, netdev@vger.kernel.org,
	bpf@vger.kernel.org, Yonghong Song <yhs@fb.com>,
	Hao Luo <haoluo@google.com>, Martin KaFai Lau <kafai@fb.com>,
	Song Liu <songliubraving@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Mark Wielaard <mjw@redhat.com>,
	Yulia Kopkova <ykopkova@redhat.com>
Subject: Re: [PATCH 2/2] bpf_encoder: Translate SHN_XINDEX in symbol's st_shndx values
Date: Fri, 22 Jan 2021 17:33:48 -0300	[thread overview]
Message-ID: <20210122203348.GC617095@kernel.org> (raw)
In-Reply-To: <20210122202403.GC35850@krava>

Em Fri, Jan 22, 2021 at 09:24:03PM +0100, Jiri Olsa escreveu:
> On Fri, Jan 22, 2021 at 04:52:28PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Fri, Jan 22, 2021 at 05:39:20PM +0100, Jiri Olsa escreveu:
> > > For very large ELF objects (with many sections), we could
> > > get special value SHN_XINDEX (65535) for symbol's st_shndx.
> > > 
> > > This patch is adding code to detect the optional extended
> > > section index table and use it to resolve symbol's section
> > > index.
> > > 
> > > Adding elf_symtab__for_each_symbol_index macro that returns
> > > symbol's section index and usign it in collect functions.
> > 
> > From a quick look it seems you addressed Andrii's review comments,
> > right?
> 
> yep, it's described in the cover email
> 
> > 
> > I've merged it locally, but would like to have some detailed set of
> > steps on how to test this, so that I can add it to a "Committer testing"
> > section in the cset commit log and probably add it to my local set of
> > regression tests.
> 
> sorry I forgot to mention that:
> 
> The test was to run pahole on kernel compiled with:
>   make KCFLAGS="-ffunction-sections -fdata-sections" -j$(nproc) vmlinux
> 
> and ensure FUNC records are generated and match normal
> build (without above KCFLAGS)
> 
> Also bpf selftest passed.

Thanks, I'll come up with some shell script to test that.

> 
> > 
> > Who originally reported this? Joe? Also can someone provide a Tested-by:
> > in addition to mine when I get this detailed set of steps to test?
> 
> oops, it was reported by Yulia Kopkova (just cc-ed)
> 
> Joe tested the v2 of the patchset, I'll make a dwarves scratch
> build with v3 and let them test it

Thanks, and there is a new comment by Andrii that I've found relevant
about using size_t instead of Elf_something.

- Arnaldo