From: Jiri Olsa <jolsa@redhat.com>
To: Mark Wielaard <mark@klomp.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Jiri Olsa <jolsa@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andriin@fb.com>,
dwarves@vger.kernel.org, Networking <netdev@vger.kernel.org>,
bpf <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>
Subject: Re: [PATCH 2/3] bpf_encoder: Translate SHN_XINDEX in symbol's st_shndx values
Date: Sat, 23 Jan 2021 21:15:14 +0100 [thread overview]
Message-ID: <20210123201514.GB117714@krava> (raw)
In-Reply-To: <d5e30947541a3571bd111e24b3a28dfb1770556c.camel@klomp.org>
On Sat, Jan 23, 2021 at 09:08:15PM +0100, Mark Wielaard wrote:
> Hi Jiri,
>
> On Sat, 2021-01-23 at 19:51 +0100, Jiri Olsa wrote:
> > On Fri, Jan 22, 2021 at 02:55:51PM -0800, Andrii Nakryiko wrote:
> > >
> > > > I don't understand this.. gelf_getsymshndx will return both
> > > > symbol and proper index, no? also sym_sec_idx is already
> > > > assigned from previou call
> > >
> > > Reading (some) implementation of gelf_getsymshndx() that I found
> > > online, it won't set sym_sec_idx, if the symbol *doesn't* use
> > > extended
> > > numbering. But it will still return symbol data. So to return the
> >
> > the latest upstream code seems to set it always,
> > but I agree we should be careful
> >
> > Mark, any insight in here? thanks
>
> GElf_Sym *
> gelf_getsymshndx (Elf_Data *symdata, Elf_Data *shndxdata, int ndx,
> GElf_Sym *dst, Elf32_Word *dstshndx)
>
> Will always set *dst, but only set *dstshndx if both it and shndxdata
> are not NULL and no error occurred (the function returns NULL and set
> libelf_error in case of error).
>
> So as long as shndxdata != NULL you can rely on *dstshndx being set.
> Otherwise you get the section index from dst->st_shndx.
ok, so it's as Andrii said, I'll make the extra check then
thanks,
jirka
next prev parent reply other threads:[~2021-01-23 20:17 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 20:22 [PATCHv2 0/3] dwarves,libbpf: Add support to use optional extended section index table Jiri Olsa
2021-01-21 20:22 ` [PATCH 1/3] elf_symtab: Add support for SHN_XINDEX index to elf_section_by_name Jiri Olsa
2021-01-21 23:10 ` Andrii Nakryiko
2021-01-21 23:34 ` Jiri Olsa
2021-01-21 20:22 ` [PATCH 2/3] bpf_encoder: Translate SHN_XINDEX in symbol's st_shndx values Jiri Olsa
2021-01-21 23:32 ` Andrii Nakryiko
2021-01-22 9:32 ` Jiri Olsa
2021-01-22 20:46 ` Jiri Olsa
2021-01-22 22:55 ` Andrii Nakryiko
2021-01-23 18:51 ` Jiri Olsa
2021-01-23 20:07 ` Andrii Nakryiko
2021-01-23 20:21 ` Mark Wielaard
2021-01-23 20:08 ` Mark Wielaard
2021-01-23 20:15 ` Jiri Olsa [this message]
2021-01-23 21:23 ` Jiri Olsa
2021-01-24 6:08 ` Andrii Nakryiko
2021-01-21 20:22 ` [PATCH bpf-next 3/3] libbpf: Use string table index from index table if needed Jiri Olsa
2021-01-21 23:46 ` Andrii Nakryiko
-- strict thread matches above, loose matches on Subject: below --
2021-01-19 22:12 [PATCH 0/3] dwarves,libbpf: Add support to use optional extended section index table Jiri Olsa
2021-01-19 22:12 ` [PATCH 2/3] bpf_encoder: Translate SHN_XINDEX in symbol's st_shndx values Jiri Olsa
2021-01-20 2:03 ` Andrii Nakryiko
2021-01-20 12:25 ` Jiri Olsa
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