Re: [PATCH 1/2] elf_symtab: Add support for SHN_XINDEX index to elf_section_by_name

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: 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>,
	Mark Wielaard <mjw@redhat.com>
Subject: Re: [PATCH 1/2] elf_symtab: Add support for SHN_XINDEX index to elf_section_by_name
Date: Fri, 22 Jan 2021 12:05:28 -0800	[thread overview]
Message-ID: <CAEf4BzZEeuw0LPVHcR_7wvt14jkWZdSa9Rf-cGwpgJ57Rg9qHA@mail.gmail.com> (raw)
In-Reply-To: <20210122163920.59177-2-jolsa@kernel.org>

On Fri, Jan 22, 2021 at 9:22 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> In case the elf's header e_shstrndx contains SHN_XINDEX,
> we need to call elf_getshdrstrndx to get the proper
> string table index.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---

Acked-by: Andrii Nakryiko <andrii@kernel.org>

>  dutil.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/dutil.c b/dutil.c
> index 7b667647420f..11fb7202049c 100644
> --- a/dutil.c
> +++ b/dutil.c
> @@ -179,12 +179,18 @@ Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
>  {
>         Elf_Scn *sec = NULL;
>         size_t cnt = 1;
> +       size_t str_idx;
> +
> +       if (elf_getshdrstrndx(elf, &str_idx))
> +               return NULL;
>
>         while ((sec = elf_nextscn(elf, sec)) != NULL) {
>                 char *str;
>
>                 gelf_getshdr(sec, shp);
> -               str = elf_strptr(elf, ep->e_shstrndx, shp->sh_name);
> +               str = elf_strptr(elf, str_idx, shp->sh_name);
> +               if (!str)
> +                       return NULL;
>                 if (!strcmp(name, str)) {
>                         if (index)
>                                 *index = cnt;
> --
> 2.26.2
>