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

From: Jiri Olsa <jolsa@kernel.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andriin@fb.com>
Cc: 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>
Subject: [PATCH 1/2] elf_symtab: Add support for SHN_XINDEX index to elf_section_by_name
Date: Fri, 22 Jan 2021 17:39:19 +0100	[thread overview]
Message-ID: <20210122163920.59177-2-jolsa@kernel.org> (raw)
In-Reply-To: <20210122163920.59177-1-jolsa@kernel.org>

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>
---
 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

