From: Jiri Olsa <jolsa@kernel.org>
Date: Thu, 21 Jan 2021 20:22:03 +0000 (+0100)
Subject: libbpf: Use string table index from index table if needed
X-Git-Tag: v5.12-rc1~200^2~28^2~86
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6095d5a271ad6dce30489526771a9040d78e0895;p=thirdparty%2Flinux.git

libbpf: Use string table index from index table if needed

For very large ELF objects (with many sections), we could
get special value SHN_XINDEX (65535) for elf object's string
table index - e_shstrndx.

Call elf_getshdrstrndx to get the proper string table index,
instead of reading it directly from ELF header.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210121202203.9346-4-jolsa@kernel.org
---

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 9970a288dda53..d9c10830d749f 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -858,6 +858,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 	Elf_Scn *scn = NULL;
 	Elf *elf = NULL;
 	GElf_Ehdr ehdr;
+	size_t shstrndx;
 
 	if (elf_version(EV_CURRENT) == EV_NONE) {
 		pr_warn("failed to init libelf for %s\n", path);
@@ -882,7 +883,14 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 		pr_warn("failed to get EHDR from %s\n", path);
 		goto done;
 	}
-	if (!elf_rawdata(elf_getscn(elf, ehdr.e_shstrndx), NULL)) {
+
+	if (elf_getshdrstrndx(elf, &shstrndx)) {
+		pr_warn("failed to get section names section index for %s\n",
+			path);
+		goto done;
+	}
+
+	if (!elf_rawdata(elf_getscn(elf, shstrndx), NULL)) {
 		pr_warn("failed to get e_shstrndx from %s\n", path);
 		goto done;
 	}
@@ -897,7 +905,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 				idx, path);
 			goto done;
 		}
-		name = elf_strptr(elf, ehdr.e_shstrndx, sh.sh_name);
+		name = elf_strptr(elf, shstrndx, sh.sh_name);
 		if (!name) {
 			pr_warn("failed to get section(%d) name from %s\n",
 				idx, path);