From: Andrii Nakryiko <andriin@fb.com>
Date: Thu, 3 Sep 2020 13:35:29 -0700
Subject: libbpf: Ensure ELF symbols table is found before further ELF
processing
Patch-mainline: v5.10-rc1
Git-commit: 0201c575831171292489f14a8b6f79f98936b4d1
References: bsc#1177028
libbpf ELF parsing logic might need symbols available before ELF parsing is
completed, so we need to make sure that symbols table section is found in
a separate pass before all the subsequent sections are processed.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200903203542.15944-2-andriin@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
tools/lib/bpf/libbpf.c | 42 ++++++++++++++++++++++++++++++------------
1 file changed, 30 insertions(+), 12 deletions(-)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2700,14 +2700,38 @@ static int bpf_object__elf_collect(struc
Elf *elf = obj->efile.elf;
Elf_Data *btf_ext_data = NULL;
Elf_Data *btf_data = NULL;
- Elf_Scn *scn = NULL;
int idx = 0, err = 0;
-
+ const char *name;
+ Elf_Data *data;
+ Elf_Scn *scn;
+ GElf_Shdr sh;
+
+ /* a bunch of ELF parsing functionality depends on processing symbols,
+ * so do the first pass and find the symbol table
+ */
+ scn = NULL;
while ((scn = elf_nextscn(elf, scn)) != NULL) {
- const char *name;
- GElf_Shdr sh;
- Elf_Data *data;
+ if (elf_sec_hdr(obj, scn, &sh))
+ return -LIBBPF_ERRNO__FORMAT;
+
+ if (sh.sh_type == SHT_SYMTAB) {
+ if (obj->efile.symbols) {
+ pr_warning("elf: multiple symbol tables in %s\n", obj->path);
+ return -LIBBPF_ERRNO__FORMAT;
+ }
+
+ data = elf_sec_data(obj, scn);
+ if (!data)
+ return -LIBBPF_ERRNO__FORMAT;
+ obj->efile.symbols = data;
+ obj->efile.symbols_shndx = elf_ndxscn(scn);
+ obj->efile.strtabidx = sh.sh_link;
+ }
+ }
+
+ scn = NULL;
+ while ((scn = elf_nextscn(elf, scn)) != NULL) {
idx++;
if (elf_sec_hdr(obj, scn, &sh))
@@ -2746,13 +2770,7 @@ static int bpf_object__elf_collect(struc
} else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) {
btf_ext_data = data;
} else if (sh.sh_type == SHT_SYMTAB) {
- if (obj->efile.symbols) {
- pr_warning("elf: multiple symbol tables in %s\n", obj->path);
- return -LIBBPF_ERRNO__FORMAT;
- }
- obj->efile.symbols = data;
- obj->efile.symbols_shndx = idx;
- obj->efile.strtabidx = sh.sh_link;
+ /* already processed during the first pass above */
} else if (sh.sh_type == SHT_PROGBITS && data->d_size > 0) {
if (sh.sh_flags & SHF_EXECINSTR) {
if (strcmp(name, ".text") == 0)