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libbpf: Ensure ELF symbols table is found before further ELF processing

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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
This commit is contained in:
Andrii Nakryiko
2020-09-03 13:35:29 -07:00
committed by Andrii Nakryiko
parent a6e9cf1532
commit 994aae7fc8
1 changed files with 29 additions and 11 deletions
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40
src/libbpf.c
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@@ -2720,14 +2720,38 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
Elf *elf = obj->efile.elf; Elf *elf = obj->efile.elf;
Elf_Data *btf_ext_data = NULL; Elf_Data *btf_ext_data = NULL;
Elf_Data *btf_data = NULL; Elf_Data *btf_data = NULL;
Elf_Scn *scn = NULL;
int idx = 0, err = 0; int idx = 0, err = 0;
while ((scn = elf_nextscn(elf, scn)) != NULL) {
const char *name; const char *name;
GElf_Shdr sh;
Elf_Data *data; 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) {
if (elf_sec_hdr(obj, scn, &sh))
return -LIBBPF_ERRNO__FORMAT;
if (sh.sh_type == SHT_SYMTAB) {
if (obj->efile.symbols) {
pr_warn("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++; idx++;
if (elf_sec_hdr(obj, scn, &sh)) if (elf_sec_hdr(obj, scn, &sh))
@@ -2766,13 +2790,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
} else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) { } else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) {
btf_ext_data = data; btf_ext_data = data;
} else if (sh.sh_type == SHT_SYMTAB) { } else if (sh.sh_type == SHT_SYMTAB) {
if (obj->efile.symbols) { /* already processed during the first pass above */
pr_warn("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;
} else if (sh.sh_type == SHT_PROGBITS && data->d_size > 0) { } else if (sh.sh_type == SHT_PROGBITS && data->d_size > 0) {
if (sh.sh_flags & SHF_EXECINSTR) { if (sh.sh_flags & SHF_EXECINSTR) {
if (strcmp(name, ".text") == 0) if (strcmp(name, ".text") == 0)