[tip: objtool/core] objtool: Use sh_info to find the base for .rela sections

[tip-bot2 for Sami Tolvanen]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     1e968bf5caf65eff3f080102879aaa5440c261b6
Gitweb:        https://git.kernel.org/tip/1e968bf5caf65eff3f080102879aaa5440c261b6
Author:        Sami Tolvanen <samitolvanen@xxxxxxxxxx>
AuthorDate:    Tue, 21 Apr 2020 11:25:01 -07:00
Committer:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
CommitterDate: Thu, 28 May 2020 11:06:05 -05:00

objtool: Use sh_info to find the base for .rela sections

ELF doesn't require .rela section names to match the base section. Use
the section index in sh_info to find the section instead of looking it
up by name.

LLD, for example, generates a .rela section that doesn't match the base
section name when we merge sections in a linker script for a binary
compiled with -ffunction-sections.

Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 tools/objtool/elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index f953d3a..5bc259c 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -508,7 +508,7 @@ static int read_relas(struct elf *elf)
 		if (sec->sh.sh_type != SHT_RELA)
 			continue;
 
-		sec->base = find_section_by_name(elf, sec->name + 5);
+		sec->base = find_section_by_index(elf, sec->sh.sh_info);
 		if (!sec->base) {
 			WARN("can't find base section for rela section %s",
 			     sec->name);