[tip:core/urgent] objtool: Use '.strtab' if '.shstrtab' doesn't exist, to support ORC tables on Clang

[tip-bot for Simon Ser <tipbot@zytor.com>]

Commit-ID:  6d77d3b43ad84a48b502f02dc618e7c36737bdfe
Gitweb:     https://git.kernel.org/tip/6d77d3b43ad84a48b502f02dc618e7c36737bdfe
Author:     Simon Ser <contact@emersion.fr>
AuthorDate: Mon, 9 Jul 2018 11:17:22 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 14 Jul 2018 14:59:42 +0200

objtool: Use '.strtab' if '.shstrtab' doesn't exist, to support ORC tables on Clang

Clang puts its section header names in the '.strtab' section instead of
'.shstrtab', which causes objtool to fail with a "can't find
.shstrtab section" warning when attempting to write ORC metadata to an
object file.

If '.shstrtab' doesn't exist, use '.strtab' instead.

Signed-off-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d1c1c3fe55872be433da7bc5e1860538506229ba.1531153015.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/objtool/elf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 0d1acb704f64..7ec85d567598 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -519,10 +519,12 @@ struct section *elf_create_section(struct elf *elf, const char *name,
 	sec->sh.sh_flags = SHF_ALLOC;
 
 
-	/* Add section name to .shstrtab */
+	/* Add section name to .shstrtab (or .strtab for Clang) */
 	shstrtab = find_section_by_name(elf, ".shstrtab");
+	if (!shstrtab)
+		shstrtab = find_section_by_name(elf, ".strtab");
 	if (!shstrtab) {
-		WARN("can't find .shstrtab section");
+		WARN("can't find .shstrtab or .strtab section");
 		return NULL;
 	}