linux-kernel - [PATCH] recordmcount: Support empty section from recent binutils

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Message-Id: <cd0f6bdfdf1ee096fb2c07e7b38940921b8e9118.1637764848.git.christophe.leroy@csgroup.eu>
Date:   Wed, 24 Nov 2021 15:43:30 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH] recordmcount: Support empty section from recent binutils

Looks like recent binutils (2.36 and over ?) may empty some section,
leading to failure like:

	Cannot find symbol for section 11: .text.unlikely.
	kernel/kexec_file.o: failed
	make[1]: *** [scripts/Makefile.build:287: kernel/kexec_file.o] Error 1

In order to avoid that, ensure that the section has a content before
returning it's name in has_rel_mcount().

Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Link: https://github.com/linuxppc/issues/issues/388
Link: https://lore.kernel.org/all/20210215162209.5e2a475b@gandalf.local.home/
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 scripts/recordmcount.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
index 1e9baa5c4fc6..cc6600b729ae 100644
--- a/scripts/recordmcount.h
+++ b/scripts/recordmcount.h
@@ -575,6 +575,8 @@ static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
 				  char const *const shstrtab,
 				  char const *const fname)
 {
+	if (!shdr0->sh_size)
+		return NULL;
 	if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
 		return NULL;
 	return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
-- 
2.33.1