linux-kernel - [PATCH 4.9 17/43] objtool: Dont fail on missing symbol table

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon,  8 Feb 2021 16:00:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Nathan Chancellor <natechancellor@...il.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 17/43] objtool: Dont fail on missing symbol table

From: Josh Poimboeuf <jpoimboe@...hat.com>

[ Upstream commit 1d489151e9f9d1647110277ff77282fe4d96d09b ]

Thanks to a recent binutils change which doesn't generate unused
symbols, it's now possible for thunk_64.o be completely empty without
CONFIG_PREEMPTION: no text, no data, no symbols.

We could edit the Makefile to only build that file when
CONFIG_PREEMPTION is enabled, but that will likely create confusion
if/when the thunks end up getting used by some other code again.

Just ignore it and move on.

Reported-by: Nathan Chancellor <natechancellor@...il.com>
Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
Reviewed-by: Miroslav Benes <mbenes@...e.cz>
Tested-by: Nathan Chancellor <natechancellor@...il.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1254
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/objtool/elf.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index d84c28eac262d..0ba5bb51bd93c 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -226,8 +226,11 @@ static int read_symbols(struct elf *elf)
 
 	symtab = find_section_by_name(elf, ".symtab");
 	if (!symtab) {
-		WARN("missing symbol table");
-		return -1;
+		/*
+		 * A missing symbol table is actually possible if it's an empty
+		 * .o file.  This can happen for thunk_64.o.
+		 */
+		return 0;
 	}
 
 	symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
-- 
2.27.0