linux-kernel - [PATCH AUTOSEL 4.9 08/13] objtool: Fix switch table detection in .text.unlikely

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Message-Id: <20200424122447.10882-8-sashal@kernel.org>
Date:   Fri, 24 Apr 2020 08:24:41 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, Borislav Petkov <bp@...e.de>,
        Miroslav Benes <mbenes@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.9 08/13] objtool: Fix switch table detection in .text.unlikely

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

[ Upstream commit b401efc120a399dfda1f4d2858a4de365c9b08ef ]

If a switch jump table's indirect branch is in a ".cold" subfunction in
.text.unlikely, objtool doesn't detect it, and instead prints a false
warning:

  drivers/media/v4l2-core/v4l2-ioctl.o: warning: objtool: v4l_print_format.cold()+0xd6: sibling call from callable instruction with modified stack frame
  drivers/hwmon/max6650.o: warning: objtool: max6650_probe.cold()+0xa5: sibling call from callable instruction with modified stack frame
  drivers/media/dvb-frontends/drxk_hard.o: warning: objtool: init_drxk.cold()+0x16f: sibling call from callable instruction with modified stack frame

Fix it by comparing the function, instead of the section and offset.

Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Miroslav Benes <mbenes@...e.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/157c35d42ca9b6354bbb1604fe9ad7d1153ccb21.1585761021.git.jpoimboe@redhat.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/objtool/check.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index a4b157dc1c45e..360845926f665 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -914,10 +914,7 @@ static struct rela *find_switch_table(struct objtool_file *file,
 	 * it.
 	 */
 	for (;
-	     &insn->list != &file->insn_list &&
-	     insn->sec == func->sec &&
-	     insn->offset >= func->offset;
-
+	     &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func;
 	     insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
 
 		if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
-- 
2.20.1