linux-kernel - [tip: x86/urgent] objtool: Fix switch table detection in .text.unlikely

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Date:   Tue, 14 Apr 2020 10:34:02 -0000
From:   "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, Borislav Petkov <bp@...e.de>,
        Miroslav Benes <mbenes@...e.cz>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/urgent] objtool: Fix switch table detection in .text.unlikely

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     b401efc120a399dfda1f4d2858a4de365c9b08ef
Gitweb:        https://git.kernel.org/tip/b401efc120a399dfda1f4d2858a4de365c9b08ef
Author:        Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate:    Wed, 01 Apr 2020 13:23:28 -05:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Tue, 14 Apr 2020 12:06:21 +02:00

objtool: Fix switch table detection in .text.unlikely

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
---
 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 4811325..cb2d299 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1050,10 +1050,7 @@ static struct rela *find_jump_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)