linux-kernel - [tip: objtool/core] objtool: Remove check preventing branches within alternative

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Date:   Fri, 01 May 2020 18:22:23 -0000
From:   "tip-bot2 for Julien Thierry" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Julien Thierry <jthierry@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Miroslav Benes <mbenes@...e.cz>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: objtool/core] objtool: Remove check preventing branches within
 alternative

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     9e98d62aa7ea1375052895650f3e6d362336c5c9
Gitweb:        https://git.kernel.org/tip/9e98d62aa7ea1375052895650f3e6d362336c5c9
Author:        Julien Thierry <jthierry@...hat.com>
AuthorDate:    Fri, 27 Mar 2020 15:28:42 
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 30 Apr 2020 20:14:31 +02:00

objtool: Remove check preventing branches within alternative

While jumping from outside an alternative region to the middle of an
alternative region is very likely wrong, jumping from an alternative
region into the same region is valid. It is a common pattern on arm64.

The first pattern is unlikely to happen in practice and checking only
for this adds a lot of complexity.

Just remove the current check.

Suggested-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Julien Thierry <jthierry@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Miroslav Benes <mbenes@...e.cz>
Link: https://lkml.kernel.org/r/20200327152847.15294-6-jthierry@redhat.com
---
 tools/objtool/check.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 12e2aea..cc52da6 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2162,12 +2162,6 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 
 	sec = insn->sec;
 
-	if (insn->alt_group && list_empty(&insn->alts)) {
-		WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
-			  sec, insn->offset);
-		return 1;
-	}
-
 	while (1) {
 		next_insn = next_insn_same_sec(file, insn);