From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1034124AbcIWVtm (ORCPT ); Fri, 23 Sep 2016 17:49:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50082 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933405AbcIWVtl (ORCPT ); Fri, 23 Sep 2016 17:49:41 -0400 Date: Fri, 23 Sep 2016 16:49:39 -0500 From: Josh Poimboeuf To: Linus Torvalds Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Linux Kernel Mailing List Subject: [PATCH] x86/alternatives: add stack frame dependency to alternative_call_2() Message-ID: <20160923214939.j5o7c67nhepzmh3t@treble> References: <20160923211437.bnp6qqwafvyp5kek@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Fri, 23 Sep 2016 21:49:40 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus reported the following objtool warning: kernel/signal.o: warning: objtool: .altinstr_replacement+0x54: call without frame pointer save/setup The warning is valid. It's caused by the fact that gcc placed the call instruction in alternative_call_2()'s inline asm before the frame pointer setup, which breaks frame pointer convention and can result in a bad stack trace. Force a stack frame to be created before the call instruction by listing the stack pointer as an output operand in the inline asm statement. Reported-by: Linus Torvalds Signed-off-by: Josh Poimboeuf --- arch/x86/include/asm/alternative.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index e77a644..1b02038 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -217,10 +217,14 @@ static inline int alternatives_text_reserved(void *start, void *end) */ #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ output, input...) \ +{ \ + register void *__sp asm(_ASM_SP); \ asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ "call %P[new2]", feature2) \ - : output : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ - [new2] "i" (newfunc2), ## input) + : output, "+r" (__sp) \ + : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ + [new2] "i" (newfunc2), ## input); \ +} /* * use this macro(s) if you need more than one output parameter -- 2.7.4