From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752108AbcDNUAg (ORCPT ); Thu, 14 Apr 2016 16:00:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41808 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751598AbcDNUAe (ORCPT ); Thu, 14 Apr 2016 16:00:34 -0400 Date: Thu, 14 Apr 2016 15:00:33 -0500 From: Josh Poimboeuf To: Ingo Molnar Cc: x86@kernel.org, Gleb Natapov , Paolo Bonzini , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/kvm: Add stack frame dependency to fastop() inline asm Message-ID: <20160414200033.xfj6at7lynyhmpnm@treble> References: <2eeab7cf095b6188b4ebd0e09a4483ddcb01066b.1457549946.git.jpoimboe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2eeab7cf095b6188b4ebd0e09a4483ddcb01066b.1457549946.git.jpoimboe@redhat.com> 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 [10.5.110.38]); Thu, 14 Apr 2016 20:00:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ingo, Ping? On Wed, Mar 09, 2016 at 12:59:50PM -0600, Josh Poimboeuf wrote: > The kbuild test robot reported this objtool warning [1]: > > arch/x86/kvm/emulate.o: warning: objtool: fastop()+0x69: call without frame pointer save/setup > > The issue seems to be caused by CONFIG_PROFILE_ALL_BRANCHES. With that > option, for some reason gcc decides not to create a stack frame in > fastop() before doing the inline asm call, which can result in a bad > stack trace. > > Force a stack frame to be created if CONFIG_FRAME_POINTER is enabled by > listing the stack pointer as an output operand for the inline asm > statement. > > This change has no effect for !CONFIG_PROFILE_ALL_BRANCHES. > > [1] https://lists.01.org/pipermail/kbuild-all/2016-March/018249.html > > Reported-by: kbuild test robot > Signed-off-by: Josh Poimboeuf > --- > arch/x86/kvm/emulate.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 0f62943..a2f24af 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -5110,13 +5110,17 @@ static void fetch_possible_mmx_operand(struct x86_emulate_ctxt *ctxt, > > static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *)) > { > + register void *__sp asm(_ASM_SP); > ulong flags = (ctxt->eflags & EFLAGS_MASK) | X86_EFLAGS_IF; > + > if (!(ctxt->d & ByteOp)) > fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE; > + > asm("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n" > : "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags), > - [fastop]"+S"(fop) > + [fastop]"+S"(fop), "+r"(__sp) > : "c"(ctxt->src2.val)); > + > ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK); > if (!fop) /* exception is returned in fop variable */ > return emulate_de(ctxt); > -- > 2.4.3 > -- Josh