From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751162AbdFAOYB (ORCPT ); Thu, 1 Jun 2017 10:24:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56484 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751078AbdFAOYA (ORCPT ); Thu, 1 Jun 2017 10:24:00 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com A5EF5C05FFD1 Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jpoimboe@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com A5EF5C05FFD1 Date: Thu, 1 Jun 2017 09:23:58 -0500 From: Josh Poimboeuf To: Andy Lutomirski Cc: X86 ML , "linux-kernel@vger.kernel.org" , live-patching@vger.kernel.org, Linus Torvalds , Jiri Slaby , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra Subject: Re: [RFC PATCH 06/10] x86/entry: add CFI hint undwarf annotations Message-ID: <20170601142358.wvasu35pvyyvjt2r@treble> References: <1d852057ba39f2f5f02f196c604b8baecce33fea.1496293620.git.jpoimboe@redhat.com> 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 [10.5.110.32]); Thu, 01 Jun 2017 14:23:59 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 01, 2017 at 07:03:18AM -0700, Andy Lutomirski wrote: > On Wed, May 31, 2017 at 10:44 PM, Josh Poimboeuf wrote: > > Add CFI hint undwarf annotations to entry_64.S. This will enable the > > undwarf unwinder to unwind through any location in the entry code > > including syscalls, interrupts, and exceptions. > > > > Signed-off-by: Josh Poimboeuf > > --- > > arch/x86/entry/Makefile | 1 - > > arch/x86/entry/calling.h | 5 +++++ > > arch/x86/entry/entry_64.S | 56 ++++++++++++++++++++++++++++++++++++++++++----- > > 3 files changed, 55 insertions(+), 7 deletions(-) > > > > diff --git a/arch/x86/entry/Makefile b/arch/x86/entry/Makefile > > index 9976fce..af28a8a 100644 > > --- a/arch/x86/entry/Makefile > > +++ b/arch/x86/entry/Makefile > > @@ -2,7 +2,6 @@ > > # Makefile for the x86 low level entry code > > # > > > > -OBJECT_FILES_NON_STANDARD_entry_$(BITS).o := y > > OBJECT_FILES_NON_STANDARD_entry_64_compat.o := y > > > > CFLAGS_syscall_64.o += $(call cc-option,-Wno-override-init,) > > diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h > > index 05ed3d3..bbec02e 100644 > > --- a/arch/x86/entry/calling.h > > +++ b/arch/x86/entry/calling.h > > @@ -1,4 +1,6 @@ > > #include > > +#include > > + > > > > /* > > > > Just to make sure I understand this, if we unwind from... > > > @@ -112,6 +114,7 @@ For 32-bit we have the following conventions - kernel is built with > > movq %rdx, 12*8+\offset(%rsp) > > movq %rsi, 13*8+\offset(%rsp) > > ...here..., will objtool think that rdx and rsi (etc) still live in > their respective regs, or will it find them in the on-stack data given > by CFI_REGS? If the former, how does undwarf deal with the > corresponding pops? It will find them in their respective registers, which is fine because they haven't been clobbered yet. > > > movq %rdi, 14*8+\offset(%rsp) > > + CFI_REGS offset=\offset extra=0 And here it will find them on the stack. > > @@ -414,6 +424,7 @@ ENTRY(ret_from_fork) > > 2: > > movq %rsp, %rdi > > call syscall_return_slowpath /* returns with IRQs disabled */ > > + CFI_REGS > > I'm confused. syscall_return_slowpath didn't change anything relevant > to unwinding, right? What's CFI_REGS here for? Yes, you're right, this CFI_REGS should be right at the '2' label. -- Josh