From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751451AbdIOQKo (ORCPT ); Fri, 15 Sep 2017 12:10:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48022 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751201AbdIOQKn (ORCPT ); Fri, 15 Sep 2017 12:10:43 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 06363C04D2BD Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=jpoimboe@redhat.com Date: Fri, 15 Sep 2017 11:10:41 -0500 From: Josh Poimboeuf To: Linus Torvalds Cc: Ingo Molnar , the arch/x86 maintainers , Linux Kernel Mailing List , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Alexander Potapenko , Dmitriy Vyukov , Matthias Kaehlcke , Arnd Bergmann , Peter Zijlstra Subject: Re: [RFC PATCH 3/4] x86/asm: Make alternative macro interfaces more clear and consistent Message-ID: <20170915161041.26lefip66zwjtrn4@treble> References: <20170831172542.k5qchwmgckdcnc6d@treble> <20170831173132.i5y5p4gdmm4iv3h3@treble> <20170902103221.5gw5vtxxknprzgdr@gmail.com> <20170914144820.4blzmlqeqc7unpod@treble> <20170914172627.sp2yrecpawovvxxy@treble> <20170914173348.jeddpkfc52dj2jvq@treble> <20170914184529.6k3q6yz3rnhlatsj@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170914184529.6k3q6yz3rnhlatsj@treble> 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 [10.5.110.31]); Fri, 15 Sep 2017 16:10:43 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 14, 2017 at 01:45:29PM -0500, Josh Poimboeuf wrote: > On Thu, Sep 14, 2017 at 11:28:30AM -0700, Linus Torvalds wrote: > > On Thu, Sep 14, 2017 at 10:33 AM, Josh Poimboeuf wrote: > > >> > > >> a) uglifying the 15 or so relevant inline asm locations with ifdefs; or > > > > > > Actually I guess we could put the "sp" in a macro... I'll try it. > > > > Exactly. Do something like > > > > #ifdef CONFIG_FRAME_POINTER > > # define EXTRA_ASM_CLOBBERS "rsp" > > #else > > # define EXTRA_ASM_CLOBBERS > > #endif > > > > and then replace the nasty > > > > register void *__sp asm(_ASM_SP); > > .. > > "+r" (__sp) > > > > games with just that EXTRA_ASM_CLOBBERS thing at the end of the clobbers. > > > > Yes, you'd probably have to document that the alternative_call_2() > > thing doesn't take a "input" argument, but a input_and_clobbers, but > > all users do that anyway. > > > > I dunno. > > There's also alternative_call(), which doesn't yet have the '__rsp' > annotation, but it probably should. It has some callers which pass > clobbers and some which don't, so its conversion would be trickier. > > So my plan is to keep patch 3 of this series, which clarifies those > alternative macro interfaces, and also separates the inputs from the > clobbers. That'll make it really easy to add something like > EXTRA_ASM_CLOBBERS above. > > In fact I'll probably keep patches 1-3, because they're all > improvements. Then I'll replace the original patch 4 (ASM_CALL) with > the "sp" clobbers thing. So I couldn't figure out how to make it any simpler than this: #ifdef CONFIG_FRAME_POINTER # define ASM_CALL_CLOBBERS "sp" # define ASM_CALL_CLOBBERS_APPEND , ASM_CALL_CLOBBERS # define ASM_CALL_CLOBBERS_ARGS(args...) ASM_CALL_CLOBBERS, ## args #else # define ASM_CALL_CLOBBERS # define ASM_CALL_CLOBBERS_APPEND # define ASM_CALL_CLOBBERS_ARGS(args...) args #endif ASM_CALL_CLOBBERS is the normal one: asm volatile("call foo" : : : ASM_CALL_CLOBBERS); ASM_CALL_CLOBBERS_APPEND is needed when combining the option with other clobbers options, like: asm volatile("call foo" : : : "memory" ASM_CALL_CLOBBERS_APPEND); ASM_CALL_CLOBBERS_ARGS is needed for the pesky alternative_call() macro so it can work with the variadic argument: #define alternative_call(oldfunc, newfunc, feature, outputs, inputs, \ clobbers...) \ asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", \ feature), \ : outputs \ : [old] "i" (oldfunc), [new] "i" (newfunc) \ ARGS_APPEND(inputs) \ : ASM_CALL_CLOBBERS_ARGS(clobbers)) So I *was* about ready to post something like the above. But, of course, the kbuild robot found that the new version of my patches manages to crash GCC with a certain randconfig. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82221 So the saga continues. Now I've managed to break clang, sparse, and GCC with each consecutive iteration of these patches... I'm starting to lose my faith in compilers. -- Josh