Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753502AbbGQUrB (ORCPT ); Fri, 17 Jul 2015 16:47:01 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:34401 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752292AbbGQUrA (ORCPT ); Fri, 17 Jul 2015 16:47:00 -0400 MIME-Version: 1.0 In-Reply-To: <20150717204438.GC12761@treble.redhat.com> References: <2ea0f0602978178eafd012e52b8bdb83cfb159d5.1437150175.git.jpoimboe@redhat.com> <20150717194307.GA26757@gmail.com> <20150717203746.GB12761@treble.redhat.com> <20150717204438.GC12761@treble.redhat.com> From: Andy Lutomirski Date: Fri, 17 Jul 2015 13:46:39 -0700 Message-ID: Subject: Re: [RFC PATCH 13/21] x86/asm/crypto: Fix frame pointer usage in aesni-intel_asm.S To: Josh Poimboeuf Cc: Ingo Molnar , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Michal Marek , Peter Zijlstra , Andy Lutomirski , Borislav Petkov , Linus Torvalds , Andi Kleen , Pedro Alves , X86 ML , live-patching@vger.kernel.org, "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3006 Lines: 88 On Fri, Jul 17, 2015 at 1:44 PM, Josh Poimboeuf wrote: > On Fri, Jul 17, 2015 at 01:39:09PM -0700, Andy Lutomirski wrote: >> On Fri, Jul 17, 2015 at 1:37 PM, Josh Poimboeuf wrote: >> > On Fri, Jul 17, 2015 at 12:44:42PM -0700, Andy Lutomirski wrote: >> >> On Fri, Jul 17, 2015 at 12:43 PM, Ingo Molnar wrote: >> >> > >> >> > * Josh Poimboeuf wrote: >> >> > >> >> >> ENTRY(aesni_set_key) >> >> >> + FRAME >> >> >> #ifndef __x86_64__ >> >> >> pushl KEYP >> >> >> movl 8(%esp), KEYP # ctx >> >> >> @@ -1905,6 +1907,7 @@ ENTRY(aesni_set_key) >> >> >> #ifndef __x86_64__ >> >> >> popl KEYP >> >> >> #endif >> >> >> + ENDFRAME >> >> >> ret >> >> >> ENDPROC(aesni_set_key) >> >> > >> >> > So cannot we make this a bit more compact and less fragile? >> >> > >> >> > Instead of: >> >> > >> >> > ENTRY(aesni_set_key) >> >> > FRAME >> >> > ... >> >> > ENDFRAME >> >> > ret >> >> > ENDPROC(aesni_set_key) >> >> > >> >> > >> >> > How about writing this as: >> >> > >> >> > FUNCTION_ENTRY(aesni_set_key) >> >> > ... >> >> > FUNCTION_RETURN(aesni_set_key) >> >> > >> >> > which does the same thing in a short, symmetric construct? >> >> > >> >> > One potential problem with this approach would be that what 'looks' like an entry >> >> > declaration, but it will now generate real code. >> >> > >> >> > OTOH if people find this intuitive enough then it's a lot harder to mess it up, >> >> > and I think 'RETURN' makes it clear enough that there's a real instruction >> >> > generated there. >> >> > >> >> >> >> How about FUNCTION_PROLOGUE and FUNCTION_EPILOGUE? >> > >> > Perhaps the macro name should describe what the epilogue does, since >> > frame pointers aren't required for _all_ functions, only those which >> > don't have call instructions. >> > >> > What do you think about ENTRY_FRAME and ENDPROC_FRAME_RETURN? The >> > ending macro is kind of long, but at least it a) matches the existing >> > ENTRY/ENDPROC convention for asm functions; b) gives a clue that frame >> > pointers are involved; and c) lets you know that the return is there. >> > >> >> This really is about frame pointers, right? How about >> ENTRY_FRAMEPTR_xyz where xyz can be prologue, epilogue, return, >> whatever? > > Wouldn't the "ENTRY" in ENTRY_FRAMEPTR_RETURN be confusing at the end of > a function? I meant ENTRY_FRAMEPTR_xyz and the beginning and ENDPROC_FRAMEPTR_xyz (ENTRY is debatable, but that's what we currently have). ENDPROC could easily be replaced with anything else. --Andy > > -- > Josh -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/