Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752660AbbDCRba (ORCPT ); Fri, 3 Apr 2015 13:31:30 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:50195 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752536AbbDCRb2 (ORCPT ); Fri, 3 Apr 2015 13:31:28 -0400 Date: Fri, 3 Apr 2015 19:33:06 +0200 From: Quentin Casasnovas To: Borislav Petkov Cc: Quentin Casasnovas , X86 ML , LKML , "H. Peter Anvin" , Ingo Molnar , Thomas Gleixner , Oleg Nesterov , Andy Lutomirski Subject: Re: [PATCH] x86/xsave: Robustify and merge macros Message-ID: <20150403173306.GG14902@chrystal.uk.oracle.com> References: <1427980282-25929-1-git-send-email-bp@alien8.de> <20150402155210.GB6703@chrystal.uk.oracle.com> <20150402161259.GE3483@pd.tnic> <20150403140630.GD14902@chrystal.uk.oracle.com> <20150403141426.GE14902@chrystal.uk.oracle.com> <20150403152324.GG3418@pd.tnic> <20150403154055.GF14902@chrystal.uk.oracle.com> <20150403170625.GJ3418@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150403170625.GJ3418@pd.tnic> User-Agent: Mutt/1.5.22 (2013-10-16) X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2017 Lines: 49 On Fri, Apr 03, 2015 at 07:06:25PM +0200, Borislav Petkov wrote: > On Fri, Apr 03, 2015 at 05:40:55PM +0200, Quentin Casasnovas wrote: > > So yeah I still think we're not properly padding, if you take my earlier > > example where repl2 = 5 bytes, repl1 = 4 bytes and orin_insn = 3. > > > > I'll let you re-read my original mail and come back to me to tell me what'd > > I really miss! :) > > Dammit, dammit, dammit! > > And I thought this aspect was taken care of. I went into the old > branches where I had done this and there I have: > > +#define OLDINSTR_2(oldinstr, num1, num2) \ > + __OLDINSTR(oldinstr, num1) \ > + ".skip -(((" alt_rlen(num2) ")-(" alt_rlen(num1) ")) > 0) * " \ > + "((" alt_rlen(num2) ")-(" alt_rlen(num1) ")),0x90\n" \ > + alt_end_marker ":\n" > + > > without the size of the orig_insn factored in into the padding. > > And that would work for your example because it would add 1+1 bytes > padding. > > Basically, the idea was: > > .skip len(repl1) - len(orig), 0x90 > .skip len(repl2) - len(repl1), 0x90 > > BUT!, for some reason I changed it to what's there now and I can't > remember why anymore. I think it would not work in the case where repl1 is smaller or equal than orig_insn (i.e. no padding in the first .skip) but orig_insn is strictly smaller than repl2 (since we're never comparing repl2 with insn in this new-old code). Anything wrong with the two different approaches I've suggested in my original mail? One is using a one-liner .skip directive inspired by yours, and the other is using .if directives. FWIW I think exploding the logic using conditionnals '.if' is way more readable and less error-prone. Quentin -- 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/