From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 129788 invoked by alias); 6 Jan 2020 09:40:10 -0000 Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org Received: (qmail 129779 invoked by uid 89); 6 Jan 2020 09:40:09 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-2.5 required=5.0 tests=AWL,BAYES_50,KAM_NUMSUBJECT,SPF_PASS autolearn=no version=3.3.1 spammy=H*c:HHHHHHHHH, multi-byte, leverage, multibyte X-HELO: smtp.ispras.ru Received: from winnie.ispras.ru (HELO smtp.ispras.ru) (83.149.199.91) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 06 Jan 2020 09:40:08 +0000 Received: from [10.10.3.121] (monopod.intra.ispras.ru [10.10.3.121]) by smtp.ispras.ru (Postfix) with ESMTP id 03ABC201D0; Mon, 6 Jan 2020 12:40:04 +0300 (MSK) Date: Mon, 06 Jan 2020 09:40:00 -0000 From: Alexander Monakov To: =?ISO-8859-15?Q?Martin_Li=A8ka?= cc: Fangrui Song , gcc@gcc.gnu.org, Jan Hubicka Subject: Re: -fpatchable-function-entry: leverage multi-byte NOP on x86 In-Reply-To: <7884fb3e-f26a-46b9-321a-0a78d8c01df5@suse.cz> Message-ID: References: <20200104204843.lwyoq3lhvgmi6f5h@gmail.com> <7884fb3e-f26a-46b9-321a-0a78d8c01df5@suse.cz> User-Agent: Alpine 2.20.13 (LNX 116 2015-12-14) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="168458499-1771019492-1578303605=:31907" X-SW-Source: 2020-01/txt/msg00030.txt.bz2 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --168458499-1771019492-1578303605=:31907 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-length: 593 On Mon, 6 Jan 2020, Martin Liška wrote: > You are right, we do not leverage multi-byte NOPs. Note that the support > depends > on a CPU model (-march) and the similar code is quite complex in binutils: > https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=gas/config/tc-i386.c;h=d0b8f2624a1885d83d2595474bfd78ae844f48f2;hb=HEAD#l1441 > > I'm not sure how worthy would it be to implement that? Huh? Surely the right move would be to ask Binutils to expose that via a new pseudo-op, like .balign but requesting a specific space rather than aligning up to a boundary. Alexander --168458499-1771019492-1578303605=:31907--