From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DBD7C3A5A1 for ; Thu, 22 Aug 2019 21:51:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B40862082F for ; Thu, 22 Aug 2019 21:51:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390743AbfHVVvR (ORCPT ); Thu, 22 Aug 2019 17:51:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:8418 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389740AbfHVVvR (ORCPT ); Thu, 22 Aug 2019 17:51:17 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id ED7033175291; Thu, 22 Aug 2019 21:51:16 +0000 (UTC) Received: from treble (ovpn-121-55.rdu2.redhat.com [10.10.121.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6269A5D713; Thu, 22 Aug 2019 21:51:15 +0000 (UTC) Date: Thu, 22 Aug 2019 16:51:12 -0500 From: Josh Poimboeuf To: Julien Cc: Raphael Gault , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, peterz@infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, raph.gault+kdev@gmail.com Subject: Re: [RFC v4 07/18] objtool: Introduce INSN_UNKNOWN type Message-ID: <20190822215112.n36slswph64nbzhb@treble> References: <20190816122403.14994-1-raphael.gault@arm.com> <20190816122403.14994-8-raphael.gault@arm.com> <20190822200406.jc3yf77pomxxwep6@treble> <3c4e3227-eeb3-371a-d015-a0e0e60e5332@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3c4e3227-eeb3-371a-d015-a0e0e60e5332@gmail.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Thu, 22 Aug 2019 21:51:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 22, 2019 at 09:45:00PM +0100, Julien wrote: > Hi Josh, > > On 22/08/19 21:04, Josh Poimboeuf wrote: > > On Fri, Aug 16, 2019 at 01:23:52PM +0100, Raphael Gault wrote: > > > On arm64 some object files contain data stored in the .text section. > > > This data is interpreted by objtool as instruction but can't be > > > identified as a valid one. In order to keep analysing those files we > > > introduce INSN_UNKNOWN type. The "unknown instruction" warning will thus > > > only be raised if such instructions are uncountered while validating an > > > execution branch. > > > > > > This change doesn't impact the x86 decoding logic since 0 is still used > > > as a way to specify an unknown type, raising the "unknown instruction" > > > warning during the decoding phase still. > > > > > > Signed-off-by: Raphael Gault > > > > Is there a reason such data can't be moved to .rodata? That would seem > > like the proper fix. > > > > Raphaël can confirm, if I remember correctly, that issue was encountered on > assembly files implementing crypto algorithms were some words/double-words > of data were in the middle of the .text. I think it is done this way to make > sure the data can be loaded in a single instruction. So moving it to another > section could impact the crypto performance depending on the relocations. > > That was my understanding at least. Thanks. If that's the case then that would be useful information to put in the patch description. A code excerpt of an example code site would be useful too. I'm not sure INSN_UNKNOWN is the right name though, since the decoder does actually know about it. Maybe INSN_DATA or something? -- Josh