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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 9E8ABC46475 for ; Tue, 23 Oct 2018 21:41:27 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B990220671 for ; Tue, 23 Oct 2018 21:41:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B990220671 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 42fmzm3950zF3Bh for ; Wed, 24 Oct 2018 08:41:24 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: lists.ozlabs.org; spf=permerror (mailfrom) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 42fmxY0wHjzF37D for ; Wed, 24 Oct 2018 08:39:28 +1100 (AEDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id w9NLdKBX005250; Tue, 23 Oct 2018 16:39:20 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id w9NLdIV4005244; Tue, 23 Oct 2018 16:39:18 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 23 Oct 2018 16:39:18 -0500 From: Segher Boessenkool To: Breno Leitao Subject: Re: [PATCH 1/2] selftests/powerpc: Allocate base registers Message-ID: <20181023213917.GS5205@gate.crashing.org> References: <1540326197-15537-1-git-send-email-leitao@debian.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1540326197-15537-1-git-send-email-leitao@debian.org> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Oct 23, 2018 at 05:23:16PM -0300, Breno Leitao wrote: > Some ptrace selftests are passing input operands using a constraint that > can allocate any register for the operand, and using these registers on > load/store operations. > > If the register allocated by the compiler happens to be zero (r0), it might > cause an invalid memory address access, since load and store operations > consider the content of 0x0 address if the base register is r0, instead > of the content of the r0 register. For example: > > r1 := 0xdeadbeef > r0 := 0xdeadbeef > > ld r2, 0(r1) /* will load into r2 the content of r1 address */ > ld r2, 0(r0) /* will load into r2 the context of 0x0 */ That isn't valid syntax: you have to write ld r2, 0(0) (s/context/content/ btw) > In order to avoid this possible problem, the inline assembly constraint > should be aware that these registers will be used as a base register, thus, > r0 should not be alocated. (allocated) The patch looks fine :-) Reviewed-by: Segher Boessenkool Segher