From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 103459 invoked by alias); 19 Oct 2017 11:21:30 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 103447 invoked by uid 89); 19 Oct 2017 11:21:29 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=Hx-languages-length:821 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 19 Oct 2017 11:21:28 +0000 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8F4023C29; Thu, 19 Oct 2017 11:21:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 8F4023C29 Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=palves@redhat.com Received: from [127.0.0.1] (ovpn04.gateway.prod.ext.ams2.redhat.com [10.39.146.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id AB621B2E52; Thu, 19 Oct 2017 11:21:26 +0000 (UTC) Subject: Re: [PATCH] [AArch64 Linux] Get rid of top byte from tagged address To: Yao Qi , gdb-patches@sourceware.org References: <1508400527-20718-1-git-send-email-yao.qi@linaro.org> From: Pedro Alves Message-ID: <583291c9-a0d8-05ad-bf5e-0288d8ddcd80@redhat.com> Date: Thu, 19 Oct 2017 11:21:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <1508400527-20718-1-git-send-email-yao.qi@linaro.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2017-10/txt/msg00603.txt.bz2 On 10/19/2017 09:08 AM, Yao Qi wrote: > ARMv8 supports tagged address, that is, the top one byte in address > is ignored. It is always enabled on aarch64-linux. The patch clear > the top byte of the virtual address, at the point before GDB/GDBserver > pass the address to /proc or ptrace syscall. The top byte of address is > still retained in the rest of GDB, because these bits can be used by > different applications in different ways. That is reason I didn't > implement gdbarch method addr_bits_remove to get rid of them. Something else that came to mind -- do we need to make GDB's stack/code caches aware of this? I.e., for the case of writing through a tagged address and reading via a non-tagged address, and vice-versa. Thanks, Pedro Alves