From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 65980 invoked by alias); 6 May 2019 21:37:15 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 65971 invoked by uid 89); 6 May 2019 21:37:15 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-5.4 required=5.0 tests=AWL,BAYES_00,SPF_PASS autolearn=ham version=3.3.1 spammy=continued, H*f:sk:5954fa7, asked, seemingly X-HELO: mx2.freebsd.org Received: from mx2.freebsd.org (HELO mx2.freebsd.org) (8.8.178.116) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 06 May 2019 21:37:14 +0000 Received: from mx1.freebsd.org (mx1.freebsd.org [96.47.72.80]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client CN "mx1.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx2.freebsd.org (Postfix) with ESMTPS id BAB896EF46; Mon, 6 May 2019 21:37:12 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from smtp.freebsd.org (smtp.freebsd.org [IPv6:2610:1c1:1:606c::24b:4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 0BAA28C007; Mon, 6 May 2019 21:37:12 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from John-Baldwins-MacBook-Pro-3.local (ralph.baldwin.cx [66.234.199.215]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) (Authenticated sender: jhb) by smtp.freebsd.org (Postfix) with ESMTPSA id 920BD17844; Mon, 6 May 2019 21:37:11 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Subject: Re: icache-dcache coherence on ARM To: Xiaozhu Meng Cc: gdb@sourceware.org References: <5954fa76-7b6a-1544-6516-5d11cb395b26@FreeBSD.org> From: John Baldwin Openpgp: preference=signencrypt Message-ID: <1b15495b-eb18-d910-2c0b-b446f5649b67@FreeBSD.org> Date: Mon, 06 May 2019 21:37:00 -0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 0BAA28C007 X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-2.98 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-1.00)[-0.999,0]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; NEURAL_HAM_SHORT(-0.98)[-0.980,0]; ASN(0.00)[asn:11403, ipnet:2610:1c1:1::/48, country:US] X-IsSubscribed: yes X-SW-Source: 2019-05/txt/msg00014.txt.bz2 On 5/6/19 2:17 PM, Xiaozhu Meng wrote: > Hi John, > > Thanks for your reply! > > I asked this question because our project on Linux actually encountered > this problem where we use ptrace to write new code into the inferior and > then continue the inferior. The continued inferior sometimes works as > expected, but sometimes crashes due to SIGILLs on seemingly legitimate > instructions. > > So, I am very interested in seeing how GDB deals with this problem on > Linux. I do not see any explicit cache management in linux-nat.c or arm-linux-nat.c, so my best guess is that GDB is relying on the kernel to manage this on Linux as well. I do see that TARGET_OBJECT_MEMORY on Linux can sometimes use /proc//mem instead of ptrace(). I'm not very familiar with the Linux kernel, but one thing to check might be that both ptrace and procfs are doing the i-cache invalidation. -- John Baldwin