From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30786 invoked by alias); 10 Sep 2013 04:06:30 -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 30758 invoked by uid 89); 10 Sep 2013 04:06:29 -0000 Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 10 Sep 2013 04:06:29 +0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=0.7 required=5.0 tests=AWL,BAYES_00,GARBLED_BODY,KHOP_THREADED,RDNS_NONE,SPF_HELO_FAIL autolearn=no version=3.3.2 X-HELO: relay1.mentorg.com Received: from svr-orw-exc-10.mgc.mentorg.com ([147.34.98.58]) by relay1.mentorg.com with esmtp id 1VJFDa-0004KF-U0 from Yao_Qi@mentor.com ; Mon, 09 Sep 2013 21:06:22 -0700 Received: from SVR-ORW-FEM-04.mgc.mentorg.com ([147.34.97.41]) by SVR-ORW-EXC-10.mgc.mentorg.com with Microsoft SMTPSVC(6.0.3790.4675); Mon, 9 Sep 2013 21:06:22 -0700 Received: from qiyao.dyndns.org (147.34.91.1) by svr-orw-fem-04.mgc.mentorg.com (147.34.97.41) with Microsoft SMTP Server id 14.2.247.3; Mon, 9 Sep 2013 21:06:21 -0700 Message-ID: <522E9A8A.7040509@codesourcery.com> Date: Tue, 10 Sep 2013 04:06:00 -0000 From: Yao Qi User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Mark Kettenis CC: Subject: Re: [PATCH 0/7 V2] Trust readonly sections if target has memory protection References: <1378432920-7731-1-git-send-email-yao@codesourcery.com> <1378641807-24256-1-git-send-email-yao@codesourcery.com> <201309091916.r89JGbpf009986@glazunov.sibelius.xs4all.nl> In-Reply-To: <201309091916.r89JGbpf009986@glazunov.sibelius.xs4all.nl> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-IsSubscribed: yes X-SW-Source: 2013-09/txt/msg00318.txt.bz2 On 09/10/2013 03:16 AM, Mark Kettenis wrote: > What does "memory protection" mean? That a target has an MMU that > allows pages to be marked read-only? That really is more a hardware > feature than a OS aatribute. "memory protection" means prevent modifying readonly sections or regions of the process. "memory protection" is a joint effort by MMU and OS together, IMO. > > Even on systems that have an MMU that can mark pages read-only, system > calls like mprotect(2) can be used to make read-only pages > (temporarily) writable. This is done by the OpenBSD dynamic linker > during relocation processing. I expect other systems implementing > strict W^X to do the same. Enabling trust-readonly-sections on such > systems would be a bad idea. If GDB can monitor mprotect syscall, it can still trust readonly sections if their pages are not changed to writable by mprotect. GDB is able to 'catch syscall mprotect', only on linux-nat unfortunately. It doesn't work on remote target "catch syscall" support in the remote protocol https://sourceware.org/bugzilla/show_bug.cgi?id=13585 Similarly, GDB can monitor function VirtualProtect on Windows target too. -- Yao (齐尧)