From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 1832 invoked by alias); 10 Mar 2008 12:02:59 -0000 Received: (qmail 1825 invoked by uid 22791); 10 Mar 2008 12:02:57 -0000 X-Spam-Status: No, hits=-1.5 required=5.0 tests=AWL,BAYES_00,J_CHICKENPOX_44,J_CHICKENPOX_84 X-Spam-Check-By: sourceware.org Received: from wildebeest.demon.nl (HELO gnu.wildebeest.org) (83.160.170.119) by sourceware.org (qpsmtpd/0.31) with ESMTP; Mon, 10 Mar 2008 12:02:40 +0000 Received: from dijkstra.wildebeest.org ([192.168.1.29]) by gnu.wildebeest.org with esmtp (Exim 4.63) (envelope-from ) id 1JYgiC-000627-QC; Mon, 10 Mar 2008 13:02:37 +0100 Subject: Re: [SCM] master: Switch to frysk.sys.ptrace. From: Mark Wielaard To: frysk@sourceware.org Cc: Andrew Cagney In-Reply-To: <1204113543.3615.22.camel@dijkstra.wildebeest.org> References: <20080212185049.22237.qmail@sourceware.org> <1202892451.3421.9.camel@dijkstra.wildebeest.org> <1204113543.3615.22.camel@dijkstra.wildebeest.org> Content-Type: text/plain Date: Mon, 10 Mar 2008 12:02:00 -0000 Message-Id: <1205150556.3356.34.camel@dijkstra.wildebeest.org> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 (2.12.3-3.fc8) Content-Transfer-Encoding: 7bit X-Spam-Score: -4.4 (----) X-IsSubscribed: yes Mailing-List: contact frysk-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: frysk-owner@sourceware.org X-SW-Source: 2008-q1/txt/msg00142.txt.bz2 Hi Andrew, On Wed, 2008-02-27 at 12:59 +0100, Mark Wielaard wrote: > On Wed, 2008-02-13 at 09:47 +0100, Mark Wielaard wrote: > > On Tue, 2008-02-12 at 18:50 +0000, cagney@sourceware.org wrote: > > > - private int peek(long index, byte[] bytes, int offset, int length) > > > - { > > > - if (mem != null) > > > - { > > > - try > > > - { > > > - return mem.pread(index, bytes, offset, length); > > > - } > > > - catch (Errno e) > > > - { > > > - // try again through address space. > > > + private void transfer(long index, byte[] bytes, int offset, int length, > > > + boolean write) { > > > + if (mem != null && !write) { > > > + try { > > > + mem.pread(index, bytes, offset, length); > > > + return; > > > + } catch (Errno e) { > > > + // Give up on mem; and fall back to ptrace. This > > > + // can happen when /proc isn't mounted, or when a > > > + // process is terminating and the kernel scrubs > > > + // the /proc entry before its time. > > > + mem = null; > > > } > > > } > > > > Are you sure this change is right? The comment is right about those 2 > > reasons for pread() possibly failing. But I don't believe that is the > > only case it can happen. Previously when a read occurred that failed, > > possibly because following a pointer in the inferior that was NULL or > > not yet initialized that would just cause a error reading from that > > particular (uninitialized) memory location. But now whenever that occurs > > once for an inferior you blow away mem so pread() can never be used > > anymore and we always fall back to having to do single peeks and pokes > > through the ptrace address space. > > Did you have time to investigate this? If not, shall we revert it to > the > original implementation till you do have time? Ping. Please do take a look. I really would like to see this resolved. I appreciate that it is hard to just revert this hunk if you don't have time right now to finalize it, because it was embedded into another rewrite commit of other stuff. So it would really help if you made separate commits for separate issues in the future. That makes these kind of reviews easier. Thanks, Mark