From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12951 invoked by alias); 13 Feb 2008 08:47:58 -0000 Received: (qmail 12944 invoked by uid 22791); 13 Feb 2008 08:47:58 -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; Wed, 13 Feb 2008 08:47:36 +0000 Received: from dijkstra.wildebeest.org ([192.168.1.29]) by gnu.wildebeest.org with esmtp (Exim 4.63) (envelope-from ) id 1JPDH9-0006VM-MS for frysk@sourceware.org; Wed, 13 Feb 2008 09:47:32 +0100 Subject: Re: [SCM] master: Switch to frysk.sys.ptrace. From: Mark Wielaard To: frysk@sourceware.org In-Reply-To: <20080212185049.22237.qmail@sourceware.org> References: <20080212185049.22237.qmail@sourceware.org> Content-Type: text/plain Date: Wed, 13 Feb 2008 08:47:00 -0000 Message-Id: <1202892451.3421.9.camel@dijkstra.wildebeest.org> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 (2.12.3-1.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/msg00065.txt.bz2 Hi Andrew, 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. Cheers, Mark