From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gdb-return-36807-listarch-gdb=sources.redhat.com@sourceware.org>
Received: (qmail 23199 invoked by alias); 4 Feb 2010 19:38:37 -0000
Received: (qmail 23191 invoked by uid 22791); 4 Feb 2010 19:38:36 -0000
X-SWARE-Spam-Status: No, hits=-2.0 required=5.0 	tests=AWL,BAYES_00,SARE_MSGID_LONG40,SPF_PASS
X-Spam-Check-By: sourceware.org
Received: from mail-ew0-f223.google.com (HELO mail-ew0-f223.google.com) (209.85.219.223)     by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 04 Feb 2010 19:38:33 +0000
Received: by ewy23 with SMTP id 23so48497ewy.4         for <gdb@sourceware.org>; Thu, 04 Feb 2010 11:38:30 -0800 (PST)
MIME-Version: 1.0
Received: by 10.216.91.10 with SMTP id g10mr834531wef.217.1265312309947; Thu,  	04 Feb 2010 11:38:29 -0800 (PST)
Date: Thu, 04 Feb 2010 19:38:00 -0000
Message-ID: <23c0f921002041138k1d989b9cs8423911108499331@mail.gmail.com>
Subject: Switching architectures from a remote target
From: Robert Barnes <robcb85@gmail.com>
To: gdb@sourceware.org
Content-Type: text/plain; charset=ISO-8859-1
Mailing-List: contact gdb-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <gdb.sourceware.org>
List-Subscribe: <mailto:gdb-subscribe@sourceware.org>
List-Archive: <http://sourceware.org/ml/gdb/>
List-Post: <mailto:gdb@sourceware.org>
List-Help: <mailto:gdb-help@sourceware.org>, <http://sourceware.org/ml/#faqs>
Sender: gdb-owner@sourceware.org
X-SW-Source: 2010-02/txt/msg00025.txt.bz2

I am using GDB to interface with a remote target over serial. The
target architecture changes during execution (e.g. 32-bit to 64-bit).
When the architecture changes I need gdb to change its internal
representation of the remote architecture at the same time. The
primary problem is the remote 'g' command, it's return packet size is
determined by the initial call. When the architecture changes, the
size and number of registers may change, thus the size of the 'g'
packet changes. Yet gdb is still expecting the old size.

This problem is addressed in section 7 of "Multi-arching Insights and
GDB" by Andrew Cagney
(http://www.gnu.org/software/gdb/papers/multi-arch/real-multi-arch/).
As far as I can tell the recommendations haven't been implemented.

Are there any workarounds or solutions to the general problem of
handling changing architectures on a remote target?

Thanks!

-Rob