From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 18985 invoked by alias); 26 May 2011 17:47:31 -0000 Mailing-List: contact archer-help@sourceware.org; run by ezmlm Sender: Precedence: bulk List-Post: List-Help: List-Subscribe: List-Id: Received: (qmail 18975 invoked by uid 22791); 26 May 2011 17:47:30 -0000 X-SWARE-Spam-Status: No, hits=-6.8 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,SPF_HELO_PASS,TW_GJ,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org From: Tom Tromey To: Paul Pluzhnikov Cc: archer@sourceware.org Subject: Re: Improved linker-debugger interface References: <20110525153649.GB3149@redhat.com> Date: Thu, 26 May 2011 17:47:00 -0000 In-Reply-To: (Paul Pluzhnikov's message of "Thu, 26 May 2011 10:36:42 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-SW-Source: 2011-q2/txt/msg00005.txt.bz2 Paul> 1. Stripped binaries. Paul> There is a DT_DEBUG entry pointing to _dl_debug_state (set by ld-linux) Paul> You might want to have a new dynamic tag, pointing to Paul> _dl_debug_state_extended(), so the debugger would be able to track Paul> shared libs using the new mechanism even when everything is stripped. SystemTap probes aren't stripped, so I think this should work fine. This is one of the big plusses (from my POV) of using probes, and it is why we introduced probes into longjmp and the exception unwinder too -- it lets gdb features work even when the user hasn't installed debuginfo for glibc and/or libgcc. This stuff is in F15. It wasn't accepted into glibc mainline. Paul> 2. In-process debuggers. Paul> B) compiles down to a single 'ret', so there is no way to place a patch Paul> on top of it. Right now a SystemTap probe is a single nop, so probably no joy there. We have talked about making it a wider nop, though, to facilitate this kind of patching, primarily I think by LTTng. What do you think of this? Paul> Perhaps co-operation with "in-process" debuggers would be more Paul> acceptable for a new interface? It is fine by me. Tom