From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15299 invoked by alias); 2 Jul 2003 06:38:44 -0000 Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sources.redhat.com Received: (qmail 15291 invoked from network); 2 Jul 2003 06:38:43 -0000 Received: from unknown (HELO Cantor.suse.de) (213.95.15.193) by sources.redhat.com with SMTP; 2 Jul 2003 06:38:43 -0000 Received: from Hermes.suse.de (Hermes.suse.de [213.95.15.136]) by Cantor.suse.de (Postfix) with ESMTP id 3296314733; Wed, 2 Jul 2003 08:38:43 +0200 (MEST) To: gdb@sources.redhat.com Cc: Josef Zlomek Subject: Re: Dwarf unwinder problems with store.exp and preserved regs References: <20030701214429.GA3913@nevyn.them.org> From: Andreas Jaeger Date: Wed, 02 Jul 2003 06:38:00 -0000 In-Reply-To: <20030701214429.GA3913@nevyn.them.org> (Daniel Jacobowitz's message of "Tue, 1 Jul 2003 17:44:30 -0400") Message-ID: User-Agent: Gnus/5.1003 (Gnus v5.10.3) XEmacs/21.4 (Portable Code, linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-SW-Source: 2003-07/txt/msg00030.txt.bz2 Daniel Jacobowitz writes: > I see two kinds of failures in store.exp right now, on the two targets I'm > testing. On i386, with DWARF 2 unwinding, I see spurious out> messages; and on ARM (without DWARF 2 unwinding) I see legitimately > corrupted values. The latter are easy, so I'll send a patch momentarily. > The former are more interesting. I see the same problem on x86-64 with the messages. > Here's the problem: the unwinder does not know what registers are considered > call saved. GDB reads some initial CIE unwind information from the debug > file: > > /* Instruction sequence to initialize a register set. */ > unsigned char *initial_instructions; > > /* True if a 'z' augmentation existed. */ > unsigned char saw_z_augmentation; > > cie->saw_z_augmentation = (*augmentation == 'z'); > if (cie->saw_z_augmentation) > { > ULONGEST length; > > length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read); > buf += bytes_read; > cie->initial_instructions = buf + length; > augmentation++; > } > > However, GCC only emits information about the CFA, not about the default > saved-ness of registers. So we get: > > 168 /* Initialize newly allocated registers. */ > 169 memset (rs->reg + rs->num_regs, 0, (num_regs - rs->num_regs) * size); > > And 0 is UNDEFINED. So $ebx - a call-saved register on i386 - shows up as > undefined. > > There are two things we can do about this, I think, and perhaps we should > do both: > - Fix GCC. I -believe-, from reading the spec, that GCC is to blame for > not emiting this information. > - Provide an architecture method to pre-initialize the register table > before initial_instructions is evaluated. I think the later is the way to go - but didn't read the spec fully to give an authoritative answer, Andreas -- Andreas Jaeger, aj@suse.de, http://www.suse.de/~aj SuSE Linux AG, Deutschherrnstr. 15-19, 90429 Nürnberg, Germany GPG fingerprint = 93A3 365E CE47 B889 DF7F FED1 389A 563C C272 A126