From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3816 invoked by alias); 14 Sep 2010 17:15:54 -0000 Received: (qmail 3808 invoked by uid 22791); 14 Sep 2010 17:15:53 -0000 X-SWARE-Spam-Status: No, hits=-4.6 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,TW_BJ,TW_DB,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from smtp-outbound-2.vmware.com (HELO smtp-outbound-2.vmware.com) (65.115.85.73) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 14 Sep 2010 17:15:42 +0000 Received: from mailhost4.vmware.com (mailhost4.vmware.com [10.16.67.124]) by smtp-outbound-2.vmware.com (Postfix) with ESMTP id 1D5F53F066; Tue, 14 Sep 2010 10:15:41 -0700 (PDT) Received: from msnyder-server.eng.vmware.com (promd-2s-dhcp138.eng.vmware.com [10.20.124.138]) by mailhost4.vmware.com (Postfix) with ESMTP id 15B41C9AEA; Tue, 14 Sep 2010 10:15:41 -0700 (PDT) Message-ID: <4C8FADBC.70301@vmware.com> Date: Tue, 14 Sep 2010 18:15:00 -0000 From: Michael Snyder User-Agent: Thunderbird 2.0.0.24 (X11/20100903) MIME-Version: 1.0 To: Pierre Muller CC: "gdb-patches@sourceware.org" Subject: Re: [RFC] Improve stabs debugging for mingw64 executables loaded at high addresses References: <000701cb541e$1160cde0$342269a0$@muller@ics-cnrs.unistra.fr> In-Reply-To: <000701cb541e$1160cde0$342269a0$@muller@ics-cnrs.unistra.fr> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2010-09/txt/msg00269.txt.bz2 Pierre Muller wrote: > On 64-bit targets, stabs suffers from the fact that addresses > are only stored as 32-bit values. > > For mingw64, I was able to debug executables loaded > at address 0x100000000 (the default location for executables > compiled by Free Pascal Compiler) by using the simple > patch below. > > The idea of the patch is quite basic: > add the 32 high bits of text_addr as > to the offsets of all sections in read_dbx_symtab. > > I don't know if this is mingw64 (possibly 64-bit PE) specific or not... > > All those offsets seemed to be at zero at the time I added > the high 32-bit part of text_addr, but maybe other > targets do something else... If this should not be applied > for other 64-bit targets, we could of course modify > the tests before changing the offsets, restricting it to > targets for which it is relevant. > > I just tried to use gcc to compile an executable > with -Wl,--image-base,0x300000000, to force high load address, > but this lead to lots of messages: > relocation truncated to fit R_X86_64_32 against .text > Free Pascal compiler doesn't seem to generate any of those > time of relocations... > > Comments welcome, I don't see any intrinsic harm in it, since it will only affect stabs binaries when BFD64 is defined. This is just a comment, though, not an approval. > 2010-09-14 Pierre Muller > > * dbxread.c (read_dbx_symtab): Add high part of text_addr value > to all section offsets. > > Index: src/gdb/dbxread.c > =================================================================== > RCS file: /cvs/src/src/gdb/dbxread.c,v > retrieving revision 1.116 > diff -u -p -r1.116 dbxread.c > --- src/gdb/dbxread.c 14 May 2010 17:53:15 -0000 1.116 > +++ src/gdb/dbxread.c 1 Sep 2010 08:01:01 -0000 > @@ -1216,6 +1216,22 @@ read_dbx_symtab (struct objfile *objfile > text_addr = DBX_TEXT_ADDR (objfile); > text_size = DBX_TEXT_SIZE (objfile); > > +#ifdef BFD64 > + { > + /* stabs internal format only has 4 bytes for address. > + Use high dword of text address to fix global addresses. > + FIXME: this only works if the whole executable has the same > + high part address. */ > + CORE_ADDR stabs_fixup = text_addr & ~((CORE_ADDR) 0xffffffff); > + if (stabs_fixup) > + { > + objfile->section_offsets->offsets[SECT_OFF_TEXT (objfile)] += stabs_fixup; > + objfile->section_offsets->offsets[SECT_OFF_DATA (objfile)] += stabs_fixup; > + objfile->section_offsets->offsets[SECT_OFF_BSS (objfile)] += stabs_fixup; > + } > + } > +#endif /* BFD64 */ > + > /* FIXME. We probably want to change stringtab_global rather than add this > while processing every symbol entry. FIXME. */ > file_string_table_offset = 0; >