From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8304 invoked by alias); 19 May 2006 00:31:09 -0000 Received: (qmail 8295 invoked by uid 22791); 19 May 2006 00:31:08 -0000 X-Spam-Check-By: sourceware.org Received: from adsl-67-116-42-147.dsl.sntc01.pacbell.net (HELO avtrex.com) (67.116.42.147) by sourceware.org (qpsmtpd/0.31) with ESMTP; Fri, 19 May 2006 00:31:06 +0000 Received: from [192.168.7.26] ([192.168.7.26]) by avtrex.com with Microsoft SMTPSVC(6.0.3790.1830); Thu, 18 May 2006 17:31:04 -0700 Message-ID: <446D11C7.2040008@avtrex.com> Date: Fri, 19 May 2006 09:26:00 -0000 From: David Daney User-Agent: Mozilla Thunderbird 1.0.7-1.1.fc3 (X11/20050929) MIME-Version: 1.0 To: Thiemo Seufer CC: Daniel Jacobowitz , binutils@sourceware.org Subject: Re: MIPS textrel fix References: <20060518213149.GA14720@nevyn.them.org> <446CEF9F.2070403@avtrex.com> <20060519001101.GA1073@networkno.de> In-Reply-To: <20060519001101.GA1073@networkno.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes Mailing-List: contact binutils-help@sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: binutils-owner@sourceware.org X-SW-Source: 2006-05/txt/msg00322.txt.bz2 Thiemo Seufer wrote: > David Daney wrote: > >>Daniel Jacobowitz wrote: >> >>>While stuck offline earlier today, I revisited the textrel-1 MIPS >>>failure. Eric originally tried setting DF_TEXTREL during section >>>relocation, but it's too late: we add the entry in size_dynamic_sections. >>>But I couldn't see any other way to get it right, since there's no >>>hook to predict whether elf-eh-frame.c will eliminate a relocation. >>> >>>The easiest approach I found was to annul the DT_TEXTREL and DT_FLAGS >>>changes in finish_dynamic_sections if no text relocations were >>>actually generated. This is not immensely pretty, but does work. >>>OK? >>> >>>For background, the problem arises from the use of absolute addresses >>>in .eh_frame. In this case, they're being produced by gas CFI >>>directives. Is there a reason we can't mix and match encodings? >>>i.e. why not have gas use a PC-relative format? I'm sure there's >>>a reason, but I can't think of it... >>> >> >>Could it be related to the reason that GCC no longer generates a >>PC-relative .eh_frame? >> >>I never fully understood the reason, but I think it has to do with >>MIPS-ELF specifications not allowing the needed relocation types (even >>though they work well in binutils/glibc/linux). > > > The needed relocation types were originally defined for embedded PIC > MIPS and are not available in the ABI spec, their use for eh_frame > was an accident. When the removal of embedded PIC support broke the > toolchain, the fix chosen was to become ABI compatible again. > Not to beat a dead horse, but it would be nice to have a gnu extension that allows us to have read-only eh_frame sections. Large C++ shared libraries have way to many relocations. It is a lot of dirty pages in the name of ABI compliance. David Daney.