From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A803C4332F for ; Fri, 10 Nov 2023 22:20:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229548AbjKJWUS convert rfc822-to-8bit (ORCPT ); Fri, 10 Nov 2023 17:20:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229451AbjKJWUS (ORCPT ); Fri, 10 Nov 2023 17:20:18 -0500 Received: from smtp.gentoo.org (woodpecker.gentoo.org [140.211.166.183]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F1DC444A4 for ; Fri, 10 Nov 2023 14:20:14 -0800 (PST) References: <87lebjz9z6.fsf@gentoo.org> <875y2jro9a.fsf@gentoo.org> <0fec2446-a523-486f-9df7-4c6af9e2e0e3@gmx.de> <7409ec05-7a28-45fe-9604-519de5ae934e@bell.net> <87sf5d8f9h.fsf@gentoo.org> <9bc4615d-122b-4c12-9537-b2eddc753a32@bell.net> User-agent: mu4e 1.10.8; emacs 30.0.50 From: Sam James To: John David Anglin Cc: Sam James , Helge Deller , "linux-parisc@vger.kernel.org" Subject: Re: prctl call wrongly succeeds on HPPA? Date: Fri, 10 Nov 2023 22:16:14 +0000 Organization: Gentoo In-reply-to: <9bc4615d-122b-4c12-9537-b2eddc753a32@bell.net> Message-ID: <87leb58d45.fsf@gentoo.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org John David Anglin writes: > On 2023-11-10 4:32 p.m., Sam James wrote: >> John David Anglin writes: >> >>> On 2023-11-10 3:38 p.m., Helge Deller wrote: >>>> On 11/10/23 21:12, John David Anglin wrote: >>>>> On 2023-11-10 3:01 p.m., Helge Deller wrote: >>>>>>>> On HPPA, we still need executable stacks, so this option doesn't work >>>>>>>> and leads to a segfault on boot. >>>>>> For kernel we don't need it any longer. >>>>>> But there might be dependencies on glibc version and/or combination. >>>>>> So, I've currently lost overview if we still need executable stacks... >>>>> FWIW, I recently changed gcc-14 to enable GNU stack notes and fixed a bug in the >>>>> 32-bit PA 2.0 trampoline template.  All execute stack tests in glibc now pass with gcc-14. >>>> Yes, I saw your commits. >>>> So, any code compiled with >= gcc-14 should be fine with non-writeable stacks? >>> Not exactly.  An executable stack is still needed for nested functions.  They are still called >>> via a stack trampoline.  The GNU stack note indicates whether an object needs an executable >>> stack or not.  These notes are collected by linker.  The glibc loader determines whether to setup >>> an executable stack or not. >>>> It would be easier if it would be a glibc dependency (for distribution maintainers)... >>> I'm not aware of any glibc dependency... >>> >>> I think once gcc-14 becomes the default compiler, we will have to enable GNU stack notes in >>> previous gcc versions.  We will still have executable stacks until everything is rebuilt. >> We will need to update that default in Binutils too, I think. That >> configure arg is working OK for me, but I did not try systemd yet. > Currently, there are no architecture dependencies in the ld --enable-warn-execstack and --enable-default-execstack > configure options.  The -z execstack and -z noexecstack ld options can override the GNU notes, or lack thereof.  We > may have to fix some assembly code.  Maybe binutils should be built with --enable-warn-execstack once we switch > to gcc-14.  I don't think we want --enable-default-execstack after switching to gcc-14. Are you sure? I just did some more digging now... * It looks like targets can set elf_backend_default_execstack in bfd/elf-*.c to override the default, see e.g. 81cd0a49c9e5f28c0fec391e449ea3272077c432 for cris. * See acd65fa610df09a0954b8fecdadf546215263c5d where HPPA's default got changed. * ld/configure.tgt still has some suppression for HPPA's default for warnings. I think we may need to, in due course, set elf_backend_default_execstack in bfd/elf32-hppa.c, and then drop those bits in ld/configure.tgt too? Let me know if missing something because the binutils configure stuff is a bit convoluted. > > Dave