From owner-freebsd-ppc@freebsd.org Wed May 17 22:22:08 2017 Return-Path: Delivered-To: freebsd-ppc@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 3E39BD71B0F for ; Wed, 17 May 2017 22:22:08 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: from asp.reflexion.net (outbound-mail-210-6.reflexion.net [208.70.210.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E41B413AF for ; Wed, 17 May 2017 22:22:07 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: (qmail 11817 invoked from network); 17 May 2017 22:22:01 -0000 Received: from unknown (HELO rtc-sm-01.app.dca.reflexion.local) (10.81.150.1) by 0 (rfx-qmail) with SMTP; 17 May 2017 22:22:01 -0000 Received: by rtc-sm-01.app.dca.reflexion.local (Reflexion email security v8.40.0) with SMTP; Wed, 17 May 2017 18:22:01 -0400 (EDT) Received: (qmail 9438 invoked from network); 17 May 2017 22:22:01 -0000 Received: from unknown (HELO iron2.pdx.net) (69.64.224.71) by 0 (rfx-qmail) with (AES256-SHA encrypted) SMTP; 17 May 2017 22:22:01 -0000 Received: from [192.168.1.106] (c-76-115-7-162.hsd1.or.comcast.net [76.115.7.162]) by iron2.pdx.net (Postfix) with ESMTPSA id EE6FDEC903F; Wed, 17 May 2017 15:22:00 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Subject: Re: llvm FreeBSD powerpc ABI target bug fix: Re: [Bug 26519] Clang 4.0.0's "Target: powerpc-unknown-freebsd11.0" code generation is violating the SVR4 ABI (SEGV can result) From: Mark Millard In-Reply-To: <893ECA11-7C80-4D24-A496-92ADC7978A07@FreeBSD.org> Date: Wed, 17 May 2017 15:22:00 -0700 Cc: FreeBSD Toolchain , FreeBSD PowerPC ML , Roman Divacky Content-Transfer-Encoding: quoted-printable Message-Id: <408D3509-3D62-4413-986B-6C1171FB6138@dsl-only.net> References: <0103401A-CEEA-4992-A45E-E60EA151119B@dsl-only.net> <893ECA11-7C80-4D24-A496-92ADC7978A07@FreeBSD.org> To: Dimitry Andric X-Mailer: Apple Mail (2.3273) X-BeenThere: freebsd-ppc@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Porting FreeBSD to the PowerPC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 17 May 2017 22:22:08 -0000 I got a notice this morning of the latest fix for covering the TARGET_ARCH=3Dpowerpc stack-handling issues for llvm bugzilla 26519: > Comment # 33 on bug 26519 from Krzysztof Parzyszek > The fix has been committed in master in r303257. >=20 > I opened PR33070 to request merging it into 4.0.1. >=20 > You are receiving this mail because: > =E2=80=A2 You reported the bug. I've been using a version of the patch for some time and for buildworld it appears that with it powerpc and powerpc64 have a similar status: the one known area not working is handling of thrown C++ exceptions --for example the required dwarf information is incomplete so programs crash. (I have one powerpc64 patch in use that is not applied upstream or in FreeBSD that is essential for the powerpc64 status. See the later side notes for the tiny patch.) For buildkernel there is a difference for TARGET_ARCH=3Dpowerpc vs. TARGET_ARCH=3Dpowerpc64 : A) powerpc46 works for building and running the kernel and world on the old G5 PowerMacs. B) powerpc FreeBSD on the same machines fails at the /sbin/init attempt and then gets an alignment exception. (I've not tried a G4 or G3 yet.) As of yet I've no clue why (B) is an issue. Side notes: Note 0: The patch I was given a fair time ago that is required for TARGET_ARCH=3Dpowerpc64 is: # svnlite diff /usr/src/contrib/llvm/tools/ Index: /usr/src/contrib/llvm/tools/lld/ELF/Target.cpp =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D --- /usr/src/contrib/llvm/tools/lld/ELF/Target.cpp (revision = 317820) +++ /usr/src/contrib/llvm/tools/lld/ELF/Target.cpp (working copy) @@ -1070,7 +1070,8 @@ } =20 PPC64TargetInfo::PPC64TargetInfo() { - PltRel =3D GotRel =3D R_PPC64_GLOB_DAT; + GotRel =3D R_PPC64_GLOB_DAT; + PltRel =3D R_PPC64_JMP_SLOT; RelativeRel =3D R_PPC64_RELATIVE; GotEntrySize =3D 8; (Thanks to Roman Divacky.) Note 1: While a pure gcc 4.2.1 buildworld buildkernel with a debug kernel is working for booting and using, a production style kernel gets occasional panics on the old G5 PowerMacs. (The powerpc64 builds work fine on the same machines.) (I've not tried any G4's or a G3 yet.) It also appears that small changes in memory layout details (from trying to get better evidence) change the behavior/failure-mode/ details. I do not expect to find out what is going on any time soon. The same problems existed when buildworld was via clang 4. A kernel from a clang buildkernel does not get far enough for me to see what it would do for the issue. As this issue is more fundamental to general operation it has been getting much of my FreeBSD time. =3D=3D=3D Mark Millard markmi at dsl-only.net