Date: Fri, 5 May 2017 18:11:11 -0700 From: Mark Millard <markmi@dsl-only.net> To: Dimitry Andric <dim@FreeBSD.org> Cc: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, FreeBSD Toolchain <freebsd-toolchain@freebsd.org> 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) Message-ID: <E177E5EE-25EB-4CBA-9C0F-7209AFF30749@dsl-only.net> In-Reply-To: <78CD5050-2B2B-4213-AF11-7EF744F608B2@dsl-only.net> References: <bug-26519-7604@http.bugs.llvm.org/> <bug-26519-7604-UhFFHDCAay@http.bugs.llvm.org/> <0103401A-CEEA-4992-A45E-E60EA151119B@dsl-only.net> <893ECA11-7C80-4D24-A496-92ADC7978A07@FreeBSD.org> <8F708AD1-055E-41BD-BD92-6A87C5FBAA60@dsl-only.net> <78CD5050-2B2B-4213-AF11-7EF744F608B2@dsl-only.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On 2017-May-5, at 1:22 AM, Mark Millard <markmi@dsl-only.net> wrote: > On 2017-May-5, at 12:45 AM, Mark Millard <markmi at dsl-only.net> = wrote: >=20 >> On 2017-May-4, at 2:41 PM, Dimitry Andric <dim at FreeBSD.org> wrote: >>=20 >>> . . . >>> Thanks for the notice. I have merged the upstream fix into head in >>> r317810, and I will MFC it after a few days. >>=20 >> I now have an old PowerMac running: >>=20 >> # uname -paKU >> FreeBSD FBSDG4S 12.0-CURRENT FreeBSD 12.0-CURRENT r317820M powerpc = powerpc 1200030 1200030 >>=20 >> where buildworld was via clang 4 (an amd64->powerpc >> cross build). Even the classic tiny program that >> previously showed C++ exception handling was broken >> and would crash the program now works when >> re-compiled and re-linked. Commands that were >> previous broken now work. I messed up and accidentally installed the gcc 4.2.1 world that I had also built. This is why C++ exceptions appeared to be working for powerpc. Both TARGET_ARCH=3Dpowerpc and TARGET_ARCH=3Dpowerpc64 have C++ exceptions still messed up. >> (But my testing is nearly minimal at this point.) >>=20 >> The kernel is from gcc421. >>=20 >>=20 >>=20 >> I did try booting a kernel built by system-clang 4 >> and it got to: >>=20 >> exec /sbin/init: error 13 >>=20 >> and a later alignment exception at sf_buf_alloc+0x260 >>=20 >> (Hand transcribed screen information.) >>=20 >> This is the same as the last time that I tried >> such. The exception involved: >>=20 >> exec_map_first_page >> kern_execve >> sys_execve >> start_init >> fork_exit >> fork_trampoline >>=20 >>=20 >>=20 >> For the gcc 4.2.1 based kernel boot I have >> had one odd fatal kernel trap (0x903a64a, >> "unknown") where the lr showed 0x907f . It >> reported being stopped at: >>=20 >> ffs_truncate+0x1080 >>=20 >> It appears that "call doadump" worked but >> I've not looked at what was put in >> /var/crash/ . >=20 > If I leave the PowerMac idle running: >=20 > # uname -paKU > FreeBSD FBSDG4S 12.0-CURRENT FreeBSD 12.0-CURRENT r317820M powerpc = powerpc 1200030 1200030 >=20 > it eventually gets the same ffs_truncate-tied fatal > kernel trap, with the same odd lr and the like. >=20 > So, while I cannot directly cause the problem > at a specific time, the problem is repeatable. >=20 > I did not build the kernel with a so-called > "red-zone" to work around any stack-operation > ordering problems that might still be around. > But I do not know that such is involved here. > It may be a while before I manage to get that > much of an analysis done. The ffs_truncate issue is odd: A) It was gcc 4.2.1 based for both kernel and world. B) I built a gcc 4.2.1 based debug kernel and installed it but that does not get the problem. I sam trying the gcc 4.2.1 debug kernel with the system clang 4 world now and will later switch to the gcc 4.2.1 non-debug kernel to see what happens. But being a pure gcc 4.2.1 environment originally suggests that the ffs_truncate issue is not clang-toolchain related. =3D=3D=3D Mark Millard markmi at dsl-only.net
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?E177E5EE-25EB-4CBA-9C0F-7209AFF30749>