Date: Fri, 5 May 2017 01:22:57 -0700 From: Mark Millard <markmi@dsl-only.net> To: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Cc: FreeBSD Toolchain <freebsd-toolchain@freebsd.org>, Dimitry Andric <dim@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: <78CD5050-2B2B-4213-AF11-7EF744F608B2@dsl-only.net> In-Reply-To: <8F708AD1-055E-41BD-BD92-6A87C5FBAA60@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>
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On 2017-May-5, at 12:45 AM, Mark Millard <markmi at dsl-only.net> wrote: > 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. >=20 > (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/ . If I leave the PowerMac idle running: # uname -paKU FreeBSD FBSDG4S 12.0-CURRENT FreeBSD 12.0-CURRENT r317820M powerpc = powerpc 1200030 1200030 it eventually gets the same ffs_truncate-tied fatal kernel trap, with the same odd lr and the like. So, while I cannot directly cause the problem at a specific time, the problem is repeatable. 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. =3D=3D=3D Mark Millard markmi at dsl-only.net
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