Date: Wed, 20 Dec 2017 11:07:59 -0800 From: John Baldwin <jhb@freebsd.org> To: Nathan Whitehorn <nwhitehorn@freebsd.org> Cc: David Chisnall <theraven@freebsd.org>, Eugene Grosbein <eugen@grosbein.net>, Konstantin Belousov <kostikbel@gmail.com>, Conrad Meyer <cem@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r326758 - in head/sys/i386: conf include Message-ID: <2357779.RlDvz1mMEe@ralph.baldwin.cx> In-Reply-To: <28f2f06b-dc46-99f1-70be-260bb408c827@freebsd.org> References: <201712110432.vBB4WbnE021090@repo.freebsd.org> <1839614.eNG2DjLqvF@ralph.baldwin.cx> <28f2f06b-dc46-99f1-70be-260bb408c827@freebsd.org>
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On Wednesday, December 20, 2017 10:16:58 AM Nathan Whitehorn wrote: >=20 > On 12/20/17 09:14, John Baldwin wrote: > > On Wednesday, December 20, 2017 09:59:26 AM David Chisnall wrote: > >> On 16 Dec 2017, at 18:05, John Baldwin <jhb@FreeBSD.org> wrote: > >>> When I build a FreeBSD/mips64 kernel with clang, > >>> _any_ simple NFS op triggers a kernel stack overflow. Kernels co= mpiled > >>> with GCC do not. > >> That is not my experience. I haven=E2=80=99t tried a MIPS64 kerne= l built with clang, but with in-tree gcc I get kernel panics as soon as= I try to use NFS, unless I use Stacey=E2=80=99s patches that increase = the kernel stack size. > > I have primarily been using modern GCC for GCC once that was workin= g, but at > > least when running a MALTA64 kernel under qemu I was not triggering= panics > > even with old GCC. With the in-tree clang 5.0 or with CHERI clang,= just > > doing an 'ls' of a NFS directory or even a tab-complete of a path t= hat > > is on NFS reliably triggers a kernel stack overflow for MALTA64 in = qemu. > > > > With Stacey's kstack pages, a clang kernel does survive, but those = are not > > in stock FreeBSD which is where I have been testing this. > > >=20 > With GCC 4, it takes a little while, but trying to build ports over N= FS=20 > is a sure-fire way to bring down the kernel. I haven't tried any othe= r=20 > compilers. Ah, I have only done things like run binaries over NFS and compile simp= le test programs over NFS with GCC 4 (I do run a gdb binary over NFS again= st itself which probably involves a bit of I/O due to debug symbols, etc. = but still not as onerous as building lots of ports. I cross-build the GDB = on the host due to qemu being too slow). clang insta-panics for even triv= ial things like 'ls' and tab-completion though. It's definitely much worse= than either version of GCC. --=20 John Baldwin
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