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Date:      Wed, 20 Dec 2017 09:14:07 -0800
From:      John Baldwin <jhb@freebsd.org>
To:        David Chisnall <theraven@freebsd.org>
Cc:        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:  <1839614.eNG2DjLqvF@ralph.baldwin.cx>
In-Reply-To: <68FECEF0-014E-4741-BE96-680E9338557B@FreeBSD.org>
References:  <201712110432.vBB4WbnE021090@repo.freebsd.org> <1705b795-46ca-bb27-6ba7-fab4eeed0aba@FreeBSD.org> <68FECEF0-014E-4741-BE96-680E9338557B@FreeBSD.org>

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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:
> >=20
> > When I build a FreeBSD/mips64 kernel with clang,
> > _any_ simple NFS op triggers a kernel stack overflow.  Kernels comp=
iled
> > with GCC do not.
>=20
> That is not my experience.  I haven=E2=80=99t tried a MIPS64 kernel b=
uilt 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 working, b=
ut at
least when running a MALTA64 kernel under qemu I was not triggering pan=
ics
even with old GCC.  With the in-tree clang 5.0 or with CHERI clang, jus=
t
doing an 'ls' of a NFS directory or even a tab-complete of a path that
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
John Baldwin



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