linux-kernel - Re: arm64: unhandled level 0 translation fault

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Message-ID: <20171215142732.GL25650@arm.com>
Date:   Fri, 15 Dec 2017 14:27:32 +0000
From:   Will Deacon <will.deacon@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Dave Martin <Dave.Martin@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Alex Bennée <alex.bennee@...aro.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: arm64: unhandled level 0 translation fault

On Fri, Dec 15, 2017 at 02:30:00PM +0100, Geert Uytterhoeven wrote:
> On Fri, Dec 15, 2017 at 12:23 PM, Dave Martin <Dave.Martin@....com> wrote:
> > The two important differences here seem to be
> >
> > 1) Staging the state via current->thread.fpsimd_state instead of loading
> > directly:
> >
> > -       fpsimd_load_state(state);
> > +       current->thread.fpsimd_state = *state;
> > +       fpsimd_load_state(&current->thread.fpsimd_state);
> 
> The change above introduces the breakage.

I finally managed to reproduce this, but only by using the exact same
compiler as Geert:

https://www.kernel.org/pub/tools/crosstool/files/bin/x86_64/4.9.0/x86_64-gcc-4.9.0-nolibc_aarch64-linux.tar.xz

I then reliably see the problem if I run:

  # /usr/bin/update-ca-certificates

from Debian Jessie.

Note that my normal toolchain (Linaro 7.1.1 build) works fine and also
if I use the toolchain above but disable CONFIG_ARM64_CRYPTO then things
work too.

So there's some toolchain-specific interaction between this change and the
crypto code...

Will