arm64: unhandled level 0 translation fault

[Dave P Martin]

On Thu, Dec 14, 2017 at 02:34:50PM +0000, Geert Uytterhoeven wrote:
> Hi Catalin, Will, Dave,
>
> On Tue, Dec 12, 2017 at 11:20 AM, Geert Uytterhoeven
> <geert at linux-m68k.org> wrote:
> > During userspace (Debian jessie NFS root) boot on arm64:
> >
> > rpcbind[1083]: unhandled level 0 translation fault (11) at 0x00000008,
> > esr 0x92000004, in dash[aaaaadf77000+1a000]
> > CPU: 0 PID: 1083 Comm: rpcbind Not tainted
> > 4.15.0-rc3-arm64-renesas-02176-g14f9a1826e48e355 #51
> > Hardware name: Renesas Salvator-X 2nd version board based on r8a7795 ES2.0+ (DT)
>
> This is a quad Cortex A57.
>
> > pstate: 80000000 (Nzcv daif -PAN -UAO)
> > pc : 0xaaaaadf8a51c
> > lr : 0xaaaaadf8ac08
> > sp : 0000ffffcffeac00
> > x29: 0000ffffcffeac00 x28: 0000aaaaadfa1000
> > x27: 0000ffffcffebf7c x26: 0000ffffcffead20
> > x25: 0000aaaacea1c5f0 x24: 0000000000000000
> > x23: 0000aaaaadfa1000 x22: 0000aaaaadfa1000
> > x21: 0000000000000000 x20: 0000000000000008
> > x19: 0000000000000000 x18: 0000ffffcffeb500
> > x17: 0000ffffa22babfc x16: 0000aaaaadfa1ae8
> > x15: 0000ffffa2363588 x14: ffffffffffffffff
> > x13: 0000000000000020 x12: 0000000000000010
> > x11: 0101010101010101 x10: 0000aaaaadfa1000
> > x9 : 00000000ffffff81 x8 : 0000aaaaadfa2000
> > x7 : 0000000000000000 x6 : 0000000000000000
> > x5 : 0000aaaaadfa2338 x4 : 0000aaaaadfa2000
> > x3 : 0000aaaaadfa2338 x2 : 0000000000000000
> > x1 : 0000aaaaadfa28b0 x0 : 0000aaaaadfa4c30
> >
> > Sometimes it happens with other processes, but the main address, esr, and
> > pstate values are always the same.
> >
> > I regularly run arm64/for-next/core (through bi-weekly renesas-drivers
> > releases, so the last time was two weeks ago), but never saw the issue
> > before until today, so probably v4.15-rc1 is OK.
> > Unfortunately it doesn't happen during every boot, which makes it
> > cumbersome to bisect.
> >
> > My first guess was UNMAP_KERNEL_AT_EL0, but even after disabling that,
> > and even without today's arm64/for-next/core merged in, I still managed to
> > reproduce the issue, so I believe it was introduced in v4.15-rc2 or
> > v4.15-rc3.
> >
> > Once, when the kernel message above wasn't shown, I got an error from
> > userspace, which may be related:
> > *** Error in `/bin/sh': free(): invalid pointer: 0x0000aaaadd970988 ***
>
> With more boots (10 instead of 6) to declare a kernel good, I bisected this
> to commit 9de52a755cfb6da5 ("arm64: fpsimd: Fix failure to restore FPSIMD
> state after signals").
>
> Reverting that commit on top of v4.15-rc3 fixed the issue for me.

Good work on the bisect -- I'll need to have a think about this...

That patch fixes a genuine problem so we can't just revert it.


What if you revert _just this function_ back to what it was in v4.14?

Cheers
---Dave
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