arm64: unhandled level 0 translation fault

[Geert Uytterhoeven]

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.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds