linux-kernel - Re: [PATCH v7 16/25] arm: Add support for generic vDSO (causing crash)

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Date:   Thu, 5 Dec 2019 10:42:40 +0100
From:   Philippe Mathieu-Daudé <f4bug@...at.org>
To:     Vincenzo Frascino <vincenzo.frascino@....com>
Cc:     Guenter Roeck <linux@...ck-us.net>, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        open list <linux-kernel@...r.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        linux-kselftest@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mark Salyzyn <salyzyn@...roid.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Shuah Khan <shuah@...nel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Huw Davies <huw@...eweavers.com>,
        Shijith Thotton <sthotton@...vell.com>,
        Andre Przywara <andre.przywara@....com>
Subject: Re: [PATCH v7 16/25] arm: Add support for generic vDSO (causing crash)

On Wed, Dec 4, 2019 at 6:23 PM Vincenzo Frascino
<vincenzo.frascino@....com> wrote:
> On 12/4/19 4:16 PM, Guenter Roeck wrote:
[...]
> --->8---
>
> Author: Vincenzo Frascino <vincenzo.frascino@....com>
> Date:   Wed Dec 4 16:58:55 2019 +0000
>
>     arm: Fix __arch_get_hw_counter() access to CNTVCT
>
>     __arch_get_hw_counter() should check clock_mode to see if it can access
>     CNTVCT. With the conversion to unified vDSO this check has been left out.
>
>     This causes on imx v6 and v7 (imx_v6_v7_defconfig) and other platforms to
>     hang at boot during the execution of the init process as per below:
>
>     [   19.976852] Run /sbin/init as init process
>     [   20.044931] Kernel panic - not syncing: Attempted to kill init!
>     exitcode=0x00000004
>
>     Fix the problem verifying that clock_mode is set coherently before
>     accessing CNTVCT.
>
>     Cc: Russell King <linux@...linux.org.uk>
>     Reported-by: Guenter Roeck <linux@...ck-us.net>
>     Investigated-by: Arnd Bergmann <arnd@...db.de>

There are only 2 "Investigated-by" vs 7k+ "Suggested-by"... Is there a
real difference?

>     Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
>
> diff --git a/arch/arm/include/asm/vdso/gettimeofday.h
> b/arch/arm/include/asm/vdso/gettimeofday.h
> index 5b879ae7afc1..0ad2429c324f 100644
> --- a/arch/arm/include/asm/vdso/gettimeofday.h
> +++ b/arch/arm/include/asm/vdso/gettimeofday.h
> @@ -75,6 +75,9 @@ static __always_inline u64 __arch_get_hw_counter(int clock_mode)
>  #ifdef CONFIG_ARM_ARCH_TIMER
>         u64 cycle_now;
>
> +       if (!clock_mode)
> +               return -EINVAL;
> +

Reviewed-by: Philippe Mathieu-Daudé <f4bug@...at.org>

>         isb();
>         cycle_now = read_sysreg(CNTVCT);
>
>