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

Guenter Roeck
2019-12-04T19:39:39Z

On Wed, Dec 04, 2019 at 05:15:26PM +0000, Vincenzo Frascino wrote:
> Hi Guenter,
>
> On 12/4/19 4:16 PM, Guenter Roeck wrote:
> > On Wed, Dec 04, 2019 at 01:58:25PM +0000, Vincenzo Frascino wrote:
> >> Hi Guenter,
> >>
> >> On 12/4/19 1:51 PM, Guenter Roeck wrote:
> >>> On Fri, Jun 21, 2019 at 10:52:43AM +0100, Vincenzo Frascino wrote:
> >>>> The arm vDSO library requires some adaptations to use to take advantage
> >>>> of the newly introduced generic vDSO library.
> >>>>
> >>>> Introduce the following changes:
> >>>> - Modification vdso.c to be compliant with the common vdso datapage
> >>>> - Use of lib/vdso for gettimeofday
> >>>> - Implementation of elf note
> >>>>
> >>>> Cc: Russell King <linux@armlinux.org.uk>
> >>>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> >>>
> >>> This patch causes a crash with qemu's mcimx6ul-evk emulation while running
> >>> imx_v6_v7_defconfig.
> >>>
> >>
> >> Thank you for reporting this. Could you please provide some details on how I can
> >> reproduce the scenario you are describing?
> >>
> > - Build imx_v6_v7_defconfig
> > - Get root file system or initrd, for example from
> > https://github.com/groeck/linux-build-test/tree/master/rootfs/arm
> > - Run image. Example, with initrd:
> > qemu-system-arm -M mcimx6ul-evk -kernel arch/arm/boot/zImage \
> > -no-reboot -initrd rootfs-armv7a.cpio \
> > -m 256 -display none -serial null \
> > --append 'rdinit=/sbin/init earlycon=ec_imx6q,mmio,0x21e8000,115200n8 console=ttymxc1,115200'
> > -dtb arch/arm/boot/dts/imx6ul-14x14-evk.dtb \
> > -nographic -monitor null -serial stdio
> >
> > qemu has to be v3.1 or later to support the machine.
> >
>
> Thanks for this. Could you please try the patch below the scissors? Seems fixing
> the issue for me.
>
> > Hope this helps,
> > Guenter
> >
>
> --
> Regards,
> Vincenzo
>
> --->8---
>
> Author: Vincenzo Frascino <vincenzo.frascino@arm.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@armlinux.org.uk>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Investigated-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>
WFM.

Tested-by: Guenter Roeck <linux@roeck-us.net>

Guenter

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