linux-kernel - Re: [PATCH v2 2/4] arm64: arch_timer: Allow an workaround descriptor to disable compat vdso

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Message-ID: <20200706165534.GA61340@C02TD0UTHF1T.local>
Date:   Mon, 6 Jul 2020 17:55:44 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/4] arm64: arch_timer: Allow an workaround descriptor
 to disable compat vdso

On Mon, Jul 06, 2020 at 05:38:00PM +0100, Marc Zyngier wrote:
> As we are about to disable the vdso for compat tasks in some circumstances,
> let's allow a workaround descriptor to express exactly that.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Marc Zyngier <maz@...nel.org>

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/include/asm/arch_timer.h  | 1 +
>  drivers/clocksource/arm_arch_timer.c | 3 +++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
> index 7ae54d7d333a..9f0ec21d6327 100644
> --- a/arch/arm64/include/asm/arch_timer.h
> +++ b/arch/arm64/include/asm/arch_timer.h
> @@ -58,6 +58,7 @@ struct arch_timer_erratum_workaround {
>  	u64 (*read_cntvct_el0)(void);
>  	int (*set_next_event_phys)(unsigned long, struct clock_event_device *);
>  	int (*set_next_event_virt)(unsigned long, struct clock_event_device *);
> +	bool disable_compat_vdso;
>  };
>  
>  DECLARE_PER_CPU(const struct arch_timer_erratum_workaround *,
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index ecf7b7db2d05..a8e4fb429f52 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -566,6 +566,9 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa
>  	if (wa->read_cntvct_el0) {
>  		clocksource_counter.vdso_clock_mode = VDSO_CLOCKMODE_NONE;
>  		vdso_default = VDSO_CLOCKMODE_NONE;
> +	} else if (wa->disable_compat_vdso && vdso_default != VDSO_CLOCKMODE_NONE) {
> +		vdso_default = VDSO_CLOCKMODE_ARCHTIMER_NOCOMPAT;
> +		clocksource_counter.vdso_clock_mode = vdso_default;
>  	}
>  }
>  
> -- 
> 2.27.0
>