linux-kernel - [PATCH 5.4 028/215] arm64: arch_timer: Allow an workaround descriptor to disable compat vdso

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Date:   Mon, 20 Jul 2020 17:35:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>
Subject: [PATCH 5.4 028/215] arm64: arch_timer: Allow an workaround descriptor to disable compat vdso

From: Marc Zyngier <maz@...nel.org>

commit c1fbec4ac0d701f350a581941d35643d5a9cd184 upstream.

As we are about to disable the vdso for compat tasks in some circumstances,
let's allow a workaround descriptor to express exactly that.

Signed-off-by: Marc Zyngier <maz@...nel.org>
Acked-by: Mark Rutland <mark.rutland@....com>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20200706163802.1836732-3-maz@kernel.org
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/include/asm/arch_timer.h  |    1 +
 drivers/clocksource/arm_arch_timer.c |    3 +++
 2 files changed, 4 insertions(+)

--- 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 *,
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -562,6 +562,9 @@ void arch_timer_enable_workaround(const
 	if (wa->read_cntvct_el0) {
 		clocksource_counter.archdata.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.archdata.clock_mode = vdso_default;
 	}
 }