linux-kernel - [Stable-5.4][PATCH 2/3] arm64: arch_timer: Allow an workaround descriptor to disable compat vdso

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Message-Id: <20200715125614.3240269-3-maz@kernel.org>
Date:   Wed, 15 Jul 2020 13:56:13 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     gregkh@...uxfoundation.org, stable@...r.kernel.org
Cc:     arnd@...db.de, sashal@...nel.org, naresh.kamboju@...aro.org,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Russell King <linux@....linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com
Subject: [Stable-5.4][PATCH 2/3] arm64: arch_timer: Allow an workaround descriptor to disable compat vdso

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>
---
 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 909fe093249e..fd2a75f0af77 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -562,6 +562,9 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa
 	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;
 	}
 }
 
-- 
2.27.0