arm: arch_timer: add arch_counter_set_user_access
Several bits in CNTKCTL reset to 0, including PL0VTEN. For architectures
using the generic timer which wish to have a fast gettimeofday vDSO
implementation, these bits must be set to 1 by the kernel. For
architectures without a vDSO, it's best to leave the bits set to 0 for
now to ensure that if and when support is added, it's implemented sanely
architecture wide.
As the bootloader might set PL0VTEN to a value that doesn't correspond
to that which the kernel prefers, we must explicitly set it to the
architecture port's preferred value.
This patch adds arch_counter_set_user_access, which sets the PL0 access
permissions to that required by the architecture. For arch/arm, this
currently means disabling all userspace access.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index 75975d9..729f6d9 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -106,6 +106,18 @@
asm volatile("mrrc p15, 1, %Q0, %R0, c14" : "=r" (cval));
return cval;
}
+
+static inline void __cpuinit arch_counter_set_user_access(void)
+{
+ u32 cntkctl;
+
+ asm volatile("mrc p15, 0, %0, c14, c1, 0" : "=r" (cntkctl));
+
+ /* disable user access to everything */
+ cntkctl &= ~((3 << 8) | (7 << 0));
+
+ asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
+}
#else
static inline int arch_timer_of_register(void)
{