@@ -10,6 +10,8 @@
#include <asm/unistd.h>
#include <uapi/linux/time.h>
+#define __VDSO_USE_SYSCALL ULLONG_MAX
+
#define VDSO_HAS_CLOCK_GETRES 1
static __always_inline
@@ -68,7 +70,24 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
{
u64 res;
+ /*
+ * clock_mode == 0 implies that vDSO are enabled otherwise
+ * fallback on syscall.
+ */
+ if (clock_mode)
+ return __VDSO_USE_SYSCALL;
+
+ /*
+ * This isb() is required to prevent that the counter value
+ * is speculated.
+ */
+ isb();
asm volatile("mrs %0, cntvct_el0" : "=r" (res) :: "memory");
+ /*
+ * This isb() is required to prevent that the seq lock is
+ * speculated.#
+ */
+ isb();
return res;
}
Provide the following fixes for the __arch_get_hw_counter() implementation on arm64: - Fallback on syscall when an unstable counter is detected. - Introduce isb()s before and after the counter read to avoid speculation of the counter value and of the seq lock respectively. The second isb() is a temporary solution that will be revisited in 5.3-rc1. These fixes restore the semantics that __arch_counter_get_cntvct() had on arm64. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> --- arch/arm64/include/asm/vdso/gettimeofday.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)