Commit-ID: 27e11a9fe2e2e7e0d13f854e89a71e488678fb17 Gitweb: https://git.kernel.org/tip/27e11a9fe2e2e7e0d13f854e89a71e488678fb17 Author: Vincenzo Frascino <[email protected]> AuthorDate: Tue, 25 Jun 2019 17:18:03 +0100 Committer: Thomas Gleixner <[email protected]> CommitDate: Wed, 26 Jun 2019 14:26:54 +0200
arm64: Fix __arch_get_hw_counter() implementation 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. Signed-off-by: Vincenzo Frascino <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: Catalin Marinas <[email protected]> Cc: Will Deacon <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- arch/arm64/include/asm/vdso/gettimeofday.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h index 447ef417de45..b08f476b72b4 100644 --- a/arch/arm64/include/asm/vdso/gettimeofday.h +++ b/arch/arm64/include/asm/vdso/gettimeofday.h @@ -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; }
