Messages in this thread Patch in this message | | | Date | Wed, 26 Jun 2019 05:38:14 -0700 | From | tip-bot for Vincenzo Frascino <> | Subject | [tip:timers/vdso] arm64: Fix __arch_get_hw_counter() implementation |
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Commit-ID: 27e11a9fe2e2e7e0d13f854e89a71e488678fb17 Gitweb: https://git.kernel.org/tip/27e11a9fe2e2e7e0d13f854e89a71e488678fb17 Author: Vincenzo Frascino <vincenzo.frascino@arm.com> AuthorDate: Tue, 25 Jun 2019 17:18:03 +0100 Committer: Thomas Gleixner <tglx@linutronix.de> 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 <vincenzo.frascino@arm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arch@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-mips@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Cc: catalin.marinas@arm.com Cc: will.deacon@arm.com Cc: arnd@arndb.de Cc: linux@armlinux.org.uk Cc: ralf@linux-mips.org Cc: paul.burton@mips.com Cc: daniel.lezcano@linaro.org Cc: salyzyn@android.com Cc: pcc@google.com Cc: shuah@kernel.org Cc: 0x7f454c46@gmail.com Cc: linux@rasmusvillemoes.dk Cc: huw@codeweavers.com Cc: sthotton@marvell.com Cc: andre.przywara@arm.com Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Link: https://lkml.kernel.org/r/20190625161804.38713-2-vincenzo.frascino@arm.com
--- 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; }
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