Commit-ID: 6241c4dc6ec56a7627b972959da8b492b765b209 Gitweb: https://git.kernel.org/tip/6241c4dc6ec56a7627b972959da8b492b765b209 Author: Vincenzo Frascino <vincenzo.frasc...@arm.com> AuthorDate: Tue, 25 Jun 2019 17:18:04 +0100 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Wed, 26 Jun 2019 14:26:54 +0200
arm64: compat: 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.frasc...@arm.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: linux-a...@vger.kernel.org Cc: linux-arm-ker...@lists.infradead.org Cc: linux-m...@vger.kernel.org Cc: linux-kselft...@vger.kernel.org Cc: catalin.mari...@arm.com Cc: will.dea...@arm.com Cc: a...@arndb.de Cc: li...@armlinux.org.uk Cc: r...@linux-mips.org Cc: paul.bur...@mips.com Cc: daniel.lezc...@linaro.org Cc: saly...@android.com Cc: p...@google.com Cc: sh...@kernel.org Cc: 0x7f454...@gmail.com Cc: li...@rasmusvillemoes.dk Cc: h...@codeweavers.com Cc: sthot...@marvell.com Cc: andre.przyw...@arm.com Cc: Catalin Marinas <catalin.mari...@arm.com> Cc: Will Deacon <will.dea...@arm.com> Link: https://lkml.kernel.org/r/20190625161804.38713-3-vincenzo.frasc...@arm.com --- arch/arm64/include/asm/vdso/compat_gettimeofday.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h b/arch/arm64/include/asm/vdso/compat_gettimeofday.h index 93dbd935b66d..f4812777f5c5 100644 --- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h +++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h @@ -12,6 +12,8 @@ #include <asm/vdso/compat_barrier.h> +#define __VDSO_USE_SYSCALL ULLONG_MAX + #define VDSO_HAS_CLOCK_GETRES 1 static __always_inline @@ -74,8 +76,24 @@ 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("mrrc p15, 1, %Q0, %R0, c14" : "=r" (res)); + /* + * This isb() is required to prevent that the seq lock is + * speculated. + */ + isb(); return res; }
