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McKenney" , Ingo Molnar Subject: RESEND [PATCH] lib: vdso: add support for time Date: Mon, 18 Jun 2018 08:05:59 -0700 Message-Id: <20180618150613.10322-14-salyzyn@android.com> X-Mailer: git-send-email 2.18.0.rc1.244.gcf134e6275-goog In-Reply-To: <20180618150613.10322-1-salyzyn@android.com> References: <20180618150613.10322-1-salyzyn@android.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mark Salyzyn Add time() vdso support to match up with existing support in the x86's vdso. Currently benefitting arm and arm64 which uses the common vgettimeofday.c implementation. On arm provides about a ~14 fold improvement in speed over the straight syscall, and about a ~5 fold improvement in speed over an alternate library implementation that relies on the vdso call to gettimeofday to fulfill the request. We can provide __vdso_time even if we can not provide a speed enhanced __vdso_gettimeofday. (arm, virtual counters). Signed-off-by: Mark Salyzyn Cc: James Morse Cc: Russell King Cc: Catalin Marinas Cc: Will Deacon Cc: Andy Lutomirski Cc: Dmitry Safonov Cc: John Stultz Cc: Mark Rutland Cc: Laura Abbott Cc: Kees Cook Cc: Ard Biesheuvel Cc: Andy Gross Cc: Kevin Brodsky Cc: Andrew Pinski Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: Jeremy Linton --- arch/arm/kernel/vdso.c | 1 + arch/arm/vdso/vdso.lds.S | 1 + arch/arm64/kernel/vdso/compiler.h | 1 + arch/arm64/kernel/vdso/vdso.lds.S | 1 + lib/vdso/vgettimeofday.c | 10 ++++++++++ 5 files changed, 14 insertions(+) diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c index 51d8dcbd9952..6721854c5ae6 100644 --- a/arch/arm/kernel/vdso.c +++ b/arch/arm/kernel/vdso.c @@ -192,6 +192,7 @@ static void __init patch_vdso(void *ehdr) vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); vdso_nullpatch_one(&einfo, "__vdso_clock_getres"); + /* do not zero out __vdso_time, no cntvct_ok dependency */ } } diff --git a/arch/arm/vdso/vdso.lds.S b/arch/arm/vdso/vdso.lds.S index 1d81e8c3acf6..1eb577091d1f 100644 --- a/arch/arm/vdso/vdso.lds.S +++ b/arch/arm/vdso/vdso.lds.S @@ -83,6 +83,7 @@ VERSION __vdso_clock_gettime; __vdso_gettimeofday; __vdso_clock_getres; + __vdso_time; local: *; }; } diff --git a/arch/arm64/kernel/vdso/compiler.h b/arch/arm64/kernel/vdso/compiler.h index 921a7191b497..fb27545640f2 100644 --- a/arch/arm64/kernel/vdso/compiler.h +++ b/arch/arm64/kernel/vdso/compiler.h @@ -65,5 +65,6 @@ static __always_inline notrace u64 arch_vdso_read_counter(void) #define __vdso_clock_gettime __kernel_clock_gettime #define __vdso_gettimeofday __kernel_gettimeofday #define __vdso_clock_getres __kernel_clock_getres +#define __vdso_time __kernel_time #endif /* __VDSO_COMPILER_H */ diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S index beca249bc2f3..9de0ffc369c5 100644 --- a/arch/arm64/kernel/vdso/vdso.lds.S +++ b/arch/arm64/kernel/vdso/vdso.lds.S @@ -88,6 +88,7 @@ VERSION __kernel_gettimeofday; __kernel_clock_gettime; __kernel_clock_getres; + __kernel_time; local: *; }; } diff --git a/lib/vdso/vgettimeofday.c b/lib/vdso/vgettimeofday.c index 54e519c99c4b..dfced9608cd3 100644 --- a/lib/vdso/vgettimeofday.c +++ b/lib/vdso/vgettimeofday.c @@ -386,3 +386,13 @@ int __vdso_clock_getres(clockid_t clock, struct timespec *res) return 0; } + +notrace time_t __vdso_time(time_t *t) +{ + const struct vdso_data *vd = __get_datapage(); + time_t result = READ_ONCE(vd->xtime_coarse_sec); + + if (t) + *t = result; + return result; +} -- 2.18.0.rc1.244.gcf134e6275-goog