* [PATCH] lib: vdso: add support for time
@ 2017-11-10 18:24 Mark Salyzyn
0 siblings, 0 replies; only message in thread
From: Mark Salyzyn @ 2017-11-10 18:24 UTC (permalink / raw)
To: linux-arm-kernel
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 <salyzyn@android.com>
Cc: James Morse <james.morse@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Andrew Pinski <apinski@cavium.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
NB: to be applied _after_
[PATCH v5 10/12] arm64: vdso: replace gettimeofday.S with global vgettimeofday.C
---
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 da52aade40a3..b8ae87b4d526 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -190,6 +190,7 @@ 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 079955162be8..d8d675d46749 100644
--- a/lib/vdso/vgettimeofday.c
+++ b/lib/vdso/vgettimeofday.c
@@ -385,3 +385,13 @@ 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;
+}
--
2.15.0.448.gf294e3d99a-goog
^ permalink raw reply related [flat|nested] only message in thread
only message in thread, other threads:[~2017-11-10 18:24 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-11-10 18:24 [PATCH] lib: vdso: add support for time Mark Salyzyn
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).