From f144a6b4d1688675d88990e29567b2335b48205e Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 23 May 2011 09:31:30 -0400 Subject: x86-64: Add time to vDSO The only fast implementation of time(2) we expose is through the vsyscall page and we want to get userspace to stop using the vsyscall page. So make it available through the vDSO as well. This is essentially a cut-n-paste job. Signed-off-by: Andy Lutomirski Cc: Andi Kleen Cc: Linus Torvalds Cc: "David S. Miller" Cc: Eric Dumazet Cc: Peter Zijlstra Cc: Borislav Petkov Link: http://lkml.kernel.org/r/%3Cbf963bac5207de4b29613f27c42705e4371812a8.1306156808.git.luto%40mit.edu%3E Signed-off-by: Thomas Gleixner --- arch/x86/vdso/vclock_gettime.c | 35 ++++++++++++++++++++++++++++++++++- arch/x86/vdso/vdso.lds.S | 2 ++ 2 files changed, 36 insertions(+), 1 deletion(-) (limited to 'arch/x86') diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c index 28b2c00bd1b..e6e9f90a8cd 100644 --- a/arch/x86/vdso/vclock_gettime.c +++ b/arch/x86/vdso/vclock_gettime.c @@ -2,7 +2,7 @@ * Copyright 2006 Andi Kleen, SUSE Labs. * Subject to the GNU Public License, v.2 * - * Fast user context implementation of clock_gettime and gettimeofday. + * Fast user context implementation of clock_gettime, gettimeofday, and time. * * The code should have no internal unresolved relocations. * Check with readelf after changing. @@ -160,3 +160,36 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz) } int gettimeofday(struct timeval *, struct timezone *) __attribute__((weak, alias("__vdso_gettimeofday"))); + +/* This will break when the xtime seconds get inaccurate, but that is + * unlikely */ + +static __always_inline long time_syscall(long *t) +{ + long secs; + asm volatile("syscall" + : "=a" (secs) + : "0" (__NR_time), "D" (t) : "cc", "r11", "cx", "memory"); + return secs; +} + +notrace time_t __vdso_time(time_t *t) +{ + unsigned seq; + time_t result; + if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled)) + return time_syscall(t); + + do { + seq = read_seqbegin(&VVAR(vsyscall_gtod_data).lock); + + result = VVAR(vsyscall_gtod_data).wall_time_sec; + + } while (read_seqretry(&VVAR(vsyscall_gtod_data).lock, seq)); + + if (t) + *t = result; + return result; +} +int time(time_t *t) + __attribute__((weak, alias("__vdso_time"))); diff --git a/arch/x86/vdso/vdso.lds.S b/arch/x86/vdso/vdso.lds.S index 81f250011f7..b96b2677cad 100644 --- a/arch/x86/vdso/vdso.lds.S +++ b/arch/x86/vdso/vdso.lds.S @@ -23,6 +23,8 @@ VERSION { __vdso_gettimeofday; getcpu; __vdso_getcpu; + time; + __vdso_time; local: *; }; } -- cgit v1.2.3