From 0d7b8547fb67d5c2a7d954c56b3715b0e708be4a Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Sun, 5 Jun 2011 13:50:20 -0400 Subject: x86-64: Remove kernel.vsyscall64 sysctl It's unnecessary overhead in code that's supposed to be highly optimized. Removing it allows us to remove one of the two syscall instructions in the vsyscall page. The only sensible use for it is for UML users, and it doesn't fully address inconsistent vsyscall results on UML. The real fix for UML is to stop using vsyscalls entirely. Signed-off-by: Andy Lutomirski Cc: Jesper Juhl Cc: Borislav Petkov Cc: Linus Torvalds Cc: Arjan van de Ven Cc: Jan Beulich Cc: richard -rw- weinberger Cc: Mikael Pettersson Cc: Andi Kleen Cc: Brian Gerst Cc: Louis Rilling Cc: Valdis.Kletnieks@vt.edu Cc: pageexec@freemail.hu Link: http://lkml.kernel.org/r/973ae803fe76f712da4b2740e66dccf452d3b1e4.1307292171.git.luto@mit.edu Signed-off-by: Ingo Molnar --- arch/x86/vdso/vclock_gettime.c | 55 ++++++++++++++++-------------------------- 1 file changed, 21 insertions(+), 34 deletions(-) (limited to 'arch/x86/vdso') diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c index a724905..cf54813 100644 --- a/arch/x86/vdso/vclock_gettime.c +++ b/arch/x86/vdso/vclock_gettime.c @@ -116,21 +116,21 @@ notrace static noinline int do_monotonic_coarse(struct timespec *ts) notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts) { - if (likely(gtod->sysctl_enabled)) - switch (clock) { - case CLOCK_REALTIME: - if (likely(gtod->clock.vread)) - return do_realtime(ts); - break; - case CLOCK_MONOTONIC: - if (likely(gtod->clock.vread)) - return do_monotonic(ts); - break; - case CLOCK_REALTIME_COARSE: - return do_realtime_coarse(ts); - case CLOCK_MONOTONIC_COARSE: - return do_monotonic_coarse(ts); - } + switch (clock) { + case CLOCK_REALTIME: + if (likely(gtod->clock.vread)) + return do_realtime(ts); + break; + case CLOCK_MONOTONIC: + if (likely(gtod->clock.vread)) + return do_monotonic(ts); + break; + case CLOCK_REALTIME_COARSE: + return do_realtime_coarse(ts); + case CLOCK_MONOTONIC_COARSE: + return do_monotonic_coarse(ts); + } + return vdso_fallback_gettime(clock, ts); } int clock_gettime(clockid_t, struct timespec *) @@ -139,7 +139,7 @@ int clock_gettime(clockid_t, struct timespec *) notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz) { long ret; - if (likely(gtod->sysctl_enabled && gtod->clock.vread)) { + if (likely(gtod->clock.vread)) { if (likely(tv != NULL)) { BUILD_BUG_ON(offsetof(struct timeval, tv_usec) != offsetof(struct timespec, tv_nsec) || @@ -161,27 +161,14 @@ 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; -} - +/* + * This will break when the xtime seconds get inaccurate, but that is + * unlikely + */ notrace time_t __vdso_time(time_t *t) { - time_t result; - - if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled)) - return time_syscall(t); - /* This is atomic on x86_64 so we don't need any locks. */ - result = ACCESS_ONCE(VVAR(vsyscall_gtod_data).wall_time_sec); + time_t result = ACCESS_ONCE(VVAR(vsyscall_gtod_data).wall_time_sec); if (t) *t = result; -- cgit v1.1