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Diffstat (limited to 'arch/x86/vdso/vclock_gettime.c')
-rw-r--r--arch/x86/vdso/vclock_gettime.c121
1 files changed, 121 insertions, 0 deletions
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
new file mode 100644
index 000000000000..5b54cdfb2b07
--- /dev/null
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -0,0 +1,121 @@
+/*
+ * Copyright 2006 Andi Kleen, SUSE Labs.
+ * Subject to the GNU Public License, v.2
+ *
+ * Fast user context implementation of clock_gettime and gettimeofday.
+ *
+ * The code should have no internal unresolved relocations.
+ * Check with readelf after changing.
+ * Also alternative() doesn't work.
+ */
+
+#include <linux/kernel.h>
+#include <linux/posix-timers.h>
+#include <linux/time.h>
+#include <linux/string.h>
+#include <asm/vsyscall.h>
+#include <asm/vgtod.h>
+#include <asm/timex.h>
+#include <asm/hpet.h>
+#include <asm/unistd.h>
+#include <asm/io.h>
+#include <asm/vgtod.h>
+#include "vextern.h"
+
+#define gtod vdso_vsyscall_gtod_data
+
+static long vdso_fallback_gettime(long clock, struct timespec *ts)
+{
+ long ret;
+ asm("syscall" : "=a" (ret) :
+ "0" (__NR_clock_gettime),"D" (clock), "S" (ts) : "memory");
+ return ret;
+}
+
+static inline long vgetns(void)
+{
+ long v;
+ cycles_t (*vread)(void);
+ vread = gtod->clock.vread;
+ v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
+ return (v * gtod->clock.mult) >> gtod->clock.shift;
+}
+
+static noinline int do_realtime(struct timespec *ts)
+{
+ unsigned long seq, ns;
+ do {
+ seq = read_seqbegin(&gtod->lock);
+ ts->tv_sec = gtod->wall_time_sec;
+ ts->tv_nsec = gtod->wall_time_nsec;
+ ns = vgetns();
+ } while (unlikely(read_seqretry(&gtod->lock, seq)));
+ timespec_add_ns(ts, ns);
+ return 0;
+}
+
+/* Copy of the version in kernel/time.c which we cannot directly access */
+static void vset_normalized_timespec(struct timespec *ts, long sec, long nsec)
+{
+ while (nsec >= NSEC_PER_SEC) {
+ nsec -= NSEC_PER_SEC;
+ ++sec;
+ }
+ while (nsec < 0) {
+ nsec += NSEC_PER_SEC;
+ --sec;
+ }
+ ts->tv_sec = sec;
+ ts->tv_nsec = nsec;
+}
+
+static noinline int do_monotonic(struct timespec *ts)
+{
+ unsigned long seq, ns, secs;
+ do {
+ seq = read_seqbegin(&gtod->lock);
+ secs = gtod->wall_time_sec;
+ ns = gtod->wall_time_nsec + vgetns();
+ secs += gtod->wall_to_monotonic.tv_sec;
+ ns += gtod->wall_to_monotonic.tv_nsec;
+ } while (unlikely(read_seqretry(&gtod->lock, seq)));
+ vset_normalized_timespec(ts, secs, ns);
+ return 0;
+}
+
+int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
+{
+ if (likely(gtod->sysctl_enabled && gtod->clock.vread))
+ switch (clock) {
+ case CLOCK_REALTIME:
+ return do_realtime(ts);
+ case CLOCK_MONOTONIC:
+ return do_monotonic(ts);
+ }
+ return vdso_fallback_gettime(clock, ts);
+}
+int clock_gettime(clockid_t, struct timespec *)
+ __attribute__((weak, alias("__vdso_clock_gettime")));
+
+int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+ long ret;
+ if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
+ BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
+ offsetof(struct timespec, tv_nsec) ||
+ sizeof(*tv) != sizeof(struct timespec));
+ do_realtime((struct timespec *)tv);
+ tv->tv_usec /= 1000;
+ if (unlikely(tz != NULL)) {
+ /* This relies on gcc inlining the memcpy. We'll notice
+ if it ever fails to do so. */
+ memcpy(tz, &gtod->sys_tz, sizeof(struct timezone));
+ }
+ return 0;
+ }
+ asm("syscall" : "=a" (ret) :
+ "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
+ return ret;
+}
+int gettimeofday(struct timeval *, struct timezone *)
+ __attribute__((weak, alias("__vdso_gettimeofday")));