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")));