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Diffstat (limited to 'arch/x86/vdso/vclock_gettime.c')
-rw-r--r--arch/x86/vdso/vclock_gettime.c351
1 files changed, 351 insertions, 0 deletions
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
new file mode 100644
index 000000000..979332275
--- /dev/null
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -0,0 +1,351 @@
+/*
+ * Copyright 2006 Andi Kleen, SUSE Labs.
+ * Subject to the GNU Public License, v.2
+ *
+ * Fast user context implementation of clock_gettime, gettimeofday, and time.
+ *
+ * 32 Bit compat layer by Stefani Seibold <stefani@seibold.net>
+ * sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
+ *
+ * The code should have no internal unresolved relocations.
+ * Check with readelf after changing.
+ */
+
+#include <uapi/linux/time.h>
+#include <asm/vgtod.h>
+#include <asm/hpet.h>
+#include <asm/vvar.h>
+#include <asm/unistd.h>
+#include <asm/msr.h>
+#include <linux/math64.h>
+#include <linux/time.h>
+
+#define gtod (&VVAR(vsyscall_gtod_data))
+
+extern int __vdso_clock_gettime(clockid_t clock, struct timespec *ts);
+extern int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz);
+extern time_t __vdso_time(time_t *t);
+
+#ifdef CONFIG_HPET_TIMER
+extern u8 hpet_page
+ __attribute__((visibility("hidden")));
+
+static notrace cycle_t vread_hpet(void)
+{
+ return *(const volatile u32 *)(&hpet_page + HPET_COUNTER);
+}
+#endif
+
+#ifndef BUILD_VDSO32
+
+#include <linux/kernel.h>
+#include <asm/vsyscall.h>
+#include <asm/fixmap.h>
+#include <asm/pvclock.h>
+
+notrace 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;
+}
+
+notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
+{
+ long ret;
+
+ asm("syscall" : "=a" (ret) :
+ "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
+ return ret;
+}
+
+#ifdef CONFIG_PARAVIRT_CLOCK
+
+static notrace const struct pvclock_vsyscall_time_info *get_pvti(int cpu)
+{
+ const struct pvclock_vsyscall_time_info *pvti_base;
+ int idx = cpu / (PAGE_SIZE/PVTI_SIZE);
+ int offset = cpu % (PAGE_SIZE/PVTI_SIZE);
+
+ BUG_ON(PVCLOCK_FIXMAP_BEGIN + idx > PVCLOCK_FIXMAP_END);
+
+ pvti_base = (struct pvclock_vsyscall_time_info *)
+ __fix_to_virt(PVCLOCK_FIXMAP_BEGIN+idx);
+
+ return &pvti_base[offset];
+}
+
+static notrace cycle_t vread_pvclock(int *mode)
+{
+ const struct pvclock_vsyscall_time_info *pvti;
+ cycle_t ret;
+ u64 last;
+ u32 version;
+ u8 flags;
+ unsigned cpu, cpu1;
+
+
+ /*
+ * Note: hypervisor must guarantee that:
+ * 1. cpu ID number maps 1:1 to per-CPU pvclock time info.
+ * 2. that per-CPU pvclock time info is updated if the
+ * underlying CPU changes.
+ * 3. that version is increased whenever underlying CPU
+ * changes.
+ *
+ */
+ do {
+ cpu = __getcpu() & VGETCPU_CPU_MASK;
+ /* TODO: We can put vcpu id into higher bits of pvti.version.
+ * This will save a couple of cycles by getting rid of
+ * __getcpu() calls (Gleb).
+ */
+
+ pvti = get_pvti(cpu);
+
+ version = __pvclock_read_cycles(&pvti->pvti, &ret, &flags);
+
+ /*
+ * Test we're still on the cpu as well as the version.
+ * We could have been migrated just after the first
+ * vgetcpu but before fetching the version, so we
+ * wouldn't notice a version change.
+ */
+ cpu1 = __getcpu() & VGETCPU_CPU_MASK;
+ } while (unlikely(cpu != cpu1 ||
+ (pvti->pvti.version & 1) ||
+ pvti->pvti.version != version));
+
+ if (unlikely(!(flags & PVCLOCK_TSC_STABLE_BIT)))
+ *mode = VCLOCK_NONE;
+
+ /* refer to tsc.c read_tsc() comment for rationale */
+ last = gtod->cycle_last;
+
+ if (likely(ret >= last))
+ return ret;
+
+ return last;
+}
+#endif
+
+#else
+
+notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
+{
+ long ret;
+
+ asm(
+ "mov %%ebx, %%edx \n"
+ "mov %2, %%ebx \n"
+ "call __kernel_vsyscall \n"
+ "mov %%edx, %%ebx \n"
+ : "=a" (ret)
+ : "0" (__NR_clock_gettime), "g" (clock), "c" (ts)
+ : "memory", "edx");
+ return ret;
+}
+
+notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
+{
+ long ret;
+
+ asm(
+ "mov %%ebx, %%edx \n"
+ "mov %2, %%ebx \n"
+ "call __kernel_vsyscall \n"
+ "mov %%edx, %%ebx \n"
+ : "=a" (ret)
+ : "0" (__NR_gettimeofday), "g" (tv), "c" (tz)
+ : "memory", "edx");
+ return ret;
+}
+
+#ifdef CONFIG_PARAVIRT_CLOCK
+
+static notrace cycle_t vread_pvclock(int *mode)
+{
+ *mode = VCLOCK_NONE;
+ return 0;
+}
+#endif
+
+#endif
+
+notrace static cycle_t vread_tsc(void)
+{
+ cycle_t ret;
+ u64 last;
+
+ /*
+ * Empirically, a fence (of type that depends on the CPU)
+ * before rdtsc is enough to ensure that rdtsc is ordered
+ * with respect to loads. The various CPU manuals are unclear
+ * as to whether rdtsc can be reordered with later loads,
+ * but no one has ever seen it happen.
+ */
+ rdtsc_barrier();
+ ret = (cycle_t)__native_read_tsc();
+
+ last = gtod->cycle_last;
+
+ if (likely(ret >= last))
+ return ret;
+
+ /*
+ * GCC likes to generate cmov here, but this branch is extremely
+ * predictable (it's just a funciton of time and the likely is
+ * very likely) and there's a data dependence, so force GCC
+ * to generate a branch instead. I don't barrier() because
+ * we don't actually need a barrier, and if this function
+ * ever gets inlined it will generate worse code.
+ */
+ asm volatile ("");
+ return last;
+}
+
+notrace static inline u64 vgetsns(int *mode)
+{
+ u64 v;
+ cycles_t cycles;
+
+ if (gtod->vclock_mode == VCLOCK_TSC)
+ cycles = vread_tsc();
+#ifdef CONFIG_HPET_TIMER
+ else if (gtod->vclock_mode == VCLOCK_HPET)
+ cycles = vread_hpet();
+#endif
+#ifdef CONFIG_PARAVIRT_CLOCK
+ else if (gtod->vclock_mode == VCLOCK_PVCLOCK)
+ cycles = vread_pvclock(mode);
+#endif
+ else
+ return 0;
+ v = (cycles - gtod->cycle_last) & gtod->mask;
+ return v * gtod->mult;
+}
+
+/* Code size doesn't matter (vdso is 4k anyway) and this is faster. */
+notrace static int __always_inline do_realtime(struct timespec *ts)
+{
+ unsigned long seq;
+ u64 ns;
+ int mode;
+
+ do {
+ seq = gtod_read_begin(gtod);
+ mode = gtod->vclock_mode;
+ ts->tv_sec = gtod->wall_time_sec;
+ ns = gtod->wall_time_snsec;
+ ns += vgetsns(&mode);
+ ns >>= gtod->shift;
+ } while (unlikely(gtod_read_retry(gtod, seq)));
+
+ ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
+ ts->tv_nsec = ns;
+
+ return mode;
+}
+
+notrace static int __always_inline do_monotonic(struct timespec *ts)
+{
+ unsigned long seq;
+ u64 ns;
+ int mode;
+
+ do {
+ seq = gtod_read_begin(gtod);
+ mode = gtod->vclock_mode;
+ ts->tv_sec = gtod->monotonic_time_sec;
+ ns = gtod->monotonic_time_snsec;
+ ns += vgetsns(&mode);
+ ns >>= gtod->shift;
+ } while (unlikely(gtod_read_retry(gtod, seq)));
+
+ ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
+ ts->tv_nsec = ns;
+
+ return mode;
+}
+
+notrace static void do_realtime_coarse(struct timespec *ts)
+{
+ unsigned long seq;
+ do {
+ seq = gtod_read_begin(gtod);
+ ts->tv_sec = gtod->wall_time_coarse_sec;
+ ts->tv_nsec = gtod->wall_time_coarse_nsec;
+ } while (unlikely(gtod_read_retry(gtod, seq)));
+}
+
+notrace static void do_monotonic_coarse(struct timespec *ts)
+{
+ unsigned long seq;
+ do {
+ seq = gtod_read_begin(gtod);
+ ts->tv_sec = gtod->monotonic_time_coarse_sec;
+ ts->tv_nsec = gtod->monotonic_time_coarse_nsec;
+ } while (unlikely(gtod_read_retry(gtod, seq)));
+}
+
+notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
+{
+ switch (clock) {
+ case CLOCK_REALTIME:
+ if (do_realtime(ts) == VCLOCK_NONE)
+ goto fallback;
+ break;
+ case CLOCK_MONOTONIC:
+ if (do_monotonic(ts) == VCLOCK_NONE)
+ goto fallback;
+ break;
+ case CLOCK_REALTIME_COARSE:
+ do_realtime_coarse(ts);
+ break;
+ case CLOCK_MONOTONIC_COARSE:
+ do_monotonic_coarse(ts);
+ break;
+ default:
+ goto fallback;
+ }
+
+ return 0;
+fallback:
+ return vdso_fallback_gettime(clock, ts);
+}
+int clock_gettime(clockid_t, struct timespec *)
+ __attribute__((weak, alias("__vdso_clock_gettime")));
+
+notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+ if (likely(tv != NULL)) {
+ if (unlikely(do_realtime((struct timespec *)tv) == VCLOCK_NONE))
+ return vdso_fallback_gtod(tv, tz);
+ tv->tv_usec /= 1000;
+ }
+ if (unlikely(tz != NULL)) {
+ tz->tz_minuteswest = gtod->tz_minuteswest;
+ tz->tz_dsttime = gtod->tz_dsttime;
+ }
+
+ return 0;
+}
+int gettimeofday(struct timeval *, struct timezone *)
+ __attribute__((weak, alias("__vdso_gettimeofday")));
+
+/*
+ * This will break when the xtime seconds get inaccurate, but that is
+ * unlikely
+ */
+notrace time_t __vdso_time(time_t *t)
+{
+ /* This is atomic on x86 so we don't need any locks. */
+ time_t result = ACCESS_ONCE(gtod->wall_time_sec);
+
+ if (t)
+ *t = result;
+ return result;
+}
+int time(time_t *t)
+ __attribute__((weak, alias("__vdso_time")));