From e5fd91f1ef340da553f7a79da9540c3db711c937 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Tue, 8 Sep 2015 01:01:14 -0300 Subject: Linux-libre 4.2-gnu --- arch/x86/entry/vdso/vclock_gettime.c | 351 +++++++++++++++++++++++++++++++++++ 1 file changed, 351 insertions(+) create mode 100644 arch/x86/entry/vdso/vclock_gettime.c (limited to 'arch/x86/entry/vdso/vclock_gettime.c') diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c new file mode 100644 index 000000000..979332275 --- /dev/null +++ b/arch/x86/entry/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 + * sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany + * + * The code should have no internal unresolved relocations. + * Check with readelf after changing. + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +#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 +#include +#include +#include + +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"))); -- cgit v1.2.3-54-g00ecf