// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2006 Andi Kleen, SUSE Labs.
 *
 * Fast user context implementation of clock_gettime, gettimeofday, and time.
 *
 * The code should have no internal unresolved relocations.
 * Check with readelf after changing.
 * Also alternative() doesn't work.
 */
/*
 * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
 */

#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/string.h>
#include <asm/io.h>
#include <asm/unistd.h>
#include <asm/timex.h>
#include <asm/clocksource.h>
#include <asm/vvar.h>

#ifdef  CONFIG_SPARC64
#define SYSCALL_STRING                                                  \
        "ta     0x6d;"                                                  \
        "bcs,a  1f;"                                                    \
        " sub   %%g0, %%o0, %%o0;"                                      \
        "1:"
#else
#define SYSCALL_STRING                                                  \
        "ta     0x10;"                                                  \
        "bcs,a  1f;"                                                    \
        " sub   %%g0, %%o0, %%o0;"                                      \
        "1:"
#endif

#define SYSCALL_CLOBBERS                                                \
        "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",                 \
        "f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",           \
        "f16", "f17", "f18", "f19", "f20", "f21", "f22", "f23",         \
        "f24", "f25", "f26", "f27", "f28", "f29", "f30", "f31",         \
        "f32", "f34", "f36", "f38", "f40", "f42", "f44", "f46",         \
        "f48", "f50", "f52", "f54", "f56", "f58", "f60", "f62",         \
        "cc", "memory"

/*
 * Compute the vvar page's address in the process address space, and return it
 * as a pointer to the vvar_data.
 */
notrace static __always_inline struct vvar_data *get_vvar_data(void)
{
        unsigned long ret;

        /*
         * vdso data page is the first vDSO page so grab the PC
         * and move up a page to get to the data page.
         */
        __asm__("rd %%pc, %0" : "=r" (ret));
        ret &= ~(8192 - 1);
        ret -= 8192;

        return (struct vvar_data *) ret;
}

notrace static long vdso_fallback_gettime(long clock, struct __kernel_old_timespec *ts)
{
        register long num __asm__("g1") = __NR_clock_gettime;
        register long o0 __asm__("o0") = clock;
        register long o1 __asm__("o1") = (long) ts;

        __asm__ __volatile__(SYSCALL_STRING : "=r" (o0) : "r" (num),
                             "0" (o0), "r" (o1) : SYSCALL_CLOBBERS);
        return o0;
}

notrace static long vdso_fallback_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
{
        register long num __asm__("g1") = __NR_gettimeofday;
        register long o0 __asm__("o0") = (long) tv;
        register long o1 __asm__("o1") = (long) tz;

        __asm__ __volatile__(SYSCALL_STRING : "=r" (o0) : "r" (num),
                             "0" (o0), "r" (o1) : SYSCALL_CLOBBERS);
        return o0;
}

#ifdef  CONFIG_SPARC64
notrace static __always_inline u64 __shr64(u64 val, int amt)
{
        return val >> amt;
}

notrace static __always_inline u64 vread_tick(void)
{
        u64     ret;

        __asm__ __volatile__("rd %%tick, %0" : "=r" (ret));
        return ret;
}

notrace static __always_inline u64 vread_tick_stick(void)
{
        u64     ret;

        __asm__ __volatile__("rd %%asr24, %0" : "=r" (ret));
        return ret;
}
#else
notrace static __always_inline u64 __shr64(u64 val, int amt)
{
        u64 ret;

        __asm__ __volatile__("sllx %H1, 32, %%g1\n\t"
                             "srl %L1, 0, %L1\n\t"
                             "or %%g1, %L1, %%g1\n\t"
                             "srlx %%g1, %2, %L0\n\t"
                             "srlx %L0, 32, %H0"
                             : "=r" (ret)
                             : "r" (val), "r" (amt)
                             : "g1");
        return ret;
}

notrace static __always_inline u64 vread_tick(void)
{
        register unsigned long long ret asm("o4");

        __asm__ __volatile__("rd %%tick, %L0\n\t"
                             "srlx %L0, 32, %H0"
                             : "=r" (ret));
        return ret;
}

notrace static __always_inline u64 vread_tick_stick(void)
{
        register unsigned long long ret asm("o4");

        __asm__ __volatile__("rd %%asr24, %L0\n\t"
                             "srlx %L0, 32, %H0"
                             : "=r" (ret));
        return ret;
}
#endif

notrace static __always_inline u64 vgetsns(struct vvar_data *vvar)
{
        u64 v;
        u64 cycles;

        cycles = vread_tick();
        v = (cycles - vvar->clock.cycle_last) & vvar->clock.mask;
        return v * vvar->clock.mult;
}

notrace static __always_inline u64 vgetsns_stick(struct vvar_data *vvar)
{
        u64 v;
        u64 cycles;

        cycles = vread_tick_stick();
        v = (cycles - vvar->clock.cycle_last) & vvar->clock.mask;
        return v * vvar->clock.mult;
}

notrace static __always_inline int do_realtime(struct vvar_data *vvar,
                                               struct __kernel_old_timespec *ts)
{
        unsigned long seq;
        u64 ns;

        do {
                seq = vvar_read_begin(vvar);
                ts->tv_sec = vvar->wall_time_sec;
                ns = vvar->wall_time_snsec;
                ns += vgetsns(vvar);
                ns = __shr64(ns, vvar->clock.shift);
        } while (unlikely(vvar_read_retry(vvar, seq)));

        ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
        ts->tv_nsec = ns;

        return 0;
}

notrace static __always_inline int do_realtime_stick(struct vvar_data *vvar,
                                                     struct __kernel_old_timespec *ts)
{
        unsigned long seq;
        u64 ns;

        do {
                seq = vvar_read_begin(vvar);
                ts->tv_sec = vvar->wall_time_sec;
                ns = vvar->wall_time_snsec;
                ns += vgetsns_stick(vvar);
                ns = __shr64(ns, vvar->clock.shift);
        } while (unlikely(vvar_read_retry(vvar, seq)));

        ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
        ts->tv_nsec = ns;

        return 0;
}

notrace static __always_inline int do_monotonic(struct vvar_data *vvar,
                                                struct __kernel_old_timespec *ts)
{
        unsigned long seq;
        u64 ns;

        do {
                seq = vvar_read_begin(vvar);
                ts->tv_sec = vvar->monotonic_time_sec;
                ns = vvar->monotonic_time_snsec;
                ns += vgetsns(vvar);
                ns = __shr64(ns, vvar->clock.shift);
        } while (unlikely(vvar_read_retry(vvar, seq)));

        ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
        ts->tv_nsec = ns;

        return 0;
}

notrace static __always_inline int do_monotonic_stick(struct vvar_data *vvar,
                                                      struct __kernel_old_timespec *ts)
{
        unsigned long seq;
        u64 ns;

        do {
                seq = vvar_read_begin(vvar);
                ts->tv_sec = vvar->monotonic_time_sec;
                ns = vvar->monotonic_time_snsec;
                ns += vgetsns_stick(vvar);
                ns = __shr64(ns, vvar->clock.shift);
        } while (unlikely(vvar_read_retry(vvar, seq)));

        ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
        ts->tv_nsec = ns;

        return 0;
}

notrace static int do_realtime_coarse(struct vvar_data *vvar,
                                      struct __kernel_old_timespec *ts)
{
        unsigned long seq;

        do {
                seq = vvar_read_begin(vvar);
                ts->tv_sec = vvar->wall_time_coarse_sec;
                ts->tv_nsec = vvar->wall_time_coarse_nsec;
        } while (unlikely(vvar_read_retry(vvar, seq)));
        return 0;
}

notrace static int do_monotonic_coarse(struct vvar_data *vvar,
                                       struct __kernel_old_timespec *ts)
{
        unsigned long seq;

        do {
                seq = vvar_read_begin(vvar);
                ts->tv_sec = vvar->monotonic_time_coarse_sec;
                ts->tv_nsec = vvar->monotonic_time_coarse_nsec;
        } while (unlikely(vvar_read_retry(vvar, seq)));

        return 0;
}

notrace int
__vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
{
        struct vvar_data *vvd = get_vvar_data();

        switch (clock) {
        case CLOCK_REALTIME:
                if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
                        break;
                return do_realtime(vvd, ts);
        case CLOCK_MONOTONIC:
                if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
                        break;
                return do_monotonic(vvd, ts);
        case CLOCK_REALTIME_COARSE:
                return do_realtime_coarse(vvd, ts);
        case CLOCK_MONOTONIC_COARSE:
                return do_monotonic_coarse(vvd, ts);
        }
        /*
         * Unknown clock ID ? Fall back to the syscall.
         */
        return vdso_fallback_gettime(clock, ts);
}
int
clock_gettime(clockid_t, struct __kernel_old_timespec *)
        __attribute__((weak, alias("__vdso_clock_gettime")));

notrace int
__vdso_clock_gettime_stick(clockid_t clock, struct __kernel_old_timespec *ts)
{
        struct vvar_data *vvd = get_vvar_data();

        switch (clock) {
        case CLOCK_REALTIME:
                if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
                        break;
                return do_realtime_stick(vvd, ts);
        case CLOCK_MONOTONIC:
                if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
                        break;
                return do_monotonic_stick(vvd, ts);
        case CLOCK_REALTIME_COARSE:
                return do_realtime_coarse(vvd, ts);
        case CLOCK_MONOTONIC_COARSE:
                return do_monotonic_coarse(vvd, ts);
        }
        /*
         * Unknown clock ID ? Fall back to the syscall.
         */
        return vdso_fallback_gettime(clock, ts);
}

notrace int
__vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
{
        struct vvar_data *vvd = get_vvar_data();

        if (likely(vvd->vclock_mode != VCLOCK_NONE)) {
                if (likely(tv != NULL)) {
                        union tstv_t {
                                struct __kernel_old_timespec ts;
                                struct __kernel_old_timeval tv;
                        } *tstv = (union tstv_t *) tv;
                        do_realtime(vvd, &tstv->ts);
                        /*
                         * Assign before dividing to ensure that the division is
                         * done in the type of tv_usec, not tv_nsec.
                         *
                         * There cannot be > 1 billion usec in a second:
                         * do_realtime() has already distributed such overflow
                         * into tv_sec.  So we can assign it to an int safely.
                         */
                        tstv->tv.tv_usec = tstv->ts.tv_nsec;
                        tstv->tv.tv_usec /= 1000;
                }
                if (unlikely(tz != NULL)) {
                        /* Avoid memcpy. Some old compilers fail to inline it */
                        tz->tz_minuteswest = vvd->tz_minuteswest;
                        tz->tz_dsttime = vvd->tz_dsttime;
                }
                return 0;
        }
        return vdso_fallback_gettimeofday(tv, tz);
}
int
gettimeofday(struct __kernel_old_timeval *, struct timezone *)
        __attribute__((weak, alias("__vdso_gettimeofday")));

notrace int
__vdso_gettimeofday_stick(struct __kernel_old_timeval *tv, struct timezone *tz)
{
        struct vvar_data *vvd = get_vvar_data();

        if (likely(vvd->vclock_mode != VCLOCK_NONE)) {
                if (likely(tv != NULL)) {
                        union tstv_t {
                                struct __kernel_old_timespec ts;
                                struct __kernel_old_timeval tv;
                        } *tstv = (union tstv_t *) tv;
                        do_realtime_stick(vvd, &tstv->ts);
                        /*
                         * Assign before dividing to ensure that the division is
                         * done in the type of tv_usec, not tv_nsec.
                         *
                         * There cannot be > 1 billion usec in a second:
                         * do_realtime() has already distributed such overflow
                         * into tv_sec.  So we can assign it to an int safely.
                         */
                        tstv->tv.tv_usec = tstv->ts.tv_nsec;
                        tstv->tv.tv_usec /= 1000;
                }
                if (unlikely(tz != NULL)) {
                        /* Avoid memcpy. Some old compilers fail to inline it */
                        tz->tz_minuteswest = vvd->tz_minuteswest;
                        tz->tz_dsttime = vvd->tz_dsttime;
                }
                return 0;
        }
        return vdso_fallback_gettimeofday(tv, tz);
}