source: asp3_tinet_ecnl_arm/trunk/musl-1.1.18/src/time/clock_gettime.c@ 352

#include <time.h>
#include <errno.h>
#include <stdint.h>
#include "syscall.h"
#include "libc.h"
#include "atomic.h"

#ifdef VDSO_CGT_SYM

void *__vdsosym(const char *, const char *);

static void *volatile vdso_func;

static int cgt_init(clockid_t clk, struct timespec *ts)
{
        void *p = __vdsosym(VDSO_CGT_VER, VDSO_CGT_SYM);
        int (*f)(clockid_t, struct timespec *) =
                (int (*)(clockid_t, struct timespec *))p;
        a_cas_p(&vdso_func, (void *)cgt_init, p);
        return f ? f(clk, ts) : -ENOSYS;
}

static void *volatile vdso_func = (void *)cgt_init;

#endif

int __clock_gettime(clockid_t clk, struct timespec *ts)
{
        int r;

#ifdef VDSO_CGT_SYM
        int (*f)(clockid_t, struct timespec *) =
                (int (*)(clockid_t, struct timespec *))vdso_func;
        if (f) {
                r = f(clk, ts);
                if (!r) return r;
                if (r == -EINVAL) return __syscall_ret(r);
                /* Fall through on errors other than EINVAL. Some buggy
                 * vdso implementations return ENOSYS for clocks they
                 * can't handle, rather than making the syscall. This
                 * also handles the case where cgt_init fails to find
                 * a vdso function to use. */
        }
#endif

        r = __syscall(SYS_clock_gettime, clk, ts);
        if (r == -ENOSYS) {
                if (clk == CLOCK_REALTIME) {
                        __syscall(SYS_gettimeofday, ts, 0);
                        ts->tv_nsec = (int)ts->tv_nsec * 1000;
                        return 0;
                }
                r = -EINVAL;
        }
        return __syscall_ret(r);
}

#ifndef __c2__
weak_alias(__clock_gettime, clock_gettime);
#else
int clock_gettime(clockid_t clk, struct timespec *ts)
{
        return __clock_gettime(clk, ts);
}
#endif