github.com/afumu/libc@v0.0.6/musl/src/time/clock_gettime.c (about)

     1  #include <time.h>
     2  #include <errno.h>
     3  #include <stdint.h>
     4  #include "syscall.h"
     5  #include "atomic.h"
     6  
     7  #ifdef VDSO_CGT_SYM
     8  
     9  static void *volatile vdso_func;
    10  
    11  #ifdef VDSO_CGT32_SYM
    12  static void *volatile vdso_func_32;
    13  static int cgt_time32_wrap(clockid_t clk, struct timespec *ts)
    14  {
    15  	long ts32[2];
    16  	int (*f)(clockid_t, long[2]) =
    17  		(int (*)(clockid_t, long[2]))vdso_func_32;
    18  	int r = f(clk, ts32);
    19  	if (!r) {
    20  		/* Fallback to syscalls if time32 overflowed. Maybe
    21  		 * we lucked out and somehow migrated to a kernel with
    22  		 * time64 syscalls available. */
    23  		if (ts32[0] < 0) {
    24  			a_cas_p(&vdso_func, (void *)cgt_time32_wrap, 0);
    25  			return -ENOSYS;
    26  		}
    27  		ts->tv_sec = ts32[0];
    28  		ts->tv_nsec = ts32[1];
    29  	}
    30  	return r;
    31  }
    32  #endif
    33  
    34  static int cgt_init(clockid_t clk, struct timespec *ts)
    35  {
    36  	void *p = __vdsosym(VDSO_CGT_VER, VDSO_CGT_SYM);
    37  #ifdef VDSO_CGT32_SYM
    38  	if (!p) {
    39  		void *q = __vdsosym(VDSO_CGT32_VER, VDSO_CGT32_SYM);
    40  		if (q) {
    41  			a_cas_p(&vdso_func_32, 0, q);
    42  			p = cgt_time32_wrap;
    43  		}
    44  	}
    45  #endif
    46  	int (*f)(clockid_t, struct timespec *) =
    47  		(int (*)(clockid_t, struct timespec *))p;
    48  	a_cas_p(&vdso_func, (void *)cgt_init, p);
    49  	return f ? f(clk, ts) : -ENOSYS;
    50  }
    51  
    52  static void *volatile vdso_func = (void *)cgt_init;
    53  
    54  #endif
    55  
    56  int __clock_gettime(clockid_t clk, struct timespec *ts)
    57  {
    58  	int r;
    59  
    60  #ifdef VDSO_CGT_SYM
    61  	int (*f)(clockid_t, struct timespec *) =
    62  		(int (*)(clockid_t, struct timespec *))vdso_func;
    63  	if (f) {
    64  		r = f(clk, ts);
    65  		if (!r) return r;
    66  		if (r == -EINVAL) return __syscall_ret(r);
    67  		/* Fall through on errors other than EINVAL. Some buggy
    68  		 * vdso implementations return ENOSYS for clocks they
    69  		 * can't handle, rather than making the syscall. This
    70  		 * also handles the case where cgt_init fails to find
    71  		 * a vdso function to use. */
    72  	}
    73  #endif
    74  
    75  #ifdef SYS_clock_gettime64
    76  	r = -ENOSYS;
    77  	if (sizeof(time_t) > 4)
    78  		r = __syscall(SYS_clock_gettime64, clk, ts);
    79  	if (SYS_clock_gettime == SYS_clock_gettime64 || r!=-ENOSYS)
    80  		return __syscall_ret(r);
    81  	long ts32[2];
    82  	r = __syscall(SYS_clock_gettime, clk, ts32);
    83  	if (r==-ENOSYS && clk==CLOCK_REALTIME) {
    84  		r = __syscall(SYS_gettimeofday, ts32, 0);
    85  		ts32[1] *= 1000;
    86  	}
    87  	if (!r) {
    88  		ts->tv_sec = ts32[0];
    89  		ts->tv_nsec = ts32[1];
    90  		return r;
    91  	}
    92  	return __syscall_ret(r);
    93  #else
    94  	r = __syscall(SYS_clock_gettime, clk, ts);
    95  	if (r == -ENOSYS) {
    96  		if (clk == CLOCK_REALTIME) {
    97  			__syscall(SYS_gettimeofday, ts, 0);
    98  			ts->tv_nsec = (int)ts->tv_nsec * 1000;
    99  			return 0;
   100  		}
   101  		r = -EINVAL;
   102  	}
   103  	return __syscall_ret(r);
   104  #endif
   105  }
   106  
   107  weak_alias(__clock_gettime, clock_gettime);