src/time/clock_gettime.c

   1 #include <time.h>
   2 #include <errno.h>
   3 #include <stdint.h>
   4 #include "syscall.h"
   5 #include "libc.h"
   6 #include "atomic.h"
   7
   8 #ifdef VDSO_CGT_SYM
   9
  10 void *__vdsosym(const char *, const char *);
  11
  12 static void *volatile vdso_func;
  13
  14 static int cgt_init(clockid_t clk, struct timespec *ts)
  15 {
  16         void *p = __vdsosym(VDSO_CGT_VER, VDSO_CGT_SYM);
  17         int (*f)(clockid_t, struct timespec *) =
  18                 (int (*)(clockid_t, struct timespec *))p;
  19         a_cas_p(&vdso_func, (void *)cgt_init, p);
  20         return f ? f(clk, ts) : -ENOSYS;
  21 }
  22
  23 static void *volatile vdso_func = (void *)cgt_init;
  24
  25 #endif
  26
  27 int __clock_gettime(clockid_t clk, struct timespec *ts)
  28 {
  29         int r;
  30
  31 #ifdef VDSO_CGT_SYM
  32         int (*f)(clockid_t, struct timespec *) =
  33                 (int (*)(clockid_t, struct timespec *))vdso_func;
  34         if (f) {
  35                 r = f(clk, ts);
  36                 if (!r) return r;
  37                 if (r == -EINVAL) return __syscall_ret(r);
  38                 /* Fall through on errors other than EINVAL. Some buggy
  39                  * vdso implementations return ENOSYS for clocks they
  40                  * can't handle, rather than making the syscall. This
  41                  * also handles the case where cgt_init fails to find
  42                  * a vdso function to use. */
  43         }
  44 #endif
  45
  46         r = __syscall(SYS_clock_gettime, clk, ts);
  47         if (r == -ENOSYS) {
  48                 if (clk == CLOCK_REALTIME) {
  49                         __syscall(SYS_gettimeofday, ts, 0);
  50                         ts->tv_nsec = (int)ts->tv_nsec * 1000;
  51                         return 0;
  52                 }
  53                 r = -EINVAL;
  54         }
  55         return __syscall_ret(r);
  56 }
  57
  58 weak_alias(__clock_gettime, clock_gettime);