src/time/clock_gettime.c

   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 #ifdef VDSO_CGT_WORKAROUND
  46         if (!__vdsosym(VDSO_CGT32_VER, VDSO_CGT32_SYM)) p = 0;
  47 #endif
  48 #endif
  49         int (*f)(clockid_t, struct timespec *) =
  50                 (int (*)(clockid_t, struct timespec *))p;
  51         a_cas_p(&vdso_func, (void *)cgt_init, p);
  52         return f ? f(clk, ts) : -ENOSYS;
  53 }
  54
  55 static void *volatile vdso_func = (void *)cgt_init;
  56
  57 #endif
  58
  59 int __clock_gettime(clockid_t clk, struct timespec *ts)
  60 {
  61         int r;
  62
  63 #ifdef VDSO_CGT_SYM
  64         int (*f)(clockid_t, struct timespec *) =
  65                 (int (*)(clockid_t, struct timespec *))vdso_func;
  66         if (f) {
  67                 r = f(clk, ts);
  68                 if (!r) return r;
  69                 if (r == -EINVAL) return __syscall_ret(r);
  70                 /* Fall through on errors other than EINVAL. Some buggy
  71                  * vdso implementations return ENOSYS for clocks they
  72                  * can't handle, rather than making the syscall. This
  73                  * also handles the case where cgt_init fails to find
  74                  * a vdso function to use. */
  75         }
  76 #endif
  77
  78 #ifdef SYS_clock_gettime64
  79         r = -ENOSYS;
  80         if (sizeof(time_t) > 4)
  81                 r = __syscall(SYS_clock_gettime64, clk, ts);
  82         if (SYS_clock_gettime == SYS_clock_gettime64 || r!=-ENOSYS)
  83                 return __syscall_ret(r);
  84         long ts32[2];
  85         r = __syscall(SYS_clock_gettime, clk, ts32);
  86 #ifdef SYS_gettimeofday
  87         if (r==-ENOSYS && clk==CLOCK_REALTIME) {
  88                 r = __syscall(SYS_gettimeofday, ts32, 0);
  89                 ts32[1] *= 1000;
  90         }
  91 #endif
  92         if (!r) {
  93                 ts->tv_sec = ts32[0];
  94                 ts->tv_nsec = ts32[1];
  95                 return r;
  96         }
  97         return __syscall_ret(r);
  98 #else
  99         r = __syscall(SYS_clock_gettime, clk, ts);
 100 #ifdef SYS_gettimeofday
 101         if (r == -ENOSYS) {
 102                 if (clk == CLOCK_REALTIME) {
 103                         __syscall(SYS_gettimeofday, ts, 0);
 104                         ts->tv_nsec = (int)ts->tv_nsec * 1000;
 105                         return 0;
 106                 }
 107                 r = -EINVAL;
 108         }
 109 #endif
 110         return __syscall_ret(r);
 111 #endif
 112 }
 113
 114 weak_alias(__clock_gettime, clock_gettime);