src/system/libroot/os/arch/x86_64/system_time.cpp

   1 /*
   2  * Copyright 2014, Paweł Dziepak, pdziepak@quarnos.org.
   3  * Distributed under the terms of the MIT License.
   4  */
   5
   6
   7 #include <stdint.h>
   8
   9
  10 static uint64_t cv_factor;
  11 static uint64_t cv_factor_nsec;
  12
  13
  14 extern "C" void
  15 __x86_setup_system_time(uint64_t cv, uint64_t cv_nsec)
  16 {
  17     cv_factor = cv;
  18     cv_factor_nsec = cv_nsec;
  19 }
  20
  21
  22 static inline uint64_t
  23 rdtsc()
  24 {
  25     uint64_t lo, hi;
  26     __asm__("rdtsc" : "=a" (lo), "=d" (hi));
  27     return lo | (hi << 32);
  28 }
  29
  30
  31 extern "C" [[gnu::optimize("omit-frame-pointer")]] int64_t
  32 system_time()
  33 {
  34     __uint128_t time = static_cast<__uint128_t>(rdtsc()) * cv_factor;
  35     return time >> 64;
  36 }
  37
  38
  39 extern "C" [[gnu::optimize("omit-frame-pointer")]] int64_t
  40 system_time_nsecs()
  41 {
  42     __uint128_t t = static_cast<__uint128_t>(rdtsc()) * cv_factor_nsec;
  43     return t >> 32;
  44 }
  45