sysdeps/unix/sysv/linux/time.c

   1 /* time -- Get number of seconds since Epoch.  Linux version.
   2    Copyright (C) 2020 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 /* Optimize the function call by setting the PLT directly to vDSO symbol.  */
  20 #ifdef USE_IFUNC_TIME
  21 # include <time.h>
  22 # include <sysdep.h>
  23 # include <sysdep-vdso.h>
  24
  25 #ifdef SHARED
  26 # include <dl-vdso.h>
  27 # include <libc-vdso.h>
  28
  29 static time_t
  30 time_syscall (time_t *t)
  31 {
  32   return INLINE_SYSCALL_CALL (time, t);
  33 }
  34
  35 # undef INIT_ARCH
  36 # define INIT_ARCH() \
  37   void *vdso_time = dl_vdso_vsym (HAVE_TIME_VSYSCALL);
  38 libc_ifunc (time,
  39             vdso_time ? VDSO_IFUNC_RET (vdso_time)
  40                       : (void *) time_syscall);
  41
  42 # else
  43 time_t
  44 time (time_t *t)
  45 {
  46   return INLINE_VSYSCALL (time, 1, t);
  47 }
  48 # endif /* !SHARED */
  49 #else /* USE_IFUNC_TIME  */
  50 # include <time/time.c>
  51 #endif