sysdeps/unix/sysv/linux/powerpc/time.c

   1 /* time system call for Linux/PowerPC.
   2    Copyright (C) 2013-2015 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    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifdef SHARED
  20
  21 # include <time.h>
  22 # include <sysdep.h>
  23 # include <dl-vdso.h>
  24 # include <bits/libc-vdso.h>
  25 # include <dl-machine.h>
  26
  27 void *time_ifunc (void) asm ("time");
  28
  29 static time_t
  30 time_syscall (time_t *t)
  31 {
  32   struct timeval tv;
  33   time_t result;
  34
  35   if (INLINE_VSYSCALL (gettimeofday, 2, &tv, NULL) < 0)
  36     result = (time_t) -1;
  37   else
  38     result = (time_t) tv.tv_sec;
  39
  40   if (t != NULL)
  41     *t = result;
  42   return result;
  43 }
  44
  45 void *
  46 time_ifunc (void)
  47 {
  48   PREPARE_VERSION (linux2615, "LINUX_2.6.15", 123718565);
  49
  50   /* If the vDSO is not available we fall back to the syscall.  */
  51   void *vdso_time = _dl_vdso_vsym ("__kernel_time", &linux2615);
  52   return (vdso_time ? VDSO_IFUNC_RET (vdso_time)
  53           : (void*)time_syscall);
  54 }
  55 asm (".type time, %gnu_indirect_function");
  56
  57 /* This is doing "libc_hidden_def (time)" but the compiler won't
  58  * let us do it in C because it doesn't know we're defining time
  59  * here in this file.  */
  60 asm (".globl __GI_time");
  61
  62 /* __GI_time is defined as hidden and for ppc32 it enables the
  63    compiler make a local call (symbol@local) for internal GLIBC usage. It
  64    means the PLT won't be used and the ifunc resolver will be called directly.
  65    For ppc64 a call to a function in another translation unit might use a
  66    different toc pointer thus disallowing direct branchess and making internal
  67    ifuncs calls safe.  */
  68 #ifdef __powerpc64__
  69 asm ("__GI_time = time");
  70 #else
  71 time_t
  72 __time_vsyscall (time_t *t)
  73 {
  74   return INLINE_VSYSCALL (time, 1, t);
  75 }
  76 asm ("__GI_time = __time_vsyscall");
  77 #endif
  78
  79 #else
  80
  81 #include <sysdeps/posix/time.c>
  82
  83 #endif