sysdeps/unix/sysv/linux/times.c

   1 /* Copyright (C) 2008-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <sys/times.h>
  20 #include <sysdep.h>
  21
  22
  23 clock_t
  24 __times (struct tms *buf)
  25 {
  26   INTERNAL_SYSCALL_DECL (err);
  27   clock_t ret = INTERNAL_SYSCALL (times, err, 1, buf);
  28   if (INTERNAL_SYSCALL_ERROR_P (ret, err)
  29       && __builtin_expect (INTERNAL_SYSCALL_ERRNO (ret, err) == EFAULT, 0)
  30       && buf)
  31     {
  32       /* This might be an error or not.  For architectures which have
  33          no separate return value and error indicators we cannot
  34          distinguish a return value of -1 from an error.  Do it the
  35          hard way.  We crash applications which pass in an invalid
  36          non-NULL BUF pointer.  Linux allows BUF to be NULL. */
  37 #define touch(v) \
  38       do {                                                                    \
  39         clock_t temp = v;                                                     \
  40         asm volatile ("" : "+r" (temp));                                      \
  41         v = temp;                                                             \
  42       } while (0)
  43       touch (buf->tms_utime);
  44       touch (buf->tms_stime);
  45       touch (buf->tms_cutime);
  46       touch (buf->tms_cstime);
  47
  48       /* If we come here the memory is valid (or BUF is NULL, which is
  49          a valid condition for the kernel syscall) and the kernel did not
  50          return an EFAULT error.  Return the value given by the kernel.  */
  51     }
  52
  53   /* Return value (clock_t) -1 signals an error, but if there wasn't any,
  54      return the following value.  */
  55   if (ret == (clock_t) -1)
  56     return (clock_t) 0;
  57
  58   return ret;
  59 }
  60 weak_alias (__times, times)