wrapper/random.c

   1 /*
   2  * wrapper/random.c
   3  *
   4  * wrapper around bootid read. Using KALLSYMS to get its address when
   5  * available, else we need to have a kernel that exports this function to GPL
   6  * modules.
   7  *
   8  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   9  *
  10  * This library is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Lesser General Public
  12  * License as published by the Free Software Foundation; only
  13  * version 2.1 of the License.
  14  *
  15  * This library is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18  * Lesser General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public
  21  * License along with this library; if not, write to the Free Software
  22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  23  */
  24
  25 #include <linux/errno.h>
  26
  27 /* boot_id depends on sysctl */
  28 #if defined(CONFIG_SYSCTL)
  29
  30 #include <linux/fs.h>
  31 #include <linux/file.h>
  32 #include <linux/sched.h>
  33 #include <linux/uaccess.h>
  34 #include <wrapper/random.h>
  35
  36 /*
  37  * Returns string boot id.
  38  */
  39 int wrapper_get_bootid(char *bootid)
  40 {
  41         struct file *file;
  42         int ret;
  43         ssize_t len;
  44         mm_segment_t old_fs;
  45
  46         file = filp_open("/proc/sys/kernel/random/boot_id", O_RDONLY, 0);
  47         if (IS_ERR(file))
  48                 return PTR_ERR(file);
  49
  50         old_fs = get_fs();
  51         set_fs(KERNEL_DS);
  52
  53         if (!file->f_op || !file->f_op->read) {
  54                 ret = -EINVAL;
  55                 goto end;
  56         }
  57
  58         len = file->f_op->read(file, bootid, BOOT_ID_LEN - 1, &file->f_pos);
  59         if (len != BOOT_ID_LEN - 1) {
  60                 ret = -EINVAL;
  61                 goto end;
  62         }
  63
  64         bootid[BOOT_ID_LEN - 1] = '\0';
  65         ret = 0;
  66 end:
  67         set_fs(old_fs);
  68         filp_close(file, current->files);
  69         return ret;
  70 }
  71
  72 #else
  73
  74 int wrapper_get_bootid(char *bootid)
  75 {
  76         return -ENOSYS;
  77 }
  78
  79 #endif