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 /* boot_id depends on sysctl */
  26 #if defined(CONFIG_SYSCTL)
  27
  28 #include <linux/fs.h>
  29 #include <linux/file.h>
  30 #include <linux/sched.h>
  31 #include <linux/uaccess.h>
  32 #include "random.h"
  33
  34 /*
  35  * Returns string boot id.
  36  */
  37 int wrapper_get_bootid(char *bootid)
  38 {
  39         struct file *file;
  40         int ret;
  41         ssize_t len;
  42         mm_segment_t old_fs;
  43
  44         file = filp_open("/proc/sys/kernel/random/boot_id", O_RDONLY, 0);
  45         if (IS_ERR(file))
  46                 return PTR_ERR(file);
  47
  48         old_fs = get_fs();
  49         set_fs(KERNEL_DS);
  50
  51         if (!file->f_op || !file->f_op->read) {
  52                 ret = -EINVAL;
  53                 goto end;
  54         }
  55
  56         len = file->f_op->read(file, bootid, BOOT_ID_LEN - 1, &file->f_pos);
  57         if (len != BOOT_ID_LEN - 1) {
  58                 ret = -EINVAL;
  59                 goto end;
  60         }
  61
  62         bootid[BOOT_ID_LEN - 1] = '\0';
  63         ret = 0;
  64 end:
  65         set_fs(old_fs);
  66         filp_close(file, current->files);
  67         return ret;
  68 }
  69
  70 #else
  71
  72 int wrapper_get_bootid(char *bootid)
  73 {
  74         return -ENOSYS;
  75 }
  76
  77 #endif