wrapper/random.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * wrapper/random.c
   4  *
   5  * wrapper around bootid read. Using KALLSYMS to get its address when
   6  * available, else we need to have a kernel that exports this function to GPL
   7  * modules.
   8  *
   9  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  */
  11
  12 #include <linux/errno.h>
  13
  14 /* boot_id depends on sysctl */
  15 #if defined(CONFIG_SYSCTL)
  16
  17 #include <linux/fs.h>
  18 #include <linux/file.h>
  19 #include <linux/sched.h>
  20 #include <linux/uaccess.h>
  21 #include <wrapper/random.h>
  22
  23 /*
  24  * Returns string boot id.
  25  */
  26 int wrapper_get_bootid(char *bootid)
  27 {
  28         struct file *file;
  29         int ret;
  30         ssize_t len;
  31         mm_segment_t old_fs;
  32
  33         file = filp_open("/proc/sys/kernel/random/boot_id", O_RDONLY, 0);
  34         if (IS_ERR(file))
  35                 return PTR_ERR(file);
  36
  37         old_fs = get_fs();
  38         set_fs(KERNEL_DS);
  39
  40         if (!file->f_op || !file->f_op->read) {
  41                 ret = -EINVAL;
  42                 goto end;
  43         }
  44
  45         len = file->f_op->read(file, bootid, BOOT_ID_LEN - 1, &file->f_pos);
  46         if (len != BOOT_ID_LEN - 1) {
  47                 ret = -EINVAL;
  48                 goto end;
  49         }
  50
  51         bootid[BOOT_ID_LEN - 1] = '\0';
  52         ret = 0;
  53 end:
  54         set_fs(old_fs);
  55         filp_close(file, current->files);
  56         return ret;
  57 }
  58 EXPORT_SYMBOL_GPL(wrapper_get_bootid);
  59
  60 #else
  61
  62 int wrapper_get_bootid(char *bootid)
  63 {
  64         return -ENOSYS;
  65 }
  66 EXPORT_SYMBOL_GPL(wrapper_get_bootid);
  67
  68 #endif