mm/rodata_test.c

   1 /*
   2  * rodata_test.c: functional test for mark_rodata_ro function
   3  *
   4  * (C) Copyright 2008 Intel Corporation
   5  * Author: Arjan van de Ven <arjan@linux.intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; version 2
  10  * of the License.
  11  */
  12 #include <linux/uaccess.h>
  13 #include <asm/sections.h>
  14
  15 const int rodata_test_data = 0xC3;
  16 EXPORT_SYMBOL_GPL(rodata_test_data);
  17
  18 void rodata_test(void)
  19 {
  20         unsigned long start, end;
  21         int zero = 0;
  22
  23         /* test 1: read the value */
  24         /* If this test fails, some previous testrun has clobbered the state */
  25         if (!rodata_test_data) {
  26                 pr_err("rodata_test: test 1 fails (start data)\n");
  27                 return;
  28         }
  29
  30         /* test 2: write to the variable; this should fault */
  31         if (!probe_kernel_write((void *)&rodata_test_data,
  32                                                 (void *)&zero, sizeof(zero))) {
  33                 pr_err("rodata_test: test data was not read only\n");
  34                 return;
  35         }
  36
  37         /* test 3: check the value hasn't changed */
  38         if (rodata_test_data == zero) {
  39                 pr_err("rodata_test: test data was changed\n");
  40                 return;
  41         }
  42
  43         /* test 4: check if the rodata section is PAGE_SIZE aligned */
  44         start = (unsigned long)__start_rodata;
  45         end = (unsigned long)__end_rodata;
  46         if (start & (PAGE_SIZE - 1)) {
  47                 pr_err("rodata_test: start of .rodata is not page size aligned\n");
  48                 return;
  49         }
  50         if (end & (PAGE_SIZE - 1)) {
  51                 pr_err("rodata_test: end of .rodata is not page size aligned\n");
  52                 return;
  53         }
  54
  55         pr_info("rodata_test: all tests were successful\n");
  56 }