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 #define pr_fmt(fmt) "rodata_test: " fmt
  13
  14 #include <linux/uaccess.h>
  15 #include <asm/sections.h>
  16
  17 static const int rodata_test_data = 0xC3;
  18
  19 void rodata_test(void)
  20 {
  21         unsigned long start, end;
  22         int zero = 0;
  23
  24         /* test 1: read the value */
  25         /* If this test fails, some previous testrun has clobbered the state */
  26         if (!rodata_test_data) {
  27                 pr_err("test 1 fails (start data)\n");
  28                 return;
  29         }
  30
  31         /* test 2: write to the variable; this should fault */
  32         if (!probe_kernel_write((void *)&rodata_test_data,
  33                                 (void *)&zero, sizeof(zero))) {
  34                 pr_err("test data was not read only\n");
  35                 return;
  36         }
  37
  38         /* test 3: check the value hasn't changed */
  39         if (rodata_test_data == zero) {
  40                 pr_err("test data was changed\n");
  41                 return;
  42         }
  43
  44         /* test 4: check if the rodata section is PAGE_SIZE aligned */
  45         start = (unsigned long)__start_rodata;
  46         end = (unsigned long)__end_rodata;
  47         if (start & (PAGE_SIZE - 1)) {
  48                 pr_err("start of .rodata is not page size aligned\n");
  49                 return;
  50         }
  51         if (end & (PAGE_SIZE - 1)) {
  52                 pr_err("end of .rodata is not page size aligned\n");
  53                 return;
  54         }
  55
  56         pr_info("all tests were successful\n");
  57 }