Linux Kernel  3.7.1
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test_rodata.c
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1 /*
2  * test_rodata.c: functional test for mark_rodata_ro function
3  *
4  * (C) Copyright 2008 Intel Corporation
5  * Author: Arjan van de Ven <[email protected]>
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/module.h>
13 #include <asm/cacheflush.h>
14 #include <asm/sections.h>
15 #include <asm/asm.h>
16 
17 int rodata_test(void)
18 {
19  unsigned long result;
20  unsigned long start, end;
21 
22  /* test 1: read the value */
23  /* If this test fails, some previous testrun has clobbered the state */
24  if (!rodata_test_data) {
25  printk(KERN_ERR "rodata_test: test 1 fails (start data)\n");
26  return -ENODEV;
27  }
28 
29  /* test 2: write to the variable; this should fault */
30  /*
31  * If this test fails, we managed to overwrite the data
32  *
33  * This is written in assembly to be able to catch the
34  * exception that is supposed to happen in the correct
35  * case
36  */
37 
38  result = 1;
39  asm volatile(
40  "0: mov %[zero],(%[rodata_test])\n"
41  " mov %[zero], %[rslt]\n"
42  "1:\n"
43  ".section .fixup,\"ax\"\n"
44  "2: jmp 1b\n"
45  ".previous\n"
46  _ASM_EXTABLE(0b,2b)
47  : [rslt] "=r" (result)
48  : [rodata_test] "r" (&rodata_test_data), [zero] "r" (0UL)
49  );
50 
51 
52  if (!result) {
53  printk(KERN_ERR "rodata_test: test data was not read only\n");
54  return -ENODEV;
55  }
56 
57  /* test 3: check the value hasn't changed */
58  /* If this test fails, we managed to overwrite the data */
59  if (!rodata_test_data) {
60  printk(KERN_ERR "rodata_test: Test 3 failes (end data)\n");
61  return -ENODEV;
62  }
63  /* test 4: check if the rodata section is 4Kb aligned */
64  start = (unsigned long)__start_rodata;
65  end = (unsigned long)__end_rodata;
66  if (start & (PAGE_SIZE - 1)) {
67  printk(KERN_ERR "rodata_test: .rodata is not 4k aligned\n");
68  return -ENODEV;
69  }
70  if (end & (PAGE_SIZE - 1)) {
71  printk(KERN_ERR "rodata_test: .rodata end is not 4k aligned\n");
72  return -ENODEV;
73  }
74 
75  return 0;
76 }
77 
78 MODULE_LICENSE("GPL");
79 MODULE_DESCRIPTION("Testcase for the DEBUG_RODATA infrastructure");
80 MODULE_AUTHOR("Arjan van de Ven <[email protected]>");