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 <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/module.h>
13 #include <asm/cacheflush.h>
14 #include <asm/sections.h>
15
rodata_test(void)16 int rodata_test(void)
17 {
18 unsigned long result;
19 unsigned long start, end;
20
21 /* test 1: read the value */
22 /* If this test fails, some previous testrun has clobbered the state */
23 if (!rodata_test_data) {
24 printk(KERN_ERR "rodata_test: test 1 fails (start data)\n");
25 return -ENODEV;
26 }
27
28 /* test 2: write to the variable; this should fault */
29 /*
30 * If this test fails, we managed to overwrite the data
31 *
32 * This is written in assembly to be able to catch the
33 * exception that is supposed to happen in the correct
34 * case
35 */
36
37 result = 1;
38 asm volatile(
39 "0: mov %[zero],(%[rodata_test])\n"
40 " mov %[zero], %[rslt]\n"
41 "1:\n"
42 ".section .fixup,\"ax\"\n"
43 "2: jmp 1b\n"
44 ".previous\n"
45 ".section __ex_table,\"a\"\n"
46 " .align 16\n"
47 #ifdef CONFIG_X86_32
48 " .long 0b,2b\n"
49 #else
50 " .quad 0b,2b\n"
51 #endif
52 ".previous"
53 : [rslt] "=r" (result)
54 : [rodata_test] "r" (&rodata_test_data), [zero] "r" (0UL)
55 );
56
57
58 if (!result) {
59 printk(KERN_ERR "rodata_test: test data was not read only\n");
60 return -ENODEV;
61 }
62
63 /* test 3: check the value hasn't changed */
64 /* If this test fails, we managed to overwrite the data */
65 if (!rodata_test_data) {
66 printk(KERN_ERR "rodata_test: Test 3 failes (end data)\n");
67 return -ENODEV;
68 }
69 /* test 4: check if the rodata section is 4Kb aligned */
70 start = (unsigned long)__start_rodata;
71 end = (unsigned long)__end_rodata;
72 if (start & (PAGE_SIZE - 1)) {
73 printk(KERN_ERR "rodata_test: .rodata is not 4k aligned\n");
74 return -ENODEV;
75 }
76 if (end & (PAGE_SIZE - 1)) {
77 printk(KERN_ERR "rodata_test: .rodata end is not 4k aligned\n");
78 return -ENODEV;
79 }
80
81 return 0;
82 }
83
84 MODULE_LICENSE("GPL");
85 MODULE_DESCRIPTION("Testcase for the DEBUG_RODATA infrastructure");
86 MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
87