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
16int 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
84MODULE_LICENSE("GPL");
85MODULE_DESCRIPTION("Testcase for the DEBUG_RODATA infrastructure");
86MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");