xref: /linux/mm/rodata_test.c (revision 9c5968db9e625019a0ee5226c7eebef5519d366a)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * rodata_test.c: functional test for mark_rodata_ro function
4  *
5  * (C) Copyright 2008 Intel Corporation
6  * Author: Arjan van de Ven <arjan@linux.intel.com>
7  */
8 #define pr_fmt(fmt) "rodata_test: " fmt
9 
10 #include <linux/rodata_test.h>
11 #include <linux/uaccess.h>
12 #include <linux/mm.h>
13 #include <asm/sections.h>
14 
15 #define TEST_VALUE 0xC3
16 static const int rodata_test_data = TEST_VALUE;
17 
18 void rodata_test(void)
19 {
20 	int zero = 0;
21 
22 	/* test 1: read the value */
23 	/* If this test fails, some previous testrun has clobbered the state */
24 	if (unlikely(READ_ONCE(rodata_test_data) != TEST_VALUE)) {
25 		pr_err("test 1 fails (start data)\n");
26 		return;
27 	}
28 
29 	/* test 2: write to the variable; this should fault */
30 	if (!copy_to_kernel_nofault((void *)&rodata_test_data,
31 				(void *)&zero, sizeof(zero))) {
32 		pr_err("test data was not read only\n");
33 		return;
34 	}
35 
36 	/* test 3: check the value hasn't changed */
37 	if (unlikely(READ_ONCE(rodata_test_data) != TEST_VALUE)) {
38 		pr_err("test data was changed\n");
39 		return;
40 	}
41 
42 	/* test 4: check if the rodata section is PAGE_SIZE aligned */
43 	if (!PAGE_ALIGNED(__start_rodata)) {
44 		pr_err("start of .rodata is not page size aligned\n");
45 		return;
46 	}
47 	if (!PAGE_ALIGNED(__end_rodata)) {
48 		pr_err("end of .rodata is not page size aligned\n");
49 		return;
50 	}
51 
52 	pr_info("all tests were successful\n");
53 }
54