rodata_test.c

 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
16static const int rodata_test_data = TEST_VALUE;
17
18void 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}