xref: /openbmc/linux/kernel/kcsan/selftest.c (revision abe9af53)
1 // SPDX-License-Identifier: GPL-2.0
2 
3 #define pr_fmt(fmt) "kcsan: " fmt
4 
5 #include <linux/init.h>
6 #include <linux/kernel.h>
7 #include <linux/printk.h>
8 #include <linux/random.h>
9 #include <linux/types.h>
10 
11 #include "encoding.h"
12 
13 #define ITERS_PER_TEST 2000
14 
15 /* Test requirements. */
16 static bool test_requires(void)
17 {
18 	/* random should be initialized for the below tests */
19 	return prandom_u32() + prandom_u32() != 0;
20 }
21 
22 /*
23  * Test watchpoint encode and decode: check that encoding some access's info,
24  * and then subsequent decode preserves the access's info.
25  */
26 static bool test_encode_decode(void)
27 {
28 	int i;
29 
30 	for (i = 0; i < ITERS_PER_TEST; ++i) {
31 		size_t size = prandom_u32_max(MAX_ENCODABLE_SIZE) + 1;
32 		bool is_write = !!prandom_u32_max(2);
33 		unsigned long addr;
34 
35 		prandom_bytes(&addr, sizeof(addr));
36 		if (WARN_ON(!check_encodable(addr, size)))
37 			return false;
38 
39 		/* Encode and decode */
40 		{
41 			const long encoded_watchpoint =
42 				encode_watchpoint(addr, size, is_write);
43 			unsigned long verif_masked_addr;
44 			size_t verif_size;
45 			bool verif_is_write;
46 
47 			/* Check special watchpoints */
48 			if (WARN_ON(decode_watchpoint(
49 				    INVALID_WATCHPOINT, &verif_masked_addr,
50 				    &verif_size, &verif_is_write)))
51 				return false;
52 			if (WARN_ON(decode_watchpoint(
53 				    CONSUMED_WATCHPOINT, &verif_masked_addr,
54 				    &verif_size, &verif_is_write)))
55 				return false;
56 
57 			/* Check decoding watchpoint returns same data */
58 			if (WARN_ON(!decode_watchpoint(
59 				    encoded_watchpoint, &verif_masked_addr,
60 				    &verif_size, &verif_is_write)))
61 				return false;
62 			if (WARN_ON(verif_masked_addr !=
63 				    (addr & WATCHPOINT_ADDR_MASK)))
64 				goto fail;
65 			if (WARN_ON(verif_size != size))
66 				goto fail;
67 			if (WARN_ON(is_write != verif_is_write))
68 				goto fail;
69 
70 			continue;
71 fail:
72 			pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n",
73 			       __func__, is_write ? "write" : "read", size,
74 			       addr, encoded_watchpoint,
75 			       verif_is_write ? "write" : "read", verif_size,
76 			       verif_masked_addr);
77 			return false;
78 		}
79 	}
80 
81 	return true;
82 }
83 
84 /* Test access matching function. */
85 static bool test_matching_access(void)
86 {
87 	if (WARN_ON(!matching_access(10, 1, 10, 1)))
88 		return false;
89 	if (WARN_ON(!matching_access(10, 2, 11, 1)))
90 		return false;
91 	if (WARN_ON(!matching_access(10, 1, 9, 2)))
92 		return false;
93 	if (WARN_ON(matching_access(10, 1, 11, 1)))
94 		return false;
95 	if (WARN_ON(matching_access(9, 1, 10, 1)))
96 		return false;
97 
98 	/*
99 	 * An access of size 0 could match another access, as demonstrated here.
100 	 * Rather than add more comparisons to 'matching_access()', which would
101 	 * end up in the fast-path for *all* checks, check_access() simply
102 	 * returns for all accesses of size 0.
103 	 */
104 	if (WARN_ON(!matching_access(8, 8, 12, 0)))
105 		return false;
106 
107 	return true;
108 }
109 
110 static int __init kcsan_selftest(void)
111 {
112 	int passed = 0;
113 	int total = 0;
114 
115 #define RUN_TEST(do_test)                                                      \
116 	do {                                                                   \
117 		++total;                                                       \
118 		if (do_test())                                                 \
119 			++passed;                                              \
120 		else                                                           \
121 			pr_err("selftest: " #do_test " failed");               \
122 	} while (0)
123 
124 	RUN_TEST(test_requires);
125 	RUN_TEST(test_encode_decode);
126 	RUN_TEST(test_matching_access);
127 
128 	pr_info("selftest: %d/%d tests passed\n", passed, total);
129 	if (passed != total)
130 		panic("selftests failed");
131 	return 0;
132 }
133 postcore_initcall(kcsan_selftest);
134