1 /* SPDX-License-Identifier: GPL-2.0 */
2
3 /*
4 * This file provides wrappers with sanitizer instrumentation for non-atomic
5 * bit operations.
6 *
7 * To use this functionality, an arch's bitops.h file needs to define each of
8 * the below bit operations with an arch_ prefix (e.g. arch_set_bit(),
9 * arch___set_bit(), etc.).
10 */
11 #ifndef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
12 #define _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
13
14 #include <linux/instrumented.h>
15
16 /**
17 * __set_bit - Set a bit in memory
18 * @nr: the bit to set
19 * @addr: the address to start counting from
20 *
21 * Unlike set_bit(), this function is non-atomic. If it is called on the same
22 * region of memory concurrently, the effect may be that only one operation
23 * succeeds.
24 */
__set_bit(long nr,volatile unsigned long * addr)25 static inline void __set_bit(long nr, volatile unsigned long *addr)
26 {
27 instrument_write(addr + BIT_WORD(nr), sizeof(long));
28 arch___set_bit(nr, addr);
29 }
30
31 /**
32 * __clear_bit - Clears a bit in memory
33 * @nr: the bit to clear
34 * @addr: the address to start counting from
35 *
36 * Unlike clear_bit(), this function is non-atomic. If it is called on the same
37 * region of memory concurrently, the effect may be that only one operation
38 * succeeds.
39 */
__clear_bit(long nr,volatile unsigned long * addr)40 static inline void __clear_bit(long nr, volatile unsigned long *addr)
41 {
42 instrument_write(addr + BIT_WORD(nr), sizeof(long));
43 arch___clear_bit(nr, addr);
44 }
45
46 /**
47 * __change_bit - Toggle a bit in memory
48 * @nr: the bit to change
49 * @addr: the address to start counting from
50 *
51 * Unlike change_bit(), this function is non-atomic. If it is called on the same
52 * region of memory concurrently, the effect may be that only one operation
53 * succeeds.
54 */
__change_bit(long nr,volatile unsigned long * addr)55 static inline void __change_bit(long nr, volatile unsigned long *addr)
56 {
57 instrument_write(addr + BIT_WORD(nr), sizeof(long));
58 arch___change_bit(nr, addr);
59 }
60
__instrument_read_write_bitop(long nr,volatile unsigned long * addr)61 static inline void __instrument_read_write_bitop(long nr, volatile unsigned long *addr)
62 {
63 if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC)) {
64 /*
65 * We treat non-atomic read-write bitops a little more special.
66 * Given the operations here only modify a single bit, assuming
67 * non-atomicity of the writer is sufficient may be reasonable
68 * for certain usage (and follows the permissible nature of the
69 * assume-plain-writes-atomic rule):
70 * 1. report read-modify-write races -> check read;
71 * 2. do not report races with marked readers, but do report
72 * races with unmarked readers -> check "atomic" write.
73 */
74 kcsan_check_read(addr + BIT_WORD(nr), sizeof(long));
75 /*
76 * Use generic write instrumentation, in case other sanitizers
77 * or tools are enabled alongside KCSAN.
78 */
79 instrument_write(addr + BIT_WORD(nr), sizeof(long));
80 } else {
81 instrument_read_write(addr + BIT_WORD(nr), sizeof(long));
82 }
83 }
84
85 /**
86 * __test_and_set_bit - Set a bit and return its old value
87 * @nr: Bit to set
88 * @addr: Address to count from
89 *
90 * This operation is non-atomic. If two instances of this operation race, one
91 * can appear to succeed but actually fail.
92 */
__test_and_set_bit(long nr,volatile unsigned long * addr)93 static inline bool __test_and_set_bit(long nr, volatile unsigned long *addr)
94 {
95 __instrument_read_write_bitop(nr, addr);
96 return arch___test_and_set_bit(nr, addr);
97 }
98
99 /**
100 * __test_and_clear_bit - Clear a bit and return its old value
101 * @nr: Bit to clear
102 * @addr: Address to count from
103 *
104 * This operation is non-atomic. If two instances of this operation race, one
105 * can appear to succeed but actually fail.
106 */
__test_and_clear_bit(long nr,volatile unsigned long * addr)107 static inline bool __test_and_clear_bit(long nr, volatile unsigned long *addr)
108 {
109 __instrument_read_write_bitop(nr, addr);
110 return arch___test_and_clear_bit(nr, addr);
111 }
112
113 /**
114 * __test_and_change_bit - Change a bit and return its old value
115 * @nr: Bit to change
116 * @addr: Address to count from
117 *
118 * This operation is non-atomic. If two instances of this operation race, one
119 * can appear to succeed but actually fail.
120 */
__test_and_change_bit(long nr,volatile unsigned long * addr)121 static inline bool __test_and_change_bit(long nr, volatile unsigned long *addr)
122 {
123 __instrument_read_write_bitop(nr, addr);
124 return arch___test_and_change_bit(nr, addr);
125 }
126
127 /**
128 * test_bit - Determine whether a bit is set
129 * @nr: bit number to test
130 * @addr: Address to start counting from
131 */
test_bit(long nr,const volatile unsigned long * addr)132 static inline bool test_bit(long nr, const volatile unsigned long *addr)
133 {
134 instrument_atomic_read(addr + BIT_WORD(nr), sizeof(long));
135 return arch_test_bit(nr, addr);
136 }
137
138 #endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H */
139