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 */
25 static __always_inline void
26 ___set_bit(unsigned long nr, volatile unsigned long *addr)
27 {
28 instrument_write(addr + BIT_WORD(nr), sizeof(long));
29 arch___set_bit(nr, addr);
30 }
31
32 /**
33 * ___clear_bit - Clears a bit in memory
34 * @nr: the bit to clear
35 * @addr: the address to start counting from
36 *
37 * Unlike clear_bit(), this function is non-atomic. If it is called on the same
38 * region of memory concurrently, the effect may be that only one operation
39 * succeeds.
40 */
41 static __always_inline void
42 ___clear_bit(unsigned long nr, volatile unsigned long *addr)
43 {
44 instrument_write(addr + BIT_WORD(nr), sizeof(long));
45 arch___clear_bit(nr, addr);
46 }
47
48 /**
49 * ___change_bit - Toggle a bit in memory
50 * @nr: the bit to change
51 * @addr: the address to start counting from
52 *
53 * Unlike change_bit(), this function is non-atomic. If it is called on the same
54 * region of memory concurrently, the effect may be that only one operation
55 * succeeds.
56 */
57 static __always_inline void
58 ___change_bit(unsigned long nr, volatile unsigned long *addr)
59 {
60 instrument_write(addr + BIT_WORD(nr), sizeof(long));
61 arch___change_bit(nr, addr);
62 }
63
64 static __always_inline void __instrument_read_write_bitop(long nr, volatile unsigned long *addr)
65 {
66 if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC)) {
67 /*
68 * We treat non-atomic read-write bitops a little more special.
69 * Given the operations here only modify a single bit, assuming
70 * non-atomicity of the writer is sufficient may be reasonable
71 * for certain usage (and follows the permissible nature of the
72 * assume-plain-writes-atomic rule):
73 * 1. report read-modify-write races -> check read;
74 * 2. do not report races with marked readers, but do report
75 * races with unmarked readers -> check "atomic" write.
76 */
77 kcsan_check_read(addr + BIT_WORD(nr), sizeof(long));
78 /*
79 * Use generic write instrumentation, in case other sanitizers
80 * or tools are enabled alongside KCSAN.
81 */
82 instrument_write(addr + BIT_WORD(nr), sizeof(long));
83 } else {
84 instrument_read_write(addr + BIT_WORD(nr), sizeof(long));
85 }
86 }
87
88 /**
89 * ___test_and_set_bit - Set a bit and return its old value
90 * @nr: Bit to set
91 * @addr: Address to count from
92 *
93 * This operation is non-atomic. If two instances of this operation race, one
94 * can appear to succeed but actually fail.
95 */
96 static __always_inline bool
97 ___test_and_set_bit(unsigned long nr, volatile unsigned long *addr)
98 {
99 __instrument_read_write_bitop(nr, addr);
100 return arch___test_and_set_bit(nr, addr);
101 }
102
103 /**
104 * ___test_and_clear_bit - Clear a bit and return its old value
105 * @nr: Bit to clear
106 * @addr: Address to count from
107 *
108 * This operation is non-atomic. If two instances of this operation race, one
109 * can appear to succeed but actually fail.
110 */
111 static __always_inline bool
112 ___test_and_clear_bit(unsigned long nr, volatile unsigned long *addr)
113 {
114 __instrument_read_write_bitop(nr, addr);
115 return arch___test_and_clear_bit(nr, addr);
116 }
117
118 /**
119 * ___test_and_change_bit - Change a bit and return its old value
120 * @nr: Bit to change
121 * @addr: Address to count from
122 *
123 * This operation is non-atomic. If two instances of this operation race, one
124 * can appear to succeed but actually fail.
125 */
126 static __always_inline bool
127 ___test_and_change_bit(unsigned long nr, volatile unsigned long *addr)
128 {
129 __instrument_read_write_bitop(nr, addr);
130 return arch___test_and_change_bit(nr, addr);
131 }
132
133 /**
134 * _test_bit - Determine whether a bit is set
135 * @nr: bit number to test
136 * @addr: Address to start counting from
137 */
138 static __always_inline bool
139 _test_bit(unsigned long nr, const volatile unsigned long *addr)
140 {
141 instrument_atomic_read(addr + BIT_WORD(nr), sizeof(long));
142 return arch_test_bit(nr, addr);
143 }
144
145 /**
146 * _test_bit_acquire - Determine, with acquire semantics, whether a bit is set
147 * @nr: bit number to test
148 * @addr: Address to start counting from
149 */
150 static __always_inline bool
151 _test_bit_acquire(unsigned long nr, const volatile unsigned long *addr)
152 {
153 instrument_atomic_read(addr + BIT_WORD(nr), sizeof(long));
154 return arch_test_bit_acquire(nr, addr);
155 }
156
157 #endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H */
158
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.