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 */
25static 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 */
40static 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 */
55static 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
61static 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 */
93static 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 */
107static 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 */
121static 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 */
132static 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