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 __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 */
 41static __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 */
 57static __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
 64static __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 */
 96static __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 */
111static __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 */
126static __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 */
138static __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 */
150static __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 */