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