1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_GUARDS_H 3 #define __LINUX_GUARDS_H 4 5 #include <linux/compiler.h> 6 7 /* 8 * DEFINE_FREE(name, type, free): 9 * simple helper macro that defines the required wrapper for a __free() 10 * based cleanup function. @free is an expression using '_T' to access 11 * the variable. 12 * 13 * __free(name): 14 * variable attribute to add a scoped based cleanup to the variable. 15 * 16 * no_free_ptr(var): 17 * like a non-atomic xchg(var, NULL), such that the cleanup function will 18 * be inhibited -- provided it sanely deals with a NULL value. 19 * 20 * return_ptr(p): 21 * returns p while inhibiting the __free(). 22 * 23 * Ex. 24 * 25 * DEFINE_FREE(kfree, void *, if (_T) kfree(_T)) 26 * 27 * struct obj *p __free(kfree) = kmalloc(...); 28 * if (!p) 29 * return NULL; 30 * 31 * if (!init_obj(p)) 32 * return NULL; 33 * 34 * return_ptr(p); 35 */ 36 37 #define DEFINE_FREE(_name, _type, _free) \ 38 static inline void __free_##_name(void *p) { _type _T = *(_type *)p; _free; } 39 40 #define __free(_name) __cleanup(__free_##_name) 41 42 #define no_free_ptr(p) \ 43 ({ __auto_type __ptr = (p); (p) = NULL; __ptr; }) 44 45 #define return_ptr(p) return no_free_ptr(p) 46 47 48 /* 49 * DEFINE_CLASS(name, type, exit, init, init_args...): 50 * helper to define the destructor and constructor for a type. 51 * @exit is an expression using '_T' -- similar to FREE above. 52 * @init is an expression in @init_args resulting in @type 53 * 54 * EXTEND_CLASS(name, ext, init, init_args...): 55 * extends class @name to @name@ext with the new constructor 56 * 57 * CLASS(name, var)(args...): 58 * declare the variable @var as an instance of the named class 59 * 60 * Ex. 61 * 62 * DEFINE_CLASS(fdget, struct fd, fdput(_T), fdget(fd), int fd) 63 * 64 * CLASS(fdget, f)(fd); 65 * if (!f.file) 66 * return -EBADF; 67 * 68 * // use 'f' without concern 69 */ 70 71 #define DEFINE_CLASS(_name, _type, _exit, _init, _init_args...) \ 72 typedef _type class_##_name##_t; \ 73 static inline void class_##_name##_destructor(_type *p) \ 74 { _type _T = *p; _exit; } \ 75 static inline _type class_##_name##_constructor(_init_args) \ 76 { _type t = _init; return t; } 77 78 #define EXTEND_CLASS(_name, ext, _init, _init_args...) \ 79 typedef class_##_name##_t class_##_name##ext##_t; \ 80 static inline void class_##_name##ext##_destructor(class_##_name##_t *p)\ 81 { class_##_name##_destructor(p); } \ 82 static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ 83 { class_##_name##_t t = _init; return t; } 84 85 #define CLASS(_name, var) \ 86 class_##_name##_t var __cleanup(class_##_name##_destructor) = \ 87 class_##_name##_constructor 88 89 90 /* 91 * DEFINE_GUARD(name, type, lock, unlock): 92 * trivial wrapper around DEFINE_CLASS() above specifically 93 * for locks. 94 * 95 * guard(name): 96 * an anonymous instance of the (guard) class 97 * 98 * scoped_guard (name, args...) { }: 99 * similar to CLASS(name, scope)(args), except the variable (with the 100 * explicit name 'scope') is declard in a for-loop such that its scope is 101 * bound to the next (compound) statement. 102 * 103 */ 104 105 #define DEFINE_GUARD(_name, _type, _lock, _unlock) \ 106 DEFINE_CLASS(_name, _type, _unlock, ({ _lock; _T; }), _type _T) 107 108 #define guard(_name) \ 109 CLASS(_name, __UNIQUE_ID(guard)) 110 111 #define scoped_guard(_name, args...) \ 112 for (CLASS(_name, scope)(args), \ 113 *done = NULL; !done; done = (void *)1) 114 115 /* 116 * Additional helper macros for generating lock guards with types, either for 117 * locks that don't have a native type (eg. RCU, preempt) or those that need a 118 * 'fat' pointer (eg. spin_lock_irqsave). 119 * 120 * DEFINE_LOCK_GUARD_0(name, lock, unlock, ...) 121 * DEFINE_LOCK_GUARD_1(name, type, lock, unlock, ...) 122 * 123 * will result in the following type: 124 * 125 * typedef struct { 126 * type *lock; // 'type := void' for the _0 variant 127 * __VA_ARGS__; 128 * } class_##name##_t; 129 * 130 * As above, both _lock and _unlock are statements, except this time '_T' will 131 * be a pointer to the above struct. 132 */ 133 134 #define __DEFINE_UNLOCK_GUARD(_name, _type, _unlock, ...) \ 135 typedef struct { \ 136 _type *lock; \ 137 __VA_ARGS__; \ 138 } class_##_name##_t; \ 139 \ 140 static inline void class_##_name##_destructor(class_##_name##_t *_T) \ 141 { \ 142 if (_T->lock) { _unlock; } \ 143 } 144 145 146 #define __DEFINE_LOCK_GUARD_1(_name, _type, _lock) \ 147 static inline class_##_name##_t class_##_name##_constructor(_type *l) \ 148 { \ 149 class_##_name##_t _t = { .lock = l }, *_T = &_t; \ 150 _lock; \ 151 return _t; \ 152 } 153 154 #define __DEFINE_LOCK_GUARD_0(_name, _lock) \ 155 static inline class_##_name##_t class_##_name##_constructor(void) \ 156 { \ 157 class_##_name##_t _t = { .lock = (void*)1 }, \ 158 *_T __maybe_unused = &_t; \ 159 _lock; \ 160 return _t; \ 161 } 162 163 #define DEFINE_LOCK_GUARD_1(_name, _type, _lock, _unlock, ...) \ 164 __DEFINE_UNLOCK_GUARD(_name, _type, _unlock, __VA_ARGS__) \ 165 __DEFINE_LOCK_GUARD_1(_name, _type, _lock) 166 167 #define DEFINE_LOCK_GUARD_0(_name, _lock, _unlock, ...) \ 168 __DEFINE_UNLOCK_GUARD(_name, void, _unlock, __VA_ARGS__) \ 169 __DEFINE_LOCK_GUARD_0(_name, _lock) 170 171 #endif /* __LINUX_GUARDS_H */ 172