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-rw-r--r--include/linux/cleanup.h171
1 files changed, 171 insertions, 0 deletions
diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
new file mode 100644
index 000000000..53f1a7a93
--- /dev/null
+++ b/include/linux/cleanup.h
@@ -0,0 +1,171 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_GUARDS_H
+#define __LINUX_GUARDS_H
+
+#include <linux/compiler.h>
+
+/*
+ * DEFINE_FREE(name, type, free):
+ * simple helper macro that defines the required wrapper for a __free()
+ * based cleanup function. @free is an expression using '_T' to access
+ * the variable.
+ *
+ * __free(name):
+ * variable attribute to add a scoped based cleanup to the variable.
+ *
+ * no_free_ptr(var):
+ * like a non-atomic xchg(var, NULL), such that the cleanup function will
+ * be inhibited -- provided it sanely deals with a NULL value.
+ *
+ * return_ptr(p):
+ * returns p while inhibiting the __free().
+ *
+ * Ex.
+ *
+ * DEFINE_FREE(kfree, void *, if (_T) kfree(_T))
+ *
+ * struct obj *p __free(kfree) = kmalloc(...);
+ * if (!p)
+ * return NULL;
+ *
+ * if (!init_obj(p))
+ * return NULL;
+ *
+ * return_ptr(p);
+ */
+
+#define DEFINE_FREE(_name, _type, _free) \
+ static inline void __free_##_name(void *p) { _type _T = *(_type *)p; _free; }
+
+#define __free(_name) __cleanup(__free_##_name)
+
+#define no_free_ptr(p) \
+ ({ __auto_type __ptr = (p); (p) = NULL; __ptr; })
+
+#define return_ptr(p) return no_free_ptr(p)
+
+
+/*
+ * DEFINE_CLASS(name, type, exit, init, init_args...):
+ * helper to define the destructor and constructor for a type.
+ * @exit is an expression using '_T' -- similar to FREE above.
+ * @init is an expression in @init_args resulting in @type
+ *
+ * EXTEND_CLASS(name, ext, init, init_args...):
+ * extends class @name to @name@ext with the new constructor
+ *
+ * CLASS(name, var)(args...):
+ * declare the variable @var as an instance of the named class
+ *
+ * Ex.
+ *
+ * DEFINE_CLASS(fdget, struct fd, fdput(_T), fdget(fd), int fd)
+ *
+ * CLASS(fdget, f)(fd);
+ * if (!f.file)
+ * return -EBADF;
+ *
+ * // use 'f' without concern
+ */
+
+#define DEFINE_CLASS(_name, _type, _exit, _init, _init_args...) \
+typedef _type class_##_name##_t; \
+static inline void class_##_name##_destructor(_type *p) \
+{ _type _T = *p; _exit; } \
+static inline _type class_##_name##_constructor(_init_args) \
+{ _type t = _init; return t; }
+
+#define EXTEND_CLASS(_name, ext, _init, _init_args...) \
+typedef class_##_name##_t class_##_name##ext##_t; \
+static inline void class_##_name##ext##_destructor(class_##_name##_t *p)\
+{ class_##_name##_destructor(p); } \
+static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
+{ class_##_name##_t t = _init; return t; }
+
+#define CLASS(_name, var) \
+ class_##_name##_t var __cleanup(class_##_name##_destructor) = \
+ class_##_name##_constructor
+
+
+/*
+ * DEFINE_GUARD(name, type, lock, unlock):
+ * trivial wrapper around DEFINE_CLASS() above specifically
+ * for locks.
+ *
+ * guard(name):
+ * an anonymous instance of the (guard) class
+ *
+ * scoped_guard (name, args...) { }:
+ * similar to CLASS(name, scope)(args), except the variable (with the
+ * explicit name 'scope') is declard in a for-loop such that its scope is
+ * bound to the next (compound) statement.
+ *
+ */
+
+#define DEFINE_GUARD(_name, _type, _lock, _unlock) \
+ DEFINE_CLASS(_name, _type, _unlock, ({ _lock; _T; }), _type _T)
+
+#define guard(_name) \
+ CLASS(_name, __UNIQUE_ID(guard))
+
+#define scoped_guard(_name, args...) \
+ for (CLASS(_name, scope)(args), \
+ *done = NULL; !done; done = (void *)1)
+
+/*
+ * Additional helper macros for generating lock guards with types, either for
+ * locks that don't have a native type (eg. RCU, preempt) or those that need a
+ * 'fat' pointer (eg. spin_lock_irqsave).
+ *
+ * DEFINE_LOCK_GUARD_0(name, lock, unlock, ...)
+ * DEFINE_LOCK_GUARD_1(name, type, lock, unlock, ...)
+ *
+ * will result in the following type:
+ *
+ * typedef struct {
+ * type *lock; // 'type := void' for the _0 variant
+ * __VA_ARGS__;
+ * } class_##name##_t;
+ *
+ * As above, both _lock and _unlock are statements, except this time '_T' will
+ * be a pointer to the above struct.
+ */
+
+#define __DEFINE_UNLOCK_GUARD(_name, _type, _unlock, ...) \
+typedef struct { \
+ _type *lock; \
+ __VA_ARGS__; \
+} class_##_name##_t; \
+ \
+static inline void class_##_name##_destructor(class_##_name##_t *_T) \
+{ \
+ if (_T->lock) { _unlock; } \
+}
+
+
+#define __DEFINE_LOCK_GUARD_1(_name, _type, _lock) \
+static inline class_##_name##_t class_##_name##_constructor(_type *l) \
+{ \
+ class_##_name##_t _t = { .lock = l }, *_T = &_t; \
+ _lock; \
+ return _t; \
+}
+
+#define __DEFINE_LOCK_GUARD_0(_name, _lock) \
+static inline class_##_name##_t class_##_name##_constructor(void) \
+{ \
+ class_##_name##_t _t = { .lock = (void*)1 }, \
+ *_T __maybe_unused = &_t; \
+ _lock; \
+ return _t; \
+}
+
+#define DEFINE_LOCK_GUARD_1(_name, _type, _lock, _unlock, ...) \
+__DEFINE_UNLOCK_GUARD(_name, _type, _unlock, __VA_ARGS__) \
+__DEFINE_LOCK_GUARD_1(_name, _type, _lock)
+
+#define DEFINE_LOCK_GUARD_0(_name, _lock, _unlock, ...) \
+__DEFINE_UNLOCK_GUARD(_name, void, _unlock, __VA_ARGS__) \
+__DEFINE_LOCK_GUARD_0(_name, _lock)
+
+#endif /* __LINUX_GUARDS_H */