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- /* SPDX-License-Identifier: GPL-2.0-only */
- /*
- * A tagged pointer implementation
- *
- * Copyright (C) 2018 Gao Xiang <gaoxiang25@huawei.com>
- */
- #ifndef __EROFS_FS_TAGPTR_H
- #define __EROFS_FS_TAGPTR_H
- #include <linux/types.h>
- #include <linux/build_bug.h>
- /*
- * the name of tagged pointer types are tagptr{1, 2, 3...}_t
- * avoid directly using the internal structs __tagptr{1, 2, 3...}
- */
- #define __MAKE_TAGPTR(n) \
- typedef struct __tagptr##n { \
- uintptr_t v; \
- } tagptr##n##_t;
- __MAKE_TAGPTR(1)
- __MAKE_TAGPTR(2)
- __MAKE_TAGPTR(3)
- __MAKE_TAGPTR(4)
- #undef __MAKE_TAGPTR
- extern void __compiletime_error("bad tagptr tags")
- __bad_tagptr_tags(void);
- extern void __compiletime_error("bad tagptr type")
- __bad_tagptr_type(void);
- /* fix the broken usage of "#define tagptr2_t tagptr3_t" by users */
- #define __tagptr_mask_1(ptr, n) \
- __builtin_types_compatible_p(typeof(ptr), struct __tagptr##n) ? \
- (1UL << (n)) - 1 :
- #define __tagptr_mask(ptr) (\
- __tagptr_mask_1(ptr, 1) ( \
- __tagptr_mask_1(ptr, 2) ( \
- __tagptr_mask_1(ptr, 3) ( \
- __tagptr_mask_1(ptr, 4) ( \
- __bad_tagptr_type(), 0)))))
- /* generate a tagged pointer from a raw value */
- #define tagptr_init(type, val) \
- ((typeof(type)){ .v = (uintptr_t)(val) })
- /*
- * directly cast a tagged pointer to the native pointer type, which
- * could be used for backward compatibility of existing code.
- */
- #define tagptr_cast_ptr(tptr) ((void *)(tptr).v)
- /* encode tagged pointers */
- #define tagptr_fold(type, ptr, _tags) ({ \
- const typeof(_tags) tags = (_tags); \
- if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(type))) \
- __bad_tagptr_tags(); \
- tagptr_init(type, (uintptr_t)(ptr) | tags); })
- /* decode tagged pointers */
- #define tagptr_unfold_ptr(tptr) \
- ((void *)((tptr).v & ~__tagptr_mask(tptr)))
- #define tagptr_unfold_tags(tptr) \
- ((tptr).v & __tagptr_mask(tptr))
- /* operations for the tagger pointer */
- #define tagptr_eq(_tptr1, _tptr2) ({ \
- typeof(_tptr1) tptr1 = (_tptr1); \
- typeof(_tptr2) tptr2 = (_tptr2); \
- (void)(&tptr1 == &tptr2); \
- (tptr1).v == (tptr2).v; })
- /* lock-free CAS operation */
- #define tagptr_cmpxchg(_ptptr, _o, _n) ({ \
- typeof(_ptptr) ptptr = (_ptptr); \
- typeof(_o) o = (_o); \
- typeof(_n) n = (_n); \
- (void)(&o == &n); \
- (void)(&o == ptptr); \
- tagptr_init(o, cmpxchg(&ptptr->v, o.v, n.v)); })
- /* wrap WRITE_ONCE if atomic update is needed */
- #define tagptr_replace_tags(_ptptr, tags) ({ \
- typeof(_ptptr) ptptr = (_ptptr); \
- *ptptr = tagptr_fold(*ptptr, tagptr_unfold_ptr(*ptptr), tags); \
- *ptptr; })
- #define tagptr_set_tags(_ptptr, _tags) ({ \
- typeof(_ptptr) ptptr = (_ptptr); \
- const typeof(_tags) tags = (_tags); \
- if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(*ptptr))) \
- __bad_tagptr_tags(); \
- ptptr->v |= tags; \
- *ptptr; })
- #define tagptr_clear_tags(_ptptr, _tags) ({ \
- typeof(_ptptr) ptptr = (_ptptr); \
- const typeof(_tags) tags = (_tags); \
- if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(*ptptr))) \
- __bad_tagptr_tags(); \
- ptptr->v &= ~tags; \
- *ptptr; })
- #endif /* __EROFS_FS_TAGPTR_H */
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