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