projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 29b24f6c GX |
1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
| 2 | /* | |
| 3 | * A tagged pointer implementation | |
| b8b58b32 | 4 | */ |
| 57b78c9f GX |
5 | #ifndef __EROFS_FS_TAGPTR_H |
| 6 | #define __EROFS_FS_TAGPTR_H | |
| b8b58b32 GX |
7 | |
| 8 | #include <linux/types.h> | |
| 9 | #include <linux/build_bug.h> | |
| 10 | ||
| 11 | /* | |
| 12 | * the name of tagged pointer types are tagptr{1, 2, 3...}_t | |
| 13 | * avoid directly using the internal structs __tagptr{1, 2, 3...} | |
| 14 | */ | |
| 15 | #define __MAKE_TAGPTR(n) \ | |
| 16 | typedef struct __tagptr##n { \ | |
| 17 | uintptr_t v; \ | |
| 18 | } tagptr##n##_t; | |
| 19 | ||
| 20 | __MAKE_TAGPTR(1) | |
| 21 | __MAKE_TAGPTR(2) | |
| 22 | __MAKE_TAGPTR(3) | |
| 23 | __MAKE_TAGPTR(4) | |
| 24 | ||
| 25 | #undef __MAKE_TAGPTR | |
| 26 | ||
| 27 | extern void __compiletime_error("bad tagptr tags") | |
| 28 | __bad_tagptr_tags(void); | |
| 29 | ||
| 30 | extern void __compiletime_error("bad tagptr type") | |
| 31 | __bad_tagptr_type(void); | |
| 32 | ||
| 33 | /* fix the broken usage of "#define tagptr2_t tagptr3_t" by users */ | |
| 34 | #define __tagptr_mask_1(ptr, n) \ | |
| 35 | __builtin_types_compatible_p(typeof(ptr), struct __tagptr##n) ? \ | |
| 36 | (1UL << (n)) - 1 : | |
| 37 | ||
| 38 | #define __tagptr_mask(ptr) (\ | |
| 39 | __tagptr_mask_1(ptr, 1) ( \ | |
| 40 | __tagptr_mask_1(ptr, 2) ( \ | |
| 41 | __tagptr_mask_1(ptr, 3) ( \ | |
| 42 | __tagptr_mask_1(ptr, 4) ( \ | |
| 43 | __bad_tagptr_type(), 0))))) | |
| 44 | ||
| 45 | /* generate a tagged pointer from a raw value */ | |
| 46 | #define tagptr_init(type, val) \ | |
| 47 | ((typeof(type)){ .v = (uintptr_t)(val) }) | |
| 48 | ||
| 49 | /* | |
| 50 | * directly cast a tagged pointer to the native pointer type, which | |
| 51 | * could be used for backward compatibility of existing code. | |
| 52 | */ | |
| 53 | #define tagptr_cast_ptr(tptr) ((void *)(tptr).v) | |
| 54 | ||
| 55 | /* encode tagged pointers */ | |
| 56 | #define tagptr_fold(type, ptr, _tags) ({ \ | |
| 57 | const typeof(_tags) tags = (_tags); \ | |
| 58 | if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(type))) \ | |
| 59 | __bad_tagptr_tags(); \ | |
| 60 | tagptr_init(type, (uintptr_t)(ptr) | tags); }) | |
| 61 | ||
| 62 | /* decode tagged pointers */ | |
| 63 | #define tagptr_unfold_ptr(tptr) \ | |
| 64 | ((void *)((tptr).v & ~__tagptr_mask(tptr))) | |
| 65 | ||
| 66 | #define tagptr_unfold_tags(tptr) \ | |
| 67 | ((tptr).v & __tagptr_mask(tptr)) | |
| 68 | ||
| 69 | /* operations for the tagger pointer */ | |
| 70 | #define tagptr_eq(_tptr1, _tptr2) ({ \ | |
| 71 | typeof(_tptr1) tptr1 = (_tptr1); \ | |
| 72 | typeof(_tptr2) tptr2 = (_tptr2); \ | |
| 73 | (void)(&tptr1 == &tptr2); \ | |
| 74 | (tptr1).v == (tptr2).v; }) | |
| 75 | ||
| 76 | /* lock-free CAS operation */ | |
| 77 | #define tagptr_cmpxchg(_ptptr, _o, _n) ({ \ | |
| 78 | typeof(_ptptr) ptptr = (_ptptr); \ | |
| 79 | typeof(_o) o = (_o); \ | |
| 80 | typeof(_n) n = (_n); \ | |
| 81 | (void)(&o == &n); \ | |
| 82 | (void)(&o == ptptr); \ | |
| 83 | tagptr_init(o, cmpxchg(&ptptr->v, o.v, n.v)); }) | |
| 84 | ||
| 85 | /* wrap WRITE_ONCE if atomic update is needed */ | |
| 86 | #define tagptr_replace_tags(_ptptr, tags) ({ \ | |
| 87 | typeof(_ptptr) ptptr = (_ptptr); \ | |
| 88 | *ptptr = tagptr_fold(*ptptr, tagptr_unfold_ptr(*ptptr), tags); \ | |
| 89 | *ptptr; }) | |
| 90 | ||
| 91 | #define tagptr_set_tags(_ptptr, _tags) ({ \ | |
| 92 | typeof(_ptptr) ptptr = (_ptptr); \ | |
| 93 | const typeof(_tags) tags = (_tags); \ | |
| 94 | if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(*ptptr))) \ | |
| 95 | __bad_tagptr_tags(); \ | |
| 96 | ptptr->v |= tags; \ | |
| 97 | *ptptr; }) | |
| 98 | ||
| 99 | #define tagptr_clear_tags(_ptptr, _tags) ({ \ | |
| 100 | typeof(_ptptr) ptptr = (_ptptr); \ | |
| 101 | const typeof(_tags) tags = (_tags); \ | |
| 102 | if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(*ptptr))) \ | |
| 103 | __bad_tagptr_tags(); \ | |
| 104 | ptptr->v &= ~tags; \ | |
| 105 | *ptptr; }) | |
| 106 | ||
| 57b78c9f | 107 | #endif /* __EROFS_FS_TAGPTR_H */ |