1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_BITMAP_H
3#define __LINUX_BITMAP_H
4
5#ifndef __ASSEMBLY__
6
7#include <linux/align.h>
8#include <linux/bitops.h>
9#include <linux/find.h>
10#include <linux/limits.h>
11#include <linux/string.h>
12#include <linux/types.h>
13
14struct device;
15
16/*
17 * bitmaps provide bit arrays that consume one or more unsigned
18 * longs. The bitmap interface and available operations are listed
19 * here, in bitmap.h
20 *
21 * Function implementations generic to all architectures are in
22 * lib/bitmap.c. Functions implementations that are architecture
23 * specific are in various include/asm-<arch>/bitops.h headers
24 * and other arch/<arch> specific files.
25 *
26 * See lib/bitmap.c for more details.
27 */
28
29/**
30 * DOC: bitmap overview
31 *
32 * The available bitmap operations and their rough meaning in the
33 * case that the bitmap is a single unsigned long are thus:
34 *
35 * The generated code is more efficient when nbits is known at
36 * compile-time and at most BITS_PER_LONG.
37 *
38 * ::
39 *
40 * bitmap_zero(dst, nbits) *dst = 0UL
41 * bitmap_fill(dst, nbits) *dst = ~0UL
42 * bitmap_copy(dst, src, nbits) *dst = *src
43 * bitmap_and(dst, src1, src2, nbits) *dst = *src1 & *src2
44 * bitmap_or(dst, src1, src2, nbits) *dst = *src1 | *src2
45 * bitmap_xor(dst, src1, src2, nbits) *dst = *src1 ^ *src2
46 * bitmap_andnot(dst, src1, src2, nbits) *dst = *src1 & ~(*src2)
47 * bitmap_complement(dst, src, nbits) *dst = ~(*src)
48 * bitmap_equal(src1, src2, nbits) Are *src1 and *src2 equal?
49 * bitmap_intersects(src1, src2, nbits) Do *src1 and *src2 overlap?
50 * bitmap_subset(src1, src2, nbits) Is *src1 a subset of *src2?
51 * bitmap_empty(src, nbits) Are all bits zero in *src?
52 * bitmap_full(src, nbits) Are all bits set in *src?
53 * bitmap_weight(src, nbits) Hamming Weight: number set bits
54 * bitmap_weight_and(src1, src2, nbits) Hamming Weight of and'ed bitmap
55 * bitmap_set(dst, pos, nbits) Set specified bit area
56 * bitmap_clear(dst, pos, nbits) Clear specified bit area
57 * bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free area
58 * bitmap_find_next_zero_area_off(buf, len, pos, n, mask, mask_off) as above
59 * bitmap_shift_right(dst, src, n, nbits) *dst = *src >> n
60 * bitmap_shift_left(dst, src, n, nbits) *dst = *src << n
61 * bitmap_cut(dst, src, first, n, nbits) Cut n bits from first, copy rest
62 * bitmap_replace(dst, old, new, mask, nbits) *dst = (*old & ~(*mask)) | (*new & *mask)
63 * bitmap_remap(dst, src, old, new, nbits) *dst = map(old, new)(src)
64 * bitmap_bitremap(oldbit, old, new, nbits) newbit = map(old, new)(oldbit)
65 * bitmap_onto(dst, orig, relmap, nbits) *dst = orig relative to relmap
66 * bitmap_fold(dst, orig, sz, nbits) dst bits = orig bits mod sz
67 * bitmap_parse(buf, buflen, dst, nbits) Parse bitmap dst from kernel buf
68 * bitmap_parse_user(ubuf, ulen, dst, nbits) Parse bitmap dst from user buf
69 * bitmap_parselist(buf, dst, nbits) Parse bitmap dst from kernel buf
70 * bitmap_parselist_user(buf, dst, nbits) Parse bitmap dst from user buf
71 * bitmap_find_free_region(bitmap, bits, order) Find and allocate bit region
72 * bitmap_release_region(bitmap, pos, order) Free specified bit region
73 * bitmap_allocate_region(bitmap, pos, order) Allocate specified bit region
74 * bitmap_from_arr32(dst, buf, nbits) Copy nbits from u32[] buf to dst
75 * bitmap_from_arr64(dst, buf, nbits) Copy nbits from u64[] buf to dst
76 * bitmap_to_arr32(buf, src, nbits) Copy nbits from buf to u32[] dst
77 * bitmap_to_arr64(buf, src, nbits) Copy nbits from buf to u64[] dst
78 * bitmap_get_value8(map, start) Get 8bit value from map at start
79 * bitmap_set_value8(map, value, start) Set 8bit value to map at start
80 *
81 * Note, bitmap_zero() and bitmap_fill() operate over the region of
82 * unsigned longs, that is, bits behind bitmap till the unsigned long
83 * boundary will be zeroed or filled as well. Consider to use
84 * bitmap_clear() or bitmap_set() to make explicit zeroing or filling
85 * respectively.
86 */
87
88/**
89 * DOC: bitmap bitops
90 *
91 * Also the following operations in asm/bitops.h apply to bitmaps.::
92 *
93 * set_bit(bit, addr) *addr |= bit
94 * clear_bit(bit, addr) *addr &= ~bit
95 * change_bit(bit, addr) *addr ^= bit
96 * test_bit(bit, addr) Is bit set in *addr?
97 * test_and_set_bit(bit, addr) Set bit and return old value
98 * test_and_clear_bit(bit, addr) Clear bit and return old value
99 * test_and_change_bit(bit, addr) Change bit and return old value
100 * find_first_zero_bit(addr, nbits) Position first zero bit in *addr
101 * find_first_bit(addr, nbits) Position first set bit in *addr
102 * find_next_zero_bit(addr, nbits, bit)
103 * Position next zero bit in *addr >= bit
104 * find_next_bit(addr, nbits, bit) Position next set bit in *addr >= bit
105 * find_next_and_bit(addr1, addr2, nbits, bit)
106 * Same as find_next_bit, but in
107 * (*addr1 & *addr2)
108 *
109 */
110
111/**
112 * DOC: declare bitmap
113 * The DECLARE_BITMAP(name,bits) macro, in linux/types.h, can be used
114 * to declare an array named 'name' of just enough unsigned longs to
115 * contain all bit positions from 0 to 'bits' - 1.
116 */
117
118/*
119 * Allocation and deallocation of bitmap.
120 * Provided in lib/bitmap.c to avoid circular dependency.
121 */
122unsigned long *bitmap_alloc(unsigned int nbits, gfp_t flags);
123unsigned long *bitmap_zalloc(unsigned int nbits, gfp_t flags);
124unsigned long *bitmap_alloc_node(unsigned int nbits, gfp_t flags, int node);
125unsigned long *bitmap_zalloc_node(unsigned int nbits, gfp_t flags, int node);
126void bitmap_free(const unsigned long *bitmap);
127
128/* Managed variants of the above. */
129unsigned long *devm_bitmap_alloc(struct device *dev,
130 unsigned int nbits, gfp_t flags);
131unsigned long *devm_bitmap_zalloc(struct device *dev,
132 unsigned int nbits, gfp_t flags);
133
134/*
135 * lib/bitmap.c provides these functions:
136 */
137
138bool __bitmap_equal(const unsigned long *bitmap1,
139 const unsigned long *bitmap2, unsigned int nbits);
140bool __pure __bitmap_or_equal(const unsigned long *src1,
141 const unsigned long *src2,
142 const unsigned long *src3,
143 unsigned int nbits);
144void __bitmap_complement(unsigned long *dst, const unsigned long *src,
145 unsigned int nbits);
146void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
147 unsigned int shift, unsigned int nbits);
148void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
149 unsigned int shift, unsigned int nbits);
150void bitmap_cut(unsigned long *dst, const unsigned long *src,
151 unsigned int first, unsigned int cut, unsigned int nbits);
152bool __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
153 const unsigned long *bitmap2, unsigned int nbits);
154void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
155 const unsigned long *bitmap2, unsigned int nbits);
156void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
157 const unsigned long *bitmap2, unsigned int nbits);
158bool __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
159 const unsigned long *bitmap2, unsigned int nbits);
160void __bitmap_replace(unsigned long *dst,
161 const unsigned long *old, const unsigned long *new,
162 const unsigned long *mask, unsigned int nbits);
163bool __bitmap_intersects(const unsigned long *bitmap1,
164 const unsigned long *bitmap2, unsigned int nbits);
165bool __bitmap_subset(const unsigned long *bitmap1,
166 const unsigned long *bitmap2, unsigned int nbits);
167unsigned int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
168unsigned int __bitmap_weight_and(const unsigned long *bitmap1,
169 const unsigned long *bitmap2, unsigned int nbits);
170void __bitmap_set(unsigned long *map, unsigned int start, int len);
171void __bitmap_clear(unsigned long *map, unsigned int start, int len);
172
173unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
174 unsigned long size,
175 unsigned long start,
176 unsigned int nr,
177 unsigned long align_mask,
178 unsigned long align_offset);
179
180/**
181 * bitmap_find_next_zero_area - find a contiguous aligned zero area
182 * @map: The address to base the search on
183 * @size: The bitmap size in bits
184 * @start: The bitnumber to start searching at
185 * @nr: The number of zeroed bits we're looking for
186 * @align_mask: Alignment mask for zero area
187 *
188 * The @align_mask should be one less than a power of 2; the effect is that
189 * the bit offset of all zero areas this function finds is multiples of that
190 * power of 2. A @align_mask of 0 means no alignment is required.
191 */
192static inline unsigned long
193bitmap_find_next_zero_area(unsigned long *map,
194 unsigned long size,
195 unsigned long start,
196 unsigned int nr,
197 unsigned long align_mask)
198{
199 return bitmap_find_next_zero_area_off(map, size, start, nr,
200 align_mask, align_offset: 0);
201}
202
203int bitmap_parse(const char *buf, unsigned int buflen,
204 unsigned long *dst, int nbits);
205int bitmap_parse_user(const char __user *ubuf, unsigned int ulen,
206 unsigned long *dst, int nbits);
207int bitmap_parselist(const char *buf, unsigned long *maskp,
208 int nmaskbits);
209int bitmap_parselist_user(const char __user *ubuf, unsigned int ulen,
210 unsigned long *dst, int nbits);
211void bitmap_remap(unsigned long *dst, const unsigned long *src,
212 const unsigned long *old, const unsigned long *new, unsigned int nbits);
213int bitmap_bitremap(int oldbit,
214 const unsigned long *old, const unsigned long *new, int bits);
215void bitmap_onto(unsigned long *dst, const unsigned long *orig,
216 const unsigned long *relmap, unsigned int bits);
217void bitmap_fold(unsigned long *dst, const unsigned long *orig,
218 unsigned int sz, unsigned int nbits);
219int bitmap_find_free_region(unsigned long *bitmap, unsigned int bits, int order);
220void bitmap_release_region(unsigned long *bitmap, unsigned int pos, int order);
221int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order);
222
223#ifdef __BIG_ENDIAN
224void bitmap_copy_le(unsigned long *dst, const unsigned long *src, unsigned int nbits);
225#else
226#define bitmap_copy_le bitmap_copy
227#endif
228int bitmap_print_to_pagebuf(bool list, char *buf,
229 const unsigned long *maskp, int nmaskbits);
230
231extern int bitmap_print_bitmask_to_buf(char *buf, const unsigned long *maskp,
232 int nmaskbits, loff_t off, size_t count);
233
234extern int bitmap_print_list_to_buf(char *buf, const unsigned long *maskp,
235 int nmaskbits, loff_t off, size_t count);
236
237#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
238#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
239
240static inline void bitmap_zero(unsigned long *dst, unsigned int nbits)
241{
242 unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
243
244 if (small_const_nbits(nbits))
245 *dst = 0;
246 else
247 memset(s: dst, c: 0, n: len);
248}
249
250static inline void bitmap_fill(unsigned long *dst, unsigned int nbits)
251{
252 unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
253
254 if (small_const_nbits(nbits))
255 *dst = ~0UL;
256 else
257 memset(s: dst, c: 0xff, n: len);
258}
259
260static inline void bitmap_copy(unsigned long *dst, const unsigned long *src,
261 unsigned int nbits)
262{
263 unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
264
265 if (small_const_nbits(nbits))
266 *dst = *src;
267 else
268 memcpy(to: dst, from: src, len);
269}
270
271/*
272 * Copy bitmap and clear tail bits in last word.
273 */
274static inline void bitmap_copy_clear_tail(unsigned long *dst,
275 const unsigned long *src, unsigned int nbits)
276{
277 bitmap_copy(dst, src, nbits);
278 if (nbits % BITS_PER_LONG)
279 dst[nbits / BITS_PER_LONG] &= BITMAP_LAST_WORD_MASK(nbits);
280}
281
282/*
283 * On 32-bit systems bitmaps are represented as u32 arrays internally. On LE64
284 * machines the order of hi and lo parts of numbers match the bitmap structure.
285 * In both cases conversion is not needed when copying data from/to arrays of
286 * u32. But in LE64 case, typecast in bitmap_copy_clear_tail() may lead
287 * to out-of-bound access. To avoid that, both LE and BE variants of 64-bit
288 * architectures are not using bitmap_copy_clear_tail().
289 */
290#if BITS_PER_LONG == 64
291void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf,
292 unsigned int nbits);
293void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap,
294 unsigned int nbits);
295#else
296#define bitmap_from_arr32(bitmap, buf, nbits) \
297 bitmap_copy_clear_tail((unsigned long *) (bitmap), \
298 (const unsigned long *) (buf), (nbits))
299#define bitmap_to_arr32(buf, bitmap, nbits) \
300 bitmap_copy_clear_tail((unsigned long *) (buf), \
301 (const unsigned long *) (bitmap), (nbits))
302#endif
303
304/*
305 * On 64-bit systems bitmaps are represented as u64 arrays internally. On LE32
306 * machines the order of hi and lo parts of numbers match the bitmap structure.
307 * In both cases conversion is not needed when copying data from/to arrays of
308 * u64.
309 */
310#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN)
311void bitmap_from_arr64(unsigned long *bitmap, const u64 *buf, unsigned int nbits);
312void bitmap_to_arr64(u64 *buf, const unsigned long *bitmap, unsigned int nbits);
313#else
314#define bitmap_from_arr64(bitmap, buf, nbits) \
315 bitmap_copy_clear_tail((unsigned long *)(bitmap), (const unsigned long *)(buf), (nbits))
316#define bitmap_to_arr64(buf, bitmap, nbits) \
317 bitmap_copy_clear_tail((unsigned long *)(buf), (const unsigned long *)(bitmap), (nbits))
318#endif
319
320static inline bool bitmap_and(unsigned long *dst, const unsigned long *src1,
321 const unsigned long *src2, unsigned int nbits)
322{
323 if (small_const_nbits(nbits))
324 return (*dst = *src1 & *src2 & BITMAP_LAST_WORD_MASK(nbits)) != 0;
325 return __bitmap_and(dst, bitmap1: src1, bitmap2: src2, nbits);
326}
327
328static inline void bitmap_or(unsigned long *dst, const unsigned long *src1,
329 const unsigned long *src2, unsigned int nbits)
330{
331 if (small_const_nbits(nbits))
332 *dst = *src1 | *src2;
333 else
334 __bitmap_or(dst, bitmap1: src1, bitmap2: src2, nbits);
335}
336
337static inline void bitmap_xor(unsigned long *dst, const unsigned long *src1,
338 const unsigned long *src2, unsigned int nbits)
339{
340 if (small_const_nbits(nbits))
341 *dst = *src1 ^ *src2;
342 else
343 __bitmap_xor(dst, bitmap1: src1, bitmap2: src2, nbits);
344}
345
346static inline bool bitmap_andnot(unsigned long *dst, const unsigned long *src1,
347 const unsigned long *src2, unsigned int nbits)
348{
349 if (small_const_nbits(nbits))
350 return (*dst = *src1 & ~(*src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
351 return __bitmap_andnot(dst, bitmap1: src1, bitmap2: src2, nbits);
352}
353
354static inline void bitmap_complement(unsigned long *dst, const unsigned long *src,
355 unsigned int nbits)
356{
357 if (small_const_nbits(nbits))
358 *dst = ~(*src);
359 else
360 __bitmap_complement(dst, src, nbits);
361}
362
363#ifdef __LITTLE_ENDIAN
364#define BITMAP_MEM_ALIGNMENT 8
365#else
366#define BITMAP_MEM_ALIGNMENT (8 * sizeof(unsigned long))
367#endif
368#define BITMAP_MEM_MASK (BITMAP_MEM_ALIGNMENT - 1)
369
370static inline bool bitmap_equal(const unsigned long *src1,
371 const unsigned long *src2, unsigned int nbits)
372{
373 if (small_const_nbits(nbits))
374 return !((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits));
375 if (__builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
376 IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
377 return !memcmp(src1, src2, nbits / 8);
378 return __bitmap_equal(bitmap1: src1, bitmap2: src2, nbits);
379}
380
381/**
382 * bitmap_or_equal - Check whether the or of two bitmaps is equal to a third
383 * @src1: Pointer to bitmap 1
384 * @src2: Pointer to bitmap 2 will be or'ed with bitmap 1
385 * @src3: Pointer to bitmap 3. Compare to the result of *@src1 | *@src2
386 * @nbits: number of bits in each of these bitmaps
387 *
388 * Returns: True if (*@src1 | *@src2) == *@src3, false otherwise
389 */
390static inline bool bitmap_or_equal(const unsigned long *src1,
391 const unsigned long *src2,
392 const unsigned long *src3,
393 unsigned int nbits)
394{
395 if (!small_const_nbits(nbits))
396 return __bitmap_or_equal(src1, src2, src3, nbits);
397
398 return !(((*src1 | *src2) ^ *src3) & BITMAP_LAST_WORD_MASK(nbits));
399}
400
401static inline bool bitmap_intersects(const unsigned long *src1,
402 const unsigned long *src2,
403 unsigned int nbits)
404{
405 if (small_const_nbits(nbits))
406 return ((*src1 & *src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
407 else
408 return __bitmap_intersects(bitmap1: src1, bitmap2: src2, nbits);
409}
410
411static inline bool bitmap_subset(const unsigned long *src1,
412 const unsigned long *src2, unsigned int nbits)
413{
414 if (small_const_nbits(nbits))
415 return ! ((*src1 & ~(*src2)) & BITMAP_LAST_WORD_MASK(nbits));
416 else
417 return __bitmap_subset(bitmap1: src1, bitmap2: src2, nbits);
418}
419
420static inline bool bitmap_empty(const unsigned long *src, unsigned nbits)
421{
422 if (small_const_nbits(nbits))
423 return ! (*src & BITMAP_LAST_WORD_MASK(nbits));
424
425 return find_first_bit(addr: src, size: nbits) == nbits;
426}
427
428static inline bool bitmap_full(const unsigned long *src, unsigned int nbits)
429{
430 if (small_const_nbits(nbits))
431 return ! (~(*src) & BITMAP_LAST_WORD_MASK(nbits));
432
433 return find_first_zero_bit(addr: src, size: nbits) == nbits;
434}
435
436static __always_inline
437unsigned int bitmap_weight(const unsigned long *src, unsigned int nbits)
438{
439 if (small_const_nbits(nbits))
440 return hweight_long(w: *src & BITMAP_LAST_WORD_MASK(nbits));
441 return __bitmap_weight(bitmap: src, nbits);
442}
443
444static __always_inline
445unsigned long bitmap_weight_and(const unsigned long *src1,
446 const unsigned long *src2, unsigned int nbits)
447{
448 if (small_const_nbits(nbits))
449 return hweight_long(w: *src1 & *src2 & BITMAP_LAST_WORD_MASK(nbits));
450 return __bitmap_weight_and(bitmap1: src1, bitmap2: src2, nbits);
451}
452
453static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
454 unsigned int nbits)
455{
456 if (__builtin_constant_p(nbits) && nbits == 1)
457 __set_bit(start, map);
458 else if (small_const_nbits(start + nbits))
459 *map |= GENMASK(start + nbits - 1, start);
460 else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
461 IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
462 __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
463 IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
464 memset(s: (char *)map + start / 8, c: 0xff, n: nbits / 8);
465 else
466 __bitmap_set(map, start, len: nbits);
467}
468
469static __always_inline void bitmap_clear(unsigned long *map, unsigned int start,
470 unsigned int nbits)
471{
472 if (__builtin_constant_p(nbits) && nbits == 1)
473 __clear_bit(start, map);
474 else if (small_const_nbits(start + nbits))
475 *map &= ~GENMASK(start + nbits - 1, start);
476 else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
477 IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
478 __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
479 IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
480 memset(s: (char *)map + start / 8, c: 0, n: nbits / 8);
481 else
482 __bitmap_clear(map, start, len: nbits);
483}
484
485static inline void bitmap_shift_right(unsigned long *dst, const unsigned long *src,
486 unsigned int shift, unsigned int nbits)
487{
488 if (small_const_nbits(nbits))
489 *dst = (*src & BITMAP_LAST_WORD_MASK(nbits)) >> shift;
490 else
491 __bitmap_shift_right(dst, src, shift, nbits);
492}
493
494static inline void bitmap_shift_left(unsigned long *dst, const unsigned long *src,
495 unsigned int shift, unsigned int nbits)
496{
497 if (small_const_nbits(nbits))
498 *dst = (*src << shift) & BITMAP_LAST_WORD_MASK(nbits);
499 else
500 __bitmap_shift_left(dst, src, shift, nbits);
501}
502
503static inline void bitmap_replace(unsigned long *dst,
504 const unsigned long *old,
505 const unsigned long *new,
506 const unsigned long *mask,
507 unsigned int nbits)
508{
509 if (small_const_nbits(nbits))
510 *dst = (*old & ~(*mask)) | (*new & *mask);
511 else
512 __bitmap_replace(dst, old, new, mask, nbits);
513}
514
515static inline void bitmap_next_set_region(unsigned long *bitmap,
516 unsigned int *rs, unsigned int *re,
517 unsigned int end)
518{
519 *rs = find_next_bit(addr: bitmap, size: end, offset: *rs);
520 *re = find_next_zero_bit(addr: bitmap, size: end, offset: *rs + 1);
521}
522
523/**
524 * BITMAP_FROM_U64() - Represent u64 value in the format suitable for bitmap.
525 * @n: u64 value
526 *
527 * Linux bitmaps are internally arrays of unsigned longs, i.e. 32-bit
528 * integers in 32-bit environment, and 64-bit integers in 64-bit one.
529 *
530 * There are four combinations of endianness and length of the word in linux
531 * ABIs: LE64, BE64, LE32 and BE32.
532 *
533 * On 64-bit kernels 64-bit LE and BE numbers are naturally ordered in
534 * bitmaps and therefore don't require any special handling.
535 *
536 * On 32-bit kernels 32-bit LE ABI orders lo word of 64-bit number in memory
537 * prior to hi, and 32-bit BE orders hi word prior to lo. The bitmap on the
538 * other hand is represented as an array of 32-bit words and the position of
539 * bit N may therefore be calculated as: word #(N/32) and bit #(N%32) in that
540 * word. For example, bit #42 is located at 10th position of 2nd word.
541 * It matches 32-bit LE ABI, and we can simply let the compiler store 64-bit
542 * values in memory as it usually does. But for BE we need to swap hi and lo
543 * words manually.
544 *
545 * With all that, the macro BITMAP_FROM_U64() does explicit reordering of hi and
546 * lo parts of u64. For LE32 it does nothing, and for BE environment it swaps
547 * hi and lo words, as is expected by bitmap.
548 */
549#if __BITS_PER_LONG == 64
550#define BITMAP_FROM_U64(n) (n)
551#else
552#define BITMAP_FROM_U64(n) ((unsigned long) ((u64)(n) & ULONG_MAX)), \
553 ((unsigned long) ((u64)(n) >> 32))
554#endif
555
556/**
557 * bitmap_from_u64 - Check and swap words within u64.
558 * @mask: source bitmap
559 * @dst: destination bitmap
560 *
561 * In 32-bit Big Endian kernel, when using ``(u32 *)(&val)[*]``
562 * to read u64 mask, we will get the wrong word.
563 * That is ``(u32 *)(&val)[0]`` gets the upper 32 bits,
564 * but we expect the lower 32-bits of u64.
565 */
566static inline void bitmap_from_u64(unsigned long *dst, u64 mask)
567{
568 bitmap_from_arr64(dst, &mask, 64);
569}
570
571/**
572 * bitmap_get_value8 - get an 8-bit value within a memory region
573 * @map: address to the bitmap memory region
574 * @start: bit offset of the 8-bit value; must be a multiple of 8
575 *
576 * Returns the 8-bit value located at the @start bit offset within the @src
577 * memory region.
578 */
579static inline unsigned long bitmap_get_value8(const unsigned long *map,
580 unsigned long start)
581{
582 const size_t index = BIT_WORD(start);
583 const unsigned long offset = start % BITS_PER_LONG;
584
585 return (map[index] >> offset) & 0xFF;
586}
587
588/**
589 * bitmap_set_value8 - set an 8-bit value within a memory region
590 * @map: address to the bitmap memory region
591 * @value: the 8-bit value; values wider than 8 bits may clobber bitmap
592 * @start: bit offset of the 8-bit value; must be a multiple of 8
593 */
594static inline void bitmap_set_value8(unsigned long *map, unsigned long value,
595 unsigned long start)
596{
597 const size_t index = BIT_WORD(start);
598 const unsigned long offset = start % BITS_PER_LONG;
599
600 map[index] &= ~(0xFFUL << offset);
601 map[index] |= value << offset;
602}
603
604#endif /* __ASSEMBLY__ */
605
606#endif /* __LINUX_BITMAP_H */
607

source code of linux/include/linux/bitmap.h