xref: /openbmc/linux/lib/bitmap.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  * lib/bitmap.c
3  * Helper functions for bitmap.h.
4  *
5  * This source code is licensed under the GNU General Public License,
6  * Version 2.  See the file COPYING for more details.
7  */
8 #include <linux/module.h>
9 #include <linux/ctype.h>
10 #include <linux/errno.h>
11 #include <linux/bitmap.h>
12 #include <linux/bitops.h>
13 #include <asm/uaccess.h>
14 
15 /*
16  * bitmaps provide an array of bits, implemented using an an
17  * array of unsigned longs.  The number of valid bits in a
18  * given bitmap does _not_ need to be an exact multiple of
19  * BITS_PER_LONG.
20  *
21  * The possible unused bits in the last, partially used word
22  * of a bitmap are 'don't care'.  The implementation makes
23  * no particular effort to keep them zero.  It ensures that
24  * their value will not affect the results of any operation.
25  * The bitmap operations that return Boolean (bitmap_empty,
26  * for example) or scalar (bitmap_weight, for example) results
27  * carefully filter out these unused bits from impacting their
28  * results.
29  *
30  * These operations actually hold to a slightly stronger rule:
31  * if you don't input any bitmaps to these ops that have some
32  * unused bits set, then they won't output any set unused bits
33  * in output bitmaps.
34  *
35  * The byte ordering of bitmaps is more natural on little
36  * endian architectures.  See the big-endian headers
37  * include/asm-ppc64/bitops.h and include/asm-s390/bitops.h
38  * for the best explanations of this ordering.
39  */
40 
41 int __bitmap_empty(const unsigned long *bitmap, int bits)
42 {
43 	int k, lim = bits/BITS_PER_LONG;
44 	for (k = 0; k < lim; ++k)
45 		if (bitmap[k])
46 			return 0;
47 
48 	if (bits % BITS_PER_LONG)
49 		if (bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
50 			return 0;
51 
52 	return 1;
53 }
54 EXPORT_SYMBOL(__bitmap_empty);
55 
56 int __bitmap_full(const unsigned long *bitmap, int bits)
57 {
58 	int k, lim = bits/BITS_PER_LONG;
59 	for (k = 0; k < lim; ++k)
60 		if (~bitmap[k])
61 			return 0;
62 
63 	if (bits % BITS_PER_LONG)
64 		if (~bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
65 			return 0;
66 
67 	return 1;
68 }
69 EXPORT_SYMBOL(__bitmap_full);
70 
71 int __bitmap_equal(const unsigned long *bitmap1,
72 		const unsigned long *bitmap2, int bits)
73 {
74 	int k, lim = bits/BITS_PER_LONG;
75 	for (k = 0; k < lim; ++k)
76 		if (bitmap1[k] != bitmap2[k])
77 			return 0;
78 
79 	if (bits % BITS_PER_LONG)
80 		if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
81 			return 0;
82 
83 	return 1;
84 }
85 EXPORT_SYMBOL(__bitmap_equal);
86 
87 void __bitmap_complement(unsigned long *dst, const unsigned long *src, int bits)
88 {
89 	int k, lim = bits/BITS_PER_LONG;
90 	for (k = 0; k < lim; ++k)
91 		dst[k] = ~src[k];
92 
93 	if (bits % BITS_PER_LONG)
94 		dst[k] = ~src[k] & BITMAP_LAST_WORD_MASK(bits);
95 }
96 EXPORT_SYMBOL(__bitmap_complement);
97 
98 /*
99  * __bitmap_shift_right - logical right shift of the bits in a bitmap
100  *   @dst - destination bitmap
101  *   @src - source bitmap
102  *   @nbits - shift by this many bits
103  *   @bits - bitmap size, in bits
104  *
105  * Shifting right (dividing) means moving bits in the MS -> LS bit
106  * direction.  Zeros are fed into the vacated MS positions and the
107  * LS bits shifted off the bottom are lost.
108  */
109 void __bitmap_shift_right(unsigned long *dst,
110 			const unsigned long *src, int shift, int bits)
111 {
112 	int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
113 	int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
114 	unsigned long mask = (1UL << left) - 1;
115 	for (k = 0; off + k < lim; ++k) {
116 		unsigned long upper, lower;
117 
118 		/*
119 		 * If shift is not word aligned, take lower rem bits of
120 		 * word above and make them the top rem bits of result.
121 		 */
122 		if (!rem || off + k + 1 >= lim)
123 			upper = 0;
124 		else {
125 			upper = src[off + k + 1];
126 			if (off + k + 1 == lim - 1 && left)
127 				upper &= mask;
128 		}
129 		lower = src[off + k];
130 		if (left && off + k == lim - 1)
131 			lower &= mask;
132 		dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem;
133 		if (left && k == lim - 1)
134 			dst[k] &= mask;
135 	}
136 	if (off)
137 		memset(&dst[lim - off], 0, off*sizeof(unsigned long));
138 }
139 EXPORT_SYMBOL(__bitmap_shift_right);
140 
141 
142 /*
143  * __bitmap_shift_left - logical left shift of the bits in a bitmap
144  *   @dst - destination bitmap
145  *   @src - source bitmap
146  *   @nbits - shift by this many bits
147  *   @bits - bitmap size, in bits
148  *
149  * Shifting left (multiplying) means moving bits in the LS -> MS
150  * direction.  Zeros are fed into the vacated LS bit positions
151  * and those MS bits shifted off the top are lost.
152  */
153 
154 void __bitmap_shift_left(unsigned long *dst,
155 			const unsigned long *src, int shift, int bits)
156 {
157 	int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
158 	int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
159 	for (k = lim - off - 1; k >= 0; --k) {
160 		unsigned long upper, lower;
161 
162 		/*
163 		 * If shift is not word aligned, take upper rem bits of
164 		 * word below and make them the bottom rem bits of result.
165 		 */
166 		if (rem && k > 0)
167 			lower = src[k - 1];
168 		else
169 			lower = 0;
170 		upper = src[k];
171 		if (left && k == lim - 1)
172 			upper &= (1UL << left) - 1;
173 		dst[k + off] = lower  >> (BITS_PER_LONG - rem) | upper << rem;
174 		if (left && k + off == lim - 1)
175 			dst[k + off] &= (1UL << left) - 1;
176 	}
177 	if (off)
178 		memset(dst, 0, off*sizeof(unsigned long));
179 }
180 EXPORT_SYMBOL(__bitmap_shift_left);
181 
182 void __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
183 				const unsigned long *bitmap2, int bits)
184 {
185 	int k;
186 	int nr = BITS_TO_LONGS(bits);
187 
188 	for (k = 0; k < nr; k++)
189 		dst[k] = bitmap1[k] & bitmap2[k];
190 }
191 EXPORT_SYMBOL(__bitmap_and);
192 
193 void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
194 				const unsigned long *bitmap2, int bits)
195 {
196 	int k;
197 	int nr = BITS_TO_LONGS(bits);
198 
199 	for (k = 0; k < nr; k++)
200 		dst[k] = bitmap1[k] | bitmap2[k];
201 }
202 EXPORT_SYMBOL(__bitmap_or);
203 
204 void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
205 				const unsigned long *bitmap2, int bits)
206 {
207 	int k;
208 	int nr = BITS_TO_LONGS(bits);
209 
210 	for (k = 0; k < nr; k++)
211 		dst[k] = bitmap1[k] ^ bitmap2[k];
212 }
213 EXPORT_SYMBOL(__bitmap_xor);
214 
215 void __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
216 				const unsigned long *bitmap2, int bits)
217 {
218 	int k;
219 	int nr = BITS_TO_LONGS(bits);
220 
221 	for (k = 0; k < nr; k++)
222 		dst[k] = bitmap1[k] & ~bitmap2[k];
223 }
224 EXPORT_SYMBOL(__bitmap_andnot);
225 
226 int __bitmap_intersects(const unsigned long *bitmap1,
227 				const unsigned long *bitmap2, int bits)
228 {
229 	int k, lim = bits/BITS_PER_LONG;
230 	for (k = 0; k < lim; ++k)
231 		if (bitmap1[k] & bitmap2[k])
232 			return 1;
233 
234 	if (bits % BITS_PER_LONG)
235 		if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
236 			return 1;
237 	return 0;
238 }
239 EXPORT_SYMBOL(__bitmap_intersects);
240 
241 int __bitmap_subset(const unsigned long *bitmap1,
242 				const unsigned long *bitmap2, int bits)
243 {
244 	int k, lim = bits/BITS_PER_LONG;
245 	for (k = 0; k < lim; ++k)
246 		if (bitmap1[k] & ~bitmap2[k])
247 			return 0;
248 
249 	if (bits % BITS_PER_LONG)
250 		if ((bitmap1[k] & ~bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
251 			return 0;
252 	return 1;
253 }
254 EXPORT_SYMBOL(__bitmap_subset);
255 
256 #if BITS_PER_LONG == 32
257 int __bitmap_weight(const unsigned long *bitmap, int bits)
258 {
259 	int k, w = 0, lim = bits/BITS_PER_LONG;
260 
261 	for (k = 0; k < lim; k++)
262 		w += hweight32(bitmap[k]);
263 
264 	if (bits % BITS_PER_LONG)
265 		w += hweight32(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));
266 
267 	return w;
268 }
269 #else
270 int __bitmap_weight(const unsigned long *bitmap, int bits)
271 {
272 	int k, w = 0, lim = bits/BITS_PER_LONG;
273 
274 	for (k = 0; k < lim; k++)
275 		w += hweight64(bitmap[k]);
276 
277 	if (bits % BITS_PER_LONG)
278 		w += hweight64(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));
279 
280 	return w;
281 }
282 #endif
283 EXPORT_SYMBOL(__bitmap_weight);
284 
285 /*
286  * Bitmap printing & parsing functions: first version by Bill Irwin,
287  * second version by Paul Jackson, third by Joe Korty.
288  */
289 
290 #define CHUNKSZ				32
291 #define nbits_to_hold_value(val)	fls(val)
292 #define unhex(c)			(isdigit(c) ? (c - '0') : (toupper(c) - 'A' + 10))
293 #define BASEDEC 10		/* fancier cpuset lists input in decimal */
294 
295 /**
296  * bitmap_scnprintf - convert bitmap to an ASCII hex string.
297  * @buf: byte buffer into which string is placed
298  * @buflen: reserved size of @buf, in bytes
299  * @maskp: pointer to bitmap to convert
300  * @nmaskbits: size of bitmap, in bits
301  *
302  * Exactly @nmaskbits bits are displayed.  Hex digits are grouped into
303  * comma-separated sets of eight digits per set.
304  */
305 int bitmap_scnprintf(char *buf, unsigned int buflen,
306 	const unsigned long *maskp, int nmaskbits)
307 {
308 	int i, word, bit, len = 0;
309 	unsigned long val;
310 	const char *sep = "";
311 	int chunksz;
312 	u32 chunkmask;
313 
314 	chunksz = nmaskbits & (CHUNKSZ - 1);
315 	if (chunksz == 0)
316 		chunksz = CHUNKSZ;
317 
318 	i = ALIGN(nmaskbits, CHUNKSZ) - CHUNKSZ;
319 	for (; i >= 0; i -= CHUNKSZ) {
320 		chunkmask = ((1ULL << chunksz) - 1);
321 		word = i / BITS_PER_LONG;
322 		bit = i % BITS_PER_LONG;
323 		val = (maskp[word] >> bit) & chunkmask;
324 		len += scnprintf(buf+len, buflen-len, "%s%0*lx", sep,
325 			(chunksz+3)/4, val);
326 		chunksz = CHUNKSZ;
327 		sep = ",";
328 	}
329 	return len;
330 }
331 EXPORT_SYMBOL(bitmap_scnprintf);
332 
333 /**
334  * bitmap_parse - convert an ASCII hex string into a bitmap.
335  * @buf: pointer to buffer in user space containing string.
336  * @buflen: buffer size in bytes.  If string is smaller than this
337  *    then it must be terminated with a \0.
338  * @maskp: pointer to bitmap array that will contain result.
339  * @nmaskbits: size of bitmap, in bits.
340  *
341  * Commas group hex digits into chunks.  Each chunk defines exactly 32
342  * bits of the resultant bitmask.  No chunk may specify a value larger
343  * than 32 bits (-EOVERFLOW), and if a chunk specifies a smaller value
344  * then leading 0-bits are prepended.  -EINVAL is returned for illegal
345  * characters and for grouping errors such as "1,,5", ",44", "," and "".
346  * Leading and trailing whitespace accepted, but not embedded whitespace.
347  */
348 int bitmap_parse(const char __user *ubuf, unsigned int ubuflen,
349         unsigned long *maskp, int nmaskbits)
350 {
351 	int c, old_c, totaldigits, ndigits, nchunks, nbits;
352 	u32 chunk;
353 
354 	bitmap_zero(maskp, nmaskbits);
355 
356 	nchunks = nbits = totaldigits = c = 0;
357 	do {
358 		chunk = ndigits = 0;
359 
360 		/* Get the next chunk of the bitmap */
361 		while (ubuflen) {
362 			old_c = c;
363 			if (get_user(c, ubuf++))
364 				return -EFAULT;
365 			ubuflen--;
366 			if (isspace(c))
367 				continue;
368 
369 			/*
370 			 * If the last character was a space and the current
371 			 * character isn't '\0', we've got embedded whitespace.
372 			 * This is a no-no, so throw an error.
373 			 */
374 			if (totaldigits && c && isspace(old_c))
375 				return -EINVAL;
376 
377 			/* A '\0' or a ',' signal the end of the chunk */
378 			if (c == '\0' || c == ',')
379 				break;
380 
381 			if (!isxdigit(c))
382 				return -EINVAL;
383 
384 			/*
385 			 * Make sure there are at least 4 free bits in 'chunk'.
386 			 * If not, this hexdigit will overflow 'chunk', so
387 			 * throw an error.
388 			 */
389 			if (chunk & ~((1UL << (CHUNKSZ - 4)) - 1))
390 				return -EOVERFLOW;
391 
392 			chunk = (chunk << 4) | unhex(c);
393 			ndigits++; totaldigits++;
394 		}
395 		if (ndigits == 0)
396 			return -EINVAL;
397 		if (nchunks == 0 && chunk == 0)
398 			continue;
399 
400 		__bitmap_shift_left(maskp, maskp, CHUNKSZ, nmaskbits);
401 		*maskp |= chunk;
402 		nchunks++;
403 		nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ;
404 		if (nbits > nmaskbits)
405 			return -EOVERFLOW;
406 	} while (ubuflen && c == ',');
407 
408 	return 0;
409 }
410 EXPORT_SYMBOL(bitmap_parse);
411 
412 /*
413  * bscnl_emit(buf, buflen, rbot, rtop, bp)
414  *
415  * Helper routine for bitmap_scnlistprintf().  Write decimal number
416  * or range to buf, suppressing output past buf+buflen, with optional
417  * comma-prefix.  Return len of what would be written to buf, if it
418  * all fit.
419  */
420 static inline int bscnl_emit(char *buf, int buflen, int rbot, int rtop, int len)
421 {
422 	if (len > 0)
423 		len += scnprintf(buf + len, buflen - len, ",");
424 	if (rbot == rtop)
425 		len += scnprintf(buf + len, buflen - len, "%d", rbot);
426 	else
427 		len += scnprintf(buf + len, buflen - len, "%d-%d", rbot, rtop);
428 	return len;
429 }
430 
431 /**
432  * bitmap_scnlistprintf - convert bitmap to list format ASCII string
433  * @buf: byte buffer into which string is placed
434  * @buflen: reserved size of @buf, in bytes
435  * @maskp: pointer to bitmap to convert
436  * @nmaskbits: size of bitmap, in bits
437  *
438  * Output format is a comma-separated list of decimal numbers and
439  * ranges.  Consecutively set bits are shown as two hyphen-separated
440  * decimal numbers, the smallest and largest bit numbers set in
441  * the range.  Output format is compatible with the format
442  * accepted as input by bitmap_parselist().
443  *
444  * The return value is the number of characters which would be
445  * generated for the given input, excluding the trailing '\0', as
446  * per ISO C99.
447  */
448 int bitmap_scnlistprintf(char *buf, unsigned int buflen,
449 	const unsigned long *maskp, int nmaskbits)
450 {
451 	int len = 0;
452 	/* current bit is 'cur', most recently seen range is [rbot, rtop] */
453 	int cur, rbot, rtop;
454 
455 	rbot = cur = find_first_bit(maskp, nmaskbits);
456 	while (cur < nmaskbits) {
457 		rtop = cur;
458 		cur = find_next_bit(maskp, nmaskbits, cur+1);
459 		if (cur >= nmaskbits || cur > rtop + 1) {
460 			len = bscnl_emit(buf, buflen, rbot, rtop, len);
461 			rbot = cur;
462 		}
463 	}
464 	return len;
465 }
466 EXPORT_SYMBOL(bitmap_scnlistprintf);
467 
468 /**
469  * bitmap_parselist - convert list format ASCII string to bitmap
470  * @buf: read nul-terminated user string from this buffer
471  * @mask: write resulting mask here
472  * @nmaskbits: number of bits in mask to be written
473  *
474  * Input format is a comma-separated list of decimal numbers and
475  * ranges.  Consecutively set bits are shown as two hyphen-separated
476  * decimal numbers, the smallest and largest bit numbers set in
477  * the range.
478  *
479  * Returns 0 on success, -errno on invalid input strings:
480  *    -EINVAL:   second number in range smaller than first
481  *    -EINVAL:   invalid character in string
482  *    -ERANGE:   bit number specified too large for mask
483  */
484 int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
485 {
486 	unsigned a, b;
487 
488 	bitmap_zero(maskp, nmaskbits);
489 	do {
490 		if (!isdigit(*bp))
491 			return -EINVAL;
492 		b = a = simple_strtoul(bp, (char **)&bp, BASEDEC);
493 		if (*bp == '-') {
494 			bp++;
495 			if (!isdigit(*bp))
496 				return -EINVAL;
497 			b = simple_strtoul(bp, (char **)&bp, BASEDEC);
498 		}
499 		if (!(a <= b))
500 			return -EINVAL;
501 		if (b >= nmaskbits)
502 			return -ERANGE;
503 		while (a <= b) {
504 			set_bit(a, maskp);
505 			a++;
506 		}
507 		if (*bp == ',')
508 			bp++;
509 	} while (*bp != '\0' && *bp != '\n');
510 	return 0;
511 }
512 EXPORT_SYMBOL(bitmap_parselist);
513 
514 /*
515  * bitmap_pos_to_ord(buf, pos, bits)
516  *	@buf: pointer to a bitmap
517  *	@pos: a bit position in @buf (0 <= @pos < @bits)
518  *	@bits: number of valid bit positions in @buf
519  *
520  * Map the bit at position @pos in @buf (of length @bits) to the
521  * ordinal of which set bit it is.  If it is not set or if @pos
522  * is not a valid bit position, map to zero (0).
523  *
524  * If for example, just bits 4 through 7 are set in @buf, then @pos
525  * values 4 through 7 will get mapped to 0 through 3, respectively,
526  * and other @pos values will get mapped to 0.  When @pos value 7
527  * gets mapped to (returns) @ord value 3 in this example, that means
528  * that bit 7 is the 3rd (starting with 0th) set bit in @buf.
529  *
530  * The bit positions 0 through @bits are valid positions in @buf.
531  */
532 static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits)
533 {
534 	int ord = 0;
535 
536 	if (pos >= 0 && pos < bits) {
537 		int i;
538 
539 		for (i = find_first_bit(buf, bits);
540 		     i < pos;
541 		     i = find_next_bit(buf, bits, i + 1))
542 	     		ord++;
543 		if (i > pos)
544 			ord = 0;
545 	}
546 	return ord;
547 }
548 
549 /**
550  * bitmap_ord_to_pos(buf, ord, bits)
551  *	@buf: pointer to bitmap
552  *	@ord: ordinal bit position (n-th set bit, n >= 0)
553  *	@bits: number of valid bit positions in @buf
554  *
555  * Map the ordinal offset of bit @ord in @buf to its position in @buf.
556  * If @ord is not the ordinal offset of a set bit in @buf, map to zero (0).
557  *
558  * If for example, just bits 4 through 7 are set in @buf, then @ord
559  * values 0 through 3 will get mapped to 4 through 7, respectively,
560  * and all other @ord valuds will get mapped to 0.  When @ord value 3
561  * gets mapped to (returns) @pos value 7 in this example, that means
562  * that the 3rd set bit (starting with 0th) is at position 7 in @buf.
563  *
564  * The bit positions 0 through @bits are valid positions in @buf.
565  */
566 static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
567 {
568 	int pos = 0;
569 
570 	if (ord >= 0 && ord < bits) {
571 		int i;
572 
573 		for (i = find_first_bit(buf, bits);
574 		     i < bits && ord > 0;
575 		     i = find_next_bit(buf, bits, i + 1))
576 	     		ord--;
577 		if (i < bits && ord == 0)
578 			pos = i;
579 	}
580 
581 	return pos;
582 }
583 
584 /**
585  * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap
586  *	@src: subset to be remapped
587  *	@dst: remapped result
588  *	@old: defines domain of map
589  *	@new: defines range of map
590  *	@bits: number of bits in each of these bitmaps
591  *
592  * Let @old and @new define a mapping of bit positions, such that
593  * whatever position is held by the n-th set bit in @old is mapped
594  * to the n-th set bit in @new.  In the more general case, allowing
595  * for the possibility that the weight 'w' of @new is less than the
596  * weight of @old, map the position of the n-th set bit in @old to
597  * the position of the m-th set bit in @new, where m == n % w.
598  *
599  * If either of the @old and @new bitmaps are empty, or if@src and @dst
600  * point to the same location, then this routine does nothing.
601  *
602  * The positions of unset bits in @old are mapped to the position of
603  * the first set bit in @new.
604  *
605  * Apply the above specified mapping to @src, placing the result in
606  * @dst, clearing any bits previously set in @dst.
607  *
608  * The resulting value of @dst will have either the same weight as
609  * @src, or less weight in the general case that the mapping wasn't
610  * injective due to the weight of @new being less than that of @old.
611  * The resulting value of @dst will never have greater weight than
612  * that of @src, except perhaps in the case that one of the above
613  * conditions was not met and this routine just returned.
614  *
615  * For example, lets say that @old has bits 4 through 7 set, and
616  * @new has bits 12 through 15 set.  This defines the mapping of bit
617  * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other
618  * bit positions to 12 (the first set bit in @new.  So if say @src
619  * comes into this routine with bits 1, 5 and 7 set, then @dst should
620  * leave with bits 12, 13 and 15 set.
621  */
622 void bitmap_remap(unsigned long *dst, const unsigned long *src,
623 		const unsigned long *old, const unsigned long *new,
624 		int bits)
625 {
626 	int s;
627 
628 	if (bitmap_weight(old, bits) == 0)
629 		return;
630 	if (bitmap_weight(new, bits) == 0)
631 		return;
632 	if (dst == src)		/* following doesn't handle inplace remaps */
633 		return;
634 
635 	bitmap_zero(dst, bits);
636 	for (s = find_first_bit(src, bits);
637 	     s < bits;
638 	     s = find_next_bit(src, bits, s + 1)) {
639 	     	int x = bitmap_pos_to_ord(old, s, bits);
640 		int y = bitmap_ord_to_pos(new, x, bits);
641 		set_bit(y, dst);
642 	}
643 }
644 EXPORT_SYMBOL(bitmap_remap);
645 
646 /**
647  * bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit
648  *	@oldbit - bit position to be mapped
649  *      @old: defines domain of map
650  *      @new: defines range of map
651  *      @bits: number of bits in each of these bitmaps
652  *
653  * Let @old and @new define a mapping of bit positions, such that
654  * whatever position is held by the n-th set bit in @old is mapped
655  * to the n-th set bit in @new.  In the more general case, allowing
656  * for the possibility that the weight 'w' of @new is less than the
657  * weight of @old, map the position of the n-th set bit in @old to
658  * the position of the m-th set bit in @new, where m == n % w.
659  *
660  * The positions of unset bits in @old are mapped to the position of
661  * the first set bit in @new.
662  *
663  * Apply the above specified mapping to bit position @oldbit, returning
664  * the new bit position.
665  *
666  * For example, lets say that @old has bits 4 through 7 set, and
667  * @new has bits 12 through 15 set.  This defines the mapping of bit
668  * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other
669  * bit positions to 12 (the first set bit in @new.  So if say @oldbit
670  * is 5, then this routine returns 13.
671  */
672 int bitmap_bitremap(int oldbit, const unsigned long *old,
673 				const unsigned long *new, int bits)
674 {
675 	int x = bitmap_pos_to_ord(old, oldbit, bits);
676 	return bitmap_ord_to_pos(new, x, bits);
677 }
678 EXPORT_SYMBOL(bitmap_bitremap);
679 
680 /**
681  *	bitmap_find_free_region - find a contiguous aligned mem region
682  *	@bitmap: an array of unsigned longs corresponding to the bitmap
683  *	@bits: number of bits in the bitmap
684  *	@order: region size to find (size is actually 1<<order)
685  *
686  * This is used to allocate a memory region from a bitmap.  The idea is
687  * that the region has to be 1<<order sized and 1<<order aligned (this
688  * makes the search algorithm much faster).
689  *
690  * The region is marked as set bits in the bitmap if a free one is
691  * found.
692  *
693  * Returns either beginning of region or negative error
694  */
695 int bitmap_find_free_region(unsigned long *bitmap, int bits, int order)
696 {
697 	unsigned long mask;
698 	int pages = 1 << order;
699 	int i;
700 
701 	if(pages > BITS_PER_LONG)
702 		return -EINVAL;
703 
704 	/* make a mask of the order */
705 	mask = (1ul << (pages - 1));
706 	mask += mask - 1;
707 
708 	/* run up the bitmap pages bits at a time */
709 	for (i = 0; i < bits; i += pages) {
710 		int index = i/BITS_PER_LONG;
711 		int offset = i - (index * BITS_PER_LONG);
712 		if((bitmap[index] & (mask << offset)) == 0) {
713 			/* set region in bimap */
714 			bitmap[index] |= (mask << offset);
715 			return i;
716 		}
717 	}
718 	return -ENOMEM;
719 }
720 EXPORT_SYMBOL(bitmap_find_free_region);
721 
722 /**
723  *	bitmap_release_region - release allocated bitmap region
724  *	@bitmap: a pointer to the bitmap
725  *	@pos: the beginning of the region
726  *	@order: the order of the bits to release (number is 1<<order)
727  *
728  * This is the complement to __bitmap_find_free_region and releases
729  * the found region (by clearing it in the bitmap).
730  */
731 void bitmap_release_region(unsigned long *bitmap, int pos, int order)
732 {
733 	int pages = 1 << order;
734 	unsigned long mask = (1ul << (pages - 1));
735 	int index = pos/BITS_PER_LONG;
736 	int offset = pos - (index * BITS_PER_LONG);
737 	mask += mask - 1;
738 	bitmap[index] &= ~(mask << offset);
739 }
740 EXPORT_SYMBOL(bitmap_release_region);
741 
742 int bitmap_allocate_region(unsigned long *bitmap, int pos, int order)
743 {
744 	int pages = 1 << order;
745 	unsigned long mask = (1ul << (pages - 1));
746 	int index = pos/BITS_PER_LONG;
747 	int offset = pos - (index * BITS_PER_LONG);
748 
749 	/* We don't do regions of pages > BITS_PER_LONG.  The
750 	 * algorithm would be a simple look for multiple zeros in the
751 	 * array, but there's no driver today that needs this.  If you
752 	 * trip this BUG(), you get to code it... */
753 	BUG_ON(pages > BITS_PER_LONG);
754 	mask += mask - 1;
755 	if (bitmap[index] & (mask << offset))
756 		return -EBUSY;
757 	bitmap[index] |= (mask << offset);
758 	return 0;
759 }
760 EXPORT_SYMBOL(bitmap_allocate_region);
761