linux/lib/bitmap.c
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   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
  41int __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}
  54EXPORT_SYMBOL(__bitmap_empty);
  55
  56int __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}
  69EXPORT_SYMBOL(__bitmap_full);
  70
  71int __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}
  85EXPORT_SYMBOL(__bitmap_equal);
  86
  87void __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}
  96EXPORT_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 *   @shift : 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 */
 109void __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}
 139EXPORT_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 *   @shift : 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
 154void __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}
 180EXPORT_SYMBOL(__bitmap_shift_left);
 181
 182int __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        unsigned long result = 0;
 188
 189        for (k = 0; k < nr; k++)
 190                result |= (dst[k] = bitmap1[k] & bitmap2[k]);
 191        return result != 0;
 192}
 193EXPORT_SYMBOL(__bitmap_and);
 194
 195void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
 196                                const unsigned long *bitmap2, int bits)
 197{
 198        int k;
 199        int nr = BITS_TO_LONGS(bits);
 200
 201        for (k = 0; k < nr; k++)
 202                dst[k] = bitmap1[k] | bitmap2[k];
 203}
 204EXPORT_SYMBOL(__bitmap_or);
 205
 206void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
 207                                const unsigned long *bitmap2, int bits)
 208{
 209        int k;
 210        int nr = BITS_TO_LONGS(bits);
 211
 212        for (k = 0; k < nr; k++)
 213                dst[k] = bitmap1[k] ^ bitmap2[k];
 214}
 215EXPORT_SYMBOL(__bitmap_xor);
 216
 217int __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
 218                                const unsigned long *bitmap2, int bits)
 219{
 220        int k;
 221        int nr = BITS_TO_LONGS(bits);
 222        unsigned long result = 0;
 223
 224        for (k = 0; k < nr; k++)
 225                result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
 226        return result != 0;
 227}
 228EXPORT_SYMBOL(__bitmap_andnot);
 229
 230int __bitmap_intersects(const unsigned long *bitmap1,
 231                                const unsigned long *bitmap2, int bits)
 232{
 233        int k, lim = bits/BITS_PER_LONG;
 234        for (k = 0; k < lim; ++k)
 235                if (bitmap1[k] & bitmap2[k])
 236                        return 1;
 237
 238        if (bits % BITS_PER_LONG)
 239                if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
 240                        return 1;
 241        return 0;
 242}
 243EXPORT_SYMBOL(__bitmap_intersects);
 244
 245int __bitmap_subset(const unsigned long *bitmap1,
 246                                const unsigned long *bitmap2, int bits)
 247{
 248        int k, lim = bits/BITS_PER_LONG;
 249        for (k = 0; k < lim; ++k)
 250                if (bitmap1[k] & ~bitmap2[k])
 251                        return 0;
 252
 253        if (bits % BITS_PER_LONG)
 254                if ((bitmap1[k] & ~bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
 255                        return 0;
 256        return 1;
 257}
 258EXPORT_SYMBOL(__bitmap_subset);
 259
 260int __bitmap_weight(const unsigned long *bitmap, int bits)
 261{
 262        int k, w = 0, lim = bits/BITS_PER_LONG;
 263
 264        for (k = 0; k < lim; k++)
 265                w += hweight_long(bitmap[k]);
 266
 267        if (bits % BITS_PER_LONG)
 268                w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));
 269
 270        return w;
 271}
 272EXPORT_SYMBOL(__bitmap_weight);
 273
 274#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))
 275
 276void bitmap_set(unsigned long *map, int start, int nr)
 277{
 278        unsigned long *p = map + BIT_WORD(start);
 279        const int size = start + nr;
 280        int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
 281        unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
 282
 283        while (nr - bits_to_set >= 0) {
 284                *p |= mask_to_set;
 285                nr -= bits_to_set;
 286                bits_to_set = BITS_PER_LONG;
 287                mask_to_set = ~0UL;
 288                p++;
 289        }
 290        if (nr) {
 291                mask_to_set &= BITMAP_LAST_WORD_MASK(size);
 292                *p |= mask_to_set;
 293        }
 294}
 295EXPORT_SYMBOL(bitmap_set);
 296
 297void bitmap_clear(unsigned long *map, int start, int nr)
 298{
 299        unsigned long *p = map + BIT_WORD(start);
 300        const int size = start + nr;
 301        int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
 302        unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
 303
 304        while (nr - bits_to_clear >= 0) {
 305                *p &= ~mask_to_clear;
 306                nr -= bits_to_clear;
 307                bits_to_clear = BITS_PER_LONG;
 308                mask_to_clear = ~0UL;
 309                p++;
 310        }
 311        if (nr) {
 312                mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
 313                *p &= ~mask_to_clear;
 314        }
 315}
 316EXPORT_SYMBOL(bitmap_clear);
 317
 318/*
 319 * bitmap_find_next_zero_area - find a contiguous aligned zero area
 320 * @map: The address to base the search on
 321 * @size: The bitmap size in bits
 322 * @start: The bitnumber to start searching at
 323 * @nr: The number of zeroed bits we're looking for
 324 * @align_mask: Alignment mask for zero area
 325 *
 326 * The @align_mask should be one less than a power of 2; the effect is that
 327 * the bit offset of all zero areas this function finds is multiples of that
 328 * power of 2. A @align_mask of 0 means no alignment is required.
 329 */
 330unsigned long bitmap_find_next_zero_area(unsigned long *map,
 331                                         unsigned long size,
 332                                         unsigned long start,
 333                                         unsigned int nr,
 334                                         unsigned long align_mask)
 335{
 336        unsigned long index, end, i;
 337again:
 338        index = find_next_zero_bit(map, size, start);
 339
 340        /* Align allocation */
 341        index = __ALIGN_MASK(index, align_mask);
 342
 343        end = index + nr;
 344        if (end > size)
 345                return end;
 346        i = find_next_bit(map, end, index);
 347        if (i < end) {
 348                start = i + 1;
 349                goto again;
 350        }
 351        return index;
 352}
 353EXPORT_SYMBOL(bitmap_find_next_zero_area);
 354
 355/*
 356 * Bitmap printing & parsing functions: first version by Bill Irwin,
 357 * second version by Paul Jackson, third by Joe Korty.
 358 */
 359
 360#define CHUNKSZ                         32
 361#define nbits_to_hold_value(val)        fls(val)
 362#define unhex(c)                        (isdigit(c) ? (c - '0') : (toupper(c) - 'A' + 10))
 363#define BASEDEC 10              /* fancier cpuset lists input in decimal */
 364
 365/**
 366 * bitmap_scnprintf - convert bitmap to an ASCII hex string.
 367 * @buf: byte buffer into which string is placed
 368 * @buflen: reserved size of @buf, in bytes
 369 * @maskp: pointer to bitmap to convert
 370 * @nmaskbits: size of bitmap, in bits
 371 *
 372 * Exactly @nmaskbits bits are displayed.  Hex digits are grouped into
 373 * comma-separated sets of eight digits per set.
 374 */
 375int bitmap_scnprintf(char *buf, unsigned int buflen,
 376        const unsigned long *maskp, int nmaskbits)
 377{
 378        int i, word, bit, len = 0;
 379        unsigned long val;
 380        const char *sep = "";
 381        int chunksz;
 382        u32 chunkmask;
 383
 384        chunksz = nmaskbits & (CHUNKSZ - 1);
 385        if (chunksz == 0)
 386                chunksz = CHUNKSZ;
 387
 388        i = ALIGN(nmaskbits, CHUNKSZ) - CHUNKSZ;
 389        for (; i >= 0; i -= CHUNKSZ) {
 390                chunkmask = ((1ULL << chunksz) - 1);
 391                word = i / BITS_PER_LONG;
 392                bit = i % BITS_PER_LONG;
 393                val = (maskp[word] >> bit) & chunkmask;
 394                len += scnprintf(buf+len, buflen-len, "%s%0*lx", sep,
 395                        (chunksz+3)/4, val);
 396                chunksz = CHUNKSZ;
 397                sep = ",";
 398        }
 399        return len;
 400}
 401EXPORT_SYMBOL(bitmap_scnprintf);
 402
 403/**
 404 * __bitmap_parse - convert an ASCII hex string into a bitmap.
 405 * @buf: pointer to buffer containing string.
 406 * @buflen: buffer size in bytes.  If string is smaller than this
 407 *    then it must be terminated with a \0.
 408 * @is_user: location of buffer, 0 indicates kernel space
 409 * @maskp: pointer to bitmap array that will contain result.
 410 * @nmaskbits: size of bitmap, in bits.
 411 *
 412 * Commas group hex digits into chunks.  Each chunk defines exactly 32
 413 * bits of the resultant bitmask.  No chunk may specify a value larger
 414 * than 32 bits (%-EOVERFLOW), and if a chunk specifies a smaller value
 415 * then leading 0-bits are prepended.  %-EINVAL is returned for illegal
 416 * characters and for grouping errors such as "1,,5", ",44", "," and "".
 417 * Leading and trailing whitespace accepted, but not embedded whitespace.
 418 */
 419int __bitmap_parse(const char *buf, unsigned int buflen,
 420                int is_user, unsigned long *maskp,
 421                int nmaskbits)
 422{
 423        int c, old_c, totaldigits, ndigits, nchunks, nbits;
 424        u32 chunk;
 425        const char __user *ubuf = buf;
 426
 427        bitmap_zero(maskp, nmaskbits);
 428
 429        nchunks = nbits = totaldigits = c = 0;
 430        do {
 431                chunk = ndigits = 0;
 432
 433                /* Get the next chunk of the bitmap */
 434                while (buflen) {
 435                        old_c = c;
 436                        if (is_user) {
 437                                if (__get_user(c, ubuf++))
 438                                        return -EFAULT;
 439                        }
 440                        else
 441                                c = *buf++;
 442                        buflen--;
 443                        if (isspace(c))
 444                                continue;
 445
 446                        /*
 447                         * If the last character was a space and the current
 448                         * character isn't '\0', we've got embedded whitespace.
 449                         * This is a no-no, so throw an error.
 450                         */
 451                        if (totaldigits && c && isspace(old_c))
 452                                return -EINVAL;
 453
 454                        /* A '\0' or a ',' signal the end of the chunk */
 455                        if (c == '\0' || c == ',')
 456                                break;
 457
 458                        if (!isxdigit(c))
 459                                return -EINVAL;
 460
 461                        /*
 462                         * Make sure there are at least 4 free bits in 'chunk'.
 463                         * If not, this hexdigit will overflow 'chunk', so
 464                         * throw an error.
 465                         */
 466                        if (chunk & ~((1UL << (CHUNKSZ - 4)) - 1))
 467                                return -EOVERFLOW;
 468
 469                        chunk = (chunk << 4) | unhex(c);
 470                        ndigits++; totaldigits++;
 471                }
 472                if (ndigits == 0)
 473                        return -EINVAL;
 474                if (nchunks == 0 && chunk == 0)
 475                        continue;
 476
 477                __bitmap_shift_left(maskp, maskp, CHUNKSZ, nmaskbits);
 478                *maskp |= chunk;
 479                nchunks++;
 480                nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ;
 481                if (nbits > nmaskbits)
 482                        return -EOVERFLOW;
 483        } while (buflen && c == ',');
 484
 485        return 0;
 486}
 487EXPORT_SYMBOL(__bitmap_parse);
 488
 489/**
 490 * bitmap_parse_user - convert an ASCII hex string in a user buffer into a bitmap
 491 *
 492 * @ubuf: pointer to user buffer containing string.
 493 * @ulen: buffer size in bytes.  If string is smaller than this
 494 *    then it must be terminated with a \0.
 495 * @maskp: pointer to bitmap array that will contain result.
 496 * @nmaskbits: size of bitmap, in bits.
 497 *
 498 * Wrapper for __bitmap_parse(), providing it with user buffer.
 499 *
 500 * We cannot have this as an inline function in bitmap.h because it needs
 501 * linux/uaccess.h to get the access_ok() declaration and this causes
 502 * cyclic dependencies.
 503 */
 504int bitmap_parse_user(const char __user *ubuf,
 505                        unsigned int ulen, unsigned long *maskp,
 506                        int nmaskbits)
 507{
 508        if (!access_ok(VERIFY_READ, ubuf, ulen))
 509                return -EFAULT;
 510        return __bitmap_parse((const char *)ubuf, ulen, 1, maskp, nmaskbits);
 511}
 512EXPORT_SYMBOL(bitmap_parse_user);
 513
 514/*
 515 * bscnl_emit(buf, buflen, rbot, rtop, bp)
 516 *
 517 * Helper routine for bitmap_scnlistprintf().  Write decimal number
 518 * or range to buf, suppressing output past buf+buflen, with optional
 519 * comma-prefix.  Return len of what would be written to buf, if it
 520 * all fit.
 521 */
 522static inline int bscnl_emit(char *buf, int buflen, int rbot, int rtop, int len)
 523{
 524        if (len > 0)
 525                len += scnprintf(buf + len, buflen - len, ",");
 526        if (rbot == rtop)
 527                len += scnprintf(buf + len, buflen - len, "%d", rbot);
 528        else
 529                len += scnprintf(buf + len, buflen - len, "%d-%d", rbot, rtop);
 530        return len;
 531}
 532
 533/**
 534 * bitmap_scnlistprintf - convert bitmap to list format ASCII string
 535 * @buf: byte buffer into which string is placed
 536 * @buflen: reserved size of @buf, in bytes
 537 * @maskp: pointer to bitmap to convert
 538 * @nmaskbits: size of bitmap, in bits
 539 *
 540 * Output format is a comma-separated list of decimal numbers and
 541 * ranges.  Consecutively set bits are shown as two hyphen-separated
 542 * decimal numbers, the smallest and largest bit numbers set in
 543 * the range.  Output format is compatible with the format
 544 * accepted as input by bitmap_parselist().
 545 *
 546 * The return value is the number of characters which would be
 547 * generated for the given input, excluding the trailing '\0', as
 548 * per ISO C99.
 549 */
 550int bitmap_scnlistprintf(char *buf, unsigned int buflen,
 551        const unsigned long *maskp, int nmaskbits)
 552{
 553        int len = 0;
 554        /* current bit is 'cur', most recently seen range is [rbot, rtop] */
 555        int cur, rbot, rtop;
 556
 557        if (buflen == 0)
 558                return 0;
 559        buf[0] = 0;
 560
 561        rbot = cur = find_first_bit(maskp, nmaskbits);
 562        while (cur < nmaskbits) {
 563                rtop = cur;
 564                cur = find_next_bit(maskp, nmaskbits, cur+1);
 565                if (cur >= nmaskbits || cur > rtop + 1) {
 566                        len = bscnl_emit(buf, buflen, rbot, rtop, len);
 567                        rbot = cur;
 568                }
 569        }
 570        return len;
 571}
 572EXPORT_SYMBOL(bitmap_scnlistprintf);
 573
 574/**
 575 * bitmap_parselist - convert list format ASCII string to bitmap
 576 * @bp: read nul-terminated user string from this buffer
 577 * @maskp: write resulting mask here
 578 * @nmaskbits: number of bits in mask to be written
 579 *
 580 * Input format is a comma-separated list of decimal numbers and
 581 * ranges.  Consecutively set bits are shown as two hyphen-separated
 582 * decimal numbers, the smallest and largest bit numbers set in
 583 * the range.
 584 *
 585 * Returns 0 on success, -errno on invalid input strings.
 586 * Error values:
 587 *    %-EINVAL: second number in range smaller than first
 588 *    %-EINVAL: invalid character in string
 589 *    %-ERANGE: bit number specified too large for mask
 590 */
 591int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
 592{
 593        unsigned a, b;
 594
 595        bitmap_zero(maskp, nmaskbits);
 596        do {
 597                if (!isdigit(*bp))
 598                        return -EINVAL;
 599                b = a = simple_strtoul(bp, (char **)&bp, BASEDEC);
 600                if (*bp == '-') {
 601                        bp++;
 602                        if (!isdigit(*bp))
 603                                return -EINVAL;
 604                        b = simple_strtoul(bp, (char **)&bp, BASEDEC);
 605                }
 606                if (!(a <= b))
 607                        return -EINVAL;
 608                if (b >= nmaskbits)
 609                        return -ERANGE;
 610                while (a <= b) {
 611                        set_bit(a, maskp);
 612                        a++;
 613                }
 614                if (*bp == ',')
 615                        bp++;
 616        } while (*bp != '\0' && *bp != '\n');
 617        return 0;
 618}
 619EXPORT_SYMBOL(bitmap_parselist);
 620
 621/**
 622 * bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap
 623 *      @buf: pointer to a bitmap
 624 *      @pos: a bit position in @buf (0 <= @pos < @bits)
 625 *      @bits: number of valid bit positions in @buf
 626 *
 627 * Map the bit at position @pos in @buf (of length @bits) to the
 628 * ordinal of which set bit it is.  If it is not set or if @pos
 629 * is not a valid bit position, map to -1.
 630 *
 631 * If for example, just bits 4 through 7 are set in @buf, then @pos
 632 * values 4 through 7 will get mapped to 0 through 3, respectively,
 633 * and other @pos values will get mapped to 0.  When @pos value 7
 634 * gets mapped to (returns) @ord value 3 in this example, that means
 635 * that bit 7 is the 3rd (starting with 0th) set bit in @buf.
 636 *
 637 * The bit positions 0 through @bits are valid positions in @buf.
 638 */
 639static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits)
 640{
 641        int i, ord;
 642
 643        if (pos < 0 || pos >= bits || !test_bit(pos, buf))
 644                return -1;
 645
 646        i = find_first_bit(buf, bits);
 647        ord = 0;
 648        while (i < pos) {
 649                i = find_next_bit(buf, bits, i + 1);
 650                ord++;
 651        }
 652        BUG_ON(i != pos);
 653
 654        return ord;
 655}
 656
 657/**
 658 * bitmap_ord_to_pos - find position of n-th set bit in bitmap
 659 *      @buf: pointer to bitmap
 660 *      @ord: ordinal bit position (n-th set bit, n >= 0)
 661 *      @bits: number of valid bit positions in @buf
 662 *
 663 * Map the ordinal offset of bit @ord in @buf to its position in @buf.
 664 * Value of @ord should be in range 0 <= @ord < weight(buf), else
 665 * results are undefined.
 666 *
 667 * If for example, just bits 4 through 7 are set in @buf, then @ord
 668 * values 0 through 3 will get mapped to 4 through 7, respectively,
 669 * and all other @ord values return undefined values.  When @ord value 3
 670 * gets mapped to (returns) @pos value 7 in this example, that means
 671 * that the 3rd set bit (starting with 0th) is at position 7 in @buf.
 672 *
 673 * The bit positions 0 through @bits are valid positions in @buf.
 674 */
 675static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
 676{
 677        int pos = 0;
 678
 679        if (ord >= 0 && ord < bits) {
 680                int i;
 681
 682                for (i = find_first_bit(buf, bits);
 683                     i < bits && ord > 0;
 684                     i = find_next_bit(buf, bits, i + 1))
 685                        ord--;
 686                if (i < bits && ord == 0)
 687                        pos = i;
 688        }
 689
 690        return pos;
 691}
 692
 693/**
 694 * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap
 695 *      @dst: remapped result
 696 *      @src: subset to be remapped
 697 *      @old: defines domain of map
 698 *      @new: defines range of map
 699 *      @bits: number of bits in each of these bitmaps
 700 *
 701 * Let @old and @new define a mapping of bit positions, such that
 702 * whatever position is held by the n-th set bit in @old is mapped
 703 * to the n-th set bit in @new.  In the more general case, allowing
 704 * for the possibility that the weight 'w' of @new is less than the
 705 * weight of @old, map the position of the n-th set bit in @old to
 706 * the position of the m-th set bit in @new, where m == n % w.
 707 *
 708 * If either of the @old and @new bitmaps are empty, or if @src and
 709 * @dst point to the same location, then this routine copies @src
 710 * to @dst.
 711 *
 712 * The positions of unset bits in @old are mapped to themselves
 713 * (the identify map).
 714 *
 715 * Apply the above specified mapping to @src, placing the result in
 716 * @dst, clearing any bits previously set in @dst.
 717 *
 718 * For example, lets say that @old has bits 4 through 7 set, and
 719 * @new has bits 12 through 15 set.  This defines the mapping of bit
 720 * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other
 721 * bit positions unchanged.  So if say @src comes into this routine
 722 * with bits 1, 5 and 7 set, then @dst should leave with bits 1,
 723 * 13 and 15 set.
 724 */
 725void bitmap_remap(unsigned long *dst, const unsigned long *src,
 726                const unsigned long *old, const unsigned long *new,
 727                int bits)
 728{
 729        int oldbit, w;
 730
 731        if (dst == src)         /* following doesn't handle inplace remaps */
 732                return;
 733        bitmap_zero(dst, bits);
 734
 735        w = bitmap_weight(new, bits);
 736        for_each_set_bit(oldbit, src, bits) {
 737                int n = bitmap_pos_to_ord(old, oldbit, bits);
 738
 739                if (n < 0 || w == 0)
 740                        set_bit(oldbit, dst);   /* identity map */
 741                else
 742                        set_bit(bitmap_ord_to_pos(new, n % w, bits), dst);
 743        }
 744}
 745EXPORT_SYMBOL(bitmap_remap);
 746
 747/**
 748 * bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit
 749 *      @oldbit: bit position to be mapped
 750 *      @old: defines domain of map
 751 *      @new: defines range of map
 752 *      @bits: number of bits in each of these bitmaps
 753 *
 754 * Let @old and @new define a mapping of bit positions, such that
 755 * whatever position is held by the n-th set bit in @old is mapped
 756 * to the n-th set bit in @new.  In the more general case, allowing
 757 * for the possibility that the weight 'w' of @new is less than the
 758 * weight of @old, map the position of the n-th set bit in @old to
 759 * the position of the m-th set bit in @new, where m == n % w.
 760 *
 761 * The positions of unset bits in @old are mapped to themselves
 762 * (the identify map).
 763 *
 764 * Apply the above specified mapping to bit position @oldbit, returning
 765 * the new bit position.
 766 *
 767 * For example, lets say that @old has bits 4 through 7 set, and
 768 * @new has bits 12 through 15 set.  This defines the mapping of bit
 769 * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other
 770 * bit positions unchanged.  So if say @oldbit is 5, then this routine
 771 * returns 13.
 772 */
 773int bitmap_bitremap(int oldbit, const unsigned long *old,
 774                                const unsigned long *new, int bits)
 775{
 776        int w = bitmap_weight(new, bits);
 777        int n = bitmap_pos_to_ord(old, oldbit, bits);
 778        if (n < 0 || w == 0)
 779                return oldbit;
 780        else
 781                return bitmap_ord_to_pos(new, n % w, bits);
 782}
 783EXPORT_SYMBOL(bitmap_bitremap);
 784
 785/**
 786 * bitmap_onto - translate one bitmap relative to another
 787 *      @dst: resulting translated bitmap
 788 *      @orig: original untranslated bitmap
 789 *      @relmap: bitmap relative to which translated
 790 *      @bits: number of bits in each of these bitmaps
 791 *
 792 * Set the n-th bit of @dst iff there exists some m such that the
 793 * n-th bit of @relmap is set, the m-th bit of @orig is set, and
 794 * the n-th bit of @relmap is also the m-th _set_ bit of @relmap.
 795 * (If you understood the previous sentence the first time your
 796 * read it, you're overqualified for your current job.)
 797 *
 798 * In other words, @orig is mapped onto (surjectively) @dst,
 799 * using the the map { <n, m> | the n-th bit of @relmap is the
 800 * m-th set bit of @relmap }.
 801 *
 802 * Any set bits in @orig above bit number W, where W is the
 803 * weight of (number of set bits in) @relmap are mapped nowhere.
 804 * In particular, if for all bits m set in @orig, m >= W, then
 805 * @dst will end up empty.  In situations where the possibility
 806 * of such an empty result is not desired, one way to avoid it is
 807 * to use the bitmap_fold() operator, below, to first fold the
 808 * @orig bitmap over itself so that all its set bits x are in the
 809 * range 0 <= x < W.  The bitmap_fold() operator does this by
 810 * setting the bit (m % W) in @dst, for each bit (m) set in @orig.
 811 *
 812 * Example [1] for bitmap_onto():
 813 *  Let's say @relmap has bits 30-39 set, and @orig has bits
 814 *  1, 3, 5, 7, 9 and 11 set.  Then on return from this routine,
 815 *  @dst will have bits 31, 33, 35, 37 and 39 set.
 816 *
 817 *  When bit 0 is set in @orig, it means turn on the bit in
 818 *  @dst corresponding to whatever is the first bit (if any)
 819 *  that is turned on in @relmap.  Since bit 0 was off in the
 820 *  above example, we leave off that bit (bit 30) in @dst.
 821 *
 822 *  When bit 1 is set in @orig (as in the above example), it
 823 *  means turn on the bit in @dst corresponding to whatever
 824 *  is the second bit that is turned on in @relmap.  The second
 825 *  bit in @relmap that was turned on in the above example was
 826 *  bit 31, so we turned on bit 31 in @dst.
 827 *
 828 *  Similarly, we turned on bits 33, 35, 37 and 39 in @dst,
 829 *  because they were the 4th, 6th, 8th and 10th set bits
 830 *  set in @relmap, and the 4th, 6th, 8th and 10th bits of
 831 *  @orig (i.e. bits 3, 5, 7 and 9) were also set.
 832 *
 833 *  When bit 11 is set in @orig, it means turn on the bit in
 834 *  @dst corresponding to whatever is the twelth bit that is
 835 *  turned on in @relmap.  In the above example, there were
 836 *  only ten bits turned on in @relmap (30..39), so that bit
 837 *  11 was set in @orig had no affect on @dst.
 838 *
 839 * Example [2] for bitmap_fold() + bitmap_onto():
 840 *  Let's say @relmap has these ten bits set:
 841 *              40 41 42 43 45 48 53 61 74 95
 842 *  (for the curious, that's 40 plus the first ten terms of the
 843 *  Fibonacci sequence.)
 844 *
 845 *  Further lets say we use the following code, invoking
 846 *  bitmap_fold() then bitmap_onto, as suggested above to
 847 *  avoid the possitility of an empty @dst result:
 848 *
 849 *      unsigned long *tmp;     // a temporary bitmap's bits
 850 *
 851 *      bitmap_fold(tmp, orig, bitmap_weight(relmap, bits), bits);
 852 *      bitmap_onto(dst, tmp, relmap, bits);
 853 *
 854 *  Then this table shows what various values of @dst would be, for
 855 *  various @orig's.  I list the zero-based positions of each set bit.
 856 *  The tmp column shows the intermediate result, as computed by
 857 *  using bitmap_fold() to fold the @orig bitmap modulo ten
 858 *  (the weight of @relmap).
 859 *
 860 *      @orig           tmp            @dst
 861 *      0                0             40
 862 *      1                1             41
 863 *      9                9             95
 864 *      10               0             40 (*)
 865 *      1 3 5 7          1 3 5 7       41 43 48 61
 866 *      0 1 2 3 4        0 1 2 3 4     40 41 42 43 45
 867 *      0 9 18 27        0 9 8 7       40 61 74 95
 868 *      0 10 20 30       0             40
 869 *      0 11 22 33       0 1 2 3       40 41 42 43
 870 *      0 12 24 36       0 2 4 6       40 42 45 53
 871 *      78 102 211       1 2 8         41 42 74 (*)
 872 *
 873 * (*) For these marked lines, if we hadn't first done bitmap_fold()
 874 *     into tmp, then the @dst result would have been empty.
 875 *
 876 * If either of @orig or @relmap is empty (no set bits), then @dst
 877 * will be returned empty.
 878 *
 879 * If (as explained above) the only set bits in @orig are in positions
 880 * m where m >= W, (where W is the weight of @relmap) then @dst will
 881 * once again be returned empty.
 882 *
 883 * All bits in @dst not set by the above rule are cleared.
 884 */
 885void bitmap_onto(unsigned long *dst, const unsigned long *orig,
 886                        const unsigned long *relmap, int bits)
 887{
 888        int n, m;               /* same meaning as in above comment */
 889
 890        if (dst == orig)        /* following doesn't handle inplace mappings */
 891                return;
 892        bitmap_zero(dst, bits);
 893
 894        /*
 895         * The following code is a more efficient, but less
 896         * obvious, equivalent to the loop:
 897         *      for (m = 0; m < bitmap_weight(relmap, bits); m++) {
 898         *              n = bitmap_ord_to_pos(orig, m, bits);
 899         *              if (test_bit(m, orig))
 900         *                      set_bit(n, dst);
 901         *      }
 902         */
 903
 904        m = 0;
 905        for_each_set_bit(n, relmap, bits) {
 906                /* m == bitmap_pos_to_ord(relmap, n, bits) */
 907                if (test_bit(m, orig))
 908                        set_bit(n, dst);
 909                m++;
 910        }
 911}
 912EXPORT_SYMBOL(bitmap_onto);
 913
 914/**
 915 * bitmap_fold - fold larger bitmap into smaller, modulo specified size
 916 *      @dst: resulting smaller bitmap
 917 *      @orig: original larger bitmap
 918 *      @sz: specified size
 919 *      @bits: number of bits in each of these bitmaps
 920 *
 921 * For each bit oldbit in @orig, set bit oldbit mod @sz in @dst.
 922 * Clear all other bits in @dst.  See further the comment and
 923 * Example [2] for bitmap_onto() for why and how to use this.
 924 */
 925void bitmap_fold(unsigned long *dst, const unsigned long *orig,
 926                        int sz, int bits)
 927{
 928        int oldbit;
 929
 930        if (dst == orig)        /* following doesn't handle inplace mappings */
 931                return;
 932        bitmap_zero(dst, bits);
 933
 934        for_each_set_bit(oldbit, orig, bits)
 935                set_bit(oldbit % sz, dst);
 936}
 937EXPORT_SYMBOL(bitmap_fold);
 938
 939/*
 940 * Common code for bitmap_*_region() routines.
 941 *      bitmap: array of unsigned longs corresponding to the bitmap
 942 *      pos: the beginning of the region
 943 *      order: region size (log base 2 of number of bits)
 944 *      reg_op: operation(s) to perform on that region of bitmap
 945 *
 946 * Can set, verify and/or release a region of bits in a bitmap,
 947 * depending on which combination of REG_OP_* flag bits is set.
 948 *
 949 * A region of a bitmap is a sequence of bits in the bitmap, of
 950 * some size '1 << order' (a power of two), aligned to that same
 951 * '1 << order' power of two.
 952 *
 953 * Returns 1 if REG_OP_ISFREE succeeds (region is all zero bits).
 954 * Returns 0 in all other cases and reg_ops.
 955 */
 956
 957enum {
 958        REG_OP_ISFREE,          /* true if region is all zero bits */
 959        REG_OP_ALLOC,           /* set all bits in region */
 960        REG_OP_RELEASE,         /* clear all bits in region */
 961};
 962
 963static int __reg_op(unsigned long *bitmap, int pos, int order, int reg_op)
 964{
 965        int nbits_reg;          /* number of bits in region */
 966        int index;              /* index first long of region in bitmap */
 967        int offset;             /* bit offset region in bitmap[index] */
 968        int nlongs_reg;         /* num longs spanned by region in bitmap */
 969        int nbitsinlong;        /* num bits of region in each spanned long */
 970        unsigned long mask;     /* bitmask for one long of region */
 971        int i;                  /* scans bitmap by longs */
 972        int ret = 0;            /* return value */
 973
 974        /*
 975         * Either nlongs_reg == 1 (for small orders that fit in one long)
 976         * or (offset == 0 && mask == ~0UL) (for larger multiword orders.)
 977         */
 978        nbits_reg = 1 << order;
 979        index = pos / BITS_PER_LONG;
 980        offset = pos - (index * BITS_PER_LONG);
 981        nlongs_reg = BITS_TO_LONGS(nbits_reg);
 982        nbitsinlong = min(nbits_reg,  BITS_PER_LONG);
 983
 984        /*
 985         * Can't do "mask = (1UL << nbitsinlong) - 1", as that
 986         * overflows if nbitsinlong == BITS_PER_LONG.
 987         */
 988        mask = (1UL << (nbitsinlong - 1));
 989        mask += mask - 1;
 990        mask <<= offset;
 991
 992        switch (reg_op) {
 993        case REG_OP_ISFREE:
 994                for (i = 0; i < nlongs_reg; i++) {
 995                        if (bitmap[index + i] & mask)
 996                                goto done;
 997                }
 998                ret = 1;        /* all bits in region free (zero) */
 999                break;
1000
1001        case REG_OP_ALLOC:
1002                for (i = 0; i < nlongs_reg; i++)
1003                        bitmap[index + i] |= mask;
1004                break;
1005
1006        case REG_OP_RELEASE:
1007                for (i = 0; i < nlongs_reg; i++)
1008                        bitmap[index + i] &= ~mask;
1009                break;
1010        }
1011done:
1012        return ret;
1013}
1014
1015/**
1016 * bitmap_find_free_region - find a contiguous aligned mem region
1017 *      @bitmap: array of unsigned longs corresponding to the bitmap
1018 *      @bits: number of bits in the bitmap
1019 *      @order: region size (log base 2 of number of bits) to find
1020 *
1021 * Find a region of free (zero) bits in a @bitmap of @bits bits and
1022 * allocate them (set them to one).  Only consider regions of length
1023 * a power (@order) of two, aligned to that power of two, which
1024 * makes the search algorithm much faster.
1025 *
1026 * Return the bit offset in bitmap of the allocated region,
1027 * or -errno on failure.
1028 */
1029int bitmap_find_free_region(unsigned long *bitmap, int bits, int order)
1030{
1031        int pos, end;           /* scans bitmap by regions of size order */
1032
1033        for (pos = 0 ; (end = pos + (1 << order)) <= bits; pos = end) {
1034                if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
1035                        continue;
1036                __reg_op(bitmap, pos, order, REG_OP_ALLOC);
1037                return pos;
1038        }
1039        return -ENOMEM;
1040}
1041EXPORT_SYMBOL(bitmap_find_free_region);
1042
1043/**
1044 * bitmap_release_region - release allocated bitmap region
1045 *      @bitmap: array of unsigned longs corresponding to the bitmap
1046 *      @pos: beginning of bit region to release
1047 *      @order: region size (log base 2 of number of bits) to release
1048 *
1049 * This is the complement to __bitmap_find_free_region() and releases
1050 * the found region (by clearing it in the bitmap).
1051 *
1052 * No return value.
1053 */
1054void bitmap_release_region(unsigned long *bitmap, int pos, int order)
1055{
1056        __reg_op(bitmap, pos, order, REG_OP_RELEASE);
1057}
1058EXPORT_SYMBOL(bitmap_release_region);
1059
1060/**
1061 * bitmap_allocate_region - allocate bitmap region
1062 *      @bitmap: array of unsigned longs corresponding to the bitmap
1063 *      @pos: beginning of bit region to allocate
1064 *      @order: region size (log base 2 of number of bits) to allocate
1065 *
1066 * Allocate (set bits in) a specified region of a bitmap.
1067 *
1068 * Return 0 on success, or %-EBUSY if specified region wasn't
1069 * free (not all bits were zero).
1070 */
1071int bitmap_allocate_region(unsigned long *bitmap, int pos, int order)
1072{
1073        if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
1074                return -EBUSY;
1075        __reg_op(bitmap, pos, order, REG_OP_ALLOC);
1076        return 0;
1077}
1078EXPORT_SYMBOL(bitmap_allocate_region);
1079
1080/**
1081 * bitmap_copy_le - copy a bitmap, putting the bits into little-endian order.
1082 * @dst:   destination buffer
1083 * @src:   bitmap to copy
1084 * @nbits: number of bits in the bitmap
1085 *
1086 * Require nbits % BITS_PER_LONG == 0.
1087 */
1088void bitmap_copy_le(void *dst, const unsigned long *src, int nbits)
1089{
1090        unsigned long *d = dst;
1091        int i;
1092
1093        for (i = 0; i < nbits/BITS_PER_LONG; i++) {
1094                if (BITS_PER_LONG == 64)
1095                        d[i] = cpu_to_le64(src[i]);
1096                else
1097                        d[i] = cpu_to_le32(src[i]);
1098        }
1099}
1100EXPORT_SYMBOL(bitmap_copy_le);
1101
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