lib/string_helpers.c

   1 /*
   2  * Helpers for formatting and printing strings
   3  *
   4  * Copyright 31 August 2008 James Bottomley
   5  * Copyright (C) 2013, Intel Corporation
   6  */
   7 #include <linux/bug.h>
   8 #include <linux/kernel.h>
   9 #include <linux/math64.h>
  10 #include <linux/export.h>
  11 #include <linux/ctype.h>
  12 #include <linux/errno.h>
  13 #include <linux/fs.h>
  14 #include <linux/limits.h>
  15 #include <linux/mm.h>
  16 #include <linux/slab.h>
  17 #include <linux/string.h>
  18 #include <linux/string_helpers.h>
  19
  20 /**
  21  * string_get_size - get the size in the specified units
  22  * @size:       The size to be converted in blocks
  23  * @blk_size:   Size of the block (use 1 for size in bytes)
  24  * @units:      units to use (powers of 1000 or 1024)
  25  * @buf:        buffer to format to
  26  * @len:        length of buffer
  27  *
  28  * This function returns a string formatted to 3 significant figures
  29  * giving the size in the required units.  @buf should have room for
  30  * at least 9 bytes and will always be zero terminated.
  31  *
  32  */
  33 void string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
  34                      char *buf, int len)
  35 {
  36         static const char *const units_10[] = {
  37                 "B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"
  38         };
  39         static const char *const units_2[] = {
  40                 "B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"
  41         };
  42         static const char *const *const units_str[] = {
  43                 [STRING_UNITS_10] = units_10,
  44                 [STRING_UNITS_2] = units_2,
  45         };
  46         static const unsigned int divisor[] = {
  47                 [STRING_UNITS_10] = 1000,
  48                 [STRING_UNITS_2] = 1024,
  49         };
  50         static const unsigned int rounding[] = { 500, 50, 5 };
  51         int i = 0, j;
  52         u32 remainder = 0, sf_cap;
  53         char tmp[8];
  54         const char *unit;
  55
  56         tmp[0] = '\0';
  57
  58         if (blk_size == 0)
  59                 size = 0;
  60         if (size == 0)
  61                 goto out;
  62
  63         /* This is Napier's algorithm.  Reduce the original block size to
  64          *
  65          * coefficient * divisor[units]^i
  66          *
  67          * we do the reduction so both coefficients are just under 32 bits so
  68          * that multiplying them together won't overflow 64 bits and we keep
  69          * as much precision as possible in the numbers.
  70          *
  71          * Note: it's safe to throw away the remainders here because all the
  72          * precision is in the coefficients.
  73          */
  74         while (blk_size >> 32) {
  75                 do_div(blk_size, divisor[units]);
  76                 i++;
  77         }
  78
  79         while (size >> 32) {
  80                 do_div(size, divisor[units]);
  81                 i++;
  82         }
  83
  84         /* now perform the actual multiplication keeping i as the sum of the
  85          * two logarithms */
  86         size *= blk_size;
  87
  88         /* and logarithmically reduce it until it's just under the divisor */
  89         while (size >= divisor[units]) {
  90                 remainder = do_div(size, divisor[units]);
  91                 i++;
  92         }
  93
  94         /* work out in j how many digits of precision we need from the
  95          * remainder */
  96         sf_cap = size;
  97         for (j = 0; sf_cap*10 < 1000; j++)
  98                 sf_cap *= 10;
  99
 100         if (units == STRING_UNITS_2) {
 101                 /* express the remainder as a decimal.  It's currently the
 102                  * numerator of a fraction whose denominator is
 103                  * divisor[units], which is 1 << 10 for STRING_UNITS_2 */
 104                 remainder *= 1000;
 105                 remainder >>= 10;
 106         }
 107
 108         /* add a 5 to the digit below what will be printed to ensure
 109          * an arithmetical round up and carry it through to size */
 110         remainder += rounding[j];
 111         if (remainder >= 1000) {
 112                 remainder -= 1000;
 113                 size += 1;
 114         }
 115
 116         if (j) {
 117                 snprintf(tmp, sizeof(tmp), ".%03u", remainder);
 118                 tmp[j+1] = '\0';
 119         }
 120
 121  out:
 122         if (i >= ARRAY_SIZE(units_2))
 123                 unit = "UNK";
 124         else
 125                 unit = units_str[units][i];
 126
 127         snprintf(buf, len, "%u%s %s", (u32)size,
 128                  tmp, unit);
 129 }
 130 EXPORT_SYMBOL(string_get_size);
 131
 132 static bool unescape_space(char **src, char **dst)
 133 {
 134         char *p = *dst, *q = *src;
 135
 136         switch (*q) {
 137         case 'n':
 138                 *p = '\n';
 139                 break;
 140         case 'r':
 141                 *p = '\r';
 142                 break;
 143         case 't':
 144                 *p = '\t';
 145                 break;
 146         case 'v':
 147                 *p = '\v';
 148                 break;
 149         case 'f':
 150                 *p = '\f';
 151                 break;
 152         default:
 153                 return false;
 154         }
 155         *dst += 1;
 156         *src += 1;
 157         return true;
 158 }
 159
 160 static bool unescape_octal(char **src, char **dst)
 161 {
 162         char *p = *dst, *q = *src;
 163         u8 num;
 164
 165         if (isodigit(*q) == 0)
 166                 return false;
 167
 168         num = (*q++) & 7;
 169         while (num < 32 && isodigit(*q) && (q - *src < 3)) {
 170                 num <<= 3;
 171                 num += (*q++) & 7;
 172         }
 173         *p = num;
 174         *dst += 1;
 175         *src = q;
 176         return true;
 177 }
 178
 179 static bool unescape_hex(char **src, char **dst)
 180 {
 181         char *p = *dst, *q = *src;
 182         int digit;
 183         u8 num;
 184
 185         if (*q++ != 'x')
 186                 return false;
 187
 188         num = digit = hex_to_bin(*q++);
 189         if (digit < 0)
 190                 return false;
 191
 192         digit = hex_to_bin(*q);
 193         if (digit >= 0) {
 194                 q++;
 195                 num = (num << 4) | digit;
 196         }
 197         *p = num;
 198         *dst += 1;
 199         *src = q;
 200         return true;
 201 }
 202
 203 static bool unescape_special(char **src, char **dst)
 204 {
 205         char *p = *dst, *q = *src;
 206
 207         switch (*q) {
 208         case '\"':
 209                 *p = '\"';
 210                 break;
 211         case '\\':
 212                 *p = '\\';
 213                 break;
 214         case 'a':
 215                 *p = '\a';
 216                 break;
 217         case 'e':
 218                 *p = '\e';
 219                 break;
 220         default:
 221                 return false;
 222         }
 223         *dst += 1;
 224         *src += 1;
 225         return true;
 226 }
 227
 228 /**
 229  * string_unescape - unquote characters in the given string
 230  * @src:        source buffer (escaped)
 231  * @dst:        destination buffer (unescaped)
 232  * @size:       size of the destination buffer (0 to unlimit)
 233  * @flags:      combination of the flags (bitwise OR):
 234  *      %UNESCAPE_SPACE:
 235  *              '\f' - form feed
 236  *              '\n' - new line
 237  *              '\r' - carriage return
 238  *              '\t' - horizontal tab
 239  *              '\v' - vertical tab
 240  *      %UNESCAPE_OCTAL:
 241  *              '\NNN' - byte with octal value NNN (1 to 3 digits)
 242  *      %UNESCAPE_HEX:
 243  *              '\xHH' - byte with hexadecimal value HH (1 to 2 digits)
 244  *      %UNESCAPE_SPECIAL:
 245  *              '\"' - double quote
 246  *              '\\' - backslash
 247  *              '\a' - alert (BEL)
 248  *              '\e' - escape
 249  *      %UNESCAPE_ANY:
 250  *              all previous together
 251  *
 252  * Description:
 253  * The function unquotes characters in the given string.
 254  *
 255  * Because the size of the output will be the same as or less than the size of
 256  * the input, the transformation may be performed in place.
 257  *
 258  * Caller must provide valid source and destination pointers. Be aware that
 259  * destination buffer will always be NULL-terminated. Source string must be
 260  * NULL-terminated as well.
 261  *
 262  * Return:
 263  * The amount of the characters processed to the destination buffer excluding
 264  * trailing '\0' is returned.
 265  */
 266 int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
 267 {
 268         char *out = dst;
 269
 270         while (*src && --size) {
 271                 if (src[0] == '\\' && src[1] != '\0' && size > 1) {
 272                         src++;
 273                         size--;
 274
 275                         if (flags & UNESCAPE_SPACE &&
 276                                         unescape_space(&src, &out))
 277                                 continue;
 278
 279                         if (flags & UNESCAPE_OCTAL &&
 280                                         unescape_octal(&src, &out))
 281                                 continue;
 282
 283                         if (flags & UNESCAPE_HEX &&
 284                                         unescape_hex(&src, &out))
 285                                 continue;
 286
 287                         if (flags & UNESCAPE_SPECIAL &&
 288                                         unescape_special(&src, &out))
 289                                 continue;
 290
 291                         *out++ = '\\';
 292                 }
 293                 *out++ = *src++;
 294         }
 295         *out = '\0';
 296
 297         return out - dst;
 298 }
 299 EXPORT_SYMBOL(string_unescape);
 300
 301 static bool escape_passthrough(unsigned char c, char **dst, char *end)
 302 {
 303         char *out = *dst;
 304
 305         if (out < end)
 306                 *out = c;
 307         *dst = out + 1;
 308         return true;
 309 }
 310
 311 static bool escape_space(unsigned char c, char **dst, char *end)
 312 {
 313         char *out = *dst;
 314         unsigned char to;
 315
 316         switch (c) {
 317         case '\n':
 318                 to = 'n';
 319                 break;
 320         case '\r':
 321                 to = 'r';
 322                 break;
 323         case '\t':
 324                 to = 't';
 325                 break;
 326         case '\v':
 327                 to = 'v';
 328                 break;
 329         case '\f':
 330                 to = 'f';
 331                 break;
 332         default:
 333                 return false;
 334         }
 335
 336         if (out < end)
 337                 *out = '\\';
 338         ++out;
 339         if (out < end)
 340                 *out = to;
 341         ++out;
 342
 343         *dst = out;
 344         return true;
 345 }
 346
 347 static bool escape_special(unsigned char c, char **dst, char *end)
 348 {
 349         char *out = *dst;
 350         unsigned char to;
 351
 352         switch (c) {
 353         case '\\':
 354                 to = '\\';
 355                 break;
 356         case '\a':
 357                 to = 'a';
 358                 break;
 359         case '\e':
 360                 to = 'e';
 361                 break;
 362         default:
 363                 return false;
 364         }
 365
 366         if (out < end)
 367                 *out = '\\';
 368         ++out;
 369         if (out < end)
 370                 *out = to;
 371         ++out;
 372
 373         *dst = out;
 374         return true;
 375 }
 376
 377 static bool escape_null(unsigned char c, char **dst, char *end)
 378 {
 379         char *out = *dst;
 380
 381         if (c)
 382                 return false;
 383
 384         if (out < end)
 385                 *out = '\\';
 386         ++out;
 387         if (out < end)
 388                 *out = '0';
 389         ++out;
 390
 391         *dst = out;
 392         return true;
 393 }
 394
 395 static bool escape_octal(unsigned char c, char **dst, char *end)
 396 {
 397         char *out = *dst;
 398
 399         if (out < end)
 400                 *out = '\\';
 401         ++out;
 402         if (out < end)
 403                 *out = ((c >> 6) & 0x07) + '0';
 404         ++out;
 405         if (out < end)
 406                 *out = ((c >> 3) & 0x07) + '0';
 407         ++out;
 408         if (out < end)
 409                 *out = ((c >> 0) & 0x07) + '0';
 410         ++out;
 411
 412         *dst = out;
 413         return true;
 414 }
 415
 416 static bool escape_hex(unsigned char c, char **dst, char *end)
 417 {
 418         char *out = *dst;
 419
 420         if (out < end)
 421                 *out = '\\';
 422         ++out;
 423         if (out < end)
 424                 *out = 'x';
 425         ++out;
 426         if (out < end)
 427                 *out = hex_asc_hi(c);
 428         ++out;
 429         if (out < end)
 430                 *out = hex_asc_lo(c);
 431         ++out;
 432
 433         *dst = out;
 434         return true;
 435 }
 436
 437 /**
 438  * string_escape_mem - quote characters in the given memory buffer
 439  * @src:        source buffer (unescaped)
 440  * @isz:        source buffer size
 441  * @dst:        destination buffer (escaped)
 442  * @osz:        destination buffer size
 443  * @flags:      combination of the flags (bitwise OR):
 444  *      %ESCAPE_SPACE: (special white space, not space itself)
 445  *              '\f' - form feed
 446  *              '\n' - new line
 447  *              '\r' - carriage return
 448  *              '\t' - horizontal tab
 449  *              '\v' - vertical tab
 450  *      %ESCAPE_SPECIAL:
 451  *              '\\' - backslash
 452  *              '\a' - alert (BEL)
 453  *              '\e' - escape
 454  *      %ESCAPE_NULL:
 455  *              '\0' - null
 456  *      %ESCAPE_OCTAL:
 457  *              '\NNN' - byte with octal value NNN (3 digits)
 458  *      %ESCAPE_ANY:
 459  *              all previous together
 460  *      %ESCAPE_NP:
 461  *              escape only non-printable characters (checked by isprint)
 462  *      %ESCAPE_ANY_NP:
 463  *              all previous together
 464  *      %ESCAPE_HEX:
 465  *              '\xHH' - byte with hexadecimal value HH (2 digits)
 466  * @only:       NULL-terminated string containing characters used to limit
 467  *              the selected escape class. If characters are included in @only
 468  *              that would not normally be escaped by the classes selected
 469  *              in @flags, they will be copied to @dst unescaped.
 470  *
 471  * Description:
 472  * The process of escaping byte buffer includes several parts. They are applied
 473  * in the following sequence.
 474  *      1. The character is matched to the printable class, if asked, and in
 475  *         case of match it passes through to the output.
 476  *      2. The character is not matched to the one from @only string and thus
 477  *         must go as-is to the output.
 478  *      3. The character is checked if it falls into the class given by @flags.
 479  *         %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any
 480  *         character. Note that they actually can't go together, otherwise
 481  *         %ESCAPE_HEX will be ignored.
 482  *
 483  * Caller must provide valid source and destination pointers. Be aware that
 484  * destination buffer will not be NULL-terminated, thus caller have to append
 485  * it if needs.
 486  *
 487  * Return:
 488  * The total size of the escaped output that would be generated for
 489  * the given input and flags. To check whether the output was
 490  * truncated, compare the return value to osz. There is room left in
 491  * dst for a '\0' terminator if and only if ret < osz.
 492  */
 493 int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
 494                       unsigned int flags, const char *only)
 495 {
 496         char *p = dst;
 497         char *end = p + osz;
 498         bool is_dict = only && *only;
 499
 500         while (isz--) {
 501                 unsigned char c = *src++;
 502
 503                 /*
 504                  * Apply rules in the following sequence:
 505                  *      - the character is printable, when @flags has
 506                  *        %ESCAPE_NP bit set
 507                  *      - the @only string is supplied and does not contain a
 508                  *        character under question
 509                  *      - the character doesn't fall into a class of symbols
 510                  *        defined by given @flags
 511                  * In these cases we just pass through a character to the
 512                  * output buffer.
 513                  */
 514                 if ((flags & ESCAPE_NP && isprint(c)) ||
 515                     (is_dict && !strchr(only, c))) {
 516                         /* do nothing */
 517                 } else {
 518                         if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
 519                                 continue;
 520
 521                         if (flags & ESCAPE_SPECIAL && escape_special(c, &p, end))
 522                                 continue;
 523
 524                         if (flags & ESCAPE_NULL && escape_null(c, &p, end))
 525                                 continue;
 526
 527                         /* ESCAPE_OCTAL and ESCAPE_HEX always go last */
 528                         if (flags & ESCAPE_OCTAL && escape_octal(c, &p, end))
 529                                 continue;
 530
 531                         if (flags & ESCAPE_HEX && escape_hex(c, &p, end))
 532                                 continue;
 533                 }
 534
 535                 escape_passthrough(c, &p, end);
 536         }
 537
 538         return p - dst;
 539 }
 540 EXPORT_SYMBOL(string_escape_mem);
 541
 542 /*
 543  * Return an allocated string that has been escaped of special characters
 544  * and double quotes, making it safe to log in quotes.
 545  */
 546 char *kstrdup_quotable(const char *src, gfp_t gfp)
 547 {
 548         size_t slen, dlen;
 549         char *dst;
 550         const int flags = ESCAPE_HEX;
 551         const char esc[] = "\f\n\r\t\v\a\e\\\"";
 552
 553         if (!src)
 554                 return NULL;
 555         slen = strlen(src);
 556
 557         dlen = string_escape_mem(src, slen, NULL, 0, flags, esc);
 558         dst = kmalloc(dlen + 1, gfp);
 559         if (!dst)
 560                 return NULL;
 561
 562         WARN_ON(string_escape_mem(src, slen, dst, dlen, flags, esc) != dlen);
 563         dst[dlen] = '\0';
 564
 565         return dst;
 566 }
 567 EXPORT_SYMBOL_GPL(kstrdup_quotable);
 568
 569 /*
 570  * Returns allocated NULL-terminated string containing process
 571  * command line, with inter-argument NULLs replaced with spaces,
 572  * and other special characters escaped.
 573  */
 574 char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp)
 575 {
 576         char *buffer, *quoted;
 577         int i, res;
 578
 579         buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
 580         if (!buffer)
 581                 return NULL;
 582
 583         res = get_cmdline(task, buffer, PAGE_SIZE - 1);
 584         buffer[res] = '\0';
 585
 586         /* Collapse trailing NULLs, leave res pointing to last non-NULL. */
 587         while (--res >= 0 && buffer[res] == '\0')
 588                 ;
 589
 590         /* Replace inter-argument NULLs. */
 591         for (i = 0; i <= res; i++)
 592                 if (buffer[i] == '\0')
 593                         buffer[i] = ' ';
 594
 595         /* Make sure result is printable. */
 596         quoted = kstrdup_quotable(buffer, gfp);
 597         kfree(buffer);
 598         return quoted;
 599 }
 600 EXPORT_SYMBOL_GPL(kstrdup_quotable_cmdline);
 601
 602 /*
 603  * Returns allocated NULL-terminated string containing pathname,
 604  * with special characters escaped, able to be safely logged. If
 605  * there is an error, the leading character will be "<".
 606  */
 607 char *kstrdup_quotable_file(struct file *file, gfp_t gfp)
 608 {
 609         char *temp, *pathname;
 610
 611         if (!file)
 612                 return kstrdup("<unknown>", gfp);
 613
 614         /* We add 11 spaces for ' (deleted)' to be appended */
 615         temp = kmalloc(PATH_MAX + 11, GFP_KERNEL);
 616         if (!temp)
 617                 return kstrdup("<no_memory>", gfp);
 618
 619         pathname = file_path(file, temp, PATH_MAX + 11);
 620         if (IS_ERR(pathname))
 621                 pathname = kstrdup("<too_long>", gfp);
 622         else
 623                 pathname = kstrdup_quotable(pathname, gfp);
 624
 625         kfree(temp);
 626         return pathname;
 627 }
 628 EXPORT_SYMBOL_GPL(kstrdup_quotable_file);