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Linux/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 = '';
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) + '';
404         ++out;
405         if (out < end)
406                 *out = ((c >> 3) & 0x07) + '';
407         ++out;
408         if (out < end)
409                 *out = ((c >> 0) & 0x07) + '';
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_TEMPORARY);
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_TEMPORARY);
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);
629 

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