summaryrefslogtreecommitdiff
path: root/lib/string_helpers.c
blob: 4403e1924f7307d190edd67f00e5e987a4d322b1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Helpers for formatting and printing strings
 *
 * Copyright 31 August 2008 James Bottomley
 * Copyright (C) 2013, Intel Corporation
 */
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/export.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/limits.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/string_helpers.h>

/**
 * string_get_size - get the size in the specified units
 * @size:	The size to be converted in blocks
 * @blk_size:	Size of the block (use 1 for size in bytes)
 * @units:	units to use (powers of 1000 or 1024)
 * @buf:	buffer to format to
 * @len:	length of buffer
 *
 * This function returns a string formatted to 3 significant figures
 * giving the size in the required units.  @buf should have room for
 * at least 9 bytes and will always be zero terminated.
 *
 */
void string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
		     char *buf, int len)
{
	static const char *const units_10[] = {
		"B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"
	};
	static const char *const units_2[] = {
		"B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"
	};
	static const char *const *const units_str[] = {
		[STRING_UNITS_10] = units_10,
		[STRING_UNITS_2] = units_2,
	};
	static const unsigned int divisor[] = {
		[STRING_UNITS_10] = 1000,
		[STRING_UNITS_2] = 1024,
	};
	static const unsigned int rounding[] = { 500, 50, 5 };
	int i = 0, j;
	u32 remainder = 0, sf_cap;
	char tmp[8];
	const char *unit;

	tmp[0] = '\0';

	if (blk_size == 0)
		size = 0;
	if (size == 0)
		goto out;

	/* This is Napier's algorithm.  Reduce the original block size to
	 *
	 * coefficient * divisor[units]^i
	 *
	 * we do the reduction so both coefficients are just under 32 bits so
	 * that multiplying them together won't overflow 64 bits and we keep
	 * as much precision as possible in the numbers.
	 *
	 * Note: it's safe to throw away the remainders here because all the
	 * precision is in the coefficients.
	 */
	while (blk_size >> 32) {
		do_div(blk_size, divisor[units]);
		i++;
	}

	while (size >> 32) {
		do_div(size, divisor[units]);
		i++;
	}

	/* now perform the actual multiplication keeping i as the sum of the
	 * two logarithms */
	size *= blk_size;

	/* and logarithmically reduce it until it's just under the divisor */
	while (size >= divisor[units]) {
		remainder = do_div(size, divisor[units]);
		i++;
	}

	/* work out in j how many digits of precision we need from the
	 * remainder */
	sf_cap = size;
	for (j = 0; sf_cap*10 < 1000; j++)
		sf_cap *= 10;

	if (units == STRING_UNITS_2) {
		/* express the remainder as a decimal.  It's currently the
		 * numerator of a fraction whose denominator is
		 * divisor[units], which is 1 << 10 for STRING_UNITS_2 */
		remainder *= 1000;
		remainder >>= 10;
	}

	/* add a 5 to the digit below what will be printed to ensure
	 * an arithmetical round up and carry it through to size */
	remainder += rounding[j];
	if (remainder >= 1000) {
		remainder -= 1000;
		size += 1;
	}

	if (j) {
		snprintf(tmp, sizeof(tmp), ".%03u", remainder);
		tmp[j+1] = '\0';
	}

 out:
	if (i >= ARRAY_SIZE(units_2))
		unit = "UNK";
	else
		unit = units_str[units][i];

	snprintf(buf, len, "%u%s %s", (u32)size,
		 tmp, unit);
}
EXPORT_SYMBOL(string_get_size);

static bool unescape_space(char **src, char **dst)
{
	char *p = *dst, *q = *src;

	switch (*q) {
	case 'n':
		*p = '\n';
		break;
	case 'r':
		*p = '\r';
		break;
	case 't':
		*p = '\t';
		break;
	case 'v':
		*p = '\v';
		break;
	case 'f':
		*p = '\f';
		break;
	default:
		return false;
	}
	*dst += 1;
	*src += 1;
	return true;
}

static bool unescape_octal(char **src, char **dst)
{
	char *p = *dst, *q = *src;
	u8 num;

	if (isodigit(*q) == 0)
		return false;

	num = (*q++) & 7;
	while (num < 32 && isodigit(*q) && (q - *src < 3)) {
		num <<= 3;
		num += (*q++) & 7;
	}
	*p = num;
	*dst += 1;
	*src = q;
	return true;
}

static bool unescape_hex(char **src, char **dst)
{
	char *p = *dst, *q = *src;
	int digit;
	u8 num;

	if (*q++ != 'x')
		return false;

	num = digit = hex_to_bin(*q++);
	if (digit < 0)
		return false;

	digit = hex_to_bin(*q);
	if (digit >= 0) {
		q++;
		num = (num << 4) | digit;
	}
	*p = num;
	*dst += 1;
	*src = q;
	return true;
}

static bool unescape_special(char **src, char **dst)
{
	char *p = *dst, *q = *src;

	switch (*q) {
	case '\"':
		*p = '\"';
		break;
	case '\\':
		*p = '\\';
		break;
	case 'a':
		*p = '\a';
		break;
	case 'e':
		*p = '\e';
		break;
	default:
		return false;
	}
	*dst += 1;
	*src += 1;
	return true;
}

/**
 * string_unescape - unquote characters in the given string
 * @src:	source buffer (escaped)
 * @dst:	destination buffer (unescaped)
 * @size:	size of the destination buffer (0 to unlimit)
 * @flags:	combination of the flags (bitwise OR):
 *	%UNESCAPE_SPACE:
 *		'\f' - form feed
 *		'\n' - new line
 *		'\r' - carriage return
 *		'\t' - horizontal tab
 *		'\v' - vertical tab
 *	%UNESCAPE_OCTAL:
 *		'\NNN' - byte with octal value NNN (1 to 3 digits)
 *	%UNESCAPE_HEX:
 *		'\xHH' - byte with hexadecimal value HH (1 to 2 digits)
 *	%UNESCAPE_SPECIAL:
 *		'\"' - double quote
 *		'\\' - backslash
 *		'\a' - alert (BEL)
 *		'\e' - escape
 *	%UNESCAPE_ANY:
 *		all previous together
 *
 * Description:
 * The function unquotes characters in the given string.
 *
 * Because the size of the output will be the same as or less than the size of
 * the input, the transformation may be performed in place.
 *
 * Caller must provide valid source and destination pointers. Be aware that
 * destination buffer will always be NULL-terminated. Source string must be
 * NULL-terminated as well.
 *
 * Return:
 * The amount of the characters processed to the destination buffer excluding
 * trailing '\0' is returned.
 */
int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
{
	char *out = dst;

	while (*src && --size) {
		if (src[0] == '\\' && src[1] != '\0' && size > 1) {
			src++;
			size--;

			if (flags & UNESCAPE_SPACE &&
					unescape_space(&src, &out))
				continue;

			if (flags & UNESCAPE_OCTAL &&
					unescape_octal(&src, &out))
				continue;

			if (flags & UNESCAPE_HEX &&
					unescape_hex(&src, &out))
				continue;

			if (flags & UNESCAPE_SPECIAL &&
					unescape_special(&src, &out))
				continue;

			*out++ = '\\';
		}
		*out++ = *src++;
	}
	*out = '\0';

	return out - dst;
}
EXPORT_SYMBOL(string_unescape);

static bool escape_passthrough(unsigned char c, char **dst, char *end)
{
	char *out = *dst;

	if (out < end)
		*out = c;
	*dst = out + 1;
	return true;
}

static bool escape_space(unsigned char c, char **dst, char *end)
{
	char *out = *dst;
	unsigned char to;

	switch (c) {
	case '\n':
		to = 'n';
		break;
	case '\r':
		to = 'r';
		break;
	case '\t':
		to = 't';
		break;
	case '\v':
		to = 'v';
		break;
	case '\f':
		to = 'f';
		break;
	default:
		return false;
	}

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = to;
	++out;

	*dst = out;
	return true;
}

static bool escape_special(unsigned char c, char **dst, char *end)
{
	char *out = *dst;
	unsigned char to;

	switch (c) {
	case '\\':
		to = '\\';
		break;
	case '\a':
		to = 'a';
		break;
	case '\e':
		to = 'e';
		break;
	default:
		return false;
	}

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = to;
	++out;

	*dst = out;
	return true;
}

static bool escape_null(unsigned char c, char **dst, char *end)
{
	char *out = *dst;

	if (c)
		return false;

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = '0';
	++out;

	*dst = out;
	return true;
}

static bool escape_octal(unsigned char c, char **dst, char *end)
{
	char *out = *dst;

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = ((c >> 6) & 0x07) + '0';
	++out;
	if (out < end)
		*out = ((c >> 3) & 0x07) + '0';
	++out;
	if (out < end)
		*out = ((c >> 0) & 0x07) + '0';
	++out;

	*dst = out;
	return true;
}

static bool escape_hex(unsigned char c, char **dst, char *end)
{
	char *out = *dst;

	if (out < end)
		*out = '\\';
	++out;
	if (out < end)
		*out = 'x';
	++out;
	if (out < end)
		*out = hex_asc_hi(c);
	++out;
	if (out < end)
		*out = hex_asc_lo(c);
	++out;

	*dst = out;
	return true;
}

/**
 * string_escape_mem - quote characters in the given memory buffer
 * @src:	source buffer (unescaped)
 * @isz:	source buffer size
 * @dst:	destination buffer (escaped)
 * @osz:	destination buffer size
 * @flags:	combination of the flags (bitwise OR):
 *	%ESCAPE_SPACE: (special white space, not space itself)
 *		'\f' - form feed
 *		'\n' - new line
 *		'\r' - carriage return
 *		'\t' - horizontal tab
 *		'\v' - vertical tab
 *	%ESCAPE_SPECIAL:
 *		'\\' - backslash
 *		'\a' - alert (BEL)
 *		'\e' - escape
 *	%ESCAPE_NULL:
 *		'\0' - null
 *	%ESCAPE_OCTAL:
 *		'\NNN' - byte with octal value NNN (3 digits)
 *	%ESCAPE_ANY:
 *		all previous together
 *	%ESCAPE_NP:
 *		escape only non-printable characters (checked by isprint)
 *	%ESCAPE_ANY_NP:
 *		all previous together
 *	%ESCAPE_HEX:
 *		'\xHH' - byte with hexadecimal value HH (2 digits)
 * @only:	NULL-terminated string containing characters used to limit
 *		the selected escape class. If characters are included in @only
 *		that would not normally be escaped by the classes selected
 *		in @flags, they will be copied to @dst unescaped.
 *
 * Description:
 * The process of escaping byte buffer includes several parts. They are applied
 * in the following sequence.
 *	1. The character is matched to the printable class, if asked, and in
 *	   case of match it passes through to the output.
 *	2. The character is not matched to the one from @only string and thus
 *	   must go as-is to the output.
 *	3. The character is checked if it falls into the class given by @flags.
 *	   %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any
 *	   character. Note that they actually can't go together, otherwise
 *	   %ESCAPE_HEX will be ignored.
 *
 * Caller must provide valid source and destination pointers. Be aware that
 * destination buffer will not be NULL-terminated, thus caller have to append
 * it if needs.
 *
 * Return:
 * The total size of the escaped output that would be generated for
 * the given input and flags. To check whether the output was
 * truncated, compare the return value to osz. There is room left in
 * dst for a '\0' terminator if and only if ret < osz.
 */
int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
		      unsigned int flags, const char *only)
{
	char *p = dst;
	char *end = p + osz;
	bool is_dict = only && *only;

	while (isz--) {
		unsigned char c = *src++;

		/*
		 * Apply rules in the following sequence:
		 *	- the character is printable, when @flags has
		 *	  %ESCAPE_NP bit set
		 *	- the @only string is supplied and does not contain a
		 *	  character under question
		 *	- the character doesn't fall into a class of symbols
		 *	  defined by given @flags
		 * In these cases we just pass through a character to the
		 * output buffer.
		 */
		if ((flags & ESCAPE_NP && isprint(c)) ||
		    (is_dict && !strchr(only, c))) {
			/* do nothing */
		} else {
			if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
				continue;

			if (flags & ESCAPE_SPECIAL && escape_special(c, &p, end))
				continue;

			if (flags & ESCAPE_NULL && escape_null(c, &p, end))
				continue;

			/* ESCAPE_OCTAL and ESCAPE_HEX always go last */
			if (flags & ESCAPE_OCTAL && escape_octal(c, &p, end))
				continue;

			if (flags & ESCAPE_HEX && escape_hex(c, &p, end))
				continue;
		}

		escape_passthrough(c, &p, end);
	}

	return p - dst;
}
EXPORT_SYMBOL(string_escape_mem);

/*
 * Return an allocated string that has been escaped of special characters
 * and double quotes, making it safe to log in quotes.
 */
char *kstrdup_quotable(const char *src, gfp_t gfp)
{
	size_t slen, dlen;
	char *dst;
	const int flags = ESCAPE_HEX;
	const char esc[] = "\f\n\r\t\v\a\e\\\"";

	if (!src)
		return NULL;
	slen = strlen(src);

	dlen = string_escape_mem(src, slen, NULL, 0, flags, esc);
	dst = kmalloc(dlen + 1, gfp);
	if (!dst)
		return NULL;

	WARN_ON(string_escape_mem(src, slen, dst, dlen, flags, esc) != dlen);
	dst[dlen] = '\0';

	return dst;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable);

/*
 * Returns allocated NULL-terminated string containing process
 * command line, with inter-argument NULLs replaced with spaces,
 * and other special characters escaped.
 */
char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp)
{
	char *buffer, *quoted;
	int i, res;

	buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!buffer)
		return NULL;

	res = get_cmdline(task, buffer, PAGE_SIZE - 1);
	buffer[res] = '\0';

	/* Collapse trailing NULLs, leave res pointing to last non-NULL. */
	while (--res >= 0 && buffer[res] == '\0')
		;

	/* Replace inter-argument NULLs. */
	for (i = 0; i <= res; i++)
		if (buffer[i] == '\0')
			buffer[i] = ' ';

	/* Make sure result is printable. */
	quoted = kstrdup_quotable(buffer, gfp);
	kfree(buffer);
	return quoted;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable_cmdline);

/*
 * Returns allocated NULL-terminated string containing pathname,
 * with special characters escaped, able to be safely logged. If
 * there is an error, the leading character will be "<".
 */
char *kstrdup_quotable_file(struct file *file, gfp_t gfp)
{
	char *temp, *pathname;

	if (!file)
		return kstrdup("<unknown>", gfp);

	/* We add 11 spaces for ' (deleted)' to be appended */
	temp = kmalloc(PATH_MAX + 11, GFP_KERNEL);
	if (!temp)
		return kstrdup("<no_memory>", gfp);

	pathname = file_path(file, temp, PATH_MAX + 11);
	if (IS_ERR(pathname))
		pathname = kstrdup("<too_long>", gfp);
	else
		pathname = kstrdup_quotable(pathname, gfp);

	kfree(temp);
	return pathname;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable_file);