summaryrefslogtreecommitdiff
path: root/wrapper.c
blob: 299d6489a6b0a148b57fa6c8a11f9245e1dfd0dd (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
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
/*
 * Various trivial helper wrappers around standard functions
 */
#include "cache.h"
#include "config.h"

static intmax_t count_fsync_writeout_only;
static intmax_t count_fsync_hardware_flush;

#ifdef HAVE_RTLGENRANDOM
/* This is required to get access to RtlGenRandom. */
#define SystemFunction036 NTAPI SystemFunction036
#include <NTSecAPI.h>
#undef SystemFunction036
#endif

static int memory_limit_check(size_t size, int gentle)
{
	static size_t limit = 0;
	if (!limit) {
		limit = git_env_ulong("GIT_ALLOC_LIMIT", 0);
		if (!limit)
			limit = SIZE_MAX;
	}
	if (size > limit) {
		if (gentle) {
			error("attempting to allocate %"PRIuMAX" over limit %"PRIuMAX,
			      (uintmax_t)size, (uintmax_t)limit);
			return -1;
		} else
			die("attempting to allocate %"PRIuMAX" over limit %"PRIuMAX,
			    (uintmax_t)size, (uintmax_t)limit);
	}
	return 0;
}

char *xstrdup(const char *str)
{
	char *ret = strdup(str);
	if (!ret)
		die("Out of memory, strdup failed");
	return ret;
}

static void *do_xmalloc(size_t size, int gentle)
{
	void *ret;

	if (memory_limit_check(size, gentle))
		return NULL;
	ret = malloc(size);
	if (!ret && !size)
		ret = malloc(1);
	if (!ret) {
		if (!gentle)
			die("Out of memory, malloc failed (tried to allocate %lu bytes)",
			    (unsigned long)size);
		else {
			error("Out of memory, malloc failed (tried to allocate %lu bytes)",
			      (unsigned long)size);
			return NULL;
		}
	}
#ifdef XMALLOC_POISON
	memset(ret, 0xA5, size);
#endif
	return ret;
}

void *xmalloc(size_t size)
{
	return do_xmalloc(size, 0);
}

static void *do_xmallocz(size_t size, int gentle)
{
	void *ret;
	if (unsigned_add_overflows(size, 1)) {
		if (gentle) {
			error("Data too large to fit into virtual memory space.");
			return NULL;
		} else
			die("Data too large to fit into virtual memory space.");
	}
	ret = do_xmalloc(size + 1, gentle);
	if (ret)
		((char*)ret)[size] = 0;
	return ret;
}

void *xmallocz(size_t size)
{
	return do_xmallocz(size, 0);
}

void *xmallocz_gently(size_t size)
{
	return do_xmallocz(size, 1);
}

/*
 * xmemdupz() allocates (len + 1) bytes of memory, duplicates "len" bytes of
 * "data" to the allocated memory, zero terminates the allocated memory,
 * and returns a pointer to the allocated memory. If the allocation fails,
 * the program dies.
 */
void *xmemdupz(const void *data, size_t len)
{
	return memcpy(xmallocz(len), data, len);
}

char *xstrndup(const char *str, size_t len)
{
	char *p = memchr(str, '\0', len);
	return xmemdupz(str, p ? p - str : len);
}

int xstrncmpz(const char *s, const char *t, size_t len)
{
	int res = strncmp(s, t, len);
	if (res)
		return res;
	return s[len] == '\0' ? 0 : 1;
}

void *xrealloc(void *ptr, size_t size)
{
	void *ret;

	if (!size) {
		free(ptr);
		return xmalloc(0);
	}

	memory_limit_check(size, 0);
	ret = realloc(ptr, size);
	if (!ret)
		die("Out of memory, realloc failed");
	return ret;
}

void *xcalloc(size_t nmemb, size_t size)
{
	void *ret;

	if (unsigned_mult_overflows(nmemb, size))
		die("data too large to fit into virtual memory space");

	memory_limit_check(size * nmemb, 0);
	ret = calloc(nmemb, size);
	if (!ret && (!nmemb || !size))
		ret = calloc(1, 1);
	if (!ret)
		die("Out of memory, calloc failed");
	return ret;
}

void xsetenv(const char *name, const char *value, int overwrite)
{
	if (setenv(name, value, overwrite))
		die_errno(_("could not setenv '%s'"), name ? name : "(null)");
}

/**
 * xopen() is the same as open(), but it die()s if the open() fails.
 */
int xopen(const char *path, int oflag, ...)
{
	mode_t mode = 0;
	va_list ap;

	/*
	 * va_arg() will have undefined behavior if the specified type is not
	 * compatible with the argument type. Since integers are promoted to
	 * ints, we fetch the next argument as an int, and then cast it to a
	 * mode_t to avoid undefined behavior.
	 */
	va_start(ap, oflag);
	if (oflag & O_CREAT)
		mode = va_arg(ap, int);
	va_end(ap);

	for (;;) {
		int fd = open(path, oflag, mode);
		if (fd >= 0)
			return fd;
		if (errno == EINTR)
			continue;

		if ((oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
			die_errno(_("unable to create '%s'"), path);
		else if ((oflag & O_RDWR) == O_RDWR)
			die_errno(_("could not open '%s' for reading and writing"), path);
		else if ((oflag & O_WRONLY) == O_WRONLY)
			die_errno(_("could not open '%s' for writing"), path);
		else
			die_errno(_("could not open '%s' for reading"), path);
	}
}

static int handle_nonblock(int fd, short poll_events, int err)
{
	struct pollfd pfd;

	if (err != EAGAIN && err != EWOULDBLOCK)
		return 0;

	pfd.fd = fd;
	pfd.events = poll_events;

	/*
	 * no need to check for errors, here;
	 * a subsequent read/write will detect unrecoverable errors
	 */
	poll(&pfd, 1, -1);
	return 1;
}

/*
 * xread() is the same a read(), but it automatically restarts read()
 * operations with a recoverable error (EAGAIN and EINTR). xread()
 * DOES NOT GUARANTEE that "len" bytes is read even if the data is available.
 */
ssize_t xread(int fd, void *buf, size_t len)
{
	ssize_t nr;
	if (len > MAX_IO_SIZE)
		len = MAX_IO_SIZE;
	while (1) {
		nr = read(fd, buf, len);
		if (nr < 0) {
			if (errno == EINTR)
				continue;
			if (handle_nonblock(fd, POLLIN, errno))
				continue;
		}
		return nr;
	}
}

/*
 * xwrite() is the same a write(), but it automatically restarts write()
 * operations with a recoverable error (EAGAIN and EINTR). xwrite() DOES NOT
 * GUARANTEE that "len" bytes is written even if the operation is successful.
 */
ssize_t xwrite(int fd, const void *buf, size_t len)
{
	ssize_t nr;
	if (len > MAX_IO_SIZE)
		len = MAX_IO_SIZE;
	while (1) {
		nr = write(fd, buf, len);
		if (nr < 0) {
			if (errno == EINTR)
				continue;
			if (handle_nonblock(fd, POLLOUT, errno))
				continue;
		}

		return nr;
	}
}

/*
 * xpread() is the same as pread(), but it automatically restarts pread()
 * operations with a recoverable error (EAGAIN and EINTR). xpread() DOES
 * NOT GUARANTEE that "len" bytes is read even if the data is available.
 */
ssize_t xpread(int fd, void *buf, size_t len, off_t offset)
{
	ssize_t nr;
	if (len > MAX_IO_SIZE)
		len = MAX_IO_SIZE;
	while (1) {
		nr = pread(fd, buf, len, offset);
		if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
			continue;
		return nr;
	}
}

ssize_t read_in_full(int fd, void *buf, size_t count)
{
	char *p = buf;
	ssize_t total = 0;

	while (count > 0) {
		ssize_t loaded = xread(fd, p, count);
		if (loaded < 0)
			return -1;
		if (loaded == 0)
			return total;
		count -= loaded;
		p += loaded;
		total += loaded;
	}

	return total;
}

ssize_t write_in_full(int fd, const void *buf, size_t count)
{
	const char *p = buf;
	ssize_t total = 0;

	while (count > 0) {
		ssize_t written = xwrite(fd, p, count);
		if (written < 0)
			return -1;
		if (!written) {
			errno = ENOSPC;
			return -1;
		}
		count -= written;
		p += written;
		total += written;
	}

	return total;
}

ssize_t pread_in_full(int fd, void *buf, size_t count, off_t offset)
{
	char *p = buf;
	ssize_t total = 0;

	while (count > 0) {
		ssize_t loaded = xpread(fd, p, count, offset);
		if (loaded < 0)
			return -1;
		if (loaded == 0)
			return total;
		count -= loaded;
		p += loaded;
		total += loaded;
		offset += loaded;
	}

	return total;
}

int xdup(int fd)
{
	int ret = dup(fd);
	if (ret < 0)
		die_errno("dup failed");
	return ret;
}

/**
 * xfopen() is the same as fopen(), but it die()s if the fopen() fails.
 */
FILE *xfopen(const char *path, const char *mode)
{
	for (;;) {
		FILE *fp = fopen(path, mode);
		if (fp)
			return fp;
		if (errno == EINTR)
			continue;

		if (*mode && mode[1] == '+')
			die_errno(_("could not open '%s' for reading and writing"), path);
		else if (*mode == 'w' || *mode == 'a')
			die_errno(_("could not open '%s' for writing"), path);
		else
			die_errno(_("could not open '%s' for reading"), path);
	}
}

FILE *xfdopen(int fd, const char *mode)
{
	FILE *stream = fdopen(fd, mode);
	if (!stream)
		die_errno("Out of memory? fdopen failed");
	return stream;
}

FILE *fopen_for_writing(const char *path)
{
	FILE *ret = fopen(path, "w");

	if (!ret && errno == EPERM) {
		if (!unlink(path))
			ret = fopen(path, "w");
		else
			errno = EPERM;
	}
	return ret;
}

static void warn_on_inaccessible(const char *path)
{
	warning_errno(_("unable to access '%s'"), path);
}

int warn_on_fopen_errors(const char *path)
{
	if (errno != ENOENT && errno != ENOTDIR) {
		warn_on_inaccessible(path);
		return -1;
	}

	return 0;
}

FILE *fopen_or_warn(const char *path, const char *mode)
{
	FILE *fp = fopen(path, mode);

	if (fp)
		return fp;

	warn_on_fopen_errors(path);
	return NULL;
}

int xmkstemp(char *filename_template)
{
	int fd;
	char origtemplate[PATH_MAX];
	strlcpy(origtemplate, filename_template, sizeof(origtemplate));

	fd = mkstemp(filename_template);
	if (fd < 0) {
		int saved_errno = errno;
		const char *nonrelative_template;

		if (strlen(filename_template) != strlen(origtemplate))
			filename_template = origtemplate;

		nonrelative_template = absolute_path(filename_template);
		errno = saved_errno;
		die_errno("Unable to create temporary file '%s'",
			nonrelative_template);
	}
	return fd;
}

/* Adapted from libiberty's mkstemp.c. */

#undef TMP_MAX
#define TMP_MAX 16384

int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
{
	static const char letters[] =
		"abcdefghijklmnopqrstuvwxyz"
		"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
		"0123456789";
	static const int num_letters = ARRAY_SIZE(letters) - 1;
	static const char x_pattern[] = "XXXXXX";
	static const int num_x = ARRAY_SIZE(x_pattern) - 1;
	char *filename_template;
	size_t len;
	int fd, count;

	len = strlen(pattern);

	if (len < num_x + suffix_len) {
		errno = EINVAL;
		return -1;
	}

	if (strncmp(&pattern[len - num_x - suffix_len], x_pattern, num_x)) {
		errno = EINVAL;
		return -1;
	}

	/*
	 * Replace pattern's XXXXXX characters with randomness.
	 * Try TMP_MAX different filenames.
	 */
	filename_template = &pattern[len - num_x - suffix_len];
	for (count = 0; count < TMP_MAX; ++count) {
		int i;
		uint64_t v;
		if (csprng_bytes(&v, sizeof(v)) < 0)
			return error_errno("unable to get random bytes for temporary file");

		/* Fill in the random bits. */
		for (i = 0; i < num_x; i++) {
			filename_template[i] = letters[v % num_letters];
			v /= num_letters;
		}

		fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, mode);
		if (fd >= 0)
			return fd;
		/*
		 * Fatal error (EPERM, ENOSPC etc).
		 * It doesn't make sense to loop.
		 */
		if (errno != EEXIST)
			break;
	}
	/* We return the null string if we can't find a unique file name.  */
	pattern[0] = '\0';
	return -1;
}

int git_mkstemp_mode(char *pattern, int mode)
{
	/* mkstemp is just mkstemps with no suffix */
	return git_mkstemps_mode(pattern, 0, mode);
}

int xmkstemp_mode(char *filename_template, int mode)
{
	int fd;
	char origtemplate[PATH_MAX];
	strlcpy(origtemplate, filename_template, sizeof(origtemplate));

	fd = git_mkstemp_mode(filename_template, mode);
	if (fd < 0) {
		int saved_errno = errno;
		const char *nonrelative_template;

		if (!filename_template[0])
			filename_template = origtemplate;

		nonrelative_template = absolute_path(filename_template);
		errno = saved_errno;
		die_errno("Unable to create temporary file '%s'",
			nonrelative_template);
	}
	return fd;
}

/*
 * Some platforms return EINTR from fsync. Since fsync is invoked in some
 * cases by a wrapper that dies on failure, do not expose EINTR to callers.
 */
static int fsync_loop(int fd)
{
	int err;

	do {
		err = fsync(fd);
	} while (err < 0 && errno == EINTR);
	return err;
}

int git_fsync(int fd, enum fsync_action action)
{
	switch (action) {
	case FSYNC_WRITEOUT_ONLY:
		count_fsync_writeout_only += 1;

#ifdef __APPLE__
		/*
		 * On macOS, fsync just causes filesystem cache writeback but
		 * does not flush hardware caches.
		 */
		return fsync_loop(fd);
#endif

#ifdef HAVE_SYNC_FILE_RANGE
		/*
		 * On linux 2.6.17 and above, sync_file_range is the way to
		 * issue a writeback without a hardware flush. An offset of
		 * 0 and size of 0 indicates writeout of the entire file and the
		 * wait flags ensure that all dirty data is written to the disk
		 * (potentially in a disk-side cache) before we continue.
		 */

		return sync_file_range(fd, 0, 0, SYNC_FILE_RANGE_WAIT_BEFORE |
						 SYNC_FILE_RANGE_WRITE |
						 SYNC_FILE_RANGE_WAIT_AFTER);
#endif

#ifdef fsync_no_flush
		return fsync_no_flush(fd);
#endif

		errno = ENOSYS;
		return -1;

	case FSYNC_HARDWARE_FLUSH:
		count_fsync_hardware_flush += 1;

		/*
		 * On macOS, a special fcntl is required to really flush the
		 * caches within the storage controller. As of this writing,
		 * this is a very expensive operation on Apple SSDs.
		 */
#ifdef __APPLE__
		return fcntl(fd, F_FULLFSYNC);
#else
		return fsync_loop(fd);
#endif
	default:
		BUG("unexpected git_fsync(%d) call", action);
	}
}

static void log_trace_fsync_if(const char *key, intmax_t value)
{
	if (value)
		trace2_data_intmax("fsync", the_repository, key, value);
}

void trace_git_fsync_stats(void)
{
	log_trace_fsync_if("fsync/writeout-only", count_fsync_writeout_only);
	log_trace_fsync_if("fsync/hardware-flush", count_fsync_hardware_flush);
}

static int warn_if_unremovable(const char *op, const char *file, int rc)
{
	int err;
	if (!rc || errno == ENOENT)
		return 0;
	err = errno;
	warning_errno("unable to %s '%s'", op, file);
	errno = err;
	return rc;
}

int unlink_or_msg(const char *file, struct strbuf *err)
{
	int rc = unlink(file);

	assert(err);

	if (!rc || errno == ENOENT)
		return 0;

	strbuf_addf(err, "unable to unlink '%s': %s",
		    file, strerror(errno));
	return -1;
}

int unlink_or_warn(const char *file)
{
	return warn_if_unremovable("unlink", file, unlink(file));
}

int rmdir_or_warn(const char *file)
{
	return warn_if_unremovable("rmdir", file, rmdir(file));
}

int remove_or_warn(unsigned int mode, const char *file)
{
	return S_ISGITLINK(mode) ? rmdir_or_warn(file) : unlink_or_warn(file);
}

static int access_error_is_ok(int err, unsigned flag)
{
	return (is_missing_file_error(err) ||
		((flag & ACCESS_EACCES_OK) && err == EACCES));
}

int access_or_warn(const char *path, int mode, unsigned flag)
{
	int ret = access(path, mode);
	if (ret && !access_error_is_ok(errno, flag))
		warn_on_inaccessible(path);
	return ret;
}

int access_or_die(const char *path, int mode, unsigned flag)
{
	int ret = access(path, mode);
	if (ret && !access_error_is_ok(errno, flag))
		die_errno(_("unable to access '%s'"), path);
	return ret;
}

char *xgetcwd(void)
{
	struct strbuf sb = STRBUF_INIT;
	if (strbuf_getcwd(&sb))
		die_errno(_("unable to get current working directory"));
	return strbuf_detach(&sb, NULL);
}

int xsnprintf(char *dst, size_t max, const char *fmt, ...)
{
	va_list ap;
	int len;

	va_start(ap, fmt);
	len = vsnprintf(dst, max, fmt, ap);
	va_end(ap);

	if (len < 0)
		BUG("your snprintf is broken");
	if (len >= max)
		BUG("attempt to snprintf into too-small buffer");
	return len;
}

void write_file_buf(const char *path, const char *buf, size_t len)
{
	int fd = xopen(path, O_WRONLY | O_CREAT | O_TRUNC, 0666);
	if (write_in_full(fd, buf, len) < 0)
		die_errno(_("could not write to '%s'"), path);
	if (close(fd))
		die_errno(_("could not close '%s'"), path);
}

void write_file(const char *path, const char *fmt, ...)
{
	va_list params;
	struct strbuf sb = STRBUF_INIT;

	va_start(params, fmt);
	strbuf_vaddf(&sb, fmt, params);
	va_end(params);

	strbuf_complete_line(&sb);

	write_file_buf(path, sb.buf, sb.len);
	strbuf_release(&sb);
}

void sleep_millisec(int millisec)
{
	poll(NULL, 0, millisec);
}

int xgethostname(char *buf, size_t len)
{
	/*
	 * If the full hostname doesn't fit in buf, POSIX does not
	 * specify whether the buffer will be null-terminated, so to
	 * be safe, do it ourselves.
	 */
	int ret = gethostname(buf, len);
	if (!ret)
		buf[len - 1] = 0;
	return ret;
}

int is_empty_or_missing_file(const char *filename)
{
	struct stat st;

	if (stat(filename, &st) < 0) {
		if (errno == ENOENT)
			return 1;
		die_errno(_("could not stat %s"), filename);
	}

	return !st.st_size;
}

int open_nofollow(const char *path, int flags)
{
#ifdef O_NOFOLLOW
	return open(path, flags | O_NOFOLLOW);
#else
	struct stat st;
	if (lstat(path, &st) < 0)
		return -1;
	if (S_ISLNK(st.st_mode)) {
		errno = ELOOP;
		return -1;
	}
	return open(path, flags);
#endif
}

int csprng_bytes(void *buf, size_t len)
{
#if defined(HAVE_ARC4RANDOM) || defined(HAVE_ARC4RANDOM_LIBBSD)
	/* This function never returns an error. */
	arc4random_buf(buf, len);
	return 0;
#elif defined(HAVE_GETRANDOM)
	ssize_t res;
	char *p = buf;
	while (len) {
		res = getrandom(p, len, 0);
		if (res < 0)
			return -1;
		len -= res;
		p += res;
	}
	return 0;
#elif defined(HAVE_GETENTROPY)
	int res;
	char *p = buf;
	while (len) {
		/* getentropy has a maximum size of 256 bytes. */
		size_t chunk = len < 256 ? len : 256;
		res = getentropy(p, chunk);
		if (res < 0)
			return -1;
		len -= chunk;
		p += chunk;
	}
	return 0;
#elif defined(HAVE_RTLGENRANDOM)
	if (!RtlGenRandom(buf, len))
		return -1;
	return 0;
#elif defined(HAVE_OPENSSL_CSPRNG)
	int res = RAND_bytes(buf, len);
	if (res == 1)
		return 0;
	if (res == -1)
		errno = ENOTSUP;
	else
		errno = EIO;
	return -1;
#else
	ssize_t res;
	char *p = buf;
	int fd, err;
	fd = open("/dev/urandom", O_RDONLY);
	if (fd < 0)
		return -1;
	while (len) {
		res = xread(fd, p, len);
		if (res < 0) {
			err = errno;
			close(fd);
			errno = err;
			return -1;
		}
		len -= res;
		p += res;
	}
	close(fd);
	return 0;
#endif
}