summaryrefslogtreecommitdiff
path: root/src/wayland-shm.c
blob: 0a11736a6da01fdcd1a6c5067dcc814563a498aa (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
/*
 * Copyright © 2008 Kristian Høgsberg
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * Authors:
 *    Kristian Høgsberg <krh@bitplanet.net>
 *    Benjamin Franzke <benjaminfranzke@googlemail.com>
 *
 */

#define _GNU_SOURCE

#include "config.h"

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include <assert.h>
#include <signal.h>
#include <pthread.h>
#include <errno.h>
#include <fcntl.h>

#include "wayland-os.h"
#include "wayland-util.h"
#include "wayland-private.h"
#include "wayland-server.h"

/* This once_t is used to synchronize installing the SIGBUS handler
 * and creating the TLS key. This will be done in the first call
 * wl_shm_buffer_begin_access which can happen from any thread */
static pthread_once_t wl_shm_sigbus_once = PTHREAD_ONCE_INIT;
static pthread_key_t wl_shm_sigbus_data_key;
static struct sigaction wl_shm_old_sigbus_action;

struct wl_shm_pool {
	struct wl_resource *resource;
	int internal_refcount;
	int external_refcount;
	char *data;
	ssize_t size;
	ssize_t new_size;
#ifndef MREMAP_MAYMOVE
	/* The following three fields are needed for mremap() emulation. */
	int mmap_fd;
	int mmap_flags;
	int mmap_prot;
#endif
	bool sigbus_is_impossible;
};

/** \class wl_shm_buffer
 *
 * \brief A SHM buffer
 *
 * wl_shm_buffer provides a helper for accessing the contents of a wl_buffer
 * resource created via the wl_shm interface.
 *
 * A wl_shm_buffer becomes invalid as soon as its #wl_resource is destroyed.
 */
struct wl_shm_buffer {
	struct wl_resource *resource;
	int32_t width, height;
	int32_t stride;
	uint32_t format;
	int offset;
	struct wl_shm_pool *pool;
};

struct wl_shm_sigbus_data {
	struct wl_shm_pool *current_pool;
	int access_count;
	int fallback_mapping_used;
};

static void *
shm_pool_grow_mapping(struct wl_shm_pool *pool)
{
	void *data;

#ifdef MREMAP_MAYMOVE
	data = mremap(pool->data, pool->size, pool->new_size, MREMAP_MAYMOVE);
#else
	data = wl_os_mremap_maymove(pool->mmap_fd, pool->data, &pool->size,
				    pool->new_size, pool->mmap_prot,
				    pool->mmap_flags);
	if (pool->size != 0 && pool->resource != NULL) {
		wl_resource_post_error(pool->resource,
				       WL_SHM_ERROR_INVALID_FD,
				       "leaked old mapping");
	}
#endif
	return data;
}

static void
shm_pool_finish_resize(struct wl_shm_pool *pool)
{
	void *data;

	if (pool->size == pool->new_size)
		return;

	data = shm_pool_grow_mapping(pool);
	if (data == MAP_FAILED) {
		if (pool->resource != NULL)
			wl_resource_post_error(pool->resource,
					       WL_SHM_ERROR_INVALID_FD,
					       "failed mremap");
		return;
	}

	pool->data = data;
	pool->size = pool->new_size;
}

static void
shm_pool_unref(struct wl_shm_pool *pool, bool external)
{
	if (external) {
		pool->external_refcount--;
		assert(pool->external_refcount >= 0);
		if (pool->external_refcount == 0)
			shm_pool_finish_resize(pool);
	} else {
		pool->internal_refcount--;
		assert(pool->internal_refcount >= 0);
	}

	if (pool->internal_refcount + pool->external_refcount > 0)
		return;

	munmap(pool->data, pool->size);
#ifndef MREMAP_MAYMOVE
	close(pool->mmap_fd);
#endif
	free(pool);
}

static void
destroy_buffer(struct wl_resource *resource)
{
	struct wl_shm_buffer *buffer = wl_resource_get_user_data(resource);

	shm_pool_unref(buffer->pool, false);
	free(buffer);
}

static void
shm_buffer_destroy(struct wl_client *client, struct wl_resource *resource)
{
	wl_resource_destroy(resource);
}

static const struct wl_buffer_interface shm_buffer_interface = {
	shm_buffer_destroy
};

static bool
format_is_supported(struct wl_client *client, uint32_t format)
{
	struct wl_display *display = wl_client_get_display(client);
	struct wl_array *formats;
	uint32_t *p;

	switch (format) {
	case WL_SHM_FORMAT_ARGB8888:
	case WL_SHM_FORMAT_XRGB8888:
		return true;
	default:
		formats = wl_display_get_additional_shm_formats(display);
		wl_array_for_each(p, formats)
			if (*p == format)
				return true;
	}

	return false;
}

static void
shm_pool_create_buffer(struct wl_client *client, struct wl_resource *resource,
		       uint32_t id, int32_t offset,
		       int32_t width, int32_t height,
		       int32_t stride, uint32_t format)
{
	struct wl_shm_pool *pool = wl_resource_get_user_data(resource);
	struct wl_shm_buffer *buffer;

	if (!format_is_supported(client, format)) {
		wl_resource_post_error(resource,
				       WL_SHM_ERROR_INVALID_FORMAT,
				       "invalid format 0x%x", format);
		return;
	}

	if (offset < 0 || width <= 0 || height <= 0 || stride < width ||
	    INT32_MAX / stride < height ||
	    offset > pool->size - stride * height) {
		wl_resource_post_error(resource,
				       WL_SHM_ERROR_INVALID_STRIDE,
				       "invalid width, height or stride (%dx%d, %u)",
				       width, height, stride);
		return;
	}

	buffer = zalloc(sizeof *buffer);
	if (buffer == NULL) {
		wl_client_post_no_memory(client);
		return;
	}

	buffer->width = width;
	buffer->height = height;
	buffer->format = format;
	buffer->stride = stride;
	buffer->offset = offset;
	buffer->pool = pool;
	pool->internal_refcount++;

	buffer->resource =
		wl_resource_create(client, &wl_buffer_interface, 1, id);
	if (buffer->resource == NULL) {
		wl_client_post_no_memory(client);
		shm_pool_unref(pool, false);
		free(buffer);
		return;
	}

	wl_resource_set_implementation(buffer->resource,
				       &shm_buffer_interface,
				       buffer, destroy_buffer);
}

static void
destroy_pool(struct wl_resource *resource)
{
	struct wl_shm_pool *pool = wl_resource_get_user_data(resource);

	pool->resource = NULL;
	shm_pool_unref(pool, false);
}

static void
shm_pool_destroy(struct wl_client *client, struct wl_resource *resource)
{
	wl_resource_destroy(resource);
}

static void
shm_pool_resize(struct wl_client *client, struct wl_resource *resource,
		int32_t size)
{
	struct wl_shm_pool *pool = wl_resource_get_user_data(resource);

	if (size < pool->size) {
		wl_resource_post_error(resource,
				       WL_SHM_ERROR_INVALID_FD,
				       "shrinking pool invalid");
		return;
	}

	pool->new_size = size;

	/* If the compositor has taken references on this pool it
	 * may be caching pointers into it. In that case we
	 * defer the resize (which may move the entire mapping)
	 * until the compositor finishes dereferencing the pool.
	 */
	if (pool->external_refcount == 0)
		shm_pool_finish_resize(pool);
}

static const struct wl_shm_pool_interface shm_pool_interface = {
	shm_pool_create_buffer,
	shm_pool_destroy,
	shm_pool_resize
};

static void
shm_create_pool(struct wl_client *client, struct wl_resource *resource,
		uint32_t id, int fd, int32_t size)
{
	struct wl_shm_pool *pool;
	struct stat statbuf;
	int seals;
	int prot;
	int flags;
	uint32_t version;

	if (size <= 0) {
		wl_resource_post_error(resource,
				       WL_SHM_ERROR_INVALID_STRIDE,
				       "invalid size (%d)", size);
		goto err_close;
	}

	pool = zalloc(sizeof *pool);
	if (pool == NULL) {
		wl_client_post_no_memory(client);
		goto err_close;
	}

#ifdef HAVE_MEMFD_CREATE
	seals = fcntl(fd, F_GET_SEALS);
	if (seals == -1)
		seals = 0;

	if ((seals & F_SEAL_SHRINK) && fstat(fd, &statbuf) >= 0)
		pool->sigbus_is_impossible = statbuf.st_size >= size;
	else
		pool->sigbus_is_impossible = false;
#else
	pool->sigbus_is_impossible = false;
#endif

	pool->internal_refcount = 1;
	pool->external_refcount = 0;
	pool->size = size;
	pool->new_size = size;
	prot = PROT_READ | PROT_WRITE;
	flags = MAP_SHARED;
	pool->data = mmap(NULL, size, prot, flags, fd, 0);
	if (pool->data == MAP_FAILED) {
		wl_resource_post_error(resource, WL_SHM_ERROR_INVALID_FD,
				       "failed mmap fd %d: %s", fd,
				       strerror(errno));
		goto err_free;
	}
#ifndef MREMAP_MAYMOVE
	/* We may need to keep the fd, prot and flags to emulate mremap(). */
	pool->mmap_fd = fd;
	pool->mmap_prot = prot;
	pool->mmap_flags = flags;
#else
	close(fd);
#endif

	version = wl_resource_get_version(resource);
	pool->resource =
		wl_resource_create(client, &wl_shm_pool_interface, version, id);
	if (!pool->resource) {
		wl_client_post_no_memory(client);
		munmap(pool->data, pool->size);
		free(pool);
		return;
	}

	wl_resource_set_implementation(pool->resource,
				       &shm_pool_interface,
				       pool, destroy_pool);

	return;

err_free:
	free(pool);
err_close:
	close(fd);
}

static void
shm_release(struct wl_client *client, struct wl_resource *resource)
{
	wl_resource_destroy(resource);
}

static const struct wl_shm_interface shm_interface = {
	shm_create_pool,
	shm_release,
};

static void
bind_shm(struct wl_client *client,
	 void *data, uint32_t version, uint32_t id)
{
	struct wl_resource *resource;
	struct wl_display *display = wl_client_get_display(client);
	struct wl_array *additional_formats;
	uint32_t *p;

	resource = wl_resource_create(client, &wl_shm_interface, version, id);
	if (!resource) {
		wl_client_post_no_memory(client);
		return;
	}

	wl_resource_set_implementation(resource, &shm_interface, data, NULL);

	wl_shm_send_format(resource, WL_SHM_FORMAT_ARGB8888);
	wl_shm_send_format(resource, WL_SHM_FORMAT_XRGB8888);

	additional_formats = wl_display_get_additional_shm_formats(display);
	wl_array_for_each(p, additional_formats)
		wl_shm_send_format(resource, *p);
}

WL_EXPORT int
wl_display_init_shm(struct wl_display *display)
{
	if (!wl_global_create(display, &wl_shm_interface, 2, NULL, bind_shm))
		return -1;

	return 0;
}

WL_EXPORT struct wl_shm_buffer *
wl_shm_buffer_get(struct wl_resource *resource)
{
	if (resource == NULL)
		return NULL;

	if (wl_resource_instance_of(resource, &wl_buffer_interface,
				    &shm_buffer_interface))
		return wl_resource_get_user_data(resource);
	else
		return NULL;
}

WL_EXPORT int32_t
wl_shm_buffer_get_stride(struct wl_shm_buffer *buffer)
{
	return buffer->stride;
}


/** Get a pointer to the memory for the SHM buffer
 *
 * \param buffer The buffer object
 *
 * Returns a pointer which can be used to read the data contained in
 * the given SHM buffer.
 *
 * As this buffer is memory-mapped, reading from it may generate
 * SIGBUS signals. This can happen if the client claims that the
 * buffer is larger than it is or if something truncates the
 * underlying file. To prevent this signal from causing the compositor
 * to crash you should call wl_shm_buffer_begin_access and
 * wl_shm_buffer_end_access around code that reads from the memory.
 *
 * \memberof wl_shm_buffer
 */
WL_EXPORT void *
wl_shm_buffer_get_data(struct wl_shm_buffer *buffer)
{
	if (buffer->pool->external_refcount &&
	    (buffer->pool->size != buffer->pool->new_size))
		wl_log("Buffer address requested when its parent pool "
		       "has an external reference and a deferred resize "
		       "pending.\n");
	return buffer->pool->data + buffer->offset;
}

WL_EXPORT uint32_t
wl_shm_buffer_get_format(struct wl_shm_buffer *buffer)
{
	return buffer->format;
}

WL_EXPORT int32_t
wl_shm_buffer_get_width(struct wl_shm_buffer *buffer)
{
	return buffer->width;
}

WL_EXPORT int32_t
wl_shm_buffer_get_height(struct wl_shm_buffer *buffer)
{
	return buffer->height;
}

/** Get a reference to a shm_buffer's shm_pool
 *
 * \param buffer The buffer object
 *
 * Returns a pointer to a buffer's shm_pool and increases the
 * shm_pool refcount.
 *
 * The compositor must remember to call wl_shm_pool_unref when
 * it no longer needs the reference to ensure proper destruction
 * of the pool.
 *
 * \memberof wl_shm_buffer
 * \sa wl_shm_pool_unref
 */
WL_EXPORT struct wl_shm_pool *
wl_shm_buffer_ref_pool(struct wl_shm_buffer *buffer)
{
	assert(buffer->pool->internal_refcount +
	       buffer->pool->external_refcount);

	buffer->pool->external_refcount++;
	return buffer->pool;
}

/** Unreference a shm_pool
 *
 * \param pool The pool object
 *
 * Drops a reference to a wl_shm_pool object.
 *
 * This is only necessary if the compositor has explicitly
 * taken a reference with wl_shm_buffer_ref_pool(), otherwise
 * the pool will be automatically destroyed when appropriate.
 *
 * \memberof wl_shm_pool
 * \sa wl_shm_buffer_ref_pool
 */
WL_EXPORT void
wl_shm_pool_unref(struct wl_shm_pool *pool)
{
	shm_pool_unref(pool, true);
}

static void
reraise_sigbus(void)
{
	/* If SIGBUS is raised for some other reason than accessing
	 * the pool then we'll uninstall the signal handler so we can
	 * reraise it. This would presumably kill the process */
	sigaction(SIGBUS, &wl_shm_old_sigbus_action, NULL);
	raise(SIGBUS);
}

static void
sigbus_handler(int signum, siginfo_t *info, void *context)
{
	struct wl_shm_sigbus_data *sigbus_data =
		pthread_getspecific(wl_shm_sigbus_data_key);
	struct wl_shm_pool *pool;

	if (sigbus_data == NULL) {
		reraise_sigbus();
		return;
	}

	pool = sigbus_data->current_pool;

	/* If the offending address is outside the mapped space for
	 * the pool then the error is a real problem so we'll reraise
	 * the signal */
	if (pool == NULL ||
	    (char *) info->si_addr < pool->data ||
	    (char *) info->si_addr >= pool->data + pool->size) {
		reraise_sigbus();
		return;
	}

	sigbus_data->fallback_mapping_used = 1;

	/* This should replace the previous mapping */
	if (mmap(pool->data, pool->size, PROT_READ | PROT_WRITE,
		 MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, 0, 0) == MAP_FAILED) {
		reraise_sigbus();
		return;
	}
}

static void
destroy_sigbus_data(void *data)
{
	struct wl_shm_sigbus_data *sigbus_data = data;

	free(sigbus_data);
}

static void
init_sigbus_data_key(void)
{
	struct sigaction new_action = {
		.sa_sigaction = sigbus_handler,
		.sa_flags = SA_SIGINFO | SA_NODEFER
	};

	sigemptyset(&new_action.sa_mask);

	sigaction(SIGBUS, &new_action, &wl_shm_old_sigbus_action);

	pthread_key_create(&wl_shm_sigbus_data_key, destroy_sigbus_data);
}

/** Mark that the given SHM buffer is about to be accessed
 *
 * \param buffer The SHM buffer
 *
 * An SHM buffer is a memory-mapped file given by the client.
 * According to POSIX, reading from a memory-mapped region that
 * extends off the end of the file will cause a SIGBUS signal to be
 * generated. Normally this would cause the compositor to terminate.
 * In order to make the compositor robust against clients that change
 * the size of the underlying file or lie about its size, you should
 * protect access to the buffer by calling this function before
 * reading from the memory and call wl_shm_buffer_end_access
 * afterwards. This will install a signal handler for SIGBUS which
 * will prevent the compositor from crashing.
 *
 * After calling this function the signal handler will remain
 * installed for the lifetime of the compositor process. Note that
 * this function will not work properly if the compositor is also
 * installing its own handler for SIGBUS.
 *
 * If a SIGBUS signal is received for an address within the range of
 * the SHM pool of the given buffer then the client will be sent an
 * error event when wl_shm_buffer_end_access is called. If the signal
 * is for an address outside that range then the signal handler will
 * reraise the signal which would will likely cause the compositor to
 * terminate.
 *
 * It is safe to nest calls to these functions as long as the nested
 * calls are all accessing the same buffer. The number of calls to
 * wl_shm_buffer_end_access must match the number of calls to
 * wl_shm_buffer_begin_access. These functions are thread-safe and it
 * is allowed to simultaneously access different buffers or the same
 * buffer from multiple threads.
 *
 * \memberof wl_shm_buffer
 */
WL_EXPORT void
wl_shm_buffer_begin_access(struct wl_shm_buffer *buffer)
{
	struct wl_shm_pool *pool = buffer->pool;
	struct wl_shm_sigbus_data *sigbus_data;

	if (pool->sigbus_is_impossible)
		return;

	pthread_once(&wl_shm_sigbus_once, init_sigbus_data_key);

	sigbus_data = pthread_getspecific(wl_shm_sigbus_data_key);
	if (sigbus_data == NULL) {
		sigbus_data = zalloc(sizeof *sigbus_data);
		if (sigbus_data == NULL)
			return;

		pthread_setspecific(wl_shm_sigbus_data_key, sigbus_data);
	}

	assert(sigbus_data->current_pool == NULL ||
	       sigbus_data->current_pool == pool);

	sigbus_data->current_pool = pool;
	sigbus_data->access_count++;
}

/** Ends the access to a buffer started by wl_shm_buffer_begin_access
 *
 * \param buffer The SHM buffer
 *
 * This should be called after wl_shm_buffer_begin_access once the
 * buffer is no longer being accessed. If a SIGBUS signal was
 * generated in-between these two calls then the resource for the
 * given buffer will be sent an error.
 *
 * \memberof wl_shm_buffer
 */
WL_EXPORT void
wl_shm_buffer_end_access(struct wl_shm_buffer *buffer)
{
	struct wl_shm_pool *pool = buffer->pool;
	struct wl_shm_sigbus_data *sigbus_data;

	if (pool->sigbus_is_impossible)
		return;

	sigbus_data = pthread_getspecific(wl_shm_sigbus_data_key);
	assert(sigbus_data && sigbus_data->access_count >= 1);

	if (--sigbus_data->access_count == 0) {
		if (sigbus_data->fallback_mapping_used) {
			wl_resource_post_error(buffer->resource,
					       WL_SHM_ERROR_INVALID_FD,
					       "error accessing SHM buffer");
			sigbus_data->fallback_mapping_used = 0;
		}

		sigbus_data->current_pool = NULL;
	}
}

/** \cond */ /* Deprecated functions below. */

WL_EXPORT struct wl_shm_buffer *
wl_shm_buffer_create(struct wl_client *client,
		     uint32_t id, int32_t width, int32_t height,
		     int32_t stride, uint32_t format)
{
	return NULL;
}

/** \endcond */

/* Functions at the end of this file are deprecated.  Instead of adding new
 * code here, add it before the comment above that states:
 * Deprecated functions below.
 */