1 /*
2  * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
3  * Copyright (c) 2012 David Airlie <airlied@linux.ie>
4  * Copyright (c) 2013 David Herrmann <dh.herrmann@gmail.com>
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a
7  * copy of this software and associated documentation files (the "Software"),
8  * to deal in the Software without restriction, including without limitation
9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10  * and/or sell copies of the Software, and to permit persons to whom the
11  * Software is furnished to do so, subject to the following conditions:
12  *
13  * The above copyright notice and this permission notice shall be included in
14  * all copies or substantial portions of the Software.
15  *
16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
19  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22  * OTHER DEALINGS IN THE SOFTWARE.
23  */
24 
25 #include <drm/drmP.h>
26 #include <drm/drm_mm.h>
27 #include <drm/drm_vma_manager.h>
28 #include <linux/fs.h>
29 #include <linux/mm.h>
30 #include <linux/module.h>
31 #include <linux/rbtree.h>
32 #include <linux/slab.h>
33 #include <linux/spinlock.h>
34 #include <linux/types.h>
35 
36 /**
37  * DOC: vma offset manager
38  *
39  * The vma-manager is responsible to map arbitrary driver-dependent memory
40  * regions into the linear user address-space. It provides offsets to the
41  * caller which can then be used on the address_space of the drm-device. It
42  * takes care to not overlap regions, size them appropriately and to not
43  * confuse mm-core by inconsistent fake vm_pgoff fields.
44  * Drivers shouldn't use this for object placement in VMEM. This manager should
45  * only be used to manage mappings into linear user-space VMs.
46  *
47  * We use drm_mm as backend to manage object allocations. But it is highly
48  * optimized for alloc/free calls, not lookups. Hence, we use an rb-tree to
49  * speed up offset lookups.
50  *
51  * You must not use multiple offset managers on a single address_space.
52  * Otherwise, mm-core will be unable to tear down memory mappings as the VM will
53  * no longer be linear.
54  *
55  * This offset manager works on page-based addresses. That is, every argument
56  * and return code (with the exception of drm_vma_node_offset_addr()) is given
57  * in number of pages, not number of bytes. That means, object sizes and offsets
58  * must always be page-aligned (as usual).
59  * If you want to get a valid byte-based user-space address for a given offset,
60  * please see drm_vma_node_offset_addr().
61  *
62  * Additionally to offset management, the vma offset manager also handles access
63  * management. For every open-file context that is allowed to access a given
64  * node, you must call drm_vma_node_allow(). Otherwise, an mmap() call on this
65  * open-file with the offset of the node will fail with -EACCES. To revoke
66  * access again, use drm_vma_node_revoke(). However, the caller is responsible
67  * for destroying already existing mappings, if required.
68  */
69 
70 /**
71  * drm_vma_offset_manager_init - Initialize new offset-manager
72  * @mgr: Manager object
73  * @page_offset: Offset of available memory area (page-based)
74  * @size: Size of available address space range (page-based)
75  *
76  * Initialize a new offset-manager. The offset and area size available for the
77  * manager are given as @page_offset and @size. Both are interpreted as
78  * page-numbers, not bytes.
79  *
80  * Adding/removing nodes from the manager is locked internally and protected
81  * against concurrent access. However, node allocation and destruction is left
82  * for the caller. While calling into the vma-manager, a given node must
83  * always be guaranteed to be referenced.
84  */
85 void drm_vma_offset_manager_init(struct drm_vma_offset_manager *mgr,
86 				 unsigned long page_offset, unsigned long size)
87 {
88 	rwlock_init(&mgr->vm_lock);
89 	mgr->vm_addr_space_rb = RB_ROOT;
90 	drm_mm_init(&mgr->vm_addr_space_mm, page_offset, size);
91 }
92 EXPORT_SYMBOL(drm_vma_offset_manager_init);
93 
94 /**
95  * drm_vma_offset_manager_destroy() - Destroy offset manager
96  * @mgr: Manager object
97  *
98  * Destroy an object manager which was previously created via
99  * drm_vma_offset_manager_init(). The caller must remove all allocated nodes
100  * before destroying the manager. Otherwise, drm_mm will refuse to free the
101  * requested resources.
102  *
103  * The manager must not be accessed after this function is called.
104  */
105 void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr)
106 {
107 	/* take the lock to protect against buggy drivers */
108 	write_lock(&mgr->vm_lock);
109 	drm_mm_takedown(&mgr->vm_addr_space_mm);
110 	write_unlock(&mgr->vm_lock);
111 }
112 EXPORT_SYMBOL(drm_vma_offset_manager_destroy);
113 
114 /**
115  * drm_vma_offset_lookup_locked() - Find node in offset space
116  * @mgr: Manager object
117  * @start: Start address for object (page-based)
118  * @pages: Size of object (page-based)
119  *
120  * Find a node given a start address and object size. This returns the _best_
121  * match for the given node. That is, @start may point somewhere into a valid
122  * region and the given node will be returned, as long as the node spans the
123  * whole requested area (given the size in number of pages as @pages).
124  *
125  * Note that before lookup the vma offset manager lookup lock must be acquired
126  * with drm_vma_offset_lock_lookup(). See there for an example. This can then be
127  * used to implement weakly referenced lookups using kref_get_unless_zero().
128  *
129  * Example:
130  *     drm_vma_offset_lock_lookup(mgr);
131  *     node = drm_vma_offset_lookup_locked(mgr);
132  *     if (node)
133  *         kref_get_unless_zero(container_of(node, sth, entr));
134  *     drm_vma_offset_unlock_lookup(mgr);
135  *
136  * RETURNS:
137  * Returns NULL if no suitable node can be found. Otherwise, the best match
138  * is returned. It's the caller's responsibility to make sure the node doesn't
139  * get destroyed before the caller can access it.
140  */
141 struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,
142 							 unsigned long start,
143 							 unsigned long pages)
144 {
145 	struct drm_vma_offset_node *node, *best;
146 	struct rb_node *iter;
147 	unsigned long offset;
148 
149 	iter = mgr->vm_addr_space_rb.rb_node;
150 	best = NULL;
151 
152 	while (likely(iter)) {
153 		node = rb_entry(iter, struct drm_vma_offset_node, vm_rb);
154 		offset = node->vm_node.start;
155 		if (start >= offset) {
156 			iter = iter->rb_right;
157 			best = node;
158 			if (start == offset)
159 				break;
160 		} else {
161 			iter = iter->rb_left;
162 		}
163 	}
164 
165 	/* verify that the node spans the requested area */
166 	if (best) {
167 		offset = best->vm_node.start + best->vm_node.size;
168 		if (offset < start + pages)
169 			best = NULL;
170 	}
171 
172 	return best;
173 }
174 EXPORT_SYMBOL(drm_vma_offset_lookup_locked);
175 
176 /* internal helper to link @node into the rb-tree */
177 static void _drm_vma_offset_add_rb(struct drm_vma_offset_manager *mgr,
178 				   struct drm_vma_offset_node *node)
179 {
180 	struct rb_node **iter = &mgr->vm_addr_space_rb.rb_node;
181 	struct rb_node *parent = NULL;
182 	struct drm_vma_offset_node *iter_node;
183 
184 	while (likely(*iter)) {
185 		parent = *iter;
186 		iter_node = rb_entry(*iter, struct drm_vma_offset_node, vm_rb);
187 
188 		if (node->vm_node.start < iter_node->vm_node.start)
189 			iter = &(*iter)->rb_left;
190 		else if (node->vm_node.start > iter_node->vm_node.start)
191 			iter = &(*iter)->rb_right;
192 		else
193 			BUG();
194 	}
195 
196 	rb_link_node(&node->vm_rb, parent, iter);
197 	rb_insert_color(&node->vm_rb, &mgr->vm_addr_space_rb);
198 }
199 
200 /**
201  * drm_vma_offset_add() - Add offset node to manager
202  * @mgr: Manager object
203  * @node: Node to be added
204  * @pages: Allocation size visible to user-space (in number of pages)
205  *
206  * Add a node to the offset-manager. If the node was already added, this does
207  * nothing and return 0. @pages is the size of the object given in number of
208  * pages.
209  * After this call succeeds, you can access the offset of the node until it
210  * is removed again.
211  *
212  * If this call fails, it is safe to retry the operation or call
213  * drm_vma_offset_remove(), anyway. However, no cleanup is required in that
214  * case.
215  *
216  * @pages is not required to be the same size as the underlying memory object
217  * that you want to map. It only limits the size that user-space can map into
218  * their address space.
219  *
220  * RETURNS:
221  * 0 on success, negative error code on failure.
222  */
223 int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,
224 		       struct drm_vma_offset_node *node, unsigned long pages)
225 {
226 	int ret;
227 
228 	write_lock(&mgr->vm_lock);
229 
230 	if (drm_mm_node_allocated(&node->vm_node)) {
231 		ret = 0;
232 		goto out_unlock;
233 	}
234 
235 	ret = drm_mm_insert_node(&mgr->vm_addr_space_mm, &node->vm_node,
236 				 pages, 0, DRM_MM_SEARCH_DEFAULT);
237 	if (ret)
238 		goto out_unlock;
239 
240 	_drm_vma_offset_add_rb(mgr, node);
241 
242 out_unlock:
243 	write_unlock(&mgr->vm_lock);
244 	return ret;
245 }
246 EXPORT_SYMBOL(drm_vma_offset_add);
247 
248 /**
249  * drm_vma_offset_remove() - Remove offset node from manager
250  * @mgr: Manager object
251  * @node: Node to be removed
252  *
253  * Remove a node from the offset manager. If the node wasn't added before, this
254  * does nothing. After this call returns, the offset and size will be 0 until a
255  * new offset is allocated via drm_vma_offset_add() again. Helper functions like
256  * drm_vma_node_start() and drm_vma_node_offset_addr() will return 0 if no
257  * offset is allocated.
258  */
259 void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
260 			   struct drm_vma_offset_node *node)
261 {
262 	write_lock(&mgr->vm_lock);
263 
264 	if (drm_mm_node_allocated(&node->vm_node)) {
265 		rb_erase(&node->vm_rb, &mgr->vm_addr_space_rb);
266 		drm_mm_remove_node(&node->vm_node);
267 		memset(&node->vm_node, 0, sizeof(node->vm_node));
268 	}
269 
270 	write_unlock(&mgr->vm_lock);
271 }
272 EXPORT_SYMBOL(drm_vma_offset_remove);
273 
274 /**
275  * drm_vma_node_allow - Add open-file to list of allowed users
276  * @node: Node to modify
277  * @filp: Open file to add
278  *
279  * Add @filp to the list of allowed open-files for this node. If @filp is
280  * already on this list, the ref-count is incremented.
281  *
282  * The list of allowed-users is preserved across drm_vma_offset_add() and
283  * drm_vma_offset_remove() calls. You may even call it if the node is currently
284  * not added to any offset-manager.
285  *
286  * You must remove all open-files the same number of times as you added them
287  * before destroying the node. Otherwise, you will leak memory.
288  *
289  * This is locked against concurrent access internally.
290  *
291  * RETURNS:
292  * 0 on success, negative error code on internal failure (out-of-mem)
293  */
294 int drm_vma_node_allow(struct drm_vma_offset_node *node, struct file *filp)
295 {
296 	struct rb_node **iter;
297 	struct rb_node *parent = NULL;
298 	struct drm_vma_offset_file *new, *entry;
299 	int ret = 0;
300 
301 	/* Preallocate entry to avoid atomic allocations below. It is quite
302 	 * unlikely that an open-file is added twice to a single node so we
303 	 * don't optimize for this case. OOM is checked below only if the entry
304 	 * is actually used. */
305 	new = kmalloc(sizeof(*entry), GFP_KERNEL);
306 
307 	write_lock(&node->vm_lock);
308 
309 	iter = &node->vm_files.rb_node;
310 
311 	while (likely(*iter)) {
312 		parent = *iter;
313 		entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
314 
315 		if (filp == entry->vm_filp) {
316 			entry->vm_count++;
317 			goto unlock;
318 		} else if (filp > entry->vm_filp) {
319 			iter = &(*iter)->rb_right;
320 		} else {
321 			iter = &(*iter)->rb_left;
322 		}
323 	}
324 
325 	if (!new) {
326 		ret = -ENOMEM;
327 		goto unlock;
328 	}
329 
330 	new->vm_filp = filp;
331 	new->vm_count = 1;
332 	rb_link_node(&new->vm_rb, parent, iter);
333 	rb_insert_color(&new->vm_rb, &node->vm_files);
334 	new = NULL;
335 
336 unlock:
337 	write_unlock(&node->vm_lock);
338 	kfree(new);
339 	return ret;
340 }
341 EXPORT_SYMBOL(drm_vma_node_allow);
342 
343 /**
344  * drm_vma_node_revoke - Remove open-file from list of allowed users
345  * @node: Node to modify
346  * @filp: Open file to remove
347  *
348  * Decrement the ref-count of @filp in the list of allowed open-files on @node.
349  * If the ref-count drops to zero, remove @filp from the list. You must call
350  * this once for every drm_vma_node_allow() on @filp.
351  *
352  * This is locked against concurrent access internally.
353  *
354  * If @filp is not on the list, nothing is done.
355  */
356 void drm_vma_node_revoke(struct drm_vma_offset_node *node, struct file *filp)
357 {
358 	struct drm_vma_offset_file *entry;
359 	struct rb_node *iter;
360 
361 	write_lock(&node->vm_lock);
362 
363 	iter = node->vm_files.rb_node;
364 	while (likely(iter)) {
365 		entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
366 		if (filp == entry->vm_filp) {
367 			if (!--entry->vm_count) {
368 				rb_erase(&entry->vm_rb, &node->vm_files);
369 				kfree(entry);
370 			}
371 			break;
372 		} else if (filp > entry->vm_filp) {
373 			iter = iter->rb_right;
374 		} else {
375 			iter = iter->rb_left;
376 		}
377 	}
378 
379 	write_unlock(&node->vm_lock);
380 }
381 EXPORT_SYMBOL(drm_vma_node_revoke);
382 
383 /**
384  * drm_vma_node_is_allowed - Check whether an open-file is granted access
385  * @node: Node to check
386  * @filp: Open-file to check for
387  *
388  * Search the list in @node whether @filp is currently on the list of allowed
389  * open-files (see drm_vma_node_allow()).
390  *
391  * This is locked against concurrent access internally.
392  *
393  * RETURNS:
394  * true iff @filp is on the list
395  */
396 bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
397 			     struct file *filp)
398 {
399 	struct drm_vma_offset_file *entry;
400 	struct rb_node *iter;
401 
402 	read_lock(&node->vm_lock);
403 
404 	iter = node->vm_files.rb_node;
405 	while (likely(iter)) {
406 		entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
407 		if (filp == entry->vm_filp)
408 			break;
409 		else if (filp > entry->vm_filp)
410 			iter = iter->rb_right;
411 		else
412 			iter = iter->rb_left;
413 	}
414 
415 	read_unlock(&node->vm_lock);
416 
417 	return iter;
418 }
419 EXPORT_SYMBOL(drm_vma_node_is_allowed);
420