Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0 OR MIT
2 : /*
3 : * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
4 : * Copyright (c) 2012 David Airlie <airlied@linux.ie>
5 : * Copyright (c) 2013 David Herrmann <dh.herrmann@gmail.com>
6 : *
7 : * Permission is hereby granted, free of charge, to any person obtaining a
8 : * copy of this software and associated documentation files (the "Software"),
9 : * to deal in the Software without restriction, including without limitation
10 : * the rights to use, copy, modify, merge, publish, distribute, sublicense,
11 : * and/or sell copies of the Software, and to permit persons to whom the
12 : * Software is furnished to do so, subject to the following conditions:
13 : *
14 : * The above copyright notice and this permission notice shall be included in
15 : * all copies or substantial portions of the Software.
16 : *
17 : * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 : * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 : * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 : * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
21 : * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
22 : * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
23 : * OTHER DEALINGS IN THE SOFTWARE.
24 : */
25 :
26 : #include <linux/mm.h>
27 : #include <linux/module.h>
28 : #include <linux/rbtree.h>
29 : #include <linux/slab.h>
30 : #include <linux/spinlock.h>
31 : #include <linux/types.h>
32 :
33 : #include <drm/drm_mm.h>
34 : #include <drm/drm_vma_manager.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 0 : 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 0 : drm_mm_init(&mgr->vm_addr_space_mm, page_offset, size);
90 0 : }
91 : EXPORT_SYMBOL(drm_vma_offset_manager_init);
92 :
93 : /**
94 : * drm_vma_offset_manager_destroy() - Destroy offset manager
95 : * @mgr: Manager object
96 : *
97 : * Destroy an object manager which was previously created via
98 : * drm_vma_offset_manager_init(). The caller must remove all allocated nodes
99 : * before destroying the manager. Otherwise, drm_mm will refuse to free the
100 : * requested resources.
101 : *
102 : * The manager must not be accessed after this function is called.
103 : */
104 0 : void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr)
105 : {
106 0 : drm_mm_takedown(&mgr->vm_addr_space_mm);
107 0 : }
108 : EXPORT_SYMBOL(drm_vma_offset_manager_destroy);
109 :
110 : /**
111 : * drm_vma_offset_lookup_locked() - Find node in offset space
112 : * @mgr: Manager object
113 : * @start: Start address for object (page-based)
114 : * @pages: Size of object (page-based)
115 : *
116 : * Find a node given a start address and object size. This returns the _best_
117 : * match for the given node. That is, @start may point somewhere into a valid
118 : * region and the given node will be returned, as long as the node spans the
119 : * whole requested area (given the size in number of pages as @pages).
120 : *
121 : * Note that before lookup the vma offset manager lookup lock must be acquired
122 : * with drm_vma_offset_lock_lookup(). See there for an example. This can then be
123 : * used to implement weakly referenced lookups using kref_get_unless_zero().
124 : *
125 : * Example:
126 : *
127 : * ::
128 : *
129 : * drm_vma_offset_lock_lookup(mgr);
130 : * node = drm_vma_offset_lookup_locked(mgr);
131 : * if (node)
132 : * kref_get_unless_zero(container_of(node, sth, entr));
133 : * drm_vma_offset_unlock_lookup(mgr);
134 : *
135 : * RETURNS:
136 : * Returns NULL if no suitable node can be found. Otherwise, the best match
137 : * is returned. It's the caller's responsibility to make sure the node doesn't
138 : * get destroyed before the caller can access it.
139 : */
140 0 : struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,
141 : unsigned long start,
142 : unsigned long pages)
143 : {
144 : struct drm_mm_node *node, *best;
145 : struct rb_node *iter;
146 : unsigned long offset;
147 :
148 0 : iter = mgr->vm_addr_space_mm.interval_tree.rb_root.rb_node;
149 0 : best = NULL;
150 :
151 0 : while (likely(iter)) {
152 0 : node = rb_entry(iter, struct drm_mm_node, rb);
153 0 : offset = node->start;
154 0 : if (start >= offset) {
155 0 : iter = iter->rb_right;
156 0 : best = node;
157 0 : if (start == offset)
158 : break;
159 : } else {
160 0 : iter = iter->rb_left;
161 : }
162 : }
163 :
164 : /* verify that the node spans the requested area */
165 0 : if (best) {
166 0 : offset = best->start + best->size;
167 0 : if (offset < start + pages)
168 0 : best = NULL;
169 : }
170 :
171 0 : if (!best)
172 : return NULL;
173 :
174 0 : return container_of(best, struct drm_vma_offset_node, vm_node);
175 : }
176 : EXPORT_SYMBOL(drm_vma_offset_lookup_locked);
177 :
178 : /**
179 : * drm_vma_offset_add() - Add offset node to manager
180 : * @mgr: Manager object
181 : * @node: Node to be added
182 : * @pages: Allocation size visible to user-space (in number of pages)
183 : *
184 : * Add a node to the offset-manager. If the node was already added, this does
185 : * nothing and return 0. @pages is the size of the object given in number of
186 : * pages.
187 : * After this call succeeds, you can access the offset of the node until it
188 : * is removed again.
189 : *
190 : * If this call fails, it is safe to retry the operation or call
191 : * drm_vma_offset_remove(), anyway. However, no cleanup is required in that
192 : * case.
193 : *
194 : * @pages is not required to be the same size as the underlying memory object
195 : * that you want to map. It only limits the size that user-space can map into
196 : * their address space.
197 : *
198 : * RETURNS:
199 : * 0 on success, negative error code on failure.
200 : */
201 0 : int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,
202 : struct drm_vma_offset_node *node, unsigned long pages)
203 : {
204 0 : int ret = 0;
205 :
206 0 : write_lock(&mgr->vm_lock);
207 :
208 0 : if (!drm_mm_node_allocated(&node->vm_node))
209 0 : ret = drm_mm_insert_node(&mgr->vm_addr_space_mm,
210 : &node->vm_node, pages);
211 :
212 0 : write_unlock(&mgr->vm_lock);
213 :
214 0 : return ret;
215 : }
216 : EXPORT_SYMBOL(drm_vma_offset_add);
217 :
218 : /**
219 : * drm_vma_offset_remove() - Remove offset node from manager
220 : * @mgr: Manager object
221 : * @node: Node to be removed
222 : *
223 : * Remove a node from the offset manager. If the node wasn't added before, this
224 : * does nothing. After this call returns, the offset and size will be 0 until a
225 : * new offset is allocated via drm_vma_offset_add() again. Helper functions like
226 : * drm_vma_node_start() and drm_vma_node_offset_addr() will return 0 if no
227 : * offset is allocated.
228 : */
229 0 : void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
230 : struct drm_vma_offset_node *node)
231 : {
232 0 : write_lock(&mgr->vm_lock);
233 :
234 0 : if (drm_mm_node_allocated(&node->vm_node)) {
235 0 : drm_mm_remove_node(&node->vm_node);
236 0 : memset(&node->vm_node, 0, sizeof(node->vm_node));
237 : }
238 :
239 0 : write_unlock(&mgr->vm_lock);
240 0 : }
241 : EXPORT_SYMBOL(drm_vma_offset_remove);
242 :
243 : /**
244 : * drm_vma_node_allow - Add open-file to list of allowed users
245 : * @node: Node to modify
246 : * @tag: Tag of file to remove
247 : *
248 : * Add @tag to the list of allowed open-files for this node. If @tag is
249 : * already on this list, the ref-count is incremented.
250 : *
251 : * The list of allowed-users is preserved across drm_vma_offset_add() and
252 : * drm_vma_offset_remove() calls. You may even call it if the node is currently
253 : * not added to any offset-manager.
254 : *
255 : * You must remove all open-files the same number of times as you added them
256 : * before destroying the node. Otherwise, you will leak memory.
257 : *
258 : * This is locked against concurrent access internally.
259 : *
260 : * RETURNS:
261 : * 0 on success, negative error code on internal failure (out-of-mem)
262 : */
263 0 : int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
264 : {
265 : struct rb_node **iter;
266 0 : struct rb_node *parent = NULL;
267 : struct drm_vma_offset_file *new, *entry;
268 0 : int ret = 0;
269 :
270 : /* Preallocate entry to avoid atomic allocations below. It is quite
271 : * unlikely that an open-file is added twice to a single node so we
272 : * don't optimize for this case. OOM is checked below only if the entry
273 : * is actually used. */
274 0 : new = kmalloc(sizeof(*entry), GFP_KERNEL);
275 :
276 0 : write_lock(&node->vm_lock);
277 :
278 0 : iter = &node->vm_files.rb_node;
279 :
280 0 : while (likely(*iter)) {
281 0 : parent = *iter;
282 0 : entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
283 :
284 0 : if (tag == entry->vm_tag) {
285 0 : entry->vm_count++;
286 0 : goto unlock;
287 0 : } else if (tag > entry->vm_tag) {
288 0 : iter = &(*iter)->rb_right;
289 : } else {
290 0 : iter = &(*iter)->rb_left;
291 : }
292 : }
293 :
294 0 : if (!new) {
295 : ret = -ENOMEM;
296 : goto unlock;
297 : }
298 :
299 0 : new->vm_tag = tag;
300 0 : new->vm_count = 1;
301 0 : rb_link_node(&new->vm_rb, parent, iter);
302 0 : rb_insert_color(&new->vm_rb, &node->vm_files);
303 0 : new = NULL;
304 :
305 : unlock:
306 0 : write_unlock(&node->vm_lock);
307 0 : kfree(new);
308 0 : return ret;
309 : }
310 : EXPORT_SYMBOL(drm_vma_node_allow);
311 :
312 : /**
313 : * drm_vma_node_revoke - Remove open-file from list of allowed users
314 : * @node: Node to modify
315 : * @tag: Tag of file to remove
316 : *
317 : * Decrement the ref-count of @tag in the list of allowed open-files on @node.
318 : * If the ref-count drops to zero, remove @tag from the list. You must call
319 : * this once for every drm_vma_node_allow() on @tag.
320 : *
321 : * This is locked against concurrent access internally.
322 : *
323 : * If @tag is not on the list, nothing is done.
324 : */
325 0 : void drm_vma_node_revoke(struct drm_vma_offset_node *node,
326 : struct drm_file *tag)
327 : {
328 : struct drm_vma_offset_file *entry;
329 : struct rb_node *iter;
330 :
331 0 : write_lock(&node->vm_lock);
332 :
333 0 : iter = node->vm_files.rb_node;
334 0 : while (likely(iter)) {
335 0 : entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
336 0 : if (tag == entry->vm_tag) {
337 0 : if (!--entry->vm_count) {
338 0 : rb_erase(&entry->vm_rb, &node->vm_files);
339 0 : kfree(entry);
340 : }
341 : break;
342 0 : } else if (tag > entry->vm_tag) {
343 0 : iter = iter->rb_right;
344 : } else {
345 0 : iter = iter->rb_left;
346 : }
347 : }
348 :
349 0 : write_unlock(&node->vm_lock);
350 0 : }
351 : EXPORT_SYMBOL(drm_vma_node_revoke);
352 :
353 : /**
354 : * drm_vma_node_is_allowed - Check whether an open-file is granted access
355 : * @node: Node to check
356 : * @tag: Tag of file to remove
357 : *
358 : * Search the list in @node whether @tag is currently on the list of allowed
359 : * open-files (see drm_vma_node_allow()).
360 : *
361 : * This is locked against concurrent access internally.
362 : *
363 : * RETURNS:
364 : * true if @filp is on the list
365 : */
366 0 : bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
367 : struct drm_file *tag)
368 : {
369 : struct drm_vma_offset_file *entry;
370 : struct rb_node *iter;
371 :
372 0 : read_lock(&node->vm_lock);
373 :
374 0 : iter = node->vm_files.rb_node;
375 0 : while (likely(iter)) {
376 0 : entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
377 0 : if (tag == entry->vm_tag)
378 : break;
379 0 : else if (tag > entry->vm_tag)
380 0 : iter = iter->rb_right;
381 : else
382 0 : iter = iter->rb_left;
383 : }
384 :
385 0 : read_unlock(&node->vm_lock);
386 :
387 0 : return iter;
388 : }
389 : EXPORT_SYMBOL(drm_vma_node_is_allowed);
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