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 <drm/drmP.h> 27 #include <drm/drm_mm.h> 28 #include <drm/drm_vma_manager.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 drm_mm_init(&mgr->vm_addr_space_mm, page_offset, size); 90 } 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 void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr) 105 { 106 /* take the lock to protect against buggy drivers */ 107 write_lock(&mgr->vm_lock); 108 drm_mm_takedown(&mgr->vm_addr_space_mm); 109 write_unlock(&mgr->vm_lock); 110 } 111 EXPORT_SYMBOL(drm_vma_offset_manager_destroy); 112 113 /** 114 * drm_vma_offset_lookup_locked() - Find node in offset space 115 * @mgr: Manager object 116 * @start: Start address for object (page-based) 117 * @pages: Size of object (page-based) 118 * 119 * Find a node given a start address and object size. This returns the _best_ 120 * match for the given node. That is, @start may point somewhere into a valid 121 * region and the given node will be returned, as long as the node spans the 122 * whole requested area (given the size in number of pages as @pages). 123 * 124 * Note that before lookup the vma offset manager lookup lock must be acquired 125 * with drm_vma_offset_lock_lookup(). See there for an example. This can then be 126 * used to implement weakly referenced lookups using kref_get_unless_zero(). 127 * 128 * Example: 129 * 130 * :: 131 * 132 * drm_vma_offset_lock_lookup(mgr); 133 * node = drm_vma_offset_lookup_locked(mgr); 134 * if (node) 135 * kref_get_unless_zero(container_of(node, sth, entr)); 136 * drm_vma_offset_unlock_lookup(mgr); 137 * 138 * RETURNS: 139 * Returns NULL if no suitable node can be found. Otherwise, the best match 140 * is returned. It's the caller's responsibility to make sure the node doesn't 141 * get destroyed before the caller can access it. 142 */ 143 struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr, 144 unsigned long start, 145 unsigned long pages) 146 { 147 struct drm_mm_node *node, *best; 148 struct rb_node *iter; 149 unsigned long offset; 150 151 iter = mgr->vm_addr_space_mm.interval_tree.rb_root.rb_node; 152 best = NULL; 153 154 while (likely(iter)) { 155 node = rb_entry(iter, struct drm_mm_node, rb); 156 offset = node->start; 157 if (start >= offset) { 158 iter = iter->rb_right; 159 best = node; 160 if (start == offset) 161 break; 162 } else { 163 iter = iter->rb_left; 164 } 165 } 166 167 /* verify that the node spans the requested area */ 168 if (best) { 169 offset = best->start + best->size; 170 if (offset < start + pages) 171 best = NULL; 172 } 173 174 if (!best) 175 return NULL; 176 177 return container_of(best, struct drm_vma_offset_node, vm_node); 178 } 179 EXPORT_SYMBOL(drm_vma_offset_lookup_locked); 180 181 /** 182 * drm_vma_offset_add() - Add offset node to manager 183 * @mgr: Manager object 184 * @node: Node to be added 185 * @pages: Allocation size visible to user-space (in number of pages) 186 * 187 * Add a node to the offset-manager. If the node was already added, this does 188 * nothing and return 0. @pages is the size of the object given in number of 189 * pages. 190 * After this call succeeds, you can access the offset of the node until it 191 * is removed again. 192 * 193 * If this call fails, it is safe to retry the operation or call 194 * drm_vma_offset_remove(), anyway. However, no cleanup is required in that 195 * case. 196 * 197 * @pages is not required to be the same size as the underlying memory object 198 * that you want to map. It only limits the size that user-space can map into 199 * their address space. 200 * 201 * RETURNS: 202 * 0 on success, negative error code on failure. 203 */ 204 int drm_vma_offset_add(struct drm_vma_offset_manager *mgr, 205 struct drm_vma_offset_node *node, unsigned long pages) 206 { 207 int ret = 0; 208 209 write_lock(&mgr->vm_lock); 210 211 if (!drm_mm_node_allocated(&node->vm_node)) 212 ret = drm_mm_insert_node(&mgr->vm_addr_space_mm, 213 &node->vm_node, pages); 214 215 write_unlock(&mgr->vm_lock); 216 217 return ret; 218 } 219 EXPORT_SYMBOL(drm_vma_offset_add); 220 221 /** 222 * drm_vma_offset_remove() - Remove offset node from manager 223 * @mgr: Manager object 224 * @node: Node to be removed 225 * 226 * Remove a node from the offset manager. If the node wasn't added before, this 227 * does nothing. After this call returns, the offset and size will be 0 until a 228 * new offset is allocated via drm_vma_offset_add() again. Helper functions like 229 * drm_vma_node_start() and drm_vma_node_offset_addr() will return 0 if no 230 * offset is allocated. 231 */ 232 void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr, 233 struct drm_vma_offset_node *node) 234 { 235 write_lock(&mgr->vm_lock); 236 237 if (drm_mm_node_allocated(&node->vm_node)) { 238 drm_mm_remove_node(&node->vm_node); 239 memset(&node->vm_node, 0, sizeof(node->vm_node)); 240 } 241 242 write_unlock(&mgr->vm_lock); 243 } 244 EXPORT_SYMBOL(drm_vma_offset_remove); 245 246 /** 247 * drm_vma_node_allow - Add open-file to list of allowed users 248 * @node: Node to modify 249 * @tag: Tag of file to remove 250 * 251 * Add @tag to the list of allowed open-files for this node. If @tag is 252 * already on this list, the ref-count is incremented. 253 * 254 * The list of allowed-users is preserved across drm_vma_offset_add() and 255 * drm_vma_offset_remove() calls. You may even call it if the node is currently 256 * not added to any offset-manager. 257 * 258 * You must remove all open-files the same number of times as you added them 259 * before destroying the node. Otherwise, you will leak memory. 260 * 261 * This is locked against concurrent access internally. 262 * 263 * RETURNS: 264 * 0 on success, negative error code on internal failure (out-of-mem) 265 */ 266 int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag) 267 { 268 struct rb_node **iter; 269 struct rb_node *parent = NULL; 270 struct drm_vma_offset_file *new, *entry; 271 int ret = 0; 272 273 /* Preallocate entry to avoid atomic allocations below. It is quite 274 * unlikely that an open-file is added twice to a single node so we 275 * don't optimize for this case. OOM is checked below only if the entry 276 * is actually used. */ 277 new = kmalloc(sizeof(*entry), GFP_KERNEL); 278 279 write_lock(&node->vm_lock); 280 281 iter = &node->vm_files.rb_node; 282 283 while (likely(*iter)) { 284 parent = *iter; 285 entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb); 286 287 if (tag == entry->vm_tag) { 288 entry->vm_count++; 289 goto unlock; 290 } else if (tag > entry->vm_tag) { 291 iter = &(*iter)->rb_right; 292 } else { 293 iter = &(*iter)->rb_left; 294 } 295 } 296 297 if (!new) { 298 ret = -ENOMEM; 299 goto unlock; 300 } 301 302 new->vm_tag = tag; 303 new->vm_count = 1; 304 rb_link_node(&new->vm_rb, parent, iter); 305 rb_insert_color(&new->vm_rb, &node->vm_files); 306 new = NULL; 307 308 unlock: 309 write_unlock(&node->vm_lock); 310 kfree(new); 311 return ret; 312 } 313 EXPORT_SYMBOL(drm_vma_node_allow); 314 315 /** 316 * drm_vma_node_revoke - Remove open-file from list of allowed users 317 * @node: Node to modify 318 * @tag: Tag of file to remove 319 * 320 * Decrement the ref-count of @tag in the list of allowed open-files on @node. 321 * If the ref-count drops to zero, remove @tag from the list. You must call 322 * this once for every drm_vma_node_allow() on @tag. 323 * 324 * This is locked against concurrent access internally. 325 * 326 * If @tag is not on the list, nothing is done. 327 */ 328 void drm_vma_node_revoke(struct drm_vma_offset_node *node, 329 struct drm_file *tag) 330 { 331 struct drm_vma_offset_file *entry; 332 struct rb_node *iter; 333 334 write_lock(&node->vm_lock); 335 336 iter = node->vm_files.rb_node; 337 while (likely(iter)) { 338 entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb); 339 if (tag == entry->vm_tag) { 340 if (!--entry->vm_count) { 341 rb_erase(&entry->vm_rb, &node->vm_files); 342 kfree(entry); 343 } 344 break; 345 } else if (tag > entry->vm_tag) { 346 iter = iter->rb_right; 347 } else { 348 iter = iter->rb_left; 349 } 350 } 351 352 write_unlock(&node->vm_lock); 353 } 354 EXPORT_SYMBOL(drm_vma_node_revoke); 355 356 /** 357 * drm_vma_node_is_allowed - Check whether an open-file is granted access 358 * @node: Node to check 359 * @tag: Tag of file to remove 360 * 361 * Search the list in @node whether @tag is currently on the list of allowed 362 * open-files (see drm_vma_node_allow()). 363 * 364 * This is locked against concurrent access internally. 365 * 366 * RETURNS: 367 * true iff @filp is on the list 368 */ 369 bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node, 370 struct drm_file *tag) 371 { 372 struct drm_vma_offset_file *entry; 373 struct rb_node *iter; 374 375 read_lock(&node->vm_lock); 376 377 iter = node->vm_files.rb_node; 378 while (likely(iter)) { 379 entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb); 380 if (tag == entry->vm_tag) 381 break; 382 else if (tag > entry->vm_tag) 383 iter = iter->rb_right; 384 else 385 iter = iter->rb_left; 386 } 387 388 read_unlock(&node->vm_lock); 389 390 return iter; 391 } 392 EXPORT_SYMBOL(drm_vma_node_is_allowed); 393