1 /* 2 * mm/kmemleak.c 3 * 4 * Copyright (C) 2008 ARM Limited 5 * Written by Catalin Marinas <catalin.marinas@arm.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write to the Free Software 18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 19 * 20 * 21 * For more information on the algorithm and kmemleak usage, please see 22 * Documentation/kmemleak.txt. 23 * 24 * Notes on locking 25 * ---------------- 26 * 27 * The following locks and mutexes are used by kmemleak: 28 * 29 * - kmemleak_lock (rwlock): protects the object_list modifications and 30 * accesses to the object_tree_root. The object_list is the main list 31 * holding the metadata (struct kmemleak_object) for the allocated memory 32 * blocks. The object_tree_root is a priority search tree used to look-up 33 * metadata based on a pointer to the corresponding memory block. The 34 * kmemleak_object structures are added to the object_list and 35 * object_tree_root in the create_object() function called from the 36 * kmemleak_alloc() callback and removed in delete_object() called from the 37 * kmemleak_free() callback 38 * - kmemleak_object.lock (spinlock): protects a kmemleak_object. Accesses to 39 * the metadata (e.g. count) are protected by this lock. Note that some 40 * members of this structure may be protected by other means (atomic or 41 * kmemleak_lock). This lock is also held when scanning the corresponding 42 * memory block to avoid the kernel freeing it via the kmemleak_free() 43 * callback. This is less heavyweight than holding a global lock like 44 * kmemleak_lock during scanning 45 * - scan_mutex (mutex): ensures that only one thread may scan the memory for 46 * unreferenced objects at a time. The gray_list contains the objects which 47 * are already referenced or marked as false positives and need to be 48 * scanned. This list is only modified during a scanning episode when the 49 * scan_mutex is held. At the end of a scan, the gray_list is always empty. 50 * Note that the kmemleak_object.use_count is incremented when an object is 51 * added to the gray_list and therefore cannot be freed. This mutex also 52 * prevents multiple users of the "kmemleak" debugfs file together with 53 * modifications to the memory scanning parameters including the scan_thread 54 * pointer 55 * 56 * The kmemleak_object structures have a use_count incremented or decremented 57 * using the get_object()/put_object() functions. When the use_count becomes 58 * 0, this count can no longer be incremented and put_object() schedules the 59 * kmemleak_object freeing via an RCU callback. All calls to the get_object() 60 * function must be protected by rcu_read_lock() to avoid accessing a freed 61 * structure. 62 */ 63 64 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 65 66 #include <linux/init.h> 67 #include <linux/kernel.h> 68 #include <linux/list.h> 69 #include <linux/sched.h> 70 #include <linux/jiffies.h> 71 #include <linux/delay.h> 72 #include <linux/module.h> 73 #include <linux/kthread.h> 74 #include <linux/prio_tree.h> 75 #include <linux/fs.h> 76 #include <linux/debugfs.h> 77 #include <linux/seq_file.h> 78 #include <linux/cpumask.h> 79 #include <linux/spinlock.h> 80 #include <linux/mutex.h> 81 #include <linux/rcupdate.h> 82 #include <linux/stacktrace.h> 83 #include <linux/cache.h> 84 #include <linux/percpu.h> 85 #include <linux/hardirq.h> 86 #include <linux/mmzone.h> 87 #include <linux/slab.h> 88 #include <linux/thread_info.h> 89 #include <linux/err.h> 90 #include <linux/uaccess.h> 91 #include <linux/string.h> 92 #include <linux/nodemask.h> 93 #include <linux/mm.h> 94 #include <linux/workqueue.h> 95 #include <linux/crc32.h> 96 97 #include <asm/sections.h> 98 #include <asm/processor.h> 99 #include <asm/atomic.h> 100 101 #include <linux/kmemcheck.h> 102 #include <linux/kmemleak.h> 103 104 /* 105 * Kmemleak configuration and common defines. 106 */ 107 #define MAX_TRACE 16 /* stack trace length */ 108 #define MSECS_MIN_AGE 5000 /* minimum object age for reporting */ 109 #define SECS_FIRST_SCAN 60 /* delay before the first scan */ 110 #define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */ 111 #define MAX_SCAN_SIZE 4096 /* maximum size of a scanned block */ 112 113 #define BYTES_PER_POINTER sizeof(void *) 114 115 /* GFP bitmask for kmemleak internal allocations */ 116 #define GFP_KMEMLEAK_MASK (GFP_KERNEL | GFP_ATOMIC) 117 118 /* scanning area inside a memory block */ 119 struct kmemleak_scan_area { 120 struct hlist_node node; 121 unsigned long start; 122 size_t size; 123 }; 124 125 #define KMEMLEAK_GREY 0 126 #define KMEMLEAK_BLACK -1 127 128 /* 129 * Structure holding the metadata for each allocated memory block. 130 * Modifications to such objects should be made while holding the 131 * object->lock. Insertions or deletions from object_list, gray_list or 132 * tree_node are already protected by the corresponding locks or mutex (see 133 * the notes on locking above). These objects are reference-counted 134 * (use_count) and freed using the RCU mechanism. 135 */ 136 struct kmemleak_object { 137 spinlock_t lock; 138 unsigned long flags; /* object status flags */ 139 struct list_head object_list; 140 struct list_head gray_list; 141 struct prio_tree_node tree_node; 142 struct rcu_head rcu; /* object_list lockless traversal */ 143 /* object usage count; object freed when use_count == 0 */ 144 atomic_t use_count; 145 unsigned long pointer; 146 size_t size; 147 /* minimum number of a pointers found before it is considered leak */ 148 int min_count; 149 /* the total number of pointers found pointing to this object */ 150 int count; 151 /* checksum for detecting modified objects */ 152 u32 checksum; 153 /* memory ranges to be scanned inside an object (empty for all) */ 154 struct hlist_head area_list; 155 unsigned long trace[MAX_TRACE]; 156 unsigned int trace_len; 157 unsigned long jiffies; /* creation timestamp */ 158 pid_t pid; /* pid of the current task */ 159 char comm[TASK_COMM_LEN]; /* executable name */ 160 }; 161 162 /* flag representing the memory block allocation status */ 163 #define OBJECT_ALLOCATED (1 << 0) 164 /* flag set after the first reporting of an unreference object */ 165 #define OBJECT_REPORTED (1 << 1) 166 /* flag set to not scan the object */ 167 #define OBJECT_NO_SCAN (1 << 2) 168 169 /* number of bytes to print per line; must be 16 or 32 */ 170 #define HEX_ROW_SIZE 16 171 /* number of bytes to print at a time (1, 2, 4, 8) */ 172 #define HEX_GROUP_SIZE 1 173 /* include ASCII after the hex output */ 174 #define HEX_ASCII 1 175 /* max number of lines to be printed */ 176 #define HEX_MAX_LINES 2 177 178 /* the list of all allocated objects */ 179 static LIST_HEAD(object_list); 180 /* the list of gray-colored objects (see color_gray comment below) */ 181 static LIST_HEAD(gray_list); 182 /* prio search tree for object boundaries */ 183 static struct prio_tree_root object_tree_root; 184 /* rw_lock protecting the access to object_list and prio_tree_root */ 185 static DEFINE_RWLOCK(kmemleak_lock); 186 187 /* allocation caches for kmemleak internal data */ 188 static struct kmem_cache *object_cache; 189 static struct kmem_cache *scan_area_cache; 190 191 /* set if tracing memory operations is enabled */ 192 static atomic_t kmemleak_enabled = ATOMIC_INIT(0); 193 /* set in the late_initcall if there were no errors */ 194 static atomic_t kmemleak_initialized = ATOMIC_INIT(0); 195 /* enables or disables early logging of the memory operations */ 196 static atomic_t kmemleak_early_log = ATOMIC_INIT(1); 197 /* set if a fata kmemleak error has occurred */ 198 static atomic_t kmemleak_error = ATOMIC_INIT(0); 199 200 /* minimum and maximum address that may be valid pointers */ 201 static unsigned long min_addr = ULONG_MAX; 202 static unsigned long max_addr; 203 204 static struct task_struct *scan_thread; 205 /* used to avoid reporting of recently allocated objects */ 206 static unsigned long jiffies_min_age; 207 static unsigned long jiffies_last_scan; 208 /* delay between automatic memory scannings */ 209 static signed long jiffies_scan_wait; 210 /* enables or disables the task stacks scanning */ 211 static int kmemleak_stack_scan = 1; 212 /* protects the memory scanning, parameters and debug/kmemleak file access */ 213 static DEFINE_MUTEX(scan_mutex); 214 /* setting kmemleak=on, will set this var, skipping the disable */ 215 static int kmemleak_skip_disable; 216 217 218 /* 219 * Early object allocation/freeing logging. Kmemleak is initialized after the 220 * kernel allocator. However, both the kernel allocator and kmemleak may 221 * allocate memory blocks which need to be tracked. Kmemleak defines an 222 * arbitrary buffer to hold the allocation/freeing information before it is 223 * fully initialized. 224 */ 225 226 /* kmemleak operation type for early logging */ 227 enum { 228 KMEMLEAK_ALLOC, 229 KMEMLEAK_FREE, 230 KMEMLEAK_FREE_PART, 231 KMEMLEAK_NOT_LEAK, 232 KMEMLEAK_IGNORE, 233 KMEMLEAK_SCAN_AREA, 234 KMEMLEAK_NO_SCAN 235 }; 236 237 /* 238 * Structure holding the information passed to kmemleak callbacks during the 239 * early logging. 240 */ 241 struct early_log { 242 int op_type; /* kmemleak operation type */ 243 const void *ptr; /* allocated/freed memory block */ 244 size_t size; /* memory block size */ 245 int min_count; /* minimum reference count */ 246 unsigned long trace[MAX_TRACE]; /* stack trace */ 247 unsigned int trace_len; /* stack trace length */ 248 }; 249 250 /* early logging buffer and current position */ 251 static struct early_log 252 early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata; 253 static int crt_early_log __initdata; 254 255 static void kmemleak_disable(void); 256 257 /* 258 * Print a warning and dump the stack trace. 259 */ 260 #define kmemleak_warn(x...) do { \ 261 pr_warning(x); \ 262 dump_stack(); \ 263 } while (0) 264 265 /* 266 * Macro invoked when a serious kmemleak condition occured and cannot be 267 * recovered from. Kmemleak will be disabled and further allocation/freeing 268 * tracing no longer available. 269 */ 270 #define kmemleak_stop(x...) do { \ 271 kmemleak_warn(x); \ 272 kmemleak_disable(); \ 273 } while (0) 274 275 /* 276 * Printing of the objects hex dump to the seq file. The number of lines to be 277 * printed is limited to HEX_MAX_LINES to prevent seq file spamming. The 278 * actual number of printed bytes depends on HEX_ROW_SIZE. It must be called 279 * with the object->lock held. 280 */ 281 static void hex_dump_object(struct seq_file *seq, 282 struct kmemleak_object *object) 283 { 284 const u8 *ptr = (const u8 *)object->pointer; 285 int i, len, remaining; 286 unsigned char linebuf[HEX_ROW_SIZE * 5]; 287 288 /* limit the number of lines to HEX_MAX_LINES */ 289 remaining = len = 290 min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE)); 291 292 seq_printf(seq, " hex dump (first %d bytes):\n", len); 293 for (i = 0; i < len; i += HEX_ROW_SIZE) { 294 int linelen = min(remaining, HEX_ROW_SIZE); 295 296 remaining -= HEX_ROW_SIZE; 297 hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE, 298 HEX_GROUP_SIZE, linebuf, sizeof(linebuf), 299 HEX_ASCII); 300 seq_printf(seq, " %s\n", linebuf); 301 } 302 } 303 304 /* 305 * Object colors, encoded with count and min_count: 306 * - white - orphan object, not enough references to it (count < min_count) 307 * - gray - not orphan, not marked as false positive (min_count == 0) or 308 * sufficient references to it (count >= min_count) 309 * - black - ignore, it doesn't contain references (e.g. text section) 310 * (min_count == -1). No function defined for this color. 311 * Newly created objects don't have any color assigned (object->count == -1) 312 * before the next memory scan when they become white. 313 */ 314 static bool color_white(const struct kmemleak_object *object) 315 { 316 return object->count != KMEMLEAK_BLACK && 317 object->count < object->min_count; 318 } 319 320 static bool color_gray(const struct kmemleak_object *object) 321 { 322 return object->min_count != KMEMLEAK_BLACK && 323 object->count >= object->min_count; 324 } 325 326 /* 327 * Objects are considered unreferenced only if their color is white, they have 328 * not be deleted and have a minimum age to avoid false positives caused by 329 * pointers temporarily stored in CPU registers. 330 */ 331 static bool unreferenced_object(struct kmemleak_object *object) 332 { 333 return (color_white(object) && object->flags & OBJECT_ALLOCATED) && 334 time_before_eq(object->jiffies + jiffies_min_age, 335 jiffies_last_scan); 336 } 337 338 /* 339 * Printing of the unreferenced objects information to the seq file. The 340 * print_unreferenced function must be called with the object->lock held. 341 */ 342 static void print_unreferenced(struct seq_file *seq, 343 struct kmemleak_object *object) 344 { 345 int i; 346 unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies); 347 348 seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n", 349 object->pointer, object->size); 350 seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n", 351 object->comm, object->pid, object->jiffies, 352 msecs_age / 1000, msecs_age % 1000); 353 hex_dump_object(seq, object); 354 seq_printf(seq, " backtrace:\n"); 355 356 for (i = 0; i < object->trace_len; i++) { 357 void *ptr = (void *)object->trace[i]; 358 seq_printf(seq, " [<%p>] %pS\n", ptr, ptr); 359 } 360 } 361 362 /* 363 * Print the kmemleak_object information. This function is used mainly for 364 * debugging special cases when kmemleak operations. It must be called with 365 * the object->lock held. 366 */ 367 static void dump_object_info(struct kmemleak_object *object) 368 { 369 struct stack_trace trace; 370 371 trace.nr_entries = object->trace_len; 372 trace.entries = object->trace; 373 374 pr_notice("Object 0x%08lx (size %zu):\n", 375 object->tree_node.start, object->size); 376 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n", 377 object->comm, object->pid, object->jiffies); 378 pr_notice(" min_count = %d\n", object->min_count); 379 pr_notice(" count = %d\n", object->count); 380 pr_notice(" flags = 0x%lx\n", object->flags); 381 pr_notice(" checksum = %d\n", object->checksum); 382 pr_notice(" backtrace:\n"); 383 print_stack_trace(&trace, 4); 384 } 385 386 /* 387 * Look-up a memory block metadata (kmemleak_object) in the priority search 388 * tree based on a pointer value. If alias is 0, only values pointing to the 389 * beginning of the memory block are allowed. The kmemleak_lock must be held 390 * when calling this function. 391 */ 392 static struct kmemleak_object *lookup_object(unsigned long ptr, int alias) 393 { 394 struct prio_tree_node *node; 395 struct prio_tree_iter iter; 396 struct kmemleak_object *object; 397 398 prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr); 399 node = prio_tree_next(&iter); 400 if (node) { 401 object = prio_tree_entry(node, struct kmemleak_object, 402 tree_node); 403 if (!alias && object->pointer != ptr) { 404 pr_warning("Found object by alias at 0x%08lx\n", ptr); 405 dump_stack(); 406 dump_object_info(object); 407 object = NULL; 408 } 409 } else 410 object = NULL; 411 412 return object; 413 } 414 415 /* 416 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note 417 * that once an object's use_count reached 0, the RCU freeing was already 418 * registered and the object should no longer be used. This function must be 419 * called under the protection of rcu_read_lock(). 420 */ 421 static int get_object(struct kmemleak_object *object) 422 { 423 return atomic_inc_not_zero(&object->use_count); 424 } 425 426 /* 427 * RCU callback to free a kmemleak_object. 428 */ 429 static void free_object_rcu(struct rcu_head *rcu) 430 { 431 struct hlist_node *elem, *tmp; 432 struct kmemleak_scan_area *area; 433 struct kmemleak_object *object = 434 container_of(rcu, struct kmemleak_object, rcu); 435 436 /* 437 * Once use_count is 0 (guaranteed by put_object), there is no other 438 * code accessing this object, hence no need for locking. 439 */ 440 hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) { 441 hlist_del(elem); 442 kmem_cache_free(scan_area_cache, area); 443 } 444 kmem_cache_free(object_cache, object); 445 } 446 447 /* 448 * Decrement the object use_count. Once the count is 0, free the object using 449 * an RCU callback. Since put_object() may be called via the kmemleak_free() -> 450 * delete_object() path, the delayed RCU freeing ensures that there is no 451 * recursive call to the kernel allocator. Lock-less RCU object_list traversal 452 * is also possible. 453 */ 454 static void put_object(struct kmemleak_object *object) 455 { 456 if (!atomic_dec_and_test(&object->use_count)) 457 return; 458 459 /* should only get here after delete_object was called */ 460 WARN_ON(object->flags & OBJECT_ALLOCATED); 461 462 call_rcu(&object->rcu, free_object_rcu); 463 } 464 465 /* 466 * Look up an object in the prio search tree and increase its use_count. 467 */ 468 static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias) 469 { 470 unsigned long flags; 471 struct kmemleak_object *object = NULL; 472 473 rcu_read_lock(); 474 read_lock_irqsave(&kmemleak_lock, flags); 475 if (ptr >= min_addr && ptr < max_addr) 476 object = lookup_object(ptr, alias); 477 read_unlock_irqrestore(&kmemleak_lock, flags); 478 479 /* check whether the object is still available */ 480 if (object && !get_object(object)) 481 object = NULL; 482 rcu_read_unlock(); 483 484 return object; 485 } 486 487 /* 488 * Save stack trace to the given array of MAX_TRACE size. 489 */ 490 static int __save_stack_trace(unsigned long *trace) 491 { 492 struct stack_trace stack_trace; 493 494 stack_trace.max_entries = MAX_TRACE; 495 stack_trace.nr_entries = 0; 496 stack_trace.entries = trace; 497 stack_trace.skip = 2; 498 save_stack_trace(&stack_trace); 499 500 return stack_trace.nr_entries; 501 } 502 503 /* 504 * Create the metadata (struct kmemleak_object) corresponding to an allocated 505 * memory block and add it to the object_list and object_tree_root. 506 */ 507 static struct kmemleak_object *create_object(unsigned long ptr, size_t size, 508 int min_count, gfp_t gfp) 509 { 510 unsigned long flags; 511 struct kmemleak_object *object; 512 struct prio_tree_node *node; 513 514 object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK); 515 if (!object) { 516 kmemleak_stop("Cannot allocate a kmemleak_object structure\n"); 517 return NULL; 518 } 519 520 INIT_LIST_HEAD(&object->object_list); 521 INIT_LIST_HEAD(&object->gray_list); 522 INIT_HLIST_HEAD(&object->area_list); 523 spin_lock_init(&object->lock); 524 atomic_set(&object->use_count, 1); 525 object->flags = OBJECT_ALLOCATED; 526 object->pointer = ptr; 527 object->size = size; 528 object->min_count = min_count; 529 object->count = 0; /* white color initially */ 530 object->jiffies = jiffies; 531 object->checksum = 0; 532 533 /* task information */ 534 if (in_irq()) { 535 object->pid = 0; 536 strncpy(object->comm, "hardirq", sizeof(object->comm)); 537 } else if (in_softirq()) { 538 object->pid = 0; 539 strncpy(object->comm, "softirq", sizeof(object->comm)); 540 } else { 541 object->pid = current->pid; 542 /* 543 * There is a small chance of a race with set_task_comm(), 544 * however using get_task_comm() here may cause locking 545 * dependency issues with current->alloc_lock. In the worst 546 * case, the command line is not correct. 547 */ 548 strncpy(object->comm, current->comm, sizeof(object->comm)); 549 } 550 551 /* kernel backtrace */ 552 object->trace_len = __save_stack_trace(object->trace); 553 554 INIT_PRIO_TREE_NODE(&object->tree_node); 555 object->tree_node.start = ptr; 556 object->tree_node.last = ptr + size - 1; 557 558 write_lock_irqsave(&kmemleak_lock, flags); 559 560 min_addr = min(min_addr, ptr); 561 max_addr = max(max_addr, ptr + size); 562 node = prio_tree_insert(&object_tree_root, &object->tree_node); 563 /* 564 * The code calling the kernel does not yet have the pointer to the 565 * memory block to be able to free it. However, we still hold the 566 * kmemleak_lock here in case parts of the kernel started freeing 567 * random memory blocks. 568 */ 569 if (node != &object->tree_node) { 570 kmemleak_stop("Cannot insert 0x%lx into the object search tree " 571 "(already existing)\n", ptr); 572 object = lookup_object(ptr, 1); 573 spin_lock(&object->lock); 574 dump_object_info(object); 575 spin_unlock(&object->lock); 576 577 goto out; 578 } 579 list_add_tail_rcu(&object->object_list, &object_list); 580 out: 581 write_unlock_irqrestore(&kmemleak_lock, flags); 582 return object; 583 } 584 585 /* 586 * Remove the metadata (struct kmemleak_object) for a memory block from the 587 * object_list and object_tree_root and decrement its use_count. 588 */ 589 static void __delete_object(struct kmemleak_object *object) 590 { 591 unsigned long flags; 592 593 write_lock_irqsave(&kmemleak_lock, flags); 594 prio_tree_remove(&object_tree_root, &object->tree_node); 595 list_del_rcu(&object->object_list); 596 write_unlock_irqrestore(&kmemleak_lock, flags); 597 598 WARN_ON(!(object->flags & OBJECT_ALLOCATED)); 599 WARN_ON(atomic_read(&object->use_count) < 2); 600 601 /* 602 * Locking here also ensures that the corresponding memory block 603 * cannot be freed when it is being scanned. 604 */ 605 spin_lock_irqsave(&object->lock, flags); 606 object->flags &= ~OBJECT_ALLOCATED; 607 spin_unlock_irqrestore(&object->lock, flags); 608 put_object(object); 609 } 610 611 /* 612 * Look up the metadata (struct kmemleak_object) corresponding to ptr and 613 * delete it. 614 */ 615 static void delete_object_full(unsigned long ptr) 616 { 617 struct kmemleak_object *object; 618 619 object = find_and_get_object(ptr, 0); 620 if (!object) { 621 #ifdef DEBUG 622 kmemleak_warn("Freeing unknown object at 0x%08lx\n", 623 ptr); 624 #endif 625 return; 626 } 627 __delete_object(object); 628 put_object(object); 629 } 630 631 /* 632 * Look up the metadata (struct kmemleak_object) corresponding to ptr and 633 * delete it. If the memory block is partially freed, the function may create 634 * additional metadata for the remaining parts of the block. 635 */ 636 static void delete_object_part(unsigned long ptr, size_t size) 637 { 638 struct kmemleak_object *object; 639 unsigned long start, end; 640 641 object = find_and_get_object(ptr, 1); 642 if (!object) { 643 #ifdef DEBUG 644 kmemleak_warn("Partially freeing unknown object at 0x%08lx " 645 "(size %zu)\n", ptr, size); 646 #endif 647 return; 648 } 649 __delete_object(object); 650 651 /* 652 * Create one or two objects that may result from the memory block 653 * split. Note that partial freeing is only done by free_bootmem() and 654 * this happens before kmemleak_init() is called. The path below is 655 * only executed during early log recording in kmemleak_init(), so 656 * GFP_KERNEL is enough. 657 */ 658 start = object->pointer; 659 end = object->pointer + object->size; 660 if (ptr > start) 661 create_object(start, ptr - start, object->min_count, 662 GFP_KERNEL); 663 if (ptr + size < end) 664 create_object(ptr + size, end - ptr - size, object->min_count, 665 GFP_KERNEL); 666 667 put_object(object); 668 } 669 670 static void __paint_it(struct kmemleak_object *object, int color) 671 { 672 object->min_count = color; 673 if (color == KMEMLEAK_BLACK) 674 object->flags |= OBJECT_NO_SCAN; 675 } 676 677 static void paint_it(struct kmemleak_object *object, int color) 678 { 679 unsigned long flags; 680 681 spin_lock_irqsave(&object->lock, flags); 682 __paint_it(object, color); 683 spin_unlock_irqrestore(&object->lock, flags); 684 } 685 686 static void paint_ptr(unsigned long ptr, int color) 687 { 688 struct kmemleak_object *object; 689 690 object = find_and_get_object(ptr, 0); 691 if (!object) { 692 kmemleak_warn("Trying to color unknown object " 693 "at 0x%08lx as %s\n", ptr, 694 (color == KMEMLEAK_GREY) ? "Grey" : 695 (color == KMEMLEAK_BLACK) ? "Black" : "Unknown"); 696 return; 697 } 698 paint_it(object, color); 699 put_object(object); 700 } 701 702 /* 703 * Mark an object permanently as gray-colored so that it can no longer be 704 * reported as a leak. This is used in general to mark a false positive. 705 */ 706 static void make_gray_object(unsigned long ptr) 707 { 708 paint_ptr(ptr, KMEMLEAK_GREY); 709 } 710 711 /* 712 * Mark the object as black-colored so that it is ignored from scans and 713 * reporting. 714 */ 715 static void make_black_object(unsigned long ptr) 716 { 717 paint_ptr(ptr, KMEMLEAK_BLACK); 718 } 719 720 /* 721 * Add a scanning area to the object. If at least one such area is added, 722 * kmemleak will only scan these ranges rather than the whole memory block. 723 */ 724 static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp) 725 { 726 unsigned long flags; 727 struct kmemleak_object *object; 728 struct kmemleak_scan_area *area; 729 730 object = find_and_get_object(ptr, 1); 731 if (!object) { 732 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n", 733 ptr); 734 return; 735 } 736 737 area = kmem_cache_alloc(scan_area_cache, gfp & GFP_KMEMLEAK_MASK); 738 if (!area) { 739 kmemleak_warn("Cannot allocate a scan area\n"); 740 goto out; 741 } 742 743 spin_lock_irqsave(&object->lock, flags); 744 if (ptr + size > object->pointer + object->size) { 745 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr); 746 dump_object_info(object); 747 kmem_cache_free(scan_area_cache, area); 748 goto out_unlock; 749 } 750 751 INIT_HLIST_NODE(&area->node); 752 area->start = ptr; 753 area->size = size; 754 755 hlist_add_head(&area->node, &object->area_list); 756 out_unlock: 757 spin_unlock_irqrestore(&object->lock, flags); 758 out: 759 put_object(object); 760 } 761 762 /* 763 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give 764 * pointer. Such object will not be scanned by kmemleak but references to it 765 * are searched. 766 */ 767 static void object_no_scan(unsigned long ptr) 768 { 769 unsigned long flags; 770 struct kmemleak_object *object; 771 772 object = find_and_get_object(ptr, 0); 773 if (!object) { 774 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr); 775 return; 776 } 777 778 spin_lock_irqsave(&object->lock, flags); 779 object->flags |= OBJECT_NO_SCAN; 780 spin_unlock_irqrestore(&object->lock, flags); 781 put_object(object); 782 } 783 784 /* 785 * Log an early kmemleak_* call to the early_log buffer. These calls will be 786 * processed later once kmemleak is fully initialized. 787 */ 788 static void __init log_early(int op_type, const void *ptr, size_t size, 789 int min_count) 790 { 791 unsigned long flags; 792 struct early_log *log; 793 794 if (crt_early_log >= ARRAY_SIZE(early_log)) { 795 pr_warning("Early log buffer exceeded, " 796 "please increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n"); 797 kmemleak_disable(); 798 return; 799 } 800 801 /* 802 * There is no need for locking since the kernel is still in UP mode 803 * at this stage. Disabling the IRQs is enough. 804 */ 805 local_irq_save(flags); 806 log = &early_log[crt_early_log]; 807 log->op_type = op_type; 808 log->ptr = ptr; 809 log->size = size; 810 log->min_count = min_count; 811 if (op_type == KMEMLEAK_ALLOC) 812 log->trace_len = __save_stack_trace(log->trace); 813 crt_early_log++; 814 local_irq_restore(flags); 815 } 816 817 /* 818 * Log an early allocated block and populate the stack trace. 819 */ 820 static void early_alloc(struct early_log *log) 821 { 822 struct kmemleak_object *object; 823 unsigned long flags; 824 int i; 825 826 if (!atomic_read(&kmemleak_enabled) || !log->ptr || IS_ERR(log->ptr)) 827 return; 828 829 /* 830 * RCU locking needed to ensure object is not freed via put_object(). 831 */ 832 rcu_read_lock(); 833 object = create_object((unsigned long)log->ptr, log->size, 834 log->min_count, GFP_ATOMIC); 835 if (!object) 836 goto out; 837 spin_lock_irqsave(&object->lock, flags); 838 for (i = 0; i < log->trace_len; i++) 839 object->trace[i] = log->trace[i]; 840 object->trace_len = log->trace_len; 841 spin_unlock_irqrestore(&object->lock, flags); 842 out: 843 rcu_read_unlock(); 844 } 845 846 /** 847 * kmemleak_alloc - register a newly allocated object 848 * @ptr: pointer to beginning of the object 849 * @size: size of the object 850 * @min_count: minimum number of references to this object. If during memory 851 * scanning a number of references less than @min_count is found, 852 * the object is reported as a memory leak. If @min_count is 0, 853 * the object is never reported as a leak. If @min_count is -1, 854 * the object is ignored (not scanned and not reported as a leak) 855 * @gfp: kmalloc() flags used for kmemleak internal memory allocations 856 * 857 * This function is called from the kernel allocators when a new object 858 * (memory block) is allocated (kmem_cache_alloc, kmalloc, vmalloc etc.). 859 */ 860 void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count, 861 gfp_t gfp) 862 { 863 pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count); 864 865 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) 866 create_object((unsigned long)ptr, size, min_count, gfp); 867 else if (atomic_read(&kmemleak_early_log)) 868 log_early(KMEMLEAK_ALLOC, ptr, size, min_count); 869 } 870 EXPORT_SYMBOL_GPL(kmemleak_alloc); 871 872 /** 873 * kmemleak_free - unregister a previously registered object 874 * @ptr: pointer to beginning of the object 875 * 876 * This function is called from the kernel allocators when an object (memory 877 * block) is freed (kmem_cache_free, kfree, vfree etc.). 878 */ 879 void __ref kmemleak_free(const void *ptr) 880 { 881 pr_debug("%s(0x%p)\n", __func__, ptr); 882 883 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) 884 delete_object_full((unsigned long)ptr); 885 else if (atomic_read(&kmemleak_early_log)) 886 log_early(KMEMLEAK_FREE, ptr, 0, 0); 887 } 888 EXPORT_SYMBOL_GPL(kmemleak_free); 889 890 /** 891 * kmemleak_free_part - partially unregister a previously registered object 892 * @ptr: pointer to the beginning or inside the object. This also 893 * represents the start of the range to be freed 894 * @size: size to be unregistered 895 * 896 * This function is called when only a part of a memory block is freed 897 * (usually from the bootmem allocator). 898 */ 899 void __ref kmemleak_free_part(const void *ptr, size_t size) 900 { 901 pr_debug("%s(0x%p)\n", __func__, ptr); 902 903 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) 904 delete_object_part((unsigned long)ptr, size); 905 else if (atomic_read(&kmemleak_early_log)) 906 log_early(KMEMLEAK_FREE_PART, ptr, size, 0); 907 } 908 EXPORT_SYMBOL_GPL(kmemleak_free_part); 909 910 /** 911 * kmemleak_not_leak - mark an allocated object as false positive 912 * @ptr: pointer to beginning of the object 913 * 914 * Calling this function on an object will cause the memory block to no longer 915 * be reported as leak and always be scanned. 916 */ 917 void __ref kmemleak_not_leak(const void *ptr) 918 { 919 pr_debug("%s(0x%p)\n", __func__, ptr); 920 921 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) 922 make_gray_object((unsigned long)ptr); 923 else if (atomic_read(&kmemleak_early_log)) 924 log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0); 925 } 926 EXPORT_SYMBOL(kmemleak_not_leak); 927 928 /** 929 * kmemleak_ignore - ignore an allocated object 930 * @ptr: pointer to beginning of the object 931 * 932 * Calling this function on an object will cause the memory block to be 933 * ignored (not scanned and not reported as a leak). This is usually done when 934 * it is known that the corresponding block is not a leak and does not contain 935 * any references to other allocated memory blocks. 936 */ 937 void __ref kmemleak_ignore(const void *ptr) 938 { 939 pr_debug("%s(0x%p)\n", __func__, ptr); 940 941 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) 942 make_black_object((unsigned long)ptr); 943 else if (atomic_read(&kmemleak_early_log)) 944 log_early(KMEMLEAK_IGNORE, ptr, 0, 0); 945 } 946 EXPORT_SYMBOL(kmemleak_ignore); 947 948 /** 949 * kmemleak_scan_area - limit the range to be scanned in an allocated object 950 * @ptr: pointer to beginning or inside the object. This also 951 * represents the start of the scan area 952 * @size: size of the scan area 953 * @gfp: kmalloc() flags used for kmemleak internal memory allocations 954 * 955 * This function is used when it is known that only certain parts of an object 956 * contain references to other objects. Kmemleak will only scan these areas 957 * reducing the number false negatives. 958 */ 959 void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp) 960 { 961 pr_debug("%s(0x%p)\n", __func__, ptr); 962 963 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) 964 add_scan_area((unsigned long)ptr, size, gfp); 965 else if (atomic_read(&kmemleak_early_log)) 966 log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0); 967 } 968 EXPORT_SYMBOL(kmemleak_scan_area); 969 970 /** 971 * kmemleak_no_scan - do not scan an allocated object 972 * @ptr: pointer to beginning of the object 973 * 974 * This function notifies kmemleak not to scan the given memory block. Useful 975 * in situations where it is known that the given object does not contain any 976 * references to other objects. Kmemleak will not scan such objects reducing 977 * the number of false negatives. 978 */ 979 void __ref kmemleak_no_scan(const void *ptr) 980 { 981 pr_debug("%s(0x%p)\n", __func__, ptr); 982 983 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) 984 object_no_scan((unsigned long)ptr); 985 else if (atomic_read(&kmemleak_early_log)) 986 log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0); 987 } 988 EXPORT_SYMBOL(kmemleak_no_scan); 989 990 /* 991 * Update an object's checksum and return true if it was modified. 992 */ 993 static bool update_checksum(struct kmemleak_object *object) 994 { 995 u32 old_csum = object->checksum; 996 997 if (!kmemcheck_is_obj_initialized(object->pointer, object->size)) 998 return false; 999 1000 object->checksum = crc32(0, (void *)object->pointer, object->size); 1001 return object->checksum != old_csum; 1002 } 1003 1004 /* 1005 * Memory scanning is a long process and it needs to be interruptable. This 1006 * function checks whether such interrupt condition occured. 1007 */ 1008 static int scan_should_stop(void) 1009 { 1010 if (!atomic_read(&kmemleak_enabled)) 1011 return 1; 1012 1013 /* 1014 * This function may be called from either process or kthread context, 1015 * hence the need to check for both stop conditions. 1016 */ 1017 if (current->mm) 1018 return signal_pending(current); 1019 else 1020 return kthread_should_stop(); 1021 1022 return 0; 1023 } 1024 1025 /* 1026 * Scan a memory block (exclusive range) for valid pointers and add those 1027 * found to the gray list. 1028 */ 1029 static void scan_block(void *_start, void *_end, 1030 struct kmemleak_object *scanned, int allow_resched) 1031 { 1032 unsigned long *ptr; 1033 unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER); 1034 unsigned long *end = _end - (BYTES_PER_POINTER - 1); 1035 1036 for (ptr = start; ptr < end; ptr++) { 1037 struct kmemleak_object *object; 1038 unsigned long flags; 1039 unsigned long pointer; 1040 1041 if (allow_resched) 1042 cond_resched(); 1043 if (scan_should_stop()) 1044 break; 1045 1046 /* don't scan uninitialized memory */ 1047 if (!kmemcheck_is_obj_initialized((unsigned long)ptr, 1048 BYTES_PER_POINTER)) 1049 continue; 1050 1051 pointer = *ptr; 1052 1053 object = find_and_get_object(pointer, 1); 1054 if (!object) 1055 continue; 1056 if (object == scanned) { 1057 /* self referenced, ignore */ 1058 put_object(object); 1059 continue; 1060 } 1061 1062 /* 1063 * Avoid the lockdep recursive warning on object->lock being 1064 * previously acquired in scan_object(). These locks are 1065 * enclosed by scan_mutex. 1066 */ 1067 spin_lock_irqsave_nested(&object->lock, flags, 1068 SINGLE_DEPTH_NESTING); 1069 if (!color_white(object)) { 1070 /* non-orphan, ignored or new */ 1071 spin_unlock_irqrestore(&object->lock, flags); 1072 put_object(object); 1073 continue; 1074 } 1075 1076 /* 1077 * Increase the object's reference count (number of pointers 1078 * to the memory block). If this count reaches the required 1079 * minimum, the object's color will become gray and it will be 1080 * added to the gray_list. 1081 */ 1082 object->count++; 1083 if (color_gray(object)) { 1084 list_add_tail(&object->gray_list, &gray_list); 1085 spin_unlock_irqrestore(&object->lock, flags); 1086 continue; 1087 } 1088 1089 spin_unlock_irqrestore(&object->lock, flags); 1090 put_object(object); 1091 } 1092 } 1093 1094 /* 1095 * Scan a memory block corresponding to a kmemleak_object. A condition is 1096 * that object->use_count >= 1. 1097 */ 1098 static void scan_object(struct kmemleak_object *object) 1099 { 1100 struct kmemleak_scan_area *area; 1101 struct hlist_node *elem; 1102 unsigned long flags; 1103 1104 /* 1105 * Once the object->lock is acquired, the corresponding memory block 1106 * cannot be freed (the same lock is acquired in delete_object). 1107 */ 1108 spin_lock_irqsave(&object->lock, flags); 1109 if (object->flags & OBJECT_NO_SCAN) 1110 goto out; 1111 if (!(object->flags & OBJECT_ALLOCATED)) 1112 /* already freed object */ 1113 goto out; 1114 if (hlist_empty(&object->area_list)) { 1115 void *start = (void *)object->pointer; 1116 void *end = (void *)(object->pointer + object->size); 1117 1118 while (start < end && (object->flags & OBJECT_ALLOCATED) && 1119 !(object->flags & OBJECT_NO_SCAN)) { 1120 scan_block(start, min(start + MAX_SCAN_SIZE, end), 1121 object, 0); 1122 start += MAX_SCAN_SIZE; 1123 1124 spin_unlock_irqrestore(&object->lock, flags); 1125 cond_resched(); 1126 spin_lock_irqsave(&object->lock, flags); 1127 } 1128 } else 1129 hlist_for_each_entry(area, elem, &object->area_list, node) 1130 scan_block((void *)area->start, 1131 (void *)(area->start + area->size), 1132 object, 0); 1133 out: 1134 spin_unlock_irqrestore(&object->lock, flags); 1135 } 1136 1137 /* 1138 * Scan the objects already referenced (gray objects). More objects will be 1139 * referenced and, if there are no memory leaks, all the objects are scanned. 1140 */ 1141 static void scan_gray_list(void) 1142 { 1143 struct kmemleak_object *object, *tmp; 1144 1145 /* 1146 * The list traversal is safe for both tail additions and removals 1147 * from inside the loop. The kmemleak objects cannot be freed from 1148 * outside the loop because their use_count was incremented. 1149 */ 1150 object = list_entry(gray_list.next, typeof(*object), gray_list); 1151 while (&object->gray_list != &gray_list) { 1152 cond_resched(); 1153 1154 /* may add new objects to the list */ 1155 if (!scan_should_stop()) 1156 scan_object(object); 1157 1158 tmp = list_entry(object->gray_list.next, typeof(*object), 1159 gray_list); 1160 1161 /* remove the object from the list and release it */ 1162 list_del(&object->gray_list); 1163 put_object(object); 1164 1165 object = tmp; 1166 } 1167 WARN_ON(!list_empty(&gray_list)); 1168 } 1169 1170 /* 1171 * Scan data sections and all the referenced memory blocks allocated via the 1172 * kernel's standard allocators. This function must be called with the 1173 * scan_mutex held. 1174 */ 1175 static void kmemleak_scan(void) 1176 { 1177 unsigned long flags; 1178 struct kmemleak_object *object; 1179 int i; 1180 int new_leaks = 0; 1181 1182 jiffies_last_scan = jiffies; 1183 1184 /* prepare the kmemleak_object's */ 1185 rcu_read_lock(); 1186 list_for_each_entry_rcu(object, &object_list, object_list) { 1187 spin_lock_irqsave(&object->lock, flags); 1188 #ifdef DEBUG 1189 /* 1190 * With a few exceptions there should be a maximum of 1191 * 1 reference to any object at this point. 1192 */ 1193 if (atomic_read(&object->use_count) > 1) { 1194 pr_debug("object->use_count = %d\n", 1195 atomic_read(&object->use_count)); 1196 dump_object_info(object); 1197 } 1198 #endif 1199 /* reset the reference count (whiten the object) */ 1200 object->count = 0; 1201 if (color_gray(object) && get_object(object)) 1202 list_add_tail(&object->gray_list, &gray_list); 1203 1204 spin_unlock_irqrestore(&object->lock, flags); 1205 } 1206 rcu_read_unlock(); 1207 1208 /* data/bss scanning */ 1209 scan_block(_sdata, _edata, NULL, 1); 1210 scan_block(__bss_start, __bss_stop, NULL, 1); 1211 1212 #ifdef CONFIG_SMP 1213 /* per-cpu sections scanning */ 1214 for_each_possible_cpu(i) 1215 scan_block(__per_cpu_start + per_cpu_offset(i), 1216 __per_cpu_end + per_cpu_offset(i), NULL, 1); 1217 #endif 1218 1219 /* 1220 * Struct page scanning for each node. The code below is not yet safe 1221 * with MEMORY_HOTPLUG. 1222 */ 1223 for_each_online_node(i) { 1224 pg_data_t *pgdat = NODE_DATA(i); 1225 unsigned long start_pfn = pgdat->node_start_pfn; 1226 unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages; 1227 unsigned long pfn; 1228 1229 for (pfn = start_pfn; pfn < end_pfn; pfn++) { 1230 struct page *page; 1231 1232 if (!pfn_valid(pfn)) 1233 continue; 1234 page = pfn_to_page(pfn); 1235 /* only scan if page is in use */ 1236 if (page_count(page) == 0) 1237 continue; 1238 scan_block(page, page + 1, NULL, 1); 1239 } 1240 } 1241 1242 /* 1243 * Scanning the task stacks (may introduce false negatives). 1244 */ 1245 if (kmemleak_stack_scan) { 1246 struct task_struct *p, *g; 1247 1248 read_lock(&tasklist_lock); 1249 do_each_thread(g, p) { 1250 scan_block(task_stack_page(p), task_stack_page(p) + 1251 THREAD_SIZE, NULL, 0); 1252 } while_each_thread(g, p); 1253 read_unlock(&tasklist_lock); 1254 } 1255 1256 /* 1257 * Scan the objects already referenced from the sections scanned 1258 * above. 1259 */ 1260 scan_gray_list(); 1261 1262 /* 1263 * Check for new or unreferenced objects modified since the previous 1264 * scan and color them gray until the next scan. 1265 */ 1266 rcu_read_lock(); 1267 list_for_each_entry_rcu(object, &object_list, object_list) { 1268 spin_lock_irqsave(&object->lock, flags); 1269 if (color_white(object) && (object->flags & OBJECT_ALLOCATED) 1270 && update_checksum(object) && get_object(object)) { 1271 /* color it gray temporarily */ 1272 object->count = object->min_count; 1273 list_add_tail(&object->gray_list, &gray_list); 1274 } 1275 spin_unlock_irqrestore(&object->lock, flags); 1276 } 1277 rcu_read_unlock(); 1278 1279 /* 1280 * Re-scan the gray list for modified unreferenced objects. 1281 */ 1282 scan_gray_list(); 1283 1284 /* 1285 * If scanning was stopped do not report any new unreferenced objects. 1286 */ 1287 if (scan_should_stop()) 1288 return; 1289 1290 /* 1291 * Scanning result reporting. 1292 */ 1293 rcu_read_lock(); 1294 list_for_each_entry_rcu(object, &object_list, object_list) { 1295 spin_lock_irqsave(&object->lock, flags); 1296 if (unreferenced_object(object) && 1297 !(object->flags & OBJECT_REPORTED)) { 1298 object->flags |= OBJECT_REPORTED; 1299 new_leaks++; 1300 } 1301 spin_unlock_irqrestore(&object->lock, flags); 1302 } 1303 rcu_read_unlock(); 1304 1305 if (new_leaks) 1306 pr_info("%d new suspected memory leaks (see " 1307 "/sys/kernel/debug/kmemleak)\n", new_leaks); 1308 1309 } 1310 1311 /* 1312 * Thread function performing automatic memory scanning. Unreferenced objects 1313 * at the end of a memory scan are reported but only the first time. 1314 */ 1315 static int kmemleak_scan_thread(void *arg) 1316 { 1317 static int first_run = 1; 1318 1319 pr_info("Automatic memory scanning thread started\n"); 1320 set_user_nice(current, 10); 1321 1322 /* 1323 * Wait before the first scan to allow the system to fully initialize. 1324 */ 1325 if (first_run) { 1326 first_run = 0; 1327 ssleep(SECS_FIRST_SCAN); 1328 } 1329 1330 while (!kthread_should_stop()) { 1331 signed long timeout = jiffies_scan_wait; 1332 1333 mutex_lock(&scan_mutex); 1334 kmemleak_scan(); 1335 mutex_unlock(&scan_mutex); 1336 1337 /* wait before the next scan */ 1338 while (timeout && !kthread_should_stop()) 1339 timeout = schedule_timeout_interruptible(timeout); 1340 } 1341 1342 pr_info("Automatic memory scanning thread ended\n"); 1343 1344 return 0; 1345 } 1346 1347 /* 1348 * Start the automatic memory scanning thread. This function must be called 1349 * with the scan_mutex held. 1350 */ 1351 static void start_scan_thread(void) 1352 { 1353 if (scan_thread) 1354 return; 1355 scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak"); 1356 if (IS_ERR(scan_thread)) { 1357 pr_warning("Failed to create the scan thread\n"); 1358 scan_thread = NULL; 1359 } 1360 } 1361 1362 /* 1363 * Stop the automatic memory scanning thread. This function must be called 1364 * with the scan_mutex held. 1365 */ 1366 static void stop_scan_thread(void) 1367 { 1368 if (scan_thread) { 1369 kthread_stop(scan_thread); 1370 scan_thread = NULL; 1371 } 1372 } 1373 1374 /* 1375 * Iterate over the object_list and return the first valid object at or after 1376 * the required position with its use_count incremented. The function triggers 1377 * a memory scanning when the pos argument points to the first position. 1378 */ 1379 static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos) 1380 { 1381 struct kmemleak_object *object; 1382 loff_t n = *pos; 1383 int err; 1384 1385 err = mutex_lock_interruptible(&scan_mutex); 1386 if (err < 0) 1387 return ERR_PTR(err); 1388 1389 rcu_read_lock(); 1390 list_for_each_entry_rcu(object, &object_list, object_list) { 1391 if (n-- > 0) 1392 continue; 1393 if (get_object(object)) 1394 goto out; 1395 } 1396 object = NULL; 1397 out: 1398 return object; 1399 } 1400 1401 /* 1402 * Return the next object in the object_list. The function decrements the 1403 * use_count of the previous object and increases that of the next one. 1404 */ 1405 static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos) 1406 { 1407 struct kmemleak_object *prev_obj = v; 1408 struct kmemleak_object *next_obj = NULL; 1409 struct list_head *n = &prev_obj->object_list; 1410 1411 ++(*pos); 1412 1413 list_for_each_continue_rcu(n, &object_list) { 1414 next_obj = list_entry(n, struct kmemleak_object, object_list); 1415 if (get_object(next_obj)) 1416 break; 1417 } 1418 1419 put_object(prev_obj); 1420 return next_obj; 1421 } 1422 1423 /* 1424 * Decrement the use_count of the last object required, if any. 1425 */ 1426 static void kmemleak_seq_stop(struct seq_file *seq, void *v) 1427 { 1428 if (!IS_ERR(v)) { 1429 /* 1430 * kmemleak_seq_start may return ERR_PTR if the scan_mutex 1431 * waiting was interrupted, so only release it if !IS_ERR. 1432 */ 1433 rcu_read_unlock(); 1434 mutex_unlock(&scan_mutex); 1435 if (v) 1436 put_object(v); 1437 } 1438 } 1439 1440 /* 1441 * Print the information for an unreferenced object to the seq file. 1442 */ 1443 static int kmemleak_seq_show(struct seq_file *seq, void *v) 1444 { 1445 struct kmemleak_object *object = v; 1446 unsigned long flags; 1447 1448 spin_lock_irqsave(&object->lock, flags); 1449 if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object)) 1450 print_unreferenced(seq, object); 1451 spin_unlock_irqrestore(&object->lock, flags); 1452 return 0; 1453 } 1454 1455 static const struct seq_operations kmemleak_seq_ops = { 1456 .start = kmemleak_seq_start, 1457 .next = kmemleak_seq_next, 1458 .stop = kmemleak_seq_stop, 1459 .show = kmemleak_seq_show, 1460 }; 1461 1462 static int kmemleak_open(struct inode *inode, struct file *file) 1463 { 1464 if (!atomic_read(&kmemleak_enabled)) 1465 return -EBUSY; 1466 1467 return seq_open(file, &kmemleak_seq_ops); 1468 } 1469 1470 static int kmemleak_release(struct inode *inode, struct file *file) 1471 { 1472 return seq_release(inode, file); 1473 } 1474 1475 static int dump_str_object_info(const char *str) 1476 { 1477 unsigned long flags; 1478 struct kmemleak_object *object; 1479 unsigned long addr; 1480 1481 addr= simple_strtoul(str, NULL, 0); 1482 object = find_and_get_object(addr, 0); 1483 if (!object) { 1484 pr_info("Unknown object at 0x%08lx\n", addr); 1485 return -EINVAL; 1486 } 1487 1488 spin_lock_irqsave(&object->lock, flags); 1489 dump_object_info(object); 1490 spin_unlock_irqrestore(&object->lock, flags); 1491 1492 put_object(object); 1493 return 0; 1494 } 1495 1496 /* 1497 * We use grey instead of black to ensure we can do future scans on the same 1498 * objects. If we did not do future scans these black objects could 1499 * potentially contain references to newly allocated objects in the future and 1500 * we'd end up with false positives. 1501 */ 1502 static void kmemleak_clear(void) 1503 { 1504 struct kmemleak_object *object; 1505 unsigned long flags; 1506 1507 rcu_read_lock(); 1508 list_for_each_entry_rcu(object, &object_list, object_list) { 1509 spin_lock_irqsave(&object->lock, flags); 1510 if ((object->flags & OBJECT_REPORTED) && 1511 unreferenced_object(object)) 1512 __paint_it(object, KMEMLEAK_GREY); 1513 spin_unlock_irqrestore(&object->lock, flags); 1514 } 1515 rcu_read_unlock(); 1516 } 1517 1518 /* 1519 * File write operation to configure kmemleak at run-time. The following 1520 * commands can be written to the /sys/kernel/debug/kmemleak file: 1521 * off - disable kmemleak (irreversible) 1522 * stack=on - enable the task stacks scanning 1523 * stack=off - disable the tasks stacks scanning 1524 * scan=on - start the automatic memory scanning thread 1525 * scan=off - stop the automatic memory scanning thread 1526 * scan=... - set the automatic memory scanning period in seconds (0 to 1527 * disable it) 1528 * scan - trigger a memory scan 1529 * clear - mark all current reported unreferenced kmemleak objects as 1530 * grey to ignore printing them 1531 * dump=... - dump information about the object found at the given address 1532 */ 1533 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, 1534 size_t size, loff_t *ppos) 1535 { 1536 char buf[64]; 1537 int buf_size; 1538 int ret; 1539 1540 buf_size = min(size, (sizeof(buf) - 1)); 1541 if (strncpy_from_user(buf, user_buf, buf_size) < 0) 1542 return -EFAULT; 1543 buf[buf_size] = 0; 1544 1545 ret = mutex_lock_interruptible(&scan_mutex); 1546 if (ret < 0) 1547 return ret; 1548 1549 if (strncmp(buf, "off", 3) == 0) 1550 kmemleak_disable(); 1551 else if (strncmp(buf, "stack=on", 8) == 0) 1552 kmemleak_stack_scan = 1; 1553 else if (strncmp(buf, "stack=off", 9) == 0) 1554 kmemleak_stack_scan = 0; 1555 else if (strncmp(buf, "scan=on", 7) == 0) 1556 start_scan_thread(); 1557 else if (strncmp(buf, "scan=off", 8) == 0) 1558 stop_scan_thread(); 1559 else if (strncmp(buf, "scan=", 5) == 0) { 1560 unsigned long secs; 1561 1562 ret = strict_strtoul(buf + 5, 0, &secs); 1563 if (ret < 0) 1564 goto out; 1565 stop_scan_thread(); 1566 if (secs) { 1567 jiffies_scan_wait = msecs_to_jiffies(secs * 1000); 1568 start_scan_thread(); 1569 } 1570 } else if (strncmp(buf, "scan", 4) == 0) 1571 kmemleak_scan(); 1572 else if (strncmp(buf, "clear", 5) == 0) 1573 kmemleak_clear(); 1574 else if (strncmp(buf, "dump=", 5) == 0) 1575 ret = dump_str_object_info(buf + 5); 1576 else 1577 ret = -EINVAL; 1578 1579 out: 1580 mutex_unlock(&scan_mutex); 1581 if (ret < 0) 1582 return ret; 1583 1584 /* ignore the rest of the buffer, only one command at a time */ 1585 *ppos += size; 1586 return size; 1587 } 1588 1589 static const struct file_operations kmemleak_fops = { 1590 .owner = THIS_MODULE, 1591 .open = kmemleak_open, 1592 .read = seq_read, 1593 .write = kmemleak_write, 1594 .llseek = seq_lseek, 1595 .release = kmemleak_release, 1596 }; 1597 1598 /* 1599 * Perform the freeing of the kmemleak internal objects after waiting for any 1600 * current memory scan to complete. 1601 */ 1602 static void kmemleak_do_cleanup(struct work_struct *work) 1603 { 1604 struct kmemleak_object *object; 1605 1606 mutex_lock(&scan_mutex); 1607 stop_scan_thread(); 1608 1609 rcu_read_lock(); 1610 list_for_each_entry_rcu(object, &object_list, object_list) 1611 delete_object_full(object->pointer); 1612 rcu_read_unlock(); 1613 mutex_unlock(&scan_mutex); 1614 } 1615 1616 static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup); 1617 1618 /* 1619 * Disable kmemleak. No memory allocation/freeing will be traced once this 1620 * function is called. Disabling kmemleak is an irreversible operation. 1621 */ 1622 static void kmemleak_disable(void) 1623 { 1624 /* atomically check whether it was already invoked */ 1625 if (atomic_cmpxchg(&kmemleak_error, 0, 1)) 1626 return; 1627 1628 /* stop any memory operation tracing */ 1629 atomic_set(&kmemleak_early_log, 0); 1630 atomic_set(&kmemleak_enabled, 0); 1631 1632 /* check whether it is too early for a kernel thread */ 1633 if (atomic_read(&kmemleak_initialized)) 1634 schedule_work(&cleanup_work); 1635 1636 pr_info("Kernel memory leak detector disabled\n"); 1637 } 1638 1639 /* 1640 * Allow boot-time kmemleak disabling (enabled by default). 1641 */ 1642 static int kmemleak_boot_config(char *str) 1643 { 1644 if (!str) 1645 return -EINVAL; 1646 if (strcmp(str, "off") == 0) 1647 kmemleak_disable(); 1648 else if (strcmp(str, "on") == 0) 1649 kmemleak_skip_disable = 1; 1650 else 1651 return -EINVAL; 1652 return 0; 1653 } 1654 early_param("kmemleak", kmemleak_boot_config); 1655 1656 /* 1657 * Kmemleak initialization. 1658 */ 1659 void __init kmemleak_init(void) 1660 { 1661 int i; 1662 unsigned long flags; 1663 1664 #ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF 1665 if (!kmemleak_skip_disable) { 1666 kmemleak_disable(); 1667 return; 1668 } 1669 #endif 1670 1671 jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE); 1672 jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000); 1673 1674 object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE); 1675 scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE); 1676 INIT_PRIO_TREE_ROOT(&object_tree_root); 1677 1678 /* the kernel is still in UP mode, so disabling the IRQs is enough */ 1679 local_irq_save(flags); 1680 if (!atomic_read(&kmemleak_error)) { 1681 atomic_set(&kmemleak_enabled, 1); 1682 atomic_set(&kmemleak_early_log, 0); 1683 } 1684 local_irq_restore(flags); 1685 1686 /* 1687 * This is the point where tracking allocations is safe. Automatic 1688 * scanning is started during the late initcall. Add the early logged 1689 * callbacks to the kmemleak infrastructure. 1690 */ 1691 for (i = 0; i < crt_early_log; i++) { 1692 struct early_log *log = &early_log[i]; 1693 1694 switch (log->op_type) { 1695 case KMEMLEAK_ALLOC: 1696 early_alloc(log); 1697 break; 1698 case KMEMLEAK_FREE: 1699 kmemleak_free(log->ptr); 1700 break; 1701 case KMEMLEAK_FREE_PART: 1702 kmemleak_free_part(log->ptr, log->size); 1703 break; 1704 case KMEMLEAK_NOT_LEAK: 1705 kmemleak_not_leak(log->ptr); 1706 break; 1707 case KMEMLEAK_IGNORE: 1708 kmemleak_ignore(log->ptr); 1709 break; 1710 case KMEMLEAK_SCAN_AREA: 1711 kmemleak_scan_area(log->ptr, log->size, GFP_KERNEL); 1712 break; 1713 case KMEMLEAK_NO_SCAN: 1714 kmemleak_no_scan(log->ptr); 1715 break; 1716 default: 1717 WARN_ON(1); 1718 } 1719 } 1720 } 1721 1722 /* 1723 * Late initialization function. 1724 */ 1725 static int __init kmemleak_late_init(void) 1726 { 1727 struct dentry *dentry; 1728 1729 atomic_set(&kmemleak_initialized, 1); 1730 1731 if (atomic_read(&kmemleak_error)) { 1732 /* 1733 * Some error occured and kmemleak was disabled. There is a 1734 * small chance that kmemleak_disable() was called immediately 1735 * after setting kmemleak_initialized and we may end up with 1736 * two clean-up threads but serialized by scan_mutex. 1737 */ 1738 schedule_work(&cleanup_work); 1739 return -ENOMEM; 1740 } 1741 1742 dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL, 1743 &kmemleak_fops); 1744 if (!dentry) 1745 pr_warning("Failed to create the debugfs kmemleak file\n"); 1746 mutex_lock(&scan_mutex); 1747 start_scan_thread(); 1748 mutex_unlock(&scan_mutex); 1749 1750 pr_info("Kernel memory leak detector initialized\n"); 1751 1752 return 0; 1753 } 1754 late_initcall(kmemleak_late_init); 1755