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 red black 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/export.h> 73 #include <linux/kthread.h> 74 #include <linux/rbtree.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 <linux/atomic.h> 100 101 #include <linux/kmemcheck.h> 102 #include <linux/kmemleak.h> 103 #include <linux/memory_hotplug.h> 104 105 /* 106 * Kmemleak configuration and common defines. 107 */ 108 #define MAX_TRACE 16 /* stack trace length */ 109 #define MSECS_MIN_AGE 5000 /* minimum object age for reporting */ 110 #define SECS_FIRST_SCAN 60 /* delay before the first scan */ 111 #define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */ 112 #define MAX_SCAN_SIZE 4096 /* maximum size of a scanned block */ 113 114 #define BYTES_PER_POINTER sizeof(void *) 115 116 /* GFP bitmask for kmemleak internal allocations */ 117 #define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \ 118 __GFP_NORETRY | __GFP_NOMEMALLOC | \ 119 __GFP_NOWARN) 120 121 /* scanning area inside a memory block */ 122 struct kmemleak_scan_area { 123 struct hlist_node node; 124 unsigned long start; 125 size_t size; 126 }; 127 128 #define KMEMLEAK_GREY 0 129 #define KMEMLEAK_BLACK -1 130 131 /* 132 * Structure holding the metadata for each allocated memory block. 133 * Modifications to such objects should be made while holding the 134 * object->lock. Insertions or deletions from object_list, gray_list or 135 * rb_node are already protected by the corresponding locks or mutex (see 136 * the notes on locking above). These objects are reference-counted 137 * (use_count) and freed using the RCU mechanism. 138 */ 139 struct kmemleak_object { 140 spinlock_t lock; 141 unsigned long flags; /* object status flags */ 142 struct list_head object_list; 143 struct list_head gray_list; 144 struct rb_node rb_node; 145 struct rcu_head rcu; /* object_list lockless traversal */ 146 /* object usage count; object freed when use_count == 0 */ 147 atomic_t use_count; 148 unsigned long pointer; 149 size_t size; 150 /* minimum number of a pointers found before it is considered leak */ 151 int min_count; 152 /* the total number of pointers found pointing to this object */ 153 int count; 154 /* checksum for detecting modified objects */ 155 u32 checksum; 156 /* memory ranges to be scanned inside an object (empty for all) */ 157 struct hlist_head area_list; 158 unsigned long trace[MAX_TRACE]; 159 unsigned int trace_len; 160 unsigned long jiffies; /* creation timestamp */ 161 pid_t pid; /* pid of the current task */ 162 char comm[TASK_COMM_LEN]; /* executable name */ 163 }; 164 165 /* flag representing the memory block allocation status */ 166 #define OBJECT_ALLOCATED (1 << 0) 167 /* flag set after the first reporting of an unreference object */ 168 #define OBJECT_REPORTED (1 << 1) 169 /* flag set to not scan the object */ 170 #define OBJECT_NO_SCAN (1 << 2) 171 172 /* number of bytes to print per line; must be 16 or 32 */ 173 #define HEX_ROW_SIZE 16 174 /* number of bytes to print at a time (1, 2, 4, 8) */ 175 #define HEX_GROUP_SIZE 1 176 /* include ASCII after the hex output */ 177 #define HEX_ASCII 1 178 /* max number of lines to be printed */ 179 #define HEX_MAX_LINES 2 180 181 /* the list of all allocated objects */ 182 static LIST_HEAD(object_list); 183 /* the list of gray-colored objects (see color_gray comment below) */ 184 static LIST_HEAD(gray_list); 185 /* search tree for object boundaries */ 186 static struct rb_root object_tree_root = RB_ROOT; 187 /* rw_lock protecting the access to object_list and object_tree_root */ 188 static DEFINE_RWLOCK(kmemleak_lock); 189 190 /* allocation caches for kmemleak internal data */ 191 static struct kmem_cache *object_cache; 192 static struct kmem_cache *scan_area_cache; 193 194 /* set if tracing memory operations is enabled */ 195 static int kmemleak_enabled; 196 /* set in the late_initcall if there were no errors */ 197 static int kmemleak_initialized; 198 /* enables or disables early logging of the memory operations */ 199 static int kmemleak_early_log = 1; 200 /* set if a kmemleak warning was issued */ 201 static int kmemleak_warning; 202 /* set if a fatal kmemleak error has occurred */ 203 static int kmemleak_error; 204 205 /* minimum and maximum address that may be valid pointers */ 206 static unsigned long min_addr = ULONG_MAX; 207 static unsigned long max_addr; 208 209 static struct task_struct *scan_thread; 210 /* used to avoid reporting of recently allocated objects */ 211 static unsigned long jiffies_min_age; 212 static unsigned long jiffies_last_scan; 213 /* delay between automatic memory scannings */ 214 static signed long jiffies_scan_wait; 215 /* enables or disables the task stacks scanning */ 216 static int kmemleak_stack_scan = 1; 217 /* protects the memory scanning, parameters and debug/kmemleak file access */ 218 static DEFINE_MUTEX(scan_mutex); 219 /* setting kmemleak=on, will set this var, skipping the disable */ 220 static int kmemleak_skip_disable; 221 /* If there are leaks that can be reported */ 222 static bool kmemleak_found_leaks; 223 224 /* 225 * Early object allocation/freeing logging. Kmemleak is initialized after the 226 * kernel allocator. However, both the kernel allocator and kmemleak may 227 * allocate memory blocks which need to be tracked. Kmemleak defines an 228 * arbitrary buffer to hold the allocation/freeing information before it is 229 * fully initialized. 230 */ 231 232 /* kmemleak operation type for early logging */ 233 enum { 234 KMEMLEAK_ALLOC, 235 KMEMLEAK_ALLOC_PERCPU, 236 KMEMLEAK_FREE, 237 KMEMLEAK_FREE_PART, 238 KMEMLEAK_FREE_PERCPU, 239 KMEMLEAK_NOT_LEAK, 240 KMEMLEAK_IGNORE, 241 KMEMLEAK_SCAN_AREA, 242 KMEMLEAK_NO_SCAN 243 }; 244 245 /* 246 * Structure holding the information passed to kmemleak callbacks during the 247 * early logging. 248 */ 249 struct early_log { 250 int op_type; /* kmemleak operation type */ 251 const void *ptr; /* allocated/freed memory block */ 252 size_t size; /* memory block size */ 253 int min_count; /* minimum reference count */ 254 unsigned long trace[MAX_TRACE]; /* stack trace */ 255 unsigned int trace_len; /* stack trace length */ 256 }; 257 258 /* early logging buffer and current position */ 259 static struct early_log 260 early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata; 261 static int crt_early_log __initdata; 262 263 static void kmemleak_disable(void); 264 265 /* 266 * Print a warning and dump the stack trace. 267 */ 268 #define kmemleak_warn(x...) do { \ 269 pr_warning(x); \ 270 dump_stack(); \ 271 kmemleak_warning = 1; \ 272 } while (0) 273 274 /* 275 * Macro invoked when a serious kmemleak condition occurred and cannot be 276 * recovered from. Kmemleak will be disabled and further allocation/freeing 277 * tracing no longer available. 278 */ 279 #define kmemleak_stop(x...) do { \ 280 kmemleak_warn(x); \ 281 kmemleak_disable(); \ 282 } while (0) 283 284 /* 285 * Printing of the objects hex dump to the seq file. The number of lines to be 286 * printed is limited to HEX_MAX_LINES to prevent seq file spamming. The 287 * actual number of printed bytes depends on HEX_ROW_SIZE. It must be called 288 * with the object->lock held. 289 */ 290 static void hex_dump_object(struct seq_file *seq, 291 struct kmemleak_object *object) 292 { 293 const u8 *ptr = (const u8 *)object->pointer; 294 int i, len, remaining; 295 unsigned char linebuf[HEX_ROW_SIZE * 5]; 296 297 /* limit the number of lines to HEX_MAX_LINES */ 298 remaining = len = 299 min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE)); 300 301 seq_printf(seq, " hex dump (first %d bytes):\n", len); 302 for (i = 0; i < len; i += HEX_ROW_SIZE) { 303 int linelen = min(remaining, HEX_ROW_SIZE); 304 305 remaining -= HEX_ROW_SIZE; 306 hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE, 307 HEX_GROUP_SIZE, linebuf, sizeof(linebuf), 308 HEX_ASCII); 309 seq_printf(seq, " %s\n", linebuf); 310 } 311 } 312 313 /* 314 * Object colors, encoded with count and min_count: 315 * - white - orphan object, not enough references to it (count < min_count) 316 * - gray - not orphan, not marked as false positive (min_count == 0) or 317 * sufficient references to it (count >= min_count) 318 * - black - ignore, it doesn't contain references (e.g. text section) 319 * (min_count == -1). No function defined for this color. 320 * Newly created objects don't have any color assigned (object->count == -1) 321 * before the next memory scan when they become white. 322 */ 323 static bool color_white(const struct kmemleak_object *object) 324 { 325 return object->count != KMEMLEAK_BLACK && 326 object->count < object->min_count; 327 } 328 329 static bool color_gray(const struct kmemleak_object *object) 330 { 331 return object->min_count != KMEMLEAK_BLACK && 332 object->count >= object->min_count; 333 } 334 335 /* 336 * Objects are considered unreferenced only if their color is white, they have 337 * not be deleted and have a minimum age to avoid false positives caused by 338 * pointers temporarily stored in CPU registers. 339 */ 340 static bool unreferenced_object(struct kmemleak_object *object) 341 { 342 return (color_white(object) && object->flags & OBJECT_ALLOCATED) && 343 time_before_eq(object->jiffies + jiffies_min_age, 344 jiffies_last_scan); 345 } 346 347 /* 348 * Printing of the unreferenced objects information to the seq file. The 349 * print_unreferenced function must be called with the object->lock held. 350 */ 351 static void print_unreferenced(struct seq_file *seq, 352 struct kmemleak_object *object) 353 { 354 int i; 355 unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies); 356 357 seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n", 358 object->pointer, object->size); 359 seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n", 360 object->comm, object->pid, object->jiffies, 361 msecs_age / 1000, msecs_age % 1000); 362 hex_dump_object(seq, object); 363 seq_printf(seq, " backtrace:\n"); 364 365 for (i = 0; i < object->trace_len; i++) { 366 void *ptr = (void *)object->trace[i]; 367 seq_printf(seq, " [<%p>] %pS\n", ptr, ptr); 368 } 369 } 370 371 /* 372 * Print the kmemleak_object information. This function is used mainly for 373 * debugging special cases when kmemleak operations. It must be called with 374 * the object->lock held. 375 */ 376 static void dump_object_info(struct kmemleak_object *object) 377 { 378 struct stack_trace trace; 379 380 trace.nr_entries = object->trace_len; 381 trace.entries = object->trace; 382 383 pr_notice("Object 0x%08lx (size %zu):\n", 384 object->pointer, object->size); 385 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n", 386 object->comm, object->pid, object->jiffies); 387 pr_notice(" min_count = %d\n", object->min_count); 388 pr_notice(" count = %d\n", object->count); 389 pr_notice(" flags = 0x%lx\n", object->flags); 390 pr_notice(" checksum = %d\n", object->checksum); 391 pr_notice(" backtrace:\n"); 392 print_stack_trace(&trace, 4); 393 } 394 395 /* 396 * Look-up a memory block metadata (kmemleak_object) in the object search 397 * tree based on a pointer value. If alias is 0, only values pointing to the 398 * beginning of the memory block are allowed. The kmemleak_lock must be held 399 * when calling this function. 400 */ 401 static struct kmemleak_object *lookup_object(unsigned long ptr, int alias) 402 { 403 struct rb_node *rb = object_tree_root.rb_node; 404 405 while (rb) { 406 struct kmemleak_object *object = 407 rb_entry(rb, struct kmemleak_object, rb_node); 408 if (ptr < object->pointer) 409 rb = object->rb_node.rb_left; 410 else if (object->pointer + object->size <= ptr) 411 rb = object->rb_node.rb_right; 412 else if (object->pointer == ptr || alias) 413 return object; 414 else { 415 kmemleak_warn("Found object by alias at 0x%08lx\n", 416 ptr); 417 dump_object_info(object); 418 break; 419 } 420 } 421 return NULL; 422 } 423 424 /* 425 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note 426 * that once an object's use_count reached 0, the RCU freeing was already 427 * registered and the object should no longer be used. This function must be 428 * called under the protection of rcu_read_lock(). 429 */ 430 static int get_object(struct kmemleak_object *object) 431 { 432 return atomic_inc_not_zero(&object->use_count); 433 } 434 435 /* 436 * RCU callback to free a kmemleak_object. 437 */ 438 static void free_object_rcu(struct rcu_head *rcu) 439 { 440 struct hlist_node *tmp; 441 struct kmemleak_scan_area *area; 442 struct kmemleak_object *object = 443 container_of(rcu, struct kmemleak_object, rcu); 444 445 /* 446 * Once use_count is 0 (guaranteed by put_object), there is no other 447 * code accessing this object, hence no need for locking. 448 */ 449 hlist_for_each_entry_safe(area, tmp, &object->area_list, node) { 450 hlist_del(&area->node); 451 kmem_cache_free(scan_area_cache, area); 452 } 453 kmem_cache_free(object_cache, object); 454 } 455 456 /* 457 * Decrement the object use_count. Once the count is 0, free the object using 458 * an RCU callback. Since put_object() may be called via the kmemleak_free() -> 459 * delete_object() path, the delayed RCU freeing ensures that there is no 460 * recursive call to the kernel allocator. Lock-less RCU object_list traversal 461 * is also possible. 462 */ 463 static void put_object(struct kmemleak_object *object) 464 { 465 if (!atomic_dec_and_test(&object->use_count)) 466 return; 467 468 /* should only get here after delete_object was called */ 469 WARN_ON(object->flags & OBJECT_ALLOCATED); 470 471 call_rcu(&object->rcu, free_object_rcu); 472 } 473 474 /* 475 * Look up an object in the object search tree and increase its use_count. 476 */ 477 static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias) 478 { 479 unsigned long flags; 480 struct kmemleak_object *object = NULL; 481 482 rcu_read_lock(); 483 read_lock_irqsave(&kmemleak_lock, flags); 484 if (ptr >= min_addr && ptr < max_addr) 485 object = lookup_object(ptr, alias); 486 read_unlock_irqrestore(&kmemleak_lock, flags); 487 488 /* check whether the object is still available */ 489 if (object && !get_object(object)) 490 object = NULL; 491 rcu_read_unlock(); 492 493 return object; 494 } 495 496 /* 497 * Save stack trace to the given array of MAX_TRACE size. 498 */ 499 static int __save_stack_trace(unsigned long *trace) 500 { 501 struct stack_trace stack_trace; 502 503 stack_trace.max_entries = MAX_TRACE; 504 stack_trace.nr_entries = 0; 505 stack_trace.entries = trace; 506 stack_trace.skip = 2; 507 save_stack_trace(&stack_trace); 508 509 return stack_trace.nr_entries; 510 } 511 512 /* 513 * Create the metadata (struct kmemleak_object) corresponding to an allocated 514 * memory block and add it to the object_list and object_tree_root. 515 */ 516 static struct kmemleak_object *create_object(unsigned long ptr, size_t size, 517 int min_count, gfp_t gfp) 518 { 519 unsigned long flags; 520 struct kmemleak_object *object, *parent; 521 struct rb_node **link, *rb_parent; 522 523 object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp)); 524 if (!object) { 525 pr_warning("Cannot allocate a kmemleak_object structure\n"); 526 kmemleak_disable(); 527 return NULL; 528 } 529 530 INIT_LIST_HEAD(&object->object_list); 531 INIT_LIST_HEAD(&object->gray_list); 532 INIT_HLIST_HEAD(&object->area_list); 533 spin_lock_init(&object->lock); 534 atomic_set(&object->use_count, 1); 535 object->flags = OBJECT_ALLOCATED; 536 object->pointer = ptr; 537 object->size = size; 538 object->min_count = min_count; 539 object->count = 0; /* white color initially */ 540 object->jiffies = jiffies; 541 object->checksum = 0; 542 543 /* task information */ 544 if (in_irq()) { 545 object->pid = 0; 546 strncpy(object->comm, "hardirq", sizeof(object->comm)); 547 } else if (in_softirq()) { 548 object->pid = 0; 549 strncpy(object->comm, "softirq", sizeof(object->comm)); 550 } else { 551 object->pid = current->pid; 552 /* 553 * There is a small chance of a race with set_task_comm(), 554 * however using get_task_comm() here may cause locking 555 * dependency issues with current->alloc_lock. In the worst 556 * case, the command line is not correct. 557 */ 558 strncpy(object->comm, current->comm, sizeof(object->comm)); 559 } 560 561 /* kernel backtrace */ 562 object->trace_len = __save_stack_trace(object->trace); 563 564 write_lock_irqsave(&kmemleak_lock, flags); 565 566 min_addr = min(min_addr, ptr); 567 max_addr = max(max_addr, ptr + size); 568 link = &object_tree_root.rb_node; 569 rb_parent = NULL; 570 while (*link) { 571 rb_parent = *link; 572 parent = rb_entry(rb_parent, struct kmemleak_object, rb_node); 573 if (ptr + size <= parent->pointer) 574 link = &parent->rb_node.rb_left; 575 else if (parent->pointer + parent->size <= ptr) 576 link = &parent->rb_node.rb_right; 577 else { 578 kmemleak_stop("Cannot insert 0x%lx into the object " 579 "search tree (overlaps existing)\n", 580 ptr); 581 kmem_cache_free(object_cache, object); 582 object = parent; 583 spin_lock(&object->lock); 584 dump_object_info(object); 585 spin_unlock(&object->lock); 586 goto out; 587 } 588 } 589 rb_link_node(&object->rb_node, rb_parent, link); 590 rb_insert_color(&object->rb_node, &object_tree_root); 591 592 list_add_tail_rcu(&object->object_list, &object_list); 593 out: 594 write_unlock_irqrestore(&kmemleak_lock, flags); 595 return object; 596 } 597 598 /* 599 * Remove the metadata (struct kmemleak_object) for a memory block from the 600 * object_list and object_tree_root and decrement its use_count. 601 */ 602 static void __delete_object(struct kmemleak_object *object) 603 { 604 unsigned long flags; 605 606 write_lock_irqsave(&kmemleak_lock, flags); 607 rb_erase(&object->rb_node, &object_tree_root); 608 list_del_rcu(&object->object_list); 609 write_unlock_irqrestore(&kmemleak_lock, flags); 610 611 WARN_ON(!(object->flags & OBJECT_ALLOCATED)); 612 WARN_ON(atomic_read(&object->use_count) < 2); 613 614 /* 615 * Locking here also ensures that the corresponding memory block 616 * cannot be freed when it is being scanned. 617 */ 618 spin_lock_irqsave(&object->lock, flags); 619 object->flags &= ~OBJECT_ALLOCATED; 620 spin_unlock_irqrestore(&object->lock, flags); 621 put_object(object); 622 } 623 624 /* 625 * Look up the metadata (struct kmemleak_object) corresponding to ptr and 626 * delete it. 627 */ 628 static void delete_object_full(unsigned long ptr) 629 { 630 struct kmemleak_object *object; 631 632 object = find_and_get_object(ptr, 0); 633 if (!object) { 634 #ifdef DEBUG 635 kmemleak_warn("Freeing unknown object at 0x%08lx\n", 636 ptr); 637 #endif 638 return; 639 } 640 __delete_object(object); 641 put_object(object); 642 } 643 644 /* 645 * Look up the metadata (struct kmemleak_object) corresponding to ptr and 646 * delete it. If the memory block is partially freed, the function may create 647 * additional metadata for the remaining parts of the block. 648 */ 649 static void delete_object_part(unsigned long ptr, size_t size) 650 { 651 struct kmemleak_object *object; 652 unsigned long start, end; 653 654 object = find_and_get_object(ptr, 1); 655 if (!object) { 656 #ifdef DEBUG 657 kmemleak_warn("Partially freeing unknown object at 0x%08lx " 658 "(size %zu)\n", ptr, size); 659 #endif 660 return; 661 } 662 __delete_object(object); 663 664 /* 665 * Create one or two objects that may result from the memory block 666 * split. Note that partial freeing is only done by free_bootmem() and 667 * this happens before kmemleak_init() is called. The path below is 668 * only executed during early log recording in kmemleak_init(), so 669 * GFP_KERNEL is enough. 670 */ 671 start = object->pointer; 672 end = object->pointer + object->size; 673 if (ptr > start) 674 create_object(start, ptr - start, object->min_count, 675 GFP_KERNEL); 676 if (ptr + size < end) 677 create_object(ptr + size, end - ptr - size, object->min_count, 678 GFP_KERNEL); 679 680 put_object(object); 681 } 682 683 static void __paint_it(struct kmemleak_object *object, int color) 684 { 685 object->min_count = color; 686 if (color == KMEMLEAK_BLACK) 687 object->flags |= OBJECT_NO_SCAN; 688 } 689 690 static void paint_it(struct kmemleak_object *object, int color) 691 { 692 unsigned long flags; 693 694 spin_lock_irqsave(&object->lock, flags); 695 __paint_it(object, color); 696 spin_unlock_irqrestore(&object->lock, flags); 697 } 698 699 static void paint_ptr(unsigned long ptr, int color) 700 { 701 struct kmemleak_object *object; 702 703 object = find_and_get_object(ptr, 0); 704 if (!object) { 705 kmemleak_warn("Trying to color unknown object " 706 "at 0x%08lx as %s\n", ptr, 707 (color == KMEMLEAK_GREY) ? "Grey" : 708 (color == KMEMLEAK_BLACK) ? "Black" : "Unknown"); 709 return; 710 } 711 paint_it(object, color); 712 put_object(object); 713 } 714 715 /* 716 * Mark an object permanently as gray-colored so that it can no longer be 717 * reported as a leak. This is used in general to mark a false positive. 718 */ 719 static void make_gray_object(unsigned long ptr) 720 { 721 paint_ptr(ptr, KMEMLEAK_GREY); 722 } 723 724 /* 725 * Mark the object as black-colored so that it is ignored from scans and 726 * reporting. 727 */ 728 static void make_black_object(unsigned long ptr) 729 { 730 paint_ptr(ptr, KMEMLEAK_BLACK); 731 } 732 733 /* 734 * Add a scanning area to the object. If at least one such area is added, 735 * kmemleak will only scan these ranges rather than the whole memory block. 736 */ 737 static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp) 738 { 739 unsigned long flags; 740 struct kmemleak_object *object; 741 struct kmemleak_scan_area *area; 742 743 object = find_and_get_object(ptr, 1); 744 if (!object) { 745 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n", 746 ptr); 747 return; 748 } 749 750 area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp)); 751 if (!area) { 752 pr_warning("Cannot allocate a scan area\n"); 753 goto out; 754 } 755 756 spin_lock_irqsave(&object->lock, flags); 757 if (size == SIZE_MAX) { 758 size = object->pointer + object->size - ptr; 759 } else if (ptr + size > object->pointer + object->size) { 760 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr); 761 dump_object_info(object); 762 kmem_cache_free(scan_area_cache, area); 763 goto out_unlock; 764 } 765 766 INIT_HLIST_NODE(&area->node); 767 area->start = ptr; 768 area->size = size; 769 770 hlist_add_head(&area->node, &object->area_list); 771 out_unlock: 772 spin_unlock_irqrestore(&object->lock, flags); 773 out: 774 put_object(object); 775 } 776 777 /* 778 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give 779 * pointer. Such object will not be scanned by kmemleak but references to it 780 * are searched. 781 */ 782 static void object_no_scan(unsigned long ptr) 783 { 784 unsigned long flags; 785 struct kmemleak_object *object; 786 787 object = find_and_get_object(ptr, 0); 788 if (!object) { 789 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr); 790 return; 791 } 792 793 spin_lock_irqsave(&object->lock, flags); 794 object->flags |= OBJECT_NO_SCAN; 795 spin_unlock_irqrestore(&object->lock, flags); 796 put_object(object); 797 } 798 799 /* 800 * Log an early kmemleak_* call to the early_log buffer. These calls will be 801 * processed later once kmemleak is fully initialized. 802 */ 803 static void __init log_early(int op_type, const void *ptr, size_t size, 804 int min_count) 805 { 806 unsigned long flags; 807 struct early_log *log; 808 809 if (kmemleak_error) { 810 /* kmemleak stopped recording, just count the requests */ 811 crt_early_log++; 812 return; 813 } 814 815 if (crt_early_log >= ARRAY_SIZE(early_log)) { 816 kmemleak_disable(); 817 return; 818 } 819 820 /* 821 * There is no need for locking since the kernel is still in UP mode 822 * at this stage. Disabling the IRQs is enough. 823 */ 824 local_irq_save(flags); 825 log = &early_log[crt_early_log]; 826 log->op_type = op_type; 827 log->ptr = ptr; 828 log->size = size; 829 log->min_count = min_count; 830 log->trace_len = __save_stack_trace(log->trace); 831 crt_early_log++; 832 local_irq_restore(flags); 833 } 834 835 /* 836 * Log an early allocated block and populate the stack trace. 837 */ 838 static void early_alloc(struct early_log *log) 839 { 840 struct kmemleak_object *object; 841 unsigned long flags; 842 int i; 843 844 if (!kmemleak_enabled || !log->ptr || IS_ERR(log->ptr)) 845 return; 846 847 /* 848 * RCU locking needed to ensure object is not freed via put_object(). 849 */ 850 rcu_read_lock(); 851 object = create_object((unsigned long)log->ptr, log->size, 852 log->min_count, GFP_ATOMIC); 853 if (!object) 854 goto out; 855 spin_lock_irqsave(&object->lock, flags); 856 for (i = 0; i < log->trace_len; i++) 857 object->trace[i] = log->trace[i]; 858 object->trace_len = log->trace_len; 859 spin_unlock_irqrestore(&object->lock, flags); 860 out: 861 rcu_read_unlock(); 862 } 863 864 /* 865 * Log an early allocated block and populate the stack trace. 866 */ 867 static void early_alloc_percpu(struct early_log *log) 868 { 869 unsigned int cpu; 870 const void __percpu *ptr = log->ptr; 871 872 for_each_possible_cpu(cpu) { 873 log->ptr = per_cpu_ptr(ptr, cpu); 874 early_alloc(log); 875 } 876 } 877 878 /** 879 * kmemleak_alloc - register a newly allocated object 880 * @ptr: pointer to beginning of the object 881 * @size: size of the object 882 * @min_count: minimum number of references to this object. If during memory 883 * scanning a number of references less than @min_count is found, 884 * the object is reported as a memory leak. If @min_count is 0, 885 * the object is never reported as a leak. If @min_count is -1, 886 * the object is ignored (not scanned and not reported as a leak) 887 * @gfp: kmalloc() flags used for kmemleak internal memory allocations 888 * 889 * This function is called from the kernel allocators when a new object 890 * (memory block) is allocated (kmem_cache_alloc, kmalloc, vmalloc etc.). 891 */ 892 void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count, 893 gfp_t gfp) 894 { 895 pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count); 896 897 if (kmemleak_enabled && ptr && !IS_ERR(ptr)) 898 create_object((unsigned long)ptr, size, min_count, gfp); 899 else if (kmemleak_early_log) 900 log_early(KMEMLEAK_ALLOC, ptr, size, min_count); 901 } 902 EXPORT_SYMBOL_GPL(kmemleak_alloc); 903 904 /** 905 * kmemleak_alloc_percpu - register a newly allocated __percpu object 906 * @ptr: __percpu pointer to beginning of the object 907 * @size: size of the object 908 * 909 * This function is called from the kernel percpu allocator when a new object 910 * (memory block) is allocated (alloc_percpu). It assumes GFP_KERNEL 911 * allocation. 912 */ 913 void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size) 914 { 915 unsigned int cpu; 916 917 pr_debug("%s(0x%p, %zu)\n", __func__, ptr, size); 918 919 /* 920 * Percpu allocations are only scanned and not reported as leaks 921 * (min_count is set to 0). 922 */ 923 if (kmemleak_enabled && ptr && !IS_ERR(ptr)) 924 for_each_possible_cpu(cpu) 925 create_object((unsigned long)per_cpu_ptr(ptr, cpu), 926 size, 0, GFP_KERNEL); 927 else if (kmemleak_early_log) 928 log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0); 929 } 930 EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu); 931 932 /** 933 * kmemleak_free - unregister a previously registered object 934 * @ptr: pointer to beginning of the object 935 * 936 * This function is called from the kernel allocators when an object (memory 937 * block) is freed (kmem_cache_free, kfree, vfree etc.). 938 */ 939 void __ref kmemleak_free(const void *ptr) 940 { 941 pr_debug("%s(0x%p)\n", __func__, ptr); 942 943 if (kmemleak_enabled && ptr && !IS_ERR(ptr)) 944 delete_object_full((unsigned long)ptr); 945 else if (kmemleak_early_log) 946 log_early(KMEMLEAK_FREE, ptr, 0, 0); 947 } 948 EXPORT_SYMBOL_GPL(kmemleak_free); 949 950 /** 951 * kmemleak_free_part - partially unregister a previously registered object 952 * @ptr: pointer to the beginning or inside the object. This also 953 * represents the start of the range to be freed 954 * @size: size to be unregistered 955 * 956 * This function is called when only a part of a memory block is freed 957 * (usually from the bootmem allocator). 958 */ 959 void __ref kmemleak_free_part(const void *ptr, size_t size) 960 { 961 pr_debug("%s(0x%p)\n", __func__, ptr); 962 963 if (kmemleak_enabled && ptr && !IS_ERR(ptr)) 964 delete_object_part((unsigned long)ptr, size); 965 else if (kmemleak_early_log) 966 log_early(KMEMLEAK_FREE_PART, ptr, size, 0); 967 } 968 EXPORT_SYMBOL_GPL(kmemleak_free_part); 969 970 /** 971 * kmemleak_free_percpu - unregister a previously registered __percpu object 972 * @ptr: __percpu pointer to beginning of the object 973 * 974 * This function is called from the kernel percpu allocator when an object 975 * (memory block) is freed (free_percpu). 976 */ 977 void __ref kmemleak_free_percpu(const void __percpu *ptr) 978 { 979 unsigned int cpu; 980 981 pr_debug("%s(0x%p)\n", __func__, ptr); 982 983 if (kmemleak_enabled && ptr && !IS_ERR(ptr)) 984 for_each_possible_cpu(cpu) 985 delete_object_full((unsigned long)per_cpu_ptr(ptr, 986 cpu)); 987 else if (kmemleak_early_log) 988 log_early(KMEMLEAK_FREE_PERCPU, ptr, 0, 0); 989 } 990 EXPORT_SYMBOL_GPL(kmemleak_free_percpu); 991 992 /** 993 * kmemleak_not_leak - mark an allocated object as false positive 994 * @ptr: pointer to beginning of the object 995 * 996 * Calling this function on an object will cause the memory block to no longer 997 * be reported as leak and always be scanned. 998 */ 999 void __ref kmemleak_not_leak(const void *ptr) 1000 { 1001 pr_debug("%s(0x%p)\n", __func__, ptr); 1002 1003 if (kmemleak_enabled && ptr && !IS_ERR(ptr)) 1004 make_gray_object((unsigned long)ptr); 1005 else if (kmemleak_early_log) 1006 log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0); 1007 } 1008 EXPORT_SYMBOL(kmemleak_not_leak); 1009 1010 /** 1011 * kmemleak_ignore - ignore an allocated object 1012 * @ptr: pointer to beginning of the object 1013 * 1014 * Calling this function on an object will cause the memory block to be 1015 * ignored (not scanned and not reported as a leak). This is usually done when 1016 * it is known that the corresponding block is not a leak and does not contain 1017 * any references to other allocated memory blocks. 1018 */ 1019 void __ref kmemleak_ignore(const void *ptr) 1020 { 1021 pr_debug("%s(0x%p)\n", __func__, ptr); 1022 1023 if (kmemleak_enabled && ptr && !IS_ERR(ptr)) 1024 make_black_object((unsigned long)ptr); 1025 else if (kmemleak_early_log) 1026 log_early(KMEMLEAK_IGNORE, ptr, 0, 0); 1027 } 1028 EXPORT_SYMBOL(kmemleak_ignore); 1029 1030 /** 1031 * kmemleak_scan_area - limit the range to be scanned in an allocated object 1032 * @ptr: pointer to beginning or inside the object. This also 1033 * represents the start of the scan area 1034 * @size: size of the scan area 1035 * @gfp: kmalloc() flags used for kmemleak internal memory allocations 1036 * 1037 * This function is used when it is known that only certain parts of an object 1038 * contain references to other objects. Kmemleak will only scan these areas 1039 * reducing the number false negatives. 1040 */ 1041 void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp) 1042 { 1043 pr_debug("%s(0x%p)\n", __func__, ptr); 1044 1045 if (kmemleak_enabled && ptr && size && !IS_ERR(ptr)) 1046 add_scan_area((unsigned long)ptr, size, gfp); 1047 else if (kmemleak_early_log) 1048 log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0); 1049 } 1050 EXPORT_SYMBOL(kmemleak_scan_area); 1051 1052 /** 1053 * kmemleak_no_scan - do not scan an allocated object 1054 * @ptr: pointer to beginning of the object 1055 * 1056 * This function notifies kmemleak not to scan the given memory block. Useful 1057 * in situations where it is known that the given object does not contain any 1058 * references to other objects. Kmemleak will not scan such objects reducing 1059 * the number of false negatives. 1060 */ 1061 void __ref kmemleak_no_scan(const void *ptr) 1062 { 1063 pr_debug("%s(0x%p)\n", __func__, ptr); 1064 1065 if (kmemleak_enabled && ptr && !IS_ERR(ptr)) 1066 object_no_scan((unsigned long)ptr); 1067 else if (kmemleak_early_log) 1068 log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0); 1069 } 1070 EXPORT_SYMBOL(kmemleak_no_scan); 1071 1072 /* 1073 * Update an object's checksum and return true if it was modified. 1074 */ 1075 static bool update_checksum(struct kmemleak_object *object) 1076 { 1077 u32 old_csum = object->checksum; 1078 1079 if (!kmemcheck_is_obj_initialized(object->pointer, object->size)) 1080 return false; 1081 1082 object->checksum = crc32(0, (void *)object->pointer, object->size); 1083 return object->checksum != old_csum; 1084 } 1085 1086 /* 1087 * Memory scanning is a long process and it needs to be interruptable. This 1088 * function checks whether such interrupt condition occurred. 1089 */ 1090 static int scan_should_stop(void) 1091 { 1092 if (!kmemleak_enabled) 1093 return 1; 1094 1095 /* 1096 * This function may be called from either process or kthread context, 1097 * hence the need to check for both stop conditions. 1098 */ 1099 if (current->mm) 1100 return signal_pending(current); 1101 else 1102 return kthread_should_stop(); 1103 1104 return 0; 1105 } 1106 1107 /* 1108 * Scan a memory block (exclusive range) for valid pointers and add those 1109 * found to the gray list. 1110 */ 1111 static void scan_block(void *_start, void *_end, 1112 struct kmemleak_object *scanned, int allow_resched) 1113 { 1114 unsigned long *ptr; 1115 unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER); 1116 unsigned long *end = _end - (BYTES_PER_POINTER - 1); 1117 1118 for (ptr = start; ptr < end; ptr++) { 1119 struct kmemleak_object *object; 1120 unsigned long flags; 1121 unsigned long pointer; 1122 1123 if (allow_resched) 1124 cond_resched(); 1125 if (scan_should_stop()) 1126 break; 1127 1128 /* don't scan uninitialized memory */ 1129 if (!kmemcheck_is_obj_initialized((unsigned long)ptr, 1130 BYTES_PER_POINTER)) 1131 continue; 1132 1133 pointer = *ptr; 1134 1135 object = find_and_get_object(pointer, 1); 1136 if (!object) 1137 continue; 1138 if (object == scanned) { 1139 /* self referenced, ignore */ 1140 put_object(object); 1141 continue; 1142 } 1143 1144 /* 1145 * Avoid the lockdep recursive warning on object->lock being 1146 * previously acquired in scan_object(). These locks are 1147 * enclosed by scan_mutex. 1148 */ 1149 spin_lock_irqsave_nested(&object->lock, flags, 1150 SINGLE_DEPTH_NESTING); 1151 if (!color_white(object)) { 1152 /* non-orphan, ignored or new */ 1153 spin_unlock_irqrestore(&object->lock, flags); 1154 put_object(object); 1155 continue; 1156 } 1157 1158 /* 1159 * Increase the object's reference count (number of pointers 1160 * to the memory block). If this count reaches the required 1161 * minimum, the object's color will become gray and it will be 1162 * added to the gray_list. 1163 */ 1164 object->count++; 1165 if (color_gray(object)) { 1166 list_add_tail(&object->gray_list, &gray_list); 1167 spin_unlock_irqrestore(&object->lock, flags); 1168 continue; 1169 } 1170 1171 spin_unlock_irqrestore(&object->lock, flags); 1172 put_object(object); 1173 } 1174 } 1175 1176 /* 1177 * Scan a memory block corresponding to a kmemleak_object. A condition is 1178 * that object->use_count >= 1. 1179 */ 1180 static void scan_object(struct kmemleak_object *object) 1181 { 1182 struct kmemleak_scan_area *area; 1183 unsigned long flags; 1184 1185 /* 1186 * Once the object->lock is acquired, the corresponding memory block 1187 * cannot be freed (the same lock is acquired in delete_object). 1188 */ 1189 spin_lock_irqsave(&object->lock, flags); 1190 if (object->flags & OBJECT_NO_SCAN) 1191 goto out; 1192 if (!(object->flags & OBJECT_ALLOCATED)) 1193 /* already freed object */ 1194 goto out; 1195 if (hlist_empty(&object->area_list)) { 1196 void *start = (void *)object->pointer; 1197 void *end = (void *)(object->pointer + object->size); 1198 1199 while (start < end && (object->flags & OBJECT_ALLOCATED) && 1200 !(object->flags & OBJECT_NO_SCAN)) { 1201 scan_block(start, min(start + MAX_SCAN_SIZE, end), 1202 object, 0); 1203 start += MAX_SCAN_SIZE; 1204 1205 spin_unlock_irqrestore(&object->lock, flags); 1206 cond_resched(); 1207 spin_lock_irqsave(&object->lock, flags); 1208 } 1209 } else 1210 hlist_for_each_entry(area, &object->area_list, node) 1211 scan_block((void *)area->start, 1212 (void *)(area->start + area->size), 1213 object, 0); 1214 out: 1215 spin_unlock_irqrestore(&object->lock, flags); 1216 } 1217 1218 /* 1219 * Scan the objects already referenced (gray objects). More objects will be 1220 * referenced and, if there are no memory leaks, all the objects are scanned. 1221 */ 1222 static void scan_gray_list(void) 1223 { 1224 struct kmemleak_object *object, *tmp; 1225 1226 /* 1227 * The list traversal is safe for both tail additions and removals 1228 * from inside the loop. The kmemleak objects cannot be freed from 1229 * outside the loop because their use_count was incremented. 1230 */ 1231 object = list_entry(gray_list.next, typeof(*object), gray_list); 1232 while (&object->gray_list != &gray_list) { 1233 cond_resched(); 1234 1235 /* may add new objects to the list */ 1236 if (!scan_should_stop()) 1237 scan_object(object); 1238 1239 tmp = list_entry(object->gray_list.next, typeof(*object), 1240 gray_list); 1241 1242 /* remove the object from the list and release it */ 1243 list_del(&object->gray_list); 1244 put_object(object); 1245 1246 object = tmp; 1247 } 1248 WARN_ON(!list_empty(&gray_list)); 1249 } 1250 1251 /* 1252 * Scan data sections and all the referenced memory blocks allocated via the 1253 * kernel's standard allocators. This function must be called with the 1254 * scan_mutex held. 1255 */ 1256 static void kmemleak_scan(void) 1257 { 1258 unsigned long flags; 1259 struct kmemleak_object *object; 1260 int i; 1261 int new_leaks = 0; 1262 1263 jiffies_last_scan = jiffies; 1264 1265 /* prepare the kmemleak_object's */ 1266 rcu_read_lock(); 1267 list_for_each_entry_rcu(object, &object_list, object_list) { 1268 spin_lock_irqsave(&object->lock, flags); 1269 #ifdef DEBUG 1270 /* 1271 * With a few exceptions there should be a maximum of 1272 * 1 reference to any object at this point. 1273 */ 1274 if (atomic_read(&object->use_count) > 1) { 1275 pr_debug("object->use_count = %d\n", 1276 atomic_read(&object->use_count)); 1277 dump_object_info(object); 1278 } 1279 #endif 1280 /* reset the reference count (whiten the object) */ 1281 object->count = 0; 1282 if (color_gray(object) && get_object(object)) 1283 list_add_tail(&object->gray_list, &gray_list); 1284 1285 spin_unlock_irqrestore(&object->lock, flags); 1286 } 1287 rcu_read_unlock(); 1288 1289 /* data/bss scanning */ 1290 scan_block(_sdata, _edata, NULL, 1); 1291 scan_block(__bss_start, __bss_stop, NULL, 1); 1292 1293 #ifdef CONFIG_SMP 1294 /* per-cpu sections scanning */ 1295 for_each_possible_cpu(i) 1296 scan_block(__per_cpu_start + per_cpu_offset(i), 1297 __per_cpu_end + per_cpu_offset(i), NULL, 1); 1298 #endif 1299 1300 /* 1301 * Struct page scanning for each node. 1302 */ 1303 lock_memory_hotplug(); 1304 for_each_online_node(i) { 1305 unsigned long start_pfn = node_start_pfn(i); 1306 unsigned long end_pfn = node_end_pfn(i); 1307 unsigned long pfn; 1308 1309 for (pfn = start_pfn; pfn < end_pfn; pfn++) { 1310 struct page *page; 1311 1312 if (!pfn_valid(pfn)) 1313 continue; 1314 page = pfn_to_page(pfn); 1315 /* only scan if page is in use */ 1316 if (page_count(page) == 0) 1317 continue; 1318 scan_block(page, page + 1, NULL, 1); 1319 } 1320 } 1321 unlock_memory_hotplug(); 1322 1323 /* 1324 * Scanning the task stacks (may introduce false negatives). 1325 */ 1326 if (kmemleak_stack_scan) { 1327 struct task_struct *p, *g; 1328 1329 read_lock(&tasklist_lock); 1330 do_each_thread(g, p) { 1331 scan_block(task_stack_page(p), task_stack_page(p) + 1332 THREAD_SIZE, NULL, 0); 1333 } while_each_thread(g, p); 1334 read_unlock(&tasklist_lock); 1335 } 1336 1337 /* 1338 * Scan the objects already referenced from the sections scanned 1339 * above. 1340 */ 1341 scan_gray_list(); 1342 1343 /* 1344 * Check for new or unreferenced objects modified since the previous 1345 * scan and color them gray until the next scan. 1346 */ 1347 rcu_read_lock(); 1348 list_for_each_entry_rcu(object, &object_list, object_list) { 1349 spin_lock_irqsave(&object->lock, flags); 1350 if (color_white(object) && (object->flags & OBJECT_ALLOCATED) 1351 && update_checksum(object) && get_object(object)) { 1352 /* color it gray temporarily */ 1353 object->count = object->min_count; 1354 list_add_tail(&object->gray_list, &gray_list); 1355 } 1356 spin_unlock_irqrestore(&object->lock, flags); 1357 } 1358 rcu_read_unlock(); 1359 1360 /* 1361 * Re-scan the gray list for modified unreferenced objects. 1362 */ 1363 scan_gray_list(); 1364 1365 /* 1366 * If scanning was stopped do not report any new unreferenced objects. 1367 */ 1368 if (scan_should_stop()) 1369 return; 1370 1371 /* 1372 * Scanning result reporting. 1373 */ 1374 rcu_read_lock(); 1375 list_for_each_entry_rcu(object, &object_list, object_list) { 1376 spin_lock_irqsave(&object->lock, flags); 1377 if (unreferenced_object(object) && 1378 !(object->flags & OBJECT_REPORTED)) { 1379 object->flags |= OBJECT_REPORTED; 1380 new_leaks++; 1381 } 1382 spin_unlock_irqrestore(&object->lock, flags); 1383 } 1384 rcu_read_unlock(); 1385 1386 if (new_leaks) { 1387 kmemleak_found_leaks = true; 1388 1389 pr_info("%d new suspected memory leaks (see " 1390 "/sys/kernel/debug/kmemleak)\n", new_leaks); 1391 } 1392 1393 } 1394 1395 /* 1396 * Thread function performing automatic memory scanning. Unreferenced objects 1397 * at the end of a memory scan are reported but only the first time. 1398 */ 1399 static int kmemleak_scan_thread(void *arg) 1400 { 1401 static int first_run = 1; 1402 1403 pr_info("Automatic memory scanning thread started\n"); 1404 set_user_nice(current, 10); 1405 1406 /* 1407 * Wait before the first scan to allow the system to fully initialize. 1408 */ 1409 if (first_run) { 1410 first_run = 0; 1411 ssleep(SECS_FIRST_SCAN); 1412 } 1413 1414 while (!kthread_should_stop()) { 1415 signed long timeout = jiffies_scan_wait; 1416 1417 mutex_lock(&scan_mutex); 1418 kmemleak_scan(); 1419 mutex_unlock(&scan_mutex); 1420 1421 /* wait before the next scan */ 1422 while (timeout && !kthread_should_stop()) 1423 timeout = schedule_timeout_interruptible(timeout); 1424 } 1425 1426 pr_info("Automatic memory scanning thread ended\n"); 1427 1428 return 0; 1429 } 1430 1431 /* 1432 * Start the automatic memory scanning thread. This function must be called 1433 * with the scan_mutex held. 1434 */ 1435 static void start_scan_thread(void) 1436 { 1437 if (scan_thread) 1438 return; 1439 scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak"); 1440 if (IS_ERR(scan_thread)) { 1441 pr_warning("Failed to create the scan thread\n"); 1442 scan_thread = NULL; 1443 } 1444 } 1445 1446 /* 1447 * Stop the automatic memory scanning thread. This function must be called 1448 * with the scan_mutex held. 1449 */ 1450 static void stop_scan_thread(void) 1451 { 1452 if (scan_thread) { 1453 kthread_stop(scan_thread); 1454 scan_thread = NULL; 1455 } 1456 } 1457 1458 /* 1459 * Iterate over the object_list and return the first valid object at or after 1460 * the required position with its use_count incremented. The function triggers 1461 * a memory scanning when the pos argument points to the first position. 1462 */ 1463 static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos) 1464 { 1465 struct kmemleak_object *object; 1466 loff_t n = *pos; 1467 int err; 1468 1469 err = mutex_lock_interruptible(&scan_mutex); 1470 if (err < 0) 1471 return ERR_PTR(err); 1472 1473 rcu_read_lock(); 1474 list_for_each_entry_rcu(object, &object_list, object_list) { 1475 if (n-- > 0) 1476 continue; 1477 if (get_object(object)) 1478 goto out; 1479 } 1480 object = NULL; 1481 out: 1482 return object; 1483 } 1484 1485 /* 1486 * Return the next object in the object_list. The function decrements the 1487 * use_count of the previous object and increases that of the next one. 1488 */ 1489 static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos) 1490 { 1491 struct kmemleak_object *prev_obj = v; 1492 struct kmemleak_object *next_obj = NULL; 1493 struct kmemleak_object *obj = prev_obj; 1494 1495 ++(*pos); 1496 1497 list_for_each_entry_continue_rcu(obj, &object_list, object_list) { 1498 if (get_object(obj)) { 1499 next_obj = obj; 1500 break; 1501 } 1502 } 1503 1504 put_object(prev_obj); 1505 return next_obj; 1506 } 1507 1508 /* 1509 * Decrement the use_count of the last object required, if any. 1510 */ 1511 static void kmemleak_seq_stop(struct seq_file *seq, void *v) 1512 { 1513 if (!IS_ERR(v)) { 1514 /* 1515 * kmemleak_seq_start may return ERR_PTR if the scan_mutex 1516 * waiting was interrupted, so only release it if !IS_ERR. 1517 */ 1518 rcu_read_unlock(); 1519 mutex_unlock(&scan_mutex); 1520 if (v) 1521 put_object(v); 1522 } 1523 } 1524 1525 /* 1526 * Print the information for an unreferenced object to the seq file. 1527 */ 1528 static int kmemleak_seq_show(struct seq_file *seq, void *v) 1529 { 1530 struct kmemleak_object *object = v; 1531 unsigned long flags; 1532 1533 spin_lock_irqsave(&object->lock, flags); 1534 if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object)) 1535 print_unreferenced(seq, object); 1536 spin_unlock_irqrestore(&object->lock, flags); 1537 return 0; 1538 } 1539 1540 static const struct seq_operations kmemleak_seq_ops = { 1541 .start = kmemleak_seq_start, 1542 .next = kmemleak_seq_next, 1543 .stop = kmemleak_seq_stop, 1544 .show = kmemleak_seq_show, 1545 }; 1546 1547 static int kmemleak_open(struct inode *inode, struct file *file) 1548 { 1549 return seq_open(file, &kmemleak_seq_ops); 1550 } 1551 1552 static int dump_str_object_info(const char *str) 1553 { 1554 unsigned long flags; 1555 struct kmemleak_object *object; 1556 unsigned long addr; 1557 1558 if (kstrtoul(str, 0, &addr)) 1559 return -EINVAL; 1560 object = find_and_get_object(addr, 0); 1561 if (!object) { 1562 pr_info("Unknown object at 0x%08lx\n", addr); 1563 return -EINVAL; 1564 } 1565 1566 spin_lock_irqsave(&object->lock, flags); 1567 dump_object_info(object); 1568 spin_unlock_irqrestore(&object->lock, flags); 1569 1570 put_object(object); 1571 return 0; 1572 } 1573 1574 /* 1575 * We use grey instead of black to ensure we can do future scans on the same 1576 * objects. If we did not do future scans these black objects could 1577 * potentially contain references to newly allocated objects in the future and 1578 * we'd end up with false positives. 1579 */ 1580 static void kmemleak_clear(void) 1581 { 1582 struct kmemleak_object *object; 1583 unsigned long flags; 1584 1585 rcu_read_lock(); 1586 list_for_each_entry_rcu(object, &object_list, object_list) { 1587 spin_lock_irqsave(&object->lock, flags); 1588 if ((object->flags & OBJECT_REPORTED) && 1589 unreferenced_object(object)) 1590 __paint_it(object, KMEMLEAK_GREY); 1591 spin_unlock_irqrestore(&object->lock, flags); 1592 } 1593 rcu_read_unlock(); 1594 1595 kmemleak_found_leaks = false; 1596 } 1597 1598 static void __kmemleak_do_cleanup(void); 1599 1600 /* 1601 * File write operation to configure kmemleak at run-time. The following 1602 * commands can be written to the /sys/kernel/debug/kmemleak file: 1603 * off - disable kmemleak (irreversible) 1604 * stack=on - enable the task stacks scanning 1605 * stack=off - disable the tasks stacks scanning 1606 * scan=on - start the automatic memory scanning thread 1607 * scan=off - stop the automatic memory scanning thread 1608 * scan=... - set the automatic memory scanning period in seconds (0 to 1609 * disable it) 1610 * scan - trigger a memory scan 1611 * clear - mark all current reported unreferenced kmemleak objects as 1612 * grey to ignore printing them, or free all kmemleak objects 1613 * if kmemleak has been disabled. 1614 * dump=... - dump information about the object found at the given address 1615 */ 1616 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, 1617 size_t size, loff_t *ppos) 1618 { 1619 char buf[64]; 1620 int buf_size; 1621 int ret; 1622 1623 buf_size = min(size, (sizeof(buf) - 1)); 1624 if (strncpy_from_user(buf, user_buf, buf_size) < 0) 1625 return -EFAULT; 1626 buf[buf_size] = 0; 1627 1628 ret = mutex_lock_interruptible(&scan_mutex); 1629 if (ret < 0) 1630 return ret; 1631 1632 if (strncmp(buf, "clear", 5) == 0) { 1633 if (kmemleak_enabled) 1634 kmemleak_clear(); 1635 else 1636 __kmemleak_do_cleanup(); 1637 goto out; 1638 } 1639 1640 if (!kmemleak_enabled) { 1641 ret = -EBUSY; 1642 goto out; 1643 } 1644 1645 if (strncmp(buf, "off", 3) == 0) 1646 kmemleak_disable(); 1647 else if (strncmp(buf, "stack=on", 8) == 0) 1648 kmemleak_stack_scan = 1; 1649 else if (strncmp(buf, "stack=off", 9) == 0) 1650 kmemleak_stack_scan = 0; 1651 else if (strncmp(buf, "scan=on", 7) == 0) 1652 start_scan_thread(); 1653 else if (strncmp(buf, "scan=off", 8) == 0) 1654 stop_scan_thread(); 1655 else if (strncmp(buf, "scan=", 5) == 0) { 1656 unsigned long secs; 1657 1658 ret = kstrtoul(buf + 5, 0, &secs); 1659 if (ret < 0) 1660 goto out; 1661 stop_scan_thread(); 1662 if (secs) { 1663 jiffies_scan_wait = msecs_to_jiffies(secs * 1000); 1664 start_scan_thread(); 1665 } 1666 } else if (strncmp(buf, "scan", 4) == 0) 1667 kmemleak_scan(); 1668 else if (strncmp(buf, "dump=", 5) == 0) 1669 ret = dump_str_object_info(buf + 5); 1670 else 1671 ret = -EINVAL; 1672 1673 out: 1674 mutex_unlock(&scan_mutex); 1675 if (ret < 0) 1676 return ret; 1677 1678 /* ignore the rest of the buffer, only one command at a time */ 1679 *ppos += size; 1680 return size; 1681 } 1682 1683 static const struct file_operations kmemleak_fops = { 1684 .owner = THIS_MODULE, 1685 .open = kmemleak_open, 1686 .read = seq_read, 1687 .write = kmemleak_write, 1688 .llseek = seq_lseek, 1689 .release = seq_release, 1690 }; 1691 1692 static void __kmemleak_do_cleanup(void) 1693 { 1694 struct kmemleak_object *object; 1695 1696 rcu_read_lock(); 1697 list_for_each_entry_rcu(object, &object_list, object_list) 1698 delete_object_full(object->pointer); 1699 rcu_read_unlock(); 1700 } 1701 1702 /* 1703 * Stop the memory scanning thread and free the kmemleak internal objects if 1704 * no previous scan thread (otherwise, kmemleak may still have some useful 1705 * information on memory leaks). 1706 */ 1707 static void kmemleak_do_cleanup(struct work_struct *work) 1708 { 1709 mutex_lock(&scan_mutex); 1710 stop_scan_thread(); 1711 1712 if (!kmemleak_found_leaks) 1713 __kmemleak_do_cleanup(); 1714 else 1715 pr_info("Kmemleak disabled without freeing internal data. " 1716 "Reclaim the memory with \"echo clear > /sys/kernel/debug/kmemleak\"\n"); 1717 mutex_unlock(&scan_mutex); 1718 } 1719 1720 static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup); 1721 1722 /* 1723 * Disable kmemleak. No memory allocation/freeing will be traced once this 1724 * function is called. Disabling kmemleak is an irreversible operation. 1725 */ 1726 static void kmemleak_disable(void) 1727 { 1728 /* atomically check whether it was already invoked */ 1729 if (cmpxchg(&kmemleak_error, 0, 1)) 1730 return; 1731 1732 /* stop any memory operation tracing */ 1733 kmemleak_enabled = 0; 1734 1735 /* check whether it is too early for a kernel thread */ 1736 if (kmemleak_initialized) 1737 schedule_work(&cleanup_work); 1738 1739 pr_info("Kernel memory leak detector disabled\n"); 1740 } 1741 1742 /* 1743 * Allow boot-time kmemleak disabling (enabled by default). 1744 */ 1745 static int kmemleak_boot_config(char *str) 1746 { 1747 if (!str) 1748 return -EINVAL; 1749 if (strcmp(str, "off") == 0) 1750 kmemleak_disable(); 1751 else if (strcmp(str, "on") == 0) 1752 kmemleak_skip_disable = 1; 1753 else 1754 return -EINVAL; 1755 return 0; 1756 } 1757 early_param("kmemleak", kmemleak_boot_config); 1758 1759 static void __init print_log_trace(struct early_log *log) 1760 { 1761 struct stack_trace trace; 1762 1763 trace.nr_entries = log->trace_len; 1764 trace.entries = log->trace; 1765 1766 pr_notice("Early log backtrace:\n"); 1767 print_stack_trace(&trace, 2); 1768 } 1769 1770 /* 1771 * Kmemleak initialization. 1772 */ 1773 void __init kmemleak_init(void) 1774 { 1775 int i; 1776 unsigned long flags; 1777 1778 kmemleak_early_log = 0; 1779 1780 #ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF 1781 if (!kmemleak_skip_disable) { 1782 kmemleak_disable(); 1783 return; 1784 } 1785 #endif 1786 1787 jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE); 1788 jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000); 1789 1790 object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE); 1791 scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE); 1792 1793 if (crt_early_log >= ARRAY_SIZE(early_log)) 1794 pr_warning("Early log buffer exceeded (%d), please increase " 1795 "DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n", crt_early_log); 1796 1797 /* the kernel is still in UP mode, so disabling the IRQs is enough */ 1798 local_irq_save(flags); 1799 if (kmemleak_error) { 1800 local_irq_restore(flags); 1801 return; 1802 } else 1803 kmemleak_enabled = 1; 1804 local_irq_restore(flags); 1805 1806 /* 1807 * This is the point where tracking allocations is safe. Automatic 1808 * scanning is started during the late initcall. Add the early logged 1809 * callbacks to the kmemleak infrastructure. 1810 */ 1811 for (i = 0; i < crt_early_log; i++) { 1812 struct early_log *log = &early_log[i]; 1813 1814 switch (log->op_type) { 1815 case KMEMLEAK_ALLOC: 1816 early_alloc(log); 1817 break; 1818 case KMEMLEAK_ALLOC_PERCPU: 1819 early_alloc_percpu(log); 1820 break; 1821 case KMEMLEAK_FREE: 1822 kmemleak_free(log->ptr); 1823 break; 1824 case KMEMLEAK_FREE_PART: 1825 kmemleak_free_part(log->ptr, log->size); 1826 break; 1827 case KMEMLEAK_FREE_PERCPU: 1828 kmemleak_free_percpu(log->ptr); 1829 break; 1830 case KMEMLEAK_NOT_LEAK: 1831 kmemleak_not_leak(log->ptr); 1832 break; 1833 case KMEMLEAK_IGNORE: 1834 kmemleak_ignore(log->ptr); 1835 break; 1836 case KMEMLEAK_SCAN_AREA: 1837 kmemleak_scan_area(log->ptr, log->size, GFP_KERNEL); 1838 break; 1839 case KMEMLEAK_NO_SCAN: 1840 kmemleak_no_scan(log->ptr); 1841 break; 1842 default: 1843 kmemleak_warn("Unknown early log operation: %d\n", 1844 log->op_type); 1845 } 1846 1847 if (kmemleak_warning) { 1848 print_log_trace(log); 1849 kmemleak_warning = 0; 1850 } 1851 } 1852 } 1853 1854 /* 1855 * Late initialization function. 1856 */ 1857 static int __init kmemleak_late_init(void) 1858 { 1859 struct dentry *dentry; 1860 1861 kmemleak_initialized = 1; 1862 1863 if (kmemleak_error) { 1864 /* 1865 * Some error occurred and kmemleak was disabled. There is a 1866 * small chance that kmemleak_disable() was called immediately 1867 * after setting kmemleak_initialized and we may end up with 1868 * two clean-up threads but serialized by scan_mutex. 1869 */ 1870 schedule_work(&cleanup_work); 1871 return -ENOMEM; 1872 } 1873 1874 dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL, 1875 &kmemleak_fops); 1876 if (!dentry) 1877 pr_warning("Failed to create the debugfs kmemleak file\n"); 1878 mutex_lock(&scan_mutex); 1879 start_scan_thread(); 1880 mutex_unlock(&scan_mutex); 1881 1882 pr_info("Kernel memory leak detector initialized\n"); 1883 1884 return 0; 1885 } 1886 late_initcall(kmemleak_late_init); 1887