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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 * Locks and mutexes are acquired/nested in the following order:
57 *
58 * scan_mutex [-> object->lock] -> kmemleak_lock -> other_object->lock (SINGLE_DEPTH_NESTING)
59 *
60 * No kmemleak_lock and object->lock nesting is allowed outside scan_mutex
61 * regions.
62 *
63 * The kmemleak_object structures have a use_count incremented or decremented
64 * using the get_object()/put_object() functions. When the use_count becomes
65 * 0, this count can no longer be incremented and put_object() schedules the
66 * kmemleak_object freeing via an RCU callback. All calls to the get_object()
67 * function must be protected by rcu_read_lock() to avoid accessing a freed
68 * structure.
69 */
70
71 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
72
73 #include <linux/init.h>
74 #include <linux/kernel.h>
75 #include <linux/list.h>
76 #include <linux/sched.h>
77 #include <linux/jiffies.h>
78 #include <linux/delay.h>
79 #include <linux/export.h>
80 #include <linux/kthread.h>
81 #include <linux/rbtree.h>
82 #include <linux/fs.h>
83 #include <linux/debugfs.h>
84 #include <linux/seq_file.h>
85 #include <linux/cpumask.h>
86 #include <linux/spinlock.h>
87 #include <linux/mutex.h>
88 #include <linux/rcupdate.h>
89 #include <linux/stacktrace.h>
90 #include <linux/cache.h>
91 #include <linux/percpu.h>
92 #include <linux/hardirq.h>
93 #include <linux/mmzone.h>
94 #include <linux/slab.h>
95 #include <linux/thread_info.h>
96 #include <linux/err.h>
97 #include <linux/uaccess.h>
98 #include <linux/string.h>
99 #include <linux/nodemask.h>
100 #include <linux/mm.h>
101 #include <linux/workqueue.h>
102 #include <linux/crc32.h>
103
104 #include <asm/sections.h>
105 #include <asm/processor.h>
106 #include <linux/atomic.h>
107
108 #include <linux/kasan.h>
109 #include <linux/kmemcheck.h>
110 #include <linux/kmemleak.h>
111 #include <linux/memory_hotplug.h>
112
113 /*
114 * Kmemleak configuration and common defines.
115 */
116 #define MAX_TRACE 16 /* stack trace length */
117 #define MSECS_MIN_AGE 5000 /* minimum object age for reporting */
118 #define SECS_FIRST_SCAN 60 /* delay before the first scan */
119 #define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */
120 #define MAX_SCAN_SIZE 4096 /* maximum size of a scanned block */
121
122 #define BYTES_PER_POINTER sizeof(void *)
123
124 /* GFP bitmask for kmemleak internal allocations */
125 #define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC | \
126 __GFP_NOACCOUNT)) | \
127 __GFP_NORETRY | __GFP_NOMEMALLOC | \
128 __GFP_NOWARN)
129
130 /* scanning area inside a memory block */
131 struct kmemleak_scan_area {
132 struct hlist_node node;
133 unsigned long start;
134 size_t size;
135 };
136
137 #define KMEMLEAK_GREY 0
138 #define KMEMLEAK_BLACK -1
139
140 /*
141 * Structure holding the metadata for each allocated memory block.
142 * Modifications to such objects should be made while holding the
143 * object->lock. Insertions or deletions from object_list, gray_list or
144 * rb_node are already protected by the corresponding locks or mutex (see
145 * the notes on locking above). These objects are reference-counted
146 * (use_count) and freed using the RCU mechanism.
147 */
148 struct kmemleak_object {
149 spinlock_t lock;
150 unsigned long flags; /* object status flags */
151 struct list_head object_list;
152 struct list_head gray_list;
153 struct rb_node rb_node;
154 struct rcu_head rcu; /* object_list lockless traversal */
155 /* object usage count; object freed when use_count == 0 */
156 atomic_t use_count;
157 unsigned long pointer;
158 size_t size;
159 /* minimum number of a pointers found before it is considered leak */
160 int min_count;
161 /* the total number of pointers found pointing to this object */
162 int count;
163 /* checksum for detecting modified objects */
164 u32 checksum;
165 /* memory ranges to be scanned inside an object (empty for all) */
166 struct hlist_head area_list;
167 unsigned long trace[MAX_TRACE];
168 unsigned int trace_len;
169 unsigned long jiffies; /* creation timestamp */
170 pid_t pid; /* pid of the current task */
171 char comm[TASK_COMM_LEN]; /* executable name */
172 };
173
174 /* flag representing the memory block allocation status */
175 #define OBJECT_ALLOCATED (1 << 0)
176 /* flag set after the first reporting of an unreference object */
177 #define OBJECT_REPORTED (1 << 1)
178 /* flag set to not scan the object */
179 #define OBJECT_NO_SCAN (1 << 2)
180
181 /* number of bytes to print per line; must be 16 or 32 */
182 #define HEX_ROW_SIZE 16
183 /* number of bytes to print at a time (1, 2, 4, 8) */
184 #define HEX_GROUP_SIZE 1
185 /* include ASCII after the hex output */
186 #define HEX_ASCII 1
187 /* max number of lines to be printed */
188 #define HEX_MAX_LINES 2
189
190 /* the list of all allocated objects */
191 static LIST_HEAD(object_list);
192 /* the list of gray-colored objects (see color_gray comment below) */
193 static LIST_HEAD(gray_list);
194 /* search tree for object boundaries */
195 static struct rb_root object_tree_root = RB_ROOT;
196 /* rw_lock protecting the access to object_list and object_tree_root */
197 static DEFINE_RWLOCK(kmemleak_lock);
198
199 /* allocation caches for kmemleak internal data */
200 static struct kmem_cache *object_cache;
201 static struct kmem_cache *scan_area_cache;
202
203 /* set if tracing memory operations is enabled */
204 static int kmemleak_enabled;
205 /* same as above but only for the kmemleak_free() callback */
206 static int kmemleak_free_enabled;
207 /* set in the late_initcall if there were no errors */
208 static int kmemleak_initialized;
209 /* enables or disables early logging of the memory operations */
210 static int kmemleak_early_log = 1;
211 /* set if a kmemleak warning was issued */
212 static int kmemleak_warning;
213 /* set if a fatal kmemleak error has occurred */
214 static int kmemleak_error;
215
216 /* minimum and maximum address that may be valid pointers */
217 static unsigned long min_addr = ULONG_MAX;
218 static unsigned long max_addr;
219
220 static struct task_struct *scan_thread;
221 /* used to avoid reporting of recently allocated objects */
222 static unsigned long jiffies_min_age;
223 static unsigned long jiffies_last_scan;
224 /* delay between automatic memory scannings */
225 static signed long jiffies_scan_wait;
226 /* enables or disables the task stacks scanning */
227 static int kmemleak_stack_scan = 1;
228 /* protects the memory scanning, parameters and debug/kmemleak file access */
229 static DEFINE_MUTEX(scan_mutex);
230 /* setting kmemleak=on, will set this var, skipping the disable */
231 static int kmemleak_skip_disable;
232 /* If there are leaks that can be reported */
233 static bool kmemleak_found_leaks;
234
235 /*
236 * Early object allocation/freeing logging. Kmemleak is initialized after the
237 * kernel allocator. However, both the kernel allocator and kmemleak may
238 * allocate memory blocks which need to be tracked. Kmemleak defines an
239 * arbitrary buffer to hold the allocation/freeing information before it is
240 * fully initialized.
241 */
242
243 /* kmemleak operation type for early logging */
244 enum {
245 KMEMLEAK_ALLOC,
246 KMEMLEAK_ALLOC_PERCPU,
247 KMEMLEAK_FREE,
248 KMEMLEAK_FREE_PART,
249 KMEMLEAK_FREE_PERCPU,
250 KMEMLEAK_NOT_LEAK,
251 KMEMLEAK_IGNORE,
252 KMEMLEAK_SCAN_AREA,
253 KMEMLEAK_NO_SCAN
254 };
255
256 /*
257 * Structure holding the information passed to kmemleak callbacks during the
258 * early logging.
259 */
260 struct early_log {
261 int op_type; /* kmemleak operation type */
262 const void *ptr; /* allocated/freed memory block */
263 size_t size; /* memory block size */
264 int min_count; /* minimum reference count */
265 unsigned long trace[MAX_TRACE]; /* stack trace */
266 unsigned int trace_len; /* stack trace length */
267 };
268
269 /* early logging buffer and current position */
270 static struct early_log
271 early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
272 static int crt_early_log __initdata;
273
274 static void kmemleak_disable(void);
275
276 /*
277 * Print a warning and dump the stack trace.
278 */
279 #define kmemleak_warn(x...) do { \
280 pr_warning(x); \
281 dump_stack(); \
282 kmemleak_warning = 1; \
283 } while (0)
284
285 /*
286 * Macro invoked when a serious kmemleak condition occurred and cannot be
287 * recovered from. Kmemleak will be disabled and further allocation/freeing
288 * tracing no longer available.
289 */
290 #define kmemleak_stop(x...) do { \
291 kmemleak_warn(x); \
292 kmemleak_disable(); \
293 } while (0)
294
295 /*
296 * Printing of the objects hex dump to the seq file. The number of lines to be
297 * printed is limited to HEX_MAX_LINES to prevent seq file spamming. The
298 * actual number of printed bytes depends on HEX_ROW_SIZE. It must be called
299 * with the object->lock held.
300 */
301 static void hex_dump_object(struct seq_file *seq,
302 struct kmemleak_object *object)
303 {
304 const u8 *ptr = (const u8 *)object->pointer;
305 size_t len;
306
307 /* limit the number of lines to HEX_MAX_LINES */
308 len = min_t(size_t, object->size, HEX_MAX_LINES * HEX_ROW_SIZE);
309
310 seq_printf(seq, " hex dump (first %zu bytes):\n", len);
311 seq_hex_dump(seq, " ", DUMP_PREFIX_NONE, HEX_ROW_SIZE,
312 HEX_GROUP_SIZE, ptr, len, HEX_ASCII);
313 }
314
315 /*
316 * Object colors, encoded with count and min_count:
317 * - white - orphan object, not enough references to it (count < min_count)
318 * - gray - not orphan, not marked as false positive (min_count == 0) or
319 * sufficient references to it (count >= min_count)
320 * - black - ignore, it doesn't contain references (e.g. text section)
321 * (min_count == -1). No function defined for this color.
322 * Newly created objects don't have any color assigned (object->count == -1)
323 * before the next memory scan when they become white.
324 */
325 static bool color_white(const struct kmemleak_object *object)
326 {
327 return object->count != KMEMLEAK_BLACK &&
328 object->count < object->min_count;
329 }
330
331 static bool color_gray(const struct kmemleak_object *object)
332 {
333 return object->min_count != KMEMLEAK_BLACK &&
334 object->count >= object->min_count;
335 }
336
337 /*
338 * Objects are considered unreferenced only if their color is white, they have
339 * not be deleted and have a minimum age to avoid false positives caused by
340 * pointers temporarily stored in CPU registers.
341 */
342 static bool unreferenced_object(struct kmemleak_object *object)
343 {
344 return (color_white(object) && object->flags & OBJECT_ALLOCATED) &&
345 time_before_eq(object->jiffies + jiffies_min_age,
346 jiffies_last_scan);
347 }
348
349 /*
350 * Printing of the unreferenced objects information to the seq file. The
351 * print_unreferenced function must be called with the object->lock held.
352 */
353 static void print_unreferenced(struct seq_file *seq,
354 struct kmemleak_object *object)
355 {
356 int i;
357 unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
358
359 seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
360 object->pointer, object->size);
361 seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
362 object->comm, object->pid, object->jiffies,
363 msecs_age / 1000, msecs_age % 1000);
364 hex_dump_object(seq, object);
365 seq_printf(seq, " backtrace:\n");
366
367 for (i = 0; i < object->trace_len; i++) {
368 void *ptr = (void *)object->trace[i];
369 seq_printf(seq, " [<%p>] %pS\n", ptr, ptr);
370 }
371 }
372
373 /*
374 * Print the kmemleak_object information. This function is used mainly for
375 * debugging special cases when kmemleak operations. It must be called with
376 * the object->lock held.
377 */
378 static void dump_object_info(struct kmemleak_object *object)
379 {
380 struct stack_trace trace;
381
382 trace.nr_entries = object->trace_len;
383 trace.entries = object->trace;
384
385 pr_notice("Object 0x%08lx (size %zu):\n",
386 object->pointer, object->size);
387 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
388 object->comm, object->pid, object->jiffies);
389 pr_notice(" min_count = %d\n", object->min_count);
390 pr_notice(" count = %d\n", object->count);
391 pr_notice(" flags = 0x%lx\n", object->flags);
392 pr_notice(" checksum = %u\n", object->checksum);
393 pr_notice(" backtrace:\n");
394 print_stack_trace(&trace, 4);
395 }
396
397 /*
398 * Look-up a memory block metadata (kmemleak_object) in the object search
399 * tree based on a pointer value. If alias is 0, only values pointing to the
400 * beginning of the memory block are allowed. The kmemleak_lock must be held
401 * when calling this function.
402 */
403 static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
404 {
405 struct rb_node *rb = object_tree_root.rb_node;
406
407 while (rb) {
408 struct kmemleak_object *object =
409 rb_entry(rb, struct kmemleak_object, rb_node);
410 if (ptr < object->pointer)
411 rb = object->rb_node.rb_left;
412 else if (object->pointer + object->size <= ptr)
413 rb = object->rb_node.rb_right;
414 else if (object->pointer == ptr || alias)
415 return object;
416 else {
417 kmemleak_warn("Found object by alias at 0x%08lx\n",
418 ptr);
419 dump_object_info(object);
420 break;
421 }
422 }
423 return NULL;
424 }
425
426 /*
427 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
428 * that once an object's use_count reached 0, the RCU freeing was already
429 * registered and the object should no longer be used. This function must be
430 * called under the protection of rcu_read_lock().
431 */
432 static int get_object(struct kmemleak_object *object)
433 {
434 return atomic_inc_not_zero(&object->use_count);
435 }
436
437 /*
438 * RCU callback to free a kmemleak_object.
439 */
440 static void free_object_rcu(struct rcu_head *rcu)
441 {
442 struct hlist_node *tmp;
443 struct kmemleak_scan_area *area;
444 struct kmemleak_object *object =
445 container_of(rcu, struct kmemleak_object, rcu);
446
447 /*
448 * Once use_count is 0 (guaranteed by put_object), there is no other
449 * code accessing this object, hence no need for locking.
450 */
451 hlist_for_each_entry_safe(area, tmp, &object->area_list, node) {
452 hlist_del(&area->node);
453 kmem_cache_free(scan_area_cache, area);
454 }
455 kmem_cache_free(object_cache, object);
456 }
457
458 /*
459 * Decrement the object use_count. Once the count is 0, free the object using
460 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
461 * delete_object() path, the delayed RCU freeing ensures that there is no
462 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
463 * is also possible.
464 */
465 static void put_object(struct kmemleak_object *object)
466 {
467 if (!atomic_dec_and_test(&object->use_count))
468 return;
469
470 /* should only get here after delete_object was called */
471 WARN_ON(object->flags & OBJECT_ALLOCATED);
472
473 call_rcu(&object->rcu, free_object_rcu);
474 }
475
476 /*
477 * Look up an object in the object search tree and increase its use_count.
478 */
479 static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
480 {
481 unsigned long flags;
482 struct kmemleak_object *object;
483
484 rcu_read_lock();
485 read_lock_irqsave(&kmemleak_lock, flags);
486 object = lookup_object(ptr, alias);
487 read_unlock_irqrestore(&kmemleak_lock, flags);
488
489 /* check whether the object is still available */
490 if (object && !get_object(object))
491 object = NULL;
492 rcu_read_unlock();
493
494 return object;
495 }
496
497 /*
498 * Look up an object in the object search tree and remove it from both
499 * object_tree_root and object_list. The returned object's use_count should be
500 * at least 1, as initially set by create_object().
501 */
502 static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int alias)
503 {
504 unsigned long flags;
505 struct kmemleak_object *object;
506
507 write_lock_irqsave(&kmemleak_lock, flags);
508 object = lookup_object(ptr, alias);
509 if (object) {
510 rb_erase(&object->rb_node, &object_tree_root);
511 list_del_rcu(&object->object_list);
512 }
513 write_unlock_irqrestore(&kmemleak_lock, flags);
514
515 return object;
516 }
517
518 /*
519 * Save stack trace to the given array of MAX_TRACE size.
520 */
521 static int __save_stack_trace(unsigned long *trace)
522 {
523 struct stack_trace stack_trace;
524
525 stack_trace.max_entries = MAX_TRACE;
526 stack_trace.nr_entries = 0;
527 stack_trace.entries = trace;
528 stack_trace.skip = 2;
529 save_stack_trace(&stack_trace);
530
531 return stack_trace.nr_entries;
532 }
533
534 /*
535 * Create the metadata (struct kmemleak_object) corresponding to an allocated
536 * memory block and add it to the object_list and object_tree_root.
537 */
538 static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
539 int min_count, gfp_t gfp)
540 {
541 unsigned long flags;
542 struct kmemleak_object *object, *parent;
543 struct rb_node **link, *rb_parent;
544
545 object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
546 if (!object) {
547 pr_warning("Cannot allocate a kmemleak_object structure\n");
548 kmemleak_disable();
549 return NULL;
550 }
551
552 INIT_LIST_HEAD(&object->object_list);
553 INIT_LIST_HEAD(&object->gray_list);
554 INIT_HLIST_HEAD(&object->area_list);
555 spin_lock_init(&object->lock);
556 atomic_set(&object->use_count, 1);
557 object->flags = OBJECT_ALLOCATED;
558 object->pointer = ptr;
559 object->size = size;
560 object->min_count = min_count;
561 object->count = 0; /* white color initially */
562 object->jiffies = jiffies;
563 object->checksum = 0;
564
565 /* task information */
566 if (in_irq()) {
567 object->pid = 0;
568 strncpy(object->comm, "hardirq", sizeof(object->comm));
569 } else if (in_softirq()) {
570 object->pid = 0;
571 strncpy(object->comm, "softirq", sizeof(object->comm));
572 } else {
573 object->pid = current->pid;
574 /*
575 * There is a small chance of a race with set_task_comm(),
576 * however using get_task_comm() here may cause locking
577 * dependency issues with current->alloc_lock. In the worst
578 * case, the command line is not correct.
579 */
580 strncpy(object->comm, current->comm, sizeof(object->comm));
581 }
582
583 /* kernel backtrace */
584 object->trace_len = __save_stack_trace(object->trace);
585
586 write_lock_irqsave(&kmemleak_lock, flags);
587
588 min_addr = min(min_addr, ptr);
589 max_addr = max(max_addr, ptr + size);
590 link = &object_tree_root.rb_node;
591 rb_parent = NULL;
592 while (*link) {
593 rb_parent = *link;
594 parent = rb_entry(rb_parent, struct kmemleak_object, rb_node);
595 if (ptr + size <= parent->pointer)
596 link = &parent->rb_node.rb_left;
597 else if (parent->pointer + parent->size <= ptr)
598 link = &parent->rb_node.rb_right;
599 else {
600 kmemleak_stop("Cannot insert 0x%lx into the object "
601 "search tree (overlaps existing)\n",
602 ptr);
603 /*
604 * No need for parent->lock here since "parent" cannot
605 * be freed while the kmemleak_lock is held.
606 */
607 dump_object_info(parent);
608 kmem_cache_free(object_cache, object);
609 object = NULL;
610 goto out;
611 }
612 }
613 rb_link_node(&object->rb_node, rb_parent, link);
614 rb_insert_color(&object->rb_node, &object_tree_root);
615
616 list_add_tail_rcu(&object->object_list, &object_list);
617 out:
618 write_unlock_irqrestore(&kmemleak_lock, flags);
619 return object;
620 }
621
622 /*
623 * Mark the object as not allocated and schedule RCU freeing via put_object().
624 */
625 static void __delete_object(struct kmemleak_object *object)
626 {
627 unsigned long flags;
628
629 WARN_ON(!(object->flags & OBJECT_ALLOCATED));
630 WARN_ON(atomic_read(&object->use_count) < 1);
631
632 /*
633 * Locking here also ensures that the corresponding memory block
634 * cannot be freed when it is being scanned.
635 */
636 spin_lock_irqsave(&object->lock, flags);
637 object->flags &= ~OBJECT_ALLOCATED;
638 spin_unlock_irqrestore(&object->lock, flags);
639 put_object(object);
640 }
641
642 /*
643 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
644 * delete it.
645 */
646 static void delete_object_full(unsigned long ptr)
647 {
648 struct kmemleak_object *object;
649
650 object = find_and_remove_object(ptr, 0);
651 if (!object) {
652 #ifdef DEBUG
653 kmemleak_warn("Freeing unknown object at 0x%08lx\n",
654 ptr);
655 #endif
656 return;
657 }
658 __delete_object(object);
659 }
660
661 /*
662 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
663 * delete it. If the memory block is partially freed, the function may create
664 * additional metadata for the remaining parts of the block.
665 */
666 static void delete_object_part(unsigned long ptr, size_t size)
667 {
668 struct kmemleak_object *object;
669 unsigned long start, end;
670
671 object = find_and_remove_object(ptr, 1);
672 if (!object) {
673 #ifdef DEBUG
674 kmemleak_warn("Partially freeing unknown object at 0x%08lx "
675 "(size %zu)\n", ptr, size);
676 #endif
677 return;
678 }
679
680 /*
681 * Create one or two objects that may result from the memory block
682 * split. Note that partial freeing is only done by free_bootmem() and
683 * this happens before kmemleak_init() is called. The path below is
684 * only executed during early log recording in kmemleak_init(), so
685 * GFP_KERNEL is enough.
686 */
687 start = object->pointer;
688 end = object->pointer + object->size;
689 if (ptr > start)
690 create_object(start, ptr - start, object->min_count,
691 GFP_KERNEL);
692 if (ptr + size < end)
693 create_object(ptr + size, end - ptr - size, object->min_count,
694 GFP_KERNEL);
695
696 __delete_object(object);
697 }
698
699 static void __paint_it(struct kmemleak_object *object, int color)
700 {
701 object->min_count = color;
702 if (color == KMEMLEAK_BLACK)
703 object->flags |= OBJECT_NO_SCAN;
704 }
705
706 static void paint_it(struct kmemleak_object *object, int color)
707 {
708 unsigned long flags;
709
710 spin_lock_irqsave(&object->lock, flags);
711 __paint_it(object, color);
712 spin_unlock_irqrestore(&object->lock, flags);
713 }
714
715 static void paint_ptr(unsigned long ptr, int color)
716 {
717 struct kmemleak_object *object;
718
719 object = find_and_get_object(ptr, 0);
720 if (!object) {
721 kmemleak_warn("Trying to color unknown object "
722 "at 0x%08lx as %s\n", ptr,
723 (color == KMEMLEAK_GREY) ? "Grey" :
724 (color == KMEMLEAK_BLACK) ? "Black" : "Unknown");
725 return;
726 }
727 paint_it(object, color);
728 put_object(object);
729 }
730
731 /*
732 * Mark an object permanently as gray-colored so that it can no longer be
733 * reported as a leak. This is used in general to mark a false positive.
734 */
735 static void make_gray_object(unsigned long ptr)
736 {
737 paint_ptr(ptr, KMEMLEAK_GREY);
738 }
739
740 /*
741 * Mark the object as black-colored so that it is ignored from scans and
742 * reporting.
743 */
744 static void make_black_object(unsigned long ptr)
745 {
746 paint_ptr(ptr, KMEMLEAK_BLACK);
747 }
748
749 /*
750 * Add a scanning area to the object. If at least one such area is added,
751 * kmemleak will only scan these ranges rather than the whole memory block.
752 */
753 static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
754 {
755 unsigned long flags;
756 struct kmemleak_object *object;
757 struct kmemleak_scan_area *area;
758
759 object = find_and_get_object(ptr, 1);
760 if (!object) {
761 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
762 ptr);
763 return;
764 }
765
766 area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
767 if (!area) {
768 pr_warning("Cannot allocate a scan area\n");
769 goto out;
770 }
771
772 spin_lock_irqsave(&object->lock, flags);
773 if (size == SIZE_MAX) {
774 size = object->pointer + object->size - ptr;
775 } else if (ptr + size > object->pointer + object->size) {
776 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
777 dump_object_info(object);
778 kmem_cache_free(scan_area_cache, area);
779 goto out_unlock;
780 }
781
782 INIT_HLIST_NODE(&area->node);
783 area->start = ptr;
784 area->size = size;
785
786 hlist_add_head(&area->node, &object->area_list);
787 out_unlock:
788 spin_unlock_irqrestore(&object->lock, flags);
789 out:
790 put_object(object);
791 }
792
793 /*
794 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
795 * pointer. Such object will not be scanned by kmemleak but references to it
796 * are searched.
797 */
798 static void object_no_scan(unsigned long ptr)
799 {
800 unsigned long flags;
801 struct kmemleak_object *object;
802
803 object = find_and_get_object(ptr, 0);
804 if (!object) {
805 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
806 return;
807 }
808
809 spin_lock_irqsave(&object->lock, flags);
810 object->flags |= OBJECT_NO_SCAN;
811 spin_unlock_irqrestore(&object->lock, flags);
812 put_object(object);
813 }
814
815 /*
816 * Log an early kmemleak_* call to the early_log buffer. These calls will be
817 * processed later once kmemleak is fully initialized.
818 */
819 static void __init log_early(int op_type, const void *ptr, size_t size,
820 int min_count)
821 {
822 unsigned long flags;
823 struct early_log *log;
824
825 if (kmemleak_error) {
826 /* kmemleak stopped recording, just count the requests */
827 crt_early_log++;
828 return;
829 }
830
831 if (crt_early_log >= ARRAY_SIZE(early_log)) {
832 crt_early_log++;
833 kmemleak_disable();
834 return;
835 }
836
837 /*
838 * There is no need for locking since the kernel is still in UP mode
839 * at this stage. Disabling the IRQs is enough.
840 */
841 local_irq_save(flags);
842 log = &early_log[crt_early_log];
843 log->op_type = op_type;
844 log->ptr = ptr;
845 log->size = size;
846 log->min_count = min_count;
847 log->trace_len = __save_stack_trace(log->trace);
848 crt_early_log++;
849 local_irq_restore(flags);
850 }
851
852 /*
853 * Log an early allocated block and populate the stack trace.
854 */
855 static void early_alloc(struct early_log *log)
856 {
857 struct kmemleak_object *object;
858 unsigned long flags;
859 int i;
860
861 if (!kmemleak_enabled || !log->ptr || IS_ERR(log->ptr))
862 return;
863
864 /*
865 * RCU locking needed to ensure object is not freed via put_object().
866 */
867 rcu_read_lock();
868 object = create_object((unsigned long)log->ptr, log->size,
869 log->min_count, GFP_ATOMIC);
870 if (!object)
871 goto out;
872 spin_lock_irqsave(&object->lock, flags);
873 for (i = 0; i < log->trace_len; i++)
874 object->trace[i] = log->trace[i];
875 object->trace_len = log->trace_len;
876 spin_unlock_irqrestore(&object->lock, flags);
877 out:
878 rcu_read_unlock();
879 }
880
881 /*
882 * Log an early allocated block and populate the stack trace.
883 */
884 static void early_alloc_percpu(struct early_log *log)
885 {
886 unsigned int cpu;
887 const void __percpu *ptr = log->ptr;
888
889 for_each_possible_cpu(cpu) {
890 log->ptr = per_cpu_ptr(ptr, cpu);
891 early_alloc(log);
892 }
893 }
894
895 /**
896 * kmemleak_alloc - register a newly allocated object
897 * @ptr: pointer to beginning of the object
898 * @size: size of the object
899 * @min_count: minimum number of references to this object. If during memory
900 * scanning a number of references less than @min_count is found,
901 * the object is reported as a memory leak. If @min_count is 0,
902 * the object is never reported as a leak. If @min_count is -1,
903 * the object is ignored (not scanned and not reported as a leak)
904 * @gfp: kmalloc() flags used for kmemleak internal memory allocations
905 *
906 * This function is called from the kernel allocators when a new object
907 * (memory block) is allocated (kmem_cache_alloc, kmalloc, vmalloc etc.).
908 */
909 void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
910 gfp_t gfp)
911 {
912 pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
913
914 if (kmemleak_enabled && ptr && !IS_ERR(ptr))
915 create_object((unsigned long)ptr, size, min_count, gfp);
916 else if (kmemleak_early_log)
917 log_early(KMEMLEAK_ALLOC, ptr, size, min_count);
918 }
919 EXPORT_SYMBOL_GPL(kmemleak_alloc);
920
921 /**
922 * kmemleak_alloc_percpu - register a newly allocated __percpu object
923 * @ptr: __percpu pointer to beginning of the object
924 * @size: size of the object
925 * @gfp: flags used for kmemleak internal memory allocations
926 *
927 * This function is called from the kernel percpu allocator when a new object
928 * (memory block) is allocated (alloc_percpu).
929 */
930 void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
931 gfp_t gfp)
932 {
933 unsigned int cpu;
934
935 pr_debug("%s(0x%p, %zu)\n", __func__, ptr, size);
936
937 /*
938 * Percpu allocations are only scanned and not reported as leaks
939 * (min_count is set to 0).
940 */
941 if (kmemleak_enabled && ptr && !IS_ERR(ptr))
942 for_each_possible_cpu(cpu)
943 create_object((unsigned long)per_cpu_ptr(ptr, cpu),
944 size, 0, gfp);
945 else if (kmemleak_early_log)
946 log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
947 }
948 EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);
949
950 /**
951 * kmemleak_free - unregister a previously registered object
952 * @ptr: pointer to beginning of the object
953 *
954 * This function is called from the kernel allocators when an object (memory
955 * block) is freed (kmem_cache_free, kfree, vfree etc.).
956 */
957 void __ref kmemleak_free(const void *ptr)
958 {
959 pr_debug("%s(0x%p)\n", __func__, ptr);
960
961 if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))
962 delete_object_full((unsigned long)ptr);
963 else if (kmemleak_early_log)
964 log_early(KMEMLEAK_FREE, ptr, 0, 0);
965 }
966 EXPORT_SYMBOL_GPL(kmemleak_free);
967
968 /**
969 * kmemleak_free_part - partially unregister a previously registered object
970 * @ptr: pointer to the beginning or inside the object. This also
971 * represents the start of the range to be freed
972 * @size: size to be unregistered
973 *
974 * This function is called when only a part of a memory block is freed
975 * (usually from the bootmem allocator).
976 */
977 void __ref kmemleak_free_part(const void *ptr, size_t size)
978 {
979 pr_debug("%s(0x%p)\n", __func__, ptr);
980
981 if (kmemleak_enabled && ptr && !IS_ERR(ptr))
982 delete_object_part((unsigned long)ptr, size);
983 else if (kmemleak_early_log)
984 log_early(KMEMLEAK_FREE_PART, ptr, size, 0);
985 }
986 EXPORT_SYMBOL_GPL(kmemleak_free_part);
987
988 /**
989 * kmemleak_free_percpu - unregister a previously registered __percpu object
990 * @ptr: __percpu pointer to beginning of the object
991 *
992 * This function is called from the kernel percpu allocator when an object
993 * (memory block) is freed (free_percpu).
994 */
995 void __ref kmemleak_free_percpu(const void __percpu *ptr)
996 {
997 unsigned int cpu;
998
999 pr_debug("%s(0x%p)\n", __func__, ptr);
1000
1001 if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))
1002 for_each_possible_cpu(cpu)
1003 delete_object_full((unsigned long)per_cpu_ptr(ptr,
1004 cpu));
1005 else if (kmemleak_early_log)
1006 log_early(KMEMLEAK_FREE_PERCPU, ptr, 0, 0);
1007 }
1008 EXPORT_SYMBOL_GPL(kmemleak_free_percpu);
1009
1010 /**
1011 * kmemleak_update_trace - update object allocation stack trace
1012 * @ptr: pointer to beginning of the object
1013 *
1014 * Override the object allocation stack trace for cases where the actual
1015 * allocation place is not always useful.
1016 */
1017 void __ref kmemleak_update_trace(const void *ptr)
1018 {
1019 struct kmemleak_object *object;
1020 unsigned long flags;
1021
1022 pr_debug("%s(0x%p)\n", __func__, ptr);
1023
1024 if (!kmemleak_enabled || IS_ERR_OR_NULL(ptr))
1025 return;
1026
1027 object = find_and_get_object((unsigned long)ptr, 1);
1028 if (!object) {
1029 #ifdef DEBUG
1030 kmemleak_warn("Updating stack trace for unknown object at %p\n",
1031 ptr);
1032 #endif
1033 return;
1034 }
1035
1036 spin_lock_irqsave(&object->lock, flags);
1037 object->trace_len = __save_stack_trace(object->trace);
1038 spin_unlock_irqrestore(&object->lock, flags);
1039
1040 put_object(object);
1041 }
1042 EXPORT_SYMBOL(kmemleak_update_trace);
1043
1044 /**
1045 * kmemleak_not_leak - mark an allocated object as false positive
1046 * @ptr: pointer to beginning of the object
1047 *
1048 * Calling this function on an object will cause the memory block to no longer
1049 * be reported as leak and always be scanned.
1050 */
1051 void __ref kmemleak_not_leak(const void *ptr)
1052 {
1053 pr_debug("%s(0x%p)\n", __func__, ptr);
1054
1055 if (kmemleak_enabled && ptr && !IS_ERR(ptr))
1056 make_gray_object((unsigned long)ptr);
1057 else if (kmemleak_early_log)
1058 log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0);
1059 }
1060 EXPORT_SYMBOL(kmemleak_not_leak);
1061
1062 /**
1063 * kmemleak_ignore - ignore an allocated object
1064 * @ptr: pointer to beginning of the object
1065 *
1066 * Calling this function on an object will cause the memory block to be
1067 * ignored (not scanned and not reported as a leak). This is usually done when
1068 * it is known that the corresponding block is not a leak and does not contain
1069 * any references to other allocated memory blocks.
1070 */
1071 void __ref kmemleak_ignore(const void *ptr)
1072 {
1073 pr_debug("%s(0x%p)\n", __func__, ptr);
1074
1075 if (kmemleak_enabled && ptr && !IS_ERR(ptr))
1076 make_black_object((unsigned long)ptr);
1077 else if (kmemleak_early_log)
1078 log_early(KMEMLEAK_IGNORE, ptr, 0, 0);
1079 }
1080 EXPORT_SYMBOL(kmemleak_ignore);
1081
1082 /**
1083 * kmemleak_scan_area - limit the range to be scanned in an allocated object
1084 * @ptr: pointer to beginning or inside the object. This also
1085 * represents the start of the scan area
1086 * @size: size of the scan area
1087 * @gfp: kmalloc() flags used for kmemleak internal memory allocations
1088 *
1089 * This function is used when it is known that only certain parts of an object
1090 * contain references to other objects. Kmemleak will only scan these areas
1091 * reducing the number false negatives.
1092 */
1093 void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
1094 {
1095 pr_debug("%s(0x%p)\n", __func__, ptr);
1096
1097 if (kmemleak_enabled && ptr && size && !IS_ERR(ptr))
1098 add_scan_area((unsigned long)ptr, size, gfp);
1099 else if (kmemleak_early_log)
1100 log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0);
1101 }
1102 EXPORT_SYMBOL(kmemleak_scan_area);
1103
1104 /**
1105 * kmemleak_no_scan - do not scan an allocated object
1106 * @ptr: pointer to beginning of the object
1107 *
1108 * This function notifies kmemleak not to scan the given memory block. Useful
1109 * in situations where it is known that the given object does not contain any
1110 * references to other objects. Kmemleak will not scan such objects reducing
1111 * the number of false negatives.
1112 */
1113 void __ref kmemleak_no_scan(const void *ptr)
1114 {
1115 pr_debug("%s(0x%p)\n", __func__, ptr);
1116
1117 if (kmemleak_enabled && ptr && !IS_ERR(ptr))
1118 object_no_scan((unsigned long)ptr);
1119 else if (kmemleak_early_log)
1120 log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0);
1121 }
1122 EXPORT_SYMBOL(kmemleak_no_scan);
1123
1124 /*
1125 * Update an object's checksum and return true if it was modified.
1126 */
1127 static bool update_checksum(struct kmemleak_object *object)
1128 {
1129 u32 old_csum = object->checksum;
1130
1131 if (!kmemcheck_is_obj_initialized(object->pointer, object->size))
1132 return false;
1133
1134 kasan_disable_current();
1135 object->checksum = crc32(0, (void *)object->pointer, object->size);
1136 kasan_enable_current();
1137
1138 return object->checksum != old_csum;
1139 }
1140
1141 /*
1142 * Memory scanning is a long process and it needs to be interruptable. This
1143 * function checks whether such interrupt condition occurred.
1144 */
1145 static int scan_should_stop(void)
1146 {
1147 if (!kmemleak_enabled)
1148 return 1;
1149
1150 /*
1151 * This function may be called from either process or kthread context,
1152 * hence the need to check for both stop conditions.
1153 */
1154 if (current->mm)
1155 return signal_pending(current);
1156 else
1157 return kthread_should_stop();
1158
1159 return 0;
1160 }
1161
1162 /*
1163 * Scan a memory block (exclusive range) for valid pointers and add those
1164 * found to the gray list.
1165 */
1166 static void scan_block(void *_start, void *_end,
1167 struct kmemleak_object *scanned)
1168 {
1169 unsigned long *ptr;
1170 unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
1171 unsigned long *end = _end - (BYTES_PER_POINTER - 1);
1172 unsigned long flags;
1173
1174 read_lock_irqsave(&kmemleak_lock, flags);
1175 for (ptr = start; ptr < end; ptr++) {
1176 struct kmemleak_object *object;
1177 unsigned long pointer;
1178
1179 if (scan_should_stop())
1180 break;
1181
1182 /* don't scan uninitialized memory */
1183 if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
1184 BYTES_PER_POINTER))
1185 continue;
1186
1187 kasan_disable_current();
1188 pointer = *ptr;
1189 kasan_enable_current();
1190
1191 if (pointer < min_addr || pointer >= max_addr)
1192 continue;
1193
1194 /*
1195 * No need for get_object() here since we hold kmemleak_lock.
1196 * object->use_count cannot be dropped to 0 while the object
1197 * is still present in object_tree_root and object_list
1198 * (with updates protected by kmemleak_lock).
1199 */
1200 object = lookup_object(pointer, 1);
1201 if (!object)
1202 continue;
1203 if (object == scanned)
1204 /* self referenced, ignore */
1205 continue;
1206
1207 /*
1208 * Avoid the lockdep recursive warning on object->lock being
1209 * previously acquired in scan_object(). These locks are
1210 * enclosed by scan_mutex.
1211 */
1212 spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
1213 if (!color_white(object)) {
1214 /* non-orphan, ignored or new */
1215 spin_unlock(&object->lock);
1216 continue;
1217 }
1218
1219 /*
1220 * Increase the object's reference count (number of pointers
1221 * to the memory block). If this count reaches the required
1222 * minimum, the object's color will become gray and it will be
1223 * added to the gray_list.
1224 */
1225 object->count++;
1226 if (color_gray(object)) {
1227 /* put_object() called when removing from gray_list */
1228 WARN_ON(!get_object(object));
1229 list_add_tail(&object->gray_list, &gray_list);
1230 }
1231 spin_unlock(&object->lock);
1232 }
1233 read_unlock_irqrestore(&kmemleak_lock, flags);
1234 }
1235
1236 /*
1237 * Scan a large memory block in MAX_SCAN_SIZE chunks to reduce the latency.
1238 */
1239 static void scan_large_block(void *start, void *end)
1240 {
1241 void *next;
1242
1243 while (start < end) {
1244 next = min(start + MAX_SCAN_SIZE, end);
1245 scan_block(start, next, NULL);
1246 start = next;
1247 cond_resched();
1248 }
1249 }
1250
1251 /*
1252 * Scan a memory block corresponding to a kmemleak_object. A condition is
1253 * that object->use_count >= 1.
1254 */
1255 static void scan_object(struct kmemleak_object *object)
1256 {
1257 struct kmemleak_scan_area *area;
1258 unsigned long flags;
1259
1260 /*
1261 * Once the object->lock is acquired, the corresponding memory block
1262 * cannot be freed (the same lock is acquired in delete_object).
1263 */
1264 spin_lock_irqsave(&object->lock, flags);
1265 if (object->flags & OBJECT_NO_SCAN)
1266 goto out;
1267 if (!(object->flags & OBJECT_ALLOCATED))
1268 /* already freed object */
1269 goto out;
1270 if (hlist_empty(&object->area_list)) {
1271 void *start = (void *)object->pointer;
1272 void *end = (void *)(object->pointer + object->size);
1273 void *next;
1274
1275 do {
1276 next = min(start + MAX_SCAN_SIZE, end);
1277 scan_block(start, next, object);
1278
1279 start = next;
1280 if (start >= end)
1281 break;
1282
1283 spin_unlock_irqrestore(&object->lock, flags);
1284 cond_resched();
1285 spin_lock_irqsave(&object->lock, flags);
1286 } while (object->flags & OBJECT_ALLOCATED);
1287 } else
1288 hlist_for_each_entry(area, &object->area_list, node)
1289 scan_block((void *)area->start,
1290 (void *)(area->start + area->size),
1291 object);
1292 out:
1293 spin_unlock_irqrestore(&object->lock, flags);
1294 }
1295
1296 /*
1297 * Scan the objects already referenced (gray objects). More objects will be
1298 * referenced and, if there are no memory leaks, all the objects are scanned.
1299 */
1300 static void scan_gray_list(void)
1301 {
1302 struct kmemleak_object *object, *tmp;
1303
1304 /*
1305 * The list traversal is safe for both tail additions and removals
1306 * from inside the loop. The kmemleak objects cannot be freed from
1307 * outside the loop because their use_count was incremented.
1308 */
1309 object = list_entry(gray_list.next, typeof(*object), gray_list);
1310 while (&object->gray_list != &gray_list) {
1311 cond_resched();
1312
1313 /* may add new objects to the list */
1314 if (!scan_should_stop())
1315 scan_object(object);
1316
1317 tmp = list_entry(object->gray_list.next, typeof(*object),
1318 gray_list);
1319
1320 /* remove the object from the list and release it */
1321 list_del(&object->gray_list);
1322 put_object(object);
1323
1324 object = tmp;
1325 }
1326 WARN_ON(!list_empty(&gray_list));
1327 }
1328
1329 /*
1330 * Scan data sections and all the referenced memory blocks allocated via the
1331 * kernel's standard allocators. This function must be called with the
1332 * scan_mutex held.
1333 */
1334 static void kmemleak_scan(void)
1335 {
1336 unsigned long flags;
1337 struct kmemleak_object *object;
1338 int i;
1339 int new_leaks = 0;
1340
1341 jiffies_last_scan = jiffies;
1342
1343 /* prepare the kmemleak_object's */
1344 rcu_read_lock();
1345 list_for_each_entry_rcu(object, &object_list, object_list) {
1346 spin_lock_irqsave(&object->lock, flags);
1347 #ifdef DEBUG
1348 /*
1349 * With a few exceptions there should be a maximum of
1350 * 1 reference to any object at this point.
1351 */
1352 if (atomic_read(&object->use_count) > 1) {
1353 pr_debug("object->use_count = %d\n",
1354 atomic_read(&object->use_count));
1355 dump_object_info(object);
1356 }
1357 #endif
1358 /* reset the reference count (whiten the object) */
1359 object->count = 0;
1360 if (color_gray(object) && get_object(object))
1361 list_add_tail(&object->gray_list, &gray_list);
1362
1363 spin_unlock_irqrestore(&object->lock, flags);
1364 }
1365 rcu_read_unlock();
1366
1367 /* data/bss scanning */
1368 scan_large_block(_sdata, _edata);
1369 scan_large_block(__bss_start, __bss_stop);
1370
1371 #ifdef CONFIG_SMP
1372 /* per-cpu sections scanning */
1373 for_each_possible_cpu(i)
1374 scan_large_block(__per_cpu_start + per_cpu_offset(i),
1375 __per_cpu_end + per_cpu_offset(i));
1376 #endif
1377
1378 /*
1379 * Struct page scanning for each node.
1380 */
1381 get_online_mems();
1382 for_each_online_node(i) {
1383 unsigned long start_pfn = node_start_pfn(i);
1384 unsigned long end_pfn = node_end_pfn(i);
1385 unsigned long pfn;
1386
1387 for (pfn = start_pfn; pfn < end_pfn; pfn++) {
1388 struct page *page;
1389
1390 if (!pfn_valid(pfn))
1391 continue;
1392 page = pfn_to_page(pfn);
1393 /* only scan if page is in use */
1394 if (page_count(page) == 0)
1395 continue;
1396 scan_block(page, page + 1, NULL);
1397 }
1398 }
1399 put_online_mems();
1400
1401 /*
1402 * Scanning the task stacks (may introduce false negatives).
1403 */
1404 if (kmemleak_stack_scan) {
1405 struct task_struct *p, *g;
1406
1407 read_lock(&tasklist_lock);
1408 do_each_thread(g, p) {
1409 scan_block(task_stack_page(p), task_stack_page(p) +
1410 THREAD_SIZE, NULL);
1411 } while_each_thread(g, p);
1412 read_unlock(&tasklist_lock);
1413 }
1414
1415 /*
1416 * Scan the objects already referenced from the sections scanned
1417 * above.
1418 */
1419 scan_gray_list();
1420
1421 /*
1422 * Check for new or unreferenced objects modified since the previous
1423 * scan and color them gray until the next scan.
1424 */
1425 rcu_read_lock();
1426 list_for_each_entry_rcu(object, &object_list, object_list) {
1427 spin_lock_irqsave(&object->lock, flags);
1428 if (color_white(object) && (object->flags & OBJECT_ALLOCATED)
1429 && update_checksum(object) && get_object(object)) {
1430 /* color it gray temporarily */
1431 object->count = object->min_count;
1432 list_add_tail(&object->gray_list, &gray_list);
1433 }
1434 spin_unlock_irqrestore(&object->lock, flags);
1435 }
1436 rcu_read_unlock();
1437
1438 /*
1439 * Re-scan the gray list for modified unreferenced objects.
1440 */
1441 scan_gray_list();
1442
1443 /*
1444 * If scanning was stopped do not report any new unreferenced objects.
1445 */
1446 if (scan_should_stop())
1447 return;
1448
1449 /*
1450 * Scanning result reporting.
1451 */
1452 rcu_read_lock();
1453 list_for_each_entry_rcu(object, &object_list, object_list) {
1454 spin_lock_irqsave(&object->lock, flags);
1455 if (unreferenced_object(object) &&
1456 !(object->flags & OBJECT_REPORTED)) {
1457 object->flags |= OBJECT_REPORTED;
1458 new_leaks++;
1459 }
1460 spin_unlock_irqrestore(&object->lock, flags);
1461 }
1462 rcu_read_unlock();
1463
1464 if (new_leaks) {
1465 kmemleak_found_leaks = true;
1466
1467 pr_info("%d new suspected memory leaks (see "
1468 "/sys/kernel/debug/kmemleak)\n", new_leaks);
1469 }
1470
1471 }
1472
1473 /*
1474 * Thread function performing automatic memory scanning. Unreferenced objects
1475 * at the end of a memory scan are reported but only the first time.
1476 */
1477 static int kmemleak_scan_thread(void *arg)
1478 {
1479 static int first_run = 1;
1480
1481 pr_info("Automatic memory scanning thread started\n");
1482 set_user_nice(current, 10);
1483
1484 /*
1485 * Wait before the first scan to allow the system to fully initialize.
1486 */
1487 if (first_run) {
1488 first_run = 0;
1489 ssleep(SECS_FIRST_SCAN);
1490 }
1491
1492 while (!kthread_should_stop()) {
1493 signed long timeout = jiffies_scan_wait;
1494
1495 mutex_lock(&scan_mutex);
1496 kmemleak_scan();
1497 mutex_unlock(&scan_mutex);
1498
1499 /* wait before the next scan */
1500 while (timeout && !kthread_should_stop())
1501 timeout = schedule_timeout_interruptible(timeout);
1502 }
1503
1504 pr_info("Automatic memory scanning thread ended\n");
1505
1506 return 0;
1507 }
1508
1509 /*
1510 * Start the automatic memory scanning thread. This function must be called
1511 * with the scan_mutex held.
1512 */
1513 static void start_scan_thread(void)
1514 {
1515 if (scan_thread)
1516 return;
1517 scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
1518 if (IS_ERR(scan_thread)) {
1519 pr_warning("Failed to create the scan thread\n");
1520 scan_thread = NULL;
1521 }
1522 }
1523
1524 /*
1525 * Stop the automatic memory scanning thread. This function must be called
1526 * with the scan_mutex held.
1527 */
1528 static void stop_scan_thread(void)
1529 {
1530 if (scan_thread) {
1531 kthread_stop(scan_thread);
1532 scan_thread = NULL;
1533 }
1534 }
1535
1536 /*
1537 * Iterate over the object_list and return the first valid object at or after
1538 * the required position with its use_count incremented. The function triggers
1539 * a memory scanning when the pos argument points to the first position.
1540 */
1541 static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
1542 {
1543 struct kmemleak_object *object;
1544 loff_t n = *pos;
1545 int err;
1546
1547 err = mutex_lock_interruptible(&scan_mutex);
1548 if (err < 0)
1549 return ERR_PTR(err);
1550
1551 rcu_read_lock();
1552 list_for_each_entry_rcu(object, &object_list, object_list) {
1553 if (n-- > 0)
1554 continue;
1555 if (get_object(object))
1556 goto out;
1557 }
1558 object = NULL;
1559 out:
1560 return object;
1561 }
1562
1563 /*
1564 * Return the next object in the object_list. The function decrements the
1565 * use_count of the previous object and increases that of the next one.
1566 */
1567 static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1568 {
1569 struct kmemleak_object *prev_obj = v;
1570 struct kmemleak_object *next_obj = NULL;
1571 struct kmemleak_object *obj = prev_obj;
1572
1573 ++(*pos);
1574
1575 list_for_each_entry_continue_rcu(obj, &object_list, object_list) {
1576 if (get_object(obj)) {
1577 next_obj = obj;
1578 break;
1579 }
1580 }
1581
1582 put_object(prev_obj);
1583 return next_obj;
1584 }
1585
1586 /*
1587 * Decrement the use_count of the last object required, if any.
1588 */
1589 static void kmemleak_seq_stop(struct seq_file *seq, void *v)
1590 {
1591 if (!IS_ERR(v)) {
1592 /*
1593 * kmemleak_seq_start may return ERR_PTR if the scan_mutex
1594 * waiting was interrupted, so only release it if !IS_ERR.
1595 */
1596 rcu_read_unlock();
1597 mutex_unlock(&scan_mutex);
1598 if (v)
1599 put_object(v);
1600 }
1601 }
1602
1603 /*
1604 * Print the information for an unreferenced object to the seq file.
1605 */
1606 static int kmemleak_seq_show(struct seq_file *seq, void *v)
1607 {
1608 struct kmemleak_object *object = v;
1609 unsigned long flags;
1610
1611 spin_lock_irqsave(&object->lock, flags);
1612 if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1613 print_unreferenced(seq, object);
1614 spin_unlock_irqrestore(&object->lock, flags);
1615 return 0;
1616 }
1617
1618 static const struct seq_operations kmemleak_seq_ops = {
1619 .start = kmemleak_seq_start,
1620 .next = kmemleak_seq_next,
1621 .stop = kmemleak_seq_stop,
1622 .show = kmemleak_seq_show,
1623 };
1624
1625 static int kmemleak_open(struct inode *inode, struct file *file)
1626 {
1627 return seq_open(file, &kmemleak_seq_ops);
1628 }
1629
1630 static int dump_str_object_info(const char *str)
1631 {
1632 unsigned long flags;
1633 struct kmemleak_object *object;
1634 unsigned long addr;
1635
1636 if (kstrtoul(str, 0, &addr))
1637 return -EINVAL;
1638 object = find_and_get_object(addr, 0);
1639 if (!object) {
1640 pr_info("Unknown object at 0x%08lx\n", addr);
1641 return -EINVAL;
1642 }
1643
1644 spin_lock_irqsave(&object->lock, flags);
1645 dump_object_info(object);
1646 spin_unlock_irqrestore(&object->lock, flags);
1647
1648 put_object(object);
1649 return 0;
1650 }
1651
1652 /*
1653 * We use grey instead of black to ensure we can do future scans on the same
1654 * objects. If we did not do future scans these black objects could
1655 * potentially contain references to newly allocated objects in the future and
1656 * we'd end up with false positives.
1657 */
1658 static void kmemleak_clear(void)
1659 {
1660 struct kmemleak_object *object;
1661 unsigned long flags;
1662
1663 rcu_read_lock();
1664 list_for_each_entry_rcu(object, &object_list, object_list) {
1665 spin_lock_irqsave(&object->lock, flags);
1666 if ((object->flags & OBJECT_REPORTED) &&
1667 unreferenced_object(object))
1668 __paint_it(object, KMEMLEAK_GREY);
1669 spin_unlock_irqrestore(&object->lock, flags);
1670 }
1671 rcu_read_unlock();
1672
1673 kmemleak_found_leaks = false;
1674 }
1675
1676 static void __kmemleak_do_cleanup(void);
1677
1678 /*
1679 * File write operation to configure kmemleak at run-time. The following
1680 * commands can be written to the /sys/kernel/debug/kmemleak file:
1681 * off - disable kmemleak (irreversible)
1682 * stack=on - enable the task stacks scanning
1683 * stack=off - disable the tasks stacks scanning
1684 * scan=on - start the automatic memory scanning thread
1685 * scan=off - stop the automatic memory scanning thread
1686 * scan=... - set the automatic memory scanning period in seconds (0 to
1687 * disable it)
1688 * scan - trigger a memory scan
1689 * clear - mark all current reported unreferenced kmemleak objects as
1690 * grey to ignore printing them, or free all kmemleak objects
1691 * if kmemleak has been disabled.
1692 * dump=... - dump information about the object found at the given address
1693 */
1694 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
1695 size_t size, loff_t *ppos)
1696 {
1697 char buf[64];
1698 int buf_size;
1699 int ret;
1700
1701 buf_size = min(size, (sizeof(buf) - 1));
1702 if (strncpy_from_user(buf, user_buf, buf_size) < 0)
1703 return -EFAULT;
1704 buf[buf_size] = 0;
1705
1706 ret = mutex_lock_interruptible(&scan_mutex);
1707 if (ret < 0)
1708 return ret;
1709
1710 if (strncmp(buf, "clear", 5) == 0) {
1711 if (kmemleak_enabled)
1712 kmemleak_clear();
1713 else
1714 __kmemleak_do_cleanup();
1715 goto out;
1716 }
1717
1718 if (!kmemleak_enabled) {
1719 ret = -EBUSY;
1720 goto out;
1721 }
1722
1723 if (strncmp(buf, "off", 3) == 0)
1724 kmemleak_disable();
1725 else if (strncmp(buf, "stack=on", 8) == 0)
1726 kmemleak_stack_scan = 1;
1727 else if (strncmp(buf, "stack=off", 9) == 0)
1728 kmemleak_stack_scan = 0;
1729 else if (strncmp(buf, "scan=on", 7) == 0)
1730 start_scan_thread();
1731 else if (strncmp(buf, "scan=off", 8) == 0)
1732 stop_scan_thread();
1733 else if (strncmp(buf, "scan=", 5) == 0) {
1734 unsigned long secs;
1735
1736 ret = kstrtoul(buf + 5, 0, &secs);
1737 if (ret < 0)
1738 goto out;
1739 stop_scan_thread();
1740 if (secs) {
1741 jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
1742 start_scan_thread();
1743 }
1744 } else if (strncmp(buf, "scan", 4) == 0)
1745 kmemleak_scan();
1746 else if (strncmp(buf, "dump=", 5) == 0)
1747 ret = dump_str_object_info(buf + 5);
1748 else
1749 ret = -EINVAL;
1750
1751 out:
1752 mutex_unlock(&scan_mutex);
1753 if (ret < 0)
1754 return ret;
1755
1756 /* ignore the rest of the buffer, only one command at a time */
1757 *ppos += size;
1758 return size;
1759 }
1760
1761 static const struct file_operations kmemleak_fops = {
1762 .owner = THIS_MODULE,
1763 .open = kmemleak_open,
1764 .read = seq_read,
1765 .write = kmemleak_write,
1766 .llseek = seq_lseek,
1767 .release = seq_release,
1768 };
1769
1770 static void __kmemleak_do_cleanup(void)
1771 {
1772 struct kmemleak_object *object;
1773
1774 rcu_read_lock();
1775 list_for_each_entry_rcu(object, &object_list, object_list)
1776 delete_object_full(object->pointer);
1777 rcu_read_unlock();
1778 }
1779
1780 /*
1781 * Stop the memory scanning thread and free the kmemleak internal objects if
1782 * no previous scan thread (otherwise, kmemleak may still have some useful
1783 * information on memory leaks).
1784 */
1785 static void kmemleak_do_cleanup(struct work_struct *work)
1786 {
1787 stop_scan_thread();
1788
1789 /*
1790 * Once the scan thread has stopped, it is safe to no longer track
1791 * object freeing. Ordering of the scan thread stopping and the memory
1792 * accesses below is guaranteed by the kthread_stop() function.
1793 */
1794 kmemleak_free_enabled = 0;
1795
1796 if (!kmemleak_found_leaks)
1797 __kmemleak_do_cleanup();
1798 else
1799 pr_info("Kmemleak disabled without freeing internal data. "
1800 "Reclaim the memory with \"echo clear > /sys/kernel/debug/kmemleak\"\n");
1801 }
1802
1803 static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup);
1804
1805 /*
1806 * Disable kmemleak. No memory allocation/freeing will be traced once this
1807 * function is called. Disabling kmemleak is an irreversible operation.
1808 */
1809 static void kmemleak_disable(void)
1810 {
1811 /* atomically check whether it was already invoked */
1812 if (cmpxchg(&kmemleak_error, 0, 1))
1813 return;
1814
1815 /* stop any memory operation tracing */
1816 kmemleak_enabled = 0;
1817
1818 /* check whether it is too early for a kernel thread */
1819 if (kmemleak_initialized)
1820 schedule_work(&cleanup_work);
1821 else
1822 kmemleak_free_enabled = 0;
1823
1824 pr_info("Kernel memory leak detector disabled\n");
1825 }
1826
1827 /*
1828 * Allow boot-time kmemleak disabling (enabled by default).
1829 */
1830 static int kmemleak_boot_config(char *str)
1831 {
1832 if (!str)
1833 return -EINVAL;
1834 if (strcmp(str, "off") == 0)
1835 kmemleak_disable();
1836 else if (strcmp(str, "on") == 0)
1837 kmemleak_skip_disable = 1;
1838 else
1839 return -EINVAL;
1840 return 0;
1841 }
1842 early_param("kmemleak", kmemleak_boot_config);
1843
1844 static void __init print_log_trace(struct early_log *log)
1845 {
1846 struct stack_trace trace;
1847
1848 trace.nr_entries = log->trace_len;
1849 trace.entries = log->trace;
1850
1851 pr_notice("Early log backtrace:\n");
1852 print_stack_trace(&trace, 2);
1853 }
1854
1855 /*
1856 * Kmemleak initialization.
1857 */
1858 void __init kmemleak_init(void)
1859 {
1860 int i;
1861 unsigned long flags;
1862
1863 #ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
1864 if (!kmemleak_skip_disable) {
1865 kmemleak_early_log = 0;
1866 kmemleak_disable();
1867 return;
1868 }
1869 #endif
1870
1871 jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
1872 jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
1873
1874 object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
1875 scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
1876
1877 if (crt_early_log > ARRAY_SIZE(early_log))
1878 pr_warning("Early log buffer exceeded (%d), please increase "
1879 "DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n", crt_early_log);
1880
1881 /* the kernel is still in UP mode, so disabling the IRQs is enough */
1882 local_irq_save(flags);
1883 kmemleak_early_log = 0;
1884 if (kmemleak_error) {
1885 local_irq_restore(flags);
1886 return;
1887 } else {
1888 kmemleak_enabled = 1;
1889 kmemleak_free_enabled = 1;
1890 }
1891 local_irq_restore(flags);
1892
1893 /*
1894 * This is the point where tracking allocations is safe. Automatic
1895 * scanning is started during the late initcall. Add the early logged
1896 * callbacks to the kmemleak infrastructure.
1897 */
1898 for (i = 0; i < crt_early_log; i++) {
1899 struct early_log *log = &early_log[i];
1900
1901 switch (log->op_type) {
1902 case KMEMLEAK_ALLOC:
1903 early_alloc(log);
1904 break;
1905 case KMEMLEAK_ALLOC_PERCPU:
1906 early_alloc_percpu(log);
1907 break;
1908 case KMEMLEAK_FREE:
1909 kmemleak_free(log->ptr);
1910 break;
1911 case KMEMLEAK_FREE_PART:
1912 kmemleak_free_part(log->ptr, log->size);
1913 break;
1914 case KMEMLEAK_FREE_PERCPU:
1915 kmemleak_free_percpu(log->ptr);
1916 break;
1917 case KMEMLEAK_NOT_LEAK:
1918 kmemleak_not_leak(log->ptr);
1919 break;
1920 case KMEMLEAK_IGNORE:
1921 kmemleak_ignore(log->ptr);
1922 break;
1923 case KMEMLEAK_SCAN_AREA:
1924 kmemleak_scan_area(log->ptr, log->size, GFP_KERNEL);
1925 break;
1926 case KMEMLEAK_NO_SCAN:
1927 kmemleak_no_scan(log->ptr);
1928 break;
1929 default:
1930 kmemleak_warn("Unknown early log operation: %d\n",
1931 log->op_type);
1932 }
1933
1934 if (kmemleak_warning) {
1935 print_log_trace(log);
1936 kmemleak_warning = 0;
1937 }
1938 }
1939 }
1940
1941 /*
1942 * Late initialization function.
1943 */
1944 static int __init kmemleak_late_init(void)
1945 {
1946 struct dentry *dentry;
1947
1948 kmemleak_initialized = 1;
1949
1950 if (kmemleak_error) {
1951 /*
1952 * Some error occurred and kmemleak was disabled. There is a
1953 * small chance that kmemleak_disable() was called immediately
1954 * after setting kmemleak_initialized and we may end up with
1955 * two clean-up threads but serialized by scan_mutex.
1956 */
1957 schedule_work(&cleanup_work);
1958 return -ENOMEM;
1959 }
1960
1961 dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
1962 &kmemleak_fops);
1963 if (!dentry)
1964 pr_warning("Failed to create the debugfs kmemleak file\n");
1965 mutex_lock(&scan_mutex);
1966 start_scan_thread();
1967 mutex_unlock(&scan_mutex);
1968
1969 pr_info("Kernel memory leak detector initialized\n");
1970
1971 return 0;
1972 }
1973 late_initcall(kmemleak_late_init);