4 * Copyright (C) 2008 ARM Limited
5 * Written by Catalin Marinas <catalin.marinas@arm.com>
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.
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.
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
21 * For more information on the algorithm and kmemleak usage, please see
22 * Documentation/kmemleak.txt.
27 * The following locks and mutexes are used by kmemleak:
29 * - kmemleak_lock (rwlock): protects the object_list modifications and
30 * accesses to the object_tree_root. The object_list is the main list
31 * holding the metadata (struct kmemleak_object) for the allocated memory
32 * blocks. The object_tree_root is a priority search tree used to look-up
33 * metadata based on a pointer to the corresponding memory block. The
34 * kmemleak_object structures are added to the object_list and
35 * object_tree_root in the create_object() function called from the
36 * kmemleak_alloc() callback and removed in delete_object() called from the
37 * kmemleak_free() callback
38 * - kmemleak_object.lock (spinlock): protects a kmemleak_object. Accesses to
39 * the metadata (e.g. count) are protected by this lock. Note that some
40 * members of this structure may be protected by other means (atomic or
41 * kmemleak_lock). This lock is also held when scanning the corresponding
42 * memory block to avoid the kernel freeing it via the kmemleak_free()
43 * callback. This is less heavyweight than holding a global lock like
44 * kmemleak_lock during scanning
45 * - scan_mutex (mutex): ensures that only one thread may scan the memory for
46 * unreferenced objects at a time. The gray_list contains the objects which
47 * are already referenced or marked as false positives and need to be
48 * scanned. This list is only modified during a scanning episode when the
49 * scan_mutex is held. At the end of a scan, the gray_list is always empty.
50 * Note that the kmemleak_object.use_count is incremented when an object is
51 * added to the gray_list and therefore cannot be freed. This mutex also
52 * prevents multiple users of the "kmemleak" debugfs file together with
53 * modifications to the memory scanning parameters including the scan_thread
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
64 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
66 #include <linux/init.h>
67 #include <linux/kernel.h>
68 #include <linux/list.h>
69 #include <linux/sched.h>
70 #include <linux/jiffies.h>
71 #include <linux/delay.h>
72 #include <linux/module.h>
73 #include <linux/kthread.h>
74 #include <linux/prio_tree.h>
75 #include <linux/gfp.h>
77 #include <linux/debugfs.h>
78 #include <linux/seq_file.h>
79 #include <linux/cpumask.h>
80 #include <linux/spinlock.h>
81 #include <linux/mutex.h>
82 #include <linux/rcupdate.h>
83 #include <linux/stacktrace.h>
84 #include <linux/cache.h>
85 #include <linux/percpu.h>
86 #include <linux/hardirq.h>
87 #include <linux/mmzone.h>
88 #include <linux/slab.h>
89 #include <linux/thread_info.h>
90 #include <linux/err.h>
91 #include <linux/uaccess.h>
92 #include <linux/string.h>
93 #include <linux/nodemask.h>
96 #include <asm/sections.h>
97 #include <asm/processor.h>
98 #include <asm/atomic.h>
100 #include <linux/kmemleak.h>
103 * Kmemleak configuration and common defines.
105 #define MAX_TRACE 16 /* stack trace length */
106 #define MSECS_MIN_AGE 5000 /* minimum object age for reporting */
107 #define SECS_FIRST_SCAN 60 /* delay before the first scan */
108 #define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */
109 #define GRAY_LIST_PASSES 25 /* maximum number of gray list scans */
110 #define MAX_SCAN_SIZE 4096 /* maximum size of a scanned block */
112 #define BYTES_PER_POINTER sizeof(void *)
114 /* GFP bitmask for kmemleak internal allocations */
115 #define GFP_KMEMLEAK_MASK (GFP_KERNEL | GFP_ATOMIC)
117 /* scanning area inside a memory block */
118 struct kmemleak_scan_area {
119 struct hlist_node node;
120 unsigned long offset;
125 * Structure holding the metadata for each allocated memory block.
126 * Modifications to such objects should be made while holding the
127 * object->lock. Insertions or deletions from object_list, gray_list or
128 * tree_node are already protected by the corresponding locks or mutex (see
129 * the notes on locking above). These objects are reference-counted
130 * (use_count) and freed using the RCU mechanism.
132 struct kmemleak_object {
134 unsigned long flags; /* object status flags */
135 struct list_head object_list;
136 struct list_head gray_list;
137 struct prio_tree_node tree_node;
138 struct rcu_head rcu; /* object_list lockless traversal */
139 /* object usage count; object freed when use_count == 0 */
141 unsigned long pointer;
143 /* minimum number of a pointers found before it is considered leak */
145 /* the total number of pointers found pointing to this object */
147 /* memory ranges to be scanned inside an object (empty for all) */
148 struct hlist_head area_list;
149 unsigned long trace[MAX_TRACE];
150 unsigned int trace_len;
151 unsigned long jiffies; /* creation timestamp */
152 pid_t pid; /* pid of the current task */
153 char comm[TASK_COMM_LEN]; /* executable name */
156 /* flag representing the memory block allocation status */
157 #define OBJECT_ALLOCATED (1 << 0)
158 /* flag set after the first reporting of an unreference object */
159 #define OBJECT_REPORTED (1 << 1)
160 /* flag set to not scan the object */
161 #define OBJECT_NO_SCAN (1 << 2)
162 /* flag set on newly allocated objects */
163 #define OBJECT_NEW (1 << 3)
165 /* the list of all allocated objects */
166 static LIST_HEAD(object_list);
167 /* the list of gray-colored objects (see color_gray comment below) */
168 static LIST_HEAD(gray_list);
169 /* prio search tree for object boundaries */
170 static struct prio_tree_root object_tree_root;
171 /* rw_lock protecting the access to object_list and prio_tree_root */
172 static DEFINE_RWLOCK(kmemleak_lock);
174 /* allocation caches for kmemleak internal data */
175 static struct kmem_cache *object_cache;
176 static struct kmem_cache *scan_area_cache;
178 /* set if tracing memory operations is enabled */
179 static atomic_t kmemleak_enabled = ATOMIC_INIT(0);
180 /* set in the late_initcall if there were no errors */
181 static atomic_t kmemleak_initialized = ATOMIC_INIT(0);
182 /* enables or disables early logging of the memory operations */
183 static atomic_t kmemleak_early_log = ATOMIC_INIT(1);
184 /* set if a fata kmemleak error has occurred */
185 static atomic_t kmemleak_error = ATOMIC_INIT(0);
187 /* minimum and maximum address that may be valid pointers */
188 static unsigned long min_addr = ULONG_MAX;
189 static unsigned long max_addr;
191 static struct task_struct *scan_thread;
192 /* used to avoid reporting of recently allocated objects */
193 static unsigned long jiffies_min_age;
194 static unsigned long jiffies_last_scan;
195 /* delay between automatic memory scannings */
196 static signed long jiffies_scan_wait;
197 /* enables or disables the task stacks scanning */
198 static int kmemleak_stack_scan = 1;
199 /* protects the memory scanning, parameters and debug/kmemleak file access */
200 static DEFINE_MUTEX(scan_mutex);
203 * Early object allocation/freeing logging. Kmemleak is initialized after the
204 * kernel allocator. However, both the kernel allocator and kmemleak may
205 * allocate memory blocks which need to be tracked. Kmemleak defines an
206 * arbitrary buffer to hold the allocation/freeing information before it is
210 /* kmemleak operation type for early logging */
222 * Structure holding the information passed to kmemleak callbacks during the
226 int op_type; /* kmemleak operation type */
227 const void *ptr; /* allocated/freed memory block */
228 size_t size; /* memory block size */
229 int min_count; /* minimum reference count */
230 unsigned long offset; /* scan area offset */
231 size_t length; /* scan area length */
234 /* early logging buffer and current position */
235 static struct early_log early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE];
236 static int crt_early_log;
238 static void kmemleak_disable(void);
241 * Print a warning and dump the stack trace.
243 #define kmemleak_warn(x...) do { \
249 * Macro invoked when a serious kmemleak condition occured and cannot be
250 * recovered from. Kmemleak will be disabled and further allocation/freeing
251 * tracing no longer available.
253 #define kmemleak_stop(x...) do { \
255 kmemleak_disable(); \
259 * Object colors, encoded with count and min_count:
260 * - white - orphan object, not enough references to it (count < min_count)
261 * - gray - not orphan, not marked as false positive (min_count == 0) or
262 * sufficient references to it (count >= min_count)
263 * - black - ignore, it doesn't contain references (e.g. text section)
264 * (min_count == -1). No function defined for this color.
265 * Newly created objects don't have any color assigned (object->count == -1)
266 * before the next memory scan when they become white.
268 static int color_white(const struct kmemleak_object *object)
270 return object->count != -1 && object->count < object->min_count;
273 static int color_gray(const struct kmemleak_object *object)
275 return object->min_count != -1 && object->count >= object->min_count;
278 static int color_black(const struct kmemleak_object *object)
280 return object->min_count == -1;
284 * Objects are considered unreferenced only if their color is white, they have
285 * not be deleted and have a minimum age to avoid false positives caused by
286 * pointers temporarily stored in CPU registers.
288 static int unreferenced_object(struct kmemleak_object *object)
290 return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
291 time_before_eq(object->jiffies + jiffies_min_age,
296 * Printing of the unreferenced objects information to the seq file. The
297 * print_unreferenced function must be called with the object->lock held.
299 static void print_unreferenced(struct seq_file *seq,
300 struct kmemleak_object *object)
304 seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
305 object->pointer, object->size);
306 seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu\n",
307 object->comm, object->pid, object->jiffies);
308 seq_printf(seq, " backtrace:\n");
310 for (i = 0; i < object->trace_len; i++) {
311 void *ptr = (void *)object->trace[i];
312 seq_printf(seq, " [<%p>] %pS\n", ptr, ptr);
317 * Print the kmemleak_object information. This function is used mainly for
318 * debugging special cases when kmemleak operations. It must be called with
319 * the object->lock held.
321 static void dump_object_info(struct kmemleak_object *object)
323 struct stack_trace trace;
325 trace.nr_entries = object->trace_len;
326 trace.entries = object->trace;
328 pr_notice("Object 0x%08lx (size %zu):\n",
329 object->tree_node.start, object->size);
330 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
331 object->comm, object->pid, object->jiffies);
332 pr_notice(" min_count = %d\n", object->min_count);
333 pr_notice(" count = %d\n", object->count);
334 pr_notice(" flags = 0x%lx\n", object->flags);
335 pr_notice(" backtrace:\n");
336 print_stack_trace(&trace, 4);
340 * Look-up a memory block metadata (kmemleak_object) in the priority search
341 * tree based on a pointer value. If alias is 0, only values pointing to the
342 * beginning of the memory block are allowed. The kmemleak_lock must be held
343 * when calling this function.
345 static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
347 struct prio_tree_node *node;
348 struct prio_tree_iter iter;
349 struct kmemleak_object *object;
351 prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr);
352 node = prio_tree_next(&iter);
354 object = prio_tree_entry(node, struct kmemleak_object,
356 if (!alias && object->pointer != ptr) {
357 kmemleak_warn("Found object by alias");
367 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
368 * that once an object's use_count reached 0, the RCU freeing was already
369 * registered and the object should no longer be used. This function must be
370 * called under the protection of rcu_read_lock().
372 static int get_object(struct kmemleak_object *object)
374 return atomic_inc_not_zero(&object->use_count);
378 * RCU callback to free a kmemleak_object.
380 static void free_object_rcu(struct rcu_head *rcu)
382 struct hlist_node *elem, *tmp;
383 struct kmemleak_scan_area *area;
384 struct kmemleak_object *object =
385 container_of(rcu, struct kmemleak_object, rcu);
388 * Once use_count is 0 (guaranteed by put_object), there is no other
389 * code accessing this object, hence no need for locking.
391 hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) {
393 kmem_cache_free(scan_area_cache, area);
395 kmem_cache_free(object_cache, object);
399 * Decrement the object use_count. Once the count is 0, free the object using
400 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
401 * delete_object() path, the delayed RCU freeing ensures that there is no
402 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
405 static void put_object(struct kmemleak_object *object)
407 if (!atomic_dec_and_test(&object->use_count))
410 /* should only get here after delete_object was called */
411 WARN_ON(object->flags & OBJECT_ALLOCATED);
413 call_rcu(&object->rcu, free_object_rcu);
417 * Look up an object in the prio search tree and increase its use_count.
419 static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
422 struct kmemleak_object *object = NULL;
425 read_lock_irqsave(&kmemleak_lock, flags);
426 if (ptr >= min_addr && ptr < max_addr)
427 object = lookup_object(ptr, alias);
428 read_unlock_irqrestore(&kmemleak_lock, flags);
430 /* check whether the object is still available */
431 if (object && !get_object(object))
439 * Create the metadata (struct kmemleak_object) corresponding to an allocated
440 * memory block and add it to the object_list and object_tree_root.
442 static void create_object(unsigned long ptr, size_t size, int min_count,
446 struct kmemleak_object *object;
447 struct prio_tree_node *node;
448 struct stack_trace trace;
450 object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK);
452 kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
456 INIT_LIST_HEAD(&object->object_list);
457 INIT_LIST_HEAD(&object->gray_list);
458 INIT_HLIST_HEAD(&object->area_list);
459 spin_lock_init(&object->lock);
460 atomic_set(&object->use_count, 1);
461 object->flags = OBJECT_ALLOCATED | OBJECT_NEW;
462 object->pointer = ptr;
464 object->min_count = min_count;
465 object->count = -1; /* no color initially */
466 object->jiffies = jiffies;
468 /* task information */
471 strncpy(object->comm, "hardirq", sizeof(object->comm));
472 } else if (in_softirq()) {
474 strncpy(object->comm, "softirq", sizeof(object->comm));
476 object->pid = current->pid;
478 * There is a small chance of a race with set_task_comm(),
479 * however using get_task_comm() here may cause locking
480 * dependency issues with current->alloc_lock. In the worst
481 * case, the command line is not correct.
483 strncpy(object->comm, current->comm, sizeof(object->comm));
486 /* kernel backtrace */
487 trace.max_entries = MAX_TRACE;
488 trace.nr_entries = 0;
489 trace.entries = object->trace;
491 save_stack_trace(&trace);
492 object->trace_len = trace.nr_entries;
494 INIT_PRIO_TREE_NODE(&object->tree_node);
495 object->tree_node.start = ptr;
496 object->tree_node.last = ptr + size - 1;
498 write_lock_irqsave(&kmemleak_lock, flags);
499 min_addr = min(min_addr, ptr);
500 max_addr = max(max_addr, ptr + size);
501 node = prio_tree_insert(&object_tree_root, &object->tree_node);
503 * The code calling the kernel does not yet have the pointer to the
504 * memory block to be able to free it. However, we still hold the
505 * kmemleak_lock here in case parts of the kernel started freeing
506 * random memory blocks.
508 if (node != &object->tree_node) {
511 kmemleak_stop("Cannot insert 0x%lx into the object search tree "
512 "(already existing)\n", ptr);
513 object = lookup_object(ptr, 1);
514 spin_lock_irqsave(&object->lock, flags);
515 dump_object_info(object);
516 spin_unlock_irqrestore(&object->lock, flags);
520 list_add_tail_rcu(&object->object_list, &object_list);
522 write_unlock_irqrestore(&kmemleak_lock, flags);
526 * Remove the metadata (struct kmemleak_object) for a memory block from the
527 * object_list and object_tree_root and decrement its use_count.
529 static void __delete_object(struct kmemleak_object *object)
533 write_lock_irqsave(&kmemleak_lock, flags);
534 prio_tree_remove(&object_tree_root, &object->tree_node);
535 list_del_rcu(&object->object_list);
536 write_unlock_irqrestore(&kmemleak_lock, flags);
538 WARN_ON(!(object->flags & OBJECT_ALLOCATED));
539 WARN_ON(atomic_read(&object->use_count) < 2);
542 * Locking here also ensures that the corresponding memory block
543 * cannot be freed when it is being scanned.
545 spin_lock_irqsave(&object->lock, flags);
546 object->flags &= ~OBJECT_ALLOCATED;
547 spin_unlock_irqrestore(&object->lock, flags);
552 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
555 static void delete_object_full(unsigned long ptr)
557 struct kmemleak_object *object;
559 object = find_and_get_object(ptr, 0);
562 kmemleak_warn("Freeing unknown object at 0x%08lx\n",
567 __delete_object(object);
572 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
573 * delete it. If the memory block is partially freed, the function may create
574 * additional metadata for the remaining parts of the block.
576 static void delete_object_part(unsigned long ptr, size_t size)
578 struct kmemleak_object *object;
579 unsigned long start, end;
581 object = find_and_get_object(ptr, 1);
584 kmemleak_warn("Partially freeing unknown object at 0x%08lx "
585 "(size %zu)\n", ptr, size);
589 __delete_object(object);
592 * Create one or two objects that may result from the memory block
593 * split. Note that partial freeing is only done by free_bootmem() and
594 * this happens before kmemleak_init() is called. The path below is
595 * only executed during early log recording in kmemleak_init(), so
596 * GFP_KERNEL is enough.
598 start = object->pointer;
599 end = object->pointer + object->size;
601 create_object(start, ptr - start, object->min_count,
603 if (ptr + size < end)
604 create_object(ptr + size, end - ptr - size, object->min_count,
610 * Make a object permanently as gray-colored so that it can no longer be
611 * reported as a leak. This is used in general to mark a false positive.
613 static void make_gray_object(unsigned long ptr)
616 struct kmemleak_object *object;
618 object = find_and_get_object(ptr, 0);
620 kmemleak_warn("Graying unknown object at 0x%08lx\n", ptr);
624 spin_lock_irqsave(&object->lock, flags);
625 object->min_count = 0;
626 spin_unlock_irqrestore(&object->lock, flags);
631 * Mark the object as black-colored so that it is ignored from scans and
634 static void make_black_object(unsigned long ptr)
637 struct kmemleak_object *object;
639 object = find_and_get_object(ptr, 0);
641 kmemleak_warn("Blacking unknown object at 0x%08lx\n", ptr);
645 spin_lock_irqsave(&object->lock, flags);
646 object->min_count = -1;
647 object->flags |= OBJECT_NO_SCAN;
648 spin_unlock_irqrestore(&object->lock, flags);
653 * Add a scanning area to the object. If at least one such area is added,
654 * kmemleak will only scan these ranges rather than the whole memory block.
656 static void add_scan_area(unsigned long ptr, unsigned long offset,
657 size_t length, gfp_t gfp)
660 struct kmemleak_object *object;
661 struct kmemleak_scan_area *area;
663 object = find_and_get_object(ptr, 0);
665 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
670 area = kmem_cache_alloc(scan_area_cache, gfp & GFP_KMEMLEAK_MASK);
672 kmemleak_warn("Cannot allocate a scan area\n");
676 spin_lock_irqsave(&object->lock, flags);
677 if (offset + length > object->size) {
678 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
679 dump_object_info(object);
680 kmem_cache_free(scan_area_cache, area);
684 INIT_HLIST_NODE(&area->node);
685 area->offset = offset;
686 area->length = length;
688 hlist_add_head(&area->node, &object->area_list);
690 spin_unlock_irqrestore(&object->lock, flags);
696 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
697 * pointer. Such object will not be scanned by kmemleak but references to it
700 static void object_no_scan(unsigned long ptr)
703 struct kmemleak_object *object;
705 object = find_and_get_object(ptr, 0);
707 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
711 spin_lock_irqsave(&object->lock, flags);
712 object->flags |= OBJECT_NO_SCAN;
713 spin_unlock_irqrestore(&object->lock, flags);
718 * Log an early kmemleak_* call to the early_log buffer. These calls will be
719 * processed later once kmemleak is fully initialized.
721 static void log_early(int op_type, const void *ptr, size_t size,
722 int min_count, unsigned long offset, size_t length)
725 struct early_log *log;
727 if (crt_early_log >= ARRAY_SIZE(early_log)) {
728 pr_warning("Early log buffer exceeded\n");
734 * There is no need for locking since the kernel is still in UP mode
735 * at this stage. Disabling the IRQs is enough.
737 local_irq_save(flags);
738 log = &early_log[crt_early_log];
739 log->op_type = op_type;
742 log->min_count = min_count;
743 log->offset = offset;
744 log->length = length;
746 local_irq_restore(flags);
750 * Memory allocation function callback. This function is called from the
751 * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc,
754 void kmemleak_alloc(const void *ptr, size_t size, int min_count, gfp_t gfp)
756 pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
758 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
759 create_object((unsigned long)ptr, size, min_count, gfp);
760 else if (atomic_read(&kmemleak_early_log))
761 log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
763 EXPORT_SYMBOL_GPL(kmemleak_alloc);
766 * Memory freeing function callback. This function is called from the kernel
767 * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.).
769 void kmemleak_free(const void *ptr)
771 pr_debug("%s(0x%p)\n", __func__, ptr);
773 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
774 delete_object_full((unsigned long)ptr);
775 else if (atomic_read(&kmemleak_early_log))
776 log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
778 EXPORT_SYMBOL_GPL(kmemleak_free);
781 * Partial memory freeing function callback. This function is usually called
782 * from bootmem allocator when (part of) a memory block is freed.
784 void kmemleak_free_part(const void *ptr, size_t size)
786 pr_debug("%s(0x%p)\n", __func__, ptr);
788 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
789 delete_object_part((unsigned long)ptr, size);
790 else if (atomic_read(&kmemleak_early_log))
791 log_early(KMEMLEAK_FREE_PART, ptr, size, 0, 0, 0);
793 EXPORT_SYMBOL_GPL(kmemleak_free_part);
796 * Mark an already allocated memory block as a false positive. This will cause
797 * the block to no longer be reported as leak and always be scanned.
799 void kmemleak_not_leak(const void *ptr)
801 pr_debug("%s(0x%p)\n", __func__, ptr);
803 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
804 make_gray_object((unsigned long)ptr);
805 else if (atomic_read(&kmemleak_early_log))
806 log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
808 EXPORT_SYMBOL(kmemleak_not_leak);
811 * Ignore a memory block. This is usually done when it is known that the
812 * corresponding block is not a leak and does not contain any references to
813 * other allocated memory blocks.
815 void kmemleak_ignore(const void *ptr)
817 pr_debug("%s(0x%p)\n", __func__, ptr);
819 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
820 make_black_object((unsigned long)ptr);
821 else if (atomic_read(&kmemleak_early_log))
822 log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
824 EXPORT_SYMBOL(kmemleak_ignore);
827 * Limit the range to be scanned in an allocated memory block.
829 void kmemleak_scan_area(const void *ptr, unsigned long offset, size_t length,
832 pr_debug("%s(0x%p)\n", __func__, ptr);
834 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
835 add_scan_area((unsigned long)ptr, offset, length, gfp);
836 else if (atomic_read(&kmemleak_early_log))
837 log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
839 EXPORT_SYMBOL(kmemleak_scan_area);
842 * Inform kmemleak not to scan the given memory block.
844 void kmemleak_no_scan(const void *ptr)
846 pr_debug("%s(0x%p)\n", __func__, ptr);
848 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
849 object_no_scan((unsigned long)ptr);
850 else if (atomic_read(&kmemleak_early_log))
851 log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0);
853 EXPORT_SYMBOL(kmemleak_no_scan);
856 * Memory scanning is a long process and it needs to be interruptable. This
857 * function checks whether such interrupt condition occured.
859 static int scan_should_stop(void)
861 if (!atomic_read(&kmemleak_enabled))
865 * This function may be called from either process or kthread context,
866 * hence the need to check for both stop conditions.
869 return signal_pending(current);
871 return kthread_should_stop();
877 * Scan a memory block (exclusive range) for valid pointers and add those
878 * found to the gray list.
880 static void scan_block(void *_start, void *_end,
881 struct kmemleak_object *scanned, int allow_resched)
884 unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
885 unsigned long *end = _end - (BYTES_PER_POINTER - 1);
887 for (ptr = start; ptr < end; ptr++) {
889 unsigned long pointer = *ptr;
890 struct kmemleak_object *object;
894 if (scan_should_stop())
897 object = find_and_get_object(pointer, 1);
900 if (object == scanned) {
901 /* self referenced, ignore */
907 * Avoid the lockdep recursive warning on object->lock being
908 * previously acquired in scan_object(). These locks are
909 * enclosed by scan_mutex.
911 spin_lock_irqsave_nested(&object->lock, flags,
912 SINGLE_DEPTH_NESTING);
913 if (!color_white(object)) {
914 /* non-orphan, ignored or new */
915 spin_unlock_irqrestore(&object->lock, flags);
921 * Increase the object's reference count (number of pointers
922 * to the memory block). If this count reaches the required
923 * minimum, the object's color will become gray and it will be
924 * added to the gray_list.
927 if (color_gray(object))
928 list_add_tail(&object->gray_list, &gray_list);
931 spin_unlock_irqrestore(&object->lock, flags);
936 * Scan a memory block corresponding to a kmemleak_object. A condition is
937 * that object->use_count >= 1.
939 static void scan_object(struct kmemleak_object *object)
941 struct kmemleak_scan_area *area;
942 struct hlist_node *elem;
946 * Once the object->lock is aquired, the corresponding memory block
947 * cannot be freed (the same lock is aquired in delete_object).
949 spin_lock_irqsave(&object->lock, flags);
950 if (object->flags & OBJECT_NO_SCAN)
952 if (!(object->flags & OBJECT_ALLOCATED))
953 /* already freed object */
955 if (hlist_empty(&object->area_list)) {
956 void *start = (void *)object->pointer;
957 void *end = (void *)(object->pointer + object->size);
959 while (start < end && (object->flags & OBJECT_ALLOCATED) &&
960 !(object->flags & OBJECT_NO_SCAN)) {
961 scan_block(start, min(start + MAX_SCAN_SIZE, end),
963 start += MAX_SCAN_SIZE;
965 spin_unlock_irqrestore(&object->lock, flags);
967 spin_lock_irqsave(&object->lock, flags);
970 hlist_for_each_entry(area, elem, &object->area_list, node)
971 scan_block((void *)(object->pointer + area->offset),
972 (void *)(object->pointer + area->offset
973 + area->length), object, 0);
975 spin_unlock_irqrestore(&object->lock, flags);
979 * Scan data sections and all the referenced memory blocks allocated via the
980 * kernel's standard allocators. This function must be called with the
983 static void kmemleak_scan(void)
986 struct kmemleak_object *object, *tmp;
987 struct task_struct *task;
990 int gray_list_pass = 0;
992 jiffies_last_scan = jiffies;
994 /* prepare the kmemleak_object's */
996 list_for_each_entry_rcu(object, &object_list, object_list) {
997 spin_lock_irqsave(&object->lock, flags);
1000 * With a few exceptions there should be a maximum of
1001 * 1 reference to any object at this point.
1003 if (atomic_read(&object->use_count) > 1) {
1004 pr_debug("object->use_count = %d\n",
1005 atomic_read(&object->use_count));
1006 dump_object_info(object);
1009 /* reset the reference count (whiten the object) */
1011 object->flags &= ~OBJECT_NEW;
1012 if (color_gray(object) && get_object(object))
1013 list_add_tail(&object->gray_list, &gray_list);
1015 spin_unlock_irqrestore(&object->lock, flags);
1019 /* data/bss scanning */
1020 scan_block(_sdata, _edata, NULL, 1);
1021 scan_block(__bss_start, __bss_stop, NULL, 1);
1024 /* per-cpu sections scanning */
1025 for_each_possible_cpu(i)
1026 scan_block(__per_cpu_start + per_cpu_offset(i),
1027 __per_cpu_end + per_cpu_offset(i), NULL, 1);
1031 * Struct page scanning for each node. The code below is not yet safe
1032 * with MEMORY_HOTPLUG.
1034 for_each_online_node(i) {
1035 pg_data_t *pgdat = NODE_DATA(i);
1036 unsigned long start_pfn = pgdat->node_start_pfn;
1037 unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
1040 for (pfn = start_pfn; pfn < end_pfn; pfn++) {
1043 if (!pfn_valid(pfn))
1045 page = pfn_to_page(pfn);
1046 /* only scan if page is in use */
1047 if (page_count(page) == 0)
1049 scan_block(page, page + 1, NULL, 1);
1054 * Scanning the task stacks may introduce false negatives and it is
1055 * not enabled by default.
1057 if (kmemleak_stack_scan) {
1058 read_lock(&tasklist_lock);
1059 for_each_process(task)
1060 scan_block(task_stack_page(task),
1061 task_stack_page(task) + THREAD_SIZE,
1063 read_unlock(&tasklist_lock);
1067 * Scan the objects already referenced from the sections scanned
1068 * above. More objects will be referenced and, if there are no memory
1069 * leaks, all the objects will be scanned. The list traversal is safe
1070 * for both tail additions and removals from inside the loop. The
1071 * kmemleak objects cannot be freed from outside the loop because their
1072 * use_count was increased.
1075 object = list_entry(gray_list.next, typeof(*object), gray_list);
1076 while (&object->gray_list != &gray_list) {
1079 /* may add new objects to the list */
1080 if (!scan_should_stop())
1081 scan_object(object);
1083 tmp = list_entry(object->gray_list.next, typeof(*object),
1086 /* remove the object from the list and release it */
1087 list_del(&object->gray_list);
1093 if (scan_should_stop() || ++gray_list_pass >= GRAY_LIST_PASSES)
1097 * Check for new objects allocated during this scanning and add them
1101 list_for_each_entry_rcu(object, &object_list, object_list) {
1102 spin_lock_irqsave(&object->lock, flags);
1103 if ((object->flags & OBJECT_NEW) && !color_black(object) &&
1104 get_object(object)) {
1105 object->flags &= ~OBJECT_NEW;
1106 list_add_tail(&object->gray_list, &gray_list);
1108 spin_unlock_irqrestore(&object->lock, flags);
1112 if (!list_empty(&gray_list))
1116 WARN_ON(!list_empty(&gray_list));
1119 * If scanning was stopped or new objects were being allocated at a
1120 * higher rate than gray list scanning, do not report any new
1121 * unreferenced objects.
1123 if (scan_should_stop() || gray_list_pass >= GRAY_LIST_PASSES)
1127 * Scanning result reporting.
1130 list_for_each_entry_rcu(object, &object_list, object_list) {
1131 spin_lock_irqsave(&object->lock, flags);
1132 if (unreferenced_object(object) &&
1133 !(object->flags & OBJECT_REPORTED)) {
1134 object->flags |= OBJECT_REPORTED;
1137 spin_unlock_irqrestore(&object->lock, flags);
1142 pr_info("%d new suspected memory leaks (see "
1143 "/sys/kernel/debug/kmemleak)\n", new_leaks);
1148 * Thread function performing automatic memory scanning. Unreferenced objects
1149 * at the end of a memory scan are reported but only the first time.
1151 static int kmemleak_scan_thread(void *arg)
1153 static int first_run = 1;
1155 pr_info("Automatic memory scanning thread started\n");
1156 set_user_nice(current, 10);
1159 * Wait before the first scan to allow the system to fully initialize.
1163 ssleep(SECS_FIRST_SCAN);
1166 while (!kthread_should_stop()) {
1167 signed long timeout = jiffies_scan_wait;
1169 mutex_lock(&scan_mutex);
1171 mutex_unlock(&scan_mutex);
1173 /* wait before the next scan */
1174 while (timeout && !kthread_should_stop())
1175 timeout = schedule_timeout_interruptible(timeout);
1178 pr_info("Automatic memory scanning thread ended\n");
1184 * Start the automatic memory scanning thread. This function must be called
1185 * with the scan_mutex held.
1187 void start_scan_thread(void)
1191 scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
1192 if (IS_ERR(scan_thread)) {
1193 pr_warning("Failed to create the scan thread\n");
1199 * Stop the automatic memory scanning thread. This function must be called
1200 * with the scan_mutex held.
1202 void stop_scan_thread(void)
1205 kthread_stop(scan_thread);
1211 * Iterate over the object_list and return the first valid object at or after
1212 * the required position with its use_count incremented. The function triggers
1213 * a memory scanning when the pos argument points to the first position.
1215 static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
1217 struct kmemleak_object *object;
1221 err = mutex_lock_interruptible(&scan_mutex);
1223 return ERR_PTR(err);
1226 list_for_each_entry_rcu(object, &object_list, object_list) {
1229 if (get_object(object))
1238 * Return the next object in the object_list. The function decrements the
1239 * use_count of the previous object and increases that of the next one.
1241 static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1243 struct kmemleak_object *prev_obj = v;
1244 struct kmemleak_object *next_obj = NULL;
1245 struct list_head *n = &prev_obj->object_list;
1249 list_for_each_continue_rcu(n, &object_list) {
1250 next_obj = list_entry(n, struct kmemleak_object, object_list);
1251 if (get_object(next_obj))
1255 put_object(prev_obj);
1260 * Decrement the use_count of the last object required, if any.
1262 static void kmemleak_seq_stop(struct seq_file *seq, void *v)
1266 * kmemleak_seq_start may return ERR_PTR if the scan_mutex
1267 * waiting was interrupted, so only release it if !IS_ERR.
1270 mutex_unlock(&scan_mutex);
1277 * Print the information for an unreferenced object to the seq file.
1279 static int kmemleak_seq_show(struct seq_file *seq, void *v)
1281 struct kmemleak_object *object = v;
1282 unsigned long flags;
1284 spin_lock_irqsave(&object->lock, flags);
1285 if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1286 print_unreferenced(seq, object);
1287 spin_unlock_irqrestore(&object->lock, flags);
1291 static const struct seq_operations kmemleak_seq_ops = {
1292 .start = kmemleak_seq_start,
1293 .next = kmemleak_seq_next,
1294 .stop = kmemleak_seq_stop,
1295 .show = kmemleak_seq_show,
1298 static int kmemleak_open(struct inode *inode, struct file *file)
1300 if (!atomic_read(&kmemleak_enabled))
1303 return seq_open(file, &kmemleak_seq_ops);
1306 static int kmemleak_release(struct inode *inode, struct file *file)
1308 return seq_release(inode, file);
1311 static int dump_str_object_info(const char *str)
1313 unsigned long flags;
1314 struct kmemleak_object *object;
1317 addr= simple_strtoul(str, NULL, 0);
1318 object = find_and_get_object(addr, 0);
1320 pr_info("Unknown object at 0x%08lx\n", addr);
1324 spin_lock_irqsave(&object->lock, flags);
1325 dump_object_info(object);
1326 spin_unlock_irqrestore(&object->lock, flags);
1333 * File write operation to configure kmemleak at run-time. The following
1334 * commands can be written to the /sys/kernel/debug/kmemleak file:
1335 * off - disable kmemleak (irreversible)
1336 * stack=on - enable the task stacks scanning
1337 * stack=off - disable the tasks stacks scanning
1338 * scan=on - start the automatic memory scanning thread
1339 * scan=off - stop the automatic memory scanning thread
1340 * scan=... - set the automatic memory scanning period in seconds (0 to
1342 * scan - trigger a memory scan
1343 * dump=... - dump information about the object found at the given address
1345 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
1346 size_t size, loff_t *ppos)
1352 buf_size = min(size, (sizeof(buf) - 1));
1353 if (strncpy_from_user(buf, user_buf, buf_size) < 0)
1357 ret = mutex_lock_interruptible(&scan_mutex);
1361 if (strncmp(buf, "off", 3) == 0)
1363 else if (strncmp(buf, "stack=on", 8) == 0)
1364 kmemleak_stack_scan = 1;
1365 else if (strncmp(buf, "stack=off", 9) == 0)
1366 kmemleak_stack_scan = 0;
1367 else if (strncmp(buf, "scan=on", 7) == 0)
1368 start_scan_thread();
1369 else if (strncmp(buf, "scan=off", 8) == 0)
1371 else if (strncmp(buf, "scan=", 5) == 0) {
1374 ret = strict_strtoul(buf + 5, 0, &secs);
1379 jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
1380 start_scan_thread();
1382 } else if (strncmp(buf, "scan", 4) == 0)
1384 else if (strncmp(buf, "dump=", 5) == 0)
1385 ret = dump_str_object_info(buf + 5);
1390 mutex_unlock(&scan_mutex);
1394 /* ignore the rest of the buffer, only one command at a time */
1399 static const struct file_operations kmemleak_fops = {
1400 .owner = THIS_MODULE,
1401 .open = kmemleak_open,
1403 .write = kmemleak_write,
1404 .llseek = seq_lseek,
1405 .release = kmemleak_release,
1409 * Perform the freeing of the kmemleak internal objects after waiting for any
1410 * current memory scan to complete.
1412 static int kmemleak_cleanup_thread(void *arg)
1414 struct kmemleak_object *object;
1416 mutex_lock(&scan_mutex);
1420 list_for_each_entry_rcu(object, &object_list, object_list)
1421 delete_object_full(object->pointer);
1423 mutex_unlock(&scan_mutex);
1429 * Start the clean-up thread.
1431 static void kmemleak_cleanup(void)
1433 struct task_struct *cleanup_thread;
1435 cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL,
1437 if (IS_ERR(cleanup_thread))
1438 pr_warning("Failed to create the clean-up thread\n");
1442 * Disable kmemleak. No memory allocation/freeing will be traced once this
1443 * function is called. Disabling kmemleak is an irreversible operation.
1445 static void kmemleak_disable(void)
1447 /* atomically check whether it was already invoked */
1448 if (atomic_cmpxchg(&kmemleak_error, 0, 1))
1451 /* stop any memory operation tracing */
1452 atomic_set(&kmemleak_early_log, 0);
1453 atomic_set(&kmemleak_enabled, 0);
1455 /* check whether it is too early for a kernel thread */
1456 if (atomic_read(&kmemleak_initialized))
1459 pr_info("Kernel memory leak detector disabled\n");
1463 * Allow boot-time kmemleak disabling (enabled by default).
1465 static int kmemleak_boot_config(char *str)
1469 if (strcmp(str, "off") == 0)
1471 else if (strcmp(str, "on") != 0)
1475 early_param("kmemleak", kmemleak_boot_config);
1478 * Kmemleak initialization.
1480 void __init kmemleak_init(void)
1483 unsigned long flags;
1485 jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
1486 jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
1488 object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
1489 scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
1490 INIT_PRIO_TREE_ROOT(&object_tree_root);
1492 /* the kernel is still in UP mode, so disabling the IRQs is enough */
1493 local_irq_save(flags);
1494 if (!atomic_read(&kmemleak_error)) {
1495 atomic_set(&kmemleak_enabled, 1);
1496 atomic_set(&kmemleak_early_log, 0);
1498 local_irq_restore(flags);
1501 * This is the point where tracking allocations is safe. Automatic
1502 * scanning is started during the late initcall. Add the early logged
1503 * callbacks to the kmemleak infrastructure.
1505 for (i = 0; i < crt_early_log; i++) {
1506 struct early_log *log = &early_log[i];
1508 switch (log->op_type) {
1509 case KMEMLEAK_ALLOC:
1510 kmemleak_alloc(log->ptr, log->size, log->min_count,
1514 kmemleak_free(log->ptr);
1516 case KMEMLEAK_FREE_PART:
1517 kmemleak_free_part(log->ptr, log->size);
1519 case KMEMLEAK_NOT_LEAK:
1520 kmemleak_not_leak(log->ptr);
1522 case KMEMLEAK_IGNORE:
1523 kmemleak_ignore(log->ptr);
1525 case KMEMLEAK_SCAN_AREA:
1526 kmemleak_scan_area(log->ptr, log->offset, log->length,
1529 case KMEMLEAK_NO_SCAN:
1530 kmemleak_no_scan(log->ptr);
1539 * Late initialization function.
1541 static int __init kmemleak_late_init(void)
1543 struct dentry *dentry;
1545 atomic_set(&kmemleak_initialized, 1);
1547 if (atomic_read(&kmemleak_error)) {
1549 * Some error occured and kmemleak was disabled. There is a
1550 * small chance that kmemleak_disable() was called immediately
1551 * after setting kmemleak_initialized and we may end up with
1552 * two clean-up threads but serialized by scan_mutex.
1558 dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
1561 pr_warning("Failed to create the debugfs kmemleak file\n");
1562 mutex_lock(&scan_mutex);
1563 start_scan_thread();
1564 mutex_unlock(&scan_mutex);
1566 pr_info("Kernel memory leak detector initialized\n");
1570 late_initcall(kmemleak_late_init);