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 */
232 unsigned long trace[MAX_TRACE]; /* stack trace */
233 unsigned int trace_len; /* stack trace length */
236 /* early logging buffer and current position */
237 static struct early_log
238 early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
239 static int crt_early_log __initdata;
241 static void kmemleak_disable(void);
244 * Print a warning and dump the stack trace.
246 #define kmemleak_warn(x...) do { \
252 * Macro invoked when a serious kmemleak condition occured and cannot be
253 * recovered from. Kmemleak will be disabled and further allocation/freeing
254 * tracing no longer available.
256 #define kmemleak_stop(x...) do { \
258 kmemleak_disable(); \
262 * Object colors, encoded with count and min_count:
263 * - white - orphan object, not enough references to it (count < min_count)
264 * - gray - not orphan, not marked as false positive (min_count == 0) or
265 * sufficient references to it (count >= min_count)
266 * - black - ignore, it doesn't contain references (e.g. text section)
267 * (min_count == -1). No function defined for this color.
268 * Newly created objects don't have any color assigned (object->count == -1)
269 * before the next memory scan when they become white.
271 static int color_white(const struct kmemleak_object *object)
273 return object->count != -1 && object->count < object->min_count;
276 static int color_gray(const struct kmemleak_object *object)
278 return object->min_count != -1 && object->count >= object->min_count;
281 static int color_black(const struct kmemleak_object *object)
283 return object->min_count == -1;
287 * Objects are considered unreferenced only if their color is white, they have
288 * not be deleted and have a minimum age to avoid false positives caused by
289 * pointers temporarily stored in CPU registers.
291 static int unreferenced_object(struct kmemleak_object *object)
293 return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
294 time_before_eq(object->jiffies + jiffies_min_age,
299 * Printing of the unreferenced objects information to the seq file. The
300 * print_unreferenced function must be called with the object->lock held.
302 static void print_unreferenced(struct seq_file *seq,
303 struct kmemleak_object *object)
307 seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
308 object->pointer, object->size);
309 seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu\n",
310 object->comm, object->pid, object->jiffies);
311 seq_printf(seq, " backtrace:\n");
313 for (i = 0; i < object->trace_len; i++) {
314 void *ptr = (void *)object->trace[i];
315 seq_printf(seq, " [<%p>] %pS\n", ptr, ptr);
320 * Print the kmemleak_object information. This function is used mainly for
321 * debugging special cases when kmemleak operations. It must be called with
322 * the object->lock held.
324 static void dump_object_info(struct kmemleak_object *object)
326 struct stack_trace trace;
328 trace.nr_entries = object->trace_len;
329 trace.entries = object->trace;
331 pr_notice("Object 0x%08lx (size %zu):\n",
332 object->tree_node.start, object->size);
333 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
334 object->comm, object->pid, object->jiffies);
335 pr_notice(" min_count = %d\n", object->min_count);
336 pr_notice(" count = %d\n", object->count);
337 pr_notice(" flags = 0x%lx\n", object->flags);
338 pr_notice(" backtrace:\n");
339 print_stack_trace(&trace, 4);
343 * Look-up a memory block metadata (kmemleak_object) in the priority search
344 * tree based on a pointer value. If alias is 0, only values pointing to the
345 * beginning of the memory block are allowed. The kmemleak_lock must be held
346 * when calling this function.
348 static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
350 struct prio_tree_node *node;
351 struct prio_tree_iter iter;
352 struct kmemleak_object *object;
354 prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr);
355 node = prio_tree_next(&iter);
357 object = prio_tree_entry(node, struct kmemleak_object,
359 if (!alias && object->pointer != ptr) {
360 kmemleak_warn("Found object by alias");
370 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
371 * that once an object's use_count reached 0, the RCU freeing was already
372 * registered and the object should no longer be used. This function must be
373 * called under the protection of rcu_read_lock().
375 static int get_object(struct kmemleak_object *object)
377 return atomic_inc_not_zero(&object->use_count);
381 * RCU callback to free a kmemleak_object.
383 static void free_object_rcu(struct rcu_head *rcu)
385 struct hlist_node *elem, *tmp;
386 struct kmemleak_scan_area *area;
387 struct kmemleak_object *object =
388 container_of(rcu, struct kmemleak_object, rcu);
391 * Once use_count is 0 (guaranteed by put_object), there is no other
392 * code accessing this object, hence no need for locking.
394 hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) {
396 kmem_cache_free(scan_area_cache, area);
398 kmem_cache_free(object_cache, object);
402 * Decrement the object use_count. Once the count is 0, free the object using
403 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
404 * delete_object() path, the delayed RCU freeing ensures that there is no
405 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
408 static void put_object(struct kmemleak_object *object)
410 if (!atomic_dec_and_test(&object->use_count))
413 /* should only get here after delete_object was called */
414 WARN_ON(object->flags & OBJECT_ALLOCATED);
416 call_rcu(&object->rcu, free_object_rcu);
420 * Look up an object in the prio search tree and increase its use_count.
422 static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
425 struct kmemleak_object *object = NULL;
428 read_lock_irqsave(&kmemleak_lock, flags);
429 if (ptr >= min_addr && ptr < max_addr)
430 object = lookup_object(ptr, alias);
431 read_unlock_irqrestore(&kmemleak_lock, flags);
433 /* check whether the object is still available */
434 if (object && !get_object(object))
442 * Save stack trace to the given array of MAX_TRACE size.
444 static int __save_stack_trace(unsigned long *trace)
446 struct stack_trace stack_trace;
448 stack_trace.max_entries = MAX_TRACE;
449 stack_trace.nr_entries = 0;
450 stack_trace.entries = trace;
451 stack_trace.skip = 2;
452 save_stack_trace(&stack_trace);
454 return stack_trace.nr_entries;
458 * Create the metadata (struct kmemleak_object) corresponding to an allocated
459 * memory block and add it to the object_list and object_tree_root.
461 static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
462 int min_count, gfp_t gfp)
465 struct kmemleak_object *object;
466 struct prio_tree_node *node;
468 object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK);
470 kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
474 INIT_LIST_HEAD(&object->object_list);
475 INIT_LIST_HEAD(&object->gray_list);
476 INIT_HLIST_HEAD(&object->area_list);
477 spin_lock_init(&object->lock);
478 atomic_set(&object->use_count, 1);
479 object->flags = OBJECT_ALLOCATED | OBJECT_NEW;
480 object->pointer = ptr;
482 object->min_count = min_count;
483 object->count = -1; /* no color initially */
484 object->jiffies = jiffies;
486 /* task information */
489 strncpy(object->comm, "hardirq", sizeof(object->comm));
490 } else if (in_softirq()) {
492 strncpy(object->comm, "softirq", sizeof(object->comm));
494 object->pid = current->pid;
496 * There is a small chance of a race with set_task_comm(),
497 * however using get_task_comm() here may cause locking
498 * dependency issues with current->alloc_lock. In the worst
499 * case, the command line is not correct.
501 strncpy(object->comm, current->comm, sizeof(object->comm));
504 /* kernel backtrace */
505 object->trace_len = __save_stack_trace(object->trace);
507 INIT_PRIO_TREE_NODE(&object->tree_node);
508 object->tree_node.start = ptr;
509 object->tree_node.last = ptr + size - 1;
511 write_lock_irqsave(&kmemleak_lock, flags);
512 min_addr = min(min_addr, ptr);
513 max_addr = max(max_addr, ptr + size);
514 node = prio_tree_insert(&object_tree_root, &object->tree_node);
516 * The code calling the kernel does not yet have the pointer to the
517 * memory block to be able to free it. However, we still hold the
518 * kmemleak_lock here in case parts of the kernel started freeing
519 * random memory blocks.
521 if (node != &object->tree_node) {
524 kmemleak_stop("Cannot insert 0x%lx into the object search tree "
525 "(already existing)\n", ptr);
526 object = lookup_object(ptr, 1);
527 spin_lock_irqsave(&object->lock, flags);
528 dump_object_info(object);
529 spin_unlock_irqrestore(&object->lock, flags);
533 list_add_tail_rcu(&object->object_list, &object_list);
535 write_unlock_irqrestore(&kmemleak_lock, flags);
540 * Remove the metadata (struct kmemleak_object) for a memory block from the
541 * object_list and object_tree_root and decrement its use_count.
543 static void __delete_object(struct kmemleak_object *object)
547 write_lock_irqsave(&kmemleak_lock, flags);
548 prio_tree_remove(&object_tree_root, &object->tree_node);
549 list_del_rcu(&object->object_list);
550 write_unlock_irqrestore(&kmemleak_lock, flags);
552 WARN_ON(!(object->flags & OBJECT_ALLOCATED));
553 WARN_ON(atomic_read(&object->use_count) < 2);
556 * Locking here also ensures that the corresponding memory block
557 * cannot be freed when it is being scanned.
559 spin_lock_irqsave(&object->lock, flags);
560 object->flags &= ~OBJECT_ALLOCATED;
561 spin_unlock_irqrestore(&object->lock, flags);
566 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
569 static void delete_object_full(unsigned long ptr)
571 struct kmemleak_object *object;
573 object = find_and_get_object(ptr, 0);
576 kmemleak_warn("Freeing unknown object at 0x%08lx\n",
581 __delete_object(object);
586 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
587 * delete it. If the memory block is partially freed, the function may create
588 * additional metadata for the remaining parts of the block.
590 static void delete_object_part(unsigned long ptr, size_t size)
592 struct kmemleak_object *object;
593 unsigned long start, end;
595 object = find_and_get_object(ptr, 1);
598 kmemleak_warn("Partially freeing unknown object at 0x%08lx "
599 "(size %zu)\n", ptr, size);
603 __delete_object(object);
606 * Create one or two objects that may result from the memory block
607 * split. Note that partial freeing is only done by free_bootmem() and
608 * this happens before kmemleak_init() is called. The path below is
609 * only executed during early log recording in kmemleak_init(), so
610 * GFP_KERNEL is enough.
612 start = object->pointer;
613 end = object->pointer + object->size;
615 create_object(start, ptr - start, object->min_count,
617 if (ptr + size < end)
618 create_object(ptr + size, end - ptr - size, object->min_count,
624 * Make a object permanently as gray-colored so that it can no longer be
625 * reported as a leak. This is used in general to mark a false positive.
627 static void make_gray_object(unsigned long ptr)
630 struct kmemleak_object *object;
632 object = find_and_get_object(ptr, 0);
634 kmemleak_warn("Graying unknown object at 0x%08lx\n", ptr);
638 spin_lock_irqsave(&object->lock, flags);
639 object->min_count = 0;
640 spin_unlock_irqrestore(&object->lock, flags);
645 * Mark the object as black-colored so that it is ignored from scans and
648 static void make_black_object(unsigned long ptr)
651 struct kmemleak_object *object;
653 object = find_and_get_object(ptr, 0);
655 kmemleak_warn("Blacking unknown object at 0x%08lx\n", ptr);
659 spin_lock_irqsave(&object->lock, flags);
660 object->min_count = -1;
661 object->flags |= OBJECT_NO_SCAN;
662 spin_unlock_irqrestore(&object->lock, flags);
667 * Add a scanning area to the object. If at least one such area is added,
668 * kmemleak will only scan these ranges rather than the whole memory block.
670 static void add_scan_area(unsigned long ptr, unsigned long offset,
671 size_t length, gfp_t gfp)
674 struct kmemleak_object *object;
675 struct kmemleak_scan_area *area;
677 object = find_and_get_object(ptr, 0);
679 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
684 area = kmem_cache_alloc(scan_area_cache, gfp & GFP_KMEMLEAK_MASK);
686 kmemleak_warn("Cannot allocate a scan area\n");
690 spin_lock_irqsave(&object->lock, flags);
691 if (offset + length > object->size) {
692 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
693 dump_object_info(object);
694 kmem_cache_free(scan_area_cache, area);
698 INIT_HLIST_NODE(&area->node);
699 area->offset = offset;
700 area->length = length;
702 hlist_add_head(&area->node, &object->area_list);
704 spin_unlock_irqrestore(&object->lock, flags);
710 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
711 * pointer. Such object will not be scanned by kmemleak but references to it
714 static void object_no_scan(unsigned long ptr)
717 struct kmemleak_object *object;
719 object = find_and_get_object(ptr, 0);
721 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
725 spin_lock_irqsave(&object->lock, flags);
726 object->flags |= OBJECT_NO_SCAN;
727 spin_unlock_irqrestore(&object->lock, flags);
732 * Log an early kmemleak_* call to the early_log buffer. These calls will be
733 * processed later once kmemleak is fully initialized.
735 static void __init log_early(int op_type, const void *ptr, size_t size,
736 int min_count, unsigned long offset, size_t length)
739 struct early_log *log;
741 if (crt_early_log >= ARRAY_SIZE(early_log)) {
742 pr_warning("Early log buffer exceeded\n");
748 * There is no need for locking since the kernel is still in UP mode
749 * at this stage. Disabling the IRQs is enough.
751 local_irq_save(flags);
752 log = &early_log[crt_early_log];
753 log->op_type = op_type;
756 log->min_count = min_count;
757 log->offset = offset;
758 log->length = length;
759 if (op_type == KMEMLEAK_ALLOC)
760 log->trace_len = __save_stack_trace(log->trace);
762 local_irq_restore(flags);
766 * Log an early allocated block and populate the stack trace.
768 static void early_alloc(struct early_log *log)
770 struct kmemleak_object *object;
774 if (!atomic_read(&kmemleak_enabled) || !log->ptr || IS_ERR(log->ptr))
778 * RCU locking needed to ensure object is not freed via put_object().
781 object = create_object((unsigned long)log->ptr, log->size,
782 log->min_count, GFP_KERNEL);
783 spin_lock_irqsave(&object->lock, flags);
784 for (i = 0; i < log->trace_len; i++)
785 object->trace[i] = log->trace[i];
786 object->trace_len = log->trace_len;
787 spin_unlock_irqrestore(&object->lock, flags);
792 * Memory allocation function callback. This function is called from the
793 * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc,
796 void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
799 pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
801 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
802 create_object((unsigned long)ptr, size, min_count, gfp);
803 else if (atomic_read(&kmemleak_early_log))
804 log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
806 EXPORT_SYMBOL_GPL(kmemleak_alloc);
809 * Memory freeing function callback. This function is called from the kernel
810 * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.).
812 void __ref kmemleak_free(const void *ptr)
814 pr_debug("%s(0x%p)\n", __func__, ptr);
816 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
817 delete_object_full((unsigned long)ptr);
818 else if (atomic_read(&kmemleak_early_log))
819 log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
821 EXPORT_SYMBOL_GPL(kmemleak_free);
824 * Partial memory freeing function callback. This function is usually called
825 * from bootmem allocator when (part of) a memory block is freed.
827 void __ref kmemleak_free_part(const void *ptr, size_t size)
829 pr_debug("%s(0x%p)\n", __func__, ptr);
831 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
832 delete_object_part((unsigned long)ptr, size);
833 else if (atomic_read(&kmemleak_early_log))
834 log_early(KMEMLEAK_FREE_PART, ptr, size, 0, 0, 0);
836 EXPORT_SYMBOL_GPL(kmemleak_free_part);
839 * Mark an already allocated memory block as a false positive. This will cause
840 * the block to no longer be reported as leak and always be scanned.
842 void __ref kmemleak_not_leak(const void *ptr)
844 pr_debug("%s(0x%p)\n", __func__, ptr);
846 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
847 make_gray_object((unsigned long)ptr);
848 else if (atomic_read(&kmemleak_early_log))
849 log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
851 EXPORT_SYMBOL(kmemleak_not_leak);
854 * Ignore a memory block. This is usually done when it is known that the
855 * corresponding block is not a leak and does not contain any references to
856 * other allocated memory blocks.
858 void __ref kmemleak_ignore(const void *ptr)
860 pr_debug("%s(0x%p)\n", __func__, ptr);
862 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
863 make_black_object((unsigned long)ptr);
864 else if (atomic_read(&kmemleak_early_log))
865 log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
867 EXPORT_SYMBOL(kmemleak_ignore);
870 * Limit the range to be scanned in an allocated memory block.
872 void __ref kmemleak_scan_area(const void *ptr, unsigned long offset,
873 size_t length, gfp_t gfp)
875 pr_debug("%s(0x%p)\n", __func__, ptr);
877 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
878 add_scan_area((unsigned long)ptr, offset, length, gfp);
879 else if (atomic_read(&kmemleak_early_log))
880 log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
882 EXPORT_SYMBOL(kmemleak_scan_area);
885 * Inform kmemleak not to scan the given memory block.
887 void __ref kmemleak_no_scan(const void *ptr)
889 pr_debug("%s(0x%p)\n", __func__, ptr);
891 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
892 object_no_scan((unsigned long)ptr);
893 else if (atomic_read(&kmemleak_early_log))
894 log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0);
896 EXPORT_SYMBOL(kmemleak_no_scan);
899 * Memory scanning is a long process and it needs to be interruptable. This
900 * function checks whether such interrupt condition occured.
902 static int scan_should_stop(void)
904 if (!atomic_read(&kmemleak_enabled))
908 * This function may be called from either process or kthread context,
909 * hence the need to check for both stop conditions.
912 return signal_pending(current);
914 return kthread_should_stop();
920 * Scan a memory block (exclusive range) for valid pointers and add those
921 * found to the gray list.
923 static void scan_block(void *_start, void *_end,
924 struct kmemleak_object *scanned, int allow_resched)
927 unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
928 unsigned long *end = _end - (BYTES_PER_POINTER - 1);
930 for (ptr = start; ptr < end; ptr++) {
932 unsigned long pointer = *ptr;
933 struct kmemleak_object *object;
937 if (scan_should_stop())
940 object = find_and_get_object(pointer, 1);
943 if (object == scanned) {
944 /* self referenced, ignore */
950 * Avoid the lockdep recursive warning on object->lock being
951 * previously acquired in scan_object(). These locks are
952 * enclosed by scan_mutex.
954 spin_lock_irqsave_nested(&object->lock, flags,
955 SINGLE_DEPTH_NESTING);
956 if (!color_white(object)) {
957 /* non-orphan, ignored or new */
958 spin_unlock_irqrestore(&object->lock, flags);
964 * Increase the object's reference count (number of pointers
965 * to the memory block). If this count reaches the required
966 * minimum, the object's color will become gray and it will be
967 * added to the gray_list.
970 if (color_gray(object))
971 list_add_tail(&object->gray_list, &gray_list);
974 spin_unlock_irqrestore(&object->lock, flags);
979 * Scan a memory block corresponding to a kmemleak_object. A condition is
980 * that object->use_count >= 1.
982 static void scan_object(struct kmemleak_object *object)
984 struct kmemleak_scan_area *area;
985 struct hlist_node *elem;
989 * Once the object->lock is aquired, the corresponding memory block
990 * cannot be freed (the same lock is aquired in delete_object).
992 spin_lock_irqsave(&object->lock, flags);
993 if (object->flags & OBJECT_NO_SCAN)
995 if (!(object->flags & OBJECT_ALLOCATED))
996 /* already freed object */
998 if (hlist_empty(&object->area_list)) {
999 void *start = (void *)object->pointer;
1000 void *end = (void *)(object->pointer + object->size);
1002 while (start < end && (object->flags & OBJECT_ALLOCATED) &&
1003 !(object->flags & OBJECT_NO_SCAN)) {
1004 scan_block(start, min(start + MAX_SCAN_SIZE, end),
1006 start += MAX_SCAN_SIZE;
1008 spin_unlock_irqrestore(&object->lock, flags);
1010 spin_lock_irqsave(&object->lock, flags);
1013 hlist_for_each_entry(area, elem, &object->area_list, node)
1014 scan_block((void *)(object->pointer + area->offset),
1015 (void *)(object->pointer + area->offset
1016 + area->length), object, 0);
1018 spin_unlock_irqrestore(&object->lock, flags);
1022 * Scan data sections and all the referenced memory blocks allocated via the
1023 * kernel's standard allocators. This function must be called with the
1026 static void kmemleak_scan(void)
1028 unsigned long flags;
1029 struct kmemleak_object *object, *tmp;
1030 struct task_struct *task;
1033 int gray_list_pass = 0;
1035 jiffies_last_scan = jiffies;
1037 /* prepare the kmemleak_object's */
1039 list_for_each_entry_rcu(object, &object_list, object_list) {
1040 spin_lock_irqsave(&object->lock, flags);
1043 * With a few exceptions there should be a maximum of
1044 * 1 reference to any object at this point.
1046 if (atomic_read(&object->use_count) > 1) {
1047 pr_debug("object->use_count = %d\n",
1048 atomic_read(&object->use_count));
1049 dump_object_info(object);
1052 /* reset the reference count (whiten the object) */
1054 object->flags &= ~OBJECT_NEW;
1055 if (color_gray(object) && get_object(object))
1056 list_add_tail(&object->gray_list, &gray_list);
1058 spin_unlock_irqrestore(&object->lock, flags);
1062 /* data/bss scanning */
1063 scan_block(_sdata, _edata, NULL, 1);
1064 scan_block(__bss_start, __bss_stop, NULL, 1);
1067 /* per-cpu sections scanning */
1068 for_each_possible_cpu(i)
1069 scan_block(__per_cpu_start + per_cpu_offset(i),
1070 __per_cpu_end + per_cpu_offset(i), NULL, 1);
1074 * Struct page scanning for each node. The code below is not yet safe
1075 * with MEMORY_HOTPLUG.
1077 for_each_online_node(i) {
1078 pg_data_t *pgdat = NODE_DATA(i);
1079 unsigned long start_pfn = pgdat->node_start_pfn;
1080 unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
1083 for (pfn = start_pfn; pfn < end_pfn; pfn++) {
1086 if (!pfn_valid(pfn))
1088 page = pfn_to_page(pfn);
1089 /* only scan if page is in use */
1090 if (page_count(page) == 0)
1092 scan_block(page, page + 1, NULL, 1);
1097 * Scanning the task stacks may introduce false negatives and it is
1098 * not enabled by default.
1100 if (kmemleak_stack_scan) {
1101 read_lock(&tasklist_lock);
1102 for_each_process(task)
1103 scan_block(task_stack_page(task),
1104 task_stack_page(task) + THREAD_SIZE,
1106 read_unlock(&tasklist_lock);
1110 * Scan the objects already referenced from the sections scanned
1111 * above. More objects will be referenced and, if there are no memory
1112 * leaks, all the objects will be scanned. The list traversal is safe
1113 * for both tail additions and removals from inside the loop. The
1114 * kmemleak objects cannot be freed from outside the loop because their
1115 * use_count was increased.
1118 object = list_entry(gray_list.next, typeof(*object), gray_list);
1119 while (&object->gray_list != &gray_list) {
1122 /* may add new objects to the list */
1123 if (!scan_should_stop())
1124 scan_object(object);
1126 tmp = list_entry(object->gray_list.next, typeof(*object),
1129 /* remove the object from the list and release it */
1130 list_del(&object->gray_list);
1136 if (scan_should_stop() || ++gray_list_pass >= GRAY_LIST_PASSES)
1140 * Check for new objects allocated during this scanning and add them
1144 list_for_each_entry_rcu(object, &object_list, object_list) {
1145 spin_lock_irqsave(&object->lock, flags);
1146 if ((object->flags & OBJECT_NEW) && !color_black(object) &&
1147 get_object(object)) {
1148 object->flags &= ~OBJECT_NEW;
1149 list_add_tail(&object->gray_list, &gray_list);
1151 spin_unlock_irqrestore(&object->lock, flags);
1155 if (!list_empty(&gray_list))
1159 WARN_ON(!list_empty(&gray_list));
1162 * If scanning was stopped or new objects were being allocated at a
1163 * higher rate than gray list scanning, do not report any new
1164 * unreferenced objects.
1166 if (scan_should_stop() || gray_list_pass >= GRAY_LIST_PASSES)
1170 * Scanning result reporting.
1173 list_for_each_entry_rcu(object, &object_list, object_list) {
1174 spin_lock_irqsave(&object->lock, flags);
1175 if (unreferenced_object(object) &&
1176 !(object->flags & OBJECT_REPORTED)) {
1177 object->flags |= OBJECT_REPORTED;
1180 spin_unlock_irqrestore(&object->lock, flags);
1185 pr_info("%d new suspected memory leaks (see "
1186 "/sys/kernel/debug/kmemleak)\n", new_leaks);
1191 * Thread function performing automatic memory scanning. Unreferenced objects
1192 * at the end of a memory scan are reported but only the first time.
1194 static int kmemleak_scan_thread(void *arg)
1196 static int first_run = 1;
1198 pr_info("Automatic memory scanning thread started\n");
1199 set_user_nice(current, 10);
1202 * Wait before the first scan to allow the system to fully initialize.
1206 ssleep(SECS_FIRST_SCAN);
1209 while (!kthread_should_stop()) {
1210 signed long timeout = jiffies_scan_wait;
1212 mutex_lock(&scan_mutex);
1214 mutex_unlock(&scan_mutex);
1216 /* wait before the next scan */
1217 while (timeout && !kthread_should_stop())
1218 timeout = schedule_timeout_interruptible(timeout);
1221 pr_info("Automatic memory scanning thread ended\n");
1227 * Start the automatic memory scanning thread. This function must be called
1228 * with the scan_mutex held.
1230 void start_scan_thread(void)
1234 scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
1235 if (IS_ERR(scan_thread)) {
1236 pr_warning("Failed to create the scan thread\n");
1242 * Stop the automatic memory scanning thread. This function must be called
1243 * with the scan_mutex held.
1245 void stop_scan_thread(void)
1248 kthread_stop(scan_thread);
1254 * Iterate over the object_list and return the first valid object at or after
1255 * the required position with its use_count incremented. The function triggers
1256 * a memory scanning when the pos argument points to the first position.
1258 static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
1260 struct kmemleak_object *object;
1264 err = mutex_lock_interruptible(&scan_mutex);
1266 return ERR_PTR(err);
1269 list_for_each_entry_rcu(object, &object_list, object_list) {
1272 if (get_object(object))
1281 * Return the next object in the object_list. The function decrements the
1282 * use_count of the previous object and increases that of the next one.
1284 static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1286 struct kmemleak_object *prev_obj = v;
1287 struct kmemleak_object *next_obj = NULL;
1288 struct list_head *n = &prev_obj->object_list;
1292 list_for_each_continue_rcu(n, &object_list) {
1293 next_obj = list_entry(n, struct kmemleak_object, object_list);
1294 if (get_object(next_obj))
1298 put_object(prev_obj);
1303 * Decrement the use_count of the last object required, if any.
1305 static void kmemleak_seq_stop(struct seq_file *seq, void *v)
1309 * kmemleak_seq_start may return ERR_PTR if the scan_mutex
1310 * waiting was interrupted, so only release it if !IS_ERR.
1313 mutex_unlock(&scan_mutex);
1320 * Print the information for an unreferenced object to the seq file.
1322 static int kmemleak_seq_show(struct seq_file *seq, void *v)
1324 struct kmemleak_object *object = v;
1325 unsigned long flags;
1327 spin_lock_irqsave(&object->lock, flags);
1328 if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1329 print_unreferenced(seq, object);
1330 spin_unlock_irqrestore(&object->lock, flags);
1334 static const struct seq_operations kmemleak_seq_ops = {
1335 .start = kmemleak_seq_start,
1336 .next = kmemleak_seq_next,
1337 .stop = kmemleak_seq_stop,
1338 .show = kmemleak_seq_show,
1341 static int kmemleak_open(struct inode *inode, struct file *file)
1343 if (!atomic_read(&kmemleak_enabled))
1346 return seq_open(file, &kmemleak_seq_ops);
1349 static int kmemleak_release(struct inode *inode, struct file *file)
1351 return seq_release(inode, file);
1354 static int dump_str_object_info(const char *str)
1356 unsigned long flags;
1357 struct kmemleak_object *object;
1360 addr= simple_strtoul(str, NULL, 0);
1361 object = find_and_get_object(addr, 0);
1363 pr_info("Unknown object at 0x%08lx\n", addr);
1367 spin_lock_irqsave(&object->lock, flags);
1368 dump_object_info(object);
1369 spin_unlock_irqrestore(&object->lock, flags);
1376 * File write operation to configure kmemleak at run-time. The following
1377 * commands can be written to the /sys/kernel/debug/kmemleak file:
1378 * off - disable kmemleak (irreversible)
1379 * stack=on - enable the task stacks scanning
1380 * stack=off - disable the tasks stacks scanning
1381 * scan=on - start the automatic memory scanning thread
1382 * scan=off - stop the automatic memory scanning thread
1383 * scan=... - set the automatic memory scanning period in seconds (0 to
1385 * scan - trigger a memory scan
1386 * dump=... - dump information about the object found at the given address
1388 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
1389 size_t size, loff_t *ppos)
1395 buf_size = min(size, (sizeof(buf) - 1));
1396 if (strncpy_from_user(buf, user_buf, buf_size) < 0)
1400 ret = mutex_lock_interruptible(&scan_mutex);
1404 if (strncmp(buf, "off", 3) == 0)
1406 else if (strncmp(buf, "stack=on", 8) == 0)
1407 kmemleak_stack_scan = 1;
1408 else if (strncmp(buf, "stack=off", 9) == 0)
1409 kmemleak_stack_scan = 0;
1410 else if (strncmp(buf, "scan=on", 7) == 0)
1411 start_scan_thread();
1412 else if (strncmp(buf, "scan=off", 8) == 0)
1414 else if (strncmp(buf, "scan=", 5) == 0) {
1417 ret = strict_strtoul(buf + 5, 0, &secs);
1422 jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
1423 start_scan_thread();
1425 } else if (strncmp(buf, "scan", 4) == 0)
1427 else if (strncmp(buf, "dump=", 5) == 0)
1428 ret = dump_str_object_info(buf + 5);
1433 mutex_unlock(&scan_mutex);
1437 /* ignore the rest of the buffer, only one command at a time */
1442 static const struct file_operations kmemleak_fops = {
1443 .owner = THIS_MODULE,
1444 .open = kmemleak_open,
1446 .write = kmemleak_write,
1447 .llseek = seq_lseek,
1448 .release = kmemleak_release,
1452 * Perform the freeing of the kmemleak internal objects after waiting for any
1453 * current memory scan to complete.
1455 static int kmemleak_cleanup_thread(void *arg)
1457 struct kmemleak_object *object;
1459 mutex_lock(&scan_mutex);
1463 list_for_each_entry_rcu(object, &object_list, object_list)
1464 delete_object_full(object->pointer);
1466 mutex_unlock(&scan_mutex);
1472 * Start the clean-up thread.
1474 static void kmemleak_cleanup(void)
1476 struct task_struct *cleanup_thread;
1478 cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL,
1480 if (IS_ERR(cleanup_thread))
1481 pr_warning("Failed to create the clean-up thread\n");
1485 * Disable kmemleak. No memory allocation/freeing will be traced once this
1486 * function is called. Disabling kmemleak is an irreversible operation.
1488 static void kmemleak_disable(void)
1490 /* atomically check whether it was already invoked */
1491 if (atomic_cmpxchg(&kmemleak_error, 0, 1))
1494 /* stop any memory operation tracing */
1495 atomic_set(&kmemleak_early_log, 0);
1496 atomic_set(&kmemleak_enabled, 0);
1498 /* check whether it is too early for a kernel thread */
1499 if (atomic_read(&kmemleak_initialized))
1502 pr_info("Kernel memory leak detector disabled\n");
1506 * Allow boot-time kmemleak disabling (enabled by default).
1508 static int kmemleak_boot_config(char *str)
1512 if (strcmp(str, "off") == 0)
1514 else if (strcmp(str, "on") != 0)
1518 early_param("kmemleak", kmemleak_boot_config);
1521 * Kmemleak initialization.
1523 void __init kmemleak_init(void)
1526 unsigned long flags;
1528 jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
1529 jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
1531 object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
1532 scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
1533 INIT_PRIO_TREE_ROOT(&object_tree_root);
1535 /* the kernel is still in UP mode, so disabling the IRQs is enough */
1536 local_irq_save(flags);
1537 if (!atomic_read(&kmemleak_error)) {
1538 atomic_set(&kmemleak_enabled, 1);
1539 atomic_set(&kmemleak_early_log, 0);
1541 local_irq_restore(flags);
1544 * This is the point where tracking allocations is safe. Automatic
1545 * scanning is started during the late initcall. Add the early logged
1546 * callbacks to the kmemleak infrastructure.
1548 for (i = 0; i < crt_early_log; i++) {
1549 struct early_log *log = &early_log[i];
1551 switch (log->op_type) {
1552 case KMEMLEAK_ALLOC:
1556 kmemleak_free(log->ptr);
1558 case KMEMLEAK_FREE_PART:
1559 kmemleak_free_part(log->ptr, log->size);
1561 case KMEMLEAK_NOT_LEAK:
1562 kmemleak_not_leak(log->ptr);
1564 case KMEMLEAK_IGNORE:
1565 kmemleak_ignore(log->ptr);
1567 case KMEMLEAK_SCAN_AREA:
1568 kmemleak_scan_area(log->ptr, log->offset, log->length,
1571 case KMEMLEAK_NO_SCAN:
1572 kmemleak_no_scan(log->ptr);
1581 * Late initialization function.
1583 static int __init kmemleak_late_init(void)
1585 struct dentry *dentry;
1587 atomic_set(&kmemleak_initialized, 1);
1589 if (atomic_read(&kmemleak_error)) {
1591 * Some error occured and kmemleak was disabled. There is a
1592 * small chance that kmemleak_disable() was called immediately
1593 * after setting kmemleak_initialized and we may end up with
1594 * two clean-up threads but serialized by scan_mutex.
1600 dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
1603 pr_warning("Failed to create the debugfs kmemleak file\n");
1604 mutex_lock(&scan_mutex);
1605 start_scan_thread();
1606 mutex_unlock(&scan_mutex);
1608 pr_info("Kernel memory leak detector initialized\n");
1612 late_initcall(kmemleak_late_init);