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 */
110 #define BYTES_PER_POINTER sizeof(void *)
112 /* GFP bitmask for kmemleak internal allocations */
113 #define GFP_KMEMLEAK_MASK (GFP_KERNEL | GFP_ATOMIC)
115 /* scanning area inside a memory block */
116 struct kmemleak_scan_area {
117 struct hlist_node node;
118 unsigned long offset;
123 * Structure holding the metadata for each allocated memory block.
124 * Modifications to such objects should be made while holding the
125 * object->lock. Insertions or deletions from object_list, gray_list or
126 * tree_node are already protected by the corresponding locks or mutex (see
127 * the notes on locking above). These objects are reference-counted
128 * (use_count) and freed using the RCU mechanism.
130 struct kmemleak_object {
132 unsigned long flags; /* object status flags */
133 struct list_head object_list;
134 struct list_head gray_list;
135 struct prio_tree_node tree_node;
136 struct rcu_head rcu; /* object_list lockless traversal */
137 /* object usage count; object freed when use_count == 0 */
139 unsigned long pointer;
141 /* minimum number of a pointers found before it is considered leak */
143 /* the total number of pointers found pointing to this object */
145 /* memory ranges to be scanned inside an object (empty for all) */
146 struct hlist_head area_list;
147 unsigned long trace[MAX_TRACE];
148 unsigned int trace_len;
149 unsigned long jiffies; /* creation timestamp */
150 pid_t pid; /* pid of the current task */
151 char comm[TASK_COMM_LEN]; /* executable name */
154 /* flag representing the memory block allocation status */
155 #define OBJECT_ALLOCATED (1 << 0)
156 /* flag set after the first reporting of an unreference object */
157 #define OBJECT_REPORTED (1 << 1)
158 /* flag set to not scan the object */
159 #define OBJECT_NO_SCAN (1 << 2)
161 /* the list of all allocated objects */
162 static LIST_HEAD(object_list);
163 /* the list of gray-colored objects (see color_gray comment below) */
164 static LIST_HEAD(gray_list);
165 /* prio search tree for object boundaries */
166 static struct prio_tree_root object_tree_root;
167 /* rw_lock protecting the access to object_list and prio_tree_root */
168 static DEFINE_RWLOCK(kmemleak_lock);
170 /* allocation caches for kmemleak internal data */
171 static struct kmem_cache *object_cache;
172 static struct kmem_cache *scan_area_cache;
174 /* set if tracing memory operations is enabled */
175 static atomic_t kmemleak_enabled = ATOMIC_INIT(0);
176 /* set in the late_initcall if there were no errors */
177 static atomic_t kmemleak_initialized = ATOMIC_INIT(0);
178 /* enables or disables early logging of the memory operations */
179 static atomic_t kmemleak_early_log = ATOMIC_INIT(1);
180 /* set if a fata kmemleak error has occurred */
181 static atomic_t kmemleak_error = ATOMIC_INIT(0);
183 /* minimum and maximum address that may be valid pointers */
184 static unsigned long min_addr = ULONG_MAX;
185 static unsigned long max_addr;
187 static struct task_struct *scan_thread;
188 /* used to avoid reporting of recently allocated objects */
189 static unsigned long jiffies_min_age;
190 static unsigned long jiffies_last_scan;
191 /* delay between automatic memory scannings */
192 static signed long jiffies_scan_wait;
193 /* enables or disables the task stacks scanning */
194 static int kmemleak_stack_scan = 1;
195 /* protects the memory scanning, parameters and debug/kmemleak file access */
196 static DEFINE_MUTEX(scan_mutex);
199 * Early object allocation/freeing logging. Kmemleak is initialized after the
200 * kernel allocator. However, both the kernel allocator and kmemleak may
201 * allocate memory blocks which need to be tracked. Kmemleak defines an
202 * arbitrary buffer to hold the allocation/freeing information before it is
206 /* kmemleak operation type for early logging */
217 * Structure holding the information passed to kmemleak callbacks during the
221 int op_type; /* kmemleak operation type */
222 const void *ptr; /* allocated/freed memory block */
223 size_t size; /* memory block size */
224 int min_count; /* minimum reference count */
225 unsigned long offset; /* scan area offset */
226 size_t length; /* scan area length */
229 /* early logging buffer and current position */
230 static struct early_log early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE];
231 static int crt_early_log;
233 static void kmemleak_disable(void);
236 * Print a warning and dump the stack trace.
238 #define kmemleak_warn(x...) do { \
244 * Macro invoked when a serious kmemleak condition occured and cannot be
245 * recovered from. Kmemleak will be disabled and further allocation/freeing
246 * tracing no longer available.
248 #define kmemleak_stop(x...) do { \
250 kmemleak_disable(); \
254 * Object colors, encoded with count and min_count:
255 * - white - orphan object, not enough references to it (count < min_count)
256 * - gray - not orphan, not marked as false positive (min_count == 0) or
257 * sufficient references to it (count >= min_count)
258 * - black - ignore, it doesn't contain references (e.g. text section)
259 * (min_count == -1). No function defined for this color.
260 * Newly created objects don't have any color assigned (object->count == -1)
261 * before the next memory scan when they become white.
263 static int color_white(const struct kmemleak_object *object)
265 return object->count != -1 && object->count < object->min_count;
268 static int color_gray(const struct kmemleak_object *object)
270 return object->min_count != -1 && object->count >= object->min_count;
274 * Objects are considered unreferenced only if their color is white, they have
275 * not be deleted and have a minimum age to avoid false positives caused by
276 * pointers temporarily stored in CPU registers.
278 static int unreferenced_object(struct kmemleak_object *object)
280 return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
281 time_before_eq(object->jiffies + jiffies_min_age,
286 * Printing of the unreferenced objects information to the seq file. The
287 * print_unreferenced function must be called with the object->lock held.
289 static void print_unreferenced(struct seq_file *seq,
290 struct kmemleak_object *object)
294 seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
295 object->pointer, object->size);
296 seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu\n",
297 object->comm, object->pid, object->jiffies);
298 seq_printf(seq, " backtrace:\n");
300 for (i = 0; i < object->trace_len; i++) {
301 void *ptr = (void *)object->trace[i];
302 seq_printf(seq, " [<%p>] %pS\n", ptr, ptr);
307 * Print the kmemleak_object information. This function is used mainly for
308 * debugging special cases when kmemleak operations. It must be called with
309 * the object->lock held.
311 static void dump_object_info(struct kmemleak_object *object)
313 struct stack_trace trace;
315 trace.nr_entries = object->trace_len;
316 trace.entries = object->trace;
318 pr_notice("Object 0x%08lx (size %zu):\n",
319 object->tree_node.start, object->size);
320 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
321 object->comm, object->pid, object->jiffies);
322 pr_notice(" min_count = %d\n", object->min_count);
323 pr_notice(" count = %d\n", object->count);
324 pr_notice(" backtrace:\n");
325 print_stack_trace(&trace, 4);
329 * Look-up a memory block metadata (kmemleak_object) in the priority search
330 * tree based on a pointer value. If alias is 0, only values pointing to the
331 * beginning of the memory block are allowed. The kmemleak_lock must be held
332 * when calling this function.
334 static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
336 struct prio_tree_node *node;
337 struct prio_tree_iter iter;
338 struct kmemleak_object *object;
340 prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr);
341 node = prio_tree_next(&iter);
343 object = prio_tree_entry(node, struct kmemleak_object,
345 if (!alias && object->pointer != ptr) {
346 kmemleak_warn("Found object by alias");
356 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
357 * that once an object's use_count reached 0, the RCU freeing was already
358 * registered and the object should no longer be used. This function must be
359 * called under the protection of rcu_read_lock().
361 static int get_object(struct kmemleak_object *object)
363 return atomic_inc_not_zero(&object->use_count);
367 * RCU callback to free a kmemleak_object.
369 static void free_object_rcu(struct rcu_head *rcu)
371 struct hlist_node *elem, *tmp;
372 struct kmemleak_scan_area *area;
373 struct kmemleak_object *object =
374 container_of(rcu, struct kmemleak_object, rcu);
377 * Once use_count is 0 (guaranteed by put_object), there is no other
378 * code accessing this object, hence no need for locking.
380 hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) {
382 kmem_cache_free(scan_area_cache, area);
384 kmem_cache_free(object_cache, object);
388 * Decrement the object use_count. Once the count is 0, free the object using
389 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
390 * delete_object() path, the delayed RCU freeing ensures that there is no
391 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
394 static void put_object(struct kmemleak_object *object)
396 if (!atomic_dec_and_test(&object->use_count))
399 /* should only get here after delete_object was called */
400 WARN_ON(object->flags & OBJECT_ALLOCATED);
402 call_rcu(&object->rcu, free_object_rcu);
406 * Look up an object in the prio search tree and increase its use_count.
408 static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
411 struct kmemleak_object *object = NULL;
414 read_lock_irqsave(&kmemleak_lock, flags);
415 if (ptr >= min_addr && ptr < max_addr)
416 object = lookup_object(ptr, alias);
417 read_unlock_irqrestore(&kmemleak_lock, flags);
419 /* check whether the object is still available */
420 if (object && !get_object(object))
428 * Create the metadata (struct kmemleak_object) corresponding to an allocated
429 * memory block and add it to the object_list and object_tree_root.
431 static void create_object(unsigned long ptr, size_t size, int min_count,
435 struct kmemleak_object *object;
436 struct prio_tree_node *node;
437 struct stack_trace trace;
439 object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK);
441 kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
445 INIT_LIST_HEAD(&object->object_list);
446 INIT_LIST_HEAD(&object->gray_list);
447 INIT_HLIST_HEAD(&object->area_list);
448 spin_lock_init(&object->lock);
449 atomic_set(&object->use_count, 1);
450 object->flags = OBJECT_ALLOCATED;
451 object->pointer = ptr;
453 object->min_count = min_count;
454 object->count = -1; /* no color initially */
455 object->jiffies = jiffies;
457 /* task information */
460 strncpy(object->comm, "hardirq", sizeof(object->comm));
461 } else if (in_softirq()) {
463 strncpy(object->comm, "softirq", sizeof(object->comm));
465 object->pid = current->pid;
467 * There is a small chance of a race with set_task_comm(),
468 * however using get_task_comm() here may cause locking
469 * dependency issues with current->alloc_lock. In the worst
470 * case, the command line is not correct.
472 strncpy(object->comm, current->comm, sizeof(object->comm));
475 /* kernel backtrace */
476 trace.max_entries = MAX_TRACE;
477 trace.nr_entries = 0;
478 trace.entries = object->trace;
480 save_stack_trace(&trace);
481 object->trace_len = trace.nr_entries;
483 INIT_PRIO_TREE_NODE(&object->tree_node);
484 object->tree_node.start = ptr;
485 object->tree_node.last = ptr + size - 1;
487 write_lock_irqsave(&kmemleak_lock, flags);
488 min_addr = min(min_addr, ptr);
489 max_addr = max(max_addr, ptr + size);
490 node = prio_tree_insert(&object_tree_root, &object->tree_node);
492 * The code calling the kernel does not yet have the pointer to the
493 * memory block to be able to free it. However, we still hold the
494 * kmemleak_lock here in case parts of the kernel started freeing
495 * random memory blocks.
497 if (node != &object->tree_node) {
500 kmemleak_stop("Cannot insert 0x%lx into the object search tree "
501 "(already existing)\n", ptr);
502 object = lookup_object(ptr, 1);
503 spin_lock_irqsave(&object->lock, flags);
504 dump_object_info(object);
505 spin_unlock_irqrestore(&object->lock, flags);
509 list_add_tail_rcu(&object->object_list, &object_list);
511 write_unlock_irqrestore(&kmemleak_lock, flags);
515 * Remove the metadata (struct kmemleak_object) for a memory block from the
516 * object_list and object_tree_root and decrement its use_count.
518 static void delete_object(unsigned long ptr)
521 struct kmemleak_object *object;
523 write_lock_irqsave(&kmemleak_lock, flags);
524 object = lookup_object(ptr, 0);
527 kmemleak_warn("Freeing unknown object at 0x%08lx\n",
530 write_unlock_irqrestore(&kmemleak_lock, flags);
533 prio_tree_remove(&object_tree_root, &object->tree_node);
534 list_del_rcu(&object->object_list);
535 write_unlock_irqrestore(&kmemleak_lock, flags);
537 WARN_ON(!(object->flags & OBJECT_ALLOCATED));
538 WARN_ON(atomic_read(&object->use_count) < 1);
541 * Locking here also ensures that the corresponding memory block
542 * cannot be freed when it is being scanned.
544 spin_lock_irqsave(&object->lock, flags);
545 object->flags &= ~OBJECT_ALLOCATED;
546 spin_unlock_irqrestore(&object->lock, flags);
551 * Make a object permanently as gray-colored so that it can no longer be
552 * reported as a leak. This is used in general to mark a false positive.
554 static void make_gray_object(unsigned long ptr)
557 struct kmemleak_object *object;
559 object = find_and_get_object(ptr, 0);
561 kmemleak_warn("Graying unknown object at 0x%08lx\n", ptr);
565 spin_lock_irqsave(&object->lock, flags);
566 object->min_count = 0;
567 spin_unlock_irqrestore(&object->lock, flags);
572 * Mark the object as black-colored so that it is ignored from scans and
575 static void make_black_object(unsigned long ptr)
578 struct kmemleak_object *object;
580 object = find_and_get_object(ptr, 0);
582 kmemleak_warn("Blacking unknown object at 0x%08lx\n", ptr);
586 spin_lock_irqsave(&object->lock, flags);
587 object->min_count = -1;
588 spin_unlock_irqrestore(&object->lock, flags);
593 * Add a scanning area to the object. If at least one such area is added,
594 * kmemleak will only scan these ranges rather than the whole memory block.
596 static void add_scan_area(unsigned long ptr, unsigned long offset,
597 size_t length, gfp_t gfp)
600 struct kmemleak_object *object;
601 struct kmemleak_scan_area *area;
603 object = find_and_get_object(ptr, 0);
605 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
610 area = kmem_cache_alloc(scan_area_cache, gfp & GFP_KMEMLEAK_MASK);
612 kmemleak_warn("Cannot allocate a scan area\n");
616 spin_lock_irqsave(&object->lock, flags);
617 if (offset + length > object->size) {
618 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
619 dump_object_info(object);
620 kmem_cache_free(scan_area_cache, area);
624 INIT_HLIST_NODE(&area->node);
625 area->offset = offset;
626 area->length = length;
628 hlist_add_head(&area->node, &object->area_list);
630 spin_unlock_irqrestore(&object->lock, flags);
636 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
637 * pointer. Such object will not be scanned by kmemleak but references to it
640 static void object_no_scan(unsigned long ptr)
643 struct kmemleak_object *object;
645 object = find_and_get_object(ptr, 0);
647 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
651 spin_lock_irqsave(&object->lock, flags);
652 object->flags |= OBJECT_NO_SCAN;
653 spin_unlock_irqrestore(&object->lock, flags);
658 * Log an early kmemleak_* call to the early_log buffer. These calls will be
659 * processed later once kmemleak is fully initialized.
661 static void log_early(int op_type, const void *ptr, size_t size,
662 int min_count, unsigned long offset, size_t length)
665 struct early_log *log;
667 if (crt_early_log >= ARRAY_SIZE(early_log)) {
668 pr_warning("Early log buffer exceeded\n");
674 * There is no need for locking since the kernel is still in UP mode
675 * at this stage. Disabling the IRQs is enough.
677 local_irq_save(flags);
678 log = &early_log[crt_early_log];
679 log->op_type = op_type;
682 log->min_count = min_count;
683 log->offset = offset;
684 log->length = length;
686 local_irq_restore(flags);
690 * Memory allocation function callback. This function is called from the
691 * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc,
694 void kmemleak_alloc(const void *ptr, size_t size, int min_count, gfp_t gfp)
696 pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
698 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
699 create_object((unsigned long)ptr, size, min_count, gfp);
700 else if (atomic_read(&kmemleak_early_log))
701 log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
703 EXPORT_SYMBOL_GPL(kmemleak_alloc);
706 * Memory freeing function callback. This function is called from the kernel
707 * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.).
709 void kmemleak_free(const void *ptr)
711 pr_debug("%s(0x%p)\n", __func__, ptr);
713 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
714 delete_object((unsigned long)ptr);
715 else if (atomic_read(&kmemleak_early_log))
716 log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
718 EXPORT_SYMBOL_GPL(kmemleak_free);
721 * Mark an already allocated memory block as a false positive. This will cause
722 * the block to no longer be reported as leak and always be scanned.
724 void kmemleak_not_leak(const void *ptr)
726 pr_debug("%s(0x%p)\n", __func__, ptr);
728 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
729 make_gray_object((unsigned long)ptr);
730 else if (atomic_read(&kmemleak_early_log))
731 log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
733 EXPORT_SYMBOL(kmemleak_not_leak);
736 * Ignore a memory block. This is usually done when it is known that the
737 * corresponding block is not a leak and does not contain any references to
738 * other allocated memory blocks.
740 void kmemleak_ignore(const void *ptr)
742 pr_debug("%s(0x%p)\n", __func__, ptr);
744 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
745 make_black_object((unsigned long)ptr);
746 else if (atomic_read(&kmemleak_early_log))
747 log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
749 EXPORT_SYMBOL(kmemleak_ignore);
752 * Limit the range to be scanned in an allocated memory block.
754 void kmemleak_scan_area(const void *ptr, unsigned long offset, size_t length,
757 pr_debug("%s(0x%p)\n", __func__, ptr);
759 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
760 add_scan_area((unsigned long)ptr, offset, length, gfp);
761 else if (atomic_read(&kmemleak_early_log))
762 log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
764 EXPORT_SYMBOL(kmemleak_scan_area);
767 * Inform kmemleak not to scan the given memory block.
769 void kmemleak_no_scan(const void *ptr)
771 pr_debug("%s(0x%p)\n", __func__, ptr);
773 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
774 object_no_scan((unsigned long)ptr);
775 else if (atomic_read(&kmemleak_early_log))
776 log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0);
778 EXPORT_SYMBOL(kmemleak_no_scan);
781 * Memory scanning is a long process and it needs to be interruptable. This
782 * function checks whether such interrupt condition occured.
784 static int scan_should_stop(void)
786 if (!atomic_read(&kmemleak_enabled))
790 * This function may be called from either process or kthread context,
791 * hence the need to check for both stop conditions.
794 return signal_pending(current);
796 return kthread_should_stop();
802 * Scan a memory block (exclusive range) for valid pointers and add those
803 * found to the gray list.
805 static void scan_block(void *_start, void *_end,
806 struct kmemleak_object *scanned, int allow_resched)
809 unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
810 unsigned long *end = _end - (BYTES_PER_POINTER - 1);
812 for (ptr = start; ptr < end; ptr++) {
814 unsigned long pointer = *ptr;
815 struct kmemleak_object *object;
819 if (scan_should_stop())
822 object = find_and_get_object(pointer, 1);
825 if (object == scanned) {
826 /* self referenced, ignore */
832 * Avoid the lockdep recursive warning on object->lock being
833 * previously acquired in scan_object(). These locks are
834 * enclosed by scan_mutex.
836 spin_lock_irqsave_nested(&object->lock, flags,
837 SINGLE_DEPTH_NESTING);
838 if (!color_white(object)) {
839 /* non-orphan, ignored or new */
840 spin_unlock_irqrestore(&object->lock, flags);
846 * Increase the object's reference count (number of pointers
847 * to the memory block). If this count reaches the required
848 * minimum, the object's color will become gray and it will be
849 * added to the gray_list.
852 if (color_gray(object))
853 list_add_tail(&object->gray_list, &gray_list);
856 spin_unlock_irqrestore(&object->lock, flags);
861 * Scan a memory block corresponding to a kmemleak_object. A condition is
862 * that object->use_count >= 1.
864 static void scan_object(struct kmemleak_object *object)
866 struct kmemleak_scan_area *area;
867 struct hlist_node *elem;
871 * Once the object->lock is aquired, the corresponding memory block
872 * cannot be freed (the same lock is aquired in delete_object).
874 spin_lock_irqsave(&object->lock, flags);
875 if (object->flags & OBJECT_NO_SCAN)
877 if (!(object->flags & OBJECT_ALLOCATED))
878 /* already freed object */
880 if (hlist_empty(&object->area_list))
881 scan_block((void *)object->pointer,
882 (void *)(object->pointer + object->size), object, 0);
884 hlist_for_each_entry(area, elem, &object->area_list, node)
885 scan_block((void *)(object->pointer + area->offset),
886 (void *)(object->pointer + area->offset
887 + area->length), object, 0);
889 spin_unlock_irqrestore(&object->lock, flags);
893 * Scan data sections and all the referenced memory blocks allocated via the
894 * kernel's standard allocators. This function must be called with the
897 static void kmemleak_scan(void)
900 struct kmemleak_object *object, *tmp;
901 struct task_struct *task;
905 jiffies_last_scan = jiffies;
907 /* prepare the kmemleak_object's */
909 list_for_each_entry_rcu(object, &object_list, object_list) {
910 spin_lock_irqsave(&object->lock, flags);
913 * With a few exceptions there should be a maximum of
914 * 1 reference to any object at this point.
916 if (atomic_read(&object->use_count) > 1) {
917 pr_debug("object->use_count = %d\n",
918 atomic_read(&object->use_count));
919 dump_object_info(object);
922 /* reset the reference count (whiten the object) */
924 if (color_gray(object) && get_object(object))
925 list_add_tail(&object->gray_list, &gray_list);
927 spin_unlock_irqrestore(&object->lock, flags);
931 /* data/bss scanning */
932 scan_block(_sdata, _edata, NULL, 1);
933 scan_block(__bss_start, __bss_stop, NULL, 1);
936 /* per-cpu sections scanning */
937 for_each_possible_cpu(i)
938 scan_block(__per_cpu_start + per_cpu_offset(i),
939 __per_cpu_end + per_cpu_offset(i), NULL, 1);
943 * Struct page scanning for each node. The code below is not yet safe
944 * with MEMORY_HOTPLUG.
946 for_each_online_node(i) {
947 pg_data_t *pgdat = NODE_DATA(i);
948 unsigned long start_pfn = pgdat->node_start_pfn;
949 unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
952 for (pfn = start_pfn; pfn < end_pfn; pfn++) {
957 page = pfn_to_page(pfn);
958 /* only scan if page is in use */
959 if (page_count(page) == 0)
961 scan_block(page, page + 1, NULL, 1);
966 * Scanning the task stacks may introduce false negatives and it is
967 * not enabled by default.
969 if (kmemleak_stack_scan) {
970 read_lock(&tasklist_lock);
971 for_each_process(task)
972 scan_block(task_stack_page(task),
973 task_stack_page(task) + THREAD_SIZE,
975 read_unlock(&tasklist_lock);
979 * Scan the objects already referenced from the sections scanned
980 * above. More objects will be referenced and, if there are no memory
981 * leaks, all the objects will be scanned. The list traversal is safe
982 * for both tail additions and removals from inside the loop. The
983 * kmemleak objects cannot be freed from outside the loop because their
984 * use_count was increased.
986 object = list_entry(gray_list.next, typeof(*object), gray_list);
987 while (&object->gray_list != &gray_list) {
990 /* may add new objects to the list */
991 if (!scan_should_stop())
994 tmp = list_entry(object->gray_list.next, typeof(*object),
997 /* remove the object from the list and release it */
998 list_del(&object->gray_list);
1003 WARN_ON(!list_empty(&gray_list));
1006 * If scanning was stopped do not report any new unreferenced objects.
1008 if (scan_should_stop())
1012 * Scanning result reporting.
1015 list_for_each_entry_rcu(object, &object_list, object_list) {
1016 spin_lock_irqsave(&object->lock, flags);
1017 if (unreferenced_object(object) &&
1018 !(object->flags & OBJECT_REPORTED)) {
1019 object->flags |= OBJECT_REPORTED;
1022 spin_unlock_irqrestore(&object->lock, flags);
1027 pr_info("%d new suspected memory leaks (see "
1028 "/sys/kernel/debug/kmemleak)\n", new_leaks);
1033 * Thread function performing automatic memory scanning. Unreferenced objects
1034 * at the end of a memory scan are reported but only the first time.
1036 static int kmemleak_scan_thread(void *arg)
1038 static int first_run = 1;
1040 pr_info("Automatic memory scanning thread started\n");
1041 set_user_nice(current, 10);
1044 * Wait before the first scan to allow the system to fully initialize.
1048 ssleep(SECS_FIRST_SCAN);
1051 while (!kthread_should_stop()) {
1052 signed long timeout = jiffies_scan_wait;
1054 mutex_lock(&scan_mutex);
1056 mutex_unlock(&scan_mutex);
1058 /* wait before the next scan */
1059 while (timeout && !kthread_should_stop())
1060 timeout = schedule_timeout_interruptible(timeout);
1063 pr_info("Automatic memory scanning thread ended\n");
1069 * Start the automatic memory scanning thread. This function must be called
1070 * with the scan_mutex held.
1072 void start_scan_thread(void)
1076 scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
1077 if (IS_ERR(scan_thread)) {
1078 pr_warning("Failed to create the scan thread\n");
1084 * Stop the automatic memory scanning thread. This function must be called
1085 * with the scan_mutex held.
1087 void stop_scan_thread(void)
1090 kthread_stop(scan_thread);
1096 * Iterate over the object_list and return the first valid object at or after
1097 * the required position with its use_count incremented. The function triggers
1098 * a memory scanning when the pos argument points to the first position.
1100 static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
1102 struct kmemleak_object *object;
1106 err = mutex_lock_interruptible(&scan_mutex);
1108 return ERR_PTR(err);
1111 list_for_each_entry_rcu(object, &object_list, object_list) {
1114 if (get_object(object))
1124 * Return the next object in the object_list. The function decrements the
1125 * use_count of the previous object and increases that of the next one.
1127 static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1129 struct kmemleak_object *prev_obj = v;
1130 struct kmemleak_object *next_obj = NULL;
1131 struct list_head *n = &prev_obj->object_list;
1136 list_for_each_continue_rcu(n, &object_list) {
1137 next_obj = list_entry(n, struct kmemleak_object, object_list);
1138 if (get_object(next_obj))
1143 put_object(prev_obj);
1148 * Decrement the use_count of the last object required, if any.
1150 static void kmemleak_seq_stop(struct seq_file *seq, void *v)
1154 * kmemleak_seq_start may return ERR_PTR if the scan_mutex
1155 * waiting was interrupted, so only release it if !IS_ERR.
1157 mutex_unlock(&scan_mutex);
1164 * Print the information for an unreferenced object to the seq file.
1166 static int kmemleak_seq_show(struct seq_file *seq, void *v)
1168 struct kmemleak_object *object = v;
1169 unsigned long flags;
1171 spin_lock_irqsave(&object->lock, flags);
1172 if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1173 print_unreferenced(seq, object);
1174 spin_unlock_irqrestore(&object->lock, flags);
1178 static const struct seq_operations kmemleak_seq_ops = {
1179 .start = kmemleak_seq_start,
1180 .next = kmemleak_seq_next,
1181 .stop = kmemleak_seq_stop,
1182 .show = kmemleak_seq_show,
1185 static int kmemleak_open(struct inode *inode, struct file *file)
1187 if (!atomic_read(&kmemleak_enabled))
1190 return seq_open(file, &kmemleak_seq_ops);
1193 static int kmemleak_release(struct inode *inode, struct file *file)
1195 return seq_release(inode, file);
1199 * File write operation to configure kmemleak at run-time. The following
1200 * commands can be written to the /sys/kernel/debug/kmemleak file:
1201 * off - disable kmemleak (irreversible)
1202 * stack=on - enable the task stacks scanning
1203 * stack=off - disable the tasks stacks scanning
1204 * scan=on - start the automatic memory scanning thread
1205 * scan=off - stop the automatic memory scanning thread
1206 * scan=... - set the automatic memory scanning period in seconds (0 to
1208 * scan - trigger a memory scan
1210 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
1211 size_t size, loff_t *ppos)
1217 buf_size = min(size, (sizeof(buf) - 1));
1218 if (strncpy_from_user(buf, user_buf, buf_size) < 0)
1222 ret = mutex_lock_interruptible(&scan_mutex);
1226 if (strncmp(buf, "off", 3) == 0)
1228 else if (strncmp(buf, "stack=on", 8) == 0)
1229 kmemleak_stack_scan = 1;
1230 else if (strncmp(buf, "stack=off", 9) == 0)
1231 kmemleak_stack_scan = 0;
1232 else if (strncmp(buf, "scan=on", 7) == 0)
1233 start_scan_thread();
1234 else if (strncmp(buf, "scan=off", 8) == 0)
1236 else if (strncmp(buf, "scan=", 5) == 0) {
1239 ret = strict_strtoul(buf + 5, 0, &secs);
1244 jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
1245 start_scan_thread();
1247 } else if (strncmp(buf, "scan", 4) == 0)
1253 mutex_unlock(&scan_mutex);
1257 /* ignore the rest of the buffer, only one command at a time */
1262 static const struct file_operations kmemleak_fops = {
1263 .owner = THIS_MODULE,
1264 .open = kmemleak_open,
1266 .write = kmemleak_write,
1267 .llseek = seq_lseek,
1268 .release = kmemleak_release,
1272 * Perform the freeing of the kmemleak internal objects after waiting for any
1273 * current memory scan to complete.
1275 static int kmemleak_cleanup_thread(void *arg)
1277 struct kmemleak_object *object;
1279 mutex_lock(&scan_mutex);
1283 list_for_each_entry_rcu(object, &object_list, object_list)
1284 delete_object(object->pointer);
1286 mutex_unlock(&scan_mutex);
1292 * Start the clean-up thread.
1294 static void kmemleak_cleanup(void)
1296 struct task_struct *cleanup_thread;
1298 cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL,
1300 if (IS_ERR(cleanup_thread))
1301 pr_warning("Failed to create the clean-up thread\n");
1305 * Disable kmemleak. No memory allocation/freeing will be traced once this
1306 * function is called. Disabling kmemleak is an irreversible operation.
1308 static void kmemleak_disable(void)
1310 /* atomically check whether it was already invoked */
1311 if (atomic_cmpxchg(&kmemleak_error, 0, 1))
1314 /* stop any memory operation tracing */
1315 atomic_set(&kmemleak_early_log, 0);
1316 atomic_set(&kmemleak_enabled, 0);
1318 /* check whether it is too early for a kernel thread */
1319 if (atomic_read(&kmemleak_initialized))
1322 pr_info("Kernel memory leak detector disabled\n");
1326 * Allow boot-time kmemleak disabling (enabled by default).
1328 static int kmemleak_boot_config(char *str)
1332 if (strcmp(str, "off") == 0)
1334 else if (strcmp(str, "on") != 0)
1338 early_param("kmemleak", kmemleak_boot_config);
1341 * Kmemleak initialization.
1343 void __init kmemleak_init(void)
1346 unsigned long flags;
1348 jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
1349 jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
1351 object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
1352 scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
1353 INIT_PRIO_TREE_ROOT(&object_tree_root);
1355 /* the kernel is still in UP mode, so disabling the IRQs is enough */
1356 local_irq_save(flags);
1357 if (!atomic_read(&kmemleak_error)) {
1358 atomic_set(&kmemleak_enabled, 1);
1359 atomic_set(&kmemleak_early_log, 0);
1361 local_irq_restore(flags);
1364 * This is the point where tracking allocations is safe. Automatic
1365 * scanning is started during the late initcall. Add the early logged
1366 * callbacks to the kmemleak infrastructure.
1368 for (i = 0; i < crt_early_log; i++) {
1369 struct early_log *log = &early_log[i];
1371 switch (log->op_type) {
1372 case KMEMLEAK_ALLOC:
1373 kmemleak_alloc(log->ptr, log->size, log->min_count,
1377 kmemleak_free(log->ptr);
1379 case KMEMLEAK_NOT_LEAK:
1380 kmemleak_not_leak(log->ptr);
1382 case KMEMLEAK_IGNORE:
1383 kmemleak_ignore(log->ptr);
1385 case KMEMLEAK_SCAN_AREA:
1386 kmemleak_scan_area(log->ptr, log->offset, log->length,
1389 case KMEMLEAK_NO_SCAN:
1390 kmemleak_no_scan(log->ptr);
1399 * Late initialization function.
1401 static int __init kmemleak_late_init(void)
1403 struct dentry *dentry;
1405 atomic_set(&kmemleak_initialized, 1);
1407 if (atomic_read(&kmemleak_error)) {
1409 * Some error occured and kmemleak was disabled. There is a
1410 * small chance that kmemleak_disable() was called immediately
1411 * after setting kmemleak_initialized and we may end up with
1412 * two clean-up threads but serialized by scan_mutex.
1418 dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
1421 pr_warning("Failed to create the debugfs kmemleak file\n");
1422 mutex_lock(&scan_mutex);
1423 start_scan_thread();
1424 mutex_unlock(&scan_mutex);
1426 pr_info("Kernel memory leak detector initialized\n");
1430 late_initcall(kmemleak_late_init);