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/kmemcheck.h>
101 #include <linux/kmemleak.h>
104 * Kmemleak configuration and common defines.
106 #define MAX_TRACE 16 /* stack trace length */
107 #define MSECS_MIN_AGE 5000 /* minimum object age for reporting */
108 #define SECS_FIRST_SCAN 60 /* delay before the first scan */
109 #define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */
110 #define GRAY_LIST_PASSES 25 /* maximum number of gray list scans */
111 #define MAX_SCAN_SIZE 4096 /* maximum size of a scanned block */
113 #define BYTES_PER_POINTER sizeof(void *)
115 /* GFP bitmask for kmemleak internal allocations */
116 #define GFP_KMEMLEAK_MASK (GFP_KERNEL | GFP_ATOMIC)
118 /* scanning area inside a memory block */
119 struct kmemleak_scan_area {
120 struct hlist_node node;
121 unsigned long offset;
126 * Structure holding the metadata for each allocated memory block.
127 * Modifications to such objects should be made while holding the
128 * object->lock. Insertions or deletions from object_list, gray_list or
129 * tree_node are already protected by the corresponding locks or mutex (see
130 * the notes on locking above). These objects are reference-counted
131 * (use_count) and freed using the RCU mechanism.
133 struct kmemleak_object {
135 unsigned long flags; /* object status flags */
136 struct list_head object_list;
137 struct list_head gray_list;
138 struct prio_tree_node tree_node;
139 struct rcu_head rcu; /* object_list lockless traversal */
140 /* object usage count; object freed when use_count == 0 */
142 unsigned long pointer;
144 /* minimum number of a pointers found before it is considered leak */
146 /* the total number of pointers found pointing to this object */
148 /* memory ranges to be scanned inside an object (empty for all) */
149 struct hlist_head area_list;
150 unsigned long trace[MAX_TRACE];
151 unsigned int trace_len;
152 unsigned long jiffies; /* creation timestamp */
153 pid_t pid; /* pid of the current task */
154 char comm[TASK_COMM_LEN]; /* executable name */
157 /* flag representing the memory block allocation status */
158 #define OBJECT_ALLOCATED (1 << 0)
159 /* flag set after the first reporting of an unreference object */
160 #define OBJECT_REPORTED (1 << 1)
161 /* flag set to not scan the object */
162 #define OBJECT_NO_SCAN (1 << 2)
163 /* flag set on newly allocated objects */
164 #define OBJECT_NEW (1 << 3)
166 /* number of bytes to print per line; must be 16 or 32 */
167 #define HEX_ROW_SIZE 16
168 /* number of bytes to print at a time (1, 2, 4, 8) */
169 #define HEX_GROUP_SIZE 1
170 /* include ASCII after the hex output */
172 /* max number of lines to be printed */
173 #define HEX_MAX_LINES 2
175 /* the list of all allocated objects */
176 static LIST_HEAD(object_list);
177 /* the list of gray-colored objects (see color_gray comment below) */
178 static LIST_HEAD(gray_list);
179 /* prio search tree for object boundaries */
180 static struct prio_tree_root object_tree_root;
181 /* rw_lock protecting the access to object_list and prio_tree_root */
182 static DEFINE_RWLOCK(kmemleak_lock);
184 /* allocation caches for kmemleak internal data */
185 static struct kmem_cache *object_cache;
186 static struct kmem_cache *scan_area_cache;
188 /* set if tracing memory operations is enabled */
189 static atomic_t kmemleak_enabled = ATOMIC_INIT(0);
190 /* set in the late_initcall if there were no errors */
191 static atomic_t kmemleak_initialized = ATOMIC_INIT(0);
192 /* enables or disables early logging of the memory operations */
193 static atomic_t kmemleak_early_log = ATOMIC_INIT(1);
194 /* set if a fata kmemleak error has occurred */
195 static atomic_t kmemleak_error = ATOMIC_INIT(0);
197 /* minimum and maximum address that may be valid pointers */
198 static unsigned long min_addr = ULONG_MAX;
199 static unsigned long max_addr;
201 static struct task_struct *scan_thread;
202 /* used to avoid reporting of recently allocated objects */
203 static unsigned long jiffies_min_age;
204 static unsigned long jiffies_last_scan;
205 /* delay between automatic memory scannings */
206 static signed long jiffies_scan_wait;
207 /* enables or disables the task stacks scanning */
208 static int kmemleak_stack_scan = 1;
209 /* protects the memory scanning, parameters and debug/kmemleak file access */
210 static DEFINE_MUTEX(scan_mutex);
213 * Early object allocation/freeing logging. Kmemleak is initialized after the
214 * kernel allocator. However, both the kernel allocator and kmemleak may
215 * allocate memory blocks which need to be tracked. Kmemleak defines an
216 * arbitrary buffer to hold the allocation/freeing information before it is
220 /* kmemleak operation type for early logging */
232 * Structure holding the information passed to kmemleak callbacks during the
236 int op_type; /* kmemleak operation type */
237 const void *ptr; /* allocated/freed memory block */
238 size_t size; /* memory block size */
239 int min_count; /* minimum reference count */
240 unsigned long offset; /* scan area offset */
241 size_t length; /* scan area length */
242 unsigned long trace[MAX_TRACE]; /* stack trace */
243 unsigned int trace_len; /* stack trace length */
246 /* early logging buffer and current position */
247 static struct early_log
248 early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
249 static int crt_early_log __initdata;
251 static void kmemleak_disable(void);
254 * Print a warning and dump the stack trace.
256 #define kmemleak_warn(x...) do { \
262 * Macro invoked when a serious kmemleak condition occured and cannot be
263 * recovered from. Kmemleak will be disabled and further allocation/freeing
264 * tracing no longer available.
266 #define kmemleak_stop(x...) do { \
268 kmemleak_disable(); \
272 * Printing of the objects hex dump to the seq file. The number of lines to be
273 * printed is limited to HEX_MAX_LINES to prevent seq file spamming. The
274 * actual number of printed bytes depends on HEX_ROW_SIZE. It must be called
275 * with the object->lock held.
277 static void hex_dump_object(struct seq_file *seq,
278 struct kmemleak_object *object)
280 const u8 *ptr = (const u8 *)object->pointer;
281 int i, len, remaining;
282 unsigned char linebuf[HEX_ROW_SIZE * 5];
284 /* limit the number of lines to HEX_MAX_LINES */
286 min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE));
288 seq_printf(seq, " hex dump (first %d bytes):\n", len);
289 for (i = 0; i < len; i += HEX_ROW_SIZE) {
290 int linelen = min(remaining, HEX_ROW_SIZE);
292 remaining -= HEX_ROW_SIZE;
293 hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE,
294 HEX_GROUP_SIZE, linebuf, sizeof(linebuf),
296 seq_printf(seq, " %s\n", linebuf);
301 * Object colors, encoded with count and min_count:
302 * - white - orphan object, not enough references to it (count < min_count)
303 * - gray - not orphan, not marked as false positive (min_count == 0) or
304 * sufficient references to it (count >= min_count)
305 * - black - ignore, it doesn't contain references (e.g. text section)
306 * (min_count == -1). No function defined for this color.
307 * Newly created objects don't have any color assigned (object->count == -1)
308 * before the next memory scan when they become white.
310 static int color_white(const struct kmemleak_object *object)
312 return object->count != -1 && object->count < object->min_count;
315 static int color_gray(const struct kmemleak_object *object)
317 return object->min_count != -1 && object->count >= object->min_count;
320 static int color_black(const struct kmemleak_object *object)
322 return object->min_count == -1;
326 * Objects are considered unreferenced only if their color is white, they have
327 * not be deleted and have a minimum age to avoid false positives caused by
328 * pointers temporarily stored in CPU registers.
330 static int unreferenced_object(struct kmemleak_object *object)
332 return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
333 time_before_eq(object->jiffies + jiffies_min_age,
338 * Printing of the unreferenced objects information to the seq file. The
339 * print_unreferenced function must be called with the object->lock held.
341 static void print_unreferenced(struct seq_file *seq,
342 struct kmemleak_object *object)
346 seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
347 object->pointer, object->size);
348 seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu\n",
349 object->comm, object->pid, object->jiffies);
350 hex_dump_object(seq, object);
351 seq_printf(seq, " backtrace:\n");
353 for (i = 0; i < object->trace_len; i++) {
354 void *ptr = (void *)object->trace[i];
355 seq_printf(seq, " [<%p>] %pS\n", ptr, ptr);
360 * Print the kmemleak_object information. This function is used mainly for
361 * debugging special cases when kmemleak operations. It must be called with
362 * the object->lock held.
364 static void dump_object_info(struct kmemleak_object *object)
366 struct stack_trace trace;
368 trace.nr_entries = object->trace_len;
369 trace.entries = object->trace;
371 pr_notice("Object 0x%08lx (size %zu):\n",
372 object->tree_node.start, object->size);
373 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
374 object->comm, object->pid, object->jiffies);
375 pr_notice(" min_count = %d\n", object->min_count);
376 pr_notice(" count = %d\n", object->count);
377 pr_notice(" flags = 0x%lx\n", object->flags);
378 pr_notice(" backtrace:\n");
379 print_stack_trace(&trace, 4);
383 * Look-up a memory block metadata (kmemleak_object) in the priority search
384 * tree based on a pointer value. If alias is 0, only values pointing to the
385 * beginning of the memory block are allowed. The kmemleak_lock must be held
386 * when calling this function.
388 static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
390 struct prio_tree_node *node;
391 struct prio_tree_iter iter;
392 struct kmemleak_object *object;
394 prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr);
395 node = prio_tree_next(&iter);
397 object = prio_tree_entry(node, struct kmemleak_object,
399 if (!alias && object->pointer != ptr) {
400 kmemleak_warn("Found object by alias");
410 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
411 * that once an object's use_count reached 0, the RCU freeing was already
412 * registered and the object should no longer be used. This function must be
413 * called under the protection of rcu_read_lock().
415 static int get_object(struct kmemleak_object *object)
417 return atomic_inc_not_zero(&object->use_count);
421 * RCU callback to free a kmemleak_object.
423 static void free_object_rcu(struct rcu_head *rcu)
425 struct hlist_node *elem, *tmp;
426 struct kmemleak_scan_area *area;
427 struct kmemleak_object *object =
428 container_of(rcu, struct kmemleak_object, rcu);
431 * Once use_count is 0 (guaranteed by put_object), there is no other
432 * code accessing this object, hence no need for locking.
434 hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) {
436 kmem_cache_free(scan_area_cache, area);
438 kmem_cache_free(object_cache, object);
442 * Decrement the object use_count. Once the count is 0, free the object using
443 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
444 * delete_object() path, the delayed RCU freeing ensures that there is no
445 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
448 static void put_object(struct kmemleak_object *object)
450 if (!atomic_dec_and_test(&object->use_count))
453 /* should only get here after delete_object was called */
454 WARN_ON(object->flags & OBJECT_ALLOCATED);
456 call_rcu(&object->rcu, free_object_rcu);
460 * Look up an object in the prio search tree and increase its use_count.
462 static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
465 struct kmemleak_object *object = NULL;
468 read_lock_irqsave(&kmemleak_lock, flags);
469 if (ptr >= min_addr && ptr < max_addr)
470 object = lookup_object(ptr, alias);
471 read_unlock_irqrestore(&kmemleak_lock, flags);
473 /* check whether the object is still available */
474 if (object && !get_object(object))
482 * Save stack trace to the given array of MAX_TRACE size.
484 static int __save_stack_trace(unsigned long *trace)
486 struct stack_trace stack_trace;
488 stack_trace.max_entries = MAX_TRACE;
489 stack_trace.nr_entries = 0;
490 stack_trace.entries = trace;
491 stack_trace.skip = 2;
492 save_stack_trace(&stack_trace);
494 return stack_trace.nr_entries;
498 * Create the metadata (struct kmemleak_object) corresponding to an allocated
499 * memory block and add it to the object_list and object_tree_root.
501 static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
502 int min_count, gfp_t gfp)
505 struct kmemleak_object *object;
506 struct prio_tree_node *node;
508 object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK);
510 kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
514 INIT_LIST_HEAD(&object->object_list);
515 INIT_LIST_HEAD(&object->gray_list);
516 INIT_HLIST_HEAD(&object->area_list);
517 spin_lock_init(&object->lock);
518 atomic_set(&object->use_count, 1);
519 object->flags = OBJECT_ALLOCATED | OBJECT_NEW;
520 object->pointer = ptr;
522 object->min_count = min_count;
523 object->count = -1; /* no color initially */
524 object->jiffies = jiffies;
526 /* task information */
529 strncpy(object->comm, "hardirq", sizeof(object->comm));
530 } else if (in_softirq()) {
532 strncpy(object->comm, "softirq", sizeof(object->comm));
534 object->pid = current->pid;
536 * There is a small chance of a race with set_task_comm(),
537 * however using get_task_comm() here may cause locking
538 * dependency issues with current->alloc_lock. In the worst
539 * case, the command line is not correct.
541 strncpy(object->comm, current->comm, sizeof(object->comm));
544 /* kernel backtrace */
545 object->trace_len = __save_stack_trace(object->trace);
547 INIT_PRIO_TREE_NODE(&object->tree_node);
548 object->tree_node.start = ptr;
549 object->tree_node.last = ptr + size - 1;
551 write_lock_irqsave(&kmemleak_lock, flags);
552 min_addr = min(min_addr, ptr);
553 max_addr = max(max_addr, ptr + size);
554 node = prio_tree_insert(&object_tree_root, &object->tree_node);
556 * The code calling the kernel does not yet have the pointer to the
557 * memory block to be able to free it. However, we still hold the
558 * kmemleak_lock here in case parts of the kernel started freeing
559 * random memory blocks.
561 if (node != &object->tree_node) {
564 kmemleak_stop("Cannot insert 0x%lx into the object search tree "
565 "(already existing)\n", ptr);
566 object = lookup_object(ptr, 1);
567 spin_lock_irqsave(&object->lock, flags);
568 dump_object_info(object);
569 spin_unlock_irqrestore(&object->lock, flags);
573 list_add_tail_rcu(&object->object_list, &object_list);
575 write_unlock_irqrestore(&kmemleak_lock, flags);
580 * Remove the metadata (struct kmemleak_object) for a memory block from the
581 * object_list and object_tree_root and decrement its use_count.
583 static void __delete_object(struct kmemleak_object *object)
587 write_lock_irqsave(&kmemleak_lock, flags);
588 prio_tree_remove(&object_tree_root, &object->tree_node);
589 list_del_rcu(&object->object_list);
590 write_unlock_irqrestore(&kmemleak_lock, flags);
592 WARN_ON(!(object->flags & OBJECT_ALLOCATED));
593 WARN_ON(atomic_read(&object->use_count) < 2);
596 * Locking here also ensures that the corresponding memory block
597 * cannot be freed when it is being scanned.
599 spin_lock_irqsave(&object->lock, flags);
600 object->flags &= ~OBJECT_ALLOCATED;
601 spin_unlock_irqrestore(&object->lock, flags);
606 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
609 static void delete_object_full(unsigned long ptr)
611 struct kmemleak_object *object;
613 object = find_and_get_object(ptr, 0);
616 kmemleak_warn("Freeing unknown object at 0x%08lx\n",
621 __delete_object(object);
626 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
627 * delete it. If the memory block is partially freed, the function may create
628 * additional metadata for the remaining parts of the block.
630 static void delete_object_part(unsigned long ptr, size_t size)
632 struct kmemleak_object *object;
633 unsigned long start, end;
635 object = find_and_get_object(ptr, 1);
638 kmemleak_warn("Partially freeing unknown object at 0x%08lx "
639 "(size %zu)\n", ptr, size);
643 __delete_object(object);
646 * Create one or two objects that may result from the memory block
647 * split. Note that partial freeing is only done by free_bootmem() and
648 * this happens before kmemleak_init() is called. The path below is
649 * only executed during early log recording in kmemleak_init(), so
650 * GFP_KERNEL is enough.
652 start = object->pointer;
653 end = object->pointer + object->size;
655 create_object(start, ptr - start, object->min_count,
657 if (ptr + size < end)
658 create_object(ptr + size, end - ptr - size, object->min_count,
664 * Make a object permanently as gray-colored so that it can no longer be
665 * reported as a leak. This is used in general to mark a false positive.
667 static void make_gray_object(unsigned long ptr)
670 struct kmemleak_object *object;
672 object = find_and_get_object(ptr, 0);
674 kmemleak_warn("Graying unknown object at 0x%08lx\n", ptr);
678 spin_lock_irqsave(&object->lock, flags);
679 object->min_count = 0;
680 spin_unlock_irqrestore(&object->lock, flags);
685 * Mark the object as black-colored so that it is ignored from scans and
688 static void make_black_object(unsigned long ptr)
691 struct kmemleak_object *object;
693 object = find_and_get_object(ptr, 0);
695 kmemleak_warn("Blacking unknown object at 0x%08lx\n", ptr);
699 spin_lock_irqsave(&object->lock, flags);
700 object->min_count = -1;
701 object->flags |= OBJECT_NO_SCAN;
702 spin_unlock_irqrestore(&object->lock, flags);
707 * Add a scanning area to the object. If at least one such area is added,
708 * kmemleak will only scan these ranges rather than the whole memory block.
710 static void add_scan_area(unsigned long ptr, unsigned long offset,
711 size_t length, gfp_t gfp)
714 struct kmemleak_object *object;
715 struct kmemleak_scan_area *area;
717 object = find_and_get_object(ptr, 0);
719 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
724 area = kmem_cache_alloc(scan_area_cache, gfp & GFP_KMEMLEAK_MASK);
726 kmemleak_warn("Cannot allocate a scan area\n");
730 spin_lock_irqsave(&object->lock, flags);
731 if (offset + length > object->size) {
732 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
733 dump_object_info(object);
734 kmem_cache_free(scan_area_cache, area);
738 INIT_HLIST_NODE(&area->node);
739 area->offset = offset;
740 area->length = length;
742 hlist_add_head(&area->node, &object->area_list);
744 spin_unlock_irqrestore(&object->lock, flags);
750 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
751 * pointer. Such object will not be scanned by kmemleak but references to it
754 static void object_no_scan(unsigned long ptr)
757 struct kmemleak_object *object;
759 object = find_and_get_object(ptr, 0);
761 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
765 spin_lock_irqsave(&object->lock, flags);
766 object->flags |= OBJECT_NO_SCAN;
767 spin_unlock_irqrestore(&object->lock, flags);
772 * Log an early kmemleak_* call to the early_log buffer. These calls will be
773 * processed later once kmemleak is fully initialized.
775 static void __init log_early(int op_type, const void *ptr, size_t size,
776 int min_count, unsigned long offset, size_t length)
779 struct early_log *log;
781 if (crt_early_log >= ARRAY_SIZE(early_log)) {
782 pr_warning("Early log buffer exceeded\n");
788 * There is no need for locking since the kernel is still in UP mode
789 * at this stage. Disabling the IRQs is enough.
791 local_irq_save(flags);
792 log = &early_log[crt_early_log];
793 log->op_type = op_type;
796 log->min_count = min_count;
797 log->offset = offset;
798 log->length = length;
799 if (op_type == KMEMLEAK_ALLOC)
800 log->trace_len = __save_stack_trace(log->trace);
802 local_irq_restore(flags);
806 * Log an early allocated block and populate the stack trace.
808 static void early_alloc(struct early_log *log)
810 struct kmemleak_object *object;
814 if (!atomic_read(&kmemleak_enabled) || !log->ptr || IS_ERR(log->ptr))
818 * RCU locking needed to ensure object is not freed via put_object().
821 object = create_object((unsigned long)log->ptr, log->size,
822 log->min_count, GFP_KERNEL);
823 spin_lock_irqsave(&object->lock, flags);
824 for (i = 0; i < log->trace_len; i++)
825 object->trace[i] = log->trace[i];
826 object->trace_len = log->trace_len;
827 spin_unlock_irqrestore(&object->lock, flags);
832 * Memory allocation function callback. This function is called from the
833 * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc,
836 void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
839 pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
841 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
842 create_object((unsigned long)ptr, size, min_count, gfp);
843 else if (atomic_read(&kmemleak_early_log))
844 log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
846 EXPORT_SYMBOL_GPL(kmemleak_alloc);
849 * Memory freeing function callback. This function is called from the kernel
850 * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.).
852 void __ref kmemleak_free(const void *ptr)
854 pr_debug("%s(0x%p)\n", __func__, ptr);
856 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
857 delete_object_full((unsigned long)ptr);
858 else if (atomic_read(&kmemleak_early_log))
859 log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
861 EXPORT_SYMBOL_GPL(kmemleak_free);
864 * Partial memory freeing function callback. This function is usually called
865 * from bootmem allocator when (part of) a memory block is freed.
867 void __ref kmemleak_free_part(const void *ptr, size_t size)
869 pr_debug("%s(0x%p)\n", __func__, ptr);
871 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
872 delete_object_part((unsigned long)ptr, size);
873 else if (atomic_read(&kmemleak_early_log))
874 log_early(KMEMLEAK_FREE_PART, ptr, size, 0, 0, 0);
876 EXPORT_SYMBOL_GPL(kmemleak_free_part);
879 * Mark an already allocated memory block as a false positive. This will cause
880 * the block to no longer be reported as leak and always be scanned.
882 void __ref kmemleak_not_leak(const void *ptr)
884 pr_debug("%s(0x%p)\n", __func__, ptr);
886 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
887 make_gray_object((unsigned long)ptr);
888 else if (atomic_read(&kmemleak_early_log))
889 log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
891 EXPORT_SYMBOL(kmemleak_not_leak);
894 * Ignore a memory block. This is usually done when it is known that the
895 * corresponding block is not a leak and does not contain any references to
896 * other allocated memory blocks.
898 void __ref kmemleak_ignore(const void *ptr)
900 pr_debug("%s(0x%p)\n", __func__, ptr);
902 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
903 make_black_object((unsigned long)ptr);
904 else if (atomic_read(&kmemleak_early_log))
905 log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
907 EXPORT_SYMBOL(kmemleak_ignore);
910 * Limit the range to be scanned in an allocated memory block.
912 void __ref kmemleak_scan_area(const void *ptr, unsigned long offset,
913 size_t length, gfp_t gfp)
915 pr_debug("%s(0x%p)\n", __func__, ptr);
917 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
918 add_scan_area((unsigned long)ptr, offset, length, gfp);
919 else if (atomic_read(&kmemleak_early_log))
920 log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
922 EXPORT_SYMBOL(kmemleak_scan_area);
925 * Inform kmemleak not to scan the given memory block.
927 void __ref kmemleak_no_scan(const void *ptr)
929 pr_debug("%s(0x%p)\n", __func__, ptr);
931 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
932 object_no_scan((unsigned long)ptr);
933 else if (atomic_read(&kmemleak_early_log))
934 log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0);
936 EXPORT_SYMBOL(kmemleak_no_scan);
939 * Memory scanning is a long process and it needs to be interruptable. This
940 * function checks whether such interrupt condition occured.
942 static int scan_should_stop(void)
944 if (!atomic_read(&kmemleak_enabled))
948 * This function may be called from either process or kthread context,
949 * hence the need to check for both stop conditions.
952 return signal_pending(current);
954 return kthread_should_stop();
960 * Scan a memory block (exclusive range) for valid pointers and add those
961 * found to the gray list.
963 static void scan_block(void *_start, void *_end,
964 struct kmemleak_object *scanned, int allow_resched)
967 unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
968 unsigned long *end = _end - (BYTES_PER_POINTER - 1);
970 for (ptr = start; ptr < end; ptr++) {
971 struct kmemleak_object *object;
973 unsigned long pointer;
977 if (scan_should_stop())
980 /* don't scan uninitialized memory */
981 if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
987 object = find_and_get_object(pointer, 1);
990 if (object == scanned) {
991 /* self referenced, ignore */
997 * Avoid the lockdep recursive warning on object->lock being
998 * previously acquired in scan_object(). These locks are
999 * enclosed by scan_mutex.
1001 spin_lock_irqsave_nested(&object->lock, flags,
1002 SINGLE_DEPTH_NESTING);
1003 if (!color_white(object)) {
1004 /* non-orphan, ignored or new */
1005 spin_unlock_irqrestore(&object->lock, flags);
1011 * Increase the object's reference count (number of pointers
1012 * to the memory block). If this count reaches the required
1013 * minimum, the object's color will become gray and it will be
1014 * added to the gray_list.
1017 if (color_gray(object))
1018 list_add_tail(&object->gray_list, &gray_list);
1021 spin_unlock_irqrestore(&object->lock, flags);
1026 * Scan a memory block corresponding to a kmemleak_object. A condition is
1027 * that object->use_count >= 1.
1029 static void scan_object(struct kmemleak_object *object)
1031 struct kmemleak_scan_area *area;
1032 struct hlist_node *elem;
1033 unsigned long flags;
1036 * Once the object->lock is aquired, the corresponding memory block
1037 * cannot be freed (the same lock is aquired in delete_object).
1039 spin_lock_irqsave(&object->lock, flags);
1040 if (object->flags & OBJECT_NO_SCAN)
1042 if (!(object->flags & OBJECT_ALLOCATED))
1043 /* already freed object */
1045 if (hlist_empty(&object->area_list)) {
1046 void *start = (void *)object->pointer;
1047 void *end = (void *)(object->pointer + object->size);
1049 while (start < end && (object->flags & OBJECT_ALLOCATED) &&
1050 !(object->flags & OBJECT_NO_SCAN)) {
1051 scan_block(start, min(start + MAX_SCAN_SIZE, end),
1053 start += MAX_SCAN_SIZE;
1055 spin_unlock_irqrestore(&object->lock, flags);
1057 spin_lock_irqsave(&object->lock, flags);
1060 hlist_for_each_entry(area, elem, &object->area_list, node)
1061 scan_block((void *)(object->pointer + area->offset),
1062 (void *)(object->pointer + area->offset
1063 + area->length), object, 0);
1065 spin_unlock_irqrestore(&object->lock, flags);
1069 * Scan data sections and all the referenced memory blocks allocated via the
1070 * kernel's standard allocators. This function must be called with the
1073 static void kmemleak_scan(void)
1075 unsigned long flags;
1076 struct kmemleak_object *object, *tmp;
1079 int gray_list_pass = 0;
1081 jiffies_last_scan = jiffies;
1083 /* prepare the kmemleak_object's */
1085 list_for_each_entry_rcu(object, &object_list, object_list) {
1086 spin_lock_irqsave(&object->lock, flags);
1089 * With a few exceptions there should be a maximum of
1090 * 1 reference to any object at this point.
1092 if (atomic_read(&object->use_count) > 1) {
1093 pr_debug("object->use_count = %d\n",
1094 atomic_read(&object->use_count));
1095 dump_object_info(object);
1098 /* reset the reference count (whiten the object) */
1100 object->flags &= ~OBJECT_NEW;
1101 if (color_gray(object) && get_object(object))
1102 list_add_tail(&object->gray_list, &gray_list);
1104 spin_unlock_irqrestore(&object->lock, flags);
1108 /* data/bss scanning */
1109 scan_block(_sdata, _edata, NULL, 1);
1110 scan_block(__bss_start, __bss_stop, NULL, 1);
1113 /* per-cpu sections scanning */
1114 for_each_possible_cpu(i)
1115 scan_block(__per_cpu_start + per_cpu_offset(i),
1116 __per_cpu_end + per_cpu_offset(i), NULL, 1);
1120 * Struct page scanning for each node. The code below is not yet safe
1121 * with MEMORY_HOTPLUG.
1123 for_each_online_node(i) {
1124 pg_data_t *pgdat = NODE_DATA(i);
1125 unsigned long start_pfn = pgdat->node_start_pfn;
1126 unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
1129 for (pfn = start_pfn; pfn < end_pfn; pfn++) {
1132 if (!pfn_valid(pfn))
1134 page = pfn_to_page(pfn);
1135 /* only scan if page is in use */
1136 if (page_count(page) == 0)
1138 scan_block(page, page + 1, NULL, 1);
1143 * Scanning the task stacks (may introduce false negatives).
1145 if (kmemleak_stack_scan) {
1146 struct task_struct *p, *g;
1148 read_lock(&tasklist_lock);
1149 do_each_thread(g, p) {
1150 scan_block(task_stack_page(p), task_stack_page(p) +
1151 THREAD_SIZE, NULL, 0);
1152 } while_each_thread(g, p);
1153 read_unlock(&tasklist_lock);
1157 * Scan the objects already referenced from the sections scanned
1158 * above. More objects will be referenced and, if there are no memory
1159 * leaks, all the objects will be scanned. The list traversal is safe
1160 * for both tail additions and removals from inside the loop. The
1161 * kmemleak objects cannot be freed from outside the loop because their
1162 * use_count was increased.
1165 object = list_entry(gray_list.next, typeof(*object), gray_list);
1166 while (&object->gray_list != &gray_list) {
1169 /* may add new objects to the list */
1170 if (!scan_should_stop())
1171 scan_object(object);
1173 tmp = list_entry(object->gray_list.next, typeof(*object),
1176 /* remove the object from the list and release it */
1177 list_del(&object->gray_list);
1183 if (scan_should_stop() || ++gray_list_pass >= GRAY_LIST_PASSES)
1187 * Check for new objects allocated during this scanning and add them
1191 list_for_each_entry_rcu(object, &object_list, object_list) {
1192 spin_lock_irqsave(&object->lock, flags);
1193 if ((object->flags & OBJECT_NEW) && !color_black(object) &&
1194 get_object(object)) {
1195 object->flags &= ~OBJECT_NEW;
1196 list_add_tail(&object->gray_list, &gray_list);
1198 spin_unlock_irqrestore(&object->lock, flags);
1202 if (!list_empty(&gray_list))
1206 WARN_ON(!list_empty(&gray_list));
1209 * If scanning was stopped or new objects were being allocated at a
1210 * higher rate than gray list scanning, do not report any new
1211 * unreferenced objects.
1213 if (scan_should_stop() || gray_list_pass >= GRAY_LIST_PASSES)
1217 * Scanning result reporting.
1220 list_for_each_entry_rcu(object, &object_list, object_list) {
1221 spin_lock_irqsave(&object->lock, flags);
1222 if (unreferenced_object(object) &&
1223 !(object->flags & OBJECT_REPORTED)) {
1224 object->flags |= OBJECT_REPORTED;
1227 spin_unlock_irqrestore(&object->lock, flags);
1232 pr_info("%d new suspected memory leaks (see "
1233 "/sys/kernel/debug/kmemleak)\n", new_leaks);
1238 * Thread function performing automatic memory scanning. Unreferenced objects
1239 * at the end of a memory scan are reported but only the first time.
1241 static int kmemleak_scan_thread(void *arg)
1243 static int first_run = 1;
1245 pr_info("Automatic memory scanning thread started\n");
1246 set_user_nice(current, 10);
1249 * Wait before the first scan to allow the system to fully initialize.
1253 ssleep(SECS_FIRST_SCAN);
1256 while (!kthread_should_stop()) {
1257 signed long timeout = jiffies_scan_wait;
1259 mutex_lock(&scan_mutex);
1261 mutex_unlock(&scan_mutex);
1263 /* wait before the next scan */
1264 while (timeout && !kthread_should_stop())
1265 timeout = schedule_timeout_interruptible(timeout);
1268 pr_info("Automatic memory scanning thread ended\n");
1274 * Start the automatic memory scanning thread. This function must be called
1275 * with the scan_mutex held.
1277 void start_scan_thread(void)
1281 scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
1282 if (IS_ERR(scan_thread)) {
1283 pr_warning("Failed to create the scan thread\n");
1289 * Stop the automatic memory scanning thread. This function must be called
1290 * with the scan_mutex held.
1292 void stop_scan_thread(void)
1295 kthread_stop(scan_thread);
1301 * Iterate over the object_list and return the first valid object at or after
1302 * the required position with its use_count incremented. The function triggers
1303 * a memory scanning when the pos argument points to the first position.
1305 static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
1307 struct kmemleak_object *object;
1311 err = mutex_lock_interruptible(&scan_mutex);
1313 return ERR_PTR(err);
1316 list_for_each_entry_rcu(object, &object_list, object_list) {
1319 if (get_object(object))
1328 * Return the next object in the object_list. The function decrements the
1329 * use_count of the previous object and increases that of the next one.
1331 static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1333 struct kmemleak_object *prev_obj = v;
1334 struct kmemleak_object *next_obj = NULL;
1335 struct list_head *n = &prev_obj->object_list;
1339 list_for_each_continue_rcu(n, &object_list) {
1340 next_obj = list_entry(n, struct kmemleak_object, object_list);
1341 if (get_object(next_obj))
1345 put_object(prev_obj);
1350 * Decrement the use_count of the last object required, if any.
1352 static void kmemleak_seq_stop(struct seq_file *seq, void *v)
1356 * kmemleak_seq_start may return ERR_PTR if the scan_mutex
1357 * waiting was interrupted, so only release it if !IS_ERR.
1360 mutex_unlock(&scan_mutex);
1367 * Print the information for an unreferenced object to the seq file.
1369 static int kmemleak_seq_show(struct seq_file *seq, void *v)
1371 struct kmemleak_object *object = v;
1372 unsigned long flags;
1374 spin_lock_irqsave(&object->lock, flags);
1375 if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1376 print_unreferenced(seq, object);
1377 spin_unlock_irqrestore(&object->lock, flags);
1381 static const struct seq_operations kmemleak_seq_ops = {
1382 .start = kmemleak_seq_start,
1383 .next = kmemleak_seq_next,
1384 .stop = kmemleak_seq_stop,
1385 .show = kmemleak_seq_show,
1388 static int kmemleak_open(struct inode *inode, struct file *file)
1390 if (!atomic_read(&kmemleak_enabled))
1393 return seq_open(file, &kmemleak_seq_ops);
1396 static int kmemleak_release(struct inode *inode, struct file *file)
1398 return seq_release(inode, file);
1401 static int dump_str_object_info(const char *str)
1403 unsigned long flags;
1404 struct kmemleak_object *object;
1407 addr= simple_strtoul(str, NULL, 0);
1408 object = find_and_get_object(addr, 0);
1410 pr_info("Unknown object at 0x%08lx\n", addr);
1414 spin_lock_irqsave(&object->lock, flags);
1415 dump_object_info(object);
1416 spin_unlock_irqrestore(&object->lock, flags);
1423 * File write operation to configure kmemleak at run-time. The following
1424 * commands can be written to the /sys/kernel/debug/kmemleak file:
1425 * off - disable kmemleak (irreversible)
1426 * stack=on - enable the task stacks scanning
1427 * stack=off - disable the tasks stacks scanning
1428 * scan=on - start the automatic memory scanning thread
1429 * scan=off - stop the automatic memory scanning thread
1430 * scan=... - set the automatic memory scanning period in seconds (0 to
1432 * scan - trigger a memory scan
1433 * dump=... - dump information about the object found at the given address
1435 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
1436 size_t size, loff_t *ppos)
1442 buf_size = min(size, (sizeof(buf) - 1));
1443 if (strncpy_from_user(buf, user_buf, buf_size) < 0)
1447 ret = mutex_lock_interruptible(&scan_mutex);
1451 if (strncmp(buf, "off", 3) == 0)
1453 else if (strncmp(buf, "stack=on", 8) == 0)
1454 kmemleak_stack_scan = 1;
1455 else if (strncmp(buf, "stack=off", 9) == 0)
1456 kmemleak_stack_scan = 0;
1457 else if (strncmp(buf, "scan=on", 7) == 0)
1458 start_scan_thread();
1459 else if (strncmp(buf, "scan=off", 8) == 0)
1461 else if (strncmp(buf, "scan=", 5) == 0) {
1464 ret = strict_strtoul(buf + 5, 0, &secs);
1469 jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
1470 start_scan_thread();
1472 } else if (strncmp(buf, "scan", 4) == 0)
1474 else if (strncmp(buf, "dump=", 5) == 0)
1475 ret = dump_str_object_info(buf + 5);
1480 mutex_unlock(&scan_mutex);
1484 /* ignore the rest of the buffer, only one command at a time */
1489 static const struct file_operations kmemleak_fops = {
1490 .owner = THIS_MODULE,
1491 .open = kmemleak_open,
1493 .write = kmemleak_write,
1494 .llseek = seq_lseek,
1495 .release = kmemleak_release,
1499 * Perform the freeing of the kmemleak internal objects after waiting for any
1500 * current memory scan to complete.
1502 static int kmemleak_cleanup_thread(void *arg)
1504 struct kmemleak_object *object;
1506 mutex_lock(&scan_mutex);
1510 list_for_each_entry_rcu(object, &object_list, object_list)
1511 delete_object_full(object->pointer);
1513 mutex_unlock(&scan_mutex);
1519 * Start the clean-up thread.
1521 static void kmemleak_cleanup(void)
1523 struct task_struct *cleanup_thread;
1525 cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL,
1527 if (IS_ERR(cleanup_thread))
1528 pr_warning("Failed to create the clean-up thread\n");
1532 * Disable kmemleak. No memory allocation/freeing will be traced once this
1533 * function is called. Disabling kmemleak is an irreversible operation.
1535 static void kmemleak_disable(void)
1537 /* atomically check whether it was already invoked */
1538 if (atomic_cmpxchg(&kmemleak_error, 0, 1))
1541 /* stop any memory operation tracing */
1542 atomic_set(&kmemleak_early_log, 0);
1543 atomic_set(&kmemleak_enabled, 0);
1545 /* check whether it is too early for a kernel thread */
1546 if (atomic_read(&kmemleak_initialized))
1549 pr_info("Kernel memory leak detector disabled\n");
1553 * Allow boot-time kmemleak disabling (enabled by default).
1555 static int kmemleak_boot_config(char *str)
1559 if (strcmp(str, "off") == 0)
1561 else if (strcmp(str, "on") != 0)
1565 early_param("kmemleak", kmemleak_boot_config);
1568 * Kmemleak initialization.
1570 void __init kmemleak_init(void)
1573 unsigned long flags;
1575 jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
1576 jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
1578 object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
1579 scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
1580 INIT_PRIO_TREE_ROOT(&object_tree_root);
1582 /* the kernel is still in UP mode, so disabling the IRQs is enough */
1583 local_irq_save(flags);
1584 if (!atomic_read(&kmemleak_error)) {
1585 atomic_set(&kmemleak_enabled, 1);
1586 atomic_set(&kmemleak_early_log, 0);
1588 local_irq_restore(flags);
1591 * This is the point where tracking allocations is safe. Automatic
1592 * scanning is started during the late initcall. Add the early logged
1593 * callbacks to the kmemleak infrastructure.
1595 for (i = 0; i < crt_early_log; i++) {
1596 struct early_log *log = &early_log[i];
1598 switch (log->op_type) {
1599 case KMEMLEAK_ALLOC:
1603 kmemleak_free(log->ptr);
1605 case KMEMLEAK_FREE_PART:
1606 kmemleak_free_part(log->ptr, log->size);
1608 case KMEMLEAK_NOT_LEAK:
1609 kmemleak_not_leak(log->ptr);
1611 case KMEMLEAK_IGNORE:
1612 kmemleak_ignore(log->ptr);
1614 case KMEMLEAK_SCAN_AREA:
1615 kmemleak_scan_area(log->ptr, log->offset, log->length,
1618 case KMEMLEAK_NO_SCAN:
1619 kmemleak_no_scan(log->ptr);
1628 * Late initialization function.
1630 static int __init kmemleak_late_init(void)
1632 struct dentry *dentry;
1634 atomic_set(&kmemleak_initialized, 1);
1636 if (atomic_read(&kmemleak_error)) {
1638 * Some error occured and kmemleak was disabled. There is a
1639 * small chance that kmemleak_disable() was called immediately
1640 * after setting kmemleak_initialized and we may end up with
1641 * two clean-up threads but serialized by scan_mutex.
1647 dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
1650 pr_warning("Failed to create the debugfs kmemleak file\n");
1651 mutex_lock(&scan_mutex);
1652 start_scan_thread();
1653 mutex_unlock(&scan_mutex);
1655 pr_info("Kernel memory leak detector initialized\n");
1659 late_initcall(kmemleak_late_init);