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 /* number of bytes to print per line; must be 16 or 32 */
166 #define HEX_ROW_SIZE 16
167 /* number of bytes to print at a time (1, 2, 4, 8) */
168 #define HEX_GROUP_SIZE 1
169 /* include ASCII after the hex output */
171 /* max number of lines to be printed */
172 #define HEX_MAX_LINES 2
174 /* the list of all allocated objects */
175 static LIST_HEAD(object_list);
176 /* the list of gray-colored objects (see color_gray comment below) */
177 static LIST_HEAD(gray_list);
178 /* prio search tree for object boundaries */
179 static struct prio_tree_root object_tree_root;
180 /* rw_lock protecting the access to object_list and prio_tree_root */
181 static DEFINE_RWLOCK(kmemleak_lock);
183 /* allocation caches for kmemleak internal data */
184 static struct kmem_cache *object_cache;
185 static struct kmem_cache *scan_area_cache;
187 /* set if tracing memory operations is enabled */
188 static atomic_t kmemleak_enabled = ATOMIC_INIT(0);
189 /* set in the late_initcall if there were no errors */
190 static atomic_t kmemleak_initialized = ATOMIC_INIT(0);
191 /* enables or disables early logging of the memory operations */
192 static atomic_t kmemleak_early_log = ATOMIC_INIT(1);
193 /* set if a fata kmemleak error has occurred */
194 static atomic_t kmemleak_error = ATOMIC_INIT(0);
196 /* minimum and maximum address that may be valid pointers */
197 static unsigned long min_addr = ULONG_MAX;
198 static unsigned long max_addr;
200 static struct task_struct *scan_thread;
201 /* used to avoid reporting of recently allocated objects */
202 static unsigned long jiffies_min_age;
203 static unsigned long jiffies_last_scan;
204 /* delay between automatic memory scannings */
205 static signed long jiffies_scan_wait;
206 /* enables or disables the task stacks scanning */
207 static int kmemleak_stack_scan = 1;
208 /* protects the memory scanning, parameters and debug/kmemleak file access */
209 static DEFINE_MUTEX(scan_mutex);
212 * Early object allocation/freeing logging. Kmemleak is initialized after the
213 * kernel allocator. However, both the kernel allocator and kmemleak may
214 * allocate memory blocks which need to be tracked. Kmemleak defines an
215 * arbitrary buffer to hold the allocation/freeing information before it is
219 /* kmemleak operation type for early logging */
231 * Structure holding the information passed to kmemleak callbacks during the
235 int op_type; /* kmemleak operation type */
236 const void *ptr; /* allocated/freed memory block */
237 size_t size; /* memory block size */
238 int min_count; /* minimum reference count */
239 unsigned long offset; /* scan area offset */
240 size_t length; /* scan area length */
241 unsigned long trace[MAX_TRACE]; /* stack trace */
242 unsigned int trace_len; /* stack trace length */
245 /* early logging buffer and current position */
246 static struct early_log
247 early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
248 static int crt_early_log __initdata;
250 static void kmemleak_disable(void);
253 * Print a warning and dump the stack trace.
255 #define kmemleak_warn(x...) do { \
261 * Macro invoked when a serious kmemleak condition occured and cannot be
262 * recovered from. Kmemleak will be disabled and further allocation/freeing
263 * tracing no longer available.
265 #define kmemleak_stop(x...) do { \
267 kmemleak_disable(); \
271 * Printing of the objects hex dump to the seq file. The number of lines to be
272 * printed is limited to HEX_MAX_LINES to prevent seq file spamming. The
273 * actual number of printed bytes depends on HEX_ROW_SIZE. It must be called
274 * with the object->lock held.
276 static void hex_dump_object(struct seq_file *seq,
277 struct kmemleak_object *object)
279 const u8 *ptr = (const u8 *)object->pointer;
280 int i, len, remaining;
281 unsigned char linebuf[HEX_ROW_SIZE * 5];
283 /* limit the number of lines to HEX_MAX_LINES */
285 min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE));
287 seq_printf(seq, " hex dump (first %d bytes):\n", len);
288 for (i = 0; i < len; i += HEX_ROW_SIZE) {
289 int linelen = min(remaining, HEX_ROW_SIZE);
291 remaining -= HEX_ROW_SIZE;
292 hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE,
293 HEX_GROUP_SIZE, linebuf, sizeof(linebuf),
295 seq_printf(seq, " %s\n", linebuf);
300 * Object colors, encoded with count and min_count:
301 * - white - orphan object, not enough references to it (count < min_count)
302 * - gray - not orphan, not marked as false positive (min_count == 0) or
303 * sufficient references to it (count >= min_count)
304 * - black - ignore, it doesn't contain references (e.g. text section)
305 * (min_count == -1). No function defined for this color.
306 * Newly created objects don't have any color assigned (object->count == -1)
307 * before the next memory scan when they become white.
309 static int color_white(const struct kmemleak_object *object)
311 return object->count != -1 && object->count < object->min_count;
314 static int color_gray(const struct kmemleak_object *object)
316 return object->min_count != -1 && object->count >= object->min_count;
319 static int color_black(const struct kmemleak_object *object)
321 return object->min_count == -1;
325 * Objects are considered unreferenced only if their color is white, they have
326 * not be deleted and have a minimum age to avoid false positives caused by
327 * pointers temporarily stored in CPU registers.
329 static int unreferenced_object(struct kmemleak_object *object)
331 return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
332 time_before_eq(object->jiffies + jiffies_min_age,
337 * Printing of the unreferenced objects information to the seq file. The
338 * print_unreferenced function must be called with the object->lock held.
340 static void print_unreferenced(struct seq_file *seq,
341 struct kmemleak_object *object)
345 seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
346 object->pointer, object->size);
347 seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu\n",
348 object->comm, object->pid, object->jiffies);
349 hex_dump_object(seq, object);
350 seq_printf(seq, " backtrace:\n");
352 for (i = 0; i < object->trace_len; i++) {
353 void *ptr = (void *)object->trace[i];
354 seq_printf(seq, " [<%p>] %pS\n", ptr, ptr);
359 * Print the kmemleak_object information. This function is used mainly for
360 * debugging special cases when kmemleak operations. It must be called with
361 * the object->lock held.
363 static void dump_object_info(struct kmemleak_object *object)
365 struct stack_trace trace;
367 trace.nr_entries = object->trace_len;
368 trace.entries = object->trace;
370 pr_notice("Object 0x%08lx (size %zu):\n",
371 object->tree_node.start, object->size);
372 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
373 object->comm, object->pid, object->jiffies);
374 pr_notice(" min_count = %d\n", object->min_count);
375 pr_notice(" count = %d\n", object->count);
376 pr_notice(" flags = 0x%lx\n", object->flags);
377 pr_notice(" backtrace:\n");
378 print_stack_trace(&trace, 4);
382 * Look-up a memory block metadata (kmemleak_object) in the priority search
383 * tree based on a pointer value. If alias is 0, only values pointing to the
384 * beginning of the memory block are allowed. The kmemleak_lock must be held
385 * when calling this function.
387 static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
389 struct prio_tree_node *node;
390 struct prio_tree_iter iter;
391 struct kmemleak_object *object;
393 prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr);
394 node = prio_tree_next(&iter);
396 object = prio_tree_entry(node, struct kmemleak_object,
398 if (!alias && object->pointer != ptr) {
399 kmemleak_warn("Found object by alias");
409 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
410 * that once an object's use_count reached 0, the RCU freeing was already
411 * registered and the object should no longer be used. This function must be
412 * called under the protection of rcu_read_lock().
414 static int get_object(struct kmemleak_object *object)
416 return atomic_inc_not_zero(&object->use_count);
420 * RCU callback to free a kmemleak_object.
422 static void free_object_rcu(struct rcu_head *rcu)
424 struct hlist_node *elem, *tmp;
425 struct kmemleak_scan_area *area;
426 struct kmemleak_object *object =
427 container_of(rcu, struct kmemleak_object, rcu);
430 * Once use_count is 0 (guaranteed by put_object), there is no other
431 * code accessing this object, hence no need for locking.
433 hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) {
435 kmem_cache_free(scan_area_cache, area);
437 kmem_cache_free(object_cache, object);
441 * Decrement the object use_count. Once the count is 0, free the object using
442 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
443 * delete_object() path, the delayed RCU freeing ensures that there is no
444 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
447 static void put_object(struct kmemleak_object *object)
449 if (!atomic_dec_and_test(&object->use_count))
452 /* should only get here after delete_object was called */
453 WARN_ON(object->flags & OBJECT_ALLOCATED);
455 call_rcu(&object->rcu, free_object_rcu);
459 * Look up an object in the prio search tree and increase its use_count.
461 static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
464 struct kmemleak_object *object = NULL;
467 read_lock_irqsave(&kmemleak_lock, flags);
468 if (ptr >= min_addr && ptr < max_addr)
469 object = lookup_object(ptr, alias);
470 read_unlock_irqrestore(&kmemleak_lock, flags);
472 /* check whether the object is still available */
473 if (object && !get_object(object))
481 * Save stack trace to the given array of MAX_TRACE size.
483 static int __save_stack_trace(unsigned long *trace)
485 struct stack_trace stack_trace;
487 stack_trace.max_entries = MAX_TRACE;
488 stack_trace.nr_entries = 0;
489 stack_trace.entries = trace;
490 stack_trace.skip = 2;
491 save_stack_trace(&stack_trace);
493 return stack_trace.nr_entries;
497 * Create the metadata (struct kmemleak_object) corresponding to an allocated
498 * memory block and add it to the object_list and object_tree_root.
500 static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
501 int min_count, gfp_t gfp)
504 struct kmemleak_object *object;
505 struct prio_tree_node *node;
507 object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK);
509 kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
513 INIT_LIST_HEAD(&object->object_list);
514 INIT_LIST_HEAD(&object->gray_list);
515 INIT_HLIST_HEAD(&object->area_list);
516 spin_lock_init(&object->lock);
517 atomic_set(&object->use_count, 1);
518 object->flags = OBJECT_ALLOCATED | OBJECT_NEW;
519 object->pointer = ptr;
521 object->min_count = min_count;
522 object->count = -1; /* no color initially */
523 object->jiffies = jiffies;
525 /* task information */
528 strncpy(object->comm, "hardirq", sizeof(object->comm));
529 } else if (in_softirq()) {
531 strncpy(object->comm, "softirq", sizeof(object->comm));
533 object->pid = current->pid;
535 * There is a small chance of a race with set_task_comm(),
536 * however using get_task_comm() here may cause locking
537 * dependency issues with current->alloc_lock. In the worst
538 * case, the command line is not correct.
540 strncpy(object->comm, current->comm, sizeof(object->comm));
543 /* kernel backtrace */
544 object->trace_len = __save_stack_trace(object->trace);
546 INIT_PRIO_TREE_NODE(&object->tree_node);
547 object->tree_node.start = ptr;
548 object->tree_node.last = ptr + size - 1;
550 write_lock_irqsave(&kmemleak_lock, flags);
551 min_addr = min(min_addr, ptr);
552 max_addr = max(max_addr, ptr + size);
553 node = prio_tree_insert(&object_tree_root, &object->tree_node);
555 * The code calling the kernel does not yet have the pointer to the
556 * memory block to be able to free it. However, we still hold the
557 * kmemleak_lock here in case parts of the kernel started freeing
558 * random memory blocks.
560 if (node != &object->tree_node) {
563 kmemleak_stop("Cannot insert 0x%lx into the object search tree "
564 "(already existing)\n", ptr);
565 object = lookup_object(ptr, 1);
566 spin_lock_irqsave(&object->lock, flags);
567 dump_object_info(object);
568 spin_unlock_irqrestore(&object->lock, flags);
572 list_add_tail_rcu(&object->object_list, &object_list);
574 write_unlock_irqrestore(&kmemleak_lock, flags);
579 * Remove the metadata (struct kmemleak_object) for a memory block from the
580 * object_list and object_tree_root and decrement its use_count.
582 static void __delete_object(struct kmemleak_object *object)
586 write_lock_irqsave(&kmemleak_lock, flags);
587 prio_tree_remove(&object_tree_root, &object->tree_node);
588 list_del_rcu(&object->object_list);
589 write_unlock_irqrestore(&kmemleak_lock, flags);
591 WARN_ON(!(object->flags & OBJECT_ALLOCATED));
592 WARN_ON(atomic_read(&object->use_count) < 2);
595 * Locking here also ensures that the corresponding memory block
596 * cannot be freed when it is being scanned.
598 spin_lock_irqsave(&object->lock, flags);
599 object->flags &= ~OBJECT_ALLOCATED;
600 spin_unlock_irqrestore(&object->lock, flags);
605 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
608 static void delete_object_full(unsigned long ptr)
610 struct kmemleak_object *object;
612 object = find_and_get_object(ptr, 0);
615 kmemleak_warn("Freeing unknown object at 0x%08lx\n",
620 __delete_object(object);
625 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
626 * delete it. If the memory block is partially freed, the function may create
627 * additional metadata for the remaining parts of the block.
629 static void delete_object_part(unsigned long ptr, size_t size)
631 struct kmemleak_object *object;
632 unsigned long start, end;
634 object = find_and_get_object(ptr, 1);
637 kmemleak_warn("Partially freeing unknown object at 0x%08lx "
638 "(size %zu)\n", ptr, size);
642 __delete_object(object);
645 * Create one or two objects that may result from the memory block
646 * split. Note that partial freeing is only done by free_bootmem() and
647 * this happens before kmemleak_init() is called. The path below is
648 * only executed during early log recording in kmemleak_init(), so
649 * GFP_KERNEL is enough.
651 start = object->pointer;
652 end = object->pointer + object->size;
654 create_object(start, ptr - start, object->min_count,
656 if (ptr + size < end)
657 create_object(ptr + size, end - ptr - size, object->min_count,
663 * Make a object permanently as gray-colored so that it can no longer be
664 * reported as a leak. This is used in general to mark a false positive.
666 static void make_gray_object(unsigned long ptr)
669 struct kmemleak_object *object;
671 object = find_and_get_object(ptr, 0);
673 kmemleak_warn("Graying unknown object at 0x%08lx\n", ptr);
677 spin_lock_irqsave(&object->lock, flags);
678 object->min_count = 0;
679 spin_unlock_irqrestore(&object->lock, flags);
684 * Mark the object as black-colored so that it is ignored from scans and
687 static void make_black_object(unsigned long ptr)
690 struct kmemleak_object *object;
692 object = find_and_get_object(ptr, 0);
694 kmemleak_warn("Blacking unknown object at 0x%08lx\n", ptr);
698 spin_lock_irqsave(&object->lock, flags);
699 object->min_count = -1;
700 object->flags |= OBJECT_NO_SCAN;
701 spin_unlock_irqrestore(&object->lock, flags);
706 * Add a scanning area to the object. If at least one such area is added,
707 * kmemleak will only scan these ranges rather than the whole memory block.
709 static void add_scan_area(unsigned long ptr, unsigned long offset,
710 size_t length, gfp_t gfp)
713 struct kmemleak_object *object;
714 struct kmemleak_scan_area *area;
716 object = find_and_get_object(ptr, 0);
718 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
723 area = kmem_cache_alloc(scan_area_cache, gfp & GFP_KMEMLEAK_MASK);
725 kmemleak_warn("Cannot allocate a scan area\n");
729 spin_lock_irqsave(&object->lock, flags);
730 if (offset + length > object->size) {
731 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
732 dump_object_info(object);
733 kmem_cache_free(scan_area_cache, area);
737 INIT_HLIST_NODE(&area->node);
738 area->offset = offset;
739 area->length = length;
741 hlist_add_head(&area->node, &object->area_list);
743 spin_unlock_irqrestore(&object->lock, flags);
749 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
750 * pointer. Such object will not be scanned by kmemleak but references to it
753 static void object_no_scan(unsigned long ptr)
756 struct kmemleak_object *object;
758 object = find_and_get_object(ptr, 0);
760 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
764 spin_lock_irqsave(&object->lock, flags);
765 object->flags |= OBJECT_NO_SCAN;
766 spin_unlock_irqrestore(&object->lock, flags);
771 * Log an early kmemleak_* call to the early_log buffer. These calls will be
772 * processed later once kmemleak is fully initialized.
774 static void __init log_early(int op_type, const void *ptr, size_t size,
775 int min_count, unsigned long offset, size_t length)
778 struct early_log *log;
780 if (crt_early_log >= ARRAY_SIZE(early_log)) {
781 pr_warning("Early log buffer exceeded\n");
787 * There is no need for locking since the kernel is still in UP mode
788 * at this stage. Disabling the IRQs is enough.
790 local_irq_save(flags);
791 log = &early_log[crt_early_log];
792 log->op_type = op_type;
795 log->min_count = min_count;
796 log->offset = offset;
797 log->length = length;
798 if (op_type == KMEMLEAK_ALLOC)
799 log->trace_len = __save_stack_trace(log->trace);
801 local_irq_restore(flags);
805 * Log an early allocated block and populate the stack trace.
807 static void early_alloc(struct early_log *log)
809 struct kmemleak_object *object;
813 if (!atomic_read(&kmemleak_enabled) || !log->ptr || IS_ERR(log->ptr))
817 * RCU locking needed to ensure object is not freed via put_object().
820 object = create_object((unsigned long)log->ptr, log->size,
821 log->min_count, GFP_KERNEL);
822 spin_lock_irqsave(&object->lock, flags);
823 for (i = 0; i < log->trace_len; i++)
824 object->trace[i] = log->trace[i];
825 object->trace_len = log->trace_len;
826 spin_unlock_irqrestore(&object->lock, flags);
831 * Memory allocation function callback. This function is called from the
832 * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc,
835 void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
838 pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
840 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
841 create_object((unsigned long)ptr, size, min_count, gfp);
842 else if (atomic_read(&kmemleak_early_log))
843 log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
845 EXPORT_SYMBOL_GPL(kmemleak_alloc);
848 * Memory freeing function callback. This function is called from the kernel
849 * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.).
851 void __ref kmemleak_free(const void *ptr)
853 pr_debug("%s(0x%p)\n", __func__, ptr);
855 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
856 delete_object_full((unsigned long)ptr);
857 else if (atomic_read(&kmemleak_early_log))
858 log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
860 EXPORT_SYMBOL_GPL(kmemleak_free);
863 * Partial memory freeing function callback. This function is usually called
864 * from bootmem allocator when (part of) a memory block is freed.
866 void __ref kmemleak_free_part(const void *ptr, size_t size)
868 pr_debug("%s(0x%p)\n", __func__, ptr);
870 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
871 delete_object_part((unsigned long)ptr, size);
872 else if (atomic_read(&kmemleak_early_log))
873 log_early(KMEMLEAK_FREE_PART, ptr, size, 0, 0, 0);
875 EXPORT_SYMBOL_GPL(kmemleak_free_part);
878 * Mark an already allocated memory block as a false positive. This will cause
879 * the block to no longer be reported as leak and always be scanned.
881 void __ref kmemleak_not_leak(const void *ptr)
883 pr_debug("%s(0x%p)\n", __func__, ptr);
885 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
886 make_gray_object((unsigned long)ptr);
887 else if (atomic_read(&kmemleak_early_log))
888 log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
890 EXPORT_SYMBOL(kmemleak_not_leak);
893 * Ignore a memory block. This is usually done when it is known that the
894 * corresponding block is not a leak and does not contain any references to
895 * other allocated memory blocks.
897 void __ref kmemleak_ignore(const void *ptr)
899 pr_debug("%s(0x%p)\n", __func__, ptr);
901 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
902 make_black_object((unsigned long)ptr);
903 else if (atomic_read(&kmemleak_early_log))
904 log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
906 EXPORT_SYMBOL(kmemleak_ignore);
909 * Limit the range to be scanned in an allocated memory block.
911 void __ref kmemleak_scan_area(const void *ptr, unsigned long offset,
912 size_t length, gfp_t gfp)
914 pr_debug("%s(0x%p)\n", __func__, ptr);
916 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
917 add_scan_area((unsigned long)ptr, offset, length, gfp);
918 else if (atomic_read(&kmemleak_early_log))
919 log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
921 EXPORT_SYMBOL(kmemleak_scan_area);
924 * Inform kmemleak not to scan the given memory block.
926 void __ref kmemleak_no_scan(const void *ptr)
928 pr_debug("%s(0x%p)\n", __func__, ptr);
930 if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
931 object_no_scan((unsigned long)ptr);
932 else if (atomic_read(&kmemleak_early_log))
933 log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0);
935 EXPORT_SYMBOL(kmemleak_no_scan);
938 * Memory scanning is a long process and it needs to be interruptable. This
939 * function checks whether such interrupt condition occured.
941 static int scan_should_stop(void)
943 if (!atomic_read(&kmemleak_enabled))
947 * This function may be called from either process or kthread context,
948 * hence the need to check for both stop conditions.
951 return signal_pending(current);
953 return kthread_should_stop();
959 * Scan a memory block (exclusive range) for valid pointers and add those
960 * found to the gray list.
962 static void scan_block(void *_start, void *_end,
963 struct kmemleak_object *scanned, int allow_resched)
966 unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
967 unsigned long *end = _end - (BYTES_PER_POINTER - 1);
969 for (ptr = start; ptr < end; ptr++) {
971 unsigned long pointer = *ptr;
972 struct kmemleak_object *object;
976 if (scan_should_stop())
979 object = find_and_get_object(pointer, 1);
982 if (object == scanned) {
983 /* self referenced, ignore */
989 * Avoid the lockdep recursive warning on object->lock being
990 * previously acquired in scan_object(). These locks are
991 * enclosed by scan_mutex.
993 spin_lock_irqsave_nested(&object->lock, flags,
994 SINGLE_DEPTH_NESTING);
995 if (!color_white(object)) {
996 /* non-orphan, ignored or new */
997 spin_unlock_irqrestore(&object->lock, flags);
1003 * Increase the object's reference count (number of pointers
1004 * to the memory block). If this count reaches the required
1005 * minimum, the object's color will become gray and it will be
1006 * added to the gray_list.
1009 if (color_gray(object))
1010 list_add_tail(&object->gray_list, &gray_list);
1013 spin_unlock_irqrestore(&object->lock, flags);
1018 * Scan a memory block corresponding to a kmemleak_object. A condition is
1019 * that object->use_count >= 1.
1021 static void scan_object(struct kmemleak_object *object)
1023 struct kmemleak_scan_area *area;
1024 struct hlist_node *elem;
1025 unsigned long flags;
1028 * Once the object->lock is aquired, the corresponding memory block
1029 * cannot be freed (the same lock is aquired in delete_object).
1031 spin_lock_irqsave(&object->lock, flags);
1032 if (object->flags & OBJECT_NO_SCAN)
1034 if (!(object->flags & OBJECT_ALLOCATED))
1035 /* already freed object */
1037 if (hlist_empty(&object->area_list)) {
1038 void *start = (void *)object->pointer;
1039 void *end = (void *)(object->pointer + object->size);
1041 while (start < end && (object->flags & OBJECT_ALLOCATED) &&
1042 !(object->flags & OBJECT_NO_SCAN)) {
1043 scan_block(start, min(start + MAX_SCAN_SIZE, end),
1045 start += MAX_SCAN_SIZE;
1047 spin_unlock_irqrestore(&object->lock, flags);
1049 spin_lock_irqsave(&object->lock, flags);
1052 hlist_for_each_entry(area, elem, &object->area_list, node)
1053 scan_block((void *)(object->pointer + area->offset),
1054 (void *)(object->pointer + area->offset
1055 + area->length), object, 0);
1057 spin_unlock_irqrestore(&object->lock, flags);
1061 * Scan data sections and all the referenced memory blocks allocated via the
1062 * kernel's standard allocators. This function must be called with the
1065 static void kmemleak_scan(void)
1067 unsigned long flags;
1068 struct kmemleak_object *object, *tmp;
1069 struct task_struct *task;
1072 int gray_list_pass = 0;
1074 jiffies_last_scan = jiffies;
1076 /* prepare the kmemleak_object's */
1078 list_for_each_entry_rcu(object, &object_list, object_list) {
1079 spin_lock_irqsave(&object->lock, flags);
1082 * With a few exceptions there should be a maximum of
1083 * 1 reference to any object at this point.
1085 if (atomic_read(&object->use_count) > 1) {
1086 pr_debug("object->use_count = %d\n",
1087 atomic_read(&object->use_count));
1088 dump_object_info(object);
1091 /* reset the reference count (whiten the object) */
1093 object->flags &= ~OBJECT_NEW;
1094 if (color_gray(object) && get_object(object))
1095 list_add_tail(&object->gray_list, &gray_list);
1097 spin_unlock_irqrestore(&object->lock, flags);
1101 /* data/bss scanning */
1102 scan_block(_sdata, _edata, NULL, 1);
1103 scan_block(__bss_start, __bss_stop, NULL, 1);
1106 /* per-cpu sections scanning */
1107 for_each_possible_cpu(i)
1108 scan_block(__per_cpu_start + per_cpu_offset(i),
1109 __per_cpu_end + per_cpu_offset(i), NULL, 1);
1113 * Struct page scanning for each node. The code below is not yet safe
1114 * with MEMORY_HOTPLUG.
1116 for_each_online_node(i) {
1117 pg_data_t *pgdat = NODE_DATA(i);
1118 unsigned long start_pfn = pgdat->node_start_pfn;
1119 unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
1122 for (pfn = start_pfn; pfn < end_pfn; pfn++) {
1125 if (!pfn_valid(pfn))
1127 page = pfn_to_page(pfn);
1128 /* only scan if page is in use */
1129 if (page_count(page) == 0)
1131 scan_block(page, page + 1, NULL, 1);
1136 * Scanning the task stacks may introduce false negatives and it is
1137 * not enabled by default.
1139 if (kmemleak_stack_scan) {
1140 read_lock(&tasklist_lock);
1141 for_each_process(task)
1142 scan_block(task_stack_page(task),
1143 task_stack_page(task) + THREAD_SIZE,
1145 read_unlock(&tasklist_lock);
1149 * Scan the objects already referenced from the sections scanned
1150 * above. More objects will be referenced and, if there are no memory
1151 * leaks, all the objects will be scanned. The list traversal is safe
1152 * for both tail additions and removals from inside the loop. The
1153 * kmemleak objects cannot be freed from outside the loop because their
1154 * use_count was increased.
1157 object = list_entry(gray_list.next, typeof(*object), gray_list);
1158 while (&object->gray_list != &gray_list) {
1161 /* may add new objects to the list */
1162 if (!scan_should_stop())
1163 scan_object(object);
1165 tmp = list_entry(object->gray_list.next, typeof(*object),
1168 /* remove the object from the list and release it */
1169 list_del(&object->gray_list);
1175 if (scan_should_stop() || ++gray_list_pass >= GRAY_LIST_PASSES)
1179 * Check for new objects allocated during this scanning and add them
1183 list_for_each_entry_rcu(object, &object_list, object_list) {
1184 spin_lock_irqsave(&object->lock, flags);
1185 if ((object->flags & OBJECT_NEW) && !color_black(object) &&
1186 get_object(object)) {
1187 object->flags &= ~OBJECT_NEW;
1188 list_add_tail(&object->gray_list, &gray_list);
1190 spin_unlock_irqrestore(&object->lock, flags);
1194 if (!list_empty(&gray_list))
1198 WARN_ON(!list_empty(&gray_list));
1201 * If scanning was stopped or new objects were being allocated at a
1202 * higher rate than gray list scanning, do not report any new
1203 * unreferenced objects.
1205 if (scan_should_stop() || gray_list_pass >= GRAY_LIST_PASSES)
1209 * Scanning result reporting.
1212 list_for_each_entry_rcu(object, &object_list, object_list) {
1213 spin_lock_irqsave(&object->lock, flags);
1214 if (unreferenced_object(object) &&
1215 !(object->flags & OBJECT_REPORTED)) {
1216 object->flags |= OBJECT_REPORTED;
1219 spin_unlock_irqrestore(&object->lock, flags);
1224 pr_info("%d new suspected memory leaks (see "
1225 "/sys/kernel/debug/kmemleak)\n", new_leaks);
1230 * Thread function performing automatic memory scanning. Unreferenced objects
1231 * at the end of a memory scan are reported but only the first time.
1233 static int kmemleak_scan_thread(void *arg)
1235 static int first_run = 1;
1237 pr_info("Automatic memory scanning thread started\n");
1238 set_user_nice(current, 10);
1241 * Wait before the first scan to allow the system to fully initialize.
1245 ssleep(SECS_FIRST_SCAN);
1248 while (!kthread_should_stop()) {
1249 signed long timeout = jiffies_scan_wait;
1251 mutex_lock(&scan_mutex);
1253 mutex_unlock(&scan_mutex);
1255 /* wait before the next scan */
1256 while (timeout && !kthread_should_stop())
1257 timeout = schedule_timeout_interruptible(timeout);
1260 pr_info("Automatic memory scanning thread ended\n");
1266 * Start the automatic memory scanning thread. This function must be called
1267 * with the scan_mutex held.
1269 void start_scan_thread(void)
1273 scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
1274 if (IS_ERR(scan_thread)) {
1275 pr_warning("Failed to create the scan thread\n");
1281 * Stop the automatic memory scanning thread. This function must be called
1282 * with the scan_mutex held.
1284 void stop_scan_thread(void)
1287 kthread_stop(scan_thread);
1293 * Iterate over the object_list and return the first valid object at or after
1294 * the required position with its use_count incremented. The function triggers
1295 * a memory scanning when the pos argument points to the first position.
1297 static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
1299 struct kmemleak_object *object;
1303 err = mutex_lock_interruptible(&scan_mutex);
1305 return ERR_PTR(err);
1308 list_for_each_entry_rcu(object, &object_list, object_list) {
1311 if (get_object(object))
1320 * Return the next object in the object_list. The function decrements the
1321 * use_count of the previous object and increases that of the next one.
1323 static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1325 struct kmemleak_object *prev_obj = v;
1326 struct kmemleak_object *next_obj = NULL;
1327 struct list_head *n = &prev_obj->object_list;
1331 list_for_each_continue_rcu(n, &object_list) {
1332 next_obj = list_entry(n, struct kmemleak_object, object_list);
1333 if (get_object(next_obj))
1337 put_object(prev_obj);
1342 * Decrement the use_count of the last object required, if any.
1344 static void kmemleak_seq_stop(struct seq_file *seq, void *v)
1348 * kmemleak_seq_start may return ERR_PTR if the scan_mutex
1349 * waiting was interrupted, so only release it if !IS_ERR.
1352 mutex_unlock(&scan_mutex);
1359 * Print the information for an unreferenced object to the seq file.
1361 static int kmemleak_seq_show(struct seq_file *seq, void *v)
1363 struct kmemleak_object *object = v;
1364 unsigned long flags;
1366 spin_lock_irqsave(&object->lock, flags);
1367 if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1368 print_unreferenced(seq, object);
1369 spin_unlock_irqrestore(&object->lock, flags);
1373 static const struct seq_operations kmemleak_seq_ops = {
1374 .start = kmemleak_seq_start,
1375 .next = kmemleak_seq_next,
1376 .stop = kmemleak_seq_stop,
1377 .show = kmemleak_seq_show,
1380 static int kmemleak_open(struct inode *inode, struct file *file)
1382 if (!atomic_read(&kmemleak_enabled))
1385 return seq_open(file, &kmemleak_seq_ops);
1388 static int kmemleak_release(struct inode *inode, struct file *file)
1390 return seq_release(inode, file);
1393 static int dump_str_object_info(const char *str)
1395 unsigned long flags;
1396 struct kmemleak_object *object;
1399 addr= simple_strtoul(str, NULL, 0);
1400 object = find_and_get_object(addr, 0);
1402 pr_info("Unknown object at 0x%08lx\n", addr);
1406 spin_lock_irqsave(&object->lock, flags);
1407 dump_object_info(object);
1408 spin_unlock_irqrestore(&object->lock, flags);
1415 * File write operation to configure kmemleak at run-time. The following
1416 * commands can be written to the /sys/kernel/debug/kmemleak file:
1417 * off - disable kmemleak (irreversible)
1418 * stack=on - enable the task stacks scanning
1419 * stack=off - disable the tasks stacks scanning
1420 * scan=on - start the automatic memory scanning thread
1421 * scan=off - stop the automatic memory scanning thread
1422 * scan=... - set the automatic memory scanning period in seconds (0 to
1424 * scan - trigger a memory scan
1425 * dump=... - dump information about the object found at the given address
1427 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
1428 size_t size, loff_t *ppos)
1434 buf_size = min(size, (sizeof(buf) - 1));
1435 if (strncpy_from_user(buf, user_buf, buf_size) < 0)
1439 ret = mutex_lock_interruptible(&scan_mutex);
1443 if (strncmp(buf, "off", 3) == 0)
1445 else if (strncmp(buf, "stack=on", 8) == 0)
1446 kmemleak_stack_scan = 1;
1447 else if (strncmp(buf, "stack=off", 9) == 0)
1448 kmemleak_stack_scan = 0;
1449 else if (strncmp(buf, "scan=on", 7) == 0)
1450 start_scan_thread();
1451 else if (strncmp(buf, "scan=off", 8) == 0)
1453 else if (strncmp(buf, "scan=", 5) == 0) {
1456 ret = strict_strtoul(buf + 5, 0, &secs);
1461 jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
1462 start_scan_thread();
1464 } else if (strncmp(buf, "scan", 4) == 0)
1466 else if (strncmp(buf, "dump=", 5) == 0)
1467 ret = dump_str_object_info(buf + 5);
1472 mutex_unlock(&scan_mutex);
1476 /* ignore the rest of the buffer, only one command at a time */
1481 static const struct file_operations kmemleak_fops = {
1482 .owner = THIS_MODULE,
1483 .open = kmemleak_open,
1485 .write = kmemleak_write,
1486 .llseek = seq_lseek,
1487 .release = kmemleak_release,
1491 * Perform the freeing of the kmemleak internal objects after waiting for any
1492 * current memory scan to complete.
1494 static int kmemleak_cleanup_thread(void *arg)
1496 struct kmemleak_object *object;
1498 mutex_lock(&scan_mutex);
1502 list_for_each_entry_rcu(object, &object_list, object_list)
1503 delete_object_full(object->pointer);
1505 mutex_unlock(&scan_mutex);
1511 * Start the clean-up thread.
1513 static void kmemleak_cleanup(void)
1515 struct task_struct *cleanup_thread;
1517 cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL,
1519 if (IS_ERR(cleanup_thread))
1520 pr_warning("Failed to create the clean-up thread\n");
1524 * Disable kmemleak. No memory allocation/freeing will be traced once this
1525 * function is called. Disabling kmemleak is an irreversible operation.
1527 static void kmemleak_disable(void)
1529 /* atomically check whether it was already invoked */
1530 if (atomic_cmpxchg(&kmemleak_error, 0, 1))
1533 /* stop any memory operation tracing */
1534 atomic_set(&kmemleak_early_log, 0);
1535 atomic_set(&kmemleak_enabled, 0);
1537 /* check whether it is too early for a kernel thread */
1538 if (atomic_read(&kmemleak_initialized))
1541 pr_info("Kernel memory leak detector disabled\n");
1545 * Allow boot-time kmemleak disabling (enabled by default).
1547 static int kmemleak_boot_config(char *str)
1551 if (strcmp(str, "off") == 0)
1553 else if (strcmp(str, "on") != 0)
1557 early_param("kmemleak", kmemleak_boot_config);
1560 * Kmemleak initialization.
1562 void __init kmemleak_init(void)
1565 unsigned long flags;
1567 jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
1568 jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
1570 object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
1571 scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
1572 INIT_PRIO_TREE_ROOT(&object_tree_root);
1574 /* the kernel is still in UP mode, so disabling the IRQs is enough */
1575 local_irq_save(flags);
1576 if (!atomic_read(&kmemleak_error)) {
1577 atomic_set(&kmemleak_enabled, 1);
1578 atomic_set(&kmemleak_early_log, 0);
1580 local_irq_restore(flags);
1583 * This is the point where tracking allocations is safe. Automatic
1584 * scanning is started during the late initcall. Add the early logged
1585 * callbacks to the kmemleak infrastructure.
1587 for (i = 0; i < crt_early_log; i++) {
1588 struct early_log *log = &early_log[i];
1590 switch (log->op_type) {
1591 case KMEMLEAK_ALLOC:
1595 kmemleak_free(log->ptr);
1597 case KMEMLEAK_FREE_PART:
1598 kmemleak_free_part(log->ptr, log->size);
1600 case KMEMLEAK_NOT_LEAK:
1601 kmemleak_not_leak(log->ptr);
1603 case KMEMLEAK_IGNORE:
1604 kmemleak_ignore(log->ptr);
1606 case KMEMLEAK_SCAN_AREA:
1607 kmemleak_scan_area(log->ptr, log->offset, log->length,
1610 case KMEMLEAK_NO_SCAN:
1611 kmemleak_no_scan(log->ptr);
1620 * Late initialization function.
1622 static int __init kmemleak_late_init(void)
1624 struct dentry *dentry;
1626 atomic_set(&kmemleak_initialized, 1);
1628 if (atomic_read(&kmemleak_error)) {
1630 * Some error occured and kmemleak was disabled. There is a
1631 * small chance that kmemleak_disable() was called immediately
1632 * after setting kmemleak_initialized and we may end up with
1633 * two clean-up threads but serialized by scan_mutex.
1639 dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
1642 pr_warning("Failed to create the debugfs kmemleak file\n");
1643 mutex_lock(&scan_mutex);
1644 start_scan_thread();
1645 mutex_unlock(&scan_mutex);
1647 pr_info("Kernel memory leak detector initialized\n");
1651 late_initcall(kmemleak_late_init);