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 REPORTS_NR 50 /* maximum number of reported leaks */
107 #define MSECS_MIN_AGE 5000 /* minimum object age for reporting */
108 #define MSECS_SCAN_YIELD 10 /* CPU yielding period */
109 #define SECS_FIRST_SCAN 60 /* delay before the first scan */
110 #define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */
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)
163 /* the list of all allocated objects */
164 static LIST_HEAD(object_list
);
165 /* the list of gray-colored objects (see color_gray comment below) */
166 static LIST_HEAD(gray_list
);
167 /* prio search tree for object boundaries */
168 static struct prio_tree_root object_tree_root
;
169 /* rw_lock protecting the access to object_list and prio_tree_root */
170 static DEFINE_RWLOCK(kmemleak_lock
);
172 /* allocation caches for kmemleak internal data */
173 static struct kmem_cache
*object_cache
;
174 static struct kmem_cache
*scan_area_cache
;
176 /* set if tracing memory operations is enabled */
177 static atomic_t kmemleak_enabled
= ATOMIC_INIT(0);
178 /* set in the late_initcall if there were no errors */
179 static atomic_t kmemleak_initialized
= ATOMIC_INIT(0);
180 /* enables or disables early logging of the memory operations */
181 static atomic_t kmemleak_early_log
= ATOMIC_INIT(1);
182 /* set if a fata kmemleak error has occurred */
183 static atomic_t kmemleak_error
= ATOMIC_INIT(0);
185 /* minimum and maximum address that may be valid pointers */
186 static unsigned long min_addr
= ULONG_MAX
;
187 static unsigned long max_addr
;
189 /* used for yielding the CPU to other tasks during scanning */
190 static unsigned long next_scan_yield
;
191 static struct task_struct
*scan_thread
;
192 static unsigned long jiffies_scan_yield
;
193 /* used to avoid reporting of recently allocated objects */
194 static unsigned long jiffies_min_age
;
195 static unsigned long jiffies_last_scan
;
196 /* delay between automatic memory scannings */
197 static signed long jiffies_scan_wait
;
198 /* enables or disables the task stacks scanning */
199 static int kmemleak_stack_scan
= 1;
200 /* protects the memory scanning, parameters and debug/kmemleak file access */
201 static DEFINE_MUTEX(scan_mutex
);
203 /* number of leaks reported (for limitation purposes) */
204 static int reported_leaks
;
207 * Early object allocation/freeing logging. Kmemleak is initialized after the
208 * kernel allocator. However, both the kernel allocator and kmemleak may
209 * allocate memory blocks which need to be tracked. Kmemleak defines an
210 * arbitrary buffer to hold the allocation/freeing information before it is
214 /* kmemleak operation type for early logging */
225 * Structure holding the information passed to kmemleak callbacks during the
229 int op_type
; /* kmemleak operation type */
230 const void *ptr
; /* allocated/freed memory block */
231 size_t size
; /* memory block size */
232 int min_count
; /* minimum reference count */
233 unsigned long offset
; /* scan area offset */
234 size_t length
; /* scan area length */
237 /* early logging buffer and current position */
238 static struct early_log early_log
[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE
];
239 static int crt_early_log
;
241 static void kmemleak_disable(void);
244 * Print a warning and dump the stack trace.
246 #define kmemleak_warn(x...) do { \
252 * Macro invoked when a serious kmemleak condition occured and cannot be
253 * recovered from. Kmemleak will be disabled and further allocation/freeing
254 * tracing no longer available.
256 #define kmemleak_stop(x...) do { \
258 kmemleak_disable(); \
262 * Object colors, encoded with count and min_count:
263 * - white - orphan object, not enough references to it (count < min_count)
264 * - gray - not orphan, not marked as false positive (min_count == 0) or
265 * sufficient references to it (count >= min_count)
266 * - black - ignore, it doesn't contain references (e.g. text section)
267 * (min_count == -1). No function defined for this color.
268 * Newly created objects don't have any color assigned (object->count == -1)
269 * before the next memory scan when they become white.
271 static int color_white(const struct kmemleak_object
*object
)
273 return object
->count
!= -1 && object
->count
< object
->min_count
;
276 static int color_gray(const struct kmemleak_object
*object
)
278 return object
->min_count
!= -1 && object
->count
>= object
->min_count
;
282 * Objects are considered unreferenced only if their color is white, they have
283 * not be deleted and have a minimum age to avoid false positives caused by
284 * pointers temporarily stored in CPU registers.
286 static int unreferenced_object(struct kmemleak_object
*object
)
288 return (object
->flags
& OBJECT_ALLOCATED
) && color_white(object
) &&
289 time_before_eq(object
->jiffies
+ jiffies_min_age
,
294 * Printing of the unreferenced objects information to the seq file. The
295 * print_unreferenced function must be called with the object->lock held.
297 static void print_unreferenced(struct seq_file
*seq
,
298 struct kmemleak_object
*object
)
302 seq_printf(seq
, "unreferenced object 0x%08lx (size %zu):\n",
303 object
->pointer
, object
->size
);
304 seq_printf(seq
, " comm \"%s\", pid %d, jiffies %lu\n",
305 object
->comm
, object
->pid
, object
->jiffies
);
306 seq_printf(seq
, " backtrace:\n");
308 for (i
= 0; i
< object
->trace_len
; i
++) {
309 void *ptr
= (void *)object
->trace
[i
];
310 seq_printf(seq
, " [<%p>] %pS\n", ptr
, ptr
);
315 * Print the kmemleak_object information. This function is used mainly for
316 * debugging special cases when kmemleak operations. It must be called with
317 * the object->lock held.
319 static void dump_object_info(struct kmemleak_object
*object
)
321 struct stack_trace trace
;
323 trace
.nr_entries
= object
->trace_len
;
324 trace
.entries
= object
->trace
;
326 pr_notice("Object 0x%08lx (size %zu):\n",
327 object
->tree_node
.start
, object
->size
);
328 pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
329 object
->comm
, object
->pid
, object
->jiffies
);
330 pr_notice(" min_count = %d\n", object
->min_count
);
331 pr_notice(" count = %d\n", object
->count
);
332 pr_notice(" backtrace:\n");
333 print_stack_trace(&trace
, 4);
337 * Look-up a memory block metadata (kmemleak_object) in the priority search
338 * tree based on a pointer value. If alias is 0, only values pointing to the
339 * beginning of the memory block are allowed. The kmemleak_lock must be held
340 * when calling this function.
342 static struct kmemleak_object
*lookup_object(unsigned long ptr
, int alias
)
344 struct prio_tree_node
*node
;
345 struct prio_tree_iter iter
;
346 struct kmemleak_object
*object
;
348 prio_tree_iter_init(&iter
, &object_tree_root
, ptr
, ptr
);
349 node
= prio_tree_next(&iter
);
351 object
= prio_tree_entry(node
, struct kmemleak_object
,
353 if (!alias
&& object
->pointer
!= ptr
) {
354 kmemleak_warn("Found object by alias");
364 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
365 * that once an object's use_count reached 0, the RCU freeing was already
366 * registered and the object should no longer be used. This function must be
367 * called under the protection of rcu_read_lock().
369 static int get_object(struct kmemleak_object
*object
)
371 return atomic_inc_not_zero(&object
->use_count
);
375 * RCU callback to free a kmemleak_object.
377 static void free_object_rcu(struct rcu_head
*rcu
)
379 struct hlist_node
*elem
, *tmp
;
380 struct kmemleak_scan_area
*area
;
381 struct kmemleak_object
*object
=
382 container_of(rcu
, struct kmemleak_object
, rcu
);
385 * Once use_count is 0 (guaranteed by put_object), there is no other
386 * code accessing this object, hence no need for locking.
388 hlist_for_each_entry_safe(area
, elem
, tmp
, &object
->area_list
, node
) {
390 kmem_cache_free(scan_area_cache
, area
);
392 kmem_cache_free(object_cache
, object
);
396 * Decrement the object use_count. Once the count is 0, free the object using
397 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
398 * delete_object() path, the delayed RCU freeing ensures that there is no
399 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
402 static void put_object(struct kmemleak_object
*object
)
404 if (!atomic_dec_and_test(&object
->use_count
))
407 /* should only get here after delete_object was called */
408 WARN_ON(object
->flags
& OBJECT_ALLOCATED
);
410 call_rcu(&object
->rcu
, free_object_rcu
);
414 * Look up an object in the prio search tree and increase its use_count.
416 static struct kmemleak_object
*find_and_get_object(unsigned long ptr
, int alias
)
419 struct kmemleak_object
*object
= NULL
;
422 read_lock_irqsave(&kmemleak_lock
, flags
);
423 if (ptr
>= min_addr
&& ptr
< max_addr
)
424 object
= lookup_object(ptr
, alias
);
425 read_unlock_irqrestore(&kmemleak_lock
, flags
);
427 /* check whether the object is still available */
428 if (object
&& !get_object(object
))
436 * Create the metadata (struct kmemleak_object) corresponding to an allocated
437 * memory block and add it to the object_list and object_tree_root.
439 static void create_object(unsigned long ptr
, size_t size
, int min_count
,
443 struct kmemleak_object
*object
;
444 struct prio_tree_node
*node
;
445 struct stack_trace trace
;
447 object
= kmem_cache_alloc(object_cache
, gfp
& GFP_KMEMLEAK_MASK
);
449 kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
453 INIT_LIST_HEAD(&object
->object_list
);
454 INIT_LIST_HEAD(&object
->gray_list
);
455 INIT_HLIST_HEAD(&object
->area_list
);
456 spin_lock_init(&object
->lock
);
457 atomic_set(&object
->use_count
, 1);
458 object
->flags
= OBJECT_ALLOCATED
;
459 object
->pointer
= ptr
;
461 object
->min_count
= min_count
;
462 object
->count
= -1; /* no color initially */
463 object
->jiffies
= jiffies
;
465 /* task information */
468 strncpy(object
->comm
, "hardirq", sizeof(object
->comm
));
469 } else if (in_softirq()) {
471 strncpy(object
->comm
, "softirq", sizeof(object
->comm
));
473 object
->pid
= current
->pid
;
475 * There is a small chance of a race with set_task_comm(),
476 * however using get_task_comm() here may cause locking
477 * dependency issues with current->alloc_lock. In the worst
478 * case, the command line is not correct.
480 strncpy(object
->comm
, current
->comm
, sizeof(object
->comm
));
483 /* kernel backtrace */
484 trace
.max_entries
= MAX_TRACE
;
485 trace
.nr_entries
= 0;
486 trace
.entries
= object
->trace
;
488 save_stack_trace(&trace
);
489 object
->trace_len
= trace
.nr_entries
;
491 INIT_PRIO_TREE_NODE(&object
->tree_node
);
492 object
->tree_node
.start
= ptr
;
493 object
->tree_node
.last
= ptr
+ size
- 1;
495 write_lock_irqsave(&kmemleak_lock
, flags
);
496 min_addr
= min(min_addr
, ptr
);
497 max_addr
= max(max_addr
, ptr
+ size
);
498 node
= prio_tree_insert(&object_tree_root
, &object
->tree_node
);
500 * The code calling the kernel does not yet have the pointer to the
501 * memory block to be able to free it. However, we still hold the
502 * kmemleak_lock here in case parts of the kernel started freeing
503 * random memory blocks.
505 if (node
!= &object
->tree_node
) {
508 kmemleak_stop("Cannot insert 0x%lx into the object search tree "
509 "(already existing)\n", ptr
);
510 object
= lookup_object(ptr
, 1);
511 spin_lock_irqsave(&object
->lock
, flags
);
512 dump_object_info(object
);
513 spin_unlock_irqrestore(&object
->lock
, flags
);
517 list_add_tail_rcu(&object
->object_list
, &object_list
);
519 write_unlock_irqrestore(&kmemleak_lock
, flags
);
523 * Remove the metadata (struct kmemleak_object) for a memory block from the
524 * object_list and object_tree_root and decrement its use_count.
526 static void delete_object(unsigned long ptr
)
529 struct kmemleak_object
*object
;
531 write_lock_irqsave(&kmemleak_lock
, flags
);
532 object
= lookup_object(ptr
, 0);
535 kmemleak_warn("Freeing unknown object at 0x%08lx\n",
538 write_unlock_irqrestore(&kmemleak_lock
, flags
);
541 prio_tree_remove(&object_tree_root
, &object
->tree_node
);
542 list_del_rcu(&object
->object_list
);
543 write_unlock_irqrestore(&kmemleak_lock
, flags
);
545 WARN_ON(!(object
->flags
& OBJECT_ALLOCATED
));
546 WARN_ON(atomic_read(&object
->use_count
) < 1);
549 * Locking here also ensures that the corresponding memory block
550 * cannot be freed when it is being scanned.
552 spin_lock_irqsave(&object
->lock
, flags
);
553 object
->flags
&= ~OBJECT_ALLOCATED
;
554 spin_unlock_irqrestore(&object
->lock
, flags
);
559 * Make a object permanently as gray-colored so that it can no longer be
560 * reported as a leak. This is used in general to mark a false positive.
562 static void make_gray_object(unsigned long ptr
)
565 struct kmemleak_object
*object
;
567 object
= find_and_get_object(ptr
, 0);
569 kmemleak_warn("Graying unknown object at 0x%08lx\n", ptr
);
573 spin_lock_irqsave(&object
->lock
, flags
);
574 object
->min_count
= 0;
575 spin_unlock_irqrestore(&object
->lock
, flags
);
580 * Mark the object as black-colored so that it is ignored from scans and
583 static void make_black_object(unsigned long ptr
)
586 struct kmemleak_object
*object
;
588 object
= find_and_get_object(ptr
, 0);
590 kmemleak_warn("Blacking unknown object at 0x%08lx\n", ptr
);
594 spin_lock_irqsave(&object
->lock
, flags
);
595 object
->min_count
= -1;
596 spin_unlock_irqrestore(&object
->lock
, flags
);
601 * Add a scanning area to the object. If at least one such area is added,
602 * kmemleak will only scan these ranges rather than the whole memory block.
604 static void add_scan_area(unsigned long ptr
, unsigned long offset
,
605 size_t length
, gfp_t gfp
)
608 struct kmemleak_object
*object
;
609 struct kmemleak_scan_area
*area
;
611 object
= find_and_get_object(ptr
, 0);
613 kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
618 area
= kmem_cache_alloc(scan_area_cache
, gfp
& GFP_KMEMLEAK_MASK
);
620 kmemleak_warn("Cannot allocate a scan area\n");
624 spin_lock_irqsave(&object
->lock
, flags
);
625 if (offset
+ length
> object
->size
) {
626 kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr
);
627 dump_object_info(object
);
628 kmem_cache_free(scan_area_cache
, area
);
632 INIT_HLIST_NODE(&area
->node
);
633 area
->offset
= offset
;
634 area
->length
= length
;
636 hlist_add_head(&area
->node
, &object
->area_list
);
638 spin_unlock_irqrestore(&object
->lock
, flags
);
644 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
645 * pointer. Such object will not be scanned by kmemleak but references to it
648 static void object_no_scan(unsigned long ptr
)
651 struct kmemleak_object
*object
;
653 object
= find_and_get_object(ptr
, 0);
655 kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr
);
659 spin_lock_irqsave(&object
->lock
, flags
);
660 object
->flags
|= OBJECT_NO_SCAN
;
661 spin_unlock_irqrestore(&object
->lock
, flags
);
666 * Log an early kmemleak_* call to the early_log buffer. These calls will be
667 * processed later once kmemleak is fully initialized.
669 static void log_early(int op_type
, const void *ptr
, size_t size
,
670 int min_count
, unsigned long offset
, size_t length
)
673 struct early_log
*log
;
675 if (crt_early_log
>= ARRAY_SIZE(early_log
)) {
676 pr_warning("Early log buffer exceeded\n");
682 * There is no need for locking since the kernel is still in UP mode
683 * at this stage. Disabling the IRQs is enough.
685 local_irq_save(flags
);
686 log
= &early_log
[crt_early_log
];
687 log
->op_type
= op_type
;
690 log
->min_count
= min_count
;
691 log
->offset
= offset
;
692 log
->length
= length
;
694 local_irq_restore(flags
);
698 * Memory allocation function callback. This function is called from the
699 * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc,
702 void kmemleak_alloc(const void *ptr
, size_t size
, int min_count
, gfp_t gfp
)
704 pr_debug("%s(0x%p, %zu, %d)\n", __func__
, ptr
, size
, min_count
);
706 if (atomic_read(&kmemleak_enabled
) && ptr
&& !IS_ERR(ptr
))
707 create_object((unsigned long)ptr
, size
, min_count
, gfp
);
708 else if (atomic_read(&kmemleak_early_log
))
709 log_early(KMEMLEAK_ALLOC
, ptr
, size
, min_count
, 0, 0);
711 EXPORT_SYMBOL_GPL(kmemleak_alloc
);
714 * Memory freeing function callback. This function is called from the kernel
715 * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.).
717 void kmemleak_free(const void *ptr
)
719 pr_debug("%s(0x%p)\n", __func__
, ptr
);
721 if (atomic_read(&kmemleak_enabled
) && ptr
&& !IS_ERR(ptr
))
722 delete_object((unsigned long)ptr
);
723 else if (atomic_read(&kmemleak_early_log
))
724 log_early(KMEMLEAK_FREE
, ptr
, 0, 0, 0, 0);
726 EXPORT_SYMBOL_GPL(kmemleak_free
);
729 * Mark an already allocated memory block as a false positive. This will cause
730 * the block to no longer be reported as leak and always be scanned.
732 void kmemleak_not_leak(const void *ptr
)
734 pr_debug("%s(0x%p)\n", __func__
, ptr
);
736 if (atomic_read(&kmemleak_enabled
) && ptr
&& !IS_ERR(ptr
))
737 make_gray_object((unsigned long)ptr
);
738 else if (atomic_read(&kmemleak_early_log
))
739 log_early(KMEMLEAK_NOT_LEAK
, ptr
, 0, 0, 0, 0);
741 EXPORT_SYMBOL(kmemleak_not_leak
);
744 * Ignore a memory block. This is usually done when it is known that the
745 * corresponding block is not a leak and does not contain any references to
746 * other allocated memory blocks.
748 void kmemleak_ignore(const void *ptr
)
750 pr_debug("%s(0x%p)\n", __func__
, ptr
);
752 if (atomic_read(&kmemleak_enabled
) && ptr
&& !IS_ERR(ptr
))
753 make_black_object((unsigned long)ptr
);
754 else if (atomic_read(&kmemleak_early_log
))
755 log_early(KMEMLEAK_IGNORE
, ptr
, 0, 0, 0, 0);
757 EXPORT_SYMBOL(kmemleak_ignore
);
760 * Limit the range to be scanned in an allocated memory block.
762 void kmemleak_scan_area(const void *ptr
, unsigned long offset
, size_t length
,
765 pr_debug("%s(0x%p)\n", __func__
, ptr
);
767 if (atomic_read(&kmemleak_enabled
) && ptr
&& !IS_ERR(ptr
))
768 add_scan_area((unsigned long)ptr
, offset
, length
, gfp
);
769 else if (atomic_read(&kmemleak_early_log
))
770 log_early(KMEMLEAK_SCAN_AREA
, ptr
, 0, 0, offset
, length
);
772 EXPORT_SYMBOL(kmemleak_scan_area
);
775 * Inform kmemleak not to scan the given memory block.
777 void kmemleak_no_scan(const void *ptr
)
779 pr_debug("%s(0x%p)\n", __func__
, ptr
);
781 if (atomic_read(&kmemleak_enabled
) && ptr
&& !IS_ERR(ptr
))
782 object_no_scan((unsigned long)ptr
);
783 else if (atomic_read(&kmemleak_early_log
))
784 log_early(KMEMLEAK_NO_SCAN
, ptr
, 0, 0, 0, 0);
786 EXPORT_SYMBOL(kmemleak_no_scan
);
789 * Yield the CPU so that other tasks get a chance to run. The yielding is
790 * rate-limited to avoid excessive number of calls to the schedule() function
791 * during memory scanning.
793 static void scan_yield(void)
797 if (time_is_before_eq_jiffies(next_scan_yield
)) {
799 next_scan_yield
= jiffies
+ jiffies_scan_yield
;
804 * Memory scanning is a long process and it needs to be interruptable. This
805 * function checks whether such interrupt condition occured.
807 static int scan_should_stop(void)
809 if (!atomic_read(&kmemleak_enabled
))
813 * This function may be called from either process or kthread context,
814 * hence the need to check for both stop conditions.
817 return signal_pending(current
);
819 return kthread_should_stop();
825 * Scan a memory block (exclusive range) for valid pointers and add those
826 * found to the gray list.
828 static void scan_block(void *_start
, void *_end
,
829 struct kmemleak_object
*scanned
)
832 unsigned long *start
= PTR_ALIGN(_start
, BYTES_PER_POINTER
);
833 unsigned long *end
= _end
- (BYTES_PER_POINTER
- 1);
835 for (ptr
= start
; ptr
< end
; ptr
++) {
837 unsigned long pointer
= *ptr
;
838 struct kmemleak_object
*object
;
840 if (scan_should_stop())
844 * When scanning a memory block with a corresponding
845 * kmemleak_object, the CPU yielding is handled in the calling
846 * code since it holds the object->lock to avoid the block
852 object
= find_and_get_object(pointer
, 1);
855 if (object
== scanned
) {
856 /* self referenced, ignore */
862 * Avoid the lockdep recursive warning on object->lock being
863 * previously acquired in scan_object(). These locks are
864 * enclosed by scan_mutex.
866 spin_lock_irqsave_nested(&object
->lock
, flags
,
867 SINGLE_DEPTH_NESTING
);
868 if (!color_white(object
)) {
869 /* non-orphan, ignored or new */
870 spin_unlock_irqrestore(&object
->lock
, flags
);
876 * Increase the object's reference count (number of pointers
877 * to the memory block). If this count reaches the required
878 * minimum, the object's color will become gray and it will be
879 * added to the gray_list.
882 if (color_gray(object
))
883 list_add_tail(&object
->gray_list
, &gray_list
);
886 spin_unlock_irqrestore(&object
->lock
, flags
);
891 * Scan a memory block corresponding to a kmemleak_object. A condition is
892 * that object->use_count >= 1.
894 static void scan_object(struct kmemleak_object
*object
)
896 struct kmemleak_scan_area
*area
;
897 struct hlist_node
*elem
;
901 * Once the object->lock is aquired, the corresponding memory block
902 * cannot be freed (the same lock is aquired in delete_object).
904 spin_lock_irqsave(&object
->lock
, flags
);
905 if (object
->flags
& OBJECT_NO_SCAN
)
907 if (!(object
->flags
& OBJECT_ALLOCATED
))
908 /* already freed object */
910 if (hlist_empty(&object
->area_list
))
911 scan_block((void *)object
->pointer
,
912 (void *)(object
->pointer
+ object
->size
), object
);
914 hlist_for_each_entry(area
, elem
, &object
->area_list
, node
)
915 scan_block((void *)(object
->pointer
+ area
->offset
),
916 (void *)(object
->pointer
+ area
->offset
917 + area
->length
), object
);
919 spin_unlock_irqrestore(&object
->lock
, flags
);
923 * Scan data sections and all the referenced memory blocks allocated via the
924 * kernel's standard allocators. This function must be called with the
927 static void kmemleak_scan(void)
930 struct kmemleak_object
*object
, *tmp
;
931 struct task_struct
*task
;
935 jiffies_last_scan
= jiffies
;
937 /* prepare the kmemleak_object's */
939 list_for_each_entry_rcu(object
, &object_list
, object_list
) {
940 spin_lock_irqsave(&object
->lock
, flags
);
943 * With a few exceptions there should be a maximum of
944 * 1 reference to any object at this point.
946 if (atomic_read(&object
->use_count
) > 1) {
947 pr_debug("object->use_count = %d\n",
948 atomic_read(&object
->use_count
));
949 dump_object_info(object
);
952 /* reset the reference count (whiten the object) */
954 if (color_gray(object
) && get_object(object
))
955 list_add_tail(&object
->gray_list
, &gray_list
);
957 spin_unlock_irqrestore(&object
->lock
, flags
);
961 /* data/bss scanning */
962 scan_block(_sdata
, _edata
, NULL
);
963 scan_block(__bss_start
, __bss_stop
, NULL
);
966 /* per-cpu sections scanning */
967 for_each_possible_cpu(i
)
968 scan_block(__per_cpu_start
+ per_cpu_offset(i
),
969 __per_cpu_end
+ per_cpu_offset(i
), NULL
);
973 * Struct page scanning for each node. The code below is not yet safe
974 * with MEMORY_HOTPLUG.
976 for_each_online_node(i
) {
977 pg_data_t
*pgdat
= NODE_DATA(i
);
978 unsigned long start_pfn
= pgdat
->node_start_pfn
;
979 unsigned long end_pfn
= start_pfn
+ pgdat
->node_spanned_pages
;
982 for (pfn
= start_pfn
; pfn
< end_pfn
; pfn
++) {
987 page
= pfn_to_page(pfn
);
988 /* only scan if page is in use */
989 if (page_count(page
) == 0)
991 scan_block(page
, page
+ 1, NULL
);
996 * Scanning the task stacks may introduce false negatives and it is
997 * not enabled by default.
999 if (kmemleak_stack_scan
) {
1000 read_lock(&tasklist_lock
);
1001 for_each_process(task
)
1002 scan_block(task_stack_page(task
),
1003 task_stack_page(task
) + THREAD_SIZE
, NULL
);
1004 read_unlock(&tasklist_lock
);
1008 * Scan the objects already referenced from the sections scanned
1009 * above. More objects will be referenced and, if there are no memory
1010 * leaks, all the objects will be scanned. The list traversal is safe
1011 * for both tail additions and removals from inside the loop. The
1012 * kmemleak objects cannot be freed from outside the loop because their
1013 * use_count was increased.
1015 object
= list_entry(gray_list
.next
, typeof(*object
), gray_list
);
1016 while (&object
->gray_list
!= &gray_list
) {
1019 /* may add new objects to the list */
1020 if (!scan_should_stop())
1021 scan_object(object
);
1023 tmp
= list_entry(object
->gray_list
.next
, typeof(*object
),
1026 /* remove the object from the list and release it */
1027 list_del(&object
->gray_list
);
1032 WARN_ON(!list_empty(&gray_list
));
1035 * If scanning was stopped do not report any new unreferenced objects.
1037 if (scan_should_stop())
1041 * Scanning result reporting.
1044 list_for_each_entry_rcu(object
, &object_list
, object_list
) {
1045 spin_lock_irqsave(&object
->lock
, flags
);
1046 if (unreferenced_object(object
) &&
1047 !(object
->flags
& OBJECT_REPORTED
)) {
1048 object
->flags
|= OBJECT_REPORTED
;
1051 spin_unlock_irqrestore(&object
->lock
, flags
);
1056 pr_info("%d new suspected memory leaks (see "
1057 "/sys/kernel/debug/kmemleak)\n", new_leaks
);
1062 * Thread function performing automatic memory scanning. Unreferenced objects
1063 * at the end of a memory scan are reported but only the first time.
1065 static int kmemleak_scan_thread(void *arg
)
1067 static int first_run
= 1;
1069 pr_info("Automatic memory scanning thread started\n");
1072 * Wait before the first scan to allow the system to fully initialize.
1076 ssleep(SECS_FIRST_SCAN
);
1079 while (!kthread_should_stop()) {
1080 signed long timeout
= jiffies_scan_wait
;
1082 mutex_lock(&scan_mutex
);
1084 mutex_unlock(&scan_mutex
);
1086 /* wait before the next scan */
1087 while (timeout
&& !kthread_should_stop())
1088 timeout
= schedule_timeout_interruptible(timeout
);
1091 pr_info("Automatic memory scanning thread ended\n");
1097 * Start the automatic memory scanning thread. This function must be called
1098 * with the scan_mutex held.
1100 void start_scan_thread(void)
1104 scan_thread
= kthread_run(kmemleak_scan_thread
, NULL
, "kmemleak");
1105 if (IS_ERR(scan_thread
)) {
1106 pr_warning("Failed to create the scan thread\n");
1112 * Stop the automatic memory scanning thread. This function must be called
1113 * with the scan_mutex held.
1115 void stop_scan_thread(void)
1118 kthread_stop(scan_thread
);
1124 * Iterate over the object_list and return the first valid object at or after
1125 * the required position with its use_count incremented. The function triggers
1126 * a memory scanning when the pos argument points to the first position.
1128 static void *kmemleak_seq_start(struct seq_file
*seq
, loff_t
*pos
)
1130 struct kmemleak_object
*object
;
1135 if (reported_leaks
>= REPORTS_NR
)
1139 list_for_each_entry_rcu(object
, &object_list
, object_list
) {
1142 if (get_object(object
))
1152 * Return the next object in the object_list. The function decrements the
1153 * use_count of the previous object and increases that of the next one.
1155 static void *kmemleak_seq_next(struct seq_file
*seq
, void *v
, loff_t
*pos
)
1157 struct kmemleak_object
*prev_obj
= v
;
1158 struct kmemleak_object
*next_obj
= NULL
;
1159 struct list_head
*n
= &prev_obj
->object_list
;
1162 if (reported_leaks
>= REPORTS_NR
)
1166 list_for_each_continue_rcu(n
, &object_list
) {
1167 next_obj
= list_entry(n
, struct kmemleak_object
, object_list
);
1168 if (get_object(next_obj
))
1173 put_object(prev_obj
);
1178 * Decrement the use_count of the last object required, if any.
1180 static void kmemleak_seq_stop(struct seq_file
*seq
, void *v
)
1187 * Print the information for an unreferenced object to the seq file.
1189 static int kmemleak_seq_show(struct seq_file
*seq
, void *v
)
1191 struct kmemleak_object
*object
= v
;
1192 unsigned long flags
;
1194 spin_lock_irqsave(&object
->lock
, flags
);
1195 if ((object
->flags
& OBJECT_REPORTED
) && unreferenced_object(object
)) {
1196 print_unreferenced(seq
, object
);
1199 spin_unlock_irqrestore(&object
->lock
, flags
);
1203 static const struct seq_operations kmemleak_seq_ops
= {
1204 .start
= kmemleak_seq_start
,
1205 .next
= kmemleak_seq_next
,
1206 .stop
= kmemleak_seq_stop
,
1207 .show
= kmemleak_seq_show
,
1210 static int kmemleak_open(struct inode
*inode
, struct file
*file
)
1214 if (!atomic_read(&kmemleak_enabled
))
1217 ret
= mutex_lock_interruptible(&scan_mutex
);
1220 if (file
->f_mode
& FMODE_READ
) {
1221 ret
= seq_open(file
, &kmemleak_seq_ops
);
1228 mutex_unlock(&scan_mutex
);
1233 static int kmemleak_release(struct inode
*inode
, struct file
*file
)
1237 if (file
->f_mode
& FMODE_READ
)
1238 seq_release(inode
, file
);
1239 mutex_unlock(&scan_mutex
);
1245 * File write operation to configure kmemleak at run-time. The following
1246 * commands can be written to the /sys/kernel/debug/kmemleak file:
1247 * off - disable kmemleak (irreversible)
1248 * stack=on - enable the task stacks scanning
1249 * stack=off - disable the tasks stacks scanning
1250 * scan=on - start the automatic memory scanning thread
1251 * scan=off - stop the automatic memory scanning thread
1252 * scan=... - set the automatic memory scanning period in seconds (0 to
1254 * scan - trigger a memory scan
1256 static ssize_t
kmemleak_write(struct file
*file
, const char __user
*user_buf
,
1257 size_t size
, loff_t
*ppos
)
1262 if (!atomic_read(&kmemleak_enabled
))
1265 buf_size
= min(size
, (sizeof(buf
) - 1));
1266 if (strncpy_from_user(buf
, user_buf
, buf_size
) < 0)
1270 if (strncmp(buf
, "off", 3) == 0)
1272 else if (strncmp(buf
, "stack=on", 8) == 0)
1273 kmemleak_stack_scan
= 1;
1274 else if (strncmp(buf
, "stack=off", 9) == 0)
1275 kmemleak_stack_scan
= 0;
1276 else if (strncmp(buf
, "scan=on", 7) == 0)
1277 start_scan_thread();
1278 else if (strncmp(buf
, "scan=off", 8) == 0)
1280 else if (strncmp(buf
, "scan=", 5) == 0) {
1284 err
= strict_strtoul(buf
+ 5, 0, &secs
);
1289 jiffies_scan_wait
= msecs_to_jiffies(secs
* 1000);
1290 start_scan_thread();
1292 } else if (strncmp(buf
, "scan", 4) == 0)
1297 /* ignore the rest of the buffer, only one command at a time */
1302 static const struct file_operations kmemleak_fops
= {
1303 .owner
= THIS_MODULE
,
1304 .open
= kmemleak_open
,
1306 .write
= kmemleak_write
,
1307 .llseek
= seq_lseek
,
1308 .release
= kmemleak_release
,
1312 * Perform the freeing of the kmemleak internal objects after waiting for any
1313 * current memory scan to complete.
1315 static int kmemleak_cleanup_thread(void *arg
)
1317 struct kmemleak_object
*object
;
1319 mutex_lock(&scan_mutex
);
1323 list_for_each_entry_rcu(object
, &object_list
, object_list
)
1324 delete_object(object
->pointer
);
1326 mutex_unlock(&scan_mutex
);
1332 * Start the clean-up thread.
1334 static void kmemleak_cleanup(void)
1336 struct task_struct
*cleanup_thread
;
1338 cleanup_thread
= kthread_run(kmemleak_cleanup_thread
, NULL
,
1340 if (IS_ERR(cleanup_thread
))
1341 pr_warning("Failed to create the clean-up thread\n");
1345 * Disable kmemleak. No memory allocation/freeing will be traced once this
1346 * function is called. Disabling kmemleak is an irreversible operation.
1348 static void kmemleak_disable(void)
1350 /* atomically check whether it was already invoked */
1351 if (atomic_cmpxchg(&kmemleak_error
, 0, 1))
1354 /* stop any memory operation tracing */
1355 atomic_set(&kmemleak_early_log
, 0);
1356 atomic_set(&kmemleak_enabled
, 0);
1358 /* check whether it is too early for a kernel thread */
1359 if (atomic_read(&kmemleak_initialized
))
1362 pr_info("Kernel memory leak detector disabled\n");
1366 * Allow boot-time kmemleak disabling (enabled by default).
1368 static int kmemleak_boot_config(char *str
)
1372 if (strcmp(str
, "off") == 0)
1374 else if (strcmp(str
, "on") != 0)
1378 early_param("kmemleak", kmemleak_boot_config
);
1381 * Kmemleak initialization.
1383 void __init
kmemleak_init(void)
1386 unsigned long flags
;
1388 jiffies_scan_yield
= msecs_to_jiffies(MSECS_SCAN_YIELD
);
1389 jiffies_min_age
= msecs_to_jiffies(MSECS_MIN_AGE
);
1390 jiffies_scan_wait
= msecs_to_jiffies(SECS_SCAN_WAIT
* 1000);
1392 object_cache
= KMEM_CACHE(kmemleak_object
, SLAB_NOLEAKTRACE
);
1393 scan_area_cache
= KMEM_CACHE(kmemleak_scan_area
, SLAB_NOLEAKTRACE
);
1394 INIT_PRIO_TREE_ROOT(&object_tree_root
);
1396 /* the kernel is still in UP mode, so disabling the IRQs is enough */
1397 local_irq_save(flags
);
1398 if (!atomic_read(&kmemleak_error
)) {
1399 atomic_set(&kmemleak_enabled
, 1);
1400 atomic_set(&kmemleak_early_log
, 0);
1402 local_irq_restore(flags
);
1405 * This is the point where tracking allocations is safe. Automatic
1406 * scanning is started during the late initcall. Add the early logged
1407 * callbacks to the kmemleak infrastructure.
1409 for (i
= 0; i
< crt_early_log
; i
++) {
1410 struct early_log
*log
= &early_log
[i
];
1412 switch (log
->op_type
) {
1413 case KMEMLEAK_ALLOC
:
1414 kmemleak_alloc(log
->ptr
, log
->size
, log
->min_count
,
1418 kmemleak_free(log
->ptr
);
1420 case KMEMLEAK_NOT_LEAK
:
1421 kmemleak_not_leak(log
->ptr
);
1423 case KMEMLEAK_IGNORE
:
1424 kmemleak_ignore(log
->ptr
);
1426 case KMEMLEAK_SCAN_AREA
:
1427 kmemleak_scan_area(log
->ptr
, log
->offset
, log
->length
,
1430 case KMEMLEAK_NO_SCAN
:
1431 kmemleak_no_scan(log
->ptr
);
1440 * Late initialization function.
1442 static int __init
kmemleak_late_init(void)
1444 struct dentry
*dentry
;
1446 atomic_set(&kmemleak_initialized
, 1);
1448 if (atomic_read(&kmemleak_error
)) {
1450 * Some error occured and kmemleak was disabled. There is a
1451 * small chance that kmemleak_disable() was called immediately
1452 * after setting kmemleak_initialized and we may end up with
1453 * two clean-up threads but serialized by scan_mutex.
1459 dentry
= debugfs_create_file("kmemleak", S_IRUGO
, NULL
, NULL
,
1462 pr_warning("Failed to create the debugfs kmemleak file\n");
1463 mutex_lock(&scan_mutex
);
1464 start_scan_thread();
1465 mutex_unlock(&scan_mutex
);
1467 pr_info("Kernel memory leak detector initialized\n");
1471 late_initcall(kmemleak_late_init
);