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3c7b4e6b CM |
1 | /* |
2 | * mm/kmemleak.c | |
3 | * | |
4 | * Copyright (C) 2008 ARM Limited | |
5 | * Written by Catalin Marinas <catalin.marinas@arm.com> | |
6 | * | |
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. | |
10 | * | |
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. | |
15 | * | |
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 | |
19 | * | |
20 | * | |
21 | * For more information on the algorithm and kmemleak usage, please see | |
22 | * Documentation/kmemleak.txt. | |
23 | * | |
24 | * Notes on locking | |
25 | * ---------------- | |
26 | * | |
27 | * The following locks and mutexes are used by kmemleak: | |
28 | * | |
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 | |
52 | * - kmemleak_mutex (mutex): prevents multiple users of the "kmemleak" debugfs | |
53 | * file together with modifications to the memory scanning parameters | |
54 | * including the scan_thread pointer | |
55 | * | |
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 | |
61 | * structure. | |
62 | */ | |
63 | ||
64 | #include <linux/init.h> | |
65 | #include <linux/kernel.h> | |
66 | #include <linux/list.h> | |
67 | #include <linux/sched.h> | |
68 | #include <linux/jiffies.h> | |
69 | #include <linux/delay.h> | |
70 | #include <linux/module.h> | |
71 | #include <linux/kthread.h> | |
72 | #include <linux/prio_tree.h> | |
73 | #include <linux/gfp.h> | |
74 | #include <linux/fs.h> | |
75 | #include <linux/debugfs.h> | |
76 | #include <linux/seq_file.h> | |
77 | #include <linux/cpumask.h> | |
78 | #include <linux/spinlock.h> | |
79 | #include <linux/mutex.h> | |
80 | #include <linux/rcupdate.h> | |
81 | #include <linux/stacktrace.h> | |
82 | #include <linux/cache.h> | |
83 | #include <linux/percpu.h> | |
84 | #include <linux/hardirq.h> | |
85 | #include <linux/mmzone.h> | |
86 | #include <linux/slab.h> | |
87 | #include <linux/thread_info.h> | |
88 | #include <linux/err.h> | |
89 | #include <linux/uaccess.h> | |
90 | #include <linux/string.h> | |
91 | #include <linux/nodemask.h> | |
92 | #include <linux/mm.h> | |
93 | ||
94 | #include <asm/sections.h> | |
95 | #include <asm/processor.h> | |
96 | #include <asm/atomic.h> | |
97 | ||
98 | #include <linux/kmemleak.h> | |
99 | ||
100 | /* | |
101 | * Kmemleak configuration and common defines. | |
102 | */ | |
103 | #define MAX_TRACE 16 /* stack trace length */ | |
104 | #define REPORTS_NR 50 /* maximum number of reported leaks */ | |
105 | #define MSECS_MIN_AGE 5000 /* minimum object age for reporting */ | |
106 | #define MSECS_SCAN_YIELD 10 /* CPU yielding period */ | |
107 | #define SECS_FIRST_SCAN 60 /* delay before the first scan */ | |
108 | #define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */ | |
109 | ||
110 | #define BYTES_PER_POINTER sizeof(void *) | |
111 | ||
112 | /* scanning area inside a memory block */ | |
113 | struct kmemleak_scan_area { | |
114 | struct hlist_node node; | |
115 | unsigned long offset; | |
116 | size_t length; | |
117 | }; | |
118 | ||
119 | /* | |
120 | * Structure holding the metadata for each allocated memory block. | |
121 | * Modifications to such objects should be made while holding the | |
122 | * object->lock. Insertions or deletions from object_list, gray_list or | |
123 | * tree_node are already protected by the corresponding locks or mutex (see | |
124 | * the notes on locking above). These objects are reference-counted | |
125 | * (use_count) and freed using the RCU mechanism. | |
126 | */ | |
127 | struct kmemleak_object { | |
128 | spinlock_t lock; | |
129 | unsigned long flags; /* object status flags */ | |
130 | struct list_head object_list; | |
131 | struct list_head gray_list; | |
132 | struct prio_tree_node tree_node; | |
133 | struct rcu_head rcu; /* object_list lockless traversal */ | |
134 | /* object usage count; object freed when use_count == 0 */ | |
135 | atomic_t use_count; | |
136 | unsigned long pointer; | |
137 | size_t size; | |
138 | /* minimum number of a pointers found before it is considered leak */ | |
139 | int min_count; | |
140 | /* the total number of pointers found pointing to this object */ | |
141 | int count; | |
142 | /* memory ranges to be scanned inside an object (empty for all) */ | |
143 | struct hlist_head area_list; | |
144 | unsigned long trace[MAX_TRACE]; | |
145 | unsigned int trace_len; | |
146 | unsigned long jiffies; /* creation timestamp */ | |
147 | pid_t pid; /* pid of the current task */ | |
148 | char comm[TASK_COMM_LEN]; /* executable name */ | |
149 | }; | |
150 | ||
151 | /* flag representing the memory block allocation status */ | |
152 | #define OBJECT_ALLOCATED (1 << 0) | |
153 | /* flag set after the first reporting of an unreference object */ | |
154 | #define OBJECT_REPORTED (1 << 1) | |
155 | /* flag set to not scan the object */ | |
156 | #define OBJECT_NO_SCAN (1 << 2) | |
157 | ||
158 | /* the list of all allocated objects */ | |
159 | static LIST_HEAD(object_list); | |
160 | /* the list of gray-colored objects (see color_gray comment below) */ | |
161 | static LIST_HEAD(gray_list); | |
162 | /* prio search tree for object boundaries */ | |
163 | static struct prio_tree_root object_tree_root; | |
164 | /* rw_lock protecting the access to object_list and prio_tree_root */ | |
165 | static DEFINE_RWLOCK(kmemleak_lock); | |
166 | ||
167 | /* allocation caches for kmemleak internal data */ | |
168 | static struct kmem_cache *object_cache; | |
169 | static struct kmem_cache *scan_area_cache; | |
170 | ||
171 | /* set if tracing memory operations is enabled */ | |
172 | static atomic_t kmemleak_enabled = ATOMIC_INIT(0); | |
173 | /* set in the late_initcall if there were no errors */ | |
174 | static atomic_t kmemleak_initialized = ATOMIC_INIT(0); | |
175 | /* enables or disables early logging of the memory operations */ | |
176 | static atomic_t kmemleak_early_log = ATOMIC_INIT(1); | |
177 | /* set if a fata kmemleak error has occurred */ | |
178 | static atomic_t kmemleak_error = ATOMIC_INIT(0); | |
179 | ||
180 | /* minimum and maximum address that may be valid pointers */ | |
181 | static unsigned long min_addr = ULONG_MAX; | |
182 | static unsigned long max_addr; | |
183 | ||
184 | /* used for yielding the CPU to other tasks during scanning */ | |
185 | static unsigned long next_scan_yield; | |
186 | static struct task_struct *scan_thread; | |
187 | static unsigned long jiffies_scan_yield; | |
188 | static unsigned long jiffies_min_age; | |
189 | /* delay between automatic memory scannings */ | |
190 | static signed long jiffies_scan_wait; | |
191 | /* enables or disables the task stacks scanning */ | |
192 | static int kmemleak_stack_scan; | |
193 | /* mutex protecting the memory scanning */ | |
194 | static DEFINE_MUTEX(scan_mutex); | |
195 | /* mutex protecting the access to the /sys/kernel/debug/kmemleak file */ | |
196 | static DEFINE_MUTEX(kmemleak_mutex); | |
197 | ||
198 | /* number of leaks reported (for limitation purposes) */ | |
199 | static int reported_leaks; | |
200 | ||
201 | /* | |
202 | * Early object allocation/freeing logging. Kkmemleak is initialized after the | |
203 | * kernel allocator. However, both the kernel allocator and kmemleak may | |
204 | * allocate memory blocks which need to be tracked. Kkmemleak defines an | |
205 | * arbitrary buffer to hold the allocation/freeing information before it is | |
206 | * fully initialized. | |
207 | */ | |
208 | ||
209 | /* kmemleak operation type for early logging */ | |
210 | enum { | |
211 | KMEMLEAK_ALLOC, | |
212 | KMEMLEAK_FREE, | |
213 | KMEMLEAK_NOT_LEAK, | |
214 | KMEMLEAK_IGNORE, | |
215 | KMEMLEAK_SCAN_AREA, | |
216 | KMEMLEAK_NO_SCAN | |
217 | }; | |
218 | ||
219 | /* | |
220 | * Structure holding the information passed to kmemleak callbacks during the | |
221 | * early logging. | |
222 | */ | |
223 | struct early_log { | |
224 | int op_type; /* kmemleak operation type */ | |
225 | const void *ptr; /* allocated/freed memory block */ | |
226 | size_t size; /* memory block size */ | |
227 | int min_count; /* minimum reference count */ | |
228 | unsigned long offset; /* scan area offset */ | |
229 | size_t length; /* scan area length */ | |
230 | }; | |
231 | ||
232 | /* early logging buffer and current position */ | |
233 | static struct early_log early_log[200]; | |
234 | static int crt_early_log; | |
235 | ||
236 | static void kmemleak_disable(void); | |
237 | ||
238 | /* | |
239 | * Print a warning and dump the stack trace. | |
240 | */ | |
241 | #define kmemleak_warn(x...) do { \ | |
242 | pr_warning(x); \ | |
243 | dump_stack(); \ | |
244 | } while (0) | |
245 | ||
246 | /* | |
247 | * Macro invoked when a serious kmemleak condition occured and cannot be | |
248 | * recovered from. Kkmemleak will be disabled and further allocation/freeing | |
249 | * tracing no longer available. | |
250 | */ | |
251 | #define kmemleak_panic(x...) do { \ | |
252 | kmemleak_warn(x); \ | |
253 | kmemleak_disable(); \ | |
254 | } while (0) | |
255 | ||
256 | /* | |
257 | * Object colors, encoded with count and min_count: | |
258 | * - white - orphan object, not enough references to it (count < min_count) | |
259 | * - gray - not orphan, not marked as false positive (min_count == 0) or | |
260 | * sufficient references to it (count >= min_count) | |
261 | * - black - ignore, it doesn't contain references (e.g. text section) | |
262 | * (min_count == -1). No function defined for this color. | |
263 | * Newly created objects don't have any color assigned (object->count == -1) | |
264 | * before the next memory scan when they become white. | |
265 | */ | |
266 | static int color_white(const struct kmemleak_object *object) | |
267 | { | |
268 | return object->count != -1 && object->count < object->min_count; | |
269 | } | |
270 | ||
271 | static int color_gray(const struct kmemleak_object *object) | |
272 | { | |
273 | return object->min_count != -1 && object->count >= object->min_count; | |
274 | } | |
275 | ||
276 | /* | |
277 | * Objects are considered referenced if their color is gray and they have not | |
278 | * been deleted. | |
279 | */ | |
280 | static int referenced_object(struct kmemleak_object *object) | |
281 | { | |
282 | return (object->flags & OBJECT_ALLOCATED) && color_gray(object); | |
283 | } | |
284 | ||
285 | /* | |
286 | * Objects are considered unreferenced only if their color is white, they have | |
287 | * not be deleted and have a minimum age to avoid false positives caused by | |
288 | * pointers temporarily stored in CPU registers. | |
289 | */ | |
290 | static int unreferenced_object(struct kmemleak_object *object) | |
291 | { | |
292 | return (object->flags & OBJECT_ALLOCATED) && color_white(object) && | |
293 | time_is_before_eq_jiffies(object->jiffies + jiffies_min_age); | |
294 | } | |
295 | ||
296 | /* | |
297 | * Printing of the (un)referenced objects information, either to the seq file | |
298 | * or to the kernel log. The print_referenced/print_unreferenced functions | |
299 | * must be called with the object->lock held. | |
300 | */ | |
301 | #define print_helper(seq, x...) do { \ | |
302 | struct seq_file *s = (seq); \ | |
303 | if (s) \ | |
304 | seq_printf(s, x); \ | |
305 | else \ | |
306 | pr_info(x); \ | |
307 | } while (0) | |
308 | ||
309 | static void print_referenced(struct kmemleak_object *object) | |
310 | { | |
311 | pr_info("kmemleak: referenced object 0x%08lx (size %zu)\n", | |
312 | object->pointer, object->size); | |
313 | } | |
314 | ||
315 | static void print_unreferenced(struct seq_file *seq, | |
316 | struct kmemleak_object *object) | |
317 | { | |
318 | int i; | |
319 | ||
320 | print_helper(seq, "kmemleak: unreferenced object 0x%08lx (size %zu):\n", | |
321 | object->pointer, object->size); | |
322 | print_helper(seq, " comm \"%s\", pid %d, jiffies %lu\n", | |
323 | object->comm, object->pid, object->jiffies); | |
324 | print_helper(seq, " backtrace:\n"); | |
325 | ||
326 | for (i = 0; i < object->trace_len; i++) { | |
327 | void *ptr = (void *)object->trace[i]; | |
328 | print_helper(seq, " [<%p>] %pS\n", ptr, ptr); | |
329 | } | |
330 | } | |
331 | ||
332 | /* | |
333 | * Print the kmemleak_object information. This function is used mainly for | |
334 | * debugging special cases when kmemleak operations. It must be called with | |
335 | * the object->lock held. | |
336 | */ | |
337 | static void dump_object_info(struct kmemleak_object *object) | |
338 | { | |
339 | struct stack_trace trace; | |
340 | ||
341 | trace.nr_entries = object->trace_len; | |
342 | trace.entries = object->trace; | |
343 | ||
344 | pr_notice("kmemleak: Object 0x%08lx (size %zu):\n", | |
345 | object->tree_node.start, object->size); | |
346 | pr_notice(" comm \"%s\", pid %d, jiffies %lu\n", | |
347 | object->comm, object->pid, object->jiffies); | |
348 | pr_notice(" min_count = %d\n", object->min_count); | |
349 | pr_notice(" count = %d\n", object->count); | |
350 | pr_notice(" backtrace:\n"); | |
351 | print_stack_trace(&trace, 4); | |
352 | } | |
353 | ||
354 | /* | |
355 | * Look-up a memory block metadata (kmemleak_object) in the priority search | |
356 | * tree based on a pointer value. If alias is 0, only values pointing to the | |
357 | * beginning of the memory block are allowed. The kmemleak_lock must be held | |
358 | * when calling this function. | |
359 | */ | |
360 | static struct kmemleak_object *lookup_object(unsigned long ptr, int alias) | |
361 | { | |
362 | struct prio_tree_node *node; | |
363 | struct prio_tree_iter iter; | |
364 | struct kmemleak_object *object; | |
365 | ||
366 | prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr); | |
367 | node = prio_tree_next(&iter); | |
368 | if (node) { | |
369 | object = prio_tree_entry(node, struct kmemleak_object, | |
370 | tree_node); | |
371 | if (!alias && object->pointer != ptr) { | |
372 | kmemleak_warn("kmemleak: Found object by alias"); | |
373 | object = NULL; | |
374 | } | |
375 | } else | |
376 | object = NULL; | |
377 | ||
378 | return object; | |
379 | } | |
380 | ||
381 | /* | |
382 | * Increment the object use_count. Return 1 if successful or 0 otherwise. Note | |
383 | * that once an object's use_count reached 0, the RCU freeing was already | |
384 | * registered and the object should no longer be used. This function must be | |
385 | * called under the protection of rcu_read_lock(). | |
386 | */ | |
387 | static int get_object(struct kmemleak_object *object) | |
388 | { | |
389 | return atomic_inc_not_zero(&object->use_count); | |
390 | } | |
391 | ||
392 | /* | |
393 | * RCU callback to free a kmemleak_object. | |
394 | */ | |
395 | static void free_object_rcu(struct rcu_head *rcu) | |
396 | { | |
397 | struct hlist_node *elem, *tmp; | |
398 | struct kmemleak_scan_area *area; | |
399 | struct kmemleak_object *object = | |
400 | container_of(rcu, struct kmemleak_object, rcu); | |
401 | ||
402 | /* | |
403 | * Once use_count is 0 (guaranteed by put_object), there is no other | |
404 | * code accessing this object, hence no need for locking. | |
405 | */ | |
406 | hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) { | |
407 | hlist_del(elem); | |
408 | kmem_cache_free(scan_area_cache, area); | |
409 | } | |
410 | kmem_cache_free(object_cache, object); | |
411 | } | |
412 | ||
413 | /* | |
414 | * Decrement the object use_count. Once the count is 0, free the object using | |
415 | * an RCU callback. Since put_object() may be called via the kmemleak_free() -> | |
416 | * delete_object() path, the delayed RCU freeing ensures that there is no | |
417 | * recursive call to the kernel allocator. Lock-less RCU object_list traversal | |
418 | * is also possible. | |
419 | */ | |
420 | static void put_object(struct kmemleak_object *object) | |
421 | { | |
422 | if (!atomic_dec_and_test(&object->use_count)) | |
423 | return; | |
424 | ||
425 | /* should only get here after delete_object was called */ | |
426 | WARN_ON(object->flags & OBJECT_ALLOCATED); | |
427 | ||
428 | call_rcu(&object->rcu, free_object_rcu); | |
429 | } | |
430 | ||
431 | /* | |
432 | * Look up an object in the prio search tree and increase its use_count. | |
433 | */ | |
434 | static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias) | |
435 | { | |
436 | unsigned long flags; | |
437 | struct kmemleak_object *object = NULL; | |
438 | ||
439 | rcu_read_lock(); | |
440 | read_lock_irqsave(&kmemleak_lock, flags); | |
441 | if (ptr >= min_addr && ptr < max_addr) | |
442 | object = lookup_object(ptr, alias); | |
443 | read_unlock_irqrestore(&kmemleak_lock, flags); | |
444 | ||
445 | /* check whether the object is still available */ | |
446 | if (object && !get_object(object)) | |
447 | object = NULL; | |
448 | rcu_read_unlock(); | |
449 | ||
450 | return object; | |
451 | } | |
452 | ||
453 | /* | |
454 | * Create the metadata (struct kmemleak_object) corresponding to an allocated | |
455 | * memory block and add it to the object_list and object_tree_root. | |
456 | */ | |
457 | static void create_object(unsigned long ptr, size_t size, int min_count, | |
458 | gfp_t gfp) | |
459 | { | |
460 | unsigned long flags; | |
461 | struct kmemleak_object *object; | |
462 | struct prio_tree_node *node; | |
463 | struct stack_trace trace; | |
464 | ||
465 | object = kmem_cache_alloc(object_cache, gfp & ~GFP_SLAB_BUG_MASK); | |
466 | if (!object) { | |
467 | kmemleak_panic("kmemleak: Cannot allocate a kmemleak_object " | |
468 | "structure\n"); | |
469 | return; | |
470 | } | |
471 | ||
472 | INIT_LIST_HEAD(&object->object_list); | |
473 | INIT_LIST_HEAD(&object->gray_list); | |
474 | INIT_HLIST_HEAD(&object->area_list); | |
475 | spin_lock_init(&object->lock); | |
476 | atomic_set(&object->use_count, 1); | |
477 | object->flags = OBJECT_ALLOCATED; | |
478 | object->pointer = ptr; | |
479 | object->size = size; | |
480 | object->min_count = min_count; | |
481 | object->count = -1; /* no color initially */ | |
482 | object->jiffies = jiffies; | |
483 | ||
484 | /* task information */ | |
485 | if (in_irq()) { | |
486 | object->pid = 0; | |
487 | strncpy(object->comm, "hardirq", sizeof(object->comm)); | |
488 | } else if (in_softirq()) { | |
489 | object->pid = 0; | |
490 | strncpy(object->comm, "softirq", sizeof(object->comm)); | |
491 | } else { | |
492 | object->pid = current->pid; | |
493 | /* | |
494 | * There is a small chance of a race with set_task_comm(), | |
495 | * however using get_task_comm() here may cause locking | |
496 | * dependency issues with current->alloc_lock. In the worst | |
497 | * case, the command line is not correct. | |
498 | */ | |
499 | strncpy(object->comm, current->comm, sizeof(object->comm)); | |
500 | } | |
501 | ||
502 | /* kernel backtrace */ | |
503 | trace.max_entries = MAX_TRACE; | |
504 | trace.nr_entries = 0; | |
505 | trace.entries = object->trace; | |
506 | trace.skip = 1; | |
507 | save_stack_trace(&trace); | |
508 | object->trace_len = trace.nr_entries; | |
509 | ||
510 | INIT_PRIO_TREE_NODE(&object->tree_node); | |
511 | object->tree_node.start = ptr; | |
512 | object->tree_node.last = ptr + size - 1; | |
513 | ||
514 | write_lock_irqsave(&kmemleak_lock, flags); | |
515 | min_addr = min(min_addr, ptr); | |
516 | max_addr = max(max_addr, ptr + size); | |
517 | node = prio_tree_insert(&object_tree_root, &object->tree_node); | |
518 | /* | |
519 | * The code calling the kernel does not yet have the pointer to the | |
520 | * memory block to be able to free it. However, we still hold the | |
521 | * kmemleak_lock here in case parts of the kernel started freeing | |
522 | * random memory blocks. | |
523 | */ | |
524 | if (node != &object->tree_node) { | |
525 | unsigned long flags; | |
526 | ||
527 | kmemleak_panic("kmemleak: Cannot insert 0x%lx into the object " | |
528 | "search tree (already existing)\n", ptr); | |
529 | object = lookup_object(ptr, 1); | |
530 | spin_lock_irqsave(&object->lock, flags); | |
531 | dump_object_info(object); | |
532 | spin_unlock_irqrestore(&object->lock, flags); | |
533 | ||
534 | goto out; | |
535 | } | |
536 | list_add_tail_rcu(&object->object_list, &object_list); | |
537 | out: | |
538 | write_unlock_irqrestore(&kmemleak_lock, flags); | |
539 | } | |
540 | ||
541 | /* | |
542 | * Remove the metadata (struct kmemleak_object) for a memory block from the | |
543 | * object_list and object_tree_root and decrement its use_count. | |
544 | */ | |
545 | static void delete_object(unsigned long ptr) | |
546 | { | |
547 | unsigned long flags; | |
548 | struct kmemleak_object *object; | |
549 | ||
550 | write_lock_irqsave(&kmemleak_lock, flags); | |
551 | object = lookup_object(ptr, 0); | |
552 | if (!object) { | |
553 | kmemleak_warn("kmemleak: Freeing unknown object at 0x%08lx\n", | |
554 | ptr); | |
555 | write_unlock_irqrestore(&kmemleak_lock, flags); | |
556 | return; | |
557 | } | |
558 | prio_tree_remove(&object_tree_root, &object->tree_node); | |
559 | list_del_rcu(&object->object_list); | |
560 | write_unlock_irqrestore(&kmemleak_lock, flags); | |
561 | ||
562 | WARN_ON(!(object->flags & OBJECT_ALLOCATED)); | |
563 | WARN_ON(atomic_read(&object->use_count) < 1); | |
564 | ||
565 | /* | |
566 | * Locking here also ensures that the corresponding memory block | |
567 | * cannot be freed when it is being scanned. | |
568 | */ | |
569 | spin_lock_irqsave(&object->lock, flags); | |
570 | if (object->flags & OBJECT_REPORTED) | |
571 | print_referenced(object); | |
572 | object->flags &= ~OBJECT_ALLOCATED; | |
573 | spin_unlock_irqrestore(&object->lock, flags); | |
574 | put_object(object); | |
575 | } | |
576 | ||
577 | /* | |
578 | * Make a object permanently as gray-colored so that it can no longer be | |
579 | * reported as a leak. This is used in general to mark a false positive. | |
580 | */ | |
581 | static void make_gray_object(unsigned long ptr) | |
582 | { | |
583 | unsigned long flags; | |
584 | struct kmemleak_object *object; | |
585 | ||
586 | object = find_and_get_object(ptr, 0); | |
587 | if (!object) { | |
588 | kmemleak_warn("kmemleak: Graying unknown object at 0x%08lx\n", | |
589 | ptr); | |
590 | return; | |
591 | } | |
592 | ||
593 | spin_lock_irqsave(&object->lock, flags); | |
594 | object->min_count = 0; | |
595 | spin_unlock_irqrestore(&object->lock, flags); | |
596 | put_object(object); | |
597 | } | |
598 | ||
599 | /* | |
600 | * Mark the object as black-colored so that it is ignored from scans and | |
601 | * reporting. | |
602 | */ | |
603 | static void make_black_object(unsigned long ptr) | |
604 | { | |
605 | unsigned long flags; | |
606 | struct kmemleak_object *object; | |
607 | ||
608 | object = find_and_get_object(ptr, 0); | |
609 | if (!object) { | |
610 | kmemleak_warn("kmemleak: Blacking unknown object at 0x%08lx\n", | |
611 | ptr); | |
612 | return; | |
613 | } | |
614 | ||
615 | spin_lock_irqsave(&object->lock, flags); | |
616 | object->min_count = -1; | |
617 | spin_unlock_irqrestore(&object->lock, flags); | |
618 | put_object(object); | |
619 | } | |
620 | ||
621 | /* | |
622 | * Add a scanning area to the object. If at least one such area is added, | |
623 | * kmemleak will only scan these ranges rather than the whole memory block. | |
624 | */ | |
625 | static void add_scan_area(unsigned long ptr, unsigned long offset, | |
626 | size_t length, gfp_t gfp) | |
627 | { | |
628 | unsigned long flags; | |
629 | struct kmemleak_object *object; | |
630 | struct kmemleak_scan_area *area; | |
631 | ||
632 | object = find_and_get_object(ptr, 0); | |
633 | if (!object) { | |
634 | kmemleak_warn("kmemleak: Adding scan area to unknown " | |
635 | "object at 0x%08lx\n", ptr); | |
636 | return; | |
637 | } | |
638 | ||
639 | area = kmem_cache_alloc(scan_area_cache, gfp & ~GFP_SLAB_BUG_MASK); | |
640 | if (!area) { | |
641 | kmemleak_warn("kmemleak: Cannot allocate a scan area\n"); | |
642 | goto out; | |
643 | } | |
644 | ||
645 | spin_lock_irqsave(&object->lock, flags); | |
646 | if (offset + length > object->size) { | |
647 | kmemleak_warn("kmemleak: Scan area larger than object " | |
648 | "0x%08lx\n", ptr); | |
649 | dump_object_info(object); | |
650 | kmem_cache_free(scan_area_cache, area); | |
651 | goto out_unlock; | |
652 | } | |
653 | ||
654 | INIT_HLIST_NODE(&area->node); | |
655 | area->offset = offset; | |
656 | area->length = length; | |
657 | ||
658 | hlist_add_head(&area->node, &object->area_list); | |
659 | out_unlock: | |
660 | spin_unlock_irqrestore(&object->lock, flags); | |
661 | out: | |
662 | put_object(object); | |
663 | } | |
664 | ||
665 | /* | |
666 | * Set the OBJECT_NO_SCAN flag for the object corresponding to the give | |
667 | * pointer. Such object will not be scanned by kmemleak but references to it | |
668 | * are searched. | |
669 | */ | |
670 | static void object_no_scan(unsigned long ptr) | |
671 | { | |
672 | unsigned long flags; | |
673 | struct kmemleak_object *object; | |
674 | ||
675 | object = find_and_get_object(ptr, 0); | |
676 | if (!object) { | |
677 | kmemleak_warn("kmemleak: Not scanning unknown object at " | |
678 | "0x%08lx\n", ptr); | |
679 | return; | |
680 | } | |
681 | ||
682 | spin_lock_irqsave(&object->lock, flags); | |
683 | object->flags |= OBJECT_NO_SCAN; | |
684 | spin_unlock_irqrestore(&object->lock, flags); | |
685 | put_object(object); | |
686 | } | |
687 | ||
688 | /* | |
689 | * Log an early kmemleak_* call to the early_log buffer. These calls will be | |
690 | * processed later once kmemleak is fully initialized. | |
691 | */ | |
692 | static void log_early(int op_type, const void *ptr, size_t size, | |
693 | int min_count, unsigned long offset, size_t length) | |
694 | { | |
695 | unsigned long flags; | |
696 | struct early_log *log; | |
697 | ||
698 | if (crt_early_log >= ARRAY_SIZE(early_log)) { | |
699 | kmemleak_panic("kmemleak: Early log buffer exceeded\n"); | |
700 | return; | |
701 | } | |
702 | ||
703 | /* | |
704 | * There is no need for locking since the kernel is still in UP mode | |
705 | * at this stage. Disabling the IRQs is enough. | |
706 | */ | |
707 | local_irq_save(flags); | |
708 | log = &early_log[crt_early_log]; | |
709 | log->op_type = op_type; | |
710 | log->ptr = ptr; | |
711 | log->size = size; | |
712 | log->min_count = min_count; | |
713 | log->offset = offset; | |
714 | log->length = length; | |
715 | crt_early_log++; | |
716 | local_irq_restore(flags); | |
717 | } | |
718 | ||
719 | /* | |
720 | * Memory allocation function callback. This function is called from the | |
721 | * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc, | |
722 | * vmalloc etc.). | |
723 | */ | |
724 | void kmemleak_alloc(const void *ptr, size_t size, int min_count, gfp_t gfp) | |
725 | { | |
726 | pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count); | |
727 | ||
728 | if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) | |
729 | create_object((unsigned long)ptr, size, min_count, gfp); | |
730 | else if (atomic_read(&kmemleak_early_log)) | |
731 | log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0); | |
732 | } | |
733 | EXPORT_SYMBOL_GPL(kmemleak_alloc); | |
734 | ||
735 | /* | |
736 | * Memory freeing function callback. This function is called from the kernel | |
737 | * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.). | |
738 | */ | |
739 | void kmemleak_free(const void *ptr) | |
740 | { | |
741 | pr_debug("%s(0x%p)\n", __func__, ptr); | |
742 | ||
743 | if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) | |
744 | delete_object((unsigned long)ptr); | |
745 | else if (atomic_read(&kmemleak_early_log)) | |
746 | log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0); | |
747 | } | |
748 | EXPORT_SYMBOL_GPL(kmemleak_free); | |
749 | ||
750 | /* | |
751 | * Mark an already allocated memory block as a false positive. This will cause | |
752 | * the block to no longer be reported as leak and always be scanned. | |
753 | */ | |
754 | void kmemleak_not_leak(const void *ptr) | |
755 | { | |
756 | pr_debug("%s(0x%p)\n", __func__, ptr); | |
757 | ||
758 | if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) | |
759 | make_gray_object((unsigned long)ptr); | |
760 | else if (atomic_read(&kmemleak_early_log)) | |
761 | log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0); | |
762 | } | |
763 | EXPORT_SYMBOL(kmemleak_not_leak); | |
764 | ||
765 | /* | |
766 | * Ignore a memory block. This is usually done when it is known that the | |
767 | * corresponding block is not a leak and does not contain any references to | |
768 | * other allocated memory blocks. | |
769 | */ | |
770 | void kmemleak_ignore(const void *ptr) | |
771 | { | |
772 | pr_debug("%s(0x%p)\n", __func__, ptr); | |
773 | ||
774 | if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) | |
775 | make_black_object((unsigned long)ptr); | |
776 | else if (atomic_read(&kmemleak_early_log)) | |
777 | log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0); | |
778 | } | |
779 | EXPORT_SYMBOL(kmemleak_ignore); | |
780 | ||
781 | /* | |
782 | * Limit the range to be scanned in an allocated memory block. | |
783 | */ | |
784 | void kmemleak_scan_area(const void *ptr, unsigned long offset, size_t length, | |
785 | gfp_t gfp) | |
786 | { | |
787 | pr_debug("%s(0x%p)\n", __func__, ptr); | |
788 | ||
789 | if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) | |
790 | add_scan_area((unsigned long)ptr, offset, length, gfp); | |
791 | else if (atomic_read(&kmemleak_early_log)) | |
792 | log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length); | |
793 | } | |
794 | EXPORT_SYMBOL(kmemleak_scan_area); | |
795 | ||
796 | /* | |
797 | * Inform kmemleak not to scan the given memory block. | |
798 | */ | |
799 | void kmemleak_no_scan(const void *ptr) | |
800 | { | |
801 | pr_debug("%s(0x%p)\n", __func__, ptr); | |
802 | ||
803 | if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) | |
804 | object_no_scan((unsigned long)ptr); | |
805 | else if (atomic_read(&kmemleak_early_log)) | |
806 | log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0); | |
807 | } | |
808 | EXPORT_SYMBOL(kmemleak_no_scan); | |
809 | ||
810 | /* | |
811 | * Yield the CPU so that other tasks get a chance to run. The yielding is | |
812 | * rate-limited to avoid excessive number of calls to the schedule() function | |
813 | * during memory scanning. | |
814 | */ | |
815 | static void scan_yield(void) | |
816 | { | |
817 | might_sleep(); | |
818 | ||
819 | if (time_is_before_eq_jiffies(next_scan_yield)) { | |
820 | schedule(); | |
821 | next_scan_yield = jiffies + jiffies_scan_yield; | |
822 | } | |
823 | } | |
824 | ||
825 | /* | |
826 | * Memory scanning is a long process and it needs to be interruptable. This | |
827 | * function checks whether such interrupt condition occured. | |
828 | */ | |
829 | static int scan_should_stop(void) | |
830 | { | |
831 | if (!atomic_read(&kmemleak_enabled)) | |
832 | return 1; | |
833 | ||
834 | /* | |
835 | * This function may be called from either process or kthread context, | |
836 | * hence the need to check for both stop conditions. | |
837 | */ | |
838 | if (current->mm) | |
839 | return signal_pending(current); | |
840 | else | |
841 | return kthread_should_stop(); | |
842 | ||
843 | return 0; | |
844 | } | |
845 | ||
846 | /* | |
847 | * Scan a memory block (exclusive range) for valid pointers and add those | |
848 | * found to the gray list. | |
849 | */ | |
850 | static void scan_block(void *_start, void *_end, | |
851 | struct kmemleak_object *scanned) | |
852 | { | |
853 | unsigned long *ptr; | |
854 | unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER); | |
855 | unsigned long *end = _end - (BYTES_PER_POINTER - 1); | |
856 | ||
857 | for (ptr = start; ptr < end; ptr++) { | |
858 | unsigned long flags; | |
859 | unsigned long pointer = *ptr; | |
860 | struct kmemleak_object *object; | |
861 | ||
862 | if (scan_should_stop()) | |
863 | break; | |
864 | ||
865 | /* | |
866 | * When scanning a memory block with a corresponding | |
867 | * kmemleak_object, the CPU yielding is handled in the calling | |
868 | * code since it holds the object->lock to avoid the block | |
869 | * freeing. | |
870 | */ | |
871 | if (!scanned) | |
872 | scan_yield(); | |
873 | ||
874 | object = find_and_get_object(pointer, 1); | |
875 | if (!object) | |
876 | continue; | |
877 | if (object == scanned) { | |
878 | /* self referenced, ignore */ | |
879 | put_object(object); | |
880 | continue; | |
881 | } | |
882 | ||
883 | /* | |
884 | * Avoid the lockdep recursive warning on object->lock being | |
885 | * previously acquired in scan_object(). These locks are | |
886 | * enclosed by scan_mutex. | |
887 | */ | |
888 | spin_lock_irqsave_nested(&object->lock, flags, | |
889 | SINGLE_DEPTH_NESTING); | |
890 | if (!color_white(object)) { | |
891 | /* non-orphan, ignored or new */ | |
892 | spin_unlock_irqrestore(&object->lock, flags); | |
893 | put_object(object); | |
894 | continue; | |
895 | } | |
896 | ||
897 | /* | |
898 | * Increase the object's reference count (number of pointers | |
899 | * to the memory block). If this count reaches the required | |
900 | * minimum, the object's color will become gray and it will be | |
901 | * added to the gray_list. | |
902 | */ | |
903 | object->count++; | |
904 | if (color_gray(object)) | |
905 | list_add_tail(&object->gray_list, &gray_list); | |
906 | else | |
907 | put_object(object); | |
908 | spin_unlock_irqrestore(&object->lock, flags); | |
909 | } | |
910 | } | |
911 | ||
912 | /* | |
913 | * Scan a memory block corresponding to a kmemleak_object. A condition is | |
914 | * that object->use_count >= 1. | |
915 | */ | |
916 | static void scan_object(struct kmemleak_object *object) | |
917 | { | |
918 | struct kmemleak_scan_area *area; | |
919 | struct hlist_node *elem; | |
920 | unsigned long flags; | |
921 | ||
922 | /* | |
923 | * Once the object->lock is aquired, the corresponding memory block | |
924 | * cannot be freed (the same lock is aquired in delete_object). | |
925 | */ | |
926 | spin_lock_irqsave(&object->lock, flags); | |
927 | if (object->flags & OBJECT_NO_SCAN) | |
928 | goto out; | |
929 | if (!(object->flags & OBJECT_ALLOCATED)) | |
930 | /* already freed object */ | |
931 | goto out; | |
932 | if (hlist_empty(&object->area_list)) | |
933 | scan_block((void *)object->pointer, | |
934 | (void *)(object->pointer + object->size), object); | |
935 | else | |
936 | hlist_for_each_entry(area, elem, &object->area_list, node) | |
937 | scan_block((void *)(object->pointer + area->offset), | |
938 | (void *)(object->pointer + area->offset | |
939 | + area->length), object); | |
940 | out: | |
941 | spin_unlock_irqrestore(&object->lock, flags); | |
942 | } | |
943 | ||
944 | /* | |
945 | * Scan data sections and all the referenced memory blocks allocated via the | |
946 | * kernel's standard allocators. This function must be called with the | |
947 | * scan_mutex held. | |
948 | */ | |
949 | static void kmemleak_scan(void) | |
950 | { | |
951 | unsigned long flags; | |
952 | struct kmemleak_object *object, *tmp; | |
953 | struct task_struct *task; | |
954 | int i; | |
955 | ||
956 | /* prepare the kmemleak_object's */ | |
957 | rcu_read_lock(); | |
958 | list_for_each_entry_rcu(object, &object_list, object_list) { | |
959 | spin_lock_irqsave(&object->lock, flags); | |
960 | #ifdef DEBUG | |
961 | /* | |
962 | * With a few exceptions there should be a maximum of | |
963 | * 1 reference to any object at this point. | |
964 | */ | |
965 | if (atomic_read(&object->use_count) > 1) { | |
966 | pr_debug("kmemleak: object->use_count = %d\n", | |
967 | atomic_read(&object->use_count)); | |
968 | dump_object_info(object); | |
969 | } | |
970 | #endif | |
971 | /* reset the reference count (whiten the object) */ | |
972 | object->count = 0; | |
973 | if (color_gray(object) && get_object(object)) | |
974 | list_add_tail(&object->gray_list, &gray_list); | |
975 | ||
976 | spin_unlock_irqrestore(&object->lock, flags); | |
977 | } | |
978 | rcu_read_unlock(); | |
979 | ||
980 | /* data/bss scanning */ | |
981 | scan_block(_sdata, _edata, NULL); | |
982 | scan_block(__bss_start, __bss_stop, NULL); | |
983 | ||
984 | #ifdef CONFIG_SMP | |
985 | /* per-cpu sections scanning */ | |
986 | for_each_possible_cpu(i) | |
987 | scan_block(__per_cpu_start + per_cpu_offset(i), | |
988 | __per_cpu_end + per_cpu_offset(i), NULL); | |
989 | #endif | |
990 | ||
991 | /* | |
992 | * Struct page scanning for each node. The code below is not yet safe | |
993 | * with MEMORY_HOTPLUG. | |
994 | */ | |
995 | for_each_online_node(i) { | |
996 | pg_data_t *pgdat = NODE_DATA(i); | |
997 | unsigned long start_pfn = pgdat->node_start_pfn; | |
998 | unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages; | |
999 | unsigned long pfn; | |
1000 | ||
1001 | for (pfn = start_pfn; pfn < end_pfn; pfn++) { | |
1002 | struct page *page; | |
1003 | ||
1004 | if (!pfn_valid(pfn)) | |
1005 | continue; | |
1006 | page = pfn_to_page(pfn); | |
1007 | /* only scan if page is in use */ | |
1008 | if (page_count(page) == 0) | |
1009 | continue; | |
1010 | scan_block(page, page + 1, NULL); | |
1011 | } | |
1012 | } | |
1013 | ||
1014 | /* | |
1015 | * Scanning the task stacks may introduce false negatives and it is | |
1016 | * not enabled by default. | |
1017 | */ | |
1018 | if (kmemleak_stack_scan) { | |
1019 | read_lock(&tasklist_lock); | |
1020 | for_each_process(task) | |
1021 | scan_block(task_stack_page(task), | |
1022 | task_stack_page(task) + THREAD_SIZE, NULL); | |
1023 | read_unlock(&tasklist_lock); | |
1024 | } | |
1025 | ||
1026 | /* | |
1027 | * Scan the objects already referenced from the sections scanned | |
1028 | * above. More objects will be referenced and, if there are no memory | |
1029 | * leaks, all the objects will be scanned. The list traversal is safe | |
1030 | * for both tail additions and removals from inside the loop. The | |
1031 | * kmemleak objects cannot be freed from outside the loop because their | |
1032 | * use_count was increased. | |
1033 | */ | |
1034 | object = list_entry(gray_list.next, typeof(*object), gray_list); | |
1035 | while (&object->gray_list != &gray_list) { | |
1036 | scan_yield(); | |
1037 | ||
1038 | /* may add new objects to the list */ | |
1039 | if (!scan_should_stop()) | |
1040 | scan_object(object); | |
1041 | ||
1042 | tmp = list_entry(object->gray_list.next, typeof(*object), | |
1043 | gray_list); | |
1044 | ||
1045 | /* remove the object from the list and release it */ | |
1046 | list_del(&object->gray_list); | |
1047 | put_object(object); | |
1048 | ||
1049 | object = tmp; | |
1050 | } | |
1051 | WARN_ON(!list_empty(&gray_list)); | |
1052 | } | |
1053 | ||
1054 | /* | |
1055 | * Thread function performing automatic memory scanning. Unreferenced objects | |
1056 | * at the end of a memory scan are reported but only the first time. | |
1057 | */ | |
1058 | static int kmemleak_scan_thread(void *arg) | |
1059 | { | |
1060 | static int first_run = 1; | |
1061 | ||
1062 | pr_info("kmemleak: Automatic memory scanning thread started\n"); | |
1063 | ||
1064 | /* | |
1065 | * Wait before the first scan to allow the system to fully initialize. | |
1066 | */ | |
1067 | if (first_run) { | |
1068 | first_run = 0; | |
1069 | ssleep(SECS_FIRST_SCAN); | |
1070 | } | |
1071 | ||
1072 | while (!kthread_should_stop()) { | |
1073 | struct kmemleak_object *object; | |
1074 | signed long timeout = jiffies_scan_wait; | |
1075 | ||
1076 | mutex_lock(&scan_mutex); | |
1077 | ||
1078 | kmemleak_scan(); | |
1079 | reported_leaks = 0; | |
1080 | ||
1081 | rcu_read_lock(); | |
1082 | list_for_each_entry_rcu(object, &object_list, object_list) { | |
1083 | unsigned long flags; | |
1084 | ||
1085 | if (reported_leaks >= REPORTS_NR) | |
1086 | break; | |
1087 | spin_lock_irqsave(&object->lock, flags); | |
1088 | if (!(object->flags & OBJECT_REPORTED) && | |
1089 | unreferenced_object(object)) { | |
1090 | print_unreferenced(NULL, object); | |
1091 | object->flags |= OBJECT_REPORTED; | |
1092 | reported_leaks++; | |
1093 | } else if ((object->flags & OBJECT_REPORTED) && | |
1094 | referenced_object(object)) { | |
1095 | print_referenced(object); | |
1096 | object->flags &= ~OBJECT_REPORTED; | |
1097 | } | |
1098 | spin_unlock_irqrestore(&object->lock, flags); | |
1099 | } | |
1100 | rcu_read_unlock(); | |
1101 | ||
1102 | mutex_unlock(&scan_mutex); | |
1103 | /* wait before the next scan */ | |
1104 | while (timeout && !kthread_should_stop()) | |
1105 | timeout = schedule_timeout_interruptible(timeout); | |
1106 | } | |
1107 | ||
1108 | pr_info("kmemleak: Automatic memory scanning thread ended\n"); | |
1109 | ||
1110 | return 0; | |
1111 | } | |
1112 | ||
1113 | /* | |
1114 | * Start the automatic memory scanning thread. This function must be called | |
1115 | * with the kmemleak_mutex held. | |
1116 | */ | |
1117 | void start_scan_thread(void) | |
1118 | { | |
1119 | if (scan_thread) | |
1120 | return; | |
1121 | scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak"); | |
1122 | if (IS_ERR(scan_thread)) { | |
1123 | pr_warning("kmemleak: Failed to create the scan thread\n"); | |
1124 | scan_thread = NULL; | |
1125 | } | |
1126 | } | |
1127 | ||
1128 | /* | |
1129 | * Stop the automatic memory scanning thread. This function must be called | |
1130 | * with the kmemleak_mutex held. | |
1131 | */ | |
1132 | void stop_scan_thread(void) | |
1133 | { | |
1134 | if (scan_thread) { | |
1135 | kthread_stop(scan_thread); | |
1136 | scan_thread = NULL; | |
1137 | } | |
1138 | } | |
1139 | ||
1140 | /* | |
1141 | * Iterate over the object_list and return the first valid object at or after | |
1142 | * the required position with its use_count incremented. The function triggers | |
1143 | * a memory scanning when the pos argument points to the first position. | |
1144 | */ | |
1145 | static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos) | |
1146 | { | |
1147 | struct kmemleak_object *object; | |
1148 | loff_t n = *pos; | |
1149 | ||
1150 | if (!n) { | |
1151 | kmemleak_scan(); | |
1152 | reported_leaks = 0; | |
1153 | } | |
1154 | if (reported_leaks >= REPORTS_NR) | |
1155 | return NULL; | |
1156 | ||
1157 | rcu_read_lock(); | |
1158 | list_for_each_entry_rcu(object, &object_list, object_list) { | |
1159 | if (n-- > 0) | |
1160 | continue; | |
1161 | if (get_object(object)) | |
1162 | goto out; | |
1163 | } | |
1164 | object = NULL; | |
1165 | out: | |
1166 | rcu_read_unlock(); | |
1167 | return object; | |
1168 | } | |
1169 | ||
1170 | /* | |
1171 | * Return the next object in the object_list. The function decrements the | |
1172 | * use_count of the previous object and increases that of the next one. | |
1173 | */ | |
1174 | static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos) | |
1175 | { | |
1176 | struct kmemleak_object *prev_obj = v; | |
1177 | struct kmemleak_object *next_obj = NULL; | |
1178 | struct list_head *n = &prev_obj->object_list; | |
1179 | ||
1180 | ++(*pos); | |
1181 | if (reported_leaks >= REPORTS_NR) | |
1182 | goto out; | |
1183 | ||
1184 | rcu_read_lock(); | |
1185 | list_for_each_continue_rcu(n, &object_list) { | |
1186 | next_obj = list_entry(n, struct kmemleak_object, object_list); | |
1187 | if (get_object(next_obj)) | |
1188 | break; | |
1189 | } | |
1190 | rcu_read_unlock(); | |
1191 | out: | |
1192 | put_object(prev_obj); | |
1193 | return next_obj; | |
1194 | } | |
1195 | ||
1196 | /* | |
1197 | * Decrement the use_count of the last object required, if any. | |
1198 | */ | |
1199 | static void kmemleak_seq_stop(struct seq_file *seq, void *v) | |
1200 | { | |
1201 | if (v) | |
1202 | put_object(v); | |
1203 | } | |
1204 | ||
1205 | /* | |
1206 | * Print the information for an unreferenced object to the seq file. | |
1207 | */ | |
1208 | static int kmemleak_seq_show(struct seq_file *seq, void *v) | |
1209 | { | |
1210 | struct kmemleak_object *object = v; | |
1211 | unsigned long flags; | |
1212 | ||
1213 | spin_lock_irqsave(&object->lock, flags); | |
1214 | if (!unreferenced_object(object)) | |
1215 | goto out; | |
1216 | print_unreferenced(seq, object); | |
1217 | reported_leaks++; | |
1218 | out: | |
1219 | spin_unlock_irqrestore(&object->lock, flags); | |
1220 | return 0; | |
1221 | } | |
1222 | ||
1223 | static const struct seq_operations kmemleak_seq_ops = { | |
1224 | .start = kmemleak_seq_start, | |
1225 | .next = kmemleak_seq_next, | |
1226 | .stop = kmemleak_seq_stop, | |
1227 | .show = kmemleak_seq_show, | |
1228 | }; | |
1229 | ||
1230 | static int kmemleak_open(struct inode *inode, struct file *file) | |
1231 | { | |
1232 | int ret = 0; | |
1233 | ||
1234 | if (!atomic_read(&kmemleak_enabled)) | |
1235 | return -EBUSY; | |
1236 | ||
1237 | ret = mutex_lock_interruptible(&kmemleak_mutex); | |
1238 | if (ret < 0) | |
1239 | goto out; | |
1240 | if (file->f_mode & FMODE_READ) { | |
1241 | ret = mutex_lock_interruptible(&scan_mutex); | |
1242 | if (ret < 0) | |
1243 | goto kmemleak_unlock; | |
1244 | ret = seq_open(file, &kmemleak_seq_ops); | |
1245 | if (ret < 0) | |
1246 | goto scan_unlock; | |
1247 | } | |
1248 | return ret; | |
1249 | ||
1250 | scan_unlock: | |
1251 | mutex_unlock(&scan_mutex); | |
1252 | kmemleak_unlock: | |
1253 | mutex_unlock(&kmemleak_mutex); | |
1254 | out: | |
1255 | return ret; | |
1256 | } | |
1257 | ||
1258 | static int kmemleak_release(struct inode *inode, struct file *file) | |
1259 | { | |
1260 | int ret = 0; | |
1261 | ||
1262 | if (file->f_mode & FMODE_READ) { | |
1263 | seq_release(inode, file); | |
1264 | mutex_unlock(&scan_mutex); | |
1265 | } | |
1266 | mutex_unlock(&kmemleak_mutex); | |
1267 | ||
1268 | return ret; | |
1269 | } | |
1270 | ||
1271 | /* | |
1272 | * File write operation to configure kmemleak at run-time. The following | |
1273 | * commands can be written to the /sys/kernel/debug/kmemleak file: | |
1274 | * off - disable kmemleak (irreversible) | |
1275 | * stack=on - enable the task stacks scanning | |
1276 | * stack=off - disable the tasks stacks scanning | |
1277 | * scan=on - start the automatic memory scanning thread | |
1278 | * scan=off - stop the automatic memory scanning thread | |
1279 | * scan=... - set the automatic memory scanning period in seconds (0 to | |
1280 | * disable it) | |
1281 | */ | |
1282 | static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, | |
1283 | size_t size, loff_t *ppos) | |
1284 | { | |
1285 | char buf[64]; | |
1286 | int buf_size; | |
1287 | ||
1288 | if (!atomic_read(&kmemleak_enabled)) | |
1289 | return -EBUSY; | |
1290 | ||
1291 | buf_size = min(size, (sizeof(buf) - 1)); | |
1292 | if (strncpy_from_user(buf, user_buf, buf_size) < 0) | |
1293 | return -EFAULT; | |
1294 | buf[buf_size] = 0; | |
1295 | ||
1296 | if (strncmp(buf, "off", 3) == 0) | |
1297 | kmemleak_disable(); | |
1298 | else if (strncmp(buf, "stack=on", 8) == 0) | |
1299 | kmemleak_stack_scan = 1; | |
1300 | else if (strncmp(buf, "stack=off", 9) == 0) | |
1301 | kmemleak_stack_scan = 0; | |
1302 | else if (strncmp(buf, "scan=on", 7) == 0) | |
1303 | start_scan_thread(); | |
1304 | else if (strncmp(buf, "scan=off", 8) == 0) | |
1305 | stop_scan_thread(); | |
1306 | else if (strncmp(buf, "scan=", 5) == 0) { | |
1307 | unsigned long secs; | |
1308 | int err; | |
1309 | ||
1310 | err = strict_strtoul(buf + 5, 0, &secs); | |
1311 | if (err < 0) | |
1312 | return err; | |
1313 | stop_scan_thread(); | |
1314 | if (secs) { | |
1315 | jiffies_scan_wait = msecs_to_jiffies(secs * 1000); | |
1316 | start_scan_thread(); | |
1317 | } | |
1318 | } else | |
1319 | return -EINVAL; | |
1320 | ||
1321 | /* ignore the rest of the buffer, only one command at a time */ | |
1322 | *ppos += size; | |
1323 | return size; | |
1324 | } | |
1325 | ||
1326 | static const struct file_operations kmemleak_fops = { | |
1327 | .owner = THIS_MODULE, | |
1328 | .open = kmemleak_open, | |
1329 | .read = seq_read, | |
1330 | .write = kmemleak_write, | |
1331 | .llseek = seq_lseek, | |
1332 | .release = kmemleak_release, | |
1333 | }; | |
1334 | ||
1335 | /* | |
1336 | * Perform the freeing of the kmemleak internal objects after waiting for any | |
1337 | * current memory scan to complete. | |
1338 | */ | |
1339 | static int kmemleak_cleanup_thread(void *arg) | |
1340 | { | |
1341 | struct kmemleak_object *object; | |
1342 | ||
1343 | mutex_lock(&kmemleak_mutex); | |
1344 | stop_scan_thread(); | |
1345 | mutex_unlock(&kmemleak_mutex); | |
1346 | ||
1347 | mutex_lock(&scan_mutex); | |
1348 | rcu_read_lock(); | |
1349 | list_for_each_entry_rcu(object, &object_list, object_list) | |
1350 | delete_object(object->pointer); | |
1351 | rcu_read_unlock(); | |
1352 | mutex_unlock(&scan_mutex); | |
1353 | ||
1354 | return 0; | |
1355 | } | |
1356 | ||
1357 | /* | |
1358 | * Start the clean-up thread. | |
1359 | */ | |
1360 | static void kmemleak_cleanup(void) | |
1361 | { | |
1362 | struct task_struct *cleanup_thread; | |
1363 | ||
1364 | cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL, | |
1365 | "kmemleak-clean"); | |
1366 | if (IS_ERR(cleanup_thread)) | |
1367 | pr_warning("kmemleak: Failed to create the clean-up thread\n"); | |
1368 | } | |
1369 | ||
1370 | /* | |
1371 | * Disable kmemleak. No memory allocation/freeing will be traced once this | |
1372 | * function is called. Disabling kmemleak is an irreversible operation. | |
1373 | */ | |
1374 | static void kmemleak_disable(void) | |
1375 | { | |
1376 | /* atomically check whether it was already invoked */ | |
1377 | if (atomic_cmpxchg(&kmemleak_error, 0, 1)) | |
1378 | return; | |
1379 | ||
1380 | /* stop any memory operation tracing */ | |
1381 | atomic_set(&kmemleak_early_log, 0); | |
1382 | atomic_set(&kmemleak_enabled, 0); | |
1383 | ||
1384 | /* check whether it is too early for a kernel thread */ | |
1385 | if (atomic_read(&kmemleak_initialized)) | |
1386 | kmemleak_cleanup(); | |
1387 | ||
1388 | pr_info("Kernel memory leak detector disabled\n"); | |
1389 | } | |
1390 | ||
1391 | /* | |
1392 | * Allow boot-time kmemleak disabling (enabled by default). | |
1393 | */ | |
1394 | static int kmemleak_boot_config(char *str) | |
1395 | { | |
1396 | if (!str) | |
1397 | return -EINVAL; | |
1398 | if (strcmp(str, "off") == 0) | |
1399 | kmemleak_disable(); | |
1400 | else if (strcmp(str, "on") != 0) | |
1401 | return -EINVAL; | |
1402 | return 0; | |
1403 | } | |
1404 | early_param("kmemleak", kmemleak_boot_config); | |
1405 | ||
1406 | /* | |
1407 | * Kkmemleak initialization. | |
1408 | */ | |
1409 | void __init kmemleak_init(void) | |
1410 | { | |
1411 | int i; | |
1412 | unsigned long flags; | |
1413 | ||
1414 | jiffies_scan_yield = msecs_to_jiffies(MSECS_SCAN_YIELD); | |
1415 | jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE); | |
1416 | jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000); | |
1417 | ||
1418 | object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE); | |
1419 | scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE); | |
1420 | INIT_PRIO_TREE_ROOT(&object_tree_root); | |
1421 | ||
1422 | /* the kernel is still in UP mode, so disabling the IRQs is enough */ | |
1423 | local_irq_save(flags); | |
1424 | if (!atomic_read(&kmemleak_error)) { | |
1425 | atomic_set(&kmemleak_enabled, 1); | |
1426 | atomic_set(&kmemleak_early_log, 0); | |
1427 | } | |
1428 | local_irq_restore(flags); | |
1429 | ||
1430 | /* | |
1431 | * This is the point where tracking allocations is safe. Automatic | |
1432 | * scanning is started during the late initcall. Add the early logged | |
1433 | * callbacks to the kmemleak infrastructure. | |
1434 | */ | |
1435 | for (i = 0; i < crt_early_log; i++) { | |
1436 | struct early_log *log = &early_log[i]; | |
1437 | ||
1438 | switch (log->op_type) { | |
1439 | case KMEMLEAK_ALLOC: | |
1440 | kmemleak_alloc(log->ptr, log->size, log->min_count, | |
1441 | GFP_KERNEL); | |
1442 | break; | |
1443 | case KMEMLEAK_FREE: | |
1444 | kmemleak_free(log->ptr); | |
1445 | break; | |
1446 | case KMEMLEAK_NOT_LEAK: | |
1447 | kmemleak_not_leak(log->ptr); | |
1448 | break; | |
1449 | case KMEMLEAK_IGNORE: | |
1450 | kmemleak_ignore(log->ptr); | |
1451 | break; | |
1452 | case KMEMLEAK_SCAN_AREA: | |
1453 | kmemleak_scan_area(log->ptr, log->offset, log->length, | |
1454 | GFP_KERNEL); | |
1455 | break; | |
1456 | case KMEMLEAK_NO_SCAN: | |
1457 | kmemleak_no_scan(log->ptr); | |
1458 | break; | |
1459 | default: | |
1460 | WARN_ON(1); | |
1461 | } | |
1462 | } | |
1463 | } | |
1464 | ||
1465 | /* | |
1466 | * Late initialization function. | |
1467 | */ | |
1468 | static int __init kmemleak_late_init(void) | |
1469 | { | |
1470 | struct dentry *dentry; | |
1471 | ||
1472 | atomic_set(&kmemleak_initialized, 1); | |
1473 | ||
1474 | if (atomic_read(&kmemleak_error)) { | |
1475 | /* | |
1476 | * Some error occured and kmemleak was disabled. There is a | |
1477 | * small chance that kmemleak_disable() was called immediately | |
1478 | * after setting kmemleak_initialized and we may end up with | |
1479 | * two clean-up threads but serialized by scan_mutex. | |
1480 | */ | |
1481 | kmemleak_cleanup(); | |
1482 | return -ENOMEM; | |
1483 | } | |
1484 | ||
1485 | dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL, | |
1486 | &kmemleak_fops); | |
1487 | if (!dentry) | |
1488 | pr_warning("kmemleak: Failed to create the debugfs kmemleak " | |
1489 | "file\n"); | |
1490 | mutex_lock(&kmemleak_mutex); | |
1491 | start_scan_thread(); | |
1492 | mutex_unlock(&kmemleak_mutex); | |
1493 | ||
1494 | pr_info("Kernel memory leak detector initialized\n"); | |
1495 | ||
1496 | return 0; | |
1497 | } | |
1498 | late_initcall(kmemleak_late_init); |