kmemleak.c 41.1 KB
Newer Older
C
Catalin Marinas 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
/*
 * mm/kmemleak.c
 *
 * Copyright (C) 2008 ARM Limited
 * Written by Catalin Marinas <catalin.marinas@arm.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 *
 * For more information on the algorithm and kmemleak usage, please see
 * Documentation/kmemleak.txt.
 *
 * Notes on locking
 * ----------------
 *
 * The following locks and mutexes are used by kmemleak:
 *
 * - kmemleak_lock (rwlock): protects the object_list modifications and
 *   accesses to the object_tree_root. The object_list is the main list
 *   holding the metadata (struct kmemleak_object) for the allocated memory
 *   blocks. The object_tree_root is a priority search tree used to look-up
 *   metadata based on a pointer to the corresponding memory block.  The
 *   kmemleak_object structures are added to the object_list and
 *   object_tree_root in the create_object() function called from the
 *   kmemleak_alloc() callback and removed in delete_object() called from the
 *   kmemleak_free() callback
 * - kmemleak_object.lock (spinlock): protects a kmemleak_object. Accesses to
 *   the metadata (e.g. count) are protected by this lock. Note that some
 *   members of this structure may be protected by other means (atomic or
 *   kmemleak_lock). This lock is also held when scanning the corresponding
 *   memory block to avoid the kernel freeing it via the kmemleak_free()
 *   callback. This is less heavyweight than holding a global lock like
 *   kmemleak_lock during scanning
 * - scan_mutex (mutex): ensures that only one thread may scan the memory for
 *   unreferenced objects at a time. The gray_list contains the objects which
 *   are already referenced or marked as false positives and need to be
 *   scanned. This list is only modified during a scanning episode when the
 *   scan_mutex is held. At the end of a scan, the gray_list is always empty.
 *   Note that the kmemleak_object.use_count is incremented when an object is
51 52 53 54
 *   added to the gray_list and therefore cannot be freed. This mutex also
 *   prevents multiple users of the "kmemleak" debugfs file together with
 *   modifications to the memory scanning parameters including the scan_thread
 *   pointer
C
Catalin Marinas 已提交
55 56 57 58 59 60 61 62 63
 *
 * The kmemleak_object structures have a use_count incremented or decremented
 * using the get_object()/put_object() functions. When the use_count becomes
 * 0, this count can no longer be incremented and put_object() schedules the
 * kmemleak_object freeing via an RCU callback. All calls to the get_object()
 * function must be protected by rcu_read_lock() to avoid accessing a freed
 * structure.
 */

J
Joe Perches 已提交
64 65
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

C
Catalin Marinas 已提交
66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/sched.h>
#include <linux/jiffies.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/prio_tree.h>
#include <linux/gfp.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/cpumask.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/stacktrace.h>
#include <linux/cache.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/mmzone.h>
#include <linux/slab.h>
#include <linux/thread_info.h>
#include <linux/err.h>
#include <linux/uaccess.h>
#include <linux/string.h>
#include <linux/nodemask.h>
#include <linux/mm.h>

#include <asm/sections.h>
#include <asm/processor.h>
#include <asm/atomic.h>

#include <linux/kmemleak.h>

/*
 * Kmemleak configuration and common defines.
 */
#define MAX_TRACE		16	/* stack trace length */
#define MSECS_MIN_AGE		5000	/* minimum object age for reporting */
#define SECS_FIRST_SCAN		60	/* delay before the first scan */
#define SECS_SCAN_WAIT		600	/* subsequent auto scanning delay */
109
#define GRAY_LIST_PASSES	25	/* maximum number of gray list scans */
C
Catalin Marinas 已提交
110 111 112

#define BYTES_PER_POINTER	sizeof(void *)

113 114 115
/* GFP bitmask for kmemleak internal allocations */
#define GFP_KMEMLEAK_MASK	(GFP_KERNEL | GFP_ATOMIC)

C
Catalin Marinas 已提交
116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160
/* scanning area inside a memory block */
struct kmemleak_scan_area {
	struct hlist_node node;
	unsigned long offset;
	size_t length;
};

/*
 * Structure holding the metadata for each allocated memory block.
 * Modifications to such objects should be made while holding the
 * object->lock. Insertions or deletions from object_list, gray_list or
 * tree_node are already protected by the corresponding locks or mutex (see
 * the notes on locking above). These objects are reference-counted
 * (use_count) and freed using the RCU mechanism.
 */
struct kmemleak_object {
	spinlock_t lock;
	unsigned long flags;		/* object status flags */
	struct list_head object_list;
	struct list_head gray_list;
	struct prio_tree_node tree_node;
	struct rcu_head rcu;		/* object_list lockless traversal */
	/* object usage count; object freed when use_count == 0 */
	atomic_t use_count;
	unsigned long pointer;
	size_t size;
	/* minimum number of a pointers found before it is considered leak */
	int min_count;
	/* the total number of pointers found pointing to this object */
	int count;
	/* memory ranges to be scanned inside an object (empty for all) */
	struct hlist_head area_list;
	unsigned long trace[MAX_TRACE];
	unsigned int trace_len;
	unsigned long jiffies;		/* creation timestamp */
	pid_t pid;			/* pid of the current task */
	char comm[TASK_COMM_LEN];	/* executable name */
};

/* flag representing the memory block allocation status */
#define OBJECT_ALLOCATED	(1 << 0)
/* flag set after the first reporting of an unreference object */
#define OBJECT_REPORTED		(1 << 1)
/* flag set to not scan the object */
#define OBJECT_NO_SCAN		(1 << 2)
161 162
/* flag set on newly allocated objects */
#define OBJECT_NEW		(1 << 3)
C
Catalin Marinas 已提交
163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190

/* the list of all allocated objects */
static LIST_HEAD(object_list);
/* the list of gray-colored objects (see color_gray comment below) */
static LIST_HEAD(gray_list);
/* prio search tree for object boundaries */
static struct prio_tree_root object_tree_root;
/* rw_lock protecting the access to object_list and prio_tree_root */
static DEFINE_RWLOCK(kmemleak_lock);

/* allocation caches for kmemleak internal data */
static struct kmem_cache *object_cache;
static struct kmem_cache *scan_area_cache;

/* set if tracing memory operations is enabled */
static atomic_t kmemleak_enabled = ATOMIC_INIT(0);
/* set in the late_initcall if there were no errors */
static atomic_t kmemleak_initialized = ATOMIC_INIT(0);
/* enables or disables early logging of the memory operations */
static atomic_t kmemleak_early_log = ATOMIC_INIT(1);
/* set if a fata kmemleak error has occurred */
static atomic_t kmemleak_error = ATOMIC_INIT(0);

/* minimum and maximum address that may be valid pointers */
static unsigned long min_addr = ULONG_MAX;
static unsigned long max_addr;

static struct task_struct *scan_thread;
191
/* used to avoid reporting of recently allocated objects */
C
Catalin Marinas 已提交
192
static unsigned long jiffies_min_age;
193
static unsigned long jiffies_last_scan;
C
Catalin Marinas 已提交
194 195 196
/* delay between automatic memory scannings */
static signed long jiffies_scan_wait;
/* enables or disables the task stacks scanning */
197
static int kmemleak_stack_scan = 1;
198
/* protects the memory scanning, parameters and debug/kmemleak file access */
C
Catalin Marinas 已提交
199 200 201
static DEFINE_MUTEX(scan_mutex);

/*
202
 * Early object allocation/freeing logging. Kmemleak is initialized after the
C
Catalin Marinas 已提交
203
 * kernel allocator. However, both the kernel allocator and kmemleak may
204
 * allocate memory blocks which need to be tracked. Kmemleak defines an
C
Catalin Marinas 已提交
205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232
 * arbitrary buffer to hold the allocation/freeing information before it is
 * fully initialized.
 */

/* kmemleak operation type for early logging */
enum {
	KMEMLEAK_ALLOC,
	KMEMLEAK_FREE,
	KMEMLEAK_NOT_LEAK,
	KMEMLEAK_IGNORE,
	KMEMLEAK_SCAN_AREA,
	KMEMLEAK_NO_SCAN
};

/*
 * Structure holding the information passed to kmemleak callbacks during the
 * early logging.
 */
struct early_log {
	int op_type;			/* kmemleak operation type */
	const void *ptr;		/* allocated/freed memory block */
	size_t size;			/* memory block size */
	int min_count;			/* minimum reference count */
	unsigned long offset;		/* scan area offset */
	size_t length;			/* scan area length */
};

/* early logging buffer and current position */
233
static struct early_log early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE];
C
Catalin Marinas 已提交
234 235 236 237 238 239 240 241 242 243 244 245 246 247
static int crt_early_log;

static void kmemleak_disable(void);

/*
 * Print a warning and dump the stack trace.
 */
#define kmemleak_warn(x...)	do {	\
	pr_warning(x);			\
	dump_stack();			\
} while (0)

/*
 * Macro invoked when a serious kmemleak condition occured and cannot be
248
 * recovered from. Kmemleak will be disabled and further allocation/freeing
C
Catalin Marinas 已提交
249 250
 * tracing no longer available.
 */
251
#define kmemleak_stop(x...)	do {	\
C
Catalin Marinas 已提交
252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275
	kmemleak_warn(x);		\
	kmemleak_disable();		\
} while (0)

/*
 * Object colors, encoded with count and min_count:
 * - white - orphan object, not enough references to it (count < min_count)
 * - gray  - not orphan, not marked as false positive (min_count == 0) or
 *		sufficient references to it (count >= min_count)
 * - black - ignore, it doesn't contain references (e.g. text section)
 *		(min_count == -1). No function defined for this color.
 * Newly created objects don't have any color assigned (object->count == -1)
 * before the next memory scan when they become white.
 */
static int color_white(const struct kmemleak_object *object)
{
	return object->count != -1 && object->count < object->min_count;
}

static int color_gray(const struct kmemleak_object *object)
{
	return object->min_count != -1 && object->count >= object->min_count;
}

276 277 278 279 280
static int color_black(const struct kmemleak_object *object)
{
	return object->min_count == -1;
}

C
Catalin Marinas 已提交
281 282 283 284 285 286 287 288
/*
 * Objects are considered unreferenced only if their color is white, they have
 * not be deleted and have a minimum age to avoid false positives caused by
 * pointers temporarily stored in CPU registers.
 */
static int unreferenced_object(struct kmemleak_object *object)
{
	return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
289 290
		time_before_eq(object->jiffies + jiffies_min_age,
			       jiffies_last_scan);
C
Catalin Marinas 已提交
291 292 293
}

/*
294 295
 * Printing of the unreferenced objects information to the seq file. The
 * print_unreferenced function must be called with the object->lock held.
C
Catalin Marinas 已提交
296 297 298 299 300 301
 */
static void print_unreferenced(struct seq_file *seq,
			       struct kmemleak_object *object)
{
	int i;

302 303 304 305 306
	seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
		   object->pointer, object->size);
	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
		   object->comm, object->pid, object->jiffies);
	seq_printf(seq, "  backtrace:\n");
C
Catalin Marinas 已提交
307 308 309

	for (i = 0; i < object->trace_len; i++) {
		void *ptr = (void *)object->trace[i];
310
		seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
C
Catalin Marinas 已提交
311 312 313 314 315 316 317 318 319 320 321 322 323 324 325
	}
}

/*
 * Print the kmemleak_object information. This function is used mainly for
 * debugging special cases when kmemleak operations. It must be called with
 * the object->lock held.
 */
static void dump_object_info(struct kmemleak_object *object)
{
	struct stack_trace trace;

	trace.nr_entries = object->trace_len;
	trace.entries = object->trace;

J
Joe Perches 已提交
326
	pr_notice("Object 0x%08lx (size %zu):\n",
C
Catalin Marinas 已提交
327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353
		  object->tree_node.start, object->size);
	pr_notice("  comm \"%s\", pid %d, jiffies %lu\n",
		  object->comm, object->pid, object->jiffies);
	pr_notice("  min_count = %d\n", object->min_count);
	pr_notice("  count = %d\n", object->count);
	pr_notice("  backtrace:\n");
	print_stack_trace(&trace, 4);
}

/*
 * Look-up a memory block metadata (kmemleak_object) in the priority search
 * tree based on a pointer value. If alias is 0, only values pointing to the
 * beginning of the memory block are allowed. The kmemleak_lock must be held
 * when calling this function.
 */
static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
{
	struct prio_tree_node *node;
	struct prio_tree_iter iter;
	struct kmemleak_object *object;

	prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr);
	node = prio_tree_next(&iter);
	if (node) {
		object = prio_tree_entry(node, struct kmemleak_object,
					 tree_node);
		if (!alias && object->pointer != ptr) {
J
Joe Perches 已提交
354
			kmemleak_warn("Found object by alias");
C
Catalin Marinas 已提交
355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446
			object = NULL;
		}
	} else
		object = NULL;

	return object;
}

/*
 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
 * that once an object's use_count reached 0, the RCU freeing was already
 * registered and the object should no longer be used. This function must be
 * called under the protection of rcu_read_lock().
 */
static int get_object(struct kmemleak_object *object)
{
	return atomic_inc_not_zero(&object->use_count);
}

/*
 * RCU callback to free a kmemleak_object.
 */
static void free_object_rcu(struct rcu_head *rcu)
{
	struct hlist_node *elem, *tmp;
	struct kmemleak_scan_area *area;
	struct kmemleak_object *object =
		container_of(rcu, struct kmemleak_object, rcu);

	/*
	 * Once use_count is 0 (guaranteed by put_object), there is no other
	 * code accessing this object, hence no need for locking.
	 */
	hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) {
		hlist_del(elem);
		kmem_cache_free(scan_area_cache, area);
	}
	kmem_cache_free(object_cache, object);
}

/*
 * Decrement the object use_count. Once the count is 0, free the object using
 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
 * delete_object() path, the delayed RCU freeing ensures that there is no
 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
 * is also possible.
 */
static void put_object(struct kmemleak_object *object)
{
	if (!atomic_dec_and_test(&object->use_count))
		return;

	/* should only get here after delete_object was called */
	WARN_ON(object->flags & OBJECT_ALLOCATED);

	call_rcu(&object->rcu, free_object_rcu);
}

/*
 * Look up an object in the prio search tree and increase its use_count.
 */
static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
{
	unsigned long flags;
	struct kmemleak_object *object = NULL;

	rcu_read_lock();
	read_lock_irqsave(&kmemleak_lock, flags);
	if (ptr >= min_addr && ptr < max_addr)
		object = lookup_object(ptr, alias);
	read_unlock_irqrestore(&kmemleak_lock, flags);

	/* check whether the object is still available */
	if (object && !get_object(object))
		object = NULL;
	rcu_read_unlock();

	return object;
}

/*
 * Create the metadata (struct kmemleak_object) corresponding to an allocated
 * memory block and add it to the object_list and object_tree_root.
 */
static void create_object(unsigned long ptr, size_t size, int min_count,
			  gfp_t gfp)
{
	unsigned long flags;
	struct kmemleak_object *object;
	struct prio_tree_node *node;
	struct stack_trace trace;

447
	object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK);
C
Catalin Marinas 已提交
448
	if (!object) {
J
Joe Perches 已提交
449
		kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
C
Catalin Marinas 已提交
450 451 452 453 454 455 456 457
		return;
	}

	INIT_LIST_HEAD(&object->object_list);
	INIT_LIST_HEAD(&object->gray_list);
	INIT_HLIST_HEAD(&object->area_list);
	spin_lock_init(&object->lock);
	atomic_set(&object->use_count, 1);
458
	object->flags = OBJECT_ALLOCATED | OBJECT_NEW;
C
Catalin Marinas 已提交
459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507
	object->pointer = ptr;
	object->size = size;
	object->min_count = min_count;
	object->count = -1;			/* no color initially */
	object->jiffies = jiffies;

	/* task information */
	if (in_irq()) {
		object->pid = 0;
		strncpy(object->comm, "hardirq", sizeof(object->comm));
	} else if (in_softirq()) {
		object->pid = 0;
		strncpy(object->comm, "softirq", sizeof(object->comm));
	} else {
		object->pid = current->pid;
		/*
		 * There is a small chance of a race with set_task_comm(),
		 * however using get_task_comm() here may cause locking
		 * dependency issues with current->alloc_lock. In the worst
		 * case, the command line is not correct.
		 */
		strncpy(object->comm, current->comm, sizeof(object->comm));
	}

	/* kernel backtrace */
	trace.max_entries = MAX_TRACE;
	trace.nr_entries = 0;
	trace.entries = object->trace;
	trace.skip = 1;
	save_stack_trace(&trace);
	object->trace_len = trace.nr_entries;

	INIT_PRIO_TREE_NODE(&object->tree_node);
	object->tree_node.start = ptr;
	object->tree_node.last = ptr + size - 1;

	write_lock_irqsave(&kmemleak_lock, flags);
	min_addr = min(min_addr, ptr);
	max_addr = max(max_addr, ptr + size);
	node = prio_tree_insert(&object_tree_root, &object->tree_node);
	/*
	 * The code calling the kernel does not yet have the pointer to the
	 * memory block to be able to free it.  However, we still hold the
	 * kmemleak_lock here in case parts of the kernel started freeing
	 * random memory blocks.
	 */
	if (node != &object->tree_node) {
		unsigned long flags;

J
Joe Perches 已提交
508 509
		kmemleak_stop("Cannot insert 0x%lx into the object search tree "
			      "(already existing)\n", ptr);
C
Catalin Marinas 已提交
510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533
		object = lookup_object(ptr, 1);
		spin_lock_irqsave(&object->lock, flags);
		dump_object_info(object);
		spin_unlock_irqrestore(&object->lock, flags);

		goto out;
	}
	list_add_tail_rcu(&object->object_list, &object_list);
out:
	write_unlock_irqrestore(&kmemleak_lock, flags);
}

/*
 * Remove the metadata (struct kmemleak_object) for a memory block from the
 * object_list and object_tree_root and decrement its use_count.
 */
static void delete_object(unsigned long ptr)
{
	unsigned long flags;
	struct kmemleak_object *object;

	write_lock_irqsave(&kmemleak_lock, flags);
	object = lookup_object(ptr, 0);
	if (!object) {
534
#ifdef DEBUG
J
Joe Perches 已提交
535
		kmemleak_warn("Freeing unknown object at 0x%08lx\n",
C
Catalin Marinas 已提交
536
			      ptr);
537
#endif
C
Catalin Marinas 已提交
538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568
		write_unlock_irqrestore(&kmemleak_lock, flags);
		return;
	}
	prio_tree_remove(&object_tree_root, &object->tree_node);
	list_del_rcu(&object->object_list);
	write_unlock_irqrestore(&kmemleak_lock, flags);

	WARN_ON(!(object->flags & OBJECT_ALLOCATED));
	WARN_ON(atomic_read(&object->use_count) < 1);

	/*
	 * Locking here also ensures that the corresponding memory block
	 * cannot be freed when it is being scanned.
	 */
	spin_lock_irqsave(&object->lock, flags);
	object->flags &= ~OBJECT_ALLOCATED;
	spin_unlock_irqrestore(&object->lock, flags);
	put_object(object);
}

/*
 * Make a object permanently as gray-colored so that it can no longer be
 * reported as a leak. This is used in general to mark a false positive.
 */
static void make_gray_object(unsigned long ptr)
{
	unsigned long flags;
	struct kmemleak_object *object;

	object = find_and_get_object(ptr, 0);
	if (!object) {
J
Joe Perches 已提交
569
		kmemleak_warn("Graying unknown object at 0x%08lx\n", ptr);
C
Catalin Marinas 已提交
570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589
		return;
	}

	spin_lock_irqsave(&object->lock, flags);
	object->min_count = 0;
	spin_unlock_irqrestore(&object->lock, flags);
	put_object(object);
}

/*
 * Mark the object as black-colored so that it is ignored from scans and
 * reporting.
 */
static void make_black_object(unsigned long ptr)
{
	unsigned long flags;
	struct kmemleak_object *object;

	object = find_and_get_object(ptr, 0);
	if (!object) {
J
Joe Perches 已提交
590
		kmemleak_warn("Blacking unknown object at 0x%08lx\n", ptr);
C
Catalin Marinas 已提交
591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612
		return;
	}

	spin_lock_irqsave(&object->lock, flags);
	object->min_count = -1;
	spin_unlock_irqrestore(&object->lock, flags);
	put_object(object);
}

/*
 * Add a scanning area to the object. If at least one such area is added,
 * kmemleak will only scan these ranges rather than the whole memory block.
 */
static void add_scan_area(unsigned long ptr, unsigned long offset,
			  size_t length, gfp_t gfp)
{
	unsigned long flags;
	struct kmemleak_object *object;
	struct kmemleak_scan_area *area;

	object = find_and_get_object(ptr, 0);
	if (!object) {
J
Joe Perches 已提交
613 614
		kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
			      ptr);
C
Catalin Marinas 已提交
615 616 617
		return;
	}

618
	area = kmem_cache_alloc(scan_area_cache, gfp & GFP_KMEMLEAK_MASK);
C
Catalin Marinas 已提交
619
	if (!area) {
J
Joe Perches 已提交
620
		kmemleak_warn("Cannot allocate a scan area\n");
C
Catalin Marinas 已提交
621 622 623 624 625
		goto out;
	}

	spin_lock_irqsave(&object->lock, flags);
	if (offset + length > object->size) {
J
Joe Perches 已提交
626
		kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
C
Catalin Marinas 已提交
627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654
		dump_object_info(object);
		kmem_cache_free(scan_area_cache, area);
		goto out_unlock;
	}

	INIT_HLIST_NODE(&area->node);
	area->offset = offset;
	area->length = length;

	hlist_add_head(&area->node, &object->area_list);
out_unlock:
	spin_unlock_irqrestore(&object->lock, flags);
out:
	put_object(object);
}

/*
 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
 * pointer. Such object will not be scanned by kmemleak but references to it
 * are searched.
 */
static void object_no_scan(unsigned long ptr)
{
	unsigned long flags;
	struct kmemleak_object *object;

	object = find_and_get_object(ptr, 0);
	if (!object) {
J
Joe Perches 已提交
655
		kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
C
Catalin Marinas 已提交
656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675
		return;
	}

	spin_lock_irqsave(&object->lock, flags);
	object->flags |= OBJECT_NO_SCAN;
	spin_unlock_irqrestore(&object->lock, flags);
	put_object(object);
}

/*
 * Log an early kmemleak_* call to the early_log buffer. These calls will be
 * processed later once kmemleak is fully initialized.
 */
static void log_early(int op_type, const void *ptr, size_t size,
		      int min_count, unsigned long offset, size_t length)
{
	unsigned long flags;
	struct early_log *log;

	if (crt_early_log >= ARRAY_SIZE(early_log)) {
676 677
		pr_warning("Early log buffer exceeded\n");
		kmemleak_disable();
C
Catalin Marinas 已提交
678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813
		return;
	}

	/*
	 * There is no need for locking since the kernel is still in UP mode
	 * at this stage. Disabling the IRQs is enough.
	 */
	local_irq_save(flags);
	log = &early_log[crt_early_log];
	log->op_type = op_type;
	log->ptr = ptr;
	log->size = size;
	log->min_count = min_count;
	log->offset = offset;
	log->length = length;
	crt_early_log++;
	local_irq_restore(flags);
}

/*
 * Memory allocation function callback. This function is called from the
 * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc,
 * vmalloc etc.).
 */
void kmemleak_alloc(const void *ptr, size_t size, int min_count, gfp_t gfp)
{
	pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		create_object((unsigned long)ptr, size, min_count, gfp);
	else if (atomic_read(&kmemleak_early_log))
		log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc);

/*
 * Memory freeing function callback. This function is called from the kernel
 * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.).
 */
void kmemleak_free(const void *ptr)
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		delete_object((unsigned long)ptr);
	else if (atomic_read(&kmemleak_early_log))
		log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free);

/*
 * Mark an already allocated memory block as a false positive. This will cause
 * the block to no longer be reported as leak and always be scanned.
 */
void kmemleak_not_leak(const void *ptr)
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		make_gray_object((unsigned long)ptr);
	else if (atomic_read(&kmemleak_early_log))
		log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
}
EXPORT_SYMBOL(kmemleak_not_leak);

/*
 * Ignore a memory block. This is usually done when it is known that the
 * corresponding block is not a leak and does not contain any references to
 * other allocated memory blocks.
 */
void kmemleak_ignore(const void *ptr)
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		make_black_object((unsigned long)ptr);
	else if (atomic_read(&kmemleak_early_log))
		log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
}
EXPORT_SYMBOL(kmemleak_ignore);

/*
 * Limit the range to be scanned in an allocated memory block.
 */
void kmemleak_scan_area(const void *ptr, unsigned long offset, size_t length,
			gfp_t gfp)
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		add_scan_area((unsigned long)ptr, offset, length, gfp);
	else if (atomic_read(&kmemleak_early_log))
		log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
}
EXPORT_SYMBOL(kmemleak_scan_area);

/*
 * Inform kmemleak not to scan the given memory block.
 */
void kmemleak_no_scan(const void *ptr)
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		object_no_scan((unsigned long)ptr);
	else if (atomic_read(&kmemleak_early_log))
		log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0);
}
EXPORT_SYMBOL(kmemleak_no_scan);

/*
 * Memory scanning is a long process and it needs to be interruptable. This
 * function checks whether such interrupt condition occured.
 */
static int scan_should_stop(void)
{
	if (!atomic_read(&kmemleak_enabled))
		return 1;

	/*
	 * This function may be called from either process or kthread context,
	 * hence the need to check for both stop conditions.
	 */
	if (current->mm)
		return signal_pending(current);
	else
		return kthread_should_stop();

	return 0;
}

/*
 * Scan a memory block (exclusive range) for valid pointers and add those
 * found to the gray list.
 */
static void scan_block(void *_start, void *_end,
814
		       struct kmemleak_object *scanned, int allow_resched)
C
Catalin Marinas 已提交
815 816 817 818 819 820 821 822 823 824
{
	unsigned long *ptr;
	unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
	unsigned long *end = _end - (BYTES_PER_POINTER - 1);

	for (ptr = start; ptr < end; ptr++) {
		unsigned long flags;
		unsigned long pointer = *ptr;
		struct kmemleak_object *object;

825 826
		if (allow_resched)
			cond_resched();
C
Catalin Marinas 已提交
827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889
		if (scan_should_stop())
			break;

		object = find_and_get_object(pointer, 1);
		if (!object)
			continue;
		if (object == scanned) {
			/* self referenced, ignore */
			put_object(object);
			continue;
		}

		/*
		 * Avoid the lockdep recursive warning on object->lock being
		 * previously acquired in scan_object(). These locks are
		 * enclosed by scan_mutex.
		 */
		spin_lock_irqsave_nested(&object->lock, flags,
					 SINGLE_DEPTH_NESTING);
		if (!color_white(object)) {
			/* non-orphan, ignored or new */
			spin_unlock_irqrestore(&object->lock, flags);
			put_object(object);
			continue;
		}

		/*
		 * Increase the object's reference count (number of pointers
		 * to the memory block). If this count reaches the required
		 * minimum, the object's color will become gray and it will be
		 * added to the gray_list.
		 */
		object->count++;
		if (color_gray(object))
			list_add_tail(&object->gray_list, &gray_list);
		else
			put_object(object);
		spin_unlock_irqrestore(&object->lock, flags);
	}
}

/*
 * Scan a memory block corresponding to a kmemleak_object. A condition is
 * that object->use_count >= 1.
 */
static void scan_object(struct kmemleak_object *object)
{
	struct kmemleak_scan_area *area;
	struct hlist_node *elem;
	unsigned long flags;

	/*
	 * Once the object->lock is aquired, the corresponding memory block
	 * cannot be freed (the same lock is aquired in delete_object).
	 */
	spin_lock_irqsave(&object->lock, flags);
	if (object->flags & OBJECT_NO_SCAN)
		goto out;
	if (!(object->flags & OBJECT_ALLOCATED))
		/* already freed object */
		goto out;
	if (hlist_empty(&object->area_list))
		scan_block((void *)object->pointer,
890
			   (void *)(object->pointer + object->size), object, 0);
C
Catalin Marinas 已提交
891 892 893 894
	else
		hlist_for_each_entry(area, elem, &object->area_list, node)
			scan_block((void *)(object->pointer + area->offset),
				   (void *)(object->pointer + area->offset
895
					    + area->length), object, 0);
C
Catalin Marinas 已提交
896 897 898 899 900 901 902 903 904 905 906 907 908 909 910
out:
	spin_unlock_irqrestore(&object->lock, flags);
}

/*
 * Scan data sections and all the referenced memory blocks allocated via the
 * kernel's standard allocators. This function must be called with the
 * scan_mutex held.
 */
static void kmemleak_scan(void)
{
	unsigned long flags;
	struct kmemleak_object *object, *tmp;
	struct task_struct *task;
	int i;
911
	int new_leaks = 0;
912
	int gray_list_pass = 0;
C
Catalin Marinas 已提交
913

914 915
	jiffies_last_scan = jiffies;

C
Catalin Marinas 已提交
916 917 918 919 920 921 922 923 924 925
	/* prepare the kmemleak_object's */
	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list) {
		spin_lock_irqsave(&object->lock, flags);
#ifdef DEBUG
		/*
		 * With a few exceptions there should be a maximum of
		 * 1 reference to any object at this point.
		 */
		if (atomic_read(&object->use_count) > 1) {
J
Joe Perches 已提交
926
			pr_debug("object->use_count = %d\n",
C
Catalin Marinas 已提交
927 928 929 930 931 932
				 atomic_read(&object->use_count));
			dump_object_info(object);
		}
#endif
		/* reset the reference count (whiten the object) */
		object->count = 0;
933
		object->flags &= ~OBJECT_NEW;
C
Catalin Marinas 已提交
934 935 936 937 938 939 940 941
		if (color_gray(object) && get_object(object))
			list_add_tail(&object->gray_list, &gray_list);

		spin_unlock_irqrestore(&object->lock, flags);
	}
	rcu_read_unlock();

	/* data/bss scanning */
942 943
	scan_block(_sdata, _edata, NULL, 1);
	scan_block(__bss_start, __bss_stop, NULL, 1);
C
Catalin Marinas 已提交
944 945 946 947 948

#ifdef CONFIG_SMP
	/* per-cpu sections scanning */
	for_each_possible_cpu(i)
		scan_block(__per_cpu_start + per_cpu_offset(i),
949
			   __per_cpu_end + per_cpu_offset(i), NULL, 1);
C
Catalin Marinas 已提交
950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970
#endif

	/*
	 * Struct page scanning for each node. The code below is not yet safe
	 * with MEMORY_HOTPLUG.
	 */
	for_each_online_node(i) {
		pg_data_t *pgdat = NODE_DATA(i);
		unsigned long start_pfn = pgdat->node_start_pfn;
		unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
		unsigned long pfn;

		for (pfn = start_pfn; pfn < end_pfn; pfn++) {
			struct page *page;

			if (!pfn_valid(pfn))
				continue;
			page = pfn_to_page(pfn);
			/* only scan if page is in use */
			if (page_count(page) == 0)
				continue;
971
			scan_block(page, page + 1, NULL, 1);
C
Catalin Marinas 已提交
972 973 974 975 976 977 978 979 980 981 982
		}
	}

	/*
	 * Scanning the task stacks may introduce false negatives and it is
	 * not enabled by default.
	 */
	if (kmemleak_stack_scan) {
		read_lock(&tasklist_lock);
		for_each_process(task)
			scan_block(task_stack_page(task),
983 984
				   task_stack_page(task) + THREAD_SIZE,
				   NULL, 0);
C
Catalin Marinas 已提交
985 986 987 988 989 990 991 992 993 994 995
		read_unlock(&tasklist_lock);
	}

	/*
	 * Scan the objects already referenced from the sections scanned
	 * above. More objects will be referenced and, if there are no memory
	 * leaks, all the objects will be scanned. The list traversal is safe
	 * for both tail additions and removals from inside the loop. The
	 * kmemleak objects cannot be freed from outside the loop because their
	 * use_count was increased.
	 */
996
repeat:
C
Catalin Marinas 已提交
997 998
	object = list_entry(gray_list.next, typeof(*object), gray_list);
	while (&object->gray_list != &gray_list) {
999
		cond_resched();
C
Catalin Marinas 已提交
1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013

		/* may add new objects to the list */
		if (!scan_should_stop())
			scan_object(object);

		tmp = list_entry(object->gray_list.next, typeof(*object),
				 gray_list);

		/* remove the object from the list and release it */
		list_del(&object->gray_list);
		put_object(object);

		object = tmp;
	}
1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037

	if (scan_should_stop() || ++gray_list_pass >= GRAY_LIST_PASSES)
		goto scan_end;

	/*
	 * Check for new objects allocated during this scanning and add them
	 * to the gray list.
	 */
	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list) {
		spin_lock_irqsave(&object->lock, flags);
		if ((object->flags & OBJECT_NEW) && !color_black(object) &&
		    get_object(object)) {
			object->flags &= ~OBJECT_NEW;
			list_add_tail(&object->gray_list, &gray_list);
		}
		spin_unlock_irqrestore(&object->lock, flags);
	}
	rcu_read_unlock();

	if (!list_empty(&gray_list))
		goto repeat;

scan_end:
C
Catalin Marinas 已提交
1038
	WARN_ON(!list_empty(&gray_list));
1039

1040
	/*
1041 1042 1043
	 * If scanning was stopped or new objects were being allocated at a
	 * higher rate than gray list scanning, do not report any new
	 * unreferenced objects.
1044
	 */
1045
	if (scan_should_stop() || gray_list_pass >= GRAY_LIST_PASSES)
1046 1047
		return;

1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066
	/*
	 * Scanning result reporting.
	 */
	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list) {
		spin_lock_irqsave(&object->lock, flags);
		if (unreferenced_object(object) &&
		    !(object->flags & OBJECT_REPORTED)) {
			object->flags |= OBJECT_REPORTED;
			new_leaks++;
		}
		spin_unlock_irqrestore(&object->lock, flags);
	}
	rcu_read_unlock();

	if (new_leaks)
		pr_info("%d new suspected memory leaks (see "
			"/sys/kernel/debug/kmemleak)\n", new_leaks);

C
Catalin Marinas 已提交
1067 1068 1069 1070 1071 1072 1073 1074 1075 1076
}

/*
 * Thread function performing automatic memory scanning. Unreferenced objects
 * at the end of a memory scan are reported but only the first time.
 */
static int kmemleak_scan_thread(void *arg)
{
	static int first_run = 1;

J
Joe Perches 已提交
1077
	pr_info("Automatic memory scanning thread started\n");
1078
	set_user_nice(current, 10);
C
Catalin Marinas 已提交
1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093

	/*
	 * Wait before the first scan to allow the system to fully initialize.
	 */
	if (first_run) {
		first_run = 0;
		ssleep(SECS_FIRST_SCAN);
	}

	while (!kthread_should_stop()) {
		signed long timeout = jiffies_scan_wait;

		mutex_lock(&scan_mutex);
		kmemleak_scan();
		mutex_unlock(&scan_mutex);
1094

C
Catalin Marinas 已提交
1095 1096 1097 1098 1099
		/* wait before the next scan */
		while (timeout && !kthread_should_stop())
			timeout = schedule_timeout_interruptible(timeout);
	}

J
Joe Perches 已提交
1100
	pr_info("Automatic memory scanning thread ended\n");
C
Catalin Marinas 已提交
1101 1102 1103 1104 1105 1106

	return 0;
}

/*
 * Start the automatic memory scanning thread. This function must be called
1107
 * with the scan_mutex held.
C
Catalin Marinas 已提交
1108 1109 1110 1111 1112 1113 1114
 */
void start_scan_thread(void)
{
	if (scan_thread)
		return;
	scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
	if (IS_ERR(scan_thread)) {
J
Joe Perches 已提交
1115
		pr_warning("Failed to create the scan thread\n");
C
Catalin Marinas 已提交
1116 1117 1118 1119 1120 1121
		scan_thread = NULL;
	}
}

/*
 * Stop the automatic memory scanning thread. This function must be called
1122
 * with the scan_mutex held.
C
Catalin Marinas 已提交
1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140
 */
void stop_scan_thread(void)
{
	if (scan_thread) {
		kthread_stop(scan_thread);
		scan_thread = NULL;
	}
}

/*
 * Iterate over the object_list and return the first valid object at or after
 * the required position with its use_count incremented. The function triggers
 * a memory scanning when the pos argument points to the first position.
 */
static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
{
	struct kmemleak_object *object;
	loff_t n = *pos;
1141 1142 1143 1144 1145
	int err;

	err = mutex_lock_interruptible(&scan_mutex);
	if (err < 0)
		return ERR_PTR(err);
C
Catalin Marinas 已提交
1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178

	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list) {
		if (n-- > 0)
			continue;
		if (get_object(object))
			goto out;
	}
	object = NULL;
out:
	rcu_read_unlock();
	return object;
}

/*
 * Return the next object in the object_list. The function decrements the
 * use_count of the previous object and increases that of the next one.
 */
static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	struct kmemleak_object *prev_obj = v;
	struct kmemleak_object *next_obj = NULL;
	struct list_head *n = &prev_obj->object_list;

	++(*pos);

	rcu_read_lock();
	list_for_each_continue_rcu(n, &object_list) {
		next_obj = list_entry(n, struct kmemleak_object, object_list);
		if (get_object(next_obj))
			break;
	}
	rcu_read_unlock();
1179

C
Catalin Marinas 已提交
1180 1181 1182 1183 1184 1185 1186 1187 1188
	put_object(prev_obj);
	return next_obj;
}

/*
 * Decrement the use_count of the last object required, if any.
 */
static void kmemleak_seq_stop(struct seq_file *seq, void *v)
{
1189 1190 1191 1192 1193 1194 1195 1196 1197
	if (!IS_ERR(v)) {
		/*
		 * kmemleak_seq_start may return ERR_PTR if the scan_mutex
		 * waiting was interrupted, so only release it if !IS_ERR.
		 */
		mutex_unlock(&scan_mutex);
		if (v)
			put_object(v);
	}
C
Catalin Marinas 已提交
1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208
}

/*
 * Print the information for an unreferenced object to the seq file.
 */
static int kmemleak_seq_show(struct seq_file *seq, void *v)
{
	struct kmemleak_object *object = v;
	unsigned long flags;

	spin_lock_irqsave(&object->lock, flags);
1209
	if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1210
		print_unreferenced(seq, object);
C
Catalin Marinas 已提交
1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226
	spin_unlock_irqrestore(&object->lock, flags);
	return 0;
}

static const struct seq_operations kmemleak_seq_ops = {
	.start = kmemleak_seq_start,
	.next  = kmemleak_seq_next,
	.stop  = kmemleak_seq_stop,
	.show  = kmemleak_seq_show,
};

static int kmemleak_open(struct inode *inode, struct file *file)
{
	if (!atomic_read(&kmemleak_enabled))
		return -EBUSY;

1227
	return seq_open(file, &kmemleak_seq_ops);
C
Catalin Marinas 已提交
1228 1229 1230 1231
}

static int kmemleak_release(struct inode *inode, struct file *file)
{
1232
	return seq_release(inode, file);
C
Catalin Marinas 已提交
1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244
}

/*
 * File write operation to configure kmemleak at run-time. The following
 * commands can be written to the /sys/kernel/debug/kmemleak file:
 *   off	- disable kmemleak (irreversible)
 *   stack=on	- enable the task stacks scanning
 *   stack=off	- disable the tasks stacks scanning
 *   scan=on	- start the automatic memory scanning thread
 *   scan=off	- stop the automatic memory scanning thread
 *   scan=...	- set the automatic memory scanning period in seconds (0 to
 *		  disable it)
1245
 *   scan	- trigger a memory scan
C
Catalin Marinas 已提交
1246 1247 1248 1249 1250 1251
 */
static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
			      size_t size, loff_t *ppos)
{
	char buf[64];
	int buf_size;
1252
	int ret;
C
Catalin Marinas 已提交
1253 1254 1255 1256 1257 1258

	buf_size = min(size, (sizeof(buf) - 1));
	if (strncpy_from_user(buf, user_buf, buf_size) < 0)
		return -EFAULT;
	buf[buf_size] = 0;

1259 1260 1261 1262
	ret = mutex_lock_interruptible(&scan_mutex);
	if (ret < 0)
		return ret;

C
Catalin Marinas 已提交
1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275
	if (strncmp(buf, "off", 3) == 0)
		kmemleak_disable();
	else if (strncmp(buf, "stack=on", 8) == 0)
		kmemleak_stack_scan = 1;
	else if (strncmp(buf, "stack=off", 9) == 0)
		kmemleak_stack_scan = 0;
	else if (strncmp(buf, "scan=on", 7) == 0)
		start_scan_thread();
	else if (strncmp(buf, "scan=off", 8) == 0)
		stop_scan_thread();
	else if (strncmp(buf, "scan=", 5) == 0) {
		unsigned long secs;

1276 1277 1278
		ret = strict_strtoul(buf + 5, 0, &secs);
		if (ret < 0)
			goto out;
C
Catalin Marinas 已提交
1279 1280 1281 1282 1283
		stop_scan_thread();
		if (secs) {
			jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
			start_scan_thread();
		}
1284 1285 1286
	} else if (strncmp(buf, "scan", 4) == 0)
		kmemleak_scan();
	else
1287 1288 1289 1290 1291 1292
		ret = -EINVAL;

out:
	mutex_unlock(&scan_mutex);
	if (ret < 0)
		return ret;
C
Catalin Marinas 已提交
1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315

	/* ignore the rest of the buffer, only one command at a time */
	*ppos += size;
	return size;
}

static const struct file_operations kmemleak_fops = {
	.owner		= THIS_MODULE,
	.open		= kmemleak_open,
	.read		= seq_read,
	.write		= kmemleak_write,
	.llseek		= seq_lseek,
	.release	= kmemleak_release,
};

/*
 * Perform the freeing of the kmemleak internal objects after waiting for any
 * current memory scan to complete.
 */
static int kmemleak_cleanup_thread(void *arg)
{
	struct kmemleak_object *object;

1316
	mutex_lock(&scan_mutex);
C
Catalin Marinas 已提交
1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337
	stop_scan_thread();

	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list)
		delete_object(object->pointer);
	rcu_read_unlock();
	mutex_unlock(&scan_mutex);

	return 0;
}

/*
 * Start the clean-up thread.
 */
static void kmemleak_cleanup(void)
{
	struct task_struct *cleanup_thread;

	cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL,
				     "kmemleak-clean");
	if (IS_ERR(cleanup_thread))
J
Joe Perches 已提交
1338
		pr_warning("Failed to create the clean-up thread\n");
C
Catalin Marinas 已提交
1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377
}

/*
 * Disable kmemleak. No memory allocation/freeing will be traced once this
 * function is called. Disabling kmemleak is an irreversible operation.
 */
static void kmemleak_disable(void)
{
	/* atomically check whether it was already invoked */
	if (atomic_cmpxchg(&kmemleak_error, 0, 1))
		return;

	/* stop any memory operation tracing */
	atomic_set(&kmemleak_early_log, 0);
	atomic_set(&kmemleak_enabled, 0);

	/* check whether it is too early for a kernel thread */
	if (atomic_read(&kmemleak_initialized))
		kmemleak_cleanup();

	pr_info("Kernel memory leak detector disabled\n");
}

/*
 * Allow boot-time kmemleak disabling (enabled by default).
 */
static int kmemleak_boot_config(char *str)
{
	if (!str)
		return -EINVAL;
	if (strcmp(str, "off") == 0)
		kmemleak_disable();
	else if (strcmp(str, "on") != 0)
		return -EINVAL;
	return 0;
}
early_param("kmemleak", kmemleak_boot_config);

/*
1378
 * Kmemleak initialization.
C
Catalin Marinas 已提交
1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457
 */
void __init kmemleak_init(void)
{
	int i;
	unsigned long flags;

	jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
	jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);

	object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
	scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
	INIT_PRIO_TREE_ROOT(&object_tree_root);

	/* the kernel is still in UP mode, so disabling the IRQs is enough */
	local_irq_save(flags);
	if (!atomic_read(&kmemleak_error)) {
		atomic_set(&kmemleak_enabled, 1);
		atomic_set(&kmemleak_early_log, 0);
	}
	local_irq_restore(flags);

	/*
	 * This is the point where tracking allocations is safe. Automatic
	 * scanning is started during the late initcall. Add the early logged
	 * callbacks to the kmemleak infrastructure.
	 */
	for (i = 0; i < crt_early_log; i++) {
		struct early_log *log = &early_log[i];

		switch (log->op_type) {
		case KMEMLEAK_ALLOC:
			kmemleak_alloc(log->ptr, log->size, log->min_count,
				       GFP_KERNEL);
			break;
		case KMEMLEAK_FREE:
			kmemleak_free(log->ptr);
			break;
		case KMEMLEAK_NOT_LEAK:
			kmemleak_not_leak(log->ptr);
			break;
		case KMEMLEAK_IGNORE:
			kmemleak_ignore(log->ptr);
			break;
		case KMEMLEAK_SCAN_AREA:
			kmemleak_scan_area(log->ptr, log->offset, log->length,
					   GFP_KERNEL);
			break;
		case KMEMLEAK_NO_SCAN:
			kmemleak_no_scan(log->ptr);
			break;
		default:
			WARN_ON(1);
		}
	}
}

/*
 * Late initialization function.
 */
static int __init kmemleak_late_init(void)
{
	struct dentry *dentry;

	atomic_set(&kmemleak_initialized, 1);

	if (atomic_read(&kmemleak_error)) {
		/*
		 * Some error occured and kmemleak was disabled. There is a
		 * small chance that kmemleak_disable() was called immediately
		 * after setting kmemleak_initialized and we may end up with
		 * two clean-up threads but serialized by scan_mutex.
		 */
		kmemleak_cleanup();
		return -ENOMEM;
	}

	dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
				     &kmemleak_fops);
	if (!dentry)
J
Joe Perches 已提交
1458
		pr_warning("Failed to create the debugfs kmemleak file\n");
1459
	mutex_lock(&scan_mutex);
C
Catalin Marinas 已提交
1460
	start_scan_thread();
1461
	mutex_unlock(&scan_mutex);
C
Catalin Marinas 已提交
1462 1463 1464 1465 1466 1467

	pr_info("Kernel memory leak detector initialized\n");

	return 0;
}
late_initcall(kmemleak_late_init);