/*
   * 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 red black 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

   *   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

   *

   * Locks and mutexes are acquired/nested in the following order:

   *

   *   scan_mutex [-> object->lock] -> kmemleak_lock -> other_object->lock (SINGLE_DEPTH_NESTING)
   *
   * No kmemleak_lock and object->lock nesting is allowed outside scan_mutex
   * regions.

   *

   * 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.
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #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/export.h>

  #include <linux/kthread.h>

  #include <linux/rbtree.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/bootmem.h>
  #include <linux/pfn.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 <linux/workqueue.h>

  #include <linux/crc32.h>

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

  #include <linux/atomic.h>

  #include <linux/kasan.h>

  #include <linux/kmemcheck.h>

  #include <linux/kmemleak.h>

  #include <linux/memory_hotplug.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 */

  #define MAX_SCAN_SIZE		4096	/* maximum size of a scanned block */

  
  #define BYTES_PER_POINTER	sizeof(void *)

  /* GFP bitmask for kmemleak internal allocations */

  #define gfp_kmemleak_mask(gfp)	(((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \

  				 __GFP_NORETRY | __GFP_NOMEMALLOC | \
  				 __GFP_NOWARN)

  /* scanning area inside a memory block */
  struct kmemleak_scan_area {
  	struct hlist_node node;

  	unsigned long start;
  	size_t size;

  };

  #define KMEMLEAK_GREY	0
  #define KMEMLEAK_BLACK	-1

  /*
   * 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

   * rb_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 rb_node rb_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;

  	/* checksum for detecting modified objects */
  	u32 checksum;

  	/* 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)

  /* number of bytes to print per line; must be 16 or 32 */
  #define HEX_ROW_SIZE		16
  /* number of bytes to print at a time (1, 2, 4, 8) */
  #define HEX_GROUP_SIZE		1
  /* include ASCII after the hex output */
  #define HEX_ASCII		1
  /* max number of lines to be printed */
  #define HEX_MAX_LINES		2

  /* 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);

  /* search tree for object boundaries */
  static struct rb_root object_tree_root = RB_ROOT;
  /* rw_lock protecting the access to object_list and object_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 int kmemleak_enabled;

  /* same as above but only for the kmemleak_free() callback */
  static int kmemleak_free_enabled;

  /* set in the late_initcall if there were no errors */

  static int kmemleak_initialized;

  /* enables or disables early logging of the memory operations */

  static int kmemleak_early_log = 1;

  /* set if a kmemleak warning was issued */

  static int kmemleak_warning;

  /* set if a fatal kmemleak error has occurred */

  static int kmemleak_error;

  
  /* 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;

  /* used to avoid reporting of recently allocated objects */

  static unsigned long jiffies_min_age;

  static unsigned long jiffies_last_scan;

  /* delay between automatic memory scannings */
  static signed long jiffies_scan_wait;
  /* enables or disables the task stacks scanning */

  static int kmemleak_stack_scan = 1;

  /* protects the memory scanning, parameters and debug/kmemleak file access */

  static DEFINE_MUTEX(scan_mutex);

  /* setting kmemleak=on, will set this var, skipping the disable */
  static int kmemleak_skip_disable;

  /* If there are leaks that can be reported */
  static bool kmemleak_found_leaks;

  /*

   * Early object allocation/freeing logging. Kmemleak is initialized after the

   * kernel allocator. However, both the kernel allocator and kmemleak may

   * allocate memory blocks which need to be tracked. Kmemleak defines an

   * arbitrary buffer to hold the allocation/freeing information before it is
   * fully initialized.
   */
  
  /* kmemleak operation type for early logging */
  enum {
  	KMEMLEAK_ALLOC,

  	KMEMLEAK_ALLOC_PERCPU,

  	KMEMLEAK_FREE,

  	KMEMLEAK_FREE_PART,

  	KMEMLEAK_FREE_PERCPU,

  	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 trace[MAX_TRACE];	/* stack trace */
  	unsigned int trace_len;		/* stack trace length */

  };
  
  /* early logging buffer and current position */

  static struct early_log
  	early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
  static int crt_early_log __initdata;

  
  static void kmemleak_disable(void);
  
  /*
   * Print a warning and dump the stack trace.
   */

  #define kmemleak_warn(x...)	do {		\

  	pr_warn(x);				\

  	dump_stack();				\

  	kmemleak_warning = 1;			\

  } while (0)
  
  /*

   * Macro invoked when a serious kmemleak condition occurred and cannot be

   * recovered from. Kmemleak will be disabled and further allocation/freeing

   * tracing no longer available.
   */

  #define kmemleak_stop(x...)	do {	\

  	kmemleak_warn(x);		\
  	kmemleak_disable();		\
  } while (0)
  
  /*

   * Printing of the objects hex dump to the seq file. The number of lines to be
   * printed is limited to HEX_MAX_LINES to prevent seq file spamming. The
   * actual number of printed bytes depends on HEX_ROW_SIZE. It must be called
   * with the object->lock held.
   */
  static void hex_dump_object(struct seq_file *seq,
  			    struct kmemleak_object *object)
  {
  	const u8 *ptr = (const u8 *)object->pointer;

  	size_t len;

  
  	/* limit the number of lines to HEX_MAX_LINES */

  	len = min_t(size_t, object->size, HEX_MAX_LINES * HEX_ROW_SIZE);

  	seq_printf(seq, "  hex dump (first %zu bytes):
  ", len);

  	kasan_disable_current();

  	seq_hex_dump(seq, "    ", DUMP_PREFIX_NONE, HEX_ROW_SIZE,
  		     HEX_GROUP_SIZE, ptr, len, HEX_ASCII);

  	kasan_enable_current();

  }
  
  /*

   * 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 bool color_white(const struct kmemleak_object *object)

  {

  	return object->count != KMEMLEAK_BLACK &&
  		object->count < object->min_count;

  }

  static bool color_gray(const struct kmemleak_object *object)

  {

  	return object->min_count != KMEMLEAK_BLACK &&
  		object->count >= object->min_count;

  }
  
  /*

   * 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 bool unreferenced_object(struct kmemleak_object *object)

  {

  	return (color_white(object) && object->flags & OBJECT_ALLOCATED) &&

  		time_before_eq(object->jiffies + jiffies_min_age,
  			       jiffies_last_scan);

  }
  
  /*

   * Printing of the unreferenced objects information to the seq file. The
   * print_unreferenced function must be called with the object->lock held.

   */

  static void print_unreferenced(struct seq_file *seq,
  			       struct kmemleak_object *object)
  {
  	int i;

  	unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);

  	seq_printf(seq, "unreferenced object 0x%08lx (size %zu):
  ",
  		   object->pointer, object->size);

  	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)
  ",
  		   object->comm, object->pid, object->jiffies,
  		   msecs_age / 1000, msecs_age % 1000);

  	hex_dump_object(seq, object);

  	seq_printf(seq, "  backtrace:
  ");

  
  	for (i = 0; i < object->trace_len; i++) {
  		void *ptr = (void *)object->trace[i];

  		seq_printf(seq, "    [<%p>] %pS
  ", ptr, ptr);

  	}
  }
  
  /*
   * 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;

  	pr_notice("Object 0x%08lx (size %zu):
  ",

  		  object->pointer, object->size);

  	pr_notice("  comm \"%s\", pid %d, jiffies %lu
  ",
  		  object->comm, object->pid, object->jiffies);
  	pr_notice("  min_count = %d
  ", object->min_count);
  	pr_notice("  count = %d
  ", object->count);

  	pr_notice("  flags = 0x%lx
  ", object->flags);

  	pr_notice("  checksum = %u
  ", object->checksum);

  	pr_notice("  backtrace:
  ");
  	print_stack_trace(&trace, 4);
  }
  
  /*

   * Look-up a memory block metadata (kmemleak_object) in the object 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 rb_node *rb = object_tree_root.rb_node;
  
  	while (rb) {
  		struct kmemleak_object *object =
  			rb_entry(rb, struct kmemleak_object, rb_node);
  		if (ptr < object->pointer)
  			rb = object->rb_node.rb_left;
  		else if (object->pointer + object->size <= ptr)
  			rb = object->rb_node.rb_right;
  		else if (object->pointer == ptr || alias)
  			return object;
  		else {

  			kmemleak_warn("Found object by alias at 0x%08lx
  ",
  				      ptr);

  			dump_object_info(object);

  			break;

  		}

  	}
  	return NULL;

  }
  
  /*
   * 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 *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, tmp, &object->area_list, node) {
  		hlist_del(&area->node);

  		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 object 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;

  
  	rcu_read_lock();
  	read_lock_irqsave(&kmemleak_lock, flags);

  	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;
  }
  
  /*

   * Look up an object in the object search tree and remove it from both
   * object_tree_root and object_list. The returned object's use_count should be
   * at least 1, as initially set by create_object().
   */
  static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int alias)
  {
  	unsigned long flags;
  	struct kmemleak_object *object;
  
  	write_lock_irqsave(&kmemleak_lock, flags);
  	object = lookup_object(ptr, alias);
  	if (object) {
  		rb_erase(&object->rb_node, &object_tree_root);
  		list_del_rcu(&object->object_list);
  	}
  	write_unlock_irqrestore(&kmemleak_lock, flags);
  
  	return object;
  }
  
  /*

   * Save stack trace to the given array of MAX_TRACE size.
   */
  static int __save_stack_trace(unsigned long *trace)
  {
  	struct stack_trace stack_trace;
  
  	stack_trace.max_entries = MAX_TRACE;
  	stack_trace.nr_entries = 0;
  	stack_trace.entries = trace;
  	stack_trace.skip = 2;
  	save_stack_trace(&stack_trace);
  
  	return stack_trace.nr_entries;
  }
  
  /*

   * Create the metadata (struct kmemleak_object) corresponding to an allocated
   * memory block and add it to the object_list and object_tree_root.
   */

  static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
  					     int min_count, gfp_t gfp)

  {
  	unsigned long flags;

  	struct kmemleak_object *object, *parent;
  	struct rb_node **link, *rb_parent;

  	object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));

  	if (!object) {

  		pr_warn("Cannot allocate a kmemleak_object structure
  ");

  		kmemleak_disable();

  		return NULL;

  	}
  
  	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);

  	object->flags = OBJECT_ALLOCATED;

  	object->pointer = ptr;
  	object->size = size;
  	object->min_count = min_count;

  	object->count = 0;			/* white color initially */

  	object->jiffies = jiffies;

  	object->checksum = 0;

  
  	/* 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 */

  	object->trace_len = __save_stack_trace(object->trace);

  	write_lock_irqsave(&kmemleak_lock, flags);

  	min_addr = min(min_addr, ptr);
  	max_addr = max(max_addr, ptr + size);

  	link = &object_tree_root.rb_node;
  	rb_parent = NULL;
  	while (*link) {
  		rb_parent = *link;
  		parent = rb_entry(rb_parent, struct kmemleak_object, rb_node);
  		if (ptr + size <= parent->pointer)
  			link = &parent->rb_node.rb_left;
  		else if (parent->pointer + parent->size <= ptr)
  			link = &parent->rb_node.rb_right;
  		else {

  			kmemleak_stop("Cannot insert 0x%lx into the object search tree (overlaps existing)
  ",

  				      ptr);

  			/*
  			 * No need for parent->lock here since "parent" cannot
  			 * be freed while the kmemleak_lock is held.
  			 */
  			dump_object_info(parent);

  			kmem_cache_free(object_cache, object);

  			object = NULL;

  			goto out;
  		}

  	}

  	rb_link_node(&object->rb_node, rb_parent, link);
  	rb_insert_color(&object->rb_node, &object_tree_root);

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

  	return object;

  }
  
  /*

   * Mark the object as not allocated and schedule RCU freeing via put_object().

   */

  static void __delete_object(struct kmemleak_object *object)

  {
  	unsigned long 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);
  }
  
  /*

   * Look up the metadata (struct kmemleak_object) corresponding to ptr and
   * delete it.
   */
  static void delete_object_full(unsigned long ptr)
  {
  	struct kmemleak_object *object;

  	object = find_and_remove_object(ptr, 0);

  	if (!object) {
  #ifdef DEBUG
  		kmemleak_warn("Freeing unknown object at 0x%08lx
  ",
  			      ptr);
  #endif
  		return;
  	}
  	__delete_object(object);

  }
  
  /*
   * Look up the metadata (struct kmemleak_object) corresponding to ptr and
   * delete it. If the memory block is partially freed, the function may create
   * additional metadata for the remaining parts of the block.
   */
  static void delete_object_part(unsigned long ptr, size_t size)
  {
  	struct kmemleak_object *object;
  	unsigned long start, end;

  	object = find_and_remove_object(ptr, 1);

  	if (!object) {
  #ifdef DEBUG

  		kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)
  ",
  			      ptr, size);

  #endif
  		return;
  	}

  
  	/*
  	 * Create one or two objects that may result from the memory block
  	 * split. Note that partial freeing is only done by free_bootmem() and
  	 * this happens before kmemleak_init() is called. The path below is
  	 * only executed during early log recording in kmemleak_init(), so
  	 * GFP_KERNEL is enough.
  	 */
  	start = object->pointer;
  	end = object->pointer + object->size;
  	if (ptr > start)
  		create_object(start, ptr - start, object->min_count,
  			      GFP_KERNEL);
  	if (ptr + size < end)
  		create_object(ptr + size, end - ptr - size, object->min_count,
  			      GFP_KERNEL);

  	__delete_object(object);

  }

  
  static void __paint_it(struct kmemleak_object *object, int color)
  {
  	object->min_count = color;
  	if (color == KMEMLEAK_BLACK)
  		object->flags |= OBJECT_NO_SCAN;
  }
  
  static void paint_it(struct kmemleak_object *object, int color)

  {
  	unsigned long flags;

  
  	spin_lock_irqsave(&object->lock, flags);
  	__paint_it(object, color);
  	spin_unlock_irqrestore(&object->lock, flags);
  }
  
  static void paint_ptr(unsigned long ptr, int color)
  {

  	struct kmemleak_object *object;
  
  	object = find_and_get_object(ptr, 0);
  	if (!object) {

  		kmemleak_warn("Trying to color unknown object at 0x%08lx as %s
  ",
  			      ptr,

  			      (color == KMEMLEAK_GREY) ? "Grey" :
  			      (color == KMEMLEAK_BLACK) ? "Black" : "Unknown");

  		return;
  	}

  	paint_it(object, color);

  	put_object(object);
  }
  
  /*

   * Mark an 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)
  {
  	paint_ptr(ptr, KMEMLEAK_GREY);
  }
  
  /*

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

  	paint_ptr(ptr, KMEMLEAK_BLACK);

  }
  
  /*
   * 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, size_t size, gfp_t gfp)

  {
  	unsigned long flags;
  	struct kmemleak_object *object;
  	struct kmemleak_scan_area *area;

  	object = find_and_get_object(ptr, 1);

  	if (!object) {

  		kmemleak_warn("Adding scan area to unknown object at 0x%08lx
  ",
  			      ptr);

  		return;
  	}

  	area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));

  	if (!area) {

  		pr_warn("Cannot allocate a scan area
  ");

  		goto out;
  	}
  
  	spin_lock_irqsave(&object->lock, flags);

  	if (size == SIZE_MAX) {
  		size = object->pointer + object->size - ptr;
  	} else if (ptr + size > object->pointer + object->size) {

  		kmemleak_warn("Scan area larger than object 0x%08lx
  ", ptr);

  		dump_object_info(object);
  		kmem_cache_free(scan_area_cache, area);
  		goto out_unlock;
  	}
  
  	INIT_HLIST_NODE(&area->node);

  	area->start = ptr;
  	area->size = size;

  
  	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) {

  		kmemleak_warn("Not scanning unknown object at 0x%08lx
  ", ptr);

  		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 __init log_early(int op_type, const void *ptr, size_t size,

  			     int min_count)

  {
  	unsigned long flags;
  	struct early_log *log;

  	if (kmemleak_error) {

  		/* kmemleak stopped recording, just count the requests */
  		crt_early_log++;
  		return;
  	}

  	if (crt_early_log >= ARRAY_SIZE(early_log)) {

  		crt_early_log++;

  		kmemleak_disable();

  		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->trace_len = __save_stack_trace(log->trace);

  	crt_early_log++;
  	local_irq_restore(flags);
  }
  
  /*

   * Log an early allocated block and populate the stack trace.
   */
  static void early_alloc(struct early_log *log)
  {
  	struct kmemleak_object *object;
  	unsigned long flags;
  	int i;

  	if (!kmemleak_enabled || !log->ptr || IS_ERR(log->ptr))

  		return;
  
  	/*
  	 * RCU locking needed to ensure object is not freed via put_object().
  	 */
  	rcu_read_lock();
  	object = create_object((unsigned long)log->ptr, log->size,

  			       log->min_count, GFP_ATOMIC);

  	if (!object)
  		goto out;

  	spin_lock_irqsave(&object->lock, flags);
  	for (i = 0; i < log->trace_len; i++)
  		object->trace[i] = log->trace[i];
  	object->trace_len = log->trace_len;
  	spin_unlock_irqrestore(&object->lock, flags);

  out:

  	rcu_read_unlock();
  }

  /*
   * Log an early allocated block and populate the stack trace.
   */
  static void early_alloc_percpu(struct early_log *log)
  {
  	unsigned int cpu;
  	const void __percpu *ptr = log->ptr;
  
  	for_each_possible_cpu(cpu) {
  		log->ptr = per_cpu_ptr(ptr, cpu);
  		early_alloc(log);
  	}
  }

  /**
   * kmemleak_alloc - register a newly allocated object
   * @ptr:	pointer to beginning of the object
   * @size:	size of the object
   * @min_count:	minimum number of references to this object. If during memory
   *		scanning a number of references less than @min_count is found,
   *		the object is reported as a memory leak. If @min_count is 0,
   *		the object is never reported as a leak. If @min_count is -1,
   *		the object is ignored (not scanned and not reported as a leak)
   * @gfp:	kmalloc() flags used for kmemleak internal memory allocations
   *
   * This function is called from the kernel allocators when a new object
   * (memory block) is allocated (kmem_cache_alloc, kmalloc, vmalloc etc.).

   */

  void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
  			  gfp_t gfp)

  {
  	pr_debug("%s(0x%p, %zu, %d)
  ", __func__, ptr, size, min_count);

  	if (kmemleak_enabled && ptr && !IS_ERR(ptr))

  		create_object((unsigned long)ptr, size, min_count, gfp);

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_ALLOC, ptr, size, min_count);

  }
  EXPORT_SYMBOL_GPL(kmemleak_alloc);

  /**

   * kmemleak_alloc_percpu - register a newly allocated __percpu object
   * @ptr:	__percpu pointer to beginning of the object
   * @size:	size of the object

   * @gfp:	flags used for kmemleak internal memory allocations

   *
   * This function is called from the kernel percpu allocator when a new object

   * (memory block) is allocated (alloc_percpu).

   */

  void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
  				 gfp_t gfp)

  {
  	unsigned int cpu;
  
  	pr_debug("%s(0x%p, %zu)
  ", __func__, ptr, size);
  
  	/*
  	 * Percpu allocations are only scanned and not reported as leaks
  	 * (min_count is set to 0).
  	 */

  	if (kmemleak_enabled && ptr && !IS_ERR(ptr))

  		for_each_possible_cpu(cpu)
  			create_object((unsigned long)per_cpu_ptr(ptr, cpu),

  				      size, 0, gfp);

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
  }
  EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);
  
  /**

   * kmemleak_free - unregister a previously registered object
   * @ptr:	pointer to beginning of the object
   *
   * This function is called from the kernel allocators when an object (memory
   * block) is freed (kmem_cache_free, kfree, vfree etc.).

   */

  void __ref kmemleak_free(const void *ptr)

  {
  	pr_debug("%s(0x%p)
  ", __func__, ptr);

  	if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))

  		delete_object_full((unsigned long)ptr);

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_FREE, ptr, 0, 0);

  }
  EXPORT_SYMBOL_GPL(kmemleak_free);

  /**
   * kmemleak_free_part - partially unregister a previously registered object
   * @ptr:	pointer to the beginning or inside the object. This also
   *		represents the start of the range to be freed
   * @size:	size to be unregistered
   *
   * This function is called when only a part of a memory block is freed
   * (usually from the bootmem allocator).

   */

  void __ref kmemleak_free_part(const void *ptr, size_t size)

  {
  	pr_debug("%s(0x%p)
  ", __func__, ptr);

  	if (kmemleak_enabled && ptr && !IS_ERR(ptr))

  		delete_object_part((unsigned long)ptr, size);

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_FREE_PART, ptr, size, 0);

  }
  EXPORT_SYMBOL_GPL(kmemleak_free_part);

  /**

   * kmemleak_free_percpu - unregister a previously registered __percpu object
   * @ptr:	__percpu pointer to beginning of the object
   *
   * This function is called from the kernel percpu allocator when an object
   * (memory block) is freed (free_percpu).
   */
  void __ref kmemleak_free_percpu(const void __percpu *ptr)
  {
  	unsigned int cpu;
  
  	pr_debug("%s(0x%p)
  ", __func__, ptr);

  	if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))

  		for_each_possible_cpu(cpu)
  			delete_object_full((unsigned long)per_cpu_ptr(ptr,
  								      cpu));

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_FREE_PERCPU, ptr, 0, 0);
  }
  EXPORT_SYMBOL_GPL(kmemleak_free_percpu);
  
  /**

   * kmemleak_update_trace - update object allocation stack trace
   * @ptr:	pointer to beginning of the object
   *
   * Override the object allocation stack trace for cases where the actual
   * allocation place is not always useful.
   */
  void __ref kmemleak_update_trace(const void *ptr)
  {
  	struct kmemleak_object *object;
  	unsigned long flags;
  
  	pr_debug("%s(0x%p)
  ", __func__, ptr);
  
  	if (!kmemleak_enabled || IS_ERR_OR_NULL(ptr))
  		return;
  
  	object = find_and_get_object((unsigned long)ptr, 1);
  	if (!object) {
  #ifdef DEBUG
  		kmemleak_warn("Updating stack trace for unknown object at %p
  ",
  			      ptr);
  #endif
  		return;
  	}
  
  	spin_lock_irqsave(&object->lock, flags);
  	object->trace_len = __save_stack_trace(object->trace);
  	spin_unlock_irqrestore(&object->lock, flags);
  
  	put_object(object);
  }
  EXPORT_SYMBOL(kmemleak_update_trace);
  
  /**

   * kmemleak_not_leak - mark an allocated object as false positive
   * @ptr:	pointer to beginning of the object
   *
   * Calling this function on an object will cause the memory block to no longer
   * be reported as leak and always be scanned.

   */

  void __ref kmemleak_not_leak(const void *ptr)

  {
  	pr_debug("%s(0x%p)
  ", __func__, ptr);

  	if (kmemleak_enabled && ptr && !IS_ERR(ptr))

  		make_gray_object((unsigned long)ptr);

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0);

  }
  EXPORT_SYMBOL(kmemleak_not_leak);

  /**
   * kmemleak_ignore - ignore an allocated object
   * @ptr:	pointer to beginning of the object
   *
   * Calling this function on an object will cause the memory block to be
   * ignored (not scanned and not reported as a leak). 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 __ref kmemleak_ignore(const void *ptr)

  {
  	pr_debug("%s(0x%p)
  ", __func__, ptr);

  	if (kmemleak_enabled && ptr && !IS_ERR(ptr))

  		make_black_object((unsigned long)ptr);

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_IGNORE, ptr, 0, 0);

  }
  EXPORT_SYMBOL(kmemleak_ignore);

  /**
   * kmemleak_scan_area - limit the range to be scanned in an allocated object
   * @ptr:	pointer to beginning or inside the object. This also
   *		represents the start of the scan area
   * @size:	size of the scan area
   * @gfp:	kmalloc() flags used for kmemleak internal memory allocations
   *
   * This function is used when it is known that only certain parts of an object
   * contain references to other objects. Kmemleak will only scan these areas
   * reducing the number false negatives.

   */

  void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)

  {
  	pr_debug("%s(0x%p)
  ", __func__, ptr);

  	if (kmemleak_enabled && ptr && size && !IS_ERR(ptr))

  		add_scan_area((unsigned long)ptr, size, gfp);

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0);

  }
  EXPORT_SYMBOL(kmemleak_scan_area);

  /**
   * kmemleak_no_scan - do not scan an allocated object
   * @ptr:	pointer to beginning of the object
   *
   * This function notifies kmemleak not to scan the given memory block. Useful
   * in situations where it is known that the given object does not contain any
   * references to other objects. Kmemleak will not scan such objects reducing
   * the number of false negatives.

   */

  void __ref kmemleak_no_scan(const void *ptr)

  {
  	pr_debug("%s(0x%p)
  ", __func__, ptr);

  	if (kmemleak_enabled && ptr && !IS_ERR(ptr))

  		object_no_scan((unsigned long)ptr);

  	else if (kmemleak_early_log)

  		log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0);

  }
  EXPORT_SYMBOL(kmemleak_no_scan);

  /**
   * kmemleak_alloc_phys - similar to kmemleak_alloc but taking a physical
   *			 address argument
   */
  void __ref kmemleak_alloc_phys(phys_addr_t phys, size_t size, int min_count,
  			       gfp_t gfp)
  {
  	if (!IS_ENABLED(CONFIG_HIGHMEM) || PHYS_PFN(phys) < max_low_pfn)
  		kmemleak_alloc(__va(phys), size, min_count, gfp);
  }
  EXPORT_SYMBOL(kmemleak_alloc_phys);
  
  /**
   * kmemleak_free_part_phys - similar to kmemleak_free_part but taking a
   *			     physical address argument
   */
  void __ref kmemleak_free_part_phys(phys_addr_t phys, size_t size)
  {
  	if (!IS_ENABLED(CONFIG_HIGHMEM) || PHYS_PFN(phys) < max_low_pfn)
  		kmemleak_free_part(__va(phys), size);
  }
  EXPORT_SYMBOL(kmemleak_free_part_phys);
  
  /**
   * kmemleak_not_leak_phys - similar to kmemleak_not_leak but taking a physical
   *			    address argument
   */
  void __ref kmemleak_not_leak_phys(phys_addr_t phys)
  {
  	if (!IS_ENABLED(CONFIG_HIGHMEM) || PHYS_PFN(phys) < max_low_pfn)
  		kmemleak_not_leak(__va(phys));
  }
  EXPORT_SYMBOL(kmemleak_not_leak_phys);
  
  /**
   * kmemleak_ignore_phys - similar to kmemleak_ignore but taking a physical
   *			  address argument
   */
  void __ref kmemleak_ignore_phys(phys_addr_t phys)
  {
  	if (!IS_ENABLED(CONFIG_HIGHMEM) || PHYS_PFN(phys) < max_low_pfn)
  		kmemleak_ignore(__va(phys));
  }
  EXPORT_SYMBOL(kmemleak_ignore_phys);

  /*

   * Update an object's checksum and return true if it was modified.
   */
  static bool update_checksum(struct kmemleak_object *object)
  {
  	u32 old_csum = object->checksum;
  
  	if (!kmemcheck_is_obj_initialized(object->pointer, object->size))
  		return false;

  	kasan_disable_current();

  	object->checksum = crc32(0, (void *)object->pointer, object->size);

  	kasan_enable_current();

  	return object->checksum != old_csum;
  }
  
  /*

   * Memory scanning is a long process and it needs to be interruptable. This

   * function checks whether such interrupt condition occurred.

   */
  static int scan_should_stop(void)
  {

  	if (!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,

  		       struct kmemleak_object *scanned)

  {
  	unsigned long *ptr;
  	unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
  	unsigned long *end = _end - (BYTES_PER_POINTER - 1);

  	unsigned long flags;

  	read_lock_irqsave(&kmemleak_lock, flags);

  	for (ptr = start; ptr < end; ptr++) {

  		struct kmemleak_object *object;

  		unsigned long pointer;

  
  		if (scan_should_stop())
  			break;

  		/* don't scan uninitialized memory */
  		if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
  						  BYTES_PER_POINTER))
  			continue;

  		kasan_disable_current();

  		pointer = *ptr;

  		kasan_enable_current();

  		if (pointer < min_addr || pointer >= max_addr)
  			continue;
  
  		/*
  		 * No need for get_object() here since we hold kmemleak_lock.
  		 * object->use_count cannot be dropped to 0 while the object
  		 * is still present in object_tree_root and object_list
  		 * (with updates protected by kmemleak_lock).
  		 */
  		object = lookup_object(pointer, 1);

  		if (!object)
  			continue;

  		if (object == scanned)

  			/* self referenced, ignore */

  			continue;

  
  		/*
  		 * Avoid the lockdep recursive warning on object->lock being
  		 * previously acquired in scan_object(). These locks are
  		 * enclosed by scan_mutex.
  		 */

  		spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);

  		if (!color_white(object)) {
  			/* non-orphan, ignored or new */

  			spin_unlock(&object->lock);

  			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)) {

  			/* put_object() called when removing from gray_list */
  			WARN_ON(!get_object(object));

  			list_add_tail(&object->gray_list, &gray_list);

  		}

  		spin_unlock(&object->lock);
  	}
  	read_unlock_irqrestore(&kmemleak_lock, flags);
  }

  /*
   * Scan a large memory block in MAX_SCAN_SIZE chunks to reduce the latency.
   */
  static void scan_large_block(void *start, void *end)
  {
  	void *next;
  
  	while (start < end) {
  		next = min(start + MAX_SCAN_SIZE, end);
  		scan_block(start, next, NULL);
  		start = next;
  		cond_resched();

  	}
  }
  
  /*
   * 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;

  	unsigned long flags;
  
  	/*

  	 * Once the object->lock is acquired, the corresponding memory block
  	 * cannot be freed (the same lock is acquired 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)) {
  		void *start = (void *)object->pointer;
  		void *end = (void *)(object->pointer + object->size);

  		void *next;
  
  		do {
  			next = min(start + MAX_SCAN_SIZE, end);
  			scan_block(start, next, object);

  			start = next;
  			if (start >= end)
  				break;

  
  			spin_unlock_irqrestore(&object->lock, flags);
  			cond_resched();
  			spin_lock_irqsave(&object->lock, flags);

  		} while (object->flags & OBJECT_ALLOCATED);

  	} else

  		hlist_for_each_entry(area, &object->area_list, node)

  			scan_block((void *)area->start,
  				   (void *)(area->start + area->size),

  				   object);

  out:
  	spin_unlock_irqrestore(&object->lock, flags);
  }
  
  /*

   * Scan the objects already referenced (gray objects). More objects will be
   * referenced and, if there are no memory leaks, all the objects are scanned.
   */
  static void scan_gray_list(void)
  {
  	struct kmemleak_object *object, *tmp;
  
  	/*
  	 * 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 incremented.
  	 */
  	object = list_entry(gray_list.next, typeof(*object), gray_list);
  	while (&object->gray_list != &gray_list) {
  		cond_resched();
  
  		/* 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;
  	}
  	WARN_ON(!list_empty(&gray_list));
  }
  
  /*

   * 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;

  	int i;

  	int new_leaks = 0;

  	jiffies_last_scan = jiffies;

  	/* 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) {

  			pr_debug("object->use_count = %d
  ",

  				 atomic_read(&object->use_count));
  			dump_object_info(object);
  		}
  #endif
  		/* reset the reference count (whiten the object) */
  		object->count = 0;
  		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 */

  	scan_large_block(_sdata, _edata);
  	scan_large_block(__bss_start, __bss_stop);

  	scan_large_block(__start_data_ro_after_init, __end_data_ro_after_init);

  
  #ifdef CONFIG_SMP
  	/* per-cpu sections scanning */
  	for_each_possible_cpu(i)

  		scan_large_block(__per_cpu_start + per_cpu_offset(i),
  				 __per_cpu_end + per_cpu_offset(i));

  #endif
  
  	/*

  	 * Struct page scanning for each node.

  	 */

  	get_online_mems();

  	for_each_online_node(i) {

  		unsigned long start_pfn = node_start_pfn(i);
  		unsigned long end_pfn = node_end_pfn(i);

  		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;

  			scan_block(page, page + 1, NULL);

  		}
  	}

  	put_online_mems();

  
  	/*

  	 * Scanning the task stacks (may introduce false negatives).

  	 */
  	if (kmemleak_stack_scan) {

  		struct task_struct *p, *g;

  		read_lock(&tasklist_lock);

  		do_each_thread(g, p) {

  			void *stack = try_get_task_stack(p);
  			if (stack) {
  				scan_block(stack, stack + THREAD_SIZE, NULL);
  				put_task_stack(p);
  			}

  		} while_each_thread(g, p);

  		read_unlock(&tasklist_lock);
  	}
  
  	/*
  	 * Scan the objects already referenced from the sections scanned

  	 * above.

  	 */

  	scan_gray_list();

  
  	/*

  	 * Check for new or unreferenced objects modified since the previous
  	 * scan and color them gray until the next scan.

  	 */
  	rcu_read_lock();
  	list_for_each_entry_rcu(object, &object_list, object_list) {
  		spin_lock_irqsave(&object->lock, flags);

  		if (color_white(object) && (object->flags & OBJECT_ALLOCATED)
  		    && update_checksum(object) && get_object(object)) {
  			/* color it gray temporarily */
  			object->count = object->min_count;

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

  	/*
  	 * Re-scan the gray list for modified unreferenced objects.
  	 */
  	scan_gray_list();

  
  	/*

  	 * If scanning was stopped do not report any new unreferenced objects.

  	 */

  	if (scan_should_stop())

  		return;
  
  	/*

  	 * 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) {
  		kmemleak_found_leaks = true;

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

  	}

  }
  
  /*
   * 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;

  	pr_info("Automatic memory scanning thread started
  ");

  	set_user_nice(current, 10);

  
  	/*
  	 * Wait before the first scan to allow the system to fully initialize.
  	 */
  	if (first_run) {

  		signed long timeout = msecs_to_jiffies(SECS_FIRST_SCAN * 1000);

  		first_run = 0;

  		while (timeout && !kthread_should_stop())
  			timeout = schedule_timeout_interruptible(timeout);

  	}
  
  	while (!kthread_should_stop()) {

  		signed long timeout = jiffies_scan_wait;
  
  		mutex_lock(&scan_mutex);

  		kmemleak_scan();

  		mutex_unlock(&scan_mutex);

  		/* wait before the next scan */
  		while (timeout && !kthread_should_stop())
  			timeout = schedule_timeout_interruptible(timeout);
  	}

  	pr_info("Automatic memory scanning thread ended
  ");

  
  	return 0;
  }
  
  /*
   * Start the automatic memory scanning thread. This function must be called

   * with the scan_mutex held.

   */

  static void start_scan_thread(void)

  {
  	if (scan_thread)
  		return;
  	scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
  	if (IS_ERR(scan_thread)) {

  		pr_warn("Failed to create the scan thread
  ");

  		scan_thread = NULL;
  	}
  }
  
  /*
   * Stop the automatic memory scanning thread. This function must be called

   * with the scan_mutex held.

   */

  static 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;

  	int err;
  
  	err = mutex_lock_interruptible(&scan_mutex);
  	if (err < 0)
  		return ERR_PTR(err);

  	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:

  	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 kmemleak_object *obj = prev_obj;

  
  	++(*pos);

  	list_for_each_entry_continue_rcu(obj, &object_list, object_list) {

  		if (get_object(obj)) {
  			next_obj = obj;

  			break;

  		}

  	}

  	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)
  {

  	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.
  		 */

  		rcu_read_unlock();

  		mutex_unlock(&scan_mutex);
  		if (v)
  			put_object(v);
  	}

  }
  
  /*
   * 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);

  	if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))

  		print_unreferenced(seq, object);

  	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)
  {

  	return seq_open(file, &kmemleak_seq_ops);

  }

  static int dump_str_object_info(const char *str)
  {
  	unsigned long flags;
  	struct kmemleak_object *object;
  	unsigned long addr;

  	if (kstrtoul(str, 0, &addr))
  		return -EINVAL;

  	object = find_and_get_object(addr, 0);
  	if (!object) {
  		pr_info("Unknown object at 0x%08lx
  ", addr);
  		return -EINVAL;
  	}
  
  	spin_lock_irqsave(&object->lock, flags);
  	dump_object_info(object);
  	spin_unlock_irqrestore(&object->lock, flags);
  
  	put_object(object);
  	return 0;
  }

  /*

   * We use grey instead of black to ensure we can do future scans on the same
   * objects. If we did not do future scans these black objects could
   * potentially contain references to newly allocated objects in the future and
   * we'd end up with false positives.
   */
  static void kmemleak_clear(void)
  {
  	struct kmemleak_object *object;
  	unsigned long flags;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(object, &object_list, object_list) {
  		spin_lock_irqsave(&object->lock, flags);
  		if ((object->flags & OBJECT_REPORTED) &&
  		    unreferenced_object(object))

  			__paint_it(object, KMEMLEAK_GREY);

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

  
  	kmemleak_found_leaks = false;

  }

  static void __kmemleak_do_cleanup(void);

  /*

   * 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)

   *   scan	- trigger a memory scan

   *   clear	- mark all current reported unreferenced kmemleak objects as

   *		  grey to ignore printing them, or free all kmemleak objects
   *		  if kmemleak has been disabled.

   *   dump=...	- dump information about the object found at the given address

   */
  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;

  	int ret;

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

  	ret = mutex_lock_interruptible(&scan_mutex);
  	if (ret < 0)
  		return ret;

  	if (strncmp(buf, "clear", 5) == 0) {

  		if (kmemleak_enabled)

  			kmemleak_clear();
  		else
  			__kmemleak_do_cleanup();
  		goto out;
  	}

  	if (!kmemleak_enabled) {

  		ret = -EBUSY;
  		goto out;
  	}

  	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;

  		ret = kstrtoul(buf + 5, 0, &secs);

  		if (ret < 0)
  			goto out;

  		stop_scan_thread();
  		if (secs) {
  			jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
  			start_scan_thread();
  		}

  	} else if (strncmp(buf, "scan", 4) == 0)
  		kmemleak_scan();

  	else if (strncmp(buf, "dump=", 5) == 0)
  		ret = dump_str_object_info(buf + 5);

  	else

  		ret = -EINVAL;
  
  out:
  	mutex_unlock(&scan_mutex);
  	if (ret < 0)
  		return ret;

  
  	/* 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	= seq_release,

  };

  static void __kmemleak_do_cleanup(void)
  {
  	struct kmemleak_object *object;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(object, &object_list, object_list)
  		delete_object_full(object->pointer);
  	rcu_read_unlock();
  }

  /*

   * Stop the memory scanning thread and free the kmemleak internal objects if
   * no previous scan thread (otherwise, kmemleak may still have some useful
   * information on memory leaks).

   */

  static void kmemleak_do_cleanup(struct work_struct *work)

  {

  	stop_scan_thread();

  	/*
  	 * Once the scan thread has stopped, it is safe to no longer track
  	 * object freeing. Ordering of the scan thread stopping and the memory
  	 * accesses below is guaranteed by the kthread_stop() function.
  	 */
  	kmemleak_free_enabled = 0;

  	if (!kmemleak_found_leaks)
  		__kmemleak_do_cleanup();
  	else

  		pr_info("Kmemleak disabled without freeing internal data. Reclaim the memory with \"echo clear > /sys/kernel/debug/kmemleak\".
  ");

  }

  static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup);

  
  /*
   * 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 (cmpxchg(&kmemleak_error, 0, 1))

  		return;
  
  	/* stop any memory operation tracing */

  	kmemleak_enabled = 0;

  
  	/* check whether it is too early for a kernel thread */

  	if (kmemleak_initialized)

  		schedule_work(&cleanup_work);

  	else
  		kmemleak_free_enabled = 0;

  
  	pr_info("Kernel memory leak detector disabled
  ");
  }
  
  /*
   * 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)
  		kmemleak_skip_disable = 1;
  	else

  		return -EINVAL;
  	return 0;
  }
  early_param("kmemleak", kmemleak_boot_config);

  static void __init print_log_trace(struct early_log *log)
  {
  	struct stack_trace trace;
  
  	trace.nr_entries = log->trace_len;
  	trace.entries = log->trace;
  
  	pr_notice("Early log backtrace:
  ");
  	print_stack_trace(&trace, 2);
  }

  /*

   * Kmemleak initialization.

   */
  void __init kmemleak_init(void)
  {
  	int i;
  	unsigned long flags;

  #ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
  	if (!kmemleak_skip_disable) {

  		kmemleak_early_log = 0;

  		kmemleak_disable();
  		return;
  	}
  #endif

  	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);

  	if (crt_early_log > ARRAY_SIZE(early_log))

  		pr_warn("Early log buffer exceeded (%d), please increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE
  ",
  			crt_early_log);

  	/* the kernel is still in UP mode, so disabling the IRQs is enough */
  	local_irq_save(flags);

  	kmemleak_early_log = 0;

  	if (kmemleak_error) {

  		local_irq_restore(flags);
  		return;

  	} else {

  		kmemleak_enabled = 1;

  		kmemleak_free_enabled = 1;
  	}

  	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:

  			early_alloc(log);

  			break;

  		case KMEMLEAK_ALLOC_PERCPU:
  			early_alloc_percpu(log);
  			break;

  		case KMEMLEAK_FREE:
  			kmemleak_free(log->ptr);
  			break;

  		case KMEMLEAK_FREE_PART:
  			kmemleak_free_part(log->ptr, log->size);
  			break;

  		case KMEMLEAK_FREE_PERCPU:
  			kmemleak_free_percpu(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->size, GFP_KERNEL);

  			break;
  		case KMEMLEAK_NO_SCAN:
  			kmemleak_no_scan(log->ptr);
  			break;
  		default:

  			kmemleak_warn("Unknown early log operation: %d
  ",
  				      log->op_type);
  		}

  		if (kmemleak_warning) {

  			print_log_trace(log);

  			kmemleak_warning = 0;

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

  	kmemleak_initialized = 1;

  	if (kmemleak_error) {

  		/*

  		 * Some error occurred 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.
  		 */

  		schedule_work(&cleanup_work);

  		return -ENOMEM;
  	}
  
  	dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
  				     &kmemleak_fops);
  	if (!dentry)

  		pr_warn("Failed to create the debugfs kmemleak file
  ");

  	mutex_lock(&scan_mutex);

  	start_scan_thread();

  	mutex_unlock(&scan_mutex);

  
  	pr_info("Kernel memory leak detector initialized
  ");
  
  	return 0;
  }
  late_initcall(kmemleak_late_init);