Message-ID: <20081216193648.GJ6681@linux.vnet.ibm.com>
Date:	Tue, 16 Dec 2008 11:36:48 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 01/15] kmemleak: Add the base support

On Wed, Dec 10, 2008 at 06:26:59PM +0000, Catalin Marinas wrote:
> This patch adds the base support for the kernel memory leak
> detector. It traces the memory allocation/freeing in a way similar to
> the Boehm's conservative garbage collector, the difference being that
> the unreferenced objects are not freed but only shown in
> /sys/kernel/debug/memleak. Enabling this feature introduces an
> overhead to memory allocations.

Looks good to me from an RCU viewpoint!

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Pekka Enberg <penberg@...helsinki.fi>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
>  include/linux/memleak.h |   93 +++
>  init/main.c             |    4 
>  mm/memleak.c            | 1263 +++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 1359 insertions(+), 1 deletions(-)
>  create mode 100644 include/linux/memleak.h
>  create mode 100644 mm/memleak.c
> 
> diff --git a/include/linux/memleak.h b/include/linux/memleak.h
> new file mode 100644
> index 0000000..340b9fc
> --- /dev/null
> +++ b/include/linux/memleak.h
> @@ -0,0 +1,93 @@
> +/*
> + * include/linux/memleak.h
> + *
> + * Copyright (C) 2008 ARM Limited
> + * Written by Catalin Marinas <catalin.marinas@....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
> + */
> +
> +#ifndef __MEMLEAK_H
> +#define __MEMLEAK_H
> +
> +#ifdef CONFIG_DEBUG_MEMLEAK
> +
> +extern void memleak_init(void);
> +extern void memleak_alloc(const void *ptr, size_t size, int min_count,
> +			  gfp_t gfp);
> +extern void memleak_free(const void *ptr);
> +extern void memleak_padding(const void *ptr, unsigned long offset, size_t size);
> +extern void memleak_not_leak(const void *ptr);
> +extern void memleak_ignore(const void *ptr);
> +extern void memleak_scan_area(const void *ptr, unsigned long offset,
> +			      size_t length, gfp_t gfp);
> +
> +static inline void memleak_alloc_recursive(const void *ptr, size_t size,
> +					   int min_count, unsigned long flags,
> +					   gfp_t gfp)
> +{
> +	if (!(flags & SLAB_NOLEAKTRACE))
> +		memleak_alloc(ptr, size, min_count, gfp);
> +}
> +
> +static inline void memleak_free_recursive(const void *ptr, unsigned long flags)
> +{
> +	if (!(flags & SLAB_NOLEAKTRACE))
> +		memleak_free(ptr);
> +}
> +
> +static inline void memleak_erase(void **ptr)
> +{
> +	*ptr = NULL;
> +}
> +
> +#else
> +
> +#define DECLARE_MEMLEAK_OFFSET(name, type, member)
> +
> +static inline void memleak_init(void)
> +{
> +}
> +static inline void memleak_alloc(const void *ptr, size_t size, int min_count,
> +				 gfp_t gfp)
> +{
> +}
> +static inline void memleak_alloc_recursive(const void *ptr, size_t size,
> +					   int min_count, unsigned long flags,
> +					   gfp_t gfp)
> +{
> +}
> +static inline void memleak_free(const void *ptr)
> +{
> +}
> +static inline void memleak_free_recursive(const void *ptr, unsigned long flags)
> +{
> +}
> +static inline void memleak_not_leak(const void *ptr)
> +{
> +}
> +static inline void memleak_ignore(const void *ptr)
> +{
> +}
> +static inline void memleak_scan_area(const void *ptr, unsigned long offset,
> +				     size_t length, gfp_t gfp)
> +{
> +}
> +static inline void memleak_erase(void **ptr)
> +{
> +}
> +
> +#endif	/* CONFIG_DEBUG_MEMLEAK */
> +
> +#endif	/* __MEMLEAK_H */
> diff --git a/init/main.c b/init/main.c
> index 7e117a2..81cbbb7 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -56,6 +56,7 @@
>  #include <linux/debug_locks.h>
>  #include <linux/debugobjects.h>
>  #include <linux/lockdep.h>
> +#include <linux/memleak.h>
>  #include <linux/pid_namespace.h>
>  #include <linux/device.h>
>  #include <linux/kthread.h>
> @@ -653,6 +654,8 @@ asmlinkage void __init start_kernel(void)
>  	enable_debug_pagealloc();
>  	cpu_hotplug_init();
>  	kmem_cache_init();
> +	prio_tree_init();
> +	memleak_init();
>  	debug_objects_mem_init();
>  	idr_init_cache();
>  	setup_per_cpu_pageset();
> @@ -662,7 +665,6 @@ asmlinkage void __init start_kernel(void)
>  	calibrate_delay();
>  	pidmap_init();
>  	pgtable_cache_init();
> -	prio_tree_init();
>  	anon_vma_init();
>  #ifdef CONFIG_X86
>  	if (efi_enabled)
> diff --git a/mm/memleak.c b/mm/memleak.c
> new file mode 100644
> index 0000000..bd84ee0
> --- /dev/null
> +++ b/mm/memleak.c
> @@ -0,0 +1,1263 @@
> +/*
> + * mm/memleak.c
> + *
> + * Copyright (C) 2008 ARM Limited
> + * Written by Catalin Marinas <catalin.marinas@....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 are used by kmemleak:
> + *
> + * - memleak_lock (rw_lock): protects the object_list modifications and
> + *   accesses to the object_tree_root. The object_list is the main
> + *   list holding the metadata (struct memleak_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 memleak_object structures are added to the object_list and
> + *   object_tree_root in the create_object() function called from the
> + *   memleak_alloc() callback and removed in delete_object() called from the
> + *   memleak_free() callback
> + * - memleak_object.lock (spinlock): protects a memleak_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
> + *   memleak_lock). This lock is also held when scanning the corresponding
> + *   memory block to avoid the kernel freeing it via the memleak_free()
> + *   callback. This is less heavyweight than holding a global lock like
> + *   memleak_lock during scanning
> + *
> + * The memleak_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
> + * memleak_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.
> + *
> + * The only mutex used is scan_mutex. This 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 memleak_object.use_count is incremented when an object
> + * is added to the gray_list and therefore cannot be freed.
> + */
> +
> +#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/kallsyms.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 <asm/sections.h>
> +#include <asm/processor.h>
> +#include <asm/atomic.h>
> +
> +#include <linux/memleak.h>
> +
> +/*
> + * Kmemleak configuration and common defines.
> + */
> +#define MAX_TRACE		16	/* stack trace length */
> +#define REPORTS_NR		100	/* maximum number of reported leaks */
> +#define MSECS_MIN_AGE		5000	/* minimum object age for reporting */
> +#define MSECS_SCAN_YIELD	10	/* CPU yielding period */
> +#define SECS_FIRST_SCAN		60	/* delay before the first scan */
> +#define SECS_SCAN_PERIOD	600	/* auto scanning period */
> +#undef SCAN_TASK_STACKS			/* scan the task kernel stacks */
> +#undef REPORT_ORPHAN_FREEING		/* notify when freeing orphan objects */
> +
> +#define BYTES_PER_POINTER	sizeof(void *)
> +
> +/* scanning area inside a memory block */
> +struct memleak_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 memleak_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)
> +
> +/* 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(memleak_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 memleak_enabled = ATOMIC_INIT(0);
> +/* set in the late_initcall if there were no errors */
> +static atomic_t memleak_initialized = ATOMIC_INIT(0);
> +/* enables or disables early logging of the memory operations */
> +static atomic_t memleak_early_log = ATOMIC_INIT(1);
> +/* set if a fata kmemleak error has occurred */
> +static atomic_t memleak_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;
> +
> +/* used for yielding the CPU to other tasks during scanning */
> +static unsigned long next_scan_yield;
> +static struct task_struct *scan_thread;
> +static unsigned long jiffies_scan_yield;
> +static unsigned long jiffies_min_age;
> +static DEFINE_MUTEX(scan_mutex);
> +
> +/* number of leaks reported (for limitation purposes) */
> +static int reported_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 {
> +	MEMLEAK_ALLOC,
> +	MEMLEAK_FREE,
> +	MEMLEAK_NOT_LEAK,
> +	MEMLEAK_IGNORE,
> +	MEMLEAK_SCAN_AREA,
> +};
> +
> +/*
> + * 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 */
> +static struct early_log __initdata early_log[200];
> +static int __initdata crt_early_log;
> +
> +static void memleak_disable(void);
> +
> +/*
> + * Macro invoked when a serious kmemleak condition occured and cannot be
> + * recovered from. Kmemleak will be disabled and further allocation/freeing
> + * tracing no longer available.
> + */
> +#define memleak_panic(x...) {	\
> +	pr_warning(x);		\
> +	memleak_disable();	\
> +}
> +
> +/*
> + * Object colors, encoded with count and min_count:
> + * - white - orphan object, not enough references to it (count < min_count)
> + * - gray  - not orphan, 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 memleak_object *object)
> +{
> +	return object->count != -1 && object->count < object->min_count;
> +}
> +
> +static int color_gray(const struct memleak_object *object)
> +{
> +	return object->min_count != -1 && 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 int unreferenced_object(struct memleak_object *object)
> +{
> +	if (color_white(object) &&
> +	    (object->flags & OBJECT_ALLOCATED) &&
> +	    time_is_before_eq_jiffies(object->jiffies + jiffies_min_age))
> +		return 1;
> +	else
> +		return 0;
> +}
> +
> +/*
> + * Printing of the unreferenced objects information, either to the seq file
> + * or to the kernel log. The print_unreferenced() function must be called with
> + * the object->lock held.
> + */
> +#define print_helper(seq, x...)			\
> +do {						\
> +	if (seq)				\
> +		seq_printf(seq, x);		\
> +	else					\
> +		pr_info(x);			\
> +} while (0)
> +
> +static void print_unreferenced(struct seq_file *seq,
> +			       struct memleak_object *object)
> +{
> +	char namebuf[KSYM_NAME_LEN + 1] = "";
> +	char *modname;
> +	unsigned long symsize;
> +	int i;
> +
> +	print_helper(seq, "unreferenced object 0x%08lx (size %zu):\n",
> +		     object->pointer, object->size);
> +	print_helper(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
> +		     object->comm, object->pid, object->jiffies);
> +	print_helper(seq, "  backtrace:\n");
> +
> +	for (i = 0; i < object->trace_len; i++) {
> +		unsigned long trace = object->trace[i];
> +		unsigned long offset = 0;
> +
> +		kallsyms_lookup(trace, &symsize, &offset, &modname, namebuf);
> +		print_helper(seq, "    [<%08lx>] %s\n", trace, namebuf);
> +	}
> +}
> +
> +/*
> + * Print the memleak_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 memleak_object *object)
> +{
> +	struct stack_trace trace;
> +
> +	trace.nr_entries = object->trace_len;
> +	trace.entries = object->trace;
> +
> +	pr_notice("kmemleak: Object 0x%08lx (size %zu):\n",
> +		  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 (memleak_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 memleak_lock must be held
> + * when calling this function.
> + */
> +static struct memleak_object *lookup_object(unsigned long ptr, int alias)
> +{
> +	struct prio_tree_node *node;
> +	struct prio_tree_iter iter;
> +	struct memleak_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 memleak_object,
> +					 tree_node);
> +		if (!alias && object->pointer != ptr) {
> +			pr_warning("kmemleak: Found object by alias");
> +			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 memleak_object *object)
> +{
> +	return atomic_inc_not_zero(&object->use_count);
> +}
> +
> +/*
> + * RCU callback to free a memleak_object.
> + */
> +static void free_object_rcu(struct rcu_head *rcu)
> +{
> +	struct hlist_node *elem, *tmp;
> +	struct memleak_scan_area *area;
> +	struct memleak_object *object =
> +		container_of(rcu, struct memleak_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 memleak_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 memleak_object *object)
> +{
> +	if (!atomic_dec_and_test(&object->use_count))
> +		return;
> +
> +	/* should only get here after delete_object was called */
> +	BUG_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 memleak_object *find_and_get_object(unsigned long ptr, int alias)
> +{
> +	unsigned long flags;
> +	struct memleak_object *object = NULL;
> +
> +	rcu_read_lock();
> +	read_lock_irqsave(&memleak_lock, flags);
> +	if (ptr >= min_addr && ptr < max_addr)
> +		object = lookup_object(ptr, alias);
> +	read_unlock_irqrestore(&memleak_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 memleak_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 memleak_object *object;
> +	struct prio_tree_node *node;
> +	struct stack_trace trace;
> +
> +	object = kmem_cache_alloc(object_cache, gfp);
> +	if (!object)
> +		memleak_panic("kmemleak: Cannot allocate a memleak_object "
> +			      "structure\n");
> +
> +	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 = -1;			/* no color initially */
> +	object->jiffies = jiffies;
> +
> +	/* task information */
> +	if (in_irq()) {
> +		object->pid = 0;
> +		strncpy(object->comm, "hardirq", TASK_COMM_LEN);
> +	} else if (in_softirq()) {
> +		object->pid = 0;
> +		strncpy(object->comm, "softirq", TASK_COMM_LEN);
> +	} else {
> +		object->pid = current->pid;
> +		get_task_comm(object->comm, current);
> +	}
> +
> +	/* 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(&memleak_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
> +	 * memleak_lock here in case parts of the kernel started freeing
> +	 * random memory blocks.
> +	 */
> +	if (node != &object->tree_node) {
> +		unsigned long flags;
> +
> +		pr_warning("kmemleak: Existing pointer\n");
> +		dump_stack();
> +
> +		object = lookup_object(ptr, 1);
> +		spin_lock_irqsave(&object->lock, flags);
> +		dump_object_info(object);
> +		spin_unlock_irqrestore(&object->lock, flags);
> +
> +		memleak_panic("kmemleak: Cannot insert 0x%lx into the object "
> +			      "search tree\n", ptr);
> +	}
> +	list_add_tail_rcu(&object->object_list, &object_list);
> +	write_unlock_irqrestore(&memleak_lock, flags);
> +}
> +
> +/*
> + * Remove the metadata (struct memleak_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 memleak_object *object;
> +
> +	write_lock_irqsave(&memleak_lock, flags);
> +	object = lookup_object(ptr, 0);
> +	if (!object) {
> +		pr_warning("kmemleak: Freeing unknown object at 0x%08lx\n",
> +			   ptr);
> +		dump_stack();
> +		write_unlock_irqrestore(&memleak_lock, flags);
> +		return;
> +	}
> +	prio_tree_remove(&object_tree_root, &object->tree_node);
> +	list_del_rcu(&object->object_list);
> +	write_unlock_irqrestore(&memleak_lock, flags);
> +
> +	BUG_ON(!(object->flags & OBJECT_ALLOCATED));
> +	BUG_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;
> +#ifdef REPORT_ORPHAN_FREEING
> +	if (color_white(object)) {
> +		pr_warning("kmemleak: Freeing orphan object 0x%08lx\n", ptr);
> +		dump_stack();
> +		dump_object_info(object);
> +	}
> +#endif
> +	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 memleak_object *object;
> +
> +	object = find_and_get_object(ptr, 0);
> +	if (!object) {
> +		dump_stack();
> +		memleak_panic("kmemleak: Graying unknown object at 0x%08lx\n",
> +			      ptr);
> +	}
> +
> +	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 memleak_object *object;
> +
> +	object = find_and_get_object(ptr, 0);
> +	if (!object) {
> +		dump_stack();
> +		memleak_panic("kmemleak: Blacking unknown object at 0x%08lx\n",
> +			      ptr);
> +	}
> +
> +	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 memleak_object *object;
> +	struct memleak_scan_area *area;
> +
> +	object = find_and_get_object(ptr, 0);
> +	if (!object) {
> +		dump_stack();
> +		memleak_panic("kmemleak: Adding scan area to unknown "
> +			      "object at 0x%08lx\n", ptr);
> +	}
> +
> +	area = kmem_cache_alloc(scan_area_cache, gfp);
> +	if (!area)
> +		memleak_panic("kmemleak: Cannot allocate a scan area\n");
> +
> +	spin_lock_irqsave(&object->lock, flags);
> +	if (offset + length > object->size) {
> +		dump_stack();
> +		dump_object_info(object);
> +		memleak_panic("kmemleak: Scan area larger than object "
> +			      "0x%08lx\n", ptr);
> +	}
> +
> +	INIT_HLIST_NODE(&area->node);
> +	area->offset = offset;
> +	area->length = length;
> +
> +	hlist_add_head(&area->node, &object->area_list);
> +	spin_unlock_irqrestore(&object->lock, flags);
> +	put_object(object);
> +}
> +
> +/*
> + * Log an early memleak_* 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 offset, size_t length)
> +{
> +	unsigned long flags;
> +	struct early_log *log;
> +
> +	if (crt_early_log >= ARRAY_SIZE(early_log))
> +		memleak_panic("kmemleak: Early log buffer exceeded\n");
> +
> +	/*
> +	 * 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 memleak_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(&memleak_enabled) && ptr)
> +		create_object((unsigned long)ptr, size, min_count, gfp);
> +	else if (atomic_read(&memleak_early_log))
> +		log_early(MEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
> +}
> +EXPORT_SYMBOL_GPL(memleak_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 memleak_free(const void *ptr)
> +{
> +	pr_debug("%s(0x%p)\n", __func__, ptr);
> +
> +	if (atomic_read(&memleak_enabled) && ptr)
> +		delete_object((unsigned long)ptr);
> +	else if (atomic_read(&memleak_early_log))
> +		log_early(MEMLEAK_FREE, ptr, 0, 0, 0, 0);
> +}
> +EXPORT_SYMBOL_GPL(memleak_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 memleak_not_leak(const void *ptr)
> +{
> +	pr_debug("%s(0x%p)\n", __func__, ptr);
> +
> +	if (atomic_read(&memleak_enabled) && ptr)
> +		make_gray_object((unsigned long)ptr);
> +	else if (atomic_read(&memleak_early_log))
> +		log_early(MEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
> +}
> +EXPORT_SYMBOL(memleak_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 memleak_ignore(const void *ptr)
> +{
> +	pr_debug("%s(0x%p)\n", __func__, ptr);
> +
> +	if (atomic_read(&memleak_enabled) && ptr)
> +		make_black_object((unsigned long)ptr);
> +	else if (atomic_read(&memleak_early_log))
> +		log_early(MEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
> +}
> +EXPORT_SYMBOL(memleak_ignore);
> +
> +/*
> + * Limit the range to be scanned in an allocated memory block.
> + */
> +void memleak_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(&memleak_enabled) && ptr)
> +		add_scan_area((unsigned long)ptr, offset, length, gfp);
> +	else if (atomic_read(&memleak_early_log))
> +		log_early(MEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
> +}
> +EXPORT_SYMBOL(memleak_scan_area);
> +
> +/*
> + * Yield the CPU so that other tasks get a chance to run.  The yielding is
> + * rate-limited to avoid excessive number of calls to the schedule() function
> + * during memory scanning.
> + */
> +static void scan_yield(void)
> +{
> +	might_sleep();
> +
> +	if (time_is_before_eq_jiffies(next_scan_yield)) {
> +		schedule();
> +		next_scan_yield = jiffies + jiffies_scan_yield;
> +	}
> +}
> +
> +/*
> + * 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(&memleak_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 && signal_pending(current)) ||
> +	    (!current->mm && kthread_should_stop()))
> +		return 1;
> +	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 memleak_object *scanned)
> +{
> +	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 memleak_object *object;
> +
> +		if (scan_should_stop())
> +			break;
> +
> +		/*
> +		 * When scanning a memory block with a corresponding
> +		 * memleak_object, the CPU yielding is handled in the calling
> +		 * code since it holds the object->lock to avoid the block
> +		 * freeing.
> +		 */
> +		if (!scanned)
> +			scan_yield();
> +
> +		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 memleak_object. A condition is
> + * that object->use_count >= 1.
> + */
> +static void scan_object(struct memleak_object *object)
> +{
> +	struct memleak_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_ALLOCATED))
> +		/* already freed object */
> +		goto out;
> +	if (hlist_empty(&object->area_list))
> +		scan_block((void *)object->pointer,
> +			   (void *)(object->pointer + object->size), object);
> +	else
> +		hlist_for_each_entry(area, elem, &object->area_list, node)
> +			scan_block((void *)(object->pointer + area->offset),
> +				   (void *)(object->pointer + area->offset
> +					    + area->length), object);
> + 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 memleak_scan(void)
> +{
> +	unsigned long flags;
> +	struct memleak_object *object, *tmp;
> +#ifdef CONFIG_SMP
> +	int i;
> +#endif
> +#ifdef SCAN_TASK_STACKS
> +	struct task_struct *task;
> +#endif
> +
> +	/* prepare the memleak_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("kmemleak: object->use_count = %d\n",
> +				 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_block(_sdata, _edata, NULL);
> +	scan_block(__bss_start, __bss_stop, NULL);
> +
> +#ifdef CONFIG_SMP
> +	/* per-cpu sections scanning */
> +	for_each_possible_cpu(i)
> +		scan_block(__per_cpu_start + per_cpu_offset(i),
> +			   __per_cpu_end + per_cpu_offset(i), NULL);
> +#endif
> +
> +#ifdef SCAN_TASK_STACKS
> +	/*
> +	 * Scanning the task stacks may introduce false negatives and it is
> +	 * not enabled by default.
> +	 */
> +	read_lock(&tasklist_lock);
> +	for_each_process(task)
> +		scan_block(task_stack_page(task),
> +			   task_stack_page(task) + THREAD_SIZE, NULL);
> +	read_unlock(&tasklist_lock);
> +#endif
> +
> +	/*
> +	 * 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
> +	 * memleak objects cannot be freed from outside the loop because their
> +	 * use_count was increased.
> +	 */
> +	object = list_entry(gray_list.next, typeof(*object), gray_list);
> +	while (&object->gray_list != &gray_list) {
> +		scan_yield();
> +
> +		/* 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;
> +	}
> +	BUG_ON(!list_empty(&gray_list));
> +}
> +
> +/*
> + * 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 *memleak_seq_start(struct seq_file *seq, loff_t *pos)
> +{
> +	struct memleak_object *object;
> +	loff_t n = *pos;
> +
> +	if (!atomic_read(&memleak_enabled)) {
> +		seq_printf(seq, "Kernel memory leak detector disabled\n");
> +		return ERR_PTR(-EBUSY);
> +	}
> +	if (!n) {
> +		memleak_scan();
> +		reported_leaks = 0;
> +	}
> +	if (reported_leaks >= REPORTS_NR)
> +		return NULL;
> +
> +	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 *memleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
> +{
> +	struct memleak_object *prev_obj = v;
> +	struct memleak_object *next_obj = NULL;
> +	struct list_head *n = &prev_obj->object_list;
> +
> +	++(*pos);
> +	if (reported_leaks >= REPORTS_NR)
> +		goto out;
> +
> +	rcu_read_lock();
> +	list_for_each_continue_rcu(n, &object_list) {
> +		next_obj = list_entry(n, struct memleak_object, object_list);
> +		if (get_object(next_obj))
> +			break;
> +	}
> +	rcu_read_unlock();
> + out:
> +	put_object(prev_obj);
> +	return next_obj;
> +}
> +
> +/*
> + * Decrement the use_count of the last object required, if any.
> + */
> +static void memleak_seq_stop(struct seq_file *seq, void *v)
> +{
> +	if (v)
> +		put_object(v);
> +}
> +
> +/*
> + * Print the information for an unreferenced object to the seq file.
> + */
> +static int memleak_seq_show(struct seq_file *seq, void *v)
> +{
> +	struct memleak_object *object = v;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&object->lock, flags);
> +	if (!unreferenced_object(object))
> +		goto out;
> +	print_unreferenced(seq, object);
> +	reported_leaks++;
> +out:
> +	spin_unlock_irqrestore(&object->lock, flags);
> +	return 0;
> +}
> +
> +static const struct seq_operations memleak_seq_ops = {
> +	.start = memleak_seq_start,
> +	.next  = memleak_seq_next,
> +	.stop  = memleak_seq_stop,
> +	.show  = memleak_seq_show,
> +};
> +
> +static int memleak_seq_open(struct inode *inode, struct file *file)
> +{
> +	int ret = mutex_lock_interruptible(&scan_mutex);
> +	if (ret < 0)
> +		return ret;
> +	ret = seq_open(file, &memleak_seq_ops);
> +	if (ret < 0)
> +		mutex_unlock(&scan_mutex);
> +	return ret;
> +}
> +
> +static int memleak_seq_release(struct inode *inode, struct file *file)
> +{
> +	int ret = seq_release(inode, file);
> +	mutex_unlock(&scan_mutex);
> +	return ret;
> +}
> +
> +static const struct file_operations memleak_fops = {
> +	.owner	 = THIS_MODULE,
> +	.open    = memleak_seq_open,
> +	.read    = seq_read,
> +	.llseek  = seq_lseek,
> +	.release = memleak_seq_release,
> +};
> +
> +/*
> + * Thread function performing automatic memory scanning. Unreferenced objects
> + * at the end of a memory scan are reported but only the first time.
> + */
> +static int memleak_scan_thread(void *arg)
> +{
> +	/*
> +	 * Wait before the first scan to allow the system to fully initialize.
> +	 */
> +	ssleep(SECS_FIRST_SCAN);
> +
> +	while (!kthread_should_stop()) {
> +		struct memleak_object *object;
> +		int ret;
> +
> +		ret = mutex_lock_interruptible(&scan_mutex);
> +		if (ret < 0)
> +			continue;
> +
> +		memleak_scan();
> +		reported_leaks = 0;
> +
> +		rcu_read_lock();
> +		list_for_each_entry_rcu(object, &object_list, object_list) {
> +			unsigned long flags;
> +
> +			if (reported_leaks >= REPORTS_NR)
> +				break;
> +			spin_lock_irqsave(&object->lock, flags);
> +			if (!(object->flags & OBJECT_REPORTED) &&
> +			    unreferenced_object(object)) {
> +				print_unreferenced(NULL, object);
> +				object->flags |= OBJECT_REPORTED;
> +				reported_leaks++;
> +			}
> +			spin_unlock_irqrestore(&object->lock, flags);
> +		}
> +		rcu_read_unlock();
> +
> +		mutex_unlock(&scan_mutex);
> +		/* sleep before the next scan */
> +		ssleep(SECS_SCAN_PERIOD);
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * Perform the freeing of the kmemleak internal objects after waiting for any
> + * current memory scan to complete.
> + */
> +static int memleak_cleanup_thread(void *arg)
> +{
> +	struct memleak_object *object;
> +
> +	mutex_lock(&scan_mutex);
> +	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 memleak_cleanup(void)
> +{
> +	struct task_struct *cleanup_thread;
> +
> +	cleanup_thread = kthread_run(memleak_cleanup_thread, NULL,
> +				     "kmemleak-cleanup");
> +	if (IS_ERR(cleanup_thread))
> +		pr_warning("kmemleak: Failed to create the clean-up thread\n");
> +}
> +
> +/*
> + * Disable kmemleak. No memory allocation/freeing will be traced once this
> + * function is called. Disabling kmemleak is an irreversible operation.
> + */
> +static void memleak_disable(void)
> +{
> +	if (atomic_cmpxchg(&memleak_error, 0, 1))
> +		return;
> +
> +	/* stop any memory operation tracing */
> +	atomic_set(&memleak_early_log, 0);
> +	atomic_set(&memleak_enabled, 0);
> +
> +	/* check whether it is too early for a kernel thread */
> +	if (atomic_read(&memleak_initialized))
> +		memleak_cleanup();
> +
> +	pr_info("Kernel memory leak detector disabled\n");
> +}
> +
> +/*
> + * Kmemleak initialization.
> + */
> +void __init memleak_init(void)
> +{
> +	int i;
> +	unsigned long flags;
> +
> +	jiffies_scan_yield = msecs_to_jiffies(MSECS_SCAN_YIELD);
> +	jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
> +
> +	object_cache = KMEM_CACHE(memleak_object, SLAB_NOLEAKTRACE);
> +	scan_area_cache = KMEM_CACHE(memleak_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(&memleak_error)) {
> +		atomic_set(&memleak_enabled, 1);
> +		atomic_set(&memleak_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 MEMLEAK_ALLOC:
> +			memleak_alloc(log->ptr, log->size, log->min_count,
> +				      GFP_ATOMIC);
> +			break;
> +		case MEMLEAK_FREE:
> +			memleak_free(log->ptr);
> +			break;
> +		case MEMLEAK_NOT_LEAK:
> +			memleak_not_leak(log->ptr);
> +			break;
> +		case MEMLEAK_IGNORE:
> +			memleak_ignore(log->ptr);
> +			break;
> +		case MEMLEAK_SCAN_AREA:
> +			memleak_scan_area(log->ptr, log->offset, log->length,
> +					  GFP_ATOMIC);
> +			break;
> +		default:
> +			BUG();
> +		}
> +	}
> +}
> +
> +/*
> + * Late initialization function.
> + */
> +static int __init memleak_late_init(void)
> +{
> +	struct dentry *dentry;
> +
> +	atomic_set(&memleak_initialized, 1);
> +
> +	if (atomic_read(&memleak_error)) {
> +		/*
> +		 * Some error occured and kmemleak was disabled. There is a
> +		 * small chance that memleak_disable() was called immediately
> +		 * after setting memleak_initialized and we may end up with
> +		 * two clean-up threads but serialized by scan_mutex.
> +		 */
> +		memleak_cleanup();
> +		return -EBUSY;
> +	}
> +
> +	dentry = debugfs_create_file("memleak", S_IRUGO, NULL, NULL,
> +				     &memleak_fops);
> +	if (!dentry)
> +		return -ENOMEM;
> +
> +	scan_thread = kthread_run(memleak_scan_thread, NULL, "kmemleak");
> +	if (IS_ERR(scan_thread))
> +		pr_warning("kmemleak: Failed to create the scan thread\n");
> +
> +	pr_info("Kernel memory leak detector initialized\n");
> +
> +	return 0;
> +}
> +late_initcall(memleak_late_init);
> 
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