[PATCH 2.6.17-rc6 1/8] Base support for kmemleak

[Catalin Marinas <catalin.marinas@gmail.com>]

From: Catalin Marinas <catalin.marinas@arm.com>

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 orphan
pointers are not freed but only shown in /proc/memleak. Enabling this
feature would introduce an overhead to memory allocations.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

 include/linux/kernel.h  |    7 
 include/linux/memleak.h |   79 +++
 init/main.c             |    3 
 lib/Kconfig.debug       |   43 ++
 mm/Makefile             |    2 
 mm/memleak.c            | 1073 +++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 1204 insertions(+), 3 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index f4fc576..9155457 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -13,6 +13,7 @@ #include <linux/stddef.h>
 #include <linux/types.h>
 #include <linux/compiler.h>
 #include <linux/bitops.h>
+#include <linux/memleak.h>
 #include <asm/byteorder.h>
 #include <asm/bug.h>
 
@@ -284,9 +285,13 @@ #define max_t(type,x,y) \
  * @member:	the name of the member within the struct.
  *
  */
-#define container_of(ptr, type, member) ({			\
+#define __container_of(ptr, type, member) ({			\
         const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
         (type *)( (char *)__mptr - offsetof(type,member) );})
+#define container_of(ptr, type, member) ({			\
+	DECLARE_MEMLEAK_OFFSET(container_of, type, member);	\
+	__container_of(ptr, type, member);			\
+})
 
 /*
  * Check at compile time that something is of a particular type.
diff --git a/include/linux/memleak.h b/include/linux/memleak.h
new file mode 100644
index 0000000..0f7528f
--- /dev/null
+++ b/include/linux/memleak.h
@@ -0,0 +1,79 @@
+/*
+ * include/linux/memleak.h
+ *
+ * Copyright (C) 2006 ARM Limited
+ * Written by Catalin Marinas <catalin.marinas@gmail.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
+
+#include <linux/stddef.h>
+
+#ifdef CONFIG_DEBUG_MEMLEAK
+
+struct memleak_offset {
+	unsigned long offset;
+	unsigned long size;
+	unsigned long member_size;
+};
+
+/* if offsetof(type, member) is not a constant known at compile time,
+ * just use 0 instead since we cannot add it to the
+ * .init.memleak_offsets section
+ */
+#define memleak_offsetof(type, member)				\
+	(__builtin_constant_p(offsetof(type, member)) ?		\
+	 offsetof(type, member) : 0)
+
+#define DECLARE_MEMLEAK_OFFSET(name, type, member)		\
+	static const struct memleak_offset			\
+	__attribute__ ((__section__ (".init.memleak_offsets")))	\
+	__attribute_used__ __memleak_offset__##name = {		\
+		memleak_offsetof(type, member),			\
+		sizeof(type),					\
+		sizeof(((type *)0)->member)			\
+	}
+
+extern void memleak_init(void);
+extern void memleak_alloc(const void *ptr, size_t size, int ref_count);
+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);
+extern void memleak_insert_aliases(struct memleak_offset *ml_off_start,
+				   struct memleak_offset *ml_off_end);
+
+#define memleak_erase(ptr)	do { (ptr) = NULL; } while (0)
+
+#else
+
+#define DECLARE_MEMLEAK_OFFSET(name, type, member)
+
+#define memleak_init()
+#define memleak_alloc(ptr, size, ref_count)
+#define memleak_free(ptr)
+#define memleak_padding(ptr, offset, size)
+#define memleak_not_leak(ptr)
+#define memleak_ignore(ptr)
+#define memleak_scan_area(ptr, offset, length)
+#define memleak_insert_aliases(ml_off_start, ml_off_end)
+#define memleak_erase(ptr)
+
+#endif	/* CONFIG_DEBUG_MEMLEAK */
+
+#endif	/* __MEMLEAK_H */
diff --git a/init/main.c b/init/main.c
index f715b9b..986487c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -513,6 +513,8 @@ #endif
 	cpuset_init_early();
 	mem_init();
 	kmem_cache_init();
+	radix_tree_init();
+	memleak_init();
 	setup_per_cpu_pageset();
 	numa_policy_init();
 	if (late_time_init)
@@ -533,7 +535,6 @@ #endif
 	key_init();
 	security_init();
 	vfs_caches_init(num_physpages);
-	radix_tree_init();
 	signals_init();
 	/* rootfs populating might need page-writeback */
 	page_writeback_init();
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ccb0c1f..fddf306 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -89,6 +89,49 @@ config DEBUG_SLAB_LEAK
 	bool "Memory leak debugging"
 	depends on DEBUG_SLAB
 
+menuconfig DEBUG_MEMLEAK
+	bool "Kernel memory leak detector"
+	default n
+	depends on EXPERIMENTAL && DEBUG_SLAB
+	depends on !NUMA
+	select DEBUG_FS
+	help
+	  Say Y here if you want to enable the memory leak
+	  detector. The memory allocation/freeing is traced in a way
+	  similar to the Boehm's conservative garbage collector, the
+	  difference being that the orphan pointers are not freed but
+	  only shown in /sys/kernel/debug/memleak. Enabling this
+	  feature will introduce an overhead to memory allocations.
+
+config DEBUG_MEMLEAK_TRACE_LENGTH
+	int "KMemLeak stack trace length"
+	default 4
+	depends on DEBUG_MEMLEAK && FRAME_POINTER
+	help
+	  This option sets the length of the stack trace for the
+	  allocated pointers tracked by kmemleak.
+
+config DEBUG_MEMLEAK_PREINIT_POINTERS
+	int "KMemLeak pre-init actions buffer size"
+	default 512
+	depends on DEBUG_MEMLEAK
+	help
+	  This is the buffer for storing the memory allocation/freeing
+	  calls before kmemleak is fully initialized. Each element in
+	  the buffer takes 20 bytes on a 32 bit architecture. This
+	  buffer will be freed once the system initialization is
+	  completed.
+
+config DEBUG_MEMLEAK_SECONDARY_ALIASES
+	bool "Create secondary level pointer aliases"
+	default y
+	depends on DEBUG_MEMLEAK
+	help
+	  This option creates aliases for container_of(container_of(member))
+	  access to pointers. Disabling this option reduces the chances of
+	  false negatives but it can slightly increase the number of false
+	  positives.
+
 config DEBUG_PREEMPT
 	bool "Debug preemptible kernel"
 	depends on DEBUG_KERNEL && PREEMPT
diff --git a/mm/Makefile b/mm/Makefile
index 0b8f73f..d487d96 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -23,4 +23,4 @@ obj-$(CONFIG_SLAB) += slab.o
 obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
 obj-$(CONFIG_FS_XIP) += filemap_xip.o
 obj-$(CONFIG_MIGRATION) += migrate.o
-
+obj-$(CONFIG_DEBUG_MEMLEAK) += memleak.o
diff --git a/mm/memleak.c b/mm/memleak.c
new file mode 100644
index 0000000..c7d18b9
--- /dev/null
+++ b/mm/memleak.c
@@ -0,0 +1,1073 @@
+/*
+ * mm/memleak.c
+ *
+ * Copyright (C) 2006 ARM Limited
+ * Written by Catalin Marinas <catalin.marinas@gmail.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
+ */
+
+/* #define DEBUG */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/radix-tree.h>
+#include <linux/gfp.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/kallsyms.h>
+#include <linux/mman.h>
+#include <linux/nodemask.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/vmalloc.h>
+#include <linux/mutex.h>
+#include <linux/cpumask.h>
+
+#include <asm/bitops.h>
+#include <asm/sections.h>
+#include <asm/percpu.h>
+#include <asm/processor.h>
+#include <asm/thread_info.h>
+#include <asm/atomic.h>
+
+#include <linux/memleak.h>
+
+#ifdef CONFIG_FRAME_POINTER
+#define MAX_TRACE		CONFIG_DEBUG_MEMLEAK_TRACE_LENGTH
+#else
+#define MAX_TRACE		1
+#endif
+
+#define PREINIT_POINTERS	CONFIG_DEBUG_MEMLEAK_PREINIT_POINTERS
+#define BYTES_PER_WORD		sizeof(void *)
+
+/* define this if you want the task stacks to be scanned (with an
+ * increased chance of false negatives) */
+/* #define TASK_STACK_SCAN */
+
+extern struct memleak_offset __memleak_offsets_start[];
+extern struct memleak_offset __memleak_offsets_end[];
+
+struct memleak_alias {
+	struct hlist_node node;
+	unsigned long offset;
+};
+
+struct memleak_scan_area {
+	struct hlist_node node;
+	unsigned long offset;
+	size_t length;
+};
+
+struct memleak_pointer {
+	struct list_head pointer_list;
+	struct list_head gray_list;
+	unsigned long pointer;
+	unsigned long offset;		/* padding */
+	size_t size;
+	int ref_count;			/* the minimum encounters of the value */
+	int count;			/* the ecounters of the value */
+	struct hlist_head *alias_list;
+	struct hlist_head area_list;	/* areas to be scanned (or empty for all) */
+	unsigned long trace[MAX_TRACE];
+};
+
+typedef enum {
+	MEMLEAK_ALLOC,
+	MEMLEAK_FREE,
+	MEMLEAK_PADDING,
+	MEMLEAK_NOT_LEAK,
+	MEMLEAK_IGNORE,
+	MEMLEAK_SCAN_AREA
+} memleak_action_t;
+
+struct memleak_preinit_pointer {
+	memleak_action_t type;
+	const void *pointer;
+	unsigned long offset;
+	size_t size;
+	int ref_count;
+};
+
+/* Pointer colors, encoded with count and ref_count:
+ *   - white - orphan block, i.e. not enough references to it (ref_count >= 1)
+ *   - gray  - referred at least once and therefore non-orphan (ref_count == 0)
+ *   - black - ignore; it doesn't contain references (text section) (ref_count == -1)
+ */
+#define COLOR_WHITE(pointer)	((pointer)->count != -1 && (pointer)->count < (pointer)->ref_count)
+#define COLOR_GRAY(pointer)	((pointer)->ref_count != -1 && (pointer)->count >= (pointer)->ref_count)
+#define COLOR_BLACK(pointer)	((pointer)->ref_count == -1)
+
+/* Tree storing the pointer aliases indexed by size */
+static RADIX_TREE(alias_tree, GFP_ATOMIC);
+/* Tree storing all the possible pointers, indexed by the pointer value */
+static RADIX_TREE(pointer_tree, GFP_ATOMIC);
+/* The list of all allocated pointers */
+static LIST_HEAD(pointer_list);
+/* The list of the gray pointers */
+static LIST_HEAD(gray_list);
+
+static kmem_cache_t *pointer_cache;
+/* Used to avoid recursive call via the kmalloc/kfree functions */
+static spinlock_t memleak_lock = SPIN_LOCK_UNLOCKED;
+static cpumask_t memleak_cpu_mask = CPU_MASK_NONE;
+static DEFINE_MUTEX(memleak_mutex);
+static atomic_t memleak_initialized = ATOMIC_INIT(0);
+static int __initdata preinit_pos = 0;
+static struct memleak_preinit_pointer __initdata preinit_pointers[PREINIT_POINTERS];
+/* last allocated pointer (optimization); protected by memleak_lock */
+static struct memleak_pointer *last_pointer = NULL;
+
+static void dump_pointer_info(struct memleak_pointer *pointer)
+{
+#ifdef CONFIG_KALLSYMS
+	char namebuf[KSYM_NAME_LEN + 1] = "";
+	char *modname;
+	unsigned long symsize;
+	unsigned long offset = 0;
+#endif
+#ifdef DEBUG
+	struct memleak_alias *alias;
+	struct hlist_node *elem;
+#endif
+	int i;
+
+	printk(KERN_NOTICE "kmemleak: pointer 0x%08lx:\n", pointer->pointer);
+#ifdef DEBUG
+	printk(KERN_NOTICE "  size = %d\n", pointer->size);
+	printk(KERN_NOTICE "  ref_count = %d\n", pointer->ref_count);
+	printk(KERN_NOTICE "  count = %d\n", pointer->count);
+	printk(KERN_NOTICE "  aliases:\n");
+	if (pointer->alias_list)
+		hlist_for_each_entry(alias, elem, pointer->alias_list, node)
+			printk(KERN_NOTICE "    0x%lx\n", alias->offset);
+	printk(KERN_NOTICE "  trace:\n");
+#endif
+	for (i = 0; i < MAX_TRACE; i++) {
+		unsigned long trace = pointer->trace[i];
+
+		if (!trace)
+			break;
+#ifdef CONFIG_KALLSYMS
+		kallsyms_lookup(trace, &symsize, &offset, &modname, namebuf);
+		printk(KERN_NOTICE "    %lx: <%s>\n", trace, namebuf);
+#else
+		printk(KERN_NOTICE "    %lx\n", trace);
+#endif
+	}
+}
+
+/* Insert an element into the aliases radix tree.
+ * Return 0 on success.
+ */
+static int insert_alias(unsigned long size, unsigned long offset)
+{
+	int ret = 0;
+	struct hlist_head *alias_list;
+	struct memleak_alias *alias;
+
+	if (size == 0 || offset == 0 || offset >= size) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	offset &= ~(BYTES_PER_WORD - 1);
+
+	alias_list = radix_tree_lookup(&alias_tree, size);
+	if (alias_list) {
+		struct hlist_node *elem;
+
+		hlist_for_each_entry(alias, elem, alias_list, node) {
+			if (alias->offset == offset) {
+				ret = -EEXIST;
+				goto out;
+			}
+		}
+	} else {
+		alias_list = kmalloc(sizeof(*alias_list), GFP_ATOMIC);
+		if (!alias_list)
+			panic("kmemleak: cannot allocate initial memory\n");
+		INIT_HLIST_HEAD(alias_list);
+
+		ret = radix_tree_insert(&alias_tree, size, alias_list);
+		if (ret)
+			panic("kmemleak: cannot insert into the aliases radix tree: %d\n", ret);
+	}
+
+	alias = kmalloc(sizeof(*alias), GFP_ATOMIC);
+	if (!alias)
+		panic("kmemleak: cannot allocate initial memory\n");
+	INIT_HLIST_NODE(&alias->node);
+	alias->offset = offset;
+
+	hlist_add_head(&alias->node, alias_list);
+
+ out:
+	return ret;
+}
+
+/* Insert pointer aliases the from the given array */
+void memleak_insert_aliases(struct memleak_offset *ml_off_start,
+				  struct memleak_offset *ml_off_end)
+{
+	struct memleak_offset *ml_off;
+	int i = 0;
+	unsigned long flags;
+	unsigned int cpu_id;
+
+	pr_debug("%s(0x%p, 0x%p)\n", __FUNCTION__, ml_off_start, ml_off_end);
+
+	spin_lock_irqsave(&memleak_lock, flags);
+
+	/* do not track the kmemleak allocated pointers */
+	cpu_id = smp_processor_id();
+	if (cpu_test_and_set(cpu_id, memleak_cpu_mask))
+		BUG();
+
+	/* primary aliases - container_of(member) */
+	for (ml_off = ml_off_start; ml_off < ml_off_end; ml_off++)
+		if (!insert_alias(ml_off->size, ml_off->offset))
+			i++;
+	pr_debug("kmemleak: found %d primary alias(es)\n", i);
+
+	/* secondary aliases - container_of(container_of(member)) */
+#ifdef CONFIG_DEBUG_MEMLEAK_SECONDARY_ALIASES
+	for (ml_off = ml_off_start; ml_off < ml_off_end; ml_off++) {
+		struct hlist_head *alias_list;
+		struct memleak_alias *alias;
+		struct hlist_node *elem;
+
+		alias_list = radix_tree_lookup(&alias_tree, ml_off->member_size);
+		if (!alias_list)
+			continue;
+
+		hlist_for_each_entry(alias, elem, alias_list, node)
+			if (!insert_alias(ml_off->size, ml_off->offset + alias->offset))
+				i++;
+	}
+	pr_debug("kmemleak: found %d alias(es)\n", i);
+#endif
+
+	cpu_clear(cpu_id, memleak_cpu_mask);
+	spin_unlock_irqrestore(&memleak_lock, flags);
+}
+EXPORT_SYMBOL_GPL(memleak_insert_aliases);
+
+static inline struct memleak_pointer *get_cached_pointer(unsigned long ptr)
+{
+	if (!last_pointer || ptr != last_pointer->pointer)
+		last_pointer = radix_tree_lookup(&pointer_tree, ptr);
+	return last_pointer;
+}
+
+static void create_pointer_aliases(struct memleak_pointer *pointer)
+{
+	struct memleak_alias *alias;
+	struct hlist_node *elem;
+	unsigned long ptr = pointer->pointer;
+	int err;
+
+	if (pointer->offset) {
+		err = radix_tree_insert(&pointer_tree, ptr + pointer->offset, pointer);
+		if (err) {
+			dump_stack();
+			panic("kmemleak: cannot insert alias into the pointer radix tree: %d\n", err);
+		}
+	}
+
+	if (pointer->alias_list) {
+		hlist_for_each_entry(alias, elem, pointer->alias_list, node) {
+			if (alias->offset >= pointer->size)
+				BUG();
+
+			err = radix_tree_insert(&pointer_tree, ptr
+						+ pointer->offset + alias->offset,
+						pointer);
+			if (err) {
+				dump_stack();
+				panic("kmemleak: cannot insert alias into the pointer radix tree: %d\n", err);
+			}
+		}
+	}
+}
+
+static void delete_pointer_aliases(struct memleak_pointer *pointer)
+{
+	struct memleak_alias *alias;
+	struct hlist_node *elem;
+	unsigned long ptr = pointer->pointer;
+
+	if (pointer->offset)
+		radix_tree_delete(&pointer_tree, ptr + pointer->offset);
+
+	if (pointer->alias_list)
+		hlist_for_each_entry(alias, elem, pointer->alias_list, node)
+			radix_tree_delete(&pointer_tree,
+					  ptr + pointer->offset + alias->offset);
+}
+
+/* Insert a pointer and its aliases into the pointer radix tree */
+static inline void create_pointer(unsigned long ptr, size_t size, int ref_count)
+{
+	struct memleak_pointer *pointer;
+	int err;
+#ifdef CONFIG_FRAME_POINTER
+	int i;
+	void *frame;
+#endif
+
+	pointer = kmem_cache_alloc(pointer_cache, SLAB_ATOMIC);
+	if (!pointer)
+		panic("kmemleak: cannot allocate a memleak_pointer structure\n");
+
+	last_pointer = pointer;
+
+	INIT_LIST_HEAD(&pointer->pointer_list);
+	INIT_LIST_HEAD(&pointer->gray_list);
+	INIT_HLIST_HEAD(&pointer->area_list);
+	pointer->pointer = ptr;
+	pointer->offset = 0;
+	pointer->size = size;
+	pointer->ref_count = ref_count;
+	pointer->count = -1;
+	pointer->alias_list = radix_tree_lookup(&alias_tree, size);
+
+#ifdef CONFIG_FRAME_POINTER
+	frame = __builtin_frame_address(0);
+	for (i = 0; i < MAX_TRACE; i++) {
+		void *stack = task_stack_page(current);
+
+		if (frame < stack || frame > stack + THREAD_SIZE - BYTES_PER_WORD) {
+			pointer->trace[i] = 0;
+			continue;
+		}
+
+		pointer->trace[i] = arch_call_address(frame);
+		frame = arch_prev_frame(frame);
+		/* we don't need the return to do_exit() */
+		if (kstack_end(frame))
+			pointer->trace[i] = 0;
+	}
+#else
+	pointer->trace[0] = (unsigned long)__builtin_return_address(0);
+#endif
+
+	err = radix_tree_insert(&pointer_tree, ptr, pointer);
+	if (err) {
+		dump_stack();
+		panic("kmemleak: cannot insert into the pointer radix tree: %d\n", err);
+	}
+
+	create_pointer_aliases(pointer);
+
+	list_add_tail(&pointer->pointer_list, &pointer_list);
+}
+
+/* Remove a pointer and its aliases from the pointer radix tree */
+static inline void delete_pointer(unsigned long ptr)
+{
+	struct hlist_node *elem, *tmp;
+	struct memleak_pointer *pointer;
+	struct memleak_scan_area *area;
+
+	pointer = radix_tree_delete(&pointer_tree, ptr);
+	if (!pointer) {
+		dump_stack();
+		printk(KERN_WARNING "kmemleak: freeing unknown pointer value 0x%08lx\n", ptr);
+		return;
+	}
+	if (pointer->pointer != ptr) {
+		dump_stack();
+		dump_pointer_info(pointer);
+		panic("kmemleak: freeing pointer by alias 0x%08lx\n", ptr);
+	}
+
+	if (last_pointer && ptr == last_pointer->pointer)
+		last_pointer = NULL;
+
+#ifdef DEBUG
+	if (COLOR_WHITE(pointer)) {
+		dump_stack();
+		dump_pointer_info(pointer);
+		printk(KERN_WARNING "kmemleak: freeing orphan pointer 0x%08lx\n", ptr);
+	}
+#endif
+
+	delete_pointer_aliases(pointer);
+
+	/* free the scanning areas */
+	hlist_for_each_entry_safe(area, elem, tmp, &pointer->area_list, node) {
+		hlist_del(elem);
+		kfree(area);
+	}
+
+	list_del(&pointer->pointer_list);
+	kmem_cache_free(pointer_cache, pointer);
+}
+
+/* Re-create the pointer aliases according to the new size/offset
+ * information */
+static inline void unpad_pointer(unsigned long ptr, unsigned long offset,
+				 size_t size)
+{
+	struct memleak_pointer *pointer;
+
+	pointer = get_cached_pointer(ptr);
+	if (!pointer) {
+		dump_stack();
+		panic("kmemleak: resizing unknown pointer value 0x%08lx\n", ptr);
+	}
+	if (pointer->pointer != ptr) {
+		dump_stack();
+		dump_pointer_info(pointer);
+		panic("kmemleak: resizing pointer by alias 0x%08lx\n", ptr);
+	}
+
+	if (offset == pointer->offset && size == pointer->size)
+		return;
+
+	delete_pointer_aliases(pointer);
+
+	/* we don't update the pointer->size because the real block
+	 * size should be scanned. We don't worry about random data in
+	 * the unused area because of the object poisoning */
+	pointer->offset = offset;
+	pointer->alias_list = radix_tree_lookup(&alias_tree, size);
+
+	create_pointer_aliases(pointer);
+}
+
+/* Make a pointer permanently gray (false positive) */
+static inline void make_gray_pointer(unsigned long ptr)
+{
+	struct memleak_pointer *pointer;
+
+	pointer = get_cached_pointer(ptr);
+	if (!pointer) {
+		dump_stack();
+		panic("kmemleak: graying unknown pointer value 0x%08lx\n", ptr);
+	}
+	if (pointer->pointer != ptr) {
+		dump_stack();
+		dump_pointer_info(pointer);
+		panic("kmemleak: graying pointer by alias 0x%08lx\n", ptr);
+	}
+
+	pointer->ref_count = 0;
+}
+
+/* Mark the pointer as black */
+static inline void make_black_pointer(unsigned long ptr)
+{
+	struct memleak_pointer *pointer;
+
+	pointer = get_cached_pointer(ptr);
+	if (!pointer) {
+		dump_stack();
+		panic("kmemleak: blacking unknown pointer value 0x%08lx\n", ptr);
+	}
+	if (pointer->pointer != ptr) {
+		dump_stack();
+		dump_pointer_info(pointer);
+		panic("kmemleak: blacking pointer by alias 0x%08lx\n", ptr);
+	}
+
+	pointer->ref_count = -1;
+}
+
+/* Add a scanning area to the pointer */
+static inline void add_scan_area(unsigned long ptr, unsigned long offset, size_t length)
+{
+	struct memleak_pointer *pointer;
+	struct memleak_scan_area *area;
+
+	pointer = get_cached_pointer(ptr);
+	if (!pointer) {
+		dump_stack();
+		panic("kmemleak: adding scan area to unknown pointer value 0x%08lx\n", ptr);
+	}
+	if (pointer->pointer != ptr) {
+		dump_stack();
+		dump_pointer_info(pointer);
+		panic("kmemleak: adding scan area to pointer by alias 0x%08lx\n", ptr);
+	}
+	if (offset + length > pointer->size) {
+		dump_stack();
+		dump_pointer_info(pointer);
+		panic("kmemleak: scan area larger than block 0x%08lx\n", ptr);
+	}
+
+	area = kmalloc(sizeof(*area), GFP_ATOMIC);
+	if (!area)
+		panic("kmemleak: cannot allocate a scan area\n");
+
+	INIT_HLIST_NODE(&area->node);
+	area->offset = offset;
+	area->length = length;
+
+	hlist_add_head(&area->node, &pointer->area_list);
+}
+
+/* Allocation function hook */
+void memleak_alloc(const void *ptr, size_t size, int ref_count)
+{
+	unsigned long flags;
+	unsigned int cpu_id;
+
+	if (!ptr)
+		return;
+
+	local_irq_save(flags);
+	cpu_id = get_cpu();
+
+	/* avoid recursive calls. After disabling the interrupts, the
+	 * only calls to this function on the same CPU should be from
+	 * kmemleak itself and we ignore them. Calls from other CPU's
+	 * would wait on the spin_lock.
+	 */
+	if (cpu_test_and_set(cpu_id, memleak_cpu_mask))
+		goto out;
+
+	pr_debug("%s(0x%p, %d, %d)\n", __FUNCTION__, ptr, size, ref_count);
+
+	if (!atomic_read(&memleak_initialized)) {
+		/* no need for SMP locking since this block is
+		 * executed before the other CPUs are started */
+		struct memleak_preinit_pointer *pointer;
+
+		BUG_ON(cpu_id != 0);
+
+		if (preinit_pos >= PREINIT_POINTERS)
+			panic("kmemleak: preinit pointers buffer overflow\n");
+		pointer = &preinit_pointers[preinit_pos++];
+
+		pointer->type = MEMLEAK_ALLOC;
+		pointer->pointer = ptr;
+		pointer->size = size;
+		pointer->ref_count = ref_count;
+
+		goto unmask;
+	}
+
+	spin_lock(&memleak_lock);
+	create_pointer((unsigned long)ptr, size, ref_count);
+	spin_unlock(&memleak_lock);
+
+ unmask:
+	cpu_clear(cpu_id, memleak_cpu_mask);
+ out:
+	put_cpu_no_resched();
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(memleak_alloc);
+
+/* Freeing function hook */
+void memleak_free(const void *ptr)
+{
+	unsigned long flags;
+	unsigned int cpu_id;
+
+	if (!ptr)
+		return;
+
+	local_irq_save(flags);
+	cpu_id = get_cpu();
+
+	/* avoid recursive calls. See memleak_alloc() for an explanation */
+	if (cpu_test_and_set(cpu_id, memleak_cpu_mask))
+		goto out;
+
+	pr_debug("%s(0x%p)\n", __FUNCTION__, ptr);
+
+	if (!atomic_read(&memleak_initialized)) {
+		struct memleak_preinit_pointer *pointer;
+
+		BUG_ON(cpu_id != 0);
+
+		if (preinit_pos >= PREINIT_POINTERS)
+			panic("kmemleak: preinit pointers buffer overflow\n");
+		pointer = &preinit_pointers[preinit_pos++];
+
+		pointer->type = MEMLEAK_FREE;
+		pointer->pointer = ptr;
+
+		goto unmask;
+	}
+
+	spin_lock(&memleak_lock);
+	delete_pointer((unsigned long)ptr);
+	spin_unlock(&memleak_lock);
+
+ unmask:
+	cpu_clear(cpu_id, memleak_cpu_mask);
+ out:
+	put_cpu_no_resched();
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(memleak_free);
+
+/* Change the size and location information of an allocated memory
+ * block (this is needed for allocations padding the object) */
+void memleak_padding(const void *ptr, unsigned long offset, size_t size)
+{
+	unsigned long flags;
+	unsigned int cpu_id;
+
+	if (!ptr)
+		return;
+
+	local_irq_save(flags);
+	cpu_id = get_cpu();
+
+	/* avoid recursive calls. See memleak_alloc() for an explanation */
+	if (cpu_test_and_set(cpu_id, memleak_cpu_mask))
+		goto out;
+
+	pr_debug("%s(0x%p, %d)\n", __FUNCTION__, ptr, size);
+
+	if (!atomic_read(&memleak_initialized)) {
+		struct memleak_preinit_pointer *pointer;
+
+		BUG_ON(cpu_id != 0);
+
+		if (preinit_pos >= PREINIT_POINTERS)
+			panic("kmemleak: preinit pointers buffer overflow\n");
+		pointer = &preinit_pointers[preinit_pos++];
+
+		pointer->type = MEMLEAK_PADDING;
+		pointer->pointer = ptr;
+		pointer->offset = offset;
+		pointer->size = size;
+
+		goto unmask;
+	}
+
+	spin_lock(&memleak_lock);
+	unpad_pointer((unsigned long)ptr, offset, size);
+	spin_unlock(&memleak_lock);
+
+ unmask:
+	cpu_clear(cpu_id, memleak_cpu_mask);
+ out:
+	put_cpu_no_resched();
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL(memleak_padding);
+
+/* Mark a pointer as a false positive */
+void memleak_not_leak(const void *ptr)
+{
+	unsigned long flags;
+	unsigned int cpu_id;
+
+	if (!ptr)
+		return;
+
+	local_irq_save(flags);
+	cpu_id = get_cpu();
+
+	/* avoid recursive calls. See memleak_alloc() for an explanation */
+	if (cpu_test_and_set(cpu_id, memleak_cpu_mask))
+		goto out;
+
+	pr_debug("%s(0x%p)\n", __FUNCTION__, ptr);
+
+	if (!atomic_read(&memleak_initialized)) {
+		struct memleak_preinit_pointer *pointer;
+
+		BUG_ON(cpu_id != 0);
+
+		if (preinit_pos >= PREINIT_POINTERS)
+			panic("kmemleak: preinit pointers buffer overflow\n");
+		pointer = &preinit_pointers[preinit_pos++];
+
+		pointer->type = MEMLEAK_NOT_LEAK;
+		pointer->pointer = ptr;
+
+		goto unmask;
+	}
+
+	spin_lock(&memleak_lock);
+	make_gray_pointer((unsigned long)ptr);
+	spin_unlock(&memleak_lock);
+
+ unmask:
+	cpu_clear(cpu_id, memleak_cpu_mask);
+ out:
+	put_cpu_no_resched();
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL(memleak_not_leak);
+
+/* Ignore this memory block */
+void memleak_ignore(const void *ptr)
+{
+	unsigned long flags;
+	unsigned int cpu_id;
+
+	if (!ptr)
+		return;
+
+	local_irq_save(flags);
+	cpu_id = get_cpu();
+
+	/* avoid recursive calls. See memleak_alloc() for an explanation */
+	if (cpu_test_and_set(cpu_id, memleak_cpu_mask))
+		goto out;
+
+	pr_debug("%s(0x%p)\n", __FUNCTION__, ptr);
+
+	if (!atomic_read(&memleak_initialized)) {
+		struct memleak_preinit_pointer *pointer;
+
+		BUG_ON(cpu_id != 0);
+
+		if (preinit_pos >= PREINIT_POINTERS)
+			panic("kmemleak: preinit pointers buffer overflow\n");
+		pointer = &preinit_pointers[preinit_pos++];
+
+		pointer->type = MEMLEAK_IGNORE;
+		pointer->pointer = ptr;
+
+		goto unmask;
+	}
+
+	spin_lock(&memleak_lock);
+	make_black_pointer((unsigned long)ptr);
+	spin_unlock(&memleak_lock);
+
+ unmask:
+	cpu_clear(cpu_id, memleak_cpu_mask);
+ out:
+	put_cpu_no_resched();
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL(memleak_ignore);
+
+/* Add a scanning area to a pointer */
+void memleak_scan_area(const void *ptr, unsigned long offset, size_t length)
+{
+	unsigned long flags;
+	unsigned int cpu_id;
+
+	if (!ptr)
+		return;
+
+	local_irq_save(flags);
+	cpu_id = get_cpu();
+
+	/* avoid recursive calls. See memleak_alloc() for an explanation */
+	if (cpu_test_and_set(cpu_id, memleak_cpu_mask))
+		goto out;
+
+	pr_debug("%s(0x%p)\n", __FUNCTION__, ptr);
+
+	if (!atomic_read(&memleak_initialized)) {
+		struct memleak_preinit_pointer *pointer;
+
+		BUG_ON(cpu_id != 0);
+
+		if (preinit_pos >= PREINIT_POINTERS)
+			panic("kmemleak: preinit pointers buffer overflow\n");
+		pointer = &preinit_pointers[preinit_pos++];
+
+		pointer->type = MEMLEAK_SCAN_AREA;
+		pointer->pointer = ptr;
+		pointer->offset = offset;
+		pointer->size = length;
+
+		goto unmask;
+	}
+
+	spin_lock(&memleak_lock);
+	add_scan_area((unsigned long)ptr, offset, length);
+	spin_unlock(&memleak_lock);
+
+ unmask:
+	cpu_clear(cpu_id, memleak_cpu_mask);
+ out:
+	put_cpu_no_resched();
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL(memleak_scan_area);
+
+/* Scan a block of memory (exclusive range) for pointers and move
+ * those found to the gray list
+ */
+static void memleak_scan_block(void *_start, void *_end)
+{
+	unsigned long *ptr;
+	unsigned long *start = (unsigned long *)ALIGN((unsigned long)_start,
+						      BYTES_PER_WORD);
+	unsigned long *end = _end;
+
+	for (ptr = start; ptr < end; ptr++) {
+		struct memleak_pointer *pointer =
+			radix_tree_lookup(&pointer_tree,
+					  (*ptr) & ~(BYTES_PER_WORD - 1));
+		if (!pointer)
+			continue;
+		if (!COLOR_WHITE(pointer))
+			continue;
+
+		pointer->count++;
+		/* this can happen during the grey_list traversal */
+		if (COLOR_GRAY(pointer))
+			list_add_tail_rcu(&pointer->gray_list, &gray_list);
+	}
+}
+
+/* Scan a memory block represented by a memleak_pointer */
+static inline void memleak_scan_pointer(struct memleak_pointer *pointer)
+{
+	struct memleak_scan_area *area;
+	struct hlist_node *elem;
+
+	if (hlist_empty(&pointer->area_list))
+		memleak_scan_block((void *)pointer->pointer,
+				   (void *)(pointer->pointer + pointer->size));
+	else
+		hlist_for_each_entry(area, elem, &pointer->area_list, node) {
+			unsigned long ptr = pointer->pointer + area->offset;
+
+			memleak_scan_block((void *)ptr, (void *)(ptr + area->length));
+		}
+}
+
+/* Scan the memory and print the orphan pointers */
+static void memleak_scan(void)
+{
+	unsigned long flags;
+	struct memleak_pointer *pointer;
+#ifdef TASK_STACK_SCAN
+	struct task_struct *task;
+#endif
+	int i;
+
+	spin_lock_irqsave(&memleak_lock, flags);
+
+	list_for_each_entry(pointer, &pointer_list, pointer_list) {
+		pointer->count = 0;
+		if (COLOR_GRAY(pointer))
+			list_add_tail(&pointer->gray_list, &gray_list);
+	}
+
+	/* data/bss scanning */
+	memleak_scan_block(_sdata, _edata);
+	memleak_scan_block(__bss_start, __bss_stop);
+
+#ifdef CONFIG_SMP
+	/* per-cpu scanning */
+	for (i = 0; i < NR_CPUS; i++)
+		memleak_scan_block(__per_cpu_offset[i] + __per_cpu_start,
+				   __per_cpu_offset[i] + __per_cpu_end);
+#endif
+
+	/* mem_map scanning */
+	for_each_online_node(i) {
+		struct page *page, *end;
+
+		page = NODE_MEM_MAP(i);
+		end  = page + NODE_DATA(i)->node_spanned_pages;
+
+		memleak_scan_block(page, end);
+	}
+
+#ifdef TASK_STACK_SCAN
+	for_each_process(task)
+		memleak_scan_block(task_stack_page(task),
+				   task_stack_page(task) + THREAD_SIZE);
+#endif
+
+	/* gray_list scanning */
+	rcu_read_lock();
+	list_for_each_entry_rcu(pointer, &gray_list, gray_list) {
+		memleak_scan_pointer(pointer);
+		list_del_rcu(&pointer->gray_list);
+	}
+	rcu_read_unlock();
+
+	spin_unlock_irqrestore(&memleak_lock, flags);
+}
+
+#ifdef CONFIG_DEBUG_FS
+static void *memleak_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct memleak_pointer *pointer;
+	loff_t n = *pos;
+	unsigned long flags;
+
+	mutex_lock(&memleak_mutex);
+
+	if (!n)
+		memleak_scan();
+
+	spin_lock_irqsave(&memleak_lock, flags);
+
+	list_for_each_entry(pointer, &pointer_list, pointer_list)
+		if (!n--)
+			goto out;
+	pointer = NULL;
+
+ out:
+	spin_unlock_irqrestore(&memleak_lock, flags);
+	return pointer;
+}
+
+static void *memleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct list_head *n = ((struct memleak_pointer *)v)->pointer_list.next;
+
+	++(*pos);
+
+	if (n != &pointer_list)
+		return list_entry(n, struct memleak_pointer, pointer_list);
+	return NULL;
+}
+
+static void memleak_seq_stop(struct seq_file *seq, void *v)
+{
+	mutex_unlock(&memleak_mutex);
+}
+
+static int memleak_seq_show(struct seq_file *seq, void *v)
+{
+	const struct memleak_pointer *pointer = v;
+#ifdef CONFIG_KALLSYMS
+	char namebuf[KSYM_NAME_LEN + 1] = "";
+	char *modname;
+	unsigned long symsize;
+	unsigned long offset = 0;
+#endif
+	int i;
+
+	if (!COLOR_WHITE(pointer))
+		return 0;
+
+	seq_printf(seq, "orphan pointer 0x%08lx (size %d):\n",
+		   pointer->pointer, pointer->size);
+
+	for (i = 0; i < MAX_TRACE; i++) {
+		unsigned long trace = pointer->trace[i];
+		if (!trace)
+			break;
+
+#ifdef CONFIG_KALLSYMS
+		kallsyms_lookup(trace, &symsize, &offset, &modname, namebuf);
+		seq_printf(seq, "  %lx: <%s>\n", trace, namebuf);
+#else
+		seq_printf(seq, "  %lx\n", trace);
+#endif
+	}
+
+	return 0;
+}
+
+static 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)
+{
+	return seq_open(file, &memleak_seq_ops);
+}
+
+static struct file_operations memleak_fops = {
+	.owner	 = THIS_MODULE,
+	.open    = memleak_seq_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = seq_release,
+};
+#endif					/* CONFIG_DEBUG_FS */
+
+/* KMemLeak initialization. Set up the radix tree for the pointer aliases */
+void __init memleak_init(void)
+{
+	int i = 0;
+	unsigned long flags;
+
+	pointer_cache = kmem_cache_create("pointer_cache", sizeof(struct memleak_pointer),
+					  0, SLAB_PANIC, NULL, NULL);
+	if (!pointer_cache)
+		panic("kmemleak: cannot create the pointer cache\n");
+
+	memleak_insert_aliases(__memleak_offsets_start, __memleak_offsets_end);
+
+	/* no need to hold the spinlock as SMP is not initialized
+	 * yet. Holding it here would lead to a deadlock */
+	local_irq_save(flags);
+
+	atomic_set(&memleak_initialized, 1);
+
+	/* execute the buffered memleak actions */
+	pr_debug("kmemleak: %d preinit actions\n", preinit_pos);
+	for (i = 0; i < preinit_pos; i++) {
+		struct memleak_preinit_pointer *pointer = &preinit_pointers[i];
+
+		switch (pointer->type) {
+		case MEMLEAK_ALLOC:
+			memleak_alloc(pointer->pointer, pointer->size,
+				      pointer->ref_count);
+			break;
+		case MEMLEAK_FREE:
+			memleak_free(pointer->pointer);
+			break;
+		case MEMLEAK_PADDING:
+			memleak_padding(pointer->pointer, pointer->offset,
+					pointer->size);
+			break;
+		case MEMLEAK_NOT_LEAK:
+			memleak_not_leak(pointer->pointer);
+			break;
+		case MEMLEAK_IGNORE:
+			memleak_ignore(pointer->pointer);
+			break;
+		case MEMLEAK_SCAN_AREA:
+			memleak_scan_area(pointer->pointer,
+					  pointer->offset, pointer->size);
+			break;
+		default:
+			BUG();
+		}
+	}
+
+	local_irq_restore(flags);
+
+	printk(KERN_INFO "Kernel memory leak detector initialized\n");
+}
+
+/* Late initialization function */
+int __init memleak_late_init(void)
+{
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *dentry;
+
+	dentry = debugfs_create_file("memleak", S_IRUGO, NULL, NULL,
+				     &memleak_fops);
+	if (!dentry)
+		return -ENOMEM;
+#endif
+	pr_debug("kmemleak: late initialization completed\n");
+
+	return 0;
+}
+late_initcall(memleak_late_init);