kmemleak.c 52.5 KB
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/*
 * 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
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 *   blocks. The object_tree_root is a red black tree used to look-up
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 *   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
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 *   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
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 *
 * 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.
 */

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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/sched.h>
#include <linux/jiffies.h>
#include <linux/delay.h>
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#include <linux/export.h>
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#include <linux/kthread.h>
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#include <linux/rbtree.h>
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#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/cpumask.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/stacktrace.h>
#include <linux/cache.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/mmzone.h>
#include <linux/slab.h>
#include <linux/thread_info.h>
#include <linux/err.h>
#include <linux/uaccess.h>
#include <linux/string.h>
#include <linux/nodemask.h>
#include <linux/mm.h>
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#include <linux/workqueue.h>
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#include <linux/crc32.h>
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#include <asm/sections.h>
#include <asm/processor.h>
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#include <linux/atomic.h>
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#include <linux/kmemcheck.h>
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#include <linux/kmemleak.h>
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#include <linux/memory_hotplug.h>
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/*
 * 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 */
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#define MAX_SCAN_SIZE		4096	/* maximum size of a scanned block */
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#define BYTES_PER_POINTER	sizeof(void *)

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/* GFP bitmask for kmemleak internal allocations */
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#define gfp_kmemleak_mask(gfp)	(((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \
				 __GFP_NORETRY | __GFP_NOMEMALLOC | \
				 __GFP_NOWARN)
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/* scanning area inside a memory block */
struct kmemleak_scan_area {
	struct hlist_node node;
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	unsigned long start;
	size_t size;
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};

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#define KMEMLEAK_GREY	0
#define KMEMLEAK_BLACK	-1

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/*
 * 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
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 * rb_node are already protected by the corresponding locks or mutex (see
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 * 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;
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	struct rb_node rb_node;
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	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;
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	/* checksum for detecting modified objects */
	u32 checksum;
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	/* 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)

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/* 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

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/* 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);
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/* 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 */
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static DEFINE_RWLOCK(kmemleak_lock);

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

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

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

static struct task_struct *scan_thread;
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/* used to avoid reporting of recently allocated objects */
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static unsigned long jiffies_min_age;
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static unsigned long jiffies_last_scan;
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/* delay between automatic memory scannings */
static signed long jiffies_scan_wait;
/* enables or disables the task stacks scanning */
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static int kmemleak_stack_scan = 1;
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/* protects the memory scanning, parameters and debug/kmemleak file access */
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static DEFINE_MUTEX(scan_mutex);
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/* setting kmemleak=on, will set this var, skipping the disable */
static int kmemleak_skip_disable;

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/*
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 * Early object allocation/freeing logging. Kmemleak is initialized after the
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 * kernel allocator. However, both the kernel allocator and kmemleak may
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 * allocate memory blocks which need to be tracked. Kmemleak defines an
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 * arbitrary buffer to hold the allocation/freeing information before it is
 * fully initialized.
 */

/* kmemleak operation type for early logging */
enum {
	KMEMLEAK_ALLOC,
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	KMEMLEAK_ALLOC_PERCPU,
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	KMEMLEAK_FREE,
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	KMEMLEAK_FREE_PART,
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	KMEMLEAK_FREE_PERCPU,
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	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 */
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	unsigned long trace[MAX_TRACE];	/* stack trace */
	unsigned int trace_len;		/* stack trace length */
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};

/* early logging buffer and current position */
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static struct early_log
	early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
static int crt_early_log __initdata;
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static void kmemleak_disable(void);

/*
 * Print a warning and dump the stack trace.
 */
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#define kmemleak_warn(x...)	do {		\
	pr_warning(x);				\
	dump_stack();				\
	atomic_set(&kmemleak_warning, 1);	\
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} while (0)

/*
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 * Macro invoked when a serious kmemleak condition occurred and cannot be
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 * recovered from. Kmemleak will be disabled and further allocation/freeing
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 * tracing no longer available.
 */
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#define kmemleak_stop(x...)	do {	\
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	kmemleak_warn(x);		\
	kmemleak_disable();		\
} while (0)

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/*
 * 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;
	int i, len, remaining;
	unsigned char linebuf[HEX_ROW_SIZE * 5];

	/* limit the number of lines to HEX_MAX_LINES */
	remaining = len =
		min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE));

	seq_printf(seq, "  hex dump (first %d bytes):\n", len);
	for (i = 0; i < len; i += HEX_ROW_SIZE) {
		int linelen = min(remaining, HEX_ROW_SIZE);

		remaining -= HEX_ROW_SIZE;
		hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE,
				   HEX_GROUP_SIZE, linebuf, sizeof(linebuf),
				   HEX_ASCII);
		seq_printf(seq, "    %s\n", linebuf);
	}
}

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/*
 * 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.
 */
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static bool color_white(const struct kmemleak_object *object)
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{
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	return object->count != KMEMLEAK_BLACK &&
		object->count < object->min_count;
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}

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

/*
 * 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.
 */
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static bool unreferenced_object(struct kmemleak_object *object)
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{
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	return (color_white(object) && object->flags & OBJECT_ALLOCATED) &&
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		time_before_eq(object->jiffies + jiffies_min_age,
			       jiffies_last_scan);
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}

/*
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 * Printing of the unreferenced objects information to the seq file. The
 * print_unreferenced function must be called with the object->lock held.
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 */
static void print_unreferenced(struct seq_file *seq,
			       struct kmemleak_object *object)
{
	int i;
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	unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
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	seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
		   object->pointer, object->size);
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	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
		   object->comm, object->pid, object->jiffies,
		   msecs_age / 1000, msecs_age % 1000);
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	hex_dump_object(seq, object);
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	seq_printf(seq, "  backtrace:\n");
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	for (i = 0; i < object->trace_len; i++) {
		void *ptr = (void *)object->trace[i];
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		seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
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	}
}

/*
 * 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;

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	pr_notice("Object 0x%08lx (size %zu):\n",
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		  object->pointer, object->size);
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	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);
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	pr_notice("  flags = 0x%lx\n", object->flags);
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	pr_notice("  checksum = %d\n", object->checksum);
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	pr_notice("  backtrace:\n");
	print_stack_trace(&trace, 4);
}

/*
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 * Look-up a memory block metadata (kmemleak_object) in the object search
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 * 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)
{
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	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 {
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			kmemleak_warn("Found object by alias at 0x%08lx\n",
				      ptr);
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			dump_object_info(object);
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			break;
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		}
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	}
	return NULL;
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}

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

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

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

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

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

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

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

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

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

	return object;
}

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/*
 * 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;
}

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/*
 * Create the metadata (struct kmemleak_object) corresponding to an allocated
 * memory block and add it to the object_list and object_tree_root.
 */
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static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
					     int min_count, gfp_t gfp)
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{
	unsigned long flags;
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	struct kmemleak_object *object, *parent;
	struct rb_node **link, *rb_parent;
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	object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
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	if (!object) {
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		pr_warning("Cannot allocate a kmemleak_object structure\n");
		kmemleak_disable();
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		return NULL;
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	}

	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);
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	object->flags = OBJECT_ALLOCATED;
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	object->pointer = ptr;
	object->size = size;
	object->min_count = min_count;
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	object->count = 0;			/* white color initially */
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	object->jiffies = jiffies;
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	object->checksum = 0;
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	/* 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 */
561
	object->trace_len = __save_stack_trace(object->trace);
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	write_lock_irqsave(&kmemleak_lock, flags);
564

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	min_addr = min(min_addr, ptr);
	max_addr = max(max_addr, ptr + size);
567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586
	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)\n",
				      ptr);
			kmem_cache_free(object_cache, object);
			object = parent;
			spin_lock(&object->lock);
			dump_object_info(object);
			spin_unlock(&object->lock);
			goto out;
		}
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	}
588 589 590
	rb_link_node(&object->rb_node, rb_parent, link);
	rb_insert_color(&object->rb_node, &object_tree_root);

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	list_add_tail_rcu(&object->object_list, &object_list);
out:
	write_unlock_irqrestore(&kmemleak_lock, flags);
594
	return object;
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}

/*
 * Remove the metadata (struct kmemleak_object) for a memory block from the
 * object_list and object_tree_root and decrement its use_count.
 */
601
static void __delete_object(struct kmemleak_object *object)
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{
	unsigned long flags;

	write_lock_irqsave(&kmemleak_lock, flags);
606
	rb_erase(&object->rb_node, &object_tree_root);
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	list_del_rcu(&object->object_list);
	write_unlock_irqrestore(&kmemleak_lock, flags);

	WARN_ON(!(object->flags & OBJECT_ALLOCATED));
611
	WARN_ON(atomic_read(&object->use_count) < 2);
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	/*
	 * 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);
}

623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680
/*
 * 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_get_object(ptr, 0);
	if (!object) {
#ifdef DEBUG
		kmemleak_warn("Freeing unknown object at 0x%08lx\n",
			      ptr);
#endif
		return;
	}
	__delete_object(object);
	put_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_get_object(ptr, 1);
	if (!object) {
#ifdef DEBUG
		kmemleak_warn("Partially freeing unknown object at 0x%08lx "
			      "(size %zu)\n", ptr, size);
#endif
		return;
	}
	__delete_object(object);

	/*
	 * 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);

	put_object(object);
}
681 682 683 684 685 686 687 688 689

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)
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{
	unsigned long flags;
692 693 694 695 696 697 698 699

	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)
{
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	struct kmemleak_object *object;

	object = find_and_get_object(ptr, 0);
	if (!object) {
704 705 706 707
		kmemleak_warn("Trying to color unknown object "
			      "at 0x%08lx as %s\n", ptr,
			      (color == KMEMLEAK_GREY) ? "Grey" :
			      (color == KMEMLEAK_BLACK) ? "Black" : "Unknown");
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		return;
	}
710
	paint_it(object, color);
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	put_object(object);
}

714
/*
715
 * Mark an object permanently as gray-colored so that it can no longer be
716 717 718 719 720 721 722
 * 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);
}

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/*
 * Mark the object as black-colored so that it is ignored from scans and
 * reporting.
 */
static void make_black_object(unsigned long ptr)
{
729
	paint_ptr(ptr, KMEMLEAK_BLACK);
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}

/*
 * 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.
 */
736
static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
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{
	unsigned long flags;
	struct kmemleak_object *object;
	struct kmemleak_scan_area *area;

742
	object = find_and_get_object(ptr, 1);
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	if (!object) {
J
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		kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
			      ptr);
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		return;
	}

749
	area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
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	if (!area) {
751
		pr_warning("Cannot allocate a scan area\n");
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		goto out;
	}

	spin_lock_irqsave(&object->lock, flags);
756
	if (ptr + size > object->pointer + object->size) {
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		kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
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		dump_object_info(object);
		kmem_cache_free(scan_area_cache, area);
		goto out_unlock;
	}

	INIT_HLIST_NODE(&area->node);
764 765
	area->start = ptr;
	area->size = size;
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	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) {
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		kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
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		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.
 */
800
static void __init log_early(int op_type, const void *ptr, size_t size,
801
			     int min_count)
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{
	unsigned long flags;
	struct early_log *log;

806 807 808 809 810 811
	if (atomic_read(&kmemleak_error)) {
		/* kmemleak stopped recording, just count the requests */
		crt_early_log++;
		return;
	}

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	if (crt_early_log >= ARRAY_SIZE(early_log)) {
813
		kmemleak_disable();
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		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;
827
	log->trace_len = __save_stack_trace(log->trace);
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	crt_early_log++;
	local_irq_restore(flags);
}

832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848
/*
 * 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 (!atomic_read(&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,
849
			       log->min_count, GFP_ATOMIC);
850 851
	if (!object)
		goto out;
852 853 854 855 856
	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);
857
out:
858 859 860
	rcu_read_unlock();
}

861 862 863 864 865 866 867 868 869 870 871 872 873 874
/*
 * 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);
	}
}

875 876 877 878 879 880 881 882 883 884 885 886 887
/**
 * 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.).
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 */
889 890
void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
			  gfp_t gfp)
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{
	pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		create_object((unsigned long)ptr, size, min_count, gfp);
	else if (atomic_read(&kmemleak_early_log))
897
		log_early(KMEMLEAK_ALLOC, ptr, size, min_count);
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}
EXPORT_SYMBOL_GPL(kmemleak_alloc);

901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928
/**
 * kmemleak_alloc_percpu - register a newly allocated __percpu object
 * @ptr:	__percpu pointer to beginning of the object
 * @size:	size of the object
 *
 * This function is called from the kernel percpu allocator when a new object
 * (memory block) is allocated (alloc_percpu). It assumes GFP_KERNEL
 * allocation.
 */
void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
{
	unsigned int cpu;

	pr_debug("%s(0x%p, %zu)\n", __func__, ptr, size);

	/*
	 * Percpu allocations are only scanned and not reported as leaks
	 * (min_count is set to 0).
	 */
	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		for_each_possible_cpu(cpu)
			create_object((unsigned long)per_cpu_ptr(ptr, cpu),
				      size, 0, GFP_KERNEL);
	else if (atomic_read(&kmemleak_early_log))
		log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);

929 930 931 932 933 934
/**
 * 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.).
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 */
936
void __ref kmemleak_free(const void *ptr)
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{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
941
		delete_object_full((unsigned long)ptr);
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	else if (atomic_read(&kmemleak_early_log))
943
		log_early(KMEMLEAK_FREE, ptr, 0, 0);
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}
EXPORT_SYMBOL_GPL(kmemleak_free);

947 948 949 950 951 952 953 954
/**
 * 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).
955
 */
956
void __ref kmemleak_free_part(const void *ptr, size_t size)
957 958 959 960 961 962
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		delete_object_part((unsigned long)ptr, size);
	else if (atomic_read(&kmemleak_early_log))
963
		log_early(KMEMLEAK_FREE_PART, ptr, size, 0);
964 965 966
}
EXPORT_SYMBOL_GPL(kmemleak_free_part);

967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988
/**
 * 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)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		for_each_possible_cpu(cpu)
			delete_object_full((unsigned long)per_cpu_ptr(ptr,
								      cpu));
	else if (atomic_read(&kmemleak_early_log))
		log_early(KMEMLEAK_FREE_PERCPU, ptr, 0, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free_percpu);

989 990 991 992 993 994
/**
 * 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.
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 */
996
void __ref kmemleak_not_leak(const void *ptr)
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{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		make_gray_object((unsigned long)ptr);
	else if (atomic_read(&kmemleak_early_log))
1003
		log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0);
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}
EXPORT_SYMBOL(kmemleak_not_leak);

1007 1008 1009 1010 1011 1012 1013 1014
/**
 * 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.
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 */
1016
void __ref kmemleak_ignore(const void *ptr)
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{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		make_black_object((unsigned long)ptr);
	else if (atomic_read(&kmemleak_early_log))
1023
		log_early(KMEMLEAK_IGNORE, ptr, 0, 0);
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}
EXPORT_SYMBOL(kmemleak_ignore);

1027 1028 1029 1030 1031 1032 1033 1034 1035 1036
/**
 * 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.
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 */
1038
void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
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{
	pr_debug("%s(0x%p)\n", __func__, ptr);

1042
	if (atomic_read(&kmemleak_enabled) && ptr && size && !IS_ERR(ptr))
1043
		add_scan_area((unsigned long)ptr, size, gfp);
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	else if (atomic_read(&kmemleak_early_log))
1045
		log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0);
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}
EXPORT_SYMBOL(kmemleak_scan_area);

1049 1050 1051 1052 1053 1054 1055 1056
/**
 * 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.
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 */
1058
void __ref kmemleak_no_scan(const void *ptr)
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{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
		object_no_scan((unsigned long)ptr);
	else if (atomic_read(&kmemleak_early_log))
1065
		log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0);
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}
EXPORT_SYMBOL(kmemleak_no_scan);

1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082
/*
 * 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;

	object->checksum = crc32(0, (void *)object->pointer, object->size);
	return object->checksum != old_csum;
}

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

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

	return 0;
}

/*
 * Scan a memory block (exclusive range) for valid pointers and add those
 * found to the gray list.
 */
static void scan_block(void *_start, void *_end,
1109
		       struct kmemleak_object *scanned, int allow_resched)
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{
	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++) {
		struct kmemleak_object *object;
1117 1118
		unsigned long flags;
		unsigned long pointer;
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1120 1121
		if (allow_resched)
			cond_resched();
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		if (scan_should_stop())
			break;

1125 1126 1127 1128 1129 1130 1131
		/* don't scan uninitialized memory */
		if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
						  BYTES_PER_POINTER))
			continue;

		pointer = *ptr;

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		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++;
1162
		if (color_gray(object)) {
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			list_add_tail(&object->gray_list, &gray_list);
1164 1165 1166 1167
			spin_unlock_irqrestore(&object->lock, flags);
			continue;
		}

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		spin_unlock_irqrestore(&object->lock, flags);
1169
		put_object(object);
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	}
}

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

	/*
1184 1185
	 * Once the object->lock is acquired, the corresponding memory block
	 * cannot be freed (the same lock is acquired in delete_object).
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	 */
	spin_lock_irqsave(&object->lock, flags);
	if (object->flags & OBJECT_NO_SCAN)
		goto out;
	if (!(object->flags & OBJECT_ALLOCATED))
		/* already freed object */
		goto out;
1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207
	if (hlist_empty(&object->area_list)) {
		void *start = (void *)object->pointer;
		void *end = (void *)(object->pointer + object->size);

		while (start < end && (object->flags & OBJECT_ALLOCATED) &&
		       !(object->flags & OBJECT_NO_SCAN)) {
			scan_block(start, min(start + MAX_SCAN_SIZE, end),
				   object, 0);
			start += MAX_SCAN_SIZE;

			spin_unlock_irqrestore(&object->lock, flags);
			cond_resched();
			spin_lock_irqsave(&object->lock, flags);
		}
	} else
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		hlist_for_each_entry(area, elem, &object->area_list, node)
1209 1210 1211
			scan_block((void *)area->start,
				   (void *)(area->start + area->size),
				   object, 0);
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out:
	spin_unlock_irqrestore(&object->lock, flags);
}

1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248
/*
 * 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));
}

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/*
 * 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;
1257
	struct kmemleak_object *object;
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	int i;
1259
	int new_leaks = 0;
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1261 1262
	jiffies_last_scan = jiffies;

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	/* 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) {
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			pr_debug("object->use_count = %d\n",
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				 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 */
1288 1289
	scan_block(_sdata, _edata, NULL, 1);
	scan_block(__bss_start, __bss_stop, NULL, 1);
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#ifdef CONFIG_SMP
	/* per-cpu sections scanning */
	for_each_possible_cpu(i)
		scan_block(__per_cpu_start + per_cpu_offset(i),
1295
			   __per_cpu_end + per_cpu_offset(i), NULL, 1);
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#endif

	/*
1299
	 * Struct page scanning for each node.
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	 */
1301
	lock_memory_hotplug();
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	for_each_online_node(i) {
		pg_data_t *pgdat = NODE_DATA(i);
		unsigned long start_pfn = pgdat->node_start_pfn;
		unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
		unsigned long pfn;

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

			if (!pfn_valid(pfn))
				continue;
			page = pfn_to_page(pfn);
			/* only scan if page is in use */
			if (page_count(page) == 0)
				continue;
1317
			scan_block(page, page + 1, NULL, 1);
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		}
	}
1320
	unlock_memory_hotplug();
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	/*
1323
	 * Scanning the task stacks (may introduce false negatives).
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	 */
	if (kmemleak_stack_scan) {
1326 1327
		struct task_struct *p, *g;

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		read_lock(&tasklist_lock);
1329 1330 1331 1332
		do_each_thread(g, p) {
			scan_block(task_stack_page(p), task_stack_page(p) +
				   THREAD_SIZE, NULL, 0);
		} while_each_thread(g, p);
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		read_unlock(&tasklist_lock);
	}

	/*
	 * Scan the objects already referenced from the sections scanned
1338
	 * above.
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	 */
1340
	scan_gray_list();
1341 1342

	/*
1343 1344
	 * Check for new or unreferenced objects modified since the previous
	 * scan and color them gray until the next scan.
1345 1346 1347 1348
	 */
	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list) {
		spin_lock_irqsave(&object->lock, flags);
1349 1350 1351 1352
		if (color_white(object) && (object->flags & OBJECT_ALLOCATED)
		    && update_checksum(object) && get_object(object)) {
			/* color it gray temporarily */
			object->count = object->min_count;
1353 1354 1355 1356 1357 1358
			list_add_tail(&object->gray_list, &gray_list);
		}
		spin_unlock_irqrestore(&object->lock, flags);
	}
	rcu_read_unlock();

1359 1360 1361 1362
	/*
	 * Re-scan the gray list for modified unreferenced objects.
	 */
	scan_gray_list();
1363

1364
	/*
1365
	 * If scanning was stopped do not report any new unreferenced objects.
1366
	 */
1367
	if (scan_should_stop())
1368 1369
		return;

1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388
	/*
	 * Scanning result reporting.
	 */
	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list) {
		spin_lock_irqsave(&object->lock, flags);
		if (unreferenced_object(object) &&
		    !(object->flags & OBJECT_REPORTED)) {
			object->flags |= OBJECT_REPORTED;
			new_leaks++;
		}
		spin_unlock_irqrestore(&object->lock, flags);
	}
	rcu_read_unlock();

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

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}

/*
 * 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;

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	pr_info("Automatic memory scanning thread started\n");
1400
	set_user_nice(current, 10);
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	/*
	 * Wait before the first scan to allow the system to fully initialize.
	 */
	if (first_run) {
		first_run = 0;
		ssleep(SECS_FIRST_SCAN);
	}

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

		mutex_lock(&scan_mutex);
		kmemleak_scan();
		mutex_unlock(&scan_mutex);
1416

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

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	pr_info("Automatic memory scanning thread ended\n");
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	return 0;
}

/*
 * Start the automatic memory scanning thread. This function must be called
1429
 * with the scan_mutex held.
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 */
1431
static void start_scan_thread(void)
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{
	if (scan_thread)
		return;
	scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
	if (IS_ERR(scan_thread)) {
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		pr_warning("Failed to create the scan thread\n");
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		scan_thread = NULL;
	}
}

/*
 * Stop the automatic memory scanning thread. This function must be called
1444
 * with the scan_mutex held.
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 */
1446
static void stop_scan_thread(void)
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{
	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;
1463 1464 1465 1466 1467
	int err;

	err = mutex_lock_interruptible(&scan_mutex);
	if (err < 0)
		return ERR_PTR(err);
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	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;
1489
	struct kmemleak_object *obj = prev_obj;
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	++(*pos);

1493
	list_for_each_entry_continue_rcu(obj, &object_list, object_list) {
1494 1495
		if (get_object(obj)) {
			next_obj = obj;
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			break;
1497
		}
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	}
1499

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	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)
{
1509 1510 1511 1512 1513
	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.
		 */
1514
		rcu_read_unlock();
1515 1516 1517 1518
		mutex_unlock(&scan_mutex);
		if (v)
			put_object(v);
	}
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}

/*
 * 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);
1530
	if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1531
		print_unreferenced(seq, object);
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	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)
{
1545
	return seq_open(file, &kmemleak_seq_ops);
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}

static int kmemleak_release(struct inode *inode, struct file *file)
{
1550
	return seq_release(inode, file);
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}

1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573
static int dump_str_object_info(const char *str)
{
	unsigned long flags;
	struct kmemleak_object *object;
	unsigned long addr;

	addr= simple_strtoul(str, NULL, 0);
	object = find_and_get_object(addr, 0);
	if (!object) {
		pr_info("Unknown object at 0x%08lx\n", addr);
		return -EINVAL;
	}

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

	put_object(object);
	return 0;
}

1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589
/*
 * 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))
1590
			__paint_it(object, KMEMLEAK_GREY);
1591 1592 1593 1594 1595
		spin_unlock_irqrestore(&object->lock, flags);
	}
	rcu_read_unlock();
}

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/*
 * 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)
1606
 *   scan	- trigger a memory scan
1607 1608
 *   clear	- mark all current reported unreferenced kmemleak objects as
 *		  grey to ignore printing them
1609
 *   dump=...	- dump information about the object found at the given address
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 */
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;
1616
	int ret;
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1618 1619 1620
	if (!atomic_read(&kmemleak_enabled))
		return -EBUSY;

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

1626 1627 1628 1629
	ret = mutex_lock_interruptible(&scan_mutex);
	if (ret < 0)
		return ret;

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	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;

1643 1644 1645
		ret = strict_strtoul(buf + 5, 0, &secs);
		if (ret < 0)
			goto out;
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		stop_scan_thread();
		if (secs) {
			jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
			start_scan_thread();
		}
1651 1652
	} else if (strncmp(buf, "scan", 4) == 0)
		kmemleak_scan();
1653 1654
	else if (strncmp(buf, "clear", 5) == 0)
		kmemleak_clear();
1655 1656
	else if (strncmp(buf, "dump=", 5) == 0)
		ret = dump_str_object_info(buf + 5);
1657
	else
1658 1659 1660 1661 1662 1663
		ret = -EINVAL;

out:
	mutex_unlock(&scan_mutex);
	if (ret < 0)
		return ret;
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	/* ignore the rest of the buffer, only one command at a time */
	*ppos += size;
	return size;
}

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

/*
1680 1681 1682
 * 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).
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 */
1684
static void kmemleak_do_cleanup(struct work_struct *work)
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{
	struct kmemleak_object *object;
1687
	bool cleanup = scan_thread == NULL;
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1689
	mutex_lock(&scan_mutex);
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	stop_scan_thread();

1692 1693 1694 1695 1696 1697
	if (cleanup) {
		rcu_read_lock();
		list_for_each_entry_rcu(object, &object_list, object_list)
			delete_object_full(object->pointer);
		rcu_read_unlock();
	}
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	mutex_unlock(&scan_mutex);
}

1701
static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup);
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/*
 * Disable kmemleak. No memory allocation/freeing will be traced once this
 * function is called. Disabling kmemleak is an irreversible operation.
 */
static void kmemleak_disable(void)
{
	/* atomically check whether it was already invoked */
	if (atomic_cmpxchg(&kmemleak_error, 0, 1))
		return;

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

	/* check whether it is too early for a kernel thread */
	if (atomic_read(&kmemleak_initialized))
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		schedule_work(&cleanup_work);
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	pr_info("Kernel memory leak detector disabled\n");
}

/*
 * Allow boot-time kmemleak disabling (enabled by default).
 */
static int kmemleak_boot_config(char *str)
{
	if (!str)
		return -EINVAL;
	if (strcmp(str, "off") == 0)
		kmemleak_disable();
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	else if (strcmp(str, "on") == 0)
		kmemleak_skip_disable = 1;
	else
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		return -EINVAL;
	return 0;
}
early_param("kmemleak", kmemleak_boot_config);

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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:\n");
	print_stack_trace(&trace, 2);
}

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

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#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
	if (!kmemleak_skip_disable) {
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		atomic_set(&kmemleak_early_log, 0);
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		kmemleak_disable();
		return;
	}
#endif

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	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);

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	if (crt_early_log >= ARRAY_SIZE(early_log))
		pr_warning("Early log buffer exceeded (%d), please increase "
			   "DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n", crt_early_log);

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	/* the kernel is still in UP mode, so disabling the IRQs is enough */
	local_irq_save(flags);
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	atomic_set(&kmemleak_early_log, 0);
	if (atomic_read(&kmemleak_error)) {
		local_irq_restore(flags);
		return;
	} else
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		atomic_set(&kmemleak_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:
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			early_alloc(log);
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			break;
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		case KMEMLEAK_ALLOC_PERCPU:
			early_alloc_percpu(log);
			break;
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		case KMEMLEAK_FREE:
			kmemleak_free(log->ptr);
			break;
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		case KMEMLEAK_FREE_PART:
			kmemleak_free_part(log->ptr, log->size);
			break;
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		case KMEMLEAK_FREE_PERCPU:
			kmemleak_free_percpu(log->ptr);
			break;
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		case KMEMLEAK_NOT_LEAK:
			kmemleak_not_leak(log->ptr);
			break;
		case KMEMLEAK_IGNORE:
			kmemleak_ignore(log->ptr);
			break;
		case KMEMLEAK_SCAN_AREA:
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			kmemleak_scan_area(log->ptr, log->size, GFP_KERNEL);
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			break;
		case KMEMLEAK_NO_SCAN:
			kmemleak_no_scan(log->ptr);
			break;
		default:
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			kmemleak_warn("Unknown early log operation: %d\n",
				      log->op_type);
		}

		if (atomic_read(&kmemleak_warning)) {
			print_log_trace(log);
			atomic_set(&kmemleak_warning, 0);
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		}
	}
}

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

	atomic_set(&kmemleak_initialized, 1);

	if (atomic_read(&kmemleak_error)) {
		/*
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		 * Some error occurred and kmemleak was disabled. There is a
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		 * 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.
		 */
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		schedule_work(&cleanup_work);
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		return -ENOMEM;
	}

	dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
				     &kmemleak_fops);
	if (!dentry)
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		pr_warning("Failed to create the debugfs kmemleak file\n");
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	mutex_lock(&scan_mutex);
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	start_scan_thread();
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	mutex_unlock(&scan_mutex);
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	pr_info("Kernel memory leak detector initialized\n");

	return 0;
}
late_initcall(kmemleak_late_init);