kmemleak.c 54.2 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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 *
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 * Locks and mutexes should only be acquired/nested in the following order:
 *
 *   scan_mutex -> object->lock -> other_object->lock (SINGLE_DEPTH_NESTING)
 *				-> kmemleak_lock
 *
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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/kasan.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_NOACCOUNT)) | \
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				 __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 */
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static int kmemleak_enabled;
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/* same as above but only for the kmemleak_free() callback */
static int kmemleak_free_enabled;
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/* set in the late_initcall if there were no errors */
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static int kmemleak_initialized;
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/* enables or disables early logging of the memory operations */
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static int kmemleak_early_log = 1;
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/* set if a kmemleak warning was issued */
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static int kmemleak_warning;
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/* set if a fatal kmemleak error has occurred */
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static int kmemleak_error;
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/* 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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/* If there are leaks that can be reported */
static bool kmemleak_found_leaks;
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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();				\
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	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 = %u\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)
{
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	struct hlist_node *tmp;
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	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.
	 */
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	hlist_for_each_entry_safe(area, tmp, &object->area_list, node) {
		hlist_del(&area->node);
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		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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/*
 * Look up an object in the object search tree and remove it from both
 * object_tree_root and object_list. The returned object's use_count should be
 * at least 1, as initially set by create_object().
 */
static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int alias)
{
	unsigned long flags;
	struct kmemleak_object *object;

	write_lock_irqsave(&kmemleak_lock, flags);
	object = lookup_object(ptr, alias);
	if (object) {
		rb_erase(&object->rb_node, &object_tree_root);
		list_del_rcu(&object->object_list);
	}
	write_unlock_irqrestore(&kmemleak_lock, flags);

	return object;
}

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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();
557
		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);
565
	object->flags = OBJECT_ALLOCATED;
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	object->pointer = ptr;
	object->size = size;
	object->min_count = min_count;
569
	object->count = 0;			/* white color initially */
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	object->jiffies = jiffies;
571
	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 */
592
	object->trace_len = __save_stack_trace(object->trace);
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	write_lock_irqsave(&kmemleak_lock, flags);
595

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	min_addr = min(min_addr, ptr);
	max_addr = max(max_addr, ptr + size);
598 599 600 601 602 603 604 605 606 607 608 609 610
	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);
611 612 613 614 615
			/*
			 * No need for parent->lock here since "parent" cannot
			 * be freed while the kmemleak_lock is held.
			 */
			dump_object_info(parent);
616
			kmem_cache_free(object_cache, object);
617
			object = NULL;
618 619
			goto out;
		}
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	}
621 622 623
	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);
627
	return object;
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}

/*
631
 * Mark the object as not allocated and schedule RCU freeing via put_object().
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 */
633
static void __delete_object(struct kmemleak_object *object)
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{
	unsigned long flags;

	WARN_ON(!(object->flags & OBJECT_ALLOCATED));
638
	WARN_ON(atomic_read(&object->use_count) < 1);
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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);
}

650 651 652 653 654 655 656 657
/*
 * 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;

658
	object = find_and_remove_object(ptr, 0);
659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678
	if (!object) {
#ifdef DEBUG
		kmemleak_warn("Freeing unknown object at 0x%08lx\n",
			      ptr);
#endif
		return;
	}
	__delete_object(object);
}

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

679
	object = find_and_remove_object(ptr, 1);
680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703
	if (!object) {
#ifdef DEBUG
		kmemleak_warn("Partially freeing unknown object at 0x%08lx "
			      "(size %zu)\n", ptr, size);
#endif
		return;
	}

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

704
	__delete_object(object);
705
}
706 707 708 709 710 711 712 713 714

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;
717 718 719 720 721 722 723 724

	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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725 726 727 728
	struct kmemleak_object *object;

	object = find_and_get_object(ptr, 0);
	if (!object) {
729 730 731 732
		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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733 734
		return;
	}
735
	paint_it(object, color);
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	put_object(object);
}

739
/*
740
 * Mark an object permanently as gray-colored so that it can no longer be
741 742 743 744 745 746 747
 * 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)
{
754
	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.
 */
761
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;

767
	object = find_and_get_object(ptr, 1);
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	if (!object) {
J
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769 770
		kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
			      ptr);
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		return;
	}

774
	area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
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	if (!area) {
776
		pr_warning("Cannot allocate a scan area\n");
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777 778 779 780
		goto out;
	}

	spin_lock_irqsave(&object->lock, flags);
781 782 783
	if (size == SIZE_MAX) {
		size = object->pointer + object->size - ptr;
	} else if (ptr + size > object->pointer + object->size) {
J
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784
		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);
791 792
	area->start = ptr;
	area->size = size;
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793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812

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

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

	object = find_and_get_object(ptr, 0);
	if (!object) {
J
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813
		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.
 */
827
static void __init log_early(int op_type, const void *ptr, size_t size,
828
			     int min_count)
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{
	unsigned long flags;
	struct early_log *log;

833
	if (kmemleak_error) {
834 835 836 837 838
		/* kmemleak stopped recording, just count the requests */
		crt_early_log++;
		return;
	}

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	if (crt_early_log >= ARRAY_SIZE(early_log)) {
840
		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;
854
	log->trace_len = __save_stack_trace(log->trace);
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	crt_early_log++;
	local_irq_restore(flags);
}

859 860 861 862 863 864 865 866 867
/*
 * 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;

868
	if (!kmemleak_enabled || !log->ptr || IS_ERR(log->ptr))
869 870 871 872 873 874 875
		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,
876
			       log->min_count, GFP_ATOMIC);
877 878
	if (!object)
		goto out;
879 880 881 882 883
	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);
884
out:
885 886 887
	rcu_read_unlock();
}

888 889 890 891 892 893 894 895 896 897 898 899 900 901
/*
 * 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);
	}
}

902 903 904 905 906 907 908 909 910 911 912 913 914
/**
 * 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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 */
916 917
void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
			  gfp_t gfp)
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918 919 920
{
	pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);

921
	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
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		create_object((unsigned long)ptr, size, min_count, gfp);
923
	else if (kmemleak_early_log)
924
		log_early(KMEMLEAK_ALLOC, ptr, size, min_count);
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}
EXPORT_SYMBOL_GPL(kmemleak_alloc);

928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946
/**
 * 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).
	 */
947
	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
948 949 950
		for_each_possible_cpu(cpu)
			create_object((unsigned long)per_cpu_ptr(ptr, cpu),
				      size, 0, GFP_KERNEL);
951
	else if (kmemleak_early_log)
952 953 954 955
		log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);

956 957 958 959 960 961
/**
 * 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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 */
963
void __ref kmemleak_free(const void *ptr)
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964 965 966
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

967
	if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))
968
		delete_object_full((unsigned long)ptr);
969
	else if (kmemleak_early_log)
970
		log_early(KMEMLEAK_FREE, ptr, 0, 0);
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}
EXPORT_SYMBOL_GPL(kmemleak_free);

974 975 976 977 978 979 980 981
/**
 * 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).
982
 */
983
void __ref kmemleak_free_part(const void *ptr, size_t size)
984 985 986
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

987
	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
988
		delete_object_part((unsigned long)ptr, size);
989
	else if (kmemleak_early_log)
990
		log_early(KMEMLEAK_FREE_PART, ptr, size, 0);
991 992 993
}
EXPORT_SYMBOL_GPL(kmemleak_free_part);

994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006
/**
 * 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);

1007
	if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))
1008 1009 1010
		for_each_possible_cpu(cpu)
			delete_object_full((unsigned long)per_cpu_ptr(ptr,
								      cpu));
1011
	else if (kmemleak_early_log)
1012 1013 1014 1015
		log_early(KMEMLEAK_FREE_PERCPU, ptr, 0, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free_percpu);

1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049
/**
 * kmemleak_update_trace - update object allocation stack trace
 * @ptr:	pointer to beginning of the object
 *
 * Override the object allocation stack trace for cases where the actual
 * allocation place is not always useful.
 */
void __ref kmemleak_update_trace(const void *ptr)
{
	struct kmemleak_object *object;
	unsigned long flags;

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

	if (!kmemleak_enabled || IS_ERR_OR_NULL(ptr))
		return;

	object = find_and_get_object((unsigned long)ptr, 1);
	if (!object) {
#ifdef DEBUG
		kmemleak_warn("Updating stack trace for unknown object at %p\n",
			      ptr);
#endif
		return;
	}

	spin_lock_irqsave(&object->lock, flags);
	object->trace_len = __save_stack_trace(object->trace);
	spin_unlock_irqrestore(&object->lock, flags);

	put_object(object);
}
EXPORT_SYMBOL(kmemleak_update_trace);

1050 1051 1052 1053 1054 1055
/**
 * 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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 */
1057
void __ref kmemleak_not_leak(const void *ptr)
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{
	pr_debug("%s(0x%p)\n", __func__, ptr);

1061
	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
C
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1062
		make_gray_object((unsigned long)ptr);
1063
	else if (kmemleak_early_log)
1064
		log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0);
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}
EXPORT_SYMBOL(kmemleak_not_leak);

1068 1069 1070 1071 1072 1073 1074 1075
/**
 * 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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 */
1077
void __ref kmemleak_ignore(const void *ptr)
C
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1078 1079 1080
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

1081
	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
C
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1082
		make_black_object((unsigned long)ptr);
1083
	else if (kmemleak_early_log)
1084
		log_early(KMEMLEAK_IGNORE, ptr, 0, 0);
C
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1085 1086 1087
}
EXPORT_SYMBOL(kmemleak_ignore);

1088 1089 1090 1091 1092 1093 1094 1095 1096 1097
/**
 * 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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1098
 */
1099
void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
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1100 1101 1102
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

1103
	if (kmemleak_enabled && ptr && size && !IS_ERR(ptr))
1104
		add_scan_area((unsigned long)ptr, size, gfp);
1105
	else if (kmemleak_early_log)
1106
		log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0);
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}
EXPORT_SYMBOL(kmemleak_scan_area);

1110 1111 1112 1113 1114 1115 1116 1117
/**
 * 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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1118
 */
1119
void __ref kmemleak_no_scan(const void *ptr)
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1120 1121 1122
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

1123
	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
C
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1124
		object_no_scan((unsigned long)ptr);
1125
	else if (kmemleak_early_log)
1126
		log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0);
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}
EXPORT_SYMBOL(kmemleak_no_scan);

1130 1131 1132 1133 1134 1135 1136 1137 1138 1139
/*
 * 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;

1140
	kasan_disable_current();
1141
	object->checksum = crc32(0, (void *)object->pointer, object->size);
1142 1143
	kasan_enable_current();

1144 1145 1146
	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)
{
1153
	if (!kmemleak_enabled)
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		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,
1173
		       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;
1181 1182
		unsigned long flags;
		unsigned long pointer;
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1184 1185
		if (allow_resched)
			cond_resched();
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		if (scan_should_stop())
			break;

1189 1190 1191 1192 1193
		/* don't scan uninitialized memory */
		if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
						  BYTES_PER_POINTER))
			continue;

1194
		kasan_disable_current();
1195
		pointer = *ptr;
1196
		kasan_enable_current();
1197

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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++;
1228
		if (color_gray(object)) {
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			list_add_tail(&object->gray_list, &gray_list);
1230 1231 1232 1233
			spin_unlock_irqrestore(&object->lock, flags);
			continue;
		}

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		spin_unlock_irqrestore(&object->lock, flags);
1235
		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;
	unsigned long flags;

	/*
1249 1250
	 * 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;
1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272
	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
1273
		hlist_for_each_entry(area, &object->area_list, node)
1274 1275 1276
			scan_block((void *)area->start,
				   (void *)(area->start + area->size),
				   object, 0);
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out:
	spin_unlock_irqrestore(&object->lock, flags);
}

1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313
/*
 * 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;
1322
	struct kmemleak_object *object;
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	int i;
1324
	int new_leaks = 0;
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1326 1327
	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) {
J
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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 */
1353 1354
	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),
1360
			   __per_cpu_end + per_cpu_offset(i), NULL, 1);
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#endif

	/*
1364
	 * Struct page scanning for each node.
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	 */
1366
	get_online_mems();
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	for_each_online_node(i) {
1368 1369
		unsigned long start_pfn = node_start_pfn(i);
		unsigned long end_pfn = node_end_pfn(i);
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		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;
1381
			scan_block(page, page + 1, NULL, 1);
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		}
	}
1384
	put_online_mems();
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	/*
1387
	 * Scanning the task stacks (may introduce false negatives).
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	 */
	if (kmemleak_stack_scan) {
1390 1391
		struct task_struct *p, *g;

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		read_lock(&tasklist_lock);
1393 1394 1395 1396
		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
1402
	 * above.
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	 */
1404
	scan_gray_list();
1405 1406

	/*
1407 1408
	 * Check for new or unreferenced objects modified since the previous
	 * scan and color them gray until the next scan.
1409 1410 1411 1412
	 */
	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list) {
		spin_lock_irqsave(&object->lock, flags);
1413 1414 1415 1416
		if (color_white(object) && (object->flags & OBJECT_ALLOCATED)
		    && update_checksum(object) && get_object(object)) {
			/* color it gray temporarily */
			object->count = object->min_count;
1417 1418 1419 1420 1421 1422
			list_add_tail(&object->gray_list, &gray_list);
		}
		spin_unlock_irqrestore(&object->lock, flags);
	}
	rcu_read_unlock();

1423 1424 1425 1426
	/*
	 * Re-scan the gray list for modified unreferenced objects.
	 */
	scan_gray_list();
1427

1428
	/*
1429
	 * If scanning was stopped do not report any new unreferenced objects.
1430
	 */
1431
	if (scan_should_stop())
1432 1433
		return;

1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448
	/*
	 * 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();

1449 1450 1451
	if (new_leaks) {
		kmemleak_found_leaks = true;

1452 1453
		pr_info("%d new suspected memory leaks (see "
			"/sys/kernel/debug/kmemleak)\n", new_leaks);
1454
	}
1455

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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;

J
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	pr_info("Automatic memory scanning thread started\n");
1467
	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);
1483

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

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1489
	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
1496
 * with the scan_mutex held.
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 */
1498
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)) {
J
Joe Perches 已提交
1504
		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
1511
 * with the scan_mutex held.
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 */
1513
static void stop_scan_thread(void)
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1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529
{
	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;
1530 1531 1532 1533 1534
	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;
1556
	struct kmemleak_object *obj = prev_obj;
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	++(*pos);

1560
	list_for_each_entry_continue_rcu(obj, &object_list, object_list) {
1561 1562
		if (get_object(obj)) {
			next_obj = obj;
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1563
			break;
1564
		}
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1565
	}
1566

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1567 1568 1569 1570 1571 1572 1573 1574 1575
	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)
{
1576 1577 1578 1579 1580
	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.
		 */
1581
		rcu_read_unlock();
1582 1583 1584 1585
		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);
1597
	if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1598
		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)
{
1612
	return seq_open(file, &kmemleak_seq_ops);
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}

1615 1616 1617 1618 1619 1620
static int dump_str_object_info(const char *str)
{
	unsigned long flags;
	struct kmemleak_object *object;
	unsigned long addr;

1621 1622
	if (kstrtoul(str, 0, &addr))
		return -EINVAL;
1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636
	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;
}

1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652
/*
 * 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))
1653
			__paint_it(object, KMEMLEAK_GREY);
1654 1655 1656
		spin_unlock_irqrestore(&object->lock, flags);
	}
	rcu_read_unlock();
1657 1658

	kmemleak_found_leaks = false;
1659 1660
}

1661 1662
static void __kmemleak_do_cleanup(void);

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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)
1673
 *   scan	- trigger a memory scan
1674
 *   clear	- mark all current reported unreferenced kmemleak objects as
1675 1676
 *		  grey to ignore printing them, or free all kmemleak objects
 *		  if kmemleak has been disabled.
1677
 *   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;
1684
	int ret;
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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;

1691 1692 1693 1694
	ret = mutex_lock_interruptible(&scan_mutex);
	if (ret < 0)
		return ret;

1695
	if (strncmp(buf, "clear", 5) == 0) {
1696
		if (kmemleak_enabled)
1697 1698 1699 1700 1701 1702
			kmemleak_clear();
		else
			__kmemleak_do_cleanup();
		goto out;
	}

1703
	if (!kmemleak_enabled) {
1704 1705 1706 1707
		ret = -EBUSY;
		goto out;
	}

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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;

1721
		ret = kstrtoul(buf + 5, 0, &secs);
1722 1723
		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();
		}
1729 1730
	} else if (strncmp(buf, "scan", 4) == 0)
		kmemleak_scan();
1731 1732
	else if (strncmp(buf, "dump=", 5) == 0)
		ret = dump_str_object_info(buf + 5);
1733
	else
1734 1735 1736 1737 1738 1739
		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,
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	.release	= seq_release,
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};

1755 1756 1757 1758 1759 1760 1761 1762 1763 1764
static void __kmemleak_do_cleanup(void)
{
	struct kmemleak_object *object;

	rcu_read_lock();
	list_for_each_entry_rcu(object, &object_list, object_list)
		delete_object_full(object->pointer);
	rcu_read_unlock();
}

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/*
1766 1767 1768
 * 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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 */
1770
static void kmemleak_do_cleanup(struct work_struct *work)
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{
	stop_scan_thread();

1774 1775 1776 1777 1778 1779 1780
	/*
	 * Once the scan thread has stopped, it is safe to no longer track
	 * object freeing. Ordering of the scan thread stopping and the memory
	 * accesses below is guaranteed by the kthread_stop() function.
	 */
	kmemleak_free_enabled = 0;

1781 1782 1783 1784 1785
	if (!kmemleak_found_leaks)
		__kmemleak_do_cleanup();
	else
		pr_info("Kmemleak disabled without freeing internal data. "
			"Reclaim the memory with \"echo clear > /sys/kernel/debug/kmemleak\"\n");
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}

1788
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 */
1797
	if (cmpxchg(&kmemleak_error, 0, 1))
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		return;

	/* stop any memory operation tracing */
1801
	kmemleak_enabled = 0;
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	/* check whether it is too early for a kernel thread */
1804
	if (kmemleak_initialized)
1805
		schedule_work(&cleanup_work);
1806 1807
	else
		kmemleak_free_enabled = 0;
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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();
1821 1822 1823
	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);

1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839
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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/*
1841
 * Kmemleak initialization.
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 */
void __init kmemleak_init(void)
{
	int i;
	unsigned long flags;

1848 1849
#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
	if (!kmemleak_skip_disable) {
1850
		kmemleak_early_log = 0;
1851 1852 1853 1854 1855
		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);

1862 1863 1864 1865
	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);
1868
	kmemleak_early_log = 0;
1869
	if (kmemleak_error) {
1870 1871
		local_irq_restore(flags);
		return;
1872
	} else {
1873
		kmemleak_enabled = 1;
1874 1875
		kmemleak_free_enabled = 1;
	}
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	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:
1888
			early_alloc(log);
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			break;
1890 1891 1892
		case KMEMLEAK_ALLOC_PERCPU:
			early_alloc_percpu(log);
			break;
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		case KMEMLEAK_FREE:
			kmemleak_free(log->ptr);
			break;
1896 1897 1898
		case KMEMLEAK_FREE_PART:
			kmemleak_free_part(log->ptr, log->size);
			break;
1899 1900 1901
		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:
1909
			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:
1915 1916 1917 1918
			kmemleak_warn("Unknown early log operation: %d\n",
				      log->op_type);
		}

1919
		if (kmemleak_warning) {
1920
			print_log_trace(log);
1921
			kmemleak_warning = 0;
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		}
	}
}

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

1933
	kmemleak_initialized = 1;
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1935
	if (kmemleak_error) {
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		/*
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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.
		 */
1942
		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");
1950
	mutex_lock(&scan_mutex);
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	start_scan_thread();
1952
	mutex_unlock(&scan_mutex);
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	pr_info("Kernel memory leak detector initialized\n");

	return 0;
}
late_initcall(kmemleak_late_init);