litmus-rt.git - The LITMUS^RT kernel.

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The LITMUS^RT kernel.

Bjoern Brandenburg

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inas@arm.com> 2009-06-11 08:22:39 -0400 committer Catalin Marinas <catalin.marinas@arm.com> 2009-06-11 12:03:28 -0400 kmemleak: Add the base support' href='/cgit/cgit.cgi/litmus-rt.git/commit/mm/kmemleak.c?h=2012.1&id=3c7b4e6b8be4c16f1e6e5c558e33b7ff0db2dfaf'>3c7b4e6b8be4

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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
 *   blocks. The object_tree_root is a priority search tree used to look-up
 *   metadata based on a pointer to the corresponding memory block.  The
 *   kmemleak_object structures are added to the object_list and
 *   object_tree_root in the create_object() function called from the
 *   kmemleak_alloc() callback and removed in delete_object() called from the
 *   kmemleak_free() callback
 * - kmemleak_object.lock (spinlock): protects a kmemleak_object. Accesses to
 *   the metadata (e.g. count) are protected by this lock. Note that some
 *   members of this structure may be protected by other means (atomic or
 *   kmemleak_lock). This lock is also held when scanning the corresponding
 *   memory block to avoid the kernel freeing it via the kmemleak_free()
 *   callback. This is less heavyweight than holding a global lock like
 *   kmemleak_lock during scanning
 * - scan_mutex (mutex): ensures that only one thread may scan the memory for
 *   unreferenced objects at a time. The gray_list contains the objects which
 *   are already referenced or marked as false positives and need to be
 *   scanned. This list is only modified during a scanning episode when the
 *   scan_mutex is held. At the end of a scan, the gray_list is always empty.
 *   Note that the kmemleak_object.use_count is incremented when an object is
 *   added to the gray_list and therefore cannot be freed. This mutex also
 *   prevents multiple users of the "kmemleak" debugfs file together with
 *   modifications to the memory scanning parameters including the scan_thread
 *   pointer
 *
 * The kmemleak_object structures have a use_count incremented or decremented
 * using the get_object()/put_object() functions. When the use_count becomes
 * 0, this count can no longer be incremented and put_object() schedules the
 * kmemleak_object freeing via an RCU callback. All calls to the get_object()
 * function must be protected by rcu_read_lock() to avoid accessing a freed
 * structure.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/sched.h>
#include <linux/jiffies.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/prio_tree.h>
#include <linux/gfp.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/cpumask.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/stacktrace.h>
#include <linux/cache.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/mmzone.h>
#include <linux/slab.h>
#include <linux/thread_info.h>
#include <linux/err.h>
#include <linux/uaccess.h>
#include <linux/string.h>
#include <linux/nodemask.h>
#include <linux/mm.h>
#include <linux/workqueue.h>

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

#include <linux/kmemcheck.h>
#include <linux/kmemleak.h>

/*
 * Kmemleak configuration and common defines.
 */
#define MAX_TRACE		16	/* stack trace length */
#define MSECS_MIN_AGE		5000	/* minimum object age for reporting */
#define SECS_FIRST_SCAN		60	/* delay before the first scan */
#define SECS_SCAN_WAIT		600	/* subsequent auto scanning delay */
#define GRAY_LIST_PASSES	25	/* maximum number of gray list scans */
#define MAX_SCAN_SIZE		4096	/* maximum size of a scanned block */

#define BYTES_PER_POINTER	sizeof(void *)

/* GFP bitmask for kmemleak internal allocations */
#define GFP_KMEMLEAK_MASK	(GFP_KERNEL | GFP_ATOMIC)

/* scanning area inside a memory block */
struct kmemleak_scan_area {
	struct hlist_node node;
	unsigned long offset;
	size_t length;
};

#define KMEMLEAK_GREY	0
#define KMEMLEAK_BLACK	-1

/*
 * Structure holding the metadata for each allocated memory block.
 * Modifications to such objects should be made while holding the
 * object->lock. Insertions or deletions from object_list, gray_list or
 * tree_node are already protected by the corresponding locks or mutex (see
 * the notes on locking above). These objects are reference-counted
 * (use_count) and freed using the RCU mechanism.
 */
struct kmemleak_object {
	spinlock_t lock;
	unsigned long flags;		/* object status flags */
	struct list_head object_list;
	struct list_head gray_list;
	struct prio_tree_node tree_node;
	struct rcu_head rcu;		/* object_list lockless traversal */
	/* object usage count; object freed when use_count == 0 */
	atomic_t use_count;
	unsigned long pointer;
	size_t size;
	/* minimum number of a pointers found before it is considered leak */
	int min_count;
	/* the total number of pointers found pointing to this object */
	int count;
	/* memory ranges to be scanned inside an object (empty for all) */
	struct hlist_head area_list;
	unsigned long trace[MAX_TRACE];
	unsigned int trace_len;
	unsigned long jiffies;		/* creation timestamp */
	pid_t pid;			/* pid of the current task */
	char comm[TASK_COMM_LEN];	/* executable name */
};

/* flag representing the memory block allocation status */
#define OBJECT_ALLOCATED	(1 << 0)
/* flag set after the first reporting of an unreference object */
#define OBJECT_REPORTED		(1 << 1)
/* flag set to not scan the object */
#define OBJECT_NO_SCAN		(1 << 2)
/* flag set on newly allocated objects */
#define OBJECT_NEW		(1 << 3)

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

/* the list of all allocated objects */
static LIST_HEAD(object_list);
/* the list of gray-colored objects (see color_gray comment below) */
static LIST_HEAD(gray_list);
/* prio search tree for object boundaries */
static struct prio_tree_root object_tree_root;
/* rw_lock protecting the access to object_list and prio_tree_root */
static DEFINE_RWLOCK(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);
/* set if a fata kmemleak error has occurred */
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;
/* used to avoid reporting of recently allocated objects */
static unsigned long jiffies_min_age;
static unsigned long jiffies_last_scan;
/* delay between automatic memory scannings */
static signed long jiffies_scan_wait;
/* enables or disables the task stacks scanning */
static int kmemleak_stack_scan = 1;
/* protects the memory scanning, parameters and debug/kmemleak file access */
static DEFINE_MUTEX(scan_mutex);

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

/* kmemleak operation type for early logging */
enum {
	KMEMLEAK_ALLOC,
	KMEMLEAK_FREE,
	KMEMLEAK_FREE_PART,
	KMEMLEAK_NOT_LEAK,
	KMEMLEAK_IGNORE,
	KMEMLEAK_SCAN_AREA,
	KMEMLEAK_NO_SCAN
};

/*
 * Structure holding the information passed to kmemleak callbacks during the
 * early logging.
 */
struct early_log {
	int op_type;			/* kmemleak operation type */
	const void *ptr;		/* allocated/freed memory block */
	size_t size;			/* memory block size */
	int min_count;			/* minimum reference count */
	unsigned long offset;		/* scan area offset */
	size_t length;			/* scan area length */
	unsigned long trace[MAX_TRACE];	/* stack trace */
	unsigned int trace_len;		/* stack trace length */
};

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

static void kmemleak_disable(void);

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

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

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

/*
 * Object colors, encoded with count and min_count:
 * - white - orphan object, not enough references to it (count < min_count)
 * - gray  - not orphan, not marked as false positive (min_count == 0) or
 *		sufficient references to it (count >= min_count)
 * - black - ignore, it doesn't contain references (e.g. text section)
 *		(min_count == -1). No function defined for this color.
 * Newly created objects don't have any color assigned (object->count == -1)
 * before the next memory scan when they become white.
 */
static bool color_white(const struct kmemleak_object *object)
{
	return object->count != KMEMLEAK_BLACK &&
		object->count < object->min_count;
}

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

static bool color_black(const struct kmemleak_object *object)
{
	return object->min_count == KMEMLEAK_BLACK;
}

/*
 * Objects are considered unreferenced only if their color is white, they have
 * not be deleted and have a minimum age to avoid false positives caused by
 * pointers temporarily stored in CPU registers.
 */
static bool unreferenced_object(struct kmemleak_object *object)
{
	return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
		time_before_eq(object->jiffies + jiffies_min_age,
			       jiffies_last_scan);
}

/*
 * Printing of the unreferenced objects information to the seq file. The
 * print_unreferenced function must be called with the object->lock held.
 */
static void print_unreferenced(struct seq_file *seq,
			       struct kmemleak_object *object)
{
	int i;

	seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
		   object->pointer, object->size);
	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
		   object->comm, object->pid, object->jiffies);
	hex_dump_object(seq, object);
	seq_printf(seq, "  backtrace:\n");

	for (i = 0; i < object->trace_len; i++) {
		void *ptr = (void *)object->trace[i];
		seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
	}
}

/*
 * Print the kmemleak_object information. This function is used mainly for
 * debugging special cases when kmemleak operations. It must be called with
 * the object->lock held.
 */
static void dump_object_info(struct kmemleak_object *object)
{
	struct stack_trace trace;

	trace.nr_entries = object->trace_len;
	trace.entries = object->trace;

	pr_notice("Object 0x%08lx (size %zu):\n",
		  object->tree_node.start, object->size);
	pr_notice("  comm \"%s\", pid %d, jiffies %lu\n",
		  object->comm, object->pid, object->jiffies);
	pr_notice("  min_count = %d\n", object->min_count);
	pr_notice("  count = %d\n", object->count);
	pr_notice("  flags = 0x%lx\n", object->flags);
	pr_notice("  backtrace:\n");
	print_stack_trace(&trace, 4);
}

/*
 * Look-up a memory block metadata (kmemleak_object) in the priority search
 * tree based on a pointer value. If alias is 0, only values pointing to the
 * beginning of the memory block are allowed. The kmemleak_lock must be held
 * when calling this function.
 */
static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
{
	struct prio_tree_node *node;
	struct prio_tree_iter iter;
	struct kmemleak_object *object;

	prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr);
	node = prio_tree_next(&iter);
	if (node) {
		object = prio_tree_entry(node, struct kmemleak_object,
					 tree_node);
		if (!alias && object->pointer != ptr) {
			kmemleak_warn("Found object by alias");
			object = NULL;
		}
	} else
		object = NULL;

	return object;
}

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

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

/*
 * Save stack trace to the given array of MAX_TRACE size.
 */
static int __save_stack_trace(unsigned long *trace)
{
	struct stack_trace stack_trace;

	stack_trace.max_entries = MAX_TRACE;
	stack_trace.nr_entries = 0;
	stack_trace.entries = trace;
	stack_trace.skip = 2;
	save_stack_trace(&stack_trace);

	return stack_trace.nr_entries;
}

/*
 * Create the metadata (struct kmemleak_object) corresponding to an allocated
 * memory block and add it to the object_list and object_tree_root.
 */
static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
					     int min_count, gfp_t gfp)
{
	unsigned long flags;
	struct kmemleak_object *object;
	struct prio_tree_node *node;

	object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK);
	if (!object) {
		kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
		return NULL;
	}

	INIT_LIST_HEAD(&object->object_list);
	INIT_LIST_HEAD(&object->gray_list);
	INIT_HLIST_HEAD(&object->area_list);
	spin_lock_init(&object->lock);
	atomic_set(&object->use_count, 1);
	object->flags = OBJECT_ALLOCATED | OBJECT_NEW;
	object->pointer = ptr;
	object->size = size;
	object->min_count = min_count;
	object->count = -1;			/* no color initially */
	object->jiffies = jiffies;

	/* task information */
	if (in_irq()) {
		object->pid = 0;
		strncpy(object->comm, "hardirq", sizeof(object->comm));
	} else if (in_softirq()) {
		object->pid = 0;
		strncpy(object->comm, "softirq", sizeof(object->comm));
	} else {
		object->pid = current->pid;
		/*
		 * There is a small chance of a race with set_task_comm(),
		 * however using get_task_comm() here may cause locking
		 * dependency issues with current->alloc_lock. In the worst
		 * case, the command line is not correct.
		 */
		strncpy(object->comm, current->comm, sizeof(object->comm));
	}

	/* kernel backtrace */
	object->trace_len = __save_stack_trace(object->trace);

	INIT_PRIO_TREE_NODE(&object->tree_node);
	object->tree_node.start = ptr;
	object->tree_node.last = ptr + size - 1;

	write_lock_irqsave(&kmemleak_lock, flags);

	min_addr = min(min_addr, ptr);
	max_addr = max(max_addr, ptr + size);
	node = prio_tree_insert(&object_tree_root, &object->tree_node);
	/*
	 * The code calling the kernel does not yet have the pointer to the
	 * memory block to be able to free it.  However, we still hold the
	 * kmemleak_lock here in case parts of the kernel started freeing
	 * random memory blocks.
	 */
	if (node != &object->tree_node) {
		kmemleak_stop("Cannot insert 0x%lx into the object search tree "
			      "(already existing)\n", ptr);
		object = lookup_object(ptr, 1);
		spin_lock(&object->lock);
		dump_object_info(object);
		spin_unlock(&object->lock);

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

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


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