debugobjects.c

Lib files of linux kernel

/*
 * Generic infrastructure for lifetime debugging of objects.
 *
 * Started by Thomas Gleixner
 *
 * Copyright (C) 2008, Thomas Gleixner <[e-mail]>
 *
 * For licencing details see kernel-base/COPYING
 */
#include <linux/debugobjects.h>
#include <linux/interrupt.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/hash.h>

#define ODEBUG_HASH_BITS	14
#define ODEBUG_HASH_SIZE	(1 << ODEBUG_HASH_BITS)

#define ODEBUG_POOL_SIZE	512
#define ODEBUG_POOL_MIN_LEVEL	256

#define ODEBUG_CHUNK_SHIFT	PAGE_SHIFT
#define ODEBUG_CHUNK_SIZE	(1 << ODEBUG_CHUNK_SHIFT)
#define ODEBUG_CHUNK_MASK	(~(ODEBUG_CHUNK_SIZE - 1))

struct debug_bucket {
	struct hlist_head	list;
	spinlock_t		lock;
};

static struct debug_bucket	obj_hash[ODEBUG_HASH_SIZE];

static struct debug_obj		obj_static_pool[ODEBUG_POOL_SIZE];

static DEFINE_SPINLOCK(pool_lock);

static HLIST_HEAD(obj_pool);

static int			obj_pool_min_free = ODEBUG_POOL_SIZE;
static int			obj_pool_free = ODEBUG_POOL_SIZE;
static int			obj_pool_used;
static int			obj_pool_max_used;
static struct kmem_cache	*obj_cache;

static int			debug_objects_maxchain __read_mostly;
static int			debug_objects_fixups __read_mostly;
static int			debug_objects_warnings __read_mostly;
static int			debug_objects_enabled __read_mostly;
static struct debug_obj_descr	*descr_test  __read_mostly;

static int __init enable_object_debug(char *str)
{
	debug_objects_enabled = 1;
	return 0;
}
early_param("debug_objects", enable_object_debug);

static const char *obj_states[ODEBUG_STATE_MAX] = {
	[ODEBUG_STATE_NONE]		= "none",
	[ODEBUG_STATE_INIT]		= "initialized",
	[ODEBUG_STATE_INACTIVE]		= "inactive",
	[ODEBUG_STATE_ACTIVE]		= "active",
	[ODEBUG_STATE_DESTROYED]	= "destroyed",
	[ODEBUG_STATE_NOTAVAILABLE]	= "not available",
};

static int fill_pool(void)
{
	gfp_t gfp = GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN;
	struct debug_obj *new;
	unsigned long flags;

	if (likely(obj_pool_free >= ODEBUG_POOL_MIN_LEVEL))
		return obj_pool_free;

	if (unlikely(!obj_cache))
		return obj_pool_free;

	while (obj_pool_free < ODEBUG_POOL_MIN_LEVEL) {

		new = kmem_cache_zalloc(obj_cache, gfp);
		if (!new)
			return obj_pool_free;

		spin_lock_irqsave(&pool_lock, flags);
		hlist_add_head(&new->node, &obj_pool);
		obj_pool_free++;
		spin_unlock_irqrestore(&pool_lock, flags);
	}
	return obj_pool_free;
}

/*
 * Lookup an object in the hash bucket.
 */
static struct debug_obj *lookup_object(void *addr, struct debug_bucket *b)
{
	struct hlist_node *node;
	struct debug_obj *obj;
	int cnt = 0;

	hlist_for_each_entry(obj, node, &b->list, node) {
		cnt++;
		if (obj->object == addr)
			return obj;
	}
	if (cnt > debug_objects_maxchain)
		debug_objects_maxchain = cnt;

	return NULL;
}

/*
 * Allocate a new object. If the pool is empty, switch off the debugger.
 * Must be called with interrupts disabled.
 */
static struct debug_obj *
alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr)
{
	struct debug_obj *obj = NULL;

	spin_lock(&pool_lock);
	if (obj_pool.first) {
		obj	    = hlist_entry(obj_pool.first, typeof(*obj), node);

		obj->object = addr;
		obj->descr  = descr;
		obj->state  = ODEBUG_STATE_NONE;
		hlist_del(&obj->node);

		hlist_add_head(&obj->node, &b->list);

		obj_pool_used++;
		if (obj_pool_used > obj_pool_max_used)
			obj_pool_max_used = obj_pool_used;

		obj_pool_free--;
		if (obj_pool_free < obj_pool_min_free)
			obj_pool_min_free = obj_pool_free;
	}
	spin_unlock(&pool_lock);

	return obj;
}

/*
 * Put the object back into the pool or give it back to kmem_cache:
 */
static void free_object(struct debug_obj *obj)
{
	unsigned long idx = (unsigned long)(obj - obj_static_pool);
	unsigned long flags;

	if (obj_pool_free < ODEBUG_POOL_SIZE || idx < ODEBUG_POOL_SIZE) {
		spin_lock_irqsave(&pool_lock, flags);
		hlist_add_head(&obj->node, &obj_pool);
		obj_pool_free++;
		obj_pool_used--;
		spin_unlock_irqrestore(&pool_lock, flags);
	} else {
		spin_lock_irqsave(&pool_lock, flags);
		obj_pool_used--;
		spin_unlock_irqrestore(&pool_lock, flags);
		kmem_cache_free(obj_cache, obj);
	}
}

/*
 * We run out of memory. That means we probably have tons of objects
 * allocated.
 */
static void debug_objects_oom(void)
{
	struct debug_bucket *db = obj_hash;
	struct hlist_node *node, *tmp;
	HLIST_HEAD(freelist);
	struct debug_obj *obj;
	unsigned long flags;
	int i;

	printk(KERN_WARNING "ODEBUG: Out of memory. ODEBUG disabled\n");

	for (i = 0; i < ODEBUG_HASH_SIZE; i++, db++) {
		spin_lock_irqsave(&db->lock, flags);
		hlist_move_list(&db->list, &freelist);
		spin_unlock_irqrestore(&db->lock, flags);

		/* Now free them */
		hlist_for_each_entry_safe(obj, node, tmp, &freelist, node) {
			hlist_del(&obj->node);
			free_object(obj);
		}
	}
}

/*
 * We use the pfn of the address for the hash. That way we can check
 * for freed objects simply by checking the affected bucket.
 */
static struct debug_bucket *get_bucket(unsigned long addr)
{
	unsigned long hash;

	hash = hash_long((addr >> ODEBUG_CHUNK_SHIFT), ODEBUG_HASH_BITS);
	return &obj_hash[hash];
}

static void debug_print_object(struct debug_obj *obj, char *msg)
{
	static int limit;

	if (limit < 5 && obj->descr != descr_test) {
		limit++;
		WARN(1, KERN_ERR "ODEBUG: %s %s object type: %s\n", msg,
		       obj_states[obj->state], obj->descr->name);
	}
	debug_objects_warnings++;
}

/*
 * Try to repair the damage, so we have a better chance to get useful
 * debug output.
 */
static void
debug_object_fixup(int (*fixup)(void *addr, enum debug_obj_state state),
		   void * addr, enum debug_obj_state state)
{
	if (fixup)
		debug_objects_fixups += fixup(addr, state);
}

static void debug_object_is_on_stack(void *addr, int onstack)
{
	int is_on_stack;
	static int limit;

	if (limit > 4)
		return;

	is_on_stack = object_is_on_stack(addr);
	if (is_on_stack == onstack)
		return;

	limit++;
	if (is_on_stack)
		printk(KERN_WARNING
		       "ODEBUG: object is on stack, but not annotated\n");
	else
		printk(KERN_WARNING
		       "ODEBUG: object is not on stack, but annotated\n");
	WARN_ON(1);
}

static void
__debug_object_init(void *addr, struct debug_obj_descr *descr, int onstack)
{
	enum debug_obj_state state;
	struct debug_bucket *db;
	struct debug_obj *obj;
	unsigned long flags;

	fill_pool();

	db = get_bucket((unsigned long) addr);

	spin_lock_irqsave(&db->lock, flags);

	obj = lookup_object(addr, db);
	if (!obj) {
		obj = alloc_object(addr, db, descr);
		if (!obj) {
			debug_objects_enabled = 0;
			spin_unlock_irqrestore(&db->lock, flags);
			debug_objects_oom();
			return;
		}
		debug_object_is_on_stack(addr, onstack);
	}

	switch (obj->state) {
	case ODEBUG_STATE_NONE:
	case ODEBUG_STATE_INIT:
	case ODEBUG_STATE_INACTIVE:
		obj->state = ODEBUG_STATE_INIT;
		break;

	case ODEBUG_STATE_ACTIVE:
		debug_print_object(obj, "init");
		state = obj->state;
		spin_unlock_irqrestore(&db->lock, flags);
		debug_object_fixup(descr->fixup_init, addr, state);
		return;

	case ODEBUG_STATE_DESTROYED:
		debug_print_object(obj, "init");
		break;
	default:
		break;
	}

	spin_unlock_irqrestore(&db->lock, flags);
}

/**
 * debug_object_init - debug checks when an object is initialized
 * @addr:	address of the object
 * @descr:	pointer to an object specific debug description structure
 */
void debug_object_init(void *addr, struct debug_obj_descr *descr)
{
	if (!debug_objects_enabled)
		return;

	__debug_object_init(addr, descr, 0);
}

/**
 * debug_object_init_on_stack - debug checks when an object on stack is
 *				initialized
 * @addr:	address of the object
 * @descr:	pointer to an object specific debug description structure
 */
void debug_object_init_on_stack(void *addr, struct debug_obj_descr *descr)
{
	if (!debug_objects_enabled)
		return;

	__debug_object_init(addr, descr, 1);
}

/**
 * debug_object_activate - debug checks when an object is activated
 * @addr:	address of the object
 * @descr:	pointer to an object specific debug description structure
 */
void debug_object_activate(void *addr, struct debug_obj_descr *descr)
{
	enum debug_obj_state state;
	struct debug_bucket *db;
	struct debug_obj *obj;
	unsigned long flags;

	if (!debug_objects_enabled)
		return;

	db = get_bucket((unsigned long) addr);

	spin_lock_irqsave(&db->lock, flags);

	obj = lookup_object(addr, db);
	if (obj) {
		switch (obj->state) {
		case ODEBUG_STATE_INIT:
		case ODEBUG_STATE_INACTIVE:
			obj->state = ODEBUG_STATE_ACTIVE;
			break;

		case ODEBUG_STATE_ACTIVE:
			debug_print_object(obj, "activate");
			state = obj->state;
			spin_unlock_irqrestore(&db->lock, flags);
			debug_object_fixup(descr->fixup_activate, addr, state);
			return;

		case ODEBUG_STATE_DESTROYED:
			debug_print_object(obj, "activate");
			break;
		default:
			break;
		}
		spin_unlock_irqrestore(&db->lock, flags);
		return;
	}

	spin_unlock_irqrestore(&db->lock, flags);
	/*
	 * This happens when a static object is activated. We
	 * let the type specific code decide whether this is
	 * true or not.
	 */
	debug_object_fixup(descr->fixup_activate, addr,
			   ODEBUG_STATE_NOTAVAILABLE);
}

/**
 * debug_object_deactivate - debug checks when an object is deactivated
 * @addr:	address of the object
 * @descr:	pointer to an object specific debug description structure
 */
void debug_object_deactivate(void *addr, struct debug_obj_descr *descr)
{
	struct debug_bucket *db;
	struct debug_obj *obj;
	unsigned long flags;

	if (!debug_objects_enabled)
		return;

	db = get_bucket((unsigned long) addr);

	spin_lock_irqsave(&db->lock, flags);

	obj = lookup_object(addr, db);
	if (obj) {
		switch (obj->state) {
		case ODEBUG_STATE_INIT:
		case ODEBUG_STATE_INACTIVE:
		case ODEBUG_STATE_ACTIVE:
			obj->state = ODEBUG_STATE_INACTIVE;
			break;

		case ODEBUG_STATE_DESTROYED:
			debug_print_object(obj, "deactivate");
			break;
		default:
			break;
		}
	} else {
		struct debug_obj o = { .object = addr,
				       .state = ODEBUG_STATE_NOTAVAILABLE,
				       .descr = descr };

		debug_print_object(&o, "deactivate");
	}

	spin_unlock_irqrestore(&db->lock, flags);
}

/**
 * debug_object_destroy - debug checks when an object is destroyed
 * @addr:	address of the object
 * @descr:	pointer to an object specific debug description structure
 */
void debug_object_destroy(void *addr, struct debug_obj_descr *descr)
{
	enum debug_obj_state state;
	struct debug_bucket *db;
	struct debug_obj *obj;
	unsigned long flags;

	if (!debug_objects_enabled)
		return;

	db = get_bucket((unsigned long) addr);

	spin_lock_irqsave(&db->lock, flags);

	obj = lookup_object(addr, db);