scripts/documentation-file-ref-check: hint: dash or underline

[mirror_ubuntu-jammy-kernel.git] / lib / debugobjects.c

/*
 * Generic infrastructure for lifetime debugging of objects.
 *
 * Started by Thomas Gleixner
 *
 * Copyright (C) 2008, Thomas Gleixner <tglx@linutronix.de>
 *
 * For licencing details see kernel-base/COPYING
 */

#define pr_fmt(fmt) "ODEBUG: " fmt

#include <linux/debugobjects.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/slab.h>
#include <linux/hash.h>
#include <linux/kmemleak.h>

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

#define ODEBUG_POOL_SIZE        1024
#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;
        raw_spinlock_t          lock;
};

static struct debug_bucket      obj_hash[ODEBUG_HASH_SIZE];

static struct debug_obj         obj_static_pool[ODEBUG_POOL_SIZE] __initdata;

static DEFINE_RAW_SPINLOCK(pool_lock);

static HLIST_HEAD(obj_pool);
static HLIST_HEAD(obj_to_free);

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;
/* The number of objs on the global free list */
static int                      obj_nr_tofree;
static struct kmem_cache        *obj_cache;

static int                      debug_objects_maxchain __read_mostly;
static int __maybe_unused       debug_objects_maxchecked __read_mostly;
static int                      debug_objects_fixups __read_mostly;
static int                      debug_objects_warnings __read_mostly;
static int                      debug_objects_enabled __read_mostly
                                = CONFIG_DEBUG_OBJECTS_ENABLE_DEFAULT;
static int                      debug_objects_pool_size __read_mostly
                                = ODEBUG_POOL_SIZE;
static int                      debug_objects_pool_min_level __read_mostly
                                = ODEBUG_POOL_MIN_LEVEL;
static struct debug_obj_descr   *descr_test  __read_mostly;

/*
 * Track numbers of kmem_cache_alloc()/free() calls done.
 */
static int                      debug_objects_allocated;
static int                      debug_objects_freed;

static void free_obj_work(struct work_struct *work);
static DECLARE_WORK(debug_obj_work, free_obj_work);

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

static int __init disable_object_debug(char *str)
{
        debug_objects_enabled = 0;
        return 0;
}

early_param("debug_objects", enable_object_debug);
early_param("no_debug_objects", disable_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 void fill_pool(void)
{
        gfp_t gfp = GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN;
        struct debug_obj *new, *obj;
        unsigned long flags;

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

        /*
         * Reuse objs from the global free list; they will be reinitialized
         * when allocating.
         */
        while (obj_nr_tofree && (obj_pool_free < obj_pool_min_free)) {
                raw_spin_lock_irqsave(&pool_lock, flags);
                /*
                 * Recheck with the lock held as the worker thread might have
                 * won the race and freed the global free list already.
                 */
                if (obj_nr_tofree) {
                        obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
                        hlist_del(&obj->node);
                        obj_nr_tofree--;
                        hlist_add_head(&obj->node, &obj_pool);
                        obj_pool_free++;
                }
                raw_spin_unlock_irqrestore(&pool_lock, flags);
        }

        if (unlikely(!obj_cache))
                return;

        while (obj_pool_free < debug_objects_pool_min_level) {

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

                kmemleak_ignore(new);
                raw_spin_lock_irqsave(&pool_lock, flags);
                hlist_add_head(&new->node, &obj_pool);
                debug_objects_allocated++;
                obj_pool_free++;
                raw_spin_unlock_irqrestore(&pool_lock, flags);
        }
}

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

        hlist_for_each_entry(obj, &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;

        raw_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;
                obj->astate = 0;
                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;
        }
        raw_spin_unlock(&pool_lock);

        return obj;
}

/*
 * workqueue function to free objects.
 *
 * To reduce contention on the global pool_lock, the actual freeing of
 * debug objects will be delayed if the pool_lock is busy.
 */
static void free_obj_work(struct work_struct *work)
{
        struct hlist_node *tmp;
        struct debug_obj *obj;
        unsigned long flags;
        HLIST_HEAD(tofree);

        if (!raw_spin_trylock_irqsave(&pool_lock, flags))
                return;

        /*
         * The objs on the pool list might be allocated before the work is
         * run, so recheck if pool list it full or not, if not fill pool
         * list from the global free list
         */
        while (obj_nr_tofree && obj_pool_free < debug_objects_pool_size) {
                obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
                hlist_del(&obj->node);
                hlist_add_head(&obj->node, &obj_pool);
                obj_pool_free++;
                obj_nr_tofree--;
        }

        /*
         * Pool list is already full and there are still objs on the free
         * list. Move remaining free objs to a temporary list to free the
         * memory outside the pool_lock held region.
         */
        if (obj_nr_tofree) {
                hlist_move_list(&obj_to_free, &tofree);
                debug_objects_freed += obj_nr_tofree;
                obj_nr_tofree = 0;
        }
        raw_spin_unlock_irqrestore(&pool_lock, flags);

        hlist_for_each_entry_safe(obj, tmp, &tofree, node) {
                hlist_del(&obj->node);
                kmem_cache_free(obj_cache, obj);
        }
}

static bool __free_object(struct debug_obj *obj)
{
        unsigned long flags;
        bool work;

        raw_spin_lock_irqsave(&pool_lock, flags);
        work = (obj_pool_free > debug_objects_pool_size) && obj_cache;
        obj_pool_used--;

        if (work) {
                obj_nr_tofree++;
                hlist_add_head(&obj->node, &obj_to_free);
        } else {
                obj_pool_free++;
                hlist_add_head(&obj->node, &obj_pool);
        }
        raw_spin_unlock_irqrestore(&pool_lock, flags);
        return work;
}

/*
 * Put the object back into the pool and schedule work to free objects
 * if necessary.
 */
static void free_object(struct debug_obj *obj)
{
        if (__free_object(obj))
                schedule_work(&debug_obj_work);
}

/*
 * 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 *tmp;
        HLIST_HEAD(freelist);
        struct debug_obj *obj;
        unsigned long flags;
        int i;

        pr_warn("Out of memory. ODEBUG disabled\n");

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

                /* Now free them */
                hlist_for_each_entry_safe(obj, 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)
{
        struct debug_obj_descr *descr = obj->descr;
        static int limit;

        if (limit < 5 && descr != descr_test) {
                void *hint = descr->debug_hint ?
                        descr->debug_hint(obj->object) : NULL;
                limit++;
                WARN(1, KERN_ERR "ODEBUG: %s %s (active state %u) "
                                 "object type: %s hint: %pS\n",
                        msg, obj_states[obj->state], obj->astate,
                        descr->name, hint);
        }
        debug_objects_warnings++;
}

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

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)
                pr_warn("object is on stack, but not annotated\n");
        else
                pr_warn("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);

        raw_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;
                        raw_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;
                raw_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;
        }

        raw_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);
}
EXPORT_SYMBOL_GPL(debug_object_init);

/**
 * 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);
}
EXPORT_SYMBOL_GPL(debug_object_init_on_stack);

/**
 * debug_object_activate - debug checks when an object is activated
 * @addr:       address of the object
 * @descr:      pointer to an object specific debug description structure
 * Returns 0 for success, -EINVAL for check failed.
 */
int 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;
        int ret;
        struct debug_obj o = { .object = addr,
                               .state = ODEBUG_STATE_NOTAVAILABLE,
                               .descr = descr };

        if (!debug_objects_enabled)
                return 0;

        db = get_bucket((unsigned long) addr);

        raw_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;
                        ret = 0;
                        break;

                case ODEBUG_STATE_ACTIVE:
                        debug_print_object(obj, "activate");
                        state = obj->state;
                        raw_spin_unlock_irqrestore(&db->lock, flags);
                        ret = debug_object_fixup(descr->fixup_activate, addr, state);
                        return ret ? 0 : -EINVAL;

                case ODEBUG_STATE_DESTROYED:
                        debug_print_object(obj, "activate");
                        ret = -EINVAL;
                        break;
                default:
                        ret = 0;
                        break;
                }
                raw_spin_unlock_irqrestore(&db->lock, flags);
                return ret;
        }

        raw_spin_unlock_irqrestore(&db->lock, flags);
        /*
         * We are here when a static object is activated. We
         * let the type specific code confirm whether this is
         * true or not. if true, we just make sure that the
         * static object is tracked in the object tracker. If
         * not, this must be a bug, so we try to fix it up.
         */
        if (descr->is_static_object && descr->is_static_object(addr)) {
                /* track this static object */
                debug_object_init(addr, descr);
                debug_object_activate(addr, descr);
        } else {
                debug_print_object(&o, "activate");
                ret = debug_object_fixup(descr->fixup_activate, addr,
                                        ODEBUG_STATE_NOTAVAILABLE);
                return ret ? 0 : -EINVAL;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(debug_object_activate);

/**
 * 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);

        raw_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:
                        if (!obj->astate)
                                obj->state = ODEBUG_STATE_INACTIVE;
                        else
                                debug_print_object(obj, "deactivate");
                        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");
        }

        raw_spin_unlock_irqrestore(&db->lock, flags);
}
EXPORT_SYMBOL_GPL(debug_object_deactivate);

/**
 * 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);

        raw_spin_lock_irqsave(&db->lock, flags);

        obj = lookup_object(addr, db);
        if (!obj)
                goto out_unlock;

        switch (obj->state) {
        case ODEBUG_STATE_NONE:
        case ODEBUG_STATE_INIT:
        case ODEBUG_STATE_INACTIVE:
                obj->state = ODEBUG_STATE_DESTROYED;
                break;
        case ODEBUG_STATE_ACTIVE:
                debug_print_object(obj, "destroy");
                state = obj->state;
                raw_spin_unlock_irqrestore(&db->lock, flags);
                debug_object_fixup(descr->fixup_destroy, addr, state);
                return;

        case ODEBUG_STATE_DESTROYED:
                debug_print_object(obj, "destroy");
                break;
        default:
                break;
        }
out_unlock:
        raw_spin_unlock_irqrestore(&db->lock, flags);
}
EXPORT_SYMBOL_GPL(debug_object_destroy);

/**
 * debug_object_free - debug checks when an object is freed
 * @addr:       address of the object
 * @descr:      pointer to an object specific debug description structure
 */
void debug_object_free(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);

        raw_spin_lock_irqsave(&db->lock, flags);

        obj = lookup_object(addr, db);
        if (!obj)
                goto out_unlock;

        switch (obj->state) {
        case ODEBUG_STATE_ACTIVE:
                debug_print_object(obj, "free");
                state = obj->state;
                raw_spin_unlock_irqrestore(&db->lock, flags);
                debug_object_fixup(descr->fixup_free, addr, state);
                return;
        default:
                hlist_del(&obj->node);
                raw_spin_unlock_irqrestore(&db->lock, flags);
                free_object(obj);
                return;
        }
out_unlock:
        raw_spin_unlock_irqrestore(&db->lock, flags);
}
EXPORT_SYMBOL_GPL(debug_object_free);

/**
 * debug_object_assert_init - debug checks when object should be init-ed
 * @addr:       address of the object
 * @descr:      pointer to an object specific debug description structure
 */
void debug_object_assert_init(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);

        raw_spin_lock_irqsave(&db->lock, flags);

        obj = lookup_object(addr, db);
        if (!obj) {
                struct debug_obj o = { .object = addr,
                                       .state = ODEBUG_STATE_NOTAVAILABLE,
                                       .descr = descr };

                raw_spin_unlock_irqrestore(&db->lock, flags);
                /*
                 * Maybe the object is static, and we let the type specific
                 * code confirm. Track this static object if true, else invoke
                 * fixup.
                 */
                if (descr->is_static_object && descr->is_static_object(addr)) {
                        /* Track this static object */
                        debug_object_init(addr, descr);
                } else {
                        debug_print_object(&o, "assert_init");
                        debug_object_fixup(descr->fixup_assert_init, addr,
                                           ODEBUG_STATE_NOTAVAILABLE);
                }
                return;
        }

        raw_spin_unlock_irqrestore(&db->lock, flags);
}
EXPORT_SYMBOL_GPL(debug_object_assert_init);

/**
 * debug_object_active_state - debug checks object usage state machine
 * @addr:       address of the object
 * @descr:      pointer to an object specific debug description structure
 * @expect:     expected state
 * @next:       state to move to if expected state is found
 */
void
debug_object_active_state(void *addr, struct debug_obj_descr *descr,
                          unsigned int expect, unsigned int next)
{
        struct debug_bucket *db;
        struct debug_obj *obj;
        unsigned long flags;

        if (!debug_objects_enabled)
                return;

        db = get_bucket((unsigned long) addr);

        raw_spin_lock_irqsave(&db->lock, flags);

        obj = lookup_object(addr, db);
        if (obj) {
                switch (obj->state) {
                case ODEBUG_STATE_ACTIVE:
                        if (obj->astate == expect)
                                obj->astate = next;
                        else
                                debug_print_object(obj, "active_state");
                        break;

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

                debug_print_object(&o, "active_state");
        }

        raw_spin_unlock_irqrestore(&db->lock, flags);
}
EXPORT_SYMBOL_GPL(debug_object_active_state);

#ifdef CONFIG_DEBUG_OBJECTS_FREE
static void __debug_check_no_obj_freed(const void *address, unsigned long size)
{
        unsigned long flags, oaddr, saddr, eaddr, paddr, chunks;
        struct debug_obj_descr *descr;
        enum debug_obj_state state;
        struct debug_bucket *db;
        struct hlist_node *tmp;
        struct debug_obj *obj;
        int cnt, objs_checked = 0;
        bool work = false;

        saddr = (unsigned long) address;
        eaddr = saddr + size;
        paddr = saddr & ODEBUG_CHUNK_MASK;
        chunks = ((eaddr - paddr) + (ODEBUG_CHUNK_SIZE - 1));
        chunks >>= ODEBUG_CHUNK_SHIFT;

        for (;chunks > 0; chunks--, paddr += ODEBUG_CHUNK_SIZE) {
                db = get_bucket(paddr);

repeat:
                cnt = 0;
                raw_spin_lock_irqsave(&db->lock, flags);
                hlist_for_each_entry_safe(obj, tmp, &db->list, node) {
                        cnt++;
                        oaddr = (unsigned long) obj->object;
                        if (oaddr < saddr || oaddr >= eaddr)
                                continue;

                        switch (obj->state) {
                        case ODEBUG_STATE_ACTIVE:
                                debug_print_object(obj, "free");
                                descr = obj->descr;
                                state = obj->state;
                                raw_spin_unlock_irqrestore(&db->lock, flags);
                                debug_object_fixup(descr->fixup_free,
                                                   (void *) oaddr, state);
                                goto repeat;
                        default:
                                hlist_del(&obj->node);
                                work |= __free_object(obj);
                                break;
                        }
                }
                raw_spin_unlock_irqrestore(&db->lock, flags);

                if (cnt > debug_objects_maxchain)
                        debug_objects_maxchain = cnt;

                objs_checked += cnt;
        }

        if (objs_checked > debug_objects_maxchecked)
                debug_objects_maxchecked = objs_checked;

        /* Schedule work to actually kmem_cache_free() objects */
        if (work)
                schedule_work(&debug_obj_work);
}

void debug_check_no_obj_freed(const void *address, unsigned long size)
{
        if (debug_objects_enabled)
                __debug_check_no_obj_freed(address, size);
}
#endif

#ifdef CONFIG_DEBUG_FS

static int debug_stats_show(struct seq_file *m, void *v)
{
        seq_printf(m, "max_chain     :%d\n", debug_objects_maxchain);
        seq_printf(m, "max_checked   :%d\n", debug_objects_maxchecked);
        seq_printf(m, "warnings      :%d\n", debug_objects_warnings);
        seq_printf(m, "fixups        :%d\n", debug_objects_fixups);
        seq_printf(m, "pool_free     :%d\n", obj_pool_free);
        seq_printf(m, "pool_min_free :%d\n", obj_pool_min_free);
        seq_printf(m, "pool_used     :%d\n", obj_pool_used);
        seq_printf(m, "pool_max_used :%d\n", obj_pool_max_used);
        seq_printf(m, "on_free_list  :%d\n", obj_nr_tofree);
        seq_printf(m, "objs_allocated:%d\n", debug_objects_allocated);
        seq_printf(m, "objs_freed    :%d\n", debug_objects_freed);
        return 0;
}

static int debug_stats_open(struct inode *inode, struct file *filp)
{
        return single_open(filp, debug_stats_show, NULL);
}

static const struct file_operations debug_stats_fops = {
        .open           = debug_stats_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
};

static int __init debug_objects_init_debugfs(void)
{
        struct dentry *dbgdir, *dbgstats;

        if (!debug_objects_enabled)
                return 0;

        dbgdir = debugfs_create_dir("debug_objects", NULL);
        if (!dbgdir)
                return -ENOMEM;

        dbgstats = debugfs_create_file("stats", 0444, dbgdir, NULL,
                                       &debug_stats_fops);
        if (!dbgstats)
                goto err;

        return 0;

err:
        debugfs_remove(dbgdir);

        return -ENOMEM;
}
__initcall(debug_objects_init_debugfs);

#else
static inline void debug_objects_init_debugfs(void) { }
#endif

#ifdef CONFIG_DEBUG_OBJECTS_SELFTEST

/* Random data structure for the self test */
struct self_test {
        unsigned long   dummy1[6];
        int             static_init;
        unsigned long   dummy2[3];
};

static __initdata struct debug_obj_descr descr_type_test;

static bool __init is_static_object(void *addr)
{
        struct self_test *obj = addr;

        return obj->static_init;
}

/*
 * fixup_init is called when:
 * - an active object is initialized
 */
static bool __init fixup_init(void *addr, enum debug_obj_state state)
{
        struct self_test *obj = addr;

        switch (state) {
        case ODEBUG_STATE_ACTIVE:
                debug_object_deactivate(obj, &descr_type_test);
                debug_object_init(obj, &descr_type_test);
                return true;
        default:
                return false;
        }
}

/*
 * fixup_activate is called when:
 * - an active object is activated
 * - an unknown non-static object is activated
 */
static bool __init fixup_activate(void *addr, enum debug_obj_state state)
{
        struct self_test *obj = addr;

        switch (state) {
        case ODEBUG_STATE_NOTAVAILABLE:
                return true;
        case ODEBUG_STATE_ACTIVE:
                debug_object_deactivate(obj, &descr_type_test);
                debug_object_activate(obj, &descr_type_test);
                return true;

        default:
                return false;
        }
}

/*
 * fixup_destroy is called when:
 * - an active object is destroyed
 */
static bool __init fixup_destroy(void *addr, enum debug_obj_state state)
{
        struct self_test *obj = addr;

        switch (state) {
        case ODEBUG_STATE_ACTIVE:
                debug_object_deactivate(obj, &descr_type_test);
                debug_object_destroy(obj, &descr_type_test);
                return true;
        default:
                return false;
        }
}

/*
 * fixup_free is called when:
 * - an active object is freed
 */
static bool __init fixup_free(void *addr, enum debug_obj_state state)
{
        struct self_test *obj = addr;

        switch (state) {
        case ODEBUG_STATE_ACTIVE:
                debug_object_deactivate(obj, &descr_type_test);
                debug_object_free(obj, &descr_type_test);
                return true;
        default:
                return false;
        }
}

static int __init
check_results(void *addr, enum debug_obj_state state, int fixups, int warnings)
{
        struct debug_bucket *db;
        struct debug_obj *obj;
        unsigned long flags;
        int res = -EINVAL;

        db = get_bucket((unsigned long) addr);

        raw_spin_lock_irqsave(&db->lock, flags);

        obj = lookup_object(addr, db);
        if (!obj && state != ODEBUG_STATE_NONE) {
                WARN(1, KERN_ERR "ODEBUG: selftest object not found\n");
                goto out;
        }
        if (obj && obj->state != state) {
                WARN(1, KERN_ERR "ODEBUG: selftest wrong state: %d != %d\n",
                       obj->state, state);
                goto out;
        }
        if (fixups != debug_objects_fixups) {
                WARN(1, KERN_ERR "ODEBUG: selftest fixups failed %d != %d\n",
                       fixups, debug_objects_fixups);
                goto out;
        }
        if (warnings != debug_objects_warnings) {
                WARN(1, KERN_ERR "ODEBUG: selftest warnings failed %d != %d\n",
                       warnings, debug_objects_warnings);
                goto out;
        }
        res = 0;
out:
        raw_spin_unlock_irqrestore(&db->lock, flags);
        if (res)
                debug_objects_enabled = 0;
        return res;
}

static __initdata struct debug_obj_descr descr_type_test = {
        .name                   = "selftest",
        .is_static_object       = is_static_object,
        .fixup_init             = fixup_init,
        .fixup_activate         = fixup_activate,
        .fixup_destroy          = fixup_destroy,
        .fixup_free             = fixup_free,
};

static __initdata struct self_test obj = { .static_init = 0 };

static void __init debug_objects_selftest(void)
{
        int fixups, oldfixups, warnings, oldwarnings;
        unsigned long flags;

        local_irq_save(flags);

        fixups = oldfixups = debug_objects_fixups;
        warnings = oldwarnings = debug_objects_warnings;
        descr_test = &descr_type_test;

        debug_object_init(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_INIT, fixups, warnings))
                goto out;
        debug_object_activate(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_ACTIVE, fixups, warnings))
                goto out;
        debug_object_activate(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_ACTIVE, ++fixups, ++warnings))
                goto out;
        debug_object_deactivate(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_INACTIVE, fixups, warnings))
                goto out;
        debug_object_destroy(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_DESTROYED, fixups, warnings))
                goto out;
        debug_object_init(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_DESTROYED, fixups, ++warnings))
                goto out;
        debug_object_activate(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_DESTROYED, fixups, ++warnings))
                goto out;
        debug_object_deactivate(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_DESTROYED, fixups, ++warnings))
                goto out;
        debug_object_free(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_NONE, fixups, warnings))
                goto out;

        obj.static_init = 1;
        debug_object_activate(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_ACTIVE, fixups, warnings))
                goto out;
        debug_object_init(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_INIT, ++fixups, ++warnings))
                goto out;
        debug_object_free(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_NONE, fixups, warnings))
                goto out;

#ifdef CONFIG_DEBUG_OBJECTS_FREE
        debug_object_init(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_INIT, fixups, warnings))
                goto out;
        debug_object_activate(&obj, &descr_type_test);
        if (check_results(&obj, ODEBUG_STATE_ACTIVE, fixups, warnings))
                goto out;
        __debug_check_no_obj_freed(&obj, sizeof(obj));
        if (check_results(&obj, ODEBUG_STATE_NONE, ++fixups, ++warnings))
                goto out;
#endif
        pr_info("selftest passed\n");

out:
        debug_objects_fixups = oldfixups;
        debug_objects_warnings = oldwarnings;
        descr_test = NULL;

        local_irq_restore(flags);
}
#else
static inline void debug_objects_selftest(void) { }
#endif

/*
 * Called during early boot to initialize the hash buckets and link
 * the static object pool objects into the poll list. After this call
 * the object tracker is fully operational.
 */
void __init debug_objects_early_init(void)
{
        int i;

        for (i = 0; i < ODEBUG_HASH_SIZE; i++)
                raw_spin_lock_init(&obj_hash[i].lock);

        for (i = 0; i < ODEBUG_POOL_SIZE; i++)
                hlist_add_head(&obj_static_pool[i].node, &obj_pool);
}

/*
 * Convert the statically allocated objects to dynamic ones:
 */
static int __init debug_objects_replace_static_objects(void)
{
        struct debug_bucket *db = obj_hash;
        struct hlist_node *tmp;
        struct debug_obj *obj, *new;
        HLIST_HEAD(objects);
        int i, cnt = 0;

        for (i = 0; i < ODEBUG_POOL_SIZE; i++) {
                obj = kmem_cache_zalloc(obj_cache, GFP_KERNEL);
                if (!obj)
                        goto free;
                kmemleak_ignore(obj);
                hlist_add_head(&obj->node, &objects);
        }

        /*
         * When debug_objects_mem_init() is called we know that only
         * one CPU is up, so disabling interrupts is enough
         * protection. This avoids the lockdep hell of lock ordering.
         */
        local_irq_disable();

        /* Remove the statically allocated objects from the pool */
        hlist_for_each_entry_safe(obj, tmp, &obj_pool, node)
                hlist_del(&obj->node);
        /* Move the allocated objects to the pool */
        hlist_move_list(&objects, &obj_pool);

        /* Replace the active object references */
        for (i = 0; i < ODEBUG_HASH_SIZE; i++, db++) {
                hlist_move_list(&db->list, &objects);

                hlist_for_each_entry(obj, &objects, node) {
                        new = hlist_entry(obj_pool.first, typeof(*obj), node);
                        hlist_del(&new->node);
                        /* copy object data */
                        *new = *obj;
                        hlist_add_head(&new->node, &db->list);
                        cnt++;
                }
        }
        local_irq_enable();

        pr_debug("%d of %d active objects replaced\n",
                 cnt, obj_pool_used);
        return 0;
free:
        hlist_for_each_entry_safe(obj, tmp, &objects, node) {
                hlist_del(&obj->node);
                kmem_cache_free(obj_cache, obj);
        }
        return -ENOMEM;
}

/*
 * Called after the kmem_caches are functional to setup a dedicated
 * cache pool, which has the SLAB_DEBUG_OBJECTS flag set. This flag
 * prevents that the debug code is called on kmem_cache_free() for the
 * debug tracker objects to avoid recursive calls.
 */
void __init debug_objects_mem_init(void)
{
        if (!debug_objects_enabled)
                return;

        obj_cache = kmem_cache_create("debug_objects_cache",
                                      sizeof (struct debug_obj), 0,
                                      SLAB_DEBUG_OBJECTS, NULL);

        if (!obj_cache || debug_objects_replace_static_objects()) {
                debug_objects_enabled = 0;
                if (obj_cache)
                        kmem_cache_destroy(obj_cache);
                pr_warn("out of memory.\n");
        } else
                debug_objects_selftest();

        /*
         * Increase the thresholds for allocating and freeing objects
         * according to the number of possible CPUs available in the system.
         */
        debug_objects_pool_size += num_possible_cpus() * 32;
        debug_objects_pool_min_level += num_possible_cpus() * 4;
}