dma-debug.c

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/*
 * Copyright (C) 2008 Advanced Micro Devices, Inc.
 *
 * Author: Joerg Roedel <[email protected]>
 *
 * 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
 */

#include <linux/scatterlist.h>
#include <linux/dma-mapping.h>
#include <linux/stacktrace.h>
#include <linux/dma-debug.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/export.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/slab.h>

#include <asm/sections.h>

#define HASH_SIZE       1024ULL
#define HASH_FN_SHIFT   13
#define HASH_FN_MASK    (HASH_SIZE - 1)

enum {
    dma_debug_single,
    dma_debug_page,
    dma_debug_sg,
    dma_debug_coherent,
};

#define DMA_DEBUG_STACKTRACE_ENTRIES 5

struct dma_debug_entry {
    struct list_head list;
    struct device    *dev;
    int              type;
    phys_addr_t      paddr;
    u64              dev_addr;
    u64              size;
    int              direction;
    int      sg_call_ents;
    int      sg_mapped_ents;
#ifdef CONFIG_STACKTRACE
    struct       stack_trace stacktrace;
    unsigned long    st_entries[DMA_DEBUG_STACKTRACE_ENTRIES];
#endif
};

typedef bool (*match_fn)(struct dma_debug_entry *, struct dma_debug_entry *);

struct hash_bucket {
    struct list_head list;
    spinlock_t lock;
} ____cacheline_aligned_in_smp;

/* Hash list to save the allocated dma addresses */
static struct hash_bucket dma_entry_hash[HASH_SIZE];
/* List of pre-allocated dma_debug_entry's */
static LIST_HEAD(free_entries);
/* Lock for the list above */
static DEFINE_SPINLOCK(free_entries_lock);

/* Global disable flag - will be set in case of an error */
static u32 global_disable __read_mostly;

/* Global error count */
static u32 error_count;

/* Global error show enable*/
static u32 show_all_errors __read_mostly;
/* Number of errors to show */
static u32 show_num_errors = 1;

static u32 num_free_entries;
static u32 min_free_entries;
static u32 nr_total_entries;

/* number of preallocated entries requested by kernel cmdline */
static u32 req_entries;

/* debugfs dentry's for the stuff above */
static struct dentry *dma_debug_dent        __read_mostly;
static struct dentry *global_disable_dent   __read_mostly;
static struct dentry *error_count_dent      __read_mostly;
static struct dentry *show_all_errors_dent  __read_mostly;
static struct dentry *show_num_errors_dent  __read_mostly;
static struct dentry *num_free_entries_dent __read_mostly;
static struct dentry *min_free_entries_dent __read_mostly;
static struct dentry *filter_dent           __read_mostly;

/* per-driver filter related state */

#define NAME_MAX_LEN    64

static char                  current_driver_name[NAME_MAX_LEN] __read_mostly;
static struct device_driver *current_driver                    __read_mostly;

static DEFINE_RWLOCK(driver_name_lock);

static const char *type2name[4] = { "single", "page",
                    "scather-gather", "coherent" };

static const char *dir2name[4] = { "DMA_BIDIRECTIONAL", "DMA_TO_DEVICE",
                   "DMA_FROM_DEVICE", "DMA_NONE" };

/*
 * The access to some variables in this macro is racy. We can't use atomic_t
 * here because all these variables are exported to debugfs. Some of them even
 * writeable. This is also the reason why a lock won't help much. But anyway,
 * the races are no big deal. Here is why:
 *
 *   error_count: the addition is racy, but the worst thing that can happen is
 *                that we don't count some errors
 *   show_num_errors: the subtraction is racy. Also no big deal because in
 *                    worst case this will result in one warning more in the
 *                    system log than the user configured. This variable is
 *                    writeable via debugfs.
 */
static inline void dump_entry_trace(struct dma_debug_entry *entry)
{
#ifdef CONFIG_STACKTRACE
    if (entry) {
        pr_warning("Mapped at:\n");
        print_stack_trace(&entry->stacktrace, 0);
    }
#endif
}

static bool driver_filter(struct device *dev)
{
    struct device_driver *drv;
    unsigned long flags;
    bool ret;

    /* driver filter off */
    if (likely(!current_driver_name[0]))
        return true;

    /* driver filter on and initialized */
    if (current_driver && dev && dev->driver == current_driver)
        return true;

    /* driver filter on, but we can't filter on a NULL device... */
    if (!dev)
        return false;

    if (current_driver || !current_driver_name[0])
        return false;

    /* driver filter on but not yet initialized */
    drv = dev->driver;
    if (!drv)
        return false;

    /* lock to protect against change of current_driver_name */
    read_lock_irqsave(&driver_name_lock, flags);

    ret = false;
    if (drv->name &&
        strncmp(current_driver_name, drv->name, NAME_MAX_LEN - 1) == 0) {
        current_driver = drv;
        ret = true;
    }

    read_unlock_irqrestore(&driver_name_lock, flags);

    return ret;
}

#define err_printk(dev, entry, format, arg...) do {         \
        error_count += 1;                   \
        if (driver_filter(dev) &&               \
            (show_all_errors || show_num_errors > 0)) {     \
            WARN(1, "%s %s: " format,           \
                 dev ? dev_driver_string(dev) : "NULL", \
                 dev ? dev_name(dev) : "NULL", ## arg); \
            dump_entry_trace(entry);            \
        }                           \
        if (!show_all_errors && show_num_errors > 0)        \
            show_num_errors -= 1;               \
    } while (0);

/*
 * Hash related functions
 *
 * Every DMA-API request is saved into a struct dma_debug_entry. To
 * have quick access to these structs they are stored into a hash.
 */
static int hash_fn(struct dma_debug_entry *entry)
{
    /*
     * Hash function is based on the dma address.
     * We use bits 20-27 here as the index into the hash
     */
    return (entry->dev_addr >> HASH_FN_SHIFT) & HASH_FN_MASK;
}

/*
 * Request exclusive access to a hash bucket for a given dma_debug_entry.
 */
static struct hash_bucket *get_hash_bucket(struct dma_debug_entry *entry,
                       unsigned long *flags)
{
    int idx = hash_fn(entry);
    unsigned long __flags;

    spin_lock_irqsave(&dma_entry_hash[idx].lock, __flags);
    *flags = __flags;
    return &dma_entry_hash[idx];
}

/*
 * Give up exclusive access to the hash bucket
 */
static void put_hash_bucket(struct hash_bucket *bucket,
                unsigned long *flags)
{
    unsigned long __flags = *flags;

    spin_unlock_irqrestore(&bucket->lock, __flags);
}

static bool exact_match(struct dma_debug_entry *a, struct dma_debug_entry *b)
{
    return ((a->dev_addr == b->dev_addr) &&
        (a->dev == b->dev)) ? true : false;
}

static bool containing_match(struct dma_debug_entry *a,
                 struct dma_debug_entry *b)
{
    if (a->dev != b->dev)
        return false;

    if ((b->dev_addr <= a->dev_addr) &&
        ((b->dev_addr + b->size) >= (a->dev_addr + a->size)))
        return true;

    return false;
}

/*
 * Search a given entry in the hash bucket list
 */
static struct dma_debug_entry *__hash_bucket_find(struct hash_bucket *bucket,
                          struct dma_debug_entry *ref,
                          match_fn match)
{
    struct dma_debug_entry *entry, *ret = NULL;
    int matches = 0, match_lvl, last_lvl = -1;

    list_for_each_entry(entry, &bucket->list, list) {
        if (!match(ref, entry))
            continue;

        /*
         * Some drivers map the same physical address multiple
         * times. Without a hardware IOMMU this results in the
         * same device addresses being put into the dma-debug
         * hash multiple times too. This can result in false
         * positives being reported. Therefore we implement a
         * best-fit algorithm here which returns the entry from
         * the hash which fits best to the reference value
         * instead of the first-fit.
         */
        matches += 1;
        match_lvl = 0;
        entry->size         == ref->size         ? ++match_lvl : 0;
        entry->type         == ref->type         ? ++match_lvl : 0;
        entry->direction    == ref->direction    ? ++match_lvl : 0;
        entry->sg_call_ents == ref->sg_call_ents ? ++match_lvl : 0;

        if (match_lvl == 4) {
            /* perfect-fit - return the result */
            return entry;
        } else if (match_lvl > last_lvl) {
            /*
             * We found an entry that fits better then the
             * previous one or it is the 1st match.
             */
            last_lvl = match_lvl;
            ret      = entry;
        }
    }

    /*
     * If we have multiple matches but no perfect-fit, just return
     * NULL.
     */
    ret = (matches == 1) ? ret : NULL;

    return ret;
}

static struct dma_debug_entry *bucket_find_exact(struct hash_bucket *bucket,
                         struct dma_debug_entry *ref)
{
    return __hash_bucket_find(bucket, ref, exact_match);
}

static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket,
                           struct dma_debug_entry *ref,
                           unsigned long *flags)
{

    unsigned int max_range = dma_get_max_seg_size(ref->dev);
    struct dma_debug_entry *entry, index = *ref;
    unsigned int range = 0;

    while (range <= max_range) {
        entry = __hash_bucket_find(*bucket, &index, containing_match);

        if (entry)
            return entry;

        /*
         * Nothing found, go back a hash bucket
         */
        put_hash_bucket(*bucket, flags);
        range          += (1 << HASH_FN_SHIFT);
        index.dev_addr -= (1 << HASH_FN_SHIFT);
        *bucket = get_hash_bucket(&index, flags);
    }

    return NULL;
}

/*
 * Add an entry to a hash bucket
 */
static void hash_bucket_add(struct hash_bucket *bucket,
                struct dma_debug_entry *entry)
{
    list_add_tail(&entry->list, &bucket->list);
}

/*
 * Remove entry from a hash bucket list
 */
static void hash_bucket_del(struct dma_debug_entry *entry)
{
    list_del(&entry->list);
}

/*
 * Dump mapping entries for debugging purposes
 */
void debug_dma_dump_mappings(struct device *dev)
{
    int idx;

    for (idx = 0; idx < HASH_SIZE; idx++) {
        struct hash_bucket *bucket = &dma_entry_hash[idx];
        struct dma_debug_entry *entry;
        unsigned long flags;

        spin_lock_irqsave(&bucket->lock, flags);

        list_for_each_entry(entry, &bucket->list, list) {
            if (!dev || dev == entry->dev) {
                dev_info(entry->dev,
                     "%s idx %d P=%Lx D=%Lx L=%Lx %s\n",
                     type2name[entry->type], idx,
                     (unsigned long long)entry->paddr,
                     entry->dev_addr, entry->size,
                     dir2name[entry->direction]);
            }
        }

        spin_unlock_irqrestore(&bucket->lock, flags);
    }
}
EXPORT_SYMBOL(debug_dma_dump_mappings);

/*
 * Wrapper function for adding an entry to the hash.
 * This function takes care of locking itself.
 */
static void add_dma_entry(struct dma_debug_entry *entry)
{
    struct hash_bucket *bucket;
    unsigned long flags;

    bucket = get_hash_bucket(entry, &flags);
    hash_bucket_add(bucket, entry);
    put_hash_bucket(bucket, &flags);
}

static struct dma_debug_entry *__dma_entry_alloc(void)
{
    struct dma_debug_entry *entry;

    entry = list_entry(free_entries.next, struct dma_debug_entry, list);
    list_del(&entry->list);
    memset(entry, 0, sizeof(*entry));

    num_free_entries -= 1;
    if (num_free_entries < min_free_entries)
        min_free_entries = num_free_entries;

    return entry;
}

/* struct dma_entry allocator
 *
 * The next two functions implement the allocator for
 * struct dma_debug_entries.
 */
static struct dma_debug_entry *dma_entry_alloc(void)
{
    struct dma_debug_entry *entry;
    unsigned long flags;

    spin_lock_irqsave(&free_entries_lock, flags);

    if (list_empty(&free_entries)) {
        pr_err("DMA-API: debugging out of memory - disabling\n");
        global_disable = true;
        spin_unlock_irqrestore(&free_entries_lock, flags);
        return NULL;
    }

    entry = __dma_entry_alloc();

    spin_unlock_irqrestore(&free_entries_lock, flags);

#ifdef CONFIG_STACKTRACE
    entry->stacktrace.max_entries = DMA_DEBUG_STACKTRACE_ENTRIES;
    entry->stacktrace.entries = entry->st_entries;
    entry->stacktrace.skip = 2;
    save_stack_trace(&entry->stacktrace);
#endif

    return entry;
}

static void dma_entry_free(struct dma_debug_entry *entry)
{
    unsigned long flags;

    /*
     * add to beginning of the list - this way the entries are
     * more likely cache hot when they are reallocated.
     */
    spin_lock_irqsave(&free_entries_lock, flags);
    list_add(&entry->list, &free_entries);
    num_free_entries += 1;
    spin_unlock_irqrestore(&free_entries_lock, flags);
}

int dma_debug_resize_entries(u32 num_entries)
{
    int i, delta, ret = 0;
    unsigned long flags;
    struct dma_debug_entry *entry;
    LIST_HEAD(tmp);

    spin_lock_irqsave(&free_entries_lock, flags);

    if (nr_total_entries < num_entries) {
        delta = num_entries - nr_total_entries;

        spin_unlock_irqrestore(&free_entries_lock, flags);

        for (i = 0; i < delta; i++) {
            entry = kzalloc(sizeof(*entry), GFP_KERNEL);
            if (!entry)
                break;

            list_add_tail(&entry->list, &tmp);
        }

        spin_lock_irqsave(&free_entries_lock, flags);

        list_splice(&tmp, &free_entries);
        nr_total_entries += i;
        num_free_entries += i;
    } else {
        delta = nr_total_entries - num_entries;

        for (i = 0; i < delta && !list_empty(&free_entries); i++) {
            entry = __dma_entry_alloc();
            kfree(entry);
        }

        nr_total_entries -= i;
    }

    if (nr_total_entries != num_entries)
        ret = 1;

    spin_unlock_irqrestore(&free_entries_lock, flags);

    return ret;
}
EXPORT_SYMBOL(dma_debug_resize_entries);

/*
 * DMA-API debugging init code
 *
 * The init code does two things:
 *   1. Initialize core data structures
 *   2. Preallocate a given number of dma_debug_entry structs
 */

static int prealloc_memory(u32 num_entries)
{
    struct dma_debug_entry *entry, *next_entry;
    int i;

    for (i = 0; i < num_entries; ++i) {
        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry)
            goto out_err;

        list_add_tail(&entry->list, &free_entries);
    }

    num_free_entries = num_entries;
    min_free_entries = num_entries;

    pr_info("DMA-API: preallocated %d debug entries\n", num_entries);

    return 0;

out_err:

    list_for_each_entry_safe(entry, next_entry, &free_entries, list) {
        list_del(&entry->list);
        kfree(entry);
    }

    return -ENOMEM;
}

static ssize_t filter_read(struct file *file, char __user *user_buf,
               size_t count, loff_t *ppos)
{
    char buf[NAME_MAX_LEN + 1];
    unsigned long flags;
    int len;

    if (!current_driver_name[0])
        return 0;

    /*
     * We can't copy to userspace directly because current_driver_name can
     * only be read under the driver_name_lock with irqs disabled. So
     * create a temporary copy first.
     */
    read_lock_irqsave(&driver_name_lock, flags);
    len = scnprintf(buf, NAME_MAX_LEN + 1, "%s\n", current_driver_name);
    read_unlock_irqrestore(&driver_name_lock, flags);

    return simple_read_from_buffer(user_buf, count, ppos, buf, len);
}

static ssize_t filter_write(struct file *file, const char __user *userbuf,
                size_t count, loff_t *ppos)
{
    char buf[NAME_MAX_LEN];
    unsigned long flags;
    size_t len;
    int i;

    /*
     * We can't copy from userspace directly. Access to
     * current_driver_name is protected with a write_lock with irqs
     * disabled. Since copy_from_user can fault and may sleep we
     * need to copy to temporary buffer first
     */
    len = min(count, (size_t)(NAME_MAX_LEN - 1));
    if (copy_from_user(buf, userbuf, len))
        return -EFAULT;

    buf[len] = 0;

    write_lock_irqsave(&driver_name_lock, flags);

    /*
     * Now handle the string we got from userspace very carefully.
     * The rules are:
     *         - only use the first token we got
     *         - token delimiter is everything looking like a space
     *           character (' ', '\n', '\t' ...)
     *
     */
    if (!isalnum(buf[0])) {
        /*
         * If the first character userspace gave us is not
         * alphanumerical then assume the filter should be
         * switched off.
         */
        if (current_driver_name[0])
            pr_info("DMA-API: switching off dma-debug driver filter\n");
        current_driver_name[0] = 0;
        current_driver = NULL;
        goto out_unlock;
    }

    /*
     * Now parse out the first token and use it as the name for the
     * driver to filter for.
     */
    for (i = 0; i < NAME_MAX_LEN - 1; ++i) {
        current_driver_name[i] = buf[i];
        if (isspace(buf[i]) || buf[i] == ' ' || buf[i] == 0)
            break;
    }
    current_driver_name[i] = 0;
    current_driver = NULL;

    pr_info("DMA-API: enable driver filter for driver [%s]\n",
        current_driver_name);

out_unlock:
    write_unlock_irqrestore(&driver_name_lock, flags);

    return count;
}

static const struct file_operations filter_fops = {
    .read  = filter_read,
    .write = filter_write,
    .llseek = default_llseek,
};

static int dma_debug_fs_init(void)
{
    dma_debug_dent = debugfs_create_dir("dma-api", NULL);
    if (!dma_debug_dent) {
        pr_err("DMA-API: can not create debugfs directory\n");
        return -ENOMEM;
    }

    global_disable_dent = debugfs_create_bool("disabled", 0444,
            dma_debug_dent,
            &global_disable);
    if (!global_disable_dent)
        goto out_err;

    error_count_dent = debugfs_create_u32("error_count", 0444,
            dma_debug_dent, &error_count);
    if (!error_count_dent)
        goto out_err;

    show_all_errors_dent = debugfs_create_u32("all_errors", 0644,
            dma_debug_dent,
            &show_all_errors);
    if (!show_all_errors_dent)
        goto out_err;

    show_num_errors_dent = debugfs_create_u32("num_errors", 0644,
            dma_debug_dent,
            &show_num_errors);
    if (!show_num_errors_dent)
        goto out_err;

    num_free_entries_dent = debugfs_create_u32("num_free_entries", 0444,
            dma_debug_dent,
            &num_free_entries);
    if (!num_free_entries_dent)
        goto out_err;

    min_free_entries_dent = debugfs_create_u32("min_free_entries", 0444,
            dma_debug_dent,
            &min_free_entries);
    if (!min_free_entries_dent)
        goto out_err;

    filter_dent = debugfs_create_file("driver_filter", 0644,
                      dma_debug_dent, NULL, &filter_fops);
    if (!filter_dent)
        goto out_err;

    return 0;

out_err:
    debugfs_remove_recursive(dma_debug_dent);

    return -ENOMEM;
}

static int device_dma_allocations(struct device *dev, struct dma_debug_entry **out_entry)
{
    struct dma_debug_entry *entry;
    unsigned long flags;
    int count = 0, i;

    local_irq_save(flags);

    for (i = 0; i < HASH_SIZE; ++i) {
        spin_lock(&dma_entry_hash[i].lock);
        list_for_each_entry(entry, &dma_entry_hash[i].list, list) {
            if (entry->dev == dev) {
                count += 1;
                *out_entry = entry;
            }
        }
        spin_unlock(&dma_entry_hash[i].lock);
    }

    local_irq_restore(flags);

    return count;
}

static int dma_debug_device_change(struct notifier_block *nb, unsigned long action, void *data)
{
    struct device *dev = data;
    struct dma_debug_entry *uninitialized_var(entry);
    int count;

    if (global_disable)
        return 0;

    switch (action) {
    case BUS_NOTIFY_UNBOUND_DRIVER:
        count = device_dma_allocations(dev, &entry);
        if (count == 0)
            break;
        err_printk(dev, entry, "DMA-API: device driver has pending "
                "DMA allocations while released from device "
                "[count=%d]\n"
                "One of leaked entries details: "
                "[device address=0x%016llx] [size=%llu bytes] "
                "[mapped with %s] [mapped as %s]\n",
            count, entry->dev_addr, entry->size,
            dir2name[entry->direction], type2name[entry->type]);
        break;
    default:
        break;
    }

    return 0;
}

void dma_debug_add_bus(struct bus_type *bus)
{
    struct notifier_block *nb;

    if (global_disable)
        return;

    nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL);
    if (nb == NULL) {
        pr_err("dma_debug_add_bus: out of memory\n");
        return;
    }

    nb->notifier_call = dma_debug_device_change;

    bus_register_notifier(bus, nb);
}

/*
 * Let the architectures decide how many entries should be preallocated.
 */
void dma_debug_init(u32 num_entries)
{
    int i;

    if (global_disable)
        return;

    for (i = 0; i < HASH_SIZE; ++i) {
        INIT_LIST_HEAD(&dma_entry_hash[i].list);
        spin_lock_init(&dma_entry_hash[i].lock);
    }

    if (dma_debug_fs_init() != 0) {
        pr_err("DMA-API: error creating debugfs entries - disabling\n");
        global_disable = true;

        return;
    }

    if (req_entries)
        num_entries = req_entries;

    if (prealloc_memory(num_entries) != 0) {
        pr_err("DMA-API: debugging out of memory error - disabled\n");
        global_disable = true;

        return;
    }

    nr_total_entries = num_free_entries;

    pr_info("DMA-API: debugging enabled by kernel config\n");
}

static __init int dma_debug_cmdline(char *str)
{
    if (!str)
        return -EINVAL;

    if (strncmp(str, "off", 3) == 0) {
        pr_info("DMA-API: debugging disabled on kernel command line\n");
        global_disable = true;
    }

    return 0;
}

static __init int dma_debug_entries_cmdline(char *str)
{
    int res;

    if (!str)
        return -EINVAL;

    res = get_option(&str, &req_entries);

    if (!res)
        req_entries = 0;

    return 0;
}

__setup("dma_debug=", dma_debug_cmdline);
__setup("dma_debug_entries=", dma_debug_entries_cmdline);

static void check_unmap(struct dma_debug_entry *ref)
{
    struct dma_debug_entry *entry;
    struct hash_bucket *bucket;
    unsigned long flags;

    if (dma_mapping_error(ref->dev, ref->dev_addr)) {
        err_printk(ref->dev, NULL, "DMA-API: device driver tries "
               "to free an invalid DMA memory address\n");
        return;
    }

    bucket = get_hash_bucket(ref, &flags);
    entry = bucket_find_exact(bucket, ref);

    if (!entry) {
        err_printk(ref->dev, NULL, "DMA-API: device driver tries "
               "to free DMA memory it has not allocated "
               "[device address=0x%016llx] [size=%llu bytes]\n",
               ref->dev_addr, ref->size);
        goto out;
    }

    if (ref->size != entry->size) {
        err_printk(ref->dev, entry, "DMA-API: device driver frees "
               "DMA memory with different size "
               "[device address=0x%016llx] [map size=%llu bytes] "
               "[unmap size=%llu bytes]\n",
               ref->dev_addr, entry->size, ref->size);
    }

    if (ref->type != entry->type) {
        err_printk(ref->dev, entry, "DMA-API: device driver frees "
               "DMA memory with wrong function "
               "[device address=0x%016llx] [size=%llu bytes] "
               "[mapped as %s] [unmapped as %s]\n",
               ref->dev_addr, ref->size,
               type2name[entry->type], type2name[ref->type]);
    } else if ((entry->type == dma_debug_coherent) &&
           (ref->paddr != entry->paddr)) {
        err_printk(ref->dev, entry, "DMA-API: device driver frees "
               "DMA memory with different CPU address "
               "[device address=0x%016llx] [size=%llu bytes] "
               "[cpu alloc address=0x%016llx] "
               "[cpu free address=0x%016llx]",
               ref->dev_addr, ref->size,
               (unsigned long long)entry->paddr,
               (unsigned long long)ref->paddr);
    }

    if (ref->sg_call_ents && ref->type == dma_debug_sg &&
        ref->sg_call_ents != entry->sg_call_ents) {
        err_printk(ref->dev, entry, "DMA-API: device driver frees "
               "DMA sg list with different entry count "
               "[map count=%d] [unmap count=%d]\n",
               entry->sg_call_ents, ref->sg_call_ents);
    }

    /*
     * This may be no bug in reality - but most implementations of the
     * DMA API don't handle this properly, so check for it here
     */
    if (ref->direction != entry->direction) {
        err_printk(ref->dev, entry, "DMA-API: device driver frees "
               "DMA memory with different direction "
               "[device address=0x%016llx] [size=%llu bytes] "
               "[mapped with %s] [unmapped with %s]\n",
               ref->dev_addr, ref->size,
               dir2name[entry->direction],
               dir2name[ref->direction]);
    }

    hash_bucket_del(entry);
    dma_entry_free(entry);

out:
    put_hash_bucket(bucket, &flags);
}

static void check_for_stack(struct device *dev, void *addr)
{
    if (object_is_on_stack(addr))
        err_printk(dev, NULL, "DMA-API: device driver maps memory from"
                "stack [addr=%p]\n", addr);
}

static inline bool overlap(void *addr, unsigned long len, void *start, void *end)
{
    unsigned long a1 = (unsigned long)addr;
    unsigned long b1 = a1 + len;
    unsigned long a2 = (unsigned long)start;
    unsigned long b2 = (unsigned long)end;

    return !(b1 <= a2 || a1 >= b2);
}

static void check_for_illegal_area(struct device *dev, void *addr, unsigned long len)
{
    if (overlap(addr, len, _text, _etext) ||
        overlap(addr, len, __start_rodata, __end_rodata))
        err_printk(dev, NULL, "DMA-API: device driver maps memory from kernel text or rodata [addr=%p] [len=%lu]\n", addr, len);
}

static void check_sync(struct device *dev,
               struct dma_debug_entry *ref,
               bool to_cpu)
{
    struct dma_debug_entry *entry;
    struct hash_bucket *bucket;
    unsigned long flags;

    bucket = get_hash_bucket(ref, &flags);

    entry = bucket_find_contain(&bucket, ref, &flags);

    if (!entry) {
        err_printk(dev, NULL, "DMA-API: device driver tries "
                "to sync DMA memory it has not allocated "
                "[device address=0x%016llx] [size=%llu bytes]\n",
                (unsigned long long)ref->dev_addr, ref->size);
        goto out;
    }

    if (ref->size > entry->size) {
        err_printk(dev, entry, "DMA-API: device driver syncs"
                " DMA memory outside allocated range "
                "[device address=0x%016llx] "
                "[allocation size=%llu bytes] "
                "[sync offset+size=%llu]\n",
                entry->dev_addr, entry->size,
                ref->size);
    }

    if (entry->direction == DMA_BIDIRECTIONAL)
        goto out;

    if (ref->direction != entry->direction) {
        err_printk(dev, entry, "DMA-API: device driver syncs "
                "DMA memory with different direction "
                "[device address=0x%016llx] [size=%llu bytes] "
                "[mapped with %s] [synced with %s]\n",
                (unsigned long long)ref->dev_addr, entry->size,
                dir2name[entry->direction],
                dir2name[ref->direction]);
    }

    if (to_cpu && !(entry->direction == DMA_FROM_DEVICE) &&
              !(ref->direction == DMA_TO_DEVICE))
        err_printk(dev, entry, "DMA-API: device driver syncs "
                "device read-only DMA memory for cpu "
                "[device address=0x%016llx] [size=%llu bytes] "
                "[mapped with %s] [synced with %s]\n",
                (unsigned long long)ref->dev_addr, entry->size,
                dir2name[entry->direction],
                dir2name[ref->direction]);

    if (!to_cpu && !(entry->direction == DMA_TO_DEVICE) &&
               !(ref->direction == DMA_FROM_DEVICE))
        err_printk(dev, entry, "DMA-API: device driver syncs "
                "device write-only DMA memory to device "
                "[device address=0x%016llx] [size=%llu bytes] "
                "[mapped with %s] [synced with %s]\n",
                (unsigned long long)ref->dev_addr, entry->size,
                dir2name[entry->direction],
                dir2name[ref->direction]);

out:
    put_hash_bucket(bucket, &flags);
}

void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
            size_t size, int direction, dma_addr_t dma_addr,
            bool map_single)
{
    struct dma_debug_entry *entry;

    if (unlikely(global_disable))
        return;

    if (unlikely(dma_mapping_error(dev, dma_addr)))
        return;

    entry = dma_entry_alloc();
    if (!entry)
        return;

    entry->dev       = dev;
    entry->type      = dma_debug_page;
    entry->paddr     = page_to_phys(page) + offset;
    entry->dev_addr  = dma_addr;
    entry->size      = size;
    entry->direction = direction;

    if (map_single)
        entry->type = dma_debug_single;

    if (!PageHighMem(page)) {
        void *addr = page_address(page) + offset;

        check_for_stack(dev, addr);
        check_for_illegal_area(dev, addr, size);
    }

    add_dma_entry(entry);
}
EXPORT_SYMBOL(debug_dma_map_page);

void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
              size_t size, int direction, bool map_single)
{
    struct dma_debug_entry ref = {
        .type           = dma_debug_page,
        .dev            = dev,
        .dev_addr       = addr,
        .size           = size,
        .direction      = direction,
    };

    if (unlikely(global_disable))
        return;

    if (map_single)
        ref.type = dma_debug_single;

    check_unmap(&ref);
}
EXPORT_SYMBOL(debug_dma_unmap_page);

void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,
              int nents, int mapped_ents, int direction)
{
    struct dma_debug_entry *entry;
    struct scatterlist *s;
    int i;

    if (unlikely(global_disable))
        return;

    for_each_sg(sg, s, mapped_ents, i) {
        entry = dma_entry_alloc();
        if (!entry)
            return;

        entry->type           = dma_debug_sg;
        entry->dev            = dev;
        entry->paddr          = sg_phys(s);
        entry->size           = sg_dma_len(s);
        entry->dev_addr       = sg_dma_address(s);
        entry->direction      = direction;
        entry->sg_call_ents   = nents;
        entry->sg_mapped_ents = mapped_ents;

        if (!PageHighMem(sg_page(s))) {
            check_for_stack(dev, sg_virt(s));
            check_for_illegal_area(dev, sg_virt(s), sg_dma_len(s));
        }

        add_dma_entry(entry);
    }
}
EXPORT_SYMBOL(debug_dma_map_sg);

static int get_nr_mapped_entries(struct device *dev,
                 struct dma_debug_entry *ref)
{
    struct dma_debug_entry *entry;
    struct hash_bucket *bucket;
    unsigned long flags;
    int mapped_ents;

    bucket       = get_hash_bucket(ref, &flags);
    entry        = bucket_find_exact(bucket, ref);
    mapped_ents  = 0;

    if (entry)
        mapped_ents = entry->sg_mapped_ents;
    put_hash_bucket(bucket, &flags);

    return mapped_ents;
}

void debug_dma_unmap_sg(struct device *dev, struct scatterlist *sglist,
            int nelems, int dir)
{
    struct scatterlist *s;
    int mapped_ents = 0, i;

    if (unlikely(global_disable))
        return;

    for_each_sg(sglist, s, nelems, i) {

        struct dma_debug_entry ref = {
            .type           = dma_debug_sg,
            .dev            = dev,
            .paddr          = sg_phys(s),
            .dev_addr       = sg_dma_address(s),
            .size           = sg_dma_len(s),
            .direction      = dir,
            .sg_call_ents   = nelems,
        };

        if (mapped_ents && i >= mapped_ents)
            break;

        if (!i)
            mapped_ents = get_nr_mapped_entries(dev, &ref);

        check_unmap(&ref);
    }
}
EXPORT_SYMBOL(debug_dma_unmap_sg);

void debug_dma_alloc_coherent(struct device *dev, size_t size,
                  dma_addr_t dma_addr, void *virt)
{
    struct dma_debug_entry *entry;

    if (unlikely(global_disable))
        return;

    if (unlikely(virt == NULL))
        return;

    entry = dma_entry_alloc();
    if (!entry)
        return;

    entry->type      = dma_debug_coherent;
    entry->dev       = dev;
    entry->paddr     = virt_to_phys(virt);
    entry->size      = size;
    entry->dev_addr  = dma_addr;
    entry->direction = DMA_BIDIRECTIONAL;

    add_dma_entry(entry);
}
EXPORT_SYMBOL(debug_dma_alloc_coherent);

void debug_dma_free_coherent(struct device *dev, size_t size,
             void *virt, dma_addr_t addr)
{
    struct dma_debug_entry ref = {
        .type           = dma_debug_coherent,
        .dev            = dev,
        .paddr          = virt_to_phys(virt),
        .dev_addr       = addr,
        .size           = size,
        .direction      = DMA_BIDIRECTIONAL,
    };

    if (unlikely(global_disable))
        return;

    check_unmap(&ref);
}
EXPORT_SYMBOL(debug_dma_free_coherent);

void debug_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
                   size_t size, int direction)
{
    struct dma_debug_entry ref;

    if (unlikely(global_disable))
        return;

    ref.type         = dma_debug_single;
    ref.dev          = dev;
    ref.dev_addr     = dma_handle;
    ref.size         = size;
    ref.direction    = direction;
    ref.sg_call_ents = 0;

    check_sync(dev, &ref, true);
}
EXPORT_SYMBOL(debug_dma_sync_single_for_cpu);

void debug_dma_sync_single_for_device(struct device *dev,
                      dma_addr_t dma_handle, size_t size,
                      int direction)
{
    struct dma_debug_entry ref;

    if (unlikely(global_disable))
        return;

    ref.type         = dma_debug_single;
    ref.dev          = dev;
    ref.dev_addr     = dma_handle;
    ref.size         = size;
    ref.direction    = direction;
    ref.sg_call_ents = 0;

    check_sync(dev, &ref, false);
}
EXPORT_SYMBOL(debug_dma_sync_single_for_device);

void debug_dma_sync_single_range_for_cpu(struct device *dev,
                     dma_addr_t dma_handle,
                     unsigned long offset, size_t size,
                     int direction)
{
    struct dma_debug_entry ref;

    if (unlikely(global_disable))
        return;

    ref.type         = dma_debug_single;
    ref.dev          = dev;
    ref.dev_addr     = dma_handle;
    ref.size         = offset + size;
    ref.direction    = direction;
    ref.sg_call_ents = 0;

    check_sync(dev, &ref, true);
}
EXPORT_SYMBOL(debug_dma_sync_single_range_for_cpu);

void debug_dma_sync_single_range_for_device(struct device *dev,
                        dma_addr_t dma_handle,
                        unsigned long offset,
                        size_t size, int direction)
{
    struct dma_debug_entry ref;

    if (unlikely(global_disable))
        return;

    ref.type         = dma_debug_single;
    ref.dev          = dev;
    ref.dev_addr     = dma_handle;
    ref.size         = offset + size;
    ref.direction    = direction;
    ref.sg_call_ents = 0;

    check_sync(dev, &ref, false);
}
EXPORT_SYMBOL(debug_dma_sync_single_range_for_device);

void debug_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
                   int nelems, int direction)
{
    struct scatterlist *s;
    int mapped_ents = 0, i;

    if (unlikely(global_disable))
        return;

    for_each_sg(sg, s, nelems, i) {

        struct dma_debug_entry ref = {
            .type           = dma_debug_sg,
            .dev            = dev,
            .paddr          = sg_phys(s),
            .dev_addr       = sg_dma_address(s),
            .size           = sg_dma_len(s),
            .direction      = direction,
            .sg_call_ents   = nelems,
        };

        if (!i)
            mapped_ents = get_nr_mapped_entries(dev, &ref);

        if (i >= mapped_ents)
            break;

        check_sync(dev, &ref, true);
    }
}
EXPORT_SYMBOL(debug_dma_sync_sg_for_cpu);

void debug_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
                  int nelems, int direction)
{
    struct scatterlist *s;
    int mapped_ents = 0, i;

    if (unlikely(global_disable))
        return;

    for_each_sg(sg, s, nelems, i) {

        struct dma_debug_entry ref = {
            .type           = dma_debug_sg,
            .dev            = dev,
            .paddr          = sg_phys(s),
            .dev_addr       = sg_dma_address(s),
            .size           = sg_dma_len(s),
            .direction      = direction,
            .sg_call_ents   = nelems,
        };
        if (!i)
            mapped_ents = get_nr_mapped_entries(dev, &ref);

        if (i >= mapped_ents)
            break;

        check_sync(dev, &ref, false);
    }
}
EXPORT_SYMBOL(debug_dma_sync_sg_for_device);

static int __init dma_debug_driver_setup(char *str)
{
    int i;

    for (i = 0; i < NAME_MAX_LEN - 1; ++i, ++str) {
        current_driver_name[i] = *str;
        if (*str == 0)
            break;
    }

    if (current_driver_name[0])
        pr_info("DMA-API: enable driver filter for driver [%s]\n",
            current_driver_name);


    return 1;
}
__setup("dma_debug_driver=", dma_debug_driver_setup);