// SPDX-License-Identifier: GPL-2.0
/*
 *   S/390 debug facility
 *
 *    Copyright IBM Corp. 1999, 2020
 *
 *    Author(s): Michael Holzheu (holzheu@de.ibm.com),
 *               Holger Smolinski (Holger.Smolinski@de.ibm.com)
 *
 *    Bugreports to: <Linux390@de.ibm.com>
 */

#define pr_fmt(fmt) "s390dbf: " fmt

#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/sysctl.h>
#include <linux/uaccess.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/math.h>
#include <linux/minmax.h>
#include <linux/debugfs.h>

#include <asm/debug.h>

#define DEBUG_PROLOG_ENTRY -1

#define ALL_AREAS 0 /* copy all debug areas */
#define NO_AREAS  1 /* copy no debug areas */

/* typedefs */

typedef struct file_private_info {
        loff_t offset;                  /* offset of last read in file */
        int    act_area;                /* number of last formatted area */
        int    act_page;                /* act page in given area */
        int    act_entry;               /* last formatted entry (offset */
                                        /* relative to beginning of last */
                                        /* formatted page) */
        size_t act_entry_offset;        /* up to this offset we copied */
                                        /* in last read the last formatted */
                                        /* entry to userland */
        char   temp_buf[2048];          /* buffer for output */
        debug_info_t *debug_info_org;   /* original debug information */
        debug_info_t *debug_info_snap;  /* snapshot of debug information */
        struct debug_view *view;        /* used view of debug info */
} file_private_info_t;

typedef struct {
        char *string;
        /*
         * This assumes that all args are converted into longs
         * on L/390 this is the case for all types of parameter
         * except of floats, and long long (32 bit)
         *
         */
        long args[];
} debug_sprintf_entry_t;

/* internal function prototypes */

static int debug_init(void);
static ssize_t debug_output(struct file *file, char __user *user_buf,
                            size_t user_len, loff_t *offset);
static ssize_t debug_input(struct file *file, const char __user *user_buf,
                           size_t user_len, loff_t *offset);
static int debug_open(struct inode *inode, struct file *file);
static int debug_close(struct inode *inode, struct file *file);
static debug_info_t *debug_info_create(const char *name, int pages_per_area,
                                       int nr_areas, int buf_size, umode_t mode);
static void debug_info_get(debug_info_t *);
static void debug_info_put(debug_info_t *);
static int debug_prolog_level_fn(debug_info_t *id,
                                 struct debug_view *view, char *out_buf,
                                 size_t out_buf_size);
static int debug_input_level_fn(debug_info_t *id, struct debug_view *view,
                                struct file *file, const char __user *user_buf,
                                size_t user_buf_size, loff_t *offset);
static int debug_prolog_pages_fn(debug_info_t *id,
                                 struct debug_view *view, char *out_buf,
                                 size_t out_buf_size);
static int debug_input_pages_fn(debug_info_t *id, struct debug_view *view,
                                struct file *file, const char __user *user_buf,
                                size_t user_buf_size, loff_t *offset);
static int debug_input_flush_fn(debug_info_t *id, struct debug_view *view,
                                struct file *file, const char __user *user_buf,
                                size_t user_buf_size, loff_t *offset);
static int debug_hex_ascii_format_fn(debug_info_t *id, struct debug_view *view,
                                     char *out_buf, size_t out_buf_size,
                                     const char *in_buf);
static void debug_areas_swap(debug_info_t *a, debug_info_t *b);
static void debug_events_append(debug_info_t *dest, debug_info_t *src);

/* globals */

struct debug_view debug_hex_ascii_view = {
        "hex_ascii",
        NULL,
        &debug_dflt_header_fn,
        &debug_hex_ascii_format_fn,
        NULL,
        NULL
};
EXPORT_SYMBOL(debug_hex_ascii_view);

static struct debug_view debug_level_view = {
        "level",
        &debug_prolog_level_fn,
        NULL,
        NULL,
        &debug_input_level_fn,
        NULL
};

static struct debug_view debug_pages_view = {
        "pages",
        &debug_prolog_pages_fn,
        NULL,
        NULL,
        &debug_input_pages_fn,
        NULL
};

static struct debug_view debug_flush_view = {
        "flush",
        NULL,
        NULL,
        NULL,
        &debug_input_flush_fn,
        NULL
};

struct debug_view debug_sprintf_view = {
        "sprintf",
        NULL,
        &debug_dflt_header_fn,
        &debug_sprintf_format_fn,
        NULL,
        NULL
};
EXPORT_SYMBOL(debug_sprintf_view);

/* used by dump analysis tools to determine version of debug feature */
static unsigned int __used debug_feature_version = __DEBUG_FEATURE_VERSION;

/* static globals */

static debug_info_t *debug_area_first;
static debug_info_t *debug_area_last;
static DEFINE_MUTEX(debug_mutex);

static int initialized;
static int debug_critical;

static const struct file_operations debug_file_ops = {
        .owner   = THIS_MODULE,
        .read    = debug_output,
        .write   = debug_input,
        .open    = debug_open,
        .release = debug_close,
};

static struct dentry *debug_debugfs_root_entry;

/* functions */

/*
 * debug_areas_alloc
 * - Debug areas are implemented as a threedimensonal array:
 *   areas[areanumber][pagenumber][pageoffset]
 */

static debug_entry_t ***debug_areas_alloc(int pages_per_area, int nr_areas)
{
        debug_entry_t ***areas;
        int i, j;

        areas = kmalloc_objs(debug_entry_t **, nr_areas);
        if (!areas)
                goto fail_malloc_areas;
        for (i = 0; i < nr_areas; i++) {
                /* GFP_NOWARN to avoid user triggerable WARN, we handle fails */
                areas[i] = kmalloc_objs(debug_entry_t *, pages_per_area,
                                        GFP_KERNEL | __GFP_NOWARN);
                if (!areas[i])
                        goto fail_malloc_areas2;
                for (j = 0; j < pages_per_area; j++) {
                        areas[i][j] = kzalloc(PAGE_SIZE, GFP_KERNEL);
                        if (!areas[i][j]) {
                                for (j--; j >= 0 ; j--)
                                        kfree(areas[i][j]);
                                kfree(areas[i]);
                                goto fail_malloc_areas2;
                        }
                }
        }
        return areas;

fail_malloc_areas2:
        for (i--; i >= 0; i--) {
                for (j = 0; j < pages_per_area; j++)
                        kfree(areas[i][j]);
                kfree(areas[i]);
        }
        kfree(areas);
fail_malloc_areas:
        return NULL;
}

/*
 * debug_info_alloc
 * - alloc new debug-info
 */
static debug_info_t *debug_info_alloc(const char *name, int pages_per_area,
                                      int nr_areas, int buf_size, int level,
                                      int mode)
{
        debug_info_t *rc;

        /* alloc everything */
        rc = kmalloc_obj(debug_info_t);
        if (!rc)
                goto fail_malloc_rc;
        rc->active_entries = kzalloc_objs(int, nr_areas);
        if (!rc->active_entries)
                goto fail_malloc_active_entries;
        rc->active_pages = kzalloc_objs(int, nr_areas);
        if (!rc->active_pages)
                goto fail_malloc_active_pages;
        if ((mode == ALL_AREAS) && (pages_per_area != 0)) {
                rc->areas = debug_areas_alloc(pages_per_area, nr_areas);
                if (!rc->areas)
                        goto fail_malloc_areas;
        } else {
                rc->areas = NULL;
        }

        /* initialize members */
        raw_spin_lock_init(&rc->lock);
        rc->pages_per_area = pages_per_area;
        rc->nr_areas       = nr_areas;
        rc->active_area    = 0;
        rc->level          = level;
        rc->buf_size       = buf_size;
        rc->entry_size     = sizeof(debug_entry_t) + buf_size;
        strscpy(rc->name, name);
        memset(rc->views, 0, DEBUG_MAX_VIEWS * sizeof(struct debug_view *));
        memset(rc->debugfs_entries, 0, DEBUG_MAX_VIEWS * sizeof(struct dentry *));
        refcount_set(&(rc->ref_count), 0);

        return rc;

fail_malloc_areas:
        kfree(rc->active_pages);
fail_malloc_active_pages:
        kfree(rc->active_entries);
fail_malloc_active_entries:
        kfree(rc);
fail_malloc_rc:
        return NULL;
}

/*
 * debug_areas_free
 * - free all debug areas
 */
static void debug_areas_free(debug_info_t *db_info)
{
        int i, j;

        if (!db_info->areas)
                return;
        for (i = 0; i < db_info->nr_areas; i++) {
                for (j = 0; j < db_info->pages_per_area; j++)
                        kfree(db_info->areas[i][j]);
                kfree(db_info->areas[i]);
        }
        kfree(db_info->areas);
        db_info->areas = NULL;
}

/*
 * debug_info_free
 * - free memory debug-info
 */
static void debug_info_free(debug_info_t *db_info)
{
        debug_areas_free(db_info);
        kfree(db_info->active_entries);
        kfree(db_info->active_pages);
        kfree(db_info);
}

/*
 * debug_info_create
 * - create new debug-info
 */

static debug_info_t *debug_info_create(const char *name, int pages_per_area,
                                       int nr_areas, int buf_size, umode_t mode)
{
        debug_info_t *rc;

        rc = debug_info_alloc(name, pages_per_area, nr_areas, buf_size,
                              DEBUG_DEFAULT_LEVEL, ALL_AREAS);
        if (!rc)
                goto out;

        rc->mode = mode & ~S_IFMT;
        refcount_set(&rc->ref_count, 1);
out:
        return rc;
}

/*
 * debug_info_copy
 * - copy debug-info
 */
static debug_info_t *debug_info_copy(debug_info_t *in, int mode)
{
        unsigned long flags;
        debug_info_t *rc;
        int i, j;

        /* get a consistent copy of the debug areas */
        do {
                rc = debug_info_alloc(in->name, in->pages_per_area,
                        in->nr_areas, in->buf_size, in->level, mode);
                raw_spin_lock_irqsave(&in->lock, flags);
                if (!rc)
                        goto out;
                /* has something changed in the meantime ? */
                if ((rc->pages_per_area == in->pages_per_area) &&
                    (rc->nr_areas == in->nr_areas)) {
                        break;
                }
                raw_spin_unlock_irqrestore(&in->lock, flags);
                debug_info_free(rc);
        } while (1);

        if (mode == NO_AREAS)
                goto out;

        for (i = 0; i < in->nr_areas; i++) {
                for (j = 0; j < in->pages_per_area; j++)
                        memcpy(rc->areas[i][j], in->areas[i][j], PAGE_SIZE);
                rc->active_pages[i] = in->active_pages[i];
                rc->active_entries[i] = in->active_entries[i];
        }
        rc->active_area = in->active_area;
out:
        raw_spin_unlock_irqrestore(&in->lock, flags);
        return rc;
}

/*
 * debug_info_get
 * - increments reference count for debug-info
 */
static void debug_info_get(debug_info_t *db_info)
{
        if (db_info)
                refcount_inc(&db_info->ref_count);
}

/*
 * debug_info_put:
 * - decreases reference count for debug-info and frees it if necessary
 */
static void debug_info_put(debug_info_t *db_info)
{
        if (!db_info)
                return;
        if (refcount_dec_and_test(&db_info->ref_count))
                debug_info_free(db_info);
}

/*
 * debug_format_entry:
 * - format one debug entry and return size of formatted data
 */
static int debug_format_entry(file_private_info_t *p_info)
{
        debug_info_t *id_snap   = p_info->debug_info_snap;
        struct debug_view *view = p_info->view;
        debug_entry_t *act_entry;
        size_t len = 0;

        if (p_info->act_entry == DEBUG_PROLOG_ENTRY) {
                /* print prolog */
                if (view->prolog_proc) {
                        len += view->prolog_proc(id_snap, view, p_info->temp_buf,
                                                 sizeof(p_info->temp_buf));
                }
                goto out;
        }
        if (!id_snap->areas) /* this is true, if we have a prolog only view */
                goto out;    /* or if 'pages_per_area' is 0 */
        act_entry = (debug_entry_t *) ((char *)id_snap->areas[p_info->act_area]
                                       [p_info->act_page] + p_info->act_entry);

        if (act_entry->clock == 0LL)
                goto out; /* empty entry */
        if (view->header_proc) {
                len += view->header_proc(id_snap, view, p_info->act_area,
                                         act_entry, p_info->temp_buf + len,
                                         sizeof(p_info->temp_buf) - len);
        }
        if (view->format_proc) {
                len += view->format_proc(id_snap, view, p_info->temp_buf + len,
                                         sizeof(p_info->temp_buf) - len,
                                         DEBUG_DATA(act_entry));
        }
out:
        return len;
}

/**
 * debug_next_entry - Go to the next entry
 * @p_info:     Private info that is manipulated
 *
 * Sets the current position in @p_info to the next entry. If no further entry
 * exists the current position is set to one after the end the return value
 * indicates that no further entries exist.
 *
 * Return: True if there are more following entries, false otherwise
 */
static inline bool debug_next_entry(file_private_info_t *p_info)
{
        debug_info_t *id;

        id = p_info->debug_info_snap;
        if (p_info->act_entry == DEBUG_PROLOG_ENTRY) {
                p_info->act_entry = 0;
                p_info->act_page  = 0;
                return true;
        }
        if (!id->areas)
                return false;
        p_info->act_entry += id->entry_size;
        /* switch to next page, if we reached the end of the page  */
        if (p_info->act_entry > (PAGE_SIZE - id->entry_size)) {
                /* next page */
                p_info->act_entry = 0;
                p_info->act_page += 1;
                if ((p_info->act_page % id->pages_per_area) == 0) {
                        /* next area */
                        p_info->act_area++;
                        p_info->act_page = 0;
                }
                if (p_info->act_area >= id->nr_areas)
                        return false;
        }
        return true;
}

/**
 * debug_to_act_entry - Go to the currently active entry
 * @p_info:     Private info that is manipulated
 *
 * Sets the current position in @p_info to the currently active
 * entry of @p_info->debug_info_snap
 */
static void debug_to_act_entry(file_private_info_t *p_info)
{
        debug_info_t *snap_id;

        snap_id = p_info->debug_info_snap;
        p_info->act_area = snap_id->active_area;
        p_info->act_page = snap_id->active_pages[snap_id->active_area];
        p_info->act_entry = snap_id->active_entries[snap_id->active_area];
}

/**
 * debug_prev_entry - Go to the previous entry
 * @p_info:     Private info that is manipulated
 *
 * Sets the current position in @p_info to the previous entry. If no previous entry
 * exists the current position is set left as DEBUG_PROLOG_ENTRY and the return value
 * indicates that no previous entries exist.
 *
 * Return: True if there are more previous entries, false otherwise
 */

static inline bool debug_prev_entry(file_private_info_t *p_info)
{
        debug_info_t *id;

        id = p_info->debug_info_snap;
        if (p_info->act_entry == DEBUG_PROLOG_ENTRY)
                debug_to_act_entry(p_info);
        if (!id->areas)
                return false;
        p_info->act_entry -= id->entry_size;
        /* switch to prev page, if we reached the beginning of the page  */
        if (p_info->act_entry < 0) {
                /* end of previous page */
                p_info->act_entry = rounddown(PAGE_SIZE, id->entry_size) - id->entry_size;
                p_info->act_page--;
                if (p_info->act_page < 0) {
                        /* previous area */
                        p_info->act_area--;
                        p_info->act_page = id->pages_per_area - 1;
                }
                if (p_info->act_area < 0)
                        p_info->act_area = (id->nr_areas - 1) % id->nr_areas;
        }
        /* check full circle */
        if (id->active_area == p_info->act_area &&
            id->active_pages[id->active_area] == p_info->act_page &&
            id->active_entries[id->active_area] == p_info->act_entry)
                return false;
        return true;
}

/**
 * debug_move_entry - Go to next entry in either the forward or backward direction
 * @p_info:     Private info that is manipulated
 * @reverse:    If true go to the next entry in reverse i.e. previous
 *
 * Sets the current position in @p_info to the next (@reverse == false) or
 * previous (@reverse == true) entry.
 *
 * Return: True if there are further entries in that direction,
 * false otherwise.
 */
static bool debug_move_entry(file_private_info_t *p_info, bool reverse)
{
        if (reverse)
                return debug_prev_entry(p_info);
        else
                return debug_next_entry(p_info);
}

/*
 * debug_output:
 * - called for user read()
 * - copies formatted debug entries to the user buffer
 */
static ssize_t debug_output(struct file *file,          /* file descriptor */
                            char __user *user_buf,      /* user buffer */
                            size_t len,                 /* length of buffer */
                            loff_t *offset)             /* offset in the file */
{
        size_t count = 0;
        size_t entry_offset;
        file_private_info_t *p_info;

        p_info = (file_private_info_t *) file->private_data;
        if (*offset != p_info->offset)
                return -EPIPE;
        if (p_info->act_area >= p_info->debug_info_snap->nr_areas)
                return 0;
        entry_offset = p_info->act_entry_offset;
        while (count < len) {
                int formatted_line_residue;
                int formatted_line_size;
                int user_buf_residue;
                size_t copy_size;

                formatted_line_size = debug_format_entry(p_info);
                formatted_line_residue = formatted_line_size - entry_offset;
                user_buf_residue = len-count;
                copy_size = min(user_buf_residue, formatted_line_residue);
                if (copy_size) {
                        if (copy_to_user(user_buf + count, p_info->temp_buf
                                         + entry_offset, copy_size))
                                return -EFAULT;
                        count += copy_size;
                        entry_offset += copy_size;
                }
                if (copy_size == formatted_line_residue) {
                        entry_offset = 0;
                        if (!debug_next_entry(p_info))
                                goto out;
                }
        }
out:
        p_info->offset           = *offset + count;
        p_info->act_entry_offset = entry_offset;
        *offset = p_info->offset;
        return count;
}

/*
 * debug_input:
 * - called for user write()
 * - calls input function of view
 */
static ssize_t debug_input(struct file *file, const char __user *user_buf,
                           size_t length, loff_t *offset)
{
        file_private_info_t *p_info;
        int rc = 0;

        mutex_lock(&debug_mutex);
        p_info = ((file_private_info_t *) file->private_data);
        if (p_info->view->input_proc) {
                rc = p_info->view->input_proc(p_info->debug_info_org,
                                              p_info->view, file, user_buf,
                                              length, offset);
        } else {
                rc = -EPERM;
        }
        mutex_unlock(&debug_mutex);
        return rc; /* number of input characters */
}

static file_private_info_t *debug_file_private_alloc(debug_info_t *debug_info,
                                                     struct debug_view *view)
{
        debug_info_t *debug_info_snapshot;
        file_private_info_t *p_info;

        /*
         * Make snapshot of current debug areas to get it consistent.
         * To copy all the areas is only needed, if we have a view which
         * formats the debug areas.
         */
        if (!view->format_proc && !view->header_proc)
                debug_info_snapshot = debug_info_copy(debug_info, NO_AREAS);
        else
                debug_info_snapshot = debug_info_copy(debug_info, ALL_AREAS);

        if (!debug_info_snapshot)
                return NULL;
        p_info = kmalloc_obj(file_private_info_t);
        if (!p_info) {
                debug_info_free(debug_info_snapshot);
                return NULL;
        }
        p_info->offset = 0;
        p_info->debug_info_snap = debug_info_snapshot;
        p_info->debug_info_org  = debug_info;
        p_info->view = view;
        p_info->act_area = 0;
        p_info->act_page = 0;
        p_info->act_entry = DEBUG_PROLOG_ENTRY;
        p_info->act_entry_offset = 0;
        debug_info_get(debug_info);

        return p_info;
}

/*
 * debug_open:
 * - called for user open()
 * - copies formatted output to private_data area of the file
 *   handle
 */
static int debug_open(struct inode *inode, struct file *file)
{
        debug_info_t *debug_info;
        file_private_info_t *p_info;
        int i, rc = 0;

        mutex_lock(&debug_mutex);
        debug_info = file_inode(file)->i_private;
        /* find debug view */
        for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
                if (!debug_info->views[i])
                        continue;
                else if (debug_info->debugfs_entries[i] == file->f_path.dentry)
                        goto found; /* found view ! */
        }
        /* no entry found */
        rc = -EINVAL;
        goto out;

found:
        p_info = debug_file_private_alloc(debug_info, debug_info->views[i]);
        if (!p_info) {
                rc = -ENOMEM;
                goto out;
        }
        file->private_data = p_info;
        nonseekable_open(inode, file);
out:
        mutex_unlock(&debug_mutex);
        return rc;
}

static void debug_file_private_free(file_private_info_t *p_info)
{
        if (p_info->debug_info_snap)
                debug_info_free(p_info->debug_info_snap);
        debug_info_put(p_info->debug_info_org);
        kfree(p_info);
}

/*
 * debug_close:
 * - called for user close()
 * - deletes  private_data area of the file handle
 */
static int debug_close(struct inode *inode, struct file *file)
{
        file_private_info_t *p_info;

        p_info = (file_private_info_t *) file->private_data;
        debug_file_private_free(p_info);
        file->private_data = NULL;
        return 0; /* success */
}

/**
 * debug_dump - Get a textual representation of debug info, or as much as fits
 * @id:         Debug information to use
 * @view:       View with which to dump the debug information
 * @buf:        Buffer the textual debug data representation is written to
 * @buf_size:   Size of the buffer, including the trailing '\0' byte
 * @reverse:    Go backwards from the last written entry
 *
 * This function may be used whenever a textual representation of the debug
 * information is required without using an s390dbf file.
 *
 * Note: It is the callers responsibility to supply a view that is compatible
 * with the debug information data.
 *
 * Return: On success returns the number of bytes written to the buffer not
 * including the trailing '\0' byte. If bug_size == 0 the function returns 0.
 * On failure an error code less than 0 is returned.
 */
ssize_t debug_dump(debug_info_t *id, struct debug_view *view,
                   char *buf, size_t buf_size, bool reverse)
{
        file_private_info_t *p_info;
        size_t size, offset = 0;

        /* Need space for '\0' byte */
        if (buf_size < 1)
                return 0;
        buf_size--;

        p_info = debug_file_private_alloc(id, view);
        if (!p_info)
                return -ENOMEM;

        /* There is always at least the DEBUG_PROLOG_ENTRY */
        do {
                size = debug_format_entry(p_info);
                size = min(size, buf_size - offset);
                memcpy(buf + offset, p_info->temp_buf, size);
                offset += size;
                if (offset >= buf_size)
                        break;
        } while (debug_move_entry(p_info, reverse));
        debug_file_private_free(p_info);
        buf[offset] = '\0';

        return offset;
}

/* Create debugfs entries and add to internal list. */
static void _debug_register(debug_info_t *id)
{
        /* create root directory */
        id->debugfs_root_entry = debugfs_create_dir(id->name,
                                                    debug_debugfs_root_entry);

        /* append new element to linked list */
        if (!debug_area_first) {
                /* first element in list */
                debug_area_first = id;
                id->prev = NULL;
        } else {
                /* append element to end of list */
                debug_area_last->next = id;
                id->prev = debug_area_last;
        }
        debug_area_last = id;
        id->next = NULL;

        debug_register_view(id, &debug_level_view);
        debug_register_view(id, &debug_flush_view);
        debug_register_view(id, &debug_pages_view);
}

/**
 * debug_register_mode() - creates and initializes debug area.
 *
 * @name:       Name of debug log (e.g. used for debugfs entry)
 * @pages_per_area:     Number of pages, which will be allocated per area
 * @nr_areas:   Number of debug areas
 * @buf_size:   Size of data area in each debug entry
 * @mode:       File mode for debugfs files. E.g. S_IRWXUGO
 * @uid:        User ID for debugfs files. Currently only 0 is supported.
 * @gid:        Group ID for debugfs files. Currently only 0 is supported.
 *
 * Return:
 * - Handle for generated debug area
 * - %NULL if register failed
 *
 * Allocates memory for a debug log.
 * Must not be called within an interrupt handler.
 */
debug_info_t *debug_register_mode(const char *name, int pages_per_area,
                                  int nr_areas, int buf_size, umode_t mode,
                                  uid_t uid, gid_t gid)
{
        debug_info_t *rc = NULL;

        /* Since debugfs currently does not support uid/gid other than root, */
        /* we do not allow gid/uid != 0 until we get support for that. */
        if ((uid != 0) || (gid != 0))
                pr_warn("Root becomes the owner of all s390dbf files in sysfs\n");
        BUG_ON(!initialized);

        /* create new debug_info */
        rc = debug_info_create(name, pages_per_area, nr_areas, buf_size, mode);
        if (rc) {
                mutex_lock(&debug_mutex);
                _debug_register(rc);
                mutex_unlock(&debug_mutex);
        } else {
                pr_err("Registering debug feature %s failed\n", name);
        }
        return rc;
}
EXPORT_SYMBOL(debug_register_mode);

/**
 * debug_register() - creates and initializes debug area with default file mode.
 *
 * @name:       Name of debug log (e.g. used for debugfs entry)
 * @pages_per_area:     Number of pages, which will be allocated per area
 * @nr_areas:   Number of debug areas
 * @buf_size:   Size of data area in each debug entry
 *
 * Return:
 * - Handle for generated debug area
 * - %NULL if register failed
 *
 * Allocates memory for a debug log.
 * The debugfs file mode access permissions are read and write for user.
 * Must not be called within an interrupt handler.
 */
debug_info_t *debug_register(const char *name, int pages_per_area,
                             int nr_areas, int buf_size)
{
        return debug_register_mode(name, pages_per_area, nr_areas, buf_size,
                                   S_IRUSR | S_IWUSR, 0, 0);
}
EXPORT_SYMBOL(debug_register);

/**
 * debug_register_static() - registers a static debug area
 *
 * @id: Handle for static debug area
 * @pages_per_area: Number of pages per area
 * @nr_areas: Number of debug areas
 *
 * Register debug_info_t defined using DEFINE_STATIC_DEBUG_INFO.
 *
 * Note: This function is called automatically via an initcall generated by
 *       DEFINE_STATIC_DEBUG_INFO.
 */
void debug_register_static(debug_info_t *id, int pages_per_area, int nr_areas)
{
        unsigned long flags;
        debug_info_t *copy;

        if (!initialized) {
                pr_err("Tried to register debug feature %s too early\n",
                       id->name);
                return;
        }

        copy = debug_info_alloc("", pages_per_area, nr_areas, id->buf_size,
                                id->level, ALL_AREAS);
        if (!copy) {
                pr_err("Registering debug feature %s failed\n", id->name);

                /* Clear pointers to prevent tracing into released initdata. */
                raw_spin_lock_irqsave(&id->lock, flags);
                id->areas = NULL;
                id->active_pages = NULL;
                id->active_entries = NULL;
                raw_spin_unlock_irqrestore(&id->lock, flags);

                return;
        }

        /* Replace static trace area with dynamic copy. */
        raw_spin_lock_irqsave(&id->lock, flags);
        debug_events_append(copy, id);
        debug_areas_swap(id, copy);
        raw_spin_unlock_irqrestore(&id->lock, flags);

        /* Clear pointers to initdata and discard copy. */
        copy->areas = NULL;
        copy->active_pages = NULL;
        copy->active_entries = NULL;
        debug_info_free(copy);

        mutex_lock(&debug_mutex);
        _debug_register(id);
        mutex_unlock(&debug_mutex);
}

/* Remove debugfs entries and remove from internal list. */
static void _debug_unregister(debug_info_t *id)
{
        int i;

        for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
                if (!id->views[i])
                        continue;
                debugfs_remove(id->debugfs_entries[i]);
        }
        debugfs_remove(id->debugfs_root_entry);
        if (id == debug_area_first)
                debug_area_first = id->next;
        if (id == debug_area_last)
                debug_area_last = id->prev;
        if (id->prev)
                id->prev->next = id->next;
        if (id->next)
                id->next->prev = id->prev;
}

/**
 * debug_unregister() - give back debug area.
 *
 * @id:         handle for debug log
 *
 * Return:
 *    none
 */
void debug_unregister(debug_info_t *id)
{
        if (!id)
                return;
        mutex_lock(&debug_mutex);
        _debug_unregister(id);
        mutex_unlock(&debug_mutex);

        debug_info_put(id);
}
EXPORT_SYMBOL(debug_unregister);

/*
 * debug_set_size:
 * - set area size (number of pages) and number of areas
 */
static int debug_set_size(debug_info_t *id, int nr_areas, int pages_per_area)
{
        debug_info_t *new_id;
        unsigned long flags;

        if (!id || (nr_areas <= 0) || (pages_per_area < 0))
                return -EINVAL;

        new_id = debug_info_alloc("", pages_per_area, nr_areas, id->buf_size,
                                  id->level, ALL_AREAS);
        if (!new_id) {
                pr_info("Allocating memory for %i pages failed\n",
                        pages_per_area);
                return -ENOMEM;
        }

        raw_spin_lock_irqsave(&id->lock, flags);
        debug_events_append(new_id, id);
        debug_areas_swap(new_id, id);
        raw_spin_unlock_irqrestore(&id->lock, flags);
        debug_info_free(new_id);
        pr_info("%s: set new size (%i pages)\n", id->name, pages_per_area);

        return 0;
}

/**
 * debug_set_level() - Sets new actual debug level if new_level is valid.
 *
 * @id:         handle for debug log
 * @new_level:  new debug level
 *
 * Return:
 *    none
 */
void debug_set_level(debug_info_t *id, int new_level)
{
        unsigned long flags;

        if (!id)
                return;

        if (new_level == DEBUG_OFF_LEVEL) {
                pr_info("%s: switched off\n", id->name);
        } else if ((new_level > DEBUG_MAX_LEVEL) || (new_level < 0)) {
                pr_info("%s: level %i is out of range (%i - %i)\n",
                        id->name, new_level, 0, DEBUG_MAX_LEVEL);
                return;
        }

        raw_spin_lock_irqsave(&id->lock, flags);
        id->level = new_level;
        raw_spin_unlock_irqrestore(&id->lock, flags);
}
EXPORT_SYMBOL(debug_set_level);

/*
 * proceed_active_entry:
 * - set active entry to next in the ring buffer
 */
static inline void proceed_active_entry(debug_info_t *id)
{
        if ((id->active_entries[id->active_area] += id->entry_size)
            > (PAGE_SIZE - id->entry_size)) {
                id->active_entries[id->active_area] = 0;
                id->active_pages[id->active_area] =
                        (id->active_pages[id->active_area] + 1) %
                        id->pages_per_area;
        }
}

/*
 * proceed_active_area:
 * - set active area to next in the ring buffer
 */
static inline void proceed_active_area(debug_info_t *id)
{
        id->active_area++;
        id->active_area = id->active_area % id->nr_areas;
}

/*
 * get_active_entry:
 */
static inline debug_entry_t *get_active_entry(debug_info_t *id)
{
        return (debug_entry_t *) (((char *) id->areas[id->active_area]
                                   [id->active_pages[id->active_area]]) +
                                  id->active_entries[id->active_area]);
}

/* Swap debug areas of a and b. */
static void debug_areas_swap(debug_info_t *a, debug_info_t *b)
{
        swap(a->nr_areas, b->nr_areas);
        swap(a->pages_per_area, b->pages_per_area);
        swap(a->areas, b->areas);
        swap(a->active_area, b->active_area);
        swap(a->active_pages, b->active_pages);
        swap(a->active_entries, b->active_entries);
}

/* Append all debug events in active area from source to destination log. */
static void debug_events_append(debug_info_t *dest, debug_info_t *src)
{
        debug_entry_t *from, *to, *last;

        if (!src->areas || !dest->areas)
                return;

        /* Loop over all entries in src, starting with oldest. */
        from = get_active_entry(src);
        last = from;
        do {
                if (from->clock != 0LL) {
                        to = get_active_entry(dest);
                        memset(to, 0, dest->entry_size);
                        memcpy(to, from, min(src->entry_size,
                                             dest->entry_size));
                        proceed_active_entry(dest);
                }

                proceed_active_entry(src);
                from = get_active_entry(src);
        } while (from != last);
}

/*
 * debug_finish_entry:
 * - set timestamp, caller address, cpu number etc.
 */

static inline void debug_finish_entry(debug_info_t *id, debug_entry_t *active,
                                      int level, int exception)
{
        unsigned long timestamp;
        union tod_clock clk;

        store_tod_clock_ext(&clk);
        timestamp = clk.us;
        timestamp -= TOD_UNIX_EPOCH >> 12;
        active->clock = timestamp;
        active->cpu = smp_processor_id();
        active->caller = __builtin_return_address(0);
        active->exception = exception;
        active->level = level;
        proceed_active_entry(id);
        if (exception)
                proceed_active_area(id);
}

static int debug_stoppable = 1;
static int debug_active = 1;

#define CTL_S390DBF_STOPPABLE 5678
#define CTL_S390DBF_ACTIVE 5679

/*
 * proc handler for the running debug_active sysctl
 * always allow read, allow write only if debug_stoppable is set or
 * if debug_active is already off
 */
static int s390dbf_procactive(const struct ctl_table *table, int write,
                              void *buffer, size_t *lenp, loff_t *ppos)
{
        if (!write || debug_stoppable || !debug_active)
                return proc_dointvec(table, write, buffer, lenp, ppos);
        else
                return 0;
}

static const struct ctl_table s390dbf_table[] = {
        {
                .procname       = "debug_stoppable",
                .data           = &debug_stoppable,
                .maxlen         = sizeof(int),
                .mode           = S_IRUGO | S_IWUSR,
                .proc_handler   = proc_dointvec,
        },
        {
                .procname       = "debug_active",
                .data           = &debug_active,
                .maxlen         = sizeof(int),
                .mode           = S_IRUGO | S_IWUSR,
                .proc_handler   = s390dbf_procactive,
        },
};

static struct ctl_table_header *s390dbf_sysctl_header;

/**
 * debug_stop_all() - stops the debug feature if stopping is allowed.
 *
 * Return:
 * -   none
 *
 * Currently used in case of a kernel oops.
 */
void debug_stop_all(void)
{
        if (debug_stoppable)
                debug_active = 0;
}
EXPORT_SYMBOL(debug_stop_all);

/**
 * debug_set_critical() - event/exception functions try lock instead of spin.
 *
 * Return:
 * -   none
 *
 * Currently used in case of stopping all CPUs but the current one.
 * Once in this state, functions to write a debug entry for an
 * event or exception no longer spin on the debug area lock,
 * but only try to get it and fail if they do not get the lock.
 */
void debug_set_critical(void)
{
        debug_critical = 1;
}

/*
 * debug_event_common:
 * - write debug entry with given size
 */
debug_entry_t *debug_event_common(debug_info_t *id, int level, const void *buf,
                                  int len)
{
        debug_entry_t *active;
        unsigned long flags;

        if (!debug_active || !id->areas)
                return NULL;
        if (debug_critical) {
                if (!raw_spin_trylock_irqsave(&id->lock, flags))
                        return NULL;
        } else {
                raw_spin_lock_irqsave(&id->lock, flags);
        }
        do {
                active = get_active_entry(id);
                memcpy(DEBUG_DATA(active), buf, min(len, id->buf_size));
                if (len < id->buf_size)
                        memset((DEBUG_DATA(active)) + len, 0, id->buf_size - len);
                debug_finish_entry(id, active, level, 0);
                len -= id->buf_size;
                buf += id->buf_size;
        } while (len > 0);

        raw_spin_unlock_irqrestore(&id->lock, flags);
        return active;
}
EXPORT_SYMBOL(debug_event_common);

/*
 * debug_exception_common:
 * - write debug entry with given size and switch to next debug area
 */
debug_entry_t *debug_exception_common(debug_info_t *id, int level,
                                      const void *buf, int len)
{
        debug_entry_t *active;
        unsigned long flags;

        if (!debug_active || !id->areas)
                return NULL;
        if (debug_critical) {
                if (!raw_spin_trylock_irqsave(&id->lock, flags))
                        return NULL;
        } else {
                raw_spin_lock_irqsave(&id->lock, flags);
        }
        do {
                active = get_active_entry(id);
                memcpy(DEBUG_DATA(active), buf, min(len, id->buf_size));
                if (len < id->buf_size)
                        memset((DEBUG_DATA(active)) + len, 0, id->buf_size - len);
                debug_finish_entry(id, active, level, len <= id->buf_size);
                len -= id->buf_size;
                buf += id->buf_size;
        } while (len > 0);

        raw_spin_unlock_irqrestore(&id->lock, flags);
        return active;
}
EXPORT_SYMBOL(debug_exception_common);

/*
 * counts arguments in format string for sprintf view
 */
static inline int debug_count_numargs(char *string)
{
        int numargs = 0;

        while (*string) {
                if (*string++ == '%')
                        numargs++;
        }
        return numargs;
}

/*
 * debug_sprintf_event:
 */
debug_entry_t *__debug_sprintf_event(debug_info_t *id, int level, char *string, ...)
{
        debug_sprintf_entry_t *curr_event;
        debug_entry_t *active;
        unsigned long flags;
        int numargs, idx;
        va_list ap;

        if (!debug_active || !id->areas)
                return NULL;
        numargs = debug_count_numargs(string);

        if (debug_critical) {
                if (!raw_spin_trylock_irqsave(&id->lock, flags))
                        return NULL;
        } else {
                raw_spin_lock_irqsave(&id->lock, flags);
        }
        active = get_active_entry(id);
        curr_event = (debug_sprintf_entry_t *) DEBUG_DATA(active);
        va_start(ap, string);
        curr_event->string = string;
        for (idx = 0; idx < min(numargs, (int)(id->buf_size / sizeof(long)) - 1); idx++)
                curr_event->args[idx] = va_arg(ap, long);
        va_end(ap);
        debug_finish_entry(id, active, level, 0);
        raw_spin_unlock_irqrestore(&id->lock, flags);

        return active;
}
EXPORT_SYMBOL(__debug_sprintf_event);

/*
 * debug_sprintf_exception:
 */
debug_entry_t *__debug_sprintf_exception(debug_info_t *id, int level, char *string, ...)
{
        debug_sprintf_entry_t *curr_event;
        debug_entry_t *active;
        unsigned long flags;
        int numargs, idx;
        va_list ap;

        if (!debug_active || !id->areas)
                return NULL;

        numargs = debug_count_numargs(string);

        if (debug_critical) {
                if (!raw_spin_trylock_irqsave(&id->lock, flags))
                        return NULL;
        } else {
                raw_spin_lock_irqsave(&id->lock, flags);
        }
        active = get_active_entry(id);
        curr_event = (debug_sprintf_entry_t *)DEBUG_DATA(active);
        va_start(ap, string);
        curr_event->string = string;
        for (idx = 0; idx < min(numargs, (int)(id->buf_size / sizeof(long)) - 1); idx++)
                curr_event->args[idx] = va_arg(ap, long);
        va_end(ap);
        debug_finish_entry(id, active, level, 1);
        raw_spin_unlock_irqrestore(&id->lock, flags);

        return active;
}
EXPORT_SYMBOL(__debug_sprintf_exception);

/**
 * debug_register_view() - registers new debug view and creates debugfs
 *                         dir entry
 *
 * @id:         handle for debug log
 * @view:       pointer to debug view struct
 *
 * Return:
 * -   0  : ok
 * -   < 0: Error
 */
int debug_register_view(debug_info_t *id, struct debug_view *view)
{
        unsigned long flags;
        struct dentry *pde;
        umode_t mode;
        int rc = 0;
        int i;

        if (!id)
                goto out;
        mode = (id->mode | S_IFREG) & ~S_IXUGO;
        if (!(view->prolog_proc || view->format_proc || view->header_proc))
                mode &= ~(S_IRUSR | S_IRGRP | S_IROTH);
        if (!view->input_proc)
                mode &= ~(S_IWUSR | S_IWGRP | S_IWOTH);
        pde = debugfs_create_file(view->name, mode, id->debugfs_root_entry,
                                  id, &debug_file_ops);
        raw_spin_lock_irqsave(&id->lock, flags);
        for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
                if (!id->views[i])
                        break;
        }
        if (i == DEBUG_MAX_VIEWS) {
                rc = -1;
        } else {
                id->views[i] = view;
                id->debugfs_entries[i] = pde;
        }
        raw_spin_unlock_irqrestore(&id->lock, flags);
        if (rc) {
                pr_err("Registering view %s/%s would exceed the maximum "
                       "number of views %i\n", id->name, view->name, i);
                debugfs_remove(pde);
        }
out:
        return rc;
}
EXPORT_SYMBOL(debug_register_view);

/**
 * debug_unregister_view() - unregisters debug view and removes debugfs
 *                           dir entry
 *
 * @id:         handle for debug log
 * @view:       pointer to debug view struct
 *
 * Return:
 * -   0  : ok
 * -   < 0: Error
 */
int debug_unregister_view(debug_info_t *id, struct debug_view *view)
{
        struct dentry *dentry = NULL;
        unsigned long flags;
        int i, rc = 0;

        if (!id)
                goto out;
        raw_spin_lock_irqsave(&id->lock, flags);
        for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
                if (id->views[i] == view)
                        break;
        }
        if (i == DEBUG_MAX_VIEWS) {
                rc = -1;
        } else {
                dentry = id->debugfs_entries[i];
                id->views[i] = NULL;
                id->debugfs_entries[i] = NULL;
        }
        raw_spin_unlock_irqrestore(&id->lock, flags);
        debugfs_remove(dentry);
out:
        return rc;
}
EXPORT_SYMBOL(debug_unregister_view);

static inline char *debug_get_user_string(const char __user *user_buf,
                                          size_t user_len)
{
        char *buffer;

        buffer = memdup_user_nul(user_buf, user_len);
        if (IS_ERR(buffer))
                return buffer;
        /* got the string, now strip linefeed. */
        if (buffer[user_len - 1] == '\n')
                buffer[user_len - 1] = 0;
        return buffer;
}

static inline int debug_get_uint(char *buf)
{
        int rc;

        buf = skip_spaces(buf);
        rc = simple_strtoul(buf, &buf, 10);
        if (*buf)
                rc = -EINVAL;
        return rc;
}

/*
 * functions for debug-views
 ***********************************
*/

/*
 * prints out actual debug level
 */

static int debug_prolog_pages_fn(debug_info_t *id, struct debug_view *view,
                                 char *out_buf, size_t out_buf_size)
{
        return scnprintf(out_buf, out_buf_size, "%i\n", id->pages_per_area);
}

/*
 * reads new size (number of pages per debug area)
 */

static int debug_input_pages_fn(debug_info_t *id, struct debug_view *view,
                                struct file *file, const char __user *user_buf,
                                size_t user_len, loff_t *offset)
{
        int rc, new_pages;
        char *str;

        if (user_len > 0x10000)
                user_len = 0x10000;
        if (*offset != 0) {
                rc = -EPIPE;
                goto out;
        }
        str = debug_get_user_string(user_buf, user_len);
        if (IS_ERR(str)) {
                rc = PTR_ERR(str);
                goto out;
        }
        new_pages = debug_get_uint(str);
        if (new_pages < 0) {
                rc = -EINVAL;
                goto free_str;
        }
        rc = debug_set_size(id, id->nr_areas, new_pages);
        if (rc != 0) {
                rc = -EINVAL;
                goto free_str;
        }
        rc = user_len;
free_str:
        kfree(str);
out:
        *offset += user_len;
        return rc;              /* number of input characters */
}

/*
 * prints out actual debug level
 */
static int debug_prolog_level_fn(debug_info_t *id, struct debug_view *view,
                                 char *out_buf, size_t out_buf_size)
{
        int rc = 0;

        if (id->level == DEBUG_OFF_LEVEL)
                rc = scnprintf(out_buf, out_buf_size, "-\n");
        else
                rc = scnprintf(out_buf, out_buf_size, "%i\n", id->level);
        return rc;
}

/*
 * reads new debug level
 */
static int debug_input_level_fn(debug_info_t *id, struct debug_view *view,
                                struct file *file, const char __user *user_buf,
                                size_t user_len, loff_t *offset)
{
        int rc, new_level;
        char *str;

        if (user_len > 0x10000)
                user_len = 0x10000;
        if (*offset != 0) {
                rc = -EPIPE;
                goto out;
        }
        str = debug_get_user_string(user_buf, user_len);
        if (IS_ERR(str)) {
                rc = PTR_ERR(str);
                goto out;
        }
        if (str[0] == '-') {
                debug_set_level(id, DEBUG_OFF_LEVEL);
                rc = user_len;
                goto free_str;
        } else {
                new_level = debug_get_uint(str);
        }
        if (new_level < 0) {
                pr_warn("%s is not a valid level for a debug feature\n", str);
                rc = -EINVAL;
        } else {
                debug_set_level(id, new_level);
                rc = user_len;
        }
free_str:
        kfree(str);
out:
        *offset += user_len;
        return rc;              /* number of input characters */
}

/*
 * flushes debug areas
 */
static void debug_flush(debug_info_t *id, int area)
{
        unsigned long flags;
        int i, j;

        if (!id || !id->areas)
                return;
        raw_spin_lock_irqsave(&id->lock, flags);
        if (area == DEBUG_FLUSH_ALL) {
                id->active_area = 0;
                memset(id->active_entries, 0, id->nr_areas * sizeof(int));
                for (i = 0; i < id->nr_areas; i++) {
                        id->active_pages[i] = 0;
                        for (j = 0; j < id->pages_per_area; j++)
                                memset(id->areas[i][j], 0, PAGE_SIZE);
                }
        } else if (area >= 0 && area < id->nr_areas) {
                id->active_entries[area] = 0;
                id->active_pages[area] = 0;
                for (i = 0; i < id->pages_per_area; i++)
                        memset(id->areas[area][i], 0, PAGE_SIZE);
        }
        raw_spin_unlock_irqrestore(&id->lock, flags);
}

/*
 * view function: flushes debug areas
 */
static int debug_input_flush_fn(debug_info_t *id, struct debug_view *view,
                                struct file *file, const char __user *user_buf,
                                size_t user_len, loff_t *offset)
{
        char input_buf[1];
        int rc = user_len;

        if (user_len > 0x10000)
                user_len = 0x10000;
        if (*offset != 0) {
                rc = -EPIPE;
                goto out;
        }
        if (copy_from_user(input_buf, user_buf, 1)) {
                rc = -EFAULT;
                goto out;
        }
        if (input_buf[0] == '-') {
                debug_flush(id, DEBUG_FLUSH_ALL);
                goto out;
        }
        if (isdigit(input_buf[0])) {
                int area = ((int) input_buf[0] - (int) '0');

                debug_flush(id, area);
                goto out;
        }

        pr_info("Flushing debug data failed because %c is not a valid "
                 "area\n", input_buf[0]);

out:
        *offset += user_len;
        return rc;              /* number of input characters */
}

/*
 * prints debug data in hex/ascii format
 */
static int debug_hex_ascii_format_fn(debug_info_t *id, struct debug_view *view,
                                     char *out_buf, size_t out_buf_size, const char *in_buf)
{
        int i, rc = 0;

        for (i = 0; i < id->buf_size; i++) {
                rc += scnprintf(out_buf + rc, out_buf_size - rc,
                                "%02x ", ((unsigned char *)in_buf)[i]);
        }
        rc += scnprintf(out_buf + rc, out_buf_size - rc, "| ");
        for (i = 0; i < id->buf_size; i++) {
                unsigned char c = in_buf[i];

                if (isascii(c) && isprint(c))
                        rc += scnprintf(out_buf + rc, out_buf_size - rc, "%c", c);
                else
                        rc += scnprintf(out_buf + rc, out_buf_size - rc, ".");
        }
        rc += scnprintf(out_buf + rc, out_buf_size - rc, "\n");
        return rc;
}

/*
 * prints header for debug entry
 */
int debug_dflt_header_fn(debug_info_t *id, struct debug_view *view,
                         int area, debug_entry_t *entry, char *out_buf,
                         size_t out_buf_size)
{
        unsigned long sec, usec;
        unsigned long caller;
        unsigned int level;
        char *except_str;
        int rc = 0;

        level = entry->level;
        sec = entry->clock;
        usec = do_div(sec, USEC_PER_SEC);

        if (entry->exception)
                except_str = "*";
        else
                except_str = "-";
        caller = (unsigned long) entry->caller;
        rc += scnprintf(out_buf, out_buf_size, "%02i %011ld:%06lu %1u %1s %04u %px  ",
                        area, sec, usec, level, except_str,
                        entry->cpu, (void *)caller);
        return rc;
}
EXPORT_SYMBOL(debug_dflt_header_fn);

/*
 * prints debug data sprintf-formatted:
 * debug_sprintf_event/exception calls must be used together with this view
 */

#define DEBUG_SPRINTF_MAX_ARGS 10

int debug_sprintf_format_fn(debug_info_t *id, struct debug_view *view,
                            char *out_buf, size_t out_buf_size, const char *inbuf)
{
        debug_sprintf_entry_t *curr_event = (debug_sprintf_entry_t *)inbuf;
        int num_longs, num_used_args = 0, i, rc = 0;
        int index[DEBUG_SPRINTF_MAX_ARGS];

        /* count of longs fit into one entry */
        num_longs = id->buf_size / sizeof(long);

        if (num_longs < 1)
                goto out; /* bufsize of entry too small */
        if (num_longs == 1) {
                /* no args, we use only the string */
                rc = strscpy(out_buf, curr_event->string, out_buf_size);
                if (rc == -E2BIG)
                        rc = out_buf_size;
                goto out;
        }

        /* number of arguments used for sprintf (without the format string) */
        num_used_args = min(DEBUG_SPRINTF_MAX_ARGS, (num_longs - 1));

        memset(index, 0, DEBUG_SPRINTF_MAX_ARGS * sizeof(int));

        for (i = 0; i < num_used_args; i++)
                index[i] = i;

        rc = scnprintf(out_buf, out_buf_size,
                       curr_event->string, curr_event->args[index[0]],
                       curr_event->args[index[1]], curr_event->args[index[2]],
                       curr_event->args[index[3]], curr_event->args[index[4]],
                       curr_event->args[index[5]], curr_event->args[index[6]],
                       curr_event->args[index[7]], curr_event->args[index[8]],
                       curr_event->args[index[9]]);
out:
        return rc;
}
EXPORT_SYMBOL(debug_sprintf_format_fn);

/*
 * debug_init:
 * - is called exactly once to initialize the debug feature
 */
static int __init debug_init(void)
{
        s390dbf_sysctl_header = register_sysctl("s390dbf", s390dbf_table);
        mutex_lock(&debug_mutex);
        debug_debugfs_root_entry = debugfs_create_dir(DEBUG_DIR_ROOT, NULL);
        initialized = 1;
        mutex_unlock(&debug_mutex);
        return 0;
}
postcore_initcall(debug_init);