path: root/arch/s390/kernel/debug.c

/*
 *  arch/s390/kernel/debug.c
 *   S/390 debug facility
 *
 *    Copyright (C) 1999, 2000 IBM Deutschland Entwicklung GmbH,
 *                             IBM Corporation
 *    Author(s): Michael Holzheu (holzheu@de.ibm.com),
 *               Holger Smolinski (Holger.Smolinski@de.ibm.com)
 *
 *    Bugreports to: <Linux390@de.ibm.com>
 */

#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/sysctl.h>
#include <asm/uaccess.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.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 formated area */
	int    act_page;                /* act page in given area */
	int    act_entry;               /* last formated entry (offset */
                                        /* relative to beginning of last */
                                        /* formated page) */
	size_t act_entry_offset;        /* up to this offset we copied */
					/* in last read the last formated */
					/* 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[0];
} debug_sprintf_entry_t;


extern void tod_to_timeval(uint64_t todval, struct timespec *xtime);

/* internal function prototyes */

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, mode_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);
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);
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, const char *in_buf);
static int debug_raw_format_fn(debug_info_t * id,
			struct debug_view *view, char *out_buf,
			const char *in_buf);
static int debug_raw_header_fn(debug_info_t * id, struct debug_view *view,
			int area, debug_entry_t * entry, char *out_buf);

static int debug_sprintf_format_fn(debug_info_t * id, struct debug_view *view,
			char *out_buf, debug_sprintf_entry_t *curr_event);

/* globals */

struct debug_view debug_raw_view = {
	"raw",
	NULL,
	&debug_raw_header_fn,
	&debug_raw_format_fn,
	NULL,
	NULL
};

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

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_format_proc_t*)&debug_sprintf_format_fn,
	NULL,
	NULL
};

/* 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 = NULL;
static debug_info_t *debug_area_last = NULL;
static DEFINE_MUTEX(debug_mutex);

static int initialized;

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(nr_areas *
					sizeof(debug_entry_t**),
					GFP_KERNEL);
	if (!areas)
		goto fail_malloc_areas;
	for (i = 0; i < nr_areas; i++) {
		areas[i] = kmalloc(pages_per_area *
				sizeof(debug_entry_t*),GFP_KERNEL);
		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(sizeof(debug_info_t), GFP_KERNEL);
	if(!rc)
		goto fail_malloc_rc;
	rc->active_entries = kcalloc(nr_areas, sizeof(int), GFP_KERNEL);
	if(!rc->active_entries)
		goto fail_malloc_active_entries;
	rc->active_pages = kcalloc(nr_areas, sizeof(int), GFP_KERNEL);
	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 */

	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;
	strlcpy(rc->name, name, sizeof(rc->name));
	memset(rc->views, 0, DEBUG_MAX_VIEWS * sizeof(struct debug_view *));
	memset(rc->debugfs_entries, 0 ,DEBUG_MAX_VIEWS *
		sizeof(struct dentry*));
	atomic_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, mode_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;

	/* create root directory */
        rc->debugfs_root_entry = debugfs_create_dir(rc->name,
					debug_debugfs_root_entry);

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

	debug_info_get(rc);
out:
	return rc;
}

/*
 * debug_info_copy
 * - copy debug-info
 */

static debug_info_t*
debug_info_copy(debug_info_t* in, int mode)
{
        int i,j;
        debug_info_t* rc;
        unsigned long flags;

	/* 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);
		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;
		}
		spin_unlock_irqrestore(&in->lock, flags);
		debug_info_free(rc);
	} while (1);

        if(!rc || (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);
		}
        }
out:
        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)
		atomic_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)
{
	int i;

	if (!db_info)
		return;
	if (atomic_dec_and_test(&db_info->ref_count)) {
		for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
			if (!db_info->views[i])
				continue;
			debugfs_remove(db_info->debugfs_entries[i]);
		}
		debugfs_remove(db_info->debugfs_root_entry);
		if(db_info == debug_area_first)
			debug_area_first = db_info->next;
		if(db_info == debug_area_last)
			debug_area_last = db_info->prev;
		if(db_info->prev) db_info->prev->next = db_info->next;
		if(db_info->next) db_info->next->prev = db_info->prev;
		debug_info_free(db_info);
	}
}

/*
 * debug_format_entry:
 * - format one debug entry and return size of formated 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);
		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->id.stck == 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);
	if (view->format_proc)
		len += view->format_proc(id_snap, view, p_info->temp_buf + len,
						DEBUG_DATA(act_entry));
out:
        return len;
}

/*
 * debug_next_entry:
 * - goto next entry in p_info
 */

static inline int
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;
		goto out;
	}
	if(!id->areas)
		return 1;
	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 1;
	}
out:
	return 0;	
}

/*
 * debug_output:
 * - called for user read()
 * - copies formated 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_size;
		int formatted_line_residue;
		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)
{
	int rc = 0;
	file_private_info_t *p_info;

	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 */
}

/*
 * debug_open:
 * - called for user open()
 * - copies formated output to private_data area of the file
 *   handle
 */

static int
debug_open(struct inode *inode, struct file *file)
{
	int i = 0, rc = 0;
	file_private_info_t *p_info;
	debug_info_t *debug_info, *debug_info_snapshot;

	mutex_lock(&debug_mutex);
	debug_info = file->f_path.dentry->d_inode->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:

	/* 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(!debug_info->views[i]->format_proc &&
		!debug_info->views[i]->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){
		rc = -ENOMEM;
		goto out;
	}
	p_info = kmalloc(sizeof(file_private_info_t),
						GFP_KERNEL);
	if(!p_info){
		if(debug_info_snapshot)
			debug_info_free(debug_info_snapshot);
		rc = -ENOMEM;
		goto out;
	}
	p_info->offset = 0;
	p_info->debug_info_snap = debug_info_snapshot;
	p_info->debug_info_org  = debug_info;
	p_info->view = debug_info->views[i];
	p_info->act_area = 0;
	p_info->act_page = 0;
	p_info->act_entry = DEBUG_PROLOG_ENTRY;
	p_info->act_entry_offset = 0;
	file->private_data = p_info;
	debug_info_get(debug_info);
out:
	mutex_unlock(&debug_mutex);
	return rc;
}

/*
 * 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;
	if(p_info->debug_info_snap)
		debug_info_free(p_info->debug_info_snap);
	debug_info_put(p_info->debug_info_org);
	kfree(file->private_data);
	return 0;		/* success */
}

/*
 * debug_register_mode:
 * - Creates and initializes debug area for the caller
 *   The mode parameter allows to specify access rights for the s390dbf files
 * - Returns handle for debug area
 */

debug_info_t *debug_register_mode(const char *name, int pages_per_area,
				  int nr_areas, int buf_size, mode_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))
		printk(KERN_WARNING "debug: Warning - Currently only uid/gid "
		       "= 0 are supported. Using root as owner now!");
	if (!initialized)
		BUG();
	mutex_lock(&debug_mutex);

        /* create new debug_info */

	rc = debug_info_create(name, pages_per_area, nr_areas, buf_size, mode);
	if(!rc) 
		goto out;
	debug_register_view(rc, &debug_level_view);
        debug_register_view(rc, &debug_flush_view);
	debug_register_view(rc, &debug_pages_view);
out:
        if (!rc){
		printk(KERN_ERR "debug: debug_register failed for %s\n",name);
        }
	mutex_unlock(&debug_mutex);
	return rc;
}
EXPORT_SYMBOL(debug_register_mode);

/*
 * debug_register:
 * - creates and initializes debug area for the caller
 * - returns handle for debug area
 */

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);
}

/*
 * debug_unregister:
 * - give back debug area
 */

void
debug_unregister(debug_info_t * id)
{
	if (!id)
		goto out;
	mutex_lock(&debug_mutex);
	debug_info_put(id);
	mutex_unlock(&debug_mutex);

out:
	return;
}

/*
 * 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)
{
	unsigned long flags;
	debug_entry_t *** new_areas;
	int rc=0;

	if(!id || (nr_areas <= 0) || (pages_per_area < 0))
		return -EINVAL;
	if(pages_per_area > 0){
		new_areas = debug_areas_alloc(pages_per_area, nr_areas);
		if(!new_areas) {
			printk(KERN_WARNING "debug: could not allocate memory "\
					 "for pagenumber: %i\n",pages_per_area);
			rc = -ENOMEM;
			goto out;
		}
	} else {
		new_areas = NULL;
	}
	spin_lock_irqsave(&id->lock,flags);
	debug_areas_free(id);
	id->areas = new_areas;
	id->nr_areas = nr_areas;
	id->pages_per_area = pages_per_area;
	id->active_area = 0;
	memset(id->active_entries,0,sizeof(int)*id->nr_areas);
	memset(id->active_pages, 0, sizeof(int)*id->nr_areas);
	spin_unlock_irqrestore(&id->lock,flags);
	printk(KERN_INFO "debug: %s: set new size (%i pages)\n"\
			 ,id->name, pages_per_area);
out:
	return rc;
}

/*
 * debug_set_level:
 * - set actual debug level
 */

void
debug_set_level(debug_info_t* id, int new_level)
{
	unsigned long flags;
	if(!id)
		return;	
	spin_lock_irqsave(&id->lock,flags);
        if(new_level == DEBUG_OFF_LEVEL){
                id->level = DEBUG_OFF_LEVEL;
                printk(KERN_INFO "debug: %s: switched off\n",id->name);
        } else if ((new_level > DEBUG_MAX_LEVEL) || (new_level < 0)) {
                printk(KERN_INFO
                        "debug: %s: level %i is out of range (%i - %i)\n",
                        id->name, new_level, 0, DEBUG_MAX_LEVEL);
        } else {
                id->level = new_level;
        }
	spin_unlock_irqrestore(&id->lock,flags);
}


/*
 * 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]);
}

/*
 * 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)
{
	active->id.stck = get_clock();
	active->id.fields.cpuid = smp_processor_id();
	active->caller = __builtin_return_address(0);
	active->id.fields.exception = exception;
	active->id.fields.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(ctl_table *table, int write, struct file *filp,
                     void __user *buffer, size_t *lenp, loff_t *ppos)
{
	if (!write || debug_stoppable || !debug_active)
		return proc_dointvec(table, write, filp, buffer, lenp, ppos);
	else
		return 0;
}


static struct ctl_table s390dbf_table[] = {
	{
		.ctl_name       = CTL_S390DBF_STOPPABLE,
		.procname       = "debug_stoppable",
		.data		= &debug_stoppable,
		.maxlen		= sizeof(int),
		.mode           = S_IRUGO | S_IWUSR,
		.proc_handler   = &proc_dointvec,
		.strategy	= &sysctl_intvec,
	},
	 {
		.ctl_name       = CTL_S390DBF_ACTIVE,
		.procname       = "debug_active",
		.data		= &debug_active,
		.maxlen		= sizeof(int),
		.mode           = S_IRUGO | S_IWUSR,
		.proc_handler   = &s390dbf_procactive,
		.strategy	= &sysctl_intvec,
	},
	{ .ctl_name = 0 }
};

static struct ctl_table s390dbf_dir_table[] = {
	{
		.ctl_name       = CTL_S390DBF,
		.procname       = "s390dbf",
		.maxlen         = 0,
		.mode           = S_IRUGO | S_IXUGO,
		.child          = s390dbf_table,
	},
	{ .ctl_name = 0 }
};

static struct ctl_table_header *s390dbf_sysctl_header;

void
debug_stop_all(void)
{
	if (debug_stoppable)
		debug_active = 0;
}


/*
 * 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)
{
	unsigned long flags;
	debug_entry_t *active;

	if (!debug_active || !id->areas)
		return NULL;
	spin_lock_irqsave(&id->lock, flags);
	active = get_active_entry(id);
	memset(DEBUG_DATA(active), 0, id->buf_size);
	memcpy(DEBUG_DATA(active), buf, min(len, id->buf_size));
	debug_finish_entry(id, active, level, 0);
	spin_unlock_irqrestore(&id->lock, flags);

	return active;
}

/*
 * 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)
{
	unsigned long flags;
	debug_entry_t *active;

	if (!debug_active || !id->areas)
		return NULL;
	spin_lock_irqsave(&id->lock, flags);
	active = get_active_entry(id);
	memset(DEBUG_DATA(active), 0, id->buf_size);
	memcpy(DEBUG_DATA(active), buf, min(len, id->buf_size));
	debug_finish_entry(id, active, level, 1);
	spin_unlock_irqrestore(&id->lock, flags);

	return active;
}

/*
 * 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,...)
{
	va_list   ap;
	int numargs,idx;
	unsigned long flags;
	debug_sprintf_entry_t *curr_event;
	debug_entry_t *active;

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

	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);
	spin_unlock_irqrestore(&id->lock, flags);

	return active;
}

/*
 * debug_sprintf_exception:
 */

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

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

	numargs=debug_count_numargs(string);

	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);
	spin_unlock_irqrestore(&id->lock, flags);

	return active;
}

/*
 * debug_init:
 * - is called exactly once to initialize the debug feature
 */

static int
__init debug_init(void)
{
	int rc = 0;

	s390dbf_sysctl_header = register_sysctl_table(s390dbf_dir_table);
	mutex_lock(&debug_mutex);
	debug_debugfs_root_entry = debugfs_create_dir(DEBUG_DIR_ROOT,NULL);
	initialized = 1;
	mutex_unlock(&debug_mutex);

	return rc;
}

/*
 * debug_register_view:
 */

int
debug_register_view(debug_info_t * id, struct debug_view *view)
{
	int rc = 0;
	int i;
	unsigned long flags;
	mode_t mode;
	struct dentry *pde;

	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);
	if (!pde){
		printk(KERN_WARNING "debug: debugfs_create_file() failed!"\
			" Cannot register view %s/%s\n", id->name,view->name);
		rc = -1;
		goto out;
	}
	spin_lock_irqsave(&id->lock, flags);
	for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
		if (!id->views[i])
			break;
	}
	if (i == DEBUG_MAX_VIEWS) {
		printk(KERN_WARNING "debug: cannot register view %s/%s\n",
			id->name,view->name);
		printk(KERN_WARNING 
			"debug: maximum number of views reached (%i)!\n", i);
		debugfs_remove(pde);
		rc = -1;
	} else {
		id->views[i] = view;
		id->debugfs_entries[i] = pde;
	}
	spin_unlock_irqrestore(&id->lock, flags);
out:
	return rc;
}

/*
 * debug_unregister_view:
 */

int
debug_unregister_view(debug_info_t * id, struct debug_view *view)
{
	int rc = 0;
	int i;
	unsigned long flags;

	if (!id)
		goto out;
	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 {
		debugfs_remove(id->debugfs_entries[i]);
		id->views[i] = NULL;
		rc = 0;
	}
	spin_unlock_irqrestore(&id->lock, flags);
out:
	return rc;
}

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

	buffer = kmalloc(user_len + 1, GFP_KERNEL);
	if (!buffer)
		return ERR_PTR(-ENOMEM);
	if (copy_from_user(buffer, user_buf, user_len) != 0) {
		kfree(buffer);
		return ERR_PTR(-EFAULT);
	}
	/* got the string, now strip linefeed. */
	if (buffer[user_len - 1] == '\n')
		buffer[user_len - 1] = 0;
	else
		buffer[user_len] = 0;
        return buffer;
}

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

	for(; isspace(*buf); 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)
{
	return sprintf(out_buf, "%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)
{
	char *str;
	int rc,new_pages;

	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)
{
	int rc = 0;

	if(id->level == DEBUG_OFF_LEVEL) {
		rc = sprintf(out_buf,"-\n");
	}
	else {
		rc = sprintf(out_buf, "%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)
{
	char *str;
	int rc,new_level;

	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) {
		printk(KERN_INFO "debug: level `%s` is not valid\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;
        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);
		}
        }
        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;
        }

        printk(KERN_INFO "debug: area `%c` is not valid\n", input_buf[0]);

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

/*
 * prints debug header in raw format
 */

static int
debug_raw_header_fn(debug_info_t * id, struct debug_view *view,
			int area, debug_entry_t * entry, char *out_buf)
{
        int rc;

	rc = sizeof(debug_entry_t);
	memcpy(out_buf,entry,sizeof(debug_entry_t));
        return rc;
}

/*
 * prints debug data in raw format
 */

static int
debug_raw_format_fn(debug_info_t * id, struct debug_view *view,
			       char *out_buf, const char *in_buf)
{
	int rc;

	rc = id->buf_size;
	memcpy(out_buf, in_buf, id->buf_size);
	return rc;
}

/*
 * 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, const char *in_buf)
{
	int i, rc = 0;

	for (i = 0; i < id->buf_size; i++) {
                rc += sprintf(out_buf + rc, "%02x ",
                              ((unsigned char *) in_buf)[i]);
        }
	rc += sprintf(out_buf + rc, "| ");
	for (i = 0; i < id->buf_size; i++) {
		unsigned char c = in_buf[i];
		if (!isprint(c))
			rc += sprintf(out_buf + rc, ".");
		else
			rc += sprintf(out_buf + rc, "%c", c);
	}
	rc += sprintf(out_buf + 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)
{
	struct timespec time_spec;
	unsigned long long time;
	char *except_str;
	unsigned long caller;
	int rc = 0;
	unsigned int level;

	level = entry->id.fields.level;
	time = entry->id.stck;
	/* adjust todclock to 1970 */
	time -= 0x8126d60e46000000LL - (0x3c26700LL * 1000000 * 4096);
	tod_to_timeval(time, &time_spec);

	if (entry->id.fields.exception)
		except_str = "*";
	else
		except_str = "-";
	caller = ((unsigned long) entry->caller) & PSW_ADDR_INSN;
	rc += sprintf(out_buf, "%02i %011lu:%06lu %1u %1s %02i %p  ",
		      area, time_spec.tv_sec, time_spec.tv_nsec / 1000, level,
		      except_str, entry->id.fields.cpuid, (void *) caller);
	return rc;
}

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

#define DEBUG_SPRINTF_MAX_ARGS 10

static int
debug_sprintf_format_fn(debug_info_t * id, struct debug_view *view,
                        char *out_buf, debug_sprintf_entry_t *curr_event)
{
	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 */
		strcpy(out_buf, curr_event->string);
		rc = strlen(curr_event->string);
		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 =  sprintf(out_buf, 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;
}

/*
 * clean up module
 */
static void __exit debug_exit(void)
{
	debugfs_remove(debug_debugfs_root_entry);
	unregister_sysctl_table(s390dbf_sysctl_header);
	return;
}

/*
 * module definitions
 */
postcore_initcall(debug_init);
module_exit(debug_exit);
MODULE_LICENSE("GPL");

EXPORT_SYMBOL(debug_register);
EXPORT_SYMBOL(debug_unregister); 
EXPORT_SYMBOL(debug_set_level);
EXPORT_SYMBOL(debug_stop_all);
EXPORT_SYMBOL(debug_register_view);
EXPORT_SYMBOL(debug_unregister_view);
EXPORT_SYMBOL(debug_event_common);
EXPORT_SYMBOL(debug_exception_common);
EXPORT_SYMBOL(debug_hex_ascii_view);
EXPORT_SYMBOL(debug_raw_view);
EXPORT_SYMBOL(debug_dflt_header_fn);
EXPORT_SYMBOL(debug_sprintf_view);
EXPORT_SYMBOL(debug_sprintf_exception);
EXPORT_SYMBOL(debug_sprintf_event);