linux/arch/s390/kernel/debug.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *   S/390 debug facility
   4 *
   5 *    Copyright IBM Corp. 1999, 2020
   6 *
   7 *    Author(s): Michael Holzheu (holzheu@de.ibm.com),
   8 *               Holger Smolinski (Holger.Smolinski@de.ibm.com)
   9 *
  10 *    Bugreports to: <Linux390@de.ibm.com>
  11 */
  12
  13#define KMSG_COMPONENT "s390dbf"
  14#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  15
  16#include <linux/stddef.h>
  17#include <linux/kernel.h>
  18#include <linux/errno.h>
  19#include <linux/slab.h>
  20#include <linux/ctype.h>
  21#include <linux/string.h>
  22#include <linux/sysctl.h>
  23#include <linux/uaccess.h>
  24#include <linux/export.h>
  25#include <linux/init.h>
  26#include <linux/fs.h>
  27#include <linux/debugfs.h>
  28
  29#include <asm/debug.h>
  30
  31#define DEBUG_PROLOG_ENTRY -1
  32
  33#define ALL_AREAS 0 /* copy all debug areas */
  34#define NO_AREAS  1 /* copy no debug areas */
  35
  36/* typedefs */
  37
  38typedef struct file_private_info {
  39        loff_t offset;                  /* offset of last read in file */
  40        int    act_area;                /* number of last formated area */
  41        int    act_page;                /* act page in given area */
  42        int    act_entry;               /* last formated entry (offset */
  43                                        /* relative to beginning of last */
  44                                        /* formated page) */
  45        size_t act_entry_offset;        /* up to this offset we copied */
  46                                        /* in last read the last formated */
  47                                        /* entry to userland */
  48        char   temp_buf[2048];          /* buffer for output */
  49        debug_info_t *debug_info_org;   /* original debug information */
  50        debug_info_t *debug_info_snap;  /* snapshot of debug information */
  51        struct debug_view *view;        /* used view of debug info */
  52} file_private_info_t;
  53
  54typedef struct {
  55        char *string;
  56        /*
  57         * This assumes that all args are converted into longs
  58         * on L/390 this is the case for all types of parameter
  59         * except of floats, and long long (32 bit)
  60         *
  61         */
  62        long args[0];
  63} debug_sprintf_entry_t;
  64
  65/* internal function prototyes */
  66
  67static int debug_init(void);
  68static ssize_t debug_output(struct file *file, char __user *user_buf,
  69                            size_t user_len, loff_t *offset);
  70static ssize_t debug_input(struct file *file, const char __user *user_buf,
  71                           size_t user_len, loff_t *offset);
  72static int debug_open(struct inode *inode, struct file *file);
  73static int debug_close(struct inode *inode, struct file *file);
  74static debug_info_t *debug_info_create(const char *name, int pages_per_area,
  75                                       int nr_areas, int buf_size, umode_t mode);
  76static void debug_info_get(debug_info_t *);
  77static void debug_info_put(debug_info_t *);
  78static int debug_prolog_level_fn(debug_info_t *id,
  79                                 struct debug_view *view, char *out_buf);
  80static int debug_input_level_fn(debug_info_t *id, struct debug_view *view,
  81                                struct file *file, const char __user *user_buf,
  82                                size_t user_buf_size, loff_t *offset);
  83static int debug_prolog_pages_fn(debug_info_t *id,
  84                                 struct debug_view *view, char *out_buf);
  85static int debug_input_pages_fn(debug_info_t *id, struct debug_view *view,
  86                                struct file *file, const char __user *user_buf,
  87                                size_t user_buf_size, loff_t *offset);
  88static int debug_input_flush_fn(debug_info_t *id, struct debug_view *view,
  89                                struct file *file, const char __user *user_buf,
  90                                size_t user_buf_size, loff_t *offset);
  91static int debug_hex_ascii_format_fn(debug_info_t *id, struct debug_view *view,
  92                                     char *out_buf, const char *in_buf);
  93static int debug_sprintf_format_fn(debug_info_t *id, struct debug_view *view,
  94                                   char *out_buf, debug_sprintf_entry_t *curr_event);
  95
  96/* globals */
  97
  98struct debug_view debug_hex_ascii_view = {
  99        "hex_ascii",
 100        NULL,
 101        &debug_dflt_header_fn,
 102        &debug_hex_ascii_format_fn,
 103        NULL,
 104        NULL
 105};
 106EXPORT_SYMBOL(debug_hex_ascii_view);
 107
 108static struct debug_view debug_level_view = {
 109        "level",
 110        &debug_prolog_level_fn,
 111        NULL,
 112        NULL,
 113        &debug_input_level_fn,
 114        NULL
 115};
 116
 117static struct debug_view debug_pages_view = {
 118        "pages",
 119        &debug_prolog_pages_fn,
 120        NULL,
 121        NULL,
 122        &debug_input_pages_fn,
 123        NULL
 124};
 125
 126static struct debug_view debug_flush_view = {
 127        "flush",
 128        NULL,
 129        NULL,
 130        NULL,
 131        &debug_input_flush_fn,
 132        NULL
 133};
 134
 135struct debug_view debug_sprintf_view = {
 136        "sprintf",
 137        NULL,
 138        &debug_dflt_header_fn,
 139        (debug_format_proc_t *)&debug_sprintf_format_fn,
 140        NULL,
 141        NULL
 142};
 143EXPORT_SYMBOL(debug_sprintf_view);
 144
 145/* used by dump analysis tools to determine version of debug feature */
 146static unsigned int __used debug_feature_version = __DEBUG_FEATURE_VERSION;
 147
 148/* static globals */
 149
 150static debug_info_t *debug_area_first;
 151static debug_info_t *debug_area_last;
 152static DEFINE_MUTEX(debug_mutex);
 153
 154static int initialized;
 155static int debug_critical;
 156
 157static const struct file_operations debug_file_ops = {
 158        .owner   = THIS_MODULE,
 159        .read    = debug_output,
 160        .write   = debug_input,
 161        .open    = debug_open,
 162        .release = debug_close,
 163        .llseek  = no_llseek,
 164};
 165
 166static struct dentry *debug_debugfs_root_entry;
 167
 168/* functions */
 169
 170/*
 171 * debug_areas_alloc
 172 * - Debug areas are implemented as a threedimensonal array:
 173 *   areas[areanumber][pagenumber][pageoffset]
 174 */
 175
 176static debug_entry_t ***debug_areas_alloc(int pages_per_area, int nr_areas)
 177{
 178        debug_entry_t ***areas;
 179        int i, j;
 180
 181        areas = kmalloc_array(nr_areas, sizeof(debug_entry_t **), GFP_KERNEL);
 182        if (!areas)
 183                goto fail_malloc_areas;
 184        for (i = 0; i < nr_areas; i++) {
 185                /* GFP_NOWARN to avoid user triggerable WARN, we handle fails */
 186                areas[i] = kmalloc_array(pages_per_area,
 187                                         sizeof(debug_entry_t *),
 188                                         GFP_KERNEL | __GFP_NOWARN);
 189                if (!areas[i])
 190                        goto fail_malloc_areas2;
 191                for (j = 0; j < pages_per_area; j++) {
 192                        areas[i][j] = kzalloc(PAGE_SIZE, GFP_KERNEL);
 193                        if (!areas[i][j]) {
 194                                for (j--; j >= 0 ; j--)
 195                                        kfree(areas[i][j]);
 196                                kfree(areas[i]);
 197                                goto fail_malloc_areas2;
 198                        }
 199                }
 200        }
 201        return areas;
 202
 203fail_malloc_areas2:
 204        for (i--; i >= 0; i--) {
 205                for (j = 0; j < pages_per_area; j++)
 206                        kfree(areas[i][j]);
 207                kfree(areas[i]);
 208        }
 209        kfree(areas);
 210fail_malloc_areas:
 211        return NULL;
 212}
 213
 214/*
 215 * debug_info_alloc
 216 * - alloc new debug-info
 217 */
 218static debug_info_t *debug_info_alloc(const char *name, int pages_per_area,
 219                                      int nr_areas, int buf_size, int level,
 220                                      int mode)
 221{
 222        debug_info_t *rc;
 223
 224        /* alloc everything */
 225        rc = kmalloc(sizeof(debug_info_t), GFP_KERNEL);
 226        if (!rc)
 227                goto fail_malloc_rc;
 228        rc->active_entries = kcalloc(nr_areas, sizeof(int), GFP_KERNEL);
 229        if (!rc->active_entries)
 230                goto fail_malloc_active_entries;
 231        rc->active_pages = kcalloc(nr_areas, sizeof(int), GFP_KERNEL);
 232        if (!rc->active_pages)
 233                goto fail_malloc_active_pages;
 234        if ((mode == ALL_AREAS) && (pages_per_area != 0)) {
 235                rc->areas = debug_areas_alloc(pages_per_area, nr_areas);
 236                if (!rc->areas)
 237                        goto fail_malloc_areas;
 238        } else {
 239                rc->areas = NULL;
 240        }
 241
 242        /* initialize members */
 243        spin_lock_init(&rc->lock);
 244        rc->pages_per_area = pages_per_area;
 245        rc->nr_areas       = nr_areas;
 246        rc->active_area    = 0;
 247        rc->level          = level;
 248        rc->buf_size       = buf_size;
 249        rc->entry_size     = sizeof(debug_entry_t) + buf_size;
 250        strlcpy(rc->name, name, sizeof(rc->name));
 251        memset(rc->views, 0, DEBUG_MAX_VIEWS * sizeof(struct debug_view *));
 252        memset(rc->debugfs_entries, 0, DEBUG_MAX_VIEWS * sizeof(struct dentry *));
 253        refcount_set(&(rc->ref_count), 0);
 254
 255        return rc;
 256
 257fail_malloc_areas:
 258        kfree(rc->active_pages);
 259fail_malloc_active_pages:
 260        kfree(rc->active_entries);
 261fail_malloc_active_entries:
 262        kfree(rc);
 263fail_malloc_rc:
 264        return NULL;
 265}
 266
 267/*
 268 * debug_areas_free
 269 * - free all debug areas
 270 */
 271static void debug_areas_free(debug_info_t *db_info)
 272{
 273        int i, j;
 274
 275        if (!db_info->areas)
 276                return;
 277        for (i = 0; i < db_info->nr_areas; i++) {
 278                for (j = 0; j < db_info->pages_per_area; j++)
 279                        kfree(db_info->areas[i][j]);
 280                kfree(db_info->areas[i]);
 281        }
 282        kfree(db_info->areas);
 283        db_info->areas = NULL;
 284}
 285
 286/*
 287 * debug_info_free
 288 * - free memory debug-info
 289 */
 290static void debug_info_free(debug_info_t *db_info)
 291{
 292        debug_areas_free(db_info);
 293        kfree(db_info->active_entries);
 294        kfree(db_info->active_pages);
 295        kfree(db_info);
 296}
 297
 298/*
 299 * debug_info_create
 300 * - create new debug-info
 301 */
 302
 303static debug_info_t *debug_info_create(const char *name, int pages_per_area,
 304                                       int nr_areas, int buf_size, umode_t mode)
 305{
 306        debug_info_t *rc;
 307
 308        rc = debug_info_alloc(name, pages_per_area, nr_areas, buf_size,
 309                              DEBUG_DEFAULT_LEVEL, ALL_AREAS);
 310        if (!rc)
 311                goto out;
 312
 313        rc->mode = mode & ~S_IFMT;
 314
 315        /* create root directory */
 316        rc->debugfs_root_entry = debugfs_create_dir(rc->name,
 317                                                    debug_debugfs_root_entry);
 318
 319        /* append new element to linked list */
 320        if (!debug_area_first) {
 321                /* first element in list */
 322                debug_area_first = rc;
 323                rc->prev = NULL;
 324        } else {
 325                /* append element to end of list */
 326                debug_area_last->next = rc;
 327                rc->prev = debug_area_last;
 328        }
 329        debug_area_last = rc;
 330        rc->next = NULL;
 331
 332        refcount_set(&rc->ref_count, 1);
 333out:
 334        return rc;
 335}
 336
 337/*
 338 * debug_info_copy
 339 * - copy debug-info
 340 */
 341static debug_info_t *debug_info_copy(debug_info_t *in, int mode)
 342{
 343        unsigned long flags;
 344        debug_info_t *rc;
 345        int i, j;
 346
 347        /* get a consistent copy of the debug areas */
 348        do {
 349                rc = debug_info_alloc(in->name, in->pages_per_area,
 350                        in->nr_areas, in->buf_size, in->level, mode);
 351                spin_lock_irqsave(&in->lock, flags);
 352                if (!rc)
 353                        goto out;
 354                /* has something changed in the meantime ? */
 355                if ((rc->pages_per_area == in->pages_per_area) &&
 356                    (rc->nr_areas == in->nr_areas)) {
 357                        break;
 358                }
 359                spin_unlock_irqrestore(&in->lock, flags);
 360                debug_info_free(rc);
 361        } while (1);
 362
 363        if (mode == NO_AREAS)
 364                goto out;
 365
 366        for (i = 0; i < in->nr_areas; i++) {
 367                for (j = 0; j < in->pages_per_area; j++)
 368                        memcpy(rc->areas[i][j], in->areas[i][j], PAGE_SIZE);
 369        }
 370out:
 371        spin_unlock_irqrestore(&in->lock, flags);
 372        return rc;
 373}
 374
 375/*
 376 * debug_info_get
 377 * - increments reference count for debug-info
 378 */
 379static void debug_info_get(debug_info_t *db_info)
 380{
 381        if (db_info)
 382                refcount_inc(&db_info->ref_count);
 383}
 384
 385/*
 386 * debug_info_put:
 387 * - decreases reference count for debug-info and frees it if necessary
 388 */
 389static void debug_info_put(debug_info_t *db_info)
 390{
 391        int i;
 392
 393        if (!db_info)
 394                return;
 395        if (refcount_dec_and_test(&db_info->ref_count)) {
 396                for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
 397                        if (!db_info->views[i])
 398                                continue;
 399                        debugfs_remove(db_info->debugfs_entries[i]);
 400                }
 401                debugfs_remove(db_info->debugfs_root_entry);
 402                if (db_info == debug_area_first)
 403                        debug_area_first = db_info->next;
 404                if (db_info == debug_area_last)
 405                        debug_area_last = db_info->prev;
 406                if (db_info->prev)
 407                        db_info->prev->next = db_info->next;
 408                if (db_info->next)
 409                        db_info->next->prev = db_info->prev;
 410                debug_info_free(db_info);
 411        }
 412}
 413
 414/*
 415 * debug_format_entry:
 416 * - format one debug entry and return size of formated data
 417 */
 418static int debug_format_entry(file_private_info_t *p_info)
 419{
 420        debug_info_t *id_snap   = p_info->debug_info_snap;
 421        struct debug_view *view = p_info->view;
 422        debug_entry_t *act_entry;
 423        size_t len = 0;
 424
 425        if (p_info->act_entry == DEBUG_PROLOG_ENTRY) {
 426                /* print prolog */
 427                if (view->prolog_proc)
 428                        len += view->prolog_proc(id_snap, view, p_info->temp_buf);
 429                goto out;
 430        }
 431        if (!id_snap->areas) /* this is true, if we have a prolog only view */
 432                goto out;    /* or if 'pages_per_area' is 0 */
 433        act_entry = (debug_entry_t *) ((char *)id_snap->areas[p_info->act_area]
 434                                       [p_info->act_page] + p_info->act_entry);
 435
 436        if (act_entry->clock == 0LL)
 437                goto out; /* empty entry */
 438        if (view->header_proc)
 439                len += view->header_proc(id_snap, view, p_info->act_area,
 440                                         act_entry, p_info->temp_buf + len);
 441        if (view->format_proc)
 442                len += view->format_proc(id_snap, view, p_info->temp_buf + len,
 443                                         DEBUG_DATA(act_entry));
 444out:
 445        return len;
 446}
 447
 448/*
 449 * debug_next_entry:
 450 * - goto next entry in p_info
 451 */
 452static inline int debug_next_entry(file_private_info_t *p_info)
 453{
 454        debug_info_t *id;
 455
 456        id = p_info->debug_info_snap;
 457        if (p_info->act_entry == DEBUG_PROLOG_ENTRY) {
 458                p_info->act_entry = 0;
 459                p_info->act_page  = 0;
 460                goto out;
 461        }
 462        if (!id->areas)
 463                return 1;
 464        p_info->act_entry += id->entry_size;
 465        /* switch to next page, if we reached the end of the page  */
 466        if (p_info->act_entry > (PAGE_SIZE - id->entry_size)) {
 467                /* next page */
 468                p_info->act_entry = 0;
 469                p_info->act_page += 1;
 470                if ((p_info->act_page % id->pages_per_area) == 0) {
 471                        /* next area */
 472                        p_info->act_area++;
 473                        p_info->act_page = 0;
 474                }
 475                if (p_info->act_area >= id->nr_areas)
 476                        return 1;
 477        }
 478out:
 479        return 0;
 480}
 481
 482/*
 483 * debug_output:
 484 * - called for user read()
 485 * - copies formated debug entries to the user buffer
 486 */
 487static ssize_t debug_output(struct file *file,          /* file descriptor */
 488                            char __user *user_buf,      /* user buffer */
 489                            size_t len,                 /* length of buffer */
 490                            loff_t *offset)             /* offset in the file */
 491{
 492        size_t count = 0;
 493        size_t entry_offset;
 494        file_private_info_t *p_info;
 495
 496        p_info = (file_private_info_t *) file->private_data;
 497        if (*offset != p_info->offset)
 498                return -EPIPE;
 499        if (p_info->act_area >= p_info->debug_info_snap->nr_areas)
 500                return 0;
 501        entry_offset = p_info->act_entry_offset;
 502        while (count < len) {
 503                int formatted_line_residue;
 504                int formatted_line_size;
 505                int user_buf_residue;
 506                size_t copy_size;
 507
 508                formatted_line_size = debug_format_entry(p_info);
 509                formatted_line_residue = formatted_line_size - entry_offset;
 510                user_buf_residue = len-count;
 511                copy_size = min(user_buf_residue, formatted_line_residue);
 512                if (copy_size) {
 513                        if (copy_to_user(user_buf + count, p_info->temp_buf
 514                                         + entry_offset, copy_size))
 515                                return -EFAULT;
 516                        count += copy_size;
 517                        entry_offset += copy_size;
 518                }
 519                if (copy_size == formatted_line_residue) {
 520                        entry_offset = 0;
 521                        if (debug_next_entry(p_info))
 522                                goto out;
 523                }
 524        }
 525out:
 526        p_info->offset           = *offset + count;
 527        p_info->act_entry_offset = entry_offset;
 528        *offset = p_info->offset;
 529        return count;
 530}
 531
 532/*
 533 * debug_input:
 534 * - called for user write()
 535 * - calls input function of view
 536 */
 537static ssize_t debug_input(struct file *file, const char __user *user_buf,
 538                           size_t length, loff_t *offset)
 539{
 540        file_private_info_t *p_info;
 541        int rc = 0;
 542
 543        mutex_lock(&debug_mutex);
 544        p_info = ((file_private_info_t *) file->private_data);
 545        if (p_info->view->input_proc) {
 546                rc = p_info->view->input_proc(p_info->debug_info_org,
 547                                              p_info->view, file, user_buf,
 548                                              length, offset);
 549        } else {
 550                rc = -EPERM;
 551        }
 552        mutex_unlock(&debug_mutex);
 553        return rc; /* number of input characters */
 554}
 555
 556/*
 557 * debug_open:
 558 * - called for user open()
 559 * - copies formated output to private_data area of the file
 560 *   handle
 561 */
 562static int debug_open(struct inode *inode, struct file *file)
 563{
 564        debug_info_t *debug_info, *debug_info_snapshot;
 565        file_private_info_t *p_info;
 566        int i, rc = 0;
 567
 568        mutex_lock(&debug_mutex);
 569        debug_info = file_inode(file)->i_private;
 570        /* find debug view */
 571        for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
 572                if (!debug_info->views[i])
 573                        continue;
 574                else if (debug_info->debugfs_entries[i] == file->f_path.dentry)
 575                        goto found; /* found view ! */
 576        }
 577        /* no entry found */
 578        rc = -EINVAL;
 579        goto out;
 580
 581found:
 582
 583        /* Make snapshot of current debug areas to get it consistent.     */
 584        /* To copy all the areas is only needed, if we have a view which  */
 585        /* formats the debug areas. */
 586
 587        if (!debug_info->views[i]->format_proc && !debug_info->views[i]->header_proc)
 588                debug_info_snapshot = debug_info_copy(debug_info, NO_AREAS);
 589        else
 590                debug_info_snapshot = debug_info_copy(debug_info, ALL_AREAS);
 591
 592        if (!debug_info_snapshot) {
 593                rc = -ENOMEM;
 594                goto out;
 595        }
 596        p_info = kmalloc(sizeof(file_private_info_t), GFP_KERNEL);
 597        if (!p_info) {
 598                debug_info_free(debug_info_snapshot);
 599                rc = -ENOMEM;
 600                goto out;
 601        }
 602        p_info->offset = 0;
 603        p_info->debug_info_snap = debug_info_snapshot;
 604        p_info->debug_info_org  = debug_info;
 605        p_info->view = debug_info->views[i];
 606        p_info->act_area = 0;
 607        p_info->act_page = 0;
 608        p_info->act_entry = DEBUG_PROLOG_ENTRY;
 609        p_info->act_entry_offset = 0;
 610        file->private_data = p_info;
 611        debug_info_get(debug_info);
 612        nonseekable_open(inode, file);
 613out:
 614        mutex_unlock(&debug_mutex);
 615        return rc;
 616}
 617
 618/*
 619 * debug_close:
 620 * - called for user close()
 621 * - deletes  private_data area of the file handle
 622 */
 623static int debug_close(struct inode *inode, struct file *file)
 624{
 625        file_private_info_t *p_info;
 626
 627        p_info = (file_private_info_t *) file->private_data;
 628        if (p_info->debug_info_snap)
 629                debug_info_free(p_info->debug_info_snap);
 630        debug_info_put(p_info->debug_info_org);
 631        kfree(file->private_data);
 632        return 0; /* success */
 633}
 634
 635/**
 636 * debug_register_mode() - creates and initializes debug area.
 637 *
 638 * @name:       Name of debug log (e.g. used for debugfs entry)
 639 * @pages_per_area:     Number of pages, which will be allocated per area
 640 * @nr_areas:   Number of debug areas
 641 * @buf_size:   Size of data area in each debug entry
 642 * @mode:       File mode for debugfs files. E.g. S_IRWXUGO
 643 * @uid:        User ID for debugfs files. Currently only 0 is supported.
 644 * @gid:        Group ID for debugfs files. Currently only 0 is supported.
 645 *
 646 * Return:
 647 * - Handle for generated debug area
 648 * - %NULL if register failed
 649 *
 650 * Allocates memory for a debug log.
 651 * Must not be called within an interrupt handler.
 652 */
 653debug_info_t *debug_register_mode(const char *name, int pages_per_area,
 654                                  int nr_areas, int buf_size, umode_t mode,
 655                                  uid_t uid, gid_t gid)
 656{
 657        debug_info_t *rc = NULL;
 658
 659        /* Since debugfs currently does not support uid/gid other than root, */
 660        /* we do not allow gid/uid != 0 until we get support for that. */
 661        if ((uid != 0) || (gid != 0))
 662                pr_warn("Root becomes the owner of all s390dbf files in sysfs\n");
 663        BUG_ON(!initialized);
 664        mutex_lock(&debug_mutex);
 665
 666        /* create new debug_info */
 667        rc = debug_info_create(name, pages_per_area, nr_areas, buf_size, mode);
 668        if (!rc)
 669                goto out;
 670        debug_register_view(rc, &debug_level_view);
 671        debug_register_view(rc, &debug_flush_view);
 672        debug_register_view(rc, &debug_pages_view);
 673out:
 674        if (!rc)
 675                pr_err("Registering debug feature %s failed\n", name);
 676        mutex_unlock(&debug_mutex);
 677        return rc;
 678}
 679EXPORT_SYMBOL(debug_register_mode);
 680
 681/**
 682 * debug_register() - creates and initializes debug area with default file mode.
 683 *
 684 * @name:       Name of debug log (e.g. used for debugfs entry)
 685 * @pages_per_area:     Number of pages, which will be allocated per area
 686 * @nr_areas:   Number of debug areas
 687 * @buf_size:   Size of data area in each debug entry
 688 *
 689 * Return:
 690 * - Handle for generated debug area
 691 * - %NULL if register failed
 692 *
 693 * Allocates memory for a debug log.
 694 * The debugfs file mode access permissions are read and write for user.
 695 * Must not be called within an interrupt handler.
 696 */
 697debug_info_t *debug_register(const char *name, int pages_per_area,
 698                             int nr_areas, int buf_size)
 699{
 700        return debug_register_mode(name, pages_per_area, nr_areas, buf_size,
 701                                   S_IRUSR | S_IWUSR, 0, 0);
 702}
 703EXPORT_SYMBOL(debug_register);
 704
 705/**
 706 * debug_unregister() - give back debug area.
 707 *
 708 * @id:         handle for debug log
 709 *
 710 * Return:
 711 *    none
 712 */
 713void debug_unregister(debug_info_t *id)
 714{
 715        if (!id)
 716                return;
 717        mutex_lock(&debug_mutex);
 718        debug_info_put(id);
 719        mutex_unlock(&debug_mutex);
 720}
 721EXPORT_SYMBOL(debug_unregister);
 722
 723/*
 724 * debug_set_size:
 725 * - set area size (number of pages) and number of areas
 726 */
 727static int debug_set_size(debug_info_t *id, int nr_areas, int pages_per_area)
 728{
 729        debug_entry_t ***new_areas;
 730        unsigned long flags;
 731        int rc = 0;
 732
 733        if (!id || (nr_areas <= 0) || (pages_per_area < 0))
 734                return -EINVAL;
 735        if (pages_per_area > 0) {
 736                new_areas = debug_areas_alloc(pages_per_area, nr_areas);
 737                if (!new_areas) {
 738                        pr_info("Allocating memory for %i pages failed\n",
 739                                pages_per_area);
 740                        rc = -ENOMEM;
 741                        goto out;
 742                }
 743        } else {
 744                new_areas = NULL;
 745        }
 746        spin_lock_irqsave(&id->lock, flags);
 747        debug_areas_free(id);
 748        id->areas = new_areas;
 749        id->nr_areas = nr_areas;
 750        id->pages_per_area = pages_per_area;
 751        id->active_area = 0;
 752        memset(id->active_entries, 0, sizeof(int)*id->nr_areas);
 753        memset(id->active_pages, 0, sizeof(int)*id->nr_areas);
 754        spin_unlock_irqrestore(&id->lock, flags);
 755        pr_info("%s: set new size (%i pages)\n", id->name, pages_per_area);
 756out:
 757        return rc;
 758}
 759
 760/**
 761 * debug_set_level() - Sets new actual debug level if new_level is valid.
 762 *
 763 * @id:         handle for debug log
 764 * @new_level:  new debug level
 765 *
 766 * Return:
 767 *    none
 768 */
 769void debug_set_level(debug_info_t *id, int new_level)
 770{
 771        unsigned long flags;
 772
 773        if (!id)
 774                return;
 775        spin_lock_irqsave(&id->lock, flags);
 776        if (new_level == DEBUG_OFF_LEVEL) {
 777                id->level = DEBUG_OFF_LEVEL;
 778                pr_info("%s: switched off\n", id->name);
 779        } else if ((new_level > DEBUG_MAX_LEVEL) || (new_level < 0)) {
 780                pr_info("%s: level %i is out of range (%i - %i)\n",
 781                        id->name, new_level, 0, DEBUG_MAX_LEVEL);
 782        } else {
 783                id->level = new_level;
 784        }
 785        spin_unlock_irqrestore(&id->lock, flags);
 786}
 787EXPORT_SYMBOL(debug_set_level);
 788
 789/*
 790 * proceed_active_entry:
 791 * - set active entry to next in the ring buffer
 792 */
 793static inline void proceed_active_entry(debug_info_t *id)
 794{
 795        if ((id->active_entries[id->active_area] += id->entry_size)
 796            > (PAGE_SIZE - id->entry_size)) {
 797                id->active_entries[id->active_area] = 0;
 798                id->active_pages[id->active_area] =
 799                        (id->active_pages[id->active_area] + 1) %
 800                        id->pages_per_area;
 801        }
 802}
 803
 804/*
 805 * proceed_active_area:
 806 * - set active area to next in the ring buffer
 807 */
 808static inline void proceed_active_area(debug_info_t *id)
 809{
 810        id->active_area++;
 811        id->active_area = id->active_area % id->nr_areas;
 812}
 813
 814/*
 815 * get_active_entry:
 816 */
 817static inline debug_entry_t *get_active_entry(debug_info_t *id)
 818{
 819        return (debug_entry_t *) (((char *) id->areas[id->active_area]
 820                                   [id->active_pages[id->active_area]]) +
 821                                  id->active_entries[id->active_area]);
 822}
 823
 824/*
 825 * debug_finish_entry:
 826 * - set timestamp, caller address, cpu number etc.
 827 */
 828
 829static inline void debug_finish_entry(debug_info_t *id, debug_entry_t *active,
 830                                      int level, int exception)
 831{
 832        unsigned long timestamp;
 833        union tod_clock clk;
 834
 835        store_tod_clock_ext(&clk);
 836        timestamp = clk.us;
 837        timestamp -= TOD_UNIX_EPOCH >> 12;
 838        active->clock = timestamp;
 839        active->cpu = smp_processor_id();
 840        active->caller = __builtin_return_address(0);
 841        active->exception = exception;
 842        active->level = level;
 843        proceed_active_entry(id);
 844        if (exception)
 845                proceed_active_area(id);
 846}
 847
 848static int debug_stoppable = 1;
 849static int debug_active = 1;
 850
 851#define CTL_S390DBF_STOPPABLE 5678
 852#define CTL_S390DBF_ACTIVE 5679
 853
 854/*
 855 * proc handler for the running debug_active sysctl
 856 * always allow read, allow write only if debug_stoppable is set or
 857 * if debug_active is already off
 858 */
 859static int s390dbf_procactive(struct ctl_table *table, int write,
 860                              void *buffer, size_t *lenp, loff_t *ppos)
 861{
 862        if (!write || debug_stoppable || !debug_active)
 863                return proc_dointvec(table, write, buffer, lenp, ppos);
 864        else
 865                return 0;
 866}
 867
 868static struct ctl_table s390dbf_table[] = {
 869        {
 870                .procname       = "debug_stoppable",
 871                .data           = &debug_stoppable,
 872                .maxlen         = sizeof(int),
 873                .mode           = S_IRUGO | S_IWUSR,
 874                .proc_handler   = proc_dointvec,
 875        },
 876        {
 877                .procname       = "debug_active",
 878                .data           = &debug_active,
 879                .maxlen         = sizeof(int),
 880                .mode           = S_IRUGO | S_IWUSR,
 881                .proc_handler   = s390dbf_procactive,
 882        },
 883        { }
 884};
 885
 886static struct ctl_table s390dbf_dir_table[] = {
 887        {
 888                .procname       = "s390dbf",
 889                .maxlen         = 0,
 890                .mode           = S_IRUGO | S_IXUGO,
 891                .child          = s390dbf_table,
 892        },
 893        { }
 894};
 895
 896static struct ctl_table_header *s390dbf_sysctl_header;
 897
 898/**
 899 * debug_stop_all() - stops the debug feature if stopping is allowed.
 900 *
 901 * Return:
 902 * -   none
 903 *
 904 * Currently used in case of a kernel oops.
 905 */
 906void debug_stop_all(void)
 907{
 908        if (debug_stoppable)
 909                debug_active = 0;
 910}
 911EXPORT_SYMBOL(debug_stop_all);
 912
 913/**
 914 * debug_set_critical() - event/exception functions try lock instead of spin.
 915 *
 916 * Return:
 917 * -   none
 918 *
 919 * Currently used in case of stopping all CPUs but the current one.
 920 * Once in this state, functions to write a debug entry for an
 921 * event or exception no longer spin on the debug area lock,
 922 * but only try to get it and fail if they do not get the lock.
 923 */
 924void debug_set_critical(void)
 925{
 926        debug_critical = 1;
 927}
 928
 929/*
 930 * debug_event_common:
 931 * - write debug entry with given size
 932 */
 933debug_entry_t *debug_event_common(debug_info_t *id, int level, const void *buf,
 934                                  int len)
 935{
 936        debug_entry_t *active;
 937        unsigned long flags;
 938
 939        if (!debug_active || !id->areas)
 940                return NULL;
 941        if (debug_critical) {
 942                if (!spin_trylock_irqsave(&id->lock, flags))
 943                        return NULL;
 944        } else {
 945                spin_lock_irqsave(&id->lock, flags);
 946        }
 947        do {
 948                active = get_active_entry(id);
 949                memcpy(DEBUG_DATA(active), buf, min(len, id->buf_size));
 950                if (len < id->buf_size)
 951                        memset((DEBUG_DATA(active)) + len, 0, id->buf_size - len);
 952                debug_finish_entry(id, active, level, 0);
 953                len -= id->buf_size;
 954                buf += id->buf_size;
 955        } while (len > 0);
 956
 957        spin_unlock_irqrestore(&id->lock, flags);
 958        return active;
 959}
 960EXPORT_SYMBOL(debug_event_common);
 961
 962/*
 963 * debug_exception_common:
 964 * - write debug entry with given size and switch to next debug area
 965 */
 966debug_entry_t *debug_exception_common(debug_info_t *id, int level,
 967                                      const void *buf, int len)
 968{
 969        debug_entry_t *active;
 970        unsigned long flags;
 971
 972        if (!debug_active || !id->areas)
 973                return NULL;
 974        if (debug_critical) {
 975                if (!spin_trylock_irqsave(&id->lock, flags))
 976                        return NULL;
 977        } else {
 978                spin_lock_irqsave(&id->lock, flags);
 979        }
 980        do {
 981                active = get_active_entry(id);
 982                memcpy(DEBUG_DATA(active), buf, min(len, id->buf_size));
 983                if (len < id->buf_size)
 984                        memset((DEBUG_DATA(active)) + len, 0, id->buf_size - len);
 985                debug_finish_entry(id, active, level, len <= id->buf_size);
 986                len -= id->buf_size;
 987                buf += id->buf_size;
 988        } while (len > 0);
 989
 990        spin_unlock_irqrestore(&id->lock, flags);
 991        return active;
 992}
 993EXPORT_SYMBOL(debug_exception_common);
 994
 995/*
 996 * counts arguments in format string for sprintf view
 997 */
 998static inline int debug_count_numargs(char *string)
 999{
1000        int numargs = 0;
1001
1002        while (*string) {
1003                if (*string++ == '%')
1004                        numargs++;
1005        }
1006        return numargs;
1007}
1008
1009/*
1010 * debug_sprintf_event:
1011 */
1012debug_entry_t *__debug_sprintf_event(debug_info_t *id, int level, char *string, ...)
1013{
1014        debug_sprintf_entry_t *curr_event;
1015        debug_entry_t *active;
1016        unsigned long flags;
1017        int numargs, idx;
1018        va_list ap;
1019
1020        if (!debug_active || !id->areas)
1021                return NULL;
1022        numargs = debug_count_numargs(string);
1023
1024        if (debug_critical) {
1025                if (!spin_trylock_irqsave(&id->lock, flags))
1026                        return NULL;
1027        } else {
1028                spin_lock_irqsave(&id->lock, flags);
1029        }
1030        active = get_active_entry(id);
1031        curr_event = (debug_sprintf_entry_t *) DEBUG_DATA(active);
1032        va_start(ap, string);
1033        curr_event->string = string;
1034        for (idx = 0; idx < min(numargs, (int)(id->buf_size / sizeof(long)) - 1); idx++)
1035                curr_event->args[idx] = va_arg(ap, long);
1036        va_end(ap);
1037        debug_finish_entry(id, active, level, 0);
1038        spin_unlock_irqrestore(&id->lock, flags);
1039
1040        return active;
1041}
1042EXPORT_SYMBOL(__debug_sprintf_event);
1043
1044/*
1045 * debug_sprintf_exception:
1046 */
1047debug_entry_t *__debug_sprintf_exception(debug_info_t *id, int level, char *string, ...)
1048{
1049        debug_sprintf_entry_t *curr_event;
1050        debug_entry_t *active;
1051        unsigned long flags;
1052        int numargs, idx;
1053        va_list ap;
1054
1055        if (!debug_active || !id->areas)
1056                return NULL;
1057
1058        numargs = debug_count_numargs(string);
1059
1060        if (debug_critical) {
1061                if (!spin_trylock_irqsave(&id->lock, flags))
1062                        return NULL;
1063        } else {
1064                spin_lock_irqsave(&id->lock, flags);
1065        }
1066        active = get_active_entry(id);
1067        curr_event = (debug_sprintf_entry_t *)DEBUG_DATA(active);
1068        va_start(ap, string);
1069        curr_event->string = string;
1070        for (idx = 0; idx < min(numargs, (int)(id->buf_size / sizeof(long)) - 1); idx++)
1071                curr_event->args[idx] = va_arg(ap, long);
1072        va_end(ap);
1073        debug_finish_entry(id, active, level, 1);
1074        spin_unlock_irqrestore(&id->lock, flags);
1075
1076        return active;
1077}
1078EXPORT_SYMBOL(__debug_sprintf_exception);
1079
1080/**
1081 * debug_register_view() - registers new debug view and creates debugfs
1082 *                         dir entry
1083 *
1084 * @id:         handle for debug log
1085 * @view:       pointer to debug view struct
1086 *
1087 * Return:
1088 * -   0  : ok
1089 * -   < 0: Error
1090 */
1091int debug_register_view(debug_info_t *id, struct debug_view *view)
1092{
1093        unsigned long flags;
1094        struct dentry *pde;
1095        umode_t mode;
1096        int rc = 0;
1097        int i;
1098
1099        if (!id)
1100                goto out;
1101        mode = (id->mode | S_IFREG) & ~S_IXUGO;
1102        if (!(view->prolog_proc || view->format_proc || view->header_proc))
1103                mode &= ~(S_IRUSR | S_IRGRP | S_IROTH);
1104        if (!view->input_proc)
1105                mode &= ~(S_IWUSR | S_IWGRP | S_IWOTH);
1106        pde = debugfs_create_file(view->name, mode, id->debugfs_root_entry,
1107                                  id, &debug_file_ops);
1108        spin_lock_irqsave(&id->lock, flags);
1109        for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
1110                if (!id->views[i])
1111                        break;
1112        }
1113        if (i == DEBUG_MAX_VIEWS) {
1114                pr_err("Registering view %s/%s would exceed the maximum "
1115                       "number of views %i\n", id->name, view->name, i);
1116                rc = -1;
1117        } else {
1118                id->views[i] = view;
1119                id->debugfs_entries[i] = pde;
1120        }
1121        spin_unlock_irqrestore(&id->lock, flags);
1122        if (rc)
1123                debugfs_remove(pde);
1124out:
1125        return rc;
1126}
1127EXPORT_SYMBOL(debug_register_view);
1128
1129/**
1130 * debug_unregister_view() - unregisters debug view and removes debugfs
1131 *                           dir entry
1132 *
1133 * @id:         handle for debug log
1134 * @view:       pointer to debug view struct
1135 *
1136 * Return:
1137 * -   0  : ok
1138 * -   < 0: Error
1139 */
1140int debug_unregister_view(debug_info_t *id, struct debug_view *view)
1141{
1142        struct dentry *dentry = NULL;
1143        unsigned long flags;
1144        int i, rc = 0;
1145
1146        if (!id)
1147                goto out;
1148        spin_lock_irqsave(&id->lock, flags);
1149        for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
1150                if (id->views[i] == view)
1151                        break;
1152        }
1153        if (i == DEBUG_MAX_VIEWS) {
1154                rc = -1;
1155        } else {
1156                dentry = id->debugfs_entries[i];
1157                id->views[i] = NULL;
1158                id->debugfs_entries[i] = NULL;
1159        }
1160        spin_unlock_irqrestore(&id->lock, flags);
1161        debugfs_remove(dentry);
1162out:
1163        return rc;
1164}
1165EXPORT_SYMBOL(debug_unregister_view);
1166
1167static inline char *debug_get_user_string(const char __user *user_buf,
1168                                          size_t user_len)
1169{
1170        char *buffer;
1171
1172        buffer = kmalloc(user_len + 1, GFP_KERNEL);
1173        if (!buffer)
1174                return ERR_PTR(-ENOMEM);
1175        if (copy_from_user(buffer, user_buf, user_len) != 0) {
1176                kfree(buffer);
1177                return ERR_PTR(-EFAULT);
1178        }
1179        /* got the string, now strip linefeed. */
1180        if (buffer[user_len - 1] == '\n')
1181                buffer[user_len - 1] = 0;
1182        else
1183                buffer[user_len] = 0;
1184        return buffer;
1185}
1186
1187static inline int debug_get_uint(char *buf)
1188{
1189        int rc;
1190
1191        buf = skip_spaces(buf);
1192        rc = simple_strtoul(buf, &buf, 10);
1193        if (*buf)
1194                rc = -EINVAL;
1195        return rc;
1196}
1197
1198/*
1199 * functions for debug-views
1200 ***********************************
1201*/
1202
1203/*
1204 * prints out actual debug level
1205 */
1206
1207static int debug_prolog_pages_fn(debug_info_t *id, struct debug_view *view,
1208                                 char *out_buf)
1209{
1210        return sprintf(out_buf, "%i\n", id->pages_per_area);
1211}
1212
1213/*
1214 * reads new size (number of pages per debug area)
1215 */
1216
1217static int debug_input_pages_fn(debug_info_t *id, struct debug_view *view,
1218                                struct file *file, const char __user *user_buf,
1219                                size_t user_len, loff_t *offset)
1220{
1221        int rc, new_pages;
1222        char *str;
1223
1224        if (user_len > 0x10000)
1225                user_len = 0x10000;
1226        if (*offset != 0) {
1227                rc = -EPIPE;
1228                goto out;
1229        }
1230        str = debug_get_user_string(user_buf, user_len);
1231        if (IS_ERR(str)) {
1232                rc = PTR_ERR(str);
1233                goto out;
1234        }
1235        new_pages = debug_get_uint(str);
1236        if (new_pages < 0) {
1237                rc = -EINVAL;
1238                goto free_str;
1239        }
1240        rc = debug_set_size(id, id->nr_areas, new_pages);
1241        if (rc != 0) {
1242                rc = -EINVAL;
1243                goto free_str;
1244        }
1245        rc = user_len;
1246free_str:
1247        kfree(str);
1248out:
1249        *offset += user_len;
1250        return rc;              /* number of input characters */
1251}
1252
1253/*
1254 * prints out actual debug level
1255 */
1256static int debug_prolog_level_fn(debug_info_t *id, struct debug_view *view,
1257                                 char *out_buf)
1258{
1259        int rc = 0;
1260
1261        if (id->level == DEBUG_OFF_LEVEL)
1262                rc = sprintf(out_buf, "-\n");
1263        else
1264                rc = sprintf(out_buf, "%i\n", id->level);
1265        return rc;
1266}
1267
1268/*
1269 * reads new debug level
1270 */
1271static int debug_input_level_fn(debug_info_t *id, struct debug_view *view,
1272                                struct file *file, const char __user *user_buf,
1273                                size_t user_len, loff_t *offset)
1274{
1275        int rc, new_level;
1276        char *str;
1277
1278        if (user_len > 0x10000)
1279                user_len = 0x10000;
1280        if (*offset != 0) {
1281                rc = -EPIPE;
1282                goto out;
1283        }
1284        str = debug_get_user_string(user_buf, user_len);
1285        if (IS_ERR(str)) {
1286                rc = PTR_ERR(str);
1287                goto out;
1288        }
1289        if (str[0] == '-') {
1290                debug_set_level(id, DEBUG_OFF_LEVEL);
1291                rc = user_len;
1292                goto free_str;
1293        } else {
1294                new_level = debug_get_uint(str);
1295        }
1296        if (new_level < 0) {
1297                pr_warn("%s is not a valid level for a debug feature\n", str);
1298                rc = -EINVAL;
1299        } else {
1300                debug_set_level(id, new_level);
1301                rc = user_len;
1302        }
1303free_str:
1304        kfree(str);
1305out:
1306        *offset += user_len;
1307        return rc;              /* number of input characters */
1308}
1309
1310/*
1311 * flushes debug areas
1312 */
1313static void debug_flush(debug_info_t *id, int area)
1314{
1315        unsigned long flags;
1316        int i, j;
1317
1318        if (!id || !id->areas)
1319                return;
1320        spin_lock_irqsave(&id->lock, flags);
1321        if (area == DEBUG_FLUSH_ALL) {
1322                id->active_area = 0;
1323                memset(id->active_entries, 0, id->nr_areas * sizeof(int));
1324                for (i = 0; i < id->nr_areas; i++) {
1325                        id->active_pages[i] = 0;
1326                        for (j = 0; j < id->pages_per_area; j++)
1327                                memset(id->areas[i][j], 0, PAGE_SIZE);
1328                }
1329        } else if (area >= 0 && area < id->nr_areas) {
1330                id->active_entries[area] = 0;
1331                id->active_pages[area] = 0;
1332                for (i = 0; i < id->pages_per_area; i++)
1333                        memset(id->areas[area][i], 0, PAGE_SIZE);
1334        }
1335        spin_unlock_irqrestore(&id->lock, flags);
1336}
1337
1338/*
1339 * view function: flushes debug areas
1340 */
1341static int debug_input_flush_fn(debug_info_t *id, struct debug_view *view,
1342                                struct file *file, const char __user *user_buf,
1343                                size_t user_len, loff_t *offset)
1344{
1345        char input_buf[1];
1346        int rc = user_len;
1347
1348        if (user_len > 0x10000)
1349                user_len = 0x10000;
1350        if (*offset != 0) {
1351                rc = -EPIPE;
1352                goto out;
1353        }
1354        if (copy_from_user(input_buf, user_buf, 1)) {
1355                rc = -EFAULT;
1356                goto out;
1357        }
1358        if (input_buf[0] == '-') {
1359                debug_flush(id, DEBUG_FLUSH_ALL);
1360                goto out;
1361        }
1362        if (isdigit(input_buf[0])) {
1363                int area = ((int) input_buf[0] - (int) '0');
1364
1365                debug_flush(id, area);
1366                goto out;
1367        }
1368
1369        pr_info("Flushing debug data failed because %c is not a valid "
1370                 "area\n", input_buf[0]);
1371
1372out:
1373        *offset += user_len;
1374        return rc;              /* number of input characters */
1375}
1376
1377/*
1378 * prints debug data in hex/ascii format
1379 */
1380static int debug_hex_ascii_format_fn(debug_info_t *id, struct debug_view *view,
1381                                     char *out_buf, const char *in_buf)
1382{
1383        int i, rc = 0;
1384
1385        for (i = 0; i < id->buf_size; i++)
1386                rc += sprintf(out_buf + rc, "%02x ", ((unsigned char *) in_buf)[i]);
1387        rc += sprintf(out_buf + rc, "| ");
1388        for (i = 0; i < id->buf_size; i++) {
1389                unsigned char c = in_buf[i];
1390
1391                if (isascii(c) && isprint(c))
1392                        rc += sprintf(out_buf + rc, "%c", c);
1393                else
1394                        rc += sprintf(out_buf + rc, ".");
1395        }
1396        rc += sprintf(out_buf + rc, "\n");
1397        return rc;
1398}
1399
1400/*
1401 * prints header for debug entry
1402 */
1403int debug_dflt_header_fn(debug_info_t *id, struct debug_view *view,
1404                         int area, debug_entry_t *entry, char *out_buf)
1405{
1406        unsigned long sec, usec;
1407        unsigned long caller;
1408        unsigned int level;
1409        char *except_str;
1410        int rc = 0;
1411
1412        level = entry->level;
1413        sec = entry->clock;
1414        usec = do_div(sec, USEC_PER_SEC);
1415
1416        if (entry->exception)
1417                except_str = "*";
1418        else
1419                except_str = "-";
1420        caller = (unsigned long) entry->caller;
1421        rc += sprintf(out_buf, "%02i %011ld:%06lu %1u %1s %04u %px  ",
1422                      area, sec, usec, level, except_str,
1423                      entry->cpu, (void *)caller);
1424        return rc;
1425}
1426EXPORT_SYMBOL(debug_dflt_header_fn);
1427
1428/*
1429 * prints debug data sprintf-formated:
1430 * debug_sprinf_event/exception calls must be used together with this view
1431 */
1432
1433#define DEBUG_SPRINTF_MAX_ARGS 10
1434
1435static int debug_sprintf_format_fn(debug_info_t *id, struct debug_view *view,
1436                                   char *out_buf, debug_sprintf_entry_t *curr_event)
1437{
1438        int num_longs, num_used_args = 0, i, rc = 0;
1439        int index[DEBUG_SPRINTF_MAX_ARGS];
1440
1441        /* count of longs fit into one entry */
1442        num_longs = id->buf_size / sizeof(long);
1443
1444        if (num_longs < 1)
1445                goto out; /* bufsize of entry too small */
1446        if (num_longs == 1) {
1447                /* no args, we use only the string */
1448                strcpy(out_buf, curr_event->string);
1449                rc = strlen(curr_event->string);
1450                goto out;
1451        }
1452
1453        /* number of arguments used for sprintf (without the format string) */
1454        num_used_args = min(DEBUG_SPRINTF_MAX_ARGS, (num_longs - 1));
1455
1456        memset(index, 0, DEBUG_SPRINTF_MAX_ARGS * sizeof(int));
1457
1458        for (i = 0; i < num_used_args; i++)
1459                index[i] = i;
1460
1461        rc = sprintf(out_buf, curr_event->string, curr_event->args[index[0]],
1462                     curr_event->args[index[1]], curr_event->args[index[2]],
1463                     curr_event->args[index[3]], curr_event->args[index[4]],
1464                     curr_event->args[index[5]], curr_event->args[index[6]],
1465                     curr_event->args[index[7]], curr_event->args[index[8]],
1466                     curr_event->args[index[9]]);
1467out:
1468        return rc;
1469}
1470
1471/*
1472 * debug_init:
1473 * - is called exactly once to initialize the debug feature
1474 */
1475static int __init debug_init(void)
1476{
1477        s390dbf_sysctl_header = register_sysctl_table(s390dbf_dir_table);
1478        mutex_lock(&debug_mutex);
1479        debug_debugfs_root_entry = debugfs_create_dir(DEBUG_DIR_ROOT, NULL);
1480        initialized = 1;
1481        mutex_unlock(&debug_mutex);
1482        return 0;
1483}
1484postcore_initcall(debug_init);
1485