ipc/util.c

   1 /*
   2  * linux/ipc/util.c
   3  * Copyright (C) 1992 Krishna Balasubramanian
   4  *
   5  * Sep 1997 - Call suser() last after "normal" permission checks so we
   6  *            get BSD style process accounting right.
   7  *            Occurs in several places in the IPC code.
   8  *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>
   9  * Nov 1999 - ipc helper functions, unified SMP locking
  10  *            Manfred Spraul <manfred@colorfullife.com>
  11  * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
  12  *            Mingming Cao <cmm@us.ibm.com>
  13  */
  14
  15 #include <linux/config.h>
  16 #include <linux/mm.h>
  17 #include <linux/shm.h>
  18 #include <linux/init.h>
  19 #include <linux/msg.h>
  20 #include <linux/smp_lock.h>
  21 #include <linux/vmalloc.h>
  22 #include <linux/slab.h>
  23 #include <linux/capability.h>
  24 #include <linux/highuid.h>
  25 #include <linux/security.h>
  26 #include <linux/rcupdate.h>
  27 #include <linux/workqueue.h>
  28 #include <linux/seq_file.h>
  29 #include <linux/proc_fs.h>
  30
  31 #include <asm/unistd.h>
  32
  33 #include "util.h"
  34
  35 struct ipc_proc_iface {
  36         const char *path;
  37         const char *header;
  38         struct ipc_ids *ids;
  39         int (*show)(struct seq_file *, void *);
  40 };
  41
  42 /**
  43  *      ipc_init        -       initialise IPC subsystem
  44  *
  45  *      The various system5 IPC resources (semaphores, messages and shared
  46  *      memory are initialised
  47  */
  48
  49 static int __init ipc_init(void)
  50 {
  51         sem_init();
  52         msg_init();
  53         shm_init();
  54         return 0;
  55 }
  56 __initcall(ipc_init);
  57
  58 /**
  59  *      ipc_init_ids            -       initialise IPC identifiers
  60  *      @ids: Identifier set
  61  *      @size: Number of identifiers
  62  *
  63  *      Given a size for the ipc identifier range (limited below IPCMNI)
  64  *      set up the sequence range to use then allocate and initialise the
  65  *      array itself.
  66  */
  67
  68 void __init ipc_init_ids(struct ipc_ids* ids, int size)
  69 {
  70         int i;
  71         sema_init(&ids->sem,1);
  72
  73         if(size > IPCMNI)
  74                 size = IPCMNI;
  75         ids->in_use = 0;
  76         ids->max_id = -1;
  77         ids->seq = 0;
  78         {
  79                 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
  80                 if(seq_limit > USHRT_MAX)
  81                         ids->seq_max = USHRT_MAX;
  82                  else
  83                         ids->seq_max = seq_limit;
  84         }
  85
  86         ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size +
  87                                      sizeof(struct ipc_id_ary));
  88
  89         if(ids->entries == NULL) {
  90                 printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
  91                 size = 0;
  92                 ids->entries = &ids->nullentry;
  93         }
  94         ids->entries->size = size;
  95         for(i=0;i<size;i++)
  96                 ids->entries->p[i] = NULL;
  97 }
  98
  99 #ifdef CONFIG_PROC_FS
 100 static struct file_operations sysvipc_proc_fops;
 101 /**
 102  *      ipc_init_proc_interface -  Create a proc interface for sysipc types
 103  *                                 using a seq_file interface.
 104  *      @path: Path in procfs
 105  *      @header: Banner to be printed at the beginning of the file.
 106  *      @ids: ipc id table to iterate.
 107  *      @show: show routine.
 108  */
 109 void __init ipc_init_proc_interface(const char *path, const char *header,
 110                                     struct ipc_ids *ids,
 111                                     int (*show)(struct seq_file *, void *))
 112 {
 113         struct proc_dir_entry *pde;
 114         struct ipc_proc_iface *iface;
 115
 116         iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 117         if (!iface)
 118                 return;
 119         iface->path     = path;
 120         iface->header   = header;
 121         iface->ids      = ids;
 122         iface->show     = show;
 123
 124         pde = create_proc_entry(path,
 125                                 S_IRUGO,        /* world readable */
 126                                 NULL            /* parent dir */);
 127         if (pde) {
 128                 pde->data = iface;
 129                 pde->proc_fops = &sysvipc_proc_fops;
 130         } else {
 131                 kfree(iface);
 132         }
 133 }
 134 #endif
 135
 136 /**
 137  *      ipc_findkey     -       find a key in an ipc identifier set
 138  *      @ids: Identifier set
 139  *      @key: The key to find
 140  *
 141  *      Requires ipc_ids.sem locked.
 142  *      Returns the identifier if found or -1 if not.
 143  */
 144
 145 int ipc_findkey(struct ipc_ids* ids, key_t key)
 146 {
 147         int id;
 148         struct kern_ipc_perm* p;
 149         int max_id = ids->max_id;
 150
 151         /*
 152          * rcu_dereference() is not needed here
 153          * since ipc_ids.sem is held
 154          */
 155         for (id = 0; id <= max_id; id++) {
 156                 p = ids->entries->p[id];
 157                 if(p==NULL)
 158                         continue;
 159                 if (key == p->key)
 160                         return id;
 161         }
 162         return -1;
 163 }
 164
 165 /*
 166  * Requires ipc_ids.sem locked
 167  */
 168 static int grow_ary(struct ipc_ids* ids, int newsize)
 169 {
 170         struct ipc_id_ary* new;
 171         struct ipc_id_ary* old;
 172         int i;
 173         int size = ids->entries->size;
 174
 175         if(newsize > IPCMNI)
 176                 newsize = IPCMNI;
 177         if(newsize <= size)
 178                 return newsize;
 179
 180         new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize +
 181                             sizeof(struct ipc_id_ary));
 182         if(new == NULL)
 183                 return size;
 184         new->size = newsize;
 185         memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size +
 186                                         sizeof(struct ipc_id_ary));
 187         for(i=size;i<newsize;i++) {
 188                 new->p[i] = NULL;
 189         }
 190         old = ids->entries;
 191
 192         /*
 193          * Use rcu_assign_pointer() to make sure the memcpyed contents
 194          * of the new array are visible before the new array becomes visible.
 195          */
 196         rcu_assign_pointer(ids->entries, new);
 197
 198         ipc_rcu_putref(old);
 199         return newsize;
 200 }
 201
 202 /**
 203  *      ipc_addid       -       add an IPC identifier
 204  *      @ids: IPC identifier set
 205  *      @new: new IPC permission set
 206  *      @size: new size limit for the id array
 207  *
 208  *      Add an entry 'new' to the IPC arrays. The permissions object is
 209  *      initialised and the first free entry is set up and the id assigned
 210  *      is returned. The list is returned in a locked state on success.
 211  *      On failure the list is not locked and -1 is returned.
 212  *
 213  *      Called with ipc_ids.sem held.
 214  */
 215
 216 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 217 {
 218         int id;
 219
 220         size = grow_ary(ids,size);
 221
 222         /*
 223          * rcu_dereference()() is not needed here since
 224          * ipc_ids.sem is held
 225          */
 226         for (id = 0; id < size; id++) {
 227                 if(ids->entries->p[id] == NULL)
 228                         goto found;
 229         }
 230         return -1;
 231 found:
 232         ids->in_use++;
 233         if (id > ids->max_id)
 234                 ids->max_id = id;
 235
 236         new->cuid = new->uid = current->euid;
 237         new->gid = new->cgid = current->egid;
 238
 239         new->seq = ids->seq++;
 240         if(ids->seq > ids->seq_max)
 241                 ids->seq = 0;
 242
 243         spin_lock_init(&new->lock);
 244         new->deleted = 0;
 245         rcu_read_lock();
 246         spin_lock(&new->lock);
 247         ids->entries->p[id] = new;
 248         return id;
 249 }
 250
 251 /**
 252  *      ipc_rmid        -       remove an IPC identifier
 253  *      @ids: identifier set
 254  *      @id: Identifier to remove
 255  *
 256  *      The identifier must be valid, and in use. The kernel will panic if
 257  *      fed an invalid identifier. The entry is removed and internal
 258  *      variables recomputed. The object associated with the identifier
 259  *      is returned.
 260  *      ipc_ids.sem and the spinlock for this ID is hold before this function
 261  *      is called, and remain locked on the exit.
 262  */
 263
 264 struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
 265 {
 266         struct kern_ipc_perm* p;
 267         int lid = id % SEQ_MULTIPLIER;
 268         if(lid >= ids->entries->size)
 269                 BUG();
 270
 271         /*
 272          * do not need a rcu_dereference()() here to force ordering
 273          * on Alpha, since the ipc_ids.sem is held.
 274          */
 275         p = ids->entries->p[lid];
 276         ids->entries->p[lid] = NULL;
 277         if(p==NULL)
 278                 BUG();
 279         ids->in_use--;
 280
 281         if (lid == ids->max_id) {
 282                 do {
 283                         lid--;
 284                         if(lid == -1)
 285                                 break;
 286                 } while (ids->entries->p[lid] == NULL);
 287                 ids->max_id = lid;
 288         }
 289         p->deleted = 1;
 290         return p;
 291 }
 292
 293 /**
 294  *      ipc_alloc       -       allocate ipc space
 295  *      @size: size desired
 296  *
 297  *      Allocate memory from the appropriate pools and return a pointer to it.
 298  *      NULL is returned if the allocation fails
 299  */
 300
 301 void* ipc_alloc(int size)
 302 {
 303         void* out;
 304         if(size > PAGE_SIZE)
 305                 out = vmalloc(size);
 306         else
 307                 out = kmalloc(size, GFP_KERNEL);
 308         return out;
 309 }
 310
 311 /**
 312  *      ipc_free        -       free ipc space
 313  *      @ptr: pointer returned by ipc_alloc
 314  *      @size: size of block
 315  *
 316  *      Free a block created with ipc_alloc. The caller must know the size
 317  *      used in the allocation call.
 318  */
 319
 320 void ipc_free(void* ptr, int size)
 321 {
 322         if(size > PAGE_SIZE)
 323                 vfree(ptr);
 324         else
 325                 kfree(ptr);
 326 }
 327
 328 /*
 329  * rcu allocations:
 330  * There are three headers that are prepended to the actual allocation:
 331  * - during use: ipc_rcu_hdr.
 332  * - during the rcu grace period: ipc_rcu_grace.
 333  * - [only if vmalloc]: ipc_rcu_sched.
 334  * Their lifetime doesn't overlap, thus the headers share the same memory.
 335  * Unlike a normal union, they are right-aligned, thus some container_of
 336  * forward/backward casting is necessary:
 337  */
 338 struct ipc_rcu_hdr
 339 {
 340         int refcount;
 341         int is_vmalloc;
 342         void *data[0];
 343 };
 344
 345
 346 struct ipc_rcu_grace
 347 {
 348         struct rcu_head rcu;
 349         /* "void *" makes sure alignment of following data is sane. */
 350         void *data[0];
 351 };
 352
 353 struct ipc_rcu_sched
 354 {
 355         struct work_struct work;
 356         /* "void *" makes sure alignment of following data is sane. */
 357         void *data[0];
 358 };
 359
 360 #define HDRLEN_KMALLOC          (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
 361                                         sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
 362 #define HDRLEN_VMALLOC          (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
 363                                         sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
 364
 365 static inline int rcu_use_vmalloc(int size)
 366 {
 367         /* Too big for a single page? */
 368         if (HDRLEN_KMALLOC + size > PAGE_SIZE)
 369                 return 1;
 370         return 0;
 371 }
 372
 373 /**
 374  *      ipc_rcu_alloc   -       allocate ipc and rcu space
 375  *      @size: size desired
 376  *
 377  *      Allocate memory for the rcu header structure +  the object.
 378  *      Returns the pointer to the object.
 379  *      NULL is returned if the allocation fails.
 380  */
 381
 382 void* ipc_rcu_alloc(int size)
 383 {
 384         void* out;
 385         /*
 386          * We prepend the allocation with the rcu struct, and
 387          * workqueue if necessary (for vmalloc).
 388          */
 389         if (rcu_use_vmalloc(size)) {
 390                 out = vmalloc(HDRLEN_VMALLOC + size);
 391                 if (out) {
 392                         out += HDRLEN_VMALLOC;
 393                         container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
 394                         container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
 395                 }
 396         } else {
 397                 out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
 398                 if (out) {
 399                         out += HDRLEN_KMALLOC;
 400                         container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
 401                         container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
 402                 }
 403         }
 404
 405         return out;
 406 }
 407
 408 void ipc_rcu_getref(void *ptr)
 409 {
 410         container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
 411 }
 412
 413 /**
 414  * ipc_schedule_free - free ipc + rcu space
 415  * @head: RCU callback structure for queued work
 416  *
 417  * Since RCU callback function is called in bh,
 418  * we need to defer the vfree to schedule_work
 419  */
 420 static void ipc_schedule_free(struct rcu_head *head)
 421 {
 422         struct ipc_rcu_grace *grace =
 423                 container_of(head, struct ipc_rcu_grace, rcu);
 424         struct ipc_rcu_sched *sched =
 425                         container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]);
 426
 427         INIT_WORK(&sched->work, vfree, sched);
 428         schedule_work(&sched->work);
 429 }
 430
 431 /**
 432  * ipc_immediate_free - free ipc + rcu space
 433  * @head: RCU callback structure that contains pointer to be freed
 434  *
 435  * Free from the RCU callback context
 436  */
 437 static void ipc_immediate_free(struct rcu_head *head)
 438 {
 439         struct ipc_rcu_grace *free =
 440                 container_of(head, struct ipc_rcu_grace, rcu);
 441         kfree(free);
 442 }
 443
 444 void ipc_rcu_putref(void *ptr)
 445 {
 446         if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
 447                 return;
 448
 449         if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
 450                 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
 451                                 ipc_schedule_free);
 452         } else {
 453                 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
 454                                 ipc_immediate_free);
 455         }
 456 }
 457
 458 /**
 459  *      ipcperms        -       check IPC permissions
 460  *      @ipcp: IPC permission set
 461  *      @flag: desired permission set.
 462  *
 463  *      Check user, group, other permissions for access
 464  *      to ipc resources. return 0 if allowed
 465  */
 466
 467 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
 468 {       /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
 469         int requested_mode, granted_mode;
 470
 471         requested_mode = (flag >> 6) | (flag >> 3) | flag;
 472         granted_mode = ipcp->mode;
 473         if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
 474                 granted_mode >>= 6;
 475         else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 476                 granted_mode >>= 3;
 477         /* is there some bit set in requested_mode but not in granted_mode? */
 478         if ((requested_mode & ~granted_mode & 0007) &&
 479             !capable(CAP_IPC_OWNER))
 480                 return -1;
 481
 482         return security_ipc_permission(ipcp, flag);
 483 }
 484
 485 /*
 486  * Functions to convert between the kern_ipc_perm structure and the
 487  * old/new ipc_perm structures
 488  */
 489
 490 /**
 491  *      kernel_to_ipc64_perm    -       convert kernel ipc permissions to user
 492  *      @in: kernel permissions
 493  *      @out: new style IPC permissions
 494  *
 495  *      Turn the kernel object 'in' into a set of permissions descriptions
 496  *      for returning to userspace (out).
 497  */
 498
 499
 500 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
 501 {
 502         out->key        = in->key;
 503         out->uid        = in->uid;
 504         out->gid        = in->gid;
 505         out->cuid       = in->cuid;
 506         out->cgid       = in->cgid;
 507         out->mode       = in->mode;
 508         out->seq        = in->seq;
 509 }
 510
 511 /**
 512  *      ipc64_perm_to_ipc_perm  -       convert old ipc permissions to new
 513  *      @in: new style IPC permissions
 514  *      @out: old style IPC permissions
 515  *
 516  *      Turn the new style permissions object in into a compatibility
 517  *      object and store it into the 'out' pointer.
 518  */
 519
 520 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
 521 {
 522         out->key        = in->key;
 523         SET_UID(out->uid, in->uid);
 524         SET_GID(out->gid, in->gid);
 525         SET_UID(out->cuid, in->cuid);
 526         SET_GID(out->cgid, in->cgid);
 527         out->mode       = in->mode;
 528         out->seq        = in->seq;
 529 }
 530
 531 /*
 532  * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
 533  * is called with shm_ids.sem locked.  Since grow_ary() is also called with
 534  * shm_ids.sem down(for Shared Memory), there is no need to add read
 535  * barriers here to gurantee the writes in grow_ary() are seen in order
 536  * here (for Alpha).
 537  *
 538  * However ipc_get() itself does not necessary require ipc_ids.sem down. So
 539  * if in the future ipc_get() is used by other places without ipc_ids.sem
 540  * down, then ipc_get() needs read memery barriers as ipc_lock() does.
 541  */
 542 struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
 543 {
 544         struct kern_ipc_perm* out;
 545         int lid = id % SEQ_MULTIPLIER;
 546         if(lid >= ids->entries->size)
 547                 return NULL;
 548         out = ids->entries->p[lid];
 549         return out;
 550 }
 551
 552 struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
 553 {
 554         struct kern_ipc_perm* out;
 555         int lid = id % SEQ_MULTIPLIER;
 556         struct ipc_id_ary* entries;
 557
 558         rcu_read_lock();
 559         entries = rcu_dereference(ids->entries);
 560         if(lid >= entries->size) {
 561                 rcu_read_unlock();
 562                 return NULL;
 563         }
 564         out = entries->p[lid];
 565         if(out == NULL) {
 566                 rcu_read_unlock();
 567                 return NULL;
 568         }
 569         spin_lock(&out->lock);
 570
 571         /* ipc_rmid() may have already freed the ID while ipc_lock
 572          * was spinning: here verify that the structure is still valid
 573          */
 574         if (out->deleted) {
 575                 spin_unlock(&out->lock);
 576                 rcu_read_unlock();
 577                 return NULL;
 578         }
 579         return out;
 580 }
 581
 582 void ipc_lock_by_ptr(struct kern_ipc_perm *perm)
 583 {
 584         rcu_read_lock();
 585         spin_lock(&perm->lock);
 586 }
 587
 588 void ipc_unlock(struct kern_ipc_perm* perm)
 589 {
 590         spin_unlock(&perm->lock);
 591         rcu_read_unlock();
 592 }
 593
 594 int ipc_buildid(struct ipc_ids* ids, int id, int seq)
 595 {
 596         return SEQ_MULTIPLIER*seq + id;
 597 }
 598
 599 int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid)
 600 {
 601         if(uid/SEQ_MULTIPLIER != ipcp->seq)
 602                 return 1;
 603         return 0;
 604 }
 605
 606 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
 607
 608
 609 /**
 610  *      ipc_parse_version       -       IPC call version
 611  *      @cmd: pointer to command
 612  *
 613  *      Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
 614  *      The cmd value is turned from an encoding command and version into
 615  *      just the command code.
 616  */
 617
 618 int ipc_parse_version (int *cmd)
 619 {
 620         if (*cmd & IPC_64) {
 621                 *cmd ^= IPC_64;
 622                 return IPC_64;
 623         } else {
 624                 return IPC_OLD;
 625         }
 626 }
 627
 628 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */
 629
 630 #ifdef CONFIG_PROC_FS
 631 static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 632 {
 633         struct ipc_proc_iface *iface = s->private;
 634         struct kern_ipc_perm *ipc = it;
 635         loff_t p;
 636
 637         /* If we had an ipc id locked before, unlock it */
 638         if (ipc && ipc != SEQ_START_TOKEN)
 639                 ipc_unlock(ipc);
 640
 641         /*
 642          * p = *pos - 1 (because id 0 starts at position 1)
 643          *          + 1 (because we increment the position by one)
 644          */
 645         for (p = *pos; p <= iface->ids->max_id; p++) {
 646                 if ((ipc = ipc_lock(iface->ids, p)) != NULL) {
 647                         *pos = p + 1;
 648                         return ipc;
 649                 }
 650         }
 651
 652         /* Out of range - return NULL to terminate iteration */
 653         return NULL;
 654 }
 655
 656 /*
 657  * File positions: pos 0 -> header, pos n -> ipc id + 1.
 658  * SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START.
 659  */
 660 static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 661 {
 662         struct ipc_proc_iface *iface = s->private;
 663         struct kern_ipc_perm *ipc;
 664         loff_t p;
 665
 666         /*
 667          * Take the lock - this will be released by the corresponding
 668          * call to stop().
 669          */
 670         down(&iface->ids->sem);
 671
 672         /* pos < 0 is invalid */
 673         if (*pos < 0)
 674                 return NULL;
 675
 676         /* pos == 0 means header */
 677         if (*pos == 0)
 678                 return SEQ_START_TOKEN;
 679
 680         /* Find the (pos-1)th ipc */
 681         for (p = *pos - 1; p <= iface->ids->max_id; p++) {
 682                 if ((ipc = ipc_lock(iface->ids, p)) != NULL) {
 683                         *pos = p + 1;
 684                         return ipc;
 685                 }
 686         }
 687         return NULL;
 688 }
 689
 690 static void sysvipc_proc_stop(struct seq_file *s, void *it)
 691 {
 692         struct kern_ipc_perm *ipc = it;
 693         struct ipc_proc_iface *iface = s->private;
 694
 695         /* If we had a locked segment, release it */
 696         if (ipc && ipc != SEQ_START_TOKEN)
 697                 ipc_unlock(ipc);
 698
 699         /* Release the lock we took in start() */
 700         up(&iface->ids->sem);
 701 }
 702
 703 static int sysvipc_proc_show(struct seq_file *s, void *it)
 704 {
 705         struct ipc_proc_iface *iface = s->private;
 706
 707         if (it == SEQ_START_TOKEN)
 708                 return seq_puts(s, iface->header);
 709
 710         return iface->show(s, it);
 711 }
 712
 713 static struct seq_operations sysvipc_proc_seqops = {
 714         .start = sysvipc_proc_start,
 715         .stop  = sysvipc_proc_stop,
 716         .next  = sysvipc_proc_next,
 717         .show  = sysvipc_proc_show,
 718 };
 719
 720 static int sysvipc_proc_open(struct inode *inode, struct file *file) {
 721         int ret;
 722         struct seq_file *seq;
 723
 724         ret = seq_open(file, &sysvipc_proc_seqops);
 725         if (!ret) {
 726                 seq = file->private_data;
 727                 seq->private = PDE(inode)->data;
 728         }
 729         return ret;
 730 }
 731
 732 static struct file_operations sysvipc_proc_fops = {
 733         .open    = sysvipc_proc_open,
 734         .read    = seq_read,
 735         .llseek  = seq_lseek,
 736         .release = seq_release,
 737 };
 738 #endif /* CONFIG_PROC_FS */