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  * Mar 2006 - support for audit of ipc object properties
  14  *            Dustin Kirkland <dustin.kirkland@us.ibm.com>
  15  * Jun 2006 - namespaces ssupport
  16  *            OpenVZ, SWsoft Inc.
  17  *            Pavel Emelianov <xemul@openvz.org>
  18  */
  19
  20 #include <linux/mm.h>
  21 #include <linux/shm.h>
  22 #include <linux/init.h>
  23 #include <linux/msg.h>
  24 #include <linux/smp_lock.h>
  25 #include <linux/vmalloc.h>
  26 #include <linux/slab.h>
  27 #include <linux/capability.h>
  28 #include <linux/highuid.h>
  29 #include <linux/security.h>
  30 #include <linux/rcupdate.h>
  31 #include <linux/workqueue.h>
  32 #include <linux/seq_file.h>
  33 #include <linux/proc_fs.h>
  34 #include <linux/audit.h>
  35 #include <linux/nsproxy.h>
  36
  37 #include <asm/unistd.h>
  38
  39 #include "util.h"
  40
  41 struct ipc_proc_iface {
  42         const char *path;
  43         const char *header;
  44         int ids;
  45         int (*show)(struct seq_file *, void *);
  46 };
  47
  48 struct ipc_namespace init_ipc_ns = {
  49         .kref = {
  50                 .refcount       = ATOMIC_INIT(2),
  51         },
  52 };
  53
  54 #ifdef CONFIG_IPC_NS
  55 static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
  56 {
  57         int err;
  58         struct ipc_namespace *ns;
  59
  60         err = -ENOMEM;
  61         ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
  62         if (ns == NULL)
  63                 goto err_mem;
  64
  65         err = sem_init_ns(ns);
  66         if (err)
  67                 goto err_sem;
  68         err = msg_init_ns(ns);
  69         if (err)
  70                 goto err_msg;
  71         err = shm_init_ns(ns);
  72         if (err)
  73                 goto err_shm;
  74
  75         kref_init(&ns->kref);
  76         return ns;
  77
  78 err_shm:
  79         msg_exit_ns(ns);
  80 err_msg:
  81         sem_exit_ns(ns);
  82 err_sem:
  83         kfree(ns);
  84 err_mem:
  85         return ERR_PTR(err);
  86 }
  87
  88 int unshare_ipcs(unsigned long unshare_flags, struct ipc_namespace **new_ipc)
  89 {
  90         struct ipc_namespace *new;
  91
  92         if (unshare_flags & CLONE_NEWIPC) {
  93                 if (!capable(CAP_SYS_ADMIN))
  94                         return -EPERM;
  95
  96                 new = clone_ipc_ns(current->nsproxy->ipc_ns);
  97                 if (IS_ERR(new))
  98                         return PTR_ERR(new);
  99
 100                 *new_ipc = new;
 101         }
 102
 103         return 0;
 104 }
 105
 106 int copy_ipcs(unsigned long flags, struct task_struct *tsk)
 107 {
 108         struct ipc_namespace *old_ns = tsk->nsproxy->ipc_ns;
 109         struct ipc_namespace *new_ns;
 110         int err = 0;
 111
 112         if (!old_ns)
 113                 return 0;
 114
 115         get_ipc_ns(old_ns);
 116
 117         if (!(flags & CLONE_NEWIPC))
 118                 return 0;
 119
 120         if (!capable(CAP_SYS_ADMIN)) {
 121                 err = -EPERM;
 122                 goto out;
 123         }
 124
 125         new_ns = clone_ipc_ns(old_ns);
 126         if (!new_ns) {
 127                 err = -ENOMEM;
 128                 goto out;
 129         }
 130
 131         tsk->nsproxy->ipc_ns = new_ns;
 132 out:
 133         put_ipc_ns(old_ns);
 134         return err;
 135 }
 136
 137 void free_ipc_ns(struct kref *kref)
 138 {
 139         struct ipc_namespace *ns;
 140
 141         ns = container_of(kref, struct ipc_namespace, kref);
 142         sem_exit_ns(ns);
 143         msg_exit_ns(ns);
 144         shm_exit_ns(ns);
 145         kfree(ns);
 146 }
 147 #endif
 148
 149 /**
 150  *      ipc_init        -       initialise IPC subsystem
 151  *
 152  *      The various system5 IPC resources (semaphores, messages and shared
 153  *      memory are initialised
 154  */
 155
 156 static int __init ipc_init(void)
 157 {
 158         sem_init();
 159         msg_init();
 160         shm_init();
 161         return 0;
 162 }
 163 __initcall(ipc_init);
 164
 165 /**
 166  *      ipc_init_ids            -       initialise IPC identifiers
 167  *      @ids: Identifier set
 168  *      @size: Number of identifiers
 169  *
 170  *      Given a size for the ipc identifier range (limited below IPCMNI)
 171  *      set up the sequence range to use then allocate and initialise the
 172  *      array itself.
 173  */
 174
 175 void __ipc_init ipc_init_ids(struct ipc_ids* ids, int size)
 176 {
 177         int i;
 178
 179         mutex_init(&ids->mutex);
 180
 181         if(size > IPCMNI)
 182                 size = IPCMNI;
 183         ids->in_use = 0;
 184         ids->max_id = -1;
 185         ids->seq = 0;
 186         {
 187                 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
 188                 if(seq_limit > USHRT_MAX)
 189                         ids->seq_max = USHRT_MAX;
 190                  else
 191                         ids->seq_max = seq_limit;
 192         }
 193
 194         ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size +
 195                                      sizeof(struct ipc_id_ary));
 196
 197         if(ids->entries == NULL) {
 198                 printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
 199                 size = 0;
 200                 ids->entries = &ids->nullentry;
 201         }
 202         ids->entries->size = size;
 203         for(i=0;i<size;i++)
 204                 ids->entries->p[i] = NULL;
 205 }
 206
 207 #ifdef CONFIG_PROC_FS
 208 static struct file_operations sysvipc_proc_fops;
 209 /**
 210  *      ipc_init_proc_interface -  Create a proc interface for sysipc types
 211  *                                 using a seq_file interface.
 212  *      @path: Path in procfs
 213  *      @header: Banner to be printed at the beginning of the file.
 214  *      @ids: ipc id table to iterate.
 215  *      @show: show routine.
 216  */
 217 void __init ipc_init_proc_interface(const char *path, const char *header,
 218                 int ids, int (*show)(struct seq_file *, void *))
 219 {
 220         struct proc_dir_entry *pde;
 221         struct ipc_proc_iface *iface;
 222
 223         iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 224         if (!iface)
 225                 return;
 226         iface->path     = path;
 227         iface->header   = header;
 228         iface->ids      = ids;
 229         iface->show     = show;
 230
 231         pde = create_proc_entry(path,
 232                                 S_IRUGO,        /* world readable */
 233                                 NULL            /* parent dir */);
 234         if (pde) {
 235                 pde->data = iface;
 236                 pde->proc_fops = &sysvipc_proc_fops;
 237         } else {
 238                 kfree(iface);
 239         }
 240 }
 241 #endif
 242
 243 /**
 244  *      ipc_findkey     -       find a key in an ipc identifier set
 245  *      @ids: Identifier set
 246  *      @key: The key to find
 247  *
 248  *      Requires ipc_ids.mutex locked.
 249  *      Returns the identifier if found or -1 if not.
 250  */
 251
 252 int ipc_findkey(struct ipc_ids* ids, key_t key)
 253 {
 254         int id;
 255         struct kern_ipc_perm* p;
 256         int max_id = ids->max_id;
 257
 258         /*
 259          * rcu_dereference() is not needed here
 260          * since ipc_ids.mutex is held
 261          */
 262         for (id = 0; id <= max_id; id++) {
 263                 p = ids->entries->p[id];
 264                 if(p==NULL)
 265                         continue;
 266                 if (key == p->key)
 267                         return id;
 268         }
 269         return -1;
 270 }
 271
 272 /*
 273  * Requires ipc_ids.mutex locked
 274  */
 275 static int grow_ary(struct ipc_ids* ids, int newsize)
 276 {
 277         struct ipc_id_ary* new;
 278         struct ipc_id_ary* old;
 279         int i;
 280         int size = ids->entries->size;
 281
 282         if(newsize > IPCMNI)
 283                 newsize = IPCMNI;
 284         if(newsize <= size)
 285                 return newsize;
 286
 287         new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize +
 288                             sizeof(struct ipc_id_ary));
 289         if(new == NULL)
 290                 return size;
 291         new->size = newsize;
 292         memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size);
 293         for(i=size;i<newsize;i++) {
 294                 new->p[i] = NULL;
 295         }
 296         old = ids->entries;
 297
 298         /*
 299          * Use rcu_assign_pointer() to make sure the memcpyed contents
 300          * of the new array are visible before the new array becomes visible.
 301          */
 302         rcu_assign_pointer(ids->entries, new);
 303
 304         ipc_rcu_putref(old);
 305         return newsize;
 306 }
 307
 308 /**
 309  *      ipc_addid       -       add an IPC identifier
 310  *      @ids: IPC identifier set
 311  *      @new: new IPC permission set
 312  *      @size: new size limit for the id array
 313  *
 314  *      Add an entry 'new' to the IPC arrays. The permissions object is
 315  *      initialised and the first free entry is set up and the id assigned
 316  *      is returned. The list is returned in a locked state on success.
 317  *      On failure the list is not locked and -1 is returned.
 318  *
 319  *      Called with ipc_ids.mutex held.
 320  */
 321
 322 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 323 {
 324         int id;
 325
 326         size = grow_ary(ids,size);
 327
 328         /*
 329          * rcu_dereference()() is not needed here since
 330          * ipc_ids.mutex is held
 331          */
 332         for (id = 0; id < size; id++) {
 333                 if(ids->entries->p[id] == NULL)
 334                         goto found;
 335         }
 336         return -1;
 337 found:
 338         ids->in_use++;
 339         if (id > ids->max_id)
 340                 ids->max_id = id;
 341
 342         new->cuid = new->uid = current->euid;
 343         new->gid = new->cgid = current->egid;
 344
 345         new->seq = ids->seq++;
 346         if(ids->seq > ids->seq_max)
 347                 ids->seq = 0;
 348
 349         spin_lock_init(&new->lock);
 350         new->deleted = 0;
 351         rcu_read_lock();
 352         spin_lock(&new->lock);
 353         ids->entries->p[id] = new;
 354         return id;
 355 }
 356
 357 /**
 358  *      ipc_rmid        -       remove an IPC identifier
 359  *      @ids: identifier set
 360  *      @id: Identifier to remove
 361  *
 362  *      The identifier must be valid, and in use. The kernel will panic if
 363  *      fed an invalid identifier. The entry is removed and internal
 364  *      variables recomputed. The object associated with the identifier
 365  *      is returned.
 366  *      ipc_ids.mutex and the spinlock for this ID is hold before this function
 367  *      is called, and remain locked on the exit.
 368  */
 369
 370 struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
 371 {
 372         struct kern_ipc_perm* p;
 373         int lid = id % SEQ_MULTIPLIER;
 374         BUG_ON(lid >= ids->entries->size);
 375
 376         /*
 377          * do not need a rcu_dereference()() here to force ordering
 378          * on Alpha, since the ipc_ids.mutex is held.
 379          */
 380         p = ids->entries->p[lid];
 381         ids->entries->p[lid] = NULL;
 382         BUG_ON(p==NULL);
 383         ids->in_use--;
 384
 385         if (lid == ids->max_id) {
 386                 do {
 387                         lid--;
 388                         if(lid == -1)
 389                                 break;
 390                 } while (ids->entries->p[lid] == NULL);
 391                 ids->max_id = lid;
 392         }
 393         p->deleted = 1;
 394         return p;
 395 }
 396
 397 /**
 398  *      ipc_alloc       -       allocate ipc space
 399  *      @size: size desired
 400  *
 401  *      Allocate memory from the appropriate pools and return a pointer to it.
 402  *      NULL is returned if the allocation fails
 403  */
 404
 405 void* ipc_alloc(int size)
 406 {
 407         void* out;
 408         if(size > PAGE_SIZE)
 409                 out = vmalloc(size);
 410         else
 411                 out = kmalloc(size, GFP_KERNEL);
 412         return out;
 413 }
 414
 415 /**
 416  *      ipc_free        -       free ipc space
 417  *      @ptr: pointer returned by ipc_alloc
 418  *      @size: size of block
 419  *
 420  *      Free a block created with ipc_alloc. The caller must know the size
 421  *      used in the allocation call.
 422  */
 423
 424 void ipc_free(void* ptr, int size)
 425 {
 426         if(size > PAGE_SIZE)
 427                 vfree(ptr);
 428         else
 429                 kfree(ptr);
 430 }
 431
 432 /*
 433  * rcu allocations:
 434  * There are three headers that are prepended to the actual allocation:
 435  * - during use: ipc_rcu_hdr.
 436  * - during the rcu grace period: ipc_rcu_grace.
 437  * - [only if vmalloc]: ipc_rcu_sched.
 438  * Their lifetime doesn't overlap, thus the headers share the same memory.
 439  * Unlike a normal union, they are right-aligned, thus some container_of
 440  * forward/backward casting is necessary:
 441  */
 442 struct ipc_rcu_hdr
 443 {
 444         int refcount;
 445         int is_vmalloc;
 446         void *data[0];
 447 };
 448
 449
 450 struct ipc_rcu_grace
 451 {
 452         struct rcu_head rcu;
 453         /* "void *" makes sure alignment of following data is sane. */
 454         void *data[0];
 455 };
 456
 457 struct ipc_rcu_sched
 458 {
 459         struct work_struct work;
 460         /* "void *" makes sure alignment of following data is sane. */
 461         void *data[0];
 462 };
 463
 464 #define HDRLEN_KMALLOC          (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
 465                                         sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
 466 #define HDRLEN_VMALLOC          (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
 467                                         sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
 468
 469 static inline int rcu_use_vmalloc(int size)
 470 {
 471         /* Too big for a single page? */
 472         if (HDRLEN_KMALLOC + size > PAGE_SIZE)
 473                 return 1;
 474         return 0;
 475 }
 476
 477 /**
 478  *      ipc_rcu_alloc   -       allocate ipc and rcu space
 479  *      @size: size desired
 480  *
 481  *      Allocate memory for the rcu header structure +  the object.
 482  *      Returns the pointer to the object.
 483  *      NULL is returned if the allocation fails.
 484  */
 485
 486 void* ipc_rcu_alloc(int size)
 487 {
 488         void* out;
 489         /*
 490          * We prepend the allocation with the rcu struct, and
 491          * workqueue if necessary (for vmalloc).
 492          */
 493         if (rcu_use_vmalloc(size)) {
 494                 out = vmalloc(HDRLEN_VMALLOC + size);
 495                 if (out) {
 496                         out += HDRLEN_VMALLOC;
 497                         container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
 498                         container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
 499                 }
 500         } else {
 501                 out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
 502                 if (out) {
 503                         out += HDRLEN_KMALLOC;
 504                         container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
 505                         container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
 506                 }
 507         }
 508
 509         return out;
 510 }
 511
 512 void ipc_rcu_getref(void *ptr)
 513 {
 514         container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
 515 }
 516
 517 /**
 518  * ipc_schedule_free - free ipc + rcu space
 519  * @head: RCU callback structure for queued work
 520  *
 521  * Since RCU callback function is called in bh,
 522  * we need to defer the vfree to schedule_work
 523  */
 524 static void ipc_schedule_free(struct rcu_head *head)
 525 {
 526         struct ipc_rcu_grace *grace =
 527                 container_of(head, struct ipc_rcu_grace, rcu);
 528         struct ipc_rcu_sched *sched =
 529                         container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]);
 530
 531         INIT_WORK(&sched->work, vfree, sched);
 532         schedule_work(&sched->work);
 533 }
 534
 535 /**
 536  * ipc_immediate_free - free ipc + rcu space
 537  * @head: RCU callback structure that contains pointer to be freed
 538  *
 539  * Free from the RCU callback context
 540  */
 541 static void ipc_immediate_free(struct rcu_head *head)
 542 {
 543         struct ipc_rcu_grace *free =
 544                 container_of(head, struct ipc_rcu_grace, rcu);
 545         kfree(free);
 546 }
 547
 548 void ipc_rcu_putref(void *ptr)
 549 {
 550         if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
 551                 return;
 552
 553         if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
 554                 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
 555                                 ipc_schedule_free);
 556         } else {
 557                 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
 558                                 ipc_immediate_free);
 559         }
 560 }
 561
 562 /**
 563  *      ipcperms        -       check IPC permissions
 564  *      @ipcp: IPC permission set
 565  *      @flag: desired permission set.
 566  *
 567  *      Check user, group, other permissions for access
 568  *      to ipc resources. return 0 if allowed
 569  */
 570
 571 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
 572 {       /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
 573         int requested_mode, granted_mode, err;
 574
 575         if (unlikely((err = audit_ipc_obj(ipcp))))
 576                 return err;
 577         requested_mode = (flag >> 6) | (flag >> 3) | flag;
 578         granted_mode = ipcp->mode;
 579         if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
 580                 granted_mode >>= 6;
 581         else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 582                 granted_mode >>= 3;
 583         /* is there some bit set in requested_mode but not in granted_mode? */
 584         if ((requested_mode & ~granted_mode & 0007) &&
 585             !capable(CAP_IPC_OWNER))
 586                 return -1;
 587
 588         return security_ipc_permission(ipcp, flag);
 589 }
 590
 591 /*
 592  * Functions to convert between the kern_ipc_perm structure and the
 593  * old/new ipc_perm structures
 594  */
 595
 596 /**
 597  *      kernel_to_ipc64_perm    -       convert kernel ipc permissions to user
 598  *      @in: kernel permissions
 599  *      @out: new style IPC permissions
 600  *
 601  *      Turn the kernel object 'in' into a set of permissions descriptions
 602  *      for returning to userspace (out).
 603  */
 604
 605
 606 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
 607 {
 608         out->key        = in->key;
 609         out->uid        = in->uid;
 610         out->gid        = in->gid;
 611         out->cuid       = in->cuid;
 612         out->cgid       = in->cgid;
 613         out->mode       = in->mode;
 614         out->seq        = in->seq;
 615 }
 616
 617 /**
 618  *      ipc64_perm_to_ipc_perm  -       convert old ipc permissions to new
 619  *      @in: new style IPC permissions
 620  *      @out: old style IPC permissions
 621  *
 622  *      Turn the new style permissions object in into a compatibility
 623  *      object and store it into the 'out' pointer.
 624  */
 625
 626 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
 627 {
 628         out->key        = in->key;
 629         SET_UID(out->uid, in->uid);
 630         SET_GID(out->gid, in->gid);
 631         SET_UID(out->cuid, in->cuid);
 632         SET_GID(out->cgid, in->cgid);
 633         out->mode       = in->mode;
 634         out->seq        = in->seq;
 635 }
 636
 637 /*
 638  * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
 639  * is called with shm_ids.mutex locked.  Since grow_ary() is also called with
 640  * shm_ids.mutex down(for Shared Memory), there is no need to add read
 641  * barriers here to gurantee the writes in grow_ary() are seen in order
 642  * here (for Alpha).
 643  *
 644  * However ipc_get() itself does not necessary require ipc_ids.mutex down. So
 645  * if in the future ipc_get() is used by other places without ipc_ids.mutex
 646  * down, then ipc_get() needs read memery barriers as ipc_lock() does.
 647  */
 648 struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
 649 {
 650         struct kern_ipc_perm* out;
 651         int lid = id % SEQ_MULTIPLIER;
 652         if(lid >= ids->entries->size)
 653                 return NULL;
 654         out = ids->entries->p[lid];
 655         return out;
 656 }
 657
 658 struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
 659 {
 660         struct kern_ipc_perm* out;
 661         int lid = id % SEQ_MULTIPLIER;
 662         struct ipc_id_ary* entries;
 663
 664         rcu_read_lock();
 665         entries = rcu_dereference(ids->entries);
 666         if(lid >= entries->size) {
 667                 rcu_read_unlock();
 668                 return NULL;
 669         }
 670         out = entries->p[lid];
 671         if(out == NULL) {
 672                 rcu_read_unlock();
 673                 return NULL;
 674         }
 675         spin_lock(&out->lock);
 676
 677         /* ipc_rmid() may have already freed the ID while ipc_lock
 678          * was spinning: here verify that the structure is still valid
 679          */
 680         if (out->deleted) {
 681                 spin_unlock(&out->lock);
 682                 rcu_read_unlock();
 683                 return NULL;
 684         }
 685         return out;
 686 }
 687
 688 void ipc_lock_by_ptr(struct kern_ipc_perm *perm)
 689 {
 690         rcu_read_lock();
 691         spin_lock(&perm->lock);
 692 }
 693
 694 void ipc_unlock(struct kern_ipc_perm* perm)
 695 {
 696         spin_unlock(&perm->lock);
 697         rcu_read_unlock();
 698 }
 699
 700 int ipc_buildid(struct ipc_ids* ids, int id, int seq)
 701 {
 702         return SEQ_MULTIPLIER*seq + id;
 703 }
 704
 705 int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid)
 706 {
 707         if(uid/SEQ_MULTIPLIER != ipcp->seq)
 708                 return 1;
 709         return 0;
 710 }
 711
 712 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
 713
 714
 715 /**
 716  *      ipc_parse_version       -       IPC call version
 717  *      @cmd: pointer to command
 718  *
 719  *      Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
 720  *      The cmd value is turned from an encoding command and version into
 721  *      just the command code.
 722  */
 723
 724 int ipc_parse_version (int *cmd)
 725 {
 726         if (*cmd & IPC_64) {
 727                 *cmd ^= IPC_64;
 728                 return IPC_64;
 729         } else {
 730                 return IPC_OLD;
 731         }
 732 }
 733
 734 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */
 735
 736 #ifdef CONFIG_PROC_FS
 737 static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 738 {
 739         struct ipc_proc_iface *iface = s->private;
 740         struct kern_ipc_perm *ipc = it;
 741         loff_t p;
 742         struct ipc_ids *ids;
 743
 744         ids = current->nsproxy->ipc_ns->ids[iface->ids];
 745
 746         /* If we had an ipc id locked before, unlock it */
 747         if (ipc && ipc != SEQ_START_TOKEN)
 748                 ipc_unlock(ipc);
 749
 750         /*
 751          * p = *pos - 1 (because id 0 starts at position 1)
 752          *          + 1 (because we increment the position by one)
 753          */
 754         for (p = *pos; p <= ids->max_id; p++) {
 755                 if ((ipc = ipc_lock(ids, p)) != NULL) {
 756                         *pos = p + 1;
 757                         return ipc;
 758                 }
 759         }
 760
 761         /* Out of range - return NULL to terminate iteration */
 762         return NULL;
 763 }
 764
 765 /*
 766  * File positions: pos 0 -> header, pos n -> ipc id + 1.
 767  * SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START.
 768  */
 769 static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 770 {
 771         struct ipc_proc_iface *iface = s->private;
 772         struct kern_ipc_perm *ipc;
 773         loff_t p;
 774         struct ipc_ids *ids;
 775
 776         ids = current->nsproxy->ipc_ns->ids[iface->ids];
 777
 778         /*
 779          * Take the lock - this will be released by the corresponding
 780          * call to stop().
 781          */
 782         mutex_lock(&ids->mutex);
 783
 784         /* pos < 0 is invalid */
 785         if (*pos < 0)
 786                 return NULL;
 787
 788         /* pos == 0 means header */
 789         if (*pos == 0)
 790                 return SEQ_START_TOKEN;
 791
 792         /* Find the (pos-1)th ipc */
 793         for (p = *pos - 1; p <= ids->max_id; p++) {
 794                 if ((ipc = ipc_lock(ids, p)) != NULL) {
 795                         *pos = p + 1;
 796                         return ipc;
 797                 }
 798         }
 799         return NULL;
 800 }
 801
 802 static void sysvipc_proc_stop(struct seq_file *s, void *it)
 803 {
 804         struct kern_ipc_perm *ipc = it;
 805         struct ipc_proc_iface *iface = s->private;
 806         struct ipc_ids *ids;
 807
 808         /* If we had a locked segment, release it */
 809         if (ipc && ipc != SEQ_START_TOKEN)
 810                 ipc_unlock(ipc);
 811
 812         ids = current->nsproxy->ipc_ns->ids[iface->ids];
 813         /* Release the lock we took in start() */
 814         mutex_unlock(&ids->mutex);
 815 }
 816
 817 static int sysvipc_proc_show(struct seq_file *s, void *it)
 818 {
 819         struct ipc_proc_iface *iface = s->private;
 820
 821         if (it == SEQ_START_TOKEN)
 822                 return seq_puts(s, iface->header);
 823
 824         return iface->show(s, it);
 825 }
 826
 827 static struct seq_operations sysvipc_proc_seqops = {
 828         .start = sysvipc_proc_start,
 829         .stop  = sysvipc_proc_stop,
 830         .next  = sysvipc_proc_next,
 831         .show  = sysvipc_proc_show,
 832 };
 833
 834 static int sysvipc_proc_open(struct inode *inode, struct file *file) {
 835         int ret;
 836         struct seq_file *seq;
 837
 838         ret = seq_open(file, &sysvipc_proc_seqops);
 839         if (!ret) {
 840                 seq = file->private_data;
 841                 seq->private = PDE(inode)->data;
 842         }
 843         return ret;
 844 }
 845
 846 static struct file_operations sysvipc_proc_fops = {
 847         .open    = sysvipc_proc_open,
 848         .read    = seq_read,
 849         .llseek  = seq_lseek,
 850         .release = seq_release,
 851 };
 852 #endif /* CONFIG_PROC_FS */