source3/locking/shmem_sysv.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4    Shared memory functions - SYSV IPC implementation
   5    Copyright (C) Erik Devriendt 1996-1997
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20
  21 */
  22
  23 #include "includes.h"
  24
  25
  26 #ifdef USE_SYSV_IPC
  27
  28 extern int DEBUGLEVEL;
  29
  30 #define SHMEM_KEY ((key_t)0x280267)
  31 #define SEMAPHORE_KEY (SHMEM_KEY+2)
  32
  33 #define SHM_MAGIC 0x53484100
  34 #define SHM_VERSION 2
  35
  36 #ifdef SHM_R
  37 #define IPC_PERMS ((SHM_R | SHM_W) | (SHM_R>>3) | (SHM_R>>6))
  38 #else
  39 #define IPC_PERMS 0644
  40 #endif
  41
  42 #ifdef SEMMSL
  43 #define SHMEM_HASH_SIZE (SEMMSL-1)
  44 #else
  45 #define SHMEM_HASH_SIZE 63
  46 #endif
  47
  48 #define MIN_SHM_SIZE 10240
  49
  50 static int shm_id;
  51 static int sem_id;
  52 static int shm_size;
  53 static int hash_size;
  54 static int global_lock_count;
  55
  56 struct ShmHeader {
  57    int shm_magic;
  58    int shm_version;
  59    int total_size;      /* in bytes */
  60    BOOL consistent;
  61    int first_free_off;
  62    int userdef_off;    /* a userdefined offset. can be used to store
  63                           root of tree or list */
  64    struct {             /* a cell is a range of bytes of sizeof(struct
  65                            ShmBlockDesc) size */
  66            int cells_free;
  67            int cells_used;
  68            int cells_system; /* number of cells used as allocated
  69                                 block descriptors */
  70    } statistics;
  71 };
  72
  73 #define SHM_NOT_FREE_OFF (-1)
  74 struct ShmBlockDesc
  75 {
  76    int next;    /* offset of next block in the free list or
  77                    SHM_NOT_FREE_OFF when block in use */
  78    int          size;   /* user size in BlockDescSize units */
  79 };
  80
  81 #define EOList_Addr     (struct ShmBlockDesc *)( 0 )
  82 #define EOList_Off      (NULL_OFFSET)
  83
  84 #define CellSize        sizeof(struct ShmBlockDesc)
  85
  86 /* HeaderSize aligned on 8 byte boundary */
  87 #define AlignedHeaderSize       ((sizeof(struct ShmHeader)+7) & ~7)
  88
  89 static struct ShmHeader *shm_header_p = (struct ShmHeader *)0;
  90
  91 static BOOL shm_initialize_called = False;
  92
  93 static int read_only;
  94
  95 static BOOL sem_lock(int i)
  96 {
  97         struct sembuf sb;
  98         if (read_only) return True;
  99
 100         sb.sem_num = i;
 101         sb.sem_op = -1;
 102         sb.sem_flg = SEM_UNDO;
 103
 104         if (semop(sem_id, &sb, 1) != 0) {
 105                 DEBUG(0,("ERROR: IPC lock failed on semaphore %d\n", i));
 106                 return False;
 107         }
 108
 109         return True;
 110 }
 111
 112 static BOOL sem_unlock(int i)
 113 {
 114         struct sembuf sb;
 115         if (read_only) return True;
 116
 117         sb.sem_num = i;
 118         sb.sem_op = 1;
 119         sb.sem_flg = SEM_UNDO;
 120
 121         if (semop(sem_id, &sb, 1) != 0) {
 122                 DEBUG(0,("ERROR: IPC unlock failed on semaphore %d\n", i));
 123                 return False;
 124         }
 125
 126         return True;
 127 }
 128
 129 static BOOL global_lock(void)
 130 {
 131         global_lock_count++;
 132         if (global_lock_count == 1)
 133                 return sem_lock(0);
 134         return True;
 135 }
 136
 137 static BOOL global_unlock(void)
 138 {
 139         global_lock_count--;
 140         if (global_lock_count == 0)
 141                 return sem_unlock(0);
 142         return True;
 143 }
 144
 145 static void *shm_offset2addr(int offset)
 146 {
 147    if (offset == NULL_OFFSET )
 148       return (void *)(0);
 149
 150    if (!shm_header_p)
 151       return (void *)(0);
 152
 153    return (void *)((char *)shm_header_p + offset );
 154 }
 155
 156 static int shm_addr2offset(void *addr)
 157 {
 158    if (!addr)
 159       return NULL_OFFSET;
 160
 161    if (!shm_header_p)
 162       return NULL_OFFSET;
 163
 164    return (int)((char *)addr - (char *)shm_header_p);
 165 }
 166
 167
 168 static int shm_alloc(int size)
 169 {
 170         unsigned num_cells ;
 171         struct ShmBlockDesc *scanner_p;
 172         struct ShmBlockDesc *prev_p;
 173         struct ShmBlockDesc *new_p;
 174         int result_offset;
 175
 176
 177         if (!shm_header_p) {
 178                 /* not mapped yet */
 179                 DEBUG(0,("ERROR shm_alloc : shmem not mapped\n"));
 180                 return NULL_OFFSET;
 181         }
 182
 183         global_lock();
 184
 185         if (!shm_header_p->consistent) {
 186                 DEBUG(0,("ERROR shm_alloc : shmem not consistent\n"));
 187                 global_unlock();
 188                 return NULL_OFFSET;
 189         }
 190
 191         /* calculate    the number of cells */
 192         num_cells = (size + CellSize -1) / CellSize;
 193
 194         /* set start    of scan */
 195         prev_p = (struct ShmBlockDesc *)shm_offset2addr(shm_header_p->first_free_off);
 196         scanner_p =     prev_p ;
 197
 198         /* scan the free list to find a matching free space */
 199         while ((scanner_p != EOList_Addr) && (scanner_p->size < num_cells)) {
 200                 prev_p = scanner_p;
 201                 scanner_p = (struct ShmBlockDesc *)shm_offset2addr(scanner_p->next);
 202         }
 203
 204         /* at this point scanner point to a block header or to the end of
 205            the list */
 206         if (scanner_p == EOList_Addr) {
 207                 DEBUG(0,("ERROR shm_alloc : alloc of %d bytes failed, no free space found\n",size));
 208                 global_unlock();
 209                 return (NULL_OFFSET);
 210         }
 211
 212         /* going to modify shared mem */
 213         shm_header_p->consistent = False;
 214
 215         /* if we found a good one : scanner == the good one */
 216         if (scanner_p->size <= num_cells + 2) {
 217                 /* there is no use in making a new one, it will be too small anyway
 218                  *       we will link out scanner
 219                  */
 220                 if ( prev_p == scanner_p ) {
 221                         shm_header_p->first_free_off = scanner_p->next ;
 222                 } else {
 223                         prev_p->next = scanner_p->next ;
 224                 }
 225                 shm_header_p->statistics.cells_free -= scanner_p->size;
 226                 shm_header_p->statistics.cells_used += scanner_p->size;
 227         } else {
 228                 /* Make a new one */
 229                 new_p = scanner_p + 1 + num_cells;
 230                 new_p->size = scanner_p->size - num_cells - 1;
 231                 new_p->next = scanner_p->next;
 232                 scanner_p->size = num_cells;
 233                 scanner_p->next = shm_addr2offset(new_p);
 234
 235                 if (prev_p != scanner_p) {
 236                         prev_p->next       = shm_addr2offset(new_p)  ;
 237                 } else {
 238                         shm_header_p->first_free_off = shm_addr2offset(new_p);
 239                 }
 240                 shm_header_p->statistics.cells_free -= num_cells+1;
 241                 shm_header_p->statistics.cells_used += num_cells;
 242                 shm_header_p->statistics.cells_system += 1;
 243         }
 244
 245         result_offset = shm_addr2offset( &(scanner_p[1]) );
 246         scanner_p->next =       SHM_NOT_FREE_OFF ;
 247
 248         /* end modification of shared mem */
 249         shm_header_p->consistent = True;
 250
 251         DEBUG(6,("shm_alloc : request for %d bytes, allocated %d bytes at offset %d\n",size,scanner_p->size*CellSize,result_offset ));
 252
 253         global_unlock();
 254         return result_offset;
 255 }
 256
 257
 258
 259 /*
 260  * Function to create the hash table for the share mode entries. Called
 261  * when smb shared memory is global locked.
 262  */
 263 static BOOL shm_create_hash_table( unsigned int size )
 264 {
 265         size *= sizeof(int);
 266
 267         global_lock();
 268         shm_header_p->userdef_off = shm_alloc( size );
 269
 270         if(shm_header_p->userdef_off == NULL_OFFSET) {
 271                 DEBUG(0,("shm_create_hash_table: Failed to create hash table of size %d\n",size));
 272                 global_unlock();
 273                 return False;
 274         }
 275
 276         /* Clear hash buckets. */
 277         memset( shm_offset2addr(shm_header_p->userdef_off), '\0', size);
 278         global_unlock();
 279         return True;
 280 }
 281
 282 static BOOL shm_validate_header(int size)
 283 {
 284         if( !shm_header_p ) {
 285                 /* not mapped yet */
 286                 DEBUG(0,("ERROR shm_validate_header : shmem not mapped\n"));
 287                 return False;
 288         }
 289
 290         if(shm_header_p->shm_magic != SHM_MAGIC) {
 291                 DEBUG(0,("ERROR shm_validate_header : bad magic\n"));
 292                 return False;
 293         }
 294
 295         if(shm_header_p->shm_version != SHM_VERSION) {
 296                 DEBUG(0,("ERROR shm_validate_header : bad version %X\n",shm_header_p->shm_version));
 297                 return False;
 298         }
 299
 300         if(shm_header_p->total_size != size) {
 301                 DEBUG(0,("ERROR shm_validate_header : shmem size mismatch (old = %d, new = %d)\n",shm_header_p->total_size,size));
 302                 return False;
 303         }
 304
 305         if(!shm_header_p->consistent) {
 306                 DEBUG(0,("ERROR shm_validate_header : shmem not consistent\n"));
 307                 return False;
 308         }
 309         return True;
 310 }
 311
 312 static BOOL shm_initialize(int size)
 313 {
 314         struct ShmBlockDesc * first_free_block_p;
 315
 316         DEBUG(5,("shm_initialize : initializing shmem file of size %d\n",size));
 317
 318         if( !shm_header_p ) {
 319                 /* not mapped yet */
 320                 DEBUG(0,("ERROR shm_initialize : shmem not mapped\n"));
 321                 return False;
 322         }
 323
 324         shm_header_p->shm_magic = SHM_MAGIC;
 325         shm_header_p->shm_version = SHM_VERSION;
 326         shm_header_p->total_size = size;
 327         shm_header_p->first_free_off = AlignedHeaderSize;
 328         shm_header_p->userdef_off = NULL_OFFSET;
 329
 330         first_free_block_p = (struct ShmBlockDesc *)shm_offset2addr(shm_header_p->first_free_off);
 331         first_free_block_p->next = EOList_Off;
 332         first_free_block_p->size = ( size - AlignedHeaderSize - CellSize ) / CellSize ;
 333
 334         shm_header_p->statistics.cells_free = first_free_block_p->size;
 335         shm_header_p->statistics.cells_used = 0;
 336         shm_header_p->statistics.cells_system = 1;
 337
 338         shm_header_p->consistent = True;
 339
 340         shm_initialize_called = True;
 341
 342         return True;
 343 }
 344
 345 static void shm_solve_neighbors(struct ShmBlockDesc *head_p )
 346 {
 347         struct ShmBlockDesc *next_p;
 348
 349         /* Check if head_p and head_p->next are neighbors and if so
 350            join them */
 351         if ( head_p == EOList_Addr ) return ;
 352         if ( head_p->next == EOList_Off ) return ;
 353
 354         next_p = (struct ShmBlockDesc *)shm_offset2addr(head_p->next);
 355         if ( ( head_p + head_p->size + 1 ) == next_p) {
 356                 head_p->size += next_p->size +1 ;       /* adapt size */
 357                 head_p->next = next_p->next       ; /* link out */
 358
 359                 shm_header_p->statistics.cells_free += 1;
 360                 shm_header_p->statistics.cells_system -= 1;
 361         }
 362 }
 363
 364
 365
 366
 367 static BOOL shm_close( void )
 368 {
 369         return True;
 370 }
 371
 372
 373 static BOOL shm_free(int offset)
 374 {
 375         struct ShmBlockDesc *header_p; /* pointer to header of
 376                                                block to free */
 377         struct ShmBlockDesc *scanner_p; /* used to scan the list */
 378         struct ShmBlockDesc *prev_p; /* holds previous in the
 379                                            list */
 380
 381         if (!shm_header_p) {
 382                 /* not mapped yet */
 383                 DEBUG(0,("ERROR shm_free : shmem not mapped\n"));
 384                 return False;
 385         }
 386
 387         global_lock();
 388
 389         if (!shm_header_p->consistent) {
 390                 DEBUG(0,("ERROR shm_free : shmem not consistent\n"));
 391                 global_unlock();
 392                 return False;
 393         }
 394
 395         /* make pointer to header of block */
 396         header_p = ((struct ShmBlockDesc *)shm_offset2addr(offset) - 1);
 397
 398         if (header_p->next != SHM_NOT_FREE_OFF) {
 399                 DEBUG(0,("ERROR shm_free : bad offset (%d)\n",offset));
 400                 global_unlock();
 401                 return False;
 402         }
 403
 404         /* find a place in the free_list to put the header in */
 405
 406         /* set scanner and previous pointer to start of list */
 407         prev_p = (struct ShmBlockDesc *)shm_offset2addr(shm_header_p->first_free_off);
 408         scanner_p = prev_p ;
 409
 410         while ((scanner_p != EOList_Addr) &&
 411                (scanner_p < header_p)) {
 412                 /* while we didn't scan past its position */
 413                 prev_p = scanner_p ;
 414                 scanner_p = (struct ShmBlockDesc *)shm_offset2addr(scanner_p->next);
 415         }
 416
 417         shm_header_p->consistent = False;
 418
 419         DEBUG(6,("shm_free : freeing %d bytes at offset %d\n",
 420                  header_p->size*CellSize,offset));
 421
 422         if (scanner_p == prev_p) {
 423                 shm_header_p->statistics.cells_free += header_p->size;
 424                 shm_header_p->statistics.cells_used -= header_p->size;
 425
 426                 /* we must free it at the beginning of the list */
 427                 shm_header_p->first_free_off = shm_addr2offset(header_p);                                                /*     set     the free_list_pointer to this block_header */
 428
 429                 /* scanner is the one that was first in the list */
 430                 header_p->next = shm_addr2offset(scanner_p);
 431                 shm_solve_neighbors( header_p ); /* if neighbors then link them */
 432
 433                 shm_header_p->consistent = True;
 434         } else {
 435                 shm_header_p->statistics.cells_free += header_p->size;
 436                 shm_header_p->statistics.cells_used -= header_p->size;
 437
 438                 prev_p->next = shm_addr2offset(header_p);
 439                 header_p->next = shm_addr2offset(scanner_p);
 440                 shm_solve_neighbors(header_p) ;
 441                 shm_solve_neighbors(prev_p) ;
 442
 443                 shm_header_p->consistent = True;
 444         }
 445
 446         global_unlock();
 447         return True;
 448 }
 449
 450
 451 static int shm_get_userdef_off(void)
 452 {
 453    if (!shm_header_p)
 454       return NULL_OFFSET;
 455    else
 456       return shm_header_p->userdef_off;
 457 }
 458
 459 /*******************************************************************
 460   Lock a particular hash bucket entry.
 461   ******************************************************************/
 462 static BOOL shm_lock_hash_entry(unsigned int entry)
 463 {
 464         DEBUG(0,("hash lock %d\n", entry));
 465         return sem_lock(entry+1);
 466 }
 467
 468 /*******************************************************************
 469   Unlock a particular hash bucket entry.
 470   ******************************************************************/
 471 static BOOL shm_unlock_hash_entry(unsigned int entry)
 472 {
 473         DEBUG(0,("hash unlock %d\n", entry));
 474         return sem_unlock(entry+1);
 475 }
 476
 477
 478 /*******************************************************************
 479   Gather statistics on shared memory usage.
 480   ******************************************************************/
 481 static BOOL shm_get_usage(int *bytes_free,
 482                           int *bytes_used,
 483                           int *bytes_overhead)
 484 {
 485         if(!shm_header_p) {
 486                 /* not mapped yet */
 487                 DEBUG(0,("ERROR shm_free : shmem not mapped\n"));
 488                 return False;
 489         }
 490
 491         *bytes_free = shm_header_p->statistics.cells_free * CellSize;
 492         *bytes_used = shm_header_p->statistics.cells_used * CellSize;
 493         *bytes_overhead = shm_header_p->statistics.cells_system * CellSize + AlignedHeaderSize;
 494
 495         return True;
 496 }
 497
 498
 499 /*******************************************************************
 500 hash a number into a hash_entry
 501   ******************************************************************/
 502 static unsigned shm_hash_size(void)
 503 {
 504         return hash_size;
 505 }
 506
 507
 508 static struct shmem_ops shmops = {
 509         shm_close,
 510         shm_alloc,
 511         shm_free,
 512         shm_get_userdef_off,
 513         shm_offset2addr,
 514         shm_addr2offset,
 515         shm_lock_hash_entry,
 516         shm_unlock_hash_entry,
 517         shm_get_usage,
 518         shm_hash_size,
 519 };
 520
 521 /*******************************************************************
 522   open the shared memory
 523   ******************************************************************/
 524 struct shmem_ops *sysv_shm_open(int ronly)
 525 {
 526         BOOL created_new = False;
 527         BOOL other_processes;
 528         struct shmid_ds shm_ds;
 529         struct semid_ds sem_ds;
 530         union semun su;
 531         int i;
 532
 533         read_only = ronly;
 534
 535         shm_size = lp_shmem_size();
 536
 537         DEBUG(4,("Trying sysv shmem open of size %d\n", shm_size));
 538
 539         /* first the semaphore */
 540         sem_id = semget(SEMAPHORE_KEY, 0, 0);
 541         if (sem_id == -1) {
 542                 if (read_only) return NULL;
 543
 544                 hash_size = SHMEM_HASH_SIZE;
 545
 546                 while (hash_size > 1) {
 547                         sem_id = semget(SEMAPHORE_KEY, hash_size+1,
 548                                         IPC_CREAT | IPC_EXCL | IPC_PERMS);
 549                         if (sem_id != -1 || errno != EINVAL) break;
 550                         hash_size--;
 551                 }
 552
 553                 if (sem_id == -1) {
 554                         DEBUG(0,("Can't create or use semaphore %s\n",
 555                                  strerror(errno)));
 556                 }
 557
 558                 if (sem_id != -1) {
 559                         su.val = 1;
 560                         for (i=0;i<hash_size+1;i++) {
 561                                 if (semctl(sem_id, i, SETVAL, su) != 0) {
 562                                         DEBUG(1,("Failed to init semaphore %d\n", i));
 563                                 }
 564                         }
 565                 }
 566         }
 567         if (shm_id == -1) {
 568                 sem_id = semget(SEMAPHORE_KEY, 0, 0);
 569         }
 570         if (sem_id == -1) {
 571                 DEBUG(0,("Can't create or use semaphore %s\n",
 572                          strerror(errno)));
 573                 return NULL;
 574         }
 575
 576         su.buf = &sem_ds;
 577         if (semctl(sem_id, 0, IPC_STAT, su) != 0) {
 578                 DEBUG(0,("ERROR shm_open : can't IPC_STAT\n"));
 579         }
 580         hash_size = sem_ds.sem_nsems-1;
 581
 582         if (!read_only) {
 583                 if (sem_ds.sem_perm.cuid != 0 || sem_ds.sem_perm.cgid != 0) {
 584                         DEBUG(0,("ERROR: root did not create the semaphore\n"));
 585                         return NULL;
 586                 }
 587         }
 588
 589
 590
 591         if (!global_lock())
 592                 return NULL;
 593
 594         /* try to use an existing key */
 595         shm_id = shmget(SHMEM_KEY, shm_size, 0);
 596
 597         /* if that failed then create one */
 598         if (shm_id == -1) {
 599                 if (read_only) return NULL;
 600                 while (shm_size > MIN_SHM_SIZE) {
 601                         shm_id = shmget(SHMEM_KEY, shm_size,
 602                                         IPC_CREAT | IPC_EXCL | IPC_PERMS);
 603                         if (shm_id != -1 || errno != EINVAL) break;
 604                         shm_size *= 0.9;
 605                 }
 606                 created_new = (shm_id != -1);
 607         }
 608
 609         if (shm_id == -1) {
 610                 DEBUG(0,("Can't create or use IPC area\n"));
 611                 global_unlock();
 612                 return NULL;
 613         }
 614
 615
 616         shm_header_p = (struct ShmHeader *)shmat(shm_id, 0,
 617                                                  read_only?SHM_RDONLY:0);
 618         if ((int)shm_header_p == -1) {
 619                 DEBUG(0,("Can't attach to IPC area\n"));
 620                 global_unlock();
 621                 return NULL;
 622         }
 623
 624         /* to find out if some other process is already mapping the file,
 625            we use a registration file containing the processids of the file
 626            mapping processes */
 627         if (shmctl(shm_id, IPC_STAT, &shm_ds) != 0) {
 628                 DEBUG(0,("ERROR shm_open : can't IPC_STAT\n"));
 629         }
 630
 631         if (!read_only) {
 632                 if (shm_ds.shm_perm.cuid != 0 || shm_ds.shm_perm.cgid != 0) {
 633                         DEBUG(0,("ERROR: root did not create the shmem\n"));
 634                         global_unlock();
 635                         return NULL;
 636                 }
 637         }
 638
 639         shm_size = shm_ds.shm_segsz;
 640
 641         other_processes = (shm_ds.shm_nattch > 1);
 642
 643         if (!read_only && !other_processes) {
 644                 memset((char *)shm_header_p, 0, shm_size);
 645                 shm_initialize(shm_size);
 646                 shm_create_hash_table(hash_size);
 647                 DEBUG(3,("Initialised IPC area of size %d\n", shm_size));
 648         } else if (!shm_validate_header(shm_size)) {
 649                 /* existing file is corrupt, samba admin should remove
 650                    it by hand */
 651                 DEBUG(0,("ERROR shm_open : corrupt IPC area - remove it!\n"));
 652                 global_unlock();
 653                 return NULL;
 654         }
 655
 656         global_unlock();
 657         return &shmops;
 658 }
 659
 660
 661
 662 #else
 663  int ipc_dummy_procedure(void)
 664 {return 0;}
 665 #endif