sys/kern/sysv_shm.c

   1 /*
   2  * Copyright (c) 1994 Adam Glass and Charles Hannum.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  * 3. All advertising materials mentioning features or use of this software
  13  *    must display the following acknowledgement:
  14  *      This product includes software developed by Adam Glass and Charles
  15  *      Hannum.
  16  * 4. The names of the authors may not be used to endorse or promote products
  17  *    derived from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #include "opt_sysvipc.h"
  32
  33 #include <sys/param.h>
  34 #include <sys/systm.h>
  35 #include <sys/sysproto.h>
  36 #include <sys/kernel.h>
  37 #include <sys/sysctl.h>
  38 #include <sys/shm.h>
  39 #include <sys/proc.h>
  40 #include <sys/malloc.h>
  41 #include <sys/mman.h>
  42 #include <sys/stat.h>
  43 #include <sys/sysent.h>
  44 #include <sys/jail.h>
  45
  46 #include <vm/vm.h>
  47 #include <vm/vm_param.h>
  48 #include <sys/lock.h>
  49 #include <vm/pmap.h>
  50 #include <vm/vm_object.h>
  51 #include <vm/vm_map.h>
  52 #include <vm/vm_page.h>
  53 #include <vm/vm_pager.h>
  54
  55 static MALLOC_DEFINE(M_SHM, "shm", "SVID compatible shared memory segments");
  56
  57 static int shmget_allocate_segment (struct proc *p, struct shmget_args *uap, int mode);
  58 static int shmget_existing (struct proc *p, struct shmget_args *uap, int mode, int segnum);
  59
  60 #define SHMSEG_FREE             0x0200
  61 #define SHMSEG_REMOVED          0x0400
  62 #define SHMSEG_ALLOCATED        0x0800
  63 #define SHMSEG_WANTED           0x1000
  64
  65 static int shm_last_free, shm_committed, shmalloced;
  66 int shm_nused;
  67 static struct shmid_ds  *shmsegs;
  68 static struct lwkt_token shm_token = LWKT_TOKEN_INITIALIZER(shm_token);
  69
  70 struct shm_handle {
  71         /* vm_offset_t kva; */
  72         vm_object_t shm_object;
  73 };
  74
  75 struct shmmap_state {
  76         vm_offset_t va;
  77         int shmid;
  78 };
  79
  80 static void shm_deallocate_segment (struct shmid_ds *);
  81 static int shm_find_segment_by_key (key_t);
  82 static struct shmid_ds *shm_find_segment_by_shmid (int);
  83 static int shm_delete_mapping (struct vmspace *vm, struct shmmap_state *);
  84 static void shmrealloc (void);
  85 static void shminit (void *);
  86
  87 /*
  88  * Tuneable values
  89  */
  90 #ifndef SHMMIN
  91 #define SHMMIN  1
  92 #endif
  93 #ifndef SHMMNI
  94 #define SHMMNI  512
  95 #endif
  96 #ifndef SHMSEG
  97 #define SHMSEG  1024
  98 #endif
  99
 100 struct  shminfo shminfo = {
 101         0,
 102         SHMMIN,
 103         SHMMNI,
 104         SHMSEG,
 105         0
 106 };
 107
 108 /*
 109  * allow-removed    Allow a shared memory segment to be attached by its shmid
 110  *                  even after it has been deleted, as long as it was still
 111  *                  being referenced by someone.  This is a trick used by
 112  *                  chrome and other applications to avoid leaving shm
 113  *                  segments hanging around after the application is killed
 114  *                  or seg-faults unexpectedly.
 115  *
 116  * use-phys         Shared memory segments are to use physical memory by
 117  *                  default, which may allow the kernel to better-optimize
 118  *                  the pmap and reduce overhead.  The pages are effectively
 119  *                  wired.
 120  */
 121 static int shm_allow_removed = 1;
 122 static int shm_use_phys = 1;
 123
 124 TUNABLE_LONG("kern.ipc.shmmin", &shminfo.shmmin);
 125 TUNABLE_LONG("kern.ipc.shmmni", &shminfo.shmmni);
 126 TUNABLE_LONG("kern.ipc.shmseg", &shminfo.shmseg);
 127 TUNABLE_LONG("kern.ipc.shmmaxpgs", &shminfo.shmall);
 128 TUNABLE_INT("kern.ipc.shm_use_phys", &shm_use_phys);
 129
 130 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmmax, CTLFLAG_RW, &shminfo.shmmax, 0,
 131     "Max shared memory segment size");
 132 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmmin, CTLFLAG_RW, &shminfo.shmmin, 0,
 133     "Min shared memory segment size");
 134 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmmni, CTLFLAG_RD, &shminfo.shmmni, 0,
 135     "Max number of shared memory identifiers");
 136 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmseg, CTLFLAG_RW, &shminfo.shmseg, 0,
 137     "Max shared memory segments per process");
 138 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmall, CTLFLAG_RW, &shminfo.shmall, 0,
 139     "Max pages of shared memory");
 140 SYSCTL_INT(_kern_ipc, OID_AUTO, shm_use_phys, CTLFLAG_RW, &shm_use_phys, 0,
 141     "Use phys pager allocation instead of swap pager allocation");
 142 SYSCTL_INT(_kern_ipc, OID_AUTO, shm_allow_removed, CTLFLAG_RW,
 143     &shm_allow_removed, 0,
 144     "Enable/Disable attachment to attached segments marked for removal");
 145
 146 static int
 147 shm_find_segment_by_key(key_t key)
 148 {
 149         int i;
 150
 151         for (i = 0; i < shmalloced; i++) {
 152                 if ((shmsegs[i].shm_perm.mode & SHMSEG_ALLOCATED) &&
 153                     shmsegs[i].shm_perm.key == key)
 154                         return i;
 155         }
 156         return -1;
 157 }
 158
 159 static struct shmid_ds *
 160 shm_find_segment_by_shmid(int shmid)
 161 {
 162         int segnum;
 163         struct shmid_ds *shmseg;
 164
 165         segnum = IPCID_TO_IX(shmid);
 166         if (segnum < 0 || segnum >= shmalloced)
 167                 return NULL;
 168         shmseg = &shmsegs[segnum];
 169         if ((shmseg->shm_perm.mode & SHMSEG_ALLOCATED) == 0 ||
 170             (!shm_allow_removed &&
 171             (shmseg->shm_perm.mode & SHMSEG_REMOVED) != 0) ||
 172             shmseg->shm_perm.seq != IPCID_TO_SEQ(shmid)) {
 173                 return NULL;
 174         }
 175         return shmseg;
 176 }
 177
 178 static void
 179 shm_deallocate_segment(struct shmid_ds *shmseg)
 180 {
 181         struct shm_handle *shm_handle;
 182         size_t size;
 183
 184         shm_handle = shmseg->shm_internal;
 185         vm_object_deallocate(shm_handle->shm_object);
 186         kfree((caddr_t)shm_handle, M_SHM);
 187         shmseg->shm_internal = NULL;
 188         size = round_page(shmseg->shm_segsz);
 189         shm_committed -= btoc(size);
 190         shm_nused--;
 191         shmseg->shm_perm.mode = SHMSEG_FREE;
 192 }
 193
 194 static int
 195 shm_delete_mapping(struct vmspace *vm, struct shmmap_state *shmmap_s)
 196 {
 197         struct shmid_ds *shmseg;
 198         int segnum, result;
 199         size_t size;
 200
 201         segnum = IPCID_TO_IX(shmmap_s->shmid);
 202         shmseg = &shmsegs[segnum];
 203         size = round_page(shmseg->shm_segsz);
 204         result = vm_map_remove(&vm->vm_map, shmmap_s->va, shmmap_s->va + size);
 205         if (result != KERN_SUCCESS)
 206                 return EINVAL;
 207         shmmap_s->shmid = -1;
 208         shmseg->shm_dtime = time_second;
 209         if ((--shmseg->shm_nattch <= 0) &&
 210             (shmseg->shm_perm.mode & SHMSEG_REMOVED)) {
 211                 shm_deallocate_segment(shmseg);
 212                 shm_last_free = segnum;
 213         }
 214         return 0;
 215 }
 216
 217 /*
 218  * MPALMOSTSAFE
 219  */
 220 int
 221 sys_shmdt(struct shmdt_args *uap)
 222 {
 223         struct thread *td = curthread;
 224         struct proc *p = td->td_proc;
 225         struct shmmap_state *shmmap_s;
 226         long i;
 227         int error;
 228
 229         if (!jail_sysvipc_allowed && td->td_ucred->cr_prison != NULL)
 230                 return (ENOSYS);
 231
 232         lwkt_gettoken(&shm_token);
 233         shmmap_s = (struct shmmap_state *)p->p_vmspace->vm_shm;
 234         if (shmmap_s == NULL) {
 235                 error = EINVAL;
 236                 goto done;
 237         }
 238         for (i = 0; i < shminfo.shmseg; i++, shmmap_s++) {
 239                 if (shmmap_s->shmid != -1 &&
 240                     shmmap_s->va == (vm_offset_t)uap->shmaddr)
 241                         break;
 242         }
 243         if (i == shminfo.shmseg)
 244                 error = EINVAL;
 245         else
 246                 error = shm_delete_mapping(p->p_vmspace, shmmap_s);
 247 done:
 248         lwkt_reltoken(&shm_token);
 249
 250         return (error);
 251 }
 252
 253 /*
 254  * MPALMOSTSAFE
 255  */
 256 int
 257 sys_shmat(struct shmat_args *uap)
 258 {
 259         struct thread *td = curthread;
 260         struct proc *p = td->td_proc;
 261         int error, flags;
 262         long i;
 263         struct shmid_ds *shmseg;
 264         struct shmmap_state *shmmap_s = NULL;
 265         struct shm_handle *shm_handle;
 266         vm_offset_t attach_va;
 267         vm_prot_t prot;
 268         vm_size_t size;
 269         vm_size_t align;
 270         int rv;
 271
 272         if (!jail_sysvipc_allowed && td->td_ucred->cr_prison != NULL)
 273                 return (ENOSYS);
 274
 275         lwkt_gettoken(&shm_token);
 276 again:
 277         shmmap_s = (struct shmmap_state *)p->p_vmspace->vm_shm;
 278         if (shmmap_s == NULL) {
 279                 size = shminfo.shmseg * sizeof(struct shmmap_state);
 280                 shmmap_s = kmalloc(size, M_SHM, M_WAITOK);
 281                 for (i = 0; i < shminfo.shmseg; i++)
 282                         shmmap_s[i].shmid = -1;
 283                 if (p->p_vmspace->vm_shm != NULL) {
 284                         kfree(shmmap_s, M_SHM);
 285                         goto again;
 286                 }
 287                 p->p_vmspace->vm_shm = (caddr_t)shmmap_s;
 288         }
 289         shmseg = shm_find_segment_by_shmid(uap->shmid);
 290         if (shmseg == NULL) {
 291                 error = EINVAL;
 292                 goto done;
 293         }
 294         error = ipcperm(p, &shmseg->shm_perm,
 295                         (uap->shmflg & SHM_RDONLY) ? IPC_R : IPC_R|IPC_W);
 296         if (error)
 297                 goto done;
 298         for (i = 0; i < shminfo.shmseg; i++) {
 299                 if (shmmap_s->shmid == -1)
 300                         break;
 301                 shmmap_s++;
 302         }
 303         if (i >= shminfo.shmseg) {
 304                 error = EMFILE;
 305                 goto done;
 306         }
 307         size = round_page(shmseg->shm_segsz);
 308 #ifdef VM_PROT_READ_IS_EXEC
 309         prot = VM_PROT_READ | VM_PROT_EXECUTE;
 310 #else
 311         prot = VM_PROT_READ;
 312 #endif
 313         if ((uap->shmflg & SHM_RDONLY) == 0)
 314                 prot |= VM_PROT_WRITE;
 315         flags = MAP_ANON | MAP_SHARED;
 316         if (uap->shmaddr) {
 317                 flags |= MAP_FIXED;
 318                 if (uap->shmflg & SHM_RND) {
 319                         attach_va = (vm_offset_t)uap->shmaddr & ~(SHMLBA-1);
 320                 } else if (((vm_offset_t)uap->shmaddr & (SHMLBA-1)) == 0) {
 321                         attach_va = (vm_offset_t)uap->shmaddr;
 322                 } else {
 323                         error = EINVAL;
 324                         goto done;
 325                 }
 326         } else {
 327                 /*
 328                  * This is just a hint to vm_map_find() about where to put it.
 329                  */
 330                 attach_va = round_page((vm_offset_t)p->p_vmspace->vm_taddr +
 331                                        maxtsiz + maxdsiz);
 332         }
 333
 334         /*
 335          * Handle alignment.  For large memory maps it is possible
 336          * that the MMU can optimize the page table so align anything
 337          * that is a multiple of SEG_SIZE to SEG_SIZE.
 338          */
 339         if ((flags & MAP_FIXED) == 0 && (size & SEG_MASK) == 0)
 340                 align = SEG_SIZE;
 341         else
 342                 align = PAGE_SIZE;
 343
 344         shm_handle = shmseg->shm_internal;
 345         vm_object_hold(shm_handle->shm_object);
 346         vm_object_reference_locked(shm_handle->shm_object);
 347         rv = vm_map_find(&p->p_vmspace->vm_map,
 348                          shm_handle->shm_object, NULL,
 349                          0, &attach_va, size,
 350                          align,
 351                          ((flags & MAP_FIXED) ? 0 : 1),
 352                          VM_MAPTYPE_NORMAL, VM_SUBSYS_SHMEM,
 353                          prot, prot, 0);
 354         vm_object_drop(shm_handle->shm_object);
 355         if (rv != KERN_SUCCESS) {
 356                 vm_object_deallocate(shm_handle->shm_object);
 357                 error = ENOMEM;
 358                 goto done;
 359         }
 360         vm_map_inherit(&p->p_vmspace->vm_map,
 361                        attach_va, attach_va + size, VM_INHERIT_SHARE);
 362
 363         KKASSERT(shmmap_s->shmid == -1);
 364         shmmap_s->va = attach_va;
 365         shmmap_s->shmid = uap->shmid;
 366         shmseg->shm_lpid = p->p_pid;
 367         shmseg->shm_atime = time_second;
 368         shmseg->shm_nattch++;
 369         uap->sysmsg_resultp = (void *)attach_va;
 370         error = 0;
 371 done:
 372         lwkt_reltoken(&shm_token);
 373
 374         return error;
 375 }
 376
 377 /*
 378  * MPALMOSTSAFE
 379  */
 380 int
 381 sys_shmctl(struct shmctl_args *uap)
 382 {
 383         struct thread *td = curthread;
 384         struct proc *p = td->td_proc;
 385         int error;
 386         struct shmid_ds inbuf;
 387         struct shmid_ds *shmseg;
 388
 389         if (!jail_sysvipc_allowed && td->td_ucred->cr_prison != NULL)
 390                 return (ENOSYS);
 391
 392         lwkt_gettoken(&shm_token);
 393         shmseg = shm_find_segment_by_shmid(uap->shmid);
 394         if (shmseg == NULL) {
 395                 error = EINVAL;
 396                 goto done;
 397         }
 398
 399         switch (uap->cmd) {
 400         case IPC_STAT:
 401                 error = ipcperm(p, &shmseg->shm_perm, IPC_R);
 402                 if (error == 0)
 403                         error = copyout(shmseg, uap->buf, sizeof(inbuf));
 404                 break;
 405         case IPC_SET:
 406                 error = ipcperm(p, &shmseg->shm_perm, IPC_M);
 407                 if (error == 0)
 408                         error = copyin(uap->buf, &inbuf, sizeof(inbuf));
 409                 if (error == 0) {
 410                         shmseg->shm_perm.uid = inbuf.shm_perm.uid;
 411                         shmseg->shm_perm.gid = inbuf.shm_perm.gid;
 412                         shmseg->shm_perm.mode =
 413                             (shmseg->shm_perm.mode & ~ACCESSPERMS) |
 414                             (inbuf.shm_perm.mode & ACCESSPERMS);
 415                         shmseg->shm_ctime = time_second;
 416                 }
 417                 break;
 418         case IPC_RMID:
 419                 error = ipcperm(p, &shmseg->shm_perm, IPC_M);
 420                 if (error == 0) {
 421                         shmseg->shm_perm.key = IPC_PRIVATE;
 422                         shmseg->shm_perm.mode |= SHMSEG_REMOVED;
 423                         if (shmseg->shm_nattch <= 0) {
 424                                 shm_deallocate_segment(shmseg);
 425                                 shm_last_free = IPCID_TO_IX(uap->shmid);
 426                         }
 427                 }
 428                 break;
 429 #if 0
 430         case SHM_LOCK:
 431         case SHM_UNLOCK:
 432 #endif
 433         default:
 434                 error = EINVAL;
 435                 break;
 436         }
 437 done:
 438         lwkt_reltoken(&shm_token);
 439
 440         return error;
 441 }
 442
 443 static int
 444 shmget_existing(struct proc *p, struct shmget_args *uap, int mode, int segnum)
 445 {
 446         struct shmid_ds *shmseg;
 447         int error;
 448
 449         shmseg = &shmsegs[segnum];
 450         if (shmseg->shm_perm.mode & SHMSEG_REMOVED) {
 451                 /*
 452                  * This segment is in the process of being allocated.  Wait
 453                  * until it's done, and look the key up again (in case the
 454                  * allocation failed or it was freed).
 455                  */
 456                 shmseg->shm_perm.mode |= SHMSEG_WANTED;
 457                 error = tsleep((caddr_t)shmseg, PCATCH, "shmget", 0);
 458                 if (error)
 459                         return error;
 460                 return EAGAIN;
 461         }
 462         if ((uap->shmflg & (IPC_CREAT | IPC_EXCL)) == (IPC_CREAT | IPC_EXCL))
 463                 return EEXIST;
 464         error = ipcperm(p, &shmseg->shm_perm, mode);
 465         if (error)
 466                 return error;
 467         if (uap->size && uap->size > shmseg->shm_segsz)
 468                 return EINVAL;
 469         uap->sysmsg_result = IXSEQ_TO_IPCID(segnum, shmseg->shm_perm);
 470         return 0;
 471 }
 472
 473 static int
 474 shmget_allocate_segment(struct proc *p, struct shmget_args *uap, int mode)
 475 {
 476         int i, segnum, shmid;
 477         size_t size;
 478         struct ucred *cred = p->p_ucred;
 479         struct shmid_ds *shmseg;
 480         struct shm_handle *shm_handle;
 481
 482         if (uap->size < shminfo.shmmin || uap->size > shminfo.shmmax)
 483                 return EINVAL;
 484         if (shm_nused >= shminfo.shmmni) /* any shmids left? */
 485                 return ENOSPC;
 486         size = round_page(uap->size);
 487         if (shm_committed + btoc(size) > shminfo.shmall)
 488                 return ENOMEM;
 489         if (shm_last_free < 0) {
 490                 shmrealloc();   /* maybe expand the shmsegs[] array */
 491                 for (i = 0; i < shmalloced; i++) {
 492                         if (shmsegs[i].shm_perm.mode & SHMSEG_FREE)
 493                                 break;
 494                 }
 495                 if (i == shmalloced)
 496                         return ENOSPC;
 497                 segnum = i;
 498         } else  {
 499                 segnum = shm_last_free;
 500                 shm_last_free = -1;
 501         }
 502         shmseg = &shmsegs[segnum];
 503         /*
 504          * In case we sleep in malloc(), mark the segment present but deleted
 505          * so that noone else tries to create the same key.
 506          */
 507         shmseg->shm_perm.mode = SHMSEG_ALLOCATED | SHMSEG_REMOVED;
 508         shmseg->shm_perm.key = uap->key;
 509         shmseg->shm_perm.seq = (shmseg->shm_perm.seq + 1) & 0x7fff;
 510         shm_handle = kmalloc(sizeof(struct shm_handle), M_SHM, M_WAITOK);
 511         shmid = IXSEQ_TO_IPCID(segnum, shmseg->shm_perm);
 512
 513         /*
 514          * We make sure that we have allocated a pager before we need
 515          * to.
 516          */
 517         if (shm_use_phys) {
 518                 shm_handle->shm_object =
 519                    phys_pager_alloc(NULL, size, VM_PROT_DEFAULT, 0);
 520         } else {
 521                 shm_handle->shm_object =
 522                    swap_pager_alloc(NULL, size, VM_PROT_DEFAULT, 0);
 523         }
 524         vm_object_clear_flag(shm_handle->shm_object, OBJ_ONEMAPPING);
 525         vm_object_set_flag(shm_handle->shm_object, OBJ_NOSPLIT);
 526
 527         shmseg->shm_internal = shm_handle;
 528         shmseg->shm_perm.cuid = shmseg->shm_perm.uid = cred->cr_uid;
 529         shmseg->shm_perm.cgid = shmseg->shm_perm.gid = cred->cr_gid;
 530         shmseg->shm_perm.mode = (shmseg->shm_perm.mode & SHMSEG_WANTED) |
 531             (mode & ACCESSPERMS) | SHMSEG_ALLOCATED;
 532         shmseg->shm_segsz = uap->size;
 533         shmseg->shm_cpid = p->p_pid;
 534         shmseg->shm_lpid = shmseg->shm_nattch = 0;
 535         shmseg->shm_atime = shmseg->shm_dtime = 0;
 536         shmseg->shm_ctime = time_second;
 537         shm_committed += btoc(size);
 538         shm_nused++;
 539
 540         /*
 541          * If a physical mapping is desired and we have a ton of free pages
 542          * we pre-allocate the pages here in order to avoid on-the-fly
 543          * allocation later.  This has a big effect on database warm-up
 544          * times since DFly supports concurrent page faults coming from the
 545          * same VM object for pages which already exist.
 546          *
 547          * This can hang the kernel for a while so only do it if shm_use_phys
 548          * is set to 2 or higher.
 549          */
 550         if (shm_use_phys > 1) {
 551                 vm_pindex_t pi, pmax;
 552                 vm_page_t m;
 553
 554                 pmax = round_page(shmseg->shm_segsz) >> PAGE_SHIFT;
 555                 vm_object_hold(shm_handle->shm_object);
 556                 if (pmax > vmstats.v_free_count)
 557                         pmax = vmstats.v_free_count;
 558                 for (pi = 0; pi < pmax; ++pi) {
 559                         m = vm_page_grab(shm_handle->shm_object, pi,
 560                                          VM_ALLOC_SYSTEM | VM_ALLOC_NULL_OK |
 561                                          VM_ALLOC_ZERO);
 562                         if (m == NULL)
 563                                 break;
 564                         vm_pager_get_page(shm_handle->shm_object, &m, 1);
 565                         vm_page_activate(m);
 566                         vm_page_wakeup(m);
 567                         lwkt_yield();
 568                 }
 569                 vm_object_drop(shm_handle->shm_object);
 570         }
 571
 572         if (shmseg->shm_perm.mode & SHMSEG_WANTED) {
 573                 /*
 574                  * Somebody else wanted this key while we were asleep.  Wake
 575                  * them up now.
 576                  */
 577                 shmseg->shm_perm.mode &= ~SHMSEG_WANTED;
 578                 wakeup((caddr_t)shmseg);
 579         }
 580         uap->sysmsg_result = shmid;
 581         return 0;
 582 }
 583
 584 /*
 585  * MPALMOSTSAFE
 586  */
 587 int
 588 sys_shmget(struct shmget_args *uap)
 589 {
 590         struct thread *td = curthread;
 591         struct proc *p = td->td_proc;
 592         int segnum, mode, error;
 593
 594         if (!jail_sysvipc_allowed && td->td_ucred->cr_prison != NULL)
 595                 return (ENOSYS);
 596
 597         mode = uap->shmflg & ACCESSPERMS;
 598
 599         lwkt_gettoken(&shm_token);
 600
 601         if (uap->key != IPC_PRIVATE) {
 602         again:
 603                 segnum = shm_find_segment_by_key(uap->key);
 604                 if (segnum >= 0) {
 605                         error = shmget_existing(p, uap, mode, segnum);
 606                         if (error == EAGAIN)
 607                                 goto again;
 608                         goto done;
 609                 }
 610                 if ((uap->shmflg & IPC_CREAT) == 0) {
 611                         error = ENOENT;
 612                         goto done;
 613                 }
 614         }
 615         error = shmget_allocate_segment(p, uap, mode);
 616 done:
 617         lwkt_reltoken(&shm_token);
 618
 619         return (error);
 620 }
 621
 622 void
 623 shmfork(struct proc *p1, struct proc *p2)
 624 {
 625         struct shmmap_state *shmmap_s;
 626         size_t size;
 627         int i;
 628
 629         lwkt_gettoken(&shm_token);
 630         size = shminfo.shmseg * sizeof(struct shmmap_state);
 631         shmmap_s = kmalloc(size, M_SHM, M_WAITOK);
 632         bcopy((caddr_t)p1->p_vmspace->vm_shm, (caddr_t)shmmap_s, size);
 633         p2->p_vmspace->vm_shm = (caddr_t)shmmap_s;
 634         for (i = 0; i < shminfo.shmseg; i++, shmmap_s++) {
 635                 if (shmmap_s->shmid != -1)
 636                         shmsegs[IPCID_TO_IX(shmmap_s->shmid)].shm_nattch++;
 637         }
 638         lwkt_reltoken(&shm_token);
 639 }
 640
 641 void
 642 shmexit(struct vmspace *vm)
 643 {
 644         struct shmmap_state *base, *shm;
 645         int i;
 646
 647         if ((base = (struct shmmap_state *)vm->vm_shm) != NULL) {
 648                 vm->vm_shm = NULL;
 649                 lwkt_gettoken(&shm_token);
 650                 for (i = 0, shm = base; i < shminfo.shmseg; i++, shm++) {
 651                         if (shm->shmid != -1)
 652                                 shm_delete_mapping(vm, shm);
 653                 }
 654                 kfree(base, M_SHM);
 655                 lwkt_reltoken(&shm_token);
 656         }
 657 }
 658
 659 static void
 660 shmrealloc(void)
 661 {
 662         int i;
 663         struct shmid_ds *newsegs;
 664
 665         if (shmalloced >= shminfo.shmmni)
 666                 return;
 667
 668         newsegs = kmalloc(shminfo.shmmni * sizeof(*newsegs), M_SHM, M_WAITOK);
 669         for (i = 0; i < shmalloced; i++)
 670                 bcopy(&shmsegs[i], &newsegs[i], sizeof(newsegs[0]));
 671         for (; i < shminfo.shmmni; i++) {
 672                 shmsegs[i].shm_perm.mode = SHMSEG_FREE;
 673                 shmsegs[i].shm_perm.seq = 0;
 674         }
 675         kfree(shmsegs, M_SHM);
 676         shmsegs = newsegs;
 677         shmalloced = shminfo.shmmni;
 678 }
 679
 680 static void
 681 shminit(void *dummy)
 682 {
 683         int i;
 684
 685         /*
 686          * If not overridden by a tunable set the maximum shm to
 687          * 2/3 of main memory.
 688          */
 689         if (shminfo.shmall == 0)
 690                 shminfo.shmall = (size_t)vmstats.v_page_count * 2 / 3;
 691
 692         shminfo.shmmax = shminfo.shmall * PAGE_SIZE;
 693         shmalloced = shminfo.shmmni;
 694         shmsegs = kmalloc(shmalloced * sizeof(shmsegs[0]), M_SHM, M_WAITOK);
 695         for (i = 0; i < shmalloced; i++) {
 696                 shmsegs[i].shm_perm.mode = SHMSEG_FREE;
 697                 shmsegs[i].shm_perm.seq = 0;
 698         }
 699         shm_last_free = 0;
 700         shm_nused = 0;
 701         shm_committed = 0;
 702 }
 703 SYSINIT(sysv_shm, SI_SUB_SYSV_SHM, SI_ORDER_FIRST, shminit, NULL);