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/sysmsg.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 sysmsg *sysmsg,
  58                         const struct shmget_args *uap, int mode);
  59 static int shmget_existing(struct proc *p, struct sysmsg *sysmsg,
  60                         const struct shmget_args *uap, int mode, int segnum);
  61
  62 #define SHMSEG_FREE             0x0200
  63 #define SHMSEG_REMOVED          0x0400
  64 #define SHMSEG_ALLOCATED        0x0800
  65 #define SHMSEG_WANTED           0x1000
  66
  67 static int shm_last_free, shm_committed, shmalloced;
  68 int shm_nused;
  69 static struct shmid_ds  *shmsegs;
  70 static struct lwkt_token shm_token = LWKT_TOKEN_INITIALIZER(shm_token);
  71
  72 struct shm_handle {
  73         /* vm_offset_t kva; */
  74         vm_object_t shm_object;
  75 };
  76
  77 struct shmmap_state {
  78         vm_offset_t va;
  79         int shmid;
  80         int reserved;
  81 };
  82
  83 static void shm_deallocate_segment (struct shmid_ds *);
  84 static int shm_find_segment_by_key (key_t);
  85 static struct shmid_ds *shm_find_segment_by_shmid (int);
  86 static int shm_delete_mapping (struct vmspace *vm, struct shmmap_state *);
  87 static void shmrealloc (void);
  88 static void shminit (void *);
  89
  90 /*
  91  * Tuneable values
  92  */
  93 #ifndef SHMMIN
  94 #define SHMMIN  1
  95 #endif
  96 #ifndef SHMMNI
  97 #define SHMMNI  512
  98 #endif
  99 #ifndef SHMSEG
 100 #define SHMSEG  1024
 101 #endif
 102
 103 struct  shminfo shminfo = {
 104         0,
 105         SHMMIN,
 106         SHMMNI,
 107         SHMSEG,
 108         0
 109 };
 110
 111 /*
 112  * allow-removed    Allow a shared memory segment to be attached by its shmid
 113  *                  even after it has been deleted, as long as it was still
 114  *                  being referenced by someone.  This is a trick used by
 115  *                  chrome and other applications to avoid leaving shm
 116  *                  segments hanging around after the application is killed
 117  *                  or seg-faults unexpectedly.
 118  *
 119  * use-phys         Shared memory segments are to use physical memory by
 120  *                  default, which may allow the kernel to better-optimize
 121  *                  the pmap and reduce overhead.  The pages are effectively
 122  *                  wired.
 123  */
 124 static int shm_allow_removed = 1;
 125 static int shm_use_phys = 1;
 126
 127 TUNABLE_LONG("kern.ipc.shmmin", &shminfo.shmmin);
 128 TUNABLE_LONG("kern.ipc.shmmni", &shminfo.shmmni);
 129 TUNABLE_LONG("kern.ipc.shmseg", &shminfo.shmseg);
 130 TUNABLE_LONG("kern.ipc.shmmaxpgs", &shminfo.shmall);
 131 TUNABLE_INT("kern.ipc.shm_use_phys", &shm_use_phys);
 132
 133 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmmax, CTLFLAG_RW, &shminfo.shmmax, 0,
 134     "Max shared memory segment size");
 135 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmmin, CTLFLAG_RW, &shminfo.shmmin, 0,
 136     "Min shared memory segment size");
 137 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmmni, CTLFLAG_RD, &shminfo.shmmni, 0,
 138     "Max number of shared memory identifiers");
 139 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmseg, CTLFLAG_RW, &shminfo.shmseg, 0,
 140     "Max shared memory segments per process");
 141 SYSCTL_LONG(_kern_ipc, OID_AUTO, shmall, CTLFLAG_RW, &shminfo.shmall, 0,
 142     "Max pages of shared memory");
 143 SYSCTL_INT(_kern_ipc, OID_AUTO, shm_use_phys, CTLFLAG_RW, &shm_use_phys, 0,
 144     "Use phys pager allocation instead of swap pager allocation");
 145 SYSCTL_INT(_kern_ipc, OID_AUTO, shm_allow_removed, CTLFLAG_RW,
 146     &shm_allow_removed, 0,
 147     "Enable/Disable attachment to attached segments marked for removal");
 148
 149 static int
 150 shm_find_segment_by_key(key_t key)
 151 {
 152         int i;
 153
 154         for (i = 0; i < shmalloced; i++) {
 155                 if ((shmsegs[i].shm_perm.mode & SHMSEG_ALLOCATED) &&
 156                     shmsegs[i].shm_perm.key == key)
 157                         return i;
 158         }
 159         return -1;
 160 }
 161
 162 static struct shmid_ds *
 163 shm_find_segment_by_shmid(int shmid)
 164 {
 165         int segnum;
 166         struct shmid_ds *shmseg;
 167
 168         segnum = IPCID_TO_IX(shmid);
 169         if (segnum < 0 || segnum >= shmalloced)
 170                 return NULL;
 171         shmseg = &shmsegs[segnum];
 172         if ((shmseg->shm_perm.mode & SHMSEG_ALLOCATED) == 0 ||
 173             (!shm_allow_removed &&
 174             (shmseg->shm_perm.mode & SHMSEG_REMOVED) != 0) ||
 175             shmseg->shm_perm.seq != IPCID_TO_SEQ(shmid)) {
 176                 return NULL;
 177         }
 178         return shmseg;
 179 }
 180
 181 static void
 182 shm_deallocate_segment(struct shmid_ds *shmseg)
 183 {
 184         struct shm_handle *shm_handle;
 185         size_t size;
 186
 187         shm_handle = shmseg->shm_internal;
 188         vm_object_deallocate(shm_handle->shm_object);
 189         kfree((caddr_t)shm_handle, M_SHM);
 190         shmseg->shm_internal = NULL;
 191         size = round_page(shmseg->shm_segsz);
 192         shm_committed -= btoc(size);
 193         shm_nused--;
 194         shmseg->shm_perm.mode = SHMSEG_FREE;
 195 }
 196
 197 static int
 198 shm_delete_mapping(struct vmspace *vm, struct shmmap_state *shmmap_s)
 199 {
 200         struct shmid_ds *shmseg;
 201         int segnum, result;
 202         size_t size;
 203
 204         segnum = IPCID_TO_IX(shmmap_s->shmid);
 205         shmseg = &shmsegs[segnum];
 206         size = round_page(shmseg->shm_segsz);
 207         result = vm_map_remove(&vm->vm_map, shmmap_s->va, shmmap_s->va + size);
 208         if (result != KERN_SUCCESS)
 209                 return EINVAL;
 210         shmmap_s->shmid = -1;
 211         shmseg->shm_dtime = time_second;
 212         if ((--shmseg->shm_nattch <= 0) &&
 213             (shmseg->shm_perm.mode & SHMSEG_REMOVED)) {
 214                 shm_deallocate_segment(shmseg);
 215                 shm_last_free = segnum;
 216         }
 217         return 0;
 218 }
 219
 220 /*
 221  * MPALMOSTSAFE
 222  */
 223 int
 224 sys_shmdt(struct sysmsg *sysmsg, const struct shmdt_args *uap)
 225 {
 226         struct thread *td = curthread;
 227         struct proc *p = td->td_proc;
 228         struct shmmap_state *shmmap_s;
 229         struct prison *pr = p->p_ucred->cr_prison;
 230
 231         long i;
 232         int error;
 233
 234         if (pr && !PRISON_CAP_ISSET(pr->pr_caps, PRISON_CAP_SYS_SYSVIPC))
 235                 return (ENOSYS);
 236
 237         lwkt_gettoken(&shm_token);
 238         shmmap_s = (struct shmmap_state *)p->p_vmspace->vm_shm;
 239         if (shmmap_s == NULL) {
 240                 error = EINVAL;
 241                 goto done;
 242         }
 243         for (i = 0; i < shminfo.shmseg; i++, shmmap_s++) {
 244                 if (shmmap_s->shmid != -1 &&
 245                     shmmap_s->va == (vm_offset_t)uap->shmaddr)
 246                         break;
 247         }
 248         if (i == shminfo.shmseg)
 249                 error = EINVAL;
 250         else
 251                 error = shm_delete_mapping(p->p_vmspace, shmmap_s);
 252 done:
 253         lwkt_reltoken(&shm_token);
 254
 255         return (error);
 256 }
 257
 258 /*
 259  * MPALMOSTSAFE
 260  */
 261 int
 262 sys_shmat(struct sysmsg *sysmsg, const struct shmat_args *uap)
 263 {
 264         struct thread *td = curthread;
 265         struct proc *p = td->td_proc;
 266         struct prison *pr = p->p_ucred->cr_prison;
 267         int error, flags;
 268         long i;
 269         struct shmid_ds *shmseg;
 270         struct shmmap_state *shmmap_s = NULL;
 271         struct shm_handle *shm_handle;
 272         vm_offset_t attach_va;
 273         vm_prot_t prot;
 274         vm_size_t size;
 275         vm_size_t align;
 276         int rv;
 277
 278         if (pr && !PRISON_CAP_ISSET(pr->pr_caps, PRISON_CAP_SYS_SYSVIPC))
 279                 return (ENOSYS);
 280
 281         lwkt_gettoken(&shm_token);
 282 again:
 283         shmmap_s = (struct shmmap_state *)p->p_vmspace->vm_shm;
 284         if (shmmap_s == NULL) {
 285                 size = shminfo.shmseg * sizeof(struct shmmap_state);
 286                 shmmap_s = kmalloc(size, M_SHM, M_WAITOK);
 287                 for (i = 0; i < shminfo.shmseg; i++) {
 288                         shmmap_s[i].shmid = -1;
 289                         shmmap_s[i].reserved = 0;
 290                 }
 291                 if (p->p_vmspace->vm_shm != NULL) {
 292                         kfree(shmmap_s, M_SHM);
 293                         goto again;
 294                 }
 295                 p->p_vmspace->vm_shm = (caddr_t)shmmap_s;
 296         }
 297         shmseg = shm_find_segment_by_shmid(uap->shmid);
 298         if (shmseg == NULL) {
 299                 error = EINVAL;
 300                 goto done;
 301         }
 302         error = ipcperm(p, &shmseg->shm_perm,
 303                         (uap->shmflg & SHM_RDONLY) ? IPC_R : IPC_R|IPC_W);
 304         if (error)
 305                 goto done;
 306
 307         /*
 308          * Find a free element and mark reserved.  This fixes races
 309          * against concurrent allocations due to the token being
 310          * interrupted by blocking operations.  The shmmap_s reservation
 311          * will be cleared upon completion or error.
 312          */
 313         for (i = 0; i < shminfo.shmseg; i++) {
 314                 if (shmmap_s->shmid == -1 && shmmap_s->reserved == 0) {
 315                         shmmap_s->reserved = 1;
 316                         break;
 317                 }
 318                 shmmap_s++;
 319         }
 320         if (i >= shminfo.shmseg) {
 321                 error = EMFILE;
 322                 goto done;
 323         }
 324         size = round_page(shmseg->shm_segsz);
 325 #ifdef VM_PROT_READ_IS_EXEC
 326         prot = VM_PROT_READ | VM_PROT_EXECUTE;
 327 #else
 328         prot = VM_PROT_READ;
 329 #endif
 330         if ((uap->shmflg & SHM_RDONLY) == 0)
 331                 prot |= VM_PROT_WRITE;
 332         flags = MAP_ANON | MAP_SHARED;
 333         if (uap->shmaddr) {
 334                 flags |= MAP_FIXED;
 335                 if (uap->shmflg & SHM_RND) {
 336                         attach_va =
 337                             rounddown2((vm_offset_t)uap->shmaddr, SHMLBA);
 338                 } else if (((vm_offset_t)uap->shmaddr & (SHMLBA-1)) == 0) {
 339                         attach_va = (vm_offset_t)uap->shmaddr;
 340                 } else {
 341                         error = EINVAL;
 342                         shmmap_s->reserved = 0;
 343                         goto done;
 344                 }
 345         } else {
 346                 /*
 347                  * This is just a hint to vm_map_find() about where to put it.
 348                  */
 349                 attach_va = round_page((vm_offset_t)p->p_vmspace->vm_taddr +
 350                                        maxtsiz + maxdsiz);
 351         }
 352
 353         /*
 354          * Handle alignment.  For large memory maps it is possible
 355          * that the MMU can optimize the page table so align anything
 356          * that is a multiple of SEG_SIZE to SEG_SIZE.
 357          */
 358         if ((flags & MAP_FIXED) == 0 && (size & SEG_MASK) == 0)
 359                 align = SEG_SIZE;
 360         else
 361                 align = PAGE_SIZE;
 362
 363         shm_handle = shmseg->shm_internal;
 364         vm_object_hold(shm_handle->shm_object);
 365         vm_object_reference_locked(shm_handle->shm_object);
 366         rv = vm_map_find(&p->p_vmspace->vm_map,
 367                          shm_handle->shm_object, NULL,
 368                          0, &attach_va, size,
 369                          align,
 370                          ((flags & MAP_FIXED) ? 0 : 1),
 371                          VM_MAPTYPE_NORMAL, VM_SUBSYS_SHMEM,
 372                          prot, prot, 0);
 373         vm_object_drop(shm_handle->shm_object);
 374         if (rv != KERN_SUCCESS) {
 375                 vm_object_deallocate(shm_handle->shm_object);
 376                 shmmap_s->reserved = 0;
 377                 error = ENOMEM;
 378                 goto done;
 379         }
 380         vm_map_inherit(&p->p_vmspace->vm_map,
 381                        attach_va, attach_va + size, VM_INHERIT_SHARE);
 382
 383         KKASSERT(shmmap_s->shmid == -1);
 384         shmmap_s->va = attach_va;
 385         shmmap_s->shmid = uap->shmid;
 386         shmmap_s->reserved = 0;
 387         shmseg->shm_lpid = p->p_pid;
 388         shmseg->shm_atime = time_second;
 389         shmseg->shm_nattch++;
 390         sysmsg->sysmsg_resultp = (void *)attach_va;
 391         error = 0;
 392 done:
 393         lwkt_reltoken(&shm_token);
 394
 395         return error;
 396 }
 397
 398 /*
 399  * MPALMOSTSAFE
 400  */
 401 int
 402 sys_shmctl(struct sysmsg *sysmsg, const struct shmctl_args *uap)
 403 {
 404         struct thread *td = curthread;
 405         struct proc *p = td->td_proc;
 406         struct prison *pr = p->p_ucred->cr_prison;
 407         int error;
 408         struct shmid_ds inbuf;
 409         struct shmid_ds *shmseg;
 410
 411         if (pr && !PRISON_CAP_ISSET(pr->pr_caps, PRISON_CAP_SYS_SYSVIPC))
 412                 return (ENOSYS);
 413
 414         lwkt_gettoken(&shm_token);
 415         shmseg = shm_find_segment_by_shmid(uap->shmid);
 416         if (shmseg == NULL) {
 417                 error = EINVAL;
 418                 goto done;
 419         }
 420
 421         switch (uap->cmd) {
 422         case IPC_STAT:
 423                 error = ipcperm(p, &shmseg->shm_perm, IPC_R);
 424                 if (error == 0)
 425                         error = copyout(shmseg, uap->buf, sizeof(inbuf));
 426                 break;
 427         case IPC_SET:
 428                 error = ipcperm(p, &shmseg->shm_perm, IPC_M);
 429                 if (error == 0)
 430                         error = copyin(uap->buf, &inbuf, sizeof(inbuf));
 431                 if (error == 0) {
 432                         shmseg->shm_perm.uid = inbuf.shm_perm.uid;
 433                         shmseg->shm_perm.gid = inbuf.shm_perm.gid;
 434                         shmseg->shm_perm.mode =
 435                             (shmseg->shm_perm.mode & ~ACCESSPERMS) |
 436                             (inbuf.shm_perm.mode & ACCESSPERMS);
 437                         shmseg->shm_ctime = time_second;
 438                 }
 439                 break;
 440         case IPC_RMID:
 441                 error = ipcperm(p, &shmseg->shm_perm, IPC_M);
 442                 if (error == 0) {
 443                         shmseg->shm_perm.key = IPC_PRIVATE;
 444                         shmseg->shm_perm.mode |= SHMSEG_REMOVED;
 445                         if (shmseg->shm_nattch <= 0) {
 446                                 shm_deallocate_segment(shmseg);
 447                                 shm_last_free = IPCID_TO_IX(uap->shmid);
 448                         }
 449                 }
 450                 break;
 451 #if 0
 452         case SHM_LOCK:
 453         case SHM_UNLOCK:
 454 #endif
 455         default:
 456                 error = EINVAL;
 457                 break;
 458         }
 459 done:
 460         lwkt_reltoken(&shm_token);
 461
 462         return error;
 463 }
 464
 465 static int
 466 shmget_existing(struct proc *p, struct sysmsg *sysmsg,
 467                 const struct shmget_args *uap, int mode, int segnum)
 468 {
 469         struct shmid_ds *shmseg;
 470         int error;
 471
 472         shmseg = &shmsegs[segnum];
 473         if (shmseg->shm_perm.mode & SHMSEG_REMOVED) {
 474                 /*
 475                  * This segment is in the process of being allocated.  Wait
 476                  * until it's done, and look the key up again (in case the
 477                  * allocation failed or it was freed).
 478                  */
 479                 shmseg->shm_perm.mode |= SHMSEG_WANTED;
 480                 error = tsleep((caddr_t)shmseg, PCATCH, "shmget", 0);
 481                 if (error)
 482                         return error;
 483                 return EAGAIN;
 484         }
 485         if ((uap->shmflg & (IPC_CREAT | IPC_EXCL)) == (IPC_CREAT | IPC_EXCL))
 486                 return EEXIST;
 487         error = ipcperm(p, &shmseg->shm_perm, mode);
 488         if (error)
 489                 return error;
 490         if (uap->size && uap->size > shmseg->shm_segsz)
 491                 return EINVAL;
 492         sysmsg->sysmsg_result = IXSEQ_TO_IPCID(segnum, shmseg->shm_perm);
 493         return 0;
 494 }
 495
 496 static int
 497 shmget_allocate_segment(struct proc *p, struct sysmsg *sysmsg,
 498                         const struct shmget_args *uap, int mode)
 499 {
 500         int i, segnum, shmid;
 501         size_t size;
 502         struct ucred *cred = p->p_ucred;
 503         struct shmid_ds *shmseg;
 504         struct shm_handle *shm_handle;
 505
 506         if (uap->size < shminfo.shmmin || uap->size > shminfo.shmmax)
 507                 return EINVAL;
 508         if (shm_nused >= shminfo.shmmni) /* any shmids left? */
 509                 return ENOSPC;
 510         size = round_page(uap->size);
 511         if (shm_committed + btoc(size) > shminfo.shmall)
 512                 return ENOMEM;
 513         if (shm_last_free < 0) {
 514                 shmrealloc();   /* maybe expand the shmsegs[] array */
 515                 for (i = 0; i < shmalloced; i++) {
 516                         if (shmsegs[i].shm_perm.mode & SHMSEG_FREE)
 517                                 break;
 518                 }
 519                 if (i == shmalloced)
 520                         return ENOSPC;
 521                 segnum = i;
 522         } else  {
 523                 segnum = shm_last_free;
 524                 shm_last_free = -1;
 525         }
 526         shmseg = &shmsegs[segnum];
 527         /*
 528          * In case we sleep in malloc(), mark the segment present but deleted
 529          * so that noone else tries to create the same key.
 530          */
 531         shmseg->shm_perm.mode = SHMSEG_ALLOCATED | SHMSEG_REMOVED;
 532         shmseg->shm_perm.key = uap->key;
 533         shmseg->shm_perm.seq = (shmseg->shm_perm.seq + 1) & 0x7fff;
 534         shm_handle = kmalloc(sizeof(struct shm_handle), M_SHM, M_WAITOK);
 535         shmid = IXSEQ_TO_IPCID(segnum, shmseg->shm_perm);
 536
 537         /*
 538          * We make sure that we have allocated a pager before we need
 539          * to.
 540          */
 541         if (shm_use_phys) {
 542                 shm_handle->shm_object =
 543                    phys_pager_alloc(NULL, size, VM_PROT_DEFAULT, 0);
 544         } else {
 545                 shm_handle->shm_object =
 546                    swap_pager_alloc(NULL, size, VM_PROT_DEFAULT, 0);
 547         }
 548         vm_object_clear_flag(shm_handle->shm_object, OBJ_ONEMAPPING);
 549         vm_object_set_flag(shm_handle->shm_object, OBJ_NOSPLIT);
 550
 551         shmseg->shm_internal = shm_handle;
 552         shmseg->shm_perm.cuid = shmseg->shm_perm.uid = cred->cr_uid;
 553         shmseg->shm_perm.cgid = shmseg->shm_perm.gid = cred->cr_gid;
 554         shmseg->shm_perm.mode = (shmseg->shm_perm.mode & SHMSEG_WANTED) |
 555             (mode & ACCESSPERMS) | SHMSEG_ALLOCATED;
 556         shmseg->shm_segsz = uap->size;
 557         shmseg->shm_cpid = p->p_pid;
 558         shmseg->shm_lpid = shmseg->shm_nattch = 0;
 559         shmseg->shm_atime = shmseg->shm_dtime = 0;
 560         shmseg->shm_ctime = time_second;
 561         shm_committed += btoc(size);
 562         shm_nused++;
 563
 564         /*
 565          * If a physical mapping is desired and we have a ton of free pages
 566          * we pre-allocate the pages here in order to avoid on-the-fly
 567          * allocation later.  This has a big effect on database warm-up
 568          * times since DFly supports concurrent page faults coming from the
 569          * same VM object for pages which already exist.
 570          *
 571          * This can hang the kernel for a while so only do it if shm_use_phys
 572          * is set to 2 or higher.
 573          */
 574         if (shm_use_phys > 1) {
 575                 vm_pindex_t pi, pmax;
 576                 vm_page_t m;
 577
 578                 pmax = round_page(shmseg->shm_segsz) >> PAGE_SHIFT;
 579                 vm_object_hold(shm_handle->shm_object);
 580                 if (pmax > vmstats.v_free_count)
 581                         pmax = vmstats.v_free_count;
 582                 for (pi = 0; pi < pmax; ++pi) {
 583                         m = vm_page_grab(shm_handle->shm_object, pi,
 584                                          VM_ALLOC_SYSTEM | VM_ALLOC_NULL_OK |
 585                                          VM_ALLOC_ZERO);
 586                         if (m == NULL)
 587                                 break;
 588                         vm_pager_get_page(shm_handle->shm_object, pi, &m, 1);
 589                         vm_page_activate(m);
 590                         vm_page_wakeup(m);
 591                         lwkt_yield();
 592                 }
 593                 vm_object_drop(shm_handle->shm_object);
 594         }
 595
 596         if (shmseg->shm_perm.mode & SHMSEG_WANTED) {
 597                 /*
 598                  * Somebody else wanted this key while we were asleep.  Wake
 599                  * them up now.
 600                  */
 601                 shmseg->shm_perm.mode &= ~SHMSEG_WANTED;
 602                 wakeup((caddr_t)shmseg);
 603         }
 604         sysmsg->sysmsg_result = shmid;
 605         return 0;
 606 }
 607
 608 /*
 609  * MPALMOSTSAFE
 610  */
 611 int
 612 sys_shmget(struct sysmsg *sysmsg, const struct shmget_args *uap)
 613 {
 614         struct thread *td = curthread;
 615         struct proc *p = td->td_proc;
 616         struct prison *pr = p->p_ucred->cr_prison;
 617         int segnum, mode, error;
 618
 619         if (pr && !PRISON_CAP_ISSET(pr->pr_caps, PRISON_CAP_SYS_SYSVIPC))
 620                 return (ENOSYS);
 621
 622         mode = uap->shmflg & ACCESSPERMS;
 623
 624         lwkt_gettoken(&shm_token);
 625
 626         if (uap->key != IPC_PRIVATE) {
 627         again:
 628                 segnum = shm_find_segment_by_key(uap->key);
 629                 if (segnum >= 0) {
 630                         error = shmget_existing(p, sysmsg, uap, mode, segnum);
 631                         if (error == EAGAIN)
 632                                 goto again;
 633                         goto done;
 634                 }
 635                 if ((uap->shmflg & IPC_CREAT) == 0) {
 636                         error = ENOENT;
 637                         goto done;
 638                 }
 639         }
 640         error = shmget_allocate_segment(p, sysmsg, uap, mode);
 641 done:
 642         lwkt_reltoken(&shm_token);
 643
 644         return (error);
 645 }
 646
 647 void
 648 shmfork(struct proc *p1, struct proc *p2)
 649 {
 650         struct shmmap_state *shmmap_s;
 651         size_t size;
 652         int i;
 653
 654         lwkt_gettoken(&shm_token);
 655         size = shminfo.shmseg * sizeof(struct shmmap_state);
 656         shmmap_s = kmalloc(size, M_SHM, M_WAITOK);
 657         bcopy((caddr_t)p1->p_vmspace->vm_shm, (caddr_t)shmmap_s, size);
 658         p2->p_vmspace->vm_shm = (caddr_t)shmmap_s;
 659         for (i = 0; i < shminfo.shmseg; i++, shmmap_s++) {
 660                 if (shmmap_s->shmid != -1)
 661                         shmsegs[IPCID_TO_IX(shmmap_s->shmid)].shm_nattch++;
 662         }
 663         lwkt_reltoken(&shm_token);
 664 }
 665
 666 void
 667 shmexit(struct vmspace *vm)
 668 {
 669         struct shmmap_state *base, *shm;
 670         int i;
 671
 672         if ((base = (struct shmmap_state *)vm->vm_shm) != NULL) {
 673                 vm->vm_shm = NULL;
 674                 lwkt_gettoken(&shm_token);
 675                 for (i = 0, shm = base; i < shminfo.shmseg; i++, shm++) {
 676                         if (shm->shmid != -1)
 677                                 shm_delete_mapping(vm, shm);
 678                 }
 679                 kfree(base, M_SHM);
 680                 lwkt_reltoken(&shm_token);
 681         }
 682 }
 683
 684 static void
 685 shmrealloc(void)
 686 {
 687         int i;
 688         struct shmid_ds *newsegs;
 689
 690         if (shmalloced >= shminfo.shmmni)
 691                 return;
 692
 693         newsegs = kmalloc(shminfo.shmmni * sizeof(*newsegs), M_SHM, M_WAITOK);
 694         for (i = 0; i < shmalloced; i++)
 695                 bcopy(&shmsegs[i], &newsegs[i], sizeof(newsegs[0]));
 696         for (; i < shminfo.shmmni; i++) {
 697                 shmsegs[i].shm_perm.mode = SHMSEG_FREE;
 698                 shmsegs[i].shm_perm.seq = 0;
 699         }
 700         kfree(shmsegs, M_SHM);
 701         shmsegs = newsegs;
 702         shmalloced = shminfo.shmmni;
 703 }
 704
 705 static void
 706 shminit(void *dummy)
 707 {
 708         int i;
 709
 710         /*
 711          * If not overridden by a tunable set the maximum shm to
 712          * 2/3 of main memory.
 713          */
 714         if (shminfo.shmall == 0)
 715                 shminfo.shmall = (size_t)vmstats.v_page_count * 2 / 3;
 716
 717         shminfo.shmmax = shminfo.shmall * PAGE_SIZE;
 718         shmalloced = shminfo.shmmni;
 719         shmsegs = kmalloc(shmalloced * sizeof(shmsegs[0]), M_SHM, M_WAITOK);
 720         for (i = 0; i < shmalloced; i++) {
 721                 shmsegs[i].shm_perm.mode = SHMSEG_FREE;
 722                 shmsegs[i].shm_perm.seq = 0;
 723         }
 724         shm_last_free = 0;
 725         shm_nused = 0;
 726         shm_committed = 0;
 727 }
 728 SYSINIT(sysv_shm, SI_SUB_SYSV_SHM, SI_ORDER_FIRST, shminit, NULL);