1 /*- 2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU) 3 * 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 1994 John S. Dyson 7 * All rights reserved. 8 * Copyright (c) 1994 David Greenman 9 * All rights reserved. 10 * 11 * 12 * This code is derived from software contributed to Berkeley by 13 * The Mach Operating System project at Carnegie-Mellon University. 14 * 15 * Redistribution and use in source and binary forms, with or without 16 * modification, are permitted provided that the following conditions 17 * are met: 18 * 1. Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 2. Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in the 22 * documentation and/or other materials provided with the distribution. 23 * 3. All advertising materials mentioning features or use of this software 24 * must display the following acknowledgement: 25 * This product includes software developed by the University of 26 * California, Berkeley and its contributors. 27 * 4. Neither the name of the University nor the names of its contributors 28 * may be used to endorse or promote products derived from this software 29 * without specific prior written permission. 30 * 31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 41 * SUCH DAMAGE. 42 * 43 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 44 * 45 * 46 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 47 * All rights reserved. 48 * 49 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 50 * 51 * Permission to use, copy, modify and distribute this software and 52 * its documentation is hereby granted, provided that both the copyright 53 * notice and this permission notice appear in all copies of the 54 * software, derivative works or modified versions, and any portions 55 * thereof, and that both notices appear in supporting documentation. 56 * 57 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 58 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 59 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 60 * 61 * Carnegie Mellon requests users of this software to return to 62 * 63 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 64 * School of Computer Science 65 * Carnegie Mellon University 66 * Pittsburgh PA 15213-3890 67 * 68 * any improvements or extensions that they make and grant Carnegie the 69 * rights to redistribute these changes. 70 */ 71 72 /* 73 * Page fault handling module. 74 */ 75 76 #include <sys/cdefs.h> 77 __FBSDID("$FreeBSD$"); 78 79 #include "opt_ktrace.h" 80 #include "opt_vm.h" 81 82 #include <sys/param.h> 83 #include <sys/systm.h> 84 #include <sys/kernel.h> 85 #include <sys/lock.h> 86 #include <sys/mman.h> 87 #include <sys/mutex.h> 88 #include <sys/proc.h> 89 #include <sys/racct.h> 90 #include <sys/refcount.h> 91 #include <sys/resourcevar.h> 92 #include <sys/rwlock.h> 93 #include <sys/signalvar.h> 94 #include <sys/sysctl.h> 95 #include <sys/sysent.h> 96 #include <sys/vmmeter.h> 97 #include <sys/vnode.h> 98 #ifdef KTRACE 99 #include <sys/ktrace.h> 100 #endif 101 102 #include <vm/vm.h> 103 #include <vm/vm_param.h> 104 #include <vm/pmap.h> 105 #include <vm/vm_map.h> 106 #include <vm/vm_object.h> 107 #include <vm/vm_page.h> 108 #include <vm/vm_pageout.h> 109 #include <vm/vm_kern.h> 110 #include <vm/vm_pager.h> 111 #include <vm/vm_extern.h> 112 #include <vm/vm_reserv.h> 113 114 #define PFBAK 4 115 #define PFFOR 4 116 117 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT) 118 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 119 120 #define VM_FAULT_DONTNEED_MIN 1048576 121 122 struct faultstate { 123 vm_page_t m; 124 vm_object_t object; 125 vm_pindex_t pindex; 126 vm_page_t first_m; 127 vm_object_t first_object; 128 vm_pindex_t first_pindex; 129 vm_map_t map; 130 vm_map_entry_t entry; 131 int map_generation; 132 bool lookup_still_valid; 133 struct vnode *vp; 134 }; 135 136 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 137 int ahead); 138 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 139 int backward, int forward, bool obj_locked); 140 141 static int vm_pfault_oom_attempts = 3; 142 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_attempts, CTLFLAG_RWTUN, 143 &vm_pfault_oom_attempts, 0, 144 "Number of page allocation attempts in page fault handler before it " 145 "triggers OOM handling"); 146 147 static int vm_pfault_oom_wait = 10; 148 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_wait, CTLFLAG_RWTUN, 149 &vm_pfault_oom_wait, 0, 150 "Number of seconds to wait for free pages before retrying " 151 "the page fault handler"); 152 153 static inline void 154 release_page(struct faultstate *fs) 155 { 156 157 if (fs->m != NULL) { 158 vm_page_xunbusy(fs->m); 159 vm_page_lock(fs->m); 160 vm_page_deactivate(fs->m); 161 vm_page_unlock(fs->m); 162 fs->m = NULL; 163 } 164 } 165 166 static inline void 167 unlock_map(struct faultstate *fs) 168 { 169 170 if (fs->lookup_still_valid) { 171 vm_map_lookup_done(fs->map, fs->entry); 172 fs->lookup_still_valid = false; 173 } 174 } 175 176 static void 177 unlock_vp(struct faultstate *fs) 178 { 179 180 if (fs->vp != NULL) { 181 vput(fs->vp); 182 fs->vp = NULL; 183 } 184 } 185 186 static void 187 fault_deallocate(struct faultstate *fs) 188 { 189 190 vm_object_pip_wakeup(fs->object); 191 if (fs->object != fs->first_object) { 192 VM_OBJECT_WLOCK(fs->first_object); 193 vm_page_free(fs->first_m); 194 vm_object_pip_wakeup(fs->first_object); 195 VM_OBJECT_WUNLOCK(fs->first_object); 196 fs->first_m = NULL; 197 } 198 vm_object_deallocate(fs->first_object); 199 unlock_map(fs); 200 unlock_vp(fs); 201 } 202 203 static void 204 unlock_and_deallocate(struct faultstate *fs) 205 { 206 207 VM_OBJECT_WUNLOCK(fs->object); 208 fault_deallocate(fs); 209 } 210 211 static void 212 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 213 vm_prot_t fault_type, int fault_flags, bool excl) 214 { 215 bool need_dirty; 216 217 if (((prot & VM_PROT_WRITE) == 0 && 218 (fault_flags & VM_FAULT_DIRTY) == 0) || 219 (m->oflags & VPO_UNMANAGED) != 0) 220 return; 221 222 VM_OBJECT_ASSERT_LOCKED(m->object); 223 VM_PAGE_OBJECT_BUSY_ASSERT(m); 224 225 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 226 (fault_flags & VM_FAULT_WIRE) == 0) || 227 (fault_flags & VM_FAULT_DIRTY) != 0; 228 229 vm_object_set_writeable_dirty(m->object); 230 231 if (!excl) 232 /* 233 * If two callers of vm_fault_dirty() with excl == 234 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 235 * flag set, other with flag clear, race, it is 236 * possible for the no-NOSYNC thread to see m->dirty 237 * != 0 and not clear PGA_NOSYNC. Take vm_page lock 238 * around manipulation of PGA_NOSYNC and 239 * vm_page_dirty() call to avoid the race. 240 */ 241 vm_page_lock(m); 242 243 /* 244 * If this is a NOSYNC mmap we do not want to set PGA_NOSYNC 245 * if the page is already dirty to prevent data written with 246 * the expectation of being synced from not being synced. 247 * Likewise if this entry does not request NOSYNC then make 248 * sure the page isn't marked NOSYNC. Applications sharing 249 * data should use the same flags to avoid ping ponging. 250 */ 251 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 252 if (m->dirty == 0) { 253 vm_page_aflag_set(m, PGA_NOSYNC); 254 } 255 } else { 256 vm_page_aflag_clear(m, PGA_NOSYNC); 257 } 258 259 /* 260 * If the fault is a write, we know that this page is being 261 * written NOW so dirty it explicitly to save on 262 * pmap_is_modified() calls later. 263 * 264 * Also, since the page is now dirty, we can possibly tell 265 * the pager to release any swap backing the page. Calling 266 * the pager requires a write lock on the object. 267 */ 268 if (need_dirty) 269 vm_page_dirty(m); 270 if (!excl) 271 vm_page_unlock(m); 272 else if (need_dirty) 273 vm_pager_page_unswapped(m); 274 } 275 276 /* 277 * Unlocks fs.first_object and fs.map on success. 278 */ 279 static int 280 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 281 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 282 { 283 vm_page_t m, m_map; 284 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \ 285 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \ 286 VM_NRESERVLEVEL > 0 287 vm_page_t m_super; 288 int flags; 289 #endif 290 int psind, rv; 291 292 MPASS(fs->vp == NULL); 293 vm_object_busy(fs->first_object); 294 m = vm_page_lookup(fs->first_object, fs->first_pindex); 295 /* A busy page can be mapped for read|execute access. */ 296 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 297 vm_page_busied(m)) || !vm_page_all_valid(m)) { 298 rv = KERN_FAILURE; 299 goto out; 300 } 301 m_map = m; 302 psind = 0; 303 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \ 304 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \ 305 VM_NRESERVLEVEL > 0 306 if ((m->flags & PG_FICTITIOUS) == 0 && 307 (m_super = vm_reserv_to_superpage(m)) != NULL && 308 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start && 309 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end && 310 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) & 311 (pagesizes[m_super->psind] - 1)) && !wired && 312 pmap_ps_enabled(fs->map->pmap)) { 313 flags = PS_ALL_VALID; 314 if ((prot & VM_PROT_WRITE) != 0) { 315 /* 316 * Create a superpage mapping allowing write access 317 * only if none of the constituent pages are busy and 318 * all of them are already dirty (except possibly for 319 * the page that was faulted on). 320 */ 321 flags |= PS_NONE_BUSY; 322 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0) 323 flags |= PS_ALL_DIRTY; 324 } 325 if (vm_page_ps_test(m_super, flags, m)) { 326 m_map = m_super; 327 psind = m_super->psind; 328 vaddr = rounddown2(vaddr, pagesizes[psind]); 329 /* Preset the modified bit for dirty superpages. */ 330 if ((flags & PS_ALL_DIRTY) != 0) 331 fault_type |= VM_PROT_WRITE; 332 } 333 } 334 #endif 335 rv = pmap_enter(fs->map->pmap, vaddr, m_map, prot, fault_type | 336 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), psind); 337 if (rv != KERN_SUCCESS) 338 goto out; 339 if (m_hold != NULL) { 340 *m_hold = m; 341 vm_page_wire(m); 342 } 343 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false); 344 if (psind == 0 && !wired) 345 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true); 346 VM_OBJECT_RUNLOCK(fs->first_object); 347 vm_map_lookup_done(fs->map, fs->entry); 348 curthread->td_ru.ru_minflt++; 349 350 out: 351 vm_object_unbusy(fs->first_object); 352 return (rv); 353 } 354 355 static void 356 vm_fault_restore_map_lock(struct faultstate *fs) 357 { 358 359 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 360 MPASS(REFCOUNT_COUNT(fs->first_object->paging_in_progress) > 0); 361 362 if (!vm_map_trylock_read(fs->map)) { 363 VM_OBJECT_WUNLOCK(fs->first_object); 364 vm_map_lock_read(fs->map); 365 VM_OBJECT_WLOCK(fs->first_object); 366 } 367 fs->lookup_still_valid = true; 368 } 369 370 static void 371 vm_fault_populate_check_page(vm_page_t m) 372 { 373 374 /* 375 * Check each page to ensure that the pager is obeying the 376 * interface: the page must be installed in the object, fully 377 * valid, and exclusively busied. 378 */ 379 MPASS(m != NULL); 380 MPASS(vm_page_all_valid(m)); 381 MPASS(vm_page_xbusied(m)); 382 } 383 384 static void 385 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first, 386 vm_pindex_t last) 387 { 388 vm_page_t m; 389 vm_pindex_t pidx; 390 391 VM_OBJECT_ASSERT_WLOCKED(object); 392 MPASS(first <= last); 393 for (pidx = first, m = vm_page_lookup(object, pidx); 394 pidx <= last; pidx++, m = vm_page_next(m)) { 395 vm_fault_populate_check_page(m); 396 vm_page_lock(m); 397 vm_page_deactivate(m); 398 vm_page_unlock(m); 399 vm_page_xunbusy(m); 400 } 401 } 402 403 static int 404 vm_fault_populate(struct faultstate *fs, vm_prot_t prot, int fault_type, 405 int fault_flags, boolean_t wired, vm_page_t *m_hold) 406 { 407 struct mtx *m_mtx; 408 vm_offset_t vaddr; 409 vm_page_t m; 410 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx; 411 int i, npages, psind, rv; 412 413 MPASS(fs->object == fs->first_object); 414 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 415 MPASS(REFCOUNT_COUNT(fs->first_object->paging_in_progress) > 0); 416 MPASS(fs->first_object->backing_object == NULL); 417 MPASS(fs->lookup_still_valid); 418 419 pager_first = OFF_TO_IDX(fs->entry->offset); 420 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1; 421 unlock_map(fs); 422 unlock_vp(fs); 423 424 /* 425 * Call the pager (driver) populate() method. 426 * 427 * There is no guarantee that the method will be called again 428 * if the current fault is for read, and a future fault is 429 * for write. Report the entry's maximum allowed protection 430 * to the driver. 431 */ 432 rv = vm_pager_populate(fs->first_object, fs->first_pindex, 433 fault_type, fs->entry->max_protection, &pager_first, &pager_last); 434 435 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 436 if (rv == VM_PAGER_BAD) { 437 /* 438 * VM_PAGER_BAD is the backdoor for a pager to request 439 * normal fault handling. 440 */ 441 vm_fault_restore_map_lock(fs); 442 if (fs->map->timestamp != fs->map_generation) 443 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 444 return (KERN_NOT_RECEIVER); 445 } 446 if (rv != VM_PAGER_OK) 447 return (KERN_FAILURE); /* AKA SIGSEGV */ 448 449 /* Ensure that the driver is obeying the interface. */ 450 MPASS(pager_first <= pager_last); 451 MPASS(fs->first_pindex <= pager_last); 452 MPASS(fs->first_pindex >= pager_first); 453 MPASS(pager_last < fs->first_object->size); 454 455 vm_fault_restore_map_lock(fs); 456 if (fs->map->timestamp != fs->map_generation) { 457 vm_fault_populate_cleanup(fs->first_object, pager_first, 458 pager_last); 459 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 460 } 461 462 /* 463 * The map is unchanged after our last unlock. Process the fault. 464 * 465 * The range [pager_first, pager_last] that is given to the 466 * pager is only a hint. The pager may populate any range 467 * within the object that includes the requested page index. 468 * In case the pager expanded the range, clip it to fit into 469 * the map entry. 470 */ 471 map_first = OFF_TO_IDX(fs->entry->offset); 472 if (map_first > pager_first) { 473 vm_fault_populate_cleanup(fs->first_object, pager_first, 474 map_first - 1); 475 pager_first = map_first; 476 } 477 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1; 478 if (map_last < pager_last) { 479 vm_fault_populate_cleanup(fs->first_object, map_last + 1, 480 pager_last); 481 pager_last = map_last; 482 } 483 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx); 484 pidx <= pager_last; 485 pidx += npages, m = vm_page_next(&m[npages - 1])) { 486 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset; 487 #if defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \ 488 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv) 489 psind = m->psind; 490 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 || 491 pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last || 492 !pmap_ps_enabled(fs->map->pmap) || wired)) 493 psind = 0; 494 #else 495 psind = 0; 496 #endif 497 npages = atop(pagesizes[psind]); 498 for (i = 0; i < npages; i++) { 499 vm_fault_populate_check_page(&m[i]); 500 vm_fault_dirty(fs->entry, &m[i], prot, fault_type, 501 fault_flags, true); 502 } 503 VM_OBJECT_WUNLOCK(fs->first_object); 504 rv = pmap_enter(fs->map->pmap, vaddr, m, prot, fault_type | 505 (wired ? PMAP_ENTER_WIRED : 0), psind); 506 #if defined(__amd64__) 507 if (psind > 0 && rv == KERN_FAILURE) { 508 for (i = 0; i < npages; i++) { 509 rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i), 510 &m[i], prot, fault_type | 511 (wired ? PMAP_ENTER_WIRED : 0), 0); 512 MPASS(rv == KERN_SUCCESS); 513 } 514 } 515 #else 516 MPASS(rv == KERN_SUCCESS); 517 #endif 518 VM_OBJECT_WLOCK(fs->first_object); 519 m_mtx = NULL; 520 for (i = 0; i < npages; i++) { 521 if ((fault_flags & VM_FAULT_WIRE) != 0) { 522 vm_page_wire(&m[i]); 523 } else { 524 vm_page_change_lock(&m[i], &m_mtx); 525 vm_page_activate(&m[i]); 526 } 527 if (m_hold != NULL && m[i].pindex == fs->first_pindex) { 528 *m_hold = &m[i]; 529 vm_page_wire(&m[i]); 530 } 531 vm_page_xunbusy(&m[i]); 532 } 533 if (m_mtx != NULL) 534 mtx_unlock(m_mtx); 535 } 536 curthread->td_ru.ru_majflt++; 537 return (KERN_SUCCESS); 538 } 539 540 static int prot_fault_translation; 541 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RWTUN, 542 &prot_fault_translation, 0, 543 "Control signal to deliver on protection fault"); 544 545 /* compat definition to keep common code for signal translation */ 546 #define UCODE_PAGEFLT 12 547 #ifdef T_PAGEFLT 548 _Static_assert(UCODE_PAGEFLT == T_PAGEFLT, "T_PAGEFLT"); 549 #endif 550 551 /* 552 * vm_fault_trap: 553 * 554 * Handle a page fault occurring at the given address, 555 * requiring the given permissions, in the map specified. 556 * If successful, the page is inserted into the 557 * associated physical map. 558 * 559 * NOTE: the given address should be truncated to the 560 * proper page address. 561 * 562 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 563 * a standard error specifying why the fault is fatal is returned. 564 * 565 * The map in question must be referenced, and remains so. 566 * Caller may hold no locks. 567 */ 568 int 569 vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 570 int fault_flags, int *signo, int *ucode) 571 { 572 int result; 573 574 MPASS(signo == NULL || ucode != NULL); 575 #ifdef KTRACE 576 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULT)) 577 ktrfault(vaddr, fault_type); 578 #endif 579 result = vm_fault(map, trunc_page(vaddr), fault_type, fault_flags, 580 NULL); 581 KASSERT(result == KERN_SUCCESS || result == KERN_FAILURE || 582 result == KERN_INVALID_ADDRESS || 583 result == KERN_RESOURCE_SHORTAGE || 584 result == KERN_PROTECTION_FAILURE || 585 result == KERN_OUT_OF_BOUNDS, 586 ("Unexpected Mach error %d from vm_fault()", result)); 587 #ifdef KTRACE 588 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULTEND)) 589 ktrfaultend(result); 590 #endif 591 if (result != KERN_SUCCESS && signo != NULL) { 592 switch (result) { 593 case KERN_FAILURE: 594 case KERN_INVALID_ADDRESS: 595 *signo = SIGSEGV; 596 *ucode = SEGV_MAPERR; 597 break; 598 case KERN_RESOURCE_SHORTAGE: 599 *signo = SIGBUS; 600 *ucode = BUS_OOMERR; 601 break; 602 case KERN_OUT_OF_BOUNDS: 603 *signo = SIGBUS; 604 *ucode = BUS_OBJERR; 605 break; 606 case KERN_PROTECTION_FAILURE: 607 if (prot_fault_translation == 0) { 608 /* 609 * Autodetect. This check also covers 610 * the images without the ABI-tag ELF 611 * note. 612 */ 613 if (SV_CURPROC_ABI() == SV_ABI_FREEBSD && 614 curproc->p_osrel >= P_OSREL_SIGSEGV) { 615 *signo = SIGSEGV; 616 *ucode = SEGV_ACCERR; 617 } else { 618 *signo = SIGBUS; 619 *ucode = UCODE_PAGEFLT; 620 } 621 } else if (prot_fault_translation == 1) { 622 /* Always compat mode. */ 623 *signo = SIGBUS; 624 *ucode = UCODE_PAGEFLT; 625 } else { 626 /* Always SIGSEGV mode. */ 627 *signo = SIGSEGV; 628 *ucode = SEGV_ACCERR; 629 } 630 break; 631 default: 632 KASSERT(0, ("Unexpected Mach error %d from vm_fault()", 633 result)); 634 break; 635 } 636 } 637 return (result); 638 } 639 640 static int 641 vm_fault_lock_vnode(struct faultstate *fs) 642 { 643 struct vnode *vp; 644 int error, locked; 645 646 if (fs->object->type != OBJT_VNODE) 647 return (KERN_SUCCESS); 648 vp = fs->object->handle; 649 if (vp == fs->vp) { 650 ASSERT_VOP_LOCKED(vp, "saved vnode is not locked"); 651 return (KERN_SUCCESS); 652 } 653 654 /* 655 * Perform an unlock in case the desired vnode changed while 656 * the map was unlocked during a retry. 657 */ 658 unlock_vp(fs); 659 660 locked = VOP_ISLOCKED(vp); 661 if (locked != LK_EXCLUSIVE) 662 locked = LK_SHARED; 663 664 /* 665 * We must not sleep acquiring the vnode lock while we have 666 * the page exclusive busied or the object's 667 * paging-in-progress count incremented. Otherwise, we could 668 * deadlock. 669 */ 670 error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT, curthread); 671 if (error == 0) { 672 fs->vp = vp; 673 return (KERN_SUCCESS); 674 } 675 676 vhold(vp); 677 release_page(fs); 678 unlock_and_deallocate(fs); 679 error = vget(vp, locked | LK_RETRY | LK_CANRECURSE, curthread); 680 vdrop(vp); 681 fs->vp = vp; 682 KASSERT(error == 0, ("vm_fault: vget failed %d", error)); 683 return (KERN_RESOURCE_SHORTAGE); 684 } 685 686 int 687 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 688 int fault_flags, vm_page_t *m_hold) 689 { 690 struct faultstate fs; 691 struct domainset *dset; 692 vm_object_t next_object, retry_object; 693 vm_offset_t e_end, e_start; 694 vm_pindex_t retry_pindex; 695 vm_prot_t prot, retry_prot; 696 int ahead, alloc_req, behind, cluster_offset, era, faultcount; 697 int nera, oom, result, rv; 698 u_char behavior; 699 boolean_t wired; /* Passed by reference. */ 700 bool dead, hardfault, is_first_object_locked; 701 702 VM_CNT_INC(v_vm_faults); 703 704 if ((curthread->td_pflags & TDP_NOFAULTING) != 0) 705 return (KERN_PROTECTION_FAILURE); 706 707 fs.vp = NULL; 708 faultcount = 0; 709 nera = -1; 710 hardfault = false; 711 712 RetryFault: 713 oom = 0; 714 RetryFault_oom: 715 716 /* 717 * Find the backing store object and offset into it to begin the 718 * search. 719 */ 720 fs.map = map; 721 result = vm_map_lookup(&fs.map, vaddr, fault_type | 722 VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object, 723 &fs.first_pindex, &prot, &wired); 724 if (result != KERN_SUCCESS) { 725 unlock_vp(&fs); 726 return (result); 727 } 728 729 fs.map_generation = fs.map->timestamp; 730 731 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 732 panic("%s: fault on nofault entry, addr: %#lx", 733 __func__, (u_long)vaddr); 734 } 735 736 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 737 fs.entry->wiring_thread != curthread) { 738 vm_map_unlock_read(fs.map); 739 vm_map_lock(fs.map); 740 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 741 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 742 unlock_vp(&fs); 743 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 744 vm_map_unlock_and_wait(fs.map, 0); 745 } else 746 vm_map_unlock(fs.map); 747 goto RetryFault; 748 } 749 750 MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0); 751 752 if (wired) 753 fault_type = prot | (fault_type & VM_PROT_COPY); 754 else 755 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 756 ("!wired && VM_FAULT_WIRE")); 757 758 /* 759 * Try to avoid lock contention on the top-level object through 760 * special-case handling of some types of page faults, specifically, 761 * those that are mapping an existing page from the top-level object. 762 * Under this condition, a read lock on the object suffices, allowing 763 * multiple page faults of a similar type to run in parallel. 764 */ 765 if (fs.vp == NULL /* avoid locked vnode leak */ && 766 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) { 767 VM_OBJECT_RLOCK(fs.first_object); 768 rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type, 769 fault_flags, wired, m_hold); 770 if (rv == KERN_SUCCESS) 771 return (rv); 772 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 773 VM_OBJECT_RUNLOCK(fs.first_object); 774 VM_OBJECT_WLOCK(fs.first_object); 775 } 776 } else { 777 VM_OBJECT_WLOCK(fs.first_object); 778 } 779 780 /* 781 * Make a reference to this object to prevent its disposal while we 782 * are messing with it. Once we have the reference, the map is free 783 * to be diddled. Since objects reference their shadows (and copies), 784 * they will stay around as well. 785 * 786 * Bump the paging-in-progress count to prevent size changes (e.g. 787 * truncation operations) during I/O. 788 */ 789 vm_object_reference_locked(fs.first_object); 790 vm_object_pip_add(fs.first_object, 1); 791 792 fs.lookup_still_valid = true; 793 794 fs.first_m = NULL; 795 796 /* 797 * Search for the page at object/offset. 798 */ 799 fs.object = fs.first_object; 800 fs.pindex = fs.first_pindex; 801 while (TRUE) { 802 /* 803 * If the object is marked for imminent termination, 804 * we retry here, since the collapse pass has raced 805 * with us. Otherwise, if we see terminally dead 806 * object, return fail. 807 */ 808 if ((fs.object->flags & OBJ_DEAD) != 0) { 809 dead = fs.object->type == OBJT_DEAD; 810 unlock_and_deallocate(&fs); 811 if (dead) 812 return (KERN_PROTECTION_FAILURE); 813 pause("vmf_de", 1); 814 goto RetryFault; 815 } 816 817 /* 818 * See if page is resident 819 */ 820 fs.m = vm_page_lookup(fs.object, fs.pindex); 821 if (fs.m != NULL) { 822 /* 823 * Wait/Retry if the page is busy. We have to do this 824 * if the page is either exclusive or shared busy 825 * because the vm_pager may be using read busy for 826 * pageouts (and even pageins if it is the vnode 827 * pager), and we could end up trying to pagein and 828 * pageout the same page simultaneously. 829 * 830 * We can theoretically allow the busy case on a read 831 * fault if the page is marked valid, but since such 832 * pages are typically already pmap'd, putting that 833 * special case in might be more effort then it is 834 * worth. We cannot under any circumstances mess 835 * around with a shared busied page except, perhaps, 836 * to pmap it. 837 */ 838 if (vm_page_tryxbusy(fs.m) == 0) { 839 /* 840 * Reference the page before unlocking and 841 * sleeping so that the page daemon is less 842 * likely to reclaim it. 843 */ 844 vm_page_aflag_set(fs.m, PGA_REFERENCED); 845 if (fs.object != fs.first_object) { 846 if (!VM_OBJECT_TRYWLOCK( 847 fs.first_object)) { 848 VM_OBJECT_WUNLOCK(fs.object); 849 VM_OBJECT_WLOCK(fs.first_object); 850 VM_OBJECT_WLOCK(fs.object); 851 } 852 vm_page_free(fs.first_m); 853 vm_object_pip_wakeup(fs.first_object); 854 VM_OBJECT_WUNLOCK(fs.first_object); 855 fs.first_m = NULL; 856 } 857 unlock_map(&fs); 858 if (fs.m == vm_page_lookup(fs.object, 859 fs.pindex)) { 860 vm_page_sleep_if_busy(fs.m, "vmpfw"); 861 } 862 vm_object_pip_wakeup(fs.object); 863 VM_OBJECT_WUNLOCK(fs.object); 864 VM_CNT_INC(v_intrans); 865 vm_object_deallocate(fs.first_object); 866 goto RetryFault; 867 } 868 869 /* 870 * The page is marked busy for other processes and the 871 * pagedaemon. If it still isn't completely valid 872 * (readable), jump to readrest, else break-out ( we 873 * found the page ). 874 */ 875 if (!vm_page_all_valid(fs.m)) 876 goto readrest; 877 break; /* break to PAGE HAS BEEN FOUND */ 878 } 879 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m)); 880 881 /* 882 * Page is not resident. If the pager might contain the page 883 * or this is the beginning of the search, allocate a new 884 * page. (Default objects are zero-fill, so there is no real 885 * pager for them.) 886 */ 887 if (fs.object->type != OBJT_DEFAULT || 888 fs.object == fs.first_object) { 889 if ((fs.object->flags & OBJ_SIZEVNLOCK) != 0) { 890 rv = vm_fault_lock_vnode(&fs); 891 MPASS(rv == KERN_SUCCESS || 892 rv == KERN_RESOURCE_SHORTAGE); 893 if (rv == KERN_RESOURCE_SHORTAGE) 894 goto RetryFault; 895 } 896 if (fs.pindex >= fs.object->size) { 897 unlock_and_deallocate(&fs); 898 return (KERN_OUT_OF_BOUNDS); 899 } 900 901 if (fs.object == fs.first_object && 902 (fs.first_object->flags & OBJ_POPULATE) != 0 && 903 fs.first_object->shadow_count == 0) { 904 rv = vm_fault_populate(&fs, prot, fault_type, 905 fault_flags, wired, m_hold); 906 switch (rv) { 907 case KERN_SUCCESS: 908 case KERN_FAILURE: 909 unlock_and_deallocate(&fs); 910 return (rv); 911 case KERN_RESOURCE_SHORTAGE: 912 unlock_and_deallocate(&fs); 913 goto RetryFault; 914 case KERN_NOT_RECEIVER: 915 /* 916 * Pager's populate() method 917 * returned VM_PAGER_BAD. 918 */ 919 break; 920 default: 921 panic("inconsistent return codes"); 922 } 923 } 924 925 /* 926 * Allocate a new page for this object/offset pair. 927 * 928 * Unlocked read of the p_flag is harmless. At 929 * worst, the P_KILLED might be not observed 930 * there, and allocation can fail, causing 931 * restart and new reading of the p_flag. 932 */ 933 dset = fs.object->domain.dr_policy; 934 if (dset == NULL) 935 dset = curthread->td_domain.dr_policy; 936 if (!vm_page_count_severe_set(&dset->ds_mask) || 937 P_KILLED(curproc)) { 938 #if VM_NRESERVLEVEL > 0 939 vm_object_color(fs.object, atop(vaddr) - 940 fs.pindex); 941 #endif 942 alloc_req = P_KILLED(curproc) ? 943 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 944 if (fs.object->type != OBJT_VNODE && 945 fs.object->backing_object == NULL) 946 alloc_req |= VM_ALLOC_ZERO; 947 fs.m = vm_page_alloc(fs.object, fs.pindex, 948 alloc_req); 949 } 950 if (fs.m == NULL) { 951 unlock_and_deallocate(&fs); 952 if (vm_pfault_oom_attempts < 0 || 953 oom < vm_pfault_oom_attempts) { 954 oom++; 955 vm_waitpfault(dset, 956 vm_pfault_oom_wait * hz); 957 goto RetryFault_oom; 958 } 959 if (bootverbose) 960 printf( 961 "proc %d (%s) failed to alloc page on fault, starting OOM\n", 962 curproc->p_pid, curproc->p_comm); 963 vm_pageout_oom(VM_OOM_MEM_PF); 964 goto RetryFault; 965 } 966 } 967 968 readrest: 969 /* 970 * At this point, we have either allocated a new page or found 971 * an existing page that is only partially valid. 972 * 973 * We hold a reference on the current object and the page is 974 * exclusive busied. 975 */ 976 977 /* 978 * If the pager for the current object might have the page, 979 * then determine the number of additional pages to read and 980 * potentially reprioritize previously read pages for earlier 981 * reclamation. These operations should only be performed 982 * once per page fault. Even if the current pager doesn't 983 * have the page, the number of additional pages to read will 984 * apply to subsequent objects in the shadow chain. 985 */ 986 if (fs.object->type != OBJT_DEFAULT && nera == -1 && 987 !P_KILLED(curproc)) { 988 KASSERT(fs.lookup_still_valid, ("map unlocked")); 989 era = fs.entry->read_ahead; 990 behavior = vm_map_entry_behavior(fs.entry); 991 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 992 nera = 0; 993 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 994 nera = VM_FAULT_READ_AHEAD_MAX; 995 if (vaddr == fs.entry->next_read) 996 vm_fault_dontneed(&fs, vaddr, nera); 997 } else if (vaddr == fs.entry->next_read) { 998 /* 999 * This is a sequential fault. Arithmetically 1000 * increase the requested number of pages in 1001 * the read-ahead window. The requested 1002 * number of pages is "# of sequential faults 1003 * x (read ahead min + 1) + read ahead min" 1004 */ 1005 nera = VM_FAULT_READ_AHEAD_MIN; 1006 if (era > 0) { 1007 nera += era + 1; 1008 if (nera > VM_FAULT_READ_AHEAD_MAX) 1009 nera = VM_FAULT_READ_AHEAD_MAX; 1010 } 1011 if (era == VM_FAULT_READ_AHEAD_MAX) 1012 vm_fault_dontneed(&fs, vaddr, nera); 1013 } else { 1014 /* 1015 * This is a non-sequential fault. 1016 */ 1017 nera = 0; 1018 } 1019 if (era != nera) { 1020 /* 1021 * A read lock on the map suffices to update 1022 * the read ahead count safely. 1023 */ 1024 fs.entry->read_ahead = nera; 1025 } 1026 1027 /* 1028 * Prepare for unlocking the map. Save the map 1029 * entry's start and end addresses, which are used to 1030 * optimize the size of the pager operation below. 1031 * Even if the map entry's addresses change after 1032 * unlocking the map, using the saved addresses is 1033 * safe. 1034 */ 1035 e_start = fs.entry->start; 1036 e_end = fs.entry->end; 1037 } 1038 1039 /* 1040 * Call the pager to retrieve the page if there is a chance 1041 * that the pager has it, and potentially retrieve additional 1042 * pages at the same time. 1043 */ 1044 if (fs.object->type != OBJT_DEFAULT) { 1045 /* 1046 * Release the map lock before locking the vnode or 1047 * sleeping in the pager. (If the current object has 1048 * a shadow, then an earlier iteration of this loop 1049 * may have already unlocked the map.) 1050 */ 1051 unlock_map(&fs); 1052 1053 rv = vm_fault_lock_vnode(&fs); 1054 MPASS(rv == KERN_SUCCESS || 1055 rv == KERN_RESOURCE_SHORTAGE); 1056 if (rv == KERN_RESOURCE_SHORTAGE) 1057 goto RetryFault; 1058 KASSERT(fs.vp == NULL || !fs.map->system_map, 1059 ("vm_fault: vnode-backed object mapped by system map")); 1060 1061 /* 1062 * Page in the requested page and hint the pager, 1063 * that it may bring up surrounding pages. 1064 */ 1065 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 1066 P_KILLED(curproc)) { 1067 behind = 0; 1068 ahead = 0; 1069 } else { 1070 /* Is this a sequential fault? */ 1071 if (nera > 0) { 1072 behind = 0; 1073 ahead = nera; 1074 } else { 1075 /* 1076 * Request a cluster of pages that is 1077 * aligned to a VM_FAULT_READ_DEFAULT 1078 * page offset boundary within the 1079 * object. Alignment to a page offset 1080 * boundary is more likely to coincide 1081 * with the underlying file system 1082 * block than alignment to a virtual 1083 * address boundary. 1084 */ 1085 cluster_offset = fs.pindex % 1086 VM_FAULT_READ_DEFAULT; 1087 behind = ulmin(cluster_offset, 1088 atop(vaddr - e_start)); 1089 ahead = VM_FAULT_READ_DEFAULT - 1 - 1090 cluster_offset; 1091 } 1092 ahead = ulmin(ahead, atop(e_end - vaddr) - 1); 1093 } 1094 rv = vm_pager_get_pages(fs.object, &fs.m, 1, 1095 &behind, &ahead); 1096 if (rv == VM_PAGER_OK) { 1097 faultcount = behind + 1 + ahead; 1098 hardfault = true; 1099 break; /* break to PAGE HAS BEEN FOUND */ 1100 } 1101 if (rv == VM_PAGER_ERROR) 1102 printf("vm_fault: pager read error, pid %d (%s)\n", 1103 curproc->p_pid, curproc->p_comm); 1104 1105 /* 1106 * If an I/O error occurred or the requested page was 1107 * outside the range of the pager, clean up and return 1108 * an error. 1109 */ 1110 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) { 1111 if (!vm_page_wired(fs.m)) 1112 vm_page_free(fs.m); 1113 else 1114 vm_page_xunbusy(fs.m); 1115 fs.m = NULL; 1116 unlock_and_deallocate(&fs); 1117 return (KERN_OUT_OF_BOUNDS); 1118 } 1119 1120 /* 1121 * The requested page does not exist at this object/ 1122 * offset. Remove the invalid page from the object, 1123 * waking up anyone waiting for it, and continue on to 1124 * the next object. However, if this is the top-level 1125 * object, we must leave the busy page in place to 1126 * prevent another process from rushing past us, and 1127 * inserting the page in that object at the same time 1128 * that we are. 1129 */ 1130 if (fs.object != fs.first_object) { 1131 if (!vm_page_wired(fs.m)) 1132 vm_page_free(fs.m); 1133 else 1134 vm_page_xunbusy(fs.m); 1135 fs.m = NULL; 1136 } 1137 } 1138 1139 /* 1140 * We get here if the object has default pager (or unwiring) 1141 * or the pager doesn't have the page. 1142 */ 1143 if (fs.object == fs.first_object) 1144 fs.first_m = fs.m; 1145 1146 /* 1147 * Move on to the next object. Lock the next object before 1148 * unlocking the current one. 1149 */ 1150 next_object = fs.object->backing_object; 1151 if (next_object == NULL) { 1152 /* 1153 * If there's no object left, fill the page in the top 1154 * object with zeros. 1155 */ 1156 if (fs.object != fs.first_object) { 1157 vm_object_pip_wakeup(fs.object); 1158 VM_OBJECT_WUNLOCK(fs.object); 1159 1160 fs.object = fs.first_object; 1161 fs.pindex = fs.first_pindex; 1162 fs.m = fs.first_m; 1163 VM_OBJECT_WLOCK(fs.object); 1164 } 1165 fs.first_m = NULL; 1166 1167 /* 1168 * Zero the page if necessary and mark it valid. 1169 */ 1170 if ((fs.m->flags & PG_ZERO) == 0) { 1171 pmap_zero_page(fs.m); 1172 } else { 1173 VM_CNT_INC(v_ozfod); 1174 } 1175 VM_CNT_INC(v_zfod); 1176 vm_page_valid(fs.m); 1177 /* Don't try to prefault neighboring pages. */ 1178 faultcount = 1; 1179 break; /* break to PAGE HAS BEEN FOUND */ 1180 } else { 1181 KASSERT(fs.object != next_object, 1182 ("object loop %p", next_object)); 1183 VM_OBJECT_WLOCK(next_object); 1184 vm_object_pip_add(next_object, 1); 1185 if (fs.object != fs.first_object) 1186 vm_object_pip_wakeup(fs.object); 1187 fs.pindex += 1188 OFF_TO_IDX(fs.object->backing_object_offset); 1189 VM_OBJECT_WUNLOCK(fs.object); 1190 fs.object = next_object; 1191 } 1192 } 1193 1194 vm_page_assert_xbusied(fs.m); 1195 1196 /* 1197 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 1198 * is held.] 1199 */ 1200 1201 /* 1202 * If the page is being written, but isn't already owned by the 1203 * top-level object, we have to copy it into a new page owned by the 1204 * top-level object. 1205 */ 1206 if (fs.object != fs.first_object) { 1207 /* 1208 * We only really need to copy if we want to write it. 1209 */ 1210 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1211 /* 1212 * This allows pages to be virtually copied from a 1213 * backing_object into the first_object, where the 1214 * backing object has no other refs to it, and cannot 1215 * gain any more refs. Instead of a bcopy, we just 1216 * move the page from the backing object to the 1217 * first object. Note that we must mark the page 1218 * dirty in the first object so that it will go out 1219 * to swap when needed. 1220 */ 1221 is_first_object_locked = false; 1222 if ( 1223 /* 1224 * Only one shadow object 1225 */ 1226 (fs.object->shadow_count == 1) && 1227 /* 1228 * No COW refs, except us 1229 */ 1230 (fs.object->ref_count == 1) && 1231 /* 1232 * No one else can look this object up 1233 */ 1234 (fs.object->handle == NULL) && 1235 /* 1236 * No other ways to look the object up 1237 */ 1238 ((fs.object->type == OBJT_DEFAULT) || 1239 (fs.object->type == OBJT_SWAP)) && 1240 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 1241 /* 1242 * We don't chase down the shadow chain 1243 */ 1244 fs.object == fs.first_object->backing_object) { 1245 1246 (void)vm_page_remove(fs.m); 1247 vm_page_replace_checked(fs.m, fs.first_object, 1248 fs.first_pindex, fs.first_m); 1249 vm_page_free(fs.first_m); 1250 vm_page_dirty(fs.m); 1251 #if VM_NRESERVLEVEL > 0 1252 /* 1253 * Rename the reservation. 1254 */ 1255 vm_reserv_rename(fs.m, fs.first_object, 1256 fs.object, OFF_TO_IDX( 1257 fs.first_object->backing_object_offset)); 1258 #endif 1259 VM_OBJECT_WUNLOCK(fs.object); 1260 fs.first_m = fs.m; 1261 fs.m = NULL; 1262 VM_CNT_INC(v_cow_optim); 1263 } else { 1264 VM_OBJECT_WUNLOCK(fs.object); 1265 /* 1266 * Oh, well, lets copy it. 1267 */ 1268 pmap_copy_page(fs.m, fs.first_m); 1269 vm_page_valid(fs.first_m); 1270 if (wired && (fault_flags & 1271 VM_FAULT_WIRE) == 0) { 1272 vm_page_wire(fs.first_m); 1273 vm_page_unwire(fs.m, PQ_INACTIVE); 1274 } 1275 /* 1276 * We no longer need the old page or object. 1277 */ 1278 release_page(&fs); 1279 } 1280 /* 1281 * fs.object != fs.first_object due to above 1282 * conditional 1283 */ 1284 vm_object_pip_wakeup(fs.object); 1285 1286 /* 1287 * We only try to prefault read-only mappings to the 1288 * neighboring pages when this copy-on-write fault is 1289 * a hard fault. In other cases, trying to prefault 1290 * is typically wasted effort. 1291 */ 1292 if (faultcount == 0) 1293 faultcount = 1; 1294 1295 /* 1296 * Only use the new page below... 1297 */ 1298 fs.object = fs.first_object; 1299 fs.pindex = fs.first_pindex; 1300 fs.m = fs.first_m; 1301 if (!is_first_object_locked) 1302 VM_OBJECT_WLOCK(fs.object); 1303 VM_CNT_INC(v_cow_faults); 1304 curthread->td_cow++; 1305 } else { 1306 prot &= ~VM_PROT_WRITE; 1307 } 1308 } 1309 1310 /* 1311 * We must verify that the maps have not changed since our last 1312 * lookup. 1313 */ 1314 if (!fs.lookup_still_valid) { 1315 if (!vm_map_trylock_read(fs.map)) { 1316 release_page(&fs); 1317 unlock_and_deallocate(&fs); 1318 goto RetryFault; 1319 } 1320 fs.lookup_still_valid = true; 1321 if (fs.map->timestamp != fs.map_generation) { 1322 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 1323 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 1324 1325 /* 1326 * If we don't need the page any longer, put it on the inactive 1327 * list (the easiest thing to do here). If no one needs it, 1328 * pageout will grab it eventually. 1329 */ 1330 if (result != KERN_SUCCESS) { 1331 release_page(&fs); 1332 unlock_and_deallocate(&fs); 1333 1334 /* 1335 * If retry of map lookup would have blocked then 1336 * retry fault from start. 1337 */ 1338 if (result == KERN_FAILURE) 1339 goto RetryFault; 1340 return (result); 1341 } 1342 if ((retry_object != fs.first_object) || 1343 (retry_pindex != fs.first_pindex)) { 1344 release_page(&fs); 1345 unlock_and_deallocate(&fs); 1346 goto RetryFault; 1347 } 1348 1349 /* 1350 * Check whether the protection has changed or the object has 1351 * been copied while we left the map unlocked. Changing from 1352 * read to write permission is OK - we leave the page 1353 * write-protected, and catch the write fault. Changing from 1354 * write to read permission means that we can't mark the page 1355 * write-enabled after all. 1356 */ 1357 prot &= retry_prot; 1358 fault_type &= retry_prot; 1359 if (prot == 0) { 1360 release_page(&fs); 1361 unlock_and_deallocate(&fs); 1362 goto RetryFault; 1363 } 1364 1365 /* Reassert because wired may have changed. */ 1366 KASSERT(wired || (fault_flags & VM_FAULT_WIRE) == 0, 1367 ("!wired && VM_FAULT_WIRE")); 1368 } 1369 } 1370 1371 /* 1372 * If the page was filled by a pager, save the virtual address that 1373 * should be faulted on next under a sequential access pattern to the 1374 * map entry. A read lock on the map suffices to update this address 1375 * safely. 1376 */ 1377 if (hardfault) 1378 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 1379 1380 vm_page_assert_xbusied(fs.m); 1381 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true); 1382 1383 /* 1384 * Page must be completely valid or it is not fit to 1385 * map into user space. vm_pager_get_pages() ensures this. 1386 */ 1387 KASSERT(vm_page_all_valid(fs.m), 1388 ("vm_fault: page %p partially invalid", fs.m)); 1389 VM_OBJECT_WUNLOCK(fs.object); 1390 1391 /* 1392 * Put this page into the physical map. We had to do the unlock above 1393 * because pmap_enter() may sleep. We don't put the page 1394 * back on the active queue until later so that the pageout daemon 1395 * won't find it (yet). 1396 */ 1397 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1398 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1399 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1400 wired == 0) 1401 vm_fault_prefault(&fs, vaddr, 1402 faultcount > 0 ? behind : PFBAK, 1403 faultcount > 0 ? ahead : PFFOR, false); 1404 1405 /* 1406 * If the page is not wired down, then put it where the pageout daemon 1407 * can find it. 1408 */ 1409 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1410 vm_page_wire(fs.m); 1411 } else { 1412 vm_page_lock(fs.m); 1413 vm_page_activate(fs.m); 1414 vm_page_unlock(fs.m); 1415 } 1416 if (m_hold != NULL) { 1417 *m_hold = fs.m; 1418 vm_page_wire(fs.m); 1419 } 1420 vm_page_xunbusy(fs.m); 1421 1422 /* 1423 * Unlock everything, and return 1424 */ 1425 fault_deallocate(&fs); 1426 if (hardfault) { 1427 VM_CNT_INC(v_io_faults); 1428 curthread->td_ru.ru_majflt++; 1429 #ifdef RACCT 1430 if (racct_enable && fs.object->type == OBJT_VNODE) { 1431 PROC_LOCK(curproc); 1432 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1433 racct_add_force(curproc, RACCT_WRITEBPS, 1434 PAGE_SIZE + behind * PAGE_SIZE); 1435 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1436 } else { 1437 racct_add_force(curproc, RACCT_READBPS, 1438 PAGE_SIZE + ahead * PAGE_SIZE); 1439 racct_add_force(curproc, RACCT_READIOPS, 1); 1440 } 1441 PROC_UNLOCK(curproc); 1442 } 1443 #endif 1444 } else 1445 curthread->td_ru.ru_minflt++; 1446 1447 return (KERN_SUCCESS); 1448 } 1449 1450 /* 1451 * Speed up the reclamation of pages that precede the faulting pindex within 1452 * the first object of the shadow chain. Essentially, perform the equivalent 1453 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1454 * the faulting pindex by the cluster size when the pages read by vm_fault() 1455 * cross a cluster-size boundary. The cluster size is the greater of the 1456 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1457 * 1458 * When "fs->first_object" is a shadow object, the pages in the backing object 1459 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1460 * function must only be concerned with pages in the first object. 1461 */ 1462 static void 1463 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1464 { 1465 vm_map_entry_t entry; 1466 vm_object_t first_object, object; 1467 vm_offset_t end, start; 1468 vm_page_t m, m_next; 1469 vm_pindex_t pend, pstart; 1470 vm_size_t size; 1471 1472 object = fs->object; 1473 VM_OBJECT_ASSERT_WLOCKED(object); 1474 first_object = fs->first_object; 1475 if (first_object != object) { 1476 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1477 VM_OBJECT_WUNLOCK(object); 1478 VM_OBJECT_WLOCK(first_object); 1479 VM_OBJECT_WLOCK(object); 1480 } 1481 } 1482 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1483 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1484 size = VM_FAULT_DONTNEED_MIN; 1485 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1486 size = pagesizes[1]; 1487 end = rounddown2(vaddr, size); 1488 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1489 (entry = fs->entry)->start < end) { 1490 if (end - entry->start < size) 1491 start = entry->start; 1492 else 1493 start = end - size; 1494 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1495 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1496 entry->start); 1497 m_next = vm_page_find_least(first_object, pstart); 1498 pend = OFF_TO_IDX(entry->offset) + atop(end - 1499 entry->start); 1500 while ((m = m_next) != NULL && m->pindex < pend) { 1501 m_next = TAILQ_NEXT(m, listq); 1502 if (!vm_page_all_valid(m) || 1503 vm_page_busied(m)) 1504 continue; 1505 1506 /* 1507 * Don't clear PGA_REFERENCED, since it would 1508 * likely represent a reference by a different 1509 * process. 1510 * 1511 * Typically, at this point, prefetched pages 1512 * are still in the inactive queue. Only 1513 * pages that triggered page faults are in the 1514 * active queue. 1515 */ 1516 vm_page_lock(m); 1517 if (!vm_page_inactive(m)) 1518 vm_page_deactivate(m); 1519 vm_page_unlock(m); 1520 } 1521 } 1522 } 1523 if (first_object != object) 1524 VM_OBJECT_WUNLOCK(first_object); 1525 } 1526 1527 /* 1528 * vm_fault_prefault provides a quick way of clustering 1529 * pagefaults into a processes address space. It is a "cousin" 1530 * of vm_map_pmap_enter, except it runs at page fault time instead 1531 * of mmap time. 1532 */ 1533 static void 1534 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1535 int backward, int forward, bool obj_locked) 1536 { 1537 pmap_t pmap; 1538 vm_map_entry_t entry; 1539 vm_object_t backing_object, lobject; 1540 vm_offset_t addr, starta; 1541 vm_pindex_t pindex; 1542 vm_page_t m; 1543 int i; 1544 1545 pmap = fs->map->pmap; 1546 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1547 return; 1548 1549 entry = fs->entry; 1550 1551 if (addra < backward * PAGE_SIZE) { 1552 starta = entry->start; 1553 } else { 1554 starta = addra - backward * PAGE_SIZE; 1555 if (starta < entry->start) 1556 starta = entry->start; 1557 } 1558 1559 /* 1560 * Generate the sequence of virtual addresses that are candidates for 1561 * prefaulting in an outward spiral from the faulting virtual address, 1562 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1563 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1564 * If the candidate address doesn't have a backing physical page, then 1565 * the loop immediately terminates. 1566 */ 1567 for (i = 0; i < 2 * imax(backward, forward); i++) { 1568 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1569 PAGE_SIZE); 1570 if (addr > addra + forward * PAGE_SIZE) 1571 addr = 0; 1572 1573 if (addr < starta || addr >= entry->end) 1574 continue; 1575 1576 if (!pmap_is_prefaultable(pmap, addr)) 1577 continue; 1578 1579 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1580 lobject = entry->object.vm_object; 1581 if (!obj_locked) 1582 VM_OBJECT_RLOCK(lobject); 1583 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1584 lobject->type == OBJT_DEFAULT && 1585 (backing_object = lobject->backing_object) != NULL) { 1586 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1587 0, ("vm_fault_prefault: unaligned object offset")); 1588 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1589 VM_OBJECT_RLOCK(backing_object); 1590 if (!obj_locked || lobject != entry->object.vm_object) 1591 VM_OBJECT_RUNLOCK(lobject); 1592 lobject = backing_object; 1593 } 1594 if (m == NULL) { 1595 if (!obj_locked || lobject != entry->object.vm_object) 1596 VM_OBJECT_RUNLOCK(lobject); 1597 break; 1598 } 1599 if (vm_page_all_valid(m) && 1600 (m->flags & PG_FICTITIOUS) == 0) 1601 pmap_enter_quick(pmap, addr, m, entry->protection); 1602 if (!obj_locked || lobject != entry->object.vm_object) 1603 VM_OBJECT_RUNLOCK(lobject); 1604 } 1605 } 1606 1607 /* 1608 * Hold each of the physical pages that are mapped by the specified range of 1609 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1610 * and allow the specified types of access, "prot". If all of the implied 1611 * pages are successfully held, then the number of held pages is returned 1612 * together with pointers to those pages in the array "ma". However, if any 1613 * of the pages cannot be held, -1 is returned. 1614 */ 1615 int 1616 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1617 vm_prot_t prot, vm_page_t *ma, int max_count) 1618 { 1619 vm_offset_t end, va; 1620 vm_page_t *mp; 1621 int count; 1622 boolean_t pmap_failed; 1623 1624 if (len == 0) 1625 return (0); 1626 end = round_page(addr + len); 1627 addr = trunc_page(addr); 1628 1629 /* 1630 * Check for illegal addresses. 1631 */ 1632 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1633 return (-1); 1634 1635 if (atop(end - addr) > max_count) 1636 panic("vm_fault_quick_hold_pages: count > max_count"); 1637 count = atop(end - addr); 1638 1639 /* 1640 * Most likely, the physical pages are resident in the pmap, so it is 1641 * faster to try pmap_extract_and_hold() first. 1642 */ 1643 pmap_failed = FALSE; 1644 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1645 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1646 if (*mp == NULL) 1647 pmap_failed = TRUE; 1648 else if ((prot & VM_PROT_WRITE) != 0 && 1649 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1650 /* 1651 * Explicitly dirty the physical page. Otherwise, the 1652 * caller's changes may go unnoticed because they are 1653 * performed through an unmanaged mapping or by a DMA 1654 * operation. 1655 * 1656 * The object lock is not held here. 1657 * See vm_page_clear_dirty_mask(). 1658 */ 1659 vm_page_dirty(*mp); 1660 } 1661 } 1662 if (pmap_failed) { 1663 /* 1664 * One or more pages could not be held by the pmap. Either no 1665 * page was mapped at the specified virtual address or that 1666 * mapping had insufficient permissions. Attempt to fault in 1667 * and hold these pages. 1668 * 1669 * If vm_fault_disable_pagefaults() was called, 1670 * i.e., TDP_NOFAULTING is set, we must not sleep nor 1671 * acquire MD VM locks, which means we must not call 1672 * vm_fault(). Some (out of tree) callers mark 1673 * too wide a code area with vm_fault_disable_pagefaults() 1674 * already, use the VM_PROT_QUICK_NOFAULT flag to request 1675 * the proper behaviour explicitly. 1676 */ 1677 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 && 1678 (curthread->td_pflags & TDP_NOFAULTING) != 0) 1679 goto error; 1680 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1681 if (*mp == NULL && vm_fault(map, va, prot, 1682 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1683 goto error; 1684 } 1685 return (count); 1686 error: 1687 for (mp = ma; mp < ma + count; mp++) 1688 if (*mp != NULL) 1689 vm_page_unwire(*mp, PQ_INACTIVE); 1690 return (-1); 1691 } 1692 1693 /* 1694 * Routine: 1695 * vm_fault_copy_entry 1696 * Function: 1697 * Create new shadow object backing dst_entry with private copy of 1698 * all underlying pages. When src_entry is equal to dst_entry, 1699 * function implements COW for wired-down map entry. Otherwise, 1700 * it forks wired entry into dst_map. 1701 * 1702 * In/out conditions: 1703 * The source and destination maps must be locked for write. 1704 * The source map entry must be wired down (or be a sharing map 1705 * entry corresponding to a main map entry that is wired down). 1706 */ 1707 void 1708 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1709 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1710 vm_ooffset_t *fork_charge) 1711 { 1712 vm_object_t backing_object, dst_object, object, src_object; 1713 vm_pindex_t dst_pindex, pindex, src_pindex; 1714 vm_prot_t access, prot; 1715 vm_offset_t vaddr; 1716 vm_page_t dst_m; 1717 vm_page_t src_m; 1718 boolean_t upgrade; 1719 1720 #ifdef lint 1721 src_map++; 1722 #endif /* lint */ 1723 1724 upgrade = src_entry == dst_entry; 1725 access = prot = dst_entry->protection; 1726 1727 src_object = src_entry->object.vm_object; 1728 src_pindex = OFF_TO_IDX(src_entry->offset); 1729 1730 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1731 dst_object = src_object; 1732 vm_object_reference(dst_object); 1733 } else { 1734 /* 1735 * Create the top-level object for the destination entry. (Doesn't 1736 * actually shadow anything - we copy the pages directly.) 1737 */ 1738 dst_object = vm_object_allocate(OBJT_DEFAULT, 1739 atop(dst_entry->end - dst_entry->start)); 1740 #if VM_NRESERVLEVEL > 0 1741 dst_object->flags |= OBJ_COLORED; 1742 dst_object->pg_color = atop(dst_entry->start); 1743 #endif 1744 dst_object->domain = src_object->domain; 1745 dst_object->charge = dst_entry->end - dst_entry->start; 1746 } 1747 1748 VM_OBJECT_WLOCK(dst_object); 1749 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1750 ("vm_fault_copy_entry: vm_object not NULL")); 1751 if (src_object != dst_object) { 1752 dst_entry->object.vm_object = dst_object; 1753 dst_entry->offset = 0; 1754 dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC; 1755 } 1756 if (fork_charge != NULL) { 1757 KASSERT(dst_entry->cred == NULL, 1758 ("vm_fault_copy_entry: leaked swp charge")); 1759 dst_object->cred = curthread->td_ucred; 1760 crhold(dst_object->cred); 1761 *fork_charge += dst_object->charge; 1762 } else if ((dst_object->type == OBJT_DEFAULT || 1763 dst_object->type == OBJT_SWAP) && 1764 dst_object->cred == NULL) { 1765 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1766 dst_entry)); 1767 dst_object->cred = dst_entry->cred; 1768 dst_entry->cred = NULL; 1769 } 1770 1771 /* 1772 * If not an upgrade, then enter the mappings in the pmap as 1773 * read and/or execute accesses. Otherwise, enter them as 1774 * write accesses. 1775 * 1776 * A writeable large page mapping is only created if all of 1777 * the constituent small page mappings are modified. Marking 1778 * PTEs as modified on inception allows promotion to happen 1779 * without taking potentially large number of soft faults. 1780 */ 1781 if (!upgrade) 1782 access &= ~VM_PROT_WRITE; 1783 1784 /* 1785 * Loop through all of the virtual pages within the entry's 1786 * range, copying each page from the source object to the 1787 * destination object. Since the source is wired, those pages 1788 * must exist. In contrast, the destination is pageable. 1789 * Since the destination object doesn't share any backing storage 1790 * with the source object, all of its pages must be dirtied, 1791 * regardless of whether they can be written. 1792 */ 1793 for (vaddr = dst_entry->start, dst_pindex = 0; 1794 vaddr < dst_entry->end; 1795 vaddr += PAGE_SIZE, dst_pindex++) { 1796 again: 1797 /* 1798 * Find the page in the source object, and copy it in. 1799 * Because the source is wired down, the page will be 1800 * in memory. 1801 */ 1802 if (src_object != dst_object) 1803 VM_OBJECT_RLOCK(src_object); 1804 object = src_object; 1805 pindex = src_pindex + dst_pindex; 1806 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1807 (backing_object = object->backing_object) != NULL) { 1808 /* 1809 * Unless the source mapping is read-only or 1810 * it is presently being upgraded from 1811 * read-only, the first object in the shadow 1812 * chain should provide all of the pages. In 1813 * other words, this loop body should never be 1814 * executed when the source mapping is already 1815 * read/write. 1816 */ 1817 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1818 upgrade, 1819 ("vm_fault_copy_entry: main object missing page")); 1820 1821 VM_OBJECT_RLOCK(backing_object); 1822 pindex += OFF_TO_IDX(object->backing_object_offset); 1823 if (object != dst_object) 1824 VM_OBJECT_RUNLOCK(object); 1825 object = backing_object; 1826 } 1827 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1828 1829 if (object != dst_object) { 1830 /* 1831 * Allocate a page in the destination object. 1832 */ 1833 dst_m = vm_page_alloc(dst_object, (src_object == 1834 dst_object ? src_pindex : 0) + dst_pindex, 1835 VM_ALLOC_NORMAL); 1836 if (dst_m == NULL) { 1837 VM_OBJECT_WUNLOCK(dst_object); 1838 VM_OBJECT_RUNLOCK(object); 1839 vm_wait(dst_object); 1840 VM_OBJECT_WLOCK(dst_object); 1841 goto again; 1842 } 1843 pmap_copy_page(src_m, dst_m); 1844 VM_OBJECT_RUNLOCK(object); 1845 dst_m->dirty = dst_m->valid = src_m->valid; 1846 } else { 1847 dst_m = src_m; 1848 if (vm_page_busy_acquire(dst_m, VM_ALLOC_WAITFAIL) == 0) 1849 goto again; 1850 if (dst_m->pindex >= dst_object->size) { 1851 /* 1852 * We are upgrading. Index can occur 1853 * out of bounds if the object type is 1854 * vnode and the file was truncated. 1855 */ 1856 vm_page_xunbusy(dst_m); 1857 break; 1858 } 1859 } 1860 VM_OBJECT_WUNLOCK(dst_object); 1861 1862 /* 1863 * Enter it in the pmap. If a wired, copy-on-write 1864 * mapping is being replaced by a write-enabled 1865 * mapping, then wire that new mapping. 1866 * 1867 * The page can be invalid if the user called 1868 * msync(MS_INVALIDATE) or truncated the backing vnode 1869 * or shared memory object. In this case, do not 1870 * insert it into pmap, but still do the copy so that 1871 * all copies of the wired map entry have similar 1872 * backing pages. 1873 */ 1874 if (vm_page_all_valid(dst_m)) { 1875 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1876 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1877 } 1878 1879 /* 1880 * Mark it no longer busy, and put it on the active list. 1881 */ 1882 VM_OBJECT_WLOCK(dst_object); 1883 1884 if (upgrade) { 1885 if (src_m != dst_m) { 1886 vm_page_unwire(src_m, PQ_INACTIVE); 1887 vm_page_wire(dst_m); 1888 } else { 1889 KASSERT(vm_page_wired(dst_m), 1890 ("dst_m %p is not wired", dst_m)); 1891 } 1892 } else { 1893 vm_page_lock(dst_m); 1894 vm_page_activate(dst_m); 1895 vm_page_unlock(dst_m); 1896 } 1897 vm_page_xunbusy(dst_m); 1898 } 1899 VM_OBJECT_WUNLOCK(dst_object); 1900 if (upgrade) { 1901 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1902 vm_object_deallocate(src_object); 1903 } 1904 } 1905 1906 /* 1907 * Block entry into the machine-independent layer's page fault handler by 1908 * the calling thread. Subsequent calls to vm_fault() by that thread will 1909 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1910 * spurious page faults. 1911 */ 1912 int 1913 vm_fault_disable_pagefaults(void) 1914 { 1915 1916 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1917 } 1918 1919 void 1920 vm_fault_enable_pagefaults(int save) 1921 { 1922 1923 curthread_pflags_restore(save); 1924 } 1925