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 /* Fault parameters. */ 124 vm_offset_t vaddr; 125 vm_page_t *m_hold; 126 vm_prot_t fault_type; 127 vm_prot_t prot; 128 int fault_flags; 129 int oom; 130 boolean_t wired; 131 132 /* Page reference for cow. */ 133 vm_page_t m_cow; 134 135 /* Current object. */ 136 vm_object_t object; 137 vm_pindex_t pindex; 138 vm_page_t m; 139 140 /* Top-level map object. */ 141 vm_object_t first_object; 142 vm_pindex_t first_pindex; 143 vm_page_t first_m; 144 145 /* Map state. */ 146 vm_map_t map; 147 vm_map_entry_t entry; 148 int map_generation; 149 bool lookup_still_valid; 150 151 /* Vnode if locked. */ 152 struct vnode *vp; 153 }; 154 155 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 156 int ahead); 157 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 158 int backward, int forward, bool obj_locked); 159 160 static int vm_pfault_oom_attempts = 3; 161 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_attempts, CTLFLAG_RWTUN, 162 &vm_pfault_oom_attempts, 0, 163 "Number of page allocation attempts in page fault handler before it " 164 "triggers OOM handling"); 165 166 static int vm_pfault_oom_wait = 10; 167 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_wait, CTLFLAG_RWTUN, 168 &vm_pfault_oom_wait, 0, 169 "Number of seconds to wait for free pages before retrying " 170 "the page fault handler"); 171 172 static inline void 173 fault_page_release(vm_page_t *mp) 174 { 175 vm_page_t m; 176 177 m = *mp; 178 if (m != NULL) { 179 /* 180 * We are likely to loop around again and attempt to busy 181 * this page. Deactivating it leaves it available for 182 * pageout while optimizing fault restarts. 183 */ 184 vm_page_deactivate(m); 185 vm_page_xunbusy(m); 186 *mp = NULL; 187 } 188 } 189 190 static inline void 191 fault_page_free(vm_page_t *mp) 192 { 193 vm_page_t m; 194 195 m = *mp; 196 if (m != NULL) { 197 VM_OBJECT_ASSERT_WLOCKED(m->object); 198 if (!vm_page_wired(m)) 199 vm_page_free(m); 200 else 201 vm_page_xunbusy(m); 202 *mp = NULL; 203 } 204 } 205 206 static inline void 207 unlock_map(struct faultstate *fs) 208 { 209 210 if (fs->lookup_still_valid) { 211 vm_map_lookup_done(fs->map, fs->entry); 212 fs->lookup_still_valid = false; 213 } 214 } 215 216 static void 217 unlock_vp(struct faultstate *fs) 218 { 219 220 if (fs->vp != NULL) { 221 vput(fs->vp); 222 fs->vp = NULL; 223 } 224 } 225 226 static void 227 fault_deallocate(struct faultstate *fs) 228 { 229 230 fault_page_release(&fs->m_cow); 231 fault_page_release(&fs->m); 232 vm_object_pip_wakeup(fs->object); 233 if (fs->object != fs->first_object) { 234 VM_OBJECT_WLOCK(fs->first_object); 235 fault_page_free(&fs->first_m); 236 VM_OBJECT_WUNLOCK(fs->first_object); 237 vm_object_pip_wakeup(fs->first_object); 238 } 239 vm_object_deallocate(fs->first_object); 240 unlock_map(fs); 241 unlock_vp(fs); 242 } 243 244 static void 245 unlock_and_deallocate(struct faultstate *fs) 246 { 247 248 VM_OBJECT_WUNLOCK(fs->object); 249 fault_deallocate(fs); 250 } 251 252 static void 253 vm_fault_dirty(struct faultstate *fs, vm_page_t m) 254 { 255 bool need_dirty; 256 257 if (((fs->prot & VM_PROT_WRITE) == 0 && 258 (fs->fault_flags & VM_FAULT_DIRTY) == 0) || 259 (m->oflags & VPO_UNMANAGED) != 0) 260 return; 261 262 VM_PAGE_OBJECT_BUSY_ASSERT(m); 263 264 need_dirty = ((fs->fault_type & VM_PROT_WRITE) != 0 && 265 (fs->fault_flags & VM_FAULT_WIRE) == 0) || 266 (fs->fault_flags & VM_FAULT_DIRTY) != 0; 267 268 vm_object_set_writeable_dirty(m->object); 269 270 /* 271 * If the fault is a write, we know that this page is being 272 * written NOW so dirty it explicitly to save on 273 * pmap_is_modified() calls later. 274 * 275 * Also, since the page is now dirty, we can possibly tell 276 * the pager to release any swap backing the page. 277 */ 278 if (need_dirty && vm_page_set_dirty(m) == 0) { 279 /* 280 * If this is a NOSYNC mmap we do not want to set PGA_NOSYNC 281 * if the page is already dirty to prevent data written with 282 * the expectation of being synced from not being synced. 283 * Likewise if this entry does not request NOSYNC then make 284 * sure the page isn't marked NOSYNC. Applications sharing 285 * data should use the same flags to avoid ping ponging. 286 */ 287 if ((fs->entry->eflags & MAP_ENTRY_NOSYNC) != 0) 288 vm_page_aflag_set(m, PGA_NOSYNC); 289 else 290 vm_page_aflag_clear(m, PGA_NOSYNC); 291 } 292 293 } 294 295 /* 296 * Unlocks fs.first_object and fs.map on success. 297 */ 298 static int 299 vm_fault_soft_fast(struct faultstate *fs) 300 { 301 vm_page_t m, m_map; 302 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \ 303 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \ 304 VM_NRESERVLEVEL > 0 305 vm_page_t m_super; 306 int flags; 307 #endif 308 int psind, rv; 309 vm_offset_t vaddr; 310 311 MPASS(fs->vp == NULL); 312 vaddr = fs->vaddr; 313 vm_object_busy(fs->first_object); 314 m = vm_page_lookup(fs->first_object, fs->first_pindex); 315 /* A busy page can be mapped for read|execute access. */ 316 if (m == NULL || ((fs->prot & VM_PROT_WRITE) != 0 && 317 vm_page_busied(m)) || !vm_page_all_valid(m)) { 318 rv = KERN_FAILURE; 319 goto out; 320 } 321 m_map = m; 322 psind = 0; 323 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \ 324 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \ 325 VM_NRESERVLEVEL > 0 326 if ((m->flags & PG_FICTITIOUS) == 0 && 327 (m_super = vm_reserv_to_superpage(m)) != NULL && 328 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start && 329 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end && 330 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) & 331 (pagesizes[m_super->psind] - 1)) && !fs->wired && 332 pmap_ps_enabled(fs->map->pmap)) { 333 flags = PS_ALL_VALID; 334 if ((fs->prot & VM_PROT_WRITE) != 0) { 335 /* 336 * Create a superpage mapping allowing write access 337 * only if none of the constituent pages are busy and 338 * all of them are already dirty (except possibly for 339 * the page that was faulted on). 340 */ 341 flags |= PS_NONE_BUSY; 342 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0) 343 flags |= PS_ALL_DIRTY; 344 } 345 if (vm_page_ps_test(m_super, flags, m)) { 346 m_map = m_super; 347 psind = m_super->psind; 348 vaddr = rounddown2(vaddr, pagesizes[psind]); 349 /* Preset the modified bit for dirty superpages. */ 350 if ((flags & PS_ALL_DIRTY) != 0) 351 fs->fault_type |= VM_PROT_WRITE; 352 } 353 } 354 #endif 355 rv = pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type | 356 PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind); 357 if (rv != KERN_SUCCESS) 358 goto out; 359 if (fs->m_hold != NULL) { 360 (*fs->m_hold) = m; 361 vm_page_wire(m); 362 } 363 if (psind == 0 && !fs->wired) 364 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true); 365 VM_OBJECT_RUNLOCK(fs->first_object); 366 vm_fault_dirty(fs, m); 367 vm_map_lookup_done(fs->map, fs->entry); 368 curthread->td_ru.ru_minflt++; 369 370 out: 371 vm_object_unbusy(fs->first_object); 372 return (rv); 373 } 374 375 static void 376 vm_fault_restore_map_lock(struct faultstate *fs) 377 { 378 379 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 380 MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0); 381 382 if (!vm_map_trylock_read(fs->map)) { 383 VM_OBJECT_WUNLOCK(fs->first_object); 384 vm_map_lock_read(fs->map); 385 VM_OBJECT_WLOCK(fs->first_object); 386 } 387 fs->lookup_still_valid = true; 388 } 389 390 static void 391 vm_fault_populate_check_page(vm_page_t m) 392 { 393 394 /* 395 * Check each page to ensure that the pager is obeying the 396 * interface: the page must be installed in the object, fully 397 * valid, and exclusively busied. 398 */ 399 MPASS(m != NULL); 400 MPASS(vm_page_all_valid(m)); 401 MPASS(vm_page_xbusied(m)); 402 } 403 404 static void 405 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first, 406 vm_pindex_t last) 407 { 408 vm_page_t m; 409 vm_pindex_t pidx; 410 411 VM_OBJECT_ASSERT_WLOCKED(object); 412 MPASS(first <= last); 413 for (pidx = first, m = vm_page_lookup(object, pidx); 414 pidx <= last; pidx++, m = vm_page_next(m)) { 415 vm_fault_populate_check_page(m); 416 vm_page_deactivate(m); 417 vm_page_xunbusy(m); 418 } 419 } 420 421 static int 422 vm_fault_populate(struct faultstate *fs) 423 { 424 vm_offset_t vaddr; 425 vm_page_t m; 426 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx; 427 int i, npages, psind, rv; 428 429 MPASS(fs->object == fs->first_object); 430 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 431 MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0); 432 MPASS(fs->first_object->backing_object == NULL); 433 MPASS(fs->lookup_still_valid); 434 435 pager_first = OFF_TO_IDX(fs->entry->offset); 436 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1; 437 unlock_map(fs); 438 unlock_vp(fs); 439 440 /* 441 * Call the pager (driver) populate() method. 442 * 443 * There is no guarantee that the method will be called again 444 * if the current fault is for read, and a future fault is 445 * for write. Report the entry's maximum allowed protection 446 * to the driver. 447 */ 448 rv = vm_pager_populate(fs->first_object, fs->first_pindex, 449 fs->fault_type, fs->entry->max_protection, &pager_first, &pager_last); 450 451 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 452 if (rv == VM_PAGER_BAD) { 453 /* 454 * VM_PAGER_BAD is the backdoor for a pager to request 455 * normal fault handling. 456 */ 457 vm_fault_restore_map_lock(fs); 458 if (fs->map->timestamp != fs->map_generation) 459 return (KERN_RESTART); 460 return (KERN_NOT_RECEIVER); 461 } 462 if (rv != VM_PAGER_OK) 463 return (KERN_FAILURE); /* AKA SIGSEGV */ 464 465 /* Ensure that the driver is obeying the interface. */ 466 MPASS(pager_first <= pager_last); 467 MPASS(fs->first_pindex <= pager_last); 468 MPASS(fs->first_pindex >= pager_first); 469 MPASS(pager_last < fs->first_object->size); 470 471 vm_fault_restore_map_lock(fs); 472 if (fs->map->timestamp != fs->map_generation) { 473 vm_fault_populate_cleanup(fs->first_object, pager_first, 474 pager_last); 475 return (KERN_RESTART); 476 } 477 478 /* 479 * The map is unchanged after our last unlock. Process the fault. 480 * 481 * The range [pager_first, pager_last] that is given to the 482 * pager is only a hint. The pager may populate any range 483 * within the object that includes the requested page index. 484 * In case the pager expanded the range, clip it to fit into 485 * the map entry. 486 */ 487 map_first = OFF_TO_IDX(fs->entry->offset); 488 if (map_first > pager_first) { 489 vm_fault_populate_cleanup(fs->first_object, pager_first, 490 map_first - 1); 491 pager_first = map_first; 492 } 493 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1; 494 if (map_last < pager_last) { 495 vm_fault_populate_cleanup(fs->first_object, map_last + 1, 496 pager_last); 497 pager_last = map_last; 498 } 499 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx); 500 pidx <= pager_last; 501 pidx += npages, m = vm_page_next(&m[npages - 1])) { 502 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset; 503 #if defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \ 504 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv) 505 psind = m->psind; 506 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 || 507 pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last || 508 !pmap_ps_enabled(fs->map->pmap) || fs->wired)) 509 psind = 0; 510 #else 511 psind = 0; 512 #endif 513 npages = atop(pagesizes[psind]); 514 for (i = 0; i < npages; i++) { 515 vm_fault_populate_check_page(&m[i]); 516 vm_fault_dirty(fs, &m[i]); 517 } 518 VM_OBJECT_WUNLOCK(fs->first_object); 519 rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot, fs->fault_type | 520 (fs->wired ? PMAP_ENTER_WIRED : 0), psind); 521 #if defined(__amd64__) 522 if (psind > 0 && rv == KERN_FAILURE) { 523 for (i = 0; i < npages; i++) { 524 rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i), 525 &m[i], fs->prot, fs->fault_type | 526 (fs->wired ? PMAP_ENTER_WIRED : 0), 0); 527 MPASS(rv == KERN_SUCCESS); 528 } 529 } 530 #else 531 MPASS(rv == KERN_SUCCESS); 532 #endif 533 VM_OBJECT_WLOCK(fs->first_object); 534 for (i = 0; i < npages; i++) { 535 if ((fs->fault_flags & VM_FAULT_WIRE) != 0) 536 vm_page_wire(&m[i]); 537 else 538 vm_page_activate(&m[i]); 539 if (fs->m_hold != NULL && m[i].pindex == fs->first_pindex) { 540 (*fs->m_hold) = &m[i]; 541 vm_page_wire(&m[i]); 542 } 543 vm_page_xunbusy(&m[i]); 544 } 545 } 546 curthread->td_ru.ru_majflt++; 547 return (KERN_SUCCESS); 548 } 549 550 static int prot_fault_translation; 551 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RWTUN, 552 &prot_fault_translation, 0, 553 "Control signal to deliver on protection fault"); 554 555 /* compat definition to keep common code for signal translation */ 556 #define UCODE_PAGEFLT 12 557 #ifdef T_PAGEFLT 558 _Static_assert(UCODE_PAGEFLT == T_PAGEFLT, "T_PAGEFLT"); 559 #endif 560 561 /* 562 * vm_fault_trap: 563 * 564 * Handle a page fault occurring at the given address, 565 * requiring the given permissions, in the map specified. 566 * If successful, the page is inserted into the 567 * associated physical map. 568 * 569 * NOTE: the given address should be truncated to the 570 * proper page address. 571 * 572 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 573 * a standard error specifying why the fault is fatal is returned. 574 * 575 * The map in question must be referenced, and remains so. 576 * Caller may hold no locks. 577 */ 578 int 579 vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 580 int fault_flags, int *signo, int *ucode) 581 { 582 int result; 583 584 MPASS(signo == NULL || ucode != NULL); 585 #ifdef KTRACE 586 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULT)) 587 ktrfault(vaddr, fault_type); 588 #endif 589 result = vm_fault(map, trunc_page(vaddr), fault_type, fault_flags, 590 NULL); 591 KASSERT(result == KERN_SUCCESS || result == KERN_FAILURE || 592 result == KERN_INVALID_ADDRESS || 593 result == KERN_RESOURCE_SHORTAGE || 594 result == KERN_PROTECTION_FAILURE || 595 result == KERN_OUT_OF_BOUNDS, 596 ("Unexpected Mach error %d from vm_fault()", result)); 597 #ifdef KTRACE 598 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULTEND)) 599 ktrfaultend(result); 600 #endif 601 if (result != KERN_SUCCESS && signo != NULL) { 602 switch (result) { 603 case KERN_FAILURE: 604 case KERN_INVALID_ADDRESS: 605 *signo = SIGSEGV; 606 *ucode = SEGV_MAPERR; 607 break; 608 case KERN_RESOURCE_SHORTAGE: 609 *signo = SIGBUS; 610 *ucode = BUS_OOMERR; 611 break; 612 case KERN_OUT_OF_BOUNDS: 613 *signo = SIGBUS; 614 *ucode = BUS_OBJERR; 615 break; 616 case KERN_PROTECTION_FAILURE: 617 if (prot_fault_translation == 0) { 618 /* 619 * Autodetect. This check also covers 620 * the images without the ABI-tag ELF 621 * note. 622 */ 623 if (SV_CURPROC_ABI() == SV_ABI_FREEBSD && 624 curproc->p_osrel >= P_OSREL_SIGSEGV) { 625 *signo = SIGSEGV; 626 *ucode = SEGV_ACCERR; 627 } else { 628 *signo = SIGBUS; 629 *ucode = UCODE_PAGEFLT; 630 } 631 } else if (prot_fault_translation == 1) { 632 /* Always compat mode. */ 633 *signo = SIGBUS; 634 *ucode = UCODE_PAGEFLT; 635 } else { 636 /* Always SIGSEGV mode. */ 637 *signo = SIGSEGV; 638 *ucode = SEGV_ACCERR; 639 } 640 break; 641 default: 642 KASSERT(0, ("Unexpected Mach error %d from vm_fault()", 643 result)); 644 break; 645 } 646 } 647 return (result); 648 } 649 650 static int 651 vm_fault_lock_vnode(struct faultstate *fs, bool objlocked) 652 { 653 struct vnode *vp; 654 int error, locked; 655 656 if (fs->object->type != OBJT_VNODE) 657 return (KERN_SUCCESS); 658 vp = fs->object->handle; 659 if (vp == fs->vp) { 660 ASSERT_VOP_LOCKED(vp, "saved vnode is not locked"); 661 return (KERN_SUCCESS); 662 } 663 664 /* 665 * Perform an unlock in case the desired vnode changed while 666 * the map was unlocked during a retry. 667 */ 668 unlock_vp(fs); 669 670 locked = VOP_ISLOCKED(vp); 671 if (locked != LK_EXCLUSIVE) 672 locked = LK_SHARED; 673 674 /* 675 * We must not sleep acquiring the vnode lock while we have 676 * the page exclusive busied or the object's 677 * paging-in-progress count incremented. Otherwise, we could 678 * deadlock. 679 */ 680 error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT, curthread); 681 if (error == 0) { 682 fs->vp = vp; 683 return (KERN_SUCCESS); 684 } 685 686 vhold(vp); 687 if (objlocked) 688 unlock_and_deallocate(fs); 689 else 690 fault_deallocate(fs); 691 error = vget(vp, locked | LK_RETRY | LK_CANRECURSE, curthread); 692 vdrop(vp); 693 fs->vp = vp; 694 KASSERT(error == 0, ("vm_fault: vget failed %d", error)); 695 return (KERN_RESOURCE_SHORTAGE); 696 } 697 698 /* 699 * Calculate the desired readahead. Handle drop-behind. 700 * 701 * Returns the number of readahead blocks to pass to the pager. 702 */ 703 static int 704 vm_fault_readahead(struct faultstate *fs) 705 { 706 int era, nera; 707 u_char behavior; 708 709 KASSERT(fs->lookup_still_valid, ("map unlocked")); 710 era = fs->entry->read_ahead; 711 behavior = vm_map_entry_behavior(fs->entry); 712 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 713 nera = 0; 714 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 715 nera = VM_FAULT_READ_AHEAD_MAX; 716 if (fs->vaddr == fs->entry->next_read) 717 vm_fault_dontneed(fs, fs->vaddr, nera); 718 } else if (fs->vaddr == fs->entry->next_read) { 719 /* 720 * This is a sequential fault. Arithmetically 721 * increase the requested number of pages in 722 * the read-ahead window. The requested 723 * number of pages is "# of sequential faults 724 * x (read ahead min + 1) + read ahead min" 725 */ 726 nera = VM_FAULT_READ_AHEAD_MIN; 727 if (era > 0) { 728 nera += era + 1; 729 if (nera > VM_FAULT_READ_AHEAD_MAX) 730 nera = VM_FAULT_READ_AHEAD_MAX; 731 } 732 if (era == VM_FAULT_READ_AHEAD_MAX) 733 vm_fault_dontneed(fs, fs->vaddr, nera); 734 } else { 735 /* 736 * This is a non-sequential fault. 737 */ 738 nera = 0; 739 } 740 if (era != nera) { 741 /* 742 * A read lock on the map suffices to update 743 * the read ahead count safely. 744 */ 745 fs->entry->read_ahead = nera; 746 } 747 748 return (nera); 749 } 750 751 static int 752 vm_fault_lookup(struct faultstate *fs) 753 { 754 int result; 755 756 KASSERT(!fs->lookup_still_valid, 757 ("vm_fault_lookup: Map already locked.")); 758 result = vm_map_lookup(&fs->map, fs->vaddr, fs->fault_type | 759 VM_PROT_FAULT_LOOKUP, &fs->entry, &fs->first_object, 760 &fs->first_pindex, &fs->prot, &fs->wired); 761 if (result != KERN_SUCCESS) { 762 unlock_vp(fs); 763 return (result); 764 } 765 766 fs->map_generation = fs->map->timestamp; 767 768 if (fs->entry->eflags & MAP_ENTRY_NOFAULT) { 769 panic("%s: fault on nofault entry, addr: %#lx", 770 __func__, (u_long)fs->vaddr); 771 } 772 773 if (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION && 774 fs->entry->wiring_thread != curthread) { 775 vm_map_unlock_read(fs->map); 776 vm_map_lock(fs->map); 777 if (vm_map_lookup_entry(fs->map, fs->vaddr, &fs->entry) && 778 (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 779 unlock_vp(fs); 780 fs->entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 781 vm_map_unlock_and_wait(fs->map, 0); 782 } else 783 vm_map_unlock(fs->map); 784 return (KERN_RESOURCE_SHORTAGE); 785 } 786 787 MPASS((fs->entry->eflags & MAP_ENTRY_GUARD) == 0); 788 789 if (fs->wired) 790 fs->fault_type = fs->prot | (fs->fault_type & VM_PROT_COPY); 791 else 792 KASSERT((fs->fault_flags & VM_FAULT_WIRE) == 0, 793 ("!fs->wired && VM_FAULT_WIRE")); 794 fs->lookup_still_valid = true; 795 796 return (KERN_SUCCESS); 797 } 798 799 static int 800 vm_fault_relookup(struct faultstate *fs) 801 { 802 vm_object_t retry_object; 803 vm_pindex_t retry_pindex; 804 vm_prot_t retry_prot; 805 int result; 806 807 if (!vm_map_trylock_read(fs->map)) 808 return (KERN_RESTART); 809 810 fs->lookup_still_valid = true; 811 if (fs->map->timestamp == fs->map_generation) 812 return (KERN_SUCCESS); 813 814 result = vm_map_lookup_locked(&fs->map, fs->vaddr, fs->fault_type, 815 &fs->entry, &retry_object, &retry_pindex, &retry_prot, 816 &fs->wired); 817 if (result != KERN_SUCCESS) { 818 /* 819 * If retry of map lookup would have blocked then 820 * retry fault from start. 821 */ 822 if (result == KERN_FAILURE) 823 return (KERN_RESTART); 824 return (result); 825 } 826 if (retry_object != fs->first_object || 827 retry_pindex != fs->first_pindex) 828 return (KERN_RESTART); 829 830 /* 831 * Check whether the protection has changed or the object has 832 * been copied while we left the map unlocked. Changing from 833 * read to write permission is OK - we leave the page 834 * write-protected, and catch the write fault. Changing from 835 * write to read permission means that we can't mark the page 836 * write-enabled after all. 837 */ 838 fs->prot &= retry_prot; 839 fs->fault_type &= retry_prot; 840 if (fs->prot == 0) 841 return (KERN_RESTART); 842 843 /* Reassert because wired may have changed. */ 844 KASSERT(fs->wired || (fs->fault_flags & VM_FAULT_WIRE) == 0, 845 ("!wired && VM_FAULT_WIRE")); 846 847 return (KERN_SUCCESS); 848 } 849 850 static void 851 vm_fault_cow(struct faultstate *fs) 852 { 853 bool is_first_object_locked; 854 855 /* 856 * This allows pages to be virtually copied from a backing_object 857 * into the first_object, where the backing object has no other 858 * refs to it, and cannot gain any more refs. Instead of a bcopy, 859 * we just move the page from the backing object to the first 860 * object. Note that we must mark the page dirty in the first 861 * object so that it will go out to swap when needed. 862 */ 863 is_first_object_locked = false; 864 if ( 865 /* 866 * Only one shadow object and no other refs. 867 */ 868 fs->object->shadow_count == 1 && fs->object->ref_count == 1 && 869 /* 870 * No other ways to look the object up 871 */ 872 fs->object->handle == NULL && (fs->object->flags & OBJ_ANON) != 0 && 873 /* 874 * We don't chase down the shadow chain and we can acquire locks. 875 */ 876 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs->first_object)) && 877 fs->object == fs->first_object->backing_object && 878 VM_OBJECT_TRYWLOCK(fs->object)) { 879 880 /* 881 * Remove but keep xbusy for replace. fs->m is moved into 882 * fs->first_object and left busy while fs->first_m is 883 * conditionally freed. 884 */ 885 vm_page_remove_xbusy(fs->m); 886 vm_page_replace(fs->m, fs->first_object, fs->first_pindex, 887 fs->first_m); 888 vm_page_dirty(fs->m); 889 #if VM_NRESERVLEVEL > 0 890 /* 891 * Rename the reservation. 892 */ 893 vm_reserv_rename(fs->m, fs->first_object, fs->object, 894 OFF_TO_IDX(fs->first_object->backing_object_offset)); 895 #endif 896 VM_OBJECT_WUNLOCK(fs->object); 897 VM_OBJECT_WUNLOCK(fs->first_object); 898 fs->first_m = fs->m; 899 fs->m = NULL; 900 VM_CNT_INC(v_cow_optim); 901 } else { 902 if (is_first_object_locked) 903 VM_OBJECT_WUNLOCK(fs->first_object); 904 /* 905 * Oh, well, lets copy it. 906 */ 907 pmap_copy_page(fs->m, fs->first_m); 908 vm_page_valid(fs->first_m); 909 if (fs->wired && (fs->fault_flags & VM_FAULT_WIRE) == 0) { 910 vm_page_wire(fs->first_m); 911 vm_page_unwire(fs->m, PQ_INACTIVE); 912 } 913 /* 914 * Save the cow page to be released after 915 * pmap_enter is complete. 916 */ 917 fs->m_cow = fs->m; 918 fs->m = NULL; 919 } 920 /* 921 * fs->object != fs->first_object due to above 922 * conditional 923 */ 924 vm_object_pip_wakeup(fs->object); 925 926 /* 927 * Only use the new page below... 928 */ 929 fs->object = fs->first_object; 930 fs->pindex = fs->first_pindex; 931 fs->m = fs->first_m; 932 VM_CNT_INC(v_cow_faults); 933 curthread->td_cow++; 934 } 935 936 static bool 937 vm_fault_next(struct faultstate *fs) 938 { 939 vm_object_t next_object; 940 941 /* 942 * The requested page does not exist at this object/ 943 * offset. Remove the invalid page from the object, 944 * waking up anyone waiting for it, and continue on to 945 * the next object. However, if this is the top-level 946 * object, we must leave the busy page in place to 947 * prevent another process from rushing past us, and 948 * inserting the page in that object at the same time 949 * that we are. 950 */ 951 if (fs->object == fs->first_object) { 952 fs->first_m = fs->m; 953 fs->m = NULL; 954 } else 955 fault_page_free(&fs->m); 956 957 /* 958 * Move on to the next object. Lock the next object before 959 * unlocking the current one. 960 */ 961 VM_OBJECT_ASSERT_WLOCKED(fs->object); 962 next_object = fs->object->backing_object; 963 if (next_object == NULL) 964 return (false); 965 MPASS(fs->first_m != NULL); 966 KASSERT(fs->object != next_object, ("object loop %p", next_object)); 967 VM_OBJECT_WLOCK(next_object); 968 vm_object_pip_add(next_object, 1); 969 if (fs->object != fs->first_object) 970 vm_object_pip_wakeup(fs->object); 971 fs->pindex += OFF_TO_IDX(fs->object->backing_object_offset); 972 VM_OBJECT_WUNLOCK(fs->object); 973 fs->object = next_object; 974 975 return (true); 976 } 977 978 static void 979 vm_fault_zerofill(struct faultstate *fs) 980 { 981 982 /* 983 * If there's no object left, fill the page in the top 984 * object with zeros. 985 */ 986 if (fs->object != fs->first_object) { 987 vm_object_pip_wakeup(fs->object); 988 fs->object = fs->first_object; 989 fs->pindex = fs->first_pindex; 990 } 991 MPASS(fs->first_m != NULL); 992 MPASS(fs->m == NULL); 993 fs->m = fs->first_m; 994 fs->first_m = NULL; 995 996 /* 997 * Zero the page if necessary and mark it valid. 998 */ 999 if ((fs->m->flags & PG_ZERO) == 0) { 1000 pmap_zero_page(fs->m); 1001 } else { 1002 VM_CNT_INC(v_ozfod); 1003 } 1004 VM_CNT_INC(v_zfod); 1005 vm_page_valid(fs->m); 1006 } 1007 1008 /* 1009 * Allocate a page directly or via the object populate method. 1010 */ 1011 static int 1012 vm_fault_allocate(struct faultstate *fs) 1013 { 1014 struct domainset *dset; 1015 int alloc_req; 1016 int rv; 1017 1018 1019 if ((fs->object->flags & OBJ_SIZEVNLOCK) != 0) { 1020 rv = vm_fault_lock_vnode(fs, true); 1021 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE); 1022 if (rv == KERN_RESOURCE_SHORTAGE) 1023 return (rv); 1024 } 1025 1026 if (fs->pindex >= fs->object->size) 1027 return (KERN_OUT_OF_BOUNDS); 1028 1029 if (fs->object == fs->first_object && 1030 (fs->first_object->flags & OBJ_POPULATE) != 0 && 1031 fs->first_object->shadow_count == 0) { 1032 rv = vm_fault_populate(fs); 1033 switch (rv) { 1034 case KERN_SUCCESS: 1035 case KERN_FAILURE: 1036 case KERN_RESTART: 1037 return (rv); 1038 case KERN_NOT_RECEIVER: 1039 /* 1040 * Pager's populate() method 1041 * returned VM_PAGER_BAD. 1042 */ 1043 break; 1044 default: 1045 panic("inconsistent return codes"); 1046 } 1047 } 1048 1049 /* 1050 * Allocate a new page for this object/offset pair. 1051 * 1052 * Unlocked read of the p_flag is harmless. At worst, the P_KILLED 1053 * might be not observed there, and allocation can fail, causing 1054 * restart and new reading of the p_flag. 1055 */ 1056 dset = fs->object->domain.dr_policy; 1057 if (dset == NULL) 1058 dset = curthread->td_domain.dr_policy; 1059 if (!vm_page_count_severe_set(&dset->ds_mask) || P_KILLED(curproc)) { 1060 #if VM_NRESERVLEVEL > 0 1061 vm_object_color(fs->object, atop(fs->vaddr) - fs->pindex); 1062 #endif 1063 alloc_req = P_KILLED(curproc) ? 1064 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 1065 if (fs->object->type != OBJT_VNODE && 1066 fs->object->backing_object == NULL) 1067 alloc_req |= VM_ALLOC_ZERO; 1068 fs->m = vm_page_alloc(fs->object, fs->pindex, alloc_req); 1069 } 1070 if (fs->m == NULL) { 1071 unlock_and_deallocate(fs); 1072 if (vm_pfault_oom_attempts < 0 || 1073 fs->oom < vm_pfault_oom_attempts) { 1074 fs->oom++; 1075 vm_waitpfault(dset, vm_pfault_oom_wait * hz); 1076 } else { 1077 if (bootverbose) 1078 printf( 1079 "proc %d (%s) failed to alloc page on fault, starting OOM\n", 1080 curproc->p_pid, curproc->p_comm); 1081 vm_pageout_oom(VM_OOM_MEM_PF); 1082 fs->oom = 0; 1083 } 1084 return (KERN_RESOURCE_SHORTAGE); 1085 } 1086 fs->oom = 0; 1087 1088 return (KERN_NOT_RECEIVER); 1089 } 1090 1091 /* 1092 * Call the pager to retrieve the page if there is a chance 1093 * that the pager has it, and potentially retrieve additional 1094 * pages at the same time. 1095 */ 1096 static int 1097 vm_fault_getpages(struct faultstate *fs, int nera, int *behindp, int *aheadp) 1098 { 1099 vm_offset_t e_end, e_start; 1100 int ahead, behind, cluster_offset, rv; 1101 u_char behavior; 1102 1103 /* 1104 * Prepare for unlocking the map. Save the map 1105 * entry's start and end addresses, which are used to 1106 * optimize the size of the pager operation below. 1107 * Even if the map entry's addresses change after 1108 * unlocking the map, using the saved addresses is 1109 * safe. 1110 */ 1111 e_start = fs->entry->start; 1112 e_end = fs->entry->end; 1113 behavior = vm_map_entry_behavior(fs->entry); 1114 1115 /* 1116 * Release the map lock before locking the vnode or 1117 * sleeping in the pager. (If the current object has 1118 * a shadow, then an earlier iteration of this loop 1119 * may have already unlocked the map.) 1120 */ 1121 unlock_map(fs); 1122 1123 rv = vm_fault_lock_vnode(fs, false); 1124 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE); 1125 if (rv == KERN_RESOURCE_SHORTAGE) 1126 return (rv); 1127 KASSERT(fs->vp == NULL || !fs->map->system_map, 1128 ("vm_fault: vnode-backed object mapped by system map")); 1129 1130 /* 1131 * Page in the requested page and hint the pager, 1132 * that it may bring up surrounding pages. 1133 */ 1134 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 1135 P_KILLED(curproc)) { 1136 behind = 0; 1137 ahead = 0; 1138 } else { 1139 /* Is this a sequential fault? */ 1140 if (nera > 0) { 1141 behind = 0; 1142 ahead = nera; 1143 } else { 1144 /* 1145 * Request a cluster of pages that is 1146 * aligned to a VM_FAULT_READ_DEFAULT 1147 * page offset boundary within the 1148 * object. Alignment to a page offset 1149 * boundary is more likely to coincide 1150 * with the underlying file system 1151 * block than alignment to a virtual 1152 * address boundary. 1153 */ 1154 cluster_offset = fs->pindex % VM_FAULT_READ_DEFAULT; 1155 behind = ulmin(cluster_offset, 1156 atop(fs->vaddr - e_start)); 1157 ahead = VM_FAULT_READ_DEFAULT - 1 - cluster_offset; 1158 } 1159 ahead = ulmin(ahead, atop(e_end - fs->vaddr) - 1); 1160 } 1161 *behindp = behind; 1162 *aheadp = ahead; 1163 rv = vm_pager_get_pages(fs->object, &fs->m, 1, behindp, aheadp); 1164 if (rv == VM_PAGER_OK) 1165 return (KERN_SUCCESS); 1166 if (rv == VM_PAGER_ERROR) 1167 printf("vm_fault: pager read error, pid %d (%s)\n", 1168 curproc->p_pid, curproc->p_comm); 1169 /* 1170 * If an I/O error occurred or the requested page was 1171 * outside the range of the pager, clean up and return 1172 * an error. 1173 */ 1174 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) 1175 return (KERN_OUT_OF_BOUNDS); 1176 return (KERN_NOT_RECEIVER); 1177 } 1178 1179 /* 1180 * Wait/Retry if the page is busy. We have to do this if the page is 1181 * either exclusive or shared busy because the vm_pager may be using 1182 * read busy for pageouts (and even pageins if it is the vnode pager), 1183 * and we could end up trying to pagein and pageout the same page 1184 * simultaneously. 1185 * 1186 * We can theoretically allow the busy case on a read fault if the page 1187 * is marked valid, but since such pages are typically already pmap'd, 1188 * putting that special case in might be more effort then it is worth. 1189 * We cannot under any circumstances mess around with a shared busied 1190 * page except, perhaps, to pmap it. 1191 */ 1192 static void 1193 vm_fault_busy_sleep(struct faultstate *fs) 1194 { 1195 /* 1196 * Reference the page before unlocking and 1197 * sleeping so that the page daemon is less 1198 * likely to reclaim it. 1199 */ 1200 vm_page_aflag_set(fs->m, PGA_REFERENCED); 1201 if (fs->object != fs->first_object) { 1202 fault_page_release(&fs->first_m); 1203 vm_object_pip_wakeup(fs->first_object); 1204 } 1205 vm_object_pip_wakeup(fs->object); 1206 unlock_map(fs); 1207 if (fs->m == vm_page_lookup(fs->object, fs->pindex)) 1208 vm_page_busy_sleep(fs->m, "vmpfw", false); 1209 else 1210 VM_OBJECT_WUNLOCK(fs->object); 1211 VM_CNT_INC(v_intrans); 1212 vm_object_deallocate(fs->first_object); 1213 } 1214 1215 int 1216 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 1217 int fault_flags, vm_page_t *m_hold) 1218 { 1219 struct faultstate fs; 1220 int ahead, behind, faultcount; 1221 int nera, result, rv; 1222 bool dead, hardfault; 1223 1224 VM_CNT_INC(v_vm_faults); 1225 1226 if ((curthread->td_pflags & TDP_NOFAULTING) != 0) 1227 return (KERN_PROTECTION_FAILURE); 1228 1229 fs.vp = NULL; 1230 fs.vaddr = vaddr; 1231 fs.m_hold = m_hold; 1232 fs.fault_flags = fault_flags; 1233 fs.map = map; 1234 fs.lookup_still_valid = false; 1235 fs.oom = 0; 1236 faultcount = 0; 1237 nera = -1; 1238 hardfault = false; 1239 1240 RetryFault: 1241 fs.fault_type = fault_type; 1242 1243 /* 1244 * Find the backing store object and offset into it to begin the 1245 * search. 1246 */ 1247 result = vm_fault_lookup(&fs); 1248 if (result != KERN_SUCCESS) { 1249 if (result == KERN_RESOURCE_SHORTAGE) 1250 goto RetryFault; 1251 return (result); 1252 } 1253 1254 /* 1255 * Try to avoid lock contention on the top-level object through 1256 * special-case handling of some types of page faults, specifically, 1257 * those that are mapping an existing page from the top-level object. 1258 * Under this condition, a read lock on the object suffices, allowing 1259 * multiple page faults of a similar type to run in parallel. 1260 */ 1261 if (fs.vp == NULL /* avoid locked vnode leak */ && 1262 (fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) { 1263 VM_OBJECT_RLOCK(fs.first_object); 1264 rv = vm_fault_soft_fast(&fs); 1265 if (rv == KERN_SUCCESS) 1266 return (rv); 1267 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 1268 VM_OBJECT_RUNLOCK(fs.first_object); 1269 VM_OBJECT_WLOCK(fs.first_object); 1270 } 1271 } else { 1272 VM_OBJECT_WLOCK(fs.first_object); 1273 } 1274 1275 /* 1276 * Make a reference to this object to prevent its disposal while we 1277 * are messing with it. Once we have the reference, the map is free 1278 * to be diddled. Since objects reference their shadows (and copies), 1279 * they will stay around as well. 1280 * 1281 * Bump the paging-in-progress count to prevent size changes (e.g. 1282 * truncation operations) during I/O. 1283 */ 1284 vm_object_reference_locked(fs.first_object); 1285 vm_object_pip_add(fs.first_object, 1); 1286 1287 fs.m_cow = fs.m = fs.first_m = NULL; 1288 1289 /* 1290 * Search for the page at object/offset. 1291 */ 1292 fs.object = fs.first_object; 1293 fs.pindex = fs.first_pindex; 1294 while (TRUE) { 1295 KASSERT(fs.m == NULL, 1296 ("page still set %p at loop start", fs.m)); 1297 /* 1298 * If the object is marked for imminent termination, 1299 * we retry here, since the collapse pass has raced 1300 * with us. Otherwise, if we see terminally dead 1301 * object, return fail. 1302 */ 1303 if ((fs.object->flags & OBJ_DEAD) != 0) { 1304 dead = fs.object->type == OBJT_DEAD; 1305 unlock_and_deallocate(&fs); 1306 if (dead) 1307 return (KERN_PROTECTION_FAILURE); 1308 pause("vmf_de", 1); 1309 goto RetryFault; 1310 } 1311 1312 /* 1313 * See if page is resident 1314 */ 1315 fs.m = vm_page_lookup(fs.object, fs.pindex); 1316 if (fs.m != NULL) { 1317 if (vm_page_tryxbusy(fs.m) == 0) { 1318 vm_fault_busy_sleep(&fs); 1319 goto RetryFault; 1320 } 1321 1322 /* 1323 * The page is marked busy for other processes and the 1324 * pagedaemon. If it still is completely valid we 1325 * are done. 1326 */ 1327 if (vm_page_all_valid(fs.m)) { 1328 VM_OBJECT_WUNLOCK(fs.object); 1329 break; /* break to PAGE HAS BEEN FOUND. */ 1330 } 1331 } 1332 VM_OBJECT_ASSERT_WLOCKED(fs.object); 1333 1334 /* 1335 * Page is not resident. If the pager might contain the page 1336 * or this is the beginning of the search, allocate a new 1337 * page. (Default objects are zero-fill, so there is no real 1338 * pager for them.) 1339 */ 1340 if (fs.m == NULL && (fs.object->type != OBJT_DEFAULT || 1341 fs.object == fs.first_object)) { 1342 rv = vm_fault_allocate(&fs); 1343 switch (rv) { 1344 case KERN_RESTART: 1345 unlock_and_deallocate(&fs); 1346 /* FALLTHROUGH */ 1347 case KERN_RESOURCE_SHORTAGE: 1348 goto RetryFault; 1349 case KERN_SUCCESS: 1350 case KERN_FAILURE: 1351 case KERN_OUT_OF_BOUNDS: 1352 unlock_and_deallocate(&fs); 1353 return (rv); 1354 case KERN_NOT_RECEIVER: 1355 break; 1356 default: 1357 panic("vm_fault: Unhandled rv %d", rv); 1358 } 1359 } 1360 1361 /* 1362 * Default objects have no pager so no exclusive busy exists 1363 * to protect this page in the chain. Skip to the next 1364 * object without dropping the lock to preserve atomicity of 1365 * shadow faults. 1366 */ 1367 if (fs.object->type != OBJT_DEFAULT) { 1368 /* 1369 * At this point, we have either allocated a new page 1370 * or found an existing page that is only partially 1371 * valid. 1372 * 1373 * We hold a reference on the current object and the 1374 * page is exclusive busied. The exclusive busy 1375 * prevents simultaneous faults and collapses while 1376 * the object lock is dropped. 1377 */ 1378 VM_OBJECT_WUNLOCK(fs.object); 1379 1380 /* 1381 * If the pager for the current object might have 1382 * the page, then determine the number of additional 1383 * pages to read and potentially reprioritize 1384 * previously read pages for earlier reclamation. 1385 * These operations should only be performed once per 1386 * page fault. Even if the current pager doesn't 1387 * have the page, the number of additional pages to 1388 * read will apply to subsequent objects in the 1389 * shadow chain. 1390 */ 1391 if (nera == -1 && !P_KILLED(curproc)) 1392 nera = vm_fault_readahead(&fs); 1393 1394 rv = vm_fault_getpages(&fs, nera, &behind, &ahead); 1395 if (rv == KERN_SUCCESS) { 1396 faultcount = behind + 1 + ahead; 1397 hardfault = true; 1398 break; /* break to PAGE HAS BEEN FOUND. */ 1399 } 1400 if (rv == KERN_RESOURCE_SHORTAGE) 1401 goto RetryFault; 1402 VM_OBJECT_WLOCK(fs.object); 1403 if (rv == KERN_OUT_OF_BOUNDS) { 1404 fault_page_free(&fs.m); 1405 unlock_and_deallocate(&fs); 1406 return (rv); 1407 } 1408 } 1409 1410 /* 1411 * The page was not found in the current object. Try to 1412 * traverse into a backing object or zero fill if none is 1413 * found. 1414 */ 1415 if (vm_fault_next(&fs)) 1416 continue; 1417 VM_OBJECT_WUNLOCK(fs.object); 1418 vm_fault_zerofill(&fs); 1419 /* Don't try to prefault neighboring pages. */ 1420 faultcount = 1; 1421 break; /* break to PAGE HAS BEEN FOUND. */ 1422 } 1423 1424 /* 1425 * PAGE HAS BEEN FOUND. A valid page has been found and exclusively 1426 * busied. The object lock must no longer be held. 1427 */ 1428 vm_page_assert_xbusied(fs.m); 1429 VM_OBJECT_ASSERT_UNLOCKED(fs.object); 1430 1431 /* 1432 * If the page is being written, but isn't already owned by the 1433 * top-level object, we have to copy it into a new page owned by the 1434 * top-level object. 1435 */ 1436 if (fs.object != fs.first_object) { 1437 /* 1438 * We only really need to copy if we want to write it. 1439 */ 1440 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1441 vm_fault_cow(&fs); 1442 /* 1443 * We only try to prefault read-only mappings to the 1444 * neighboring pages when this copy-on-write fault is 1445 * a hard fault. In other cases, trying to prefault 1446 * is typically wasted effort. 1447 */ 1448 if (faultcount == 0) 1449 faultcount = 1; 1450 1451 } else { 1452 fs.prot &= ~VM_PROT_WRITE; 1453 } 1454 } 1455 1456 /* 1457 * We must verify that the maps have not changed since our last 1458 * lookup. 1459 */ 1460 if (!fs.lookup_still_valid) { 1461 result = vm_fault_relookup(&fs); 1462 if (result != KERN_SUCCESS) { 1463 fault_deallocate(&fs); 1464 if (result == KERN_RESTART) 1465 goto RetryFault; 1466 return (result); 1467 } 1468 } 1469 VM_OBJECT_ASSERT_UNLOCKED(fs.object); 1470 1471 /* 1472 * If the page was filled by a pager, save the virtual address that 1473 * should be faulted on next under a sequential access pattern to the 1474 * map entry. A read lock on the map suffices to update this address 1475 * safely. 1476 */ 1477 if (hardfault) 1478 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 1479 1480 /* 1481 * Page must be completely valid or it is not fit to 1482 * map into user space. vm_pager_get_pages() ensures this. 1483 */ 1484 vm_page_assert_xbusied(fs.m); 1485 KASSERT(vm_page_all_valid(fs.m), 1486 ("vm_fault: page %p partially invalid", fs.m)); 1487 1488 vm_fault_dirty(&fs, fs.m); 1489 1490 /* 1491 * Put this page into the physical map. We had to do the unlock above 1492 * because pmap_enter() may sleep. We don't put the page 1493 * back on the active queue until later so that the pageout daemon 1494 * won't find it (yet). 1495 */ 1496 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, 1497 fs.fault_type | (fs.wired ? PMAP_ENTER_WIRED : 0), 0); 1498 if (faultcount != 1 && (fs.fault_flags & VM_FAULT_WIRE) == 0 && 1499 fs.wired == 0) 1500 vm_fault_prefault(&fs, vaddr, 1501 faultcount > 0 ? behind : PFBAK, 1502 faultcount > 0 ? ahead : PFFOR, false); 1503 1504 /* 1505 * If the page is not wired down, then put it where the pageout daemon 1506 * can find it. 1507 */ 1508 if ((fs.fault_flags & VM_FAULT_WIRE) != 0) 1509 vm_page_wire(fs.m); 1510 else 1511 vm_page_activate(fs.m); 1512 if (fs.m_hold != NULL) { 1513 (*fs.m_hold) = fs.m; 1514 vm_page_wire(fs.m); 1515 } 1516 vm_page_xunbusy(fs.m); 1517 fs.m = NULL; 1518 1519 /* 1520 * Unlock everything, and return 1521 */ 1522 fault_deallocate(&fs); 1523 if (hardfault) { 1524 VM_CNT_INC(v_io_faults); 1525 curthread->td_ru.ru_majflt++; 1526 #ifdef RACCT 1527 if (racct_enable && fs.object->type == OBJT_VNODE) { 1528 PROC_LOCK(curproc); 1529 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1530 racct_add_force(curproc, RACCT_WRITEBPS, 1531 PAGE_SIZE + behind * PAGE_SIZE); 1532 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1533 } else { 1534 racct_add_force(curproc, RACCT_READBPS, 1535 PAGE_SIZE + ahead * PAGE_SIZE); 1536 racct_add_force(curproc, RACCT_READIOPS, 1); 1537 } 1538 PROC_UNLOCK(curproc); 1539 } 1540 #endif 1541 } else 1542 curthread->td_ru.ru_minflt++; 1543 1544 return (KERN_SUCCESS); 1545 } 1546 1547 /* 1548 * Speed up the reclamation of pages that precede the faulting pindex within 1549 * the first object of the shadow chain. Essentially, perform the equivalent 1550 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1551 * the faulting pindex by the cluster size when the pages read by vm_fault() 1552 * cross a cluster-size boundary. The cluster size is the greater of the 1553 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1554 * 1555 * When "fs->first_object" is a shadow object, the pages in the backing object 1556 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1557 * function must only be concerned with pages in the first object. 1558 */ 1559 static void 1560 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1561 { 1562 vm_map_entry_t entry; 1563 vm_object_t first_object, object; 1564 vm_offset_t end, start; 1565 vm_page_t m, m_next; 1566 vm_pindex_t pend, pstart; 1567 vm_size_t size; 1568 1569 object = fs->object; 1570 VM_OBJECT_ASSERT_UNLOCKED(object); 1571 first_object = fs->first_object; 1572 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1573 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1574 VM_OBJECT_RLOCK(first_object); 1575 size = VM_FAULT_DONTNEED_MIN; 1576 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1577 size = pagesizes[1]; 1578 end = rounddown2(vaddr, size); 1579 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1580 (entry = fs->entry)->start < end) { 1581 if (end - entry->start < size) 1582 start = entry->start; 1583 else 1584 start = end - size; 1585 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1586 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1587 entry->start); 1588 m_next = vm_page_find_least(first_object, pstart); 1589 pend = OFF_TO_IDX(entry->offset) + atop(end - 1590 entry->start); 1591 while ((m = m_next) != NULL && m->pindex < pend) { 1592 m_next = TAILQ_NEXT(m, listq); 1593 if (!vm_page_all_valid(m) || 1594 vm_page_busied(m)) 1595 continue; 1596 1597 /* 1598 * Don't clear PGA_REFERENCED, since it would 1599 * likely represent a reference by a different 1600 * process. 1601 * 1602 * Typically, at this point, prefetched pages 1603 * are still in the inactive queue. Only 1604 * pages that triggered page faults are in the 1605 * active queue. The test for whether the page 1606 * is in the inactive queue is racy; in the 1607 * worst case we will requeue the page 1608 * unnecessarily. 1609 */ 1610 if (!vm_page_inactive(m)) 1611 vm_page_deactivate(m); 1612 } 1613 } 1614 VM_OBJECT_RUNLOCK(first_object); 1615 } 1616 } 1617 1618 /* 1619 * vm_fault_prefault provides a quick way of clustering 1620 * pagefaults into a processes address space. It is a "cousin" 1621 * of vm_map_pmap_enter, except it runs at page fault time instead 1622 * of mmap time. 1623 */ 1624 static void 1625 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1626 int backward, int forward, bool obj_locked) 1627 { 1628 pmap_t pmap; 1629 vm_map_entry_t entry; 1630 vm_object_t backing_object, lobject; 1631 vm_offset_t addr, starta; 1632 vm_pindex_t pindex; 1633 vm_page_t m; 1634 int i; 1635 1636 pmap = fs->map->pmap; 1637 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1638 return; 1639 1640 entry = fs->entry; 1641 1642 if (addra < backward * PAGE_SIZE) { 1643 starta = entry->start; 1644 } else { 1645 starta = addra - backward * PAGE_SIZE; 1646 if (starta < entry->start) 1647 starta = entry->start; 1648 } 1649 1650 /* 1651 * Generate the sequence of virtual addresses that are candidates for 1652 * prefaulting in an outward spiral from the faulting virtual address, 1653 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1654 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1655 * If the candidate address doesn't have a backing physical page, then 1656 * the loop immediately terminates. 1657 */ 1658 for (i = 0; i < 2 * imax(backward, forward); i++) { 1659 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1660 PAGE_SIZE); 1661 if (addr > addra + forward * PAGE_SIZE) 1662 addr = 0; 1663 1664 if (addr < starta || addr >= entry->end) 1665 continue; 1666 1667 if (!pmap_is_prefaultable(pmap, addr)) 1668 continue; 1669 1670 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1671 lobject = entry->object.vm_object; 1672 if (!obj_locked) 1673 VM_OBJECT_RLOCK(lobject); 1674 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1675 lobject->type == OBJT_DEFAULT && 1676 (backing_object = lobject->backing_object) != NULL) { 1677 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1678 0, ("vm_fault_prefault: unaligned object offset")); 1679 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1680 VM_OBJECT_RLOCK(backing_object); 1681 if (!obj_locked || lobject != entry->object.vm_object) 1682 VM_OBJECT_RUNLOCK(lobject); 1683 lobject = backing_object; 1684 } 1685 if (m == NULL) { 1686 if (!obj_locked || lobject != entry->object.vm_object) 1687 VM_OBJECT_RUNLOCK(lobject); 1688 break; 1689 } 1690 if (vm_page_all_valid(m) && 1691 (m->flags & PG_FICTITIOUS) == 0) 1692 pmap_enter_quick(pmap, addr, m, entry->protection); 1693 if (!obj_locked || lobject != entry->object.vm_object) 1694 VM_OBJECT_RUNLOCK(lobject); 1695 } 1696 } 1697 1698 /* 1699 * Hold each of the physical pages that are mapped by the specified range of 1700 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1701 * and allow the specified types of access, "prot". If all of the implied 1702 * pages are successfully held, then the number of held pages is returned 1703 * together with pointers to those pages in the array "ma". However, if any 1704 * of the pages cannot be held, -1 is returned. 1705 */ 1706 int 1707 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1708 vm_prot_t prot, vm_page_t *ma, int max_count) 1709 { 1710 vm_offset_t end, va; 1711 vm_page_t *mp; 1712 int count; 1713 boolean_t pmap_failed; 1714 1715 if (len == 0) 1716 return (0); 1717 end = round_page(addr + len); 1718 addr = trunc_page(addr); 1719 1720 /* 1721 * Check for illegal addresses. 1722 */ 1723 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1724 return (-1); 1725 1726 if (atop(end - addr) > max_count) 1727 panic("vm_fault_quick_hold_pages: count > max_count"); 1728 count = atop(end - addr); 1729 1730 /* 1731 * Most likely, the physical pages are resident in the pmap, so it is 1732 * faster to try pmap_extract_and_hold() first. 1733 */ 1734 pmap_failed = FALSE; 1735 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1736 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1737 if (*mp == NULL) 1738 pmap_failed = TRUE; 1739 else if ((prot & VM_PROT_WRITE) != 0 && 1740 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1741 /* 1742 * Explicitly dirty the physical page. Otherwise, the 1743 * caller's changes may go unnoticed because they are 1744 * performed through an unmanaged mapping or by a DMA 1745 * operation. 1746 * 1747 * The object lock is not held here. 1748 * See vm_page_clear_dirty_mask(). 1749 */ 1750 vm_page_dirty(*mp); 1751 } 1752 } 1753 if (pmap_failed) { 1754 /* 1755 * One or more pages could not be held by the pmap. Either no 1756 * page was mapped at the specified virtual address or that 1757 * mapping had insufficient permissions. Attempt to fault in 1758 * and hold these pages. 1759 * 1760 * If vm_fault_disable_pagefaults() was called, 1761 * i.e., TDP_NOFAULTING is set, we must not sleep nor 1762 * acquire MD VM locks, which means we must not call 1763 * vm_fault(). Some (out of tree) callers mark 1764 * too wide a code area with vm_fault_disable_pagefaults() 1765 * already, use the VM_PROT_QUICK_NOFAULT flag to request 1766 * the proper behaviour explicitly. 1767 */ 1768 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 && 1769 (curthread->td_pflags & TDP_NOFAULTING) != 0) 1770 goto error; 1771 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1772 if (*mp == NULL && vm_fault(map, va, prot, 1773 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1774 goto error; 1775 } 1776 return (count); 1777 error: 1778 for (mp = ma; mp < ma + count; mp++) 1779 if (*mp != NULL) 1780 vm_page_unwire(*mp, PQ_INACTIVE); 1781 return (-1); 1782 } 1783 1784 /* 1785 * Routine: 1786 * vm_fault_copy_entry 1787 * Function: 1788 * Create new shadow object backing dst_entry with private copy of 1789 * all underlying pages. When src_entry is equal to dst_entry, 1790 * function implements COW for wired-down map entry. Otherwise, 1791 * it forks wired entry into dst_map. 1792 * 1793 * In/out conditions: 1794 * The source and destination maps must be locked for write. 1795 * The source map entry must be wired down (or be a sharing map 1796 * entry corresponding to a main map entry that is wired down). 1797 */ 1798 void 1799 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1800 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1801 vm_ooffset_t *fork_charge) 1802 { 1803 vm_object_t backing_object, dst_object, object, src_object; 1804 vm_pindex_t dst_pindex, pindex, src_pindex; 1805 vm_prot_t access, prot; 1806 vm_offset_t vaddr; 1807 vm_page_t dst_m; 1808 vm_page_t src_m; 1809 boolean_t upgrade; 1810 1811 #ifdef lint 1812 src_map++; 1813 #endif /* lint */ 1814 1815 upgrade = src_entry == dst_entry; 1816 access = prot = dst_entry->protection; 1817 1818 src_object = src_entry->object.vm_object; 1819 src_pindex = OFF_TO_IDX(src_entry->offset); 1820 1821 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1822 dst_object = src_object; 1823 vm_object_reference(dst_object); 1824 } else { 1825 /* 1826 * Create the top-level object for the destination entry. 1827 * Doesn't actually shadow anything - we copy the pages 1828 * directly. 1829 */ 1830 dst_object = vm_object_allocate_anon(atop(dst_entry->end - 1831 dst_entry->start), NULL, NULL, 0); 1832 #if VM_NRESERVLEVEL > 0 1833 dst_object->flags |= OBJ_COLORED; 1834 dst_object->pg_color = atop(dst_entry->start); 1835 #endif 1836 dst_object->domain = src_object->domain; 1837 dst_object->charge = dst_entry->end - dst_entry->start; 1838 } 1839 1840 VM_OBJECT_WLOCK(dst_object); 1841 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1842 ("vm_fault_copy_entry: vm_object not NULL")); 1843 if (src_object != dst_object) { 1844 dst_entry->object.vm_object = dst_object; 1845 dst_entry->offset = 0; 1846 dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC; 1847 } 1848 if (fork_charge != NULL) { 1849 KASSERT(dst_entry->cred == NULL, 1850 ("vm_fault_copy_entry: leaked swp charge")); 1851 dst_object->cred = curthread->td_ucred; 1852 crhold(dst_object->cred); 1853 *fork_charge += dst_object->charge; 1854 } else if ((dst_object->type == OBJT_DEFAULT || 1855 dst_object->type == OBJT_SWAP) && 1856 dst_object->cred == NULL) { 1857 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1858 dst_entry)); 1859 dst_object->cred = dst_entry->cred; 1860 dst_entry->cred = NULL; 1861 } 1862 1863 /* 1864 * If not an upgrade, then enter the mappings in the pmap as 1865 * read and/or execute accesses. Otherwise, enter them as 1866 * write accesses. 1867 * 1868 * A writeable large page mapping is only created if all of 1869 * the constituent small page mappings are modified. Marking 1870 * PTEs as modified on inception allows promotion to happen 1871 * without taking potentially large number of soft faults. 1872 */ 1873 if (!upgrade) 1874 access &= ~VM_PROT_WRITE; 1875 1876 /* 1877 * Loop through all of the virtual pages within the entry's 1878 * range, copying each page from the source object to the 1879 * destination object. Since the source is wired, those pages 1880 * must exist. In contrast, the destination is pageable. 1881 * Since the destination object doesn't share any backing storage 1882 * with the source object, all of its pages must be dirtied, 1883 * regardless of whether they can be written. 1884 */ 1885 for (vaddr = dst_entry->start, dst_pindex = 0; 1886 vaddr < dst_entry->end; 1887 vaddr += PAGE_SIZE, dst_pindex++) { 1888 again: 1889 /* 1890 * Find the page in the source object, and copy it in. 1891 * Because the source is wired down, the page will be 1892 * in memory. 1893 */ 1894 if (src_object != dst_object) 1895 VM_OBJECT_RLOCK(src_object); 1896 object = src_object; 1897 pindex = src_pindex + dst_pindex; 1898 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1899 (backing_object = object->backing_object) != NULL) { 1900 /* 1901 * Unless the source mapping is read-only or 1902 * it is presently being upgraded from 1903 * read-only, the first object in the shadow 1904 * chain should provide all of the pages. In 1905 * other words, this loop body should never be 1906 * executed when the source mapping is already 1907 * read/write. 1908 */ 1909 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1910 upgrade, 1911 ("vm_fault_copy_entry: main object missing page")); 1912 1913 VM_OBJECT_RLOCK(backing_object); 1914 pindex += OFF_TO_IDX(object->backing_object_offset); 1915 if (object != dst_object) 1916 VM_OBJECT_RUNLOCK(object); 1917 object = backing_object; 1918 } 1919 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1920 1921 if (object != dst_object) { 1922 /* 1923 * Allocate a page in the destination object. 1924 */ 1925 dst_m = vm_page_alloc(dst_object, (src_object == 1926 dst_object ? src_pindex : 0) + dst_pindex, 1927 VM_ALLOC_NORMAL); 1928 if (dst_m == NULL) { 1929 VM_OBJECT_WUNLOCK(dst_object); 1930 VM_OBJECT_RUNLOCK(object); 1931 vm_wait(dst_object); 1932 VM_OBJECT_WLOCK(dst_object); 1933 goto again; 1934 } 1935 pmap_copy_page(src_m, dst_m); 1936 VM_OBJECT_RUNLOCK(object); 1937 dst_m->dirty = dst_m->valid = src_m->valid; 1938 } else { 1939 dst_m = src_m; 1940 if (vm_page_busy_acquire(dst_m, VM_ALLOC_WAITFAIL) == 0) 1941 goto again; 1942 if (dst_m->pindex >= dst_object->size) { 1943 /* 1944 * We are upgrading. Index can occur 1945 * out of bounds if the object type is 1946 * vnode and the file was truncated. 1947 */ 1948 vm_page_xunbusy(dst_m); 1949 break; 1950 } 1951 } 1952 VM_OBJECT_WUNLOCK(dst_object); 1953 1954 /* 1955 * Enter it in the pmap. If a wired, copy-on-write 1956 * mapping is being replaced by a write-enabled 1957 * mapping, then wire that new mapping. 1958 * 1959 * The page can be invalid if the user called 1960 * msync(MS_INVALIDATE) or truncated the backing vnode 1961 * or shared memory object. In this case, do not 1962 * insert it into pmap, but still do the copy so that 1963 * all copies of the wired map entry have similar 1964 * backing pages. 1965 */ 1966 if (vm_page_all_valid(dst_m)) { 1967 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1968 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1969 } 1970 1971 /* 1972 * Mark it no longer busy, and put it on the active list. 1973 */ 1974 VM_OBJECT_WLOCK(dst_object); 1975 1976 if (upgrade) { 1977 if (src_m != dst_m) { 1978 vm_page_unwire(src_m, PQ_INACTIVE); 1979 vm_page_wire(dst_m); 1980 } else { 1981 KASSERT(vm_page_wired(dst_m), 1982 ("dst_m %p is not wired", dst_m)); 1983 } 1984 } else { 1985 vm_page_activate(dst_m); 1986 } 1987 vm_page_xunbusy(dst_m); 1988 } 1989 VM_OBJECT_WUNLOCK(dst_object); 1990 if (upgrade) { 1991 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1992 vm_object_deallocate(src_object); 1993 } 1994 } 1995 1996 /* 1997 * Block entry into the machine-independent layer's page fault handler by 1998 * the calling thread. Subsequent calls to vm_fault() by that thread will 1999 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 2000 * spurious page faults. 2001 */ 2002 int 2003 vm_fault_disable_pagefaults(void) 2004 { 2005 2006 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 2007 } 2008 2009 void 2010 vm_fault_enable_pagefaults(int save) 2011 { 2012 2013 curthread_pflags_restore(save); 2014 } 2015