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) 118 119 #define VM_FAULT_DONTNEED_MIN 1048576 120 121 struct faultstate { 122 /* Fault parameters. */ 123 vm_offset_t vaddr; 124 vm_page_t *m_hold; 125 vm_prot_t fault_type; 126 vm_prot_t prot; 127 int fault_flags; 128 int oom; 129 boolean_t wired; 130 131 /* Page reference for cow. */ 132 vm_page_t m_cow; 133 134 /* Current object. */ 135 vm_object_t object; 136 vm_pindex_t pindex; 137 vm_page_t m; 138 139 /* Top-level map object. */ 140 vm_object_t first_object; 141 vm_pindex_t first_pindex; 142 vm_page_t first_m; 143 144 /* Map state. */ 145 vm_map_t map; 146 vm_map_entry_t entry; 147 int map_generation; 148 bool lookup_still_valid; 149 150 /* Vnode if locked. */ 151 struct vnode *vp; 152 }; 153 154 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 155 int ahead); 156 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 157 int backward, int forward, bool obj_locked); 158 159 static int vm_pfault_oom_attempts = 3; 160 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_attempts, CTLFLAG_RWTUN, 161 &vm_pfault_oom_attempts, 0, 162 "Number of page allocation attempts in page fault handler before it " 163 "triggers OOM handling"); 164 165 static int vm_pfault_oom_wait = 10; 166 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_wait, CTLFLAG_RWTUN, 167 &vm_pfault_oom_wait, 0, 168 "Number of seconds to wait for free pages before retrying " 169 "the page fault handler"); 170 171 static inline void 172 fault_page_release(vm_page_t *mp) 173 { 174 vm_page_t m; 175 176 m = *mp; 177 if (m != NULL) { 178 /* 179 * We are likely to loop around again and attempt to busy 180 * this page. Deactivating it leaves it available for 181 * pageout while optimizing fault restarts. 182 */ 183 vm_page_deactivate(m); 184 vm_page_xunbusy(m); 185 *mp = NULL; 186 } 187 } 188 189 static inline void 190 fault_page_free(vm_page_t *mp) 191 { 192 vm_page_t m; 193 194 m = *mp; 195 if (m != NULL) { 196 VM_OBJECT_ASSERT_WLOCKED(m->object); 197 if (!vm_page_wired(m)) 198 vm_page_free(m); 199 else 200 vm_page_xunbusy(m); 201 *mp = NULL; 202 } 203 } 204 205 static inline void 206 unlock_map(struct faultstate *fs) 207 { 208 209 if (fs->lookup_still_valid) { 210 vm_map_lookup_done(fs->map, fs->entry); 211 fs->lookup_still_valid = false; 212 } 213 } 214 215 static void 216 unlock_vp(struct faultstate *fs) 217 { 218 219 if (fs->vp != NULL) { 220 vput(fs->vp); 221 fs->vp = NULL; 222 } 223 } 224 225 static void 226 fault_deallocate(struct faultstate *fs) 227 { 228 229 fault_page_release(&fs->m_cow); 230 fault_page_release(&fs->m); 231 vm_object_pip_wakeup(fs->object); 232 if (fs->object != fs->first_object) { 233 VM_OBJECT_WLOCK(fs->first_object); 234 fault_page_free(&fs->first_m); 235 VM_OBJECT_WUNLOCK(fs->first_object); 236 vm_object_pip_wakeup(fs->first_object); 237 } 238 vm_object_deallocate(fs->first_object); 239 unlock_map(fs); 240 unlock_vp(fs); 241 } 242 243 static void 244 unlock_and_deallocate(struct faultstate *fs) 245 { 246 247 VM_OBJECT_WUNLOCK(fs->object); 248 fault_deallocate(fs); 249 } 250 251 static void 252 vm_fault_dirty(struct faultstate *fs, vm_page_t m) 253 { 254 bool need_dirty; 255 256 if (((fs->prot & VM_PROT_WRITE) == 0 && 257 (fs->fault_flags & VM_FAULT_DIRTY) == 0) || 258 (m->oflags & VPO_UNMANAGED) != 0) 259 return; 260 261 VM_PAGE_OBJECT_BUSY_ASSERT(m); 262 263 need_dirty = ((fs->fault_type & VM_PROT_WRITE) != 0 && 264 (fs->fault_flags & VM_FAULT_WIRE) == 0) || 265 (fs->fault_flags & VM_FAULT_DIRTY) != 0; 266 267 vm_object_set_writeable_dirty(m->object); 268 269 /* 270 * If the fault is a write, we know that this page is being 271 * written NOW so dirty it explicitly to save on 272 * pmap_is_modified() calls later. 273 * 274 * Also, since the page is now dirty, we can possibly tell 275 * the pager to release any swap backing the page. 276 */ 277 if (need_dirty && vm_page_set_dirty(m) == 0) { 278 /* 279 * If this is a NOSYNC mmap we do not want to set PGA_NOSYNC 280 * if the page is already dirty to prevent data written with 281 * the expectation of being synced from not being synced. 282 * Likewise if this entry does not request NOSYNC then make 283 * sure the page isn't marked NOSYNC. Applications sharing 284 * data should use the same flags to avoid ping ponging. 285 */ 286 if ((fs->entry->eflags & MAP_ENTRY_NOSYNC) != 0) 287 vm_page_aflag_set(m, PGA_NOSYNC); 288 else 289 vm_page_aflag_clear(m, PGA_NOSYNC); 290 } 291 292 } 293 294 /* 295 * Unlocks fs.first_object and fs.map on success. 296 */ 297 static int 298 vm_fault_soft_fast(struct faultstate *fs) 299 { 300 vm_page_t m, m_map; 301 #if VM_NRESERVLEVEL > 0 302 vm_page_t m_super; 303 int flags; 304 #endif 305 int psind, rv; 306 vm_offset_t vaddr; 307 308 MPASS(fs->vp == NULL); 309 vaddr = fs->vaddr; 310 vm_object_busy(fs->first_object); 311 m = vm_page_lookup(fs->first_object, fs->first_pindex); 312 /* A busy page can be mapped for read|execute access. */ 313 if (m == NULL || ((fs->prot & VM_PROT_WRITE) != 0 && 314 vm_page_busied(m)) || !vm_page_all_valid(m)) { 315 rv = KERN_FAILURE; 316 goto out; 317 } 318 m_map = m; 319 psind = 0; 320 #if VM_NRESERVLEVEL > 0 321 if ((m->flags & PG_FICTITIOUS) == 0 && 322 (m_super = vm_reserv_to_superpage(m)) != NULL && 323 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start && 324 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end && 325 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) & 326 (pagesizes[m_super->psind] - 1)) && !fs->wired && 327 pmap_ps_enabled(fs->map->pmap)) { 328 flags = PS_ALL_VALID; 329 if ((fs->prot & VM_PROT_WRITE) != 0) { 330 /* 331 * Create a superpage mapping allowing write access 332 * only if none of the constituent pages are busy and 333 * all of them are already dirty (except possibly for 334 * the page that was faulted on). 335 */ 336 flags |= PS_NONE_BUSY; 337 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0) 338 flags |= PS_ALL_DIRTY; 339 } 340 if (vm_page_ps_test(m_super, flags, m)) { 341 m_map = m_super; 342 psind = m_super->psind; 343 vaddr = rounddown2(vaddr, pagesizes[psind]); 344 /* Preset the modified bit for dirty superpages. */ 345 if ((flags & PS_ALL_DIRTY) != 0) 346 fs->fault_type |= VM_PROT_WRITE; 347 } 348 } 349 #endif 350 rv = pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type | 351 PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind); 352 if (rv != KERN_SUCCESS) 353 goto out; 354 if (fs->m_hold != NULL) { 355 (*fs->m_hold) = m; 356 vm_page_wire(m); 357 } 358 if (psind == 0 && !fs->wired) 359 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true); 360 VM_OBJECT_RUNLOCK(fs->first_object); 361 vm_fault_dirty(fs, m); 362 vm_map_lookup_done(fs->map, fs->entry); 363 curthread->td_ru.ru_minflt++; 364 365 out: 366 vm_object_unbusy(fs->first_object); 367 return (rv); 368 } 369 370 static void 371 vm_fault_restore_map_lock(struct faultstate *fs) 372 { 373 374 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 375 MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0); 376 377 if (!vm_map_trylock_read(fs->map)) { 378 VM_OBJECT_WUNLOCK(fs->first_object); 379 vm_map_lock_read(fs->map); 380 VM_OBJECT_WLOCK(fs->first_object); 381 } 382 fs->lookup_still_valid = true; 383 } 384 385 static void 386 vm_fault_populate_check_page(vm_page_t m) 387 { 388 389 /* 390 * Check each page to ensure that the pager is obeying the 391 * interface: the page must be installed in the object, fully 392 * valid, and exclusively busied. 393 */ 394 MPASS(m != NULL); 395 MPASS(vm_page_all_valid(m)); 396 MPASS(vm_page_xbusied(m)); 397 } 398 399 static void 400 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first, 401 vm_pindex_t last) 402 { 403 vm_page_t m; 404 vm_pindex_t pidx; 405 406 VM_OBJECT_ASSERT_WLOCKED(object); 407 MPASS(first <= last); 408 for (pidx = first, m = vm_page_lookup(object, pidx); 409 pidx <= last; pidx++, m = vm_page_next(m)) { 410 vm_fault_populate_check_page(m); 411 vm_page_deactivate(m); 412 vm_page_xunbusy(m); 413 } 414 } 415 416 static int 417 vm_fault_populate(struct faultstate *fs) 418 { 419 vm_offset_t vaddr; 420 vm_page_t m; 421 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx; 422 int bdry_idx, i, npages, psind, rv; 423 424 MPASS(fs->object == fs->first_object); 425 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 426 MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0); 427 MPASS(fs->first_object->backing_object == NULL); 428 MPASS(fs->lookup_still_valid); 429 430 pager_first = OFF_TO_IDX(fs->entry->offset); 431 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1; 432 unlock_map(fs); 433 unlock_vp(fs); 434 435 /* 436 * Call the pager (driver) populate() method. 437 * 438 * There is no guarantee that the method will be called again 439 * if the current fault is for read, and a future fault is 440 * for write. Report the entry's maximum allowed protection 441 * to the driver. 442 */ 443 rv = vm_pager_populate(fs->first_object, fs->first_pindex, 444 fs->fault_type, fs->entry->max_protection, &pager_first, 445 &pager_last); 446 447 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 448 if (rv == VM_PAGER_BAD) { 449 /* 450 * VM_PAGER_BAD is the backdoor for a pager to request 451 * normal fault handling. 452 */ 453 vm_fault_restore_map_lock(fs); 454 if (fs->map->timestamp != fs->map_generation) 455 return (KERN_RESTART); 456 return (KERN_NOT_RECEIVER); 457 } 458 if (rv != VM_PAGER_OK) 459 return (KERN_FAILURE); /* AKA SIGSEGV */ 460 461 /* Ensure that the driver is obeying the interface. */ 462 MPASS(pager_first <= pager_last); 463 MPASS(fs->first_pindex <= pager_last); 464 MPASS(fs->first_pindex >= pager_first); 465 MPASS(pager_last < fs->first_object->size); 466 467 vm_fault_restore_map_lock(fs); 468 bdry_idx = (fs->entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) >> 469 MAP_ENTRY_SPLIT_BOUNDARY_SHIFT; 470 if (fs->map->timestamp != fs->map_generation) { 471 if (bdry_idx == 0) { 472 vm_fault_populate_cleanup(fs->first_object, pager_first, 473 pager_last); 474 } else { 475 m = vm_page_lookup(fs->first_object, pager_first); 476 if (m != fs->m) 477 vm_page_xunbusy(m); 478 } 479 return (KERN_RESTART); 480 } 481 482 /* 483 * The map is unchanged after our last unlock. Process the fault. 484 * 485 * First, the special case of largepage mappings, where 486 * populate only busies the first page in superpage run. 487 */ 488 if (bdry_idx != 0) { 489 KASSERT(PMAP_HAS_LARGEPAGES, 490 ("missing pmap support for large pages")); 491 m = vm_page_lookup(fs->first_object, pager_first); 492 vm_fault_populate_check_page(m); 493 VM_OBJECT_WUNLOCK(fs->first_object); 494 vaddr = fs->entry->start + IDX_TO_OFF(pager_first) - 495 fs->entry->offset; 496 /* assert alignment for entry */ 497 KASSERT((vaddr & (pagesizes[bdry_idx] - 1)) == 0, 498 ("unaligned superpage start %#jx pager_first %#jx offset %#jx vaddr %#jx", 499 (uintmax_t)fs->entry->start, (uintmax_t)pager_first, 500 (uintmax_t)fs->entry->offset, (uintmax_t)vaddr)); 501 KASSERT((VM_PAGE_TO_PHYS(m) & (pagesizes[bdry_idx] - 1)) == 0, 502 ("unaligned superpage m %p %#jx", m, 503 (uintmax_t)VM_PAGE_TO_PHYS(m))); 504 rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot, 505 fs->fault_type | (fs->wired ? PMAP_ENTER_WIRED : 0) | 506 PMAP_ENTER_LARGEPAGE, bdry_idx); 507 VM_OBJECT_WLOCK(fs->first_object); 508 vm_page_xunbusy(m); 509 if (rv != KERN_SUCCESS) 510 goto out; 511 if ((fs->fault_flags & VM_FAULT_WIRE) != 0) { 512 for (i = 0; i < atop(pagesizes[bdry_idx]); i++) 513 vm_page_wire(m + i); 514 } 515 if (fs->m_hold != NULL) { 516 *fs->m_hold = m + (fs->first_pindex - pager_first); 517 vm_page_wire(*fs->m_hold); 518 } 519 goto out; 520 } 521 522 /* 523 * The range [pager_first, pager_last] that is given to the 524 * pager is only a hint. The pager may populate any range 525 * within the object that includes the requested page index. 526 * In case the pager expanded the range, clip it to fit into 527 * the map entry. 528 */ 529 map_first = OFF_TO_IDX(fs->entry->offset); 530 if (map_first > pager_first) { 531 vm_fault_populate_cleanup(fs->first_object, pager_first, 532 map_first - 1); 533 pager_first = map_first; 534 } 535 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1; 536 if (map_last < pager_last) { 537 vm_fault_populate_cleanup(fs->first_object, map_last + 1, 538 pager_last); 539 pager_last = map_last; 540 } 541 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx); 542 pidx <= pager_last; 543 pidx += npages, m = vm_page_next(&m[npages - 1])) { 544 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset; 545 546 psind = m->psind; 547 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 || 548 pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last || 549 !pmap_ps_enabled(fs->map->pmap) || fs->wired)) 550 psind = 0; 551 552 npages = atop(pagesizes[psind]); 553 for (i = 0; i < npages; i++) { 554 vm_fault_populate_check_page(&m[i]); 555 vm_fault_dirty(fs, &m[i]); 556 } 557 VM_OBJECT_WUNLOCK(fs->first_object); 558 rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot, fs->fault_type | 559 (fs->wired ? PMAP_ENTER_WIRED : 0), psind); 560 561 /* 562 * pmap_enter() may fail for a superpage mapping if additional 563 * protection policies prevent the full mapping. 564 * For example, this will happen on amd64 if the entire 565 * address range does not share the same userspace protection 566 * key. Revert to single-page mappings if this happens. 567 */ 568 MPASS(rv == KERN_SUCCESS || 569 (psind > 0 && rv == KERN_PROTECTION_FAILURE)); 570 if (__predict_false(psind > 0 && 571 rv == KERN_PROTECTION_FAILURE)) { 572 for (i = 0; i < npages; i++) { 573 rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i), 574 &m[i], fs->prot, fs->fault_type | 575 (fs->wired ? PMAP_ENTER_WIRED : 0), 0); 576 MPASS(rv == KERN_SUCCESS); 577 } 578 } 579 580 VM_OBJECT_WLOCK(fs->first_object); 581 for (i = 0; i < npages; i++) { 582 if ((fs->fault_flags & VM_FAULT_WIRE) != 0) 583 vm_page_wire(&m[i]); 584 else 585 vm_page_activate(&m[i]); 586 if (fs->m_hold != NULL && m[i].pindex == fs->first_pindex) { 587 (*fs->m_hold) = &m[i]; 588 vm_page_wire(&m[i]); 589 } 590 vm_page_xunbusy(&m[i]); 591 } 592 } 593 out: 594 curthread->td_ru.ru_majflt++; 595 return (rv); 596 } 597 598 static int prot_fault_translation; 599 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RWTUN, 600 &prot_fault_translation, 0, 601 "Control signal to deliver on protection fault"); 602 603 /* compat definition to keep common code for signal translation */ 604 #define UCODE_PAGEFLT 12 605 #ifdef T_PAGEFLT 606 _Static_assert(UCODE_PAGEFLT == T_PAGEFLT, "T_PAGEFLT"); 607 #endif 608 609 /* 610 * vm_fault_trap: 611 * 612 * Handle a page fault occurring at the given address, 613 * requiring the given permissions, in the map specified. 614 * If successful, the page is inserted into the 615 * associated physical map. 616 * 617 * NOTE: the given address should be truncated to the 618 * proper page address. 619 * 620 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 621 * a standard error specifying why the fault is fatal is returned. 622 * 623 * The map in question must be referenced, and remains so. 624 * Caller may hold no locks. 625 */ 626 int 627 vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 628 int fault_flags, int *signo, int *ucode) 629 { 630 int result; 631 632 MPASS(signo == NULL || ucode != NULL); 633 #ifdef KTRACE 634 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULT)) 635 ktrfault(vaddr, fault_type); 636 #endif 637 result = vm_fault(map, trunc_page(vaddr), fault_type, fault_flags, 638 NULL); 639 KASSERT(result == KERN_SUCCESS || result == KERN_FAILURE || 640 result == KERN_INVALID_ADDRESS || 641 result == KERN_RESOURCE_SHORTAGE || 642 result == KERN_PROTECTION_FAILURE || 643 result == KERN_OUT_OF_BOUNDS, 644 ("Unexpected Mach error %d from vm_fault()", result)); 645 #ifdef KTRACE 646 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULTEND)) 647 ktrfaultend(result); 648 #endif 649 if (result != KERN_SUCCESS && signo != NULL) { 650 switch (result) { 651 case KERN_FAILURE: 652 case KERN_INVALID_ADDRESS: 653 *signo = SIGSEGV; 654 *ucode = SEGV_MAPERR; 655 break; 656 case KERN_RESOURCE_SHORTAGE: 657 *signo = SIGBUS; 658 *ucode = BUS_OOMERR; 659 break; 660 case KERN_OUT_OF_BOUNDS: 661 *signo = SIGBUS; 662 *ucode = BUS_OBJERR; 663 break; 664 case KERN_PROTECTION_FAILURE: 665 if (prot_fault_translation == 0) { 666 /* 667 * Autodetect. This check also covers 668 * the images without the ABI-tag ELF 669 * note. 670 */ 671 if (SV_CURPROC_ABI() == SV_ABI_FREEBSD && 672 curproc->p_osrel >= P_OSREL_SIGSEGV) { 673 *signo = SIGSEGV; 674 *ucode = SEGV_ACCERR; 675 } else { 676 *signo = SIGBUS; 677 *ucode = UCODE_PAGEFLT; 678 } 679 } else if (prot_fault_translation == 1) { 680 /* Always compat mode. */ 681 *signo = SIGBUS; 682 *ucode = UCODE_PAGEFLT; 683 } else { 684 /* Always SIGSEGV mode. */ 685 *signo = SIGSEGV; 686 *ucode = SEGV_ACCERR; 687 } 688 break; 689 default: 690 KASSERT(0, ("Unexpected Mach error %d from vm_fault()", 691 result)); 692 break; 693 } 694 } 695 return (result); 696 } 697 698 static int 699 vm_fault_lock_vnode(struct faultstate *fs, bool objlocked) 700 { 701 struct vnode *vp; 702 int error, locked; 703 704 if (fs->object->type != OBJT_VNODE) 705 return (KERN_SUCCESS); 706 vp = fs->object->handle; 707 if (vp == fs->vp) { 708 ASSERT_VOP_LOCKED(vp, "saved vnode is not locked"); 709 return (KERN_SUCCESS); 710 } 711 712 /* 713 * Perform an unlock in case the desired vnode changed while 714 * the map was unlocked during a retry. 715 */ 716 unlock_vp(fs); 717 718 locked = VOP_ISLOCKED(vp); 719 if (locked != LK_EXCLUSIVE) 720 locked = LK_SHARED; 721 722 /* 723 * We must not sleep acquiring the vnode lock while we have 724 * the page exclusive busied or the object's 725 * paging-in-progress count incremented. Otherwise, we could 726 * deadlock. 727 */ 728 error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT); 729 if (error == 0) { 730 fs->vp = vp; 731 return (KERN_SUCCESS); 732 } 733 734 vhold(vp); 735 if (objlocked) 736 unlock_and_deallocate(fs); 737 else 738 fault_deallocate(fs); 739 error = vget(vp, locked | LK_RETRY | LK_CANRECURSE); 740 vdrop(vp); 741 fs->vp = vp; 742 KASSERT(error == 0, ("vm_fault: vget failed %d", error)); 743 return (KERN_RESOURCE_SHORTAGE); 744 } 745 746 /* 747 * Calculate the desired readahead. Handle drop-behind. 748 * 749 * Returns the number of readahead blocks to pass to the pager. 750 */ 751 static int 752 vm_fault_readahead(struct faultstate *fs) 753 { 754 int era, nera; 755 u_char behavior; 756 757 KASSERT(fs->lookup_still_valid, ("map unlocked")); 758 era = fs->entry->read_ahead; 759 behavior = vm_map_entry_behavior(fs->entry); 760 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 761 nera = 0; 762 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 763 nera = VM_FAULT_READ_AHEAD_MAX; 764 if (fs->vaddr == fs->entry->next_read) 765 vm_fault_dontneed(fs, fs->vaddr, nera); 766 } else if (fs->vaddr == fs->entry->next_read) { 767 /* 768 * This is a sequential fault. Arithmetically 769 * increase the requested number of pages in 770 * the read-ahead window. The requested 771 * number of pages is "# of sequential faults 772 * x (read ahead min + 1) + read ahead min" 773 */ 774 nera = VM_FAULT_READ_AHEAD_MIN; 775 if (era > 0) { 776 nera += era + 1; 777 if (nera > VM_FAULT_READ_AHEAD_MAX) 778 nera = VM_FAULT_READ_AHEAD_MAX; 779 } 780 if (era == VM_FAULT_READ_AHEAD_MAX) 781 vm_fault_dontneed(fs, fs->vaddr, nera); 782 } else { 783 /* 784 * This is a non-sequential fault. 785 */ 786 nera = 0; 787 } 788 if (era != nera) { 789 /* 790 * A read lock on the map suffices to update 791 * the read ahead count safely. 792 */ 793 fs->entry->read_ahead = nera; 794 } 795 796 return (nera); 797 } 798 799 static int 800 vm_fault_lookup(struct faultstate *fs) 801 { 802 int result; 803 804 KASSERT(!fs->lookup_still_valid, 805 ("vm_fault_lookup: Map already locked.")); 806 result = vm_map_lookup(&fs->map, fs->vaddr, fs->fault_type | 807 VM_PROT_FAULT_LOOKUP, &fs->entry, &fs->first_object, 808 &fs->first_pindex, &fs->prot, &fs->wired); 809 if (result != KERN_SUCCESS) { 810 unlock_vp(fs); 811 return (result); 812 } 813 814 fs->map_generation = fs->map->timestamp; 815 816 if (fs->entry->eflags & MAP_ENTRY_NOFAULT) { 817 panic("%s: fault on nofault entry, addr: %#lx", 818 __func__, (u_long)fs->vaddr); 819 } 820 821 if (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION && 822 fs->entry->wiring_thread != curthread) { 823 vm_map_unlock_read(fs->map); 824 vm_map_lock(fs->map); 825 if (vm_map_lookup_entry(fs->map, fs->vaddr, &fs->entry) && 826 (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 827 unlock_vp(fs); 828 fs->entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 829 vm_map_unlock_and_wait(fs->map, 0); 830 } else 831 vm_map_unlock(fs->map); 832 return (KERN_RESOURCE_SHORTAGE); 833 } 834 835 MPASS((fs->entry->eflags & MAP_ENTRY_GUARD) == 0); 836 837 if (fs->wired) 838 fs->fault_type = fs->prot | (fs->fault_type & VM_PROT_COPY); 839 else 840 KASSERT((fs->fault_flags & VM_FAULT_WIRE) == 0, 841 ("!fs->wired && VM_FAULT_WIRE")); 842 fs->lookup_still_valid = true; 843 844 return (KERN_SUCCESS); 845 } 846 847 static int 848 vm_fault_relookup(struct faultstate *fs) 849 { 850 vm_object_t retry_object; 851 vm_pindex_t retry_pindex; 852 vm_prot_t retry_prot; 853 int result; 854 855 if (!vm_map_trylock_read(fs->map)) 856 return (KERN_RESTART); 857 858 fs->lookup_still_valid = true; 859 if (fs->map->timestamp == fs->map_generation) 860 return (KERN_SUCCESS); 861 862 result = vm_map_lookup_locked(&fs->map, fs->vaddr, fs->fault_type, 863 &fs->entry, &retry_object, &retry_pindex, &retry_prot, 864 &fs->wired); 865 if (result != KERN_SUCCESS) { 866 /* 867 * If retry of map lookup would have blocked then 868 * retry fault from start. 869 */ 870 if (result == KERN_FAILURE) 871 return (KERN_RESTART); 872 return (result); 873 } 874 if (retry_object != fs->first_object || 875 retry_pindex != fs->first_pindex) 876 return (KERN_RESTART); 877 878 /* 879 * Check whether the protection has changed or the object has 880 * been copied while we left the map unlocked. Changing from 881 * read to write permission is OK - we leave the page 882 * write-protected, and catch the write fault. Changing from 883 * write to read permission means that we can't mark the page 884 * write-enabled after all. 885 */ 886 fs->prot &= retry_prot; 887 fs->fault_type &= retry_prot; 888 if (fs->prot == 0) 889 return (KERN_RESTART); 890 891 /* Reassert because wired may have changed. */ 892 KASSERT(fs->wired || (fs->fault_flags & VM_FAULT_WIRE) == 0, 893 ("!wired && VM_FAULT_WIRE")); 894 895 return (KERN_SUCCESS); 896 } 897 898 static void 899 vm_fault_cow(struct faultstate *fs) 900 { 901 bool is_first_object_locked; 902 903 KASSERT(fs->object != fs->first_object, 904 ("source and target COW objects are identical")); 905 906 /* 907 * This allows pages to be virtually copied from a backing_object 908 * into the first_object, where the backing object has no other 909 * refs to it, and cannot gain any more refs. Instead of a bcopy, 910 * we just move the page from the backing object to the first 911 * object. Note that we must mark the page dirty in the first 912 * object so that it will go out to swap when needed. 913 */ 914 is_first_object_locked = false; 915 if ( 916 /* 917 * Only one shadow object and no other refs. 918 */ 919 fs->object->shadow_count == 1 && fs->object->ref_count == 1 && 920 /* 921 * No other ways to look the object up 922 */ 923 fs->object->handle == NULL && (fs->object->flags & OBJ_ANON) != 0 && 924 /* 925 * We don't chase down the shadow chain and we can acquire locks. 926 */ 927 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs->first_object)) && 928 fs->object == fs->first_object->backing_object && 929 VM_OBJECT_TRYWLOCK(fs->object)) { 930 /* 931 * Remove but keep xbusy for replace. fs->m is moved into 932 * fs->first_object and left busy while fs->first_m is 933 * conditionally freed. 934 */ 935 vm_page_remove_xbusy(fs->m); 936 vm_page_replace(fs->m, fs->first_object, fs->first_pindex, 937 fs->first_m); 938 vm_page_dirty(fs->m); 939 #if VM_NRESERVLEVEL > 0 940 /* 941 * Rename the reservation. 942 */ 943 vm_reserv_rename(fs->m, fs->first_object, fs->object, 944 OFF_TO_IDX(fs->first_object->backing_object_offset)); 945 #endif 946 VM_OBJECT_WUNLOCK(fs->object); 947 VM_OBJECT_WUNLOCK(fs->first_object); 948 fs->first_m = fs->m; 949 fs->m = NULL; 950 VM_CNT_INC(v_cow_optim); 951 } else { 952 if (is_first_object_locked) 953 VM_OBJECT_WUNLOCK(fs->first_object); 954 /* 955 * Oh, well, lets copy it. 956 */ 957 pmap_copy_page(fs->m, fs->first_m); 958 vm_page_valid(fs->first_m); 959 if (fs->wired && (fs->fault_flags & VM_FAULT_WIRE) == 0) { 960 vm_page_wire(fs->first_m); 961 vm_page_unwire(fs->m, PQ_INACTIVE); 962 } 963 /* 964 * Save the cow page to be released after 965 * pmap_enter is complete. 966 */ 967 fs->m_cow = fs->m; 968 fs->m = NULL; 969 970 /* 971 * Typically, the shadow object is either private to this 972 * address space (OBJ_ONEMAPPING) or its pages are read only. 973 * In the highly unusual case where the pages of a shadow object 974 * are read/write shared between this and other address spaces, 975 * we need to ensure that any pmap-level mappings to the 976 * original, copy-on-write page from the backing object are 977 * removed from those other address spaces. 978 * 979 * The flag check is racy, but this is tolerable: if 980 * OBJ_ONEMAPPING is cleared after the check, the busy state 981 * ensures that new mappings of m_cow can't be created. 982 * pmap_enter() will replace an existing mapping in the current 983 * address space. If OBJ_ONEMAPPING is set after the check, 984 * removing mappings will at worse trigger some unnecessary page 985 * faults. 986 */ 987 vm_page_assert_xbusied(fs->m_cow); 988 if ((fs->first_object->flags & OBJ_ONEMAPPING) == 0) 989 pmap_remove_all(fs->m_cow); 990 } 991 992 vm_object_pip_wakeup(fs->object); 993 994 /* 995 * Only use the new page below... 996 */ 997 fs->object = fs->first_object; 998 fs->pindex = fs->first_pindex; 999 fs->m = fs->first_m; 1000 VM_CNT_INC(v_cow_faults); 1001 curthread->td_cow++; 1002 } 1003 1004 static bool 1005 vm_fault_next(struct faultstate *fs) 1006 { 1007 vm_object_t next_object; 1008 1009 /* 1010 * The requested page does not exist at this object/ 1011 * offset. Remove the invalid page from the object, 1012 * waking up anyone waiting for it, and continue on to 1013 * the next object. However, if this is the top-level 1014 * object, we must leave the busy page in place to 1015 * prevent another process from rushing past us, and 1016 * inserting the page in that object at the same time 1017 * that we are. 1018 */ 1019 if (fs->object == fs->first_object) { 1020 fs->first_m = fs->m; 1021 fs->m = NULL; 1022 } else 1023 fault_page_free(&fs->m); 1024 1025 /* 1026 * Move on to the next object. Lock the next object before 1027 * unlocking the current one. 1028 */ 1029 VM_OBJECT_ASSERT_WLOCKED(fs->object); 1030 next_object = fs->object->backing_object; 1031 if (next_object == NULL) 1032 return (false); 1033 MPASS(fs->first_m != NULL); 1034 KASSERT(fs->object != next_object, ("object loop %p", next_object)); 1035 VM_OBJECT_WLOCK(next_object); 1036 vm_object_pip_add(next_object, 1); 1037 if (fs->object != fs->first_object) 1038 vm_object_pip_wakeup(fs->object); 1039 fs->pindex += OFF_TO_IDX(fs->object->backing_object_offset); 1040 VM_OBJECT_WUNLOCK(fs->object); 1041 fs->object = next_object; 1042 1043 return (true); 1044 } 1045 1046 static void 1047 vm_fault_zerofill(struct faultstate *fs) 1048 { 1049 1050 /* 1051 * If there's no object left, fill the page in the top 1052 * object with zeros. 1053 */ 1054 if (fs->object != fs->first_object) { 1055 vm_object_pip_wakeup(fs->object); 1056 fs->object = fs->first_object; 1057 fs->pindex = fs->first_pindex; 1058 } 1059 MPASS(fs->first_m != NULL); 1060 MPASS(fs->m == NULL); 1061 fs->m = fs->first_m; 1062 fs->first_m = NULL; 1063 1064 /* 1065 * Zero the page if necessary and mark it valid. 1066 */ 1067 if ((fs->m->flags & PG_ZERO) == 0) { 1068 pmap_zero_page(fs->m); 1069 } else { 1070 VM_CNT_INC(v_ozfod); 1071 } 1072 VM_CNT_INC(v_zfod); 1073 vm_page_valid(fs->m); 1074 } 1075 1076 /* 1077 * Allocate a page directly or via the object populate method. 1078 */ 1079 static int 1080 vm_fault_allocate(struct faultstate *fs) 1081 { 1082 struct domainset *dset; 1083 int alloc_req; 1084 int rv; 1085 1086 if ((fs->object->flags & OBJ_SIZEVNLOCK) != 0) { 1087 rv = vm_fault_lock_vnode(fs, true); 1088 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE); 1089 if (rv == KERN_RESOURCE_SHORTAGE) 1090 return (rv); 1091 } 1092 1093 if (fs->pindex >= fs->object->size) 1094 return (KERN_OUT_OF_BOUNDS); 1095 1096 if (fs->object == fs->first_object && 1097 (fs->first_object->flags & OBJ_POPULATE) != 0 && 1098 fs->first_object->shadow_count == 0) { 1099 rv = vm_fault_populate(fs); 1100 switch (rv) { 1101 case KERN_SUCCESS: 1102 case KERN_FAILURE: 1103 case KERN_PROTECTION_FAILURE: 1104 case KERN_RESTART: 1105 return (rv); 1106 case KERN_NOT_RECEIVER: 1107 /* 1108 * Pager's populate() method 1109 * returned VM_PAGER_BAD. 1110 */ 1111 break; 1112 default: 1113 panic("inconsistent return codes"); 1114 } 1115 } 1116 1117 /* 1118 * Allocate a new page for this object/offset pair. 1119 * 1120 * Unlocked read of the p_flag is harmless. At worst, the P_KILLED 1121 * might be not observed there, and allocation can fail, causing 1122 * restart and new reading of the p_flag. 1123 */ 1124 dset = fs->object->domain.dr_policy; 1125 if (dset == NULL) 1126 dset = curthread->td_domain.dr_policy; 1127 if (!vm_page_count_severe_set(&dset->ds_mask) || P_KILLED(curproc)) { 1128 #if VM_NRESERVLEVEL > 0 1129 vm_object_color(fs->object, atop(fs->vaddr) - fs->pindex); 1130 #endif 1131 alloc_req = P_KILLED(curproc) ? 1132 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 1133 if (fs->object->type != OBJT_VNODE && 1134 fs->object->backing_object == NULL) 1135 alloc_req |= VM_ALLOC_ZERO; 1136 fs->m = vm_page_alloc(fs->object, fs->pindex, alloc_req); 1137 } 1138 if (fs->m == NULL) { 1139 unlock_and_deallocate(fs); 1140 if (vm_pfault_oom_attempts < 0 || 1141 fs->oom < vm_pfault_oom_attempts) { 1142 fs->oom++; 1143 vm_waitpfault(dset, vm_pfault_oom_wait * hz); 1144 } else { 1145 if (bootverbose) 1146 printf( 1147 "proc %d (%s) failed to alloc page on fault, starting OOM\n", 1148 curproc->p_pid, curproc->p_comm); 1149 vm_pageout_oom(VM_OOM_MEM_PF); 1150 fs->oom = 0; 1151 } 1152 return (KERN_RESOURCE_SHORTAGE); 1153 } 1154 fs->oom = 0; 1155 1156 return (KERN_NOT_RECEIVER); 1157 } 1158 1159 /* 1160 * Call the pager to retrieve the page if there is a chance 1161 * that the pager has it, and potentially retrieve additional 1162 * pages at the same time. 1163 */ 1164 static int 1165 vm_fault_getpages(struct faultstate *fs, int nera, int *behindp, int *aheadp) 1166 { 1167 vm_offset_t e_end, e_start; 1168 int ahead, behind, cluster_offset, rv; 1169 u_char behavior; 1170 1171 /* 1172 * Prepare for unlocking the map. Save the map 1173 * entry's start and end addresses, which are used to 1174 * optimize the size of the pager operation below. 1175 * Even if the map entry's addresses change after 1176 * unlocking the map, using the saved addresses is 1177 * safe. 1178 */ 1179 e_start = fs->entry->start; 1180 e_end = fs->entry->end; 1181 behavior = vm_map_entry_behavior(fs->entry); 1182 1183 /* 1184 * Release the map lock before locking the vnode or 1185 * sleeping in the pager. (If the current object has 1186 * a shadow, then an earlier iteration of this loop 1187 * may have already unlocked the map.) 1188 */ 1189 unlock_map(fs); 1190 1191 rv = vm_fault_lock_vnode(fs, false); 1192 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE); 1193 if (rv == KERN_RESOURCE_SHORTAGE) 1194 return (rv); 1195 KASSERT(fs->vp == NULL || !fs->map->system_map, 1196 ("vm_fault: vnode-backed object mapped by system map")); 1197 1198 /* 1199 * Page in the requested page and hint the pager, 1200 * that it may bring up surrounding pages. 1201 */ 1202 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 1203 P_KILLED(curproc)) { 1204 behind = 0; 1205 ahead = 0; 1206 } else { 1207 /* Is this a sequential fault? */ 1208 if (nera > 0) { 1209 behind = 0; 1210 ahead = nera; 1211 } else { 1212 /* 1213 * Request a cluster of pages that is 1214 * aligned to a VM_FAULT_READ_DEFAULT 1215 * page offset boundary within the 1216 * object. Alignment to a page offset 1217 * boundary is more likely to coincide 1218 * with the underlying file system 1219 * block than alignment to a virtual 1220 * address boundary. 1221 */ 1222 cluster_offset = fs->pindex % VM_FAULT_READ_DEFAULT; 1223 behind = ulmin(cluster_offset, 1224 atop(fs->vaddr - e_start)); 1225 ahead = VM_FAULT_READ_DEFAULT - 1 - cluster_offset; 1226 } 1227 ahead = ulmin(ahead, atop(e_end - fs->vaddr) - 1); 1228 } 1229 *behindp = behind; 1230 *aheadp = ahead; 1231 rv = vm_pager_get_pages(fs->object, &fs->m, 1, behindp, aheadp); 1232 if (rv == VM_PAGER_OK) 1233 return (KERN_SUCCESS); 1234 if (rv == VM_PAGER_ERROR) 1235 printf("vm_fault: pager read error, pid %d (%s)\n", 1236 curproc->p_pid, curproc->p_comm); 1237 /* 1238 * If an I/O error occurred or the requested page was 1239 * outside the range of the pager, clean up and return 1240 * an error. 1241 */ 1242 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) 1243 return (KERN_OUT_OF_BOUNDS); 1244 return (KERN_NOT_RECEIVER); 1245 } 1246 1247 /* 1248 * Wait/Retry if the page is busy. We have to do this if the page is 1249 * either exclusive or shared busy because the vm_pager may be using 1250 * read busy for pageouts (and even pageins if it is the vnode pager), 1251 * and we could end up trying to pagein and pageout the same page 1252 * simultaneously. 1253 * 1254 * We can theoretically allow the busy case on a read fault if the page 1255 * is marked valid, but since such pages are typically already pmap'd, 1256 * putting that special case in might be more effort then it is worth. 1257 * We cannot under any circumstances mess around with a shared busied 1258 * page except, perhaps, to pmap it. 1259 */ 1260 static void 1261 vm_fault_busy_sleep(struct faultstate *fs) 1262 { 1263 /* 1264 * Reference the page before unlocking and 1265 * sleeping so that the page daemon is less 1266 * likely to reclaim it. 1267 */ 1268 vm_page_aflag_set(fs->m, PGA_REFERENCED); 1269 if (fs->object != fs->first_object) { 1270 fault_page_release(&fs->first_m); 1271 vm_object_pip_wakeup(fs->first_object); 1272 } 1273 vm_object_pip_wakeup(fs->object); 1274 unlock_map(fs); 1275 if (fs->m == vm_page_lookup(fs->object, fs->pindex)) 1276 vm_page_busy_sleep(fs->m, "vmpfw", false); 1277 else 1278 VM_OBJECT_WUNLOCK(fs->object); 1279 VM_CNT_INC(v_intrans); 1280 vm_object_deallocate(fs->first_object); 1281 } 1282 1283 int 1284 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 1285 int fault_flags, vm_page_t *m_hold) 1286 { 1287 struct faultstate fs; 1288 int ahead, behind, faultcount; 1289 int nera, result, rv; 1290 bool dead, hardfault; 1291 1292 VM_CNT_INC(v_vm_faults); 1293 1294 if ((curthread->td_pflags & TDP_NOFAULTING) != 0) 1295 return (KERN_PROTECTION_FAILURE); 1296 1297 fs.vp = NULL; 1298 fs.vaddr = vaddr; 1299 fs.m_hold = m_hold; 1300 fs.fault_flags = fault_flags; 1301 fs.map = map; 1302 fs.lookup_still_valid = false; 1303 fs.oom = 0; 1304 faultcount = 0; 1305 nera = -1; 1306 hardfault = false; 1307 1308 RetryFault: 1309 fs.fault_type = fault_type; 1310 1311 /* 1312 * Find the backing store object and offset into it to begin the 1313 * search. 1314 */ 1315 result = vm_fault_lookup(&fs); 1316 if (result != KERN_SUCCESS) { 1317 if (result == KERN_RESOURCE_SHORTAGE) 1318 goto RetryFault; 1319 return (result); 1320 } 1321 1322 /* 1323 * Try to avoid lock contention on the top-level object through 1324 * special-case handling of some types of page faults, specifically, 1325 * those that are mapping an existing page from the top-level object. 1326 * Under this condition, a read lock on the object suffices, allowing 1327 * multiple page faults of a similar type to run in parallel. 1328 */ 1329 if (fs.vp == NULL /* avoid locked vnode leak */ && 1330 (fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) == 0 && 1331 (fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) { 1332 VM_OBJECT_RLOCK(fs.first_object); 1333 rv = vm_fault_soft_fast(&fs); 1334 if (rv == KERN_SUCCESS) 1335 return (rv); 1336 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 1337 VM_OBJECT_RUNLOCK(fs.first_object); 1338 VM_OBJECT_WLOCK(fs.first_object); 1339 } 1340 } else { 1341 VM_OBJECT_WLOCK(fs.first_object); 1342 } 1343 1344 /* 1345 * Make a reference to this object to prevent its disposal while we 1346 * are messing with it. Once we have the reference, the map is free 1347 * to be diddled. Since objects reference their shadows (and copies), 1348 * they will stay around as well. 1349 * 1350 * Bump the paging-in-progress count to prevent size changes (e.g. 1351 * truncation operations) during I/O. 1352 */ 1353 vm_object_reference_locked(fs.first_object); 1354 vm_object_pip_add(fs.first_object, 1); 1355 1356 fs.m_cow = fs.m = fs.first_m = NULL; 1357 1358 /* 1359 * Search for the page at object/offset. 1360 */ 1361 fs.object = fs.first_object; 1362 fs.pindex = fs.first_pindex; 1363 1364 if ((fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) != 0) { 1365 rv = vm_fault_allocate(&fs); 1366 switch (rv) { 1367 case KERN_RESTART: 1368 unlock_and_deallocate(&fs); 1369 /* FALLTHROUGH */ 1370 case KERN_RESOURCE_SHORTAGE: 1371 goto RetryFault; 1372 case KERN_SUCCESS: 1373 case KERN_FAILURE: 1374 case KERN_PROTECTION_FAILURE: 1375 case KERN_OUT_OF_BOUNDS: 1376 unlock_and_deallocate(&fs); 1377 return (rv); 1378 case KERN_NOT_RECEIVER: 1379 break; 1380 default: 1381 panic("vm_fault: Unhandled rv %d", rv); 1382 } 1383 } 1384 1385 while (TRUE) { 1386 KASSERT(fs.m == NULL, 1387 ("page still set %p at loop start", fs.m)); 1388 /* 1389 * If the object is marked for imminent termination, 1390 * we retry here, since the collapse pass has raced 1391 * with us. Otherwise, if we see terminally dead 1392 * object, return fail. 1393 */ 1394 if ((fs.object->flags & OBJ_DEAD) != 0) { 1395 dead = fs.object->type == OBJT_DEAD; 1396 unlock_and_deallocate(&fs); 1397 if (dead) 1398 return (KERN_PROTECTION_FAILURE); 1399 pause("vmf_de", 1); 1400 goto RetryFault; 1401 } 1402 1403 /* 1404 * See if page is resident 1405 */ 1406 fs.m = vm_page_lookup(fs.object, fs.pindex); 1407 if (fs.m != NULL) { 1408 if (vm_page_tryxbusy(fs.m) == 0) { 1409 vm_fault_busy_sleep(&fs); 1410 goto RetryFault; 1411 } 1412 1413 /* 1414 * The page is marked busy for other processes and the 1415 * pagedaemon. If it still is completely valid we 1416 * are done. 1417 */ 1418 if (vm_page_all_valid(fs.m)) { 1419 VM_OBJECT_WUNLOCK(fs.object); 1420 break; /* break to PAGE HAS BEEN FOUND. */ 1421 } 1422 } 1423 VM_OBJECT_ASSERT_WLOCKED(fs.object); 1424 1425 /* 1426 * Page is not resident. If the pager might contain the page 1427 * or this is the beginning of the search, allocate a new 1428 * page. (Default objects are zero-fill, so there is no real 1429 * pager for them.) 1430 */ 1431 if (fs.m == NULL && (fs.object->type != OBJT_DEFAULT || 1432 fs.object == fs.first_object)) { 1433 rv = vm_fault_allocate(&fs); 1434 switch (rv) { 1435 case KERN_RESTART: 1436 unlock_and_deallocate(&fs); 1437 /* FALLTHROUGH */ 1438 case KERN_RESOURCE_SHORTAGE: 1439 goto RetryFault; 1440 case KERN_SUCCESS: 1441 case KERN_FAILURE: 1442 case KERN_PROTECTION_FAILURE: 1443 case KERN_OUT_OF_BOUNDS: 1444 unlock_and_deallocate(&fs); 1445 return (rv); 1446 case KERN_NOT_RECEIVER: 1447 break; 1448 default: 1449 panic("vm_fault: Unhandled rv %d", rv); 1450 } 1451 } 1452 1453 /* 1454 * Default objects have no pager so no exclusive busy exists 1455 * to protect this page in the chain. Skip to the next 1456 * object without dropping the lock to preserve atomicity of 1457 * shadow faults. 1458 */ 1459 if (fs.object->type != OBJT_DEFAULT) { 1460 /* 1461 * At this point, we have either allocated a new page 1462 * or found an existing page that is only partially 1463 * valid. 1464 * 1465 * We hold a reference on the current object and the 1466 * page is exclusive busied. The exclusive busy 1467 * prevents simultaneous faults and collapses while 1468 * the object lock is dropped. 1469 */ 1470 VM_OBJECT_WUNLOCK(fs.object); 1471 1472 /* 1473 * If the pager for the current object might have 1474 * the page, then determine the number of additional 1475 * pages to read and potentially reprioritize 1476 * previously read pages for earlier reclamation. 1477 * These operations should only be performed once per 1478 * page fault. Even if the current pager doesn't 1479 * have the page, the number of additional pages to 1480 * read will apply to subsequent objects in the 1481 * shadow chain. 1482 */ 1483 if (nera == -1 && !P_KILLED(curproc)) 1484 nera = vm_fault_readahead(&fs); 1485 1486 rv = vm_fault_getpages(&fs, nera, &behind, &ahead); 1487 if (rv == KERN_SUCCESS) { 1488 faultcount = behind + 1 + ahead; 1489 hardfault = true; 1490 break; /* break to PAGE HAS BEEN FOUND. */ 1491 } 1492 if (rv == KERN_RESOURCE_SHORTAGE) 1493 goto RetryFault; 1494 VM_OBJECT_WLOCK(fs.object); 1495 if (rv == KERN_OUT_OF_BOUNDS) { 1496 fault_page_free(&fs.m); 1497 unlock_and_deallocate(&fs); 1498 return (rv); 1499 } 1500 } 1501 1502 /* 1503 * The page was not found in the current object. Try to 1504 * traverse into a backing object or zero fill if none is 1505 * found. 1506 */ 1507 if (vm_fault_next(&fs)) 1508 continue; 1509 if ((fs.fault_flags & VM_FAULT_NOFILL) != 0) { 1510 if (fs.first_object == fs.object) 1511 fault_page_free(&fs.first_m); 1512 unlock_and_deallocate(&fs); 1513 return (KERN_OUT_OF_BOUNDS); 1514 } 1515 VM_OBJECT_WUNLOCK(fs.object); 1516 vm_fault_zerofill(&fs); 1517 /* Don't try to prefault neighboring pages. */ 1518 faultcount = 1; 1519 break; /* break to PAGE HAS BEEN FOUND. */ 1520 } 1521 1522 /* 1523 * PAGE HAS BEEN FOUND. A valid page has been found and exclusively 1524 * busied. The object lock must no longer be held. 1525 */ 1526 vm_page_assert_xbusied(fs.m); 1527 VM_OBJECT_ASSERT_UNLOCKED(fs.object); 1528 1529 /* 1530 * If the page is being written, but isn't already owned by the 1531 * top-level object, we have to copy it into a new page owned by the 1532 * top-level object. 1533 */ 1534 if (fs.object != fs.first_object) { 1535 /* 1536 * We only really need to copy if we want to write it. 1537 */ 1538 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1539 vm_fault_cow(&fs); 1540 /* 1541 * We only try to prefault read-only mappings to the 1542 * neighboring pages when this copy-on-write fault is 1543 * a hard fault. In other cases, trying to prefault 1544 * is typically wasted effort. 1545 */ 1546 if (faultcount == 0) 1547 faultcount = 1; 1548 1549 } else { 1550 fs.prot &= ~VM_PROT_WRITE; 1551 } 1552 } 1553 1554 /* 1555 * We must verify that the maps have not changed since our last 1556 * lookup. 1557 */ 1558 if (!fs.lookup_still_valid) { 1559 result = vm_fault_relookup(&fs); 1560 if (result != KERN_SUCCESS) { 1561 fault_deallocate(&fs); 1562 if (result == KERN_RESTART) 1563 goto RetryFault; 1564 return (result); 1565 } 1566 } 1567 VM_OBJECT_ASSERT_UNLOCKED(fs.object); 1568 1569 /* 1570 * If the page was filled by a pager, save the virtual address that 1571 * should be faulted on next under a sequential access pattern to the 1572 * map entry. A read lock on the map suffices to update this address 1573 * safely. 1574 */ 1575 if (hardfault) 1576 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 1577 1578 /* 1579 * Page must be completely valid or it is not fit to 1580 * map into user space. vm_pager_get_pages() ensures this. 1581 */ 1582 vm_page_assert_xbusied(fs.m); 1583 KASSERT(vm_page_all_valid(fs.m), 1584 ("vm_fault: page %p partially invalid", fs.m)); 1585 1586 vm_fault_dirty(&fs, fs.m); 1587 1588 /* 1589 * Put this page into the physical map. We had to do the unlock above 1590 * because pmap_enter() may sleep. We don't put the page 1591 * back on the active queue until later so that the pageout daemon 1592 * won't find it (yet). 1593 */ 1594 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, 1595 fs.fault_type | (fs.wired ? PMAP_ENTER_WIRED : 0), 0); 1596 if (faultcount != 1 && (fs.fault_flags & VM_FAULT_WIRE) == 0 && 1597 fs.wired == 0) 1598 vm_fault_prefault(&fs, vaddr, 1599 faultcount > 0 ? behind : PFBAK, 1600 faultcount > 0 ? ahead : PFFOR, false); 1601 1602 /* 1603 * If the page is not wired down, then put it where the pageout daemon 1604 * can find it. 1605 */ 1606 if ((fs.fault_flags & VM_FAULT_WIRE) != 0) 1607 vm_page_wire(fs.m); 1608 else 1609 vm_page_activate(fs.m); 1610 if (fs.m_hold != NULL) { 1611 (*fs.m_hold) = fs.m; 1612 vm_page_wire(fs.m); 1613 } 1614 vm_page_xunbusy(fs.m); 1615 fs.m = NULL; 1616 1617 /* 1618 * Unlock everything, and return 1619 */ 1620 fault_deallocate(&fs); 1621 if (hardfault) { 1622 VM_CNT_INC(v_io_faults); 1623 curthread->td_ru.ru_majflt++; 1624 #ifdef RACCT 1625 if (racct_enable && fs.object->type == OBJT_VNODE) { 1626 PROC_LOCK(curproc); 1627 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1628 racct_add_force(curproc, RACCT_WRITEBPS, 1629 PAGE_SIZE + behind * PAGE_SIZE); 1630 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1631 } else { 1632 racct_add_force(curproc, RACCT_READBPS, 1633 PAGE_SIZE + ahead * PAGE_SIZE); 1634 racct_add_force(curproc, RACCT_READIOPS, 1); 1635 } 1636 PROC_UNLOCK(curproc); 1637 } 1638 #endif 1639 } else 1640 curthread->td_ru.ru_minflt++; 1641 1642 return (KERN_SUCCESS); 1643 } 1644 1645 /* 1646 * Speed up the reclamation of pages that precede the faulting pindex within 1647 * the first object of the shadow chain. Essentially, perform the equivalent 1648 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1649 * the faulting pindex by the cluster size when the pages read by vm_fault() 1650 * cross a cluster-size boundary. The cluster size is the greater of the 1651 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1652 * 1653 * When "fs->first_object" is a shadow object, the pages in the backing object 1654 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1655 * function must only be concerned with pages in the first object. 1656 */ 1657 static void 1658 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1659 { 1660 vm_map_entry_t entry; 1661 vm_object_t first_object, object; 1662 vm_offset_t end, start; 1663 vm_page_t m, m_next; 1664 vm_pindex_t pend, pstart; 1665 vm_size_t size; 1666 1667 object = fs->object; 1668 VM_OBJECT_ASSERT_UNLOCKED(object); 1669 first_object = fs->first_object; 1670 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1671 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1672 VM_OBJECT_RLOCK(first_object); 1673 size = VM_FAULT_DONTNEED_MIN; 1674 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1675 size = pagesizes[1]; 1676 end = rounddown2(vaddr, size); 1677 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1678 (entry = fs->entry)->start < end) { 1679 if (end - entry->start < size) 1680 start = entry->start; 1681 else 1682 start = end - size; 1683 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1684 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1685 entry->start); 1686 m_next = vm_page_find_least(first_object, pstart); 1687 pend = OFF_TO_IDX(entry->offset) + atop(end - 1688 entry->start); 1689 while ((m = m_next) != NULL && m->pindex < pend) { 1690 m_next = TAILQ_NEXT(m, listq); 1691 if (!vm_page_all_valid(m) || 1692 vm_page_busied(m)) 1693 continue; 1694 1695 /* 1696 * Don't clear PGA_REFERENCED, since it would 1697 * likely represent a reference by a different 1698 * process. 1699 * 1700 * Typically, at this point, prefetched pages 1701 * are still in the inactive queue. Only 1702 * pages that triggered page faults are in the 1703 * active queue. The test for whether the page 1704 * is in the inactive queue is racy; in the 1705 * worst case we will requeue the page 1706 * unnecessarily. 1707 */ 1708 if (!vm_page_inactive(m)) 1709 vm_page_deactivate(m); 1710 } 1711 } 1712 VM_OBJECT_RUNLOCK(first_object); 1713 } 1714 } 1715 1716 /* 1717 * vm_fault_prefault provides a quick way of clustering 1718 * pagefaults into a processes address space. It is a "cousin" 1719 * of vm_map_pmap_enter, except it runs at page fault time instead 1720 * of mmap time. 1721 */ 1722 static void 1723 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1724 int backward, int forward, bool obj_locked) 1725 { 1726 pmap_t pmap; 1727 vm_map_entry_t entry; 1728 vm_object_t backing_object, lobject; 1729 vm_offset_t addr, starta; 1730 vm_pindex_t pindex; 1731 vm_page_t m; 1732 int i; 1733 1734 pmap = fs->map->pmap; 1735 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1736 return; 1737 1738 entry = fs->entry; 1739 1740 if (addra < backward * PAGE_SIZE) { 1741 starta = entry->start; 1742 } else { 1743 starta = addra - backward * PAGE_SIZE; 1744 if (starta < entry->start) 1745 starta = entry->start; 1746 } 1747 1748 /* 1749 * Generate the sequence of virtual addresses that are candidates for 1750 * prefaulting in an outward spiral from the faulting virtual address, 1751 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1752 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1753 * If the candidate address doesn't have a backing physical page, then 1754 * the loop immediately terminates. 1755 */ 1756 for (i = 0; i < 2 * imax(backward, forward); i++) { 1757 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1758 PAGE_SIZE); 1759 if (addr > addra + forward * PAGE_SIZE) 1760 addr = 0; 1761 1762 if (addr < starta || addr >= entry->end) 1763 continue; 1764 1765 if (!pmap_is_prefaultable(pmap, addr)) 1766 continue; 1767 1768 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1769 lobject = entry->object.vm_object; 1770 if (!obj_locked) 1771 VM_OBJECT_RLOCK(lobject); 1772 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1773 lobject->type == OBJT_DEFAULT && 1774 (backing_object = lobject->backing_object) != NULL) { 1775 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1776 0, ("vm_fault_prefault: unaligned object offset")); 1777 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1778 VM_OBJECT_RLOCK(backing_object); 1779 if (!obj_locked || lobject != entry->object.vm_object) 1780 VM_OBJECT_RUNLOCK(lobject); 1781 lobject = backing_object; 1782 } 1783 if (m == NULL) { 1784 if (!obj_locked || lobject != entry->object.vm_object) 1785 VM_OBJECT_RUNLOCK(lobject); 1786 break; 1787 } 1788 if (vm_page_all_valid(m) && 1789 (m->flags & PG_FICTITIOUS) == 0) 1790 pmap_enter_quick(pmap, addr, m, entry->protection); 1791 if (!obj_locked || lobject != entry->object.vm_object) 1792 VM_OBJECT_RUNLOCK(lobject); 1793 } 1794 } 1795 1796 /* 1797 * Hold each of the physical pages that are mapped by the specified range of 1798 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1799 * and allow the specified types of access, "prot". If all of the implied 1800 * pages are successfully held, then the number of held pages is returned 1801 * together with pointers to those pages in the array "ma". However, if any 1802 * of the pages cannot be held, -1 is returned. 1803 */ 1804 int 1805 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1806 vm_prot_t prot, vm_page_t *ma, int max_count) 1807 { 1808 vm_offset_t end, va; 1809 vm_page_t *mp; 1810 int count; 1811 boolean_t pmap_failed; 1812 1813 if (len == 0) 1814 return (0); 1815 end = round_page(addr + len); 1816 addr = trunc_page(addr); 1817 1818 if (!vm_map_range_valid(map, addr, end)) 1819 return (-1); 1820 1821 if (atop(end - addr) > max_count) 1822 panic("vm_fault_quick_hold_pages: count > max_count"); 1823 count = atop(end - addr); 1824 1825 /* 1826 * Most likely, the physical pages are resident in the pmap, so it is 1827 * faster to try pmap_extract_and_hold() first. 1828 */ 1829 pmap_failed = FALSE; 1830 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1831 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1832 if (*mp == NULL) 1833 pmap_failed = TRUE; 1834 else if ((prot & VM_PROT_WRITE) != 0 && 1835 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1836 /* 1837 * Explicitly dirty the physical page. Otherwise, the 1838 * caller's changes may go unnoticed because they are 1839 * performed through an unmanaged mapping or by a DMA 1840 * operation. 1841 * 1842 * The object lock is not held here. 1843 * See vm_page_clear_dirty_mask(). 1844 */ 1845 vm_page_dirty(*mp); 1846 } 1847 } 1848 if (pmap_failed) { 1849 /* 1850 * One or more pages could not be held by the pmap. Either no 1851 * page was mapped at the specified virtual address or that 1852 * mapping had insufficient permissions. Attempt to fault in 1853 * and hold these pages. 1854 * 1855 * If vm_fault_disable_pagefaults() was called, 1856 * i.e., TDP_NOFAULTING is set, we must not sleep nor 1857 * acquire MD VM locks, which means we must not call 1858 * vm_fault(). Some (out of tree) callers mark 1859 * too wide a code area with vm_fault_disable_pagefaults() 1860 * already, use the VM_PROT_QUICK_NOFAULT flag to request 1861 * the proper behaviour explicitly. 1862 */ 1863 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 && 1864 (curthread->td_pflags & TDP_NOFAULTING) != 0) 1865 goto error; 1866 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1867 if (*mp == NULL && vm_fault(map, va, prot, 1868 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1869 goto error; 1870 } 1871 return (count); 1872 error: 1873 for (mp = ma; mp < ma + count; mp++) 1874 if (*mp != NULL) 1875 vm_page_unwire(*mp, PQ_INACTIVE); 1876 return (-1); 1877 } 1878 1879 /* 1880 * Routine: 1881 * vm_fault_copy_entry 1882 * Function: 1883 * Create new shadow object backing dst_entry with private copy of 1884 * all underlying pages. When src_entry is equal to dst_entry, 1885 * function implements COW for wired-down map entry. Otherwise, 1886 * it forks wired entry into dst_map. 1887 * 1888 * In/out conditions: 1889 * The source and destination maps must be locked for write. 1890 * The source map entry must be wired down (or be a sharing map 1891 * entry corresponding to a main map entry that is wired down). 1892 */ 1893 void 1894 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1895 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1896 vm_ooffset_t *fork_charge) 1897 { 1898 vm_object_t backing_object, dst_object, object, src_object; 1899 vm_pindex_t dst_pindex, pindex, src_pindex; 1900 vm_prot_t access, prot; 1901 vm_offset_t vaddr; 1902 vm_page_t dst_m; 1903 vm_page_t src_m; 1904 boolean_t upgrade; 1905 1906 #ifdef lint 1907 src_map++; 1908 #endif /* lint */ 1909 1910 upgrade = src_entry == dst_entry; 1911 access = prot = dst_entry->protection; 1912 1913 src_object = src_entry->object.vm_object; 1914 src_pindex = OFF_TO_IDX(src_entry->offset); 1915 1916 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1917 dst_object = src_object; 1918 vm_object_reference(dst_object); 1919 } else { 1920 /* 1921 * Create the top-level object for the destination entry. 1922 * Doesn't actually shadow anything - we copy the pages 1923 * directly. 1924 */ 1925 dst_object = vm_object_allocate_anon(atop(dst_entry->end - 1926 dst_entry->start), NULL, NULL, 0); 1927 #if VM_NRESERVLEVEL > 0 1928 dst_object->flags |= OBJ_COLORED; 1929 dst_object->pg_color = atop(dst_entry->start); 1930 #endif 1931 dst_object->domain = src_object->domain; 1932 dst_object->charge = dst_entry->end - dst_entry->start; 1933 } 1934 1935 VM_OBJECT_WLOCK(dst_object); 1936 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1937 ("vm_fault_copy_entry: vm_object not NULL")); 1938 if (src_object != dst_object) { 1939 dst_entry->object.vm_object = dst_object; 1940 dst_entry->offset = 0; 1941 dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC; 1942 } 1943 if (fork_charge != NULL) { 1944 KASSERT(dst_entry->cred == NULL, 1945 ("vm_fault_copy_entry: leaked swp charge")); 1946 dst_object->cred = curthread->td_ucred; 1947 crhold(dst_object->cred); 1948 *fork_charge += dst_object->charge; 1949 } else if ((dst_object->type == OBJT_DEFAULT || 1950 (dst_object->flags & OBJ_SWAP) != 0) && 1951 dst_object->cred == NULL) { 1952 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1953 dst_entry)); 1954 dst_object->cred = dst_entry->cred; 1955 dst_entry->cred = NULL; 1956 } 1957 1958 /* 1959 * If not an upgrade, then enter the mappings in the pmap as 1960 * read and/or execute accesses. Otherwise, enter them as 1961 * write accesses. 1962 * 1963 * A writeable large page mapping is only created if all of 1964 * the constituent small page mappings are modified. Marking 1965 * PTEs as modified on inception allows promotion to happen 1966 * without taking potentially large number of soft faults. 1967 */ 1968 if (!upgrade) 1969 access &= ~VM_PROT_WRITE; 1970 1971 /* 1972 * Loop through all of the virtual pages within the entry's 1973 * range, copying each page from the source object to the 1974 * destination object. Since the source is wired, those pages 1975 * must exist. In contrast, the destination is pageable. 1976 * Since the destination object doesn't share any backing storage 1977 * with the source object, all of its pages must be dirtied, 1978 * regardless of whether they can be written. 1979 */ 1980 for (vaddr = dst_entry->start, dst_pindex = 0; 1981 vaddr < dst_entry->end; 1982 vaddr += PAGE_SIZE, dst_pindex++) { 1983 again: 1984 /* 1985 * Find the page in the source object, and copy it in. 1986 * Because the source is wired down, the page will be 1987 * in memory. 1988 */ 1989 if (src_object != dst_object) 1990 VM_OBJECT_RLOCK(src_object); 1991 object = src_object; 1992 pindex = src_pindex + dst_pindex; 1993 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1994 (backing_object = object->backing_object) != NULL) { 1995 /* 1996 * Unless the source mapping is read-only or 1997 * it is presently being upgraded from 1998 * read-only, the first object in the shadow 1999 * chain should provide all of the pages. In 2000 * other words, this loop body should never be 2001 * executed when the source mapping is already 2002 * read/write. 2003 */ 2004 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 2005 upgrade, 2006 ("vm_fault_copy_entry: main object missing page")); 2007 2008 VM_OBJECT_RLOCK(backing_object); 2009 pindex += OFF_TO_IDX(object->backing_object_offset); 2010 if (object != dst_object) 2011 VM_OBJECT_RUNLOCK(object); 2012 object = backing_object; 2013 } 2014 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 2015 2016 if (object != dst_object) { 2017 /* 2018 * Allocate a page in the destination object. 2019 */ 2020 dst_m = vm_page_alloc(dst_object, (src_object == 2021 dst_object ? src_pindex : 0) + dst_pindex, 2022 VM_ALLOC_NORMAL); 2023 if (dst_m == NULL) { 2024 VM_OBJECT_WUNLOCK(dst_object); 2025 VM_OBJECT_RUNLOCK(object); 2026 vm_wait(dst_object); 2027 VM_OBJECT_WLOCK(dst_object); 2028 goto again; 2029 } 2030 pmap_copy_page(src_m, dst_m); 2031 VM_OBJECT_RUNLOCK(object); 2032 dst_m->dirty = dst_m->valid = src_m->valid; 2033 } else { 2034 dst_m = src_m; 2035 if (vm_page_busy_acquire(dst_m, VM_ALLOC_WAITFAIL) == 0) 2036 goto again; 2037 if (dst_m->pindex >= dst_object->size) { 2038 /* 2039 * We are upgrading. Index can occur 2040 * out of bounds if the object type is 2041 * vnode and the file was truncated. 2042 */ 2043 vm_page_xunbusy(dst_m); 2044 break; 2045 } 2046 } 2047 VM_OBJECT_WUNLOCK(dst_object); 2048 2049 /* 2050 * Enter it in the pmap. If a wired, copy-on-write 2051 * mapping is being replaced by a write-enabled 2052 * mapping, then wire that new mapping. 2053 * 2054 * The page can be invalid if the user called 2055 * msync(MS_INVALIDATE) or truncated the backing vnode 2056 * or shared memory object. In this case, do not 2057 * insert it into pmap, but still do the copy so that 2058 * all copies of the wired map entry have similar 2059 * backing pages. 2060 */ 2061 if (vm_page_all_valid(dst_m)) { 2062 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 2063 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 2064 } 2065 2066 /* 2067 * Mark it no longer busy, and put it on the active list. 2068 */ 2069 VM_OBJECT_WLOCK(dst_object); 2070 2071 if (upgrade) { 2072 if (src_m != dst_m) { 2073 vm_page_unwire(src_m, PQ_INACTIVE); 2074 vm_page_wire(dst_m); 2075 } else { 2076 KASSERT(vm_page_wired(dst_m), 2077 ("dst_m %p is not wired", dst_m)); 2078 } 2079 } else { 2080 vm_page_activate(dst_m); 2081 } 2082 vm_page_xunbusy(dst_m); 2083 } 2084 VM_OBJECT_WUNLOCK(dst_object); 2085 if (upgrade) { 2086 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 2087 vm_object_deallocate(src_object); 2088 } 2089 } 2090 2091 /* 2092 * Block entry into the machine-independent layer's page fault handler by 2093 * the calling thread. Subsequent calls to vm_fault() by that thread will 2094 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 2095 * spurious page faults. 2096 */ 2097 int 2098 vm_fault_disable_pagefaults(void) 2099 { 2100 2101 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 2102 } 2103 2104 void 2105 vm_fault_enable_pagefaults(int save) 2106 { 2107 2108 curthread_pflags_restore(save); 2109 } 2110