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