/* * Copyright (c) 1991, 1993 * The Regents of the University of California. All rights reserved. * Copyright (c) 1994 John S. Dyson * All rights reserved. * Copyright (c) 1994 David Greenman * All rights reserved. * * * This code is derived from software contributed to Berkeley by * The Mach Operating System project at Carnegie-Mellon University. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 * * * Copyright (c) 1987, 1990 Carnegie-Mellon University. * All rights reserved. * * Authors: Avadis Tevanian, Jr., Michael Wayne Young * * Permission to use, copy, modify and distribute this software and * its documentation is hereby granted, provided that both the copyright * notice and this permission notice appear in all copies of the * software, derivative works or modified versions, and any portions * thereof, and that both notices appear in supporting documentation. * * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. * * Carnegie Mellon requests users of this software to return to * * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU * School of Computer Science * Carnegie Mellon University * Pittsburgh PA 15213-3890 * * any improvements or extensions that they make and grant Carnegie the * rights to redistribute these changes. * * $Id: vm_fault.c,v 1.39 1995/12/11 04:58:06 dyson Exp $ */ /* * Page fault handling module. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include int vm_fault_additional_pages __P((vm_page_t, int, int, vm_page_t *, int *)); #define VM_FAULT_READ_AHEAD 4 #define VM_FAULT_READ_BEHIND 3 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) /* * vm_fault: * * Handle a page fault occuring at the given address, * requiring the given permissions, in the map specified. * If successful, the page is inserted into the * associated physical map. * * NOTE: the given address should be truncated to the * proper page address. * * KERN_SUCCESS is returned if the page fault is handled; otherwise, * a standard error specifying why the fault is fatal is returned. * * * The map in question must be referenced, and remains so. * Caller may hold no locks. */ int vm_fault(map, vaddr, fault_type, change_wiring) vm_map_t map; vm_offset_t vaddr; vm_prot_t fault_type; boolean_t change_wiring; { vm_object_t first_object; vm_pindex_t first_pindex; vm_map_entry_t entry; register vm_object_t object; register vm_pindex_t pindex; vm_page_t m; vm_page_t first_m; vm_prot_t prot; int result; boolean_t wired; boolean_t su; boolean_t lookup_still_valid; vm_page_t old_m; vm_object_t next_object; vm_page_t marray[VM_FAULT_READ]; int hardfault = 0; struct vnode *vp = NULL; cnt.v_vm_faults++; /* needs lock XXX */ /* * Recovery actions */ #define FREE_PAGE(m) { \ PAGE_WAKEUP(m); \ vm_page_free(m); \ } #define RELEASE_PAGE(m) { \ PAGE_WAKEUP(m); \ if (m->queue != PQ_ACTIVE) vm_page_activate(m); \ } #define UNLOCK_MAP { \ if (lookup_still_valid) { \ vm_map_lookup_done(map, entry); \ lookup_still_valid = FALSE; \ } \ } #define UNLOCK_THINGS { \ vm_object_pip_wakeup(object); \ if (object != first_object) { \ FREE_PAGE(first_m); \ vm_object_pip_wakeup(first_object); \ } \ UNLOCK_MAP; \ if (vp != NULL) VOP_UNLOCK(vp); \ } #define UNLOCK_AND_DEALLOCATE { \ UNLOCK_THINGS; \ vm_object_deallocate(first_object); \ } RetryFault:; /* * Find the backing store object and offset into it to begin the * search. */ if ((result = vm_map_lookup(&map, vaddr, fault_type, &entry, &first_object, &first_pindex, &prot, &wired, &su)) != KERN_SUCCESS) { return (result); } vp = vnode_pager_lock(first_object); lookup_still_valid = TRUE; if (wired) fault_type = prot; first_m = NULL; /* * Make a reference to this object to prevent its disposal while we * are messing with it. Once we have the reference, the map is free * to be diddled. Since objects reference their shadows (and copies), * they will stay around as well. */ first_object->ref_count++; first_object->paging_in_progress++; /* * INVARIANTS (through entire routine): * * 1) At all times, we must either have the object lock or a busy * page in some object to prevent some other process from trying to * bring in the same page. * * Note that we cannot hold any locks during the pager access or when * waiting for memory, so we use a busy page then. * * Note also that we aren't as concerned about more than one thead * attempting to pager_data_unlock the same page at once, so we don't * hold the page as busy then, but do record the highest unlock value * so far. [Unlock requests may also be delivered out of order.] * * 2) Once we have a busy page, we must remove it from the pageout * queues, so that the pageout daemon will not grab it away. * * 3) To prevent another process from racing us down the shadow chain * and entering a new page in the top object before we do, we must * keep a busy page in the top object while following the shadow * chain. * * 4) We must increment paging_in_progress on any object for which * we have a busy page, to prevent vm_object_collapse from removing * the busy page without our noticing. */ /* * Search for the page at object/offset. */ object = first_object; pindex = first_pindex; /* * See whether this page is resident */ while (TRUE) { m = vm_page_lookup(object, pindex); if (m != NULL) { /* * If the page is being brought in, wait for it and * then retry. */ if ((m->flags & PG_BUSY) || m->busy) { int s; UNLOCK_THINGS; s = splhigh(); if ((m->flags & PG_BUSY) || m->busy) { m->flags |= PG_WANTED | PG_REFERENCED; cnt.v_intrans++; tsleep(m, PSWP, "vmpfw", 0); } splx(s); vm_object_deallocate(first_object); goto RetryFault; } /* * Mark page busy for other processes, and the pagedaemon. */ m->flags |= PG_BUSY; if ((m->queue == PQ_CACHE) && (cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_reserved) { UNLOCK_AND_DEALLOCATE; VM_WAIT; PAGE_WAKEUP(m); goto RetryFault; } if (m->valid && ((m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && m->object != kernel_object && m->object != kmem_object) { goto readrest; } break; } if (((object->type != OBJT_DEFAULT) && (!change_wiring || wired)) || (object == first_object)) { if (pindex >= object->size) { UNLOCK_AND_DEALLOCATE; return (KERN_PROTECTION_FAILURE); } /* * Allocate a new page for this object/offset pair. */ m = vm_page_alloc(object, pindex, vp?VM_ALLOC_NORMAL:VM_ALLOC_ZERO); if (m == NULL) { UNLOCK_AND_DEALLOCATE; VM_WAIT; goto RetryFault; } } readrest: if (object->type != OBJT_DEFAULT && (!change_wiring || wired)) { int rv; int faultcount; int reqpage; /* * now we find out if any other pages should be paged * in at this time this routine checks to see if the * pages surrounding this fault reside in the same * object as the page for this fault. If they do, * then they are faulted in also into the object. The * array "marray" returned contains an array of * vm_page_t structs where one of them is the * vm_page_t passed to the routine. The reqpage * return value is the index into the marray for the * vm_page_t passed to the routine. */ faultcount = vm_fault_additional_pages( m, VM_FAULT_READ_BEHIND, VM_FAULT_READ_AHEAD, marray, &reqpage); /* * Call the pager to retrieve the data, if any, after * releasing the lock on the map. */ UNLOCK_MAP; rv = faultcount ? vm_pager_get_pages(object, marray, faultcount, reqpage) : VM_PAGER_FAIL; if (rv == VM_PAGER_OK) { /* * Found the page. Leave it busy while we play * with it. */ /* * Relookup in case pager changed page. Pager * is responsible for disposition of old page * if moved. */ m = vm_page_lookup(object, pindex); if( !m) { UNLOCK_AND_DEALLOCATE; goto RetryFault; } hardfault++; break; } /* * Remove the bogus page (which does not exist at this * object/offset); before doing so, we must get back * our object lock to preserve our invariant. * * Also wake up any other process that may want to bring * in this page. * * If this is the top-level object, we must leave the * busy page to prevent another process from rushing * past us, and inserting the page in that object at * the same time that we are. */ if (rv == VM_PAGER_ERROR) printf("vm_fault: pager input (probably hardware) error, PID %d failure\n", curproc->p_pid); /* * Data outside the range of the pager or an I/O error */ /* * XXX - the check for kernel_map is a kludge to work * around having the machine panic on a kernel space * fault w/ I/O error. */ if (((map != kernel_map) && (rv == VM_PAGER_ERROR)) || (rv == VM_PAGER_BAD)) { FREE_PAGE(m); UNLOCK_AND_DEALLOCATE; return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); } if (object != first_object) { FREE_PAGE(m); /* * XXX - we cannot just fall out at this * point, m has been freed and is invalid! */ } } /* * We get here if the object has default pager (or unwiring) or the * pager doesn't have the page. */ if (object == first_object) first_m = m; /* * Move on to the next object. Lock the next object before * unlocking the current one. */ pindex += OFF_TO_IDX(object->backing_object_offset); next_object = object->backing_object; if (next_object == NULL) { /* * If there's no object left, fill the page in the top * object with zeros. */ if (object != first_object) { vm_object_pip_wakeup(object); object = first_object; pindex = first_pindex; m = first_m; } first_m = NULL; if ((m->flags & PG_ZERO) == 0) vm_page_zero_fill(m); m->valid = VM_PAGE_BITS_ALL; cnt.v_zfod++; break; } else { if (object != first_object) { vm_object_pip_wakeup(object); } object = next_object; object->paging_in_progress++; } } if ((m->flags & PG_BUSY) == 0) panic("vm_fault: not busy after main loop"); /* * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock * is held.] */ old_m = m; /* save page that would be copied */ /* * If the page is being written, but isn't already owned by the * top-level object, we have to copy it into a new page owned by the * top-level object. */ if (object != first_object) { /* * We only really need to copy if we want to write it. */ if (fault_type & VM_PROT_WRITE) { /* * If we try to collapse first_object at this point, * we may deadlock when we try to get the lock on an * intermediate object (since we have the bottom * object locked). We can't unlock the bottom object, * because the page we found may move (by collapse) if * we do. * * Instead, we first copy the page. Then, when we have * no more use for the bottom object, we unlock it and * try to collapse. * * Note that we copy the page even if we didn't need * to... that's the breaks. */ /* * We already have an empty page in first_object - use * it. */ vm_page_copy(m, first_m); first_m->valid = VM_PAGE_BITS_ALL; /* * If another map is truly sharing this page with us, * we have to flush all uses of the original page, * since we can't distinguish those which want the * original from those which need the new copy. * * XXX If we know that only one map has access to this * page, then we could avoid the pmap_page_protect() * call. */ if (m->queue != PQ_ACTIVE) vm_page_activate(m); /* * We no longer need the old page or object. */ PAGE_WAKEUP(m); vm_object_pip_wakeup(object); /* * Only use the new page below... */ cnt.v_cow_faults++; m = first_m; object = first_object; pindex = first_pindex; /* * Now that we've gotten the copy out of the way, * let's try to collapse the top object. * * But we have to play ugly games with * paging_in_progress to do that... */ vm_object_pip_wakeup(object); vm_object_collapse(object); object->paging_in_progress++; } else { prot &= ~VM_PROT_WRITE; } } /* * We must verify that the maps have not changed since our last * lookup. */ if (!lookup_still_valid) { vm_object_t retry_object; vm_pindex_t retry_pindex; vm_prot_t retry_prot; /* * Since map entries may be pageable, make sure we can take a * page fault on them. */ /* * To avoid trying to write_lock the map while another process * has it read_locked (in vm_map_pageable), we do not try for * write permission. If the page is still writable, we will * get write permission. If it is not, or has been marked * needs_copy, we enter the mapping without write permission, * and will merely take another fault. */ result = vm_map_lookup(&map, vaddr, fault_type & ~VM_PROT_WRITE, &entry, &retry_object, &retry_pindex, &retry_prot, &wired, &su); /* * If we don't need the page any longer, put it on the active * list (the easiest thing to do here). If no one needs it, * pageout will grab it eventually. */ if (result != KERN_SUCCESS) { RELEASE_PAGE(m); UNLOCK_AND_DEALLOCATE; return (result); } lookup_still_valid = TRUE; if ((retry_object != first_object) || (retry_pindex != first_pindex)) { RELEASE_PAGE(m); UNLOCK_AND_DEALLOCATE; goto RetryFault; } /* * Check whether the protection has changed or the object has * been copied while we left the map unlocked. Changing from * read to write permission is OK - we leave the page * write-protected, and catch the write fault. Changing from * write to read permission means that we can't mark the page * write-enabled after all. */ prot &= retry_prot; } /* * (the various bits we're fiddling with here are locked by the * object's lock) */ /* * It's critically important that a wired-down page be faulted only * once in each map for which it is wired. */ /* * Put this page into the physical map. We had to do the unlock above * because pmap_enter may cause other faults. We don't put the page * back on the active queue until later so that the page-out daemon * won't find us (yet). */ if (prot & VM_PROT_WRITE) { m->flags |= PG_WRITEABLE; m->object->flags |= OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY; /* * If the fault is a write, we know that this page is being * written NOW. This will save on the pmap_is_modified() calls * later. */ if (fault_type & VM_PROT_WRITE) { m->dirty = VM_PAGE_BITS_ALL; } } m->flags |= PG_MAPPED|PG_REFERENCED; m->flags &= ~PG_ZERO; pmap_enter(map->pmap, vaddr, VM_PAGE_TO_PHYS(m), prot, wired); #if 0 if (change_wiring == 0 && wired == 0) pmap_prefault(map->pmap, vaddr, entry, first_object); #endif /* * If the page is not wired down, then put it where the pageout daemon * can find it. */ if (change_wiring) { if (wired) vm_page_wire(m); else vm_page_unwire(m); } else { if (m->queue != PQ_ACTIVE) vm_page_activate(m); } if (curproc && (curproc->p_flag & P_INMEM) && curproc->p_stats) { if (hardfault) { curproc->p_stats->p_ru.ru_majflt++; } else { curproc->p_stats->p_ru.ru_minflt++; } } /* * Unlock everything, and return */ PAGE_WAKEUP(m); UNLOCK_AND_DEALLOCATE; return (KERN_SUCCESS); } /* * vm_fault_wire: * * Wire down a range of virtual addresses in a map. */ int vm_fault_wire(map, start, end) vm_map_t map; vm_offset_t start, end; { register vm_offset_t va; register pmap_t pmap; int rv; pmap = vm_map_pmap(map); /* * Inform the physical mapping system that the range of addresses may * not fault, so that page tables and such can be locked down as well. */ pmap_pageable(pmap, start, end, FALSE); /* * We simulate a fault to get the page and enter it in the physical * map. */ for (va = start; va < end; va += PAGE_SIZE) { while( curproc != pageproc && (cnt.v_free_count <= cnt.v_pageout_free_min)) VM_WAIT; rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE, TRUE); if (rv) { if (va != start) vm_fault_unwire(map, start, va); return (rv); } } return (KERN_SUCCESS); } /* * vm_fault_unwire: * * Unwire a range of virtual addresses in a map. */ void vm_fault_unwire(map, start, end) vm_map_t map; vm_offset_t start, end; { register vm_offset_t va, pa; register pmap_t pmap; pmap = vm_map_pmap(map); /* * Since the pages are wired down, we must be able to get their * mappings from the physical map system. */ for (va = start; va < end; va += PAGE_SIZE) { pa = pmap_extract(pmap, va); if (pa == (vm_offset_t) 0) { panic("unwire: page not in pmap"); } pmap_change_wiring(pmap, va, FALSE); vm_page_unwire(PHYS_TO_VM_PAGE(pa)); } /* * Inform the physical mapping system that the range of addresses may * fault, so that page tables and such may be unwired themselves. */ pmap_pageable(pmap, start, end, TRUE); } /* * Routine: * vm_fault_copy_entry * Function: * Copy all of the pages from a wired-down map entry to another. * * In/out conditions: * The source and destination maps must be locked for write. * The source map entry must be wired down (or be a sharing map * entry corresponding to a main map entry that is wired down). */ void vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) vm_map_t dst_map; vm_map_t src_map; vm_map_entry_t dst_entry; vm_map_entry_t src_entry; { vm_object_t dst_object; vm_object_t src_object; vm_ooffset_t dst_offset; vm_ooffset_t src_offset; vm_prot_t prot; vm_offset_t vaddr; vm_page_t dst_m; vm_page_t src_m; #ifdef lint src_map++; #endif /* lint */ src_object = src_entry->object.vm_object; src_offset = src_entry->offset; /* * Create the top-level object for the destination entry. (Doesn't * actually shadow anything - we copy the pages directly.) */ dst_object = vm_object_allocate(OBJT_DEFAULT, (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); dst_entry->object.vm_object = dst_object; dst_entry->offset = 0; prot = dst_entry->max_protection; /* * Loop through all of the pages in the entry's range, copying each * one from the source object (it should be there) to the destination * object. */ for (vaddr = dst_entry->start, dst_offset = 0; vaddr < dst_entry->end; vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { /* * Allocate a page in the destination object */ do { dst_m = vm_page_alloc(dst_object, OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); if (dst_m == NULL) { VM_WAIT; } } while (dst_m == NULL); /* * Find the page in the source object, and copy it in. * (Because the source is wired down, the page will be in * memory.) */ src_m = vm_page_lookup(src_object, OFF_TO_IDX(dst_offset + src_offset)); if (src_m == NULL) panic("vm_fault_copy_wired: page missing"); vm_page_copy(src_m, dst_m); /* * Enter it in the pmap... */ dst_m->flags |= PG_WRITEABLE|PG_MAPPED; dst_m->flags &= ~PG_ZERO; pmap_enter(dst_map->pmap, vaddr, VM_PAGE_TO_PHYS(dst_m), prot, FALSE); /* * Mark it no longer busy, and put it on the active list. */ vm_page_activate(dst_m); PAGE_WAKEUP(dst_m); } } /* * This routine checks around the requested page for other pages that * might be able to be faulted in. This routine brackets the viable * pages for the pages to be paged in. * * Inputs: * m, rbehind, rahead * * Outputs: * marray (array of vm_page_t), reqpage (index of requested page) * * Return value: * number of pages in marray */ int vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) vm_page_t m; int rbehind; int rahead; vm_page_t *marray; int *reqpage; { int i; vm_object_t object; vm_pindex_t pindex, startpindex, endpindex, tpindex; vm_offset_t size; vm_page_t rtm; int treqpage; int cbehind, cahead; object = m->object; pindex = m->pindex; /* * if the requested page is not available, then give up now */ if (!vm_pager_has_page(object, OFF_TO_IDX(object->paging_offset) + pindex, &cbehind, &cahead)) return 0; if ((cbehind == 0) && (cahead == 0)) { *reqpage = 0; marray[0] = m; return 1; } if (rahead > cahead) { rahead = cahead; } if (rbehind > cbehind) { rbehind = cbehind; } /* * try to do any readahead that we might have free pages for. */ if ((rahead + rbehind) > ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) { pagedaemon_wakeup(); *reqpage = 0; marray[0] = m; return 1; } /* * scan backward for the read behind pages -- in memory or on disk not * in same object */ tpindex = pindex - 1; if (tpindex < pindex) { if (rbehind > pindex) rbehind = pindex; startpindex = pindex - rbehind; while (tpindex >= startpindex) { if (vm_page_lookup( object, tpindex)) { startpindex = tpindex + 1; break; } if (tpindex == 0) break; tpindex -= 1; } } else { startpindex = pindex; } /* * scan forward for the read ahead pages -- in memory or on disk not * in same object */ tpindex = pindex + 1; endpindex = pindex + (rahead + 1); if (endpindex > object->size) endpindex = object->size; while (tpindex < endpindex) { if ( vm_page_lookup(object, tpindex)) { break; } tpindex += 1; } endpindex = tpindex; /* calculate number of bytes of pages */ size = endpindex - startpindex; /* calculate the page offset of the required page */ treqpage = pindex - startpindex; /* see if we have space (again) */ if ((cnt.v_free_count + cnt.v_cache_count) > (cnt.v_free_reserved + size)) { /* * get our pages and don't block for them */ for (i = 0; i < size; i++) { if (i != treqpage) { rtm = vm_page_alloc(object, startpindex + i, VM_ALLOC_NORMAL); if (rtm == NULL) { if (i < treqpage) { int j; for (j = 0; j < i; j++) { FREE_PAGE(marray[j]); } *reqpage = 0; marray[0] = m; return 1; } else { size = i; *reqpage = treqpage; return size; } } marray[i] = rtm; } else { marray[i] = m; } } *reqpage = treqpage; return size; } *reqpage = 0; marray[0] = m; return 1; }