/* $OpenBSD: uvm_fault.c,v 1.69 2013/05/30 18:02:04 tedu Exp $ */ /* $NetBSD: uvm_fault.c,v 1.51 2000/08/06 00:22:53 thorpej Exp $ */ /* * * Copyright (c) 1997 Charles D. Cranor and Washington University. * All rights reserved. * * 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 Charles D. Cranor and * Washington University. * 4. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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: Id: uvm_fault.c,v 1.1.2.23 1998/02/06 05:29:05 chs Exp */ /* * uvm_fault.c: fault handler */ #include #include #include #include #include #include #include #include /* * * a word on page faults: * * types of page faults we handle: * * CASE 1: upper layer faults CASE 2: lower layer faults * * CASE 1A CASE 1B CASE 2A CASE 2B * read/write1 write>1 read/write +-cow_write/zero * | | | | * +--|--+ +--|--+ +-----+ + | + | +-----+ * amap | V | | ----------->new| | | | ^ | * +-----+ +-----+ +-----+ + | + | +--|--+ * | | | * +-----+ +-----+ +--|--+ | +--|--+ * uobj | d/c | | d/c | | V | +----| | * +-----+ +-----+ +-----+ +-----+ * * d/c = don't care * * case [0]: layerless fault * no amap or uobj is present. this is an error. * * case [1]: upper layer fault [anon active] * 1A: [read] or [write with anon->an_ref == 1] * I/O takes place in top level anon and uobj is not touched. * 1B: [write with anon->an_ref > 1] * new anon is alloc'd and data is copied off ["COW"] * * case [2]: lower layer fault [uobj] * 2A: [read on non-NULL uobj] or [write to non-copy_on_write area] * I/O takes place directly in object. * 2B: [write to copy_on_write] or [read on NULL uobj] * data is "promoted" from uobj to a new anon. * if uobj is null, then we zero fill. * * we follow the standard UVM locking protocol ordering: * * MAPS => AMAP => UOBJ => ANON => PAGE QUEUES (PQ) * we hold a PG_BUSY page if we unlock for I/O * * * the code is structured as follows: * * - init the "IN" params in the ufi structure * ReFault: * - do lookups [locks maps], check protection, handle needs_copy * - check for case 0 fault (error) * - establish "range" of fault * - if we have an amap lock it and extract the anons * - if sequential advice deactivate pages behind us * - at the same time check pmap for unmapped areas and anon for pages * that we could map in (and do map it if found) * - check object for resident pages that we could map in * - if (case 2) goto Case2 * - >>> handle case 1 * - ensure source anon is resident in RAM * - if case 1B alloc new anon and copy from source * - map the correct page in * Case2: * - >>> handle case 2 * - ensure source page is resident (if uobj) * - if case 2B alloc new anon and copy from source (could be zero * fill if uobj == NULL) * - map the correct page in * - done! * * note on paging: * if we have to do I/O we place a PG_BUSY page in the correct object, * unlock everything, and do the I/O. when I/O is done we must reverify * the state of the world before assuming that our data structures are * valid. [because mappings could change while the map is unlocked] * * alternative 1: unbusy the page in question and restart the page fault * from the top (ReFault). this is easy but does not take advantage * of the information that we already have from our previous lookup, * although it is possible that the "hints" in the vm_map will help here. * * alternative 2: the system already keeps track of a "version" number of * a map. [i.e. every time you write-lock a map (e.g. to change a * mapping) you bump the version number up by one...] so, we can save * the version number of the map before we release the lock and start I/O. * then when I/O is done we can relock and check the version numbers * to see if anything changed. this might save us some over 1 because * we don't have to unbusy the page and may be less compares(?). * * alternative 3: put in backpointers or a way to "hold" part of a map * in place while I/O is in progress. this could be complex to * implement (especially with structures like amap that can be referenced * by multiple map entries, and figuring out what should wait could be * complex as well...). * * given that we are not currently multiprocessor or multithreaded we might * as well choose alternative 2 now. maybe alternative 3 would be useful * in the future. XXX keep in mind for future consideration//rechecking. */ /* * local data structures */ struct uvm_advice { int advice; int nback; int nforw; }; /* * page range array: * note: index in array must match "advice" value * XXX: borrowed numbers from freebsd. do they work well for us? */ static struct uvm_advice uvmadvice[] = { { MADV_NORMAL, 3, 4 }, { MADV_RANDOM, 0, 0 }, { MADV_SEQUENTIAL, 8, 7}, }; #define UVM_MAXRANGE 16 /* must be max() of nback+nforw+1 */ /* * private prototypes */ static void uvmfault_amapcopy(struct uvm_faultinfo *); static __inline void uvmfault_anonflush(struct vm_anon **, int); void uvmfault_unlockmaps(struct uvm_faultinfo *, boolean_t); void uvmfault_update_stats(struct uvm_faultinfo *); /* * inline functions */ /* * uvmfault_anonflush: try and deactivate pages in specified anons * * => does not have to deactivate page if it is busy */ static __inline void uvmfault_anonflush(struct vm_anon **anons, int n) { int lcv; struct vm_page *pg; for (lcv = 0 ; lcv < n ; lcv++) { if (anons[lcv] == NULL) continue; pg = anons[lcv]->an_page; if (pg && (pg->pg_flags & PG_BUSY) == 0 && pg->loan_count == 0) { uvm_lock_pageq(); if (pg->wire_count == 0) { #ifdef UBC pmap_clear_reference(pg); #else pmap_page_protect(pg, VM_PROT_NONE); #endif uvm_pagedeactivate(pg); } uvm_unlock_pageq(); } } } /* * normal functions */ /* * uvmfault_amapcopy: clear "needs_copy" in a map. * * => if we are out of RAM we sleep (waiting for more) */ static void uvmfault_amapcopy(struct uvm_faultinfo *ufi) { /* * while we haven't done the job */ while (1) { /* * no mapping? give up. */ if (uvmfault_lookup(ufi, TRUE) == FALSE) return; /* * copy if needed. */ if (UVM_ET_ISNEEDSCOPY(ufi->entry)) amap_copy(ufi->map, ufi->entry, M_NOWAIT, TRUE, ufi->orig_rvaddr, ufi->orig_rvaddr + 1); /* * didn't work? must be out of RAM. sleep. */ if (UVM_ET_ISNEEDSCOPY(ufi->entry)) { uvmfault_unlockmaps(ufi, TRUE); uvm_wait("fltamapcopy"); continue; } /* * got it! */ uvmfault_unlockmaps(ufi, TRUE); return; } /*NOTREACHED*/ } /* * uvmfault_anonget: get data in an anon into a non-busy, non-released * page in that anon. * * => we don't move the page on the queues [gets moved later] * => if we allocate a new page [we_own], it gets put on the queues. * either way, the result is that the page is on the queues at return time * => for pages which are on loan from a uvm_object (and thus are not * owned by the anon): if successful, we return with the owning object */ int uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap, struct vm_anon *anon) { boolean_t we_own; /* we own anon's page? */ boolean_t locked; /* did we relock? */ struct vm_page *pg; int result; result = 0; /* XXX shut up gcc */ uvmexp.fltanget++; /* bump rusage counters */ if (anon->an_page) curproc->p_ru.ru_minflt++; else curproc->p_ru.ru_majflt++; /* * loop until we get it, or fail. */ while (1) { we_own = FALSE; /* TRUE if we set PG_BUSY on a page */ pg = anon->an_page; /* * if there is a resident page and it is loaned, then anon * may not own it. call out to uvm_anon_lockpage() to ensure * the real owner of the page has been identified. */ if (pg && pg->loan_count) pg = uvm_anon_lockloanpg(anon); /* * page there? make sure it is not busy/released. */ if (pg) { /* * at this point, if the page has a uobject [meaning * we have it on loan], then that uobject is locked * by us! if the page is busy, we drop all the * locks (including uobject) and try again. */ if ((pg->pg_flags & (PG_BUSY|PG_RELEASED)) == 0) { return (VM_PAGER_OK); } atomic_setbits_int(&pg->pg_flags, PG_WANTED); uvmexp.fltpgwait++; /* * the last unlock must be an atomic unlock+wait on * the owner of page */ if (pg->uobject) { /* owner is uobject ? */ uvmfault_unlockall(ufi, amap, NULL, anon); UVM_WAIT(pg, FALSE, "anonget1",0); } else { /* anon owns page */ uvmfault_unlockall(ufi, amap, NULL, NULL); UVM_WAIT(pg, 0, "anonget2", 0); } /* ready to relock and try again */ } else { /* * no page, we must try and bring it in. */ pg = uvm_pagealloc(NULL, 0, anon, 0); if (pg == NULL) { /* out of RAM. */ uvmfault_unlockall(ufi, amap, NULL, anon); uvmexp.fltnoram++; uvm_wait("flt_noram1"); /* ready to relock and try again */ } else { /* we set the PG_BUSY bit */ we_own = TRUE; uvmfault_unlockall(ufi, amap, NULL, anon); /* * we are passing a PG_BUSY+PG_FAKE+PG_CLEAN * page into the uvm_swap_get function with * all data structures unlocked. note that * it is ok to read an_swslot here because * we hold PG_BUSY on the page. */ uvmexp.pageins++; result = uvm_swap_get(pg, anon->an_swslot, PGO_SYNCIO); /* * we clean up after the i/o below in the * "we_own" case */ /* ready to relock and try again */ } } /* * now relock and try again */ locked = uvmfault_relock(ufi); /* * if we own the page (i.e. we set PG_BUSY), then we need * to clean up after the I/O. there are three cases to * consider: * [1] page released during I/O: free anon and ReFault. * [2] I/O not OK. free the page and cause the fault * to fail. * [3] I/O OK! activate the page and sync with the * non-we_own case (i.e. drop anon lock if not locked). */ if (we_own) { if (pg->pg_flags & PG_WANTED) { wakeup(pg); } /* un-busy! */ atomic_clearbits_int(&pg->pg_flags, PG_WANTED|PG_BUSY|PG_FAKE); UVM_PAGE_OWN(pg, NULL); /* * if we were RELEASED during I/O, then our anon is * no longer part of an amap. we need to free the * anon and try again. */ if (pg->pg_flags & PG_RELEASED) { pmap_page_protect(pg, VM_PROT_NONE); uvm_anfree(anon); /* frees page for us */ if (locked) uvmfault_unlockall(ufi, amap, NULL, NULL); uvmexp.fltpgrele++; return (VM_PAGER_REFAULT); /* refault! */ } if (result != VM_PAGER_OK) { KASSERT(result != VM_PAGER_PEND); /* remove page from anon */ anon->an_page = NULL; /* * remove the swap slot from the anon * and mark the anon as having no real slot. * don't free the swap slot, thus preventing * it from being used again. */ uvm_swap_markbad(anon->an_swslot, 1); anon->an_swslot = SWSLOT_BAD; /* * note: page was never !PG_BUSY, so it * can't be mapped and thus no need to * pmap_page_protect it... */ uvm_lock_pageq(); uvm_pagefree(pg); uvm_unlock_pageq(); if (locked) uvmfault_unlockall(ufi, amap, NULL, anon); return (VM_PAGER_ERROR); } /* * must be OK, clear modify (already PG_CLEAN) * and activate */ pmap_clear_modify(pg); uvm_lock_pageq(); uvm_pageactivate(pg); uvm_unlock_pageq(); } /* * we were not able to relock. restart fault. */ if (!locked) return (VM_PAGER_REFAULT); /* * verify no one has touched the amap and moved the anon on us. */ if (ufi != NULL && amap_lookup(&ufi->entry->aref, ufi->orig_rvaddr - ufi->entry->start) != anon) { uvmfault_unlockall(ufi, amap, NULL, anon); return (VM_PAGER_REFAULT); } /* * try it again! */ uvmexp.fltanretry++; continue; } /* while (1) */ /*NOTREACHED*/ } /* * Update statistics after fault resolution. * - maxrss */ void uvmfault_update_stats(struct uvm_faultinfo *ufi) { struct vm_map *map; struct proc *p; vsize_t res; #ifndef pmap_resident_count struct vm_space *vm; #endif map = ufi->orig_map; /* * Update the maxrss for the process. */ if (map->flags & VM_MAP_ISVMSPACE) { p = curproc; KASSERT(p != NULL && &p->p_vmspace->vm_map == map); #ifdef pmap_resident_count res = pmap_resident_count(map->pmap); #else /* * Rather inaccurate, but this is the current anon size * of the vmspace. It's basically the resident size * minus the mmapped in files/text. */ vm = (struct vmspace*)map; res = vm->dsize; #endif /* Convert res from pages to kilobytes. */ res <<= (PAGE_SHIFT - 10); if (p->p_ru.ru_maxrss < res) p->p_ru.ru_maxrss = res; } } /* * F A U L T - m a i n e n t r y p o i n t */ /* * uvm_fault: page fault handler * * => called from MD code to resolve a page fault * => VM data structures usually should be unlocked. however, it is * possible to call here with the main map locked if the caller * gets a write lock, sets it recursive, and then calls us (c.f. * uvm_map_pageable). this should be avoided because it keeps * the map locked off during I/O. */ #define MASK(entry) (UVM_ET_ISCOPYONWRITE(entry) ? \ ~VM_PROT_WRITE : VM_PROT_ALL) int uvm_fault(vm_map_t orig_map, vaddr_t vaddr, vm_fault_t fault_type, vm_prot_t access_type) { struct uvm_faultinfo ufi; vm_prot_t enter_prot; boolean_t wired, narrow, promote, locked, shadowed; int npages, nback, nforw, centeridx, result, lcv, gotpages; vaddr_t startva, currva; voff_t uoff; paddr_t pa; struct vm_amap *amap; struct uvm_object *uobj; struct vm_anon *anons_store[UVM_MAXRANGE], **anons, *anon, *oanon; struct vm_page *pages[UVM_MAXRANGE], *pg, *uobjpage; anon = NULL; pg = NULL; uvmexp.faults++; /* XXX: locking? */ /* * init the IN parameters in the ufi */ ufi.orig_map = orig_map; ufi.orig_rvaddr = trunc_page(vaddr); ufi.orig_size = PAGE_SIZE; /* can't get any smaller than this */ if (fault_type == VM_FAULT_WIRE) narrow = TRUE; /* don't look for neighborhood * pages on wire */ else narrow = FALSE; /* normal fault */ /* * "goto ReFault" means restart the page fault from ground zero. */ ReFault: /* * lookup and lock the maps */ if (uvmfault_lookup(&ufi, FALSE) == FALSE) { return (EFAULT); } #ifdef DIAGNOSTIC if ((ufi.map->flags & VM_MAP_PAGEABLE) == 0) panic("uvm_fault: fault on non-pageable map (%p, 0x%lx)", ufi.map, vaddr); #endif /* * check protection */ if ((ufi.entry->protection & access_type) != access_type) { uvmfault_unlockmaps(&ufi, FALSE); return (EACCES); } /* * "enter_prot" is the protection we want to enter the page in at. * for certain pages (e.g. copy-on-write pages) this protection can * be more strict than ufi.entry->protection. "wired" means either * the entry is wired or we are fault-wiring the pg. */ enter_prot = ufi.entry->protection; wired = VM_MAPENT_ISWIRED(ufi.entry) || (fault_type == VM_FAULT_WIRE); if (wired) access_type = enter_prot; /* full access for wired */ /* * handle "needs_copy" case. */ if (UVM_ET_ISNEEDSCOPY(ufi.entry)) { if ((access_type & VM_PROT_WRITE) || (ufi.entry->object.uvm_obj == NULL)) { /* need to clear */ uvmfault_unlockmaps(&ufi, FALSE); uvmfault_amapcopy(&ufi); uvmexp.fltamcopy++; goto ReFault; } else { /* * ensure that we pmap_enter page R/O since * needs_copy is still true */ enter_prot &= ~VM_PROT_WRITE; } } /* * identify the players */ amap = ufi.entry->aref.ar_amap; /* top layer */ uobj = ufi.entry->object.uvm_obj; /* bottom layer */ /* * check for a case 0 fault. if nothing backing the entry then * error now. */ if (amap == NULL && uobj == NULL) { uvmfault_unlockmaps(&ufi, FALSE); return (EFAULT); } /* * establish range of interest based on advice from mapper * and then clip to fit map entry. note that we only want * to do this the first time through the fault. if we * ReFault we will disable this by setting "narrow" to true. */ if (narrow == FALSE) { /* wide fault (!narrow) */ KASSERT(uvmadvice[ufi.entry->advice].advice == ufi.entry->advice); nback = min(uvmadvice[ufi.entry->advice].nback, (ufi.orig_rvaddr - ufi.entry->start) >> PAGE_SHIFT); startva = ufi.orig_rvaddr - (nback << PAGE_SHIFT); nforw = min(uvmadvice[ufi.entry->advice].nforw, ((ufi.entry->end - ufi.orig_rvaddr) >> PAGE_SHIFT) - 1); /* * note: "-1" because we don't want to count the * faulting page as forw */ npages = nback + nforw + 1; centeridx = nback; narrow = TRUE; /* ensure only once per-fault */ } else { /* narrow fault! */ nback = nforw = 0; startva = ufi.orig_rvaddr; npages = 1; centeridx = 0; } /* * if we've got an amap, extract current anons. */ if (amap) { anons = anons_store; amap_lookups(&ufi.entry->aref, startva - ufi.entry->start, anons, npages); } else { anons = NULL; /* to be safe */ } /* * for MADV_SEQUENTIAL mappings we want to deactivate the back pages * now and then forget about them (for the rest of the fault). */ if (ufi.entry->advice == MADV_SEQUENTIAL && nback != 0) { /* flush back-page anons? */ if (amap) uvmfault_anonflush(anons, nback); /* flush object? */ if (uobj) { uoff = (startva - ufi.entry->start) + ufi.entry->offset; (void) uobj->pgops->pgo_flush(uobj, uoff, uoff + (nback << PAGE_SHIFT), PGO_DEACTIVATE); } /* now forget about the backpages */ if (amap) anons += nback; startva += (nback << PAGE_SHIFT); npages -= nback; centeridx = 0; } /* * map in the backpages and frontpages we found in the amap in hopes * of preventing future faults. we also init the pages[] array as * we go. */ currva = startva; shadowed = FALSE; for (lcv = 0 ; lcv < npages ; lcv++, currva += PAGE_SIZE) { /* * dont play with VAs that are already mapped * except for center) */ if (lcv != centeridx && pmap_extract(ufi.orig_map->pmap, currva, &pa)) { pages[lcv] = PGO_DONTCARE; continue; } /* * unmapped or center page. check if any anon at this level. */ if (amap == NULL || anons[lcv] == NULL) { pages[lcv] = NULL; continue; } /* * check for present page and map if possible. re-activate it. */ pages[lcv] = PGO_DONTCARE; if (lcv == centeridx) { /* save center for later! */ shadowed = TRUE; continue; } anon = anons[lcv]; /* ignore loaned pages */ if (anon->an_page && anon->an_page->loan_count == 0 && (anon->an_page->pg_flags & (PG_RELEASED|PG_BUSY)) == 0) { uvm_lock_pageq(); uvm_pageactivate(anon->an_page); /* reactivate */ uvm_unlock_pageq(); uvmexp.fltnamap++; /* * Since this isn't the page that's actually faulting, * ignore pmap_enter() failures; it's not critical * that we enter these right now. */ (void) pmap_enter(ufi.orig_map->pmap, currva, VM_PAGE_TO_PHYS(anon->an_page), (anon->an_ref > 1) ? (enter_prot & ~VM_PROT_WRITE) : enter_prot, PMAP_CANFAIL | (VM_MAPENT_ISWIRED(ufi.entry) ? PMAP_WIRED : 0)); } pmap_update(ufi.orig_map->pmap); } /* (shadowed == TRUE) if there is an anon at the faulting address */ /* * note that if we are really short of RAM we could sleep in the above * call to pmap_enter. bad? * * XXX Actually, that is bad; pmap_enter() should just fail in that * XXX case. --thorpej */ /* * if the desired page is not shadowed by the amap and we have a * backing object, then we check to see if the backing object would * prefer to handle the fault itself (rather than letting us do it * with the usual pgo_get hook). the backing object signals this by * providing a pgo_fault routine. */ if (uobj && shadowed == FALSE && uobj->pgops->pgo_fault != NULL) { result = uobj->pgops->pgo_fault(&ufi, startva, pages, npages, centeridx, fault_type, access_type, PGO_LOCKED); if (result == VM_PAGER_OK) return (0); /* pgo_fault did pmap enter */ else if (result == VM_PAGER_REFAULT) goto ReFault; /* try again! */ else return (EACCES); } /* * now, if the desired page is not shadowed by the amap and we have * a backing object that does not have a special fault routine, then * we ask (with pgo_get) the object for resident pages that we care * about and attempt to map them in. we do not let pgo_get block * (PGO_LOCKED). * * ("get" has the option of doing a pmap_enter for us) */ if (uobj && shadowed == FALSE) { uvmexp.fltlget++; gotpages = npages; (void) uobj->pgops->pgo_get(uobj, ufi.entry->offset + (startva - ufi.entry->start), pages, &gotpages, centeridx, access_type & MASK(ufi.entry), ufi.entry->advice, PGO_LOCKED); /* * check for pages to map, if we got any */ uobjpage = NULL; if (gotpages) { currva = startva; for (lcv = 0 ; lcv < npages ; lcv++, currva += PAGE_SIZE) { if (pages[lcv] == NULL || pages[lcv] == PGO_DONTCARE) continue; KASSERT((pages[lcv]->pg_flags & PG_RELEASED) == 0); /* * if center page is resident and not * PG_BUSY, then pgo_get made it PG_BUSY * for us and gave us a handle to it. * remember this page as "uobjpage." * (for later use). */ if (lcv == centeridx) { uobjpage = pages[lcv]; continue; } /* * note: calling pgo_get with locked data * structures returns us pages which are * neither busy nor released, so we don't * need to check for this. we can just * directly enter the page (after moving it * to the head of the active queue [useful?]). */ uvm_lock_pageq(); uvm_pageactivate(pages[lcv]); /* reactivate */ uvm_unlock_pageq(); uvmexp.fltnomap++; /* * Since this page isn't the page that's * actually fauling, ignore pmap_enter() * failures; it's not critical that we * enter these right now. */ (void) pmap_enter(ufi.orig_map->pmap, currva, VM_PAGE_TO_PHYS(pages[lcv]), enter_prot & MASK(ufi.entry), PMAP_CANFAIL | (wired ? PMAP_WIRED : 0)); /* * NOTE: page can't be PG_WANTED because * we've held the lock the whole time * we've had the handle. */ atomic_clearbits_int(&pages[lcv]->pg_flags, PG_BUSY); UVM_PAGE_OWN(pages[lcv], NULL); } /* for "lcv" loop */ pmap_update(ufi.orig_map->pmap); } /* "gotpages" != 0 */ /* note: object still _locked_ */ } else { uobjpage = NULL; } /* * note that at this point we are done with any front or back pages. * we are now going to focus on the center page (i.e. the one we've * faulted on). if we have faulted on the top (anon) layer * [i.e. case 1], then the anon we want is anons[centeridx] (we have * not touched it yet). if we have faulted on the bottom (uobj) * layer [i.e. case 2] and the page was both present and available, * then we've got a pointer to it as "uobjpage" and we've already * made it BUSY. */ /* * there are four possible cases we must address: 1A, 1B, 2A, and 2B */ /* * redirect case 2: if we are not shadowed, go to case 2. */ if (shadowed == FALSE) goto Case2; /* * handle case 1: fault on an anon in our amap */ anon = anons[centeridx]; /* * no matter if we have case 1A or case 1B we are going to need to * have the anon's memory resident. ensure that now. */ /* * let uvmfault_anonget do the dirty work. * also, if it is OK, then the anon's page is on the queues. */ result = uvmfault_anonget(&ufi, amap, anon); switch (result) { case VM_PAGER_OK: break; case VM_PAGER_REFAULT: goto ReFault; case VM_PAGER_ERROR: /* * An error occured while trying to bring in the * page -- this is the only error we return right * now. */ return (EACCES); /* XXX */ default: #ifdef DIAGNOSTIC panic("uvm_fault: uvmfault_anonget -> %d", result); #else return (EACCES); #endif } /* * uobj is non null if the page is on loan from an object (i.e. uobj) */ uobj = anon->an_page->uobject; /* * special handling for loaned pages */ if (anon->an_page->loan_count) { if ((access_type & VM_PROT_WRITE) == 0) { /* * for read faults on loaned pages we just cap the * protection at read-only. */ enter_prot = enter_prot & ~VM_PROT_WRITE; } else { /* * note that we can't allow writes into a loaned page! * * if we have a write fault on a loaned page in an * anon then we need to look at the anon's ref count. * if it is greater than one then we are going to do * a normal copy-on-write fault into a new anon (this * is not a problem). however, if the reference count * is one (a case where we would normally allow a * write directly to the page) then we need to kill * the loan before we continue. */ /* >1 case is already ok */ if (anon->an_ref == 1) { /* get new un-owned replacement page */ pg = uvm_pagealloc(NULL, 0, NULL, 0); if (pg == NULL) { uvmfault_unlockall(&ufi, amap, uobj, anon); uvm_wait("flt_noram2"); goto ReFault; } /* * copy data, kill loan */ /* copy old -> new */ uvm_pagecopy(anon->an_page, pg); /* force reload */ pmap_page_protect(anon->an_page, VM_PROT_NONE); uvm_lock_pageq(); /* KILL loan */ if (uobj) /* if we were loaning */ anon->an_page->loan_count--; anon->an_page->uanon = NULL; /* in case we owned */ atomic_clearbits_int( &anon->an_page->pg_flags, PQ_ANON); uvm_pageactivate(pg); uvm_unlock_pageq(); if (uobj) { uobj = NULL; } /* install new page in anon */ anon->an_page = pg; pg->uanon = anon; atomic_setbits_int(&pg->pg_flags, PQ_ANON); atomic_clearbits_int(&pg->pg_flags, PG_BUSY|PG_FAKE); UVM_PAGE_OWN(pg, NULL); /* done! */ } /* ref == 1 */ } /* write fault */ } /* loan count */ /* * if we are case 1B then we will need to allocate a new blank * anon to transfer the data into. note that we have a lock * on anon, so no one can busy or release the page until we are done. * also note that the ref count can't drop to zero here because * it is > 1 and we are only dropping one ref. * * in the (hopefully very rare) case that we are out of RAM we * will wait for more RAM, and refault. * * if we are out of anon VM we kill the process (XXX: could wait?). */ if ((access_type & VM_PROT_WRITE) != 0 && anon->an_ref > 1) { uvmexp.flt_acow++; oanon = anon; /* oanon = old */ anon = uvm_analloc(); if (anon) { pg = uvm_pagealloc(NULL, 0, anon, 0); } /* check for out of RAM */ if (anon == NULL || pg == NULL) { if (anon) uvm_anfree(anon); uvmfault_unlockall(&ufi, amap, uobj, oanon); KASSERT(uvmexp.swpgonly <= uvmexp.swpages); if (anon == NULL || uvmexp.swpgonly == uvmexp.swpages) { uvmexp.fltnoanon++; return (ENOMEM); } uvmexp.fltnoram++; uvm_wait("flt_noram3"); /* out of RAM, wait for more */ goto ReFault; } /* got all resources, replace anon with nanon */ uvm_pagecopy(oanon->an_page, pg); /* pg now !PG_CLEAN */ /* un-busy! new page */ atomic_clearbits_int(&pg->pg_flags, PG_BUSY|PG_FAKE); UVM_PAGE_OWN(pg, NULL); amap_add(&ufi.entry->aref, ufi.orig_rvaddr - ufi.entry->start, anon, 1); /* deref: can not drop to zero here by defn! */ oanon->an_ref--; /* * note: anon is _not_ locked, but we have the sole references * to in from amap. * thus, no one can get at it until we are done with it. */ } else { uvmexp.flt_anon++; oanon = anon; pg = anon->an_page; if (anon->an_ref > 1) /* disallow writes to ref > 1 anons */ enter_prot = enter_prot & ~VM_PROT_WRITE; } /* * now map the page in ... * XXX: old fault unlocks object before pmap_enter. this seems * suspect since some other thread could blast the page out from * under us between the unlock and the pmap_enter. */ if (pmap_enter(ufi.orig_map->pmap, ufi.orig_rvaddr, VM_PAGE_TO_PHYS(pg), enter_prot, access_type | PMAP_CANFAIL | (wired ? PMAP_WIRED : 0)) != 0) { /* * No need to undo what we did; we can simply think of * this as the pmap throwing away the mapping information. * * We do, however, have to go through the ReFault path, * as the map may change while we're asleep. */ uvmfault_unlockall(&ufi, amap, uobj, oanon); KASSERT(uvmexp.swpgonly <= uvmexp.swpages); if (uvmexp.swpgonly == uvmexp.swpages) { /* XXX instrumentation */ return (ENOMEM); } /* XXX instrumentation */ uvm_wait("flt_pmfail1"); goto ReFault; } /* * ... update the page queues. */ uvm_lock_pageq(); if (fault_type == VM_FAULT_WIRE) { uvm_pagewire(pg); /* * since the now-wired page cannot be paged out, * release its swap resources for others to use. * since an anon with no swap cannot be PG_CLEAN, * clear its clean flag now. */ atomic_clearbits_int(&pg->pg_flags, PG_CLEAN); uvm_anon_dropswap(anon); } else { /* activate it */ uvm_pageactivate(pg); } uvm_unlock_pageq(); /* * done case 1! finish up by unlocking everything and returning success */ uvmfault_unlockall(&ufi, amap, uobj, oanon); pmap_update(ufi.orig_map->pmap); return (0); Case2: /* * handle case 2: faulting on backing object or zero fill */ /* * note that uobjpage can not be PGO_DONTCARE at this point. we now * set uobjpage to PGO_DONTCARE if we are doing a zero fill. if we * have a backing object, check and see if we are going to promote * the data up to an anon during the fault. */ if (uobj == NULL) { uobjpage = PGO_DONTCARE; promote = TRUE; /* always need anon here */ } else { KASSERT(uobjpage != PGO_DONTCARE); promote = (access_type & VM_PROT_WRITE) && UVM_ET_ISCOPYONWRITE(ufi.entry); } /* * if uobjpage is not null then we do not need to do I/O to get the * uobjpage. * * if uobjpage is null, then we need to ask the pager to * get the data for us. once we have the data, we need to reverify * the state the world. we are currently not holding any resources. */ if (uobjpage) { /* update rusage counters */ curproc->p_ru.ru_minflt++; } else { /* update rusage counters */ curproc->p_ru.ru_majflt++; uvmfault_unlockall(&ufi, amap, NULL, NULL); uvmexp.fltget++; gotpages = 1; uoff = (ufi.orig_rvaddr - ufi.entry->start) + ufi.entry->offset; result = uobj->pgops->pgo_get(uobj, uoff, &uobjpage, &gotpages, 0, access_type & MASK(ufi.entry), ufi.entry->advice, PGO_SYNCIO); /* * recover from I/O */ if (result != VM_PAGER_OK) { KASSERT(result != VM_PAGER_PEND); if (result == VM_PAGER_AGAIN) { tsleep(&lbolt, PVM, "fltagain2", 0); goto ReFault; } return (EACCES); /* XXX i/o error */ } /* * re-verify the state of the world. */ locked = uvmfault_relock(&ufi); /* * Re-verify that amap slot is still free. if there is * a problem, we clean up. */ if (locked && amap && amap_lookup(&ufi.entry->aref, ufi.orig_rvaddr - ufi.entry->start)) { if (locked) uvmfault_unlockall(&ufi, amap, NULL, NULL); locked = FALSE; } /* * didn't get the lock? release the page and retry. */ if (locked == FALSE) { if (uobjpage->pg_flags & PG_WANTED) /* still holding object lock */ wakeup(uobjpage); uvm_lock_pageq(); /* make sure it is in queues */ uvm_pageactivate(uobjpage); uvm_unlock_pageq(); atomic_clearbits_int(&uobjpage->pg_flags, PG_BUSY|PG_WANTED); UVM_PAGE_OWN(uobjpage, NULL); goto ReFault; } /* * we have the data in uobjpage which is PG_BUSY */ } /* * notes: * - at this point uobjpage can not be NULL * - at this point uobjpage could be PG_WANTED (handle later) */ if (promote == FALSE) { /* * we are not promoting. if the mapping is COW ensure that we * don't give more access than we should (e.g. when doing a read * fault on a COPYONWRITE mapping we want to map the COW page in * R/O even though the entry protection could be R/W). * * set "pg" to the page we want to map in (uobjpage, usually) */ uvmexp.flt_obj++; if (UVM_ET_ISCOPYONWRITE(ufi.entry)) enter_prot &= ~VM_PROT_WRITE; pg = uobjpage; /* map in the actual object */ /* assert(uobjpage != PGO_DONTCARE) */ /* * we are faulting directly on the page. be careful * about writing to loaned pages... */ if (uobjpage->loan_count) { if ((access_type & VM_PROT_WRITE) == 0) { /* read fault: cap the protection at readonly */ /* cap! */ enter_prot = enter_prot & ~VM_PROT_WRITE; } else { /* write fault: must break the loan here */ /* alloc new un-owned page */ pg = uvm_pagealloc(NULL, 0, NULL, 0); if (pg == NULL) { /* * drop ownership of page, it can't * be released */ if (uobjpage->pg_flags & PG_WANTED) wakeup(uobjpage); atomic_clearbits_int( &uobjpage->pg_flags, PG_BUSY|PG_WANTED); UVM_PAGE_OWN(uobjpage, NULL); uvm_lock_pageq(); /* activate: we will need it later */ uvm_pageactivate(uobjpage); uvm_unlock_pageq(); uvmfault_unlockall(&ufi, amap, uobj, NULL); uvmexp.fltnoram++; uvm_wait("flt_noram4"); goto ReFault; } /* * copy the data from the old page to the new * one and clear the fake/clean flags on the * new page (keep it busy). force a reload * of the old page by clearing it from all * pmaps. then lock the page queues to * rename the pages. */ uvm_pagecopy(uobjpage, pg); /* old -> new */ atomic_clearbits_int(&pg->pg_flags, PG_FAKE|PG_CLEAN); pmap_page_protect(uobjpage, VM_PROT_NONE); if (uobjpage->pg_flags & PG_WANTED) wakeup(uobjpage); atomic_clearbits_int(&uobjpage->pg_flags, PG_BUSY|PG_WANTED); UVM_PAGE_OWN(uobjpage, NULL); uvm_lock_pageq(); uoff = uobjpage->offset; /* remove old page */ uvm_pagerealloc(uobjpage, NULL, 0); /* * at this point we have absolutely no * control over uobjpage */ /* install new page */ uvm_pagerealloc(pg, uobj, uoff); uvm_unlock_pageq(); /* * done! loan is broken and "pg" is * PG_BUSY. it can now replace uobjpage. */ uobjpage = pg; } /* write fault case */ } /* if loan_count */ } else { /* * if we are going to promote the data to an anon we * allocate a blank anon here and plug it into our amap. */ #ifdef DIAGNOSTIC if (amap == NULL) panic("uvm_fault: want to promote data, but no anon"); #endif anon = uvm_analloc(); if (anon) { /* * In `Fill in data...' below, if * uobjpage == PGO_DONTCARE, we want * a zero'd, dirty page, so have * uvm_pagealloc() do that for us. */ pg = uvm_pagealloc(NULL, 0, anon, (uobjpage == PGO_DONTCARE) ? UVM_PGA_ZERO : 0); } /* * out of memory resources? */ if (anon == NULL || pg == NULL) { /* * arg! must unbusy our page and fail or sleep. */ if (uobjpage != PGO_DONTCARE) { if (uobjpage->pg_flags & PG_WANTED) wakeup(uobjpage); uvm_lock_pageq(); uvm_pageactivate(uobjpage); uvm_unlock_pageq(); atomic_clearbits_int(&uobjpage->pg_flags, PG_BUSY|PG_WANTED); UVM_PAGE_OWN(uobjpage, NULL); } /* unlock and fail ... */ uvmfault_unlockall(&ufi, amap, uobj, NULL); KASSERT(uvmexp.swpgonly <= uvmexp.swpages); if (anon == NULL || uvmexp.swpgonly == uvmexp.swpages) { uvmexp.fltnoanon++; return (ENOMEM); } uvm_anfree(anon); uvmexp.fltnoram++; uvm_wait("flt_noram5"); goto ReFault; } /* * fill in the data */ if (uobjpage != PGO_DONTCARE) { uvmexp.flt_prcopy++; /* copy page [pg now dirty] */ uvm_pagecopy(uobjpage, pg); /* * promote to shared amap? make sure all sharing * procs see it */ if ((amap_flags(amap) & AMAP_SHARED) != 0) { pmap_page_protect(uobjpage, VM_PROT_NONE); } /* * dispose of uobjpage. drop handle to uobj as well. */ if (uobjpage->pg_flags & PG_WANTED) wakeup(uobjpage); atomic_clearbits_int(&uobjpage->pg_flags, PG_BUSY|PG_WANTED); UVM_PAGE_OWN(uobjpage, NULL); uvm_lock_pageq(); uvm_pageactivate(uobjpage); uvm_unlock_pageq(); uobj = NULL; } else { uvmexp.flt_przero++; /* * Page is zero'd and marked dirty by uvm_pagealloc() * above. */ } amap_add(&ufi.entry->aref, ufi.orig_rvaddr - ufi.entry->start, anon, 0); } /* * note: pg is either the uobjpage or the new page in the new anon */ /* * all resources are present. we can now map it in and free our * resources. */ if (pmap_enter(ufi.orig_map->pmap, ufi.orig_rvaddr, VM_PAGE_TO_PHYS(pg), enter_prot, access_type | PMAP_CANFAIL | (wired ? PMAP_WIRED : 0)) != 0) { /* * No need to undo what we did; we can simply think of * this as the pmap throwing away the mapping information. * * We do, however, have to go through the ReFault path, * as the map may change while we're asleep. */ if (pg->pg_flags & PG_WANTED) wakeup(pg); atomic_clearbits_int(&pg->pg_flags, PG_BUSY|PG_FAKE|PG_WANTED); UVM_PAGE_OWN(pg, NULL); uvmfault_unlockall(&ufi, amap, uobj, NULL); KASSERT(uvmexp.swpgonly <= uvmexp.swpages); if (uvmexp.swpgonly == uvmexp.swpages) { /* XXX instrumentation */ return (ENOMEM); } /* XXX instrumentation */ uvm_wait("flt_pmfail2"); goto ReFault; } uvm_lock_pageq(); if (fault_type == VM_FAULT_WIRE) { uvm_pagewire(pg); if (pg->pg_flags & PQ_AOBJ) { /* * since the now-wired page cannot be paged out, * release its swap resources for others to use. * since an aobj page with no swap cannot be PG_CLEAN, * clear its clean flag now. */ atomic_clearbits_int(&pg->pg_flags, PG_CLEAN); uao_dropswap(uobj, pg->offset >> PAGE_SHIFT); } } else { /* activate it */ uvm_pageactivate(pg); } uvm_unlock_pageq(); if (pg->pg_flags & PG_WANTED) wakeup(pg); atomic_clearbits_int(&pg->pg_flags, PG_BUSY|PG_FAKE|PG_WANTED); UVM_PAGE_OWN(pg, NULL); uvmfault_unlockall(&ufi, amap, uobj, NULL); pmap_update(ufi.orig_map->pmap); return (0); } /* * uvm_fault_wire: wire down a range of virtual addresses in a map. * * => map may be read-locked by caller, but MUST NOT be write-locked. * => if map is read-locked, any operations which may cause map to * be write-locked in uvm_fault() must be taken care of by * the caller. See uvm_map_pageable(). */ int uvm_fault_wire(vm_map_t map, vaddr_t start, vaddr_t end, vm_prot_t access_type) { vaddr_t va; pmap_t pmap; int rv; pmap = vm_map_pmap(map); /* * now fault it in a page at a time. if the fault fails then we have * to undo what we have done. note that in uvm_fault VM_PROT_NONE * is replaced with the max protection if fault_type is VM_FAULT_WIRE. */ for (va = start ; va < end ; va += PAGE_SIZE) { rv = uvm_fault(map, va, VM_FAULT_WIRE, access_type); if (rv) { if (va != start) { uvm_fault_unwire(map, start, va); } return (rv); } } return (0); } /* * uvm_fault_unwire(): unwire range of virtual space. */ void uvm_fault_unwire(vm_map_t map, vaddr_t start, vaddr_t end) { vm_map_lock_read(map); uvm_fault_unwire_locked(map, start, end); vm_map_unlock_read(map); } /* * uvm_fault_unwire_locked(): the guts of uvm_fault_unwire(). * * => map must be at least read-locked. */ void uvm_fault_unwire_locked(vm_map_t map, vaddr_t start, vaddr_t end) { vm_map_entry_t entry, next; pmap_t pmap = vm_map_pmap(map); vaddr_t va; paddr_t pa; struct vm_page *pg; KASSERT((map->flags & VM_MAP_INTRSAFE) == 0); /* * we assume that the area we are unwiring has actually been wired * in the first place. this means that we should be able to extract * the PAs from the pmap. we also lock out the page daemon so that * we can call uvm_pageunwire. */ uvm_lock_pageq(); /* * find the beginning map entry for the region. */ KASSERT(start >= vm_map_min(map) && end <= vm_map_max(map)); if (uvm_map_lookup_entry(map, start, &entry) == FALSE) panic("uvm_fault_unwire_locked: address not in map"); for (va = start; va < end ; va += PAGE_SIZE) { if (pmap_extract(pmap, va, &pa) == FALSE) continue; /* * find the map entry for the current address. */ KASSERT(va >= entry->start); while (va >= entry->end) { next = RB_NEXT(uvm_map_addr, &map->addr, entry); KASSERT(next != NULL && next->start <= entry->end); entry = next; } /* * if the entry is no longer wired, tell the pmap. */ if (VM_MAPENT_ISWIRED(entry) == 0) pmap_unwire(pmap, va); pg = PHYS_TO_VM_PAGE(pa); if (pg) uvm_pageunwire(pg); } uvm_unlock_pageq(); } /* * uvmfault_unlockmaps: unlock the maps */ void uvmfault_unlockmaps(struct uvm_faultinfo *ufi, boolean_t write_locked) { /* * ufi can be NULL when this isn't really a fault, * but merely paging in anon data. */ if (ufi == NULL) { return; } uvmfault_update_stats(ufi); if (write_locked) { vm_map_unlock(ufi->map); } else { vm_map_unlock_read(ufi->map); } } /* * uvmfault_unlockall: unlock everything passed in. * * => maps must be read-locked (not write-locked). */ void uvmfault_unlockall(struct uvm_faultinfo *ufi, struct vm_amap *amap, struct uvm_object *uobj, struct vm_anon *anon) { uvmfault_unlockmaps(ufi, FALSE); } /* * uvmfault_lookup: lookup a virtual address in a map * * => caller must provide a uvm_faultinfo structure with the IN * params properly filled in * => we will lookup the map entry (handling submaps) as we go * => if the lookup is a success we will return with the maps locked * => if "write_lock" is TRUE, we write_lock the map, otherwise we only * get a read lock. * => note that submaps can only appear in the kernel and they are * required to use the same virtual addresses as the map they * are referenced by (thus address translation between the main * map and the submap is unnecessary). */ boolean_t uvmfault_lookup(struct uvm_faultinfo *ufi, boolean_t write_lock) { vm_map_t tmpmap; /* * init ufi values for lookup. */ ufi->map = ufi->orig_map; ufi->size = ufi->orig_size; /* * keep going down levels until we are done. note that there can * only be two levels so we won't loop very long. */ while (1) { if (ufi->orig_rvaddr < ufi->map->min_offset || ufi->orig_rvaddr >= ufi->map->max_offset) return(FALSE); /* * lock map */ if (write_lock) { vm_map_lock(ufi->map); } else { vm_map_lock_read(ufi->map); } /* * lookup */ if (!uvm_map_lookup_entry(ufi->map, ufi->orig_rvaddr, &ufi->entry)) { uvmfault_unlockmaps(ufi, write_lock); return(FALSE); } /* * reduce size if necessary */ if (ufi->entry->end - ufi->orig_rvaddr < ufi->size) ufi->size = ufi->entry->end - ufi->orig_rvaddr; /* * submap? replace map with the submap and lookup again. * note: VAs in submaps must match VAs in main map. */ if (UVM_ET_ISSUBMAP(ufi->entry)) { tmpmap = ufi->entry->object.sub_map; uvmfault_unlockmaps(ufi, write_lock); ufi->map = tmpmap; continue; } /* * got it! */ ufi->mapv = ufi->map->timestamp; return(TRUE); } /* while loop */ /*NOTREACHED*/ } /* * uvmfault_relock: attempt to relock the same version of the map * * => fault data structures should be unlocked before calling. * => if a success (TRUE) maps will be locked after call. */ boolean_t uvmfault_relock(struct uvm_faultinfo *ufi) { /* * ufi can be NULL when this isn't really a fault, * but merely paging in anon data. */ if (ufi == NULL) { return TRUE; } uvmexp.fltrelck++; /* * relock map. fail if version mismatch (in which case nothing * gets locked). */ vm_map_lock_read(ufi->map); if (ufi->mapv != ufi->map->timestamp) { vm_map_unlock_read(ufi->map); return(FALSE); } uvmexp.fltrelckok++; return(TRUE); /* got it! */ }