/* $NetBSD: uvm_amap.c,v 1.52 2003/02/01 06:23:54 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. */ /* * uvm_amap.c: amap operations */ /* * this file contains functions that perform operations on amaps. see * uvm_amap.h for a brief explanation of the role of amaps in uvm. */ #include __KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.52 2003/02/01 06:23:54 thorpej Exp $"); #undef UVM_AMAP_INLINE /* enable/disable amap inlines */ #include "opt_uvmhist.h" #include #include #include #include #include #include #define UVM_AMAP_C /* ensure disabled inlines are in */ #include #include /* * pool for allocation of vm_map structures. note that the pool has * its own simplelock for its protection. also note that in order to * avoid an endless loop, the amap pool's allocator cannot allocate * memory from an amap (it currently goes through the kernel uobj, so * we are ok). */ struct pool uvm_amap_pool; MALLOC_DEFINE(M_UVMAMAP, "UVM amap", "UVM amap and related structures"); /* * local functions */ static struct vm_amap *amap_alloc1 __P((int, int, int)); #ifdef UVM_AMAP_PPREF /* * what is ppref? ppref is an _optional_ amap feature which is used * to keep track of reference counts on a per-page basis. it is enabled * when UVM_AMAP_PPREF is defined. * * when enabled, an array of ints is allocated for the pprefs. this * array is allocated only when a partial reference is added to the * map (either by unmapping part of the amap, or gaining a reference * to only a part of an amap). if the malloc of the array fails * (M_NOWAIT), then we set the array pointer to PPREF_NONE to indicate * that we tried to do ppref's but couldn't alloc the array so just * give up (after all, this is an optional feature!). * * the array is divided into page sized "chunks." for chunks of length 1, * the chunk reference count plus one is stored in that chunk's slot. * for chunks of length > 1 the first slot contains (the reference count * plus one) * -1. [the negative value indicates that the length is * greater than one.] the second slot of the chunk contains the length * of the chunk. here is an example: * * actual REFS: 2 2 2 2 3 1 1 0 0 0 4 4 0 1 1 1 * ppref: -3 4 x x 4 -2 2 -1 3 x -5 2 1 -2 3 x * <----------><-><----><-------><----><-><-------> * (x = don't care) * * this allows us to allow one int to contain the ref count for the whole * chunk. note that the "plus one" part is needed because a reference * count of zero is neither positive or negative (need a way to tell * if we've got one zero or a bunch of them). * * here are some in-line functions to help us. */ static __inline void pp_getreflen __P((int *, int, int *, int *)); static __inline void pp_setreflen __P((int *, int, int, int)); /* * pp_getreflen: get the reference and length for a specific offset * * => ppref's amap must be locked */ static __inline void pp_getreflen(ppref, offset, refp, lenp) int *ppref, offset, *refp, *lenp; { if (ppref[offset] > 0) { /* chunk size must be 1 */ *refp = ppref[offset] - 1; /* don't forget to adjust */ *lenp = 1; } else { *refp = (ppref[offset] * -1) - 1; *lenp = ppref[offset+1]; } } /* * pp_setreflen: set the reference and length for a specific offset * * => ppref's amap must be locked */ static __inline void pp_setreflen(ppref, offset, ref, len) int *ppref, offset, ref, len; { if (len == 0) return; if (len == 1) { ppref[offset] = ref + 1; } else { ppref[offset] = (ref + 1) * -1; ppref[offset+1] = len; } } #endif /* * amap_init: called at boot time to init global amap data structures */ void amap_init(void) { /* * Initialize the vm_amap pool. */ pool_init(&uvm_amap_pool, sizeof(struct vm_amap), 0, 0, 0, "amappl", &pool_allocator_nointr); } /* * amap_alloc1: internal function that allocates an amap, but does not * init the overlay. * * => lock on returned amap is init'd */ static inline struct vm_amap * amap_alloc1(slots, padslots, waitf) int slots, padslots, waitf; { struct vm_amap *amap; int totalslots; amap = pool_get(&uvm_amap_pool, (waitf == M_WAITOK) ? PR_WAITOK : 0); if (amap == NULL) return(NULL); totalslots = malloc_roundup((slots + padslots) * sizeof(int)) / sizeof(int); simple_lock_init(&amap->am_l); amap->am_ref = 1; amap->am_flags = 0; #ifdef UVM_AMAP_PPREF amap->am_ppref = NULL; #endif amap->am_maxslot = totalslots; amap->am_nslot = slots; amap->am_nused = 0; amap->am_slots = malloc(totalslots * sizeof(int), M_UVMAMAP, waitf); if (amap->am_slots == NULL) goto fail1; amap->am_bckptr = malloc(totalslots * sizeof(int), M_UVMAMAP, waitf); if (amap->am_bckptr == NULL) goto fail2; amap->am_anon = malloc(totalslots * sizeof(struct vm_anon *), M_UVMAMAP, waitf); if (amap->am_anon == NULL) goto fail3; return(amap); fail3: free(amap->am_bckptr, M_UVMAMAP); fail2: free(amap->am_slots, M_UVMAMAP); fail1: pool_put(&uvm_amap_pool, amap); return (NULL); } /* * amap_alloc: allocate an amap to manage "sz" bytes of anonymous VM * * => caller should ensure sz is a multiple of PAGE_SIZE * => reference count to new amap is set to one * => new amap is returned unlocked */ struct vm_amap * amap_alloc(sz, padsz, waitf) vaddr_t sz, padsz; int waitf; { struct vm_amap *amap; int slots, padslots; UVMHIST_FUNC("amap_alloc"); UVMHIST_CALLED(maphist); AMAP_B2SLOT(slots, sz); AMAP_B2SLOT(padslots, padsz); amap = amap_alloc1(slots, padslots, waitf); if (amap) memset(amap->am_anon, 0, amap->am_maxslot * sizeof(struct vm_anon *)); UVMHIST_LOG(maphist,"<- done, amap = 0x%x, sz=%d", amap, sz, 0, 0); return(amap); } /* * amap_free: free an amap * * => the amap must be unlocked * => the amap should have a zero reference count and be empty */ void amap_free(amap) struct vm_amap *amap; { UVMHIST_FUNC("amap_free"); UVMHIST_CALLED(maphist); KASSERT(amap->am_ref == 0 && amap->am_nused == 0); LOCK_ASSERT(!simple_lock_held(&amap->am_l)); free(amap->am_slots, M_UVMAMAP); free(amap->am_bckptr, M_UVMAMAP); free(amap->am_anon, M_UVMAMAP); #ifdef UVM_AMAP_PPREF if (amap->am_ppref && amap->am_ppref != PPREF_NONE) free(amap->am_ppref, M_UVMAMAP); #endif pool_put(&uvm_amap_pool, amap); UVMHIST_LOG(maphist,"<- done, freed amap = 0x%x", amap, 0, 0, 0); } /* * amap_extend: extend the size of an amap (if needed) * * => called from uvm_map when we want to extend an amap to cover * a new mapping (rather than allocate a new one) * => amap should be unlocked (we will lock it) * => to safely extend an amap it should have a reference count of * one (thus it can't be shared) */ int amap_extend(entry, addsize, flags) struct vm_map_entry *entry; vsize_t addsize; int flags; { struct vm_amap *amap = entry->aref.ar_amap; int slotoff = entry->aref.ar_pageoff; int slotmapped, slotadd, slotneed, slotadded, slotalloc; int slotadj, slotspace; #ifdef UVM_AMAP_PPREF int *newppref, *oldppref; #endif int i, *newsl, *newbck, *oldsl, *oldbck; struct vm_anon **newover, **oldover; int mflag = (flags & AMAP_EXTEND_NOWAIT) ? M_NOWAIT : (M_WAITOK | M_CANFAIL); UVMHIST_FUNC("amap_extend"); UVMHIST_CALLED(maphist); UVMHIST_LOG(maphist, " (entry=0x%x, addsize=0x%x, flags=0x%x)", entry, addsize, flags, 0); /* * first, determine how many slots we need in the amap. don't * forget that ar_pageoff could be non-zero: this means that * there are some unused slots before us in the amap. */ amap_lock(amap); AMAP_B2SLOT(slotmapped, entry->end - entry->start); /* slots mapped */ AMAP_B2SLOT(slotadd, addsize); /* slots to add */ if (flags & AMAP_EXTEND_FORWARDS) { slotneed = slotoff + slotmapped + slotadd; slotadj = 0; slotspace = 0; } else { slotneed = slotadd + slotmapped; slotadj = slotadd - slotoff; slotspace = amap->am_maxslot - slotmapped; } /* * case 1: we already have enough slots in the map and thus * only need to bump the reference counts on the slots we are * adding. */ if (flags & AMAP_EXTEND_FORWARDS) { if (amap->am_nslot >= slotneed) { #ifdef UVM_AMAP_PPREF if (amap->am_ppref && amap->am_ppref != PPREF_NONE) { amap_pp_adjref(amap, slotoff + slotmapped, slotadd, 1); } #endif amap_unlock(amap); UVMHIST_LOG(maphist, "<- done (case 1f), amap = 0x%x, sltneed=%d", amap, slotneed, 0, 0); return 0; } } else { if (slotadj <= 0) { slotoff -= slotadd; entry->aref.ar_pageoff = slotoff; #ifdef UVM_AMAP_PPREF if (amap->am_ppref && amap->am_ppref != PPREF_NONE) { amap_pp_adjref(amap, slotoff, slotadd, 1); } #endif amap_unlock(amap); UVMHIST_LOG(maphist, "<- done (case 1b), amap = 0x%x, sltneed=%d", amap, slotneed, 0, 0); return 0; } } /* * case 2: we pre-allocated slots for use and we just need to * bump nslot up to take account for these slots. */ if (amap->am_maxslot >= slotneed) { if (flags & AMAP_EXTEND_FORWARDS) { #ifdef UVM_AMAP_PPREF if (amap->am_ppref && amap->am_ppref != PPREF_NONE) { if ((slotoff + slotmapped) < amap->am_nslot) amap_pp_adjref(amap, slotoff + slotmapped, (amap->am_nslot - (slotoff + slotmapped)), 1); pp_setreflen(amap->am_ppref, amap->am_nslot, 1, slotneed - amap->am_nslot); } #endif amap->am_nslot = slotneed; amap_unlock(amap); /* * no need to zero am_anon since that was done at * alloc time and we never shrink an allocation. */ UVMHIST_LOG(maphist,"<- done (case 2f), amap = 0x%x, " "slotneed=%d", amap, slotneed, 0, 0); return 0; } else { #ifdef UVM_AMAP_PPREF if (amap->am_ppref && amap->am_ppref != PPREF_NONE) { /* * Slide up the ref counts on the pages that * are actually in use. */ memmove(amap->am_ppref + slotspace, amap->am_ppref + slotoff, slotmapped * sizeof(int)); /* * Mark the (adjusted) gap at the front as * referenced/not referenced. */ pp_setreflen(amap->am_ppref, 0, 0, slotspace - slotadd); pp_setreflen(amap->am_ppref, slotspace - slotadd, 1, slotadd); } #endif /* * Slide the anon pointers up and clear out * the space we just made. */ memmove(amap->am_anon + slotspace, amap->am_anon + slotoff, slotmapped * sizeof(struct vm_anon*)); memset(amap->am_anon + slotoff, 0, (slotspace - slotoff) * sizeof(struct vm_anon *)); /* * Slide the backpointers up, but don't bother * wiping out the old slots. */ memmove(amap->am_bckptr + slotspace, amap->am_bckptr + slotoff, slotmapped * sizeof(int)); /* * Adjust all the useful active slot numbers. */ for (i = 0; i < amap->am_nused; i++) amap->am_slots[i] += (slotspace - slotoff); /* * We just filled all the empty space in the * front of the amap by activating a few new * slots. */ amap->am_nslot = amap->am_maxslot; entry->aref.ar_pageoff = slotspace - slotadd; amap_unlock(amap); UVMHIST_LOG(maphist,"<- done (case 2b), amap = 0x%x, " "slotneed=%d", amap, slotneed, 0, 0); return 0; } } /* * case 3: we need to malloc a new amap and copy all the amap * data over from old amap to the new one. * * note that the use of a kernel realloc() probably would not * help here, since we wish to abort cleanly if one of the * three (or four) mallocs fails. */ amap_unlock(amap); /* unlock in case we sleep in malloc */ slotalloc = malloc_roundup(slotneed * sizeof(int)) / sizeof(int); #ifdef UVM_AMAP_PPREF newppref = NULL; if (amap->am_ppref && amap->am_ppref != PPREF_NONE) newppref = malloc(slotalloc * sizeof(int), M_UVMAMAP, mflag); #endif newsl = malloc(slotalloc * sizeof(int), M_UVMAMAP, mflag); newbck = malloc(slotalloc * sizeof(int), M_UVMAMAP, mflag); newover = malloc(slotalloc * sizeof(struct vm_anon *), M_UVMAMAP, mflag); if (newsl == NULL || newbck == NULL || newover == NULL) { #ifdef UVM_AMAP_PPREF if (newppref != NULL) { free(newppref, M_UVMAMAP); } #endif if (newsl != NULL) { free(newsl, M_UVMAMAP); } if (newbck != NULL) { free(newbck, M_UVMAMAP); } if (newover != NULL) { free(newover, M_UVMAMAP); } return ENOMEM; } amap_lock(amap); KASSERT(amap->am_maxslot < slotneed); /* * now copy everything over to new malloc'd areas... */ slotadded = slotalloc - amap->am_nslot; if (!(flags & AMAP_EXTEND_FORWARDS)) slotspace = slotalloc - slotmapped; /* do am_slots */ oldsl = amap->am_slots; if (flags & AMAP_EXTEND_FORWARDS) memcpy(newsl, oldsl, sizeof(int) * amap->am_nused); else for (i = 0; i < amap->am_nused; i++) newsl[i] = oldsl[i] + slotspace - slotoff; amap->am_slots = newsl; /* do am_anon */ oldover = amap->am_anon; if (flags & AMAP_EXTEND_FORWARDS) { memcpy(newover, oldover, sizeof(struct vm_anon *) * amap->am_nslot); memset(newover + amap->am_nslot, 0, sizeof(struct vm_anon *) * slotadded); } else { memcpy(newover + slotspace, oldover + slotoff, sizeof(struct vm_anon *) * slotmapped); memset(newover, 0, sizeof(struct vm_anon *) * slotspace); } amap->am_anon = newover; /* do am_bckptr */ oldbck = amap->am_bckptr; if (flags & AMAP_EXTEND_FORWARDS) memcpy(newbck, oldbck, sizeof(int) * amap->am_nslot); else memcpy(newbck + slotspace, oldbck + slotoff, sizeof(int) * slotmapped); amap->am_bckptr = newbck; #ifdef UVM_AMAP_PPREF /* do ppref */ oldppref = amap->am_ppref; if (newppref) { if (flags & AMAP_EXTEND_FORWARDS) { memcpy(newppref, oldppref, sizeof(int) * amap->am_nslot); memset(newppref + amap->am_nslot, 0, sizeof(int) * slotadded); } else { memcpy(newppref + slotspace, oldppref + slotoff, sizeof(int) * slotmapped); } amap->am_ppref = newppref; if ((flags & AMAP_EXTEND_FORWARDS) && (slotoff + slotmapped) < amap->am_nslot) amap_pp_adjref(amap, slotoff + slotmapped, (amap->am_nslot - (slotoff + slotmapped)), 1); if (flags & AMAP_EXTEND_FORWARDS) pp_setreflen(newppref, amap->am_nslot, 1, slotneed - amap->am_nslot); else { pp_setreflen(newppref, 0, 0, slotalloc - slotneed); pp_setreflen(newppref, slotalloc - slotneed, 1, slotneed - slotmapped); } } else { if (amap->am_ppref) amap->am_ppref = PPREF_NONE; } #endif /* update master values */ if (flags & AMAP_EXTEND_FORWARDS) amap->am_nslot = slotneed; else { entry->aref.ar_pageoff = slotspace - slotadd; amap->am_nslot = slotalloc; } amap->am_maxslot = slotalloc; amap_unlock(amap); free(oldsl, M_UVMAMAP); free(oldbck, M_UVMAMAP); free(oldover, M_UVMAMAP); #ifdef UVM_AMAP_PPREF if (oldppref && oldppref != PPREF_NONE) free(oldppref, M_UVMAMAP); #endif UVMHIST_LOG(maphist,"<- done (case 3), amap = 0x%x, slotneed=%d", amap, slotneed, 0, 0); return 0; } /* * amap_share_protect: change protection of anons in a shared amap * * for shared amaps, given the current data structure layout, it is * not possible for us to directly locate all maps referencing the * shared anon (to change the protection). in order to protect data * in shared maps we use pmap_page_protect(). [this is useful for IPC * mechanisms like map entry passing that may want to write-protect * all mappings of a shared amap.] we traverse am_anon or am_slots * depending on the current state of the amap. * * => entry's map and amap must be locked by the caller */ void amap_share_protect(entry, prot) struct vm_map_entry *entry; vm_prot_t prot; { struct vm_amap *amap = entry->aref.ar_amap; int slots, lcv, slot, stop; LOCK_ASSERT(simple_lock_held(&amap->am_l)); AMAP_B2SLOT(slots, (entry->end - entry->start)); stop = entry->aref.ar_pageoff + slots; if (slots < amap->am_nused) { /* cheaper to traverse am_anon */ for (lcv = entry->aref.ar_pageoff ; lcv < stop ; lcv++) { if (amap->am_anon[lcv] == NULL) continue; if (amap->am_anon[lcv]->u.an_page != NULL) pmap_page_protect(amap->am_anon[lcv]->u.an_page, prot); } return; } /* cheaper to traverse am_slots */ for (lcv = 0 ; lcv < amap->am_nused ; lcv++) { slot = amap->am_slots[lcv]; if (slot < entry->aref.ar_pageoff || slot >= stop) continue; if (amap->am_anon[slot]->u.an_page != NULL) pmap_page_protect(amap->am_anon[slot]->u.an_page, prot); } } /* * amap_wipeout: wipeout all anon's in an amap; then free the amap! * * => called from amap_unref when the final reference to an amap is * discarded (i.e. when reference count == 1) * => the amap should be locked (by the caller) */ void amap_wipeout(amap) struct vm_amap *amap; { int lcv, slot; struct vm_anon *anon; UVMHIST_FUNC("amap_wipeout"); UVMHIST_CALLED(maphist); UVMHIST_LOG(maphist,"(amap=0x%x)", amap, 0,0,0); amap_unlock(amap); for (lcv = 0 ; lcv < amap->am_nused ; lcv++) { int refs; slot = amap->am_slots[lcv]; anon = amap->am_anon[slot]; if (anon == NULL || anon->an_ref == 0) panic("amap_wipeout: corrupt amap"); simple_lock(&anon->an_lock); UVMHIST_LOG(maphist," processing anon 0x%x, ref=%d", anon, anon->an_ref, 0, 0); refs = --anon->an_ref; simple_unlock(&anon->an_lock); if (refs == 0) { /* * we had the last reference to a vm_anon. free it. */ uvm_anfree(anon); } /* * XXX * releasing the swap space held by an N anons is an O(N^2) * operation because of the implementation of extents. * if there are many anons, tearing down an exiting process' * address space can take many seconds, which causes very * annoying pauses. we yield here to give other processes * a chance to run. this should be removed once the performance * of swap space management is improved. */ if (curlwp->l_cpu->ci_schedstate.spc_flags & SPCF_SHOULDYIELD) preempt(1); } /* * now we free the map */ amap->am_ref = 0; /* ... was one */ amap->am_nused = 0; amap_free(amap); /* will unlock and free amap */ UVMHIST_LOG(maphist,"<- done!", 0,0,0,0); } /* * amap_copy: ensure that a map entry's "needs_copy" flag is false * by copying the amap if necessary. * * => an entry with a null amap pointer will get a new (blank) one. * => the map that the map entry belongs to must be locked by caller. * => the amap currently attached to "entry" (if any) must be unlocked. * => if canchunk is true, then we may clip the entry into a chunk * => "startva" and "endva" are used only if canchunk is true. they are * used to limit chunking (e.g. if you have a large space that you * know you are going to need to allocate amaps for, there is no point * in allowing that to be chunked) */ void amap_copy(map, entry, waitf, canchunk, startva, endva) struct vm_map *map; struct vm_map_entry *entry; int waitf; boolean_t canchunk; vaddr_t startva, endva; { struct vm_amap *amap, *srcamap; int slots, lcv; vaddr_t chunksize; UVMHIST_FUNC("amap_copy"); UVMHIST_CALLED(maphist); UVMHIST_LOG(maphist, " (map=%p, entry=%p, waitf=%d)", map, entry, waitf, 0); /* * is there a map to copy? if not, create one from scratch. */ if (entry->aref.ar_amap == NULL) { /* * check to see if we have a large amap that we can * chunk. we align startva/endva to chunk-sized * boundaries and then clip to them. */ if (canchunk && atop(entry->end - entry->start) >= UVM_AMAP_LARGE) { /* convert slots to bytes */ chunksize = UVM_AMAP_CHUNK << PAGE_SHIFT; startva = (startva / chunksize) * chunksize; endva = roundup(endva, chunksize); UVMHIST_LOG(maphist, " chunk amap ==> clip 0x%x->0x%x" "to 0x%x->0x%x", entry->start, entry->end, startva, endva); UVM_MAP_CLIP_START(map, entry, startva); /* watch out for endva wrap-around! */ if (endva >= startva) UVM_MAP_CLIP_END(map, entry, endva); } UVMHIST_LOG(maphist, "<- done [creating new amap 0x%x->0x%x]", entry->start, entry->end, 0, 0); entry->aref.ar_pageoff = 0; entry->aref.ar_amap = amap_alloc(entry->end - entry->start, 0, waitf); if (entry->aref.ar_amap != NULL) entry->etype &= ~UVM_ET_NEEDSCOPY; return; } /* * first check and see if we are the only map entry * referencing the amap we currently have. if so, then we can * just take it over rather than copying it. note that we are * reading am_ref with the amap unlocked... the value can only * be one if we have the only reference to the amap (via our * locked map). if we are greater than one we fall through to * the next case (where we double check the value). */ if (entry->aref.ar_amap->am_ref == 1) { entry->etype &= ~UVM_ET_NEEDSCOPY; UVMHIST_LOG(maphist, "<- done [ref cnt = 1, took it over]", 0, 0, 0, 0); return; } /* * looks like we need to copy the map. */ UVMHIST_LOG(maphist," amap=%p, ref=%d, must copy it", entry->aref.ar_amap, entry->aref.ar_amap->am_ref, 0, 0); AMAP_B2SLOT(slots, entry->end - entry->start); amap = amap_alloc1(slots, 0, waitf); if (amap == NULL) { UVMHIST_LOG(maphist, " amap_alloc1 failed", 0,0,0,0); return; } srcamap = entry->aref.ar_amap; amap_lock(srcamap); /* * need to double check reference count now that we've got the * src amap locked down. the reference count could have * changed while we were in malloc. if the reference count * dropped down to one we take over the old map rather than * copying the amap. */ if (srcamap->am_ref == 1) { /* take it over? */ entry->etype &= ~UVM_ET_NEEDSCOPY; amap->am_ref--; /* drop final reference to map */ amap_free(amap); /* dispose of new (unused) amap */ amap_unlock(srcamap); return; } /* * we must copy it now. */ UVMHIST_LOG(maphist, " copying amap now",0, 0, 0, 0); for (lcv = 0 ; lcv < slots; lcv++) { amap->am_anon[lcv] = srcamap->am_anon[entry->aref.ar_pageoff + lcv]; if (amap->am_anon[lcv] == NULL) continue; simple_lock(&amap->am_anon[lcv]->an_lock); amap->am_anon[lcv]->an_ref++; simple_unlock(&amap->am_anon[lcv]->an_lock); amap->am_bckptr[lcv] = amap->am_nused; amap->am_slots[amap->am_nused] = lcv; amap->am_nused++; } memset(&amap->am_anon[lcv], 0, (amap->am_maxslot - lcv) * sizeof(struct vm_anon *)); /* * drop our reference to the old amap (srcamap) and unlock. * we know that the reference count on srcamap is greater than * one (we checked above), so there is no way we could drop * the count to zero. [and no need to worry about freeing it] */ srcamap->am_ref--; if (srcamap->am_ref == 1 && (srcamap->am_flags & AMAP_SHARED) != 0) srcamap->am_flags &= ~AMAP_SHARED; /* clear shared flag */ #ifdef UVM_AMAP_PPREF if (srcamap->am_ppref && srcamap->am_ppref != PPREF_NONE) { amap_pp_adjref(srcamap, entry->aref.ar_pageoff, (entry->end - entry->start) >> PAGE_SHIFT, -1); } #endif amap_unlock(srcamap); /* * install new amap. */ entry->aref.ar_pageoff = 0; entry->aref.ar_amap = amap; entry->etype &= ~UVM_ET_NEEDSCOPY; UVMHIST_LOG(maphist, "<- done",0, 0, 0, 0); } /* * amap_cow_now: resolve all copy-on-write faults in an amap now for fork(2) * * called during fork(2) when the parent process has a wired map * entry. in that case we want to avoid write-protecting pages * in the parent's map (e.g. like what you'd do for a COW page) * so we resolve the COW here. * * => assume parent's entry was wired, thus all pages are resident. * => assume pages that are loaned out (loan_count) are already mapped * read-only in all maps, and thus no need for us to worry about them * => assume both parent and child vm_map's are locked * => caller passes child's map/entry in to us * => if we run out of memory we will unlock the amap and sleep _with_ the * parent and child vm_map's locked(!). we have to do this since * we are in the middle of a fork(2) and we can't let the parent * map change until we are done copying all the map entrys. * => XXXCDC: out of memory should cause fork to fail, but there is * currently no easy way to do this (needs fix) * => page queues must be unlocked (we may lock them) */ void amap_cow_now(map, entry) struct vm_map *map; struct vm_map_entry *entry; { struct vm_amap *amap = entry->aref.ar_amap; int lcv, slot; struct vm_anon *anon, *nanon; struct vm_page *pg, *npg; /* * note that if we unlock the amap then we must ReStart the "lcv" for * loop because some other process could reorder the anon's in the * am_anon[] array on us while the lock is dropped. */ ReStart: amap_lock(amap); for (lcv = 0 ; lcv < amap->am_nused ; lcv++) { /* * get the page */ slot = amap->am_slots[lcv]; anon = amap->am_anon[slot]; simple_lock(&anon->an_lock); pg = anon->u.an_page; /* * page must be resident since parent is wired */ if (pg == NULL) panic("amap_cow_now: non-resident wired page in anon %p", anon); /* * if the anon ref count is one and the page is not loaned, * then we are safe (the child has exclusive access to the * page). if the page is loaned, then it must already be * mapped read-only. * * we only need to get involved when these are not true. * [note: if loan_count == 0, then the anon must own the page] */ if (anon->an_ref > 1 && pg->loan_count == 0) { /* * if the page is busy then we have to unlock, wait for * it and then restart. */ if (pg->flags & PG_BUSY) { pg->flags |= PG_WANTED; amap_unlock(amap); UVM_UNLOCK_AND_WAIT(pg, &anon->an_lock, FALSE, "cownow", 0); goto ReStart; } /* * ok, time to do a copy-on-write to a new anon */ nanon = uvm_analloc(); if (nanon) { /* nanon is locked! */ npg = uvm_pagealloc(NULL, 0, nanon, 0); } else npg = NULL; /* XXX: quiet gcc warning */ if (nanon == NULL || npg == NULL) { /* out of memory */ /* * XXXCDC: we should cause fork to fail, but * we can't ... */ if (nanon) { nanon->an_ref--; simple_unlock(&nanon->an_lock); uvm_anfree(nanon); } simple_unlock(&anon->an_lock); amap_unlock(amap); uvm_wait("cownowpage"); goto ReStart; } /* * got it... now we can copy the data and replace anon * with our new one... */ uvm_pagecopy(pg, npg); /* old -> new */ anon->an_ref--; /* can't drop to zero */ amap->am_anon[slot] = nanon; /* replace */ /* * drop PG_BUSY on new page ... since we have had it's * owner locked the whole time it can't be * PG_RELEASED | PG_WANTED. */ uvm_lock_pageq(); uvm_pageactivate(npg); uvm_unlock_pageq(); npg->flags &= ~(PG_BUSY|PG_FAKE); UVM_PAGE_OWN(npg, NULL); simple_unlock(&nanon->an_lock); } simple_unlock(&anon->an_lock); } amap_unlock(amap); } /* * amap_splitref: split a single reference into two separate references * * => called from uvm_map's clip routines * => origref's map should be locked * => origref->ar_amap should be unlocked (we will lock) */ void amap_splitref(origref, splitref, offset) struct vm_aref *origref, *splitref; vaddr_t offset; { int leftslots; AMAP_B2SLOT(leftslots, offset); if (leftslots == 0) panic("amap_splitref: split at zero offset"); amap_lock(origref->ar_amap); /* * now: amap is locked and we have a valid am_mapped array. */ if (origref->ar_amap->am_nslot - origref->ar_pageoff - leftslots <= 0) panic("amap_splitref: map size check failed"); #ifdef UVM_AMAP_PPREF /* * establish ppref before we add a duplicate reference to the amap */ if (origref->ar_amap->am_ppref == NULL) amap_pp_establish(origref->ar_amap, origref->ar_pageoff); #endif splitref->ar_amap = origref->ar_amap; splitref->ar_amap->am_ref++; /* not a share reference */ splitref->ar_pageoff = origref->ar_pageoff + leftslots; amap_unlock(origref->ar_amap); } #ifdef UVM_AMAP_PPREF /* * amap_pp_establish: add a ppref array to an amap, if possible * * => amap locked by caller */ void amap_pp_establish(amap, offset) struct vm_amap *amap; vaddr_t offset; { amap->am_ppref = malloc(sizeof(int) * amap->am_maxslot, M_UVMAMAP, M_NOWAIT); /* * if we fail then we just won't use ppref for this amap */ if (amap->am_ppref == NULL) { amap->am_ppref = PPREF_NONE; /* not using it */ return; } memset(amap->am_ppref, 0, sizeof(int) * amap->am_maxslot); pp_setreflen(amap->am_ppref, 0, 0, offset); pp_setreflen(amap->am_ppref, offset, amap->am_ref, amap->am_nslot - offset); return; } /* * amap_pp_adjref: adjust reference count to a part of an amap using the * per-page reference count array. * * => map and amap locked by caller * => caller must check that ppref != PPREF_NONE before calling */ void amap_pp_adjref(amap, curslot, slotlen, adjval) struct vm_amap *amap; int curslot; vsize_t slotlen; int adjval; { int stopslot, *ppref, lcv, prevlcv; int ref, len, prevref, prevlen; stopslot = curslot + slotlen; ppref = amap->am_ppref; prevlcv = 0; /* * first advance to the correct place in the ppref array, * fragment if needed. */ for (lcv = 0 ; lcv < curslot ; lcv += len) { pp_getreflen(ppref, lcv, &ref, &len); if (lcv + len > curslot) { /* goes past start? */ pp_setreflen(ppref, lcv, ref, curslot - lcv); pp_setreflen(ppref, curslot, ref, len - (curslot -lcv)); len = curslot - lcv; /* new length of entry @ lcv */ } prevlcv = lcv; } if (lcv != 0) pp_getreflen(ppref, prevlcv, &prevref, &prevlen); else { /* Ensure that the "prevref == ref" test below always * fails, since we're starting from the beginning of * the ppref array; that is, there is no previous * chunk. */ prevref = -1; prevlen = 0; } /* * now adjust reference counts in range. merge the first * changed entry with the last unchanged entry if possible. */ if (lcv != curslot) panic("amap_pp_adjref: overshot target"); for (/* lcv already set */; lcv < stopslot ; lcv += len) { pp_getreflen(ppref, lcv, &ref, &len); if (lcv + len > stopslot) { /* goes past end? */ pp_setreflen(ppref, lcv, ref, stopslot - lcv); pp_setreflen(ppref, stopslot, ref, len - (stopslot - lcv)); len = stopslot - lcv; } ref += adjval; if (ref < 0) panic("amap_pp_adjref: negative reference count"); if (lcv == prevlcv + prevlen && ref == prevref) { pp_setreflen(ppref, prevlcv, ref, prevlen + len); } else { pp_setreflen(ppref, lcv, ref, len); } if (ref == 0) amap_wiperange(amap, lcv, len); } } /* * amap_wiperange: wipe out a range of an amap * [different from amap_wipeout because the amap is kept intact] * * => both map and amap must be locked by caller. */ void amap_wiperange(amap, slotoff, slots) struct vm_amap *amap; int slotoff, slots; { int byanon, lcv, stop, curslot, ptr, slotend; struct vm_anon *anon; /* * we can either traverse the amap by am_anon or by am_slots depending * on which is cheaper. decide now. */ if (slots < amap->am_nused) { byanon = TRUE; lcv = slotoff; stop = slotoff + slots; slotend = 0; } else { byanon = FALSE; lcv = 0; stop = amap->am_nused; slotend = slotoff + slots; } while (lcv < stop) { int refs; if (byanon) { curslot = lcv++; /* lcv advances here */ if (amap->am_anon[curslot] == NULL) continue; } else { curslot = amap->am_slots[lcv]; if (curslot < slotoff || curslot >= slotend) { lcv++; /* lcv advances here */ continue; } stop--; /* drop stop, since anon will be removed */ } anon = amap->am_anon[curslot]; /* * remove it from the amap */ amap->am_anon[curslot] = NULL; ptr = amap->am_bckptr[curslot]; if (ptr != (amap->am_nused - 1)) { amap->am_slots[ptr] = amap->am_slots[amap->am_nused - 1]; amap->am_bckptr[amap->am_slots[ptr]] = ptr; /* back ptr. */ } amap->am_nused--; /* * drop anon reference count */ simple_lock(&anon->an_lock); refs = --anon->an_ref; simple_unlock(&anon->an_lock); if (refs == 0) { /* * we just eliminated the last reference to an anon. * free it. */ uvm_anfree(anon); } } } #endif