uvm_amap.c

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/*	$NetBSD: uvm_amap.c,v 1.27 2000/11/25 06:27:59 chs 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.
 */

#undef UVM_AMAP_INLINE		/* enable/disable amap inlines */

#include "opt_uvmhist.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/kernel.h>
#include <sys/pool.h>

#define UVM_AMAP_C		/* ensure disabled inlines are in */
#include <uvm/uvm.h>
#include <uvm/uvm_swap.h>

/*
 * 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;

/*
 * 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 == 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()

{
	/*
	 * Initialize the vm_amap pool.
	 */
	pool_init(&uvm_amap_pool, sizeof(struct vm_amap), 0, 0, 0,
	    "amappl", 0, pool_page_alloc_nointr, pool_page_free_nointr, 
	    M_UVMAMAP);
}

/*
 * 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 = slots + padslots;

	amap = pool_get(&uvm_amap_pool, (waitf == M_WAITOK) ? PR_WAITOK : 0);
	if (amap == NULL)
		return(NULL);

	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);		/* load slots */
	AMAP_B2SLOT(padslots, padsz);

	amap = amap_alloc1(slots, padslots, waitf);
	if (amap)
		memset(amap->am_anon, 0, (slots + padslots) * 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 locked (mainly for simplelock accounting)
 * => 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);

#ifdef DIAGNOSTIC
	if (amap->am_ref || amap->am_nused)
		panic("amap_free");
#endif

	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
	amap_unlock(amap);	/* mainly for lock debugging */
	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)
 * => XXXCDC: needs a waitflag or failure return value?
 * => XXXCDC: support padding at this level?
 */
void
amap_extend(entry, addsize)
	vm_map_entry_t entry;
	vsize_t addsize;
{
	struct vm_amap *amap = entry->aref.ar_amap;
	int slotoff = entry->aref.ar_pageoff;
	int slotmapped, slotadd, slotneed;
#ifdef UVM_AMAP_PPREF
	int *newppref, *oldppref;
#endif
	u_int *newsl, *newbck, *oldsl, *oldbck;
	struct vm_anon **newover, **oldover;
	int slotadded;
	UVMHIST_FUNC("amap_extend"); UVMHIST_CALLED(maphist);

	UVMHIST_LOG(maphist, "  (entry=0x%x, addsize=0x%x)", entry,addsize,0,0);

	/*
	 * 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);					/* lock! */

	AMAP_B2SLOT(slotmapped, entry->end - entry->start); /* slots mapped */
	AMAP_B2SLOT(slotadd, addsize);			/* slots to add */
	slotneed = slotoff + slotmapped + slotadd;

	/*
	 * 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 (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 1), amap = 0x%x, sltneed=%d", 
		    amap, slotneed, 0, 0);
		return;				/* done! */
	}

	/*
	 * 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) {
#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 2), amap = 0x%x, slotneed=%d", 
		    amap, slotneed, 0, 0);
		return;
	}

	/*
	 * case 3: we need to malloc a new amap and copy all the amap
	 * data over from old amap to the new one.
	 *
	 * XXXCDC: could we take advantage of a kernel realloc()?  
	 */

	amap_unlock(amap);	/* unlock in case we sleep in malloc */
#ifdef UVM_AMAP_PPREF
	newppref = NULL;
	if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
		newppref = malloc(slotneed * sizeof(int), M_UVMAMAP, M_NOWAIT);
		if (newppref == NULL) {
			/* give up if malloc fails */
			free(amap->am_ppref, M_UVMAMAP);
			amap->am_ppref = PPREF_NONE;
		}
	}
#endif
	newsl = malloc(slotneed * sizeof(int), M_UVMAMAP, M_WAITOK);
	newbck = malloc(slotneed * sizeof(int), M_UVMAMAP, M_WAITOK);
	newover = malloc(slotneed * sizeof(struct vm_anon *),
	    M_UVMAMAP, M_WAITOK);
	amap_lock(amap);			/* re-lock! */

#ifdef DIAGNOSTIC
	if (amap->am_maxslot >= slotneed)
		panic("amap_extend: amap changed during malloc");
#endif

	/*
	 * now copy everything over to new malloc'd areas...
	 */

	slotadded = slotneed - amap->am_nslot;

	/* do am_slots */
	oldsl = amap->am_slots;
	memcpy(newsl, oldsl, sizeof(int) * amap->am_nused);
	amap->am_slots = newsl;

	/* do am_anon */
	oldover = amap->am_anon;
	memcpy(newover, oldover, sizeof(struct vm_anon *) * amap->am_nslot);
	memset(newover + amap->am_nslot, 0, sizeof(struct vm_anon *) * slotadded);
	amap->am_anon = newover;

	/* do am_bckptr */
	oldbck = amap->am_bckptr;
	memcpy(newbck, oldbck, sizeof(int) * amap->am_nslot);
	memset(newbck + amap->am_nslot, 0, sizeof(int) * slotadded); /* XXX: needed? */
	amap->am_bckptr = newbck;

#ifdef UVM_AMAP_PPREF
	/* do ppref */
	oldppref = amap->am_ppref;
	if (newppref) {
		memcpy(newppref, oldppref, sizeof(int) * amap->am_nslot);
		memset(newppref + amap->am_nslot, 0, sizeof(int) * slotadded);
		amap->am_ppref = newppref;
		if ((slotoff + slotmapped) < amap->am_nslot)
			amap_pp_adjref(amap, slotoff + slotmapped, 
			    (amap->am_nslot - (slotoff + slotmapped)), 1);
		pp_setreflen(newppref, amap->am_nslot, 1, slotadded);
	}
#endif

	/* update master values */
	amap->am_nslot = slotneed;
	amap->am_maxslot = slotneed;

	/* unlock */
	amap_unlock(amap);

	/* and free */
	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);
}

/*
 * 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)
	vm_map_entry_t entry;
	vm_prot_t prot;
{
	struct vm_amap *amap = entry->aref.ar_amap;
	int slots, lcv, slot, stop;

	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);
	}
	return;
}

/*
 * 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);

	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); /* lock anon */

		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);
		}
	}