Source to kern/subr_rmap.c


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/*-
 * Copyright (c) 1982, 1986, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This module is believed to contain source code proprietary to AT&T.
 * Use and redistribution is subject to the Berkeley Software License
 * Agreement and your Software Agreement with AT&T (Western Electric).
 *
 *	@(#)subr_rmap.c	8.1 (Berkeley) 6/10/93
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/map.h>
#include <sys/dmap.h>		/* XXX */
#include <sys/proc.h>
#include <sys/kernel.h>

/*
 * Resource map handling routines.
 *
 * A resource map is an array of structures each
 * of which describes a segment of the address space of an available
 * resource.  The segments are described by their base address and
 * length, and sorted in address order.  Each resource map has a fixed
 * maximum number of segments allowed.  Resources are allocated
 * by taking part or all of one of the segments of the map.
 *
 * Returning of resources will require another segment if
 * the returned resources are not adjacent in the address
 * space to an existing segment.  If the return of a segment
 * would require a slot which is not available, then one of
 * the resource map segments is discarded after a warning is printed.
 * Returning of resources may also cause the map to collapse
 * by coalescing two existing segments and the returned space
 * into a single segment.  In this case the resource map is
 * made smaller by copying together to fill the resultant gap.
 *
 * N.B.: the current implementation uses a dense array and does
 * not admit the value ``0'' as a legal address, since that is used
 * as a delimiter.
 */

/*
 * Initialize map mp to have (mapsize-2) segments
 * and to be called ``name'', which we print if
 * the slots become so fragmented that we lose space.
 * The map itself is initialized with size elements free
 * starting at addr.
 */
void
rminit(mp, size, addr, name, mapsize)
	register struct map *mp;
	long size, addr;
	char *name;
	int mapsize;
{
	register struct mapent *ep = (struct mapent *)(mp+1);

	mp->m_name = name;
/* N.B.: WE ASSUME HERE THAT sizeof (struct map) == sizeof (struct mapent) */
	/*
	 * One of the mapsize slots is taken by the map structure,
	 * segments has size 0 and addr 0, and acts as a delimiter.
	 * We insure that we never use segments past the end of
	 * the array which is given by mp->m_limit.
	 * Instead, when excess segments occur we discard some resources.
	 */
	mp->m_limit = (struct mapent *)&mp[mapsize];
	/*
	 * Simulate a rmfree(), but with the option to
	 * call with size 0 and addr 0 when we just want
	 * to initialize without freeing.
	 */
	ep->m_size = size;
	ep->m_addr = addr;
	(++ep)->m_size = 0;
	ep->m_addr = 0;
}

/*
 * A piece of memory of at least size units is allocated from the
 * specified map using a first-fit algorithm. It returns the starting
 * address of the allocated space.
 *
 * This routine knows about and handles the interleaving of the swapmap.
 */
long
rmalloc(mp, size)
	register struct map *mp;
	long size;
{
	register struct mapent *ep = (struct mapent *)(mp+1);
	register int addr;
	register struct mapent *bp;
	swblk_t first, rest;

	if (size <= 0 || mp == swapmap && size > dmmax)
		panic("rmalloc");
	/*
	 * Search for a piece of the resource map which has enough
	 * free space to accomodate the request.
	 */
	for (bp = ep; bp->m_size; bp++) {
		if (bp->m_size >= size) {
			/*
			 * If allocating from swapmap,
			 * then have to respect interleaving
			 * boundaries.
			 */
			if (mp == swapmap && nswdev > 1 &&
			    (first = dmmax - bp->m_addr%dmmax) < size) {
				if (bp->m_size - first < size)
					continue;
				addr = bp->m_addr + first;
				rest = bp->m_size - first - size;
				bp->m_size = first;
				if (rest)
					rmfree(swapmap, rest, addr+size);
				return (addr);
			}
			/*
			 * Allocate from the map.
			 * If there is no space left of the piece
			 * we allocated from, move the rest of
			 * the pieces to the left.
			 */
			addr = bp->m_addr;
			bp->m_addr += size;
			if ((bp->m_size -= size) == 0) {
				do {
					bp++;
					(bp-1)->m_addr = bp->m_addr;
				} while ((bp-1)->m_size = bp->m_size);
			}
			if (mp == swapmap && addr % CLSIZE)
				panic("rmalloc swapmap");
			return (addr);
		}
	}
	return (0);
}

/*
 * The previously allocated space at addr of size units is freed
 * into the specified map. This routine is responsible for sorting
 * the frred space into the correct location in the map, and coalescing
 * it with free space on either side if they adjoin.
 */
void
rmfree(mp, size, addr)
	struct map *mp;
	long size, addr;
{
	struct mapent *firstbp;
	register struct mapent *bp;
	register int t;

	/*
	 * Both address and size must be
	 * positive, or the protocol has broken down.
	 */
	if (addr <= 0 || size <= 0)
		goto badrmfree;
	/*
	 * Locate the piece of the map which starts after the
	 * returned space (or the end of the map).
	 */
	firstbp = bp = (struct mapent *)(mp + 1);
	for (; bp->m_addr <= addr && bp->m_size != 0; bp++)
		continue;
	/*
	 * If the piece on the left abuts us,
	 * then we should combine with it.
	 */
	if (bp > firstbp && (bp-1)->m_addr+(bp-1)->m_size >= addr) {
		/*
		 * Check no overlap (internal error).
		 */
		if ((bp-1)->m_addr+(bp-1)->m_size > addr)
			goto badrmfree;
		/*
		 * Add into piece on the left by increasing its size.
		 */
		(bp-1)->m_size += size;
		/*
		 * If the combined piece abuts the piece on
		 * the right now, compress it in also,
		 * by shifting the remaining pieces of the map over.
		 */
		if (bp->m_addr && addr+size >= bp->m_addr) {
			if (addr+size > bp->m_addr)
				goto badrmfree;
			(bp-1)->m_size += bp->m_size;
			while (bp->m_size) {
				bp++;
				(bp-1)->m_addr = bp->m_addr;
				(bp-1)->m_size = bp->m_size;
			}
		}
		return;
	}
	/*
	 * Don't abut on the left, check for abutting on
	 * the right.
	 */
	if (addr+size >= bp->m_addr && bp->m_size) {
		if (addr+size > bp->m_addr)
			goto badrmfree;
		bp->m_addr -= size;
		bp->m_size += size;
		return;
	}
	/*
	 * Don't abut at all.  Make a new entry
	 * and check for map overflow.
	 */
	do {
		t = bp->m_addr;
		bp->m_addr = addr;
		addr = t;
		t = bp->m_size;
		bp->m_size = size;
		bp++;
	} while (size = t);
	/*
	 * Segment at bp is to be the delimiter;
	 * If there is not room for it 
	 * then the table is too full
	 * and we must discard something.
	 */
	if (bp+1 > mp->m_limit) {
		/*
		 * Back bp up to last available segment.
		 * which contains a segment already and must
		 * be made into the delimiter.
		 * Discard second to last entry,
		 * since it is presumably smaller than the last
		 * and move the last entry back one.
		 */
		bp--;
		printf("%s: rmap ovflo, lost [%d,%d)\n", mp->m_name,
		    (bp-1)->m_addr, (bp-1)->m_addr+(bp-1)->m_size);
		bp[-1] = bp[0];
		bp[0].m_size = bp[0].m_addr = 0;
	}
	return;
badrmfree:
	panic("bad rmfree");
}