boot/common/heap_kmem.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#if 1
#undef DEBUG
#endif

/*  #define	DEBUG ON */

/*
 * Conditions on use:
 * kmem_alloc and kmem_free must not be called from interrupt level,
 * except from software interrupt level.  This is because they are
 * not reentrant, and only block out software interrupts.  They take
 * too long to block any real devices.  There is a routine
 * kmem_free_intr that can be used to free blocks at interrupt level,
 * but only up to splimp, not higher.  This is because kmem_free_intr
 * only spl's to splimp.
 *
 * Also, these routines are not that fast, so they should not be used
 * in very frequent operations (e.g. operations that happen more often
 * than, say, once every few seconds).
 */

/*
 * description:
 *	Yet another memory allocator, this one based on a method
 *	described in C.J. Stephenson, "Fast Fits", IBM Sys. Journal
 *
 *	The basic data structure is a "Cartesian" binary tree, in which
 *	nodes are ordered by ascending addresses (thus minimizing free
 *	list insertion time) and block sizes decrease with depth in the
 *	tree (thus minimizing search time for a block of a given size).
 *
 *	In other words, for any node s, letting D(s) denote
 *	the set of descendents of s, we have:
 *
 *	a. addr(D(left(s))) <  addr(s) <  addr(D(right(s)))
 *	b. len(D(left(s)))  <= len(s)  >= len(D(right(s)))
 */

#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/salib.h>
#include <sys/saio.h>
#include <sys/promif.h>

/*
 * The node header structure.
 *
 * To reduce storage consumption, a header block is associated with
 * free blocks only, not allocated blocks.
 * When a free block is allocated, its header block is put on
 * a free header block list.
 *
 * This creates a header space and a free block space.
 * The left pointer of a header blocks is used to chain free header
 * blocks together.
 */

typedef enum {false, true} bool;
typedef struct	freehdr	*Freehdr;
typedef struct	dblk	*Dblk;

/*
 * Description of a header for a free block
 * Only free blocks have such headers.
 */
struct 	freehdr	{
	Freehdr	left;			/* Left tree pointer */
	Freehdr	right;			/* Right tree pointer */
	Dblk	block;			/* Ptr to the data block */
	size_t	size;			/* Size of the data block */
};

#define	NIL		((Freehdr) 0)
#define	WORDSIZE	sizeof (int)
#define	SMALLEST_BLK	1		/* Size of smallest block */

/*
 * Description of a data block.
 */
struct	dblk	{
	char	data[1];		/* Addr returned to the caller */
};

/*
 * weight(x) is the size of a block, in bytes; or 0 if and only if x
 *	is a null pointer. It is the responsibility of kmem_alloc() and
 *	kmem_free() to keep zero-length blocks out of the arena.
 */

#define	weight(x)	((x) == NIL? 0: (x->size))
#define	nextblk(p, size) ((Dblk) ((char *)(p) + (size)))
#define	max(a, b)	((a) < (b)? (b): (a))

void		*kmem_alloc(size_t, int);
void		kmem_free(void *ptr, size_t nbytes);
Freehdr		getfreehdr(void);
static bool	morecore(size_t);
void		insert(Dblk p, size_t len, Freehdr *tree);
void		freehdr(Freehdr p);
void		delete(Freehdr *p);
static void	check_need_to_free(void);
extern caddr_t	resalloc(enum RESOURCES, size_t, caddr_t, int);
#ifdef	__sparc
extern void	resalloc_init(void);
#endif
extern int	splnet(void);
extern int	splimp(void);
extern void	splx(int);

/*
 * Structure containing various info about allocated memory.
 */
#define	NEED_TO_FREE_SIZE	5
struct kmem_info {
	Freehdr	free_root;
	Freehdr	free_hdr_list;
	struct map *map;
	struct pte *pte;
	caddr_t	vaddr;
	struct need_to_free {
		caddr_t addr;
		size_t	nbytes;
	} need_to_free_list, need_to_free[NEED_TO_FREE_SIZE];
} kmem_info;


struct map *kernelmap;

#ifdef DEBUG
static void prtree(Freehdr, char *);
#endif

/*
 * Initialize kernel memory allocator
 */

void
kmem_init(void)
{
	int i;
	struct need_to_free *ntf;

#ifdef DEBUG
printf("kmem_init entered\n");
#endif

#ifdef __sparc
	resalloc_init();
#endif

	kmem_info.free_root = NIL;
	kmem_info.free_hdr_list = NULL;
	kmem_info.map = kernelmap;
	kmem_info.need_to_free_list.addr = 0;
	ntf = kmem_info.need_to_free;
	for (i = 0; i < NEED_TO_FREE_SIZE; i++) {
		ntf[i].addr = 0;
	}
#ifdef DEBUG
printf("kmem_init returning\n");
prtree(kmem_info.free_root, "kmem_init");
#endif
}

/*
 * Insert a new node in a cartesian tree or subtree, placing it
 *	in the correct position with respect to the existing nodes.
 *
 * algorithm:
 *	Starting from the root, a binary search is made for the new
 *	node. If this search were allowed to continue, it would
 *	eventually fail (since there cannot already be a node at the
 *	given address); but in fact it stops when it reaches a node in
 *	the tree which has a length less than that of the new node (or
 *	when it reaches a null tree pointer).  The new node is then
 *	inserted at the root of the subtree for which the shorter node
 *	forms the old root (or in place of the null pointer).
 */


void
insert(Dblk p,		/* Ptr to the block to insert */
    size_t len,		/* Length of new node */
    Freehdr *tree)	/* Address of ptr to root */
{
	Freehdr x;
	Freehdr *left_hook;	/* Temp for insertion */
	Freehdr *right_hook;	/* Temp for insertion */
	Freehdr newhdr;

	x = *tree;
	/*
	 * Search for the first node which has a weight less
	 *	than that of the new node; this will be the
	 *	point at which we insert the new node.
	 */

	while (weight(x) >= len) {
		if (p < x->block)
			tree = &x->left;
		else
			tree = &x->right;
		x = *tree;
	}

	/*
	 * Perform root insertion. The variable x traces a path through
	 *	the tree, and with the help of left_hook and right_hook,
	 *	rewrites all links that cross the territory occupied
	 *	by p.  Note that this improves performance under
	 *	paging.
	 */

	newhdr = getfreehdr();
	*tree = newhdr;
	left_hook = &newhdr->left;
	right_hook = &newhdr->right;

	newhdr->left = NIL;
	newhdr->right = NIL;
	newhdr->block = p;
	newhdr->size = len;

	while (x != NIL) {
		/*
		 * Remark:
		 *	The name 'left_hook' is somewhat confusing, since
		 *	it is always set to the address of a .right link
		 *	field.  However, its value is always an address
		 *	below (i.e., to the left of) p. Similarly
		 *	for right_hook. The values of left_hook and
		 *	right_hook converge toward the value of p,
		 *	as in a classical binary search.
		 */
		if (x->block < p) {
			/*
			 * rewrite link crossing from the left
			 */
			*left_hook = x;
			left_hook = &x->right;
			x = x->right;
		} else {
			/*
			 * rewrite link crossing from the right
			 */
			*right_hook = x;
			right_hook = &x->left;
			x = x->left;
		} /* else */
	} /* while */

	*left_hook = *right_hook = NIL;		/* clear remaining hooks */

} /* insert */


/*
 * Delete a node from a cartesian tree. p is the address of
 *	a pointer to the node which is to be deleted.
 *
 * algorithm:
 *	The left and right sons of the node to be deleted define two
 *	subtrees which are to be merged and attached in place of the
 *	deleted node.  Each node on the inside edges of these two
 *	subtrees is examined and longer nodes are placed above the
 *	shorter ones.
 *
 * On entry:
 *	*p is assumed to be non-null.
 */

void
delete(Freehdr *p)
{
	Freehdr x;
	Freehdr left_branch;	/* left subtree of deleted node */
	Freehdr right_branch;	/* right subtree of deleted node */

	x = *p;
	left_branch = x->left;
	right_branch = x->right;

	while (left_branch != right_branch) {
		/*
		 * iterate until left branch and right branch are
		 * both NIL.
		 */
		if (weight(left_branch) >= weight(right_branch)) {
			/*
			 * promote the left branch
			 */
			*p = left_branch;
			p = &left_branch->right;
			left_branch = left_branch->right;
		} else {
			/*
			 * promote the right branch
			 */
			*p = right_branch;
			p = &right_branch->left;
			right_branch = right_branch->left;
		} /* else */
	} /* while */
	*p = NIL;
	freehdr(x);
} /* delete */


/*
 * Demote a node in a cartesian tree, if necessary, to establish
 *	the required vertical ordering.
 *
 * algorithm:
 *	The left and right subtrees of the node to be demoted are to
 *	be partially merged and attached in place of the demoted node.
 *	The nodes on the inside edges of these two subtrees are
 *	examined and the longer nodes are placed above the shorter
 *	ones, until a node is reached which has a length no greater
 *	than that of the node being demoted (or until a null pointer
 *	is reached).  The node is then attached at this point, and
 *	the remaining subtrees (if any) become its descendants.
 *
 * on entry:
 *   a. All the nodes in the tree, including the one to be demoted,
 *	must be correctly ordered horizontally;
 *   b. All the nodes except the one to be demoted must also be
 *	correctly positioned vertically.  The node to be demoted
 *	may be already correctly positioned vertically, or it may
 *	have a length which is less than that of one or both of
 *	its progeny.
 *   c. *p is non-null
 */


static void
demote(Freehdr *p)
{
	Freehdr x;		/* addr of node to be demoted */
	Freehdr left_branch;
	Freehdr right_branch;
	size_t    wx;

	x = *p;
	left_branch = x->left;
	right_branch = x->right;
	wx = weight(x);

	while (weight(left_branch) > wx || weight(right_branch) > wx) {
		/*
		 * select a descendant branch for promotion
		 */
		if (weight(left_branch) >= weight(right_branch)) {
			/*
			 * promote the left branch
			 */
			*p = left_branch;
			p = &left_branch->right;
			left_branch = *p;
		} else {
			/*
			 * promote the right branch
			 */
			*p = right_branch;
			p = &right_branch->left;
			right_branch = *p;
		} /* else */
	} /* while */

	*p = x;				/* attach demoted node here */
	x->left = left_branch;
	x->right = right_branch;
} /* demote */

/*
 * Allocate a block of storage
 *
 * algorithm:
 *	The freelist is searched by descending the tree from the root
 *	so that at each decision point the "better fitting" child node
 *	is chosen (i.e., the shorter one, if it is long enough, or
 *	the longer one, otherwise).  The descent stops when both
 *	child nodes are too short.
 *
 * function result:
 *	kmem_alloc returns a pointer to the allocated block; a null
 *	pointer indicates storage could not be allocated.
 */
/*
 * We need to return blocks that are on word boundaries so that callers
 * that are putting int's into the area will work.  Since we allow
 * arbitrary free'ing, we need a weight function that considers
 * free blocks starting on an odd boundary special.  Allocation is
 * aligned to 8 byte boundaries (ALIGN).
 */
#define	ALIGN		8		/* doubleword aligned .. */
#define	ALIGNMASK	(ALIGN-1)
#define	ALIGNMORE(addr)	(ALIGN - ((uintptr_t)(addr) & ALIGNMASK))

/*
 * If it is empty then weight == 0
 * If it is aligned then weight == size
 * If it is unaligned
 *	if not enough room to align then weight == 0
 *	else weight == aligned size
 */
#define	mweight(x) ((x) == NIL ? 0 : \
	((((uintptr_t)(x)->block) & ALIGNMASK) == 0 ? (x)->size : \
		(((x)->size <= ALIGNMORE((x)->block)) ? 0 : \
			(x)->size - ALIGNMORE((x)->block))))

/*ARGSUSED1*/
void *
kmem_alloc(size_t nbytes, int kmflag)
{
	Freehdr a;		/* ptr to node to be allocated */
	Freehdr *p;		/* address of ptr to node */
	size_t	 left_weight;
	size_t	 right_weight;
	Freehdr left_son;
	Freehdr right_son;
	char	 *retblock;	/* Address returned to the user */
	int s;
#ifdef	DEBUG
	printf("kmem_alloc(nbytes 0x%lx)\n", nbytes);
#endif	/* DEBUG */

	if (nbytes == 0) {
		return (NULL);
	}
	s = splnet();

	if (nbytes < SMALLEST_BLK) {
		printf("illegal kmem_alloc call for %lx bytes\n", nbytes);
		prom_panic("kmem_alloc");
	}
	check_need_to_free();

	/*
	 * ensure that at least one block is big enough to satisfy
	 *	the request.
	 */

	if (mweight(kmem_info.free_root) <= nbytes) {
		/*
		 * the largest block is not enough.
		 */
		if (!morecore(nbytes)) {
			printf("kmem_alloc failed, nbytes %lx\n", nbytes);
			prom_panic("kmem_alloc");
		}
	}

	/*
	 * search down through the tree until a suitable block is
	 *	found.  At each decision point, select the better
	 *	fitting node.
	 */

	p = (Freehdr *) &kmem_info.free_root;
	a = *p;
	left_son = a->left;
	right_son = a->right;
	left_weight = mweight(left_son);
	right_weight = mweight(right_son);

	while (left_weight >= nbytes || right_weight >= nbytes) {
		if (left_weight <= right_weight) {
			if (left_weight >= nbytes) {
				p = &a->left;
				a = left_son;
			} else {
				p = &a->right;
				a = right_son;
			}
		} else {
			if (right_weight >= nbytes) {
				p = &a->right;
				a = right_son;
			} else {
				p = &a->left;
				a = left_son;
			}
		}
		left_son = a->left;
		right_son = a->right;
		left_weight = mweight(left_son);
		right_weight = mweight(right_son);
	} /* while */

	/*
	 * allocate storage from the selected node.
	 */

	if (a->size - nbytes < SMALLEST_BLK) {
		/*
		 * not big enough to split; must leave at least
		 * a dblk's worth of space.
		 */
		retblock = a->block->data;
		delete(p);
	} else {

		/*
		 * split the node, allocating nbytes from the top.
		 *	Remember we've already accounted for the
		 *	allocated node's header space.
		 */
		Freehdr x;
		x = getfreehdr();
		if ((uintptr_t)a->block->data & ALIGNMASK) {
			size_t size;
			if (a->size <= ALIGNMORE(a->block->data))
				prom_panic("kmem_alloc: short block allocated");
			size = nbytes + ALIGNMORE(a->block->data);
			x->block = a->block;
			x->size = ALIGNMORE(a->block->data);
			x->left = a->left;
			x->right = a->right;
			/*
			 * the node pointed to by *p has become smaller;
			 *	move it down to its appropriate place in
			 *	the tree.
			 */
			*p = x;
			demote(p);
			retblock = a->block->data + ALIGNMORE(a->block->data);
			if (a->size > size) {
				kmem_free((caddr_t)nextblk(a->block, size),
				    (size_t)(a->size - size));
			}
			freehdr(a);
		} else {
			x->block = nextblk(a->block, nbytes);
			x->size = a->size - nbytes;
			x->left = a->left;
			x->right = a->right;
			/*
			 * the node pointed to by *p has become smaller;
			 *	move it down to its appropriate place in
			 *	the tree.
			 */
			*p = x;
			demote(p);
			retblock = a->block->data;
			freehdr(a);
		}
	}
#ifdef DEBUG
	prtree(kmem_info.free_root, "kmem_alloc");
#endif

	splx(s);
	bzero(retblock, nbytes);
#ifdef DEBUG
	printf("kmem_alloc  bzero complete - returning %p\n", retblock);
#endif
	return (retblock);

} /* kmem_alloc */

/*
 * Return a block to the free space tree.
 *
 * algorithm:
 *	Starting at the root, search for and coalesce free blocks
 *	adjacent to one given.  When the appropriate place in the
 *	tree is found, insert the given block.
 *
 * Do some sanity checks to avoid total confusion in the tree.
 * If the block has already been freed, prom_panic.
 * If the ptr is not from the arena, prom_panic.
 */
void
kmem_free(void *ptr, size_t nbytes)
{
	Freehdr *np;		/* For deletion from free list */
	Freehdr neighbor;	/* Node to be coalesced */
	char	 *neigh_block;	/* Ptr to potential neighbor */
	size_t	 neigh_size;	/* Size of potential neighbor */
	int s;

#ifdef DEBUG
printf("kmem_free (ptr %p nbytes %lx)\n", ptr, nbytes);
prtree(kmem_info.free_root, "kmem_free");
#endif

#ifdef	lint
	neigh_block = bkmem_zalloc(nbytes);
	neigh_block = neigh_block;
#endif
	if (nbytes == 0) {
		return;
	}

	if (ptr == 0) {
		prom_panic("kmem_free of 0");
	}
	s = splnet();

	/*
	 * Search the tree for the correct insertion point for this
	 *	node, coalescing adjacent free blocks along the way.
	 */
	np = &kmem_info.free_root;
	neighbor = *np;
	while (neighbor != NIL) {
		neigh_block = (char *)neighbor->block;
		neigh_size = neighbor->size;
		if ((char *)ptr < neigh_block) {
			if ((char *)ptr + nbytes == neigh_block) {
				/*
				 * Absorb and delete right neighbor
				 */
				nbytes += neigh_size;
				delete(np);
			} else if ((char *)ptr + nbytes > neigh_block) {
				/*
				 * The block being freed overlaps
				 * another block in the tree.  This
				 * is bad news.
				 */
				printf("kmem_free: free block overlap %p+%lx"
				    " over %p\n", (void *)ptr, nbytes,
				    (void *)neigh_block);
				prom_panic("kmem_free: free block overlap");
			} else {
				/*
				 * Search to the left
				 */
				np = &neighbor->left;
			}
		} else if ((char *)ptr > neigh_block) {
			if (neigh_block + neigh_size == ptr) {
				/*
				 * Absorb and delete left neighbor
				 */
				ptr = neigh_block;
				nbytes += neigh_size;
				delete(np);
			} else if (neigh_block + neigh_size > (char *)ptr) {
				/*
				 * This block has already been freed
				 */
				prom_panic("kmem_free block already free");
			} else {
				/*
				 * search to the right
				 */
				np = &neighbor->right;
			}
		} else {
			/*
			 * This block has already been freed
			 * as "ptr == neigh_block"
			 */
			prom_panic("kmem_free: block already free as neighbor");
		} /* else */
		neighbor = *np;
	} /* while */

	/*
	 * Insert the new node into the free space tree
	 */
	insert((Dblk) ptr, nbytes, &kmem_info.free_root);
#ifdef DEBUG
printf("exiting kmem_free\n");
prtree(kmem_info.free_root, "kmem_free");
#endif
	splx(s);
} /* kmem_free */

/*
 *  Sigh.  We include a header file which the kernel
 *  uses to declare (one of its many) kmem_free prototypes.
 *  In order not to use the kernel's namespace, then, we must
 *  define another name here for use by boot.
 */
void *
bkmem_alloc(size_t size)
{
	return (kmem_alloc(size, 0));
}

/*
 * Boot's kmem_alloc is really kmem_zalloc().
 */
void *
bkmem_zalloc(size_t size)
{
	return (kmem_alloc(size, 0));
}

void
bkmem_free(void *p, size_t bytes)
{
	kmem_free(p, bytes);
}

static void
check_need_to_free(void)
{
	int i;
	struct need_to_free *ntf;
	caddr_t addr;
	size_t nbytes;
	int s;

again:
	s = splimp();
	ntf = &kmem_info.need_to_free_list;
	if (ntf->addr) {
		addr = ntf->addr;
		nbytes = ntf->nbytes;
		*ntf = *(struct need_to_free *)ntf->addr;
		splx(s);
		kmem_free(addr, nbytes);
		goto again;
	}
	ntf = kmem_info.need_to_free;
	for (i = 0; i < NEED_TO_FREE_SIZE; i++) {
		if (ntf[i].addr) {
			addr = ntf[i].addr;
			nbytes = ntf[i].nbytes;
			ntf[i].addr = 0;
			splx(s);
			kmem_free(addr, nbytes);
			goto again;
		}
	}
	splx(s);
}

/*
 * Add a block of at least nbytes to the free space tree.
 *
 * return value:
 *	true	if at least nbytes can be allocated
 *	false	otherwise
 *
 * remark:
 *	free space (delimited by the static variable ubound) is
 *	extended by an amount determined by rounding nbytes up to
 *	a multiple of the system page size.
 */

static bool
morecore(size_t nbytes)
{
#ifdef	__sparc
	enum RESOURCES type = RES_BOOTSCRATCH_NOFAIL;
#else
	enum RESOURCES type = RES_BOOTSCRATCH;
#endif
	Dblk p;
#ifdef	DEBUG
	printf("morecore(nbytes 0x%lx)\n", nbytes);
#endif	/* DEBUG */


	nbytes = roundup(nbytes, PAGESIZE);
	p = (Dblk) resalloc(type, nbytes, (caddr_t)0, 0);
	if (p == 0) {
		return (false);
	}
	kmem_free((caddr_t)p, nbytes);
#ifdef DEBUG
	printf("morecore() returing, p = %p\n", p);
#endif
	return (true);

} /* morecore */

/*
 * Get a free block header
 * There is a list of available free block headers.
 * When the list is empty, allocate another pagefull.
 */
Freehdr
getfreehdr(void)
{
	Freehdr	r;
	int	n = 0;
#ifdef	DEBUG
	printf("getfreehdr()\n");
#endif	/* DEBUG */

	if (kmem_info.free_hdr_list != NIL) {
		r = kmem_info.free_hdr_list;
		kmem_info.free_hdr_list = kmem_info.free_hdr_list->left;
	} else {
		r = (Freehdr)resalloc(RES_BOOTSCRATCH, PAGESIZE, (caddr_t)0, 0);
		if (r == 0) {
			prom_panic("getfreehdr");
		}
		for (n = 1; n < PAGESIZE / sizeof (*r); n++) {
			freehdr(&r[n]);
		}
	}
#ifdef	DEBUG
	printf("getfreehdr: freed %x headers\n", n);
	printf("getfreehdr: returning %p\n", r);
#endif	/* DEBUG */
	return (r);
}

/*
 * Free a free block header
 * Add it to the list of available headers.
 */

void
freehdr(Freehdr p)
{
#ifdef	DEBUG
	printf("freehdr(%p)\n", p);
#endif	/* DEBUG */
	p->left = kmem_info.free_hdr_list;
	p->right = NIL;
	p->block = NULL;
	kmem_info.free_hdr_list = p;
}

#ifdef DEBUG
/*
 * Diagnostic routines
 */
static int depth = 0;

static void
prtree(Freehdr p, char *cp)
{
	int n;
	if (depth == 0) {
		printf("prtree(p %p cp %s)\n", p, cp);
	}
	if (p != NIL) {
		depth++;
		prtree(p->left, (char *)NULL);
		depth--;

		for (n = 0; n < depth; n++) {
			printf("   ");
		}
		printf(
		    "(%p): (left = %p, right = %p, block = %p, size = %lx)\n",
			p, p->left, p->right, p->block, p->size);

		depth++;
		prtree(p->right, (char *)NULL);
		depth--;
	}
}
#endif /* DEBUG */