/*
 *  linux/mm/memory.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file README.legal in the main directory of this archive
 * for more details.
 */

/*
 *  Heavily modified 1993 by Hamish Macdonald for MC680X0 support
 *  Atari Support by Bj”rn Brauel
 */

/*
 * demand-loading started 01.12.91 - seems it is high on the list of
 * things wanted, and it should be easy to implement. - Linus
 */

/*
 * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
 * pages started 02.12.91, seems to work. - Linus.
 *
 * Tested sharing by executing about 30 /bin/sh: under the old kernel it
 * would have taken more than the 6M I have free, but it worked well as
 * far as I could see.
 *
 * Also corrected some "invalidate()"s - I wasn't doing enough of them.
 */

/*
 * Real VM (paging to/from disk) started 18.12.91. Much more work and
 * thought has to go into this. Oh, well..
 * 19.12.91  -	works, somewhat. Sometimes I get faults, don't know why.
 *		Found it. Everything seems to work now.
 * 20.12.91  -	Ok, making the swap-device changeable like the root.
 */

#include <asm/system.h>
#include <asm/segment.h>
#include <linux/config.h>

#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/traps.h>
#include <linux/head.h>
#include <linux/kernel.h>
#include <linux/malloc.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/bootinfo.h>

#include <linux/mm.h>
#include <linux/mman.h>

unsigned long high_memory = 0;

extern void die_if_kernel(char *,struct frame *,int);

int nr_swap_pages = 0;
int nr_free_pages = 0;
unsigned long free_page_list = 0;
/*
 * The secondary free_page_list is used for malloc() etc things that
 * may need pages during interrupts etc. Normal get_free_page() operations
 * don't touch it, so it stays as a kind of "panic-list", that can be
 * accessed when all other mm tricks have failed.
 */
int nr_secondary_pages = 0;
unsigned long secondary_page_list = 0;

#define copy_page(from,to) (memcpy((void*)to,(const void *)from,PAGE_SIZE))

unsigned short * mem_map = NULL;

static unsigned long *get_pointer_table (void);
#define get_root_table() get_pointer_table()
static void free_pointer_table (unsigned long *);
#define free_root_table(ptr) free_pointer_table((ptr))
static unsigned long *get_page_table (unsigned long *);

/*
 * oom() prints a message (so that the user knows why the process died),
 * and gives the process an untrappable SIGSEGV.
 */
void oom(struct task_struct * task)
{
	printk("\nout of memory\n");
	task->sigaction[SIGKILL-1].sa_handler = NULL;
	task->blocked &= ~(1<<(SIGKILL-1));
	send_sig(SIGKILL,task,1);
}

static inline void nocache_page (unsigned long vaddr)
{
	if (boot_info.cputype & CPU_68040) {
		/* address of kernel root table */
		extern unsigned long *krt;
		unsigned long desc, *kptr, *ktbl;

		desc = krt[L1_INDEX(vaddr)];
		kptr = (unsigned long *)PTOV(desc & PAGE_MASK);
		desc = kptr[L2_INDEX(vaddr)];
		ktbl = (unsigned long *)PTOV(desc & PAGE_MASK);
		desc = ktbl[L3_INDEX(vaddr)];
		ktbl[L3_INDEX(vaddr)] = (desc & CACHEMASK040) | PAGE_NOCACHE;
	}
}

static inline void cache_page (unsigned long vaddr)
{
	if (boot_info.cputype & CPU_68040) {
		/* address of kernel root table */
		extern unsigned long *krt;
		unsigned long desc, *kptr, *ktbl;

		desc = krt[L1_INDEX(vaddr)];
		kptr = (unsigned long *)PTOV(desc & PAGE_MASK);
		desc = kptr[L2_INDEX(vaddr)];
		ktbl = (unsigned long *)PTOV(desc & PAGE_MASK);
		desc = ktbl[L3_INDEX(vaddr)];
		ktbl[L3_INDEX(vaddr)] = (desc & CACHEMASK040) | PAGE_CACHE040;
	}
}

static void free_one_table(unsigned long *page_ptr)
{
	int j;
	unsigned long pg_table = *page_ptr;
	unsigned long *page_table, pg_table_v;

	if (!pg_table)
		return;
	*page_ptr = 0;
	pg_table_v = PTOV(pg_table & PAGE_MASK);
	if (pg_table_v >= high_memory || !(pg_table & PAGE_TABLE)) {
		printk("Bad page table: [%p]=%08lx\n",page_ptr,pg_table);
		return;
	}
	if (mem_map[MAP_NR(pg_table_v)] & MAP_PAGE_RESERVED)
		return;
	page_table = (unsigned long *) pg_table_v;

	for (j = 0 ; j < NUM_L3_ENTRIES ; j++, page_table++) {
		unsigned long pg = *page_table;

		if (!pg)
			continue;
		*page_table = 0;
		if (pg & PAGE_PRESENT)
			free_page(PTOV(PAGE_MASK & pg));
		else
			swap_free(pg);
	}
	cache_page (pg_table_v);
	free_page(pg_table_v);
}

static void free_one_ptr_table(unsigned long *root)
{
	int j;
	unsigned long ptr_desc = *root;
	unsigned long *ptr_table, ptr_table_v;

	if (!ptr_desc)
		return;
	*root = 0;
	ptr_table_v = PTOV(ptr_desc & TABLE_MASK);
	if (ptr_table_v >= high_memory || !(ptr_desc & PAGE_TABLE)) {
		printk("Bad pointer table: [%p]=%08lx\n",root,ptr_desc);
		return;
	}
	ptr_table = (unsigned long *) ptr_table_v;

	for (j = 0 ; j < NUM_L2_ENTRIES ; j++, ptr_table += 16)
		free_one_table (ptr_table);
	free_pointer_table ((unsigned long *)ptr_table_v);
}

/*
 * This function clears all user-level page tables of a process - this
 * is needed by execve(), so that old pages aren't in the way. Note that
 * unlike 'free_page_tables()', this function still leaves a valid
 * page-table-tree in memory: it just removes the user pages. The two
 * functions are similar, but there is a fundamental difference.
 */
void clear_page_tables(struct task_struct * tsk)
{
	int i;
	unsigned long *root;

	if (!tsk)
		return;
	if (tsk == task[0])
		panic("task[0] (swapper) doesn't support exec()\n");

	root = tsk->tss.pagedir_v;
	if (!root || root == task[0]->tss.pagedir_v) {
		printk("Trying to clear kernel page-directory: not good\n");
		return;
	}

	/*
	 * setup the user-mode root table, in case we were using the
	 * swapper root table.
	 */
	tsk->tss.crp[1] = tsk->tss.pagedir_p;
	if (tsk == current)
		if (boot_info.machtype & CPU_68040)
			asm ("movel %0,d0\n\t"
			     ".long 0x4e7b0806"	/* movec d0,urp */
			     : /* no outputs */
			     : "g" (tsk->tss.crp[1])
			     : "d0");
		else
			asm ("pmove %0@,crp"
			     : /* no outputs */
			     : "a" (tsk->tss.crp));

	/* XXX */
	/*
	 * root tables haven't got a use count in the mem_map
	 * since there isn't a 1-1 relationship between pages
	 * and root tables.
	 *
	 * Because of this, we will use a bletcherous hack where
	 * the last entry in the root table (entry 127) contains
	 * the number of uses - 1.
	 * Thus a regular root table will have 0 in this entry.
	 * A cloned root table will have > 0 in this entry.
	 *
	 * Note that this entry is never used by a user process.
	 */
	if (root[NUM_L1_ENTRIES-1] > 0) {
		unsigned long *new_root;

		if (!(new_root = get_root_table ())) {
			oom(tsk);
			return;
		}
		for (i = 0; i < NUM_L1_ENTRIES-1; i++)
			new_root[i] = root[i];
		new_root[NUM_L1_ENTRIES-1] = 0;
		root[NUM_L1_ENTRIES-1]--;
		tsk->tss.pagedir_v = new_root;
		tsk->tss.pagedir_p = VTOP(new_root);
		return;
	}
	for (i = 0 ; i < NUM_L1_ENTRIES; i++, root++)
		free_one_ptr_table(root);
	invalidate();
	return;
}

/*
 * This function frees up all page tables of a process when it exits.
 */
void free_page_tables(struct task_struct * tsk)
{
	int i;
	unsigned long *root;

	if (!tsk)
		return;
	if (tsk == task[0]) {
		printk("task[0] (swapper) killed: unable to recover\n");
		panic("Trying to free up swapper memory space");
	}
	root = tsk->tss.pagedir_v;
	if (!root || root == task[0]->tss.pagedir_v) {
		printk("Trying to free kernel root table: not good\n");
		return;
	}
	/* XXX */
	/*
	 * root tables haven't got a use count in the mem_map
	 * since there isn't a 1-1 relationship between pages
	 * and root tables.
	 *
	 * Because of this, we will use a bletcherous hack where
	 * the last entry in the root table (entry 127) contains
	 * the number of uses - 1.
	 * Thus a regular root table will have 0 in this entry.
	 * A cloned root table will have > 0 in this entry.
	 *
	 * Note that this entry is never used by a user process.
	 */
	if (root[NUM_L1_ENTRIES-1] > 0) {
		root[NUM_L1_ENTRIES-1]--;
		return;
	}

	for (i = 0 ; i < NUM_L1_ENTRIES; i++, root++)
		free_one_ptr_table(root);

	free_root_table (tsk->tss.pagedir_v);
	tsk->tss.pagedir_v = 0;
	tsk->tss.pagedir_p = 0;
	invalidate();
}

/*
 * clone_page_tables() clones the page table for a process - both
 * processes will have the exact same pages in memory. There are
 * probably races in the memory management with cloning, but we'll
 * see..
 */
int clone_page_tables(struct task_struct * tsk)
{
	unsigned long *root;

	root = current->tss.pagedir_v;

	/* XXX */
	/*
	 * root tables haven't got a use count in the mem_map
	 * since there isn't a 1-1 relationship between pages
	 * and root tables.
	 *
	 * Because of this, we will use a bletcherous hack where
	 * the last entry in the root table (entry 127) contains
	 * the number of uses - 1.
	 * Thus a regular root table will have 0 in this entry.
	 * A cloned root table will have > 0 in this entry.
	 *
	 * Note that this entry is never used by a user process.
	 */
	root[NUM_L1_ENTRIES]++;
	tsk->tss.pagedir_v = root;
	tsk->tss.pagedir_p = VTOP (root);
	tsk->tss.crp[0] = 0x80000000 | PAGE_SHORT;
	tsk->tss.crp[1] = tsk->tss.pagedir_p;
	return 0;
}

static int copy_pointer_table (struct task_struct *tsk,
			       unsigned long old_ptr_desc,
			       unsigned long *new_root)
{
	int i;
	unsigned long *old_ptr_table, *new_ptr_table, new_ptr_vaddr;

	/* get a new pointer table, can't allocate, no fork */
	if (!(new_ptr_table = get_pointer_table ())) {
		free_page_tables(tsk);
		return -ENOMEM;
	}
	new_ptr_vaddr = (unsigned long)new_ptr_table;

	/* process each page table in the pointer table */
	old_ptr_table = (unsigned long *)PTOV(old_ptr_desc & TABLE_MASK);

	for (i = 0 ; i < NUM_L2_ENTRIES ;
	     i++,old_ptr_table += 16, new_ptr_table += 16) {
		int j;
		unsigned long old_pg_table, *old_page_tablep;
		unsigned long *new_page_tablep;

		/* read descriptor for page table */
		old_pg_table = *old_ptr_table;

		/* if it is an invalid descriptor, continue to the next */
		if (!old_pg_table)
			continue;

		/*
		 * if the address is too high, or it is not a short
		 * descriptor, things are screwy.
		 */
		if (PTOV(old_pg_table) >= high_memory
		    || !(old_pg_table & PAGE_TABLE)) {
			printk("copy_page_tables: bad page table: "
			       "probable memory corruption\n");
			*old_ptr_table = 0;
			continue;
		}

		/*
		 * if it is a reserved entry (won't be, with the separate kernel
		 * and user virtual address spaces for the M68K port.
		 */
		if (mem_map[MAP_NR(PTOV(old_pg_table))]
		    & MAP_PAGE_RESERVED) {
			*new_ptr_table = old_pg_table;
			continue;
		}

		/* setup a page table */
		if (!(new_page_tablep = get_page_table (new_ptr_table)))
			return -ENOMEM;

		/* process each page in the page table */
		old_page_tablep = (unsigned long *)PTOV(old_pg_table & PAGE_MASK);
		for (j = 0 ; j < PTRS_PER_PAGE ; j++,old_page_tablep++,new_page_tablep++) {
			unsigned long pg;

			/* read page descriptor from table */
			pg = *old_page_tablep;

			/* if invalid page, continue */
			if (!pg)
				continue;

			/* check for swapped out page (invalid desc, nonzero) */
			if (!(pg & PAGE_PRESENT)) {
				*new_page_tablep = swap_duplicate(pg);
				continue;
			}

			/*
			 * share the page in both process maps, but write protect
			 * it in both, to catch attempts to write (copy on write)
			 */
			if ((pg & (PAGE_RONLY | PAGE_COW)) == PAGE_COW)
				pg |= PAGE_RONLY;
			*new_page_tablep = pg;
			if (mem_map[MAP_NR(PTOV(pg & PAGE_MASK))] & MAP_PAGE_RESERVED)
				continue;
			*old_page_tablep = pg;
			mem_map[MAP_NR(PTOV(pg & PAGE_MASK))]++;
		}
	}

	/* write the new pointer table descriptor to the new root table */
	*new_root = VTOP(new_ptr_vaddr) | PAGE_TABLE;

	return 0;
}

/*
 * copy_page_tables() just copies the whole process memory range:
 * note the special handling of RESERVED (ie kernel) pages, which
 * means that they are always shared by all processes.
 */
int copy_page_tables(struct task_struct * tsk)
{
	int i;
	unsigned long *old_root;
	unsigned long *new_root;

	if (!(new_root = get_root_table ()))
		return -ENOMEM;
	old_root = current->tss.pagedir_v;
	tsk->tss.pagedir_v = new_root;
	tsk->tss.pagedir_p = VTOP(new_root);
	tsk->tss.crp[0] = 0x80000000 | PAGE_SHORT;
	tsk->tss.crp[1] = tsk->tss.pagedir_p;

	/*
	 * if old root table is the same as in the swapper task (task 0),
	 * just re-use the swapper root table.
	 */
	if (current->tss.crp[1] == task[0]->tss.crp[1]) {
		tsk->tss.crp[1] = task[0]->tss.pagedir_p;
		goto end;
	}

	for (i = 0 ; i < NUM_L1_ENTRIES ; i++, old_root++,new_root++) {
		unsigned long old_ptr_desc;

		/* read descriptor for pointer table */
		old_ptr_desc = *old_root;

		/* if it an invalid descriptor, continue to the next */
		if (!old_ptr_desc)
			continue;

		/*
		 * if the address is too high, or it is not a short
		 * descriptor, things are screwy.
		 */
		if (PTOV(old_ptr_desc) >= high_memory
		    || !(old_ptr_desc & PAGE_TABLE)) {
			printk("copy_page_tables: bad pointer table: "
			       "probable memory corruption\n");
			*old_root = 0;
			continue;
		}

		if (copy_pointer_table (tsk, old_ptr_desc, new_root))
			return -ENOMEM;
	}
end:
	invalidate();
	return 0;
}

/*
 * a more complete version of free_page_tables which performs with page
 * granularity.
 */
int unmap_page_range(unsigned long from, unsigned long size)
{
	unsigned long address;

	if (from & ~PAGE_MASK) {
		printk ("unmap_page_range called with wrong alignment\n");
		return -EINVAL;
	}
	size = (size + ~PAGE_MASK) >> PAGE_SHIFT;

	for (address = from; size--; address += PAGE_SIZE) {
		unsigned long *page_table, *rootp, *ptrp, page;

		rootp = &current->tss.pagedir_v[L1_INDEX(address)];
		if (!(PAGE_TABLE & *rootp))
			continue;
		ptrp = (unsigned long *)PTOV(*rootp & TABLE_MASK);
		ptrp += L2_INDEX(address);
		if (!(PAGE_TABLE & *ptrp))
			continue;
		page_table = (unsigned long *)PTOV(*ptrp & PAGE_MASK);
		page_table += L3_INDEX(address);
		if ((page = *page_table) != 0) {
			*page_table = 0;
			if (page & PAGE_PRESENT) {
				if (!(mem_map[MAP_NR(PTOV(page & PAGE_MASK))]
				      & MAP_PAGE_RESERVED))
					--current->rss;
				free_page(PTOV(page & PAGE_MASK));
			} else
				swap_free(page);
		}
	}
	invalidate();
	return 0;
}

int zeromap_page_range(unsigned long from, unsigned long size, int mask)
{
	unsigned long address;

	if (mask) {
		if ((mask & (PAGE_MASK|PAGE_PRESENT)) != PAGE_PRESENT) {
			printk("zeromap_page_range: mask = %08x\n",mask);
			return -EINVAL;
		}
		mask |= VTOP(ZERO_PAGE);
	}

	if (from & ~PAGE_MASK) {
		printk("zeromap_page_range: from = %08lx\n",from);
		return -EINVAL;
	}
	size = (size + ~PAGE_MASK) >> PAGE_SHIFT;

	for (address = from; size--; address += PAGE_SIZE) {
		unsigned long *page_table, *rootp, *ptrp, page;

		rootp = &current->tss.pagedir_v[L1_INDEX(address)];
		if (!(PAGE_TABLE & *rootp)) {
			ptrp = get_pointer_table ();
			if (PAGE_TABLE & *rootp)
				free_pointer_table (ptrp);
			else if (!ptrp)
				return -ENOMEM;
			*rootp = VTOP(ptrp) | PAGE_TABLE;
		}
		ptrp = (unsigned long *)PTOV(*rootp & TABLE_MASK);
		ptrp += L2_INDEX(address);
		if (!(PAGE_TABLE & *ptrp)) {
			page_table = get_page_table (ptrp);
			if (!page_table)
				return -ENOMEM;
		} else
			page_table = (unsigned long *)PTOV(*ptrp & PAGE_MASK);
		page_table += L3_INDEX(address);
		if ((page = *page_table) != 0) {
			*page_table = 0;
			if (page & PAGE_PRESENT) {
				if (!(mem_map[MAP_NR(PTOV(page & PAGE_MASK))]
				      & MAP_PAGE_RESERVED))
					--current->rss;
				free_page(PTOV(page & PAGE_MASK));
			} else
				swap_free(page);
		}
		*page_table = mask;
	}
	invalidate();
	return 0;
}

/*
 * maps a range of physical memory into the requested pages. the old
 * mappings are removed. any references to nonexistent pages results
 * in null mappings (currently treated as "copy-on-access")
 */
int remap_page_range(unsigned long from, unsigned long to, unsigned long size, int mask)
{
	unsigned long address;

	if (mask) {
		if ((mask & (PAGE_MASK|PAGE_PRESENT)) != PAGE_PRESENT) {
			printk("remap_page_range: mask = %08x\n",mask);
			return -EINVAL;
		}
	}
	if ((from & ~PAGE_MASK) || (to & ~PAGE_MASK)) {
		printk("remap_page_range: from = %08lx, to=%08lx\n",from,to);
		return -EINVAL;
	}
	/* add cache bits if 68040 */
	if (boot_info.cputype & CPU_68040)
		mask = (mask & CACHEMASK040) | PAGE_CACHE040;

	size = (size + ~PAGE_MASK) >> PAGE_SHIFT;

	for (address = from; size--; address += PAGE_SIZE) {
		unsigned long *page_table, *rootp, *ptrp, page;

		rootp = &current->tss.pagedir_v[L1_INDEX(address)];
		if (!(PAGE_TABLE & *rootp)) {
			ptrp = get_pointer_table ();
			if (PAGE_TABLE & *rootp)
				free_pointer_table (ptrp);
			else if (!ptrp)
				return -ENOMEM;
			*rootp = VTOP(ptrp) | PAGE_TABLE;
		}
		ptrp = (unsigned long *)PTOV(*rootp & TABLE_MASK);
		ptrp += L2_INDEX(address);
		if (!(PAGE_TABLE & *ptrp)) {
			page_table = get_page_table (ptrp);
			if (!page_table)
				return -ENOMEM;
		} else
			page_table = (unsigned long *)PTOV(*ptrp & PAGE_MASK);
		page_table += L3_INDEX(address);
		if ((page = *page_table) != 0) {
			*page_table = 0;
			if (page & PAGE_PRESENT) {
				if (!(mem_map[MAP_NR(PTOV(page & PAGE_MASK))]
				      & MAP_PAGE_RESERVED))
					--current->rss;
				free_page(PTOV(page & PAGE_MASK));
			} else
				swap_free(page);
		}

		/*
		 * the first condition should return an invalid access
		 * when the page is referenced. current assumptions
		 * cause it to be treated as demand allocation in some
		 * cases.
		 */
		if (!mask)
			*page_table = 0;	/* not present */
		else if (to >= high_memory)
			*page_table = (VTOP(to) | mask);
		else if (!mem_map[MAP_NR(to)])
			*page_table = 0;	/* not present */
		else {
			*page_table = VTOP(to) | mask;
			if (!(mem_map[MAP_NR(to)] & MAP_PAGE_RESERVED)) {
				++current->rss;
				mem_map[MAP_NR(to)]++;
			}
		}
		to += PAGE_SIZE;
	}
	invalidate();
	return 0;
}

/*
 * This function puts a page in memory at the wanted address.
 * It returns the physical address of the page gotten, 0 if
 * out of memory (either when trying to access page-table or
 * page.)
 */
unsigned long put_page(struct task_struct * tsk,unsigned long page,
		       unsigned long address, int prot)
{
    unsigned long *ptr_table, *page_table;

    if ((prot & (PAGE_MASK|PAGE_PRESENT)) != PAGE_PRESENT)
	    printk("put_page: prot = %08x\n",prot);

    if (page >= high_memory) {
	    printk("put_page: trying to put page %08lx at %08lx\n",page,
		   address);
	    return 0;
    }

    ptr_table = &tsk->tss.pagedir_v[L1_INDEX(address)];
    if (*ptr_table & PAGE_TABLE)
	    ptr_table = (unsigned long *) PTOV(*ptr_table & TABLE_MASK);
    else {
	    printk("put_page: bad page root table entry\n");
	    oom(tsk);
	    return 0;
    }
    page_table = &ptr_table[L2_INDEX(address)];
    if (*page_table & PAGE_TABLE)
	page_table = (unsigned long *) PTOV(*page_table & PAGE_MASK);
    else {
	printk("put_page: bad pointer table entry\n");
	oom(tsk);
	*ptr_table = BAD_PAGETABLE | PAGE_TABLE;
	return 0;
    }
    page_table += L3_INDEX(address);
    if (*page_table) {
	printk("put_page: page already exists\n");
	*page_table = 0;
	invalidate();
    }
    *page_table = VTOP(page) | prot;
    /* no need for invalidate (why not?) */
    return page;
}

/*
 * The previous function doesn't work very well if you also want to mark
 * the page dirty: exec.c wants this, as it has earlier changed the page,
 * and we want the dirty-status to be correct (for VM). Thus the same
 * routine, but this time we mark it dirty too.
 */
unsigned long put_dirty_page (struct task_struct * tsk,
			      unsigned long page,
			      unsigned long address)
{
	unsigned long *page_table, *ptr_table, *rootp;

	if (page >= high_memory)
		printk("put_dirty_page: trying to put page %08lx at %08lx\n",
		       page,address);
	if (mem_map[MAP_NR(page)] != 1)
		printk("mem_map disagrees with %08lx at %08lx\n",page,address);
	rootp = &tsk->tss.pagedir_v[L1_INDEX(address)];
	if (*rootp & PAGE_TABLE)
		ptr_table = (unsigned long *)PTOV(*rootp & TABLE_MASK);
	else if (!*rootp) {
		ptr_table = get_pointer_table ();
		*rootp = VTOP(ptr_table) | PAGE_TABLE;
	} else {
		printk("put_dirty_page: bad root table entry\n");
		return 0;
	}
	ptr_table += L2_INDEX(address);
	if (*ptr_table & PAGE_TABLE)
		page_table = (unsigned long *)PTOV(*ptr_table & PAGE_MASK);
	else if (!*ptr_table) {
		if (!(page_table = get_page_table (ptr_table)))
			return 0;
	} else {
		printk("put_dirty_page: bad pointer table entry\n");
		return 0;
	}
	page_table += L3_INDEX(address);
	if (*page_table) {
		printk("put_dirty_page: page already exists\n");
		*page_table = 0;
		invalidate();
	}
	*page_table = VTOP(page) | (PAGE_DIRTY | PAGE_PRIVATE);
	/* no need for invalidate */
	return page;
}

/*
 * This routine handles present pages, when users try to write
 * to a shared page. It is done by copying the page to a new address
 * and decrementing the shared-page counter for the old page.
 *
 * Note that we do many checks twice (look at do_wp_page()), as
 * we have to be careful about race-conditions.
 *
 * Goto-purists beware: the only reason for goto's here is that it results
 * in better assembly code.. The "default" path will see no jumps at all.
 */
static void __do_wp_page(unsigned long writecycle, unsigned long address,
			 struct task_struct * tsk, unsigned long user_usp)
{
	unsigned long *rootp, desc, *ptep, *ptrp, old_page, prot;
	unsigned long new_page;

#ifdef DEBUG
	if (user_usp)
		printk ("write protected page fault at addr %#lx in task %p\n",
			address, tsk);
#endif
	new_page = __get_free_page(GFP_KERNEL);
	rootp = &tsk->tss.pagedir_v[L1_INDEX(address)];
	desc = *rootp;
	if ((desc & PAGE_TABLE) != PAGE_TABLE
	    || PTOV (desc & TABLE_MASK) >= high_memory)
		panic ("do_wp_page: invalid root table entry %08lx", desc);
	ptrp = (unsigned long *)PTOV(desc & TABLE_MASK);
	ptrp += L2_INDEX(address);
	desc = *ptrp;
	if ((desc & PAGE_TABLE) != PAGE_TABLE
	    || PTOV (desc & TABLE_MASK) >= high_memory)
		goto bad_wp_pagetable;
	ptep = (unsigned long *)PTOV(desc & PAGE_MASK) + L3_INDEX(address);
	old_page = *ptep;
	if (!(old_page & PAGE_PRESENT))
		goto end_wp_page;
	if (PTOV (old_page) >= high_memory)
		goto bad_wp_page;
	if (!(old_page & PAGE_RONLY))
		goto end_wp_page;
	/* minor page fault (copy on write) */
	tsk->min_flt++;
	prot = ((old_page & ~PAGE_MASK) & ~PAGE_RONLY) | PAGE_RW;
	old_page = PTOV(old_page & PAGE_MASK);
	/* if page was used only once (no longer shared) enable read write */
	if (mem_map[MAP_NR(old_page)] != 1) {
		if (new_page) {
			if (mem_map[MAP_NR(old_page)] & MAP_PAGE_RESERVED)
				++tsk->rss;
			copy_page (old_page, new_page);
			*ptep = VTOP (new_page) | prot;
			free_page (old_page);
			invalidate();
			return;
		}
		free_page(old_page);
		oom (tsk);
		*ptep = VTOP (BAD_PAGE) | prot;
		invalidate();
		return;
	}
	*ptep &= ~PAGE_RONLY;
	invalidate ();
	if (new_page)
		free_page (new_page);
	return;
bad_wp_page:
	printk ("do_wp_page: bogus page at address %08lx (%08lx)\n", address,
		old_page);
	*ptep = VTOP (BAD_PAGE) | PAGE_SHARED;
	send_sig (SIGKILL, tsk, 1);
	goto end_wp_page;
bad_wp_pagetable:
	printk ("do_wp_page: bogus page-table at address %08lx (%08lx)\n",
		address, desc);
	*ptrp = VTOP (BAD_PAGETABLE) | PAGE_TABLE;
	send_sig (SIGKILL, tsk, 1);
end_wp_page:
	if (new_page)
		free_page (new_page);
	return;
}

/*
 * check that a page table change is actually needed, and call
 * the low-level function only in that case..
 */
void do_wp_page(unsigned long error_code, unsigned long address,
		struct task_struct * tsk, unsigned long user_usp)
{
	unsigned long page, ptrdesc;
	unsigned long *rootp, *pg_table;

#ifdef DEBUG
	printk ("do_wp_page (address=%#lx, user_usp=%#lx\n", address,
		user_usp);
#endif
	rootp = &tsk->tss.pagedir_v[L1_INDEX(address)];
	ptrdesc = *rootp;
	if (!ptrdesc) {
		/*
		 * this code just had "return", but that doesn't seem correct;
		 * it will just trap again.  I added a printk
		 * Hamish Macdonald Tue May 18 17:29:00 1993
		 * Changed printk/return to panic.
		 * Hamish Macdonald Friday 19-Nov-93 22:46:45
		 */
		panic ("do_wp_page: unexplained null root table entry for %lx",
		       address);
	}
	pg_table = (unsigned long *)PTOV(ptrdesc & TABLE_MASK);
	pg_table += L2_INDEX(address);
	page = *pg_table;
	if (!page) {
		/*
		 * this code just had "return", but that doesn't seem correct;
		 * it will just trap again.  I added a printk
		 * Hamish Macdonald Tue May 18 17:29:00 1993
		 * Changed printk/return to panic.
		 * Hamish Macdonald Friday 19-Nov-93 22:46:45
		 */
		panic ("do_wp_page: unexplained null pointer table entry for %lx", address);
	}
	if ((page & PAGE_TABLE) && PTOV(page) < high_memory) {
		pg_table = (unsigned long *)PTOV(page & PAGE_MASK) + L3_INDEX(address);
		page = *pg_table;
		if (!(page & PAGE_PRESENT))
			return;
		if (!(page & PAGE_RONLY))
			return;
		if (!(page & PAGE_COW)) {
			if (user_usp && tsk == current) {
				send_sig(SIGSEGV, tsk, 1);
				return;
			}
		}
		if (mem_map[MAP_NR(PTOV(page))] == 1) {
			*pg_table = (*pg_table & ~PAGE_RONLY) | PAGE_DIRTY;
#ifdef DEBUG
			printk ("do_wp_page: just marking page RW\n");
#endif
			invalidate();
			return;
		}
		__do_wp_page(error_code, address, tsk, user_usp);
		return;
	}
	printk("bad page table entry %08lx\n",page);
	*pg_table = 0;
}

int verify_area(int type, void * addr, unsigned long size)
{
	unsigned long start;

	start = (unsigned long) addr;
#ifdef __i386__
	if (start >= TASK_SIZE)
		return -EFAULT;
	if (size > TASK_SIZE - start)
		return -EFAULT;
#endif
	if (wp_works_ok || type == VERIFY_READ || !size)
		return 0;
	if (!size)
		return 0;
	size--;
	size += start & ~PAGE_MASK;
	size >>= PAGE_SHIFT;
	start &= PAGE_MASK;
	do {
		do_wp_page(1,start,current,0);
		start += PAGE_SIZE;
	} while (size--);
	return 0;
}

static inline void get_empty_page(struct task_struct * tsk, unsigned long address)
{
    unsigned long tmp;

    if (!(tmp = get_free_page(GFP_KERNEL))) {
	oom(tsk);
	tmp = BAD_PAGE;
    }
    if (!put_page(tsk,tmp,address,PAGE_PRIVATE))
	free_page(tmp);
}

/*
 * try_to_share() checks the page at address "address" in the task "p",
 * to see if it exists, and if it is clean. If so, share it with the current
 * task.
 *
 * NOTE! This assumes we have checked that p != current, and that they
 * share the same executable or library.
 *
 * We may want to fix this to allow page sharing for PIC pages at different
 * addresses so that ELF will really perform properly. As long as the vast
 * majority of sharable libraries load at fixed addresses this is not a
 * big concern. Any sharing of pages between the buffer cache and the
 * code space reduces the need for this as well.  - ERY
 */
static int try_to_share(unsigned long address, struct task_struct * tsk,
			struct task_struct * p, unsigned long writecycle,
			unsigned long newpage)
{
    unsigned long from, to, desc;
    unsigned long *rootp_f, *from_ptr, *from_page;
    unsigned long *rootp_t, *to_ptr, *to_page;
    unsigned long virt_addr;

    rootp_f = &p->tss.pagedir_v[L1_INDEX(address)];
    rootp_t = &tsk->tss.pagedir_v[L1_INDEX(address)];

    /* is there a pointer table in from? */
    desc = *rootp_f;
    if (!(desc & PAGE_TABLE))
	return 0;
    from_ptr = (unsigned long *)PTOV(desc & TABLE_MASK) + L2_INDEX(address);
    /* is there a page table in from? */
    desc = *from_ptr;
    if (!(desc & PAGE_TABLE))
	return 0;
    from_page = (unsigned long *)PTOV(desc & PAGE_MASK) + L3_INDEX(address);
    from = *from_page;
    /* is the page clean and present? */
    if ((from & (PAGE_PRESENT | PAGE_DIRTY)) != PAGE_PRESENT)
	return 0;
    virt_addr = PTOV(from & PAGE_MASK);
    if (virt_addr >= high_memory)
	return 0;
    if (mem_map[MAP_NR(virt_addr)] & MAP_PAGE_RESERVED)
	return 0;
    /* is the destination ok? */
    desc = *rootp_t;
    if (!(desc & PAGE_TABLE))
	return 0;
    to_ptr = (unsigned long *)PTOV(desc & TABLE_MASK) + L2_INDEX(address);
    desc = *to_ptr;
    if (!(desc & PAGE_TABLE))
	return 0;
    to_page = (unsigned long *)PTOV(desc & PAGE_MASK) + L3_INDEX(address);
    if (*to_page)
	return 0;
    /* share them if read - do COW immediately otherwise */
    if (writecycle) {
	    if (!newpage) /* did the page exist?  SRB. */
		    return 0;
	    copy_page(virt_addr,newpage);
	    to = VTOP(newpage) | PAGE_PRIVATE;
    } else {
	    mem_map[MAP_NR(virt_addr)]++;
	    from |= PAGE_RONLY;
	    to = from;
	    if (newpage)
		    free_page(newpage);
    }
    *from_page = from;
    *to_page = to;
    invalidate();
    return 1;
}

/*
 * share_page() tries to find a process that could share a page with
 * the current one. Address is the address of the wanted page relative
 * to the current data space.
 *
 * We first check if it is at all feasible by checking executable->i_count.
 * It should be >1 if there are other tasks sharing this inode.
 */
 int share_page(struct vm_area_struct * area, struct task_struct * tsk,
		struct inode * inode,
		unsigned long address, unsigned long error_code, unsigned long newpage)
{
	struct task_struct ** p;

	if (!inode || inode->i_count < 2 || !area->vm_ops)
		return 0;
	for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
		if (!*p)
			continue;
		if (tsk == *p)
			continue;
		if (inode != (*p)->executable) {
			  if(!area) continue;
			/* Now see if there is something in the VMM that
			   we can share pages with */
			if(area){
			  struct vm_area_struct * mpnt;
			  for (mpnt = (*p)->mmap; mpnt; mpnt = mpnt->vm_next) {
			    if (mpnt->vm_ops == area->vm_ops &&
			       mpnt->vm_inode->i_ino == area->vm_inode->i_ino&&
			       mpnt->vm_inode->i_dev == area->vm_inode->i_dev){
			      if (mpnt->vm_ops->share(mpnt, area, address))
				break;
			    };
			  };
			  if (!mpnt) continue;  /* Nope.  Nuthin here */
			};
		}
		if (try_to_share(address,tsk,*p,error_code,newpage))
			return 1;
	}
	return 0;
}

static struct ptable_desc {
	struct ptable_desc *prev;
	struct ptable_desc *next;
	unsigned long	   page;
	unsigned char	   alloced;
} ptable_list = { &ptable_list, &ptable_list, 0, 0xff };

#define PD_NONEFREE(dp) ((dp)->alloced == 0xff)
#define PD_ALLFREE(dp) ((dp)->alloced == 0)
#define PD_TABLEFREE(dp,i) (!((dp)->alloced & (1<<(i))))
#define PD_MARKUSED(dp,i) ((dp)->alloced |= (1<<(i)))
#define PD_MARKFREE(dp,i) ((dp)->alloced &= ~(1<<(i)))

static unsigned long *get_pointer_table (void)
{
	unsigned long table = 0, flags;
	struct ptable_desc *dp = ptable_list.next;
	int i;

	/*
	 * For a pointer table for a user process address space, a
	 * table is taken from a page allocated for the purpose.  Each
	 * page can hold 8 pointer tables.  The page is remapped in
	 * virtual address space to be noncacheable.
	 */
	if (PD_NONEFREE (dp)) {
		if (!(dp = kmalloc (sizeof(struct ptable_desc),GFP_KERNEL))) {
			return 0;
		}
		if (!(dp->page = __get_free_page (GFP_KERNEL))) {
			kfree (dp);
			return 0;
		}
		nocache_page (dp->page);
		dp->alloced = 0;
		/* put at head of list */
		save_flags (flags);
		cli ();
		dp->next = ptable_list.next;
		dp->prev = ptable_list.next->prev;
		ptable_list.next->prev = dp;
		ptable_list.next = dp;
		restore_flags (flags);
	}

	for (i = 0; i < 8; i++)
		if (PD_TABLEFREE (dp, i)) {
			PD_MARKUSED (dp, i);
			table = dp->page + PTABLE_SIZE*i;
			break;
		}

	if (PD_NONEFREE (dp)) {
		/* move to end of list */
		save_flags (flags);
		cli ();
		dp->prev->next = dp->next;
		dp->next->prev = dp->prev;

		dp->next = ptable_list.next->prev;
		dp->prev = ptable_list.prev;
		ptable_list.prev->next = dp;
		ptable_list.prev = dp;
		restore_flags (flags);
	}

	memset ((void *)table, 0, PTABLE_SIZE);

	return (unsigned long *)table;
}

static void free_pointer_table (unsigned long *ptable)
{
	struct ptable_desc *dp;
	unsigned long page = (unsigned long)ptable & PAGE_MASK;
	int index = ((unsigned long)ptable - page)/PTABLE_SIZE;
	unsigned long flags;

	for (dp = ptable_list.next; dp->page && dp->page != page; dp = dp->next)
		;

	if (!dp->page)
		panic ("unable to find desc for ptable %p on list!", ptable);

	if (PD_TABLEFREE (dp, index))
		panic ("table already free!");

	PD_MARKFREE (dp, index);

	if (PD_ALLFREE (dp)) {
		/* all tables in page are free, free page */
		save_flags (flags);
		cli ();
		dp->prev->next = dp->next;
		dp->next->prev = dp->prev;
		restore_flags (flags);
		cache_page (dp->page);
		free_page (dp->page);
		kfree (dp);
		return;
	} else {
		/*
		 * move this descriptor the the front of the list, since
		 * it has one or more free tables.
		 */
		save_flags (flags);
		cli ();
		dp->prev->next = dp->next;
		dp->next->prev = dp->prev;

		dp->next = ptable_list.next;
		dp->prev = ptable_list.next->prev;
		ptable_list.next->prev = dp;
		ptable_list.next = dp;
		restore_flags (flags);
	}
}

static unsigned long *get_page_table (unsigned long *ptr)
{
	unsigned long page, tmp;
	int i;

	page = get_free_page(GFP_KERNEL);
	if (PAGE_TABLE & *ptr) {
		free_page (page);
		return (unsigned long *)PTOV(*ptr & PAGE_MASK);
	}
	if (page) {
		nocache_page (page);
		tmp = VTOP(page) | PAGE_TABLE;
		for (i = 0; i < 16; i++, tmp += 256)
			ptr[i] = tmp;
		return (unsigned long *)page;
	}

	return NULL;
}

/*
 * fill in an empty page-table if none exists.
 */
static inline unsigned long get_empty_pgtable(struct task_struct *tsk,
					      unsigned long address)
{
    unsigned long tmp, *pagep;
    unsigned long *rptr, *ptr;
    int i;

    rptr = &tsk->tss.pagedir_v[L1_INDEX(address)];
    if (!*rptr) {
	    /* no pointer table, allocate one */
	    ptr = get_pointer_table ();
	    if (*rptr & PAGE_TABLE)
		    free_pointer_table (ptr);
	    else
		    *rptr = VTOP(ptr) | PAGE_TABLE;
    } else if (!(PAGE_TABLE & *rptr))
	    panic("get_empty_pgtable: bad root table entry %#lx\n", *rptr);

    ptr = (unsigned long *)PTOV (*rptr & TABLE_MASK);
    ptr += L2_INDEX(address);

    if (PAGE_TABLE & *ptr)
	    return *ptr;
    else if (*ptr) {
	    printk("get_empty_pgtable: bad pointer table entry \n");
	    *ptr = 0;
    }

    pagep = get_page_table (ptr);
    if (pagep)
	    return *ptr;
    oom(current);
    tmp = VTOP(BAD_PAGETABLE) | PAGE_TABLE;
    for (i = 0; i < 16; i++, tmp += 256)
	    ptr[i] = tmp;
    return 0;
}

void do_no_page(unsigned long error_code, unsigned long address,
		struct task_struct *tsk, unsigned long usp)
{
	unsigned long tmp;
	unsigned long page, *p;
	struct vm_area_struct * mpnt;

	page = get_empty_pgtable(tsk,address);
#ifdef DEBUG
	if (!page)
		printk ("do_no_page: null return from get_empty_pgtable\n");
	else {
		printk ("do_no_page: empty_pgtable is %#lx\n", page);
		printk ("address=%#lx, usp=%#lx\n", address, usp);
		waitbut();
	}
#endif
	if (!page)
		return;
	p = (unsigned long *)PTOV(page & PAGE_MASK);
	tmp = p[L3_INDEX(address)];
	if (tmp & PAGE_PRESENT)
		return;

	/* resident set size has increased */
	++tsk->rss;

	/* page was swapped out, flag major fault and swap it in */
	if (tmp) {
		++tsk->maj_flt;
		swap_in((unsigned long *) page);
		return;
	}
	address &= 0xfffff000;
	tmp = 0;
	for (mpnt = tsk->mmap ; mpnt != NULL; mpnt = mpnt->vm_next) {
		if (address < mpnt->vm_start)
			break;
		if (address >= mpnt->vm_end) {
			tmp = mpnt->vm_end;
			continue;
		}
		if (!mpnt->vm_ops || !mpnt->vm_ops->nopage) {
			++tsk->min_flt;
			get_empty_page(tsk,address);
			return;
		}
		mpnt->vm_ops->nopage(error_code, mpnt, address);
		return;
	}

	++tsk->min_flt;
	get_empty_page(tsk,address);
	if (tsk != current)
		return;
	if (address >= tsk->end_data && address < tsk->brk)
		return;
	if (mpnt && mpnt == tsk->stk_vma &&
	    address - tmp > mpnt->vm_start - address &&
	    tsk->rlim[RLIMIT_STACK].rlim_cur > mpnt->vm_end - address) {
		mpnt->vm_start = address;
		return;
	}
	send_sig(SIGSEGV,tsk,1);
	return;
}

/*
 * This routine handles page faults.  It determines the problem, and
 * then passes it off to one of the appropriate routines.
 */
asmlinkage void do_page_fault(struct frame *fp, unsigned long address,
			      unsigned long error_code)
{
	unsigned long user_esp = 0;

	if (!(fp->sr & PS_S))
		/* if !supervisor mode, set user stack pointer */
		user_esp = fp->usp;

#ifdef DEBUG
	printk ("fp->pc=%#lx\n", fp->pc);
#endif
	if (address < TASK_SIZE) {
		if (error_code & 1)
			do_wp_page (error_code, address, current, user_esp);
		else
			do_no_page (error_code, address, current, user_esp);
		return;
	}
	printk("Unable to handle kernel paging request at address %08lx\n",address);
	die_if_kernel("Oops", fp, error_code);
	do_exit(SIGKILL);
}

/* This handles a generic mmap of a disk file */
void file_mmap_nopage(int error_code, struct vm_area_struct * area, unsigned long address)
{
	struct inode * inode = area->vm_inode;
	unsigned int block;
	unsigned long page;
	int nr[8];
	int i, j;
	int prot = area->vm_page_prot;

	address &= PAGE_MASK;
	block = address - area->vm_start + area->vm_offset;
	block >>= inode->i_sb->s_blocksize_bits;

	page = get_free_page(GFP_KERNEL);
	if (share_page(area, area->vm_task, inode, address, error_code, page)) {
		++area->vm_task->min_flt;
		return;
	}

	++area->vm_task->maj_flt;
	if (!page) {
		oom(current);
		put_page(area->vm_task, BAD_PAGE, address, PAGE_PRIVATE);
		return;
	}
	for (i=0, j=0; i< PAGE_SIZE ; j++, block++, i += inode->i_sb->s_blocksize)
		nr[j] = bmap(inode,block);
	if (error_code & 1)
		prot = (prot & ~PAGE_RONLY) | PAGE_DIRTY;
	page = bread_page(page, inode->i_dev, nr, inode->i_sb->s_blocksize, prot);
	if (prot & PAGE_RONLY) {
		if (share_page(area, area->vm_task, inode, address, error_code, page))
			return;
	}
	if (put_page(area->vm_task,page,address,prot))
		return;
	free_page(page);
	oom(current);
}

void file_mmap_free(struct vm_area_struct * area)
{
	if (area->vm_inode)
		iput(area->vm_inode);
#if 0
	if (area->vm_inode)
		printk("Free inode %x:%d (%d)\n",area->vm_inode->i_dev,
				 area->vm_inode->i_ino, area->vm_inode->i_count);
#endif
}

/*
 * Compare the contents of the mmap entries, and decide if we are allowed to
 * share the pages
 */
int file_mmap_share(struct vm_area_struct * area1,
		    struct vm_area_struct * area2,
		    unsigned long address)
{
	if (area1->vm_inode != area2->vm_inode)
		return 0;
	if (area1->vm_start != area2->vm_start)
		return 0;
	if (area1->vm_end != area2->vm_end)
		return 0;
	if (area1->vm_offset != area2->vm_offset)
		return 0;
	if (area1->vm_page_prot != area2->vm_page_prot)
		return 0;
	return 1;
}

struct vm_operations_struct file_mmap = {
	NULL,			/* open */
	file_mmap_free, 	/* close */
	file_mmap_nopage,	/* nopage */
	NULL,			/* wppage */
	file_mmap_share,	/* share */
	NULL,			/* unmap */
};

/*
 * BAD_PAGE is the page that is used for page faults when linux
 * is out-of-memory. Older versions of linux just did a
 * do_exit(), but using this instead means there is less risk
 * for a process dying in kernel mode, possibly leaving a inode
 * unused etc..
 *
 * BAD_PAGETABLE is the accompanying page-table: it is initialized
 * to point to BAD_PAGE entries.
 *
 * ZERO_PAGE is a special page that is used for zero-initialized
 * data and COW.
 */
static unsigned long empty_bad_page_table;

unsigned long __bad_pagetable(void)
{
    int i;

    for( i = 0; i < PTRS_PER_PAGE; i++ )
	((unsigned long *)empty_bad_page_table)[i] = VTOP(BAD_PAGE) | PAGE_PRIVATE;

    return empty_bad_page_table;
}

static unsigned long empty_bad_page;

unsigned long __bad_page(void)
{
    memset ((void *)empty_bad_page, 0, PAGE_SIZE);

    return empty_bad_page;
}

static unsigned long empty_zero_page;

unsigned long __zero_page(void)
{
    memset ((void *)empty_zero_page, 0, PAGE_SIZE);

    return empty_zero_page;
}

void show_mem(void)
{
    unsigned long i;
    int free = 0, total = 0, reserved = 0, nonshared = 0, shared = 0;

    printk("Mem-info:\n");
    printk("Free pages:      %6dkB\n",nr_free_pages<<(PAGE_SHIFT-10));
    printk("Secondary pages: %6dkB\n",nr_secondary_pages<<(PAGE_SHIFT-10));
    printk("Free swap:       %6dkB\n",nr_swap_pages<<(PAGE_SHIFT-10));
    printk("Buffer memory:   %6dkB\n",buffermem>>10);
    printk("Buffer heads:    %6d\n",nr_buffer_heads);
    printk("Buffer blocks:   %6d\n",nr_buffers);
    i = (high_memory-0xC0000000) >> PAGE_SHIFT;
    while (i-- > 0) {
	total++;
	if (mem_map[i] & MAP_PAGE_RESERVED)
	    reserved++;
	else if (!mem_map[i])
	    free++;
	else if (mem_map[i] == 1)
	    nonshared++;
	else
	    shared++;
    }
    printk("%d pages of RAM\n",total);
    printk("%d free pages\n",free);
    printk("%d reserved pages\n",reserved);
    printk("%d pages nonshared\n",nonshared);
    printk("%d pages shared\n",shared);
}

/* kernel code start address */
asmlinkage void start(void);
/* "end" marks the end of the kernel text/data/bss */
extern int end;

/*
 * The following two routines map from a physical address to a kernel
 * virtual address and vice versa.
 */
unsigned long mm_vtop (unsigned long vaddr)
{
	unsigned long offset = PSTART_ADDR;

  if(vaddr < boot_info.memory[0].addr)
   {
#ifdef DEBUG
    printk("vtop: p= %#lx  v= %#lx\n",vaddr,offset+vaddr);
#endif
    return ( offset + vaddr);
   }
  else if(vaddr > offset)
   {
#ifdef DEBUG
    printk("ptov: p= %#lx  v= %#lx\n",vaddr,vaddr-offset);
#endif
    return ( vaddr - offset);
   }
  else 
   {
#ifdef DEBUG
    printk("ptov: p=v= %#lx\n",vaddr);
#endif
    return vaddr;
   }
	panic ("VTOP: bad virtual address %08lx", vaddr);
}

unsigned long mm_ptov (unsigned long paddr)
{
	unsigned long offset = PSTART_ADDR;

  if(paddr < boot_info.memory[0].addr)
   {
#ifdef DEBUG
    printk("ptov: p= %#lx  v= %#lx\n",paddr,offset+paddr);
#endif
    return ( offset + paddr);
   }
  else if(paddr > boot_info.memory[0].addr+boot_info.memory[0].size)
   {
#ifdef DEBUG
    printk("ptov: p= %#lx  v= %#lx\n",paddr,paddr-offset);
#endif
    return ( paddr - offset);
   }
  else 
   {
#ifdef DEBUG
    printk("ptov: p=v= %#lx\n",paddr);
#endif
    return paddr;
   }
	panic ("PTOV: bad physical address %08lx (called from %p)\n",
	       paddr, __builtin_return_address(0));
}

static unsigned long *kernel_pointer_table (void)
{
	/*
	 * For a pointer table for the kernel virtual address space,
	 * use one of the pointer tables in the page holding the root
	 * table.  This page can hold up to 8 pointer tables.  3 of
	 * these tables are always reserved (root table, kernel
	 * pointer table, stack pointer table).  In addition, the 4th
	 * pointer table in this page is reserved.  If you are running
	 * on an '040 Amiga, this pointer table is used to map in the
	 * Amiga hardware.  It may be used for other purposes on other
	 * 68K machines.  This leaves 4 pointer tables available for
	 * use by the kernel.  This allows mapping of 5 * 32 = 160M of
	 * physical memory.  This should be sufficient for now.
	 */
	extern unsigned long *krt; /* address of kernel root table */
	unsigned long *ptable;
	/* index of available table */
	static int kptavail = PAGE_SIZE/(sizeof(long)*128) - 4;

	ptable = (unsigned long *)&krt[kptavail*128];
	kptavail++;
	if (kptavail == PAGE_SIZE/(sizeof(long)*128))
		panic ("no space for kernel pointer table");

	return ptable;
}


static unsigned long *kernel_page_table (unsigned long *memavailp)
{
	unsigned long *ptablep;

	ptablep = (unsigned long *)*memavailp;
	*memavailp += PAGE_SIZE;

	nocache_page ((unsigned long)ptablep);

	return ptablep;
}

static unsigned long map_chunk (unsigned long addr,
				unsigned long size,
				unsigned long *memavailp)
{
#define ONEMEG	(1024*1024)

	int is040 = (boot_info.cputype & CPU_68040);
	static unsigned long mem_mapped = 0;
	static unsigned long virtaddr = KSTART_ADDR;
	static unsigned long *ktablep = NULL;
	unsigned long *kpointerp, physaddr;
	extern unsigned long *krt, *kpt;
	int pindex;   /* index into pointer table */
  
	kpointerp = (unsigned long *)(krt[L1_INDEX(virtaddr)] & 0xfffffff0);
	if (kpointerp)
		kpointerp = (unsigned long *)PTOV(kpointerp);
	/*
	 * pindex is the offset into the pointer table for the
	 * descriptors for the current virtual address being mapped.
	 */
	pindex = (virtaddr >> 18) & 0x1f;

#ifdef DEBUG 
	printk ("mm=%ld, krt=%p, kpointerp=%p, pindex=%d\n", mem_mapped,
		krt, kpointerp, pindex);
#endif 

	/*
	 * if this is running on an '040, we already allocated a page
	 * table for the first 4M.  The address is stored in kpt by
	 * arch/head.S
	 */
	if (is040 && mem_mapped == 0)
		ktablep = kpt;

	for (physaddr = addr;
	     physaddr < addr + size;
	     mem_mapped += ONEMEG, virtaddr += ONEMEG) {

#ifdef DEBUG
		printk ("pa=%#lx va=%#lx ", physaddr, virtaddr);
#endif

		if (pindex > 128 && mem_mapped >= 32*ONEMEG) {
			/* we need a new pointer table every 32M */
#ifdef DEBUG
			printk ("[new pointer]");
#endif

			kpointerp = kernel_pointer_table ();
			krt[L1_INDEX(addr)] = VTOP(kpointerp) | PAGE_TABLE;
			pindex = 0;
		}

		if (is040) {
			int i;
			unsigned long ktable;

#ifdef DEBUG
			printk ("[setup table]");
#endif

			/*
			 * 68040, use page tables pointed to by the
			 * kernel pointer table.
			 */

			if ((pindex & 15) == 0 && mem_mapped >= 4*ONEMEG) {
				/* Need new page table every 4M on the '040 */
#ifdef DEBUG
				printk ("[new table]");
#endif
				ktablep = kernel_page_table (memavailp);
			}

			ktable = (unsigned long)ktablep;

			/*
			 * initialize section of the page table mapping
			 * this 1M portion (
			 */
			for (i = 0; i < 256; i++) {
				ktablep[i] = physaddr | PAGE_PRESENT
					| PAGE_CACHE040 | PAGE_GLOBAL040;
				physaddr += 4096;
			}
			ktablep += 256;

			/*
			 * make the kernel pointer table point to the
			 * kernel page table.  4 entries point to a
			 * different 64 entry section of the page table.
			 */
			kpointerp[pindex++] = ktable | PAGE_TABLE;
			ktable += 256;
			kpointerp[pindex++] = ktable | PAGE_TABLE;
			ktable += 256;
			kpointerp[pindex++] = ktable | PAGE_TABLE;
			ktable += 256;
			kpointerp[pindex++] = ktable | PAGE_TABLE;
			ktable += 256;
		} else {
			/*
			 * 68030, use early termination page descriptors.
			 * Each one points to 64 pages (256K).  Using 4
			 * page descriptors results in a mapping of 1M
			 */
#ifdef DEBUG
			printk ("[early term] ");
#endif

			kpointerp[pindex++] = physaddr | PAGE_PRESENT;
#ifdef DEBUG
			printk ("%lx=%lx ", VTOP(&kpointerp[pindex-1]),
				kpointerp[pindex-1]);
#endif
			physaddr += 64 * 4096;
			kpointerp[pindex++] = physaddr | PAGE_PRESENT;
#ifdef DEBUG
			printk ("%lx=%lx ", VTOP(&kpointerp[pindex-1]),
				kpointerp[pindex-1]);
#endif
			physaddr += 64 * 4096;
			kpointerp[pindex++] = physaddr | PAGE_PRESENT;
#ifdef DEBUG
			printk ("%lx=%lx ", VTOP(&kpointerp[pindex-1]),
				kpointerp[pindex-1]);
#endif
			physaddr += 64 * 4096;
			kpointerp[pindex++] = physaddr | PAGE_PRESENT;
#ifdef DEBUG
			printk ("%lx=%lx ", VTOP(&kpointerp[pindex-1]),
				kpointerp[pindex-1]);
#endif
			physaddr += 64 * 4096;
		}

#ifdef DEBUG
		printk ("\n");
#endif
	}

	return mem_mapped;
}

void cache_clear (unsigned long paddr, int len)
{

	if (boot_info.machtype & CPU_68040)
		/* on 68040, invalidate cache lines for pages in the range */
		while (len > 0) {
			asm volatile ("movel %0,a0\n\t"
				      ".word 0xf4d0" /* CINVP I/D (a0) */
				      : : "g" (paddr)
				      : "a0");
			len -= PAGE_SIZE;
		}
	else /* 68030 or 68020 */
		asm volatile ("movec cacr,d0\n\t"
			      "oriw %0,d0\n\t"
			      "movec d0,cacr"
			      : : "i" (FLUSH_I_AND_D)
			      : "d0");
}


void cache_push (unsigned long paddr, int len)
{
	if (boot_info.machtype & CPU_68040)
		/* on 68040, push cache lines for pages in the range */
		while (len > 0) {
			asm volatile ("movel %0,a0\n\t"
				      ".word 0xf4f0" /* CPUSHP I/D (a0) */
				      : : "g" (paddr)
				      : "a0");
			len -= PAGE_SIZE;
		}
	/* 68030/68020 have no writeback cache */
}

/*
 * Bits to add to page descriptors for "normal" caching mode.
 * For 68020/030 this is 0.
 * For 68040, this is PAGE_CACHE040 (cachable, copyback)
 */
unsigned long mm_cachebits;

unsigned long interrupt_stack[1024];

/*
 * paging_init() continues the virtual memory environment setup which
 * was begun by the code in arch/head.S.
 * The sole parameter is the starting address of available memory.
 */
void paging_init(unsigned long *startp,
		 unsigned long *endp)
{
	int chunk;
	unsigned long virtual_start, virtual_end;
	unsigned long mem_avail = 0;
	/* pointer to page table for kernel stacks */
	extern unsigned long *krt, availmem;

	/*
	 * Setup cache bits
	 */
	mm_cachebits = boot_info.cputype & CPU_68040 ? PAGE_CACHE040 : 0;

	/*
	 * Indicate that the 680x0 can handle write protect faults
	 * from kernel mode.
	 */
	wp_works_ok = 1;

	/*
	 * Map the physical memory available into the kernel virtual
	 * address space.  It may allocate some memory for page
	 * tables and thus modify availmem.
	 */
  boot_info.num_memory=1;
  chunk=0;
 /*   For F030 this is done in head.S 
	for (chunk = 0; chunk < boot_info.num_memory; chunk++)
		mem_avail = map_chunk (boot_info.memory[chunk].addr,
				       boot_info.memory[chunk].size,
				       &availmem); */
	mem_avail=boot_info.memory[0].size;

#ifdef DEBUG
	printk ("memory available is %ld\n", mem_avail);
#endif
    
	/*
	 * virtual address after end of kernel
	 * "availmem" is setup by the code in head.S.
	 */
	virtual_start = availmem;

	/* virtual address of end of available memory 
	virtual_end = (unsigned long)start + mem_avail;*/
	virtual_end = virtual_start + mem_avail;

#ifdef DEBUG
	printk ("virtual_start is %#lx\nvirtual_end is %#lx\n",
		virtual_start, virtual_end);
#endif

	/*
	 * initialize the bad page table and bad page to point
	 * to a couple of allocated pages
	 */
	empty_bad_page_table = virtual_start;
	virtual_start += PAGE_SIZE;
	empty_bad_page = virtual_start;
	virtual_start += PAGE_SIZE;
	empty_zero_page = virtual_start;
	virtual_start += PAGE_SIZE;

	/* record in task 0 (swapper) tss */
	task[0]->tss.pagedir_v = krt;
	task[0]->tss.pagedir_p = VTOP (krt);

#ifdef DEBUG
	printk ("task 0 pagedir at %p virt, %#lx phys\n",
		task[0]->tss.pagedir_v, task[0]->tss.pagedir_p);
#endif

	/* setup CPU root pointer for swapper task */
	task[0]->tss.crp[0] = 0x80000000 | PAGE_SHORT;
	task[0]->tss.crp[1] = task[0]->tss.pagedir_p;

/*	if (boot_info.cputype & CPU_68040)
		asm ("movel %0,d0\n\t"
		     ".long 0x4e7b0806"  movec d0,urp 
		     "movel d0,urp\n\t"
		     : 
		     : "g" (task[0]->tss.crp[1])
		     : "d0");
	else */
		asm ("pmove %0@,crp"
		     : /* no outputs */
		     : "a" (task[0]->tss.crp));

#ifdef DEBUG
	printk ("set crp\n");
#endif

	/*
	 * Setup interrupt stack pointer
	 */
	asm ("movec %0,isp" : : "r" ((unsigned long)((unsigned long)interrupt_stack+PAGE_SIZE)));

#ifdef DEBUG
	printk ("setup istack (%lx)\n", interrupt_stack);
#endif

	/*
	 * Set up SFC/DFC registers (user data space)
	 */
	set_fs (USER_DATA); 
	*startp = virtual_start;
	*endp = virtual_end;
}

void mem_init(unsigned long low_mem_init,
	      unsigned long start_mem, unsigned long end_mem)
{
	int codepages = 0;
	int reservedpages = 0;
	int datapages = 0;
	unsigned long tmp;
	unsigned short * p;
	extern int etext;


	end_mem &= PAGE_MASK;
	high_memory = end_mem;
	start_mem += 0x0000000f;
	start_mem &= ~0x0000000f;
  
	tmp = MAP_NR(end_mem);
	mem_map = (unsigned short *) start_mem;


	p = mem_map + tmp;
	start_mem = (unsigned long) p;
	while (p > mem_map)
		*--p = MAP_PAGE_RESERVED;
	start_mem = PAGE_ALIGN(start_mem);
	while (start_mem < end_mem) {
		mem_map[MAP_NR(start_mem)] = 0;
		start_mem += PAGE_SIZE;
	}

#ifdef DEBUG
	printk ("task[0] root table is %p\n", task[0]->tss.pagedir_v);
#endif

	free_page_list = 0;
	nr_free_pages = 0;
	for (tmp = KSTART_ADDR ; tmp < end_mem ; tmp += PAGE_SIZE) {
		if (mem_map[MAP_NR(tmp)]) {
			if (tmp >= 0xA0000 && tmp < 0x100000)
				reservedpages++;
			else if (tmp < (unsigned long)&etext)
				codepages++;
			else
				datapages++;
			continue;
		}
		*(unsigned long *) tmp = free_page_list;
		free_page_list = tmp;
		nr_free_pages++;
	}
	tmp = nr_free_pages << PAGE_SHIFT;
	printk("Memory: %luk/%luk available (%dk kernel code, %dk reserved, %dk data)\n",
	       tmp >> 10,
	       (end_mem-KSTART_ADDR) >> 10,
	       codepages << (PAGE_SHIFT-10),
	       reservedpages << (PAGE_SHIFT-10),
	       datapages << (PAGE_SHIFT-10));
}

unsigned long mm_phys_to_virt (unsigned long addr)
{
    return PTOV (addr);
}

void si_meminfo(struct sysinfo *val)
{
    unsigned long i;

    i = high_memory >> PAGE_SHIFT;
    val->totalram = 0;
    val->freeram = 0;
    val->sharedram = 0;
    val->bufferram = buffermem;
    while (i-- > (KSTART_ADDR >> PAGE_SHIFT))  {
	if (mem_map[i] & MAP_PAGE_RESERVED)
	    continue;
	val->totalram++;
	if (!mem_map[i]) {
	    val->freeram++;
	    continue;
	}
	val->sharedram += mem_map[i]-1;
    }
    val->totalram <<= PAGE_SHIFT;
    val->freeram <<= PAGE_SHIFT;
    val->sharedram <<= PAGE_SHIFT;
    return;
}

/*
 * abstract out the high memory variable
 */
int valid_addr(unsigned long addr, int count)
{
    /* otherwise, kernel virtual memory */
    if (addr >= KSTART_ADDR && addr < high_memory)
	if (addr + count > high_memory)
	    return high_memory - addr;
	else
	    return count;

    /* not valid memory */
    return 0;
}