/* 
 * Mach Operating System
 * Copyright (c) 1991,1990 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */

#include <vm/vm_fault.h>
#include <mach/kern_return.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/pmap.h>

#include <kern/macros.h>

/*
 *	Expansion of vm_fault for read fault in kernel mode.
 *	Must enter the mapping as writable, since the i386
 *	ignores write protection in kernel mode.
 */
kern_return_t
intel_read_fault(
	vm_map_t	map,
	vm_offset_t	vaddr)
{
	vm_map_version_t	version;	/* Map version for
						   verification */
	vm_object_t		object;		/* Top-level object */
	vm_offset_t		offset;		/* Top-level offset */
	vm_prot_t		prot;		/* Protection for mapping */
	vm_page_t		result_page;	/* Result of vm_fault_page */
	vm_page_t		top_page;	/* Placeholder page */
	boolean_t		wired;		/* Is map region wired? */
	kern_return_t		result;
	vm_page_t		m;

    RetryFault:

	/*
	 *	Find the backing store object and offset into it
	 *	to begin search.
	 */
	result = vm_map_lookup(&map, vaddr, VM_PROT_READ, &version,
			&object, &offset, &prot, &wired);
	if (result != KERN_SUCCESS)
	    return (result);

	/*
	 *	Make a reference to this object to prevent its
	 *	disposal while we are playing with it.
	 */
	assert(object->ref_count > 0);
	object->ref_count++;
	vm_object_paging_begin(object);

	result = vm_fault_page(object, offset, VM_PROT_READ, FALSE, TRUE,
			       &prot, &result_page, &top_page,
			       FALSE, (void (*)()) 0);

	if (result != VM_FAULT_SUCCESS) {
	    vm_object_deallocate(object);

	    switch (result) {
		case VM_FAULT_RETRY:
		    goto RetryFault;
		case VM_FAULT_INTERRUPTED:
		    return (KERN_SUCCESS);
		case VM_FAULT_MEMORY_SHORTAGE:
		    VM_PAGE_WAIT((void (*)()) 0);
		    goto RetryFault;
		case VM_FAULT_FICTITIOUS_SHORTAGE:
		    vm_page_more_fictitious();
		    goto RetryFault;
		case VM_FAULT_MEMORY_ERROR:
		    return (KERN_MEMORY_ERROR);
	    }
	}

	m = result_page;

	/*
	 *	How to clean up the result of vm_fault_page.  This
	 *	happens whether the mapping is entered or not.
	 */

#define UNLOCK_AND_DEALLOCATE				\
	MACRO_BEGIN					\
	vm_fault_cleanup(m->object, top_page);		\
	vm_object_deallocate(object);			\
	MACRO_END

	/*
	 *	What to do with the resulting page from vm_fault_page
	 *	if it doesn't get entered into the physical map:
	 */

#define RELEASE_PAGE(m)					\
	MACRO_BEGIN					\
	PAGE_WAKEUP_DONE(m);				\
	vm_page_lock_queues();				\
	if (!m->active && !m->inactive)			\
		vm_page_activate(m);			\
	vm_page_unlock_queues();			\
	MACRO_END

	/*
	 *	We must verify that the maps have not changed.
	 */
	vm_object_unlock(m->object);
	while (!vm_map_verify(map, &version)) {
	    vm_object_t		retry_object;
	    vm_offset_t		retry_offset;
	    vm_prot_t		retry_prot;

	    result = vm_map_lookup(&map, vaddr, VM_PROT_READ, &version,
				&retry_object, &retry_offset, &retry_prot,
				&wired);
	    if (result != KERN_SUCCESS) {
		vm_object_lock(m->object);
		RELEASE_PAGE(m);
		UNLOCK_AND_DEALLOCATE;
		return (result);
	    }

	    vm_object_unlock(retry_object);

	    if (retry_object != object || retry_offset != offset) {
		vm_object_lock(m->object);
		RELEASE_PAGE(m);
		UNLOCK_AND_DEALLOCATE;
		goto RetryFault;
	    }
	}

	/*
	 *	Put the page in the physical map.
	 */
	PMAP_ENTER(map->pmap, vaddr, m, VM_PROT_READ|VM_PROT_WRITE, wired);

	vm_object_lock(m->object);
	vm_page_lock_queues();
	if (!m->active && !m->inactive)
		vm_page_activate(m);
	m->reference = TRUE;
	vm_page_unlock_queues();

	vm_map_verify_done(map, &version);
	PAGE_WAKEUP_DONE(m);

	UNLOCK_AND_DEALLOCATE;

#undef	UNLOCK_AND_DEALLOCATE
#undef	RELEASE_PAGE

	return (KERN_SUCCESS);
}