xnu-517.12.7.tar.gz

[apple/xnu.git] / osfmk / mach / vm_prot.h

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/*
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/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
 * All Rights Reserved.
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/*
 */
/*
 *	File:	mach/vm_prot.h
 *	Author:	Avadis Tevanian, Jr., Michael Wayne Young
 *
 *	Virtual memory protection definitions.
 *
 */

#ifndef	VM_PROT_H_
#define	VM_PROT_H_

/*
 *	Types defined:
 *
 *	vm_prot_t		VM protection values.
 */

typedef int		vm_prot_t;

/*
 *	Protection values, defined as bits within the vm_prot_t type
 */

#define	VM_PROT_NONE	((vm_prot_t) 0x00)

#define VM_PROT_READ	((vm_prot_t) 0x01)	/* read permission */
#define VM_PROT_WRITE	((vm_prot_t) 0x02)	/* write permission */
#define VM_PROT_EXECUTE	((vm_prot_t) 0x04)	/* execute permission */

/*
 *	The default protection for newly-created virtual memory
 */

#define VM_PROT_DEFAULT	(VM_PROT_READ|VM_PROT_WRITE)

/*
 *	The maximum privileges possible, for parameter checking.
 */

#define VM_PROT_ALL	(VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE)

/*
 *	An invalid protection value.
 *	Used only by memory_object_lock_request to indicate no change
 *	to page locks.  Using -1 here is a bad idea because it
 *	looks like VM_PROT_ALL and then some.
 */
#define VM_PROT_NO_CHANGE	((vm_prot_t) 0x08)

/* 
 *      When a caller finds that he cannot obtain write permission on a
 *      mapped entry, the following flag can be used.  The entry will
 *      be made "needs copy" effectively copying the object (using COW),
 *      and write permission will be added to the maximum protections
 *      for the associated entry. 
 */        
#define VM_PROT_COPY            ((vm_prot_t) 0x10)


/*
 *	Another invalid protection value.
 *	Used only by memory_object_data_request upon an object
 *	which has specified a copy_call copy strategy. It is used
 *	when the kernel wants a page belonging to a copy of the
 *	object, and is only asking the object as a result of
 *	following a shadow chain. This solves the race between pages
 *	being pushed up by the memory manager and the kernel
 *	walking down the shadow chain.
 */
#define VM_PROT_WANTS_COPY	((vm_prot_t) 0x10)

#endif	/* VM_PROT_H_ */