Set Page Attributes

Call With

AX = 0507H
ESI = memory block handle
EBX = offset within memory block of page(s) whose attributes are to be modified
ECX = number of pages
ES:EDX = selector:offset of a buffer containing page attributes, 1 word (16-bits) per page (see Note)

Returns

if function successful
Carry flag = clear

if function unsuccessful
Carry flag = set
AX = error code

8001H	unsupported function (16-bit host)
8002H	invalid state (page in wrong state for request)
8013H	physical memory unavailable
8014H	backing store unavailable
8021H	invalid value (illegal request in bits 0-2 of one or more page attribute words)
8023H	invalid handle (in ESI)
8025H	invalid linear address (specified range is not within specified block)

ECX = number of pages that have been set

Notes

• A DPMI 1.0 host that is 16-bit only will not support this function.

• A 16-bit client of a 32-bit DPMI 1.0 host can use this function.

• If EBX is not aligned, it will be rounded down to the next lower page boundary.

• An uncommitted page can be created from:
  • a committed page, by releasing the physical memory or backing store allocated to the page;
  • a mapped page, by marking it uncommitted; or an uncommitted page, by doing nothing.

• A committed page can be created from:
  • an uncommitted page or mapped page, by allocating physical memory or backing store (with undefined, or zero-filled contents) for the page; or
  • a committed page, by doing nothing (page contents unmodified).

• The attribute word (16-bits) specified for a page has the following format (bits 3-6 are only relevant if page is being created committed or its attributes are being modified, i.e. the value in bits 0-2 of the page attribute is 1 or 3):

  Bits	Significance
  0-2	page type (0-7)
  	Value	Meaning
  	0	create page uncommitted
  	1	create page committed
  	2	not allowed
  	3	modify attributes without changing page type
  	4-7	not allowed
  3	0 = page is read-only
  	1 = page is read/write
  4	0 = don't modify accessed/dirty bits for page
  	1 = set accessed/dirty bits as specified in bits 5-6
  5	0 = mark page as not accessed (if bit 4=1)
  	1 = mark page as accessed (if bit 4=1)
  6	0 = mark page as not dirty (if bit 4=1)
  	1 = mark page as dirty (if bit 4=1)
  7-15	reserved, should be zero

• This function, and the optional Map Device and Map Conventional Memory functions (Int 31H Functions 0508H and 0509H), are the only means of changing the type of a page within an existing memory block.

• The page read/write bit, and optionally the accessed and dirty bits, can be modified on an existing committed or mapped page, or on a committed page when it is initially created from an uncommitted page or a mapped page. However, the accessed and dirty bits are ignored if the host does not support the Page Accessed/Dirty capability. See Int 31H Function 0401H.

• Visible page faults (page faults that can be serviced by a client-installed exception handler) can only occur for uncommitted pages or read-only pages (for definitions of transparent page fault and visible page fault, see Appendix A: Glossary).