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\ Hypervisor Software File: dynamic-user.fth
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id: @(#)dynamic-user.fth 1.2 03/12/08 13:21:46
purpose: 
copyright: Copyright 2000-2003 Sun Microsystems, Inc.  All Rights Reserved
copyright: Use is subject to license terms.

\ The use of this code will give all machines almost 512Kb of user space
\ without sacrificing RAM unless it is required.
\
\
h# 400 constant /user-margin

: ?user-space-exhausted ( abort? -- )
   abort" ERROR: User area used up!"
;

: detect-recursive-enter ( #bytes -- #bytes )
   dup #user @ + user-size /user-margin + > ?user-space-exhausted
;

: enlarge-user-space ( #bytes -- #bytes ) recursive
   #user @ 2dup +			( #bytes #user new-#user )
   dup user-size <= if			( #bytes #user new-#user )
      2drop exit
   then 				( #bytes #user new-#user )

   ['] detect-recursive-enter is check-user-size

   \ OK we want more user space, so we need to
   \ claim a new page and map it if possible.

   RAMsize HEAPsize - > ?user-space-exhausted	( #bytes #user )

   over mmu-pagesize round-up			( #bytes #user #to-claim )
   swap up0 @ + mmu-pagesize round-up		( #bytes #to-claim va )
   over dup mmu-pagesize mem-claim
				( #bytes #to-claim va #to-claim pa.lo pa.hi )

   2swap map-pages				( #bytes #to-claim ) 
   user-size + is user-size			( #bytes )
   ['] enlarge-user-space is check-user-size
;

stand-init: Grow user space to fill RAMsize-start
   RAMbase RAMsize-start + up0 @ - /user-margin - is user-size
   ['] enlarge-user-space is check-user-size
;