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59 lines
1.8 KiB
Plaintext
59 lines
1.8 KiB
Plaintext
; ======================================================================
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; VMPatch.a © 1988 by Apple Computer Inc
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; by Chris Derossi 4/10/89
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; ======================================================================
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PrNonPortable EQU 1 ; We're building System SW. This is ok.
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PRINT OFF
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INCLUDE 'Traps.a'
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INCLUDE 'SysEqu.a'
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INCLUDE 'ToolEqu.a'
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INCLUDE 'Private.a'
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INCLUDE 'quickequ.a'
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INCLUDE 'colorequ.a'
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INCLUDE 'VMCalls.a'
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PRINT ON
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; ======================================================================
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; Header to main init code.
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; ======================================================================
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MACHINE MC68020
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VMPatch PROC EXPORT
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; During a page fault exception, MacVM continues to service the cursor interrupt. Now that
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; the cursor code is not in ROM, and not in the System heap, it must not get paged out.
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; Otherwise, nested page faults could occur, and this is bad.
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;
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; This patch tells MacVM to keep the cursor code in memory at all times. This patch does
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; nothing if MacVM isn't around.
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;
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; Note: This patch knows that the cursor code is pointed to by JCrsrTask, and ends at the
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; location pointed to by JScrnAddr.
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Unimplemented EQU $A89F ; the Unimplemented trap number
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MemoryDispatch EQU $A05C ; trap number for MacVM Dispatcher
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; Does the MacVM dispatch trap exist?
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MOVE.W #MemoryDispatch, D0 ; MacVM Trap number
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_GetTrapAddress ,NewOS ; get the address of _MemoryDispatch
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MOVEA.L A0, A1 ; Hold it for a sec
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MOVE.W #Unimplemented, D0 ; get address of Unimplemented trap
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_GetTrapAddress
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CMPA.L A0,A1 ; see if MacVM is around
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BEQ.S @0 ; if not, we're done
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MOVE.L jCrsrTask, A0 ; Point to cursor code
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MOVE.L jScrnAddr, A1 ; Get end of code
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SUBA.L jCrsrTask, A1 ; Calculate length of cursor code
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_HoldMemory ; Tell VM to keep it around
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@0
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RTS
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END
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