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80 lines
987 B
ArmAsm
80 lines
987 B
ArmAsm
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; void __fastcall__ _sys (struct regs* r);
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;
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; Ullrich von Bassewitz, 16.12.1998
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;
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;
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; The function could also export jmpvec as general purpose jump vector that
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; lies in the data segment so it's address may be patched at runtime.
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;
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.export __sys
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.importzp ptr1
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__sys: sta ptr1
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stx ptr1+1 ; Save the pointer to r
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; Fetch the PC and store it into the jump vector
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ldy #5
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lda (ptr1),y
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sta jmpvec+2
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dey
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lda (ptr1),y
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sta jmpvec+1
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; Get the flags, mask unnecessary bits and push them. Push a
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dey
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lda (ptr1),y
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and #%11001011
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pha
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ldy #0
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lda (ptr1),y
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pha
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; Get and assign X and Y
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iny
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lda (ptr1),y
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tay
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iny
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lda (ptr1),y
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tay
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; Set a and the flags, call the machine code routine
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pla
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plp
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jsr jmpvec
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; Back from the routine. Save the flags and a
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php
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pha
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; Put the register values into the regs structure
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tya
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ldy #2
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sta (ptr1),y
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dey
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txa
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sta (ptr1),y
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dey
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pla
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sta (ptr1),y
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ldy #3
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pla
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sta (ptr1),y
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; Done
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rts
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.data
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jmpvec: jmp $FFFF
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