fixed VECTOR defaults location, needed by GEOS

c64/kernal/vector_real.s

@@ -0,0 +1,40 @@
+
+vector_real:
+
+	// Temporary storage location - checked on real C64 that this is the
+	// address originally used; after calling VECTOR and checking zero page
+	// area afterwards, the address could be found there
+	.label _caller_arr_ptr = MEMUSS
+
+	// According to 'Compute's Mapping the Commodore 64' page 237,
+	// the CBM implementation does not disable IRQs - yet, the
+	// 'C64 Programmers Reference Guide' does not contain such
+	// warning and does not mention any preparations needed, so...
+	// better safe than sorry, disable the IRQ for the duration
+	// of vector manipulation
+	php
+	cli
+	
+	// Prepare the user data pointer - strange order to reduce risk
+	// of potential similarity to the original routine
+	sty _caller_arr_ptr + 1
+	stx _caller_arr_ptr + 0
+	
+	// Select routine variant - store or restore vectors
+	ldy #$1F
+	bcc vector_restore
+	
+	lda CINV, y
+	sta (_caller_arr_ptr), y
+
+	// FALLTHROUGH
+	
+vector_restore:
+	lda (_caller_arr_ptr), y
+	sta CINV, y
+	dey
+	bpl vector_restore
+
+	// Restore status register (IRQ) before return
+	plp
+	rts