safer vector handling in some Kernal routines

src/kernal/interrupts/hw_entry_irq.s

@@ -29,8 +29,8 @@ hw_entry_irq:
 	bne irq_handler_brk
 
 	// Not caused by BRK - call interrupt routine (only if initialised)
-	lda CINV
-	ora CINV+1
+	// Routine on zeropage = assuming not initialized
+	lda CINV+1
 	beq !+
 	jmp (CINV)
 !:

src/kernal/keyboard/scnkey.s

@@ -147,7 +147,22 @@ scnkey_bucky_loop:
 
 	// Set KEYTAB vector
 
-	jsr via_keylog // XXX for some CPUs we have indirect jsr
+	lda KEYLOG+1
+	bne !+
+	jsr scnkey_set_keytab              // KEYLOG routine on zeropage? most likely vector not set
+#if HAS_OPCODES_65C02
+	bra scnkey_keytab_set_done
+#else
+	jmp scnkey_keytab_set_done
+#endif
+!:
+#if HAS_OPCODES_65CE02
+	jsr_ind KEYLOG
+#else
+	jsr scnkey_via_keylog
+#endif
+
+scnkey_keytab_set_done:
 
 #if CONFIG_JOY2_CURSOR
 
@@ -483,8 +498,4 @@ scnkey_early_repeat:
 
 	rts
 
-via_keylog:
-	jmp (KEYLOG)
-
-
 #endif // no CONFIG_LEGACY_SCNKEY

src/kernal/keyboard/scnkey_set_keytab.s

@@ -38,8 +38,8 @@ scnkey_set_keytab:
 	cmp #$FF
 	bne scnkey_valid_offset
 
-	// $FF means we shouldn't decode anything, mark this by setting high byte
-	// of KEYTAB to 0 (I don't think anyone would put keyboard decoding table
+	// $FF means we should not decode anything, mark this by setting high byte
+	// of KEYTAB to 0 (I do not think anyone would put keyboard decoding table
     // at zeropage)
 	lda #$00
 	beq !+ // branch always

src/kernal/keyboard/scnkey_via_keylog.s

@@ -0,0 +1,14 @@
+// #LAYOUT# STD *        #TAKE
+// #LAYOUT# X16 *        #IGNORE
+// #LAYOUT# *   KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+// Short helper jump-via-vector routine, to set the keyboard matrix
+
+#if !HAS_OPCODES_65CE02
+
+scnkey_via_keylog:
+
+	jmp (KEYLOG)
+
+#endif