rework to make handling flags simpler, from ecm

kernel/intr.asm

@@ -41,9 +41,7 @@
                 push    es
 %endif
                 push	ds
-		pushf
-	; Flags are preserved across the entire
-	;  function call, particularly IF.
+				pushf
 
 arg nr, {rp,%1}
                 mov	ax, [.nr]		; interrupt number
@@ -55,38 +53,18 @@ arg nr, {rp,%1}
 %else
 		mov	bx, [.rp]		; regpack structure
 %endif
+		mov	cx, [bx+4]
 		mov	dx, [bx+6]
 		mov	si, [bx+8]
 		mov	di, [bx+10]
 		mov	bp, [bx+12]
 		push	word [bx+14]		; ds
 		mov	es, [bx+16]
-		pushf
-		pop	cx
-		and	cx, 0F02Ah
-	; Get the current reserved bits from the FL
-	;  register. Hardens against possible weirdness
-	;  around eg the NEC V20/V30 MD flag.
-
-		mov	ax, [bx + 22]		; flags
-		and	ax, ~ 0F72Ah
-	; Clear most of the top bits of the FL input.
-	;  Particularly, clear DF, IF, and TF. Callers
-	;  often do not initialise all of the iregs
-	;  structure passed to us. Avoid weirdness
-	;  when DF would be set (DN) or when TF would
-	;  enable tracing randomly.
-
-		or	ax, cx
-	; Set reserved bits to same as current FL.
-
-		push	ax
+		mov	ah, byte [bx+22]	; flags
+		sahf
 		mov	ax, [bx]
-		mov	cx, [bx+4]
 		mov	bx, [bx+2]
-		popf				; set live FL
 		pop	ds
-		sti
 		int	0
 %%intr_1: