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intr: avoid random trace in (init_)call_intr

This commit is contained in:
C. Masloch 2022-06-04 17:53:14 +02:00 committed by Kenneth J Davis
parent 3ef6d61609
commit 1c2f541689
1 changed files with 26 additions and 5 deletions
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29
kernel/intr.asm
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@ -42,6 +42,8 @@
%endif %endif
push ds push ds
pushf pushf
; Flags are preserved across the entire
; function call, particularly IF.
arg nr, {rp,%1} arg nr, {rp,%1}
mov ax, [.nr] ; interrupt number mov ax, [.nr] ; interrupt number
@ -53,17 +55,36 @@ arg nr, {rp,%1}
%else %else
mov bx, [.rp] ; regpack structure mov bx, [.rp] ; regpack structure
%endif %endif
mov ax, [bx]
mov cx, [bx+4]
mov dx, [bx+6] mov dx, [bx+6]
mov si, [bx+8] mov si, [bx+8]
mov di, [bx+10] mov di, [bx+10]
mov bp, [bx+12] mov bp, [bx+12]
push word [bx+14] ; ds push word [bx+14] ; ds
mov es, [bx+16] mov es, [bx+16]
push word [bx+22] ; flags pushf
popf 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 ax, [bx]
mov cx, [bx+4]
mov bx, [bx+2] mov bx, [bx+2]
popf ; set live FL
pop ds pop ds
int 0 int 0
%%intr_1: %%intr_1: