core/pm.inc: shorten the time until we have a valid stack

Cut the time until we have a valid RM stack as much as possible.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/core/pm.inc b/core/pm.inc
index bcc95ce..8b24c2c 100644 (file)
--- a/core/pm.inc
+++ b/core/pm.inc
@@ -163,19 +163,19 @@ enter_rm:
                mov gs,ax
 
                lidt [RM_IDT_ptr]       ; Real-mode IDT (rm needs no GDT)
+               xor dx,dx
                mov eax,cr0
                and al,~1
                mov cr0,eax
                jmp 0:.in_rm
 
 .in_rm:                                        ; Back in real mode
-               mov ax,cs               ; Set up sane segments
-               mov ds,ax
-               lss sp,[RealModeSSSP]   ; Restore stack
+               lss sp,[cs:RealModeSSSP]        ; Restore stack
                movzx esp,sp            ; Make sure the high bits are zero
-               mov es,ax
-               mov fs,ax
-               mov gs,ax
+               mov ds,dx               ; Set up sane segments
+               mov es,dx
+               mov fs,dx
+               mov gs,dx
                jmp bx                  ; Go to whereever we need to go...
 
                section .data