backported fixes from 256boss

[bootcensus] / src / lowcode.s

diff --git a/src/lowcode.s b/src/lowcode.s
index 67901e4..48bf290 100644 (file)
--- a/src/lowcode.s
+++ b/src/lowcode.s
@@ -35,6 +35,7 @@ saved_eax: .long 0
 saved_es: .word 0
 saved_ds: .word 0
 saved_flags: .word 0
+saved_if: .byte 0
 saved_pic1_mask: .byte 0
 saved_pic2_mask: .byte 0
 
@@ -44,6 +45,8 @@ int86:
        push %ebp
        mov %esp, %ebp
        pushal
+       call get_intr_flag
+       mov %al, saved_if
        cli
        # save protected mode IDTR and replace it with the real mode vectors
        sidt (saved_idtr)
@@ -80,6 +83,8 @@ int86:
        mov %ax, %ds
        mov %ax, %es
        mov %ax, %ss
+       mov %ax, %fs
+       mov %ax, %gs
        nop
 
        # load registers from the int86regs struct
@@ -93,6 +98,11 @@ int86:
        pop %ds
        # ignore fs and gs for now, don't think I'm going to need them
 
+       # move to the real-mode stack, at the top of conventional memory
+       #mov $0x9000, %sp
+       #mov %sp, %ss
+       #mov $0, %esp
+
        # move to the real-mode stack, accessible from ss=0
        # just in case the BIOS call screws up our unreal mode
        mov $0x7be0, %esp
@@ -124,6 +134,8 @@ int_op:     int $0
        mov %ax, %ds
        mov %ax, %es
        mov %ax, %ss
+       mov %ax, %fs
+       mov %ax, %gs
        nop
 
        # point the esp to our regs struct, to fill it with pusha/pushf
@@ -168,11 +180,14 @@ int_op:   int $0
        # can't receive any more keyboard interrupts afterwards. Reading from
        # the keyboard data port (60h) once, seems to resolve this. And it's
        # cheap enough, so why not... I give up.
-       push %eax
        in $0x60, %al
-       pop %eax
 
-       sti
+       # restore interrupts to their previous state
+       movzbl saved_if, %eax
+       pushl %eax
+       call set_intr_flag
+       add $4, %esp
+
        popal
        pop %ebp
        ret