diff options
Diffstat (limited to 'sys/arch/i386/boot/asm.S')
| -rw-r--r-- | sys/arch/i386/boot/asm.S | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/sys/arch/i386/boot/asm.S b/sys/arch/i386/boot/asm.S index 18261ffad28..5d9f708eef5 100644 --- a/sys/arch/i386/boot/asm.S +++ b/sys/arch/i386/boot/asm.S @@ -103,10 +103,13 @@ xprot: */ ENTRY(prot_to_real) # set up a dummy stack frame for the second seg change. - movl _ourseg, %eax - pushw %ax - movl $xreal, %eax # gas botches pushw $xreal - extra bytes 0, 0 - pushw %ax # decode to add %al, (%eax) (%al usually 0) + # Adjust the intersegment jump instruction following + # the clearing of protected mode bit. + # This is self-modifying code, but we need a writable + # code segment, and an intersegment return does not give us that. + movl _ourseg, %eax + movw %ax, xreal-2 + # Change to use16 mode. ljmp $0x28, $x16 @@ -121,7 +124,10 @@ x16: # make intersegment jmp to flush the processor pipeline # using the fake stack frame set up earlier # and reload CS register - lret + # Here we have an 16 bits intersegment jump. + .byte 0xea + .word xreal + .word 0 xreal: # we are in real mode now |