bioscall.S
1.55 KB
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/* -----------------------------------------------------------------------
*
* Copyright 2009-2014 Intel Corporation; author H. Peter Anvin
*
* This file is part of the Linux kernel, and is made available under
* the terms of the GNU General Public License version 2 or (at your
* option) any later version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* "Glove box" for BIOS calls. Avoids the constant problems with BIOSes
* touching registers they shouldn't be.
*/
.code16
.section ".inittext","ax"
.globl intcall
.type intcall, @function
intcall:
/* Self-modify the INT instruction. Ugly, but works. */
cmpb %al, 3f
je 1f
movb %al, 3f
jmp 1f /* Synchronize pipeline */
1:
/* Save state */
pushfl
pushw %fs
pushw %gs
pushal
/* Copy input state to stack frame */
subw $44, %sp
movw %dx, %si
movw %sp, %di
movw $11, %cx
rep; movsd
/* Pop full state from the stack */
popal
popw %gs
popw %fs
popw %es
popw %ds
popfl
/* Actual INT */
.byte 0xcd /* INT opcode */
3: .byte 0
/* Push full state to the stack */
pushfl
pushw %ds
pushw %es
pushw %fs
pushw %gs
pushal
/* Re-establish C environment invariants */
cld
movzwl %sp, %esp
movw %cs, %ax
movw %ax, %ds
movw %ax, %es
/* Copy output state from stack frame */
movw 68(%esp), %di /* Original %cx == 3rd argument */
andw %di, %di
jz 4f
movw %sp, %si
movw $11, %cx
rep; movsd
4: addw $44, %sp
/* Restore state and return */
popal
popw %gs
popw %fs
popfl
retl
.size intcall, .-intcall