cf9972a921
Impact: Comment change only The glove box is about avoiding problems with *registers* being touched, not *memory*. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
83 lines
1.5 KiB
ArmAsm
83 lines
1.5 KiB
ArmAsm
/* -----------------------------------------------------------------------
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*
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* Copyright 2009 Intel Corporation; author H. Peter Anvin
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2 or (at your
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* option) any later version; incorporated herein by reference.
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*
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* ----------------------------------------------------------------------- */
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/*
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* "Glove box" for BIOS calls. Avoids the constant problems with BIOSes
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* touching registers they shouldn't be.
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*/
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.code16
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.text
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.globl intcall
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.type intcall, @function
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intcall:
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/* Self-modify the INT instruction. Ugly, but works. */
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cmpb %al, 3f
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je 1f
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movb %al, 3f
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jmp 1f /* Synchronize pipeline */
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1:
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/* Save state */
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pushfl
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pushw %fs
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pushw %gs
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pushal
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/* Copy input state to stack frame */
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subw $44, %sp
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movw %dx, %si
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movw %sp, %di
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movw $11, %cx
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rep; movsd
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/* Pop full state from the stack */
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popal
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popw %gs
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popw %fs
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popw %es
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popw %ds
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popfl
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/* Actual INT */
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.byte 0xcd /* INT opcode */
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3: .byte 0
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/* Push full state to the stack */
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pushfl
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pushw %ds
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pushw %es
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pushw %fs
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pushw %gs
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pushal
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/* Re-establish C environment invariants */
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cld
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movzwl %sp, %esp
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movw %cs, %ax
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movw %ax, %ds
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movw %ax, %es
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/* Copy output state from stack frame */
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movw 68(%esp), %di /* Original %cx == 3rd argument */
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andw %di, %di
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jz 4f
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movw %sp, %si
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movw $11, %cx
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rep; movsd
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4: addw $44, %sp
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/* Restore state and return */
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popal
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popw %gs
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popw %fs
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popfl
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retl
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.size intcall, .-intcall
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