kernel-ark/arch/x86/boot/pmjump.S
H. Peter Anvin 2ee2394b68 x86: fix regression: boot failure on AMD Elan TS-5500
Jeremy Fitzhardinge wrote:
>
> Maybe it really does require the far jump immediately after setting PE
> in cr0...
>
> Hm, I don't remember this paragraph being in vol 3a, section 8.9.1
> before.  Is it a recent addition?
>
>    Random failures can occur if other instructions exist between steps
>    3 and 4 above.  Failures will be readily seen in some situations,
>    such as when instructions that reference memory are inserted between
>    steps 3 and 4 while in system management mode.
>

I don't remember that, either.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-01 10:53:29 +02:00

83 lines
1.8 KiB
ArmAsm

/* ----------------------------------------------------------------------- *
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright 2007 rPath, Inc. - All Rights Reserved
*
* This file is part of the Linux kernel, and is made available under
* the terms of the GNU General Public License version 2.
*
* ----------------------------------------------------------------------- */
/*
* The actual transition into protected mode
*/
#include <asm/boot.h>
#include <asm/processor-flags.h>
#include <asm/segment.h>
.text
.globl protected_mode_jump
.type protected_mode_jump, @function
.code16
/*
* void protected_mode_jump(u32 entrypoint, u32 bootparams);
*/
protected_mode_jump:
movl %edx, %esi # Pointer to boot_params table
xorl %ebx, %ebx
movw %cs, %bx
shll $4, %ebx
addl %ebx, 2f
jmp 1f # Short jump to serialize on 386/486
1:
movw $__BOOT_DS, %cx
movw $__BOOT_TSS, %di
movl %cr0, %edx
orb $X86_CR0_PE, %dl # Protected mode
movl %edx, %cr0
# Transition to 32-bit mode
.byte 0x66, 0xea # ljmpl opcode
2: .long in_pm32 # offset
.word __BOOT_CS # segment
.size protected_mode_jump, .-protected_mode_jump
.code32
.type in_pm32, @function
in_pm32:
# Set up data segments for flat 32-bit mode
movl %ecx, %ds
movl %ecx, %es
movl %ecx, %fs
movl %ecx, %gs
movl %ecx, %ss
# The 32-bit code sets up its own stack, but this way we do have
# a valid stack if some debugging hack wants to use it.
addl %ebx, %esp
# Set up TR to make Intel VT happy
ltr %di
# Clear registers to allow for future extensions to the
# 32-bit boot protocol
xorl %ecx, %ecx
xorl %edx, %edx
xorl %ebx, %ebx
xorl %ebp, %ebp
xorl %edi, %edi
# Set up LDTR to make Intel VT happy
lldt %cx
jmpl *%eax # Jump to the 32-bit entrypoint
.size in_pm32, .-in_pm32