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#------------------------------------------------------------------------------
#
# Copyright (c) 2006 - 2008, Intel Corporation
# All rights reserved. This program and the accompanying materials
# are licensed and made available under the terms and conditions of the BSD License
# which accompanies this distribution. The full text of the license may be found at
# http://opensource.org/licenses/bsd-license.php
#
# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
#
# Module Name:
#
# DisablePaging64.S
#
# Abstract:
#
# AsmDisablePaging64 function
#
# Notes:
#
#------------------------------------------------------------------------------
#------------------------------------------------------------------------------
# VOID
# EFIAPI
# InternalX86DisablePaging64 (
# IN UINT16 Cs,
# IN UINT32 EntryPoint,
# IN UINT32 Context1, OPTIONAL
# IN UINT32 Context2, OPTIONAL
# IN UINT32 NewStack
# );
#------------------------------------------------------------------------------
ASM_GLOBAL ASM_PFX(InternalX86DisablePaging64)
ASM_PFX(InternalX86DisablePaging64):
cli
lea L1(%rip), %rsi # rsi <- The start address of transition code
mov 0x28(%rsp), %edi # rdi <- New stack
sub $64, %edi # rdi <- use 64 byte in stack to hold transition code
mov %edi, %r10d # r10 <- The start address of transicition code below 4G
lea _mTransitionEnd(%rip), %rax # rax <- end of transition code
sub %rsi, %rax # rax <- The size of transition piece code
push %rcx # save rcx to stack
mov %rax, %rcx # rcx <- The size of transition piece code
rep
movsb # copy transition code to (new stack - 64byte) below 4G
pop %rcx # restore rcx
mov %r8d, %esi
mov %r9d, %edi
mov 0x28(%rsp), %eax # eax <- New Stack
push %rcx # push Cs to stack
push %r10
.byte 0x48, 0xcb # retq: Use far return to load CS register from stack
# (Use raw byte code since some GNU assemblers generates incorrect code for "retq")
L1:
mov %eax,%esp # set up new stack
mov %cr0,%rax
btr $0x1f,%eax
mov %rax,%cr0 # disable paging
mov %rdx,%rbx # save EntryPoint to rbx, for rdmsr will overwrite rdx
mov $0xc0000080,%ecx
rdmsr
and $0xfe,%ah # clear LME
wrmsr
mov %cr4,%rax
and $0xdf,%al # clear PAE
mov %rax,%cr4
push %rdi # push Context2
push %rsi # push Context1
callq *%rbx # transfer control to EntryPoint
jmp . # no one should get here
_mTransitionEnd :
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