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#*****************************************************************************
#*
#* Copyright (c) 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:
#*
#* Thunk.S
#*
#* Abstract:
#*
#* Real mode thunk
#*
#*****************************************************************************
#include <EfiBind.h>
.data
.globl ASM_PFX(mCode16Size)
.data
mCode16Size: .long _Code16End - _Code16Addr
NullSegSel: .quad 0
_16CsSegSel:
.word -1
.word 0
.byte 0
.byte 0x9b
.byte 0x8f #16-bit segment
.byte 0
_16DsSegSel:
.word -1
.word 0
.byte 0
.byte 0x93
.byte 0x8f #16-bit segment
.byte 0
_16Gdtr:
.word _16Gdtr - NullSegSel - 1
.long NullSegSel
.code:
#IA32_REGS STRUC 4t
#_EDI DD ?
#_ESI DD ?
#_EBP DD ?
#_ESP DD ?
#_EBX DD ?
#_EDX DD ?
#_ECX DD ?
#_EAX DD ?
#_DS DW ?
#_ES DW ?
#_FS DW ?
#_GS DW ?
#_RFLAGS DQ ?
#_EIP DD ?
#_CS DW ?
#_SS DW ?
#IA32_REGS ENDS
#_STK16 STRUC 1t
#RetEip DD ?
#RetCs DW ?
#ThunkFlags DW ?
#SavedGdtr FWORD ?
#Resvd1 DW ?
#SavedCr0 DD ?
#SavedCr4 DD ?
#_STK16 ENDS
ASM_PFX(Thunk16):
push %rbp
push %rbx
push %rsi
push %rdi
push %r12
push %r13
push %r14
push %r15
pushq %fs
pushq %gs
movl %ds,%r12d
movl %es,%r13d
movl %ss,%r14d
mov %rsp,%r15
mov %rcx,%rsi
movzwq 0x36(%rsi),%r10 #movzx r10, (IA32_REGS ptr [rsi])._SS
xor %rdi,%rdi
mov 0xc(%rsi),%edi #mov edi, (IA32_REGS ptr [rsi])._ESP
add $0xffffffffffffffb0,%rdi #add rdi, - sizeof (IA32_REGS) - sizeof (_STK16)
push %rdi
imul $0x10,%r10,%rax
add %rax,%rdi
pushq $0xe #push sizeof (IA32_REGS) / 4
pop %rcx
rep movsl %ds:(%rsi),%es:(%rdi)
pop %rbx #rbx <- 16-bit stack offset
lea Label,%eax #42 <_Thunk16+0x42>
stos %eax,%es:(%rdi)
movl %cs,%eax #return segment
stos %ax,%es:(%rdi)
mov %edx,%eax #THUNK Flags
stos %ax,%es:(%rdi)
sgdt 0x58(%rsp) #save GDTR
mov 0x58(%rsp),%rax
stos %rax,%es:(%rdi)
mov %cr0,%rax #save CR0
mov %eax,%esi #esi <- CR0 to set
stos %eax,%es:(%rdi)
mov %cr4,%rax #save CR4
stos %eax,%es:(%rdi)
sidt 0x58(%rsp) #save IDTR
and $0x7ffffffe,%esi #clear PE & PG bits
mov %r10,%rdi #rdi <- 16-bit stack segment
shl $0x10,%r8
push %r8 #far jmp address
lea Label_16Bit,%eax
push %rax
movw $0x8,0x4(%rsp)
lgdt _16Gdtr #bugbug: may not match.
lret
Label_16Bit:
.byte 0x66
movl $0xc0000080,%ecx
mov %rsi,%cr0 #disable PE & PG
rdmsr
and $0xfe,%ah
wrmsr #clear LME bit
mov %cr4,%rax
and $0xcf,%al #clear PAE & PSE
mov %rax,%cr4
lret
Label:
xor %rax,%rax
movl %ss,%eax
shl $0x4,%eax
add %esp,%eax
mov %r15,%rsp
lidt 0x58(%rsp)
movl %r12d,%ds
movl %r13d,%es
movl %r14d,%ss
popq %gs
popq %fs
pop %r15
pop %r14
pop %r13
pop %r12
pop %rdi
pop %rsi
pop %rbx
pop %rbp
retq
.align 0x10
_Code16Addr:
ASM_PFX(RealMode):
movl %edi,%ss
mov %bx,%sp #set up 16-bit stack
.byte 0x2e
.byte 0x0f
.byte 0x01
.byte 0x1e
.word _16Idtr - _Code16Addr #lidt _16Idtr
.byte 0x66
.byte 0x61 #popad
.byte 0x1f #pop ds
.byte 0x07 #pop es
popq %fs
popq %gs
add $0x8,%esp #skip RFLAGS
.byte 0x67 #test [esp + 0eh], 1
.byte 0xf7
.byte 0x44
.byte 0x24
.byte 0x0e
.byte 0x01
.byte 0x00
jz 1f
pushfq #pushf, actually
1:
.byte 0x0e #push cs
.byte 0x68 #push /iw
.word FarCallRet - _Code16Addr
jz 2f
.byte 0x66
ljmp *6(%esp)
2:
.byte 0x66
ljmp *4(%esp)
FarCallRet:
.byte 0x66
push $0x00 #push a dword of zero
.byte 0x66
pushf #pushfd, actually
pushq %gs
pushq %fs
.byte 0x06 #push %es
.byte 0x1e #push %ds
.byte 0x66
.byte 0x60
cli
.byte 0x66 #sizeof (IA32_REGS) = 13 * 4 = 52
lgdt 64(%esp) #lgdt (_STK16 ptr [esp + sizeof (IA32_REGS)]).SavedGdtr
.byte 0x66
mov 76(%esp), %eax
mov %rax, %cr4
.byte 0x66
mov $0xc0000080, %ecx
rdmsr
orb $1, %ah
wrmsr
.byte 0x66
mov 72(%esp), %eax
mov %rax, %cr0 #restore CR0
.byte 0x66
ljmpl *52(%esp)
_16Idtr:
.word 0x3ff #FWORD (1 SHL 10) - 1
.byte 0x00
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