;------------------------------------------------------------------------------ | |
; | |
; Copyright (c) 2006 - 2022, Intel Corporation. All rights reserved.<BR> | |
; SPDX-License-Identifier: BSD-2-Clause-Patent | |
; | |
; Module Name: | |
; | |
; DisablePaging64.Asm | |
; | |
; Abstract: | |
; | |
; AsmDisablePaging64 function | |
; | |
; Notes: | |
; | |
;------------------------------------------------------------------------------ | |
DEFAULT REL | |
SECTION .text | |
;------------------------------------------------------------------------------ | |
; VOID | |
; EFIAPI | |
; InternalX86DisablePaging64 ( | |
; IN UINT16 Cs, | |
; IN UINT32 EntryPoint, | |
; IN UINT32 Context1, OPTIONAL | |
; IN UINT32 Context2, OPTIONAL | |
; IN UINT32 NewStack | |
; ); | |
;------------------------------------------------------------------------------ | |
global ASM_PFX(InternalX86DisablePaging64) | |
ASM_PFX(InternalX86DisablePaging64): | |
cli | |
lea rsi, [.0] ; rsi <- The start address of transition code | |
mov edi, [rsp + 0x28] ; rdi <- New stack | |
lea rax, [mTransitionEnd] ; rax <- end of transition code | |
sub rax, rsi ; rax <- The size of transition piece code | |
add rax, 4 ; Round RAX up to the next 4 byte boundary | |
and al, 0xfc | |
sub rdi, rax ; rdi <- Use stack to hold transition code | |
mov r10d, edi ; r10 <- The start address of transicition code below 4G | |
push rcx ; save rcx to stack | |
mov rcx, rax ; rcx <- The size of transition piece code | |
rep movsb ; copy transition code to top of new stack which must be below 4GB | |
pop rcx ; restore rcx | |
mov esi, r8d | |
mov edi, r9d | |
mov eax, r10d ; eax <- start of the transition code on the stack | |
sub eax, 4 ; eax <- One slot below transition code on the stack | |
push rcx ; push Cs to stack | |
push r10 ; push address of tansition code on stack | |
retfq | |
; Start of transition code | |
.0: | |
mov esp, eax ; set up new stack | |
mov rax, cr0 | |
btr eax, 31 ; Clear CR0.PG | |
mov cr0, rax ; disable paging and caches | |
mov ebx, edx ; save EntryPoint to rbx, for rdmsr will overwrite rdx | |
mov ecx, 0xc0000080 | |
rdmsr | |
and ah, ~ 1 ; clear LME | |
wrmsr | |
mov rax, cr4 | |
and al, ~ (1 << 5) ; clear PAE | |
mov cr4, rax | |
push rdi ; push Context2 | |
push rsi ; push Context1 | |
call rbx ; transfer control to EntryPoint | |
hlt ; no one should get here | |
mTransitionEnd: | |