;------------------------------------------------------------------------------ ; ; Copyright (c) 2006 - 2008, 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 DB 0x48 ; prefix to composite "retq" with next "retf" retf ; Use far return to load CS register from stack ; 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: