1 ;------------------------------------------------------------------------------ 2 ; 3 ; Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR> 4 ; This program and the accompanying materials 5 ; are licensed and made available under the terms and conditions of the BSD License 6 ; which accompanies this distribution. The full text of the license may be found at 7 ; http://opensource.org/licenses/bsd-license.php. 8 ; 9 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 10 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. 11 ; 12 ; Module Name: 13 ; 14 ; DisablePaging64.Asm 15 ; 16 ; Abstract: 17 ; 18 ; AsmDisablePaging64 function 19 ; 20 ; Notes: 21 ; 22 ;------------------------------------------------------------------------------ 23 24 DEFAULT REL 25 SECTION .text 26 27 ;------------------------------------------------------------------------------ 28 ; VOID 29 ; EFIAPI 30 ; InternalX86DisablePaging64 ( 31 ; IN UINT16 Cs, 32 ; IN UINT32 EntryPoint, 33 ; IN UINT32 Context1, OPTIONAL 34 ; IN UINT32 Context2, OPTIONAL 35 ; IN UINT32 NewStack 36 ; ); 37 ;------------------------------------------------------------------------------ 38 global ASM_PFX(InternalX86DisablePaging64) 39 ASM_PFX(InternalX86DisablePaging64): 40 cli 41 lea rsi, [.0] ; rsi <- The start address of transition code 42 mov edi, [rsp + 0x28] ; rdi <- New stack 43 lea rax, [mTransitionEnd] ; rax <- end of transition code 44 sub rax, rsi ; rax <- The size of transition piece code 45 add rax, 4 ; Round RAX up to the next 4 byte boundary 46 and al, 0xfc 47 sub rdi, rax ; rdi <- Use stack to hold transition code 48 mov r10d, edi ; r10 <- The start address of transicition code below 4G 49 push rcx ; save rcx to stack 50 mov rcx, rax ; rcx <- The size of transition piece code 51 rep movsb ; copy transition code to top of new stack which must be below 4GB 52 pop rcx ; restore rcx 53 54 mov esi, r8d 55 mov edi, r9d 56 mov eax, r10d ; eax <- start of the transition code on the stack 57 sub eax, 4 ; eax <- One slot below transition code on the stack 58 push rcx ; push Cs to stack 59 push r10 ; push address of tansition code on stack 60 DB 0x48 ; prefix to composite "retq" with next "retf" 61 retf ; Use far return to load CS register from stack 62 63 ; Start of transition code 64 .0: 65 mov esp, eax ; set up new stack 66 mov rax, cr0 67 btr eax, 31 ; Clear CR0.PG 68 mov cr0, rax ; disable paging and caches 69 70 mov ebx, edx ; save EntryPoint to rbx, for rdmsr will overwrite rdx 71 mov ecx, 0xc0000080 72 rdmsr 73 and ah, ~ 1 ; clear LME 74 wrmsr 75 mov rax, cr4 76 and al, ~ (1 << 5) ; clear PAE 77 mov cr4, rax 78 push rdi ; push Context2 79 push rsi ; push Context1 80 call rbx ; transfer control to EntryPoint 81 hlt ; no one should get here 82 83 mTransitionEnd: 84 85
