MdePkg/Library/BaseLib/X64/DisablePaging64.nasm

   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