1 files changed, 84 insertions, 0 deletions
diff --git a/UnixPkg/Library/UnixBaseLib/X64/DisablePaging64.asm b/UnixPkg/Library/UnixBaseLib/X64/DisablePaging64.asm
new file mode 100644
index 0000000000..32dcd5aa1f
--- /dev/null
+++ b/UnixPkg/Library/UnixBaseLib/X64/DisablePaging64.asm
@@ -0,0 +1,84 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
+; 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:
+;
+;   DisablePaging64.Asm
+;
+; Abstract:
+;
+;   AsmDisablePaging64 function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+    .code
+
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; InternalX86DisablePaging64 (
+;   IN      UINT16                    Cs,
+;   IN      UINT32                    EntryPoint,
+;   IN      UINT32                    Context1,  OPTIONAL
+;   IN      UINT32                    Context2,  OPTIONAL
+;   IN      UINT32                    NewStack
+;   );
+;------------------------------------------------------------------------------
+InternalX86DisablePaging64    PROC
+    cli
+    lea     rsi, @F                     ; rsi <- The start address of transition code
+    mov     edi, [rsp + 28h]            ; 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, 0fch
+    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      48h                         ; prefix to composite "retq" with next "retf"
+    retf                                ; Use far return to load CS register from stack
+
+; Start of transition code
+@@:
+    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, 0c0000080h
+    rdmsr
+    and     ah, NOT 1                   ; clear LME
+    wrmsr
+    mov     rax, cr4
+    and     al, NOT (1 SHL 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
+InternalX86DisablePaging64    ENDP
+
+mTransitionEnd LABEL    BYTE
+
+    END