Fix the bug that if code is run above 4G, AsmDisablePaging64 will be failure.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@8478 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 15 insertions, 1 deletions

diff --git a/MdePkg/Library/BaseLib/X64/DisablePaging64.asm b/MdePkg/Library/BaseLib/X64/DisablePaging64.asm
index f11f6ff291..502a54c4e5 100644
--- a/MdePkg/Library/BaseLib/X64/DisablePaging64.asm
+++ b/MdePkg/Library/BaseLib/X64/DisablePaging64.asm
@@ -36,7 +36,17 @@
 ;------------------------------------------------------------------------------

 InternalX86DisablePaging64    PROC

     cli

-    lea     r10, @F

+    lea     rsi, @F                     ; rsi <- The start address of transition code

+    mov     rdi, [rsp + 28h]            ; rdi <- New stack

+    sub     rdi, 64                     ; rdi <- use 64 byte in stack to hold transition code  

+    mov     r10, rdi                    ; r10 <- The start address of transicition code below 4G

+    lea     rax, mTransitionEnd         ; rax <- end of transition code

+    sub     rax, rsi                    ; rax <- The size of transition piece code 

+    push    rcx                         ; save rcx to stack

+    mov     rcx, rax                    ; rcx <- The size of transition piece code

+    rep     movsb                       ; copy transition code to (new stack - 64byte) below 4G

+    pop     rcx                         ; restore rcx

+    

     mov     esi, r8d

     mov     edi, r9d

     mov     eax, [rsp + 28h]            ; eax <- New Stack

@@ -44,6 +54,8 @@ InternalX86DisablePaging64    PROC
     push    r10

     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

@@ -64,4 +76,6 @@ InternalX86DisablePaging64    PROC
     hlt                                 ; no one should get here

 InternalX86DisablePaging64    ENDP

 

+mTransitionEnd LABEL    BYTE

+

     END