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

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@8479 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 14 insertions, 3 deletions

diff --git a/MdePkg/Library/BaseLib/X64/DisablePaging64.S b/MdePkg/Library/BaseLib/X64/DisablePaging64.S
index 038af71..242c0a0 100644
--- a/MdePkg/Library/BaseLib/X64/DisablePaging64.S
+++ b/MdePkg/Library/BaseLib/X64/DisablePaging64.S
@@ -37,8 +37,19 @@
 

 ASM_GLOBAL ASM_PFX(InternalX86DisablePaging64)

 ASM_PFX(InternalX86DisablePaging64):

-    cli    

-    lea    L1(%rip), %r10

+    cli    
+    lea    L1(%rip), %rsi                 # rsi <- The start address of transition code
+    mov    0x28(%rsp), %rdi               # rdi <- New stack
+    sub    $64, %rdi                      # rdi <- use 64 byte in stack to hold transition code  
+    mov    %rdi, %r10                     # r10 <- The start address of transicition code below 4G
+    lea    _mTransitionEnd(%rip), %rax    # rax <- end of transition code
+    sub    %rsi, %rax                     # rax <- The size of transition piece code
+    push   %rcx                           # save rcx to stack
+    mov    %rax, %rcx                     # rcx <- The size of transition piece code
+    rep
+    movsb                                 # copy transition code to (new stack - 64byte) below 4G
+    pop    %rcx                           # restore rcx
+   

     mov    %r8d, %esi 

     mov    %r9d, %edi 

     mov    0x28(%rsp), %eax               # eax <- New Stack

@@ -64,4 +75,4 @@ L1:
     push   %rsi                           # push Context1

     callq  *%rbx                          # transfer control to EntryPoint

     jmp    .                              # no one should get here

-

+
_mTransitionEnd :