MdePkg: Clean up source files

[mirror_edk2.git] / MdePkg / Library / BaseLib / X64 / DisablePaging64.S

diff --git a/MdePkg/Library/BaseLib/X64/DisablePaging64.S b/MdePkg/Library/BaseLib/X64/DisablePaging64.S
index 038af71d2f8b52de5db7fc9e1480b19d17424f51..220a59127b84d9c2606c91b664bbe2ab307fc137 100644 (file)
--- a/MdePkg/Library/BaseLib/X64/DisablePaging64.S
+++ b/MdePkg/Library/BaseLib/X64/DisablePaging64.S
@@ -1,10 +1,10 @@
 #------------------------------------------------------------------------------\r
 #\r
-# Copyright (c) 2006 - 2008, Intel Corporation\r
-# All rights reserved. This program and the accompanying materials\r
+# Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>\r
+# This program and the accompanying materials\r
 # are licensed and made available under the terms and conditions of the BSD License\r
 # which accompanies this distribution.  The full text of the license may be found at\r
-# http://opensource.org/licenses/bsd-license.php\r
+# http://opensource.org/licenses/bsd-license.php.\r
 #\r
 # THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
 # WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
@@ -21,7 +21,7 @@
 #\r
 #------------------------------------------------------------------------------\r
 \r
-    \r
+\r
 \r
 #------------------------------------------------------------------------------\r
 # VOID\r
@@ -37,26 +37,40 @@
 \r
 ASM_GLOBAL ASM_PFX(InternalX86DisablePaging64)\r
 ASM_PFX(InternalX86DisablePaging64):\r
-    cli    \r
-    lea    L1(%rip), %r10\r
-    mov    %r8d, %esi \r
-    mov    %r9d, %edi \r
-    mov    0x28(%rsp), %eax               # eax <- New Stack\r
+    cli\r
+    lea    L1(%rip), %rsi                 # rsi <- The start address of transition code\r
+    mov    0x28(%rsp), %edi               # rdi <- New stack\r
+    lea    _mTransitionEnd(%rip), %rax    # rax <- end of transition code\r
+    sub    %rsi, %rax                     # rax <- The size of transition piece code\r
+    add    $4, %rax                       # round rax up to the next 4 byte boundary\r
+    and    $0xfc, %al\r
+    sub    %rax, %rdi                     # rdi <- use stack to hold transition code\r
+    mov    %edi, %r10d                    # r10 <- The start address of transicition code below 4G\r
+    push   %rcx                           # save rcx to stack\r
+    mov    %rax, %rcx                     # rcx <- The size of transition piece code\r
+    rep\r
+    movsb                                 # copy transition code to (new stack - 64byte) below 4G\r
+    pop    %rcx                           # restore rcx\r
+\r
+    mov    %r8d, %esi\r
+    mov    %r9d, %edi\r
+    mov    %r10d, %eax\r
+    sub    $4, %eax\r
     push   %rcx                           # push Cs to stack\r
-    push   %r10\r
+    push   %r10                           # push address of transition code on stack\r
     .byte  0x48, 0xcb                     # retq: Use far return to load CS register from stack\r
-                                          # (Use raw byte code since some GNU assemblers generates incorrect code for "retq")  \r
+                                          # (Use raw byte code since some GNU assemblers generates incorrect code for "retq")\r
 L1:\r
     mov    %eax,%esp                      # set up new stack\r
     mov    %cr0,%rax\r
-    btr    $0x1f,%eax\r
+    btr    $0x1f,%eax                     # clear CR0.PG\r
     mov    %rax,%cr0                      # disable paging\r
 \r
-    mov    %rdx,%rbx                      # save EntryPoint to rbx, for rdmsr will overwrite rdx\r
+    mov    %edx,%ebx                      # save EntryPoint to ebx, for rdmsr will overwrite edx\r
     mov    $0xc0000080,%ecx\r
-    rdmsr  \r
+    rdmsr\r
     and    $0xfe,%ah                      # clear LME\r
-    wrmsr  \r
+    wrmsr\r
     mov    %cr4,%rax\r
     and    $0xdf,%al                      # clear PAE\r
     mov    %rax,%cr4\r
@@ -65,3 +79,4 @@ L1:
     callq  *%rbx                          # transfer control to EntryPoint\r
     jmp    .                              # no one should get here\r
 \r
+_mTransitionEnd :\r