From fe2876127550a7c8a0e7d2d0f47203154a5d6969 Mon Sep 17 00:00:00 2001
From: lgao4 <lgao4@6f19259b-4bc3-4df7-8a09-765794883524>
Date: Tue, 20 Dec 2011 09:50:19 +0000
Subject: Clean up the hard code offset in MdePkg BaseLib Ia32 Thunk16.S and
 EcpPkg GlueLib BaseLib Ia32 Thunk16.S. Signed-off-by: lgao4 Reviewed-by:
 rsun3

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12889 6f19259b-4bc3-4df7-8a09-765794883524
---
 MdePkg/Library/BaseLib/Ia32/Thunk16.S | 63 ++++++++++++++++++++++++-----------
 1 file changed, 43 insertions(+), 20 deletions(-)

(limited to 'MdePkg/Library/BaseLib')

diff --git a/MdePkg/Library/BaseLib/Ia32/Thunk16.S b/MdePkg/Library/BaseLib/Ia32/Thunk16.S
index d45a0d40b1..2cb781582a 100644
--- a/MdePkg/Library/BaseLib/Ia32/Thunk16.S
+++ b/MdePkg/Library/BaseLib/Ia32/Thunk16.S
@@ -24,6 +24,27 @@
 ASM_GLOBAL ASM_PFX(m16Start), ASM_PFX(m16Size), ASM_PFX(mThunk16Attr), ASM_PFX(m16Gdt), ASM_PFX(m16GdtrBase), ASM_PFX(mTransition)
 ASM_GLOBAL ASM_PFX(InternalAsmThunk16)
 
+# define the structure of IA32_REGS
+.set  _EDI, 0       #size 4
+.set  _ESI, 4       #size 4
+.set  _EBP, 8       #size 4
+.set  _ESP, 12      #size 4
+.set  _EBX, 16      #size 4
+.set  _EDX, 20      #size 4
+.set  _ECX, 24      #size 4
+.set  _EAX, 28      #size 4
+.set  _DS,  32      #size 2
+.set  _ES,  34      #size 2
+.set  _FS,  36      #size 2
+.set  _GS,  38      #size 2
+.set  _EFLAGS, 40   #size 4
+.set  _EIP, 44      #size 4
+.set  _CS, 48       #size 2
+.set  _SS, 50       #size 2
+.set  IA32_REGS_SIZE, 52
+
+    .text
+
 ASM_PFX(m16Start):
 
 SavedGdt:     .space  6
@@ -57,15 +78,17 @@ ASM_PFX(ThunkAttr): .space  4
 2:
     xorw    %ax, %ax                    # xor eax, eax
     movl    %ss, %eax                   # mov ax, ss
-    .byte   0x67, 0x66, 0x8d, 0x6c, 0x24, 0x34, 0x66
-    mov     %ebp, 0xffffffd8(%esi)
-    mov     0xfffffff8(%esi), %ebx
+    .byte   0x67
+    lea     IA32_REGS_SIZE(%esp), %bp
+    .byte   0x66
+    mov     %ebp, (_ESP - IA32_REGS_SIZE)(%esi)
+    mov     (_EIP - IA32_REGS_SIZE)(%esi), %ebx
     shlw    $4, %ax                     # shl eax, 4
     addw    %ax, %bp                    # add ebp, eax
     .byte   0x66, 0xb8                   # mov eax, imm32
 SavedCr4:   .space  4
     movl    %eax, %cr4
-    lgdtw   %cs:0xfffffff2(%edi)
+    lgdtw   %cs:(SavedGdt - L_Base1)(%edi)
     .byte   0x66, 0xb8                   # mov eax, imm32
 SavedCr0:   .space  4
     movl    %eax, %cr0
@@ -100,15 +123,15 @@ ASM_PFX(ToUserCode):
 L_Base:
     popw    %bp                         # ebp <- offset L_Base
     .byte   0x67;                       # address size override
-    push    54(%esp)
-    lea     0xc(%esi), %eax
+    push    (IA32_REGS_SIZE + 2)(%esp)
+    lea     (L_RealMode - L_Base)(%esi), %eax
     push    %eax
     lret
 
 L_RealMode:
-    mov     %edx, %cs:0xffffffc5(%esi)
-    mov     %bx, %cs:0xffffffcb(%esi)
-    lidtw   %cs:0xffffffd7(%esi)
+    mov     %edx, %cs:(SavedSs - L_Base)(%esi)
+    mov     %bx, %cs:(SavedEsp - L_Base)(%esi)
+    lidtw   %cs:(_16Idtr - L_Base)(%esi)
     popaw                               # popad actually
     pop     %ds
     pop     %es
@@ -149,41 +172,41 @@ ASM_PFX(InternalAsmThunk16):
     push    %fs
     push    %gs
     movl    36(%esp), %esi              # esi <- RegSet
-    movzwl  0x32(%esi), %edx
-    mov     0xc(%esi), %edi
-    add     $0xffffffc8, %edi
+    movzwl  _SS(%esi), %edx
+    mov     _ESP(%esi), %edi
+    add     $(-(IA32_REGS_SIZE + 4)), %edi
     movl    %edi, %ebx                  # ebx <- stack offset
     imul    $0x10, %edx, %eax
-    push    $0xd
+    push    $(IA32_REGS_SIZE / 4)
     addl    %eax, %edi                  # edi <- linear address of 16-bit stack
     pop     %ecx
     rep
     movsl                               # copy RegSet
     movl    40(%esp), %eax              # eax <- address of transition code
     movl    %edx, %esi                  # esi <- 16-bit stack segment
-    lea     0x5f(%eax), %edx
+    lea     (SavedCr0 - ASM_PFX(m16Start))(%eax), %edx
     movl    %eax, %ecx
     andl    $0xf, %ecx
     shll    $12, %eax
-    lea     0x6(%ecx), %ecx
+    lea     (ASM_PFX(BackFromUserCode) - ASM_PFX(m16Start))(%ecx), %ecx
     movw    %cx, %ax
     stosl                               # [edi] <- return address of user code
-    sgdtl   0xffffffa1(%edx)
+    sgdtl   (SavedGdt - SavedCr0)(%edx)
     sidtl   0x24(%esp)
     movl    %cr0, %eax
     movl    %eax, (%edx)                # save CR0 in SavedCr0
     andl    $0x7ffffffe, %eax           # clear PE, PG bits
     movl    %cr4, %ebp
-    mov     %ebp, 0xfffffff1(%edx)
+    mov     %ebp, (SavedCr4 - SavedCr0)(%edx)
     andl    $0x300, %ebp                # clear all but PCE and OSFXSR bits
     pushl   $0x10
     pop     %ecx                        # ecx <- selector for data segments
-    lgdtl   0x20(%edx)
+    lgdtl   (_16Gdtr - SavedCr0)(%edx)
     pushfl
-    lcall   *0x14(%edx)
+    lcall   *(_EntryPoint - SavedCr0)(%edx)
     popfl
     lidtl   0x24(%esp)
-    lea     0xffffffcc(%ebp), %eax
+    lea     -IA32_REGS_SIZE(%ebp), %eax
     pop     %gs
     pop     %fs
     pop     %es
-- 
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