1. Updated function headers in all assembly files.

[mirror_edk2.git] / MdePkg / Library / BaseLib / Ia32 / Thunk16.asm

diff --git a/MdePkg/Library/BaseLib/Ia32/Thunk16.asm b/MdePkg/Library/BaseLib/Ia32/Thunk16.asm
index 4d5b47017d47fd603f17ff8b01a74cf2409571f7..5e357991271d07efb15e95075027833d4075512a 100644 (file)
--- a/MdePkg/Library/BaseLib/Ia32/Thunk16.asm
+++ b/MdePkg/Library/BaseLib/Ia32/Thunk16.asm
@@ -29,6 +29,10 @@ EXTERNDEF   C   m16Gdt:WORD
 EXTERNDEF   C   m16GdtrBase:WORD\r
 EXTERNDEF   C   mTransition:WORD\r
 \r
+;\r
+; Here is the layout of the real mode stack. _ToUserCode() is responsible for\r
+; loading all these registers from real mode stack.\r
+;\r
 IA32_REGS   STRUC   4t\r
 _EDI        DD      ?\r
 _ESI        DD      ?\r
@@ -50,20 +54,26 @@ IA32_REGS   ENDS
 \r
     .const\r
 \r
-m16Size         DW      offset InternalAsmThunk16 - offset m16Start\r
-mThunk16Attr    DW      offset _ThunkAttr - offset m16Start\r
-m16Gdt          DW      offset _NullSegDesc - offset m16Start\r
-m16GdtrBase     DW      offset _16GdtrBase - offset m16Start\r
-mTransition     DW      offset _EntryPoint - offset m16Start\r
+;\r
+; These are global constant to convey information to C code.\r
+;\r
+m16Size         DW      InternalAsmThunk16 - m16Start\r
+mThunk16Attr    DW      _ThunkAttr - m16Start\r
+m16Gdt          DW      _NullSegDesc - m16Start\r
+m16GdtrBase     DW      _16GdtrBase - m16Start\r
+mTransition     DW      _EntryPoint - m16Start\r
 \r
     .code\r
 \r
 m16Start    LABEL   BYTE\r
 \r
-SavedGdt        LABEL   FWORD\r
-                DW      ?\r
-                DD      ?\r
-\r
+SavedGdt    LABEL   FWORD\r
+            DW      ?\r
+            DD      ?\r
+;------------------------------------------------------------------------------\r
+; _BackFromUserCode() takes control in real mode after 'retf' has been executed\r
+; by user code. It will be shadowed to somewhere in memory below 1MB.\r
+;------------------------------------------------------------------------------\r
 _BackFromUserCode   PROC\r
     push    ss\r
     push    cs\r
@@ -102,7 +112,7 @@ _ThunkAttr  DD      ?
 SavedCr4    DD      ?\r
     mov     cr4, eax\r
     DB      66h\r
-    lgdt    fword ptr cs:[edi + (offset SavedGdt - offset @Base)]\r
+    lgdt    fword ptr cs:[edi + (SavedGdt - @Base)]\r
     DB      66h, 0b8h                   ; mov eax, imm32\r
 SavedCr0    DD      ?\r
     mov     cr0, eax\r
@@ -115,13 +125,17 @@ SavedEsp    DD      ?
     retf                                ; return to protected mode\r
 _BackFromUserCode   ENDP\r
 \r
-_EntryPoint     DD      offset _ToUserCode - offset m16Start\r
-                DW      8h\r
-_16Idtr         FWORD   (1 SHL 10) - 1\r
-_16Gdtr         LABEL   FWORD\r
-                DW      offset GdtEnd - offset _NullSegDesc - 1\r
-_16GdtrBase     DD      offset _NullSegDesc\r
+_EntryPoint DD      _ToUserCode - m16Start\r
+            DW      8h\r
+_16Idtr     FWORD   (1 SHL 10) - 1\r
+_16Gdtr     LABEL   FWORD\r
+            DW      GdtEnd - _NullSegDesc - 1\r
+_16GdtrBase DD      _NullSegDesc\r
 \r
+;------------------------------------------------------------------------------\r
+; _ToUserCode() takes control in real mode before passing control to user code.\r
+; It will be shadowed to somewhere in memory below 1MB.\r
+;------------------------------------------------------------------------------\r
 _ToUserCode PROC\r
     mov     edx, ss\r
     mov     ss, ecx                     ; set new segment selectors\r
@@ -136,17 +150,17 @@ _ToUserCode PROC
     DB      66h\r
     call    @Base                       ; push eip\r
 @Base:\r
-    pop     bp                          ; ebp <- offset @Base\r
+    pop     bp                          ; ebp <- address of @Base\r
     DB      67h                         ; address size override\r
     push    [esp + sizeof (IA32_REGS) + 2]\r
-    lea     eax, [esi + (offset @RealMode - offset @Base)]\r
+    lea     eax, [esi + (@RealMode - @Base)]\r
     push    eax\r
     retf\r
 @RealMode:\r
-    mov     cs:[esi + (offset SavedSs - offset @Base)], edx\r
-    mov     cs:[esi + (offset SavedEsp - offset @Base)], bx\r
+    mov     cs:[esi + (SavedSs - @Base)], edx\r
+    mov     cs:[esi + (SavedEsp - @Base)], bx\r
     DB      66h\r
-    lidt    fword ptr cs:[esi + (offset _16Idtr - offset @Base)]\r
+    lidt    fword ptr cs:[esi + (_16Idtr - @Base)]\r
     popaw                               ; popad actually\r
     pop     ds\r
     pop     es\r
@@ -174,11 +188,14 @@ _16DsDesc       LABEL   QWORD
                 DB      0\r
 GdtEnd          LABEL   QWORD\r
 \r
-;\r
-;   @param  RegSet  Pointer to a IA32_DWORD_REGS structure\r
-;   @param  Transition  Pointer to the transition code\r
-;   @return The address of the 16-bit stack after returning from user code\r
-;\r
+;------------------------------------------------------------------------------\r
+; IA32_REGISTER_SET *\r
+; EFIAPI\r
+; InternalAsmThunk16 (\r
+;   IN      IA32_REGISTER_SET         *RegisterSet,\r
+;   IN OUT  VOID                      *Transition\r
+;   );\r
+;------------------------------------------------------------------------------\r
 InternalAsmThunk16  PROC    USES    ebp ebx esi edi ds  es  fs  gs\r
     mov     esi, [esp + 36]             ; esi <- RegSet\r
     movzx   edx, (IA32_REGS ptr [esi])._SS\r
@@ -192,26 +209,26 @@ InternalAsmThunk16  PROC    USES    ebp ebx esi edi ds  es  fs  gs
     rep     movsd                       ; copy RegSet\r
     mov     eax, [esp + 40]             ; eax <- address of transition code\r
     mov     esi, edx                    ; esi <- 16-bit stack segment\r
-    lea     edx, [eax + (offset SavedCr0 - offset m16Start)]\r
+    lea     edx, [eax + (SavedCr0 - m16Start)]\r
     mov     ecx, eax\r
     and     ecx, 0fh\r
     shl     eax, 12\r
-    lea     ecx, [ecx + (offset _BackFromUserCode - offset m16Start)]\r
+    lea     ecx, [ecx + (_BackFromUserCode - m16Start)]\r
     mov     ax, cx\r
     stosd                               ; [edi] <- return address of user code\r
-    sgdt    fword ptr [edx + (offset SavedGdt - offset SavedCr0)]\r
+    sgdt    fword ptr [edx + (SavedGdt - SavedCr0)]\r
     sidt    fword ptr [esp + 36]        ; save IDT stack in argument space\r
     mov     eax, cr0\r
     mov     [edx], eax                  ; save CR0 in SavedCr0\r
     and     eax, 7ffffffeh              ; clear PE, PG bits\r
     mov     ebp, cr4\r
-    mov     [edx + (offset SavedCr4 - offset SavedCr0)], ebp\r
+    mov     [edx + (SavedCr4 - SavedCr0)], ebp\r
     and     ebp, 300h                   ; clear all but PCE and OSFXSR bits\r
     push    10h\r
     pop     ecx                         ; ecx <- selector for data segments\r
-    lgdt    fword ptr [edx + (offset _16Gdtr - offset SavedCr0)]\r
+    lgdt    fword ptr [edx + (_16Gdtr - SavedCr0)]\r
     pushfd\r
-    call    fword ptr [edx + (offset _EntryPoint - offset SavedCr0)]\r
+    call    fword ptr [edx + (_EntryPoint - SavedCr0)]\r
     popfd\r
     lidt    fword ptr [esp + 36]        ; restore protected mode IDTR\r
     lea     eax, [ebp - sizeof (IA32_REGS)]\r