+\r
+#include "BaseLibInternals.h"\r
+\r
;------------------------------------------------------------------------------\r
;\r
-; Copyright (c) 2006, Intel Corporation\r
+; Copyright (c) 2006 - 2008, Intel Corporation\r
; All rights reserved. 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
EXTERNDEF C m16GdtrBase:WORD\r
EXTERNDEF C mTransition:WORD\r
\r
-THUNK_ATTRIBUTE_BIG_REAL_MODE EQU 1\r
-THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 EQU 2\r
-THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL EQU 4\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
\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
+ ;\r
+ ; The order of saved registers on the stack matches the order they appears\r
+ ; in IA32_REGS structure. This facilitates wrapper function to extract them\r
+ ; into that structure.\r
+ ;\r
push ss\r
push cs\r
DB 66h\r
mov eax, ss\r
DB 67h\r
lea bp, [esp + sizeof (IA32_REGS)]\r
+ ;\r
+ ; esi's in the following 2 instructions are indeed bp in 16-bit code. Fact\r
+ ; is "esi" in 32-bit addressing mode has the same encoding of "bp" in 16-\r
+ ; bit addressing mode.\r
+ ;\r
mov word ptr (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._ESP, bp\r
mov ebx, (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._EIP\r
shl ax, 4 ; shl eax, 4\r
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
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
DB 66h\r
call @Base ; push eip\r
@Base:\r
- pop bp ; ebp <- offset @Base\r
- mov cs:[esi + (offset SavedSs - offset @Base)], edx\r
- mov cs:[esi + (offset SavedEsp - offset @Base)], bx\r
+ pop bp ; ebp <- address of @Base\r
+ DB 67h ; address size override\r
+ push [esp + sizeof (IA32_REGS) + 2]\r
+ lea eax, [esi + (@RealMode - @Base)]\r
+ push eax\r
+ retf\r
+@RealMode:\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
pop fs\r
pop gs\r
popf ; popfd\r
- DB 66h\r
+ DB 66h ; Use 32-bit addressing for "retf" below\r
retf ; transfer control to user code\r
_ToUserCode ENDP\r
\r
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
+ mov esi, [esp + 36] ; esi <- RegSet, the 1st parameter\r
movzx edx, (IA32_REGS ptr [esi])._SS\r
mov edi, (IA32_REGS ptr [esi])._ESP\r
add edi, - (sizeof (IA32_REGS) + 4) ; reserve stack space\r
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
- call fword ptr [edx + (offset _EntryPoint - offset SavedCr0)]\r
+ lgdt fword ptr [edx + (_16Gdtr - SavedCr0)]\r
+ pushfd ; Save df/if indeed\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
+ lea eax, [ebp - sizeof (IA32_REGS)] ; eax <- the address of IA32_REGS\r
ret\r
InternalAsmThunk16 ENDP\r
\r
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