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audk
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Added an extra GDT entry to the GDT used by thunk code. SS register will always be loaded as flat segment before switching to 16-bit mode, since SS might not be always valid for NULL selector is allowed in 64-bit mode. 

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@1541 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
bxing 2006-09-14 16:04:47 +00:00
parent 0f008d9ad4
commit f23d790a79
1 changed files with 40 additions and 24 deletions
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64
MdePkg/Library/BaseLib/X64/Thunk16.asm
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@ -49,7 +49,7 @@ IA32_REGS ENDS
m16Size DW InternalAsmThunk16 - m16Start
mThunk16Attr DW _ThunkAttr - m16Start
m16Gdt DW _NullSegDesc - m16Start
m16Gdt DW _NullSeg - m16Start
m16GdtrBase DW _16GdtrBase - m16Start
mTransition DW _EntryPoint - m16Start
@ -123,10 +123,10 @@ SavedEsp DD ?
_BackFromUserCode ENDP
_EntryPoint DD _ToUserCode - m16Start
DW 8h
DW CODE16
_16Gdtr LABEL FWORD
DW GdtEnd - _NullSegDesc - 1
_16GdtrBase DQ _NullSegDesc
DW GDT_SIZE - 1
_16GdtrBase DQ _NullSeg
_16Idtr FWORD (1 SHL 10) - 1
;------------------------------------------------------------------------------
@ -134,7 +134,6 @@ _16Idtr FWORD (1 SHL 10) - 1
; It will be shadowed to somewhere in memory below 1MB.
;------------------------------------------------------------------------------
_ToUserCode PROC
mov edi, ss
mov ss, edx ; set new segment selectors
mov ds, edx
mov es, edx
@ -158,8 +157,9 @@ _ToUserCode PROC
push rax
retf
@RealMode:
DB 6ah, DATA32
DB 2eh ; cs:
mov [rsi + (SavedSs - @Base)], edi
pop [rsi + (SavedSs - @Base)]
DB 2eh ; cs:
mov [rsi + (SavedEsp - @Base)], bx
DB 66h, 2eh ; CS and operand size override
@ -175,22 +175,34 @@ _ToUserCode PROC
retf ; transfer control to user code
_ToUserCode ENDP
_NullSegDesc DQ 0
_16CsDesc LABEL QWORD
DW -1
DW 0
DB 0
DB 9bh
DB 8fh ; 16-bit segment, 4GB limit
DB 0
_16DsDesc LABEL QWORD
DW -1
DW 0
DB 0
DB 93h
DB 8fh ; 16-bit segment, 4GB limit
DB 0
GdtEnd LABEL QWORD
CODE16 = _16Code - $
DATA16 = _16Data - $
DATA32 = _32Data - $
_NullSeg DQ 0
_16Code LABEL QWORD
DW -1
DW 0
DB 0
DB 9bh
DB 8fh ; 16-bit segment, 4GB limit
DB 0
_16Data LABEL QWORD
DW -1
DW 0
DB 0
DB 93h
DB 8fh ; 16-bit segment, 4GB limit
DB 0
_32Data LABEL QWORD
DW -1
DW 0
DB 0
DB 93h
DB 0cfh ; 16-bit segment, 4GB limit
DB 0
GDT_SIZE = $ - _NullSeg
;------------------------------------------------------------------------------
; IA32_REGISTER_SET *
@ -203,6 +215,7 @@ GdtEnd LABEL QWORD
InternalAsmThunk16 PROC USES rbp rbx rsi rdi
mov r10d, ds
mov r11d, es
mov r9d, ss
push fs
push gs
mov rsi, rcx
@ -231,16 +244,19 @@ InternalAsmThunk16 PROC USES rbp rbx rsi rdi
mov [rcx], ebp ; save CR4 in SavedCr4
and ebp, 300h ; clear all but PCE and OSFXSR bits
mov esi, r8d ; esi <- 16-bit stack segment
push 10h
pop rdx ; rdx <- selector for data segments
DB 6ah, DATA32 ; push DATA32
pop rdx ; rdx <- 32-bit data segment selector
lgdt fword ptr [rcx + (_16Gdtr - SavedCr4)]
mov ss, edx
pushfq
lea edx, [rdx + DATA16 - DATA32]
call fword ptr [rcx + (_EntryPoint - SavedCr4)]
popfq
lidt fword ptr [rsp + 38h] ; restore protected mode IDTR
lea eax, [rbp - sizeof (IA32_REGS)]
pop gs
pop fs
mov ss, r9d
mov es, r11d
mov ds, r10d
ret