diff options
| -rw-r--r-- | MdePkg/Library/BaseLib/X64/Thunk16.asm | 64 |
1 files changed, 40 insertions, 24 deletions
diff --git a/MdePkg/Library/BaseLib/X64/Thunk16.asm b/MdePkg/Library/BaseLib/X64/Thunk16.asm index 2c35c72a57..631b0fd1e1 100644 --- a/MdePkg/Library/BaseLib/X64/Thunk16.asm +++ b/MdePkg/Library/BaseLib/X64/Thunk16.asm @@ -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
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