diff options
Diffstat (limited to 'MdePkg/Library/BaseLib/Ia32/Thunk16.S')
| -rw-r--r-- | MdePkg/Library/BaseLib/Ia32/Thunk16.S | 75 |
1 files changed, 34 insertions, 41 deletions
diff --git a/MdePkg/Library/BaseLib/Ia32/Thunk16.S b/MdePkg/Library/BaseLib/Ia32/Thunk16.S index 97b49f5a38..aad6bbe26b 100644 --- a/MdePkg/Library/BaseLib/Ia32/Thunk16.S +++ b/MdePkg/Library/BaseLib/Ia32/Thunk16.S @@ -19,16 +19,10 @@ #
#------------------------------------------------------------------------------
-.global _m16Start, _m16Size, _mThunk16Attr, _m16GdtrBase, _m16Gdt, _m16GdtrBase, _mTransition
+.global _m16Start, _m16Size, _mThunk16Attr, _m16Gdt, _m16GdtrBase, _mTransition
.global _InternalAsmThunk16
-#THUNK_ATTRIBUTE_BIG_REAL_MODE EQU 1
-#THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 EQU 2
-#THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL EQU 4
-
- .code:
-
-_m16Start:
+_m16Start:
SavedGdt: .space 6
@@ -37,7 +31,7 @@ _BackFromUserCode: push %cs
.byte 0x66
call @Base1 # push eip
-@Base1:
+@Base1:
pushfw # pushfd actually
cli # disable interrupts
push %gs
@@ -45,37 +39,37 @@ _BackFromUserCode: push %es
push %ds
pushaw # pushad actually
- .byte 0x66,0xba # mov edx, imm32
+ .byte 0x66, 0xba # mov edx, imm32
_ThunkAttr: .space 4
testb $THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15, %dl
jz @1
movl $0x15cd2401, %eax # mov ax, 2401h & int 15h
cli # disable interrupts
jnc @2
-@1:
+@1:
testb $THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL, %dl
jz @2
inb $0x92, %al
orb $2, %al
outb %al, $0x92 # deactivate A20M#
-@2:
+@2:
movl %ss, %eax
.byte 0x67, 0x66, 0x8d, 0x6c, 0x24, 0x34, 0x66
- mov %ebp,0xffffffd8(%esi)
- mov 0xfffffff8(%esi),%ebx
+ mov %ebp, 0xffffffd8(%esi)
+ mov 0xfffffff8(%esi), %ebx
shlw $4, %ax # shl eax, 4
addw %ax, %bp # add ebp, eax
- .byte 0x66,0xb8 # mov eax, imm32
+ .byte 0x66, 0xb8 # mov eax, imm32
SavedCr4: .space 4
movl %eax, %cr4
- lgdtw %cs:0xfffffff2(%edi)
- .byte 0x66,0xb8 # mov eax, imm32
+ lgdtw %cs:0xfffffff2(%edi)
+ .byte 0x66, 0xb8 # mov eax, imm32
SavedCr0: .space 4
movl %eax, %cr0
.byte 0xb8 # mov ax, imm16
SavedSs: .space 2
movl %eax, %ss
- .byte 0x66,0xbc # mov esp, imm32
+ .byte 0x66, 0xbc # mov esp, imm32
SavedEsp: .space 4
.byte 0x66
lret # return to protected mode
@@ -100,23 +94,23 @@ _ToUserCode: xchgw %bx, %sp # set up 16-bit stack pointer
.byte 0x66
call @Base # push eip
-@Base:
+@Base:
popw %bp # ebp <- offset @Base
addr16 pushl 36(%si)
.byte 0x36
- lea 0xc(%esi),%eax
- pushl %eax
+ lea 0xc(%esi), %eax
+ push %eax
lret
-@RealMode:
- mov %edx,%cs:0xffffffc5(%esi)
- mov %bx,%cs:0xffffffcb(%esi)
+@RealMode:
+ mov %edx, %cs:0xffffffc5(%esi)
+ mov %bx, %cs:0xffffffcb(%esi)
lidtw %cs:0xffffffd7(%esi)
popaw # popad actually
- popl %ds
- popl %es
- popl %fs
- popl %gs
+ pop %ds
+ pop %es
+ pop %fs
+ pop %gs
popfw # popfd
lretw # transfer control to user code
@@ -152,41 +146,41 @@ _InternalAsmThunk16: push %fs
push %gs
movl 36(%esp), %esi # esi <- RegSet
- movzwl 0x32(%esi),%edx
- mov 0xc(%esi),%edi
- add $0xffffffc8,%edi
+ movzwl 0x32(%esi), %edx
+ mov 0xc(%esi), %edi
+ add $0xffffffc8, %edi
movl %edi, %ebx # ebx <- stack offset
- imul $0x10,%edx,%eax
+ imul $0x10, %edx, %eax
push $0xd
addl %eax, %edi # edi <- linear address of 16-bit stack
- popl %ecx
+ pop %ecx
rep
movsl # copy RegSet
movl 40(%esp), %eax # eax <- address of transition code
movl %edx, %esi # esi <- 16-bit stack segment
- lea 0x5e(%eax),%edx
+ lea 0x5e(%eax), %edx
movl %eax, %ecx
andl $0xf, %ecx
shll $12, %eax
- lea 0x6(%ecx),%ecx
+ lea 0x6(%ecx), %ecx
movw %cx, %ax
stosl # [edi] <- return address of user code
- sgdtl 0xffffffa2(%edx)
+ sgdtl 0xffffffa2(%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, 0xfffffff1(%edx)
andl $0x300, %ebp # clear all but PCE and OSFXSR bits
pushl $0x10
- popl %ecx # ecx <- selector for data segments
+ pop %ecx # ecx <- selector for data segments
lgdtl 0x20(%edx)
pushfl
lcall *0x14(%edx)
popfl
lidtl 0x24(%esp)
- lea 0xffffffcc(%ebp),%eax
+ lea 0xffffffcc(%ebp), %eax
pop %gs
pop %fs
pop %es
@@ -197,11 +191,10 @@ _InternalAsmThunk16: pop %ebp
ret
- .const:
+ .const:
_m16Size: .word _InternalAsmThunk16 - _m16Start
_mThunk16Attr: .word _ThunkAttr - _m16Start
_m16Gdt: .word _NullSegDesc - _m16Start
_m16GdtrBase: .word _16GdtrBase - _m16Start
_mTransition: .word _EntryPoint - _m16Start
-
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