diff options
Diffstat (limited to 'Core/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm')
| -rw-r--r-- | Core/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm | 263 |
1 files changed, 263 insertions, 0 deletions
diff --git a/Core/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm b/Core/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm new file mode 100644 index 0000000000..794d83159a --- /dev/null +++ b/Core/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm @@ -0,0 +1,263 @@ +
+#include "BaseLibInternals.h"
+
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006 - 2013, Intel Corporation. All rights reserved.<BR>
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution. The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+; Module Name:
+;
+; Thunk.asm
+;
+; Abstract:
+;
+; Real mode thunk
+;
+;------------------------------------------------------------------------------
+
+global ASM_PFX(m16Size)
+global ASM_PFX(mThunk16Attr)
+global ASM_PFX(m16Gdt)
+global ASM_PFX(m16GdtrBase)
+global ASM_PFX(mTransition)
+global ASM_PFX(m16Start)
+
+struc IA32_REGS
+
+ ._EDI: resd 1
+ ._ESI: resd 1
+ ._EBP: resd 1
+ ._ESP: resd 1
+ ._EBX: resd 1
+ ._EDX: resd 1
+ ._ECX: resd 1
+ ._EAX: resd 1
+ ._DS: resw 1
+ ._ES: resw 1
+ ._FS: resw 1
+ ._GS: resw 1
+ ._EFLAGS: resd 1
+ ._EIP: resd 1
+ ._CS: resw 1
+ ._SS: resw 1
+ .size:
+
+endstruc
+
+;; .const
+
+SECTION .data
+
+;
+; These are global constant to convey information to C code.
+;
+ASM_PFX(m16Size) DW ASM_PFX(InternalAsmThunk16) - ASM_PFX(m16Start)
+ASM_PFX(mThunk16Attr) DW _BackFromUserCode.ThunkAttrEnd - 4 - ASM_PFX(m16Start)
+ASM_PFX(m16Gdt) DW _NullSegDesc - ASM_PFX(m16Start)
+ASM_PFX(m16GdtrBase) DW _16GdtrBase - ASM_PFX(m16Start)
+ASM_PFX(mTransition) DW _EntryPoint - ASM_PFX(m16Start)
+
+SECTION .text
+
+ASM_PFX(m16Start):
+
+SavedGdt:
+ dw 0
+ dd 0
+
+;------------------------------------------------------------------------------
+; _BackFromUserCode() takes control in real mode after 'retf' has been executed
+; by user code. It will be shadowed to somewhere in memory below 1MB.
+;------------------------------------------------------------------------------
+_BackFromUserCode:
+ ;
+ ; The order of saved registers on the stack matches the order they appears
+ ; in IA32_REGS structure. This facilitates wrapper function to extract them
+ ; into that structure.
+ ;
+BITS 16
+ push ss
+ push cs
+ ;
+ ; Note: We can't use o32 on the next instruction because of a bug
+ ; in NASM 2.09.04 through 2.10rc1.
+ ;
+ call dword .Base ; push eip
+.Base:
+ pushfd
+ cli ; disable interrupts
+ push gs
+ push fs
+ push es
+ push ds
+ pushad
+ mov edx, strict dword 0
+.ThunkAttrEnd:
+ test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15
+ jz .1
+ mov ax, 2401h
+ int 15h
+ cli ; disable interrupts
+ jnc .2
+.1:
+ test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL
+ jz .2
+ in al, 92h
+ or al, 2
+ out 92h, al ; deactivate A20M#
+.2:
+ xor eax, eax
+ mov ax, ss
+ lea ebp, [esp + IA32_REGS.size]
+ mov [bp - IA32_REGS.size + IA32_REGS._ESP], ebp
+ mov bx, [bp - IA32_REGS.size + IA32_REGS._EIP]
+ shl eax, 4 ; shl eax, 4
+ add ebp, eax ; add ebp, eax
+ mov eax, strict dword 0
+.SavedCr4End:
+ mov cr4, eax
+o32 lgdt [cs:bx + (SavedGdt - .Base)]
+ mov eax, strict dword 0
+.SavedCr0End:
+ mov cr0, eax
+ mov ax, strict word 0
+.SavedSsEnd:
+ mov ss, eax
+ mov esp, strict dword 0
+.SavedEspEnd:
+o32 retf ; return to protected mode
+
+_EntryPoint:
+ DD _ToUserCode - ASM_PFX(m16Start)
+ DW 8h
+_16Idtr:
+ DW (1 << 10) - 1
+ DD 0
+_16Gdtr:
+ DW GdtEnd - _NullSegDesc - 1
+_16GdtrBase:
+ DD 0
+
+;------------------------------------------------------------------------------
+; _ToUserCode() takes control in real mode before passing control to user code.
+; It will be shadowed to somewhere in memory below 1MB.
+;------------------------------------------------------------------------------
+_ToUserCode:
+BITS 16
+ mov dx, ss
+ mov ss, cx ; set new segment selectors
+ mov ds, cx
+ mov es, cx
+ mov fs, cx
+ mov gs, cx
+ mov cr0, eax ; real mode starts at next instruction
+ ; which (per SDM) *must* be a far JMP.
+ jmp 0:strict word 0
+.RealAddrEnd:
+ mov cr4, ebp
+ mov ss, si ; set up 16-bit stack segment
+ xchg esp, ebx ; set up 16-bit stack pointer
+ mov bp, [esp + IA32_REGS.size]
+ mov [cs:bp + (_BackFromUserCode.SavedSsEnd - 2 - _BackFromUserCode)], dx
+ mov [cs:bp + (_BackFromUserCode.SavedEspEnd - 4 - _BackFromUserCode)], ebx
+ lidt [cs:bp + (_16Idtr - _BackFromUserCode)]
+
+ popad
+ pop ds
+ pop es
+ pop fs
+ pop gs
+ popfd
+
+o32 retf ; transfer control to user code
+
+ALIGN 16
+_NullSegDesc DQ 0
+_16CsDesc:
+ DW -1
+ DW 0
+ DB 0
+ DB 9bh
+ DB 8fh ; 16-bit segment, 4GB limit
+ DB 0
+_16DsDesc:
+ DW -1
+ DW 0
+ DB 0
+ DB 93h
+ DB 8fh ; 16-bit segment, 4GB limit
+ DB 0
+GdtEnd:
+
+;------------------------------------------------------------------------------
+; IA32_REGISTER_SET *
+; EFIAPI
+; InternalAsmThunk16 (
+; IN IA32_REGISTER_SET *RegisterSet,
+; IN OUT VOID *Transition
+; );
+;------------------------------------------------------------------------------
+global ASM_PFX(InternalAsmThunk16)
+ASM_PFX(InternalAsmThunk16):
+BITS 32
+ push ebp
+ push ebx
+ push esi
+ push edi
+ push ds
+ push es
+ push fs
+ push gs
+ mov esi, [esp + 36] ; esi <- RegSet, the 1st parameter
+ movzx edx, word [esi + IA32_REGS._SS]
+ mov edi, [esi + IA32_REGS._ESP]
+ add edi, - (IA32_REGS.size + 4) ; reserve stack space
+ mov ebx, edi ; ebx <- stack offset
+ imul eax, edx, 16 ; eax <- edx * 16
+ push IA32_REGS.size / 4
+ add edi, eax ; edi <- linear address of 16-bit stack
+ pop ecx
+ rep movsd ; copy RegSet
+ mov eax, [esp + 40] ; eax <- address of transition code
+ mov esi, edx ; esi <- 16-bit stack segment
+ lea edx, [eax + (_BackFromUserCode.SavedCr0End - ASM_PFX(m16Start))]
+ mov ecx, eax
+ and ecx, 0fh
+ shl eax, 12
+ lea ecx, [ecx + (_BackFromUserCode - ASM_PFX(m16Start))]
+ mov ax, cx
+ stosd ; [edi] <- return address of user code
+ add eax, _ToUserCode.RealAddrEnd - _BackFromUserCode
+ mov [edx + (_ToUserCode.RealAddrEnd - 4 - _BackFromUserCode.SavedCr0End)], eax
+ sgdt [edx + (SavedGdt - _BackFromUserCode.SavedCr0End)]
+ sidt [esp + 36] ; save IDT stack in argument space
+ mov eax, cr0
+ mov [edx - 4], eax ; save CR0 in _BackFromUserCode.SavedCr0End - 4
+ and eax, 7ffffffeh ; clear PE, PG bits
+ mov ebp, cr4
+ mov [edx + (_BackFromUserCode.SavedCr4End - 4 - _BackFromUserCode.SavedCr0End)], ebp
+ and ebp, ~30h ; clear PAE, PSE bits
+ push 10h
+ pop ecx ; ecx <- selector for data segments
+ lgdt [edx + (_16Gdtr - _BackFromUserCode.SavedCr0End)]
+ pushfd ; Save df/if indeed
+ call dword far [edx + (_EntryPoint - _BackFromUserCode.SavedCr0End)]
+ popfd
+ lidt [esp + 36] ; restore protected mode IDTR
+ lea eax, [ebp - IA32_REGS.size] ; eax <- the address of IA32_REGS
+ pop gs
+ pop fs
+ pop es
+ pop ds
+ pop edi
+ pop esi
+ pop ebx
+ pop ebp
+ ret
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