diff options
Diffstat (limited to 'MdePkg/Library/BaseLib/Ia32/Thunk16.asm')
| -rw-r--r-- | MdePkg/Library/BaseLib/Ia32/Thunk16.asm | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/MdePkg/Library/BaseLib/Ia32/Thunk16.asm b/MdePkg/Library/BaseLib/Ia32/Thunk16.asm new file mode 100644 index 000000000000..9311c1161f0e --- /dev/null +++ b/MdePkg/Library/BaseLib/Ia32/Thunk16.asm @@ -0,0 +1,260 @@ + +#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 +; +;------------------------------------------------------------------------------ + + .686p + .model flat,C + +EXTERNDEF C m16Start:BYTE +EXTERNDEF C m16Size:WORD +EXTERNDEF C mThunk16Attr:WORD +EXTERNDEF C m16Gdt:WORD +EXTERNDEF C m16GdtrBase:WORD +EXTERNDEF C mTransition:WORD + +; +; Here is the layout of the real mode stack. _ToUserCode() is responsible for +; loading all these registers from real mode stack. +; +IA32_REGS STRUC 4t +_EDI DD ? +_ESI DD ? +_EBP DD ? +_ESP DD ? +_EBX DD ? +_EDX DD ? +_ECX DD ? +_EAX DD ? +_DS DW ? +_ES DW ? +_FS DW ? +_GS DW ? +_EFLAGS DD ? +_EIP DD ? +_CS DW ? +_SS DW ? +IA32_REGS ENDS + + .const + +; +; These are global constant to convey information to C code. +; +m16Size DW InternalAsmThunk16 - m16Start +mThunk16Attr DW _ThunkAttr - m16Start +m16Gdt DW _NullSegDesc - m16Start +m16GdtrBase DW _16GdtrBase - m16Start +mTransition DW _EntryPoint - m16Start + + .code + +m16Start LABEL BYTE + +SavedGdt LABEL FWORD + DW ? + DD ? +;------------------------------------------------------------------------------ +; _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 PROC + ; + ; 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. + ; + push ss + push cs + DB 66h + call @Base ; push eip +@Base: + pushf ; pushfd actually + cli ; disable interrupts + push gs + push fs + push es + push ds + pushaw ; pushad actually + DB 66h, 0bah ; mov edx, imm32 +_ThunkAttr DD ? + test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 + jz @1 + mov eax, 15cd2401h ; 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 ax, ax ; xor eax, eax + mov eax, ss ; mov ax, ss + DB 67h + lea bp, [esp + sizeof (IA32_REGS)] + ; + ; esi's in the following 2 instructions are indeed bp in 16-bit code. Fact + ; is "esi" in 32-bit addressing mode has the same encoding of "bp" in 16- + ; bit addressing mode. + ; + mov word ptr (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._ESP, bp + mov ebx, (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._EIP + shl ax, 4 ; shl eax, 4 + add bp, ax ; add ebp, eax + DB 66h, 0b8h ; mov eax, imm32 +SavedCr4 DD ? + mov cr4, eax + DB 66h + lgdt fword ptr cs:[edi + (SavedGdt - @Base)] + DB 66h, 0b8h ; mov eax, imm32 +SavedCr0 DD ? + mov cr0, eax + DB 0b8h ; mov ax, imm16 +SavedSs DW ? + mov ss, eax + DB 66h, 0bch ; mov esp, imm32 +SavedEsp DD ? + DB 66h + retf ; return to protected mode +_BackFromUserCode ENDP + +_EntryPoint DD _ToUserCode - m16Start + DW 8h +_16Idtr FWORD (1 SHL 10) - 1 +_16Gdtr LABEL FWORD + DW GdtEnd - _NullSegDesc - 1 +_16GdtrBase DD _NullSegDesc + +;------------------------------------------------------------------------------ +; _ToUserCode() takes control in real mode before passing control to user code. +; It will be shadowed to somewhere in memory below 1MB. +;------------------------------------------------------------------------------ +_ToUserCode PROC + mov edx, ss + mov ss, ecx ; set new segment selectors + mov ds, ecx + mov es, ecx + mov fs, ecx + mov gs, ecx + mov cr0, eax ; real mode starts at next instruction + ; which (per SDM) *must* be a far JMP. + DB 0eah +_RealAddr DW 0,0 ; filled in by InternalAsmThunk16 + + mov cr4, ebp + mov ss, esi ; set up 16-bit stack segment + xchg sp, bx ; set up 16-bit stack pointer + +; mov bp, [esp + sizeof(IA32_REGS) + DB 67h + mov ebp, [esp + sizeof(IA32_REGS)] ; BackFromUserCode address from stack + +; mov cs:[bp + (SavedSs - _BackFromUserCode)], dx + mov cs:[esi + (SavedSs - _BackFromUserCode)], edx + +; mov cs:[bp + (SavedEsp - _BackFromUserCode)], ebx + DB 2eh, 66h, 89h, 9eh + DW SavedEsp - _BackFromUserCode + +; lidt cs:[bp + (_16Idtr - _BackFromUserCode)] + DB 2eh, 66h, 0fh, 01h, 9eh + DW _16Idtr - _BackFromUserCode + + popaw ; popad actually + pop ds + pop es + pop fs + pop gs + popf ; popfd + DB 66h ; Use 32-bit addressing for "retf" below + 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 + +;------------------------------------------------------------------------------ +; IA32_REGISTER_SET * +; EFIAPI +; InternalAsmThunk16 ( +; IN IA32_REGISTER_SET *RegisterSet, +; IN OUT VOID *Transition +; ); +;------------------------------------------------------------------------------ +InternalAsmThunk16 PROC USES ebp ebx esi edi ds es fs gs + mov esi, [esp + 36] ; esi <- RegSet, the 1st parameter + movzx edx, (IA32_REGS ptr [esi])._SS + mov edi, (IA32_REGS ptr [esi])._ESP + add edi, - (sizeof (IA32_REGS) + 4) ; reserve stack space + mov ebx, edi ; ebx <- stack offset + imul eax, edx, 16 ; eax <- edx * 16 + push sizeof (IA32_REGS) / 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 + (SavedCr0 - m16Start)] + mov ecx, eax + and ecx, 0fh + shl eax, 12 + lea ecx, [ecx + (_BackFromUserCode - m16Start)] + mov ax, cx + stosd ; [edi] <- return address of user code + add eax, _RealAddr + 4 - _BackFromUserCode + mov dword ptr [edx + (_RealAddr - SavedCr0)], eax + sgdt fword ptr [edx + (SavedGdt - SavedCr0)] + sidt fword ptr [esp + 36] ; save IDT stack in argument space + mov eax, cr0 + mov [edx], eax ; save CR0 in SavedCr0 + and eax, 7ffffffeh ; clear PE, PG bits + mov ebp, cr4 + mov [edx + (SavedCr4 - SavedCr0)], ebp + and ebp, NOT 30h ; clear PAE, PSE bits + push 10h + pop ecx ; ecx <- selector for data segments + lgdt fword ptr [edx + (_16Gdtr - SavedCr0)] + pushfd ; Save df/if indeed + call fword ptr [edx + (_EntryPoint - SavedCr0)] + popfd + lidt fword ptr [esp + 36] ; restore protected mode IDTR + lea eax, [ebp - sizeof (IA32_REGS)] ; eax <- the address of IA32_REGS + ret +InternalAsmThunk16 ENDP + + END |