+++ /dev/null
-;------------------------------------------------------------------------------\r
-;\r
-; Copyright (c) 2006, Intel Corporation\r
-; All rights reserved. This program and the accompanying materials\r
-; are licensed and made available under the terms and conditions of the BSD License\r
-; which accompanies this distribution. The full text of the license may be found at\r
-; http://opensource.org/licenses/bsd-license.php\r
-;\r
-; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
-; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
-;\r
-; Module Name:\r
-;\r
-; Thunk.asm\r
-;\r
-; Abstract:\r
-;\r
-; Real mode thunk\r
-;\r
-;------------------------------------------------------------------------------\r
-\r
- .686p\r
- .model flat,C\r
-\r
-EXTERNDEF C m16Start:BYTE\r
-EXTERNDEF C m16Size:WORD\r
-EXTERNDEF C mThunk16Attr:WORD\r
-EXTERNDEF C m16Gdt:WORD\r
-EXTERNDEF C m16GdtrBase:WORD\r
-EXTERNDEF C mTransition:WORD\r
-\r
-;\r
-; Here is the layout of the real mode stack. _ToUserCode() is responsible for\r
-; loading all these registers from real mode stack.\r
-;\r
-IA32_REGS STRUC 4t\r
-_EDI DD ?\r
-_ESI DD ?\r
-_EBP DD ?\r
-_ESP DD ?\r
-_EBX DD ?\r
-_EDX DD ?\r
-_ECX DD ?\r
-_EAX DD ?\r
-_DS DW ?\r
-_ES DW ?\r
-_FS DW ?\r
-_GS DW ?\r
-_EFLAGS DD ?\r
-_EIP DD ?\r
-_CS DW ?\r
-_SS DW ?\r
-IA32_REGS ENDS\r
-\r
- .const\r
-\r
-;\r
-; These are global constant to convey information to C code.\r
-;\r
-m16Size DW InternalAsmThunk16 - m16Start\r
-mThunk16Attr DW _ThunkAttr - m16Start\r
-m16Gdt DW _NullSegDesc - m16Start\r
-m16GdtrBase DW _16GdtrBase - m16Start\r
-mTransition DW _EntryPoint - m16Start\r
-\r
- .code\r
-\r
-m16Start LABEL BYTE\r
-\r
-SavedGdt LABEL FWORD\r
- DW ?\r
- DD ?\r
-;------------------------------------------------------------------------------\r
-; _BackFromUserCode() takes control in real mode after 'retf' has been executed\r
-; by user code. It will be shadowed to somewhere in memory below 1MB.\r
-;------------------------------------------------------------------------------\r
-_BackFromUserCode PROC\r
- ;\r
- ; The order of saved registers on the stack matches the order they appears\r
- ; in IA32_REGS structure. This facilitates wrapper function to extract them\r
- ; into that structure.\r
- ;\r
- push ss\r
- push cs\r
- DB 66h\r
- call @Base ; push eip\r
-@Base:\r
- pushf ; pushfd actually\r
- cli ; disable interrupts\r
- push gs\r
- push fs\r
- push es\r
- push ds\r
- pushaw ; pushad actually\r
- DB 66h, 0bah ; mov edx, imm32\r
-_ThunkAttr DD ?\r
- test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15\r
- jz @1\r
- mov eax, 15cd2401h ; mov ax, 2401h & int 15h\r
- cli ; disable interrupts\r
- jnc @2\r
-@1:\r
- test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL\r
- jz @2\r
- in al, 92h\r
- or al, 2\r
- out 92h, al ; deactivate A20M#\r
-@2:\r
- mov eax, ss\r
- DB 67h\r
- lea bp, [esp + sizeof (IA32_REGS)]\r
- ;\r
- ; esi's in the following 2 instructions are indeed bp in 16-bit code. Fact\r
- ; is "esi" in 32-bit addressing mode has the same encoding of "bp" in 16-\r
- ; bit addressing mode.\r
- ;\r
- mov word ptr (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._ESP, bp\r
- mov ebx, (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._EIP\r
- shl ax, 4 ; shl eax, 4\r
- add bp, ax ; add ebp, eax\r
- DB 66h, 0b8h ; mov eax, imm32\r
-SavedCr4 DD ?\r
- mov cr4, eax\r
- DB 66h\r
- lgdt fword ptr cs:[edi + (SavedGdt - @Base)]\r
- DB 66h, 0b8h ; mov eax, imm32\r
-SavedCr0 DD ?\r
- mov cr0, eax\r
- DB 0b8h ; mov ax, imm16\r
-SavedSs DW ?\r
- mov ss, eax\r
- DB 66h, 0bch ; mov esp, imm32\r
-SavedEsp DD ?\r
- DB 66h\r
- retf ; return to protected mode\r
-_BackFromUserCode ENDP\r
-\r
-_EntryPoint DD _ToUserCode - m16Start\r
- DW 8h\r
-_16Idtr FWORD (1 SHL 10) - 1\r
-_16Gdtr LABEL FWORD\r
- DW GdtEnd - _NullSegDesc - 1\r
-_16GdtrBase DD _NullSegDesc\r
-\r
-;------------------------------------------------------------------------------\r
-; _ToUserCode() takes control in real mode before passing control to user code.\r
-; It will be shadowed to somewhere in memory below 1MB.\r
-;------------------------------------------------------------------------------\r
-_ToUserCode PROC\r
- mov edx, ss\r
- mov ss, ecx ; set new segment selectors\r
- mov ds, ecx\r
- mov es, ecx\r
- mov fs, ecx\r
- mov gs, ecx\r
- mov cr0, eax\r
- mov cr4, ebp ; real mode starts at next instruction\r
- mov ss, esi ; set up 16-bit stack segment\r
- xchg sp, bx ; set up 16-bit stack pointer\r
- DB 66h\r
- call @Base ; push eip\r
-@Base:\r
- pop bp ; ebp <- address of @Base\r
- DB 67h ; address size override\r
- push [esp + sizeof (IA32_REGS) + 2]\r
- lea eax, [esi + (@RealMode - @Base)]\r
- push eax\r
- retf\r
-@RealMode:\r
- mov cs:[esi + (SavedSs - @Base)], edx\r
- mov cs:[esi + (SavedEsp - @Base)], bx\r
- DB 66h\r
- lidt fword ptr cs:[esi + (_16Idtr - @Base)]\r
- popaw ; popad actually\r
- pop ds\r
- pop es\r
- pop fs\r
- pop gs\r
- popf ; popfd\r
- DB 66h ; Use 32-bit addressing for "retf" below\r
- retf ; transfer control to user code\r
-_ToUserCode ENDP\r
-\r
-_NullSegDesc DQ 0\r
-_16CsDesc LABEL QWORD\r
- DW -1\r
- DW 0\r
- DB 0\r
- DB 9bh\r
- DB 8fh ; 16-bit segment, 4GB limit\r
- DB 0\r
-_16DsDesc LABEL QWORD\r
- DW -1\r
- DW 0\r
- DB 0\r
- DB 93h\r
- DB 8fh ; 16-bit segment, 4GB limit\r
- DB 0\r
-GdtEnd LABEL QWORD\r
-\r
-;------------------------------------------------------------------------------\r
-; IA32_REGISTER_SET *\r
-; EFIAPI\r
-; InternalAsmThunk16 (\r
-; IN IA32_REGISTER_SET *RegisterSet,\r
-; IN OUT VOID *Transition\r
-; );\r
-;------------------------------------------------------------------------------\r
-InternalAsmThunk16 PROC USES ebp ebx esi edi ds es fs gs\r
- mov esi, [esp + 36] ; esi <- RegSet, the 1st parameter\r
- movzx edx, (IA32_REGS ptr [esi])._SS\r
- mov edi, (IA32_REGS ptr [esi])._ESP\r
- add edi, - (sizeof (IA32_REGS) + 4) ; reserve stack space\r
- mov ebx, edi ; ebx <- stack offset\r
- imul eax, edx, 16 ; eax <- edx * 16\r
- push sizeof (IA32_REGS) / 4\r
- add edi, eax ; edi <- linear address of 16-bit stack\r
- pop ecx\r
- rep movsd ; copy RegSet\r
- mov eax, [esp + 40] ; eax <- address of transition code\r
- mov esi, edx ; esi <- 16-bit stack segment\r
- lea edx, [eax + (SavedCr0 - m16Start)]\r
- mov ecx, eax\r
- and ecx, 0fh\r
- shl eax, 12\r
- lea ecx, [ecx + (_BackFromUserCode - m16Start)]\r
- mov ax, cx\r
- stosd ; [edi] <- return address of user code\r
- sgdt fword ptr [edx + (SavedGdt - SavedCr0)]\r
- sidt fword ptr [esp + 36] ; save IDT stack in argument space\r
- mov eax, cr0\r
- mov [edx], eax ; save CR0 in SavedCr0\r
- and eax, 7ffffffeh ; clear PE, PG bits\r
- mov ebp, cr4\r
- mov [edx + (SavedCr4 - SavedCr0)], ebp\r
- and ebp, 300h ; clear all but PCE and OSFXSR bits\r
- push 10h\r
- pop ecx ; ecx <- selector for data segments\r
- lgdt fword ptr [edx + (_16Gdtr - SavedCr0)]\r
- pushfd ; Save df/if indeed\r
- call fword ptr [edx + (_EntryPoint - SavedCr0)]\r
- popfd\r
- lidt fword ptr [esp + 36] ; restore protected mode IDTR\r
- lea eax, [ebp - sizeof (IA32_REGS)] ; eax <- the address of IA32_REGS\r
- ret\r
-InternalAsmThunk16 ENDP\r
-\r
- END\r
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