+++ /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
- .data\r
-\r
-NullSegSel DQ 0\r
-_16CsSegSel LABEL QWORD\r
- DW -1\r
- DW 0\r
- DB 0\r
- DB 9bh\r
- DB 8fh ; 16-bit segment\r
- DB 0\r
-_16BitDsSel LABEL QWORD\r
- DW -1\r
- DW 0\r
- DB 0\r
- DB 93h\r
- DB 8fh ; 16-bit segment\r
- DB 0\r
-GdtEnd LABEL QWORD\r
-\r
- .const\r
-\r
-_16Gdtr LABEL FWORD\r
- DW offset GdtEnd - offset NullSegSel - 1\r
- DQ offset NullSegSel\r
-\r
-_16Idtr FWORD (1 SHL 10) - 1\r
-\r
- .code\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
-_RFLAGS DQ ?\r
-_EIP DD ?\r
-_CS DW ?\r
-_SS DW ?\r
-IA32_REGS ENDS\r
-\r
-InternalAsmThunk16 PROC USES rbp rbx rsi rdi r12 r13 r14 r15\r
- mov eax, ds\r
- push rax\r
- mov eax, es\r
- push rax\r
- push fs\r
- push gs\r
- mov rsi, rcx ; rsi <- RegSet\r
- push sizeof (IA32_REGS)\r
- pop rcx\r
- movzx r8, (IA32_REGS ptr [rsi])._SS\r
- xor rdi, rdi\r
- mov edi, (IA32_REGS ptr [rsi])._ESP\r
- sub rdi, rcx ; reserve space on realmode stack\r
- push rdi ; save stack offset\r
- imul rax, r8, 16\r
- add rdi, rax ; rdi <- linear address of 16-bit stack\r
- rep movsb ; copy RegSet\r
- mov rsi, r8 ; si <- 16-bit stack segment\r
- pop rbx ; rbx <- 16-bit stack offset\r
- mov rdi, rdx ; rdi <- realmode patch\r
- lea eax, @BackToThunk ; rax <- address to back from real mode\r
- push rax ; use in a far return\r
- mov eax, cs\r
- mov [rsp + 4], eax ; save CS\r
- lea eax, @16Return ; thus @Return must < 4GB\r
- stosd ; set ret address offset\r
- xor eax, eax\r
- stosw ; set ret CS base to 0\r
- mov eax, esp\r
- stosd ; rsp must < 4GB\r
- mov eax, ss\r
- stosd\r
- mov rax, cr0\r
- mov ecx, eax ; ecx <- CR0\r
- and ecx, 7ffffffeh ; clear PE, PG bits\r
- stosd\r
- mov rax, cr4\r
- mov ebp, eax\r
- and ebp, 300h ; clear all but PCE and OSFXSR bits\r
- stosd\r
- sidt fword ptr [rsp + 70h] ; use parameter space to save IDTR\r
- sgdt fword ptr [rdi]\r
- lea edi, _16Idtr\r
- lea eax, @16Start ; rax <- seg:offset of @16Start\r
- push rax\r
- mov dword ptr [rsp + 4], 8\r
- push 10h\r
- pop rax ; rax <- 10h as dataseg selector\r
- lgdt _16Gdtr\r
- retf\r
-@16Start: ; 16-bit starts here\r
- mov ss, eax ; set SS to be a 16-bit segment\r
- mov cr0, rcx ; disable protected mode\r
- mov cr4, rbp\r
- DB 66h\r
- mov ecx, 0c0000080h\r
- rdmsr\r
- and ah, NOT 1 ; clear LME\r
- wrmsr\r
- mov ss, esi ; set up 16-bit stack\r
- mov sp, bx ; mov esp, ebx actually\r
- lidt fword ptr [edi]\r
- DB 66h, 61h ; popad\r
- DB 1fh ; pop ds\r
- DB 7 ; pop es\r
- pop fs\r
- pop gs\r
- add sp, 8 ; skip _RFLAGS\r
- DB 66h\r
- retf ; transfer control to 16-bit code\r
-@16Return:\r
- DB 66h\r
- push 0 ; high order 32 bits of rflags\r
- pushf ; pushfd actually\r
- push gs\r
- push fs\r
- DB 6 ; push es\r
- DB 1eh ; push ds\r
- DB 66h, 60h ; pushad\r
- DB 67h, 66h, 0c5h, 74h, 24h, 30h ; lds esi, [esp + 12*4]\r
- DB 66h\r
- mov eax, [esi + 12]\r
- mov cr4, rax ; restore CR4\r
- DB 66h\r
- lgdt fword ptr [esi + 16]\r
- DB 66h\r
- mov ecx, 0c0000080h\r
- rdmsr\r
- or ah, 1 ; set LME\r
- wrmsr\r
- DB 66h\r
- mov eax, [esi + 8]\r
- mov cr0, rax ; restore CR0\r
- xor ax, ax ; xor eax, eax actually\r
- mov eax, ss\r
- mov dword ptr (IA32_REGS ptr [esp])._SS, eax\r
- shl ax, 4 ; shl eax, 4 actually\r
- add ax, sp ; add eax, esp actually\r
- add sp, sizeof (IA32_REGS) ; add esp, sizeof (IA32_REGS)\r
- DB 66h\r
- mov dword ptr (IA32_REGS ptr [esp - sizeof (IA32_REGS)])._ESP, esp\r
- DB 66h\r
- lss esp, fword ptr [esi] ; restore protected mode stack\r
- DB 66h\r
- retf ; go back to protected mode\r
-@BackToThunk:\r
- lidt fword ptr [rsp + 68h] ; restore protected mode IDTR\r
- shl rax, 32\r
- shr rax, 32 ; clear high order 32 bits of RAX\r
- pop gs\r
- pop fs\r
- pop rcx\r
- mov es, ecx\r
- pop rcx\r
- mov ds, ecx\r
- ret\r
-InternalAsmThunk16 ENDP\r
-\r
- END\r
projects / mirror_edk2.git / blobdiff