#include "BaseLibInternals.h" | |
;------------------------------------------------------------------------------ | |
; | |
; Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR> | |
; SPDX-License-Identifier: BSD-2-Clause-Patent | |
; | |
; 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: resq 1 | |
._EIP: resd 1 | |
._CS: resw 1 | |
._SS: resw 1 | |
.size: | |
endstruc | |
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 _NullSeg - 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 | |
dq 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: | |
push dword 0 ; reserved high order 32 bits of EFlags | |
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 ebx, [bp - IA32_REGS.size + IA32_REGS._EIP] | |
shl eax, 4 ; shl eax, 4 | |
add ebp, eax ; add ebp, eax | |
mov eax, cs | |
shl eax, 4 | |
lea eax, [eax + ebx + (.X64JmpEnd - .Base)] | |
mov [cs:bx + (.X64JmpEnd - 6 - .Base)], eax | |
mov eax, strict dword 0 | |
.SavedCr4End: | |
mov cr4, eax | |
o32 lgdt [cs:bx + (SavedGdt - .Base)] | |
mov ecx, 0c0000080h | |
rdmsr | |
or ah, 1 | |
wrmsr | |
mov eax, strict dword 0 | |
.SavedCr0End: | |
mov cr0, eax | |
jmp 0:strict dword 0 | |
.X64JmpEnd: | |
BITS 64 | |
nop | |
mov rsp, strict qword 0 | |
.SavedSpEnd: | |
nop | |
ret | |
_EntryPoint: | |
DD _ToUserCode - ASM_PFX(m16Start) | |
DW CODE16 | |
_16Gdtr: | |
DW GDT_SIZE - 1 | |
_16GdtrBase: | |
DQ 0 | |
_16Idtr: | |
DW (1 << 10) - 1 | |
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 ss, dx ; set new segment selectors | |
mov ds, dx | |
mov es, dx | |
mov fs, dx | |
mov gs, dx | |
mov ecx, 0c0000080h | |
mov cr0, eax ; real mode starts at next instruction | |
rdmsr | |
and ah, ~1 | |
wrmsr | |
mov cr4, ebp | |
mov ss, si ; set up 16-bit stack segment | |
mov esp, ebx ; set up 16-bit stack pointer | |
call dword .Base ; push eip | |
.Base: | |
pop ebp ; ebp <- address of .Base | |
push word [dword esp + IA32_REGS.size + 2] | |
lea ax, [bp + (.RealMode - .Base)] | |
push ax | |
retf ; execution begins at next instruction | |
.RealMode: | |
o32 lidt [cs:bp + (_16Idtr - .Base)] | |
popad | |
pop ds | |
pop es | |
pop fs | |
pop gs | |
popfd | |
lea esp, [esp + 4] ; skip high order 32 bits of EFlags | |
o32 retf ; transfer control to user code | |
ALIGN 8 | |
CODE16 equ _16Code - $ | |
DATA16 equ _16Data - $ | |
DATA32 equ _32Data - $ | |
_NullSeg DQ 0 | |
_16Code: | |
DW -1 | |
DW 0 | |
DB 0 | |
DB 9bh | |
DB 8fh ; 16-bit segment, 4GB limit | |
DB 0 | |
_16Data: | |
DW -1 | |
DW 0 | |
DB 0 | |
DB 93h | |
DB 8fh ; 16-bit segment, 4GB limit | |
DB 0 | |
_32Data: | |
DW -1 | |
DW 0 | |
DB 0 | |
DB 93h | |
DB 0cfh ; 16-bit segment, 4GB limit | |
DB 0 | |
GDT_SIZE equ $ - _NullSeg | |
;------------------------------------------------------------------------------ | |
; IA32_REGISTER_SET * | |
; EFIAPI | |
; InternalAsmThunk16 ( | |
; IN IA32_REGISTER_SET *RegisterSet, | |
; IN OUT VOID *Transition | |
; ); | |
;------------------------------------------------------------------------------ | |
global ASM_PFX(InternalAsmThunk16) | |
ASM_PFX(InternalAsmThunk16): | |
BITS 64 | |
push rbp | |
push rbx | |
push rsi | |
push rdi | |
mov ebx, ds | |
push rbx ; Save ds segment register on the stack | |
mov ebx, es | |
push rbx ; Save es segment register on the stack | |
mov ebx, ss | |
push rbx ; Save ss segment register on the stack | |
push fs | |
push gs | |
mov rsi, rcx | |
movzx r8d, word [rsi + IA32_REGS._SS] | |
mov edi, [rsi + IA32_REGS._ESP] | |
lea rdi, [edi - (IA32_REGS.size + 4)] | |
imul eax, r8d, 16 ; eax <- r8d(stack segment) * 16 | |
mov ebx, edi ; ebx <- stack for 16-bit code | |
push IA32_REGS.size / 4 | |
add edi, eax ; edi <- linear address of 16-bit stack | |
pop rcx | |
rep movsd ; copy RegSet | |
lea ecx, [rdx + (_BackFromUserCode.SavedCr4End - ASM_PFX(m16Start))] | |
mov eax, edx ; eax <- transition code address | |
and edx, 0fh | |
shl eax, 12 ; segment address in high order 16 bits | |
lea ax, [rdx + (_BackFromUserCode - ASM_PFX(m16Start))] ; offset address | |
stosd ; [edi] <- return address of user code | |
sgdt [rsp + 60h] ; save GDT stack in argument space | |
movzx r10, word [rsp + 60h] ; r10 <- GDT limit | |
lea r11, [rcx + (ASM_PFX(InternalAsmThunk16) - _BackFromUserCode.SavedCr4End) + 0xf] | |
and r11, ~0xf ; r11 <- 16-byte aligned shadowed GDT table in real mode buffer | |
mov [rcx + (SavedGdt - _BackFromUserCode.SavedCr4End)], r10w ; save the limit of shadowed GDT table | |
mov [rcx + (SavedGdt - _BackFromUserCode.SavedCr4End) + 2], r11 ; save the base address of shadowed GDT table | |
mov rsi, [rsp + 62h] ; rsi <- the original GDT base address | |
xchg rcx, r10 ; save rcx to r10 and initialize rcx to be the limit of GDT table | |
inc rcx ; rcx <- the size of memory to copy | |
xchg rdi, r11 ; save rdi to r11 and initialize rdi to the base address of shadowed GDT table | |
rep movsb ; perform memory copy to shadow GDT table | |
mov rcx, r10 ; restore the orignal rcx before memory copy | |
mov rdi, r11 ; restore the original rdi before memory copy | |
sidt [rsp + 50h] ; save IDT stack in argument space | |
mov rax, cr0 | |
mov [rcx + (_BackFromUserCode.SavedCr0End - 4 - _BackFromUserCode.SavedCr4End)], eax | |
and eax, 7ffffffeh ; clear PE, PG bits | |
mov rbp, cr4 | |
mov [rcx - 4], ebp ; save CR4 in _BackFromUserCode.SavedCr4End - 4 | |
and ebp, ~30h ; clear PAE, PSE bits | |
mov esi, r8d ; esi <- 16-bit stack segment | |
push DATA32 | |
pop rdx ; rdx <- 32-bit data segment selector | |
lgdt [rcx + (_16Gdtr - _BackFromUserCode.SavedCr4End)] | |
mov ss, edx | |
pushfq | |
lea edx, [rdx + DATA16 - DATA32] | |
lea r8, [REL .RetFromRealMode] | |
push r8 | |
mov r8d, cs | |
mov [rcx + (_BackFromUserCode.X64JmpEnd - 2 - _BackFromUserCode.SavedCr4End)], r8w | |
mov [rcx + (_BackFromUserCode.SavedSpEnd - 8 - _BackFromUserCode.SavedCr4End)], rsp | |
jmp dword far [rcx + (_EntryPoint - _BackFromUserCode.SavedCr4End)] | |
.RetFromRealMode: | |
popfq | |
lgdt [rsp + 60h] ; restore protected mode GDTR | |
lidt [rsp + 50h] ; restore protected mode IDTR | |
lea eax, [rbp - IA32_REGS.size] | |
pop gs | |
pop fs | |
pop rbx | |
mov ss, ebx | |
pop rbx | |
mov es, ebx | |
pop rbx | |
mov ds, ebx | |
pop rdi | |
pop rsi | |
pop rbx | |
pop rbp | |
ret |