我主要用 C++ 制作操作系统，但对于引导加载程序，我使用的是 FASM。当我尝试设置 GDT 时，Qemu 清除屏幕并在顶部重新打印“SeaBIOS”。它继续像这样循环，直到我关闭它。这是它的 GIF：
我尝试使用 -nographic 运行它，但它在 Windows 控制台中执行相同的操作。
哦，是的，操作系统/版本信息。
Windows：20H2
FASM：1.73.25
Qemu：5.1.0
这是我的代码：
gdt_start:
dd 0x00
dd 0x00
gdt_code:
dw 0xffff
dw 0x0
db 0x0
db 10011010b
db 11001111b
db 0x0
gdt_data:
dw 0xffff
dw 0x0
db 0x0
db 10010010b
db 11001111b
db 0x0
gdt_end:
gdt_descriptor:
dw gdt_end - gdt_start - 1
dd gdt_start
CODE_SEG equ gdt_code - gdt_start
DATA_SEG equ gdt_data - gdt_start
switch_to_pm:
cli
lgdt [gdt_descriptor]
mov eax, cr0
or eax, 0x1
mov cr0, eax
jmp CODE_SEG:init_pm
use32
init_pm:
mov ax, DATA_SEG
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 0x90000
mov esp, ebp
call BEGIN_PM
BEGIN_PM:
mov ebx, MSG_PROT_MODE
call print_string_pm
call KERNEL_OFFSET
jmp $
更新：完整代码：
; boot.asm
org 0x7c00
KERNEL_OFFSET equ 0x1000
mov [BOOT_DRIVE], dl
mov bp, 0x9000
mov sp, bp
mov bx, MSG_REAL_MODE
call print
call print_nl
call load_kernel
call switch_to_pm
jmp $
print:
pusha
start:
mov al, [bx]
cmp al, 0
je done
mov ah, 0x0e
int 0x10
add bx, 1
jmp start
done:
popa
ret
print_nl:
pusha
mov ah, 0x0e
mov al, 0x0a
int 0x10
mov al, 0x0d
int 0x10
popa
ret
load_kernel:
mov bx, MSG_LOAD_KERNEL
call print
call print_nl
mov bx, KERNEL_OFFSET
mov dh, 1
mov dl, [BOOT_DRIVE]
call disk_load
ret
disk_load:
pusha
push dx
mov ah, 0x02
mov al, dh
mov cl, 0x02
mov ch, 0x00
mov dh, 0x00
int 0x13
jc disk_error
pop dx
cmp al, dh
jne sectors_error
popa
ret
disk_error:
mov bx, DISK_ERROR
call print
call print_nl
mov dh, ah
call print_hex
jmp disk_loop
sectors_error:
mov bx, SECTORS_ERROR
call print
disk_loop:
jmp $
print_hex:
pusha
mov cx, 0
hex_loop:
cmp cx, 4
je end_hex
mov ax, dx
and ax, 0x000f
add al, 0x30
cmp al, 0x39
jle step2
add al, 7
step2:
mov bx, HEX_OUT + 5
sub bx, cx
mov [bx], al
ror dx, 4
add cx, 1
jmp hex_loop
end_hex:
mov bx, HEX_OUT
call print
popa
ret
HEX_OUT:
db '0x0000', 0
gdt_start:
dd 0x00
dd 0x00
gdt_code:
dw 0xffff
dw 0x0
db 0x0
db 10011010b
db 11001111b
db 0x0
gdt_data:
dw 0xffff
dw 0x0
db 0x0
db 10010010b
db 11001111b
db 0x0
gdt_end:
gdt_descriptor:
dw gdt_end - gdt_start - 1
dd gdt_start
CODE_SEG equ gdt_code - gdt_start
DATA_SEG equ gdt_data - gdt_start
switch_to_pm:
cli
lgdt [gdt_descriptor]
mov eax, cr0
or eax, 0x1
mov cr0, eax
jmp CODE_SEG:init_pm
use32
init_pm:
mov ax, DATA_SEG
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 0x90000
mov esp, ebp
call BEGIN_PM
BEGIN_PM:
mov ebx, MSG_PROT_MODE
call print_string_pm
call KERNEL_OFFSET
jmp $
VIDEO_MEMORY equ 0xb8000
WHITE_ON_BLACK equ 0x0f
print_string_pm:
pusha
mov edx, VIDEO_MEMORY
print_string_pm_loop:
mov al, [ebx]
mov ah, WHITE_ON_BLACK
cmp al, 0
je print_string_pm_done
mov [edx], ax
add ebx, 1
add edx, 2
jmp print_string_pm_loop
print_string_pm_done:
popa
ret
BOOT_DRIVE db 0
MSG_REAL_MODE db "Started in 16-bit real mode", 0
MSG_LOAD_KERNEL db "Loading kernel into memory", 0
DISK_ERROR db "Disk read error", 0
SECTORS_ERROR db "Incorrect number of sectors read", 0
MSG_PROT_MODE db "Loaded 32-bit protected mode", 0
times 510-($-$$) db 0
dw 0xAA55
; loader.asm
format ELF
extrn main
public _start
_start:
call main
jmp $
// kernel.cpp
void main() {
char* video_memory = (char*) 0xb8000;
*video_memory = 'X';
}
rem compile.bat
@echo off
<NUL set /p="Cleaning binaries..."
del *.bin > NUL
del *.o > NUL
del *.elf > NUL
echo Done
<NUL set /p="Compiling boot.asm..."
fasm boot.asm > NUL
echo Done
<NUL set /p="Compiling loader.asm..."
fasm loader.asm > NUL
echo Done
<NUL set /p="Compiling kernel.c..."
wsl gcc -m32 -ffreestanding -c kernel.cpp -o kernel.o
echo Done
<NUL set /p="Linking..."
wsl objcopy kernel.o -O elf32-i386 kernel.elf
wsl /usr/local/i386elfgcc/bin/i386-elf-ld -o kernel.bin -Ttext 0x1000 loader.o kernel.elf
type boot.bin kernel.bin > os_image.bin
echo Done
<NUL set /p="Running..."
qemu-system-i386 os_image.bin
echo Done