我有一个用MASM编写的引导加载程序，它由JWASM编译。到目前为止，它工作得很完美，然而，当它应该跳到保护模式时，什么也没发生。它应该在屏幕左上角打印一个黄色的P，但它没有出现。
boot.asm:
.386p
option segment:use16, casemap:none
.model TINY, C, NEARSTACK
;------------------------------
; CODE
;------------------------------
.code
org 07C00h
Error PROTO lpStr:WORD
Print PROTO lpStr:WORD
ReadDisk PROTO nSectorsRead:BYTE, nCylinder:BYTE, nSector:BYTE, nHead:BYTE, nDrive:BYTE, lpBuffer:WORD
NewLine PROTO
PrintLn PROTO lpStr:WORD
PrintWord PROTO num:WORD
ReadKey PROTO
_start:
mov [bootDisk], dl
xor ax, ax
mov ds, ax
mov ss, ax
mov es, ax
mov bp, 07BFFh
mov sp, bp
INVOKE PrintLn, OFFSET bootInfo ;Onyl works because we are using JWASM as our compiler!
INVOKE PrintLn, OFFSET loadingInfo
INVOKE ReadDisk, 1, 0, 2, 0, [bootDisk], 07E00h
INVOKE Print, OFFSET pageInfo
INVOKE PrintWord, MEM_PAGE_COUNT
INVOKE NewLine
INVOKE PrintLn, OFFSET protectedInfo
lgdt fword ptr [GDT_desc]
mov eax, cr0
or eax, 1
mov cr0, eax
db 66h ;manually encoded far jump = CODE_SEG:start_protected_mode
db 0EAh
dd OFFSET start_protected_mode
dw CODE_SEG
Error PROC lpStr:WORD
INVOKE Print, lpStr
mov ah, 0
int 16h
db 0EAh ;manually encoded reboot
dw 0000h
dw 0FFFFh
Error ENDP
Print PROC USES ax si lpStr:WORD
mov si, lpStr
mov ah, 0Eh
@@loop:
lodsb
cmp al, 0
je @@done
int 10h
jmp @@loop
@@done:
ret
Print ENDP
NewLine PROC USES ax
mov ah, 0Eh
mov al, 13
int 10h
mov al, 10
int 10h
ret
NewLine ENDP
PrintLn PROC lpStr:WORD
INVOKE Print, lpStr
INVOKE NewLine
ret
PrintLn ENDP
ReadDisk PROC uses ax cx dx bx nSectorsRead:BYTE, nCylinder:BYTE, nSector:BYTE, nHead:BYTE, nDrive:BYTE, lpBuffer:WORD
mov ah, 02h
mov al, nSectorsRead
mov ch, nCylinder
mov cl, nSector
mov dh, nHead
mov dl, nDrive
mov bx, lpBuffer
int 13h
jnc @@end
INVOKE Error, OFFSET diskReadError
@@end:
ret
ReadDisk ENDP
;------------------------------
; DATA
;------------------------------
bootDisk byte 1
bootInfo db "Booting CompatOS...", 0
loadingInfo db "Loading extra sector...", 0
diskReadError db "Disk read failed!", 0
pageInfo db "Page count: ", 0
GDT_null dq 0
GDT_code dw 0FFFFh
dw 0
db 0
db 10011010b
db 11001111b
db 0
GDT_data dw 0FFFFh
dw 0
db 0
db 10010010b
db 11001111b
db 0
GDT_desc dw OFFSET GDT_desc - OFFSET GDT_null - 1
GDT_addr dd OFFSET GDT_null
CODE_SEG equ GDT_code - GDT_null
DATA_SEG equ GDT_data - GDT_null
;------------------------------
; PADDING
;------------------------------
byte 510-($-_start) dup (0)
dw 0AA55h
org 07E00h
MEM_BEG equ 08000h
MEM_END equ 0FFFFh
MEM_PAGE_COUNT equ (MEM_END - MEM_BEG) / 0200h
;------------------------------
; CODE
;------------------------------
PrintWord PROC USES ax bx dx num:WORD
LOCAL digit:BYTE
.if num >= 10
mov ax, num
mov dx, 0
mov bx, 10
div bx
INVOKE PrintWord, ax
.endif
mov ax, num
mov dx, 0
mov bx, 10
div bx
mov digit, dl
mov ah, 0Eh
mov al, '0'
add al, digit
int 10h
ret
PrintWord ENDP
ReadKey PROC
mov ah, 0
int 16h
xor ah, ah
ret
ReadKey ENDP
option segment:use32
start_protected_mode:
mov ax, DATA_SEG
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 90000h
mov esp, ebp
mov eax, 0B8000h
mov [eax], 'P'
mov [eax+1], 14
cli
hlt
;------------------------------
; DATA
;------------------------------
protectedInfo db "Entering protected mode...", 0
;------------------------------
; PADDING
;------------------------------
byte 1024-($-_start) dup (0)
END _start
反汇编：
00000000 8816E47C mov [0x7ce4],dl
00000004 33C0 xor ax,ax
00000006 8ED8 mov ds,ax
00000008 8ED0 mov ss,ax
0000000A 8EC0 mov es,ax
0000000C BDFF7B mov bp,0x7bff
0000000F 8BE5 mov sp,bp
00000011 68E57C push word 0x7ce5
00000014 E88E00 call 0xa5
00000017 83C402 add sp,byte +0x2
0000001A 68F97C push word 0x7cf9
0000001D E88500 call 0xa5
00000020 83C402 add sp,byte +0x2
00000023 68007E push word 0x7e00
00000026 A0E47C mov al,[0x7ce4]
00000029 50 push ax
0000002A 6A00 push byte +0x0
0000002C 6A02 push byte +0x2
0000002E 6A00 push byte +0x0
00000030 6A01 push byte +0x1
00000032 E88100 call 0xb6
00000035 83C40C add sp,byte +0xc
00000038 68237D push word 0x7d23
0000003B E84300 call 0x81
0000003E 83C402 add sp,byte +0x2
00000041 6A3F push byte +0x3f
00000043 E8BA01 call 0x200
00000046 83C402 add sp,byte +0x2
00000049 E84C00 call 0x98
0000004C 686B7E push word 0x7e6b
0000004F E85300 call 0xa5
00000052 83C402 add sp,byte +0x2
00000055 0F0116487D lgdt [0x7d48]
0000005A 0F20C0 mov eax,cr0
0000005D 6683C801 or eax,byte +0x1
00000061 0F22C0 mov cr0,eax
00000064 66EA447E00000800 jmp dword 0x8:0x7e44
0000006C 55 push bp
0000006D 8BEC mov bp,sp
0000006F FF7604 push word [bp+0x4]
00000072 E80C00 call 0x81
00000075 83C402 add sp,byte +0x2
00000078 B400 mov ah,0x0
0000007A CD16 int 0x16
0000007C EA0000FFFF jmp 0xffff:0x0
00000081 55 push bp
00000082 8BEC mov bp,sp
00000084 50 push ax
00000085 56 push si
00000086 8B7604 mov si,[bp+0x4]
00000089 B40E mov ah,0xe
0000008B AC lodsb
0000008C 3C00 cmp al,0x0
0000008E 7404 jz 0x94
00000090 CD10 int 0x10
00000092 EBF7 jmp short 0x8b
00000094 5E pop si
00000095 58 pop ax
00000096 C9 leave
00000097 C3 ret
00000098 50 push ax
00000099 B40E mov ah,0xe
0000009B B00D mov al,0xd
0000009D CD10 int 0x10
0000009F B00A mov al,0xa
000000A1 CD10 int 0x10
000000A3 58 pop ax
000000A4 C3 ret
000000A5 55 push bp
000000A6 8BEC mov bp,sp
000000A8 FF7604 push word [bp+0x4]
000000AB E8D3FF call 0x81
000000AE 83C402 add sp,byte +0x2
000000B1 E8E4FF call 0x98
000000B4 C9 leave
000000B5 C3 ret
000000B6 55 push bp
000000B7 8BEC mov bp,sp
000000B9 50 push ax
000000BA 51 push cx
000000BB 52 push dx
000000BC 53 push bx
000000BD B402 mov ah,0x2
000000BF 8A4604 mov al,[bp+0x4]
000000C2 8A6E06 mov ch,[bp+0x6]
000000C5 8A4E08 mov cl,[bp+0x8]
000000C8 8A760A mov dh,[bp+0xa]
000000CB 8A560C mov dl,[bp+0xc]
000000CE 8B5E0E mov bx,[bp+0xe]
000000D1 CD13 int 0x13
000000D3 7309 jnc 0xde
000000D5 68117D push word 0x7d11
000000D8 E891FF call 0x6c
000000DB 83C402 add sp,byte +0x2
000000DE 5B pop bx
000000DF 5A pop dx
000000E0 59 pop cx
000000E1 58 pop ax
000000E2 C9 leave
000000E3 C3 ret
000000E4 01426F add [bp+si+0x6f],ax
000000E7 6F outsw
000000E8 7469 jz 0x153
000000EA 6E outsb
000000EB 6720436F and [ebx+0x6f],al
000000EF 6D insw
000000F0 7061 jo 0x153
000000F2 744F jz 0x143
000000F4 53 push bx
000000F5 2E2E2E004C6F add [cs:si+0x6f],cl
000000FB 61 popa
000000FC 64696E672065 imul bp,[fs:bp+0x67],word 0x6520
00000102 7874 js 0x178
00000104 7261 jc 0x167
00000106 207365 and [bp+di+0x65],dh
00000109 63746F arpl [si+0x6f],si
0000010C 722E jc 0x13c
0000010E 2E2E004469 add [cs:si+0x69],al
00000113 736B jnc 0x180
00000115 207265 and [bp+si+0x65],dh
00000118 61 popa
00000119 64206661 and [fs:bp+0x61],ah
0000011D 696C656421 imul bp,[si+0x65],word 0x2164
00000122 005061 add [bx+si+0x61],dl
00000125 676520636F and [gs:ebx+0x6f],ah
0000012A 756E jnz 0x19a
0000012C 743A jz 0x168
0000012E 2000 and [bx+si],al
00000130 0000 add [bx+si],al
00000132 0000 add [bx+si],al
00000134 0000 add [bx+si],al
00000136 0000 add [bx+si],al
00000138 FF db 0xff
00000139 FF00 inc word [bx+si]
0000013B 0000 add [bx+si],al
0000013D 9ACF00FFFF call 0xffff:0xcf
00000142 0000 add [bx+si],al
00000144 0092CF00 add [bp+si+0xcf],dl
00000148 17 pop ss
00000149 0030 add [bx+si],dh
0000014B 7D00 jnl 0x14d
0000014D 0000 add [bx+si],al
0000014F 0000 add [bx+si],al
00000151 0000 add [bx+si],al
00000153 0000 add [bx+si],al
00000155 0000 add [bx+si],al
00000157 0000 add [bx+si],al
00000159 0000 add [bx+si],al
0000015B 0000 add [bx+si],al
0000015D 0000 add [bx+si],al
0000015F 0000 add [bx+si],al
00000161 0000 add [bx+si],al
00000163 0000 add [bx+si],al
00000165 0000 add [bx+si],al
00000167 0000 add [bx+si],al
00000169 0000 add [bx+si],al
0000016B 0000 add [bx+si],al
0000016D 0000 add [bx+si],al
0000016F 0000 add [bx+si],al
00000171 0000 add [bx+si],al
00000173 0000 add [bx+si],al
00000175 0000 add [bx+si],al
00000177 0000 add [bx+si],al
00000179 0000 add [bx+si],al
0000017B 0000 add [bx+si],al
0000017D 0000 add [bx+si],al
0000017F 0000 add [bx+si],al
00000181 0000 add [bx+si],al
00000183 0000 add [bx+si],al
00000185 0000 add [bx+si],al
00000187 0000 add [bx+si],al
00000189 0000 add [bx+si],al
0000018B 0000 add [bx+si],al
0000018D 0000 add [bx+si],al
0000018F 0000 add [bx+si],al
00000191 0000 add [bx+si],al
00000193 0000 add [bx+si],al
00000195 0000 add [bx+si],al
00000197 0000 add [bx+si],al
00000199 0000 add [bx+si],al
0000019B 0000 add [bx+si],al
0000019D 0000 add [bx+si],al
0000019F 0000 add [bx+si],al
000001A1 0000 add [bx+si],al
000001A3 0000 add [bx+si],al
000001A5 0000 add [bx+si],al
000001A7 0000 add [bx+si],al
000001A9 0000 add [bx+si],al
000001AB 0000 add [bx+si],al
000001AD 0000 add [bx+si],al
000001AF 0000 add [bx+si],al
000001B1 0000 add [bx+si],al
000001B3 0000 add [bx+si],al
000001B5 0000 add [bx+si],al
000001B7 0000 add [bx+si],al
000001B9 0000 add [bx+si],al
000001BB 0000 add [bx+si],al
000001BD 0000 add [bx+si],al
000001BF 0000 add [bx+si],al
000001C1 0000 add [bx+si],al
000001C3 0000 add [bx+si],al
000001C5 0000 add [bx+si],al
000001C7 0000 add [bx+si],al
000001C9 0000 add [bx+si],al
000001CB 0000 add [bx+si],al
000001CD 0000 add [bx+si],al
000001CF 0000 add [bx+si],al
000001D1 0000 add [bx+si],al
000001D3 0000 add [bx+si],al
000001D5 0000 add [bx+si],al
000001D7 0000 add [bx+si],al
000001D9 0000 add [bx+si],al
000001DB 0000 add [bx+si],al
000001DD 0000 add [bx+si],al
000001DF 0000 add [bx+si],al
000001E1 0000 add [bx+si],al
000001E3 0000 add [bx+si],al
000001E5 0000 add [bx+si],al
000001E7 0000 add [bx+si],al
000001E9 0000 add [bx+si],al
000001EB 0000 add [bx+si],al
000001ED 0000 add [bx+si],al
000001EF 0000 add [bx+si],al
000001F1 0000 add [bx+si],al
000001F3 0000 add [bx+si],al
000001F5 0000 add [bx+si],al
000001F7 0000 add [bx+si],al
000001F9 0000 add [bx+si],al
000001FB 0000 add [bx+si],al
000001FD 0055AA add [di-0x56],dl
00000200 55 push bp
00000201 8BEC mov bp,sp
00000203 83EC02 sub sp,byte +0x2
00000206 50 push ax
00000207 53 push bx
00000208 52 push dx
00000209 837E040A cmp word [bp+0x4],byte +0xa
0000020D 7212 jc 0x221
0000020F 8B4604 mov ax,[bp+0x4]
00000212 BA0000 mov dx,0x0
00000215 BB0A00 mov bx,0xa
00000218 F7F3 div bx
0000021A 50 push ax
0000021B E8E2FF call 0x200
0000021E 83C402 add sp,byte +0x2
00000221 8B4604 mov ax,[bp+0x4]
00000224 BA0000 mov dx,0x0
00000227 BB0A00 mov bx,0xa
0000022A F7F3 div bx
0000022C 8856FF mov [bp-0x1],dl
0000022F B40E mov ah,0xe
00000231 B030 mov al,0x30
00000233 0246FF add al,[bp-0x1]
00000236 CD10 int 0x10
00000238 5A pop dx
00000239 5B pop bx
0000023A 58 pop ax
0000023B C9 leave
0000023C C3 ret
0000023D B400 mov ah,0x0
0000023F CD16 int 0x16
00000241 32E4 xor ah,ah
00000243 C3 ret
00000244 B81000 mov ax,0x10
00000247 8ED8 mov ds,ax
00000249 8ED0 mov ss,ax
0000024B 8EC0 mov es,ax
0000024D 8EE0 mov fs,ax
0000024F 8EE8 mov gs,ax
00000251 66BD00000900 mov ebp,0x90000
00000257 668BE5 mov esp,ebp
0000025A 66B800800B00 mov eax,0xb8000
00000260 67C60050 mov byte [eax],0x50
00000264 67C640010E mov byte [eax+0x1],0xe
00000269 FA cli
0000026A F4 hlt
0000026B 45 inc bp
0000026C 6E outsb
0000026D 7465 jz 0x2d4
0000026F 7269 jc 0x2da
00000271 6E outsb
00000272 67207072 and [eax+0x72],dh
00000276 6F outsw
00000277 7465 jz 0x2de
00000279 637465 arpl [si+0x65],si
0000027C 64206D6F and [fs:di+0x6f],ch
00000280 64652E2E2E0000 add [cs:bx+si],al
00000287 0000 add [bx+si],al
00000289 0000 add [bx+si],al
0000028B 0000 add [bx+si],al
0000028D 0000 add [bx+si],al
0000028F 0000 add [bx+si],al
00000291 0000 add [bx+si],al
00000293 0000 add [bx+si],al
00000295 0000 add [bx+si],al
00000297 0000 add [bx+si],al
00000299 0000 add [bx+si],al
0000029B 0000 add [bx+si],al
0000029D 0000 add [bx+si],al
0000029F 0000 add [bx+si],al
000002A1 0000 add [bx+si],al
000002A3 0000 add [bx+si],al
000002A5 0000 add [bx+si],al
000002A7 0000 add [bx+si],al
000002A9 0000 add [bx+si],al
000002AB 0000 add [bx+si],al
000002AD 0000 add [bx+si],al
000002AF 0000 add [bx+si],al
000002B1 0000 add [bx+si],al
000002B3 0000 add [bx+si],al
000002B5 0000 add [bx+si],al
000002B7 0000 add [bx+si],al
000002B9 0000 add [bx+si],al
000002BB 0000 add [bx+si],al
000002BD 0000 add [bx+si],al
000002BF 0000 add [bx+si],al
000002C1 0000 add [bx+si],al
000002C3 0000 add [bx+si],al
000002C5 0000 add [bx+si],al
000002C7 0000 add [bx+si],al
000002C9 0000 add [bx+si],al
000002CB 0000 add [bx+si],al
000002CD 0000 add [bx+si],al
000002CF 0000 add [bx+si],al
000002D1 0000 add [bx+si],al
000002D3 0000 add [bx+si],al
000002D5 0000 add [bx+si],al
000002D7 0000 add [bx+si],al
000002D9 0000 add [bx+si],al
000002DB 0000 add [bx+si],al
000002DD 0000 add [bx+si],al
000002DF 0000 add [bx+si],al
000002E1 0000 add [bx+si],al
000002E3 0000 add [bx+si],al
000002E5 0000 add [bx+si],al
000002E7 0000 add [bx+si],al
000002E9 0000 add [bx+si],al
000002EB 0000 add [bx+si],al
000002ED 0000 add [bx+si],al
000002EF 0000 add [bx+si],al
000002F1 0000 add [bx+si],al
000002F3 0000 add [bx+si],al
000002F5 0000 add [bx+si],al
000002F7 0000 add [bx+si],al
000002F9 0000 add [bx+si],al
000002FB 0000 add [bx+si],al
000002FD 0000 add [bx+si],al
000002FF 0000 add [bx+si],al
00000301 0000 add [bx+si],al
00000303 0000 add [bx+si],al
00000305 0000 add [bx+si],al
00000307 0000 add [bx+si],al
00000309 0000 add [bx+si],al
0000030B 0000 add [bx+si],al
0000030D 0000 add [bx+si],al
0000030F 0000 add [bx+si],al
00000311 0000 add [bx+si],al
00000313 0000 add [bx+si],al
00000315 0000 add [bx+si],al
00000317 0000 add [bx+si],al
00000319 0000 add [bx+si],al
0000031B 0000 add [bx+si],al
0000031D 0000 add [bx+si],al
0000031F 0000 add [bx+si],al
00000321 0000 add [bx+si],al
00000323 0000 add [bx+si],al
00000325 0000 add [bx+si],al
00000327 0000 add [bx+si],al
00000329 0000 add [bx+si],al
0000032B 0000 add [bx+si],al
0000032D 0000 add [bx+si],al
0000032F 0000 add [bx+si],al
00000331 0000 add [bx+si],al
00000333 0000 add [bx+si],al
00000335 0000 add [bx+si],al
00000337 0000 add [bx+si],al
00000339 0000 add [bx+si],al
0000033B 0000 add [bx+si],al
0000033D 0000 add [bx+si],al
0000033F 0000 add [bx+si],al
00000341 0000 add [bx+si],al
00000343 0000 add [bx+si],al
00000345 0000 add [bx+si],al
00000347 0000 add [bx+si],al
00000349 0000 add [bx+si],al
0000034B 0000 add [bx+si],al
0000034D 0000 add [bx+si],al
0000034F 0000 add [bx+si],al
00000351 0000 add [bx+si],al
00000353 0000 add [bx+si],al
00000355 0000 add [bx+si],al
00000357 0000 add [bx+si],al
00000359 0000 add [bx+si],al
0000035B 0000 add [bx+si],al
0000035D 0000 add [bx+si],al
0000035F 0000 add [bx+si],al
00000361 0000 add [bx+si],al
00000363 0000 add [bx+si],al
00000365 0000 add [bx+si],al
00000367 0000 add [bx+si],al
00000369 0000 add [bx+si],al
0000036B 0000 add [bx+si],al
0000036D 0000 add [bx+si],al
0000036F 0000 add [bx+si],al
00000371 0000 add [bx+si],al
00000373 0000 add [bx+si],al
00000375 0000 add [bx+si],al
00000377 0000 add [bx+si],al
00000379 0000 add [bx+si],al
0000037B 0000 add [bx+si],al
0000037D 0000 add [bx+si],al
0000037F 0000 add [bx+si],al
00000381 0000 add [bx+si],al
00000383 0000 add [bx+si],al
00000385 0000 add [bx+si],al
00000387 0000 add [bx+si],al
00000389 0000 add [bx+si],al
0000038B 0000 add [bx+si],al
0000038D 0000 add [bx+si],al
0000038F 0000 add [bx+si],al
00000391 0000 add [bx+si],al
00000393 0000 add [bx+si],al
00000395 0000 add [bx+si],al
00000397 0000 add [bx+si],al
00000399 0000 add [bx+si],al
0000039B 0000 add [bx+si],al
0000039D 0000 add [bx+si],al
0000039F 0000 add [bx+si],al
000003A1 0000 add [bx+si],al
000003A3 0000 add [bx+si],al
000003A5 0000 add [bx+si],al
000003A7 0000 add [bx+si],al
000003A9 0000 add [bx+si],al
000003AB 0000 add [bx+si],al
000003AD 0000 add [bx+si],al
000003AF 0000 add [bx+si],al
000003B1 0000 add [bx+si],al
000003B3 0000 add [bx+si],al
000003B5 0000 add [bx+si],al
000003B7 0000 add [bx+si],al
000003B9 0000 add [bx+si],al
000003BB 0000 add [bx+si],al
000003BD 0000 add [bx+si],al
000003BF 0000 add [bx+si],al
000003C1 0000 add [bx+si],al
000003C3 0000 add [bx+si],al
000003C5 0000 add [bx+si],al
000003C7 0000 add [bx+si],al
000003C9 0000 add [bx+si],al
000003CB 0000 add [bx+si],al
000003CD 0000 add [bx+si],al
000003CF 0000 add [bx+si],al
000003D1 0000 add [bx+si],al
000003D3 0000 add [bx+si],al
000003D5 0000 add [bx+si],al
000003D7 0000 add [bx+si],al
000003D9 0000 add [bx+si],al
000003DB 0000 add [bx+si],al
000003DD 0000 add [bx+si],al
000003DF 0000 add [bx+si],al
000003E1 0000 add [bx+si],al
000003E3 0000 add [bx+si],al
000003E5 0000 add [bx+si],al
000003E7 0000 add [bx+si],al
000003E9 0000 add [bx+si],al
000003EB 0000 add [bx+si],al
000003ED 0000 add [bx+si],al
000003EF 0000 add [bx+si],al
000003F1 0000 add [bx+si],al
000003F3 0000 add [bx+si],al
000003F5 0000 add [bx+si],al
000003F7 0000 add [bx+si],al
000003F9 0000 add [bx+si],al
000003FB 0000 add [bx+si],al
000003FD 0000 add [bx+si],al
000003FF 00 db 0x00
如上所述，我必须手动编码一个跳远，因为MASM不支持它们。反汇编表明它得到了正确的编码(参见00000064(，但它根本不起作用。
如果你好奇，以下是用于构建源代码的命令：
jwasm /nologo /AT /c /Fotmp\boot.obj src\boot\boot.asm
masm_615/bin/link /nologo /TINY /NOD tmp\boot.obj, bin\CompatOS.img, NUL, NUL, NUL
任何帮助都是值得的。
问题是我认为这个option segment:use32将用32位编码以下代码。然而，要做到这一点，你必须将代码划分为多个段，你可以将属性分配给这些段
示例：
_TEXT16 SEGMENT USE16 'CODE'
;16bit code here
_TEXT16 ENDS
_TEXT32 SEGMENT USE32 'CODE'
;32bit code here
_TEXT32 ENDS
我的最终结果是这样的：
.386p
.model TINY, C, NEARSTACK
;------------------------------
; CODE
;------------------------------
_TEXT16 SEGMENT STACK USE16 'CODE'
org 07C00h
Error PROTO lpStr:WORD
Print PROTO lpStr:WORD
ReadDisk PROTO nSectorsRead:BYTE, nCylinder:BYTE, nSector:BYTE, nHead:BYTE, nDrive:BYTE, lpBuffer:WORD
NewLine PROTO
PrintLn PROTO lpStr:WORD
PrintWord PROTO num:WORD
ReadKey PROTO
_start:
xor ax, ax
mov ds, ax
mov ss, ax
mov es, ax
mov bp, 07C00h
mov sp, bp
mov [bootDisk], dl
INVOKE PrintLn, OFFSET bootInfo ;Onyl works because we are using JWASM as our compiler!
INVOKE PrintLn, OFFSET loadingInfo
INVOKE ReadDisk, 1, 0, 2, 0, [bootDisk], 07E00h
INVOKE Print, OFFSET pageInfo
INVOKE PrintWord, MEM_PAGE_COUNT
INVOKE NewLine
INVOKE PrintLn, OFFSET protectedInfo
lgdt fword ptr [GDT_desc]
mov eax, cr0
or eax, 1
mov cr0, eax
db 66h ;manually encoded far jump = CODE_SEG:start_protected_mode
db 0EAh
dd OFFSET start_protected_mode
dw CODE_SEG
Error PROC lpStr:WORD
INVOKE Print, lpStr
mov ah, 0
int 16h
db 0EAh ;manually encoded reboot
dw 0000h
dw 0FFFFh
Error ENDP
Print PROC USES ax si lpStr:WORD
mov si, lpStr
mov ah, 0Eh
@@loop:
lodsb
cmp al, 0
je @@done
int 10h
jmp @@loop
@@done:
ret
Print ENDP
NewLine PROC USES ax
mov ah, 0Eh
mov al, 13
int 10h
mov al, 10
int 10h
ret
NewLine ENDP
PrintLn PROC lpStr:WORD
INVOKE Print, lpStr
INVOKE NewLine
ret
PrintLn ENDP
ReadDisk PROC uses ax cx dx bx nSectorsRead:BYTE, nCylinder:BYTE, nSector:BYTE, nHead:BYTE, nDrive:BYTE, lpBuffer:WORD
mov ah, 02h
mov al, nSectorsRead
mov ch, nCylinder
mov cl, nSector
mov dh, nHead
mov dl, nDrive
mov bx, lpBuffer
int 13h
jnc @@end
INVOKE Error, OFFSET diskReadError
@@end:
ret
ReadDisk ENDP
;------------------------------
; DATA
;------------------------------
bootDisk byte 1
bootInfo db "Booting CompatOS...", 0
loadingInfo db "Loading extra sector...", 0
diskReadError db "Disk read failed!", 0
pageInfo db "Page count: ", 0
GDT_null dq 0
GDT_code dw 0FFFFh
dw 0
db 0
db 10011010b
db 11001111b
db 0
GDT_data dw 0FFFFh
dw 0
db 0
db 10010010b
db 11001111b
db 0
GDT_desc dw OFFSET GDT_desc - OFFSET GDT_null - 1
GDT_addr dd OFFSET GDT_null
CODE_SEG equ GDT_code - GDT_null
DATA_SEG equ GDT_data - GDT_null
;------------------------------
; PADDING
;------------------------------
byte 510-($-_start) dup (0)
dw 0AA55h
org 07E00h
MEM_BEG equ 08000h
MEM_END equ 0FFFFh
MEM_PAGE_COUNT equ (MEM_END - MEM_BEG) / 0200h
;------------------------------
; CODE
;------------------------------
PrintWord PROC USES ax bx dx num:WORD
LOCAL digit:BYTE
.if num >= 10
mov ax, num
mov dx, 0
mov bx, 10
div bx
INVOKE PrintWord, ax
.endif
mov ax, num
mov dx, 0
mov bx, 10
div bx
mov digit, dl
mov ah, 0Eh
mov al, '0'
add al, digit
int 10h
ret
PrintWord ENDP
ReadKey PROC
mov ah, 0
int 16h
xor ah, ah
ret
ReadKey ENDP
_TEXT16 ENDS
_TEXT32 SEGMENT USE32 'CODE'
start_protected_mode:
mov ax, DATA_SEG
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 90000h
mov esp, ebp
mov eax, 0B8000h
mov [eax], 'P'
mov [eax+1], 14
cli
hlt
;------------------------------
; DATA
;------------------------------
protectedInfo db "Entering protected mode...", 0
;------------------------------
; PADDING
;------------------------------
byte 1024-($-start_protected_mode) dup (0)
_TEXT32 ENDS
END _start