Question

我正在使用BIOS并希望制作一个自制的操作系统。

我正在使用LBA方法（int 0x13, ah=0x42）并成功使其在QEMU上运行。但是，当我让它在真正的PC上工作时，它不起作用。它只能从USB读取512字节。

当我使用int 0x10来显示问题时，我终于找到了问题所在。内存根本不会移动到引用的内存中。我的代码写在下面。

[bits 16]
[ORG 0x7c00]
        ;; BPB Structure                                                                                                                     
JMP     entry           ;BS_jmpBoot
NOP                                                                                                  
BS_OEMName      DB "HARIBOTE"
BPB_BytsPerSec  DW 0x0200
BPB_SecPerClus  DB 0x01
BPB_RsvdSecCnt  DW 0x0001
BPB_NumFATs     DB 0x02
BPB_RootEntCnt  DW 0x0000
BPB_TotSec16    DW 0x0000
BPB_Media       DB 0xf8
BPB_FATSz16     DW 0x0000
BPB_SecPerTrk   DW 0xffff
BPB_NumHeads    DW 0x0001
BPB_HiDDSec     DD 0x00000000
BPB_TotSec32    DD 0x00ee5000
BPB_FATSz32     DD 0x000000ed
BPB_ExtFlags    DW 0x0000
BPB_FSVer       DW 0x0000
BPB_RootClus    DD 0x00000000
BPB_FSInfo      DW 0x0001
BPB_BkBootSec   DW 0x0000
        times   12      DB 0    ;BPB_Reserverd                                                                                               
BS_DrvNum       DB 0x80
BS_Reserved1    DB 0x00
BS_BootSig      DB 0x29
BS_VolID        DD 0xa0a615c
BS_VolLab       DB "ISHIHA BOOT"
BS_FileSysType  DB "FAT32   "



entry:  
    CLI

        MOV AX, 0 
        MOV DS, AX
        MOV ES, AX
        MOV BX, AX
    MOV CX, AX
    MOV SP, 0x7c00
prepare:
        PUSH    CS
        POP     DS
        PUSH    CS
        POP     ES
    STI
    mov ah, 0x41                ; Set Function 0x41
        mov word bx, 0x55AA          
        push dx                     ; Save old Drive Identifier
        mov dl, 0x80                ; Load 'Active' ID Into dl, commented out to keep bios setting of dl (should be active drive)
        int 0x13                    ; Call Interupt
        jc unsupported        ; If Extentions aren't Supported, Jump
        xor ax, ax
        add ax, 1                   ; clear carry flag
    XOR EDI, EDI

    MOV AH, 0x45
    MOV AL, 0x01
    MOV DL, 0x80
    INT 0x13

loop:
    MOV CL, 0
retry:
    PUSH DS
    PUSHAD
        MOV DL, 0x80
        MOV AH, 0x42
    MOV AL, 0x00
        MOV SI, DAPS
        INT 0x13
        JNC next

        ADD CL, 1
        MOV DL, 0x80 
        MOV AH, 0x00
        INT 0x13
        CMP CL, 6
        JAE error
        JMP retry
next:

    XOR EAX, EAX
    XOR EBX, EBX
    XOR ECX, ECX

    ADD EDI, 1
    MOV ECX, lba0
    MOV [ECX], EDI

    XOR EAX, EAX
    XOR ECX, ECX
    XOR EBP, EBP

    MOV AX, [addr]
    MOV ECX, addr
    MOV EBX, segm
    ADD AX, 0x200
    ADC BP, 0
    SHL BP, 12
    ADD BP, [segm]
    MOV [EBX], BP


    MOV [ECX], AX
    MOV [EBX], BP

    CMP EDI, 0x16a
    JB loop

    MOV ECX, 0xc200
    JMP check
interrupt:
    MOV EAX, 0x0000
    MOV EBX, EAX
    MOV EDX, EAX
    MOV EBP, EAX
    MOV ESI, EAX
    MOV EDI, EAX

    MOV CH, 10
    MOV [0x0ff0], CH

    MOV ECX, EAX
        JMP 0xc200
error:
    POPAD
    POP DS
        MOV     SI,msg
putloop:
        MOV     AL,[SI]
        ADD     SI,1            
        CMP     AL,0
        JE      fin
        MOV     AH,0x0e         
        MOV     BX,15       
        INT     0x10           
        JMP     putloop
fin:
        HLT                     
        JMP     fin            
msg:
        DB      0x0a, 0x0a      
        DB      "load error"
        DB      0x0a            
        DB      0
msg1:
        DB      0x0a, 0x0a      
        DB      "not supported"
        DB      0x0a            
        DB      0

unsupported:
    MOV SI, msg1
    JMP putloop

drv:    DB 0x80
DAPS:   DB 0x10               ; Size of Structure (16 bytes, always this for DAPS)
        DB 0                  ; Always 0
        DB 1                  ; Number of Sectors to Read (1x512)
        DB 0                  ; Always 0 
addr:   DW 0x8000             ; Target Location for Reading To (0x8000 = 0x0800:0x0000)  
segm:   DW 0x0000             ; Page Table (0, Disabled)
lba0:   DD 1                  ; Read from 2nd block (code I want to load)
    DD 0                  ; Large LBAs, dunno what this does
check:
    MOV AH, 0x0e
    MOV AL, [ECX]
    ADD AL, 48
    MOV BX, 0
    INT 0x10
    ADD ECX, 1
    CMP ECX, 0xc400
    JNE  check

    JMP interrupt


        RESB    0x01fe-($-$$)       
        DW 0AA55h

所以我的问题是：
某些时段内BIOS访问内存是否受到限制？我的BIOS是SMBIOS 3.0.0，型号是华硕x540la。

Answer 1

   [bits 16]
[ORG 0x7c00]
        ;; BPB Structure                                                                                                                     
JMP     entry           ;BS_jmpBoot
NOP                                                                                                  
BS_OEMName      DB "HARIBOTE"
BPB_BytsPerSec  DW 0x0200
BPB_SecPerClus  DB 0x01
BPB_RsvdSecCnt  DW 0x0001
BPB_NumFATs     DB 0x02
BPB_RootEntCnt  DW 0x0000
BPB_TotSec16    DW 0x0000
BPB_Media       DB 0xf8
BPB_FATSz16     DW 0x0000
BPB_SecPerTrk   DW 0xffff
BPB_NumHeads    DW 0x0001
BPB_HiDDSec     DD 0x00000000
BPB_TotSec32    DD 0x00ee5000
BPB_FATSz32     DD 0x000000ed
BPB_ExtFlags    DW 0x0000
BPB_FSVer       DW 0x0000
BPB_RootClus    DD 0x00000000
BPB_FSInfo      DW 0x0001
BPB_BkBootSec   DW 0x0000
        times   12      DB 0    ;BPB_Reserverd                                                                                               
BS_DrvNum       DB 0x80
BS_Reserved1    DB 0x00
BS_BootSig      DB 0x29
BS_VolID        DD 0xa0a615c
BS_VolLab       DB "ISHIHA BOOT"
BS_FileSysType  DB "FAT32   "



entry:  
    CLI

        MOV AX, 0
        MOV DS, AX
    MOV SS, AX
        MOV ES, AX
        MOV BX, AX
    MOV CX, AX
    MOV SP, 0x7c00
prepare:
    STI
    MOV [drv], DL
        CMP     DL, 0x80
        JB      unsupported    ; HDD系デバイスでなければエラー

    MOV AH, 0x0e
    MOV AL, [drv]
    MOV BX, 0
    INT 0x10

    mov ah, 0x41                ; Set Function 0x41
        mov word bx, 0x55aa          
        int 0x13                   ; Call Interupt
        jc unsupported        ; If Extentions aren't Supported, Jump




        xor ax, ax
        add ax, 1                   ; clear carry flag
    XOR EDI, EDI

    MOV AH, 0x45
    MOV AL, 0x01
    MOV DL, 0x80
    INT 0x13

    MOV AX, 0
    MOV DS, AX

loop:
    MOV CL, 0
retry:
    PUSH DS
    PUSHAD
        MOV DL, [drv]
        MOV AH, 0x42
    MOV AL, 0x00
        MOV SI, DAPS
        INT 0x13
        JNC next

        ADD CL, 1
        MOV DL, 0x80 
        MOV AH, 0x00
        INT 0x13
        CMP CL, 6
        JAE error
        JMP retry
next:

    XOR EAX, EAX
    XOR EBX, EBX
    XOR ECX, ECX

    ADD EDI, 1
    MOV ECX, lba0
    MOV [ECX], EDI

    XOR EAX, EAX
    XOR ECX, ECX
    XOR EBP, EBP

    MOV AX, [addr]
    MOV ECX, addr
    MOV EBX, segm
    ADD AX, 0x200
    ADC BP, 0
    SHL BP, 12
    ADD BP, [segm]
    MOV [EBX], BP


    MOV [ECX], AX
    MOV [EBX], BP

    CMP EDI, 0x16a
    JB loop

    MOV ECX, 0xc200
    JMP check
interrupt:
    MOV EAX, 0x0000
    MOV EBX, EAX
    MOV EDX, EAX
    MOV EBP, EAX
    MOV ESI, EAX
    MOV EDI, EAX

    MOV CH, 10
    MOV [0x0ff0], CH

    MOV ECX, EAX
        JMP 0x0000:0xc200
error:
    POPAD
    POP DS
        MOV     SI,msg
putloop:
        MOV     AL,[SI]
        ADD     SI,1            
        CMP     AL,0
        JE      fin
        MOV     AH,0x0e         
        MOV     BX,0       
        INT     0x10           
        JMP     putloop
fin:
        HLT                     
        JMP     fin            
msg:
        DB      0x0a, 0x0a      
        DB      "load error"
        DB      0x0a            
        DB      0
msg1:
        DB      0x0a, 0x0a      
        DB      "not supported"
        DB      0x0a            
        DB      0

unsupported:
    MOV SI, msg1
    JMP putloop

drv:    DB 0x80
DAPS:   DB 0x10               ; Size of Structure (16 bytes, always this for DAPS)
        DB 0                  ; Always 0
        DB 1                  ; Number of Sectors to Read (1x512)
        DB 0                  ; Always 0 
addr:   DW 0x8000             ; Target Location for Reading To (0x8000 = 0x0800:0x0000)  
segm:   DW 0x0000             ; Page Table (0, Disabled)
lba0:   DD 1                  ; Read from 2nd block (code I want to load)
    DD 0                  ; Large LBAs, dunno what this does
check:
    MOV AH, 0x0e
    MOV AL, [ECX]
    ADD AL, 48
    MOV BX, 0
    INT 0x10
    ADD ECX, 1
    CMP ECX, 0xc400
    JNE  check

    JMP interrupt


        RESB    0x01fe-($-$$)       
        DW 0AA55h

谢谢，我终于找出了原因。当我执行上面的代码时，它返回＆＃34;不支持＆＃34;。看来我的BIOS不支持纯usb-hdd启动，我的bios是usb-fdd模拟器所有问题都已经解决了，谢谢。

使用BIOS INT 13h，ah = 42h从USB读取

1 个答案: