BIOS int 13h/AH=42 未读取磁盘或读取到内存中的正确位置

Question

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我正在尝试让 BIOS 从磁盘读取一小部分并执行它。到目前为止我有

; Boot sector if you didn't know. The entire purpose of this is to jump to protected mode setup (PMS)
%define BIOS_ERROR_FREQUENCY 440
%define ERR_LBA_NOT_FOUND    1
%define ERR_BIOS_WRITE       2

extern BIOS_BLOCK_SIZE
extern boot_sector_e
extern pms_s
extern pms_e
extern pms_number_of_blocks

section .boot
    ; Check if the BIOS supports LBA
    mov ah, 0x41
    mov bx, 0x55AA
    ; dl has already been set to the boot drive
    int 0x13
    ; Error handle
    mov al, ERR_LBA_NOT_FOUND
    jc boot_error

    ; If it does support LBA, we read in PMS to memory and start executing it
    mov ah, 0x42
    ; dl already set
    mov si, bios_lba_packet_s
    int 0x13
    mov al, ERR_BIOS_WRITE
    jc boot_error
    jmp pms_s
    ; Please note that this will overwrite and read extra from the disk. We don't know what this is however, we can just ignore it :)

    ; Misc
    bios_lba_packet_s:
    db bios_lba_packet_e - bios_lba_packet_s ; Size
    db 0 ; Reserved
    dw pms_number_of_blocks
    dw boot_sector_e ; Offset of transfer buffer location
    dw 0x0 ; Section
    dq 0 ; Starting block. We have the ability to hardcode this because it's at the set position of one sector off (boot sector is 0)
    bios_lba_packet_e:

    boot_error: ; Will just print out a upon error
        mov ah, 0x0E
        mov al, "a"
        int 0x10
        jmp $

section .boot-header
    dw 0xAA55 ; 55AA tells the BIOS that this is bootable (reversed because of endians)

和

section .pms
    mov ah, 0x0E
    mov al, "w"
    int 0x10

这就是我想要加载的内容，并且在工作时只会打印出“w”

我 link 和

SECTIONS {
    .boot ORG : {
        boot_sector_s = .;
        *( .boot );
    }
    . += BIOS_BLOCK_SIZE - boot_header_size - boot_size;
    .boot-header : {
        *( .boot-header );
        boot_sector_e = .;
    }
    
    .pms : {
        pms_s = .;
        *( .pms );
        pms_e = .;
    }
}
/* Constants */
BIOS_BLOCK_SIZE = 512;
ORG = 0x7C00;

boot_size = SIZEOF( .boot );
boot_header_size = SIZEOF( .boot-header ); /* This has be defined after the .boot-header section has been defined (it's weird, I know) */
pms_number_of_blocks = ((pms_e - pms_s) + BIOS_BLOCK_SIZE) / BIOS_BLOCK_SIZE;

我已经把内存转储出来了，没有找到载入的部分。我还检查了进位标志，但没有设置。这可能与我的最终二进制文件没有填充以使我要加载的部分成为完整的 512 字节有关吗？

Answer 1

InstallationCheck 函数 41h 报告的事实 CF=0 并不代表一切。
您仍然需要验证 BX=AA55h 以查看 IBM/MS INT 13 扩展是否确实安装.
并检查 CX 中的 SubsetSupportBitmap。如果设置 CX 的位 0，则 支持 ExtendedRead 函数 42h。

pms_number_of_blocks = ((pms_e - pms_s) + BIOS_BLOCK_SIZE) / BIOS_BLOCK_SIZE;

这会将您的 pms_number_of_blocks 设置为 1。您需要将 StartingAbsoluteBlockNumber 设置为 1 而不是 0。（0 将重新读取引导扇区。）

bios_lba_packet_s:
db 16
db 0
dw pms_number_of_blocks
dd 0:pms_s
dq 1

Could it have something to do with my final binary not having padding in order to make the section I want to load in be a full 512 bytes?

继续垫吧！无论如何你都应该这样做。

奇怪地看到“ERR_BIOS_WRITE”报告了一个读取的函数。

BIOS.Teletype 函数 0Eh 使用 BH DisplayPage 参数。将其设置为 0。

  section .pms
      mov  bh, 0
      mov  ax, 0x0E * 256 + "w"
      int  0x10
      times (512 - 7) db 0

BIOS 仅将 DL 寄存器中的引导驱动器传递给您。没有其他的！不要相信段寄存器的任何特定设置。明确设置DS=0。
始终在安全的地方设置堆栈。这里设置在bootsector下面：
```
  xor  ax, ax
  mov  ds, ax
  mov  ss, ax
  mov  sp, 0x7C00
```

BIOS int 13h/AH=42 未读取磁盘或读取到内存中的正确位置

BIOS int 13h/AH=42 not reading disk or reading into right place in memory

assembly

x86

operating-system

nasm

bios