NASM - 从 USB 驱动器加载代码

发布于 2024-10-12 09:06:49 字数 952 浏览 8 评论 0原文

任何汇编专家都知道表示第一个 USB 驱动器的参数（寄存器dl）吗？

我正在学习一些 NASM 教程，并且希望获得一个物理启动（我可以使用 qemu 获得一个干净的启动）。

这是从磁盘加载“内核”数据的代码部分：

loadkernel:
    mov si, LMSG ;; 'Loading kernel',13,10,0
    call prints  ;; ex puts()

    mov dl, 0x00 ;; The disk to load from
    mov ah, 0x02 ;; Read operation
    mov al, 0x01 ;; Sectors to read
    mov ch, 0x00 ;; Track
    mov cl, 0x02 ;; Sector
    mov dh, 0x00 ;; Head
    mov bx, 0x2000 ;; Buffer end
    mov es, bx
    mov bx, 0x0000 ;; Buffer start

    int 0x13
    jc loadkernel

    mov ax, 0x2000
    mov ds, ax

    jmp 0x2000:0x00

如果有什么区别的话，我正在运行普通的 Dell Inspiron 15 BIOS。

显然，对我来说正确的值是 0x80。

BIOS 加载硬盘驱动器并从 0x80 开始标记它们根据这个答案。

由于某种原因，我的特定 BIOS 决定将 USB 驱动器作为第一个加载，这样我就可以从那里启动。

原文

Would any assembly gurus know the argument (register dl) that signifies the first USB drive?

I'm working through a couple of NASM tutorials, and would like to get a physical boot (I can get a clean one with qemu).

This is the section of code that loads the "kernel" data from disk:

loadkernel:
    mov si, LMSG ;; 'Loading kernel',13,10,0
    call prints  ;; ex puts()

    mov dl, 0x00 ;; The disk to load from
    mov ah, 0x02 ;; Read operation
    mov al, 0x01 ;; Sectors to read
    mov ch, 0x00 ;; Track
    mov cl, 0x02 ;; Sector
    mov dh, 0x00 ;; Head
    mov bx, 0x2000 ;; Buffer end
    mov es, bx
    mov bx, 0x0000 ;; Buffer start

    int 0x13
    jc loadkernel

    mov ax, 0x2000
    mov ds, ax

    jmp 0x2000:0x00

If it makes any difference, I'm running a stock Dell Inspiron 15 BIOS.

Apparently, the correct value for me is 0x80.

The BIOS loads the hard drives and labels them starting at 0x80 according to this answer.

My particular BIOS decides to load the USB drive up as the first, for some reason, so I can boot from there.

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