如何从第二阶段引导加载程序将更多代码加载到内存中? [英] How i can load more code to memory from a second-stage bootloader?

问题描述

我使用该代码加载我的第二个扇区(引导加载程序扩展):

i load my second sector( a bootloader expansion ), with that code:

mov ah, 00;                     // reset disk
int 13h;                        // disk interrupt

mov ax, 0x0000;                 // register ax [0000]:1000
mov bx, 0x1000;                 // register bx  0000:[1000]

mov ah, 0x2;                    // read sector instruction
mov al, 0x2;                    // sectors to read
mov ch, 0x0;                    // cylinder
mov cl, 0x6;                    // local to write
mov dh, 0x0;                    // head

int 0x13;                       // call the disk interupter

jmp 0x0000:0x1000;              // Jump to kernel

但是我想在内存中加载另一个内核(保护模式内核)，我该如何使用此代码加载它或者我必须使用其他方式?

but i want to load another kernel at memory( the protected mode kernel ), how i can use this code to load it or i got to use other way?

bootloader = 1 个扇区 512 字节

bootloader = 1 sector 512 bytes

内核 x16 = 2 个扇区 1024 字节

kernel x16 = 2 sector 1024 bytes

内核 x32 = 2 个扇区 1024 字节(我知道我可以加载更多，更改 AL)

kernel x32 = 2 sector 1024 bytes ( i know that i can load more, changing AL )

推荐答案

您不想在 16 位内核运行时在 16 位内核上加载 32 位内核，因此您需要为数据使用不同的内存地址要加载.(在磁盘读取调用和远 jmp 中).

You don't want to load the 32-bit kernel over your 16-bit kernel while it's running so you need to use a different memory address for the data to be loaded. (In the disk-read call and the far jmp).

但是，很明显，当您仍处于 16 位实模式时，相同的 BIOS 调用以相同的方式工作.@MichaelPetch 评论了 我必须不断改变扇区，或者我可以加载多个，您可以安全地加载多个扇区，但为了便于携带有问题的 BIOS，您应该避免加载太多以至于跨越柱面边界.如果是这种情况，请使用多个调用.

But yes, obviously the same BIOS call works the same way while you're still in 16-bit real mode. @MichaelPetch commented on Do I have to keep changing sectors or can I load multiple that you can safely load multiple sectors but for portability to buggy BIOSes you should avoid loading so many that you cross a cylinder boundary. If that's the case use multiple calls.

制作一个带有 16 位入口点的组合内核并使用一个 4 扇区加载从引导加载程序加载整个内容会更简单.

It would be simpler to just make a combined kernel with a 16-bit entry point and load the whole thing from your bootloader with one 4-sector load.

您可以在一个 NASM 源文件中使用 BITS 16 和 BITS 32 来组装 16 位与 32 位模式.您甚至可以将 far-jmp 标签用于 32 位代码，而不是用于加载代码的硬编码地址.

You can use BITS 16 and BITS 32 within one NASM source file to assemble for 16-bit vs. 32-bit mode. You can even use a label for the far-jmp to 32-bit code instead of to a hard-coded address where you load the code.

另见:

• 引导加载程序不会跳转到内核代码
• 如何为我的引导加载程序制作内核?
• 如何从第一阶段加载第二阶段引导加载程序阶段?(两阶段引导加载程序设置类似于您要问的内容.)

• Boot loader doesn't jump to kernel code
• How to make the kernel for my bootloader?
• How to load second stage boot loader from first stage? (a two-stage bootloader setup is something like what you're asking about.)

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