在通过汇编引导程序级别上执行的C程序 [英] Execute C program at bootloader level via Assembler
问题描述
我写了一个自定义的（很基本的Hello world！）bootloader的汇编，我想在执行C程序。请问C程序的工作，或由于不能丢失 stdio.h中文件？我怎么能启动加载到一个单一的.bin文件到 DD 捆绑一起的C程序到闪存驱动器/ CD？
I wrote a custom (VERY basic "Hello world!") bootloader in Assembler and I would like to execute a C program in that. Would the C program work, or fail due to a lost stdio.h file? And how could I bundle the C program along with the bootloader into a single .bin file to dd to a flash drive/CD?
推荐答案
我不知道你所说的失去 stdio.h中的意思，但很多C运行时功能，包括那些在 stdio.h中原型，使用系统调用来实现。如果没有操作系统运行，这些系统调用将无法正常工作。
I'm not sure what you mean by "lost stdio.h", but many C runtime functions, including those prototyped in stdio.h, are implemented using system calls. Without an OS running, those system calls won't work.
有可能写出运行没有安装操作系统，例如最常见的引导程序有汇编的只是一个很小的量，大多C code C code。关键是要避免使用运行时库。替代的系统调用，例如为显示，有BIOS调用和特定硬件的I / O。
It is possible to write C code that runs without an OS, for example most common bootloaders have just a tiny amount of assembler and mostly C code. The trick is to avoid using runtime libraries. Alternatives to syscalls, for e.g. display, are BIOS calls and hardware-specific I/O.
要举一个例子，除了动态分配，的fopen 在读模式下需要以下的低级别操作：
To take just one example, in addition to dynamic allocation, fopen in read mode needs the following low-level operations:
- 从存储中读取数据块
- 读取文件系统元数据（通常，超级块和根目录）
- 处理文件系统元数据，找出文件内容存储
- 创建包含足够的信息，
FREAD和龟etc找到磁盘上的数据
- Reading a block of data from storage
- Reading the file system metadata (often, superblock and root directory)
- Processing file system metadata to find out where the file content is stored
- Creating a FILE object that contains enough information for
freadandfgetcto find the data on disk
您没有一个操作系统来帮助任何的是，你的C code将需要实现一个驱动器（可能是在调用BIOS）块的读取，并执行的其他步骤的行为。
You don't have an OS to help with any of that, your C code will need to implement a driver (possibly calling the BIOS) for block read, and implement the behavior of the other steps.
这篇关于在通过汇编引导程序级别上执行的C程序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
