Design and usage documents have been moved to /src/doc. Everything below this section is no longer maintained and may be inaccurate.
In order to build, simply type "make" command under the repo's root directory. The makefile will automatically dispatch make commands to subdirectories under ./src folder.
Use "make" without any argument to build all components and save the output to ./bin, which will be loaded as the booting image later if you run emulation.
Use "make run" to load the boot disk and start running simulation on bochs, which is a handy tool for running lightweight x86 virtual machines. As an alternative, you can also use "make qemu" to load the boot disk and start QEMU. Both Bochs and QEMU are capable of emulating a x86 environment.
In addition, you can also use VirtualBox to load the boot image as the first floppy device and start the virtual machine. VirtualBox provides a slightly different environment, which is closer to a real physical machine. For example, VirtualBox does not enable A20 gate at system startup, while both Bochs and QEMU by default enables A20. This forces programmers to check and activate it manually in the bootloader.
Under ./src/util directory, there are a few tools that are developed to aid the development of this project.
This utility tool patchs a given binary file to a specified length, with optionally custom padding value. We use this tool to make a 1.44MB floppy disk out of the compiled bootloader image.
Due to the way we assemble the bootloader (use "cat" command to conbine separate source files into a single flat file before calling the assembler), when nasm finds an error in the source file, it reports the line number in the combined file, which is nonsense. In order to translate the combined line number into individual files, we developed the peek_line.py tool to scan each file and remember their starting line and compare the lines in the combined source and locate each file's offset. Run "make peek_line LINE=ddd" where "ddd" is the line number in combined loader source file.
nasm: The assembler we use to translate the bootloader into a binary file
Bochs: The emulation tool for debugging real mode code and protected mode code
QEMU: An alternative to Bochs
Python: To run some of the utility tools