SiBoLo - Simple Bootloader

The name SiBoLo is an acronym for simple bootloader. SiBoLo is a simple single staged bootloader for fat12 formatted floppys, which loads a single file from by its name.

More information about the project is available on my blog.

Usage

Build process

To build the bootloader The Netwide Assembler (nasm) has to be installed.

The bootloader binary (bootloader.bin) can be built with

make

Configuring the bootloader

The bootloader needs to know the 8.3 or short filename of the file it should boot. The filename needs to be written to the offset 498 of the bootloader.

This can be done with the following command:

echo "TEST    BIN" | dd of=<bootloader binary> conv=notrunc  bs=1 count=11 seek=498

Write the bootloader to an image

The bootloader can be written to an image with dd:

dd if=<bootloader binary> of=<image file> conv=notrunc  bs=512 count=1

Development

Debugging

The bootloader can be debugged with qemu and gdb.

In one terminal window execute

make debug

and in another terminal window connect with gdb using:

gdb \
    -ex "target remote :1234" \
    -ex "set tdesc filename target.xml" \
    -ex "break *0x7c00" \
    -ex "layout asm" \
    -ex "set disassembly-flavor intel" \
    -ex "continue"

Testing

The project has build processes for three floppy images and testcode to verify that the bootloader works.

The test process is documented in the tests directory.