ASBL

A Simple Boot Loader

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ASBL is a minimalistic boot loader for hobby OS development. It can load and launch a basic 32 bit binary kernel from a FAT12 file system.

###Compiling

####Requirements

• binutils - the assembler and linker
• make - automate the build
• mkfs.msdos - filesystem creation utility

Making ASBL is as simple as typing make into the terminal.

cd ASBL
make

This should produce the following files in the bin directory.

• STAGE1.BIN
• STAGE2.BIN
• KERNEL.BIN
• floppy.img

###Using

1. Mount floppy.img to the filesystem.

losetup -f # get the next loop device eg /dev/loop0 losetup /dev/loop0 bin/floppy.img mount /dev/loop0 ~/mnt umount ~/mnt # Then when you are done unmount losetup -d /dev/loop0

 2. Place a copy of `STAGE2.BIN` into the root directory.
 3. Call your kernel `KERNEL.BIN` and place a copy into the root directory.

    **Important!** Your kernel **must** be in plain binary format.
    This can be achieved by passing `--oformat binary` to the linker
    or by adding the line `OUTPUT_FORMAT("binary")` to the linker script.
    Alternatively a tool such as `objcopy` can be used to rip
    a plain binary out of an executable.

     **Important!** The kernel **must** be no bigger than 64KiB to be loaded.