A toy OS consisting of a multi-stage bootloader and a kernel. This is purely an exercise in x86 OS development out of curiosity. Please be smart and don't brick any real hardware using my code.
In order to compile the project you'll need a cross-compiler and matching
binutils for the generic i686-elf target platform. This must be your
target as the OS is 32-bit and made for the x86 ISA. You may do as I have and
follow the instructions here: https://wiki.osdev.org/GCC_Cross-Compiler
GNU make and coreutils are also required.
After aquiring the dependencies simply run make which will produce a file
named floppy.img that you can use with an emulator like qemu or bochs.
The project book I followed can be found in the doc directory. The book also
includes several links to other relevant documents you can download online, such
as the multiboot, BIOS, and IA-32 specifications.
Online copy of the project book: http://www.cs.cmu.edu/~410-s07/p4/p4-boot.pdf
boot0:
- Does BIOS service to reset device controller (
int 0x13, %ah = 0) only work with floppies? If so, how to make it work with more types of storage?
boot1:
- BIOS service to query upper memory size (
INT 0x15, %ax = 0xE801) is limited and the more advanced function (ax = 0xE820) should be used instead. See: https://wiki.osdev.org/Detecting_Memory_(x86) - The boot loader complies with Multiboot v1 when improved v2 exists. Using the word "complies" very loosely here, it does bare minimum for the kernel.
- No support for any filesystems or object files. This is fine unless the kernel grows >576 KiB in size or the boot loader must be anything more than a toy.
himem.sassumes the PS/2 controller exists and is properly configured. Ideally it would first do some setup and test those assumptions.