HL-OS

A toy operating system for HashLink VM

This allows you to create a self-contained bootable image binary that includes:

• a very small kernel (kernel.c)
• the HashLink VM
• a minimal libc required to run the HLVM (libc.c)
• your application code compiled into HL bytecode (App.hx compiled into out/app.hl with Haxe)
• some extra data files

The boot sequence is the following:

• BootLoader:
  • read the device data
  • map the kernel code, symbold and VM bytecode into memory
  • enter into protected mode
  • call the kernel
• Kernel:
  • clear the screen
  • init the symbols table
  • load the HLVM bytecode
  • run it (the HLVM will translate it to machine code first)
• Congratulations ! You are now running your Haxe App in Kernel mode

Features

HLOS currently supports the following:

• VGA Text and 320x200 256 colors graphics mode (hlos.Vga)
• Keyboard events (hlos.Keyboard)
• Mouse events (hlos.Mouse)
• Handlers for Interrupts and IRQs (hlos.Interrupts)
• Bios interrupts and ports read (hlos.Bios)
• some tools to access Kernel functions (hlos.Kernel)

Compiling and Running

In order to compile HL-OS, you need GCC/LD/NASM/OBJDUMP toolchain. On Windows and OSX you need a cross compiler version capable of outputing ELF x86 code.

This can be downloaded from here

Look at Makefile for more details.

In order to run the HLOS kernel, you can use QEmu, then simply make run

Creating a bootable USB

In order to create a bootable standalone USB key, you need first to install the GRUB boot loader on it.

On windows, download Grub 2.06 and run grub-install.exe --force --no-floppy --target=i386-pc --boot-directory=X:\boot //./PHYSICALDRIVE#. You need to change your drive number and physical drive number with ones that match your system (see this tutorial).

Once your GRUB USB is ready, simply use make USB_DRIVE=X: install_usb to copy the files to it.

Testing can be done by booting QEmu directly on the usb key with make run_usb. This requires to run the command in administrator mode.

Injecting files

The kernel comes with a mini file system that allows to add and change files contained into the image without having to use any compilation. For this you can simply run haxe --run InjectFile -path out out/kernel.elf app.hl, this will add or replace the app.hl found in kernel file by the newest out/app.hl.

Please note that the kernel is compiled with a fixed amount of reserved data for files. It is defined in kernel_main.s and can be increased by recompiling the kernel.

Assembly programming

Starting from this haxe commit, you can now emit native assembly directly from Haxe using HLVM.

Use the hlos.Asm class that provides macro helpers. For instance you can do the following:

var v1 = 111, v2 = 222;
hlos.Asm.set(Edi, 0xFF); // set cpu register const value
hlos.Asm.set(Esi, v1); // set cpu register to local variable value
hlos.Asm.set(v2, Esi); // set local variable to cpu register

Please note that each HLVM local variable might currently be stored in a CPU register, so if you are doing an operation that changes the value of one Cpu register, you should call hlos.Asm.discard(Eax) to make sure that the local variable doesn't get corrupted (Asm.set does that for you automatically).

Legacy boot loader

The initial boot loader (in tools/boot.asm) was responsible of loading the kernel and calling it, however it is only working with the 1.44MB Floppy emulator and does not support kernel in the ELF format. Some extra work would be required to be able to load our kernel correctly.