itskernel

Table of contents

• itskernel
  • Table of contents
  • Building
    • Prerequisites
    • Compiling build environment
    • Compiling the kernel and user-space programs
    • Creating a disk image
  • License

Building

Prerequisites

The provided scripts assume a Debian-style Linux system with, among others, following packages installed:

• build-essential
• libgmp3-dev
• libmpfr-dev
• libmpc-dev
• texinfo
• bison
• flex
• nasm

The kernel expects the following features on the target system:

• x86 architecture with 64-bit long mode
• PCI Express
• AVX, including XSAVE/XRSTOR instructions

Compiling build environment

The kernel requires a special GCC-based cross-compiler.

Navigate into the compiler sub directory and run the buildcompiler.sh script. This will download binutils and GCC and perform all necessary build steps. The generated binaries x86_64-elf-name are stored in the compiler/bin sub directory, and can subsequently be used for compiling the kernel.

Compiling the kernel and user-space UI application

The entire source tree is contained in the code sub directory. The directory has a central Makefile that allows to compile each of the components, by invoking make target. Supported targets:

• kernel: Builds the kernel itself.
• lib: Builds the user-space standard library.
• net: Builds the user-space network library (only for use by the UI process).
• ui: Builds the UI application.
• all: Builds all of the above.
• clean: Removes all compiler outputs, temporary files and binaries.

Creating a disk image

After compiling all components these have to be combined into a disk image, to copy to an USB stick or load in a VM. This is done by executing create_image.sh from the image sub directory (sudo permission needed). To flash the image to an USB stick mounted at /dev/sdb invoke sudo dd if=disk.img of=/dev/sdb (be careful with this command).

Implementing user-space applications

Other user-space applications are stored in the code/apps/ sub directory; this directory already contains a "Hello World" program called test (which might be used as a template), and some apps written for research purposes.

The preferred way to load a user-space binary is using the network; otherwise, this can be achieved by adding the app to the OS image:

• In image/grub.cfg, add a line module2 /bin/appname.elf appname (the first argument specifies the path in the boot image, the second determines the application as shown in the OS file system)
• In image/create_image.sh, add a line sudo cp ../code/apps/appname/appname.elf mnt/bin Then the application binary will be automatically mounted at /apps/appname during system startup.

Debugging

VMware

The directory image/vm/ provides a pre-configured virtual machine file itskernel.vmx and a GDB input file gdb.in. The former configures VMware to open a debug port 1234, the latter attaches a GDB process to the running VM.

It is important to attach the debugger after GRUB has completed; this can be achieved automatically by adding the line

monitor.debugOnStartGuest64 = "TRUE"

to the virtual machine configuration file, which causes the VM to automatically pause when hitting the kernel's start function.

The GDB input file automatically loads the kernel symbols and sets a break point at init; to debug user-space programs instead, set the respective executable as symbol file, and change the break point to e.g. main.

License

The kernel itself is based on the Arc Operating System by Graham Edgecombe and licensed under the permissive ISC license.

Other components:

• dlmalloc: The kernel uses Doug Lea's memory allocator, as released into the public domain using the CC0 license. The license text can be found in LICENSE.dlmalloc.
• LWIP: Provides TCP/IP stack for network communication. Licensed under a BSD license, which can be found in LICENSE.lwip.