izix

A hobby *nix OS (Homepage)

This is a small kernel for i386 aiming to provide a POSIX compatible API. Currently, izix only boots with izixboot. This is still a very young project which is nowhere near ready for userland.

Building:

Tool-chain:

• First you will need to build GNU binutils for i386-elf (or better). I used version 2.28 and my configure options were --target="i686-elf" --prefix="/opt/i686-elf" --with-sysroot --disable-nls --disable-werror
• Next you will need to build GCC for i386-elf (or better) with a valid crtbegin.o and crtend.o. I used version 6.3.0 and my configure options were --target="i686-elf" --prefix="/opt/i686-elf" --with-as="/opt/i686-elf/bin/i686-elf-as" --with-ld="/opt/i686-elf/bin/i686-elf-ld" --without-headers --enable-languages="c,c++" --disable-nls --disable-werror
• That's it! Because it's all freestanding right now, we just need that stage 1 tool-chain.

The build:

Just run make (well, sorta). You'll have to set the appropriate PATH and provide the appropriate CC and AR on the command line like this: PATH="/opt/i686-elf/bin:$PATH" make CC=i686-elf-gcc AR=i686-elf-ar This will produce the izix.kernel ELF object. The strip make target will remove unnecessary symbols form izix.kernel, but don't forget to specify the correct STRIP on the command line like this: make STRIP=/opt/i686-elf/bin/i686-elf-strip strip.

Installing:

See izixboot/README.md#installing for details.

Hacking:

Debugging:

• You can generate a debug symbol file at izix.debug with the debug make target, but don't forget to specify the correct OBJCOPY on the command line like this: make OBJCOPY=/opt/i686-elf/bin/i686-elf-objcopy. You must run this target before any stripping you want to do on izix.kernel. You can load the symbols with GDB like this: gdb -s izix.debug.
• You can debug with QEMU by opening a GDB server and stopping the CPU at startup by specifying the -s and -S command line options to your qemu-system-<target> where target is either i386 or x86_64.
• A convenient GDB script has been placed in debug/gdb.x which will connect to a GDB server at port 1234, set the architecture to i386:intel, and drop you off at 0x9000 in _start.
• Bringing it all together, I suggest the following commands:

# Build your kernel image with debug symbols by setting CFLAGS and ASFLAGS to "-O0 -ggdb -Wall -Wextra" ...
make OBJCOPY=/opt/i686-elf/bin/i686-elf-objcopy debug  # Generate izix.debug symbol file.
make OBJCOPY=/opt/i686-elf/bin/i686-elf-objcopy strip  # Strip the debug symbols that are no longer needed.
# Install your kernel image with izixboot to a disk image ...
qemu-system-i386 -hda path/to/your_disk_image -s -S &> /dev/null &  # Start QEMU with a GDB server at localhost:1234 and stop the CPU at startup.
gdb -x debug/gdb.x -s izix.debug  # Access the GDB server, set the correct architecture, break at 0x9000, and load the debuging symbols.

License:

izix --  A hobby *nix OS
Copyright (C) 2017  Isabell Cowan

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.