saiputravu / saios

Developing a custom kernel + bootloader in x86 (real, protected and long mode) and C for the fun of it

SaiOS

Building instructions

Windows change pwd to %cd%

Docker building

docker build -t linux-build-env .
docker run -it --rm -v `pwd`:/root/env linux-build-env
make 

Emulation

There are multiple options for emulators including, but not limited to:

• QEMU (Which I picked)
• Bochs
• Oracle VMBox
• VMWare

qemu-system-x86_64 -fda ./build/img/disk.img

Debugging

For debugging, I tried using gdb-multiarch, but radare2 dealt with it the best

# 0x9000 is kmain (Look at ./build/img/os.map for updated values)
qemu-system-x86_64 -fda ./build/img/disk.img -gdb tcp::9001 -S & \
    r2 -m 0x9000 -b 64 -d gdb://localhost:9001

Inside radare2

e dbg.bpinmaps=0 # Might not have to do this, it caused issues for me though
db 0x9000
dc
V!

# Step into
s
# Step over 
S 

# Seek to PC / RIP
.
# Commands 
:
# Help
?