LarvaOS

A multitasking operating system and kernel with an interactive shell.

Using bless command to see our kernel image

bless - graphical hexadecimal Gtk# editor. Edit the FILEs as a sequence of bytes, allowing read/write, search, pattern finding, efficient query-replace, multi-tabbing, customized data-views, plugins, and many other features. Using bless command:

bless ./bin/LavaOS.img

Run your OS using qemu

qemu-system-x86_64 -hda ./bin/LavaOS.img

Using cross compiler

./bin/cross/bin/$TARGET-gcc --version   # For compile C files.
./bin/cross/bin/$TARGET-g++ --version   # For compile C++ files.
./bin/cross/bin/$TARGET-ld              # Linker.

Assemble a assembly file with nasm

nasm -f bin file_name.asm -o file_name.bin

To disassemble it, simply using ndisasm command:

ndisasm boot.binemu-system-x86_64 -hda file_name.bin -S -gdb stdio

Debug my kernel image with gdb

NOTE: We should use kernel.elf (kernel image) to add symbol instead of using disk image.

First, entering to gdb mode:

gdb

Adding traceable symbol file:

add-symbol-file /bin/kernel.o 0x0100000

Set break point in symbol:

break kernel_entry_point

Start debugging with remote target:

target remote | qemu-system-x86_64 -hda ./bin/LavaOS.img -S -gdb stdio

Switching to assembly:

layout asm

And step by step. prints out registers in both raw format (hex) and natural format in gdb:

info registers

debug variable

gdb

In gdb:

add-symbol-file ./src/kernel/core/kernel.o 0x0100000
target remote | qemu-system-x86_64 -hda ./bin/LavaOS.img -S -gdb stdio
# Set break point in file-line
break kernel.cc:21
# continue
c
# print value of ptr variable
print ptr

mount the disk image to your host

sudo mount -t vfat ./bin/LavaOS.img /mnt/d/
# do some thing ...
sudo umount /mnt/d/