ayllon/dalek

dalek

Few years ago I messed around a bit with how to boot a computer. Felt nostalgic and brought it back to life.

Build

MacOs X

Using ports, you will need to install cmake, i386-elf-gcc and mtools. Then, run these commands

mkdir build
cd build
cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/modules/Platform/i386.cmake -DCMAKE_BUILD_TYPE=DEBUG ..
make floppy

Linux

Assuming a 64 bits Linux machine, you will need to install cmake, gcc and mtools.

mkdir build
cd build
cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/modules/Platform/i386.cmake -DCMAKE_BUILD_TYPE=DEBUG ..
make floppy

Debugging

As a result of the compilation, inside your build directory under root, there will be two files: stage2.bin and stage2.sym

• stage2.bin is the plain binary code that is loaded by stage1
• stage2.sym contains the debug symbols

stage2.bin is copied into floppy.img, which can be booted using qemu for debugging as follows

qemu-system-i386 -fda floppy.img -s -S

This will start qemu opening the port 1234 for debugging, and waiting for gdb to connect. Then, open gdb pointing to the .sym file, and connect to qemu

gdb root/stage2.sym
(gdb) target remote :1234
Remote debugging using :1234
0x0000fff0 in ?? () 

Press c to start the system, and use gdb as usual!

(gdb) bt
#0  kb_getc () at .../dalek/bootloader/stage2/keyboard.c:135
#1  0x000011dc in getc () at .../dalek/bootloader/stage2/get.c:16
#2  0x0000120a in gets (dest=0x6d40 <buffer> "a") at .../dalek/bootloader/stage2/get.c:33
#3  0x00000b88 in CLI () at .../dalek/bootloader/stage2/cli.c:50
#4  0x00002153 in main (boot_info=0x641 <bootInformation>) at .../dalek/bootloader/stage2/main.c:44