A haribote OS. Just run it by $ make run.

1. Start BIOS.
2. BIOS reads the first 1 sector(2048 bytes), which is called IPL(initial boot loader), from a floppy disk into the memory 0x7c00.
3. [ipl10.asm] IPL reads 10 cylinders from a floppy disk into the memory 0x8200.
4. [nasmhead.asm] OS prepares boot(setting an image mode, enabling memory access more than 1MB, moving 32 bits mode, etc.)
5. [nasmhead.asm] Execute the segment on bootpack.
6. [bootpack.c and other c files] Execute haribote OS.

• 512 bytes binary assembled from ipl10.asm
• binary assembled from nasmhead.asm
• binary compiled from bootpack.c and other c files.

• 0x07C00ー0x07DFF: IPL. The first 1 sector(2048 bytes) of a floopy disk. This is the boot sector.
• 0x08200ー0x34FFF: The content of a floopy disk(10 cylinders. Except IPL.)

• 0x00000000ー0x000FFFFF: Use during startup phase, but becomes empty after that (1MB)
• 0x00100000ー0x00267FFF: Content storage for a floppy disk (1440KB)
• 0x00268000ー0x0026F7FF: Empty (30KB)
• 0x0026F800ー0x0026FFFF: IDT (2KB)
• 0x00270000ー0x0027FFFF: GDT (64KB)
• 0x00280000ー0x002FFFFF: bootpack.brb (512KB)
• 0x00300000ー0x003FFFFF: Stack etc. (1MB)
• 0x00400000ー: Empty

$ nasm -version
NASM version 2.11.08

$ qemu-system-i386 --version
QEMU emulator version 2.12.0

$ gcc --version
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609

TODO: gdb-peda

$ make debug
gdb
(gdb) target remote localhost:10000

$ gdb --args qemu-system-i386 -m 32 -rtc base=localtime -vga std -fda  os.img

Create a log file

$ qemu-system-i386 -monitor stdio -m 32 -rtc base=localtime -vga std -d cpu_reset -D ./a.log -fda os.img

Disassemble

$ objdump -D -m i386 -b binary os.img > os.txt

GDB

QEMU_ARGS = -L . -m 32 -localtime -vga std -fda fdimage0.bin -monitor stdio -s -S
$ make run
gdb -ex 'target remote localhost:1234'

$ gdb ./a.out
gpb> p <function_name>

OR

$ objdump -d a.out | grep -C 20 <function_name>

(gdb) b *0x7x00 // Create break point to the beginning of IPL
(gdb) c

(gdb) x/16bx $eip // Dump as a binary
(gdb) x/i $eip // Dump as a assembly

When initial boot loader. https://speakerdeck.com/yuyabu/gong-kai-yong

• BIOS settings: http://oswiki.osask.jp/?(AT)BIOS
• Memory maps: http://oswiki.osask.jp/?(AT)memorymap
• VGA hardware
• How to format to an img file
• How to debug qemu by gdb
• x86 Assembly/x86 Instructions
• x86 アセンブラ
• 10シリンダ分読み込んでみる