i386 baremetal program development kit based on MIT JOS
- by default kernel will be load at physical address 0x400000
- there is only linear address at runtime，did not enable the page
- debug with qemu-system-i386
- user program entrypoint: void baremetal_main();
- user module put under 'user' directory，manually add into 'Makefrag' file
- use 'make' to build kernel.img (kernel with MBR)