JOS-LAB1 Boot the PC

Start up flow of PC:

1. BIOS

A. At the very beginning, BIOS would load 512-byte boot sector into [0X7C00,0X7DFF];

B. Then set cs:ip = 0000:7c00

2. Boot Loader

A. Switch from real mode to protected mode (+ bit), mainly by setting GDTR.

B. Load kernel image from hard disk.

(Void (*) (void)) (Elfhdr->e_entry ()) (); Check the kernel image, it ' s 0x0010000c

3. Kernel

A. In Kern/entry. S, it'll turn on the MMU first, set CR3 & CR0 with Entry_pgdir

B. Set esp and EBP.

C. I386_init ()
I386_init ()
|--> Cons_init ()
| |--> Cga_init ()
| |--> Kbd_init ()
| |--> Serial_init ()
|--> Mem_init ()
|--> Env_init ()
|--> Trap_init ()
|--> Mp_init ()
|--> Lapic_init ()
|--> Pic_init ()
|--> Boot_aps ()
|--> Env_create ()