operating system kernel experiment 1

system boot part

experiment goal

• /boot/bootsect.s custom print information
• /boot/setup.s print hardware information

source code analysis

boot/bootsect.s

this step first copies itself to the position of 0x90000, and jumps over to execute,

then read setup.s to position of 0x90200,

print information and copy system to the address 0x10000,

deter the device number of the file system,

and jump to the setup program to run.

boot/setup.s

the setup program obtains and stores hardware information in the from of bios interruption

these data are stored starting from 0x90000

yes, it will directly overwrite the original bootsect program

then setup moves the whole block of system from 0x10000 down to 0x00000,

then load idtr and gdtr, prefrom hardware settings, entry 32-bit, protected mode operation, and jump to the head.s program at the top of system to run.

experiment details

this experiment is relatively simple, mainly for printing control

print information

mov $0x3, %ax;
xor %bh, %bh;
int 0x10;
# get current cursor position 

mov $len, %cx;
mov $msg, %bp;
mov $0x0007, %bx; 
mov $0x1301, %ax;
int 0x10;
# print msg