2021-11-03 19:03:38 +00:00
|
|
|
/* Tell processor to use our gdt*/
|
|
|
|
|
gdt:
|
|
|
|
|
.word (gdt_end - gdt_start -1) # Size of the GDT in bytes minus 1 for math reasons
|
|
|
|
|
.int gdt_start # linear address of our GDT
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
.att_syntax
|
|
|
|
|
|
2021-11-16 12:57:15 +00:00
|
|
|
.global load_gdt
|
|
|
|
|
load_gdt:
|
|
|
|
|
lgdt gdt
|
2021-11-03 19:03:38 +00:00
|
|
|
|
2021-11-16 12:57:15 +00:00
|
|
|
# set the segment selecters
|
|
|
|
|
|
|
|
|
|
movw $0x10, %ax
|
|
|
|
|
movw %ax, %ds
|
|
|
|
|
movw %ax, %es
|
|
|
|
|
movw %ax, %fs
|
|
|
|
|
movw %ax, %gs
|
|
|
|
|
movw %ax, %ss
|
|
|
|
|
ljmp $0x08, $flush
|
|
|
|
|
|
|
|
|
|
flush:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
#load idt
|
|
|
|
|
call init_idt
|
|
|
|
|
sti
|
|
|
|
|
|
|
|
|
|
# Try enable A20
|
|
|
|
|
# mov $0x2401, %ax
|
|
|
|
|
# int $0x15
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
# enable protected mode
|
|
|
|
|
mov %cr0, %eax
|
|
|
|
|
or $1, %eax
|
|
|
|
|
mov %eax, %cr0
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
call kernel_main
|
2021-11-03 19:03:38 +00:00
|
|
|
|
|
|
|
|
|
2021-11-16 12:57:15 +00:00
|
|
|
cli
|
|
|
|
|
1: hlt
|
|
|
|
|
jmp 1b
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
.size _start, . - _start
|
|
|
|
|
|
2021-11-03 19:03:38 +00:00
|
|
|
/*
|
|
|
|
|
* Create the GDT
|
|
|
|
|
*/
|
|
|
|
|
.section .data
|
|
|
|
|
gdt_start:
|
|
|
|
|
gdt_null:
|
|
|
|
|
.long 0x0
|
|
|
|
|
.long 0x0
|
|
|
|
|
|
|
|
|
|
gdt_kcode:
|
|
|
|
|
.word 0xFFFF # limit
|
|
|
|
|
.word 0x0 # base
|
|
|
|
|
.byte 0x0 # base
|
|
|
|
|
.byte 0b10011010 # 1st flags | type flags
|
|
|
|
|
.byte 0b11001111 # 2nd flags | limit
|
|
|
|
|
.byte 0x0 # base
|
|
|
|
|
|
|
|
|
|
gdt_kdata:
|
|
|
|
|
.word 0xFFFF # limit
|
|
|
|
|
.word 0x0 # base
|
|
|
|
|
.byte 0x0 # base
|
|
|
|
|
.byte 0b10010010 # 1st flags | type flags
|
|
|
|
|
.byte 0b11001111 # 2nd flags | limit
|
|
|
|
|
.byte 0x0 # base
|
|
|
|
|
gdt_end:
|
