74 lines
904 B
PHP
74 lines
904 B
PHP
;; File: gdt.inc
|
|
|
|
gdt:
|
|
; null descriptor
|
|
dd 0
|
|
dd 0
|
|
|
|
; kernel code descriptor
|
|
dw 0xFFFF, 0x0000
|
|
db 0x00, 0x9a, 0xCF, 0x00
|
|
|
|
; kernel data descriptor
|
|
dw 0xFFFF, 0x0000
|
|
db 0x00, 0x92, 0xCF, 0x00
|
|
|
|
; user code descriptor
|
|
dw 0xFFFF, 0x0000
|
|
db 0x00, 0xFA, 0xCF, 0x00
|
|
|
|
; user data descriptor
|
|
dw 0xFFFF, 0x0000
|
|
db 0x00, 0xF2, 0xCF, 0x00
|
|
|
|
; Tss
|
|
.tss:
|
|
.limit dw ?
|
|
.base dw ?
|
|
.baseh0 db ?
|
|
.access db ?
|
|
.flags db ?
|
|
.baseh1 db ?
|
|
|
|
.end:
|
|
|
|
pGDT:
|
|
dw gdt.end - gdt - 1
|
|
dd gdt
|
|
|
|
gdt_set_tss:
|
|
mov ecx, sizeof.TSS
|
|
mov [gdt.limit], cx
|
|
mov [gdt.base], ax
|
|
|
|
shr ecx, 16
|
|
shr eax, 16
|
|
|
|
mov [gdt.baseh0], al
|
|
mov [gdt.baseh1], ah
|
|
mov al, 0x89
|
|
mov [gdt.access], al
|
|
|
|
and cl, 0xF
|
|
or cl, 0x40
|
|
mov [gdt.flags], cl
|
|
ret
|
|
|
|
gdt_flush:
|
|
; load kernel gdt
|
|
lgdt [pGDT]
|
|
jmp 0x08:@f
|
|
@@:
|
|
mov ax, 0x10
|
|
mov ds, ax
|
|
mov es, ax
|
|
mov fs, ax
|
|
mov gs, ax
|
|
mov ss, ax
|
|
ret
|
|
|
|
tss_flush:
|
|
mov ax, 0x2B
|
|
ltr ax
|
|
ret
|