2015-10-04 19:59:15 +02:00
|
|
|
/*
|
|
|
|
|
# Protected mode
|
|
|
|
|
|
2015-10-18 14:56:12 +02:00
|
|
|
Major changes from real moe:
|
2015-10-06 12:27:24 +02:00
|
|
|
|
|
|
|
|
- BIOS cannot be used anymore
|
|
|
|
|
|
2015-10-18 14:56:12 +02:00
|
|
|
- GDT and segmentation take effect immediately so we *have*
|
|
|
|
|
to deal with it now.
|
2015-10-06 12:27:24 +02:00
|
|
|
|
2015-10-18 14:56:12 +02:00
|
|
|
- we have to encode instructions differently, thus a `.code32` is needed.
|
|
|
|
|
Note that in 16-bit, 32-bit instructions were encodable, but with a prefix.
|
2015-10-06 12:27:24 +02:00
|
|
|
|
2015-10-27 09:04:46 +01:00
|
|
|
## Linux kernel
|
|
|
|
|
|
|
|
|
|
arch/x86/include/asm/segment.h contains a lot of action:
|
|
|
|
|
|
|
|
|
|
- the user privilege level
|
|
|
|
|
- the segment steup (kernel an user code and data segments)
|
|
|
|
|
|
2015-10-17 00:03:05 +02:00
|
|
|
## Bibliography
|
2015-10-04 19:59:15 +02:00
|
|
|
|
2015-10-18 14:56:12 +02:00
|
|
|
- http://stackoverflow.com/questions/28645439/how-do-i-enter-32-bit-protected-mode-in-nasm-assembly Initially adapted from this.
|
2015-10-04 19:59:15 +02:00
|
|
|
- http://wiki.osdev.org/Journey_To_The_Protected_Land
|
|
|
|
|
- http://wiki.osdev.org/Protected_Mode
|
|
|
|
|
- https://github.com/chrisdew/xv6/blob/master/bootasm.S
|
|
|
|
|
- https://thiscouldbebetter.wordpress.com/2011/03/17/entering-protected-mode-from-assembly/ FASM based. Did not word on first try, but looks real clean.
|
2015-10-17 00:03:05 +02:00
|
|
|
- http://skelix.net/skelixos/tutorial02_en.html
|
2015-10-04 19:59:15 +02:00
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
#include "common.h"
|
|
|
|
|
|
2015-10-18 14:56:12 +02:00
|
|
|
BEGIN
|
2015-10-17 00:03:05 +02:00
|
|
|
CLEAR
|
2015-10-18 14:56:12 +02:00
|
|
|
PROTECTED_MODE
|
2015-10-20 12:21:22 +02:00
|
|
|
VGA_PRINT_STRING $message
|
2015-10-17 00:03:05 +02:00
|
|
|
jmp .
|
2015-10-18 14:56:12 +02:00
|
|
|
message:
|
|
|
|
|
.asciz "hello world"
|
