Joshua Wise's Git repositories - netwatch.git/blame_incremental

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Commit	Line	Data
	1	; realmode.asm
	2	; Routines to return the system to real mode
	3	; NetWatch multiboot loader
	4	;
	5	; Copyright (c) 2008 Jacob Potter and Joshua Wise. All rights reserved.
	6	; This program is free software; you can redistribute and/or modify it under
	7	; the terms found in the file LICENSE in the root of this source tree.
	8
	9	[bits 32] ; Starts in 32 bit mode, then will drop back later.
	10	org 0x4000
	11	entry:
	12	cli
	13	; clean up 32 bit regs
	14	mov eax, 0x0
	15	mov ebx, 0x0
	16	mov ecx, 0x0
	17	mov edx, 0x0
	18	mov esi, 0x0
	19	mov edi, 0x0
	20	mov ebp, 0x0
	21	mov esp, 0x0
	22
	23	lgdt [gdtp]
	24
	25	mov ax, 0x10
	26	mov ds, ax
	27	mov es, ax
	28	mov fs, ax
	29	mov gs, ax
	30	mov ss, ax
	31
	32	jmp 0x8:nextp ; Clear CS bits now too
	33
	34	nextp:
	35
	36	mov eax, cr0
	37	xor eax, 0x1 ; Clear PE
	38	mov cr0, eax
	39
	40	jmp 0x0:nowreal ; and jmp away
	41
	42
	43	[bits 16]
	44	nowreal:
	45	mov long eax, 0x0000
	46	mov ds, ax
	47	mov es, ax
	48	mov fs, ax
	49	mov gs, ax
	50	mov ss, ax
	51
	52	mov sp, 0xFFFF ; set up the stack
	53
	54	mov al, 0xAB
	55	out 0x80, al
	56
	57	cli
	58	lidt [idtp]
	59
	60	mov si, RETMSG
	61	call disp
	62
	63	int 0x19 ; warm boot without clearing RAM.
	64	call handload_drive ; hopefully shouldn't happen
	65	; ok, we give up
	66	cli
	67	halt: hlt
	68	jmp halt
	69
	70	disp:
	71	lodsb
	72	or al, al
	73	jz .done
	74	mov ah, 0x0E
	75	mov bx, 0x0007
	76	int 0x10
	77	jmp disp
	78	.done:
	79	ret
	80
	81	; handload_drive should be unnecessary; int 19 should take care of it for
	82	; us...
	83	handload_drive:
	84	mov ax, 0x07C0
	85	mov es, ax
	86	mov ax, 0x0201 ; read one sector
	87	mov bx, 0x0000 ; to the normal location
	88	mov cx, 0x0001 ; disk sector 1
	89	mov dx, 0x0080 ; drive 0
	90	int 0x13
	91	jc readerr
	92
	93	mov si, READSUCC
	94	call disp
	95
	96	jmp 0x7C0:0x0 ; and return control to grub!
	97	readerr:
	98	mov si, READFAIL
	99	call disp
	100	ret
	101
	102	RETMSG db "SMM installer finished, booting your system of choice.",10,13,0
	103	READSUCC db "Read successful; rebooting into boot sector.",10,13,0
	104	READFAIL db "Boot disk read failure; system halted.",10,13,0
	105
	106
	107	idtp db 0xFF, 0x03, 0x00, 0x00, 0x00, 0x00
	108
	109	gdtp dw 0x1F
	110	dd gdt
	111
	112	gdt dd 0, 0
	113	dd 0x0000FFFF, 0x00009e00 ; CS
	114	dd 0x0000FFFF, 0x00009300 ; DS