[netwatch.git] / grubload / realmode.asm

	[bits 32]	; Starts in 32 bit mode, then will drop back later.
	org 0x4000
entry:
	cli
	; clean up 32 bit regs
	mov eax, 0x0
	mov ebx, 0x0
	mov ecx, 0x0
	mov edx, 0x0
	mov esi, 0x0
	mov edi, 0x0
	mov ebp, 0x0
	mov esp, 0x0
	
	lgdt [gdtp]
	
	mov ax, 0x10
	mov ds, ax
	mov es, ax
	mov fs, ax
	mov gs, ax
	mov ss, ax
	
	jmp 0x8:nextp	; Clear CS bits now too

nextp:
	
	mov eax, cr0
	xor eax, 0x1	; Clear PE
	mov cr0, eax
	
	jmp 0x0:nowreal	; and jmp away


	[bits 16]
nowreal:
	mov long eax, 0x0000
	mov ds, ax
	mov es, ax
	mov fs, ax
	mov gs, ax
	mov ss, ax
	
	mov sp, 0xFFFF	; set up the stack

	mov al, 0xAB
	out 0x80, al

	cli
	lidt [idtp]

	mov si, RETMSG
	call disp

	int 0x19		; warm boot without clearing RAM.
	call handload_drive	; hopefully shouldn't happen
	; ok, we give up
	cli
halt:	hlt
	jmp halt

disp:
	lodsb
	or al, al
	jz .done
	mov ah, 0x0E
	mov bx, 0x0007
	int 0x10
	jmp disp
.done:
	ret

; handload_drive should be unnecessary; int 19 should take care of it for
; us...
handload_drive:
	mov ax, 0x07C0
	mov es, ax
	mov ax, 0x0201	; read one sector
	mov bx, 0x0000	; to the normal location
	mov cx, 0x0001	; disk sector 1
	mov dx, 0x0080	; drive 0
	int 0x13
	jc readerr
	
	mov si, READSUCC
	call disp
	
	jmp 0x7C0:0x0	; and return control to grub!
readerr:
	mov si, READFAIL
	call disp
	ret

RETMSG	db "SMM installer finished, booting your system of choice.",10,13,0
READSUCC db "Read successful; rebooting into boot sector.",10,13,0
READFAIL db "Boot disk read failure; system halted.",10,13,0


idtp	db 0xFF, 0x03, 0x00, 0x00, 0x00, 0x00

gdtp	dw 0x1F
	dd gdt

gdt	dd 0, 0
	dd 0x0000FFFF, 0x00009e00	; CS
	dd 0x0000FFFF, 0x00009300	; DS
Commit	Line	Data
042eafc7 JW	1	[bits 32] ; Starts in 32 bit mode, then will drop back later.
	2	org 0x4000
	3	entry:
	4	cli
	5	; clean up 32 bit regs
	6	mov eax, 0x0
	7	mov ebx, 0x0
	8	mov ecx, 0x0
	9	mov edx, 0x0
	10	mov esi, 0x0
	11	mov edi, 0x0
	12	mov ebp, 0x0
	13	mov esp, 0x0
	14
	15	lgdt [gdtp]
	16
	17	mov ax, 0x10
	18	mov ds, ax
	19	mov es, ax
	20	mov fs, ax
	21	mov gs, ax
	22	mov ss, ax
	23
	24	jmp 0x8:nextp ; Clear CS bits now too
	25
	26	nextp:
	27
	28	mov eax, cr0
	29	xor eax, 0x1 ; Clear PE
	30	mov cr0, eax
	31
	32	jmp 0x0:nowreal ; and jmp away
	33
	34
	35	[bits 16]
	36	nowreal:
	37	mov long eax, 0x0000
	38	mov ds, ax
	39	mov es, ax
	40	mov fs, ax
	41	mov gs, ax
	42	mov ss, ax
	43
	44	mov sp, 0xFFFF ; set up the stack
	45
	46	mov al, 0xAB
	47	out 0x80, al
	48
	49	cli
	50	lidt [idtp]
	51
	52	mov si, RETMSG
	53	call disp
	54
	55	int 0x19 ; warm boot without clearing RAM.
	56	call handload_drive ; hopefully shouldn't happen
	57	; ok, we give up
	58	cli
	59	halt: hlt
	60	jmp halt
	61
	62	disp:
	63	lodsb
	64	or al, al
65	jz .done
66	mov ah, 0x0E
67	mov bx, 0x0007
68	int 0x10
69	jmp disp
70	.done:
71	ret
72
73	; handload_drive should be unnecessary; int 19 should take care of it for
74	; us...
75	handload_drive:
76	mov ax, 0x07C0
77	mov es, ax
78	mov ax, 0x0201 ; read one sector
79	mov bx, 0x0000 ; to the normal location
80	mov cx, 0x0001 ; disk sector 1
81	mov dx, 0x0080 ; drive 0
82	int 0x13
83	jc readerr
84
85	mov si, READSUCC
86	call disp
87
88	jmp 0x7C0:0x0 ; and return control to grub!
89	readerr:
90	mov si, READFAIL
91	call disp
92	ret
93
94	RETMSG db "SMM installer finished, booting your system of choice.",10,13,0
95	READSUCC db "Read successful; rebooting into boot sector.",10,13,0
96	READFAIL db "Boot disk read failure; system halted.",10,13,0
97
98
99	idtp db 0xFF, 0x03, 0x00, 0x00, 0x00, 0x00
100
101	gdtp dw 0x1F
102	dd gdt
103
104	gdt dd 0, 0
105	dd 0x0000FFFF, 0x00009e00 ; CS
106	dd 0x0000FFFF, 0x00009300 ; DS