setup.s

LINUX 1.0 内核c源代码,是一份精简的linux内核源代码

!
!	setup.S		Copyright (C) 1991, 1992 Linus Torvalds
!
! setup.s is responsible for getting the system data from the BIOS,
! and putting them into the appropriate places in system memory.
! both setup.s and system has been loaded by the bootblock.
!
! This code asks the bios for memory/disk/other parameters, and
! puts them in a "safe" place: 0x90000-0x901FF, ie where the
! boot-block used to be. It is then up to the protected mode
! system to read them from there before the area is overwritten
! for buffer-blocks.
!
! Move PS/2 aux init code to psaux.c
! ([e-mail]) 03Oct92
!
! some changes and additional features by Christoph Niemann, March 1993
! ([e-mail])
!

! NOTE! These had better be the same as in bootsect.s!
#include <linux/config.h>
#include <linux/segment.h>

#ifndef SVGA_MODE
#define SVGA_MODE ASK_VGA
#endif

INITSEG  = DEF_INITSEG	! we move boot here - out of the way
SYSSEG   = DEF_SYSSEG	! system loaded at 0x10000 (65536).
SETUPSEG = DEF_SETUPSEG	! this is the current segment

.globl begtext, begdata, begbss, endtext, enddata, endbss
.text
begtext:
.data
begdata:
.bss
begbss:
.text

entry start
start:

! ok, the read went well so we get current cursor position and save it for
! posterity.

	mov	ax,#INITSEG	! this is done in bootsect already, but...
	mov	ds,ax

! Get memory size (extended mem, kB)

	mov	ah,#0x88
	int	0x15
	mov	[2],ax

! set the keyboard repeat rate to the max

	mov	ax,#0x0305
	xor	bx,bx		! clear bx
	int	0x16

! check for EGA/VGA and some config parameters

	mov	ah,#0x12
	mov	bl,#0x10
	int	0x10
	mov	[8],ax
	mov	[10],bx
	mov	[12],cx
	mov	ax,#0x5019
	cmp	bl,#0x10
	je	novga
	mov	ax,#0x1a00	! Added check for EGA/VGA discrimination
	int	0x10
	mov	bx,ax
	mov	ax,#0x5019
	cmp	bl,#0x1a	! 1a means VGA, anything else EGA or lower
	jne	novga	
	call	chsvga
novga:	mov	[14],ax
	mov	ah,#0x03	! read cursor pos
	xor	bh,bh		! clear bh
	int	0x10		! save it in known place, con_init fetches
	mov	[0],dx		! it from 0x90000.
	
! Get video-card data:
	
	mov	ah,#0x0f
	int	0x10
	mov	[4],bx		! bh = display page
	mov	[6],ax		! al = video mode, ah = window width

! Get hd0 data

	xor	ax,ax		! clear ax
	mov	ds,ax
	lds	si,[4*0x41]
	mov	ax,#INITSEG
	mov	es,ax
	mov	di,#0x0080
	mov	cx,#0x10
	cld
	rep
	movsb

! Get hd1 data

	xor	ax,ax		! clear ax
	mov	ds,ax
	lds	si,[4*0x46]
	mov	ax,#INITSEG
	mov	es,ax
	mov	di,#0x0090
	mov	cx,#0x10
	cld
	rep
	movsb

! Check that there IS a hd1 :-)

	mov	ax,#0x01500
	mov	dl,#0x81
	int	0x13
	jc	no_disk1
	cmp	ah,#3
	je	is_disk1
no_disk1:
	mov	ax,#INITSEG
	mov	es,ax
	mov	di,#0x0090
	mov	cx,#0x10
	xor	ax,ax		! clear ax
	cld
	rep
	stosb
is_disk1:

! check for PS/2 pointing device

	mov	ax,#INITSEG
	mov	ds,ax
	mov	[0x1ff],#0	! default is no pointing device
	int	0x11		! int 0x11: equipment determination
	test	al,#0x04	! check if pointing device installed
	jz	no_psmouse
	mov	[0x1ff],#0xaa	! device present
no_psmouse:
! now we want to move to protected mode ...

	cli			! no interrupts allowed !
	mov	al,#0x80	! disable NMI for the bootup sequence
	out	#0x70,al

! first we move the system to its rightful place

	mov	ax,#0x100	! start of destination segment
	mov	bx,#0x1000	! start of source segment
	cld			! 'direction'=0, movs moves forward
do_move:
	mov	es,ax		! destination segment
	add	ax,#0x100
	cmp	ax,#0x9000
	jz	end_move
	mov	ds,bx		! source segment
	add	bx,#0x100
	sub	di,di
	sub	si,si
	mov 	cx,#0x800
	rep
	movsw
	jmp	do_move

! then we load the segment descriptors

end_move:
	mov	ax,#SETUPSEG	! right, forgot this at first. didn't work :-)
	mov	ds,ax
	lidt	idt_48		! load idt with 0,0
	lgdt	gdt_48		! load gdt with whatever appropriate

! that was painless, now we enable A20

	call	empty_8042
	mov	al,#0xD1		! command write
	out	#0x64,al
	call	empty_8042
	mov	al,#0xDF		! A20 on
	out	#0x60,al
	call	empty_8042

! make sure any possible coprocessor is properly reset..

	xor	ax,ax
	out	#0xf0,al
	call	delay
	out	#0xf1,al
	call	delay

! well, that went ok, I hope. Now we have to reprogram the interrupts :-(
! we put them right after the intel-reserved hardware interrupts, at
! int 0x20-0x2F. There they won't mess up anything. Sadly IBM really
! messed this up with the original PC, and they haven't been able to
! rectify it afterwards. Thus the bios puts interrupts at 0x08-0x0f,
! which is used for the internal hardware interrupts as well. We just
! have to reprogram the 8259's, and it isn't fun.

	mov	al,#0x11		! initialization sequence
	out	#0x20,al		! send it to 8259A-1
	call	delay
	out	#0xA0,al		! and to 8259A-2
	call	delay
	mov	al,#0x20		! start of hardware int's (0x20)
	out	#0x21,al
	call	delay
	mov	al,#0x28		! start of hardware int's 2 (0x28)
	out	#0xA1,al
	call	delay
	mov	al,#0x04		! 8259-1 is master
	out	#0x21,al
	call	delay
	mov	al,#0x02		! 8259-2 is slave
	out	#0xA1,al
	call	delay
	mov	al,#0x01		! 8086 mode for both
	out	#0x21,al
	call	delay
	out	#0xA1,al
	call	delay
	mov	al,#0xFF		! mask off all interrupts for now
	out	#0xA1,al
	call	delay
	mov	al,#0xFB		! mask all irq's but irq2 which
	out	#0x21,al		! is cascaded

! well, that certainly wasn't fun :-(. Hopefully it works, and we don't
! need no steenking BIOS anyway (except for the initial loading :-).
! The BIOS-routine wants lots of unnecessary data, and it's less
! "interesting" anyway. This is how REAL programmers do it.
!
! Well, now's the time to actually move into protected mode. To make
! things as simple as possible, we do no register set-up or anything,
! we let the gnu-compiled 32-bit programs do that. We just jump to
! absolute address 0x00000, in 32-bit protected mode.
!
! Note that the short jump isn't strictly needed, althought there are
! reasons why it might be a good idea. It won't hurt in any case.
!
	mov	ax,#0x0001	! protected mode (PE) bit
	lmsw	ax		! This is it!
	jmp	flush_instr
flush_instr:
	jmpi	0x1000,KERNEL_CS	! jmp offset 1000 of segment 0x10 (cs)

! This routine checks that the keyboard command queue is empty
! (after emptying the output buffers)
!
! No timeout is used - if this hangs there is something wrong with
! the machine, and we probably couldn't proceed anyway.
empty_8042:
	call	delay
	in	al,#0x64	! 8042 status port
	test	al,#1		! output buffer?
	jz	no_output
	call	delay
	in	al,#0x60	! read it
	jmp	empty_8042
no_output:
	test	al,#2		! is input buffer full?
	jnz	empty_8042	! yes - loop
	ret
!
! Read a key and return the (US-)ascii code in al, scan code in ah
!
getkey:
	xor	ah,ah
	int	0x16
	ret

!
! Read a key with a timeout of 30 seconds. The cmos clock is used to get
! the time.
!
getkt:
	call	gettime
	add	al,#30		! wait 30 seconds
	cmp	al,#60
	jl	lminute
	sub	al,#60
lminute:
	mov	cl,al
again:	mov	ah,#0x01
	int	0x16
	jnz	getkey		! key pressed, so get it
	call	gettime
	cmp	al,cl
	jne	again
	mov	al,#0x20	! timeout, return default char `space'
	ret

!
! Flush the keyboard buffer
!
flush:	mov	ah,#0x01
	int	0x16
	jz	empty
	xor	ah,ah
	int	0x16
	jmp	flush
empty:	ret

!
! Read the cmos clock. Return the seconds in al
!
gettime:
	push	cx
	mov	ah,#0x02
	int	0x1a
	mov	al,dh			! dh contains the seconds
	and	al,#0x0f
	mov	ah,dh
	mov	cl,#0x04
	shr	ah,cl
	aad
	pop	cx
	ret

!
! Delay is needed after doing i/o
!
delay:
	.word	0x00eb			! jmp $+2
	ret

! Routine trying to recognize type of SVGA-board present (if any)
! and if it recognize one gives the choices of resolution it offers.
! If one is found the resolution chosen is given by al,ah (rows,cols).

chsvga:	cld
	push	ds
	push	cs
	mov	ax,[0x01fa]
	pop	ds
	mov	modesave,ax
	mov 	ax,#0xc000
	mov	es,ax
	mov	ax,modesave
	cmp	ax,#NORMAL_VGA
	je	defvga
	cmp	ax,#EXTENDED_VGA
	je	vga50
	cmp	ax,#ASK_VGA
	jne	svga
	lea	si,msg1
	call	prtstr
	call	flush
nokey:	call	getkt
	cmp	al,#0x0d		! enter ?
	je	svga			! yes - svga selection
	cmp	al,#0x20		! space ?
	je	defvga			! no - repeat
	call 	beep
	jmp	nokey
defvga:	mov	ax,#0x5019
	pop	ds
	ret
/* extended vga mode: 80x50 */
vga50:
	mov	ax,#0x1112
	xor	bl,bl
	int	0x10		! use 8x8 font set (50 lines on VGA)
	mov	ax,#0x1200
	mov	bl,#0x20
	int	0x10		! use alternate print screen
	mov	ax,#0x1201
	mov	bl,#0x34
	int	0x10		! turn off cursor emulation
	mov	ah,#0x01
	mov	cx,#0x0607
	int	0x10		! turn on cursor (scan lines 6 to 7)
	pop	ds
	mov	ax,#0x5032	! return 80x50
	ret
/* extended vga mode: 80x28 */
vga28:
	pop	ax		! clean the stack
	mov	ax,#0x1111
	xor	bl,bl
	int	0x10		! use 9x14 fontset (28 lines on VGA)
	mov	ah, #0x01
	mov	cx,#0x0b0c
	int	0x10		! turn on cursor (scan lines 11 to 12)
	pop	ds
	mov	ax,#0x501c	! return 80x28
	ret
/* svga modes */
svga:   cld
        lea     si,id9GXE	! Check for the #9GXE ([e-mail],thanks [e-mail])
        mov     di,#0x49	! id string is at c000:049
        mov     cx,#0x11	! length of "Graphics Power By"
        repe
        cmpsb
        jne     of1280
is9GXE:	lea 	si,dsc9GXE	! table of descriptions of video modes for BIOS
	lea	di,mo9GXE	! table of sizes of video modes for my BIOS
	br	selmod		! go ask for video mode
of1280:	cld	
	lea	si,idf1280	! Check for Orchid F1280 ([e-mail])
	mov	di,#0x10a	! id string is at c000:010a
	mov	cx,#0x21	! length
	repe
	cmpsb
	jne	nf1280	
isVRAM:	lea	si,dscf1280
	lea	di,mof1280
	br	selmod
nf1280:	lea	si,idVRAM
	mov	di,#0x10a
	mov	cx,#0x0c
	repe
	cmpsb
	je	isVRAM
	cld
	lea 	si,idati		! Check ATI 'clues'
	mov	di,#0x31
	mov 	cx,#0x09
	repe
	cmpsb
	jne	noati
	lea	si,dscati
	lea	di,moati
	br	selmod
noati:	mov	ax,#0x200f		! Check Ahead 'clues'
	mov	dx,#0x3ce
	out	dx,ax