arch-i386-bootsetup.s

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/*
 *	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/June 1994 ([e-mail])
 *
 * add APM BIOS checking by Stephen Rothwell, May 1994
 * ([e-mail])
 *
 * High load stuff, initrd support and position independency
 * by Hans Lermen & Werner Almesberger, February 1996
 * <[e-mail]>, <[e-mail]>
 *
 * Video handling moved to video.S by Martin Mares, March 1996
 * <[e-mail]>
 *
 * Extended memory detection scheme retwiddled by [e-mail] (david
 * parsons) to avoid loadlin confusion, July 1997
 *
 * Transcribed from Intel (as86) -> AT&T (gas) by Chris Noe, May 1999.
 * <[e-mail]>
 */

#define __ASSEMBLY__
#include <linux/config.h>
#include <asm/segment.h>
#include <linux/version.h>
#include <linux/compile.h>
#include <asm/boot.h>
#include <asm/e820.h>

/* Signature words to ensure LILO loaded us right */
#define SIG1	0xAA55
#define SIG2	0x5A5A

INITSEG  = DEF_INITSEG		# 0x9000, we move boot here, out of the way
SYSSEG   = DEF_SYSSEG		# 0x1000, system loaded at 0x10000 (65536).
SETUPSEG = DEF_SETUPSEG		# 0x9020, this is the current segment
				# ... and the former contents of CS

DELTA_INITSEG = SETUPSEG - INITSEG	# 0x0020

.code16
.globl begtext, begdata, begbss, endtext, enddata, endbss

.text
begtext:
.data
begdata:
.bss
begbss:
.text

start:
	jmp	trampoline

# This is the setup header, and it must start at %cs:2 (old 0x9020:2)

		.ascii	"HdrS"		# header signature
		.word	0x0202		# header version number (>= 0x0105)
					# or else old loadlin-1.5 will fail)
realmode_swtch:	.word	0, 0		# default_switch, SETUPSEG
start_sys_seg:	.word	SYSSEG
		.word	kernel_version	# pointing to kernel version string
					# above section of header is compatible
					# with loadlin-1.5 (header v1.5). Don't
					# change it.

type_of_loader:	.byte	0		# = 0, old one (LILO, Loadlin,
					#      Bootlin, SYSLX, bootsect...)
					# Else it is set by the loader:
					# 0xTV: T=0 for LILO
					#	T=1 for Loadlin
					#	T=2 for bootsect-loader
					#	T=3 for SYSLX
					#	T=4 for ETHERBOOT
					#       V = version

# flags, unused bits must be zero (RFU) bit within loadflags
loadflags:
LOADED_HIGH	= 1			# If set, the kernel is loaded high
CAN_USE_HEAP	= 0x80			# If set, the loader also has set
					# heap_end_ptr to tell how much
					# space behind setup.S can be used for
					# heap purposes.
					# Only the loader knows what is free
#ifndef __BIG_KERNEL__
		.byte	0
#else
		.byte	LOADED_HIGH
#endif

setup_move_size: .word  0x8000		# size to move, when setup is not
					# loaded at 0x90000. We will move setup 
					# to 0x90000 then just before jumping
					# into the kernel. However, only the
					# loader knows how much data behind
					# us also needs to be loaded.

code32_start:				# here loaders can put a different
					# start address for 32-bit code.
#ifndef __BIG_KERNEL__
		.long	0x1000		#   0x1000 = default for zImage
#else
		.long	0x100000	# 0x100000 = default for big kernel
#endif

ramdisk_image:	.long	0		# address of loaded ramdisk image
					# Here the loader puts the 32-bit
					# address where it loaded the image.
					# This only will be read by the kernel.

ramdisk_size:	.long	0		# its size in bytes

bootsect_kludge:
		.word  bootsect_helper, SETUPSEG

heap_end_ptr:	.word	modelist+1024	# (Header version 0x0201 or later)
					# space from here (exclusive) down to
					# end of setup code can be used by setup
					# for local heap purposes.

pad1:		.word	0
cmd_line_ptr:	.long 0			# (Header version 0x0202 or later)
					# If nonzero, a 32-bit pointer
					# to the kernel command line.
					# The command line should be
					# located between the start of
					# setup and the end of low
					# memory (0xa0000), or it may
					# get overwritten before it
					# gets read.  If this field is
					# used, there is no longer
					# anything magical about the
					# 0x90000 segment; the setup
					# can be located anywhere in
					# low memory 0x10000 or higher.

trampoline:	call	start_of_setup
		.space	1024
# End of setup header #####################################################

start_of_setup:
# Bootlin depends on this being done early
	movw	$0x01500, %ax
	movb	$0x81, %dl
	int	$0x13

#ifdef SAFE_RESET_DISK_CONTROLLER
# Reset the disk controller.
	movw	$0x0000, %ax
	movb	$0x80, %dl
	int	$0x13
#endif

# Set %ds = %cs, we know that SETUPSEG = %cs at this point
	movw	%cs, %ax		# aka SETUPSEG
	movw	%ax, %ds
# Check signature at end of setup
	cmpw	$SIG1, setup_sig1
	jne	bad_sig

	cmpw	$SIG2, setup_sig2
	jne	bad_sig

	jmp	good_sig1

# Routine to print asciiz string at ds:si
prtstr:
	lodsb
	andb	%al, %al
	jz	fin

	call	prtchr
	jmp	prtstr

fin:	ret

# Space printing
prtsp2:	call	prtspc		# Print double space
prtspc:	movb	$0x20, %al	# Print single space (note: fall-thru)

# Part of above routine, this one just prints ascii al
prtchr:	pushw	%ax
	pushw	%cx
	xorb	%bh, %bh
	movw	$0x01, %cx
	movb	$0x0e, %ah
	int	$0x10
	popw	%cx
	popw	%ax
	ret

beep:	movb	$0x07, %al
	jmp	prtchr
	
no_sig_mess: .string	"No setup signature found ..."

good_sig1:
	jmp	good_sig

# We now have to find the rest of the setup code/data
bad_sig:
	movw	%cs, %ax			# SETUPSEG
	subw	$DELTA_INITSEG, %ax		# INITSEG
	movw	%ax, %ds
	xorb	%bh, %bh
	movb	(497), %bl			# get setup sect from bootsect
	subw	$4, %bx				# LILO loads 4 sectors of setup
	shlw	$8, %bx				# convert to words (1sect=2^8 words)
	movw	%bx, %cx
	shrw	$3, %bx				# convert to segment
	addw	$SYSSEG, %bx
	movw	%bx, %cs:start_sys_seg
# Move rest of setup code/data to here
	movw	$2048, %di			# four sectors loaded by LILO
	subw	%si, %si
	movw	%cs, %ax			# aka SETUPSEG
	movw	%ax, %es
	movw	$SYSSEG, %ax
	movw	%ax, %ds
	rep
	movsw
	movw	%cs, %ax			# aka SETUPSEG
	movw	%ax, %ds
	cmpw	$SIG1, setup_sig1
	jne	no_sig

	cmpw	$SIG2, setup_sig2
	jne	no_sig

	jmp	good_sig

no_sig:
	lea	no_sig_mess, %si
	call	prtstr

no_sig_loop:
	jmp	no_sig_loop

good_sig:
	movw	%cs, %ax			# aka SETUPSEG
	subw	$DELTA_INITSEG, %ax 		# aka INITSEG
	movw	%ax, %ds
# Check if an old loader tries to load a big-kernel
	testb	$LOADED_HIGH, %cs:loadflags	# Do we have a big kernel?
	jz	loader_ok			# No, no danger for old loaders.

	cmpb	$0, %cs:type_of_loader 		# Do we have a loader that
						# can deal with us?
	jnz	loader_ok			# Yes, continue.

	pushw	%cs				# No, we have an old loader,
	popw	%ds				# die. 
	lea	loader_panic_mess, %si
	call	prtstr

	jmp	no_sig_loop

loader_panic_mess: .string "Wrong loader, giving up..."

loader_ok:
# Get memory size (extended mem, kB)

	xorl	%eax, %eax
	movl	%eax, (0x1e0)
#ifndef STANDARD_MEMORY_BIOS_CALL
	movb	%al, (E820NR)
# Try three different memory detection schemes.  First, try
# e820h, which lets us assemble a memory map, then try e801h,
# which returns a 32-bit memory size, and finally 88h, which
# returns 0-64m

# method E820H:
# the memory map from hell.  e820h returns memory classified into
# a whole bunch of different types, and allows memory holes and
# everything.  We scan through this memory map and build a list
# of the first 32 memory areas, which we return at [E820MAP].
# This is documented at http://www.teleport.com/~acpi/acpihtml/topic245.htm

#define SMAP  0x534d4150

meme820:
	xorl	%ebx, %ebx			# continuation counter
	movw	$E820MAP, %di			# point into the whitelist
						# so we can have the bios
						# directly write into it.

jmpe820:
	movl	$0x0000e820, %eax		# e820, upper word zeroed
	movl	$SMAP, %edx			# ascii 'SMAP'
	movl	$20, %ecx			# size of the e820rec
	pushw	%ds				# data record.
	popw	%es
	int	$0x15				# make the call
	jc	bail820				# fall to e801 if it fails

	cmpl	$SMAP, %eax			# check the return is `SMAP'
	jne	bail820				# fall to e801 if it fails

#	cmpl	$1, 16(%di)			# is this usable memory?
#	jne	again820

	# If this is usable memory, we save it by simply advancing %di by
	# sizeof(e820rec).
	#
good820:
	movb	(E820NR), %al			# up to 32 entries
	cmpb	$E820MAX, %al
	jnl	bail820

	incb	(E820NR)
	movw	%di, %ax
	addw	$20, %ax
	movw	%ax, %di
again820:
	cmpl	$0, %ebx			# check to see if
	jne	jmpe820				# %ebx is set to EOF
bail820:


# method E801H:
# memory size is in 1k chunksizes, to avoid confusing loadlin.
# we store the 0xe801 memory size in a completely different place,
# because it will most likely be longer than 16 bits.
# (use 1e0 because that's what Larry Augustine uses in his
# alternative new memory detection scheme, and it's sensible
# to write everything into the same place.)

meme801:
	movw	$0xe801, %ax
	int	$0x15
	jc	mem88

	andl	$0xffff, %edx			# clear sign extend
	shll	$6, %edx			# and go from 64k to 1k chunks
	movl	%edx, (0x1e0)			# store extended memory size
	andl	$0xffff, %ecx			# clear sign extend
 	addl	%ecx, (0x1e0)			# and add lower memory into
						# total size.

# Ye Olde Traditional Methode.  Returns the memory size (up to 16mb or
# 64mb, depending on the bios) in ax.
mem88:

#endif
	movb	$0x88, %ah
	int	$0x15
	movw	%ax, (2)

# Set the keyboard repeat rate to the max
	movw	$0x0305, %ax
	xorw	%bx, %bx
	int	$0x16

# Check for video adapter and its parameters and allow the
# user to browse video modes.
	call	video				# NOTE: we need %ds pointing
						# to bootsector

# Get hd0 data...
	xorw	%ax, %ax
	movw	%ax, %ds
	ldsw	(4 * 0x41), %si
	movw	%cs, %ax			# aka SETUPSEG
	subw	$DELTA_INITSEG, %ax		# aka INITSEG
	pushw	%ax
	movw	%ax, %es
	movw	$0x0080, %di
	movw	$0x10, %cx
	pushw	%cx
	cld
	rep
 	movsb
# Get hd1 data...
	xorw	%ax, %ax
	movw	%ax, %ds
	ldsw	(4 * 0x46), %si
	popw	%cx
	popw	%es
	movw	$0x0090, %di
	rep
	movsb
# Check that there IS a hd1 :-)
	movw	$0x01500, %ax
	movb	$0x81, %dl
	int	$0x13
	jc	no_disk1
	
	cmpb	$3, %ah
	je	is_disk1

no_disk1:
	movw	%cs, %ax			# aka SETUPSEG
	subw	$DELTA_INITSEG, %ax 		# aka INITSEG
	movw	%ax, %es
	movw	$0x0090, %di
	movw	$0x10, %cx
	xorw	%ax, %ax
	cld
	rep
	stosb
is_disk1:
# check for Micro Channel (MCA) bus
	movw	%cs, %ax			# aka SETUPSEG
	subw	$DELTA_INITSEG, %ax		# aka INITSEG
	movw	%ax, %ds
	xorw	%ax, %ax
	movw	%ax, (0xa0)			# set table length to 0
	movb	$0xc0, %ah
	stc
	int	$0x15				# moves feature table to es:bx
	jc	no_mca

	pushw	%ds
	movw	%es, %ax
	movw	%ax, %ds
	movw	%cs, %ax			# aka SETUPSEG
	subw	$DELTA_INITSEG, %ax		# aka INITSEG
	movw	%ax, %es
	movw	%bx, %si
	movw	$0xa0, %di
	movw	(%si), %cx
	addw	$2, %cx				# table length is a short
	cmpw	$0x10, %cx
	jc	sysdesc_ok

	movw	$0x10, %cx			# we keep only first 16 bytes
sysdesc_ok:
	rep
	movsb
	popw	%ds
no_mca:
# Check for PS/2 pointing device
	movw	%cs, %ax			# aka SETUPSEG
	subw	$DELTA_INITSEG, %ax		# aka INITSEG
	movw	%ax, %ds
	movw	$0, (0x1ff)			# default is no pointing device
	int	$0x11				# int 0x11: equipment list
	testb	$0x04, %al			# check if mouse installed
	jz	no_psmouse

	movw	$0xAA, (0x1ff)			# device present
no_psmouse:

#if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)
# Then check for an APM BIOS...
						# %ds points to the bootsector
	movw	$0, 0x40			# version = 0 means no APM BIOS
	movw	$0x05300, %ax			# APM BIOS installation check
	xorw	%bx, %bx