patch-2.4.20 linux-2.4.20/arch/x86_64/boot/setup.S

• Lines: 864
• Date: Thu Nov 28 15:53:12 2002
• Orig file: linux-2.4.19/arch/x86_64/boot/setup.S
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/x86_64/boot/setup.S linux-2.4.20/arch/x86_64/boot/setup.S
@@ -0,0 +1,863 @@
+/*
+ *	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
+ * (troyer@saifr00.cfsat.Honeywell.COM) 03Oct92
+ *
+ * some changes and additional features by Christoph Niemann,
+ * March 1993/June 1994 (Christoph.Niemann@linux.org)
+ *
+ * add APM BIOS checking by Stephen Rothwell, May 1994
+ * (sfr@canb.auug.org.au)
+ *
+ * High load stuff, initrd support and position independency
+ * by Hans Lermen & Werner Almesberger, February 1996
+ * <lermen@elserv.ffm.fgan.de>, <almesber@lrc.epfl.ch>
+ *
+ * Video handling moved to video.S by Martin Mares, March 1996
+ * <mj@k332.feld.cvut.cz>
+ *
+ * Extended memory detection scheme retwiddled by orc@pell.chi.il.us (david
+ * parsons) to avoid loadlin confusion, July 1997
+ *
+ * Transcribed from Intel (as86) -> AT&T (gas) by Chris Noe, May 1999.
+ * <stiker@northlink.com>
+ *
+ * Fix to work around buggy BIOSes which dont use carry bit correctly
+ * and/or report extended memory in CX/DX for e801h memory size detection 
+ * call.  As a result the kernel got wrong figures.  The int15/e801h docs
+ * from Ralf Brown interrupt list seem to indicate AX/BX should be used
+ * anyway.  So to avoid breaking many machines (presumably there was a reason
+ * to orginally use CX/DX instead of AX/BX), we do a kludge to see
+ * if CX/DX have been changed in the e801 call and if so use AX/BX .
+ * Michael Miller, April 2001 <michaelm@mjmm.org>
+ *
+ */
+
+#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...)
+					# See Documentation/i386/boot.txt for
+					# assigned ids
+	
+# 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:
+	stc					# fix to work around buggy
+	xorw	%cx,%cx				# BIOSes which dont clear/set
+	xorw	%dx,%dx				# carry on pass/error of
+						# e801h memory size call
+						# or merely pass cx,dx though
+						# without changing them.
+	movw	$0xe801, %ax
+	int	$0x15
+	jc	mem88
+
+	cmpw	$0x0, %cx			# Kludge to handle BIOSes
+	jne	e801usecxdx			# which report their extended
+	cmpw	$0x0, %dx			# memory in AX/BX rather than
+	jne	e801usecxdx			# CX/DX.  The spec I have read
+	movw	%ax, %cx			# seems to indicate AX/BX 
+	movw	%bx, %dx			# are more reasonable anyway...
+
+e801usecxdx:
+	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 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:
+
+# Now we want to move to protected mode ...
+	cmpw	$0, %cs:realmode_swtch
+	jz	rmodeswtch_normal
+
+	lcall	%cs:realmode_swtch
+
+	jmp	rmodeswtch_end
+
+rmodeswtch_normal:
+        pushw	%cs
+	call	default_switch
+
+rmodeswtch_end:
+# we get the code32 start address and modify the below 'jmpi'
+# (loader may have changed it)
+	movl	%cs:code32_start, %eax
+	movl	%eax, %cs:code32
+
+# Now we move the system to its rightful place ... but we check if we have a
+# big-kernel. In that case we *must* not move it ...
+	testb	$LOADED_HIGH, %cs:loadflags
+	jz	do_move0			# .. then we have a normal low
+						# loaded zImage
+						# .. or else we have a high
+						# loaded bzImage
+	jmp	end_move			# ... and we skip moving
+
+do_move0:
+	movw	$0x100, %ax			# start of destination segment
+	movw	%cs, %bp			# aka SETUPSEG
+	subw	$DELTA_INITSEG, %bp		# aka INITSEG
+	movw	%cs:start_sys_seg, %bx		# start of source segment
+	cld
+do_move:
+	movw	%ax, %es			# destination segment
+	incb	%ah				# instead of add ax,#0x100
+	movw	%bx, %ds			# source segment
+	addw	$0x100, %bx
+	subw	%di, %di
+	subw	%si, %si
+	movw 	$0x800, %cx
+	rep
+	movsw
+	cmpw	%bp, %bx			# assume start_sys_seg > 0x200,
+						# so we will perhaps read one
+						# page more than needed, but
+						# never overwrite INITSEG
+						# because destination is a
+						# minimum one page below source
+	jb	do_move
+
+end_move:
+# then we load the segment descriptors
+	movw	%cs, %ax			# aka SETUPSEG
+	movw	%ax, %ds
+		
+# Check whether we need to be downward compatible with version <=201
+	cmpl	$0, cmd_line_ptr
+	jne	end_move_self		# loader uses version >=202 features
+	cmpb	$0x20, type_of_loader
+	je	end_move_self		# bootsect loader, we know of it
+
+# Boot loader doesnt support boot protocol version 2.02.
+# If we have our code not at 0x90000, we need to move it there now.
+# We also then need to move the params behind it (commandline)
+# Because we would overwrite the code on the current IP, we move
+# it in two steps, jumping high after the first one.
+	movw	%cs, %ax
+	cmpw	$SETUPSEG, %ax
+	je	end_move_self
+
+	cli					# make sure we really have
+						# interrupts disabled !
+						# because after this the stack
+						# should not be used
+	subw	$DELTA_INITSEG, %ax		# aka INITSEG
+	movw	%ss, %dx
+	cmpw	%ax, %dx
+	jb	move_self_1
+
+	addw	$INITSEG, %dx
+	subw	%ax, %dx			# this will go into %ss after
+						# the move
+move_self_1:
+	movw	%ax, %ds
+	movw	$INITSEG, %ax			# real INITSEG
+	movw	%ax, %es
+	movw	%cs:setup_move_size, %cx
+	std					# we have to move up, so we use
+						# direction down because the
+						# areas may overlap
+	movw	%cx, %di
+	decw	%di
+	movw	%di, %si
+	subw	$move_self_here+0x200, %cx
+	rep
+	movsb
+	ljmp	$SETUPSEG, $move_self_here
+
+move_self_here:
+	movw	$move_self_here+0x200, %cx
+	rep
+	movsb
+	movw	$SETUPSEG, %ax
+	movw	%ax, %ds
+	movw	%dx, %ss
+end_move_self:					# now we are at the right place
+	lidt	idt_48				# load idt with 0,0
+	xorl	%eax, %eax			# Compute gdt_base
+	movw	%ds, %ax			# (Convert %ds:gdt to a linear ptr)
+	shll	$4, %eax
+	addl	$gdt, %eax
+	movl	%eax, (gdt_48+2)
+	lgdt	gdt_48				# load gdt with whatever is
+						# appropriate
+
+# that was painless, now we enable a20
+	call	empty_8042
+
+	movb	$0xD1, %al			# command write
+	outb	%al, $0x64
+	call	empty_8042
+
+	movb	$0xDF, %al			# A20 on
+	outb	%al, $0x60
+	call	empty_8042
+
+#
+#	You must preserve the other bits here. Otherwise embarrasing things
+#	like laptops powering off on boot happen. Corrected version by Kira
+#	Brown from Linux 2.2
+#
+	inb	$0x92, %al			# 
+	orb	$02, %al			# "fast A20" version
+	outb	%al, $0x92			# some chips have only this
+
+# wait until a20 really *is* enabled; it can take a fair amount of
+# time on certain systems; Toshiba Tecras are known to have this
+# problem.  The memory location used here (0x200) is the int 0x80
+# vector, which should be safe to use.
+
+	xorw	%ax, %ax			# segment 0x0000
+	movw	%ax, %fs
+	decw	%ax				# segment 0xffff (HMA)
+	movw	%ax, %gs
+a20_wait:
+	incw	%ax				# unused memory location <0xfff0
+	movw	%ax, %fs:(0x200)		# we use the "int 0x80" vector
+	cmpw	%gs:(0x210), %ax		# and its corresponding HMA addr
+	je	a20_wait			# loop until no longer aliased
+
+# make sure any possible coprocessor is properly reset..
+	xorw	%ax, %ax
+	outb	%al, $0xf0
+	call	delay
+
+	outb	%al, $0xf1
+	call	delay
+
+# well, that went ok, I hope. Now we mask all interrupts - the rest
+# is done in init_IRQ().
+	movb	$0xFF, %al			# mask all interrupts for now
+	outb	%al, $0xA1
+	call	delay
+	
+	movb	$0xFB, %al			# mask all irq's but irq2 which
+	outb	%al, $0x21			# 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 0x1000 (or the loader supplied one),
+# in 32-bit protected mode.
+#
+# Note that the short jump isn't strictly needed, although there are
+# reasons why it might be a good idea. It won't hurt in any case.
+	movw	$1, %ax				# protected mode (PE) bit
+	lmsw	%ax				# This is it!
+	jmp	flush_instr
+
+flush_instr:
+	xorw	%bx, %bx			# Flag to indicate a boot
+	xorl	%esi, %esi			# Pointer to real-mode code
+	movw	%cs, %si
+	subw	$DELTA_INITSEG, %si
+	shll	$4, %esi			# Convert to 32-bit pointer
+# NOTE: For high loaded big kernels we need a
+#	jmpi    0x100000,__KERNEL_CS
+#
+#	but we yet haven't reloaded the CS register, so the default size 
+#	of the target offset still is 16 bit.
+#       However, using an operand prefix (0x66), the CPU will properly
+#	take our 48 bit far pointer. (INTeL 80386 Programmer's Reference
+#	Manual, Mixing 16-bit and 32-bit code, page 16-6)
+
+	.byte 0x66, 0xea			# prefix + jmpi-opcode
+code32:	.long	0x1000				# will be set to 0x100000
+						# for big kernels
+	.word	__KERNEL_CS
+
+# Here's a bunch of information about your current kernel..
+kernel_version:	.ascii	UTS_RELEASE
+		.ascii	" ("
+		.ascii	LINUX_COMPILE_BY
+		.ascii	"@"
+		.ascii	LINUX_COMPILE_HOST
+		.ascii	") "
+		.ascii	UTS_VERSION
+		.byte	0
+
+# This is the default real mode switch routine.
+# to be called just before protected mode transition
+default_switch:
+	cli					# no interrupts allowed !
+	movb	$0x80, %al			# disable NMI for bootup
+						# sequence
+	outb	%al, $0x70
+	lret
+
+# This routine only gets called, if we get loaded by the simple
+# bootsect loader _and_ have a bzImage to load.
+# Because there is no place left in the 512 bytes of the boot sector,
+# we must emigrate to code space here.
+bootsect_helper:
+	cmpw	$0, %cs:bootsect_es
+	jnz	bootsect_second
+
+	movb	$0x20, %cs:type_of_loader
+	movw	%es, %ax
+	shrw	$4, %ax
+	movb	%ah, %cs:bootsect_src_base+2
+	movw	%es, %ax
+	movw	%ax, %cs:bootsect_es
+	subw	$SYSSEG, %ax
+	lret					# nothing else to do for now
+
+bootsect_second:
+	pushw	%cx
+	pushw	%si
+	pushw	%bx
+	testw	%bx, %bx			# 64K full?
+	jne	bootsect_ex
+
+	movw	$0x8000, %cx			# full 64K, INT15 moves words
+	pushw	%cs
+	popw	%es
+	movw	$bootsect_gdt, %si
+	movw	$0x8700, %ax
+	int	$0x15
+	jc	bootsect_panic			# this, if INT15 fails
+
+	movw	%cs:bootsect_es, %es		# we reset %es to always point
+	incb	%cs:bootsect_dst_base+2		# to 0x10000
+bootsect_ex:
+	movb	%cs:bootsect_dst_base+2, %ah
+	shlb	$4, %ah				# we now have the number of
+						# moved frames in %ax
+	xorb	%al, %al
+	popw	%bx
+	popw	%si
+	popw	%cx
+	lret
+
+bootsect_gdt:
+	.word	0, 0, 0, 0
+	.word	0, 0, 0, 0
+
+bootsect_src:
+	.word	0xffff
+
+bootsect_src_base:
+	.byte	0x00, 0x00, 0x01		# base = 0x010000
+	.byte	0x93				# typbyte
+	.word	0				# limit16,base24 =0
+
+bootsect_dst:
+	.word	0xffff
+
+bootsect_dst_base:
+	.byte	0x00, 0x00, 0x10		# base = 0x100000
+	.byte	0x93				# typbyte
+	.word	0				# limit16,base24 =0
+	.word	0, 0, 0, 0			# BIOS CS
+	.word	0, 0, 0, 0			# BIOS DS
+
+bootsect_es:
+	.word	0
+
+bootsect_panic:
+	pushw	%cs
+	popw	%ds
+	cld
+	leaw	bootsect_panic_mess, %si
+	call	prtstr
+	
+bootsect_panic_loop:
+	jmp	bootsect_panic_loop
+
+bootsect_panic_mess:
+	.string	"INT15 refuses to access high mem, giving up."
+
+# This routine checks that the keyboard command queue is empty
+# (after emptying the output buffers)
+#
+# Some machines have delusions that the keyboard buffer is always full
+# with no keyboard attached...
+#
+# If there is no keyboard controller, we will usually get 0xff
+# to all the reads.  With each IO taking a microsecond and
+# a timeout of 100,000 iterations, this can take about half a
+# second ("delay" == outb to port 0x80). That should be ok,
+# and should also be plenty of time for a real keyboard controller
+# to empty.
+#
+
+empty_8042:
+	pushl	%ecx
+	movl	$100000, %ecx
+
+empty_8042_loop:
+	decl	%ecx
+	jz	empty_8042_end_loop
+
+	call	delay
+
+	inb	$0x64, %al			# 8042 status port
+	testb	$1, %al				# output buffer?
+	jz	no_output
+
+	call	delay
+	inb	$0x60, %al			# read it
+	jmp	empty_8042_loop
+
+no_output:
+	testb	$2, %al				# is input buffer full?
+	jnz	empty_8042_loop			# yes - loop
+empty_8042_end_loop:
+	popl	%ecx
+	ret
+
+# Read the cmos clock. Return the seconds in al
+gettime:
+	pushw	%cx
+	movb	$0x02, %ah
+	int	$0x1a
+	movb	%dh, %al			# %dh contains the seconds
+	andb	$0x0f, %al
+	movb	%dh, %ah
+	movb	$0x04, %cl
+	shrb	%cl, %ah
+	aad
+	popw	%cx
+	ret
+
+# Delay is needed after doing I/O
+delay:
+	outb	%al,$0x80
+	ret
+
+# Descriptor tables
+gdt:
+	.word	0, 0, 0, 0			# dummy
+
+	.word	0, 0, 0, 0			# unused
+
+	.word	0xFFFF				# 4Gb - (0x100000*0x1000 = 4Gb)
+	.word	0				# base address = 0
+	.word	0x9A00				# code read/exec
+	.word	0x00CF				# granularity = 4096, 386
+						#  (+5th nibble of limit)
+
+	.word	0xFFFF				# 4Gb - (0x100000*0x1000 = 4Gb)
+	.word	0				# base address = 0
+	.word	0x9200				# data read/write
+	.word	0x00CF				# granularity = 4096, 386
+						#  (+5th nibble of limit)
+# this is 64bit descriptor for code
+	.word	0xFFFF
+	.word	0
+	.word	0x9A00				# code read/exec
+	.word	0x00AF				# as above, but it is long mode and with D=0
+						# it does not seem to do the trick.
+
+idt_48:
+	.word	0				# idt limit = 0
+	.word	0, 0				# idt base = 0L
+gdt_48:
+	.word	0x8000				# gdt limit=2048,
+						#  256 GDT entries
+
+	.word	0, 0				# gdt base (filled in later)
+
+# Include video setup & detection code
+
+#include "video.S"
+
+# Setup signature -- must be last
+setup_sig1:	.word	SIG1
+setup_sig2:	.word	SIG2
+
+# After this point, there is some free space which is used by the video mode
+# handling code to store the temporary mode table (not used by the kernel).
+
+modelist:
+
+.text
+endtext:
+.data
+enddata:
+.bss
+endbss: