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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
 * (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>
 *
 * Added long mode checking and SSE force. March 2003, Andi Kleen.              
 */

#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)

prtchr: 
        pushw   %ax
        pushw   %cx
        movw    $0007,%bx
        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:
        /* check for long mode. */
        /* we have to do this before the VESA setup, otherwise the user
           can't see the error message. */
        
        pushw   %ds
        movw    %cs,%ax
        movw    %ax,%ds
        
        /* minimum CPUID flags for x86-64 */
        /* see http://www.x86-64.org/lists/discuss/msg02971.html */             
#define SSE_MASK ((1<<25)|(1<<26))
#define REQUIRED_MASK1 ((1<<0)|(1<<3)|(1<<4)|(1<<5)|(1<<6)|(1<<8)|\
                                           (1<<13)|(1<<15)|(1<<24))
#define REQUIRED_MASK2 (1<<29)

        pushfl                          /* standard way to check for cpuid */
        popl    %eax
        movl    %eax,%ebx
        xorl    $0x200000,%eax
        pushl   %eax
        popfl
        pushfl
        popl    %eax
        cmpl    %eax,%ebx
        jz      no_longmode             /* cpu has no cpuid */
        movl    $0x0,%eax
        cpuid
        cmpl    $0x1,%eax
        jb      no_longmode             /* no cpuid 1 */
        xor     %di,%di
        cmpl    $0x68747541,%ebx        /* AuthenticAMD */
        jnz     noamd
        cmpl    $0x69746e65,%edx
        jnz     noamd
        cmpl    $0x444d4163,%ecx
        jnz     noamd
        mov     $1,%di                  /* cpu is from AMD */
noamd:          
        movl    $0x1,%eax
        cpuid
        andl    $REQUIRED_MASK1,%edx
        xorl    $REQUIRED_MASK1,%edx
        jnz     no_longmode
        movl    $0x80000000,%eax
        cpuid
        cmpl    $0x80000001,%eax
        jb      no_longmode             /* no extended cpuid */
        movl    $0x80000001,%eax
        cpuid
        andl    $REQUIRED_MASK2,%edx
        xorl    $REQUIRED_MASK2,%edx
        jnz     no_longmode
sse_test:               
        movl    $1,%eax
        cpuid
        andl    $SSE_MASK,%edx
        cmpl    $SSE_MASK,%edx
        je      sse_ok
        test    %di,%di
        jz      no_longmode     /* only try to force SSE on AMD */ 
        movl    $0xc0010015,%ecx        /* HWCR */
        rdmsr
        btr     $15,%eax        /* enable SSE */
        wrmsr
        xor     %di,%di         /* don't loop */
        jmp     sse_test        /* try again */ 
no_longmode:
        call    beep
        lea     long_mode_panic,%si
        call    prtstr
no_longmode_loop:               
        jmp     no_longmode_loop
long_mode_panic:
        .string "Your CPU does not support long mode. Use a 32bit distribution."
        .byte 0
        
sse_ok:
        popw    %ds
        
# tell BIOS we want to go to long mode
        movl  $0xec00,%eax      # declare target operating mode
        movl  $2,%ebx           # long mode
        int $0x15                       
        
# 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: