sys/i386/boot/asm.s

/*
 * Ported to boot 386BSD by Julian Elischer (julian@tfs.com) Sept 1992
 *
 * Mach Operating System
 * Copyright (c) 1992, 1991 Carnegie Mellon University
 * All Rights Reserved.
 *
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */

/*
 * HISTORY
 * $Log:        asm.s,v $
 * Revision 2.2  92/04/04  11:34:13  rpd
 *      Fix Intel Copyright as per B. Davies authorization.
 *      [92/04/03            rvb]
 *      From 2.5 boot: pruned inb(), outb(), and pzero().
 *      [92/03/30            rvb]
 *
 * Revision 2.2  91/04/02  14:35:10  mbj
 *      Added _sp() => where is the stack at. [kupfer]
 *      Add Intel copyright
 *      [90/02/09            rvb]
 *
 */

/*
  Copyright 1988, 1989, 1990, 1991, 1992
   by Intel Corporation, Santa Clara, California.

                All Rights Reserved

Permission to use, copy, modify, and distribute this software and
its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appears in all
copies and that both the copyright notice and this permission notice
appear in supporting documentation, and that the name of Intel
not be used in advertising or publicity pertaining to distribution
of the software without specific, written prior permission.

INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

        .file "asm.s"

#include "asm.h"


CR0_PE_ON       =       0x1
CR0_PE_OFF      =       0xfffffffe

.globl  _ouraddr
        .text

/*
#
# real_to_prot()
#       transfer from real mode to protected mode.
*/

ENTRY(real_to_prot)
        # guarantee that interrupt is disabled when in prot mode
        cli

        # load the gdtr
        addr16
        data32
        lgdt    EXT(Gdtr)

        # set the PE bit of CR0
        mov     %cr0, %eax

        data32
        or      $CR0_PE_ON, %eax
        mov     %eax, %cr0

        # make intrasegment jump to flush the processor pipeline and
        # reload CS register
        data32
        ljmp    $0x18, $xprot

xprot:
        # we are in USE32 mode now
        # set up the protective mode segment registers : DS, SS, ES
        mov     $0x20, %eax
        movw    %ax, %ds
        movw    %ax, %ss
        movw    %ax, %es

        ret

/*
#
# prot_to_real()
#       transfer from protected mode to real mode
#
*/

ENTRY(prot_to_real)

        # set up a dummy stack frame for the second seg change.
        movl    _ouraddr, %eax
        sarl    $4, %eax
        pushw   %ax
        pushw   $xreal

        # Change to use16 mode.
        ljmp    $0x28, $x16

x16:
        # clear the PE bit of CR0
        mov     %cr0, %eax
        data32
        and     $CR0_PE_OFF, %eax
        mov     %eax, %cr0


        # make intersegment jmp to flush the processor pipeline
        # using the fake stack frame set up earlier
        # and reload CS register
        lret


xreal:
        # we are in real mode now
        # set up the real mode segment registers : DS, SS, ES
        movw    %cs, %ax
        movw    %ax, %ds
        movw    %ax, %ss
        movw    %ax, %es

        data32
        ret

/*
#
# startprog(phyaddr)
#       start the program on protected mode where phyaddr is the entry point
#
*/

ENTRY(startprog)
        push    %ebp
        mov     %esp, %ebp


        # get things we need into registers
        movl    0x8(%ebp), %ecx         # entry offset
        movl    0x0c(%ebp), %eax        # &argv

        # make a new stack at 0:0xa0000 (big segs)
        mov     $0x10, %ebx
        movw    %bx, %ss
        movl    $0xa0000,%ebx
        movl    %ebx,%esp


        # push some number of args onto the stack
        pushl   $0                      # nominally a cyl offset in the boot.
        pushl   0x8(%eax)               # argv[2] = bootdev
        pushl   0x4(%eax)               # argv[1] = howto
        pushl   $0                      # dummy 'return' address

        # push on our entry address
        mov     $0x08, %ebx             # segment
        pushl   %ebx
        pushl   %ecx

        # convert over the other data segs
        mov     $0x10, %ebx
        movw    %bx, %ds
        movw    %bx, %es

        # convert the PC (and code seg)
        lret
/*
#
# pbzero( dst, cnt)
#       where src is a virtual address and dst is a physical address
*/

ENTRY(pbzero)
        push    %ebp
        mov     %esp, %ebp
        push    %es
        push    %esi
        push    %edi
        push    %ecx

        cld

        # set %es to point at the flat segment
        mov     $0x10, %eax
        movw    %ax, %es

        mov     0x8(%ebp), %edi         # destination
        mov     0xc(%ebp), %ecx         # count
        mov     $0x0,%eax               # value

        rep
        stosb

        pop     %ecx
        pop     %edi
        pop     %esi
        pop     %es
        pop     %ebp

        ret
/*
#
# pcpy(src, dst, cnt)
#       where src is a virtual address and dst is a physical address
#
*/

ENTRY(pcpy)
        push    %ebp
        mov     %esp, %ebp
        push    %es
        push    %esi
        push    %edi
        push    %ecx

        cld

        # set %es to point at the flat segment
        mov     $0x10, %eax
        movw    %ax, %es

        mov     0x8(%ebp), %esi         # source
        mov     0xc(%ebp), %edi         # destination
        mov     0x10(%ebp), %ecx        # count

        rep
        movsb

        pop     %ecx
        pop     %edi
        pop     %esi
        pop     %es
        pop     %ebp

        ret