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Annotation of sys/arch/mvme68k/stand/libsa/SRT0.S, Revision 1.1

1.1     ! nbrk        1: |      $OpenBSD: SRT0.S,v 1.7 2001/07/04 08:06:56 niklas Exp $
        !             2: |      $NetBSD: SRT0.S,v 1.2 1995/08/12 18:38:55 gwr Exp $
        !             3:
        !             4: | Copyright (c) 1995 Gordon W. Ross
        !             5: | All rights reserved.
        !             6: |
        !             7: | Redistribution and use in source and binary forms, with or without
        !             8: | modification, are permitted provided that the following conditions
        !             9: | are met:
        !            10: | 1. Redistributions of source code must retain the above copyright
        !            11: |    notice, this list of conditions and the following disclaimer.
        !            12: | 2. Redistributions in binary form must reproduce the above copyright
        !            13: |    notice, this list of conditions and the following disclaimer in the
        !            14: |    documentation and/or other materials provided with the distribution.
        !            15: | 3. The name of the author may not be used to endorse or promote products
        !            16: |    derived from this software without specific prior written permission.
        !            17: | 4. All advertising materials mentioning features or use of this software
        !            18: |    must display the following acknowledgement:
        !            19: |      This product includes software developed by Gordon Ross
        !            20: |
        !            21: | THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
        !            22: | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
        !            23: | OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
        !            24: | IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
        !            25: | INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
        !            26: | NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
        !            27: | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
        !            28: | THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
        !            29: | (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
        !            30: | THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
        !            31:
        !            32: |      this is a pre-startup wrapper for bugcrt which relocates the
        !            33: |      code to the correct place before exec()ing.
        !            34:
        !            35: |      SRT0.S - Stand-alone Run-Time startup code, part 0
        !            36:        .file   "SRT0.S"
        !            37:        .text
        !            38:        .globl  __estack
        !            39: __estack:
        !            40:        .globl  xstart
        !            41: xstart:
        !            42: | first, relocate code to correct place without touching critical regs
        !            43: | (args are in: d0, d1, d4, a0, a1, a2, a3, a4, a5, a6)
        !            44: |      [a3 and a4 only when netbooting]
        !            45:        movl    a3, d3                  | SAVE a3 in d3
        !            46:        movl    a4, d5                  | SAVE a4 in d5
        !            47:        lea     pc@(xstart:w), a3       | a3 = current addr (could be anywhere)
        !            48:        lea     xstart:l, a4            | a4 = desired location (LINKADDR)
        !            49:        cmpl    a3, a4                  | already there?
        !            50:        beqs    restart                 | short-circuit out
        !            51:
        !            52:                                        | Relocate the code and data
        !            53:        movl    #_edata,d2              | Desired end of program
        !            54:        subl    a4,d2                   | Calculate length, round up.
        !            55:        lsrl    #2,d2
        !            56: Lcp:
        !            57:        movl    a3@+, a4@+
        !            58:        dbra    d2, Lcp
        !            59:
        !            60: | Force a long jump to the relocated code (not pc-relative)
        !            61:        lea     restart:l, a3
        !            62:        jmp     a3@
        !            63:
        !            64: restart:
        !            65: | now in the relocated code
        !            66:
        !            67: | Set up stack (just before relocated text)
        !            68:        lea     __estack:l, a3
        !            69:        movl    a3, sp
        !            70:
        !            71: | now that we have relocated, call the bugcrt  (note we skip over the special
        !            72: |      bug header which has a PC and SP in it)
        !            73:        movl    d3, a3                  | RESTORE a3
        !            74:        movl    d5, a4                  | RESTORE a4
        !            75:        jmp     _start
        !            76:
        !            77: | The end.