1|         $NetBSD: SRT0.S,v 1.4 2009/10/21 23:12:09 snj Exp $
2
3| Copyright (c) 1995 Gordon W. Ross
4| All rights reserved.
5|
6| Redistribution and use in source and binary forms, with or without
7| modification, are permitted provided that the following conditions
8| are met:
9| 1. Redistributions of source code must retain the above copyright
10|    notice, this list of conditions and the following disclaimer.
11| 2. Redistributions in binary form must reproduce the above copyright
12|    notice, this list of conditions and the following disclaimer in the
13|    documentation and/or other materials provided with the distribution.
14|
15| THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16| IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17| OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18| IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19| INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20| NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21| DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22| THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24| THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25
26|         this is a pre-startup wrapper for bugcrt which relocates the
27|         code to the correct place before exec()ing.
28
29|         SRT0.S - Stand-alone Run-Time startup code, part 0
30
31#include <m68k/asm.h>
32
33          .file     "SRT0.S"
34          .text
35GLOBAL(_estack)
36
37xstart:
38| first, relocate code to correct place without touching critical regs
39| (args are in: d0, d1, d4, a0, a1, a2, a3, a4, a5, a6)
40|         [a3 and a4 only when netbooting]
41          movl      %a3, %d3            | SAVE a3 in d3
42          movl      %a4, %d5            | SAVE a4 in d5
43          lea       %pc@(xstart:w), %a3 | a3 = current addr (could be anywhere)
44          lea       xstart:l, %a4                 | a4 = desired location (LINKADDR)
45          cmpl      %a3, %a4            | already there?
46          beqs      restart                       | short-circuit out
47
48                                                  | Relocate the code and data
49          movl      #_C_LABEL(edata),%d2          | Desired end of program
50          subl      %a4,%d2                       | Calculate length, round up.
51          lsrl      #2,%d2
52Lcp:
53          movl      %a3@+, %a4@+
54          dbra      %d2, Lcp
55
56| Force a long jump to the relocated code (not pc-relative)
57          lea       restart:l, %a3
58          jmp       %a3@
59
60restart:
61| now in the relocated code
62
63| Set up stack (just before relocated text)
64          lea       _C_LABEL(_estack):l, %a3
65          movl      %a3, %sp
66
67| now that we have relocated, call the bugcrt  (note we skip over the special
68|         bug header which has a PC and SP in it)
69          movl      %d3, %a3            | RESTORE a3
70          movl      %d5, %a4            | RESTORE a4
71          jmp       _start
72
73| The end.
74