1| $NetBSD: SRT0.S,v 1.2 2008/05/04 00:18:16 martin Exp $
2
3| Copyright (c) 1998 The NetBSD Foundation, Inc.
4| All rights reserved.
5|
6| This code is derived from software contributed to The NetBSD Foundation
7| by Gordon W. Ross.
8|
9| Redistribution and use in source and binary forms, with or without
10| modification, are permitted provided that the following conditions
11| are met:
12| 1. Redistributions of source code must retain the above copyright
13|    notice, this list of conditions and the following disclaimer.
14| 2. Redistributions in binary form must reproduce the above copyright
15|    notice, this list of conditions and the following disclaimer in the
16|    documentation and/or other materials provided with the distribution.
17|
18| THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
19| ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
20| TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21| PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
22| BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23| CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24| SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25| INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26| CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27| ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28| POSSIBILITY OF SUCH DAMAGE.
29
30#include <machine/asm.h>
31
32|         SRT0.S - Stand-alone Run-Time startup code, part 0
33          .file     "SRT0.S"
34          .data
35
36| Flush the CPU cache using MC68020 values just to be safe.
37| This will cause the MC68030 to run with the data cache
38| disabled, but that is OK for boot programs.
39          .set      IC_CLEAR,0x9
40          .set      PSL_HIGHIPL,0x2700
41
42          .text
43
44ASENTRY_NOPROFILE(start)
45| Disable interrupts (just in case...)
46          movw      #PSL_HIGHIPL,%sr
47
48| Check to see if the code is located correctly.
49| Get current location via PC-relative load, then...
50          lea       %pc@(start:w),%a0   | current location (0x4000)
51| ...force a long (not PC-relative) load to a1 and compare.
52          lea       start:l,%a1                   | desired location (LINKADDR)
53          cmpl      %a0,%a1
54          beqs      restart
55
56| Relocate the code and data to where they belong.
57          movl      #_edata,%d0                   | Desired end of program
58          subl      %a1,%d0                       | Calculate length, round up.
59          lsrl      #2,%d0
60Lcp:
61          movl      %a0@+,%a1@+
62          dbra      %d0,Lcp
63
64| If we are on a sun2, we don't want to clear the I-cache
65| because we don't have one.  We are on a sun2 if the PROM
66| has pointed the vector base register to zero.  This is
67| similar to the test that SRT1.c's _start does.
68          movc      %vbr, %d0
69          tstl      %d0
70          beqs      Ljmpreloc
71| Clear the I-cache in case the copied code was cached.
72          movl      #IC_CLEAR,%d0
73          movc      %d0,%cacr
74Ljmpreloc:
75| Force a long jump to the relocated code (not pc-relative)
76          lea       restart:l,%a0
77          jmp       %a0@
78
79| Define the location of our stack (just before relocated text).
80| Leave room the exit jmpbuf at the end of our stack.
81          .set      estack,start-60
82
83restart:
84| Now in the relocated code, using the monitor stack.
85| Save this context so we can return with it.
86          pea       estack
87          jsr       _C_LABEL(setjmp)
88          addqw     #4,%sp
89          tstl      %d0
90          bne       Ldone     | here via longjmp
91
92| Switch to our own stack.
93          lea       estack,%a0
94          movl      %a0,%sp
95          subl      %a6,%a6
96
97| Clear out BSS...
98          lea       _edata,%a0
99          lea       _end,%a1
100Lclrbss:
101          clrl      %a0@+
102          cmpl      %a1,%a0
103          ble       Lclrbss
104
105| Call the run-time startup C code, which will:
106|   initialize, call main, call exit.
107          jsr       _C_LABEL(_start)
108
109| Switch back to the monitor stack, then either
110| "chain" to the next program or return.
111ENTRY(exit)
112          pea       estack
113          jsr       _C_LABEL(longjmp)   | to next line
114Ldone:
115          movl      _C_LABEL(chain_to_func),%a0
116          movl      %a0,%d0
117          beq       Lret
118          jmp       %a0@
119Lret:
120          rts
121
122| function to clear the I-cache
123ENTRY(ICIA)
124          tstl      _C_LABEL(_is2)
125          bne       Lret
126          movl      #IC_CLEAR,%d0
127          movc      %d0,%cacr
128          rts
129
130| function to get the vector base register
131ENTRY(getvbr)
132          movc      %vbr,%a0
133          rts
134
135| Kernel version of setjmp/longjmp (label_t is 16 words)
136
137ENTRY(setjmp)
138          movl      %sp@(4),%a0         | savearea pointer
139          moveml    #0xFCFC,%a0@        | save d2-d7/a2-a7
140          movl      %sp@,%a0@(48)       | and return address
141          movl      #0,%d0              | return 0
142          rts
143
144ENTRY(longjmp)
145          movl      %sp@(4),%a0         | savearea pointer
146          moveml    %a0@+,#0xFCFC       | restore d2-d7/a2-a7
147          | Note: just changed sp!
148          movl      %a0@,%sp@ | and return address
149          movl      #1,%d0              | return 1
150          rts
151
152| The end.
153