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      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 
     44 ASENTRY_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
     60 Lcp:
     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
     74 Ljmpreloc:
     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 
     83 restart:
     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
    100 Lclrbss:
    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.
    111 ENTRY(exit)
    112 	pea	estack
    113 	jsr	_C_LABEL(longjmp)	| to next line
    114 Ldone:
    115 	movl	_C_LABEL(chain_to_func),%a0
    116 	movl	%a0,%d0
    117 	beq	Lret
    118 	jmp	%a0@
    119 Lret:
    120 	rts
    121 
    122 | function to clear the I-cache
    123 ENTRY(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
    131 ENTRY(getvbr)
    132 	movc	%vbr,%a0
    133 	rts
    134 
    135 | Kernel version of setjmp/longjmp (label_t is 16 words)
    136 
    137 ENTRY(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 
    144 ENTRY(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