xref: /netbsd/sys/arch/mvmeppc/stand/libsa/srt0.S (revision bf9ec67e)
1/*	$NetBSD: srt0.S,v 1.1 2002/02/27 21:02:27 scw Exp $	*/
2
3/*-
4 * Copyright (c) 2002 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Steve C. Woodford.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 *    must display the following acknowledgement:
20 *        This product includes software developed by the NetBSD
21 *        Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 *    contributors may be used to endorse or promote products derived
24 *    from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39#include <machine/asm.h>
40#include <machine/psl.h>
41#include <powerpc/spr.h>
42
43#define	STACK_SIZE	8192
44
45/*
46 * The main entry point when loaded by PPC-Bug.
47 *
48 * There are two possible entry conditions here:
49 *
50 *   1) We were booted in `PReP' mode, either from disk or the network.
51 *      In this case, we have no control over the load address so we
52 *      have to relocate ourselves to the appropriate place.
53 *      The firmware passes us the following registers:
54 *
55 *        r1  -> Temporary stack
56 *        r3  -> Residual Data
57 *        r4  -> The address we were loaded to
58 *        r5  -> Zero
59 *
60 *   2) We were booted over the network in Non-PReP mode. In this case,
61 *      the load address is usually set using PPC-Bug's "niot" command,
62 *      but we won't depend on it so relocation may be required. The
63 *      firmware passes us the following registers:
64 *
65 *        r1  -> Temporary stack
66 *        r3  -> CLUN of the network device we booted from
67 *        r4  -> DLUN of the network device we booted from
68 *        r5  -> Non-zero
69 *        r6  -> Base address of network device
70 *        r7  -> Execution address of loaded program
71 *        r8  -> Address of IP-address data structure
72 *        r9  -> Pointer to start of filename string
73 *        r10 -> Pointer to end+1 of filename string
74 *        r11 -> Pointer to start of argument string
75 *        r12 -> Pointer to end+1 of argument string
76 *
77 * The obvious way to distinguish between the two boot modes is by
78 * checking the value of r5.
79 */
80ENTRY(_start)
81	bl	1f
821:	xor	r0,r0,r0
83
84	/* First, switch off Instruction and Data caches. */
85	mfspr	r13,SPR_HID0
86	LDCONST(r14, HID0_DCE|HID0_ICE)
87	andc	r13,r13,r14
88	sync
89	mtspr	SPR_HID0,r13
90
91
92	/*
93	 * All registers now available. Let's see if we need to relocate
94	 */
95	LDCONST(r13,_C_LABEL(_start))	/* Where we'd like to be */
96	LDCONST(r14,_C_LABEL(edata))	/* End of data section */
97	LDCONST(r15,0x3)
98	add	r14,r14,r15
99	andc	r14,r14,r15		/* Rounded up to the nearest 32-bits */
100	sub	r15,r14,r13		/* Our size, in bytes */
101	mflr	r16			/* Get address we were loaded to */
102	subi	r16,r16,0x4		/* Correct for branch */
103	cmp	cr0,r13,r16		/* Do we need to relocate? */
104	beq	_ASM_LABEL(clrbss)	/* No relocation necessary */
105	li	r17,0x4
106	bgt	1f			/* Relocate using forward copy? */
107
108	/* Nope. Need to copy in reverse in case of overlap */
109	mr	r13,r14			/* dest -> end */
110	add	r16,r16,r15		/* src + size */
111	subi	r17,r17,0x8		/* Increment is -4 */
112
113	/*
114	 * Do the relocation
115	 *  r13  -> dest
116	 *  r15  -> number of bytes
117	 *  r16  -> src
118	 *  r17  -> Increment (+4 or -4)
119	 */
1201:	srwi	r15,r15,0x2		/* Convert length to 32-bit words */
121	mtctr	r15			/* Save in counter register */
122
1232:	lwz	r15,0(r16)
124	stw	r15,0(r13)
125	add	r16,r16,r17
126	add	r13,r13,r17
127	bdnz	2b
128
129	/* Now do an absolute jump to the relocated code */
130	LDCONST(r13,_ASM_LABEL(clrbss))
131	mtlr	r13
132	blr
133
134ASENTRY(clrbss)
135	LDCONST(r13,_C_LABEL(edata))	/* End of the data section */
136	LDCONST(r14,_C_LABEL(end))	/* End of BSS */
137	LDCONST(r15,0x3)
138	add	r14,r14,r15
139	andc	r14,r14,r15		/* Round-up end of BSS to 32-bits */
140	sub	r15,r14,r13		/* r15 == length of BSS */
141	srwi	r15,r15,0x2
142	mtctr	r15			/* CTR == # of 32-bit words in BSS */
1431:	stw	r0,0(r13)		/* Clear BSS */
144	addi	r13,r13,4
145	bdnz	1b
146
147	/* Fix up our own stack */
148	LDCONST(r1,stack)
149	addi	r1,r1,STACK_SIZE-0x10
150	LDCONST(r13,0x0f)
151	andc	r1,r1,r13
152
153	/*
154	 * Copy the arguments passed in from Bug into bug_bootinfo
155	 *
156	 * See bugsyscalls.h for details.
157	 */
158	LDCONST(r13,_C_LABEL(bug_bootinfo))
159	stw	r5,0x00(r13)
160	stw	r3,0x04(r13)
161	stw	r4,0x08(r13)
162	stw	r6,0x0c(r13)
163	stw	r7,0x10(r13)
164	stw	r8,0x14(r13)
165	stw	r9,0x18(r13)
166	stw	r10,0x1c(r13)
167	stw	r11,0x20(r13)
168	stw	r12,0x24(r13)
169
170	mr	r3,r13
171	bl	_C_LABEL(main)		/* void main(void) */
172	/* FALLTHROUGH */
173
174/*
175 * Return to the debugger, either because main() returned or via panic().
176 */
177ENTRY(_rtt)
178	addi	r10,0,0x0063
179	sc
1801:	nop
181	b	1b
182
183	/*
184	 * C code runs on this stack.
185	 */
186	.comm	stack,STACK_SIZE,4
187	.comm	errno,4,4
188	.comm	debug,4,4
189