1/*
2 * crt0_cygmon.S -- Minimal startup file for MIPS targets running Cygmon.
3 *
4 * Copyright (c) 1995, 1996, 1997, 2000 Red Hat, Inc.
5 *
6 * The authors hereby grant permission to use, copy, modify, distribute,
7 * and license this software and its documentation for any purpose, provided
8 * that existing copyright notices are retained in all copies and that this
9 * notice is included verbatim in any distributions. No written agreement,
10 * license, or royalty fee is required for any of the authorized uses.
11 * Modifications to this software may be copyrighted by their authors
12 * and need not follow the licensing terms described here, provided that
13 * the new terms are clearly indicated on the first page of each file where
14 * they apply.
15 */
16
17/*
18 * This file contains the minimal startup code necessary.
19 * This will not do any hardware initialization.  It is assumed that we are talking to Cygmon
20 * and therefore the hardware will be initialized properly.
21 */
22
23#ifdef __mips16
24/* This file contains 32 bit assembly code.  */
25	.set nomips16
26#endif
27
28#include "regs.S"
29
30/*
31 * Set up some room for a stack. We just grab a chunk of memory.
32 */
33#define STACK_SIZE  0x4000
34#define GLOBAL_SIZE 0x2000
35
36#define STARTUP_STACK_SIZE	0x0100
37
38	.comm	__memsize, 12
39	.comm	__lstack, STARTUP_STACK_SIZE
40	.comm   __stackbase,4
41
42	.text
43	.align	4
44    /*
45     * Without the following nop, GDB thinks _start is a data variable.
46     * This is probably a bug in GDB in handling a symbol that is at the
47     * start of the .text section.
48     */
49	nop
50
51	.globl	_start
52	.ent	_start
53_start:
54	.set	noreorder
55	la		gp, _gp					# set the global data pointer, defined in the linker script
56	.end	_start
57
58    /*
59     * zero out the bss section.
60     */
61	.globl	__memsize
62	.globl	get_mem_info .text
63	.globl	zerobss
64	.ent	zerobss
65zerobss:
66	la		v0, _fbss				# These variables are defined in the linker script
67	la		v1, _end
68
693:
70	sw		zero, 0(v0)
71	bltu	v0, v1, 3b
72	addiu	v0, v0, 4				# executed in delay slot
73
74    /*
75     * Setup a small stack so we can run some C code,
76     * and get the usable memory size.
77     */
78	la		t0, __lstack
79	addiu	sp, t0, STARTUP_STACK_SIZE
80	la		a0, __memsize
81	jal		get_mem_info
82	nop
83
84	/*
85     * Setup the stack pointer --
86     *    get_mem_info returns the top of memory, so just use that In
87     *    addition, we must subtract 24 bytes for the 3 8 byte
88     *    arguments to main, in case main wants to write them back to
89     *    the stack.  The caller is supposed to allocate stack space
90     *    for parameters in registers in the old MIPS ABIs.  We must
91     *    do this even though we aren't passing arguments, because
92     *    main might be declared to have them.
93	 *    Some ports need a larger alignment for the stack, so we
94	 *    subtract 32, which satisifes the stack for the arguments and
95	 *    keeps the stack pointer better aligned.
96     */
97	subu	v0, v0, 32
98	move	sp, v0
99
100	sw		sp, __stackbase			# keep this for future ref
101	.end	zerobss
102
103    /*
104     * initialize target specific stuff. Only execute these
105     * functions it they exist.
106     */
107	.globl	hardware_init_hook .text
108	.globl	software_init_hook .text
109	.globl	__do_global_dtors .text
110	.globl	atexit .text
111	.globl	exit .text
112	.globl	init
113	.ent	init
114init:
115	la		t9, hardware_init_hook	# init the hardware if needed
116	beq		t9, zero, 6f
117	nop
118	jal		t9
119	nop
1206:
121	la		t9, software_init_hook	# init the software if needed
122	beq		t9, zero, 7f
123	nop
124	jal		t9
125	nop
1267:
127	la		a0, __do_global_dtors
128	jal		atexit
129	nop
130
131#ifdef GCRT0
132	.globl	_ftext
133	.globl	_extext
134	la		a0, _ftext
135	la		a1, _etext
136	jal		monstartup
137	nop
138#endif
139
140	move	a0,zero					# set argc to 0
141	jal		main					# call the program start function
142	nop
143
144	# fall through to the "exit" routine
145	jal		exit					# call libc exit to run the G++
146									# destructors
147	move	a0, v0					# pass through the exit code
148	.end	init
149
150/*
151 * _exit -- Exit from the application. Normally we cause a user trap
152 *          to return to the ROM monitor for another run. NOTE: This is
153 *          the only other routine we provide in the crt0.o object, since
154 *          it may be tied to the "_start" routine. It also allows
155 *          executables that contain a complete world to be linked with
156 *          just the crt0.o object.
157 */
158	.globl	_exit
159	.ent	_exit
160_exit:
1617:
162#ifdef GCRT0
163	jal		_mcleanup
164	nop
165#endif
166	# Cygmon expects a break 5
167	break	5
168	nop
169	b		7b						# loop back just in-case
170	nop
171	.end	_exit
172
173/* EOF crt0.S */
174