source: trunk/libs/newlib/src/libgloss/mips/crt0_cygmon.S @ 444

Last change on this file since 444 was 444, checked in by satin@…, 6 years ago

add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc

File size: 4.3 KB
Line 
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 */
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