source: trunk/libs/newlib/src/libgloss/rs6000/crt0.S @ 620

Last change on this file since 620 was 444, checked in by satin@…, 6 years ago

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

File size: 3.3 KB
Line 
1/*
2 * crt0.S -- startup file for PowerPC systems.
3 *
4 * Copyright (c) 1995 Cygnus Support
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#include "ppc-asm.h"
18
19        .file   "crt0.S"
20        .section ".got2","aw"
21        .align  2
22
23.LCTOC1 = .+32768
24
25        .extern FUNC_NAME(atexit)
26        .globl  FUNC_NAME(__atexit)
27        .section ".sdata","aw"
28        .align  2
29FUNC_NAME(__atexit):                    /* tell C's eabi-ctor's we have an atexit function */
30        .long   FUNC_NAME(atexit)@fixup /* and that it is to register __do_global_dtors */
31
32        .section ".fixup","aw"
33        .align  2
34        .long   FUNC_NAME(__atexit)
35
36        .section ".got2","aw"
37.Ltable = .-.LCTOC1
38        .long   .LCTOC1                 /* address we think .LCTOC1 is loaded at */
39
40.Lsbss_start = .-.LCTOC1
41        .long   __sbss_start
42
43.Lsbss_end = .-.LCTOC1
44        .long   __sbss_end
45
46.Lbss_start = .-.LCTOC1
47        .long   __bss_start
48
49.Lend = .-.LCTOC1
50        .long   _end
51
52.Lstack = .-.LCTOC1                     /* stack address if set by user */
53        .long   __stack
54
55        .text
56.Lptr:
57        .long .LCTOC1-.Laddr
58
59        .globl  _start
60        .type   _start,@function
61_start:
62        bl      .Laddr                  /* get current address */
63.Laddr:
64        mflr    r4                      /* real address of .Laddr */
65        lwz     r5,(.Lptr-.Laddr)(r4)   /* linker generated address of .LCTOC1 */
66        add     r5,r5,r4                /* correct to real pointer */
67        lwz     r4,.Ltable(r5)          /* get linker's idea of where .Laddr is */
68        subf    r4,r4,r5                /* calculate difference between where linked and current */
69
70        /* clear bss and sbss */
71        lwz     r6,.Lbss_start(r5)      /* calculate beginning of the BSS */
72        lwz     r7,.Lend(r5)            /* calculate end of the BSS */
73        add     r6,r6,r4                /* adjust pointers */
74        add     r7,r7,r4
75
76        cmplw   1,r6,r7
77        bc      4,4,.Ldone1
78
79        subf    r8,r6,r7                /* number of bytes to zero */
80        srwi    r9,r8,2                 /* number of words to zero */
81        mtctr   r9
82        li      r0,0                    /* zero to clear memory */
83        addi    r6,r6,-4                /* adjust so we can use stwu */
84.Lloop:
85        stwu    r0,4(r6)                /* zero bss */
86        bdnz    .Lloop
87
88.Ldone1:
89
90        lwz     r6,.Lsbss_start(r5)     /* calculate beginning of the SBSS */
91        lwz     r7,.Lsbss_end(r5)       /* calculate end of the SBSS */
92        add     r6,r6,r4                /* adjust pointers */
93        add     r7,r7,r4
94
95        cmplw   1,r6,r7
96        bc      4,4,.Ldone
97
98        subf    r8,r6,r7                /* number of bytes to zero */
99        srwi    r9,r8,2                 /* number of words to zero */
100        mtctr   r9
101        li      r0,0                    /* zero to clear memory */
102        addi    r6,r6,-4                /* adjust so we can use stwu */
103.Lloop2:
104        stwu    r0,4(r6)                /* zero bss */
105        bdnz    .Lloop2
106
107.Ldone:
108
109        lwz     r0,.Lstack(r5)          /* stack address or 0 */
110        cmplwi  1,r0,0                  /* equal to 0? */
111        bc      12,6,.Lnostack          /* use default stack if == 0 */
112        mr      sp,r0                   /* use user defined stack */
113
114.Lnostack:
115        /* set up initial stack frame */
116        addi    sp,sp,-4                /* make sure we don't overwrite debug mem */
117        lis     r0,0
118        stw     r0,0(sp)                /* clear back chain */
119        stwu    sp,-64(sp)              /* push another stack frame */
120
121        /* Let her rip */
122        bl      FUNC_NAME(main)
123
124        /* return value from main is argument to exit */
125        bl      FUNC_NAME(exit)
126        trap
127.Lstart:
128        .size   _start,.Lstart-_start
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