| 1 | /* |
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| 2 | * crt0.S -- startup file for PowerPC systems. |
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| 3 | * |
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| 4 | * Copyright (c) 1995 Cygnus Support |
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| 5 | * |
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| 6 | * The authors hereby grant permission to use, copy, modify, distribute, |
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| 7 | * and license this software and its documentation for any purpose, provided |
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| 8 | * that existing copyright notices are retained in all copies and that this |
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| 9 | * notice is included verbatim in any distributions. No written agreement, |
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| 10 | * license, or royalty fee is required for any of the authorized uses. |
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| 11 | * Modifications to this software may be copyrighted by their authors |
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| 12 | * and need not follow the licensing terms described here, provided that |
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| 13 | * the new terms are clearly indicated on the first page of each file where |
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| 14 | * they apply. |
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| 15 | */ |
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| 16 | |
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| 17 | #include "ppc-asm.h" |
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| 18 | |
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| 19 | .file "crt0.S" |
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| 20 | .section ".got2","aw" |
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| 21 | .align 2 |
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| 22 | |
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| 23 | .LCTOC1 = .+32768 |
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| 24 | |
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| 25 | .extern FUNC_NAME(atexit) |
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| 26 | .globl FUNC_NAME(__atexit) |
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| 27 | .section ".sdata","aw" |
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| 28 | .align 2 |
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| 29 | FUNC_NAME(__atexit): /* tell C's eabi-ctor's we have an atexit function */ |
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| 30 | .long FUNC_NAME(atexit)@fixup /* and that it is to register __do_global_dtors */ |
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| 31 | |
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| 32 | .section ".fixup","aw" |
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| 33 | .align 2 |
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| 34 | .long FUNC_NAME(__atexit) |
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| 35 | |
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| 36 | .section ".got2","aw" |
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| 37 | .Ltable = .-.LCTOC1 |
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| 38 | .long .LCTOC1 /* address we think .LCTOC1 is loaded at */ |
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| 39 | |
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| 40 | .Lsbss_start = .-.LCTOC1 |
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| 41 | .long __sbss_start |
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| 42 | |
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| 43 | .Lsbss_end = .-.LCTOC1 |
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| 44 | .long __sbss_end |
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| 45 | |
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| 46 | .Lbss_start = .-.LCTOC1 |
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| 47 | .long __bss_start |
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| 48 | |
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| 49 | .Lend = .-.LCTOC1 |
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| 50 | .long _end |
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| 51 | |
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| 52 | .Lstack = .-.LCTOC1 /* stack address if set by user */ |
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| 53 | .long __stack |
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| 54 | |
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| 55 | .text |
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| 56 | .Lptr: |
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| 57 | .long .LCTOC1-.Laddr |
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| 58 | |
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| 59 | .globl _start |
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| 60 | .type _start,@function |
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| 61 | _start: |
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| 62 | bl .Laddr /* get current address */ |
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| 63 | .Laddr: |
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| 64 | mflr r4 /* real address of .Laddr */ |
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| 65 | lwz r5,(.Lptr-.Laddr)(r4) /* linker generated address of .LCTOC1 */ |
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| 66 | add r5,r5,r4 /* correct to real pointer */ |
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| 67 | lwz r4,.Ltable(r5) /* get linker's idea of where .Laddr is */ |
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| 68 | subf r4,r4,r5 /* calculate difference between where linked and current */ |
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| 69 | |
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| 70 | /* clear bss and sbss */ |
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| 71 | lwz r6,.Lbss_start(r5) /* calculate beginning of the BSS */ |
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| 72 | lwz r7,.Lend(r5) /* calculate end of the BSS */ |
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| 73 | add r6,r6,r4 /* adjust pointers */ |
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| 74 | add r7,r7,r4 |
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| 75 | |
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| 76 | cmplw 1,r6,r7 |
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| 77 | bc 4,4,.Ldone1 |
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| 78 | |
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| 79 | subf r8,r6,r7 /* number of bytes to zero */ |
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| 80 | srwi r9,r8,2 /* number of words to zero */ |
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| 81 | mtctr r9 |
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| 82 | li r0,0 /* zero to clear memory */ |
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| 83 | addi r6,r6,-4 /* adjust so we can use stwu */ |
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| 84 | .Lloop: |
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| 85 | stwu r0,4(r6) /* zero bss */ |
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| 86 | bdnz .Lloop |
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| 87 | |
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| 88 | .Ldone1: |
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| 89 | |
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| 90 | lwz r6,.Lsbss_start(r5) /* calculate beginning of the SBSS */ |
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| 91 | lwz r7,.Lsbss_end(r5) /* calculate end of the SBSS */ |
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| 92 | add r6,r6,r4 /* adjust pointers */ |
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| 93 | add r7,r7,r4 |
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| 94 | |
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| 95 | cmplw 1,r6,r7 |
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| 96 | bc 4,4,.Ldone |
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| 97 | |
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| 98 | subf r8,r6,r7 /* number of bytes to zero */ |
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| 99 | srwi r9,r8,2 /* number of words to zero */ |
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| 100 | mtctr r9 |
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| 101 | li r0,0 /* zero to clear memory */ |
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| 102 | addi r6,r6,-4 /* adjust so we can use stwu */ |
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| 103 | .Lloop2: |
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| 104 | stwu r0,4(r6) /* zero bss */ |
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| 105 | bdnz .Lloop2 |
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| 106 | |
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| 107 | .Ldone: |
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| 108 | |
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| 109 | lwz r0,.Lstack(r5) /* stack address or 0 */ |
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| 110 | cmplwi 1,r0,0 /* equal to 0? */ |
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| 111 | bc 12,6,.Lnostack /* use default stack if == 0 */ |
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| 112 | mr sp,r0 /* use user defined stack */ |
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| 113 | |
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| 114 | .Lnostack: |
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| 115 | /* set up initial stack frame */ |
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| 116 | addi sp,sp,-4 /* make sure we don't overwrite debug mem */ |
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| 117 | lis r0,0 |
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| 118 | stw r0,0(sp) /* clear back chain */ |
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| 119 | stwu sp,-64(sp) /* push another stack frame */ |
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| 120 | |
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| 121 | /* Let her rip */ |
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| 122 | bl FUNC_NAME(main) |
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| 123 | |
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| 124 | /* return value from main is argument to exit */ |
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| 125 | bl FUNC_NAME(exit) |
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| 126 | trap |
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| 127 | .Lstart: |
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| 128 | .size _start,.Lstart-_start |
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