1 | /* dlentry.s |
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2 | * |
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3 | * This file contains the entry code for RTEMS programs starting |
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4 | * after download to RAM |
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5 | * |
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6 | * Author: Thomas Doerfler <td@imd.m.isar.de> |
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7 | * IMD Ingenieurbuero fuer Microcomputertechnik |
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8 | * |
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9 | * COPYRIGHT (c) 1998 by IMD |
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10 | * |
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11 | * Changes from IMD are covered by the original distributions terms. |
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12 | * This file has been derived from the papyrus BSP: |
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13 | * |
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14 | * This file contains the entry veneer for RTEMS programs |
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15 | * downloaded to Papyrus. |
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16 | * |
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17 | * Author: Andrew Bray <andy@i-cubed.co.uk> |
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18 | * |
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19 | * COPYRIGHT (c) 1995 by i-cubed ltd. |
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20 | * |
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21 | * To anyone who acknowledges that this file is provided "AS IS" |
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22 | * without any express or implied warranty: |
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23 | * permission to use, copy, modify, and distribute this file |
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24 | * for any purpose is hereby granted without fee, provided that |
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25 | * the above copyright notice and this notice appears in all |
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26 | * copies, and that the name of i-cubed limited not be used in |
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27 | * advertising or publicity pertaining to distribution of the |
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28 | * software without specific, written prior permission. |
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29 | * i-cubed limited makes no representations about the suitability |
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30 | * of this software for any purpose. |
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31 | * |
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32 | * $Id$ |
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33 | */ |
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34 | |
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35 | #include "asm.h" |
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36 | |
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37 | /* |
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38 | * The helas403 ELF link scripts support three special sections: |
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39 | * .entry The actual entry point |
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40 | * .vectors The section containing the interrupt entry veneers. |
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41 | */ |
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42 | |
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43 | /* |
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44 | * Downloaded code loads the vectors separately to 0x00000100, |
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45 | * so .entry can be over 256 bytes. |
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46 | * |
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47 | * The other sections are linked in the following order: |
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48 | * .entry |
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49 | * .text |
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50 | * .data |
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51 | * .bss |
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52 | * see linker command file for section placement |
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53 | * |
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54 | * The initial stack is set to stack.end |
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55 | * |
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56 | * All the entry veneer has to do is to clear the BSS. |
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57 | */ |
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58 | |
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59 | /* |
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60 | * GDB likes to have debugging information for the entry veneer. |
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61 | * Here was some DWARF information. IMD removed it, because we |
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62 | * could not check, whether it was still correct. Sorry. |
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63 | |
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64 | */ |
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65 | |
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66 | #if PPC_ASM == PPC_ASM_ELF |
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67 | .section .entry |
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68 | #else |
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69 | .csect .text[PR] |
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70 | #endif |
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71 | |
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72 | PUBLIC_VAR (download_entry) |
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73 | SYM(download_entry): |
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74 | bl .startup |
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75 | base_addr: |
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76 | |
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77 | /*--------------------------------------------------------------------------- |
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78 | * Parameters from linker |
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79 | *--------------------------------------------------------------------------*/ |
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80 | toc_pointer: |
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81 | #if PPC_ASM == PPC_ASM_ELF |
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82 | .long s.got |
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83 | #else |
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84 | .long TOC[tc0] |
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85 | #endif |
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86 | bss_length: |
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87 | .long bss.size |
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88 | bss_addr: |
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89 | .long bss.start |
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90 | stack_top: |
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91 | .long stack.end |
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92 | /*--------------------------------------------------------------------------- |
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93 | * Reset_entry. |
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94 | *--------------------------------------------------------------------------*/ |
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95 | .startup: |
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96 | /* Get start address, stack grows down from here... */ |
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97 | mflr r1 |
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98 | |
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99 | /* Assume Bank regs set up..., cache etc. */ |
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100 | bl bssclr |
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101 | |
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102 | .extern SYM(__vectors) |
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103 | |
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104 | lis r2,__vectors@h /* set EVPR exc. vector prefix */ |
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105 | mtspr evpr,r2 |
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106 | |
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107 | /*------------------------------------------------------------------- |
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108 | * C_setup. |
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109 | *------------------------------------------------------------------*/ |
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110 | lwz r2,toc_pointer-base_addr(r1) /* set r2 to toc */ |
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111 | lwz r1,stack_top-base_addr(r1) /* set r1 to stack_top */ |
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112 | |
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113 | addi r1,r1,-56-4 /* start stack at text_addr - 56 */ |
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114 | addi r3,r0,0x0 /* clear r3 */ |
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115 | stw r3, 0(r1) /* Clear stack chain */ |
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116 | stw r3, 4(r1) |
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117 | stw r3, 8(r1) |
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118 | stw r3, 12(r1) |
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119 | .extern SYM (boot_card) |
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120 | b SYM (boot_card) /* call the first C routine */ |
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121 | |
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122 | /*--------------------------------------------------------------------------- |
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123 | * bssclr. |
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124 | *--------------------------------------------------------------------------*/ |
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125 | bssclr: |
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126 | /*------------------------------------------------------------------- |
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127 | * Data move finished, zero out bss. |
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128 | *------------------------------------------------------------------*/ |
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129 | lwz r2,bss_addr-base_addr(r1) /* start of bss set by loader */ |
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130 | lwz r3,bss_length-base_addr(r1) /* bss length */ |
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131 | rlwinm. r3,r3,30,0x3FFFFFFF /* form length/4 */ |
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132 | beqlr /* no bss */ |
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133 | mtctr r3 /* set ctr reg */ |
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134 | xor r6,r6,r6 /* r6 = 0 */ |
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135 | clear_bss: |
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136 | stswi r6,r2,0x4 /* store r6 */ |
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137 | addi r2,r2,0x4 /* update r2 */ |
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138 | bdnz clear_bss /* decrement counter and loop */ |
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139 | blr /* return */ |
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140 | .L_text_e: |
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141 | |
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142 | #if PPC_ABI == PPC_ABI_POWEROPEN |
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143 | DESCRIPTOR (startup) |
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144 | #endif |
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