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1 | ################################################################################# |
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2 | # File : reset.s |
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3 | # Author : Alain Greiner |
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4 | # Date : 28/08/2006 |
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5 | ################################################################################# |
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6 | # This is a minimal boot code : |
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7 | # - It initializes the Status Register (SR) |
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8 | # - It defines the stack size and initializes the stack pointer ($29) |
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9 | # - It initializes the global pointer ($28) that is used by GCC to |
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10 | # optimize acces to the global variables. |
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11 | # - It initializes the EPC register, and jump to the main address |
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12 | ################################################################################# |
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13 | |
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14 | .section .reset,"ax",@progbits |
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15 | |
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16 | .extern seg_stack_base |
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17 | .extern seg_data_base |
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18 | .extern main |
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19 | |
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20 | .globl reset # makes reset an external symbol |
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21 | .ent reset |
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22 | .func reset |
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23 | .align 2 |
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24 | |
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25 | reset: |
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26 | .set noreorder |
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27 | |
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28 | # initializes SR register |
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29 | li $26, 0x00000013 |
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30 | mtc0 $26, $12 |
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31 | |
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32 | # initializes stack pointer |
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33 | la $29, seg_stack_base |
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34 | addiu $29, $29, 0x4000 |
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35 | |
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36 | # initializes global pointer |
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37 | la $28, seg_data_base |
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38 | |
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39 | # jump to main in kernel mode |
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40 | la $26, main |
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41 | mtc0 $26, $14 |
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42 | eret |
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43 | |
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44 | .end reset |
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45 | .size reset, .-reset |
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46 | |
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47 | .set reorder |
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