1 | /* |
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2 | (C) Copyright IBM Corp. 2008 |
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3 | |
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4 | All rights reserved. |
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5 | |
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6 | Redistribution and use in source and binary forms, with or without |
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7 | modification, are permitted provided that the following conditions are met: |
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8 | |
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9 | * Redistributions of source code must retain the above copyright notice, |
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10 | this list of conditions and the following disclaimer. |
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11 | * Redistributions in binary form must reproduce the above copyright |
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12 | notice, this list of conditions and the following disclaimer in the |
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13 | documentation and/or other materials provided with the distribution. |
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14 | * Neither the name of IBM nor the names of its contributors may be |
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15 | used to endorse or promote products derived from this software without |
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16 | specific prior written permission. |
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17 | |
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18 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
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19 | AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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20 | IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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21 | ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
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22 | LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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23 | CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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24 | SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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25 | INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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26 | CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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27 | ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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28 | POSSIBILITY OF SUCH DAMAGE. |
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29 | |
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30 | Author: Ken Werner <ken.werner@de.ibm.com> |
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31 | */ |
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32 | |
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33 | /* _mcount extracts the address of the function just entered and the address |
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34 | of the caller of that function and then calls __mcount_internal. The |
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35 | prologue calls mcount without saving any registers. The return address is |
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36 | stored in $75. The _mcount function has to: |
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37 | - create a new stack frame |
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38 | - save registers $2 to $75 on the stack |
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39 | - copy the two addresses ($0 and $75) into the argument registers $3 and $4 |
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40 | - call __mcount_internal |
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41 | - restore registers |
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42 | - return to $75 */ |
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43 | |
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44 | /* The following two convenience macros assist in the coding of the |
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45 | saving and restoring the register. |
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46 | |
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47 | saveregs first, last Saves registers from first to the last. |
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48 | restoreregs first, last Restores registers from last down to first. |
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49 | |
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50 | Note: first must be less than or equal to last. */ |
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51 | .macro saveregs first, last |
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52 | stqd $\first, \first*16($SP) |
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53 | .if \last-\first |
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54 | saveregs "(\first+1)",\last |
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55 | .endif |
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56 | .endm |
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57 | |
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58 | .macro restoreregs first, last |
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59 | lqd $\last, \last*16($SP) |
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60 | .if \last-\first |
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61 | restoreregs \first,"(\last-1)" |
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62 | .endif |
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63 | .endm |
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64 | |
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65 | /* _mcount needs to be resident since the overlay manager uses the scratch |
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66 | registers too. */ |
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67 | .text |
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68 | .align 3 /* 8 byte alignment. */ |
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69 | .global _mcount |
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70 | .type _mcount, @function |
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71 | |
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72 | _mcount: |
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73 | stqd $lr, 16($sp) /* Save link register in the callers stack frame. */ |
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74 | stqd $lr, -1216($sp) /* Store back pointer. */ |
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75 | il $lr, -1216 /* Push a new stack frame. */ |
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76 | a $sp, $sp, $lr /* Frame size: 16 * (74 + 2) = 1216. */ |
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77 | |
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78 | /* Save registers $2 to $75 on the stack. */ |
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79 | saveregs 2, 75 |
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80 | |
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81 | /* Bring the __mcount_internal arguments in place. */ |
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82 | lqd $3, 1232($sp) /* frompc (the link register). */ |
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83 | ori $4, $75, 0 /* selfpc (the gcc prologue puts "brsl $75, _mcount" in |
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84 | front of every function). */ |
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85 | brsl $lr, __mcount_internal |
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86 | |
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87 | /* Restore register $2 to $75 from the stack. */ |
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88 | restoreregs 2, 75 |
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89 | |
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90 | il $lr, 1216 |
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91 | a $sp, $sp, $lr /* Pop the stack frame. */ |
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92 | lqd $lr, 16($sp) /* Restore link register. */ |
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93 | bi $75 /* Branch to the called function. */ |
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