1 | /* |
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2 | * Heap Handler |
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3 | * |
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4 | * COPYRIGHT (c) 1989-1999. |
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5 | * On-Line Applications Research Corporation (OAR). |
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6 | * |
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7 | * The license and distribution terms for this file may be |
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8 | * found in the file LICENSE in this distribution or at |
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9 | * http://www.rtems.com/license/LICENSE. |
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10 | * |
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11 | * $Id$ |
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12 | */ |
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13 | |
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14 | |
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15 | #include <rtems/system.h> |
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16 | #include <rtems/score/sysstate.h> |
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17 | #include <rtems/score/heap.h> |
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18 | |
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19 | /*PAGE |
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20 | * |
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21 | * _Heap_Allocate |
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22 | * |
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23 | * This kernel routine allocates the requested size of memory |
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24 | * from the specified heap. |
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25 | * |
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26 | * Input parameters: |
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27 | * the_heap - pointer to heap header. |
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28 | * size - size in bytes of the memory block to allocate. |
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29 | * |
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30 | * Output parameters: |
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31 | * returns - starting address of memory block allocated |
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32 | */ |
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33 | |
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34 | void *_Heap_Allocate( |
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35 | Heap_Control *the_heap, |
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36 | uint32_t size |
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37 | ) |
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38 | { |
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39 | uint32_t excess; |
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40 | uint32_t the_size; |
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41 | Heap_Block *the_block; |
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42 | Heap_Block *next_block; |
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43 | Heap_Block *temporary_block; |
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44 | void *ptr; |
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45 | uint32_t offset; |
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46 | |
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47 | /* |
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48 | * Catch the case of a user allocating close to the limit of the |
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49 | * uint32_t . |
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50 | */ |
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51 | |
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52 | if ( size >= (-1 - HEAP_BLOCK_USED_OVERHEAD) ) |
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53 | return( NULL ); |
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54 | |
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55 | excess = size % the_heap->page_size; |
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56 | the_size = size + the_heap->page_size + HEAP_BLOCK_USED_OVERHEAD; |
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57 | |
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58 | if ( excess ) |
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59 | the_size += the_heap->page_size - excess; |
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60 | |
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61 | if ( the_size < sizeof( Heap_Block ) ) |
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62 | the_size = sizeof( Heap_Block ); |
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63 | |
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64 | for ( the_block = the_heap->first; |
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65 | ; |
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66 | the_block = the_block->next ) { |
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67 | if ( the_block == _Heap_Tail( the_heap ) ) |
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68 | return( NULL ); |
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69 | if ( the_block->front_flag >= the_size ) |
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70 | break; |
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71 | } |
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72 | |
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73 | if ( (the_block->front_flag - the_size) > |
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74 | (the_heap->page_size + HEAP_BLOCK_USED_OVERHEAD) ) { |
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75 | the_block->front_flag -= the_size; |
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76 | next_block = _Heap_Next_block( the_block ); |
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77 | next_block->back_flag = the_block->front_flag; |
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78 | |
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79 | temporary_block = _Heap_Block_at( next_block, the_size ); |
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80 | temporary_block->back_flag = |
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81 | next_block->front_flag = _Heap_Build_flag( the_size, |
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82 | HEAP_BLOCK_USED ); |
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83 | ptr = _Heap_Start_of_user_area( next_block ); |
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84 | } else { |
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85 | next_block = _Heap_Next_block( the_block ); |
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86 | next_block->back_flag = _Heap_Build_flag( the_block->front_flag, |
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87 | HEAP_BLOCK_USED ); |
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88 | the_block->front_flag = next_block->back_flag; |
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89 | the_block->next->previous = the_block->previous; |
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90 | the_block->previous->next = the_block->next; |
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91 | ptr = _Heap_Start_of_user_area( the_block ); |
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92 | } |
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93 | |
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94 | /* |
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95 | * round ptr up to a multiple of page size |
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96 | * Have to save the bump amount in the buffer so that free can figure it out |
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97 | */ |
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98 | |
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99 | offset = the_heap->page_size - (((uint32_t ) ptr) & (the_heap->page_size - 1)); |
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100 | ptr = _Addresses_Add_offset( ptr, offset ); |
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101 | *(((uint32_t *) ptr) - 1) = offset; |
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102 | |
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103 | #ifdef RTEMS_DEBUG |
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104 | { |
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105 | uint32_t ptr_u32; |
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106 | ptr_u32 = (uint32_t ) ptr; |
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107 | if (ptr_u32 & (the_heap->page_size - 1)) |
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108 | abort(); |
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109 | } |
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110 | #endif |
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111 | |
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112 | return ptr; |
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113 | } |
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