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4850 | mario79 | 1 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |
2 | ;; ;; |
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9715 | Doczom | 3 | ;; Copyright (C) KolibriOS team 2013-2022. All rights reserved. ;; |
4850 | mario79 | 4 | ;; Distributed under terms of the GNU General Public License ;; |
5 | ;; ;; |
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6 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |
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7 | |||
8 | $Revision: 9715 $ |
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9 | |||
8037 | dunkaist | 10 | ; Memory management for slab structures. |
11 | ; The allocator meets special requirements: |
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12 | ; * memory blocks are properly aligned |
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13 | ; * memory blocks do not cross page boundary |
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14 | ; The allocator manages fixed-size blocks. |
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15 | ; Thus, the specific allocator works as follows: |
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3520 | clevermous | 16 | ; allocate one page, split into blocks, maintain the single-linked |
17 | ; list of all free blocks in each page. |
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18 | |||
19 | ; Note: size must be a multiple of required alignment. |
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20 | |||
21 | ; Data for one pool: dd pointer to the first page, MUTEX lock. |
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22 | |||
23 | ; Allocator for fixed-size blocks: allocate a block. |
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24 | ; [ebx-4] = pointer to the first page, ebx = pointer to MUTEX structure. |
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8037 | dunkaist | 25 | proc slab_alloc |
3520 | clevermous | 26 | push edi ; save used register to be stdcall |
27 | virtual at esp |
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28 | dd ? ; saved edi |
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29 | dd ? ; return address |
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30 | .size dd ? |
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31 | end virtual |
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32 | ; 1. Take the lock. |
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33 | mov ecx, ebx |
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34 | call mutex_lock |
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35 | ; 2. Find the first allocated page with a free block, if any. |
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36 | ; 2a. Initialize for the loop. |
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37 | mov edx, ebx |
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38 | .pageloop: |
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39 | ; 2b. Get the next page, keeping the current in eax. |
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40 | mov eax, edx |
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41 | mov edx, [edx-4] |
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42 | ; 2c. If there is no next page, we're out of luck; go to 4. |
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43 | test edx, edx |
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44 | jz .newpage |
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45 | add edx, 0x1000 |
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46 | @@: |
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47 | ; 2d. Get the pointer to the first free block on this page. |
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48 | ; If there is no free block, continue to 2b. |
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49 | mov eax, [edx-8] |
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50 | test eax, eax |
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51 | jz .pageloop |
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52 | ; 2e. Get the pointer to the next free block. |
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53 | mov ecx, [eax] |
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54 | ; 2f. Update the pointer to the first free block from eax to ecx. |
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55 | ; Normally [edx-8] still contains eax, if so, atomically set it to ecx |
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56 | ; and proceed to 3. |
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8037 | dunkaist | 57 | ; However, the price of simplicity of slab_free (in particular, it doesn't take |
58 | ; the lock) is that [edx-8] could (rarely) be changed while we processed steps |
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59 | ; 2d+2e. If so, return to 2d and retry. |
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3520 | clevermous | 60 | lock cmpxchg [edx-8], ecx |
61 | jnz @b |
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62 | .return: |
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63 | ; 3. Release the lock taken in step 1 and return. |
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64 | push eax |
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65 | mov ecx, ebx |
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66 | call mutex_unlock |
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67 | pop eax |
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68 | pop edi ; restore used register to be stdcall |
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69 | ret 4 |
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70 | .newpage: |
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71 | ; 4. Allocate a new page. |
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72 | push eax |
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73 | stdcall kernel_alloc, 0x1000 |
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74 | pop edx |
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75 | ; If failed, say something to the debug board and return zero. |
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76 | test eax, eax |
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77 | jz .nomemory |
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78 | ; 5. Add the new page to the tail of list of allocated pages. |
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79 | mov [edx-4], eax |
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80 | ; 6. Initialize two service dwords in the end of page: |
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81 | ; first free block is (start of page) + (block size) |
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82 | ; (we will return first block at (start of page), so consider it allocated), |
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83 | ; no next page. |
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84 | mov edx, eax |
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85 | lea edi, [eax+0x1000-8] |
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86 | add edx, [.size] |
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87 | mov [edi], edx |
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88 | and dword [edi+4], 0 |
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89 | ; 7. All blocks starting from edx are free; join them in a single-linked list. |
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90 | @@: |
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91 | mov ecx, edx |
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92 | add edx, [.size] |
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93 | mov [ecx], edx |
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94 | cmp edx, edi |
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95 | jbe @b |
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96 | sub ecx, [.size] |
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97 | and dword [ecx], 0 |
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98 | ; 8. Return (start of page). |
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99 | jmp .return |
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100 | .nomemory: |
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8037 | dunkaist | 101 | dbgstr 'no memory for slab allocation' |
3520 | clevermous | 102 | xor eax, eax |
103 | jmp .return |
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104 | endp |
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105 | |||
106 | ; Allocator for fixed-size blocks: free a block. |
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8037 | dunkaist | 107 | proc slab_free |
3520 | clevermous | 108 | push ecx edx |
109 | virtual at esp |
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110 | rd 2 ; saved registers |
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111 | dd ? ; return address |
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112 | .block dd ? |
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113 | end virtual |
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114 | ; Insert the given block to the head of free blocks in this page. |
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115 | mov ecx, [.block] |
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116 | mov edx, ecx |
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117 | or edx, 0xFFF |
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118 | @@: |
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119 | mov eax, [edx+1-8] |
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120 | mov [ecx], eax |
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121 | lock cmpxchg [edx+1-8], ecx |
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122 | jnz @b |
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123 | pop edx ecx |
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124 | ret 4 |
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125 | endp |