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24
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1 #include "kernel.h"
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2
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3 #define HEAP_MAGIC 0xc0ffee
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4 #define HEAP_START 0x400000
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5 #define HEAP_SIZE 0x200000
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6 #define HEAP_INUSE 1
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7 #define HEAP_FREE 0
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8
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9 typedef struct {
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10 uint64_t magic;
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11 uint64_t state;
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12 uint64_t size;
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13 } heap_t;
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14
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15 /*
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16 malloc and free divide the chunks of memory present at the heap
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17 of the kernel into smaller parts.
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18 The heap is located at: 0x
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19 */
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20 static heap_t* kernel_heap = (heap_t*) 0x400000; // 4 MB - 6 MB is heap
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21 /* Allocates 'size' bytes and returns the pointer if succesfull.
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22 Kernelpanic in case of failure..
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23 */
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24
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25 void* kmalloc(uint64_t size) {
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26 // printf("Malloc %d bytes\n", size);
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27
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28 // Start at the beginning of our heap and search a free block:
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29 heap_t *current = kernel_heap;
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30 while (current->magic == HEAP_MAGIC)
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31 {
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32 if ((current->state == HEAP_FREE) && (current->size >= size))
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33 {
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34 // Mark block as used:
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35 current->state = HEAP_INUSE;
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36
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37 // Insert a heap header if required:
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38 if (current->size > size + sizeof(heap_t) + 1)
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39 {
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40 // Calculate location of the inserted header:
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41 heap_t *newheader = (heap_t*) (((char*)current)+size+sizeof(heap_t));
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42
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43 // Set the new header fields:
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44 newheader->size = current->size - size - sizeof(heap_t);
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45 newheader->state = HEAP_FREE;
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46 newheader->magic = HEAP_MAGIC;
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47
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48 // Set the size of this block
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49 current->size = size;
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50 }
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51 else
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52 {
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53 // We allocate this whole block
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54 }
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55 // Calculate the size of the block:
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56 char *address = ((char*)current)+sizeof(heap_t);
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57 return address;
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58
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59 }
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60 // Goto next heap block:
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61 current = (heap_t*)(((char*) current) + current->size + sizeof(heap_t));
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62 }
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63 return 0x0;
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64 }
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65
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66 void kfree(void* ptr) {
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67 printf("Free address %x\n", ptr);
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68 }
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69
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70 void init_heap(void)
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71 {
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72 // Initialize the kernel heap:
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73 kernel_heap->magic = HEAP_MAGIC;
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74 kernel_heap->state = HEAP_FREE;
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75 kernel_heap->size = HEAP_SIZE - sizeof(heap_t);
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76 }
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