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28
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1 /* Memory manager functions,
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2 *
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3 * Uses a bitmap to keep track of 4k pages that are in use.
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4 *
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5 * */
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26
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6
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7 #include "kernel.h"
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8
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29
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9 static uint64_t *frames = 0;
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10 static uint64_t nframes = 0;
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26
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11
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29
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12 memmap_t* kernel_map = 0; // kernel memory mapping
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13 memmap_t* current_map = 0; // The currently active memory mapping
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14
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15 static void set_frame(uint64_t frame)
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26
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16 {
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17 uint64_t idx = frame / 64;
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18 uint64_t off = frame % 64;
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19 frames[idx] |= (0x1 << off);
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20 }
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21
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29
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22 static void clear_frame(uint64_t frame)
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26
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23 {
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24 uint64_t idx = frame / 64;
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25 uint64_t off = frame % 64;
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26 frames[idx] &= ~(0x1 << off);
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27 }
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28
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29 uint64_t test_frame(uint64_t frame)
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30 {
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31 uint64_t idx = frame / 64;
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32 uint64_t off = frame % 64;
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33 return (frames[idx] & (0x1 << off));
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34 }
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35
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29
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36 static uint64_t first_frame()
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26
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37 {
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38 uint64_t i, j;
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28
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39 for (i = 0; i < nframes / 64; i++)
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26
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40 {
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41 if (frames[i] != 0xFFFFFFFFFFFFFFFF)
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42 {
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43 for (j = 0; j < 64; j++)
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44 {
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45 uint64_t dut = 0x1 << j;
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46 if ((frames[i] & dut) != dut)
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47 {
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48 return i*64+j;
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49 }
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50 }
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51 }
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52 }
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29
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53
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54 // No frame found:
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55 return (uint64_t) -1;
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26
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56 }
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57
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58 // Memory manager functions:
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28
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59 void init_memory(uint64_t total_mem_size)
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60 {
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30
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61 printf("Size of PT_t = %d\n", sizeof(PD_t));
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62 printf("Size of page_t = %d\n", sizeof(page_t));
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29
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63 // Allocate and clear bits to remember which 4kb-frames are in use:
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64 nframes = (total_mem_size / 0x1000);
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65 frames = (uint64_t*)kmalloc_int( (nframes / 64) * sizeof(uint64_t) );
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66 memset(frames, 0, (nframes / 64) * sizeof(uint64_t));
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67
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68 // Create kernel map:
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69 kernel_map = (memmap_t*)kmalloc_aligned_int(sizeof(memmap_t));
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70 memset(kernel_map, 0, sizeof(memmap_t));
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71
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72 // Identity map lower memory and mark as used by the kernel.
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73 // Mark as used by the kernel:
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74 uint64_t i;
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75 i = 0;
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76 while ( i <= placement_address)
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77 {
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78 page_t *page;
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79
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80 page = get_page(i, kernel_map); // Get page for address
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81 page->address = i >> 12; // Set the address of this page.
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82 page->present = 1;
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83 page->rw = 1;
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84 page->us = 1; // Make all things accessable for users for now.
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30
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85 //page->pwt = 1; // Is this bit required?
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29
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86
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87 set_frame(i / 0x1000);
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88
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89 i += 0x1000; // Increase a 4 k frame
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90 }
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91
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92 // Set the created mapping as active:
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30
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93 switch_mapping(kernel_map);
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94
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29
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95 // TODO: set the use of placement malloc to invalid after here.
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28
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96 }
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97
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29
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98 void alloc_frame(page_t *page)
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26
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99 {
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29
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100 if (page->address != 0)
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101 {
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102 return;
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103 }
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26
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104 uint64_t idx = first_frame();
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105 if (idx == (uint64_t) -1)
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106 {
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107 panic("No more memory!");
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108 }
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109 set_frame(idx);
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29
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110
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111 page->present = 1;
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112 page->rw = 1;
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113 page->us = 0;
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114 page->address = idx; // set address in frame number, the byte address is 0x1000 times this value.
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26
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115 }
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116
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28
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117 void free_frame(page_t *page)
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118 {
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29
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119 clear_frame(page->address / 0x1000);
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120 page->address = 0;
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121 page->present = 0;
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122 }
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123
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124 void switch_mapping(memmap_t* mapping)
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125 {
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126 current_map = mapping;
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127 printf("Switching to use of other at %x\n", &mapping->table);
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128
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129 asm volatile("mov %0, %%cr3" :: "r"(&mapping->table));
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130
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131 // Enable paging (and flush cache):
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132 uint64_t cr0;
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133 asm volatile("mov %%cr0, %0": "=r"(cr0));
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134 cr0 |= 0x80000000;
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135 asm volatile("mov %0, %%cr0":: "r"(cr0));
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28
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136 }
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26
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137
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29
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138 /* Get a page for a virtual address, and create other tables if required */
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139 page_t* get_page(uint64_t address, memmap_t *mapping)
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140 {
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141 // Retrieve the correct PDP (page dir pointer table):
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142 uint64_t pml4index = (address >> 39) & 0x1FF;
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143 PDPT_t *pdpt = 0;
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144 if (mapping->table[pml4index].present == 1)
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145 {
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146 pdpt = (PDPT_t*)((uint64_t)mapping->table[pml4index].address << 12);
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147 }
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148 else
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149 {
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150 // Create new table:
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151 pdpt = (PDPT_t*)kmalloc_aligned_int(sizeof(PDPT_t));
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152 memset(pdpt, 0, sizeof(PDPT_t));
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153
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154 // TODO: get function like virt2phys or something here
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155 uint64_t address = (uint64_t)pdpt; // get the physical address
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156 mapping->table[pml4index].address = address >> 12; // shift right
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157 mapping->table[pml4index].rw = 1;
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158 mapping->table[pml4index].us = 1;
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159 mapping->table[pml4index].present = 1;
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160 }
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161
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162 uint64_t pdptindex = (address >> 30) & 0x1FF;
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163 // Retrieve the correct page directory:
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164 PD_t *pd = 0;
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165 if (pdpt->table[pdptindex].present == 1)
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166 {
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167 pd = (PD_t*)((uint64_t)pdpt->table[pdptindex].address << 12);
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168 }
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169 else
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170 {
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171 // Create a new table:
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172 pd = (PD_t*)kmalloc_aligned_int(sizeof(PD_t));
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173 memset(pd, 0, sizeof(PD_t));
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174
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175 // Enter table into PDPT:
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176 // TODO: make virt2phys function:
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177 uint64_t address = (uint64_t)pd;
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178 pdpt->table[pdptindex].address = address >> 12;
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179 pdpt->table[pdptindex].rw = 1;
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180 pdpt->table[pdptindex].us = 1;
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181 pdpt->table[pdptindex].present = 1;
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182 }
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183
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184 // Retrieve the correct page table:
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185 uint64_t pdindex = (address >> 21) & 0x1FF;
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186 PT_t *pt = 0;
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187 if (pd->table[pdindex].present == 1)
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188 {
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189 pt = (PT_t*)((uint64_t)pd->table[pdindex].address << 12);
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190 }
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191 else
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192 {
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193 // Create table:
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194 pt = (PT_t*)kmalloc_aligned_int(sizeof(PD_t));
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195 memset(pt, 0, sizeof(PT_t));
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196
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197 // Enter PT into PD:
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198 uint64_t address = (uint64_t)pt;
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199 pd->table[pdindex].address = address >> 12;
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200 pd->table[pdindex].rw = 1;
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201 pd->table[pdindex].us = 1;
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202 pd->table[pdindex].present = 1;
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203 }
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204
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205 // Finally get the page from the directory:
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206 // TODO: convert from physical address to virtual address:
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207 uint64_t ptindex = (address >> 12) & 0x1FF;
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208 return &pt->table[ptindex];
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209 }
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210
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