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1 #include "param.h"
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2 #include "types.h"
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3 #include "defs.h"
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4 #include "arm.h"
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5 #include "memlayout.h"
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6 #include "mmu.h"
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7 #include "proc.h"
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8 #include "spinlock.h"
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9 #include "elf.h"
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10
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11 extern char data[]; // defined by kernel.ld
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12 pde_t *kpgdir; // for use in scheduler()
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13
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14 // Xv6 can only allocate memory in 4KB blocks. This is fine
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15 // for x86. ARM's page table and page directory (for 28-bit
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16 // user address) have a size of 1KB. kpt_alloc/free is used
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17 // as a wrapper to support allocating page tables during boot
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18 // (use the initial kernel map, and during runtime, use buddy
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19 // memory allocator.
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20 struct run {
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21 struct run *next;
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22 };
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23
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24 struct {
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25 struct spinlock lock;
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26 struct run *freelist;
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27 } kpt_mem;
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28
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29 void init_vmm (void)
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30 {
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31 initlock(&kpt_mem.lock, "vm");
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32 kpt_mem.freelist = NULL;
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33 }
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34
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35 static void _kpt_free (char *v)
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36 {
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37 struct run *r;
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38
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39 r = (struct run*) v;
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40 r->next = kpt_mem.freelist;
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41 kpt_mem.freelist = r;
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42 }
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43
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44
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45 static void kpt_free (char *v)
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46 {
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47 if (v >= (char*)P2V(INIT_KERNMAP)) {
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48 kfree(v, PT_ORDER);
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49 return;
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50 }
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51
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52 acquire(&kpt_mem.lock);
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53 _kpt_free (v);
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54 release(&kpt_mem.lock);
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55 }
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56
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57 // add some memory used for page tables (initialization code)
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58 void kpt_freerange (uint32 low, uint32 hi)
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59 {
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60 while (low < hi) {
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61 _kpt_free ((char*)low);
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62 low += PT_SZ;
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63 }
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64 }
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65
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66 void* kpt_alloc (void)
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67 {
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68 struct run *r;
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69
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70 acquire(&kpt_mem.lock);
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71
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72 if ((r = kpt_mem.freelist) != NULL ) {
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73 kpt_mem.freelist = r->next;
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74 }
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75
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76 release(&kpt_mem.lock);
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77
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78 // Allocate a PT page if no inital pages is available
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79 if ((r == NULL) && ((r = kmalloc (PT_ORDER)) == NULL)) {
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80 panic("oom: kpt_alloc");
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81 }
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82
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83 memset(r, 0, PT_SZ);
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84 return (char*) r;
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85 }
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86
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87 // Return the address of the PTE in page directory that corresponds to
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88 // virtual address va. If alloc!=0, create any required page table pages.
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89 static pte_t* walkpgdir (pde_t *pgdir, const void *va, int alloc)
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90 {
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91 pde_t *pde;
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92 pte_t *pgtab;
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93
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94 // pgdir points to the page directory, get the page direcotry entry (pde)
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95 pde = &pgdir[PDE_IDX(va)];
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96
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97 if (*pde & PE_TYPES) {
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98 pgtab = (pte_t*) p2v(PT_ADDR(*pde));
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99
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100 } else {
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101 if (!alloc || (pgtab = (pte_t*) kpt_alloc()) == 0) {
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102 return 0;
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103 }
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104
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105 // Make sure all those PTE_P bits are zero.
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106 memset(pgtab, 0, PT_SZ);
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107
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108 // The permissions here are overly generous, but they can
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109 // be further restricted by the permissions in the page table
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110 // entries, if necessary.
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111 *pde = v2p(pgtab) | UPDE_TYPE;
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112 }
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113
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114 return &pgtab[PTE_IDX(va)];
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115 }
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116
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117 // Create PTEs for virtual addresses starting at va that refer to
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118 // physical addresses starting at pa. va and size might not
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119 // be page-aligned.
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120 static int mappages (pde_t *pgdir, void *va, uint size, uint pa, int ap)
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121 {
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122 char *a, *last;
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123 pte_t *pte;
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124
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125 a = (char*) align_dn(va, PTE_SZ);
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126 last = (char*) align_dn((uint)va + size - 1, PTE_SZ);
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127
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128 for (;;) {
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129 if ((pte = walkpgdir(pgdir, a, 1)) == 0) {
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130 return -1;
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131 }
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132
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133 if (*pte & PE_TYPES) {
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134 panic("remap");
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135 }
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136
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137 *pte = pa | ((ap & 0x3) << 4) | PE_CACHE | PE_BUF | PTE_TYPE;
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138
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139 if (a == last) {
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140 break;
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141 }
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142
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143 a += PTE_SZ;
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144 pa += PTE_SZ;
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145 }
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146
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147 return 0;
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148 }
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149
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150 // flush all TLB
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151 static void flush_tlb (void)
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152 {
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153 uint val = 0;
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154 asm("MCR p15, 0, %[r], c8, c7, 0" : :[r]"r" (val):);
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155
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156 // invalid entire data and instruction cache
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157 asm ("MCR p15,0,%[r],c7,c10,0": :[r]"r" (val):);
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158 asm ("MCR p15,0,%[r],c7,c11,0": :[r]"r" (val):);
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159 }
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160
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161 // Switch to the user page table (TTBR0)
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162 void switchuvm (struct proc *p)
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163 {
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164 uint val;
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165
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166 pushcli();
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167
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168 if (p->pgdir == 0) {
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169 panic("switchuvm: no pgdir");
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170 }
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171
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172 val = (uint) V2P(p->pgdir) | 0x00;
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173
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174 asm("MCR p15, 0, %[v], c2, c0, 0": :[v]"r" (val):);
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175 flush_tlb();
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176
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177 popcli();
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178 }
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179
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180 // Load the initcode into address 0 of pgdir. sz must be less than a page.
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181 void inituvm (pde_t *pgdir, char *init, uint sz)
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182 {
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183 char *mem;
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184
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185 if (sz >= PTE_SZ) {
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186 panic("inituvm: more than a page");
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187 }
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188
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189 mem = alloc_page();
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190 memset(mem, 0, PTE_SZ);
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191 mappages(pgdir, 0, PTE_SZ, v2p(mem), AP_KU);
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192 memmove(mem, init, sz);
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193 }
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194
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195 // Load a program segment into pgdir. addr must be page-aligned
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196 // and the pages from addr to addr+sz must already be mapped.
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197 int loaduvm (pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
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198 {
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199 uint i, pa, n;
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200 pte_t *pte;
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201
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202 if ((uint) addr % PTE_SZ != 0) {
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203 panic("loaduvm: addr must be page aligned");
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204 }
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205
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206 for (i = 0; i < sz; i += PTE_SZ) {
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207 if ((pte = walkpgdir(pgdir, addr + i, 0)) == 0) {
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208 panic("loaduvm: address should exist");
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209 }
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210
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211 pa = PTE_ADDR(*pte);
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212
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213 if (sz - i < PTE_SZ) {
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214 n = sz - i;
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215 } else {
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216 n = PTE_SZ;
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217 }
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218
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219 if (readi(ip, p2v(pa), offset + i, n) != n) {
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220 return -1;
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221 }
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222 }
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223
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224 return 0;
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225 }
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226
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227 // Allocate page tables and physical memory to grow process from oldsz to
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228 // newsz, which need not be page aligned. Returns new size or 0 on error.
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229 int allocuvm (pde_t *pgdir, uint oldsz, uint newsz)
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230 {
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231 char *mem;
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232 uint a;
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233
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234 if (newsz >= UADDR_SZ) {
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235 return 0;
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236 }
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237
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238 if (newsz < oldsz) {
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239 return oldsz;
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240 }
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241
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242 a = align_up(oldsz, PTE_SZ);
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243
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244 for (; a < newsz; a += PTE_SZ) {
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245 mem = alloc_page();
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246
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247 if (mem == 0) {
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248 cprintf("allocuvm out of memory\n");
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249 deallocuvm(pgdir, newsz, oldsz);
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250 return 0;
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251 }
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252
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253 memset(mem, 0, PTE_SZ);
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254 mappages(pgdir, (char*) a, PTE_SZ, v2p(mem), AP_KU);
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255 }
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256
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257 return newsz;
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258 }
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259
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260 // Deallocate user pages to bring the process size from oldsz to
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261 // newsz. oldsz and newsz need not be page-aligned, nor does newsz
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262 // need to be less than oldsz. oldsz can be larger than the actual
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263 // process size. Returns the new process size.
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264 int deallocuvm (pde_t *pgdir, uint oldsz, uint newsz)
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265 {
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266 pte_t *pte;
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267 uint a;
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268 uint pa;
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269
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270 if (newsz >= oldsz) {
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271 return oldsz;
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272 }
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273
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274 for (a = align_up(newsz, PTE_SZ); a < oldsz; a += PTE_SZ) {
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275 pte = walkpgdir(pgdir, (char*) a, 0);
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276
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277 if (!pte) {
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278 // pte == 0 --> no page table for this entry
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279 // round it up to the next page directory
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280 a = align_up (a, PDE_SZ);
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281
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282 } else if ((*pte & PE_TYPES) != 0) {
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283 pa = PTE_ADDR(*pte);
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284
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285 if (pa == 0) {
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286 panic("deallocuvm");
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287 }
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288
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289 free_page(p2v(pa));
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290 *pte = 0;
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291 }
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292 }
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293
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294 return newsz;
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295 }
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296
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297 // Free a page table and all the physical memory pages
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298 // in the user part.
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299 void freevm (pde_t *pgdir)
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300 {
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301 uint i;
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302 char *v;
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303
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304 if (pgdir == 0) {
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305 panic("freevm: no pgdir");
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306 }
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307
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308 // release the user space memroy, but not page tables
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309 deallocuvm(pgdir, UADDR_SZ, 0);
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310
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311 // release the page tables
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312 for (i = 0; i < NUM_UPDE; i++) {
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313 if (pgdir[i] & PE_TYPES) {
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314 v = p2v(PT_ADDR(pgdir[i]));
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315 kpt_free(v);
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316 }
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317 }
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318
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319 kpt_free((char*) pgdir);
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320 }
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321
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322 // Clear PTE_U on a page. Used to create an inaccessible page beneath
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323 // the user stack (to trap stack underflow).
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324 void clearpteu (pde_t *pgdir, char *uva)
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325 {
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326 pte_t *pte;
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327
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328 pte = walkpgdir(pgdir, uva, 0);
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329 if (pte == 0) {
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330 panic("clearpteu");
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331 }
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332
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333 // in ARM, we change the AP field (ap & 0x3) << 4)
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334 *pte = (*pte & ~(0x03 << 4)) | AP_KO << 4;
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335 }
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336
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337 // Given a parent process's page table, create a copy
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338 // of it for a child.
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339 pde_t* copyuvm (pde_t *pgdir, uint sz)
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340 {
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341 pde_t *d;
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342 pte_t *pte;
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343 uint pa, i, ap;
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344 char *mem;
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345
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346 // allocate a new first level page directory
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347 d = kpt_alloc();
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348 if (d == NULL ) {
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349 return NULL ;
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350 }
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351
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352 // copy the whole address space over (no COW)
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353 for (i = 0; i < sz; i += PTE_SZ) {
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354 if ((pte = walkpgdir(pgdir, (void *) i, 0)) == 0) {
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355 panic("copyuvm: pte should exist");
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356 }
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357
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358 if (!(*pte & PE_TYPES)) {
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359 panic("copyuvm: page not present");
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360 }
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361
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362 pa = PTE_ADDR (*pte);
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363 ap = PTE_AP (*pte);
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364
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365 if ((mem = alloc_page()) == 0) {
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366 goto bad;
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367 }
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368
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369 memmove(mem, (char*) p2v(pa), PTE_SZ);
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370
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371 if (mappages(d, (void*) i, PTE_SZ, v2p(mem), ap) < 0) {
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372 goto bad;
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373 }
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374 }
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375 return d;
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376
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377 bad: freevm(d);
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378 return 0;
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379 }
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380
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381 //PAGEBREAK!
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382 // Map user virtual address to kernel address.
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383 char* uva2ka (pde_t *pgdir, char *uva)
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384 {
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385 pte_t *pte;
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386
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387 pte = walkpgdir(pgdir, uva, 0);
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388
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389 // make sure it exists
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390 if ((*pte & PE_TYPES) == 0) {
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391 return 0;
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392 }
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393
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394 // make sure it is a user page
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395 if (PTE_AP(*pte) != AP_KU) {
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396 return 0;
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397 }
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398
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399 return (char*) p2v(PTE_ADDR(*pte));
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400 }
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401
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402 // Copy len bytes from p to user address va in page table pgdir.
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403 // Most useful when pgdir is not the current page table.
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404 // uva2ka ensures this only works for user pages.
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405 int copyout (pde_t *pgdir, uint va, void *p, uint len)
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406 {
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407 char *buf, *pa0;
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408 uint n, va0;
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409
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410 buf = (char*) p;
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411
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412 while (len > 0) {
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413 va0 = align_dn(va, PTE_SZ);
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414 pa0 = uva2ka(pgdir, (char*) va0);
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415
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416 if (pa0 == 0) {
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417 return -1;
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418 }
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419
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420 n = PTE_SZ - (va - va0);
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421
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422 if (n > len) {
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423 n = len;
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424 }
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425
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426 memmove(pa0 + (va - va0), buf, n);
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427
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428 len -= n;
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429 buf += n;
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430 va = va0 + PTE_SZ;
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431 }
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432
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433 return 0;
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434 }
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435
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436
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437 // 1:1 map the memory [phy_low, phy_hi] in kernel. We need to
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438 // use 2-level mapping for this block of memory. The rumor has
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439 // it that ARMv6's small brain cannot handle the case that memory
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440 // be mapped in both 1-level page table and 2-level page. For
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441 // initial kernel, we use 1MB mapping, other memory needs to be
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442 // mapped as 4KB pages
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443 void paging_init (uint phy_low, uint phy_hi)
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444 {
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445 mappages (P2V(&_kernel_pgtbl), P2V(phy_low), phy_hi - phy_low, phy_low, AP_KU);
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446 flush_tlb ();
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447 }
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