{"id":1273,"date":"2012-02-16T23:12:39","date_gmt":"2012-02-16T05:12:39","guid":{"rendered":"http:\/\/peta.okechan.net\/blog\/?p=1273"},"modified":"2012-05-31T15:16:50","modified_gmt":"2012-05-31T06:16:50","slug":"xv6%e3%82%bd%e3%83%bc%e3%82%b9%e3%82%b3%e3%83%bc%e3%83%89%e3%83%aa%e3%83%bc%e3%83%87%e3%82%a3%e3%83%b3%e3%82%b0-%e3%81%9d%e3%81%ae12","status":"publish","type":"post","link":"https:\/\/peta.okechan.net\/blog\/archives\/1273","title":{"rendered":"[xv6 #12] Chapter 1 – The first process – Code: creating an address space"},"content":{"rendered":"

\u30c6\u30ad\u30b9\u30c8\u306e21\u301c22\u30da\u30fc\u30b8<\/p>\n

\u672c\u6587<\/h3>\n

main\u95a2\u6570\u306f\u3001\u30ab\u30fc\u30cd\u30eb\u3092\u5b9f\u884c\u3059\u308b\u305f\u3081\u306b\u5fc5\u8981\u3068\u3055\u308c\u308bKERNBASE\u3088\u308a\u4e0a\u4f4d\u3078\u306e\u5bfe\u5fdc\u4ed8\u3051\u3092\u6301\u3064\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\u3092\u3001\u751f\u6210\u3057\u305f\u308a\u5207\u308a\u66ff\u3048\u305f\u308a\u3059\u308b\u305f\u3081\u306b\u3001kvmalloc\u95a2\u6570\u3092\u547c\u3076\u3002
\n\uff08kvmalloc\u95a2\u6570\u306e\u30bd\u30fc\u30b9\u306f\u524d\u56de\u53c2\u7167\uff09
\nkvmalloc\u95a2\u6570\u306e\u6a5f\u80fd\u306e\u5927\u90e8\u5206\u3092setupkvm\u95a2\u6570\u304c\u62c5\u3063\u3066\u3044\u308b\u3002
\nsetupkvm\u95a2\u6570\u306f\u307e\u305a\u3001\u30da\u30fc\u30b8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3092\u4fdd\u6301\u3059\u308b\u305f\u3081\u306e\u30e1\u30e2\u30ea\u9818\u57df\u306e\u30da\u30fc\u30b8\u3092\u5272\u308a\u5f53\u3066\u308b\u3002
\n\u305d\u3057\u305f\u3089\u3001\u30ab\u30fc\u30cd\u30eb\u304c\u5fc5\u8981\u3068\u3059\u308bkmap\u914d\u5217\u306e\u4e2d\u306b\u8a18\u3055\u308c\u305f\u5909\u63db\u3092\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3059\u308b\u305f\u3081\u306b\u3001mappages\u95a2\u6570\u3092\u547c\u3076\u3002\u305d\u306e\u5909\u63db\u306f\u3001\u30ab\u30fc\u30cd\u30eb\u306e\u547d\u4ee4\u3068\u30c7\u30fc\u30bf\u3001PHYSTOP\u307e\u3067\u306e\u7269\u7406\u30e1\u30e2\u30ea\u3001\u5b9f\u969b\u306eI\/O\u30c7\u30d0\u30a4\u30b9\u7528\u306e\u30e1\u30e2\u30ea\u7bc4\u56f2\u3092\u542b\u3080\u3002
\nsetupkvm\u95a2\u6570\u306f\u3001\u30e6\u30fc\u30b6\u30e1\u30e2\u30ea\u306b\u95a2\u3059\u308b\u5bfe\u5fdc\u4ed8\u3051\u306f\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3057\u306a\u3044\u3002
\n\u30e6\u30fc\u30b6\u30e1\u30e2\u30ea\u306b\u95a2\u3059\u308b\u5bfe\u5fdc\u4ed8\u3051\u306f\u5f8c\u3067\u884c\u308f\u308c\u308b\u3002
\n\uff08\u3053\u306e\u6bb5\u843d\u3067\u8a00\u53ca\u3055\u308c\u3066\u3044\u308b\u90e8\u5206\u3092vm.c\u304b\u3089\u629c\u7c8b\uff09<\/p>\n

\/\/ This table defines the kernel's mappings, which are present in\r\n\/\/ every process's page table.\r\nstatic struct kmap {\r\n  void *virt;\r\n  uint phys_start;\r\n  uint phys_end;\r\n  int perm;\r\n} kmap[] = {\r\n  { (void*) KERNBASE, 0,             EXTMEM,    PTE_W},  \/\/ I\/O space\r\n  { (void*) KERNLINK, V2P(KERNLINK), V2P(data), 0}, \/\/ kernel text+rodata\r\n  { (void*) data,     V2P(data),     PHYSTOP,   PTE_W},  \/\/ kernel data, memory\r\n  { (void*) DEVSPACE, DEVSPACE,      0,         PTE_W},  \/\/ more devices\r\n};\r\n\r\n\/\/ Set up kernel part of a page table.\r\npde_t*\r\nsetupkvm()\r\n{\r\n  pde_t *pgdir;\r\n  struct kmap *k;\r\n\r\n  if((pgdir = (pde_t*)kalloc()) == 0)\r\n    return 0;\r\n  memset(pgdir, 0, PGSIZE);\r\n  if (p2v(PHYSTOP) > (void*)DEVSPACE)\r\n    panic("PHYSTOP too high");\r\n  for(k = kmap; k < &kmap[NELEM(kmap)]; k++)\r\n    if(mappages(pgdir, k->virt, k->phys_end - k->phys_start, \r\n                (uint)k->phys_start, k->perm) < 0)\r\n      return 0;\r\n  return pgdir;\r\n}\r\n\r\n\/\/ Allocate one page table for the machine for the kernel address\r\n\/\/ space for scheduler processes.\r\nvoid\r\nkvmalloc(void)\r\n{\r\n  kpgdir = setupkvm();\r\n  switchkvm();\r\n}<\/pre>\n
mappages\u95a2\u6570\u306f\u3001\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u306e\u7bc4\u56f2\u304b\u3089\u7269\u7406\u30a2\u30c9\u30ec\u30b9\u306b\u5bfe\u5fdc\u3059\u308b\u7bc4\u56f2\u306e\u305f\u3081\u306e\u5bfe\u5fdc\u4ed8\u3051\u3092\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\u3078\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3059\u308b\u3002
\n\u5bfe\u5fdc\u4ed8\u3051\u3089\u308c\u308b\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u5168\u3066\u306b\u5bfe\u3057\u3066\u3001mappages\u95a2\u6570\u306f\u305d\u306e\u30a2\u30c9\u30ec\u30b9\u306ePTE\u306e\u30a2\u30c9\u30ec\u30b9\u3092\u63a2\u3059\u305f\u3081\u306bwalkpgdir\u95a2\u6570\u3092\u547c\u3076\u3002
\n\u305d\u3057\u3066\u3001\u9069\u5207\u306a\u7269\u7406\u30da\u30fc\u30b8\u756a\u53f7\u3092\u4fdd\u6301\u3059\u308b\u3088\u3046\u306b\u3059\u308b\u305f\u3081\u306b\u305d\u306ePTE\u3092\u9069\u5207\u306a\u30d1\u30fc\u30df\u30c3\u30b7\u30e7\u30f3\uff08PTE_W\u3068PTE_U\uff09\u3067\u521d\u671f\u5316\u3057\u3001\u305d\u3057\u3066\u6e96\u5099\u5b8c\u4e86\u3068\u3044\u3046\u3053\u3068\u3067\u305d\u306ePTE\u306bPTE_P\u3092\u8a2d\u5b9a\u3059\u308b\u3002
\n\uff08\u3053\u306e\u6bb5\u843d\u3067\u8a00\u53ca\u3055\u308c\u3066\u3044\u308b\u90e8\u5206\u3092vm.c\u304b\u3089\u629c\u7c8b\uff09<\/p>\n
\/\/ Return the address of the PTE in page table pgdir\r\n\/\/ that corresponds to virtual address va.  If alloc!=0,\r\n\/\/ create any required page table pages.\r\nstatic pte_t *\r\nwalkpgdir(pde_t *pgdir, const void *va, int alloc)\r\n{\r\n  pde_t *pde;\r\n  pte_t *pgtab;\r\n\r\n  pde = &pgdir[PDX(va)];\r\n  if(*pde & PTE_P){\r\n    pgtab = (pte_t*)p2v(PTE_ADDR(*pde));\r\n  } else {\r\n    if(!alloc || (pgtab = (pte_t*)kalloc()) == 0)\r\n      return 0;\r\n    \/\/ Make sure all those PTE_P bits are zero.\r\n    memset(pgtab, 0, PGSIZE);\r\n    \/\/ The permissions here are overly generous, but they can\r\n    \/\/ be further restricted by the permissions in the page table \r\n    \/\/ entries, if necessary.\r\n    *pde = v2p(pgtab) | PTE_P | PTE_W | PTE_U;\r\n  }\r\n  return &pgtab[PTX(va)];\r\n}\r\n\r\n\/\/ Create PTEs for virtual addresses starting at va that refer to\r\n\/\/ physical addresses starting at pa. va and size might not\r\n\/\/ be page-aligned.\r\nstatic int\r\nmappages(pde_t *pgdir, void *va, uint size, uint pa, int perm)\r\n{\r\n  char *a, *last;\r\n  pte_t *pte;\r\n  \r\n  a = (char*)PGROUNDDOWN((uint)va);\r\n  last = (char*)PGROUNDDOWN(((uint)va) + size - 1);\r\n  for(;;){\r\n    if((pte = walkpgdir(pgdir, a, 1)) == 0)\r\n      return -1;\r\n    if(*pte & PTE_P)\r\n      panic("remap");\r\n    *pte = pa | perm | PTE_P;\r\n    if(a == last)\r\n      break;\r\n    a += PGSIZE;\r\n    pa += PGSIZE;\r\n  }\r\n  return 0;\r\n}\r\n<\/pre>\n
walkpgdir\u95a2\u6570\u306f\u3001\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u5909\u63db\u306e\u305f\u3081\u306bx86\u306e\u30da\u30fc\u30b8\u30f3\u30b0\u30cf\u30fc\u30c9\u30a6\u30a7\u30a2\u304cPTE\u3092\u53c2\u7167\u3059\u308b\u52d5\u304d\u3092\u30a8\u30df\u30e5\u30ec\u30fc\u30c8\u3059\u308b\u3002\uff08\u56f31-1\u53c2\u7167\uff09
\nwalkpgdir\u306f\u3001\u30da\u30fc\u30b8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u898b\u3064\u3051\u308b\u305f\u3081\u306b\u3001\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u306e\u4e0a\u4f4d10\u30d3\u30c3\u30c8\u3092\u5229\u7528\u3059\u308b\u3002
\n\uff08pde = &pgdir[PDX(va)]; \u306e\u90e8\u5206\u3002\u30de\u30af\u30edPDX()\u3067\u4e0a\u4f4d10\u30d3\u30c3\u30c8\u3092\u53d6\u5f97\u3057\u3066\u3044\u308b\u3002\uff09
\n\u30da\u30fc\u30b8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u304c\u6e96\u5099\u51fa\u6765\u3066\u3044\u306a\u3051\u308c\u3070\u3001\u8981\u6c42\u3055\u308c\u305f\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\u306e\u30da\u30fc\u30b8\u306f\u307e\u3060\u5272\u308a\u5f53\u3066\u3089\u308c\u3066\u3044\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u306b\u306a\u308b\u3002
\n\u3082\u3057\u5f15\u6570alloc\u304c\u30bb\u30c3\u30c8\u3055\u308c\u3066\u3044\u308c\u3070\u3001walkpgdir\u95a2\u6570\u306f\u305d\u308c\u3092\u5272\u308a\u5f53\u3066\u3001\u305d\u306e\u30da\u30fc\u30b8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u4e2d\u306e\u7269\u7406\u30a2\u30c9\u30ec\u30b9\u306b\u914d\u7f6e\u3059\u308b\u3002
\n\u6700\u5f8c\u306b\u3001\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\u306e\u30da\u30fc\u30b8\u306e\u4e2d\u306ePTE\u306e\u30a2\u30c9\u30ec\u30b9\u3092\u898b\u3064\u3051\u308b\u305f\u3081\u306b\u3001\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u306e\u6b21\u306e10\u30d3\u30c3\u30c8\u3092\u5229\u7528\u3059\u308b\u3002
\n\uff08return &pgtab[PTX(va)]; \u306e\u90e8\u5206\u3002\u30de\u30af\u30edPTX()\u3067\u4e0a\u4f4d10\u30d3\u30c3\u30c8\u306e\u3055\u3089\u306b\u6b21\u306e10\u30d3\u30c3\u30c8\u3092\u53d6\u5f97\u3057\u3066\u3044\u308b\u3002\uff09<\/p>\n
\u56f31-1 x86\u4e0a\u306e\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\uff08\u4ee5\u524d\u3082\u8f09\u305b\u307e\u3057\u305f\u304c\u3082\u3046\u4e00\u56de\u8f09\u305b\u3068\u304d\u307e\u3059\uff09
\n\"\"<\/a><\/p>\n
\u611f\u60f3<\/h3>\n
xv6\u304c\u30a2\u30c9\u30ec\u30b9\u7a7a\u9593\u3092\u3069\u3046\u4f5c\u3063\u3066\u308b\u304b\u3067\u3059\u306d\u3002
\n\u30bd\u30fc\u30b9\u306f\u666e\u901a\u306eC\u306a\u3093\u3067\u8aad\u307f\u3084\u3059\u3044\u3067\u3059\u304c\u3001\u3069\u3046\u3044\u3046\u30e1\u30e2\u30ea\u64cd\u4f5c\u3092\u3057\u3066\u308b\u306e\u304b\u5177\u4f53\u7684\u306b\u30a4\u30e1\u30fc\u30b8\u3057\u306a\u304c\u3089\u8aad\u307e\u306a\u3044\u3068\u8aac\u660e\u3068\u306e\u5bfe\u5fdc\u304c\u3088\u304f\u5206\u304b\u3089\u306a\u3044\u304b\u3068\u601d\u3044\u307e\u3059\u3002<\/p>\n
\u3053\u3053\u306f\u307e\u3060\u8d77\u52d5\u9014\u4e2d\u306e\u8a71\u306a\u306e\u3067\u305d\u308c\u3092\u5fd8\u308c\u306a\u3044\u3088\u3046\u306b\u3057\u306a\u3044\u3068\u3002
\n\uff08OS\u304c\u8d77\u52d5\u3057\u305f\u5f8c\u3001\u30d7\u30ed\u30bb\u30b9\u3092\u8d77\u52d5\u3059\u308b\u3068\u304d\u306a\u3069\u306b\u52d5\u304f\u51e6\u7406\u3067\u306f\u306a\u3044\uff09<\/p>\n","protected":false},"excerpt":{"rendered":"
\u30c6\u30ad\u30b9\u30c8\u306e21\u301c22\u30da\u30fc\u30b8<\/p>\n
\u672c\u6587<\/h3>\n
main\u95a2\u6570\u306f\u3001\u30ab\u30fc\u30cd\u30eb\u3092\u5b9f\u884c\u3059\u308b\u305f\u3081\u306b\u5fc5\u8981\u3068\u3055\u308c\u308bKERNBASE\u3088\u308a\u4e0a\u4f4d\u3078\u306e\u5bfe\u5fdc\u4ed8\u3051\u3092\u6301\u3064\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\u3092\u3001\u751f\u6210\u3057\u305f\u308a\u5207\u308a\u66ff\u3048\u305f\u308a\u3059\u308b\u305f\u3081\u306b\u3001kvmalloc\u95a2\u6570\u3092\u547c\u3076\u3002
\n\uff08kvmalloc\u95a2\u6570\u306e\u30bd\u30fc\u30b9\u306f\u524d\u56de\u53c2\u7167\uff09
\nkvmalloc\u95a2\u6570\u306e\u6a5f\u80fd\u306e\u5927\u90e8\u5206\u3092setupkvm\u95a2\u6570\u304c\u62c5\u3063\u3066\u3044\u308b\u3002
\nsetupkvm\u95a2\u6570\u306f\u307e\u305a\u3001\u30da\u30fc\u30b8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3092\u4fdd\u6301\u3059\u308b\u305f\u3081\u306e\u30e1\u30e2\u30ea\u9818\u57df\u306e\u30da\u30fc\u30b8\u3092\u5272\u308a\u5f53\u3066\u308b\u3002
\n\u305d\u3057\u305f\u3089\u3001\u30ab\u30fc\u30cd\u30eb\u304c\u5fc5\u8981\u3068\u3059\u308bkmap\u914d\u5217\u306e\u4e2d\u306b\u8a18\u3055\u308c\u305f\u5909\u63db\u3092\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3059\u308b\u305f\u3081\u306b\u3001mappages\u95a2\u6570\u3092\u547c\u3076\u3002\u305d\u306e\u5909\u63db\u306f\u3001\u30ab\u30fc\u30cd\u30eb\u306e\u547d\u4ee4\u3068\u30c7\u30fc\u30bf\u3001PHYSTOP\u307e\u3067\u306e\u7269\u7406\u30e1\u30e2\u30ea\u3001\u5b9f\u969b\u306eI\/O\u30c7\u30d0\u30a4\u30b9\u7528\u306e\u30e1\u30e2\u30ea\u7bc4\u56f2\u3092\u542b\u3080\u3002
\nsetupkvm\u95a2\u6570\u306f\u3001\u30e6\u30fc\u30b6\u30e1\u30e2\u30ea\u306b\u95a2\u3059\u308b\u5bfe\u5fdc\u4ed8\u3051\u306f\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3057\u306a\u3044\u3002
\n\u30e6\u30fc\u30b6\u30e1\u30e2\u30ea\u306b\u95a2\u3059\u308b\u5bfe\u5fdc\u4ed8\u3051\u306f\u5f8c\u3067\u884c\u308f\u308c\u308b\u3002
\n\uff08\u3053\u306e\u6bb5\u843d\u3067\u8a00\u53ca\u3055\u308c\u3066\u3044\u308b\u90e8\u5206\u3092vm.c\u304b\u3089\u629c\u7c8b\uff09<\/p>\n
\/\/ This table defines the kernel's mappings, which are present in\r\n\/\/ every process's page table.\r\nstatic struct kmap {\r\n  void *virt;\r\n  uint phys_start;\r\n  uint phys_end;\r\n  int perm;\r\n} kmap[] = {\r\n  { (void*) KERNBASE, 0,             EXTMEM,    PTE_W},  \/\/ I\/O space\r\n  { (void*) KERNLINK, V2P(KERNLINK), V2P(data), 0}, \/\/ kernel text+rodata\r\n  { (void*) data,     V2P(data),     PHYSTOP,   PTE_W},  \/\/ kernel data, memory\r\n  { (void*) DEVSPACE, DEVSPACE,      0,         PTE_W},  \/\/ more devices\r\n};\r\n\r\n\/\/ Set up kernel part of a page table.\r\npde_t*\r\nsetupkvm()\r\n{\r\n  pde_t *pgdir;\r\n  struct kmap *k;\r\n\r\n  if((pgdir = (pde_t*)kalloc()) == 0)\r\n    return 0;\r\n  memset(pgdir, 0, PGSIZE);\r\n  if (p2v(PHYSTOP) > (void*)DEVSPACE)\r\n    panic("PHYSTOP too high");\r\n  for(k = kmap; k < &kmap[NELEM(kmap)]; k++)\r\n    if(mappages(pgdir, k->virt, k->phys_end - k->phys_start, \r\n                (uint)k->phys_start, k->perm) < 0)\r\n      return 0;\r\n  return pgdir;\r\n}\r\n\r\n\/\/ Allocate one page table for the machine for the kernel address\r\n\/\/ space for scheduler processes.\r\nvoid\r\nkvmalloc(void)\r\n{\r\n  kpgdir = setupkvm();\r\n  switchkvm();\r\n}<\/pre>\n
mappages\u95a2\u6570\u306f\u3001\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u306e\u7bc4\u56f2\u304b\u3089\u7269\u7406\u30a2\u30c9\u30ec\u30b9\u306b\u5bfe\u5fdc\u3059\u308b\u7bc4\u56f2\u306e\u305f\u3081\u306e\u5bfe\u5fdc\u4ed8\u3051\u3092\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\u3078\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3059\u308b\u3002
\n\u5bfe\u5fdc\u4ed8\u3051\u3089\u308c\u308b\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u5168\u3066\u306b\u5bfe\u3057\u3066\u3001mappages\u95a2\u6570\u306f\u305d\u306e\u30a2\u30c9\u30ec\u30b9\u306ePTE\u306e\u30a2\u30c9\u30ec\u30b9\u3092\u63a2\u3059\u305f\u3081\u306bwalkpgdir\u95a2\u6570\u3092\u547c\u3076\u3002
\n\u305d\u3057\u3066\u3001\u9069\u5207\u306a\u7269\u7406\u30da\u30fc\u30b8\u756a\u53f7\u3092\u4fdd\u6301\u3059\u308b\u3088\u3046\u306b\u3059\u308b\u305f\u3081\u306b\u305d\u306ePTE\u3092\u9069\u5207\u306a\u30d1\u30fc\u30df\u30c3\u30b7\u30e7\u30f3\uff08PTE_W\u3068PTE_U\uff09\u3067\u521d\u671f\u5316\u3057\u3001\u305d\u3057\u3066\u6e96\u5099\u5b8c\u4e86\u3068\u3044\u3046\u3053\u3068\u3067\u305d\u306ePTE\u306bPTE_P\u3092\u8a2d\u5b9a\u3059\u308b\u3002
\n\uff08\u3053\u306e\u6bb5\u843d\u3067\u8a00\u53ca\u3055\u308c\u3066\u3044\u308b\u90e8\u5206\u3092vm.c\u304b\u3089\u629c\u7c8b\uff09<\/p>\n
\/\/ Return the address of the PTE in page table pgdir\r\n\/\/ that corresponds to virtual address va.  If alloc!=0,\r\n\/\/ create any required page table pages.\r\nstatic pte_t *\r\nwalkpgdir(pde_t *pgdir, const void *va, int alloc)\r\n{\r\n  pde_t *pde;\r\n  pte_t *pgtab;\r\n\r\n  pde = &pgdir[PDX(va)];\r\n  if(*pde & PTE_P){\r\n    pgtab = (pte_t*)p2v(PTE_ADDR(*pde));\r\n  } else {\r\n    if(!alloc || (pgtab = (pte_t*)kalloc()) == 0)\r\n      return 0;\r\n    \/\/ Make sure all those PTE_P bits are zero.\r\n    memset(pgtab, 0, PGSIZE);\r\n    \/\/ The permissions here are overly generous, but they can\r\n    \/\/ be further restricted by the permissions in the page table \r\n    \/\/ entries, if necessary.\r\n    *pde = v2p(pgtab) | PTE_P | PTE_W | PTE_U;\r\n  }\r\n  return &pgtab[PTX(va)];\r\n}\r\n\r\n\/\/ Create PTEs for virtual addresses starting at va that refer to\r\n\/\/ physical addresses starting at pa. va and size might not\r\n\/\/ be page-aligned.\r\nstatic int\r\nmappages(pde_t *pgdir, void *va, uint size, uint pa, int perm)\r\n{\r\n  char *a, *last;\r\n  pte_t *pte;\r\n  \r\n  a = (char*)PGROUNDDOWN((uint)va);\r\n  last = (char*)PGROUNDDOWN(((uint)va) + size - 1);\r\n  for(;;){\r\n    if((pte = walkpgdir(pgdir, a, 1)) == 0)\r\n      return -1;\r\n    if(*pte & PTE_P)\r\n      panic("remap");\r\n    *pte = pa | perm | PTE_P;\r\n    if(a == last)\r\n      break;\r\n    a += PGSIZE;\r\n    pa += PGSIZE;\r\n  }\r\n  return 0;\r\n}\r\n<\/pre>\n
walkpgdir\u95a2\u6570\u306f\u3001\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u5909\u63db\u306e\u305f\u3081\u306bx86\u306e\u30da\u30fc\u30b8\u30f3\u30b0\u30cf\u30fc\u30c9\u30a6\u30a7\u30a2\u304cPTE\u3092\u53c2\u7167\u3059\u308b\u52d5\u304d\u3092\u30a8\u30df\u30e5\u30ec\u30fc\u30c8\u3059\u308b\u3002\uff08\u56f31-1\u53c2\u7167\uff09
\nwalkpgdir\u306f\u3001\u30da\u30fc\u30b8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u898b\u3064\u3051\u308b\u305f\u3081\u306b\u3001\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u306e\u4e0a\u4f4d10\u30d3\u30c3\u30c8\u3092\u5229\u7528\u3059\u308b\u3002
\n\uff08pde = &pgdir[PDX(va)]; \u306e\u90e8\u5206\u3002\u30de\u30af\u30edPDX()\u3067\u4e0a\u4f4d10\u30d3\u30c3\u30c8\u3092\u53d6\u5f97\u3057\u3066\u3044\u308b\u3002\uff09
\n\u30da\u30fc\u30b8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u304c\u6e96\u5099\u51fa\u6765\u3066\u3044\u306a\u3051\u308c\u3070\u3001\u8981\u6c42\u3055\u308c\u305f\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\u306e\u30da\u30fc\u30b8\u306f\u307e\u3060\u5272\u308a\u5f53\u3066\u3089\u308c\u3066\u3044\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u306b\u306a\u308b\u3002
\n\u3082\u3057\u5f15\u6570alloc\u304c\u30bb\u30c3\u30c8\u3055\u308c\u3066\u3044\u308c\u3070\u3001walkpgdir\u95a2\u6570\u306f\u305d\u308c\u3092\u5272\u308a\u5f53\u3066\u3001\u305d\u306e\u30da\u30fc\u30b8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u4e2d\u306e\u7269\u7406\u30a2\u30c9\u30ec\u30b9\u306b\u914d\u7f6e\u3059\u308b\u3002
\n\u6700\u5f8c\u306b\u3001\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\u306e\u30da\u30fc\u30b8\u306e\u4e2d\u306ePTE\u306e\u30a2\u30c9\u30ec\u30b9\u3092\u898b\u3064\u3051\u308b\u305f\u3081\u306b\u3001\u4eee\u60f3\u30a2\u30c9\u30ec\u30b9\u306e\u6b21\u306e10\u30d3\u30c3\u30c8\u3092\u5229\u7528\u3059\u308b\u3002
\n\uff08return &pgtab[PTX(va)]; \u306e\u90e8\u5206\u3002\u30de\u30af\u30edPTX()\u3067\u4e0a\u4f4d10\u30d3\u30c3\u30c8\u306e\u3055\u3089\u306b\u6b21\u306e10\u30d3\u30c3\u30c8\u3092\u53d6\u5f97\u3057\u3066\u3044\u308b\u3002\uff09<\/p>\n
\u56f31-1 x86\u4e0a\u306e\u30da\u30fc\u30b8\u30c6\u30fc\u30d6\u30eb\uff08\u4ee5\u524d\u3082\u8f09\u305b\u307e\u3057\u305f\u304c\u3082\u3046\u4e00\u56de\u8f09\u305b\u3068\u304d\u307e\u3059\uff09
\n\"\"<\/a><\/p>\n
\u611f\u60f3<\/h3>\n
xv6\u304c\u30a2\u30c9\u30ec\u30b9\u7a7a\u9593\u3092\u3069\u3046\u4f5c\u3063\u3066\u308b\u304b\u3067\u3059\u306d\u3002
\n\u30bd\u30fc\u30b9\u306f\u666e\u901a\u306eC\u306a\u3093\u3067\u8aad\u307f\u3084\u3059\u3044\u3067\u3059\u304c\u3001\u3069\u3046\u3044\u3046\u30e1\u30e2\u30ea\u64cd\u4f5c\u3092\u3057\u3066\u308b\u306e\u304b\u5177\u4f53\u7684\u306b\u30a4\u30e1\u30fc\u30b8\u3057\u306a\u304c\u3089\u8aad\u307e\u306a\u3044\u3068\u8aac\u660e\u3068\u306e\u5bfe\u5fdc\u304c\u3088\u304f\u5206\u304b\u3089\u306a\u3044\u304b\u3068\u601d\u3044\u307e\u3059\u3002<\/p>\n
\u3053\u3053\u306f\u307e\u3060\u8d77\u52d5\u9014\u4e2d\u306e\u8a71\u306a\u306e\u3067\u305d\u308c\u3092\u5fd8\u308c\u306a\u3044\u3088\u3046\u306b\u3057\u306a\u3044\u3068\u3002
\n\uff08OS\u304c\u8d77\u52d5\u3057\u305f\u5f8c\u3001\u30d7\u30ed\u30bb\u30b9\u3092\u8d77\u52d5\u3059\u308b\u3068\u304d\u306a\u3069\u306b\u52d5\u304f\u51e6\u7406\u3067\u306f\u306a\u3044\uff09<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[405],"class_list":["post-1273","post","type-post","status-publish","format-standard","hentry","category-tech","tag-xv6"],"_links":{"self":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/1273","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/comments?post=1273"}],"version-history":[{"count":0,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/1273\/revisions"}],"wp:attachment":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/media?parent=1273"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/categories?post=1273"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/tags?post=1273"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}