Ioremap 코드 분석

부팅 시,

           iomem_resource에 structmemblock_region를 add

1)    System RAM 영역 요청

이는 "System RAM" 임 (kernel code section과 data section의 start / end를 가지고 – symbol 참고 – region을 결정)

이 부분의 page frame들에 대해서 request_resource 함

2)    Kernel code 영역(section)

request_resource(res, &kernel_code);

3)    Kernel datasection

request_resource(res, &kernel_data);

 

Ioremap은

           Virtual address에서 page들을 할당하여 physical address의 page frame들에 대한 page table entry를 mapping(치환) 하는 것

 

 

#define ioremap(addr, size)                   __ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRE))   // ioremap_cache   void __iomem *__ioremap(phys_addr_t phys_addr, size_t size, pgprot_t prot) {            return __ioremap_caller(phys_addr, size, prot,                                           __builtin_return_address(0)); }

 

static void __iomem *__ioremap_caller(phys_addr_t phys_addr, size_t size,                                                 pgprot_t prot, void *caller) { phys_addr &= PAGE_MASK;  ß address를 page단위로 align size = PAGE_ALIGN(size + offset);   pfn_valid(__phys_to_pfn(phys_addr))    ß physical address가 실제 memory 상의 page frame에 존재하는지 확인 (해당 page frame이 memory block에 존재하는지 확인)    area = get_vm_area_caller(size, VM_IOREMAP, caller);    ß virtual memory 할당 (vmalloc의 구현부) addr = (unsigned long)area->addr;   ioremap_page_range(addr, addr + size, phys_addr, prot);   ß virtual address와 physical address를 mapping     page upper directory à page mid-level directory à page table à page(4KB) 순서대로 top-down 하여 page mapping }   static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,                      unsigned long end, phys_addr_t phys_addr, pgprot_t prot) { pfn = phys_addr >> PAGE_SHIFT; pte = pte_alloc_kernel(pmd, addr); do { set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot));  ß physical address의 PTE와 pte_alloc_kernel에서 할당한 virtual address의 pfn++;                                                  virtual address의 pte에 physical address의 pte 설정 } while (pte++, addr += PAGE_SIZE, addr != end); … }   int __pte_alloc_kernel(pmd_t *pmd, unsigned long address) {  pte_t *new = pte_alloc_one_kernel(&init_mm, address); }   static inline pte_t * pte_alloc_one_kernel(struct mm_struct *mm, unsigned long addr) {            return (pte_t *)__get_free_page(PGALLOC_GFP);    ß page의 virtual이 pte_t 임 (page table entry) }   unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)  ß order is ‘0’ { struct page * page = alloc_pages(gfp_mask, order); return (unsigned long) page_address(page);    ß highmem.c에서 page의 virtual을 리턴 (kernel virtual address) }   static inline struct page * alloc_pages(gfp_t gfp_mask, unsigned int order) {            return alloc_pages_current(gfp_mask, order); }   struct page *alloc_pages_current(gfp_t gfp, unsigned order) { struct page *page;            if (pol->mode == MPOL_INTERLEAVE)                      page = alloc_page_interleave(gfp, order, interleave_nodes(pol));            else                      page = __alloc_pages_nodemask(gfp, order,                                           policy_zonelist(gfp, pol, numa_node_id()),                                           policy_nodemask(gfp, pol)); }   static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,                                                      unsigned nid) { page = __alloc_pages(gfp, order, zl); }   static inline struct page * __alloc_pages(gfp_t gfp_mask, unsigned int order,                      struct zonelist *zonelist) {            return __alloc_pages_nodemask(gfp_mask, order, zonelist, NULL); }   struct page * __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,                                 struct zonelist *zonelist, nodemask_t *nodemask) { struct page *page = NULL; page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order, …); … }   static struct page * get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order,                      struct zonelist *zonelist, int high_zoneidx, int alloc_flags,                      struct zone *preferred_zone, int migratetype) { struct page *page = NULL; page = buffered_rmqueue(preferred_zone, zone, order, gfp_mask, migratetype); … }   static inline struct page *buffered_rmqueue(struct zone *preferred_zone,                                 struct zone *zone, int order, gfp_t gfp_flags,                                 int migratetype) { struct page *page;   if (likely(order == 0)) {   struct per_cpu_pages *pcp; struct list_head *list;   pcp = &this_cpu_ptr(zone->pageset)->pcp; list = &pcp->lists[migratetype]; … } else {  page = __rmqueue(zone, order, migratetype); } }   static struct page *__rmqueue(struct zone *zone, unsigned int order,    // from the buddy allocator                                                                 int migratetype) { struct page *page; page = __rmqueue_smallest(zone, order, migratetype); }   static inline struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,                                                                 int migratetype) { struct free_area * area; struct page *page;   for (current_order = order; current_order < MAX_ORDER; ++current_order) {   ß order is ‘0’  area = &(zone->free_area[current_order]); if (list_empty(&area->free_list[migratetype])) continue; page = list_entry(area->free_list[migratetype].next, struct page, lru); list_del(&page->lru); area->nr_free--; … }

 

한 개의 zone에는free_area들이 존재 (11개), area에는 page들이 존재 (list로서)

 

static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr) {    // memblock_type은 memblock_region을 지님            unsigned int left = 0, right = type->cnt;              do {                      unsigned int mid = (right + left) / 2;                        if (addr < type->regions[mid].base)                                 right = mid;                      else if (addr >= (type->regions[mid].base +                                             type->regions[mid].size))                                 left = mid + 1;                      else                                 return mid;            } while (left < right);            return -1; }