Linux核心頁表初始化

linux在核心啟動過程中start_kernel->setup_arch會呼叫如下兩個函式對頁表進行初始化和建立。

static inline void prepare_page_table(void)

初始化頁表裡也會flush對應的tlb。

typedef unsigned long pgd_t[2];

#define pmd_clear(pmdp)			\

do while (0)

static inline pmd_t *pmd_off_k(unsigned long virt)

#define pgd_offset_k(addr)	pgd_offset(&init_mm, addr)

/* to find an entry in a page-table-directory */

#define pgd_index(addr) ((addr) >> pgdir_shift)
#define pgd_offset(mm, addr) ((mm)->pgd+pgd_index(addr))
/* to find an entry in a kernel page-table-directory */
#define pgd_offset_k(addr) pgd_offset(&init_mm, addr)
/* find an entry in the second-level page table.. */
#define pmd_offset(dir, addr) ((pmd_t *)(dir))
/* find an entry in the third-level page table.. */
#define __pte_index(addr) (((addr) >> page_shift) & (ptrs_per_pte - 1))

/*

* create the page directory entries and any necessary
* are able to cope here with varying sizes and address
* offsets, and we take full advantage of sections and
* supersections.
*///高階記憶體通過alloc_page+kmap的形式對映，在初始化階段不可能有bank的虛擬位址落在vmalloc線性位址空間
if ((md->type == mt_device || md->type == mt_rom) &&
md->virtual >= page_offset && md->virtual < vmalloc_end) 
type = &mem_types[md->type];
//如果有大於4g的物理記憶體，單獨建立
/* * catch 36-bit addresses
*/if (md->pfn >= 0x100000) 
addr = md->virtual & page_mask;
phys = (unsigned long)__pfn_to_phys(md->pfn);
length = page_align(md->length + (md->virtual & ~page_mask));//將bank整頁對齊
if (type->prot_l1 == 0 && ((addr | phys | length) & ~section_mask)) 
pgd = pgd_offset_k(addr);
end = addr + length;
do while (pgd++, addr != end);
}static void __init alloc_init_section(pgd_t *pgd, unsigned long addr,
unsigned long end, unsigned long phys,
const struct mem_type *type)
while (pmd++, addr += section_size, addr != end);
flush_pmd_entry(p);
} else 
}static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
unsigned long end, unsigned long pfn,
const struct mem_type *type)
pte = pte_offset_kernel(pmd, addr);//建立pte
do while (pte++, addr += page_size, addr != end);}

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