kernel_physical_mapping_init()

最新推荐文章于 2024-09-22 18:37:26 发布

kernel_details

最新推荐文章于 2024-09-22 18:37:26 发布

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分类专栏： Memory Management 文章标签： table

本文链接：https://blog.youkuaiyun.com/kernel_details/article/details/1483701

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pagetable_init() --> kernel_physical_mapping_init()

static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
{
    unsigned long pfn;
    pgd_t *pgd;
    pmd_t *pmd;
    pte_t *pte;
    int pgd_idx, pmd_idx, pte_ofs;

定位主内核页全局目录(master kernel page global directory)的起始项pgd=768:
|--------------------------------------|
|   pgd_idx = pgd_index(PAGE_OFFSET); |
|   pgd = pgd_base + pgd_idx;          |
|--------------------------------------|

物理地址从0x0000 0000开始,起始页框号(page frame number)为pfn；
|-----------------|
|   pfn = 0;      |
|-----------------|

    for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {

直接返回pgd(pmd和pgd指向同一个页目录项)
|-------------------------------------|
|       pmd = one_md_table_init(pgd); |
|-------------------------------------|

        if (pfn >= max_low_pfn)
            continue;
        for (pmd_idx = 0; pmd_idx < PTRS_PER_PMD && pfn < max_low_pfn; pmd++, pmd_idx++) {

计算第pfn个页框对应的内核空间的线性地址:
|-----------------------------------------------------------------|
|           unsigned int address = pfn * PAGE_SIZE + PAGE_OFFSET; |
|-----------------------------------------------------------------|
            if (cpu_has_pse) {
                unsigned int address2 = (pfn + PTRS_PER_PTE - 1)
                                * PAGE_SIZE + PAGE_OFFSET + PAGE_SIZE-1;
                if (is_kernel_text(address) || is_kernel_text(address2))
                    set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE_EXEC));
                else
                    set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE));
                pfn += PTRS_PER_PTE;

填写一个页目录项pmd(pgd)，并填写该目录项所对应的页表的所有项
为页目录项pmd分配页表pte，将该页表pte的物理地址写入pmd中，并初始化页表pte的每个页表项；
|--------------------------------------------------------------------------|
|           } else {                                                       |
|               pte = one_page_table_init(pmd);                            |
|               for (pte_ofs = 0;                                          |
|                    pte_ofs < PTRS_PER_PTE && pfn < max_low_pfn;          |
|                    pte++, pfn++, pte_ofs++) {                            |
|                       if ( is_kernel_text(address))                       |
|                           set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC)); |
|                       else                                               |
|                           set_pte(pte, pfn_pte(pfn, PAGE_KERNEL));       |
|               }                                                          |
|           }                                                              |
|--------------------------------------------------------------------------|
        }
    }
}