page_table_walk.c

#define PAGE_OFFSET_MASK (~(~0UL << PAGE_SHIFT))

unsigned long page_table_walk(unsigned long addr, struct mm_struct *mm_str)
{
    pgd_t *pgd;
    p4d_t *p4d;
    pud_t *pud;
    pmd_t *pmd;
    pte_t *pte;
    unsigned long pfn, phys_page_addr, page_offset, phys_addr;

    pgd = pgd_offset(mm_str, addr);
    if (pgd_none(*pgd))
        return 0;

    p4d = p4d_offset(pgd, addr);
    if (p4d_none(*p4d))
        return 0;

    pud = pud_offset(p4d, addr);
    if (pud_none(*pud))
        return 0;

    pmd = pmd_offset(pud, addr);
    if (pmd_none(*pmd))
        return 0;

    pte = pte_offset_map(pmd, addr);
    if (!pte || !pte_present(*pte) || pte_none(*pte) || is_zero_pfn(pte_pfn(*pte)))
    {
        //printk("pagetrackd: can't get pte\n");
        return 0;
    }

    pfn = pte_pfn(*pte);
    phys_page_addr = PFN_PHYS(pfn);
    page_offset = addr & PAGE_OFFSET_MASK;
    phys_addr = phys_page_addr | page_offset;
    
    pte_unmap(pte);
    
    return phys_addr;
}