Problem with accessing page tables

Ameya Mitragotri
2003-11-08T04:28:38Z

Hi,

I wrote following piece of code to traverse the page table for a
particular
Kernel variable. But the PMD access is always a failure.

I'm using Itanium 2 with linux-2.6.0-test5.
Any pointers will be really helpful.
Thanks and regards,
Ameya

pgd_t *pgd;
pmd_t *pmd;
pte_t *ptep, pte;
unsigned long pfn;

printk(KERN_EMERG "The address is %lx\n\n\n",address);

pgd = pgd_offset_k(address);
if (pgd_none(*pgd) || pgd_bad(*pgd))
goto out;

>> pmd = pmd_offset(pgd, address); <<<
One of the checks below fails because the call pmd_offset gives pmd
With value o.

if (pmd_none(*pmd))
goto out;
if (pmd_bad(*pmd))
goto out;

ptep = pte_offset_kernel(pmd, address);
if (!ptep)
goto out;
pte = *ptep;
pte_unmap(ptep);
if (pte_present(pte)) {
if (!write || (pte_write(pte) && pte_dirty(pte))) {
pfn = pte_pfn(pte);
if (pfn_valid(pfn)) {
struct page *page = pfn_to_page(pfn);

//mark_page_accessed(page);
return page;
}
}
}
else
{
printk(KERN_EMERG "pte entry not present \n");
}

out:
printk(KERN_EMERG "At out \n");