Issue
In a kernel module (2.6.32-358.el6.x86_64) I'd like to print out all the physical addresses, which are mapped into a process' virtual memory. Given task->mm
, I attempt to traverse the process' struct page
's as follows:
int i, j, k, l;
for (i = 0; i < PTRS_PER_PGD; ++i)
{
pgd_t *pgd = mm->pgd + i;
if (pgd_none(*pgd) || pgd_bad(*pgd))
continue;
for (j = 0; j < PTRS_PER_PUD; ++j)
{
pud_t *pud = (pud_t *)pgd_page_vaddr(*pgd) + j;
if (pud_none(*pud) || pud_bad(*pud))
continue;
for (k = 0; k < PTRS_PER_PMD; ++k)
{
pmd_t *pmd = (pmd_t *)pud_page_vaddr(*pud) + k;
if (pmd_none(*pmd) || pmd_bad(*pmd))
continue;
for (l = 0; l < PTRS_PER_PTE; ++l)
{
pte_t *pte = (pte_t *)pmd_page_vaddr(*pmd) + l;
if (!pte || pte_none(*pte))
continue;
struct page *p = pte_page(*pte);
unsigned long phys = page_to_phys(p);
printk(KERN_NOTICE "addr %lx", phys);
}
}
}
}
The output looks a bit strange (in particular, there are serieses of identical addresses), so I'd like to ask whether the above is correct, in theory.
Solution
A better approach would be to traverse process' VMAs and translate each VMA to physical pages/addresses by means of the page directory:
struct vm_area_struct *vma = 0;
unsigned long vpage;
if (task->mm && task->mm->mmap)
for (vma = task->mm->mmap; vma; vma = vma->vm_next)
for (vpage = vma->vm_start; vpage < vma->vm_end; vpage += PAGE_SIZE)
unsigned long phys = virt2phys(task->mm, vpage);
//...
Where virt2phys
would look like this:
//...
pgd_t *pgd = pgd_offset(mm, virt);
if (pgd_none(*pgd) || pgd_bad(*pgd))
return 0;
pud = pud_offset(pgd, virt);
if (pud_none(*pud) || pud_bad(*pud))
return 0;
pmd = pmd_offset(pud, virt);
if (pmd_none(*pmd) || pmd_bad(*pmd))
return 0;
if (!(pte = pte_offset_map(pmd, virt)))
return 0;
if (!(page = pte_page(*pte)))
return 0;
phys = page_to_phys(page);
pte_unmap(pte);
return phys;
Answered By - Igor R. Answer Checked By - Robin (WPSolving Admin)