On Tue, 2014-12-02 at 13:01 +0530, Aneesh Kumar K.V wrote:
> Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> writes:
>
> > On Fri, 2014-11-21 at 13:57 +0000, Mel Gorman wrote:
> >> void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
> >> pte_t pte)
> >> {
> >> -#ifdef CONFIG_DEBUG_VM
> >> - WARN_ON(pte_val(*ptep) & _PAGE_PRESENT);
> >> -#endif
> >> + /*
> >> + * When handling numa faults, we already have the pte marked
> >> + * _PAGE_PRESENT, but we can be sure that it is not in hpte.
> >> + * Hence we can use set_pte_at for them.
> >> + */
> >> + VM_WARN_ON((pte_val(*ptep) & (_PAGE_PRESENT | _PAGE_USER)) ==
> >> + (_PAGE_PRESENT | _PAGE_USER));
> >> +
> >
> > His is that going to fare with set_pte_at() called for kernel pages ?
> >
>
> Yes, we won't capture those errors now. But is there any other debug
> check i could use to capture the wrong usage of set_pte_at ?
Actually the above is fine, for some reason I mis-read the test as
blowing on kernel pages, it doesn't.
We probably do need to make sure however that protnone isn't used for
kernel pages.
Cheers,
Ben.
> -aneesh
>
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