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SubjectRe: [PATCH 12/16] x86/mm/pae: Populate the user page-table with user pgd's
On Tue, 16 Jan 2018, Joerg Roedel wrote:
>
> +#ifdef CONFIG_X86_64
> /*
> * If this is normal user memory, make it NX in the kernel
> * pagetables so that, if we somehow screw up and return to
> @@ -134,10 +135,16 @@ pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
> * may execute from it
> * - we don't have NX support
> * - we're clearing the PGD (i.e. the new pgd is not present).
> + * - We run on a 32 bit kernel. 2-level paging doesn't support NX at
> + * all and PAE paging does not support it on the PGD level. We can
> + * set it in the PMD level there in the future, but that means we
> + * need to unshare the PMDs between the kernel and the user
> + * page-tables.
> */
> if ((pgd.pgd & (_PAGE_USER|_PAGE_PRESENT)) == (_PAGE_USER|_PAGE_PRESENT) &&
> (__supported_pte_mask & _PAGE_NX))
> pgd.pgd |= _PAGE_NX;

I'd suggest to have:

static inline pteval_t supported_pgd_mask(void)
{
if (IS_ENABLED(CONFIG_X86_64))
return __supported_pte_mask;
return __supported_pte_mask & ~_PAGE_NX);
}

and get rid of the ifdeffery completely.

Thanks,

tglx

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