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SubjectRe: [PATCH 4/6] x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>
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On 03/17/2017 09:55 PM, Kirill A. Shutemov wrote:
> With folded p4d, pgd_clear() is nop. Change clear_pgds() to use
> p4d_clear() instead.
>

You could probably just use set_pgd(pgd_offset_k(start), __pgd(0)); instead of pgd_clear()
as we already do in arm64.
It's basically pgd_clear() except it's not a nop wih p4d folded.


> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> ---
> arch/x86/mm/kasan_init_64.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
> index 0a56059a95c7..b775ffd7989d 100644
> --- a/arch/x86/mm/kasan_init_64.c
> +++ b/arch/x86/mm/kasan_init_64.c
> @@ -35,8 +35,19 @@ static int __init map_range(struct range *range)
> static void __init clear_pgds(unsigned long start,
> unsigned long end)
> {
> - for (; start < end; start += PGDIR_SIZE)
> - pgd_clear(pgd_offset_k(start));
> + pgd_t *pgd;
> +
> + for (; start < end; start += PGDIR_SIZE) {
> + pgd = pgd_offset_k(start);
> + /*
> + * With folded p4d, pgd_clear() is nop, use p4d_clear()
> + * instead.
> + */
> + if (CONFIG_PGTABLE_LEVELS < 5)
> + p4d_clear(p4d_offset(pgd, start));
> + else
> + pgd_clear(pgd);
> + }
> }
>
> static void __init kasan_map_early_shadow(pgd_t *pgd)
>

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