Re: [PATCH v11 6/6] powerpc: Book3S 64-bit outline-only KASAN support

Christophe Leroy
2021-04-21T12:29:42Z

Le 19/03/2021 à 15:40, Daniel Axtens a écrit :
> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> index aca354fb670b..63672aa656e8 100644
> --- a/arch/powerpc/mm/ptdump/ptdump.c
> +++ b/arch/powerpc/mm/ptdump/ptdump.c
> @@ -20,6 +20,7 @@
> #include <linux/seq_file.h>
> #include <asm/fixmap.h>
> #include <linux/const.h>
> +#include <linux/kasan.h>
> #include <asm/page.h>
> #include <asm/hugetlb.h>
>
> @@ -317,6 +318,23 @@ static void walk_pud(struct pg_state *st, p4d_t *p4d, unsigned long start)
> unsigned long addr;
> unsigned int i;
>
> +#if defined(CONFIG_KASAN) && defined(CONFIG_PPC_BOOK3S_64)
> + /*
> + * On radix + KASAN, we want to check for the KASAN "early" shadow
> + * which covers huge quantities of memory with the same set of
> + * read-only PTEs. If it is, we want to note the first page (to see
> + * the status change), and then note the last page. This gives us good
> + * results without spending ages noting the exact same PTEs over 100s of
> + * terabytes of memory.
> + */
> + if (p4d_page(*p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud))) {
> + walk_pmd(st, pud, start);
> + addr = start + (PTRS_PER_PUD - 1) * PUD_SIZE;
> + walk_pmd(st, pud, addr);
> + return;
> + }
> +#endif
> +
> for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
> addr = start + i * PUD_SIZE;
> if (!pud_none(*pud) && !pud_is_leaf(*pud))

The above changes should not be necessary once PPC_PTDUMP is converted to GENERIC_PTDUMP.

See https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=239795

Christophe