linux-kernel - Re: [PATCH v3 06/10] mm/kasan: Use pXd_leaf() in shadow

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Date: Wed, 6 Mar 2024 08:28:30 +0200
From: Mike Rapoport <rppt@...nel.org>
To: peterx@...hat.com
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Christophe Leroy <christophe.leroy@...roup.eu>, x86@...nel.org,
	"Kirill A . Shutemov" <kirill@...temov.name>,
	Jason Gunthorpe <jgg@...dia.com>, Yang Shi <shy828301@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linuxppc-dev@...ts.ozlabs.org, Muchun Song <muchun.song@...ux.dev>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	kasan-dev@...glegroups.com
Subject: Re: [PATCH v3 06/10] mm/kasan: Use pXd_leaf() in shadow_mapped()

On Tue, Mar 05, 2024 at 12:37:46PM +0800, peterx@...hat.com wrote:
> From: Peter Xu <peterx@...hat.com>
> 
> There is an old trick in shadow_mapped() to use pXd_bad() to detect huge
> pages.  After commit 93fab1b22ef7 ("mm: add generic p?d_leaf() macros") we
> have a global API for huge mappings.  Use that to replace the trick.
> 
> Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>
> Cc: Alexander Potapenko <glider@...gle.com>
> Cc: Andrey Konovalov <andreyknvl@...il.com>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Vincenzo Frascino <vincenzo.frascino@....com>
> Cc: kasan-dev@...glegroups.com
> Signed-off-by: Peter Xu <peterx@...hat.com>

Reviewed-by: Mike Rapoport (IBM) <rppt@...nel.org>

> ---
>  mm/kasan/shadow.c | 11 ++---------
>  1 file changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
> index 9ef84f31833f..d6210ca48dda 100644
> --- a/mm/kasan/shadow.c
> +++ b/mm/kasan/shadow.c
> @@ -199,19 +199,12 @@ static bool shadow_mapped(unsigned long addr)
>  	pud = pud_offset(p4d, addr);
>  	if (pud_none(*pud))
>  		return false;
> -
> -	/*
> -	 * We can't use pud_large() or pud_huge(), the first one is
> -	 * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
> -	 * pud_bad(), if pud is bad then it's bad because it's huge.
> -	 */
> -	if (pud_bad(*pud))
> +	if (pud_leaf(*pud))
>  		return true;
>  	pmd = pmd_offset(pud, addr);
>  	if (pmd_none(*pmd))
>  		return false;
> -
> -	if (pmd_bad(*pmd))
> +	if (pmd_leaf(*pmd))
>  		return true;
>  	pte = pte_offset_kernel(pmd, addr);
>  	return !pte_none(ptep_get(pte));
> -- 
> 2.44.0
> 
> 

-- 
Sincerely yours,
Mike.