linux-kernel - Re: [PATCH v9 3/6] kasan: define and use MAX_PTRS_PER

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Date:   Tue, 1 Dec 2020 17:54:34 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Daniel Axtens <dja@...ens.net>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        kasan-dev@...glegroups.com, christophe.leroy@....fr,
        aneesh.kumar@...ux.ibm.com, bsingharora@...il.com
Subject: Re: [PATCH v9 3/6] kasan: define and use MAX_PTRS_PER_* for early
 shadow tables



Le 01/12/2020 à 17:16, Daniel Axtens a écrit :
> powerpc has a variable number of PTRS_PER_*, set at runtime based
> on the MMU that the kernel is booted under.
> 
> This means the PTRS_PER_* are no longer constants, and therefore
> breaks the build.
> 
> Define default MAX_PTRS_PER_*s in the same style as MAX_PTRS_PER_P4D.
> As KASAN is the only user at the moment, just define them in the kasan
> header, and have them default to PTRS_PER_* unless overridden in arch
> code.
> 
> Suggested-by: Christophe Leroy <christophe.leroy@....fr>

My neww address is : christophe.leroy@...roup.eu

> Suggested-by: Balbir Singh <bsingharora@...il.com>
> Reviewed-by: Christophe Leroy <christophe.leroy@....fr>

Same

> Reviewed-by: Balbir Singh <bsingharora@...il.com>
> Signed-off-by: Daniel Axtens <dja@...ens.net>
> ---
>   include/linux/kasan.h | 18 +++++++++++++++---
>   mm/kasan/init.c       |  6 +++---
>   2 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 3df66fdf6662..893d054aad6f 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -24,10 +24,22 @@ struct kunit_kasan_expectation {
>   static inline bool kasan_arch_is_ready(void)	{ return true; }
>   #endif
>   
> +#ifndef MAX_PTRS_PER_PTE
> +#define MAX_PTRS_PER_PTE PTRS_PER_PTE
> +#endif
> +
> +#ifndef MAX_PTRS_PER_PMD
> +#define MAX_PTRS_PER_PMD PTRS_PER_PMD
> +#endif
> +
> +#ifndef MAX_PTRS_PER_PUD
> +#define MAX_PTRS_PER_PUD PTRS_PER_PUD
> +#endif
> +
>   extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
> -extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
> -extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
> -extern pud_t kasan_early_shadow_pud[PTRS_PER_PUD];
> +extern pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE];
> +extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
> +extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
>   extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
>   
>   int kasan_populate_early_shadow(const void *shadow_start,
> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
> index fe6be0be1f76..42bca3d27db8 100644
> --- a/mm/kasan/init.c
> +++ b/mm/kasan/init.c
> @@ -46,7 +46,7 @@ static inline bool kasan_p4d_table(pgd_t pgd)
>   }
>   #endif
>   #if CONFIG_PGTABLE_LEVELS > 3
> -pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
> +pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
>   static inline bool kasan_pud_table(p4d_t p4d)
>   {
>   	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
> @@ -58,7 +58,7 @@ static inline bool kasan_pud_table(p4d_t p4d)
>   }
>   #endif
>   #if CONFIG_PGTABLE_LEVELS > 2
> -pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
> +pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
>   static inline bool kasan_pmd_table(pud_t pud)
>   {
>   	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
> @@ -69,7 +69,7 @@ static inline bool kasan_pmd_table(pud_t pud)
>   	return false;
>   }
>   #endif
> -pte_t kasan_early_shadow_pte[PTRS_PER_PTE] __page_aligned_bss;
> +pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE] __page_aligned_bss;
>   
>   static inline bool kasan_pte_table(pmd_t pmd)
>   {
>