[PATCH v3 2/3] powerpc: mm: add p{te,md,ud}_user_accessible_page helpers

[Christophe Leroy]

Le 24/10/2022 à 02:35, Rohan McLure a écrit :
> Add the following helpers for detecting whether a page table entry
> is a leaf and is accessible to user space.
> 
>   * pte_user_accessible_page
>   * pmd_user_accessible_page
>   * pud_user_accessible_page
> 
> Also implement missing pud_user definitions for both Book3S/nohash 64-bit
> systems, and pmd_user for Book3S/nohash 32-bit systems.
> 
> Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
> ---
> V2: Provide missing pud_user implementations, use p{u,m}d_is_leaf.
> V3: Provide missing pmd_user implementations as stubs in 32-bit.
> ---
>   arch/powerpc/include/asm/book3s/32/pgtable.h |  4 ++++
>   arch/powerpc/include/asm/book3s/64/pgtable.h | 10 ++++++++++
>   arch/powerpc/include/asm/nohash/32/pgtable.h |  1 +
>   arch/powerpc/include/asm/nohash/64/pgtable.h | 10 ++++++++++
>   arch/powerpc/include/asm/pgtable.h           | 15 +++++++++++++++
>   5 files changed, 40 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
> index 40041ac713d9..8bf1c538839a 100644
> --- a/arch/powerpc/include/asm/book3s/32/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
> @@ -531,6 +531,10 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
>   	return __pte((pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot));
>   }
>   
> +static inline bool pmd_user(pmd_t pmd)
> +{
> +	return 0;
> +}
>   
>   
>   /* This low level function performs the actual PTE insertion
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index f9aefa492df0..3083111f9d0a 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -621,6 +621,16 @@ static inline bool pte_user(pte_t pte)
>   	return !(pte_raw(pte) & cpu_to_be64(_PAGE_PRIVILEGED));
>   }
>   
> +static inline bool pmd_user(pmd_t pmd)
> +{
> +	return !(pmd_raw(pmd) & cpu_to_be64(_PAGE_PRIVILEGED));
> +}
> +
> +static inline bool pud_user(pud_t pud)
> +{
> +	return !(pud_raw(pud) & cpu_to_be64(_PAGE_PRIVILEGED));
> +}
> +
>   #define pte_access_permitted pte_access_permitted
>   static inline bool pte_access_permitted(pte_t pte, bool write)
>   {
> diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
> index 9091e4904a6b..b92044d9d778 100644
> --- a/arch/powerpc/include/asm/nohash/32/pgtable.h
> +++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
> @@ -354,6 +354,7 @@ static inline int pte_young(pte_t pte)
>   #endif
>   
>   #define pmd_page(pmd)		pfn_to_page(pmd_pfn(pmd))
> +#define pmd_user(pmd)		0
>   /*
>    * Encode and decode a swap entry.
>    * Note that the bits we use in a PTE for representing a swap entry
> diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
> index 599921cc257e..23c5135178d1 100644
> --- a/arch/powerpc/include/asm/nohash/64/pgtable.h
> +++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
> @@ -123,6 +123,11 @@ static inline pte_t pmd_pte(pmd_t pmd)
>   	return __pte(pmd_val(pmd));
>   }
>   
> +static inline bool pmd_user(pmd_t pmd)
> +{
> +	return (pmd_val(pmd) & _PAGE_USER) == _PAGE_USER;
> +}
> +
>   #define pmd_none(pmd)		(!pmd_val(pmd))
>   #define	pmd_bad(pmd)		(!is_kernel_addr(pmd_val(pmd)) \
>   				 || (pmd_val(pmd) & PMD_BAD_BITS))
> @@ -158,6 +163,11 @@ static inline pte_t pud_pte(pud_t pud)
>   	return __pte(pud_val(pud));
>   }
>   
> +static inline bool pud_user(pud_t pud)
> +{
> +	return (pud_val(pud) & _PAGE_USER) == _PAGE_USER;
> +}
> +
>   static inline pud_t pte_pud(pte_t pte)
>   {
>   	return __pud(pte_val(pte));
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index 36956fb440e1..3cb5de9f1aa4 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -172,6 +172,21 @@ static inline int pud_pfn(pud_t pud)
>   }
>   #endif
>   
> +static inline bool pte_user_accessible_page(pte_t pte)
> +{
> +	return pte_present(pte) && pte_user(pte);
> +}
> +
> +static inline bool pmd_user_accessible_page(pmd_t pmd)
> +{
> +	return pmd_is_leaf(pmd) && pmd_present(pmd) && pmd_user(pmd);

pmd_is_leaf() is specific to powerpc and we may want to get rid of it.

Can you use pmd_leaf() instead ?

> +}
> +
> +static inline bool pud_user_accessible_page(pud_t pud)
> +{
> +	return pud_is_leaf(pud) && pud_present(pud) && pud_user(pud);

pud_is_leaf() is specific to powerpc and we may want to get rid of it.

Can you use pud_leaf() instead ?

> +}
> +
>   #endif /* __ASSEMBLY__ */
>   
>   #endif /* _ASM_POWERPC_PGTABLE_H */