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From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Ard Biesheuvel <ardb@kernel.org>, linux-arm-kernel@lists.infradead.org
Cc: maz@kernel.org, catalin.marinas@arm.com, will@kernel.org,
	mark.rutland@arm.com, qperret@google.com,
	kernel-team@android.com
Subject: Re: [PATCH v2 3/3] arm64: mm: use XN table mapping attributes for user/kernel mappings
Date: Tue, 9 Mar 2021 11:10:59 +0530	[thread overview]
Message-ID: <883eda2e-64fa-20c1-da76-44b5a9d4451f@arm.com> (raw)
In-Reply-To: <20210308181535.16230-4-ardb@kernel.org>



On 3/8/21 11:45 PM, Ard Biesheuvel wrote:
> As the kernel and user space page tables are strictly mutually exclusive
> when it comes to executable permissions, we can set the UXN table attribute
> on all table entries that are created while creating kernel mappings in the
> swapper page tables, and the PXN table attribute on all table entries that
> are created while creating user space mappings in user space page tables.
> 
> While at it, get rid of a redundant comment.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

> ---
>  arch/arm64/include/asm/pgalloc.h | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
> index 27cc643d0509..31fbab3d6f99 100644
> --- a/arch/arm64/include/asm/pgalloc.h
> +++ b/arch/arm64/include/asm/pgalloc.h
> @@ -27,7 +27,10 @@ static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot)
>  
>  static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp)
>  {
> -	__pud_populate(pudp, __pa(pmdp), PUD_TYPE_TABLE);
> +	pudval_t pudval = PUD_TYPE_TABLE;
> +
> +	pudval |= (mm == &init_mm) ? PUD_TABLE_UXN : PUD_TABLE_PXN;
> +	__pud_populate(pudp, __pa(pmdp), pudval);
>  }
>  #else
>  static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot)
> @@ -45,7 +48,10 @@ static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot)
>  
>  static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4dp, pud_t *pudp)
>  {
> -	__p4d_populate(p4dp, __pa(pudp), P4D_TYPE_TABLE);
> +	p4dval_t p4dval = P4D_TYPE_TABLE;
> +
> +	p4dval |= (mm == &init_mm) ? P4D_TABLE_UXN : P4D_TABLE_PXN;
> +	__p4d_populate(p4dp, __pa(pudp), p4dval);
>  }
>  #else
>  static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot)
> @@ -70,16 +76,15 @@ static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t ptep,
>  static inline void
>  pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep)
>  {
> -	/*
> -	 * The pmd must be loaded with the physical address of the PTE table
> -	 */
> -	__pmd_populate(pmdp, __pa(ptep), PMD_TYPE_TABLE);
> +	VM_BUG_ON(mm != &init_mm);
> +	__pmd_populate(pmdp, __pa(ptep), PMD_TYPE_TABLE | PMD_TABLE_UXN);
>  }
>  
>  static inline void
>  pmd_populate(struct mm_struct *mm, pmd_t *pmdp, pgtable_t ptep)
>  {
> -	__pmd_populate(pmdp, page_to_phys(ptep), PMD_TYPE_TABLE);
> +	VM_BUG_ON(mm == &init_mm);
> +	__pmd_populate(pmdp, page_to_phys(ptep), PMD_TYPE_TABLE | PMD_TABLE_PXN);
>  }
>  #define pmd_pgtable(pmd) pmd_page(pmd)
>  
> 

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      reply	other threads:[~2021-03-09  5:42 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-08 18:15 [PATCH v2 0/3] arm64: use hierarchical XN permissions for all page tables Ard Biesheuvel
2021-03-08 18:15 ` [PATCH v2 1/3] arm64: mm: add missing P4D definitions and use them consistently Ard Biesheuvel
2021-03-09  4:56   ` Anshuman Khandual
2021-03-08 18:15 ` [PATCH v2 2/3] arm64: mm: use XN table mapping attributes for the linear region Ard Biesheuvel
2021-03-09  5:09   ` Anshuman Khandual
2021-03-09 12:36     ` Ard Biesheuvel
2021-03-10  6:48       ` Anshuman Khandual
2021-03-09  5:52   ` Anshuman Khandual
2021-03-08 18:15 ` [PATCH v2 3/3] arm64: mm: use XN table mapping attributes for user/kernel mappings Ard Biesheuvel
2021-03-09  5:40   ` Anshuman Khandual [this message]

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