linux-kernel - Re: [RFC v5 31/38] powerpc: introduce get_pte

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Message-Id: <58e0d9ff-727f-c960-5c5f-16d19a89e181@linux.vnet.ibm.com>
Date:   Mon, 10 Jul 2017 08:41:30 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Ram Pai <linuxram@...ibm.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, dave.hansen@...el.com, hbabu@...ibm.com,
        arnd@...db.de, akpm@...ux-foundation.org, corbet@....net,
        mingo@...hat.com
Subject: Re: [RFC v5 31/38] powerpc: introduce get_pte_pkey() helper

On 07/06/2017 02:52 AM, Ram Pai wrote:
> get_pte_pkey() helper returns the pkey associated with
> a address corresponding to a given mm_struct.
> 
> Signed-off-by: Ram Pai <linuxram@...ibm.com>
> ---
>  arch/powerpc/include/asm/book3s/64/mmu-hash.h |    5 ++++
>  arch/powerpc/mm/hash_utils_64.c               |   28 +++++++++++++++++++++++++
>  2 files changed, 33 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> index f7a6ed3..369f9ff 100644
> --- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> @@ -450,6 +450,11 @@ extern int hash_page(unsigned long ea, unsigned long access, unsigned long trap,
>  int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
>  		     pte_t *ptep, unsigned long trap, unsigned long flags,
>  		     int ssize, unsigned int shift, unsigned int mmu_psize);
> +
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> +u16 get_pte_pkey(struct mm_struct *mm, unsigned long address);
> +#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
> +
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  extern int __hash_page_thp(unsigned long ea, unsigned long access,
>  			   unsigned long vsid, pmd_t *pmdp, unsigned long trap,
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 1e74529..591990c 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -1573,6 +1573,34 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
>  	local_irq_restore(flags);
>  }
>  
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> +/*
> + * return the protection key associated with the given address
> + * and the mm_struct.
> + */
> +u16 get_pte_pkey(struct mm_struct *mm, unsigned long address)
> +{
> +	pte_t *ptep;
> +	u16 pkey = 0;
> +	unsigned long flags;
> +
> +	if (REGION_ID(address) == VMALLOC_REGION_ID)
> +		mm = &init_mm;

IIUC, protection keys are only applicable for user space. This
function is getting used to populate siginfo structure. Then how
can we ever request this for any address in VMALLOC region.

> +
> +	if (!mm || !mm->pgd)
> +		return 0;

Is this really required at this stage ?