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Date: Wed, 18 Oct 2017 15:27:33 +1100
From: Balbir Singh <bsingharora@gmail.com>
To: Ram Pai <linuxram@us.ibm.com>
Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
 benh@kernel.crashing.org, paulus@samba.org, khandual@linux.vnet.ibm.com,
 aneesh.kumar@linux.vnet.ibm.com, hbabu@us.ibm.com, mhocko@kernel.org,
 bauerman@linux.vnet.ibm.com, ebiederm@xmission.com
Subject: Re: [PATCH 12/25] powerpc: ability to associate pkey to a vma
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On Fri,  8 Sep 2017 15:45:00 -0700
Ram Pai <linuxram@us.ibm.com> wrote:

> arch-independent code expects the arch to  map
> a  pkey  into the vma's protection bit setting.
> The patch provides that ability.
> 
> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> ---
>  arch/powerpc/include/asm/mman.h  |    8 +++++++-
>  arch/powerpc/include/asm/pkeys.h |   18 ++++++++++++++++++
>  2 files changed, 25 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/mman.h b/arch/powerpc/include/asm/mman.h
> index 30922f6..067eec2 100644
> --- a/arch/powerpc/include/asm/mman.h
> +++ b/arch/powerpc/include/asm/mman.h
> @@ -13,6 +13,7 @@
>  
>  #include <asm/cputable.h>
>  #include <linux/mm.h>
> +#include <linux/pkeys.h>
>  #include <asm/cpu_has_feature.h>
>  
>  /*
> @@ -22,7 +23,12 @@
>  static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
>  		unsigned long pkey)
>  {
> -	return (prot & PROT_SAO) ? VM_SAO : 0;
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> +	return (((prot & PROT_SAO) ? VM_SAO : 0) |
> +			pkey_to_vmflag_bits(pkey));
> +#else
> +	return ((prot & PROT_SAO) ? VM_SAO : 0);
> +#endif
>  }
>  #define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
>  
> diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
> index 0cf115f..f13e913 100644
> --- a/arch/powerpc/include/asm/pkeys.h
> +++ b/arch/powerpc/include/asm/pkeys.h
> @@ -23,6 +23,24 @@
>  #define VM_PKEY_BIT4	VM_HIGH_ARCH_4
>  #endif
>  
> +/* override any generic PKEY Permission defines */
> +#define PKEY_DISABLE_EXECUTE   0x4
> +#define PKEY_ACCESS_MASK       (PKEY_DISABLE_ACCESS |\
> +				PKEY_DISABLE_WRITE  |\
> +				PKEY_DISABLE_EXECUTE)
> +
> +static inline u64 pkey_to_vmflag_bits(u16 pkey)
> +{
> +	if (!pkey_inited)
> +		return 0x0UL;
> +
> +	return (((pkey & 0x1UL) ? VM_PKEY_BIT0 : 0x0UL) |
> +		((pkey & 0x2UL) ? VM_PKEY_BIT1 : 0x0UL) |
> +		((pkey & 0x4UL) ? VM_PKEY_BIT2 : 0x0UL) |
> +		((pkey & 0x8UL) ? VM_PKEY_BIT3 : 0x0UL) |
> +		((pkey & 0x10UL) ? VM_PKEY_BIT4 : 0x0UL));
> +}

Assuming that there is a linear order between VM_PKEY_BIT4 to
VM_PKEY_BIT0, the conditional checks can be removed

(pkey & 0x1fUL) << VM_PKEY_BIT0?


Balbir Singh