[PATCH v4 13/29] arm64: convert protection key into vm_flags and pgprot values

[Anshuman Khandual]

On 5/3/24 18:31, Joey Gouly wrote:
> Modify arch_calc_vm_prot_bits() and vm_get_page_prot() such that the pkey
> value is set in the vm_flags and then into the pgprot value.
> 
> Signed-off-by: Joey Gouly <joey.gouly at arm.com>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Will Deacon <will at kernel.org>
> ---
>  arch/arm64/include/asm/mman.h | 8 +++++++-
>  arch/arm64/mm/mmap.c          | 9 +++++++++
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
> index 5966ee4a6154..ecb2d18dc4d7 100644
> --- a/arch/arm64/include/asm/mman.h
> +++ b/arch/arm64/include/asm/mman.h
> @@ -7,7 +7,7 @@
>  #include <uapi/asm/mman.h>
>  
>  static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
> -	unsigned long pkey __always_unused)
> +	unsigned long pkey)
>  {
>  	unsigned long ret = 0;
>  
> @@ -17,6 +17,12 @@ static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
>  	if (system_supports_mte() && (prot & PROT_MTE))
>  		ret |= VM_MTE;
>  
> +#if defined(CONFIG_ARCH_HAS_PKEYS)
> +	ret |= pkey & 0x1 ? VM_PKEY_BIT0 : 0;
> +	ret |= pkey & 0x2 ? VM_PKEY_BIT1 : 0;
> +	ret |= pkey & 0x4 ? VM_PKEY_BIT2 : 0;

0x1, 0x2, 0x4 here are standard bit positions for their corresponding
VM_KEY_XXX based protection values ? Although this is similar to what
x86 is doing currently, hence just trying to understand if these bit
positions here are related to the user visible ABI, which should be
standardized ?

Agree with previous comments about the need for system_supports_poe()
based additional check for the above code block.

> +#endif
> +
>  	return ret;
>  }
>  #define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
> diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
> index 642bdf908b22..86eda6bc7893 100644
> --- a/arch/arm64/mm/mmap.c
> +++ b/arch/arm64/mm/mmap.c
> @@ -102,6 +102,15 @@ pgprot_t vm_get_page_prot(unsigned long vm_flags)
>  	if (vm_flags & VM_MTE)
>  		prot |= PTE_ATTRINDX(MT_NORMAL_TAGGED);
>  
> +#ifdef CONFIG_ARCH_HAS_PKEYS
> +	if (vm_flags & VM_PKEY_BIT0)
> +		prot |= PTE_PO_IDX_0;
> +	if (vm_flags & VM_PKEY_BIT1)
> +		prot |= PTE_PO_IDX_1;
> +	if (vm_flags & VM_PKEY_BIT2)
> +		prot |= PTE_PO_IDX_2;
> +#endif
> +
>  	return __pgprot(prot);
>  }
>  EXPORT_SYMBOL(vm_get_page_prot);