Re: [PATCH v3 09/25] arm64: define VM_PKEY_BIT* for arm64

[Catalin Marinas <catalin.marinas@arm.com>]

On Fri, Nov 24, 2023 at 04:34:54PM +0000, Joey Gouly wrote:
>  arch/arm64/include/asm/mman.h   |  8 +++++++-
>  arch/arm64/include/asm/page.h   | 10 ++++++++++
>  arch/arm64/mm/mmap.c            |  9 +++++++++
>  arch/powerpc/include/asm/page.h | 11 +++++++++++
>  arch/x86/include/asm/page.h     | 10 ++++++++++
>  fs/proc/task_mmu.c              |  2 ++
>  include/linux/mm.h              | 13 -------------
>  7 files changed, 49 insertions(+), 14 deletions(-)

It might be worth splitting out the powerpc/x86/generic parts into a
separate patch.

> 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;
> +#endif

Is there anywhere that rejects pkey & 8 on arm64? Because with 128-bit
PTEs, if we ever support them, we can have 4-bit pkeys.

>  #define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
> diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
> index 2312e6ee595f..aabfda2516d2 100644
> --- a/arch/arm64/include/asm/page.h
> +++ b/arch/arm64/include/asm/page.h
> @@ -49,6 +49,16 @@ int pfn_is_map_memory(unsigned long pfn);
>  
>  #define VM_DATA_DEFAULT_FLAGS	(VM_DATA_FLAGS_TSK_EXEC | VM_MTE_ALLOWED)
>  
> +#if defined(CONFIG_ARCH_HAS_PKEYS)
> +/* A protection key is a 3-bit value */
> +# define VM_PKEY_SHIFT	VM_HIGH_ARCH_BIT_2
> +# define VM_PKEY_BIT0	VM_HIGH_ARCH_2
> +# define VM_PKEY_BIT1	VM_HIGH_ARCH_3
> +# define VM_PKEY_BIT2	VM_HIGH_ARCH_4
> +# define VM_PKEY_BIT3	0
> +# define VM_PKEY_BIT4	0
> +#endif

I think we should start from VM_HIGH_ARCH_BIT_0 and just move the
VM_MTE, VM_MTE_ALLOWED to VM_HIGH_ARCH_BIT_{4,5}.

> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
> index e5fcc79b5bfb..a5e75ec333ad 100644
> --- a/arch/powerpc/include/asm/page.h
> +++ b/arch/powerpc/include/asm/page.h
> @@ -330,6 +330,17 @@ static inline unsigned long kaslr_offset(void)
>  }
>  
>  #include <asm-generic/memory_model.h>
> +
> +#if defined(CONFIG_ARCH_HAS_PKEYS)
> +# define VM_PKEY_SHIFT	VM_HIGH_ARCH_BIT_0
> +/* A protection key is a 5-bit value */
> +# define VM_PKEY_BIT0	VM_HIGH_ARCH_0
> +# define VM_PKEY_BIT1	VM_HIGH_ARCH_1
> +# define VM_PKEY_BIT2	VM_HIGH_ARCH_2
> +# define VM_PKEY_BIT3	VM_HIGH_ARCH_3
> +# define VM_PKEY_BIT4	VM_HIGH_ARCH_4
> +#endif /* CONFIG_ARCH_HAS_PKEYS */
> +
>  #endif /* __ASSEMBLY__ */
>  
>  #endif /* _ASM_POWERPC_PAGE_H */
> diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
> index d18e5c332cb9..b770db1a21e7 100644
> --- a/arch/x86/include/asm/page.h
> +++ b/arch/x86/include/asm/page.h
> @@ -87,5 +87,15 @@ static __always_inline u64 __is_canonical_address(u64 vaddr, u8 vaddr_bits)
>  
>  #define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
>  
> +#if defined(CONFIG_ARCH_HAS_PKEYS)
> +# define VM_PKEY_SHIFT	VM_HIGH_ARCH_BIT_0
> +/* A protection key is a 4-bit value */
> +# define VM_PKEY_BIT0	VM_HIGH_ARCH_0
> +# define VM_PKEY_BIT1	VM_HIGH_ARCH_1
> +# define VM_PKEY_BIT2	VM_HIGH_ARCH_2
> +# define VM_PKEY_BIT3	VM_HIGH_ARCH_3
> +# define VM_PKEY_BIT4	0
> +#endif /* CONFIG_ARCH_HAS_PKEYS */

Rather than moving these to arch code, we could instead keep the generic
definitions with some additional CONFIG_ARCH_HAS_PKEYS_{3,4,5}BIT
selected from the arch code.

-- 
Catalin