Subject: Re: [RFC V1 04/31] powerpc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

From: Mike Rapoport <[email-masked]>
Date: Thu, 3 Feb 2022 20:15:43 +0200

On Mon, Jan 24, 2022 at 06:26:41PM +0530, Anshuman Khandual wrote:
> This defines and exports a platform specific custom vm_get_page_prot() via
> subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX
> macros can be dropped which are no longer needed. While here, this also
> localizes arch_vm_get_page_prot() as powerpc_vm_get_page_prot().
> 
> Cc: Michael Ellerman <[email-masked]>
> Cc: Paul Mackerras <[email-masked]>
> Cc: [email-masked]
> Cc: [email-masked]
> Signed-off-by: Anshuman Khandual <[email-masked]>
> ---
>  arch/powerpc/Kconfig               |  1 +
>  arch/powerpc/include/asm/mman.h    |  3 +-
>  arch/powerpc/include/asm/pgtable.h | 19 ------------
>  arch/powerpc/mm/mmap.c             | 47 ++++++++++++++++++++++++++++++
>  4 files changed, 49 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index b779603978e1..ddb4a3687c05 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -135,6 +135,7 @@ config PPC
>  	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>  	select ARCH_HAS_UACCESS_FLUSHCACHE
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
> +	select ARCH_HAS_VM_GET_PAGE_PROT
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>  	select ARCH_KEEP_MEMBLOCK
>  	select ARCH_MIGHT_HAVE_PC_PARPORT
> diff --git a/arch/powerpc/include/asm/mman.h b/arch/powerpc/include/asm/mman.h
> index 7cb6d18f5cd6..7b10c2031e82 100644
> --- a/arch/powerpc/include/asm/mman.h
> +++ b/arch/powerpc/include/asm/mman.h
> @@ -24,7 +24,7 @@ static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
>  }
>  #define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
>  
> -static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags)
> +static inline pgprot_t powerpc_vm_get_page_prot(unsigned long vm_flags)
>  {
>  #ifdef CONFIG_PPC_MEM_KEYS
>  	return (vm_flags & VM_SAO) ?
> @@ -34,7 +34,6 @@ static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags)
>  	return (vm_flags & VM_SAO) ? __pgprot(_PAGE_SAO) : __pgprot(0);
>  #endif
>  }
> -#define arch_vm_get_page_prot(vm_flags) arch_vm_get_page_prot(vm_flags)
>  
>  static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
>  {
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index d564d0ecd4cd..3cbb6de20f9d 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -20,25 +20,6 @@ struct mm_struct;
>  #include <asm/nohash/pgtable.h>
>  #endif /* !CONFIG_PPC_BOOK3S */
>  
> -/* Note due to the way vm flags are laid out, the bits are XWR */
> -#define __P000	PAGE_NONE
> -#define __P001	PAGE_READONLY
> -#define __P010	PAGE_COPY
> -#define __P011	PAGE_COPY
> -#define __P100	PAGE_READONLY_X
> -#define __P101	PAGE_READONLY_X
> -#define __P110	PAGE_COPY_X
> -#define __P111	PAGE_COPY_X
> -
> -#define __S000	PAGE_NONE
> -#define __S001	PAGE_READONLY
> -#define __S010	PAGE_SHARED
> -#define __S011	PAGE_SHARED
> -#define __S100	PAGE_READONLY_X
> -#define __S101	PAGE_READONLY_X
> -#define __S110	PAGE_SHARED_X
> -#define __S111	PAGE_SHARED_X
> -
>  #ifndef __ASSEMBLY__
>  
>  #ifndef MAX_PTRS_PER_PGD
> diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
> index c475cf810aa8..7f05e7903bd2 100644
> --- a/arch/powerpc/mm/mmap.c
> +++ b/arch/powerpc/mm/mmap.c
> @@ -254,3 +254,50 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
>  		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
>  	}
>  }
> +
> +static inline pgprot_t __vm_get_page_prot(unsigned long vm_flags)
> +{
> +	switch (vm_flags & (VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)) {
> +	case VM_NONE:
> +		return PAGE_NONE;
> +	case VM_READ:
> +		return PAGE_READONLY;
> +	case VM_WRITE:
> +		return PAGE_COPY;
> +	case VM_READ | VM_WRITE:
> +		return PAGE_COPY;
> +	case VM_EXEC:
> +		return PAGE_READONLY_X;
> +	case VM_EXEC | VM_READ:
> +		return PAGE_READONLY_X;
> +	case VM_EXEC | VM_WRITE:
> +		return PAGE_COPY_X;
> +	case VM_EXEC | VM_READ | VM_WRITE:
> +		return PAGE_COPY_X;
> +	case VM_SHARED:
> +		return PAGE_NONE;
> +	case VM_SHARED | VM_READ:
> +		return PAGE_READONLY;
> +	case VM_SHARED | VM_WRITE:
> +		return PAGE_SHARED;
> +	case VM_SHARED | VM_READ | VM_WRITE:
> +		return PAGE_SHARED;
> +	case VM_SHARED | VM_EXEC:
> +		return PAGE_READONLY_X;
> +	case VM_SHARED | VM_EXEC | VM_READ:
> +		return PAGE_READONLY_X;
> +	case VM_SHARED | VM_EXEC | VM_WRITE:
> +		return PAGE_SHARED_X;
> +	case VM_SHARED | VM_EXEC | VM_READ | VM_WRITE:
> +		return PAGE_SHARED_X;
> +	default:
> +		BUILD_BUG();
> +	}
> +}
> +
> +pgprot_t vm_get_page_prot(unsigned long vm_flags)
> +{
> +	return __pgprot(pgprot_val(__vm_get_page_prot(vm_flags)) |
> +	       pgprot_val(powerpc_vm_get_page_prot(vm_flags)));

Any reason to keep powerpc_vm_get_page_prot() rather than open code it
here?

This applies to other architectures that implement arch_vm_get_page_prot()
and/or arch_filter_pgprot() as well.

> +}
> +EXPORT_SYMBOL(vm_get_page_prot);
> -- 
> 2.25.1
> 
> 

-- 
Sincerely yours,
Mike.