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

From: Anshuman Khandual <[email-masked]>
Date: Fri, 4 Feb 2022 08:27:37 +0530

On 2/3/22 11:45 PM, Mike Rapoport wrote:
> 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.

Just to minimize the code churn ! But I will be happy to open code them
here (and in other platforms) if that will be preferred.