Re: [PATCH V3 2/2] mm/mmap: Drop generic protection_map[] array

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 17/06/2022 à 05:43, Anshuman Khandual a écrit :
> 
> 
> On 6/16/22 11:15, Christophe Leroy wrote:
>>
>> Le 16/06/2022 à 06:09, Anshuman Khandual a écrit :
>>> Move the protection_array[] array inside the arch for those platforms which
>>> do not enable ARCH_HAS_VM_GET_PAGE_PROT. Afterwards __SXXX/__PXX macros can
>>> be dropped completely which are now redundant.
>>>
>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>> Cc: linux-mm@kvack.org
>>> Cc: linux-kernel@vger.kernel.org
>>> Reported-by: kernel test robot <lkp@intel.com>
>>> Acked-by: Christoph Hellwig <hch@lst.de>
>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>>> ---
>>>    arch/alpha/include/asm/pgtable.h          | 17 -------
>>>    arch/alpha/mm/init.c                      | 21 +++++++++
>>>    arch/arc/include/asm/pgtable-bits-arcv2.h | 18 --------
>>>    arch/arc/mm/mmap.c                        | 19 ++++++++
>>>    arch/arm/include/asm/pgtable.h            | 17 -------
>>>    arch/arm/lib/uaccess_with_memcpy.c        |  2 +-
>>>    arch/arm/mm/mmu.c                         | 19 ++++++++
>>>    arch/csky/include/asm/pgtable.h           | 18 --------
>>>    arch/csky/mm/init.c                       | 19 ++++++++
>>>    arch/hexagon/include/asm/pgtable.h        | 27 ------------
>>>    arch/hexagon/mm/init.c                    | 41 +++++++++++++++++
>>>    arch/ia64/include/asm/pgtable.h           | 18 --------
>>>    arch/ia64/mm/init.c                       | 27 +++++++++++-
>>>    arch/loongarch/include/asm/pgtable-bits.h | 19 --------
>>>    arch/loongarch/mm/cache.c                 | 45 +++++++++++++++++++
>>>    arch/m68k/include/asm/mcf_pgtable.h       | 54 -----------------------
>>>    arch/m68k/include/asm/motorola_pgtable.h  | 22 ---------
>>>    arch/m68k/include/asm/sun3_pgtable.h      | 17 -------
>>>    arch/m68k/mm/mcfmmu.c                     | 54 +++++++++++++++++++++++
>>>    arch/m68k/mm/motorola.c                   | 19 ++++++++
>>>    arch/m68k/mm/sun3mmu.c                    | 19 ++++++++
>>>    arch/microblaze/include/asm/pgtable.h     | 17 -------
>>>    arch/microblaze/mm/init.c                 | 19 ++++++++
>>>    arch/mips/include/asm/pgtable.h           | 22 ---------
>>>    arch/mips/mm/cache.c                      |  2 +
>>>    arch/nios2/include/asm/pgtable.h          | 16 -------
>>>    arch/nios2/mm/init.c                      | 19 ++++++++
>>>    arch/openrisc/include/asm/pgtable.h       | 18 --------
>>>    arch/openrisc/mm/init.c                   | 19 ++++++++
>>>    arch/parisc/include/asm/pgtable.h         | 18 --------
>>>    arch/parisc/mm/init.c                     | 19 ++++++++
>>>    arch/powerpc/include/asm/pgtable.h        | 20 ---------
>>>    arch/powerpc/mm/book3s64/pgtable.c        | 24 +++-------
>>>    arch/powerpc/mm/pgtable.c                 | 20 +++++++++
>>>    arch/riscv/include/asm/pgtable.h          | 20 ---------
>>>    arch/riscv/mm/init.c                      | 19 ++++++++
>>>    arch/s390/include/asm/pgtable.h           | 17 -------
>>>    arch/s390/mm/mmap.c                       | 19 ++++++++
>>>    arch/sh/include/asm/pgtable.h             | 17 -------
>>>    arch/sh/mm/mmap.c                         | 19 ++++++++
>>>    arch/sparc/include/asm/pgtable_32.h       | 19 --------
>>>    arch/sparc/mm/init_32.c                   | 19 ++++++++
>>>    arch/sparc/mm/init_64.c                   |  2 +-
>>>    arch/um/include/asm/pgtable.h             | 17 -------
>>>    arch/um/kernel/mem.c                      | 19 ++++++++
>>>    arch/x86/um/mem_32.c                      |  2 +-
>>>    arch/xtensa/include/asm/pgtable.h         | 18 --------
>>>    arch/xtensa/mm/init.c                     | 19 ++++++++
>>>    include/linux/mm.h                        |  2 +-
>>>    mm/mmap.c                                 | 19 --------
>>>    50 files changed, 503 insertions(+), 489 deletions(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
>>> index 8ed2a80c896e..bd636295a794 100644
>>> --- a/arch/powerpc/include/asm/pgtable.h
>>> +++ b/arch/powerpc/include/asm/pgtable.h
>>> @@ -21,26 +21,6 @@ struct mm_struct;
>>>    #endif /* !CONFIG_PPC_BOOK3S */
>>>    
>>>    /* Note due to the way vm flags are laid out, the bits are XWR */
>>> -#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
>>> -#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
>>> -#endif
>>> -
>>>    #ifndef __ASSEMBLY__
>>>    
>>>    #ifndef MAX_PTRS_PER_PGD
>>> diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
>>> index d3b019b95c1d..de76dd4d447c 100644
>>> --- a/arch/powerpc/mm/book3s64/pgtable.c
>>> +++ b/arch/powerpc/mm/book3s64/pgtable.c
>>> @@ -551,25 +551,11 @@ unsigned long memremap_compat_align(void)
>>>    EXPORT_SYMBOL_GPL(memremap_compat_align);
>>>    #endif
>>>    
>>> -/* Note due to the way vm flags are laid out, the bits are XWR */
>>> -static const pgprot_t protection_map[16] = {
>>> -	[VM_NONE]					= PAGE_NONE,
>>> -	[VM_READ]					= PAGE_READONLY,
>>> -	[VM_WRITE]					= PAGE_COPY,
>>> -	[VM_WRITE | VM_READ]				= PAGE_COPY,
>>> -	[VM_EXEC]					= PAGE_READONLY_X,
>>> -	[VM_EXEC | VM_READ]				= PAGE_READONLY_X,
>>> -	[VM_EXEC | VM_WRITE]				= PAGE_COPY_X,
>>> -	[VM_EXEC | VM_WRITE | VM_READ]			= PAGE_COPY_X,
>>> -	[VM_SHARED]					= PAGE_NONE,
>>> -	[VM_SHARED | VM_READ]				= PAGE_READONLY,
>>> -	[VM_SHARED | VM_WRITE]				= PAGE_SHARED,
>>> -	[VM_SHARED | VM_WRITE | VM_READ]		= PAGE_SHARED,
>>> -	[VM_SHARED | VM_EXEC]				= PAGE_READONLY_X,
>>> -	[VM_SHARED | VM_EXEC | VM_READ]			= PAGE_READONLY_X,
>>> -	[VM_SHARED | VM_EXEC | VM_WRITE]		= PAGE_SHARED_X,
>>> -	[VM_SHARED | VM_EXEC | VM_WRITE | VM_READ]	= PAGE_SHARED_X
>>> -};
>>> +/*
>>> + * Generic declaration in (include/linux/mm.h) is not available
>>> + * here as the platform enables ARCH_HAS_VM_GET_PAGE_PROT.
>>> + */
>>> +extern pgprot_t protection_map[16];
>>>    
>>>    pgprot_t vm_get_page_prot(unsigned long vm_flags)
>>>    {
>>> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
>>> index e6166b71d36d..780fbecd7bf6 100644
>>> --- a/arch/powerpc/mm/pgtable.c
>>> +++ b/arch/powerpc/mm/pgtable.c
>>> @@ -472,3 +472,23 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea,
>>>    	return ret_pte;
>>>    }
>>>    EXPORT_SYMBOL_GPL(__find_linux_pte);
>>> +
>>> +/* Note due to the way vm flags are laid out, the bits are XWR */
>>> +pgprot_t protection_map[16] = {
>>
>> Was const previously, now back to non const ? Maybe due to a conflict
>> with linux/mm.h ? At least it should be __ro_after_init.
>>
> 
> Right, the generic declaration in linux/mm.h prevents different types
> for protection_map[] on different platforms. As mentioned before, may
> be we should move generic vm_get_page_prot() inside the platforms ?

Not sure that's the best way forward.

You can probably just drop the generic declaration of protection_map[] 
in linux/mm.h and have each architecture provides its own declaration of 
protection_map[], then you can keep a generic vm_get_page_prot()

Christophe