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

From: Anshuman Khandual
Date: Thu Jun 16 2022 - 23:43:55 EST



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@xxxxxxxxxxxxxxxxxxxx>
>> Cc: linux-mm@xxxxxxxxx
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>> Acked-by: Christoph Hellwig <hch@xxxxxx>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>> ---
>> 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 ?