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

From: Christophe Leroy
Date: Fri Jun 17 2022 - 01:40:45 EST



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@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 ?

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