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Message-ID: <7cf922f4-2367-e173-0280-cb498391d9f7@csgroup.eu>
Date:   Thu, 16 Jun 2022 05:45:39 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
CC:     "hch@...radead.org" <hch@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel test robot <lkp@...el.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH V3 2/2] mm/mmap: Drop generic protection_map[] array



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@...ux-foundation.org>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Reported-by: kernel test robot <lkp@...el.com>
> Acked-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....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.

> +	[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
> +};
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 2254c1980c8e..65b7f3d9ff87 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -420,11 +420,11 @@ extern unsigned int kobjsize(const void *objp);
>   #endif
>   #define VM_FLAGS_CLEAR	(ARCH_VM_PKEY_FLAGS | VM_ARCH_CLEAR)
>   
> -#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
>   /*
>    * mapping from the currently active vm_flags protection bits (the
>    * low four bits) to a page protection mask..
>    */
> +#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
>   extern pgprot_t protection_map[16];
>   #endif
>   
> diff --git a/mm/mmap.c b/mm/mmap.c
> index e66920414945..012261c8efb8 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -102,25 +102,6 @@ static void unmap_region(struct mm_struct *mm,
>    *								x: (yes) yes
>    */
>   #ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
> -pgprot_t protection_map[16] __ro_after_init = {
> -	[VM_NONE]					= __P000,
> -	[VM_READ]					= __P001,
> -	[VM_WRITE]					= __P010,
> -	[VM_WRITE | VM_READ]				= __P011,
> -	[VM_EXEC]					= __P100,
> -	[VM_EXEC | VM_READ]				= __P101,
> -	[VM_EXEC | VM_WRITE]				= __P110,
> -	[VM_EXEC | VM_WRITE | VM_READ]			= __P111,
> -	[VM_SHARED]					= __S000,
> -	[VM_SHARED | VM_READ]				= __S001,
> -	[VM_SHARED | VM_WRITE]				= __S010,
> -	[VM_SHARED | VM_WRITE | VM_READ]		= __S011,
> -	[VM_SHARED | VM_EXEC]				= __S100,
> -	[VM_SHARED | VM_EXEC | VM_READ]			= __S101,
> -	[VM_SHARED | VM_EXEC | VM_WRITE]		= __S110,
> -	[VM_SHARED | VM_EXEC | VM_WRITE | VM_READ]	= __S111
> -};
> -
>   pgprot_t vm_get_page_prot(unsigned long vm_flags)
>   {
>   	return protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];

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