linux-kernel - Re: [PATCH V4 07/26] mm/mmap: Build protect protection_map[] with ARCH_HAS_VM_GET_PAGE

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Date:   Fri, 24 Jun 2022 05:22:39 +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>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
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Subject: Re: [PATCH V4 07/26] mm/mmap: Build protect protection_map[] with
 ARCH_HAS_VM_GET_PAGE_PROT



Le 24/06/2022 à 06:43, Anshuman Khandual a écrit :
> protection_map[] has already been moved inside those platforms which enable

Usually "already" means before your series.

Your series is the one that moves protection_map[] so I would have just 
said "Now that protection_map[] has been moved inside those platforms 
which enable ...."

> ARCH_HAS_VM_GET_PAGE_PROT. Hence generic protection_map[] array now can be
> protected with CONFIG_ARCH_HAS_VM_GET_PAGE_PROT intead of __P000.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
>   include/linux/mm.h | 2 +-
>   mm/mmap.c          | 5 +----
>   2 files changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 237828c2bae2..70d900f6df43 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -424,7 +424,7 @@ extern unsigned int kobjsize(const void *objp);
>    * mapping from the currently active vm_flags protection bits (the
>    * low four bits) to a page protection mask..
>    */
> -#ifdef __P000
> +#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
>   extern pgprot_t protection_map[16];

Is this declaration still needed ? I have the feeling that 
protection_map[] is only used in mm/mmap.c now.

>   #endif
>   
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 55c30aee3999..43db3bd49071 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -101,7 +101,7 @@ static void unmap_region(struct mm_struct *mm,
>    *								w: (no) no
>    *								x: (yes) yes
>    */
> -#ifdef __P000
> +#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
>   pgprot_t protection_map[16] __ro_after_init = {

Should this be static, as it seems to now be used only in this file ?
And it could also be 'const' instead of __ro_after_init.

>   	[VM_NONE]					= __P000,
>   	[VM_READ]					= __P001,
> @@ -120,9 +120,6 @@ pgprot_t protection_map[16] __ro_after_init = {
>   	[VM_SHARED | VM_EXEC | VM_WRITE]		= __S110,
>   	[VM_SHARED | VM_EXEC | VM_WRITE | VM_READ]	= __S111
>   };
> -#endif
> -
> -#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
>   DECLARE_VM_GET_PAGE_PROT
>   #endif	/* CONFIG_ARCH_HAS_VM_GET_PAGE_PROT */
>