Re: [PATCH V4 07/26] mm/mmap: Build protect protection_map[] with ARCH_HAS_VM_GET_PAGE_PROT

Christophe Leroy
2022-06-24T05:22:39Z

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@linux-foundation.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.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 */
>