Re: [PATCH V4 03/26] powerpc/mm: Move protection_map[] inside the platform

[Christophe Leroy]

Le 24/06/2022 à 06:43, Anshuman Khandual a écrit :
> This moves protection_map[] inside the platform and while here, also enable
> ARCH_HAS_VM_GET_PAGE_PROT on 32 bit platforms via DECLARE_VM_GET_PAGE_PROT.

Not only 32 bit platforms, also nohash 64 (aka book3e/64)

> 
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
>   arch/powerpc/Kconfig               |  2 +-
>   arch/powerpc/include/asm/pgtable.h | 20 +-------------------
>   arch/powerpc/mm/pgtable.c          | 24 ++++++++++++++++++++++++
>   3 files changed, 26 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index c2ce2e60c8f0..1035d172c7dd 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -140,7 +140,7 @@ config PPC
>   	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_HAS_UACCESS_FLUSHCACHE
>   	select ARCH_HAS_UBSAN_SANITIZE_ALL
> -	select ARCH_HAS_VM_GET_PAGE_PROT	if PPC_BOOK3S_64
> +	select ARCH_HAS_VM_GET_PAGE_PROT
>   	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>   	select ARCH_KEEP_MEMBLOCK
>   	select ARCH_MIGHT_HAVE_PC_PARPORT
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index d564d0ecd4cd..bf98db844579 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -20,25 +20,6 @@ struct mm_struct;
>   #include <asm/nohash/pgtable.h>
>   #endif /* !CONFIG_PPC_BOOK3S */
>   
> -/* Note due to the way vm flags are laid out, the bits are XWR */
> -#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
> -
>   #ifndef __ASSEMBLY__
>   
>   #ifndef MAX_PTRS_PER_PGD
> @@ -79,6 +60,7 @@ extern void paging_init(void);
>   void poking_init(void);
>   
>   extern unsigned long ioremap_bot;
> +extern pgprot_t protection_map[16] __ro_after_init;
>   
>   /*
>    * kern_addr_valid is intended to indicate whether an address is a valid
> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index e6166b71d36d..618f30d35b17 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -472,3 +472,27 @@ 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] __ro_after_init = {

I can't see any place where protection_map[] gets modified. This could 
be made const.

> +	[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
> +};
> +
> +#ifndef CONFIG_PPC_BOOK3S_64
> +DECLARE_VM_GET_PAGE_PROT
> +#endif