Re: [RFC 1/3] mm/vma: Define a default value for VM_DATA_DEFAULT_FLAGS

[Vlastimil Babka]

On 3/2/20 7:47 AM, Anshuman Khandual wrote:
> There are many platforms with exact same value for VM_DATA_DEFAULT_FLAGS
> This creates a default value for VM_DATA_DEFAULT_FLAGS in line with the
> existing VM_STACK_DEFAULT_FLAGS. While here, also define some more macros
> with standard VMA access flag combinations that are used frequently across
> many platforms. Apart from simplification, this reduces code duplication
> as well.
> 
> Cc: Richard Henderson <rth@xxxxxxxxxxx>
> Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Mark Salter <msalter@xxxxxxxxxx>
> Cc: Guo Ren <guoren@xxxxxxxxxx>
> Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
> Cc: Brian Cain <bcain@xxxxxxxxxxxxxx>
> Cc: Tony Luck <tony.luck@xxxxxxxxx>
> Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> Cc: Michal Simek <monstr@xxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Paul Burton <paulburton@xxxxxxxxxx>
> Cc: Nick Hu <nickhu@xxxxxxxxxxxxx>
> Cc: Ley Foon Tan <ley.foon.tan@xxxxxxxxx>
> Cc: Jonas Bonn <jonas@xxxxxxxxxxxx>
> Cc: "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: Rich Felker <dalias@xxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Guan Xuetao <gxt@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Jeff Dike <jdike@xxxxxxxxxxx>
> Cc: Chris Zankel <chris@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: linux-alpha@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-snps-arc@xxxxxxxxxxxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-c6x-dev@xxxxxxxxxxxxx
> Cc: uclinux-h8-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: linux-hexagon@xxxxxxxxxxxxxxx
> Cc: linux-ia64@xxxxxxxxxxxxxxx
> Cc: linux-m68k@xxxxxxxxxxxxxxxxxxxx
> Cc: linux-mips@xxxxxxxxxxxxxxx
> Cc: nios2-dev@xxxxxxxxxxxxxxxxxxxxxx
> Cc: openrisc@xxxxxxxxxxxxxxxxxxxx
> Cc: linux-parisc@xxxxxxxxxxxxxxx
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx
> Cc: linux-s390@xxxxxxxxxxxxxxx
> Cc: linux-sh@xxxxxxxxxxxxxxx
> Cc: sparclinux@xxxxxxxxxxxxxxx
> Cc: linux-um@xxxxxxxxxxxxxxxxxxx
> Cc: linux-xtensa@xxxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>

Nit:

> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index b0e53ef13ff1..7a764ae6ab68 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -342,6 +342,21 @@ extern unsigned int kobjsize(const void *objp);
>  /* Bits set in the VMA until the stack is in its final location */
>  #define VM_STACK_INCOMPLETE_SETUP	(VM_RAND_READ | VM_SEQ_READ)
>  
> +#define TASK_EXEC ((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0)
> +
> +/* Common data flag combinations */
> +#define VM_DATA_FLAGS_TSK_EXEC	(VM_READ | VM_WRITE | TASK_EXEC | \
> +				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
> +#define VM_DATA_FLAGS_NON_EXEC	(VM_READ | VM_WRITE | VM_MAYREAD | \
> +				 VM_MAYWRITE | VM_MAYEXEC)
> +#define VM_DATA_FLAGS_EXEC	(VM_READ | VM_WRITE | VM_EXEC | \
> +				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
> +
> +#ifndef VM_DATA_DEFAULT_FLAGS		/* arch can override this */
> +#define VM_DATA_DEFAULT_FLAGS	(VM_READ | VM_WRITE | VM_EXEC | \
> +				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)

Should you use VM_DATA_FLAGS_EXEC here? Yeah one more macro to expand, but it's
right above this.

> +#endif
> +
>  #ifndef VM_STACK_DEFAULT_FLAGS		/* arch can override this */
>  #define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS
>  #endif
>