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SubjectRe: [PATCH v4 03/12] mm: Reserve asm-generic prot flag 0x10 for arch use
On Wed, Dec 11, 2019 at 03:41:57PM +0000, Mark Brown wrote:
> From: Dave Martin <Dave.Martin@arm.com>
>
> The asm-generic mman definitions are used by a few architectures
> that also define an arch-specific PROT flag with value 0x10. This
> currently applies to sparc and powerpc, and arm64 will soon join
> in.
>
> To help future maintainers, document the use of this flag in the
> asm-generic header too.
>
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
> include/uapi/asm-generic/mman-common.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
> index c160a5354eb6..81442d2aaecb 100644
> --- a/include/uapi/asm-generic/mman-common.h
> +++ b/include/uapi/asm-generic/mman-common.h
> @@ -11,6 +11,7 @@
> #define PROT_WRITE 0x2 /* page can be written */
> #define PROT_EXEC 0x4 /* page can be executed */
> #define PROT_SEM 0x8 /* page may be used for atomic ops */
> + /* 0x10 reserved for arch-specific use */
> #define PROT_NONE 0x0 /* page can not be accessed */
> #define PROT_GROWSDOWN 0x01000000 /* mprotect flag: extend change to start of growsdown vma */
> #define PROT_GROWSUP 0x02000000 /* mprotect flag: extend change to end of growsup vma */

Since the BTI will likely be merged before the MTE series, please
consider reserving 0x20 as well. The updated patch, acked by Arnd:

https://lore.kernel.org/linux-arm-kernel/20191211184027.20130-2-catalin.marinas@arm.com/

--
Catalin

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