Re: [PATCH v2] uaccess: add noop untagged_addr definition

[Jason Gunthorpe]

On Tue, Jun 04, 2019 at 02:04:47PM +0200, Andrey Konovalov wrote:
> Architectures that support memory tagging have a need to perform untagging
> (stripping the tag) in various parts of the kernel. This patch adds an
> untagged_addr() macro, which is defined as noop for architectures that do
> not support memory tagging. The oncoming patch series will define it at
> least for sparc64 and arm64.
> 
> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Reviewed-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>  include/linux/mm.h | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 0e8834ac32b7..dd0b5f4e1e45 100644
> +++ b/include/linux/mm.h
> @@ -99,6 +99,17 @@ extern int mmap_rnd_compat_bits __read_mostly;
>  #include <asm/pgtable.h>
>  #include <asm/processor.h>
>  
> +/*
> + * Architectures that support memory tagging (assigning tags to memory regions,
> + * embedding these tags into addresses that point to these memory regions, and
> + * checking that the memory and the pointer tags match on memory accesses)
> + * redefine this macro to strip tags from pointers.
> + * It's defined as noop for arcitectures that don't support memory tagging.
> + */
> +#ifndef untagged_addr
> +#define untagged_addr(addr) (addr)

Can you please make this a static inline instead of this macro? Then
we can actually know what the input/output types are supposed to be.

Is it

static inline unsigned long untagged_addr(void __user *ptr) {return ptr;}

?

Which would sort of make sense to me.

Jason