Re: [PATCH] uaccess: add noop untagged_addr definition

[Andrey Konovalov <andreyknvl@google.com>]

On Tue, Jun 4, 2019 at 1:46 PM Koenig, Christian
<Christian.Koenig@amd.com> wrote:
>
> Am 04.06.19 um 13:44 schrieb Andrey Konovalov:
> > 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@arm.com>
> > Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > ---
> >   include/linux/mm.h | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 0e8834ac32b7..949d43e9c0b6 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -99,6 +99,10 @@ extern int mmap_rnd_compat_bits __read_mostly;
> >   #include <asm/pgtable.h>
> >   #include <asm/processor.h>
> >
> > +#ifndef untagged_addr
> > +#define untagged_addr(addr) (addr)
> > +#endif
> > +
>
> Maybe add a comment what tagging actually is? Cause that is not really
> obvious from the context.

Hi,

Do you mean a comment in the code or an explanation in the patch description?

Thanks!

>
> Christian.
>
> >   #ifndef __pa_symbol
> >   #define __pa_symbol(x)  __pa(RELOC_HIDE((unsigned long)(x), 0))
> >   #endif
>