linux-kernel - Re: [PATCH v15 01/17] uaccess: add untagged

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Date:   Wed, 29 May 2019 08:49:09 -0600
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        linux-media@...r.kernel.org, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>,
        Yishai Hadas <yishaih@...lanox.com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Alexander Deucher <Alexander.Deucher@....com>,
        Christian Koenig <Christian.Koenig@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Leon Romanovsky <leon@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Robin Murphy <robin.murphy@....com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Dave Martin <Dave.Martin@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>
Subject: Re: [PATCH v15 01/17] uaccess: add untagged_addr definition for
 other arches

On Mon, 2019-05-06 at 18:30 +0200, Andrey Konovalov wrote:
> To allow arm64 syscalls to accept tagged pointers from userspace, we
> must
> untag them when they are passed to the kernel. Since untagging is
> done in
> generic parts of the kernel, the untagged_addr macro needs to be
> defined
> for all architectures.
> 
> Define it as a noop for architectures other than arm64.
> 
> Acked-by: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> ---
>  include/linux/mm.h | 4 ++++
>  1 file changed, 4 insertions(+)

As discussed in the other thread Chris started, there is a generic need
to untag addresses in kernel and this patch gets us ready for that.

Reviewed-by: Khalid Aziz <khalid.aziz@...cle.com>

> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 6b10c21630f5..44041df804a6 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
> +
>  #ifndef __pa_symbol
>  #define __pa_symbol(x)  __pa(RELOC_HIDE((unsigned long)(x), 0))
>  #endif