linux-kernel - Re: [PATCH] uaccess: add noop untagged

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Date:   Tue, 4 Jun 2019 11:49:52 +0000
From:   "Koenig, Christian" <Christian.Koenig@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        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>,
        "Kuehling, Felix" <Felix.Kuehling@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Leon Romanovsky <leon@...nel.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Dave Martin <Dave.Martin@....com>,
        Khalid Aziz <khalid.aziz@...cle.com>, enh <enh@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christoph Hellwig <hch@...radead.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>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>
Subject: Re: [PATCH] uaccess: add noop untagged_addr definition

Am 04.06.19 um 13:48 schrieb Andrey Konovalov:
> On Tue, Jun 4, 2019 at 1:46 PM Koenig, Christian
> <Christian.Koenig@....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@....com>
>>> Reviewed-by: Khalid Aziz <khalid.aziz@...cle.com>
>>> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.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?

The code, the patch description actually sounds good to me.

Christian.

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