linux-kernel - Re: [PATCHv7 03/19] x86/kasan: Use the same shadow offset for 4- and 5-level paging

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Date:   Thu, 28 Sep 2017 10:15:12 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Borislav Petkov <bp@...e.de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: Re: [PATCHv7 03/19] x86/kasan: Use the same shadow offset for 4- and
 5-level paging


* Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> wrote:

> We are going to support boot-time switching between 4- and 5-level
> paging. For KASAN it means we cannot have different KASAN_SHADOW_OFFSET
> for different paging modes: the constant is passed to gcc to generate
> code and cannot be changed at runtime.
> 
> This patch changes KASAN code to use 0xdffffc0000000000 as shadow offset
> for both 4- and 5-level paging.
> 
> For 5-level paging it means that shadow memory region is not aligned to
> PGD boundary anymore and we have to handle unaligned parts of the region
> properly.
> 
> In addition, we have to exclude paravirt code from KASAN instrumentation
> as we now use set_pgd() before KASAN is fully ready.
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> [kirill.shutemov@...ux.intel.com: clenaup, changelog message]
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Bad SOB chain. If Andrey the true author of this patch then it be reflected in a 
"From:" line.

> ---
>  arch/x86/Kconfig            |  1 -
>  arch/x86/kernel/Makefile    |  3 +-
>  arch/x86/mm/kasan_init_64.c | 86 ++++++++++++++++++++++++++++++++++-----------
>  3 files changed, 67 insertions(+), 23 deletions(-)

This is a lot of complex code added with exactly zero lines of comments that 
explains all the complexity ...

Thanks,

	Ingo