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From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Dmitry Vyukov <dvyukov@google.com>,
	"Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Alexander Potapenko <glider@google.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"x86@kernel.org" <x86@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Andy Lutomirski <luto@amacapital.net>,
	linux-arch@vger.kernel.org,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: KASAN vs. boot-time switching between 4- and 5-level paging
Date: Mon, 29 May 2017 14:18:52 +0300	[thread overview]
Message-ID: <71e11033-f95c-887f-4e4e-351bcc3df71e@virtuozzo.com> (raw)
In-Reply-To: <CACT4Y+YyFWg3fbj4ta3tSKoeBaw7hbL2YoBatAFiFB1_cMg9=Q@mail.gmail.com>



On 05/29/2017 01:02 PM, Dmitry Vyukov wrote:
> On Sat, May 27, 2017 at 12:10 AM, Kirill A. Shutemov
> <kirill@shutemov.name> wrote:
>> On Thu, May 25, 2017 at 11:33:33PM +0300, Kirill A. Shutemov wrote:
>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>>> index 0bf81e837cbf..c795207d8a3c 100644
>>> --- a/arch/x86/Kconfig
>>> +++ b/arch/x86/Kconfig
>>> @@ -100,7 +100,7 @@ config X86
>>>       select HAVE_ARCH_AUDITSYSCALL
>>>       select HAVE_ARCH_HUGE_VMAP              if X86_64 || X86_PAE
>>>       select HAVE_ARCH_JUMP_LABEL
>>> -     select HAVE_ARCH_KASAN                  if X86_64 && SPARSEMEM_VMEMMAP
>>> +     select HAVE_ARCH_KASAN                  if X86_64 && SPARSEMEM_VMEMMAP && !X86_5LEVEL
>>>       select HAVE_ARCH_KGDB
>>>       select HAVE_ARCH_KMEMCHECK
>>>       select HAVE_ARCH_MMAP_RND_BITS          if MMU
>>
>> Looks like KASAN will be a problem for boot-time paging mode switching.
>> It wants to know CONFIG_KASAN_SHADOW_OFFSET at compile-time to pass to
>> gcc -fasan-shadow-offset=. But this value varies between paging modes...
>>
>> I don't see how to solve it. Folks, any ideas?
> 
> +kasan-dev
> 
> I wonder if we can use the same offset for both modes. If we use
> 0xFFDFFC0000000000 as start of shadow for 5 levels, then the same
> offset that we use for 4 levels (0xdffffc0000000000) will also work
> for 5 levels. Namely, ending of 5 level shadow will overlap with 4
> level mapping (both end at 0xfffffbffffffffff), but 5 level mapping
> extends towards lower addresses. The current 5 level start of shadow
> is actually close -- 0xffd8000000000000 and it seems that the required
> space after it is unused at the moment (at least looking at mm.txt).
> So just try to move it to 0xFFDFFC0000000000?
> 

Yeah, this should work, but note that 0xFFDFFC0000000000 is not PGDIR aligned address. Our init code
assumes that kasan shadow stars and ends on the PGDIR aligned address.
Fortunately this is fixable, we'd need two more pages for page tables to map unaligned start/end
of the shadow.

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  reply	other threads:[~2017-05-29 11:17 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-25 20:33 [PATCHv1, RFC 0/8] Boot-time switching between 4- and 5-level paging Kirill A. Shutemov
2017-05-25 20:33 ` [PATCHv1, RFC 1/8] x86/boot/compressed/64: Detect and handle 5-level paging at boot-time Kirill A. Shutemov
2017-05-25 20:33 ` [PATCHv1, RFC 2/8] x86/mm: Make virtual memory layout movable for CONFIG_X86_5LEVEL Kirill A. Shutemov
2017-05-25 20:33 ` [PATCHv1, RFC 3/8] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable Kirill A. Shutemov
2017-05-25 20:33 ` [PATCHv1, RFC 4/8] x86/mm: Handle boot-time paging mode switching at early boot Kirill A. Shutemov
2017-05-25 20:33 ` [PATCHv1, RFC 5/8] x86/mm: Fold p4d page table layer at runtime Kirill A. Shutemov
2017-05-27 15:09   ` Brian Gerst
2017-05-27 22:46     ` Kirill A. Shutemov
2017-05-27 22:56       ` Brian Gerst
2017-05-25 20:33 ` [PATCHv1, RFC 6/8] x86/mm: Replace compile-time checks for 5-level with runtime-time Kirill A. Shutemov
2017-05-25 20:33 ` [PATCHv1, RFC 7/8] x86/mm: Hacks for boot-time switching between 4- and 5-level paging Kirill A. Shutemov
2017-05-26 22:10   ` KASAN vs. " Kirill A. Shutemov
2017-05-29 10:02     ` Dmitry Vyukov
2017-05-29 11:18       ` Andrey Ryabinin [this message]
2017-05-29 11:19         ` Dmitry Vyukov
2017-05-29 11:45           ` Andrey Ryabinin
2017-05-29 12:46             ` Andrey Ryabinin
2017-06-01 14:56               ` Andrey Ryabinin
2017-07-10 12:33                 ` Kirill A. Shutemov
2017-07-10 12:43                   ` Dmitry Vyukov
2017-07-10 14:17                     ` Kirill A. Shutemov
2017-07-10 15:56                       ` Andy Lutomirski
2017-07-10 18:47                         ` Kirill A. Shutemov
2017-07-10 20:07                           ` Andy Lutomirski
2017-07-10 21:24                             ` Kirill A. Shutemov
2017-07-11  0:30                               ` Andy Lutomirski
2017-07-11 10:35                                 ` Kirill A. Shutemov
2017-07-11 15:06                                   ` Andy Lutomirski
2017-07-11 15:15                                     ` Andrey Ryabinin
2017-07-11 16:45                                       ` Andrey Ryabinin
2017-07-11 17:03                                         ` Kirill A. Shutemov
2017-07-11 17:29                                           ` Andrey Ryabinin
2017-07-11 19:05                                             ` Kirill A. Shutemov
2017-07-13 12:58                                               ` Andrey Ryabinin
2017-07-13 13:52                                                 ` Kirill A. Shutemov
2017-07-13 14:15                                                   ` Kirill A. Shutemov
2017-07-13 14:19                                                     ` Andrey Ryabinin
2017-07-24 12:13                                                       ` Kirill A. Shutemov
2017-07-24 14:07                                                         ` Andrey Ryabinin
2017-07-10 16:57                   ` Andrey Ryabinin
2017-05-25 20:33 ` [PATCHv1, RFC 8/8] x86/mm: Allow to boot without la57 if CONFIG_X86_5LEVEL=y Kirill A. Shutemov
2017-05-25 23:24 ` [PATCHv1, RFC 0/8] Boot-time switching between 4- and 5-level paging Linus Torvalds
2017-05-26  0:40   ` Andy Lutomirski
2017-05-26  4:18     ` Kevin Easton
2017-05-26  7:21       ` Andy Lutomirski
2017-05-26 13:00   ` Kirill A. Shutemov
2017-05-26 13:35     ` Andi Kleen
2017-05-26 15:51     ` Linus Torvalds
2017-05-26 15:58       ` Kirill A. Shutemov
2017-05-26 16:13         ` Linus Torvalds
2017-05-26 18:24       ` hpa
2017-05-26 19:23         ` Dave Hansen
2017-05-26 19:36           ` hpa
2017-05-26 19:40     ` hpa

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