From: Benjamin Herrenschmidt <benh@kernel•crashing.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux•vnet.ibm.com>,
paulus@samba•org, mpe@ellerman•id.au, ryabinin.a.a@gmail•com
Cc: linuxppc-dev@lists•ozlabs.org
Subject: Re: [RFC PATCH V1 0/8] KASAN ppc64 support
Date: Mon, 17 Aug 2015 20:01:24 +1000 [thread overview]
Message-ID: <1439805684.2416.16.camel@kernel.crashing.org> (raw)
In-Reply-To: <87mvxqp7l5.fsf@linux.vnet.ibm.com>
On Mon, 2015-08-17 at 15:20 +0530, Aneesh Kumar K.V wrote:
> For kernel linear mapping, our address space looks like
> 0xc000000000000000 - 0xc0003fffffffffff (64TB)
>
> We can't have virtual address(effective address) above that range
> in 0xc region. Hence in-order to shadow the linear mapping, I am
> using region 0xe. ie, the shadow mapping now looks liwe
>
> 0xc000000000000000 -> 0xe000000000000000
Why ? IE. Why can't you put the shadow at address +64T and have it work
for everything ?
.../...
> Another reason why inline instrumentation is difficult is that for
> inline instrumentation to work, we need to create a mapping for
> _possible_
> virtual address space before kasan is fully initialized. ie, we need
> to create page table entries for the shadow of the entire 64TB range,
> with zero page, even though we have lesser ram. We definitely can't
> bolt those entries. I am yet to get the shadow for kernel linear
> mapping to work without bolting. Also we will have to get the page
> table allocated for that, because we can't share page table entries.
> Our fault path use pte entries for storing hash slot index.
Hrm, that means we might want to start considering a page table to
cover the linear mapping...
> If we are ok to steal part of that 64TB range, for kasan mapping , ie
> we make shadow of each region part of the same region, may be we can
> get inline instrumentation to work. But that still doesn't solve the
> page table allocation overhead issue mentioned above.
>
> -aneesh
next prev parent reply other threads:[~2015-08-17 10:01 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-17 6:36 [RFC PATCH V1 0/8] KASAN ppc64 support Aneesh Kumar K.V
2015-08-17 6:36 ` [RFC PATCH V1 1/8] powerpc/mm: Add virt_to_pfn and use this instead of opencoding Aneesh Kumar K.V
2015-08-17 6:36 ` [RFC PATCH V1 2/8] kasan: MODULE_VADDR is not available on all archs Aneesh Kumar K.V
2015-08-17 6:36 ` [RFC PATCH V1 3/8] kasan: Rename kasan_enabled to kasan_report_enabled Aneesh Kumar K.V
2015-08-17 6:36 ` [RFC PATCH V1 4/8] kasan: Don't use kasan shadow pointer in generic functions Aneesh Kumar K.V
2015-08-17 11:36 ` Andrey Ryabinin
2015-08-18 5:29 ` Aneesh Kumar K.V
2015-08-18 9:12 ` Andrey Ryabinin
2015-08-17 6:36 ` [RFC PATCH V1 5/8] kasan: Enable arch to hook into kasan callbacks Aneesh Kumar K.V
2015-08-17 6:36 ` [RFC PATCH V1 6/8] kasan: Allow arch to overrride kasan shadow offsets Aneesh Kumar K.V
2015-08-17 6:36 ` [RFC PATCH V1 7/8] powerpc/mm: kasan: Add kasan support for ppc64 Aneesh Kumar K.V
2015-08-17 12:13 ` Andrey Ryabinin
2015-08-17 12:17 ` Andrey Ryabinin
2015-08-18 5:36 ` Aneesh Kumar K.V
2015-08-18 8:40 ` Andrey Ryabinin
2015-08-18 5:34 ` Aneesh Kumar K.V
2015-08-17 6:36 ` [RFC PATCH V1 8/8] powerpc: Disable kasan for kernel/ and mm/ directory Aneesh Kumar K.V
2015-08-17 6:54 ` [RFC PATCH V1 0/8] KASAN ppc64 support Benjamin Herrenschmidt
2015-08-17 9:50 ` Aneesh Kumar K.V
2015-08-17 10:01 ` Benjamin Herrenschmidt [this message]
2015-08-17 10:50 ` Aneesh Kumar K.V
2015-08-17 11:21 ` Benjamin Herrenschmidt
2015-08-17 11:29 ` Andrey Ryabinin
2015-08-18 5:42 ` Aneesh Kumar K.V
2015-08-18 8:50 ` Andrey Ryabinin
2015-08-18 9:21 ` Aneesh Kumar K.V
2015-08-18 9:30 ` Andrey Ryabinin
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