From: Mark Rutland <mark.rutland@arm.com>
To: Daniel Axtens <dja@axtens.net>
Cc: kasan-dev@googlegroups.com, linux-mm@kvack.org, x86@kernel.org,
aryabinin@virtuozzo.com, glider@google.com, luto@kernel.org,
linux-kernel@vger.kernel.org, dvyukov@google.com,
christophe.leroy@c-s.fr, linuxppc-dev@lists.ozlabs.org,
gor@linux.ibm.com
Subject: Re: [PATCH v8 1/5] kasan: support backing vmalloc space with real shadow memory
Date: Mon, 14 Oct 2019 16:43:59 +0100 [thread overview]
Message-ID: <20191014154359.GC20438@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <20191001065834.8880-2-dja@axtens.net>
On Tue, Oct 01, 2019 at 04:58:30PM +1000, Daniel Axtens wrote:
> Hook into vmalloc and vmap, and dynamically allocate real shadow
> memory to back the mappings.
>
> Most mappings in vmalloc space are small, requiring less than a full
> page of shadow space. Allocating a full shadow page per mapping would
> therefore be wasteful. Furthermore, to ensure that different mappings
> use different shadow pages, mappings would have to be aligned to
> KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE.
>
> Instead, share backing space across multiple mappings. Allocate a
> backing page when a mapping in vmalloc space uses a particular page of
> the shadow region. This page can be shared by other vmalloc mappings
> later on.
>
> We hook in to the vmap infrastructure to lazily clean up unused shadow
> memory.
>
> To avoid the difficulties around swapping mappings around, this code
> expects that the part of the shadow region that covers the vmalloc
> space will not be covered by the early shadow page, but will be left
> unmapped. This will require changes in arch-specific code.
>
> This allows KASAN with VMAP_STACK, and may be helpful for architectures
> that do not have a separate module space (e.g. powerpc64, which I am
> currently working on). It also allows relaxing the module alignment
> back to PAGE_SIZE.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=202009
> Acked-by: Vasily Gorbik <gor@linux.ibm.com>
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> [Mark: rework shadow allocation]
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Sorry to point this out so late, but your S-o-B should come last in the
chain per Documentation/process/submitting-patches.rst. Judging by the
rest of that, I think you want something like:
Co-developed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com> [shadow rework]
Signed-off-by: Daniel Axtens <dja@axtens.net>
... leaving yourself as the Author in the headers.
Sorry to have made that more complicated!
[...]
> +static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
> + void *unused)
> +{
> + unsigned long page;
> +
> + page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);
> +
> + spin_lock(&init_mm.page_table_lock);
> +
> + if (likely(!pte_none(*ptep))) {
> + pte_clear(&init_mm, addr, ptep);
> + free_page(page);
> + }
There should be TLB maintenance between clearing the PTE and freeing the
page here.
Thanks,
Mark.
next prev parent reply other threads:[~2019-10-14 15:44 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-01 6:58 [PATCH v8 0/5] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 1/5] " Daniel Axtens
2019-10-01 10:17 ` Uladzislau Rezki
2019-10-02 1:23 ` Daniel Axtens
2019-10-02 7:13 ` Christophe Leroy
2019-10-02 11:49 ` Uladzislau Rezki
2019-10-07 8:02 ` Uladzislau Rezki
2019-10-11 5:15 ` Daniel Axtens
2019-10-11 19:57 ` Andrey Ryabinin
2019-10-14 13:57 ` Daniel Axtens
2019-10-14 15:27 ` Mark Rutland
2019-10-15 6:32 ` Daniel Axtens
2019-10-15 6:29 ` Daniel Axtens
2019-10-16 12:19 ` Andrey Ryabinin
2019-10-16 13:22 ` Mark Rutland
2019-10-18 10:43 ` Andrey Ryabinin
2019-10-28 7:39 ` Daniel Axtens
2019-10-28 1:26 ` Daniel Axtens
2019-10-14 15:43 ` Mark Rutland [this message]
2019-10-15 6:27 ` Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 2/5] kasan: add test for vmalloc Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 3/5] fork: support VMAP_STACK with KASAN_VMALLOC Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 4/5] x86/kasan: support KASAN_VMALLOC Daniel Axtens
2019-10-01 6:58 ` [PATCH v8 5/5] kasan debug: track pages allocated for vmalloc shadow Daniel Axtens
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