From: David Gow <davidgow@google.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>,
Patricia Alfonso <trishalfonso@google.com>,
Jeff Dike <jdike@addtoit.com>,
Richard Weinberger <richard@nod.at>,
Anton Ivanov <anton.ivanov@cambridgegreys.com>,
Dmitry Vyukov <dvyukov@google.com>,
Brendan Higgins <brendanhiggins@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andrey Konovalov <andreyknvl@gmail.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
kasan-dev <kasan-dev@googlegroups.com>,
linux-um <linux-um@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Daniel Latypov <dlatypov@google.com>,
Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [PATCH v2 2/2] UML: add support for KASAN under x86_64
Date: Thu, 30 Jun 2022 15:53:22 +0800 [thread overview]
Message-ID: <CABVgOSmcwGa4tw8EvuxbeOvrTLh8d7V3mFxGyj2spnqqWkFp9Q@mail.gmail.com> (raw)
In-Reply-To: <1a4e51a4d2ed51e7ae1ff55bd4da6a47fad7c0bf.camel@sipsolutions.net>
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On Mon, May 30, 2022 at 1:04 AM Johannes Berg <johannes@sipsolutions.net> wrote:
>
> On Fri, 2022-05-27 at 11:56 -0700, David Gow wrote:
> >
> > The UML-specific KASAN initializer uses mmap to map the roughly 2.25TB
>
> You say 2.25TB here, and
>
> > +config KASAN_SHADOW_OFFSET
> > + hex
> > + depends on KASAN
> > + default 0x100000000000
> > + help
> > + This is the offset at which the ~2.25TB of shadow memory is
>
> here too, of course.
>
> But I notice that I get ~16TB address space use when running,
>
> > +/* used in kasan_mem_to_shadow to divide by 8 */
> > +#define KASAN_SHADOW_SCALE_SHIFT 3
> > +
> > +#ifdef CONFIG_X86_64
> > +#define KASAN_HOST_USER_SPACE_END_ADDR 0x00007fffffffffffUL
> > +/* KASAN_SHADOW_SIZE is the size of total address space divided by 8 */
> > +#define KASAN_SHADOW_SIZE ((KASAN_HOST_USER_SPACE_END_ADDR + 1) >> \
> > + KASAN_SHADOW_SCALE_SHIFT)
>
> because this ends up being 0x100000000000, i.e. 16 TiB.
>
> Is that intentional? Was something missed? Maybe
> KASAN_HOST_USER_SPACE_END_ADDR was too big?
>
> It doesn't really matter, but I guess then the documentation should be
> updated.
Whoops, the amount of shadow memory allocated was changed for v1 of
this patch (it was ~2.25 TB in the original RFC). I've updated these
comments in v3:
https://lore.kernel.org/lkml/20220630074757.2739000-2-davidgow@google.com/
-- David
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next prev parent reply other threads:[~2022-06-30 7:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-27 18:55 [PATCH v2 1/2] mm: Add PAGE_ALIGN_DOWN macro David Gow
2022-05-27 18:56 ` [PATCH v2 2/2] UML: add support for KASAN under x86_64 David Gow
2022-05-27 20:14 ` Johannes Berg
2022-05-29 17:55 ` Johannes Berg
2022-06-30 7:53 ` David Gow
2022-05-29 17:04 ` Johannes Berg
2022-06-30 7:53 ` David Gow [this message]
2022-05-30 18:03 ` Andrey Konovalov
2022-06-30 7:54 ` David Gow
2022-05-30 0:06 ` [PATCH v2 1/2] mm: Add PAGE_ALIGN_DOWN macro Andrew Morton
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