From: Lecopzer Chen <lecopzer@gmail.com>
To: will@kernel.org
Cc: akpm@linux-foundation.org, andreyknvl@google.com,
ardb@kernel.org, aryabinin@virtuozzo.com, broonie@kernel.org,
catalin.marinas@arm.com, dan.j.williams@intel.com,
dvyukov@google.com, glider@google.com, gustavoars@kernel.org,
kasan-dev@googlegroups.com, lecopzer.chen@mediatek.com,
lecopzer@gmail.com, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
linux-mm@kvack.org, linux@roeck-us.net, robin.murphy@arm.com,
rppt@kernel.org, tyhicks@linux.microsoft.com,
vincenzo.frascino@arm.com, yj.chiang@mediatek.com
Subject: Re: [PATCH v2 1/4] arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC
Date: Fri, 5 Feb 2021 00:37:21 +0800 [thread overview]
Message-ID: <20210204163721.91295-1-lecopzer@gmail.com> (raw)
In-Reply-To: <20210204150100.GE20815@willie-the-truck>
> On Thu, Feb 04, 2021 at 10:46:12PM +0800, Lecopzer Chen wrote:
> > > On Sat, Jan 09, 2021 at 06:32:49PM +0800, Lecopzer Chen wrote:
> > > > Linux support KAsan for VMALLOC since commit 3c5c3cfb9ef4da9
> > > > ("kasan: support backing vmalloc space with real shadow memory")
> > > >
> > > > Like how the MODULES_VADDR does now, just not to early populate
> > > > the VMALLOC_START between VMALLOC_END.
> > > > similarly, the kernel code mapping is now in the VMALLOC area and
> > > > should keep these area populated.
> > > >
> > > > Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
> > > > ---
> > > > arch/arm64/mm/kasan_init.c | 23 ++++++++++++++++++-----
> > > > 1 file changed, 18 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> > > > index d8e66c78440e..39b218a64279 100644
> > > > --- a/arch/arm64/mm/kasan_init.c
> > > > +++ b/arch/arm64/mm/kasan_init.c
> > > > @@ -214,6 +214,7 @@ static void __init kasan_init_shadow(void)
> > > > {
> > > > u64 kimg_shadow_start, kimg_shadow_end;
> > > > u64 mod_shadow_start, mod_shadow_end;
> > > > + u64 vmalloc_shadow_start, vmalloc_shadow_end;
> > > > phys_addr_t pa_start, pa_end;
> > > > u64 i;
> > > >
> > > > @@ -223,6 +224,9 @@ static void __init kasan_init_shadow(void)
> > > > mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
> > > > mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
> > > >
> > > > + vmalloc_shadow_start = (u64)kasan_mem_to_shadow((void *)VMALLOC_START);
> > > > + vmalloc_shadow_end = (u64)kasan_mem_to_shadow((void *)VMALLOC_END);
> > > > +
> > > > /*
> > > > * We are going to perform proper setup of shadow memory.
> > > > * At first we should unmap early shadow (clear_pgds() call below).
> > > > @@ -241,12 +245,21 @@ static void __init kasan_init_shadow(void)
> > > >
> > > > kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
> > > > (void *)mod_shadow_start);
> > > > - kasan_populate_early_shadow((void *)kimg_shadow_end,
> > > > - (void *)KASAN_SHADOW_END);
> > > > + if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
> > >
> > > Do we really need yet another CONFIG option for KASAN? What's the use-case
> > > for *not* enabling this if you're already enabling one of the KASAN
> > > backends?
> >
> > As I know, KASAN_VMALLOC now only supports KASAN_GENERIC and also
> > KASAN_VMALLOC uses more memory to map real shadow memory (1/8 of vmalloc va).
>
> The shadow is allocated dynamically though, isn't it?
Yes, but It's still a cost.
> > There should be someone can enable KASAN_GENERIC but can't use VMALLOC
> > due to memory issue.
>
> That doesn't sound particularly realistic to me. The reason I'm pushing here
> is because I would _really_ like to move to VMAP stack unconditionally, and
> that would effectively force KASAN_VMALLOC to be set if KASAN is in use.
>
> So unless there's a really good reason not to do that, please can we make
> this unconditional for arm64? Pretty please?
I think it's fine since we have a good reason.
Also if someone have memory issue in KASAN_VMALLOC,
they can use SW_TAG, right?
However the SW_TAG/HW_TAG is not supported VMALLOC yet.
So the code would be like
if (IS_ENABLED(CONFIG_KASAN_GENERIC))
/* explain the relationship between
* KASAN_GENERIC and KASAN_VMALLOC in arm64
* XXX: because we want VMAP stack....
*/
kasan_populate_early_shadow((void *)vmalloc_shadow_end,
(void *)KASAN_SHADOW_END);
else {
kasan_populate_early_shadow((void *)kimg_shadow_end,
(void *)KASAN_SHADOW_END);
if (kimg_shadow_start > mod_shadow_end)
kasan_populate_early_shadow((void *)mod_shadow_end,
(void *)kimg_shadow_start);
}
and the arch/arm64/Kconfig will add
select KASAN_VMALLOC if KASAN_GENERIC
Is this code same as your thought?
BRs,
Lecopzer
next prev parent reply other threads:[~2021-02-04 16:37 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-09 10:32 [PATCH v2 0/4] arm64: kasan: support CONFIG_KASAN_VMALLOC Lecopzer Chen
2021-01-09 10:32 ` [PATCH v2 1/4] arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC Lecopzer Chen
2021-02-03 18:37 ` Ard Biesheuvel
2021-02-04 6:21 ` Lecopzer Chen
2021-02-04 12:45 ` Will Deacon
2021-02-04 14:46 ` Lecopzer Chen
2021-02-04 15:01 ` Will Deacon
2021-02-04 16:37 ` Lecopzer Chen [this message]
2021-02-05 17:18 ` Will Deacon
2021-02-05 17:30 ` Andrey Konovalov
2021-02-05 17:43 ` Will Deacon
2021-02-05 20:50 ` Andrey Konovalov
2021-02-05 18:10 ` Lecopzer Chen
2021-01-09 10:32 ` [PATCH v2 2/4] arm64: kasan: abstract _text and _end to KERNEL_START/END Lecopzer Chen
2021-02-04 12:46 ` Will Deacon
2021-02-04 14:51 ` Lecopzer Chen
2021-02-04 14:55 ` Will Deacon
2021-02-04 16:06 ` Lecopzer Chen
2021-02-05 17:02 ` Will Deacon
2021-01-09 10:32 ` [PATCH v2 3/4] arm64: Kconfig: support CONFIG_KASAN_VMALLOC Lecopzer Chen
2021-01-09 10:32 ` [PATCH v2 4/4] arm64: kaslr: support randomized module area with KASAN_VMALLOC Lecopzer Chen
2021-01-27 23:04 ` Will Deacon
2021-01-28 8:53 ` Lecopzer Chen
2021-01-28 20:26 ` Will Deacon
2021-01-21 10:19 ` [PATCH v2 0/4] arm64: kasan: support CONFIG_KASAN_VMALLOC Lecopzer Chen
2021-01-21 17:44 ` Andrey Konovalov
2021-01-22 19:05 ` Will Deacon
2021-02-03 18:31 ` Ard Biesheuvel
2021-02-04 12:49 ` Will Deacon
2021-02-04 15:53 ` Lecopzer Chen
2021-02-04 17:57 ` Will Deacon
2021-02-04 18:32 ` Lecopzer Chen
2021-02-04 18:41 ` Lecopzer Chen
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