Re: [PATCH v3 1/2] arm: kasan: support CONFIG_KASAN_VMALLOC

From: Lecopzer Chen <lecopzer.chen@mediatek.com>
To: <linux@armlinux.org.uk>
Cc: <andreyknvl@gmail.com>, <anshuman.khandual@arm.com>,
	<ardb@kernel.org>, <arnd@arndb.de>, <dvyukov@google.com>,
	<geert+renesas@glider.be>, <glider@google.com>,
	<kasan-dev@googlegroups.com>, <lecopzer.chen@mediatek.com>,
	<linus.walleij@linaro.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <lukas.bulwahn@gmail.com>,
	<mark.rutland@arm.com>, <masahiroy@kernel.org>,
	<matthias.bgg@gmail.com>, <ryabinin.a.a@gmail.com>,
	<yj.chiang@mediatek.com>
Subject: Re: [PATCH v3 1/2] arm: kasan: support CONFIG_KASAN_VMALLOC
Date: Fri, 11 Mar 2022 18:47:52 +0800	[thread overview]
Message-ID: <20220311104752.2616-1-lecopzer.chen@mediatek.com> (raw)
In-Reply-To: <YislvzIg3Tvwj2+J@shell.armlinux.org.uk>

> On Sun, Feb 27, 2022 at 09:47:25PM +0800, Lecopzer Chen wrote:
> > Simply make shadow of vmalloc area mapped on demand.
> > 
> > Since the virtual address of vmalloc for Arm is also between
> > MODULE_VADDR and 0x100000000 (ZONE_HIGHMEM), which means the shadow
> > address has already included between KASAN_SHADOW_START and
> > KASAN_SHADOW_END.
> > Thus we need to change nothing for memory map of Arm.
> > 
> > This can fix ARM_MODULE_PLTS with KASan, support KASan for higmem
> > and provide the first step to support CONFIG_VMAP_STACK with Arm.
> > 
> > Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
> > ---
> >  arch/arm/Kconfig                 |  1 +
> >  arch/arm/include/asm/kasan_def.h | 11 ++++++++++-
> >  arch/arm/mm/kasan_init.c         |  6 +++++-
> >  3 files changed, 16 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index 4c97cb40eebb..78250e246cc6 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -72,6 +72,7 @@ config ARM
> >  	select HAVE_ARCH_KFENCE if MMU && !XIP_KERNEL
> >  	select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> >  	select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
> > +	select HAVE_ARCH_KASAN_VMALLOC if HAVE_ARCH_KASAN
> >  	select HAVE_ARCH_MMAP_RND_BITS if MMU
> >  	select HAVE_ARCH_PFN_VALID
> >  	select HAVE_ARCH_SECCOMP
> > diff --git a/arch/arm/include/asm/kasan_def.h b/arch/arm/include/asm/kasan_def.h
> > index 5739605aa7cf..96fd1d3b5a0c 100644
> > --- a/arch/arm/include/asm/kasan_def.h
> > +++ b/arch/arm/include/asm/kasan_def.h
> > @@ -19,7 +19,16 @@
> >   * space to use as shadow memory for KASan as follows:
> >   *
> >   * +----+ 0xffffffff
> > - * |    |							\
> > + * |    |\
> > + * |    | |-> ZONE_HIGHMEM for vmalloc virtual address space.
> > + * |    | |   Such as vmalloc(), GFP_HIGHUSER (__GFP__HIGHMEM),
> > + * |    | |   module address using ARM_MODULE_PLTS, etc.
> > + * |    | |
> > + * |    | |   If CONFIG_KASAN_VMALLOC=y, this area would populate
> > + * |    | |   shadow address on demand.
> > + * |    |/
> 
> This diagram is incorrect. We already have the memory layout in
> Documentation/arm/memory.rst, so we don't need another set of
> documentation that is misleading.

 Ok, should I send a v4 to remove this?

BRs,
Lecopzer

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