linux-kernel - Re: [PATCH 3/7] Disable instrumentation for some code

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Message-ID: <5ec51db8-196e-fd3d-8cce-2bdaccc52424@arm.com>
Date:   Mon, 19 Mar 2018 08:38:04 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Abbott Liu <liuwenliang@...wei.com>, linux@...linux.org.uk,
        aryabinin@...tuozzo.com, kstewart@...uxfoundation.org,
        gregkh@...uxfoundation.org, f.fainelli@...il.com,
        akpm@...ux-foundation.org, afzal.mohd.ma@...il.com,
        alexander.levin@...izon.com
Cc:     glider@...gle.com, dvyukov@...gle.com, christoffer.dall@...aro.org,
        linux@...musvillemoes.dk, mawilcox@...rosoft.com,
        pombredanne@...b.com, ard.biesheuvel@...aro.org,
        vladimir.murzin@....com, nicolas.pitre@...aro.org,
        tglx@...utronix.de, thgarnie@...gle.com, dhowells@...hat.com,
        keescook@...omium.org, arnd@...db.de, geert@...ux-m68k.org,
        tixy@...aro.org, mark.rutland@....com, james.morse@....com,
        zhichao.huang@...aro.org, jinb.park7@...il.com, labbott@...hat.com,
        philip@....systems, grygorii.strashko@...aro.org,
        catalin.marinas@....com, opendmb@...il.com,
        kirill.shutemov@...ux.intel.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, kvmarm@...ts.cs.columbia.edu,
        linux-mm@...ck.org
Subject: Re: [PATCH 3/7] Disable instrumentation for some code

On 18/03/18 12:53, Abbott Liu wrote:
> From: Andrey Ryabinin <a.ryabinin@...sung.com>
> 
> Disable instrumentation for arch/arm/boot/compressed/*
> and arch/arm/vdso/* because those code won't linkd with
> kernel image.
> 
> Disable kasan check in the function unwind_pop_register
> because it doesn't matter that kasan checks failed when
> unwind_pop_register read stack memory of task.
> 
> Reviewed-by: Russell King - ARM Linux <linux@...linux.org.uk>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> Tested-by: Florian Fainelli <f.fainelli@...il.com>
> Signed-off-by: Abbott Liu <liuwenliang@...wei.com>
> ---
>  arch/arm/boot/compressed/Makefile | 1 +
>  arch/arm/kernel/unwind.c          | 3 ++-
>  arch/arm/vdso/Makefile            | 2 ++
>  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index 45a6b9b..966103e 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -24,6 +24,7 @@ OBJS		+= hyp-stub.o
>  endif
>  
>  GCOV_PROFILE		:= n
> +KASAN_SANITIZE		:= n
>  
>  #
>  # Architecture dependencies
> diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
> index 0bee233..2e55c7d 100644
> --- a/arch/arm/kernel/unwind.c
> +++ b/arch/arm/kernel/unwind.c
> @@ -249,7 +249,8 @@ static int unwind_pop_register(struct unwind_ctrl_block *ctrl,
>  		if (*vsp >= (unsigned long *)ctrl->sp_high)
>  			return -URC_FAILURE;
>  
> -	ctrl->vrs[reg] = *(*vsp)++;
> +	ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp));
> +	(*vsp)++;
>  	return URC_OK;
>  }
>  
> diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile
> index bb411821..87abbb7 100644
> --- a/arch/arm/vdso/Makefile
> +++ b/arch/arm/vdso/Makefile
> @@ -30,6 +30,8 @@ CFLAGS_vgettimeofday.o = -O2
>  # Disable gcov profiling for VDSO code
>  GCOV_PROFILE := n
>  
> +KASAN_SANITIZE := n
> +
>  # Force dependency
>  $(obj)/vdso.o : $(obj)/vdso.so
>  
> 

You need to extend this at least to arch/arm/kvm/hyp/Makefile, as the
KASAN shadow region won't be mapped in HYP. See commit a6cdf1c08cbfe for
more details (all the arm64 comments in this patch apply to 32bit as well).

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...