linux-kernel - Re: [PATCH] powerpc/kasan: KASAN is not supported on RELOCATABLE && FSL

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Message-ID: <fc48b5bc-45c1-e4e0-7b56-a23cc045ee0e@c-s.fr>
Date:   Fri, 29 Nov 2019 08:46:31 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Lexi Shao <shaolexi@...wei.com>, benh@...nel.crashing.org,
        paulus@...ba.org, mpe@...erman.id.au
Cc:     liucheng32@...wei.com, yi.zhang@...wei.com,
        wangkefeng.wang@...wei.com, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/kasan: KASAN is not supported on RELOCATABLE &&
 FSL_BOOKE



Le 29/11/2019 à 08:04, Lexi Shao a écrit :
> CONFIG_RELOCATABLE and CONFIG_KASAN cannot be enabled at the same time
> on ppce500 fsl_booke. All functions called before kasan_early_init()
> should be disabled with kasan check. When CONFIG_RELOCATABLE is enabled
> on ppce500 fsl_booke, relocate_init() is called before kasan_early_init()
> which triggers kasan check and results in boot failure.
> Call trace and functions which triggers kasan check(*):
>    - _start
>     - set_ivor
>      - relocate_init(*)
>       - early_get_first_memblock_info(*)
>        - of_scan_flat_dt(*)
> 	...
>      - kasan_early_init
> 
> Potential solutions could be 1. implement relocate_init and all its children
> function in a seperate file or 2. introduce a global vairable in KASAN, only
> enable KASAN check when init is done.

Solution 1 seems uneasy. of_scan_flat_dt() and children are general 
functions that can't be set aside.
Solution 2 would destroy performance, and would anyway not work with 
inline instrumentation.

Have you tried moving the call to kasan_early_init() before the call of 
relocate_init() ?
On other PPC32, kasan_early_init() is the first thing done after 
activating the MMU. But AFAIU, MMU is always active on BOOKE though.

Christophe

> 
> Disable KASAN when RELOCATABLE is selected on fsl_booke for now until
> it is supported.
> 
> Signed-off-by: Lexi Shao <shaolexi@...wei.com>
> ---
>   arch/powerpc/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 3e56c9c2f16e..14f3da63c088 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -171,7 +171,7 @@ config PPC
>   	select HAVE_ARCH_AUDITSYSCALL
>   	select HAVE_ARCH_HUGE_VMAP		if PPC_BOOK3S_64 && PPC_RADIX_MMU
>   	select HAVE_ARCH_JUMP_LABEL
> -	select HAVE_ARCH_KASAN			if PPC32
> +	select HAVE_ARCH_KASAN			if PPC32 && !(RELOCATABLE && FSL_BOOKE)
>   	select HAVE_ARCH_KGDB
>   	select HAVE_ARCH_MMAP_RND_BITS
>   	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT
>