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

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Date:   Fri, 29 Nov 2019 15:13:24 +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:     linux-kernel@...r.kernel.org, wangkefeng.wang@...wei.com,
        linuxppc-dev@...ts.ozlabs.org, liucheng32@...wei.com,
        yi.zhang@...wei.com
Subject: Re: [PATCH] powerpc/kasan: KASAN is not supported on RELOCATABLE &&
 FSL_BOOKE



Le 29/11/2019 à 08:46, Christophe Leroy a écrit :
> 
> 
> 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() ?

I just tried it with QEMU, it works. I'll send a patch out soon.

Christophe


> 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
>>