linux-kernel - Re: [PATCH v7 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support

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Message-ID: <87wo7xpr42.fsf@dja-thinkpad.axtens.net>
Date:   Sat, 07 Mar 2020 00:09:17 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Christophe Leroy <christophe.leroy@....fr>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org, kasan-dev@...glegroups.com,
        aneesh.kumar@...ux.ibm.com, bsingharora@...il.com
Cc:     Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v7 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support

Christophe Leroy <christophe.leroy@....fr> writes:

> Le 13/02/2020 à 01:47, Daniel Axtens a écrit :
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index 497b7d0b2d7e..f1c54c08a88e 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -169,7 +169,9 @@ config PPC
>>   	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 PPC_BOOK3S_64 && PPC_RADIX_MMU
>
> That's probably detail, but as it is necessary to deeply define the HW 
> when selecting that (I mean giving the exact amount of memory and with 
> restrictions like having a wholeblock memory), should it also depend of 
> EXPERT ?

If it weren't a debug feature I would definitely agree with you, but I
think being a debug feature it's not so necessary. Also anything with
more memory than the config option specifies will still boot - it's just
less memory that won't boot. I've set the default to 1024MB: I know
that's a lot of memory for an embedded system but I think for anything
with the Radix MMU it's an OK default.

I'm sure if mpe disagrees he can add EXPERT when he's merging :)

> Maybe we could have
>
> -  	select HAVE_ARCH_KASAN_VMALLOC		if PPC32
> +	select HAVE_ARCH_KASAN_VMALLOC		if HAVE_ARCH_KASAN

That's a good idea. Done.

Thanks for the review!

Regards,
Daniel

>
>>   	select HAVE_ARCH_KGDB
>>   	select HAVE_ARCH_MMAP_RND_BITS
>>   	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT
>
>
> Christophe