From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>
Cc:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        Maxime Bizon <mbizon@freebox.fr>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH v2] powerpc/32s: Fix kasan_init_region() for KASAN
In-Reply-To: <90826d123e3e28b840f284412b150a1e13ed62fb.1638799954.git.christophe.leroy@csgroup.eu>
References: <90826d123e3e28b840f284412b150a1e13ed62fb.1638799954.git.christophe.leroy@csgroup.eu>
Date:   Wed, 29 Dec 2021 09:45:51 +1100
Message-ID: <87pmpg1h7k.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> It has been reported some configuration where the kernel doesn't
> boot with KASAN enabled.
>
> This is due to wrong BAT allocation for the KASAN area:
>
> 	---[ Data Block Address Translation ]---
> 	0: 0xc0000000-0xcfffffff 0x00000000       256M Kernel rw      m
> 	1: 0xd0000000-0xdfffffff 0x10000000       256M Kernel rw      m
> 	2: 0xe0000000-0xefffffff 0x20000000       256M Kernel rw      m
> 	3: 0xf8000000-0xf9ffffff 0x2a000000        32M Kernel rw      m
> 	4: 0xfa000000-0xfdffffff 0x2c000000        64M Kernel rw      m
>
> A BAT must have both virtual and physical addresses alignment matching
> the size of the BAT. This is not the case for BAT 4 above.
>
> Fix kasan_init_region() by using block_size() function that is in
> book3s32/mmu.c. To be able to reuse it here, make it non static and
> change its name to bat_block_size() in order to avoid name conflict
> with block_size() defined in <linux/blkdev.h>
>
> Also reuse find_free_bat() to avoid an error message from setbat()
> when no BAT is available.
>
> And allocate memory outside of linear memory mapping to avoid
> wasting that precious space.
>
> With this change we get correct alignment for BATs and KASAN shadow
> memory is allocated outside the linear memory space.
>
> 	---[ Data Block Address Translation ]---
> 	0: 0xc0000000-0xcfffffff 0x00000000       256M Kernel rw
> 	1: 0xd0000000-0xdfffffff 0x10000000       256M Kernel rw
> 	2: 0xe0000000-0xefffffff 0x20000000       256M Kernel rw
> 	3: 0xf8000000-0xfbffffff 0x7c000000        64M Kernel rw
> 	4: 0xfc000000-0xfdffffff 0x7a000000        32M Kernel rw
>
> Reported-by: Maxime Bizon <mbizon@freebox.fr>
> Fixes: 7974c4732642 ("powerpc/32s: Implement dedicated kasan_init_region()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> v2:
> - Allocate kasan shadow memory outside precious kernel linear memory
> - Properly zeroise kasan shadow memory
> ---
>  arch/powerpc/include/asm/book3s/32/mmu-hash.h |  2 +
>  arch/powerpc/mm/book3s32/mmu.c                | 10 ++--
>  arch/powerpc/mm/kasan/book3s_32.c             | 58 ++++++++++---------
>  3 files changed, 38 insertions(+), 32 deletions(-)

Sorry this now conflicts with other changes in next. Can you rebase it please?

cheers