Re: [PATCH v2] powerpc/32s: Fix kasan_init_region() for KASAN

[Michael Ellerman]

Christophe Leroy <christophe.leroy@xxxxxxxxxx> 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@xxxxxxxxxx>
> Fixes: 7974c4732642 ("powerpc/32s: Implement dedicated kasan_init_region()")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> ---
> 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