[RFC PATCH 5/5] powerpc: KASAN for 64bit Book3E

[Christophe Leroy]

Le 15/02/2019 à 01:04, Daniel Axtens a écrit :
> Wire up KASAN. Only outline instrumentation is supported.
> 
> The KASAN shadow area is mapped into vmemmap space:
> 0x8000 0400 0000 0000 to 0x8000 0600 0000 0000.
> To do this we require that vmemmap be disabled. (This is the default
> in the kernel config that QorIQ provides for the machine in their
> SDK anyway - they use flat memory.)
> 
> Only the kernel linear mapping (0xc000...) is checked. The vmalloc and
> ioremap areas (also in 0x800...) are all mapped to a zero page. As
> with the Book3S hash series, this requires overriding the memory <->
> shadow mapping.
> 
> Also, as with both previous 64-bit series, early instrumentation is not
> supported.  It would allow us to drop the check_return_arch_not_ready()
> hook in the KASAN core, but it's tricky to get it set up early enough:
> we need it setup before the first call to instrumented code like printk().
> Perhaps in the future.
> 
> Only KASAN_MINIMAL works.
> 
> Lightly tested on e6500. KVM, kexec and xmon have not been tested.
> 
> The test_kasan module fires warnings as expected, except for the
> following tests:
> 
>   - Expected/by design:
> kasan test: memcg_accounted_kmem_cache allocate memcg accounted object
> 
>   - Due to only supporting KASAN_MINIMAL:
> kasan test: kasan_stack_oob out-of-bounds on stack
> kasan test: kasan_global_oob out-of-bounds global variable
> kasan test: kasan_alloca_oob_left out-of-bounds to left on alloca
> kasan test: kasan_alloca_oob_right out-of-bounds to right on alloca
> kasan test: use_after_scope_test use-after-scope on int
> kasan test: use_after_scope_test use-after-scope on array
> 
> Thanks to those who have done the heavy lifting over the past several years:
>   - Christophe's 32 bit series: https://lists.ozlabs.org/pipermail/linuxppc-dev/2019-February/185379.html
>   - Aneesh's Book3S hash series: https://lwn.net/Articles/655642/
>   - Balbir's Book3S radix series: https://patchwork.ozlabs.org/patch/795211/
> 
> Cc: Christophe Leroy <christophe.leroy at c-s.fr>
> Cc: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
> Cc: Balbir Singh <bsingharora at gmail.com>
> Signed-off-by: Daniel Axtens <dja at axtens.net>
> 
> ---
> 
> While useful if you have a book3e device, this is mostly intended
> as a warm-up exercise for reviving Aneesh's series for book3s hash.
> In particular, changes to the kasan core are going to be required
> for hash and radix as well.
> ---
>   arch/powerpc/Kconfig                         |  1 +
>   arch/powerpc/Makefile                        |  2 +
>   arch/powerpc/include/asm/kasan.h             | 77 ++++++++++++++++++--
>   arch/powerpc/include/asm/ppc_asm.h           |  7 ++
>   arch/powerpc/include/asm/string.h            |  7 +-
>   arch/powerpc/lib/mem_64.S                    |  6 +-
>   arch/powerpc/lib/memcmp_64.S                 |  5 +-
>   arch/powerpc/lib/memcpy_64.S                 |  3 +-
>   arch/powerpc/lib/string.S                    | 15 ++--
>   arch/powerpc/mm/Makefile                     |  2 +
>   arch/powerpc/mm/kasan/Makefile               |  1 +
>   arch/powerpc/mm/kasan/kasan_init_book3e_64.c | 53 ++++++++++++++
>   arch/powerpc/purgatory/Makefile              |  3 +
>   arch/powerpc/xmon/Makefile                   |  1 +
>   14 files changed, 164 insertions(+), 19 deletions(-)
>   create mode 100644 arch/powerpc/mm/kasan/kasan_init_book3e_64.c

[snip]

> diff --git a/arch/powerpc/mm/kasan/kasan_init_book3e_64.c b/arch/powerpc/mm/kasan/kasan_init_book3e_64.c
> new file mode 100644
> index 000000000000..93b9afcf1020
> --- /dev/null
> +++ b/arch/powerpc/mm/kasan/kasan_init_book3e_64.c
> @@ -0,0 +1,53 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#define DISABLE_BRANCH_PROFILING
> +
> +#include <linux/kasan.h>
> +#include <linux/printk.h>
> +#include <linux/memblock.h>
> +#include <linux/sched/task.h>
> +#include <asm/pgalloc.h>
> +
> +DEFINE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
> +EXPORT_SYMBOL(powerpc_kasan_enabled_key);

Why does this symbol need to be exported ?

Christophe