Re: [PATCH v10 05/22] kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS

[Andrey Konovalov]

On Wed, Nov 7, 2018 at 6:04 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote:
> On Tue, Nov 06, 2018 at 06:30:20PM +0100, Andrey Konovalov wrote:
>> This commit splits the current CONFIG_KASAN config option into two:
>> 1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one
>>    that exists now);
>> 2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode.
>>
>> The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have
>> another hardware tag-based KASAN mode, that will rely on hardware memory
>> tagging support in arm64.
>>
>> With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to
>> instrument kernel files with -fsantize=kernel-hwaddress (except the ones
>> for which KASAN_SANITIZE := n is set).
>>
>> Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both
>> CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes.
>>
>> This commit also adds empty placeholder (for now) implementation of
>> tag-based KASAN specific hooks inserted by the compiler and adjusts
>> common hooks implementation to compile correctly with each of the
>> config options.
>>
>> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
>> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
>> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>> ---
>>  arch/arm64/Kconfig                  |  1 +
>>  include/linux/compiler-clang.h      |  5 +-
>>  include/linux/compiler-gcc.h        |  6 ++
>>  include/linux/compiler_attributes.h | 13 -----
>>  include/linux/kasan.h               | 16 ++++--
>>  lib/Kconfig.kasan                   | 87 +++++++++++++++++++++++------
>>  mm/kasan/Makefile                   |  6 +-
>>  mm/kasan/generic.c                  |  2 +-
>>  mm/kasan/kasan.h                    |  3 +-
>>  mm/kasan/tags.c                     | 75 +++++++++++++++++++++++++
>>  mm/slub.c                           |  2 +-
>>  scripts/Makefile.kasan              | 27 ++++++++-
>>  12 files changed, 201 insertions(+), 42 deletions(-)
>>  create mode 100644 mm/kasan/tags.c
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 787d7850e064..8b331dcfb48e 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -111,6 +111,7 @@ config ARM64
>>       select HAVE_ARCH_JUMP_LABEL
>>       select HAVE_ARCH_JUMP_LABEL_RELATIVE
>>       select HAVE_ARCH_KASAN if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
>> +     select HAVE_ARCH_KASAN_SW_TAGS if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
>
> Given this relies on a compiler feature, can we please gate this on
> compiler feature detection? e.g. in some common Kconfig have:
>
>         select CC_HAS_ASAN_HWADDRESS if $(cc-option -fsanitize=kernel-hwaddress)
>
> ... and on arm64 we can do:
>
>         select HAVE_ARCH_KASAN_SW_TAGS if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
>
> ... and core KASAN Kconfig can have:
>
> config KASAN_SW_TAGS
>         depends on HAVE_ARCH_KASAN_SW_TAGS
>         depends on CC_HAS_ASAN_HWADDRESS
>
> [...]
>
>> +ifeq ($(call cc-option, $(CFLAGS_KASAN) -Werror),)
>> +    ifneq ($(CONFIG_COMPILE_TEST),y)
>> +        $(warning Cannot use CONFIG_KASAN_SW_TAGS: \
>> +            -fsanitize=hwaddress is not supported by compiler)
>> +    endif
>> +endif
>
> ... and then this warning shouldn't be possible, and can go.

Will do in v11, thanks!