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Message-ID: <CAG_fn=URYEvbfdZrdpZs8Uv7ui15oeBDNqB2WTXE2erFucQG4w@mail.gmail.com>
Date: Wed, 18 Nov 2020 17:04:02 +0100
From: Alexander Potapenko <glider@...gle.com>
To: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Marco Elver <elver@...gle.com>,
Evgenii Stepanov <eugenis@...gle.com>,
Branislav Rankov <Branislav.Rankov@....com>,
Kevin Brodsky <kevin.brodsky@....com>,
kasan-dev <kasan-dev@...glegroups.com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Memory Management List <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH mm v10 23/42] kasan: introduce CONFIG_KASAN_HW_TAGS
On Fri, Nov 13, 2020 at 11:17 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> This patch adds a configuration option for a new KASAN mode called
> hardware tag-based KASAN. This mode uses the memory tagging approach
> like the software tag-based mode, but relies on arm64 Memory Tagging
> Extension feature for tag management and access checking.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Co-developed-by: Vincenzo Frascino <vincenzo.frascino@....com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
> Reviewed-by: Marco Elver <elver@...gle.com>
Reviewed-by: Alexander Potapenko <glider@...gle.com>
> ---
> Change-Id: I246c2def9fffa6563278db1bddfbe742ca7bdefe
> ---
> lib/Kconfig.kasan | 61 ++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 44 insertions(+), 17 deletions(-)
>
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index c0e9e7874122..f5fa4ba126bf 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -6,7 +6,10 @@ config HAVE_ARCH_KASAN
> config HAVE_ARCH_KASAN_SW_TAGS
> bool
>
> -config HAVE_ARCH_KASAN_VMALLOC
> +config HAVE_ARCH_KASAN_HW_TAGS
> + bool
> +
> +config HAVE_ARCH_KASAN_VMALLOC
> bool
>
> config CC_HAS_KASAN_GENERIC
> @@ -15,16 +18,19 @@ config CC_HAS_KASAN_GENERIC
> config CC_HAS_KASAN_SW_TAGS
> def_bool $(cc-option, -fsanitize=kernel-hwaddress)
>
> +# This option is only required for software KASAN modes.
> +# Old GCC versions don't have proper support for no_sanitize_address.
> +# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89124 for details.
> config CC_HAS_WORKING_NOSANITIZE_ADDRESS
> def_bool !CC_IS_GCC || GCC_VERSION >= 80300
>
> menuconfig KASAN
> bool "KASAN: runtime memory debugger"
> - depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
> - (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
> + depends on (((HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
> + (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)) && \
> + CC_HAS_WORKING_NOSANITIZE_ADDRESS) || \
> + HAVE_ARCH_KASAN_HW_TAGS
> depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
> - depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
> - select CONSTRUCTORS
> select STACKDEPOT
> help
> Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
> @@ -37,18 +43,24 @@ choice
> prompt "KASAN mode"
> default KASAN_GENERIC
> help
> - KASAN has two modes: generic KASAN (similar to userspace ASan,
> - x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and
> - software tag-based KASAN (a version based on software memory
> - tagging, arm64 only, similar to userspace HWASan, enabled with
> - CONFIG_KASAN_SW_TAGS).
> + KASAN has three modes:
> + 1. generic KASAN (similar to userspace ASan,
> + x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC),
> + 2. software tag-based KASAN (arm64 only, based on software
> + memory tagging (similar to userspace HWASan), enabled with
> + CONFIG_KASAN_SW_TAGS), and
> + 3. hardware tag-based KASAN (arm64 only, based on hardware
> + memory tagging, enabled with CONFIG_KASAN_HW_TAGS).
> +
> + All KASAN modes are strictly debugging features.
>
> - Both generic and tag-based KASAN are strictly debugging features.
> + For better error reports enable CONFIG_STACKTRACE.
>
> config KASAN_GENERIC
> bool "Generic mode"
> depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
> select SLUB_DEBUG if SLUB
> + select CONSTRUCTORS
> help
> Enables generic KASAN mode.
>
> @@ -61,8 +73,6 @@ config KASAN_GENERIC
> and introduces an overhead of ~x1.5 for the rest of the allocations.
> The performance slowdown is ~x3.
>
> - For better error detection enable CONFIG_STACKTRACE.
> -
> Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
> (the resulting kernel does not boot).
>
> @@ -70,11 +80,15 @@ config KASAN_SW_TAGS
> bool "Software tag-based mode"
> depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
> select SLUB_DEBUG if SLUB
> + select CONSTRUCTORS
> help
> Enables software tag-based KASAN mode.
>
> - This mode requires Top Byte Ignore support by the CPU and therefore
> - is only supported for arm64. This mode requires Clang.
> + This mode require software memory tagging support in the form of
> + HWASan-like compiler instrumentation.
> +
> + Currently this mode is only implemented for arm64 CPUs and relies on
> + Top Byte Ignore. This mode requires Clang.
>
> This mode consumes about 1/16th of available memory at kernel start
> and introduces an overhead of ~20% for the rest of the allocations.
> @@ -82,15 +96,27 @@ config KASAN_SW_TAGS
> casting and comparison, as it embeds tags into the top byte of each
> pointer.
>
> - For better error detection enable CONFIG_STACKTRACE.
> -
> Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB
> (the resulting kernel does not boot).
>
> +config KASAN_HW_TAGS
> + bool "Hardware tag-based mode"
> + depends on HAVE_ARCH_KASAN_HW_TAGS
> + depends on SLUB
> + help
> + Enables hardware tag-based KASAN mode.
> +
> + This mode requires hardware memory tagging support, and can be used
> + by any architecture that provides it.
> +
> + Currently this mode is only implemented for arm64 CPUs starting from
> + ARMv8.5 and relies on Memory Tagging Extension and Top Byte Ignore.
> +
> endchoice
>
> choice
> prompt "Instrumentation type"
> + depends on KASAN_GENERIC || KASAN_SW_TAGS
> default KASAN_OUTLINE
>
> config KASAN_OUTLINE
> @@ -114,6 +140,7 @@ endchoice
>
> config KASAN_STACK_ENABLE
> bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> + depends on KASAN_GENERIC || KASAN_SW_TAGS
> help
> The LLVM stack address sanitizer has a know problem that
> causes excessive stack usage in a lot of functions, see
> --
> 2.29.2.299.gdc1121823c-goog
>
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
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