From: Daniel Axtens <dja@xxxxxxxxxx> Subject: kasan: allow an architecture to disable inline instrumentation Patch series "KASAN core changes for ppc64 radix KASAN", v16. Building on the work of Christophe, Aneesh and Balbir, I've ported KASAN to 64-bit Book3S kernels running on the Radix MMU. I've been trying this for a while, but we keep having collisions between the kasan code in the mm tree and the code I want to put in to the ppc tree. This series just contains the kasan core changes that we need. There should be no noticeable changes to other platforms. This patch (of 4): For annoying architectural reasons, it's very difficult to support inline instrumentation on powerpc64.* Add a Kconfig flag to allow an arch to disable inline. (It's a bit annoying to be 'backwards', but I'm not aware of any way to have an arch force a symbol to be 'n', rather than 'y'.) We also disable stack instrumentation in this case as it does things that are functionally equivalent to inline instrumentation, namely adding code that touches the shadow directly without going through a C helper. * on ppc64 atm, the shadow lives in virtual memory and isn't accessible in real mode. However, before we turn on virtual memory, we parse the device tree to determine which platform and MMU we're running under. That calls generic DT code, which is instrumented. Inline instrumentation in DT would unconditionally attempt to touch the shadow region, which we won't have set up yet, and would crash. We can make outline mode wait for the arch to be ready, but we can't change what the compiler inserts for inline mode. Link: https://lkml.kernel.org/r/20210624034050.511391-1-dja@xxxxxxxxxx Link: https://lkml.kernel.org/r/20210624034050.511391-2-dja@xxxxxxxxxx Signed-off-by: Daniel Axtens <dja@xxxxxxxxxx> Reviewed-by: Marco Elver <elver@xxxxxxxxxx> Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx> Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx> Cc: Balbir Singh <bsingharora@xxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/Kconfig.kasan | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/lib/Kconfig.kasan~kasan-allow-an-architecture-to-disable-inline-instrumentation +++ a/lib/Kconfig.kasan @@ -12,6 +12,13 @@ config HAVE_ARCH_KASAN_HW_TAGS config HAVE_ARCH_KASAN_VMALLOC bool +config ARCH_DISABLE_KASAN_INLINE + bool + help + An architecture might not support inline instrumentation. + When this option is selected, inline and stack instrumentation are + disabled. + config CC_HAS_KASAN_GENERIC def_bool $(cc-option, -fsanitize=kernel-address) @@ -130,6 +137,7 @@ config KASAN_OUTLINE config KASAN_INLINE bool "Inline instrumentation" + depends on !ARCH_DISABLE_KASAN_INLINE help Compiler directly inserts code checking shadow memory before memory accesses. This is faster than outline (in some workloads @@ -141,6 +149,7 @@ endchoice config KASAN_STACK bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST depends on KASAN_GENERIC || KASAN_SW_TAGS + depends on !ARCH_DISABLE_KASAN_INLINE default y if CC_IS_GCC help The LLVM stack address sanitizer has a know problem that @@ -154,6 +163,9 @@ config KASAN_STACK but clang users can still enable it for builds without CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe to use and enabled by default. + If the architecture disables inline instrumentation, stack + instrumentation is also disabled as it adds inline-style + instrumentation that is run unconditionally. config KASAN_SW_TAGS_IDENTIFY bool "Enable memory corruption identification" _
