On Tue, Sep 15, 2020 at 11:16PM +0200, Andrey Konovalov 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@xxxxxxxxxx> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> > --- > Change-Id: I246c2def9fffa6563278db1bddfbe742ca7bdefe > --- > lib/Kconfig.kasan | 56 +++++++++++++++++++++++++++++++++-------------- > 1 file changed, 39 insertions(+), 17 deletions(-) > > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > index b4cf6c519d71..17c9ecfaecb9 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 > @@ -20,10 +23,11 @@ config CC_HAS_WORKING_NOSANITIZE_ADDRESS > > 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 SLUB_DEBUG if SLUB Is SLUB_DEBUG necessary with HW_TAGS? > select CONSTRUCTORS > select STACKDEPOT > @@ -38,13 +42,18 @@ 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). > > - Both generic and tag-based KASAN are strictly debugging features. > + All KASAN modes are strictly debugging features. > + > + For better error detection enable CONFIG_STACKTRACE. I don't think CONFIG_STACKTRACE improves error detection, right? It only makes the reports more readable > > config KASAN_GENERIC > bool "Generic mode" > @@ -61,8 +70,6 @@ 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). > > @@ -72,9 +79,11 @@ config KASAN_SW_TAGS > 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 version 7.0.0 > - or later. > + 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 version 7.0.0 or later. > > 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 +91,27 @@ 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 +135,7 @@ 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 How about something like the below change (introduce KASAN_INSTRUMENTED Kconfig var) to avoid the repeated "KASAN_GENERIC || KASAN_SW_TAGS". This could then also be used in the various .c/.h files (and make some of the code more readable hopefully). +config KASAN_INSTRUMENTED + def_bool KASAN_GENERIC || KASAN_SW_TAGS + choice prompt "Instrumentation type" - depends on KASAN_GENERIC || KASAN_SW_TAGS + depends on KASAN_INSTRUMENTED default KASAN_OUTLINE config KASAN_OUTLINE @@ -135,7 +141,7 @@ endchoice config KASAN_STACK_ENABLE bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST - depends on KASAN_GENERIC || KASAN_SW_TAGS + depends on KASAN_INSTRUMENTED help The LLVM stack address sanitizer has a know problem that causes excessive stack usage in a lot of functions, see Thanks, -- Marco
