On Wed, 21 Oct 2015, Andrey Ryabinin wrote: > It's recommended to have slub's user tracking enabled with CONFIG_KASAN, > because: > a) User tracking disables slab merging which improves > detecting out-of-bounds accesses. > b) User tracking metadata acts as redzone which also improves > detecting out-of-bounds accesses. > c) User tracking provides additional information about object. > This information helps to understand bugs. > > Currently it is not enabled by default. Besides recompiling the kernel > with KASAN and reinstalling it, user also have to change the boot cmdline, > which is not very handy. > > Enable slub user tracking by default with KASAN=y, since there is no > good reason to not do this. > > Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Makes sense. I don't imagine users of CONFIG_KASAN would be concerned about additional performance degradation for better diagnostics. > --- > Documentation/kasan.txt | 3 +-- > lib/Kconfig.kasan | 3 +-- > mm/slub.c | 2 ++ > 3 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/Documentation/kasan.txt b/Documentation/kasan.txt > index 94c88157..3107467 100644 > --- a/Documentation/kasan.txt > +++ b/Documentation/kasan.txt > @@ -28,8 +28,7 @@ the latter is 1.1 - 2 times faster. Inline instrumentation requires a GCC > version 5.0 or later. > > Currently KASAN works only with the SLUB memory allocator. > -For better bug detection and nicer report, enable CONFIG_STACKTRACE and put > -at least 'slub_debug=U' in the boot cmdline. > +For better bug detection and nicer report and enable CONFIG_STACKTRACE. > > To disable instrumentation for specific files or directories, add a line > similar to the following to the respective kernel Makefile: One too many "and"s in that sentence. > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > index 39f24d6..0fee5ac 100644 > --- a/lib/Kconfig.kasan > +++ b/lib/Kconfig.kasan > @@ -15,8 +15,7 @@ config KASAN > global variables requires gcc 5.0 or later. > This feature consumes about 1/8 of available memory and brings about > ~x3 performance slowdown. > - For better error detection enable CONFIG_STACKTRACE, > - and add slub_debug=U to boot cmdline. > + For better error detection enable CONFIG_STACKTRACE. > > choice > prompt "Instrumentation type" > diff --git a/mm/slub.c b/mm/slub.c > index ae28dff..f208835 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -463,6 +463,8 @@ static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map) > */ > #ifdef CONFIG_SLUB_DEBUG_ON > static int slub_debug = DEBUG_DEFAULT_FLAGS; > +#elif defined(CONFIG_KASAN) > +static int slub_debug = SLAB_STORE_USER; > #else > static int slub_debug; > #endif Typically you would convert the #ifdef to #if defined(CONFIG_SLUB_DEBUG_ON) as well. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>