On Thu, 2019-09-12 at 16:31 +0200, Vlastimil Babka wrote: > On 9/12/19 4:08 PM, Walter Wu wrote: > > > >> extern void __reset_page_owner(struct page *page, unsigned int order); > >> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > >> index 6c9682ce0254..dc560c7562e8 100644 > >> --- a/lib/Kconfig.kasan > >> +++ b/lib/Kconfig.kasan > >> @@ -41,6 +41,8 @@ config KASAN_GENERIC > >> select SLUB_DEBUG if SLUB > >> select CONSTRUCTORS > >> select STACKDEPOT > >> + select PAGE_OWNER > >> + select PAGE_OWNER_FREE_STACK > >> help > >> Enables generic KASAN mode. > >> Supported in both GCC and Clang. With GCC it requires version 4.9.2 > >> @@ -63,6 +65,8 @@ config KASAN_SW_TAGS > >> select SLUB_DEBUG if SLUB > >> select CONSTRUCTORS > >> select STACKDEPOT > >> + select PAGE_OWNER > >> + select PAGE_OWNER_FREE_STACK > >> help > > > > What is the difference between PAGE_OWNER+PAGE_OWNER_FREE_STACK and > > DEBUG_PAGEALLOC? > > Same memory usage, but debug_pagealloc means also extra checks and > restricting memory access to freed pages to catch UAF. > > > If you directly enable PAGE_OWNER+PAGE_OWNER_FREE_STACK > > PAGE_OWNER_FREE_STACK,don't you think low-memory device to want to use > > KASAN? > > OK, so it should be optional? But I think it's enough to distinguish no > PAGE_OWNER at all, and PAGE_OWNER+PAGE_OWNER_FREE_STACK together - I > don't see much point in PAGE_OWNER only for this kind of debugging. > If it's possible, it should be optional. My experience is that PAGE_OWNER usually debug memory leakage.
> So how about this? KASAN wouldn't select PAGE_OWNER* but it would be > recommended in the help+docs. When PAGE_OWNER and KASAN are selected by > user, PAGE_OWNER_FREE_STACK gets also selected, and both will be also > runtime enabled without explicit page_owner=on. > I mostly want to avoid another boot-time option for enabling > PAGE_OWNER_FREE_STACK. > Would that be enough flexibility for low-memory devices vs full-fledged > debugging? We usually see feature option to decide whether it meet the platform. The boot-time option isn't troubled to us, because enable the feature owner should know what he should add to do.
