On Tue, Nov 10, 2020 at 11:20PM +0100, Andrey Konovalov wrote: > The reason cache merging is disabled with KASAN is because KASAN puts its > metadata right after the allocated object. When the merged caches have > slightly different sizes, the metadata ends up in different places, which > KASAN doesn't support. > > It might be possible to adjust the metadata allocation algorithm and make > it friendly to the cache merging code. Instead this change takes a simpler > approach and allows merging caches when no metadata is present. Which is > the case for hardware tag-based KASAN with kasan.mode=prod. > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > Link: https://linux-review.googlesource.com/id/Ia114847dfb2244f297d2cb82d592bf6a07455dba > --- > include/linux/kasan.h | 26 ++++++++++++++++++++++++-- > mm/kasan/common.c | 11 +++++++++++ > mm/slab_common.c | 11 ++++++++--- > 3 files changed, 43 insertions(+), 5 deletions(-) > [...] > > +/* > + * Only allow cache merging when stack collection is disabled and no metadata > + * is present. > + */ > +slab_flags_t __kasan_never_merge(slab_flags_t flags) I'm getting mm/kasan/common.c:88:14: warning: no previous prototype for ‘__kasan_never_merge’ [-Wmissing-prototypes] for a KASAN x86 build with W=1. Presumably because if !KASAN_HW_TAGS then this is never needed and defined static inline in the header. > +{ > + if (kasan_stack_collection_enabled()) > + return flags; > + return flags & ~SLAB_KASAN; > +} Thanks, -- Marco
