On Fri, Apr 22, 2022 at 10:40:08AM -0700, Peter Collingbourne wrote: > On Fri, Apr 22, 2022 at 9:09 AM Andrey Konovalov <andreyknvl@xxxxxxxxx> wrote: > > > > On Fri, Apr 22, 2022 at 2:39 PM Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> wrote: > > > > > > > > kasan_hw_tags_enabled() is also false when kasan is just not initialized yet. > > > > > What about writing a new helper something like kasan_is_disabled() > > > > > instead? > > > > > > > > The decision of whether to enable KASAN is made early, before the slab > > > > allocator is initialized (start_kernel -> smp_prepare_boot_cpu -> > > > > kasan_init_hw_tags vs start_kernel -> mm_init -> kmem_cache_init). If > > > > you think about it, this needs to be the case for KASAN to operate > > > > correctly because it influences the behavior of the slab allocator via > > > > the kasan_*poison* hooks. So I don't think we can end up calling this > > > > function before then. > > > > > > Sounds not bad. I wanted to make sure the value of arch_slab_minaligned() > > > is not changed during its execution. > > > > > > Just some part of me thought something like this would be more > > > intuitive/robust. > > > > > > if (systems_supports_mte() && kasan_arg != KASAN_ARG_OFF) > > > return MTE_GRANULE_SIZE; > > > else > > > return __alignof__(unsigned long long); > > > > Hi Hyeonggon, > > > > We could add and use kasan_hw_rags_requested(), which would return > > (systems_supports_mte() && kasan_arg != KASAN_ARG_OFF). > > > > However, I'm not sure we will get a fully static behavior: > > systems_supports_mte() also only starts returning proper result at > > some point during CPU bring-up if I'm not mistaken. > > > > Thanks! > > Yes, either way we are going to rely on something that hasn't > obviously been initialized yet, so I think we should stick with what I > have since it's used by the rest of the KASAN code as well. > Okay then we should anyway rely on something not initialized at early stage of boot process. And I don't expect much problem on current version. Thanks! > Peter -- Thanks, Hyeonggon
