On Tue, 2019-10-29 at 15:09 +0100, Alexander Potapenko wrote: > On Fri, Oct 18, 2019 at 5:02 PM Qian Cai <cai@xxxxxx> wrote: > > > > On Fri, 2019-10-18 at 11:42 +0200, glider@xxxxxxxxxx wrote: > > > Insert KMSAN hooks that check for potential memory errors and/or make > > > necessary bookkeeping changes: > > > - allocate/split/deallocate metadata pages in > > > alloc_pages()/split_page()/free_page(); > > > > This also seems unnecessary where there are options like page_poison and > > debug_pagealloc should be able detect uninitialized memory access in the page > > allocator as well. Even KASAN has some of the functionality. > > I still believe there's some misunderstanding between us because I > didn't CC you on KMSAN runtime or the documentation. > I'll do this and will be happy to answer questions if you still have them. > Without these hooks, KMSAN will be virtually unusable, because it > won't know about heap allocations. > > When a buffer is allocated on heap, KMSAN updates the metadata for > that region of memory, writing 0xFF (meaning uninitialized) to every > shadow byte and a stack ID to every 4 region bytes. > Note that shadow and origin bytes are stored separately and are > generally incompatible with what debug pagealloc/page poison do. That makes more sense to me now. I was a bit worry about some of those options could stub one's toe with KMSAN, but I had shared with you the MM debug config in another email before, so you could try it out, so I don't need to spam you later once this hit the linux-next.
