On Mon, Oct 11, 2021 at 06:20:25PM -0700, Suren Baghdasaryan wrote: > On Mon, Oct 11, 2021 at 6:18 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > > > On Mon, Oct 11, 2021 at 1:36 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > On Fri 08-10-21 13:58:01, Kees Cook wrote: > > > > - Strings for "anon" specifically have no required format (this is good) > > > > it's informational like the task_struct::comm and can (roughly) > > > > anything. There's no naming convention for memfds, AF_UNIX, etc. Why > > > > is one needed here? That seems like a completely unreasonable > > > > requirement. > > > > > > I might be misreading the justification for the feature. Patch 2 is > > > talking about tools that need to understand memeory usage to make > > > further actions. Also Suren was suggesting "numbering convetion" as an > > > argument against. > > > > > > So can we get a clear example how is this being used actually? If this > > > is just to be used to debug by humans than I can see an argument for > > > human readable form. If this is, however, meant to be used by tools to > > > make some actions then the argument for strings is much weaker. > > > > The simplest usecase is when we notice that a process consumes more > > memory than usual and we do "cat /proc/$(pidof my_process)/maps" to > > check which area is contributing to this growth. The names we assign > > to anonymous areas are descriptive enough for a developer to get an > > idea where the increased consumption is coming from and how to proceed > > with their investigation. > > There are of course cases when tools are involved, but the end-user is > > always a human and the final report should contain easily > > understandable data. > > > > IIUC, the main argument here is whether the userspace can provide > > tools to perform the translations between ids and names, with the > > kernel accepting and reporting ids instead of strings. Technically > > it's possible, but to be practical that conversion should be fast > > because we will need to make name->id conversion potentially for each > > mmap. On the consumer side the performance is not as critical, but the > > fact that instead of dumping /proc/$pid/maps we will have to parse the > > file, do id->name conversion and replace all [anon:id] with > > [anon:name] would be an issue when we do that in bulk, for example > > when collecting system-wide data for a bugreport. Is that something you need to do client-side? Or could the bug tool upload the userspace-maintained name:ids database alongside the /proc/pid/maps dump for external processing?
