On Thu, Nov 29, 2018 at 10:02:13PM +0100, Arnd Bergmann wrote: > On Thu, Nov 29, 2018 at 9:14 PM Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > > > On Nov 29, 2018, at 11:55 AM, Christian Brauner <christian@xxxxxxxxxx> wrote: > > >> On Thu, Nov 29, 2018 at 11:22:58AM -0800, Andy Lutomirski wrote: > > >>> On Thu, Nov 29, 2018 at 11:17 AM Christian Brauner <christian@xxxxxxxxxx> wrote: > > >>>> On November 30, 2018 5:54:18 AM GMT+13:00, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > > >> > > >> The #1 fix would add a copy_siginfo_from_user64() or similar. > > > > > > Thanks very much! That all helped a bunch already! I'll try to go the > > > copy_siginfo_from_user64() way first and see if I can make this work. If > > > we do this I would however only want to use it for the new syscall first > > > and not change all other signal syscalls over to it too. I'd rather keep > > > this patchset focussed and small and do such conversions caused by the > > > new approach later. Does that sound reasonable? > > > > Absolutely. I don’t think we can change old syscalls — the ABI is set in stone. > > But for new syscalls, I think the always-64-bit behavior makes sense. > > It looks like we already have a 'struct signalfd_siginfo' that is defined in a > sane architecture-independent way, so I'd suggest we use that. Just so that I understand you correctly: swapping out struct signinfo for struct signalfd_siginfo in procfd_<whatever-suffix>? If so that sounds great to me! > > We may then also want to make sure that any system call that takes a > siginfo has a replacement that takes a signalfd_siginfo, and that this > replacement can be used to implement the old version purely in > user space. Sounds good but is unrelated to this patchset I take it. :) > > Is the current procfd_signal() proposal (under whichever name) sufficient > to correctly implement both sys_rt_sigqueueinfo() and sys_rt_tgsigqueueinfo()? Yes, I see no reason why not. My idea is to extend it - after we have a basic version in - to also work with: /proc/<pid>/task/<tid> If I'm not mistaken this should be sufficient to get rt_tgsigqueueinfo. The thread will be uniquely identified by the tid descriptor and no combination of /proc/<pid> and /proc/<pid>/task/<tid> is needed. Does that sound reasonable? > Can we implement sys_rt_sigtimedwait() based on signalfd()? > If yes, that would leave waitid(), which already needs a replacement > for y2038, and that should then also return a signalfd_siginfo. > My current preference for waitid() would be to do a version that > closely resembles the current interface, but takes a signalfd_siginfo > and a __kernel_timespec based rusage replacement (possibly > two of them to let us map wait6), but does not operate on procfd or > take a signal mask. That would require yet another syscall, but I > don't think I can do that before we want to have the set of y2038 > safe syscalls. All sounds reasonable to me but that's not a blocker for the current syscall though, is it? Christian
