On Thu, 2014-09-25 at 19:33 +0100, Ingo Molnar wrote: > > How would we select tasks that can write to a given buffer? Maybe an > > ioctl() on a perf fd? Something like this? > > > > ioctl(perf_fd, PERF_EVENT_IOC_ENABLE_UEVENT, pid); > > ioctl(perf_fd, PERF_EVENT_IOC_DISABLE_UEVENT, pid); > > No, I think there's a simpler way: this should be a regular > perf_attr flag, which defaults to '0' (tasks cannot do this), but > which can be set to 1 if the profiler explicitly allows such > event injection. As in: allows *all* tasks to inject the data? Are you sure we don't want more fine-grained control, in particular per task? If we have two buffers, both created with the "injecting allowed" flag, do we inject a given uevent into both of them? > I.e. whether user-events are allowed is controlled by the > profiling/tracing context, via the regular perf syscall. It would > propagate into the perf context, so it would be easy to check at > event generation time. It would definitely be the profiling/tracing tools that would decide if the injection is allowed, no question about that. I just feel that it should be able to select the tasks that can do that, not just flip a big switch saying "everyone is welcome". Other question is: should a non-root context be able to receive events from root processes? Wouldn't it be a security hole (for example, it could be used as a kind of covert channel)? Maybe we should do what ptrace does? As in: if a task can ptrace another task, it can also receive uevents from it. Pawel -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
