On Mon, 14 Apr 2014, Michael Kerrisk (man-pages) wrote: > > EACCES Returned when the requested event requires root permis‐ > sions (or a more permissive perf_event paranoid set‐ > ting). Some common cases where an unprivileged process > may encounter this error: are attaching to a process > owned by a different user; monitoring all processes on a > given CPU; and not setting exclude_kernel when the para‐ > noid setting requires it. > > But, now I have some more questions: > > * What are "root permissions" here? It's these days usual to express > things precisely in terms of the required capability. Yes, I guess that should really be CAP_SYS_ADMIN > * I am puzzled by "monitoring all processes on a CPU"? So, monitoring > _some_ (i.e., < all) processes on a CPU won't trigger this error? I was a bit confused here. A regular user can monitor "the specified process on CPU X" or "the specified process on any CPU". A user running as root can also monitor "all procceses belonging to anyone on CPU X" Other combinations aren't possible. > >>> +.B EPERM > >>> +Returned if sufficient permissions not available to create the event. > > Again, somewhere here, the text should mention the required capability. Yes, it's CAP_SYS_ADMIN again. > > This is a recent change. > > So, the text should mention a kernel version number. Could you patch > that please. I guess it should be something like: > > and (since Linux 3.??) setting an ftrace function-trace tracepoint Yes, I'll do that. Vince
