When an event probe is to be removed via the API that created it via the
dynamic events, an -ENOENT error is returned.

This is because the removal of the event probe does not expect to see the
event system and name that the event probe is attached to, even though
that's part of the API to create it. As the removal of probes is to use
the same API as they are created.

In fact, the removal is not consistent with the kprobes and uprobes
removal. Fix that by allowing various ways to remove the eprobe.

The eprobe is created with:

 e:[GROUP/]NAME SYSTEM/EVENT [OPTIONS]

Have it get removed by echoing in the following into dynamic_events:

 # Remove all eprobes with NAME
 echo '-:NAME' >> dynamic_events

 # Remove a specific eprobe
 echo '-:GROUP/NAME' >> dynamic_events
 echo '-:GROUP/NAME SYSTEM/EVENT' >> dynamic_events
 echo '-:NAME SYSTEM/EVENT' >> dynamic_events
 echo '-:GROUP/NAME SYSTEM/EVENT OPTIONS' >> dynamic_events
 echo '-:NAME SYSTEM/EVENT OPTIONS' >> dynamic_events

Link: https://lkml.kernel.org/r/20211012081925.0e19cc4f@gandalf.local.home
Link: https://lkml.kernel.org/r/20211013205533.630722129@goodmis.org



Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 7491e2c4

 ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>