On Tue, 10 Feb 2015 22:33:05 -0800 Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote: > fair enough. > Something like TRACE_MARKER(arg1, arg2) that prints > it was hit without accessing the args would be enough. > Without any args it is indeed a 'fast kprobe' only. > Debug info would still be needed to access > function arguments. > On x64 function entry point and x64 abi make it easy > to access args, but i386 or kprobe in the middle > lose visibility when debug info is not available. > TRACE_MARKER (with few key args that function > is operating on) is enough to achieve roughly the same > as kprobe without debug info. Actually, what about a TRACE_EVENT_DEBUG(), that has a few args and possibly a full trace event layout. The difference would be that the trace events do not show up unless you have "trace_debug" on the command line. This should prevent applications from depending on them. I could even do the nasty dmesg output like I do with trace_printk()s, that would definitely keep a production kernel from adding it by default. When trace_debug is not there, the trace points could still be accessed but perhaps only via bpf, or act like a simple trace marker. Note, if you need ids, I rather have them in another directory than tracefs. Make a eventfs perhaps that holds these. I rather keep tracefs simple. This is something that needs to probably be discussed at bit. -- Steve -- 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
