documentation for user-space usage?

[Grant Edwards <grant dot b dot edwards at gmail dot com>]

I've figured out how to do kernel-tracing on an embedded system by
cross-compiling .stp files and then running them on a target that has
only staprun installed.

But, I've been trying on-and-off for a few months to figure out what
system-tap user-space tracing is and how it works, and I've made very
little progress.

What I need is basically a low overhead alternative to syslog for
embedded system use.

I want to put logging statements in user application source code that
log various events along with maybe one or two parameter values along
with an event.  I need to log up to a few thousand events/second for
short periods of time into a circular buffer and then transfer the raw
log data to a different machine for display/analysis.  I need to start
stop tracing and enable/disable various subsets of those trace points
at runtime (hopefully without having to restart the processes doing
the logging).

About the only documentation I can find on systemtap user-space stuff
is http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps,
and that's not been very helpful -- it seems mostly to be about
autoconf and RPM. I was hoping to see some example of instrumented C
source, but if it's there, I'm too dumb to find it.

I was under the impression that uprobes support was required, but that
page says only mentions utrace as a requirement.

Is ubprobes support required, or just utrace?

All the examples I can find of user-space probes seem to require that
stap be installed on the machine where the probed user-processes are
being run.  If that's true, then using systemtap isn't feasible for
me.

Am I on the right track looking at systemtap for user application
event logging, or not?

-- 
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