copy faults from user_string* functions

[Eric Wong]

Hi all, just to clarify, not all of these faults are user errors, right?

I get these sometimes with some strings (constants, I think):

ERROR: user string copy fault -14 at 000000000042f16c near identifier 'user_string_n' at $prefix/share/systemtap/tapset/uconversions.stp:120:10

I'm using systemtap release-2.3-1-g5033017

Things are heavily multi-threaded and there's an occasional fork/exec
happening for iostat.

Without systemtap, valgrind runs the test suite fine, so it's less
likely to be a bug in the code.


This is for cmogstored, if anybody is interested in reproducing this,
I've pushed my work-in-progress to the "st-wip-broken" branch of
git://bogomips.org/cmogstored.git   The HACKING doc in the top-level
should document all the build-dependencies if you want to try to
reproduce it.

Once built and all the dev dependencies installed, I just run:
	stap -v tapset/all.stp

And in another terminal: make -jXX check

(note: having slow mount points may increase the chance of test suite
failure since it needs to scan mount points for disk usage reports and
iostat device name <-> MogileFS devid mapping)

Thanks for reading!