ZFS SET_ERROR dtrace probe possible under FreeBSD?

[Steven Hartland]

The following commit added SET_ERROR dtrace probes to illumos
https://github.com/illumos/illumos-gate/commit/be6fd75

Now we have all the SET_ERROR calls but the FreeBSD's ZFS implementation
but our SET_ERROR in sys/cddl/compat/opensolaris/sys/sdt.h is simply:
#define SET_ERROR(err)  (err)

I tried using the illumos version but that resulted being unable
to mount ZFS root, so clearly not right.

/*
 * the set-error SDT probe is extra static, in that we declare its fake
 * function literally, rather than with the DTRACE_PROBE1() macro. This is
 * necessary so that SET_ERROR() can evaluate to a value, which wouldn't
 * be possible if it required multiple statements (to declare the function
 * and then call it).
 *
 * SET_ERROR() uses the comma operator so that it can be used without much
 * additional code. For example, "return (EINVAL);" becomes
 * "return (SET_ERROR(EINVAL));". Note that the argument will be evaluated
 * twice, so it should not have side effects (e.g. something like:
 * "return (SET_ERROR(log_error(EINVAL, info)));" would log the error twice).
 */
extern void __dtrace_probe_set__error(uintptr_t);
#define SET_ERROR(err) (__dtrace_probe_set__error(err), err)


For those that know the the ins and outs of our dtrace is it
possible for us to add support for this trace point?

    Regards
    Steve