Help needed to identify golang fork / memory corruption issue on FreeBSD

[Steven Hartland]

OK now the similar but unrelated issue with signal stacks is solved I've 
moved back to the initial issue.

I've made some progress with a reproduction case as detailed here:
https://github.com/golang/go/issues/15658#issuecomment-288747812

In short it seems that having a running child, while the parent runs GC, 
is some how responsible for memory corruption in the parent.

The reason I believe this is if I run the same GC in the parent after 
the child exits instead of while its running, I've been unable to 
reproduce the issue.

As the memory segments are COW then the issue might be in VM subsystem.

In order to confirm / deny this I was wondering if there was a way to 
force a full copy of all segments for the child instead of using the COW 
optimisation.

Is this something that would be relatively easy to hack into the kernel, 
and if so pointers would be appreciated.

     Regards
     Steve