[RFC v3 08/19] arch: um: add shim to trap to allow installing a fault catcher for tests

[Luis Chamberlain]

On Wed, Nov 28, 2018 at 11:36:25AM -0800, Brendan Higgins wrote:
> +static void segv_run_catcher(jmp_buf *catcher, void *fault_addr)
> +{
> +	current->thread.fault_addr = fault_addr;
> +	UML_LONGJMP(catcher, 1);
> +}

Some documentation about what this does exactly would be appreciated.
With the goal it may be useful to others wanting to consider support
for other archs -- if that actually ends up being desirable.

  Luis