[RFA] Displaced stepping just enable in non-stop mode

[Michael Snyder]

Daniel Jacobowitz wrote:

>> We could also try to detect if it works, and display a warning if we
>> think it won't (RE the cases you described above).
> 
> Hmm, that's an interesting idea.  Pedro, what do you think - would
> autodetection work for the cases we've seen trouble?  Something as
> simple as "can we write to _start" is probably enough, but I don't
> remember what the failure looked like with the record target; and in
> that case it may be complicated by the fact that we're initially going
> forwards and could write.

What it looks like is that you try to write to memory
that's write-protected.

This is because most replay targets will treat all of memory
as write-protected when they are in replay mode.

Where this usually manifests is, you'll say "continue"
(probably for the first time since attaching to the target),
and it'll croak because it's trying to step over some
"invisible" breakpoint such as the one that handles
shared libraries.

> 
>>> I'm not sure what else to call displaced stepping.  "Step around
>>> breakpoints"?
>> The text mentions "out-of-line stepping", which sounds better to me.
> 
> I like "set step out-of-line"...

Arr arr...  step up-against-the-wall...