kdump: decode pollfd struct arrays coming from poll(2)

[kevans]

Summary

We'll handle these just as we do kevents, one per line with subsequent
lines indented sufficiently to distinguish them from the upcoming
return value.

Sample, with indentation stripped and revents changed to '...' in the
first one to keep the line length down:

CALL poll(0x820610560,0x3,0)
STRU struct pollfd[] = { { fd=0, events=0x1<POLLIN>, revents=0x11<...>
{ fd=1, events=0x4<POLLOUT>, revents=0x4<POLLOUT>}
{ fd=-1, events=0x4<POLLOUT>, revents=0} }
RET poll 2

[bapt]

I love it, thank you!

[jhb]

Next you might consider adding this to truss as well. :)

[kevans]

In D44160#1008533, @jhb wrote:

Next you might consider adding this to truss as well. :)

I'm actually not sure what this would look like for truss... it does some decoding of events already, just not returned events:

820 100189: poll({ 0/POLLIN 1/POLLOUT -1/POLLOUT 1/POLLHUP },4,0) = 1 (0x1)

It's a little more obvious with kqueue since the results are returned in a separate parameter, so that gives a natural representation... the best I can come up with off the top of my head is maybe something like:

820 100189: poll({ 0/{POLLIN -> 0} 1/{POLLOUT -> POLLOUT} -1/{POLLOUT -> 0} 1/{POLLHUP -> 0} },4,0) = 1 (0x1)

but I'm afraid that might get a little convoluted

[kevans]

Oh, that probably won't work... we probably printed the entire left-hand side before the return, so it'd need to be on a separate line or something