[DynInst_API:] Building a local struct for a funcCall parameter

[Josh Stone <jistone@xxxxxxxxxx>]

Hi,

I've been experimenting with access to registers in instrumentation,
including the newly available rsp/rbp, which is working fine.  But what
I'd really like is a way to pass them all as a struct pt_regs* parameter
in a funcCallExpr.  (I'm aware that some registers of pt_regs are not
available, which is ok - I'll fill in zeros.)

But I haven't figured out how I can locally allocate such a struct in
the first place.  I don't want a fully global allocation, because the
instrumentation needs to be thread safe.  I tried accessing a
compiled-in TLS global, but Dyninst couldn't find it.  Really, a
stack-allocated struct would be best, but I can't find any way to create
that.  Is it possible in the BPatch API?

As a fallback, I'm considering passing all of those register values as
individual parameters, but I'm hoping there's a better way.

Also, while I'm trying to figure out this struct question generically,
it might be neat if Dyninst had specific support for struct pt_regs.  An
array of DWARF-numbered registers might work well too.  But I expect
either way, Dyninst could save and provide these more efficiently
internally, perhaps as part of the existing state-saving.

Thanks,
Josh