On Sat, 2013-08-31 at 18:53 +0200, Jan Kratochvil wrote:
This would correspond to your suggested value 15 (PC) for ARM.
But no elfutils code uses that value. I have no idea if systemtap uses it.
Currently it is indeed not used. As you point out, the CIE will always
set up a return register value. But seems a good idea to keep it
consistent with the other CFI ABI setup if set. SystemTap doesn't use it
(sadly it has to run in kernel space and can only use elfutils support
during translation time, not at runtime). And the libebl backend
interfaces are NOT public API. So SystemTap really shouldn't use them
directly (and doesn't). They are only used internally in other elfutils
code. And we can (and should) change them whenever we feel we could do
something better with a different setup.