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.
Cheers,
Mark