Endless loop on execution attempt on non-executable page

[Florian Weimer <fweimer@redhat.com>]

The GCC compile farm has a big-endian 64-bit MIPS box.  The kernel is:

Linux erpro8-fsf1 3.14.10-er8mod-00013-ge0fe977 #1 SMP PREEMPT Wed Jan
14 12:33:22 PST 2015 mips64 GNU/Linux

Which is a vendor kernel for the EdgeRouter Pro-8.

/proc/cpuinfo reports:

system type             : UBNT_E200 (CN6120p1.1-1000-NSP)
machine                 : Unknown
processor               : 0
cpu model               : Cavium Octeon II V0.1

While testing W^X (execmod, DEP, NX) stack enforcement, I noticed that 
once I try to execute code off a non-executable page, I do not get a 
signal, but the code appears to enter an infinite loop.  The generated 
function starts with a jump instruction to return to the caller, but 
instead, the program counter does not seem to change at all.

“si” in GDB also hangs (but can be interrupted with ^C).

My test code is here:

   https://pagure.io/execmod-tests

Is this a kernel bug or an issue with the silicon?

Thanks,
Florian