A change was made a while ago to test for a valid RA during ia64 stack
unwind. The test compares the RA against KERN_START and KERN_END.
Unfortunately, it's possible for text addresses to fall within VMALLOC
space (they are from a kernel module). As things stand now, such an
address causes a premature termination of the backtrace. The original
test was added because an invalid non-NULL RA caused the unwind code to
endlessly loop. In this patch, the test for a valid RA is expanded to
test for a VMALLOC space address. If I don't get any negative feedback,
I will go ahead and check this fix into the tree.