SystemTap registration error

Question

Did you ever see this Warning: probe kernel.function("some function@some file") (address 0xSomething) registration error (rc -84) ? If so, what did you do to solve it? It is an warning, and occurs during runtime (after Pass 5). But it skips tapping that specific function with registration error. But, I need to probe this functions. Note that, these functions are not __kprobes.

My kernel is 3.11.0-15-generic (Ubuntu 12.04) and SystemTap version is 2.4.

Update apparently I have messed up the installation of SytemTap. Please see second comment (by me) here.

Answer 1

Error -84 is EILSEQ: "illegal byte sequence". The kernel can return this signal, for example if it cannot decode its own binary in the region nearby the requested kprobe, or it finds instruction patterns that its decoder has not been taught to handle. It's not a systemtap bug.

To figure out the exact cause, we'd need to see the systemtap script, the address stap picks for the probe (see stap -p2 -v ...), and a (objdump -d) disassembly of the kernel in that region.