On Fri, May 27, 2022 at 3:07 AM John Mazzie <john.p.mazzie@xxxxxxxxx> wrote: > > While attempting to learn more about BPF and libbpf, I ran into an > issue I can't quite seem to resolve. > > While writing some tools to practice tracing with libbpf, I came > across a situation where I get an error when using BPF_CORE_READ, > which appears to be that CO-RE relocation failed to find a > corresponding field. Compilation doesn't complain, just when I try to > execute. > > Error Message: > --------------------------------------------- > 8: (85) call unknown#195896080 > invalid func unknown#195896080 This means CO-RE relocation failed. If you update libbpf submodule (or maybe we already did it for libbpf-bootstrap recently), you'll get more meaningful error and details. But basically in running kernel there is no cmd->common.opcode. > > I'm using the Makefile from libbpf-bootstrap to build my program. The > other example programs build and execute properly, and I've also > successfully used tracepoints to trace the nvme_setup_cmd and > nvme_complete_rq functions. My issue appears to be when I attempt to > use kprobes for the nvme_submit_cmd function. > [...]
