On Sun, Jul 22, 2018 at 3:00 PM, ma...@kevac.org <ma...@kevac.org> wrote: > Hi! > > Imagine I have an interpreter that runs some program in some custom > language. If I were to get a stack trace, it would look like: > > sys_read() [k] > read() > execute_fn() > execute_fn() > execute_fn() > execute_fn() > main() > > These execute_fn() functions execute functions defined in my custom > language. Such stack trace is not very helpful. > > But I know that I can get to real function name through execute_fn() > arguments. Imagine it is as simple as execute_fn(char *real_fn_name). > > I know I can trace execute_fn() invocations and get to this function name > through BCC/eBPF. But I would like to have tool similar to profile.py to be > able to profile my programs written in my custom language. > > So I need to get stack traces periodically (49 Hz say) and I need to > substitute name of a function from execute_fn() to the real one from > arguments. > > Can you give me some pointers how to do that or if it is possible at all. > I couldn't find any example that walks stack trace. All of the examples just > record them.
We did not have such an example in BCC. In Facebook, we have a bpf program to catch stack traces for python programs. It is very similar to what you want to achieve in the above. Basically, you need to walk the stack by yourself. Since verifier do not support unbounded loops, you need to have a fully-unrollable loop with progma unroll. During each loop iteration, you can access the frame pointer, you need some mechanism to get the real function name based on that level frame pointer and then you move on to the next. In bpf program, you can access current task structure, which contains some data related to TLS which could be used by the bpf program. > > Thanks! > Marko. > -=-=-=-=-=-=-=-=-=-=-=- Links: You receive all messages sent to this group. View/Reply Online (#1391): https://lists.iovisor.org/g/iovisor-dev/message/1391 Mute This Topic: https://lists.iovisor.org/mt/23787733/21656 Group Owner: iovisor-dev+ow...@lists.iovisor.org Unsubscribe: https://lists.iovisor.org/g/iovisor-dev/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
