Compiling profile files in libbpf-bootstrap/examples/c/

[deepakpjose]

Hi,

I like to see the stacktrace using ebpf. I see some example code under profile.c file under libbpf-bootstrap/examples/c. But it's not included in the Makefile. What is the reason for it? I tried to include them. But including it caused blaze library is not linked. Is blaze part of your docker or has to be built?

Thanks, Deepak

[danielocfb]

Did you check the Makefile? The program is very much part of the build process, but you need a Rust toolchain installed.

https://github.com/libbpf/libbpf-bootstrap/blob/2dffae1fca82fd9ef4ba15df67606cbfd2eb5412/examples/c/Makefile#L30-L38

[danielocfb]

For Docker specifically, I am not really familiar with the infra we have there. It's possible that the container does not come with a Rust toolchain and so it would suffer from the aforementioned problem. Feel free to open a pull request if you have a fix.

[deepakpjose]

With installing rustc and cargo in my ubuntu docker, I'm able to build and run profile program now.

Followint are the steps. curl https://sh.rustup.rs -sSf | sh -s -- -y PATH="/root/.cargo/bin:${PATH}" cargo --version && rustc --version cargo build --release <--- From blazesym directory.

But I got following error when executed profile. Are there any limitation in doing perf from docker. I'm running in a mac system?

root@c1da7c025d63:/src/libbpf-bootstrap/build# ./profile Fail to set up performance monitor on a CPU/Core err: No such file or directory fd: -1 cpu: 0

In file profile.c, of libbpf-bootstrap, I get this error while calling perf_event_open.

    for (cpu = 0; cpu < num_cpus; cpu++) {
            /* skip offline/not present CPUs */
            if (cpu >= num_online_cpus || !online_mask[cpu])
                    continue;

            /* Set up performance monitoring on a CPU/Core */
            pefd = perf_event_open(&attr, pid, cpu, -1, PERF_FLAG_FD_CLOEXEC);
            if (pefd < 0) {
                    fprintf(stderr, "Fail to set up performance monitor on a CPU/Core err: %s fd: %d cpu: %d\n", strerror(errno), pefd, cpu);
                    fprintf(stderr, "Cpu cycles: %lld", attr.config);
                    err = -1;
                    goto cleanup;
            }

Thanks, Deepak

[d-e-s-o]

I guess this has been solved as evidenced by the progress here. Can we close it?

[deepakpjose]

Sure. I'll close it. Do you see value in adding a Docker file to run bpf into this repository so that, it's easy for users to do tinkering in libbpf without other head aches.

[danielocfb]

May be a good idea. Feel free to open a PR.