psc: The ps utility, with an eBPF twist and container context (github.com)

> psc uses eBPF iterators to read process and file descriptor information directly from kernel data structures. This bypasses the /proc filesystem entirely, providing visibility that cannot be subverted by userland rootkits or LD_PRELOAD tricks.

Is there a trade off here?

Thanks for including so many examples! Perhaps include one example output. Other than mention of the optional '--tree' parameter, it's unclear if the default result would be a list, table, JSON, etc.

This is neat but the examples comparing the tool against piping grep seem to counter the argument to me. A couple of pipes to grep seems much easier to remember and type, especially with all the quotes needed for psc. For scripts where you need exact output this looks great.

I'm not convinced with the need to embed CEL. You could just output json and pipe to jq.

Their first example is bad:

    ps aux | grep nginx | grep root | grep -v grep

can be done instead (from memory, not at a Linux machine ATM):

    ps -u root -C nginx

which is arguably better than their solution:

    psc 'process.name == "nginx" && process.user == "root"'

An unfortunate name that triggers everybody who’s ever worked at Meta :)

  # Find processes connected to a specific port
  psc 'socket.dstPort == uint(443)'

  # Filter by PID range
  psc 'process.pid > 1000 && process.pid < 2000'

It seems weird to require the user to remember that ports have to be marked uint when it doesn't look like anything else does.

I've played with bpf iterators and wrote a post about them [1]. The benefit of iterating over tasks instead of scanning procfs is a pretty astounding performance difference:

> I ran benchmarks on current code in the datadog-agent which reads the relevant data from procfs as described at the beginning of this post. I then implemented benchmarks for capturing the same data with bpf. The performance results were a major improvement.

> On a linux system with around 250 Procs it took the procfs implemention 5.45 ms vs 75.6 us for bpf (bpf is ~72x faster). On a linux system with around 10,000 Procs it took the procfs implemention ~296us vs 3ms for bpf (bpf is ~100x faster).

[1] https://www.grant.pizza/blog/bpf-iter/

how about comparing it to something sensible like osquery instead of doing silly strawman ps pipelines

I like this tool. I just replaced a multi-step script to find running processes with deleted files open (e.g., updated shared library or binary) that used to be as follows:

- grep /proc/*/maps for " (deleted)" (needs root)

- exclude irrelevancies like paths starting with "/memfd:" (I have lots of other similar exclusions) with grep -v

- extract the pid from the filename part of grep's output with sed

- for each pid, generate readable output from /proc/$pid/cmdline (which is NUL separated) with tr, xargs, bash printf

- show the pid, cmdline, file path

Yes, this is what needs-restarting does too.

With this tool, this pipe chain is now just:

    doas psc -o "process.pid,process.cmdline,file.path" \
      'file.path.endsWith(" (deleted)") && !file.path.startsWith("/memfd:") && !...' \
      | sed 1d

Hey! thanks for publishing my tool, and thanks everybody for the great feedback here. Just started addressing some of your points.

Anyway, my need for the tool was mostly because of these few points:

- scripting can be much easier with psc, especially when you can output what you want

- ebpf iterators are so flexible: we can get anything that is defined in the task_struct that is not even exposed in the proc filesytem if we want. This alone makes the tool extremely powerful, with a reasonable amount of effort for just adding a new field

- I really like querying my system with a simple language. Sometimes I tend to forget about specific ss, lsof, or ps options. In this way, it's much easier for me to get what I need

- no traditional tooling has native container context. It can be extended to even retrieve data from the kubelet, for instance, but I'll think about it

Feel free to reach out if you have any particular need