Implement FdLink conversions

[astoycos]

Implement TryFrom functions to convert Fdlink to PerfLink/TracePointLink/ KprobeLink, and UprobeLink and vice-versa.

This allows us to pin taken links for perf programs, ultimately ensuring the link isn't dropped when the loading process exits.

Required for bpfman/bpfman#306

TODO: It'd be nice to add some documentation around this API somewhere...

    let mut bpf = BpfLoader::new()
    // load pinned maps from /sys/fs/bpf/my-program
    .map_pin_path("/sys/fs/bpf")
    // finally load the code
    .load_file("/home/astoycos/go/src/github.com/redhat-et/bpfd/examples/go-tracepoint-counter/bpf_bpfel.o")?;
    let program: &mut TracePoint = bpf.program_mut("tracepoint_kill_recorder").unwrap().try_into()?;
    program.load()?;
    let link_id = program.attach("syscalls", "sys_enter_kill")?;
    program.pin("/sys/fs/bpf/tracepoint_kill_recorder_pin")?;
    let owned_link: TracePointLink = program.take_link(link_id)?;
    let fd_link: FdLink = owned_link.try_into()?;
    fd_link.pin("/sys/fs/bpf/tracepoint_kill_recorder_link")?;

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[astoycos]

Hrm I don't think this error is related:

Error: e: 19:33:45 [ERROR] llvm: Unknown attribute kind (86) (Producer: 'LLVM16.0.0-rust-1.70.0-nightly' Reader: 'LLVM 15.0.7')
          error: failure linking module /home/fedora/aya/test/integration-ebpf/../../target/bpfel-unknown-none/debug/deps/map_test-a9de5ef8344e854d.3hyxcigylsh430vj.rcgu.o
          19:33:45 [ WARN] ignoring file "/tmp/rustcIDSCW0/symbols.o": no embedded bitcode
          

error: could not compile `integration-ebpf` (bin "map_test") due to previous error

[dave-tucker]

LGTM! Thanks, we already do this for XDP and I'd forgotten to do this for the PerfLinks 😓

[alessandrod]

Thanks!

I agree that this should be documented. We could add docs here https://docs.aya-rs.dev/user/aya/programs/links/struct.fdlink? Explain that FdLink allows you to pin, and that many links can be converted to FdLink by using either into() or try_into(), giving examples of both.

[astoycos]

Sorry It's been so long @alessandrod I fixed the issues and added integration testing for TracePoint, Uprobe and Kprobe programs. I'm happy to do it for perf_event progs here or in a follow up I'm just not 100% sure how to ATM and this is what I got to today. :)

@dave-tucker PTAL at how I also changed the integration test tooling to verify that a program is loaded AND linked in certain cases.

[astoycos]

We could add docs here https://docs.aya-rs.dev/user/aya/programs/links/struct.fdlink? Explain that FdLink allows you to pin, and that many links can be converted to FdLink by using either into() or try_into(), giving examples of both.

Shoot and I still need to do this.

[astoycos]

Shoot and I still need to do this.

done

[astoycos]

Poke @alessandrod :)

[astoycos]

Rebased 👍

[ajwerner]

@tamird and I are working on redoing the integration test infrastructure such that the tests themselves do not rely on userspace to execute. Today the cycle time of compiling and running tests in the VM is less than wonderful. I chatted with @alessandrod about it here.

The preferred solution would be to have aya provide the relevant APIs for reading these links. If it's easy to implement the functionality you need in aya as opposed to shelling out, would you be open to it?

[astoycos]

Hiya @ajwerner and yeah I totally agree, we need a loaded_links() API for bpfd regardless to go along with the work I did here: #637

I'd rather go ahead and get this bit in for now since I've been carrying it for quite some time 😄 , but in the meantime I'll start working on a basic loaded_links() API.

[tamird]

Reviewed 7 of 8 files at r1, all commit messages.
Reviewable status: 7 of 8 files reviewed, 8 unresolved discussions (waiting on @alessandrod, @astoycos, and @dave-tucker)

---

aya/src/programs/kprobe.rs line 140 at r1 (raw file):

    fn try_from(fd_link: FdLink) -> Result<Self, Self::Error> {
        // unwrap of fd_link.fd will not panic since it's only None when being dropped.

there's no unwrap here?

---

aya/src/programs/links.rs line 89 at r1 (raw file):

/// process closes. Additionally many program specific links can be converted into
/// FdLinks by using either into() or try_into() implementations. For examples of such functions
/// see [`TracePointLink::try_from()`](crate::programs::trace_point::TracePointLink::try_from()) and [`FdLink::try_from()`].

nit: long line

---

aya/src/programs/perf_event.rs line 209 at r1 (raw file):

    fn try_from(fd_link: FdLink) -> Result<Self, Self::Error> {
        // unwrap of fd_link.fd will not panic since it's only None when being dropped.

ditto?

---

aya/src/programs/trace_point.rs line 135 at r1 (raw file):

    fn try_from(fd_link: FdLink) -> Result<Self, Self::Error> {
        // unwrap of fd_link.fd will not panic since it's only None when being dropped.

ditto

---

aya/src/programs/uprobe.rs line 180 at r1 (raw file):

    fn try_from(fd_link: FdLink) -> Result<Self, Self::Error> {
        // unwrap of fd_link.fd will not panic since it's only None when being dropped.

here

---

test/integration-test/tests/load.rs line 67 at r1 (raw file):

}

macro_rules! assert_loaded_and_linked {

can this just be assert_loaded followed by assert linked? i don't think we need to retry the bpftool invocation separately from waiting for loadedness

[tamird]

Reviewed 1 of 8 files at r1.
Reviewable status: all files reviewed, 9 unresolved discussions (waiting on @alessandrod, @astoycos, and @dave-tucker)

---

test/integration-ebpf/src/test.rs line 23 at r1 (raw file):

#[kprobe]
// truncated name to match bpftool output

the names were previously truncated to 15 characters, this comment is detritus

[astoycos]

can this just be assert_loaded followed by assert linked? i don't think we need to retry the bpftool invocation separately from waiting for loadedness

This is the only thing I didn't get to, simply because these functions are built as macros and if we were to reuse them I'd need to return the program id from assert_loaded!() since we need that ID to find the corresponding link. This will change anyways with #645 so I think it's alright for now.

[tamird]

Reviewed 8 of 8 files at r2, 2 of 2 files at r3, all commit messages.
Reviewable status: all files reviewed, 4 unresolved discussions (waiting on @alessandrod, @astoycos, and @dave-tucker)

---

test/integration-test/tests/load.rs line 59 at r3 (raw file):

fn is_linked(prog_id: &u32) -> bool {
    let output = Command::new("bpftool").args(["link"]).output();
    let output = match output {

i think this is output.expect(...)

[tamird]

Reviewed 1 of 1 files at r5, 4 of 4 files at r7, all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @alessandrod and @dave-tucker)

[astoycos]

Whelp ended up having to rebase again :/