full path for open / openat relative filenames

Question

Using the opensnoop.py from iovisor/bcc, I'm trying to extend the ebpf code to handle extraction of full paths from a relative one.

For example, running opensnoop.py and in another terminal running cat anything.txt, the output in opensnoop will show the relative filename, not an absolute path:

$ sudo ./venv/bin/python bcc/tools/opensnoop.py | grep anything.txt &

$ cat anything.txt 2>/dev/null
19536  cat                -1   2 anything.txt

$ cat /tmp/anything.txt 2>/dev/null
19540  cat                -1   2 /tmp/anything.txt

I've narrored down the code block in opensnoop.py that i should look into amending, and adding in some logic similar to:

    // .. existing code
    bpf_probe_read_user(&data.fname, sizeof(data.fname), (void *)filename);
    data.id    = id;
    data.ts    = tsp / 1000;
    data.uid   = bpf_get_current_uid_gid();
    data.flags = flags; // EXTENDED_STRUCT_MEMBER
    data.ret   = ret;
    
    // new code to handle relative paths:
    if (data.fname[0] != '/' && data.fname[0] != '\\0') {
        // TODO if filename doesn't start with a /, need to convert relative path to abs
        struct fs_struct *fs = ((struct task_struct *) bpf_get_current_task())->fs;
        
        // TODO: get pwd path from fs->pwd
        struct path *pwd_path = &fs->pwd // ?

        // TODO: call bpf_d_path(pwd_path, buf, sz)

        // TODO: update data.fname to insert buf pwd)
    }

    events.perf_submit(ctx, &data, sizeof(data));

Where I'm stuck is the TODO parts, there doesn't seem to be many / any good examples of using the new bpf_d_path helper function