Re: [iovisor-dev] New helper bpf_get_current_pidns_info

[cnb]

Hi,

I have resumed work on issue https://github.com/iovisor/bcc/issues/1329. I
just added the needed fields in this helper structure and also I updated
the bcc code to use this helper, but I have a couple of questions,
regarding my implementation.

- Should I be reading /proc/self/ns/pid using vfst_stat?.
- For Major/Minor I'm not sure if I should be getting the value from
stat.dev or stat.rdev.

I'm missing to put bcc in a container and replicate the actual issue, but I
wanted to share what I have at this point and check if I'm in the right
direction or something else is needed in this same helper.


BPF_CALL_2(bpf_get_current_pidns_info, void *, buf, u32, size)
{
        struct task_struct *ts = current;
        struct task_struct *ns_task = NULL;
        struct pid_namespace *pidns = NULL;
        pid_t pid = 0;
        int res = 0;
        const char ppath[] = "/proc/self/ns/pid";
        mm_segment_t oldsegfs;
        struct kstat stat;

        if (unlikely(!ts))
            return -EINVAL;

        pidns = task_active_pid_ns(ts);

        if (unlikely(!pidns))
            return -EINVAL;

        ((struct bpf_current_pidns_info*)buf)->ns_id = (u64) pidns->ns.inum;

        pid = task_pid_nr_ns(ts, pidns);

        if (unlikely(!pid))
            return -EINVAL;

        ns_task = find_task_by_pid_ns(pid, pidns);

        if (unlikely(!ns_task))
                return -EINVAL;

        ((struct bpf_current_pidns_info*)buf)->tgid = (s32)ns_task->tgid;
        ((struct bpf_current_pidns_info*)buf)->pid = (s32) ns_task->pid;

        oldsegfs = get_fs();
        set_fs(KERNEL_DS);
        res = vfs_stat((const char __user*)&ppath[0], &stat);
        set_fs(oldsegfs);

        if(unlikely(res))
                return -EINVAL;

        ((struct bpf_current_pidns_info*)buf)->major = (u32)
MAJOR(stat.dev);
        ((struct bpf_current_pidns_info*)buf)->minor = (u32)
MINOR(stat.dev);

        return 0;
}


const struct bpf_func_proto bpf_get_current_pidns_info_proto = {
        .func           = bpf_get_current_pidns_info,
        .gpl_only     = false,
        .ret_type     = RET_INTEGER,
    .arg1_type    = ARG_PTR_TO_RAW_STACK,
    .arg2_type    = ARG_CONST_STACK_SIZE,
};

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