According to [1], we can get all iter types supported by the current kernel according to the 'bpf_ter__' prefix

[1]: https://www.kernel.org/doc/html/latest/bpf/bpf_iterators.html#how-to-use-bpf-iterators

Signed-off-by: Shuyi Cheng <[email protected]>

Run bpftrace -l iter:* the output is as follows:

	iter:task
	iter:task_file
	iter:task_vma

But the current kernel does not support 'iter:task_vma'. After applying this patch, run the command again, the output is as follows:

	iter:bpf_map
	iter:bpf_map_elem
	iter:bpf_prog
	iter:bpf_sk_storage_map
	iter:ipv6_route
	iter:netlink
	iter:sockmap
	iter:task
	iter:task_file
	iter:tcp
	iter:udp

Signed-off-by: Shuyi Cheng <[email protected]>

For each iter, the kernel will have a bpf_iter_$ITER function, so we can get the parameters of iter through bpf_iter_$ITER.

Run `bpftrace -l iter:*` and shows:

```
iter:task
    struct task_struct * task
iter:task_file
    struct task_struct * task
    int fd
    struct file * file
iter:task_vma
    struct task_struct * task
    struct vm_area_struct * vma
```

The output after applying this patch is as follows:

```
iter:bpf_map
    struct bpf_map * map
iter:bpf_map_elem
    struct bpf_map * map
    void * key
    void * value
iter:bpf_prog
    struct bpf_prog * prog
iter:bpf_sk_storage_map
    struct bpf_map * map
    struct sock * sk
    void * value
iter:ipv6_route
    struct fib6_info * rt
iter:netlink
    struct netlink_sock * sk
iter:sockmap
    struct bpf_map * map
    void * key
    struct sock * sk
iter:task
    struct task_struct * task
iter:task_file
    struct task_struct * task
    u32 fd
    struct file * file
iter:tcp
    struct sock_common * sk_common
    uid_t uid
iter:udp
    struct udp_sock * udp_sk
    uid_t uid
    int bucket
```

Signed-off-by: Shuyi Cheng <[email protected]>

Support all iters, this patch mainly modifies the following places:

- Delete the hard code, and get the type of iter by concatenating `bpf_iter__` and the function name
- Use has_iter to check whether the iter exists
- add iter tracing function for tests
- clean up older iter related code

Signed-off-by: Shuyi Cheng <[email protected]>

When ap.func is empty, the input parameter tokens of the wildcard_match function will be empty, and a panic will occur when tokens[0] is obtained. Therefore, iter should be similar to kfunc, and avoid ap.func being empty during the semantic analysis stage.

```
bpftrace -l kfunc:
stdin:1:1-7: ERROR: kfunc should specify a function
kfunc:
~~~~~~

bpftrace -l iter:
stdin:1:1-6: ERROR: iter should specify a iterator's name
iter:
~~~~~
```

Signed-off-by: Shuyi Cheng <[email protected]>

Signed-off-by: Shuyi Cheng <[email protected]>