On 6/28/20 1:16 PM, Jiri Olsa wrote:
On Fri, Jun 26, 2020 at 02:36:37PM -0700, Yonghong Song wrote:
SNIP
- }
-
- t = btf_type_by_id(btf_vmlinux, t->type);
- if (!btf_type_is_ptr(t))
- return -EFAULT;
- t = btf_type_by_id(btf_vmlinux, t->type);
- if (!btf_type_is_func_proto(t))
- return -EFAULT;
-
- args = (const struct btf_param *)(t + 1);
- if (arg >= btf_type_vlen(t)) {
- bpf_log(log, "bpf helper %s doesn't have %d-th argument\n",
- fnname, arg);
+ if (WARN_ON_ONCE(!fn->btf_id))
The original code does not have this warning. It directly did
"ret = READ_ONCE(*btf_id);" after testing reg arg type ARG_PTR_TO_BTF_ID.
not sure why I put it in there, it's probably enough guarded
by arg_type having ARG_PTR_TO_BTF_ID, will remove
return -EINVAL;
- }
- t = btf_type_by_id(btf_vmlinux, args[arg].type);
- if (!btf_type_is_ptr(t) || !t->type) {
- /* anything but the pointer to struct is a helper config bug */
- bpf_log(log, "ARG_PTR_TO_BTF is misconfigured\n");
- return -EFAULT;
- }
- btf_id = t->type;
- t = btf_type_by_id(btf_vmlinux, t->type);
- /* skip modifiers */
- while (btf_type_is_modifier(t)) {
- btf_id = t->type;
- t = btf_type_by_id(btf_vmlinux, t->type);
- }
- if (!btf_type_is_struct(t)) {
- bpf_log(log, "ARG_PTR_TO_BTF is not a struct\n");
- return -EFAULT;
- }
- bpf_log(log, "helper %s arg%d has btf_id %d struct %s\n", fnname + 4,
- arg, btf_id, __btf_name_by_offset(btf_vmlinux, t->name_off));
- return btf_id;
-}
+ id = fn->btf_id[arg];
The corresponding BTF_ID definition here is:
BTF_ID_LIST(bpf_skb_output_btf_ids)
BTF_ID(struct, sk_buff)
The bpf helper writer needs to ensure proper declarations
of BTF_IDs like the above matching helpers definition.
Support we have arg1 and arg3 as BTF_ID. then the list
definition may be
BTF_ID_LIST(bpf_skb_output_btf_ids)
BTF_ID(struct, sk_buff)
BTF_ID(struct, __unused)
BTF_ID(struct, task_struct)
This probably okay, I guess.
right, AFAIK we don't have such case yet, but would be good
to be ready and have something like
BTF_ID(struct, __unused)
maybe adding new type for that will be better:
BTF_ID(none, unused)
Maybe we can have a separate macro BTF_ID_UNUSED macro
which simply adds 4 bytes hole in the .btf_ids* section.
jirka
