On Thu, Nov 19, 2020 at 03:22:42PM -0800, Andrii Nakryiko wrote:
[ ... ]

> +static int load_module_btfs(struct bpf_object *obj)
> +{
> +     struct bpf_btf_info info;
> +     struct module_btf *mod_btf;
> +     struct btf *btf;
> +     char name[64];
> +     __u32 id, len;
> +     int err, fd;
> +
> +     if (obj->btf_modules_loaded)
> +             return 0;
> +
> +     /* don't do this again, even if we find no module BTFs */
> +     obj->btf_modules_loaded = true;
> +
> +     /* kernel too old to support module BTFs */
> +     if (!kernel_supports(FEAT_MODULE_BTF))
> +             return 0;
> +
> +     while (true) {
> +             err = bpf_btf_get_next_id(id, &id);
> +             if (err && errno == ENOENT)
> +                     return 0;
> +             if (err) {
> +                     err = -errno;
> +                     pr_warn("failed to iterate BTF objects: %d\n", err);
> +                     return err;
> +             }
> +
> +             fd = bpf_btf_get_fd_by_id(id);
> +             if (fd < 0) {
> +                     if (errno == ENOENT)
> +                             continue; /* expected race: BTF was unloaded */
> +                     err = -errno;
> +                     pr_warn("failed to get BTF object #%d FD: %d\n", id, 
> err);
> +                     return err;
> +             }
> +
> +             len = sizeof(info);
> +             memset(&info, 0, sizeof(info));
> +             info.name = ptr_to_u64(name);
> +             info.name_len = sizeof(name);
> +
> +             err = bpf_obj_get_info_by_fd(fd, &info, &len);
> +             if (err) {
> +                     err = -errno;
> +                     pr_warn("failed to get BTF object #%d info: %d\n", id, 
> err);

                        close(fd);

> +                     return err;
> +             }
> +
> +             /* ignore non-module BTFs */
> +             if (!info.kernel_btf || strcmp(name, "vmlinux") == 0) {
> +                     close(fd);
> +                     continue;
> +             }
> +

[ ... ]

> @@ -8656,9 +8815,6 @@ static inline int __find_vmlinux_btf_id(struct btf 
> *btf, const char *name,
>       else
>               err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
>  
> -     if (err <= 0)
> -             pr_warn("%s is not found in vmlinux BTF\n", name);
> -
>       return err;
>  }
>  
> @@ -8675,6 +8831,9 @@ int libbpf_find_vmlinux_btf_id(const char *name,
>       }
>  
>       err = __find_vmlinux_btf_id(btf, name, attach_type);
> +     if (err <= 0)
> +             pr_warn("%s is not found in vmlinux BTF\n", name);
> +
Please explain this move in the commit message.

>       btf__free(btf);
>       return err;
>  }
> -- 
> 2.24.1
> 

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