On Fri, Nov 20, 2020 at 3:06 PM Martin KaFai Lau <kafai@xxxxxx> wrote:
>
> 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.
ok, I'll add something about that. The short answer is that
__find_vmlinux_btf_id() is now expected to not find a type in vmlinux
BTF, so emitting error would be wrong. So I moved it up a level where
it's not expected.
>
> > btf__free(btf);
> > return err;
> > }
> > --
> > 2.24.1
> >
