On Sun, Sep 29, 2024 at 2:31 AM Eric Long via B4 Relay
<devnull+i.hack3r.moe@xxxxxxxxxx> wrote:
>
> From: Eric Long <i@xxxxxxxxxx>
>
> FUNCs do not have sizes, thus currently btf__resolve_size will fail
> with -EINVAL. Add conditions so that we only update size when the BTF
> object is not function or function prototype.
>
> Signed-off-by: Eric Long <i@xxxxxxxxxx>
> ---
> tools/lib/bpf/linker.c | 23 +++++++++++++----------
> 1 file changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
> index 81dbbdd79a7c65a4b048b85e1dba99cb5f7cb56b..cffb388fa40ef054c2661b8363120f8a4d3c3784 100644
> --- a/tools/lib/bpf/linker.c
> +++ b/tools/lib/bpf/linker.c
> @@ -2452,17 +2452,20 @@ static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
> __s64 sz;
>
> dst_var = &dst_sec->sec_vars[glob_sym->var_idx];
> - /* Because underlying BTF type might have
> - * changed, so might its size have changed, so
> - * re-calculate and update it in sec_var.
> - */
> - sz = btf__resolve_size(linker->btf, glob_sym->underlying_btf_id);
> - if (sz < 0) {
> - pr_warn("global '%s': failed to resolve size of underlying type: %d\n",
> - name, (int)sz);
> - return -EINVAL;
> + t = btf__type_by_id(linker->btf, glob_sym->underlying_btf_id);
> + if (btf_kind(t) != BTF_KIND_FUNC && btf_kind(t) != BTF_KIND_FUNC_PROTO) {
> + /* Because underlying BTF type might have
> + * changed, so might its size have changed, so
> + * re-calculate and update it in sec_var.
> + */
> + sz = btf__resolve_size(linker->btf, glob_sym->underlying_btf_id);
> + if (sz < 0) {
> + pr_warn("global '%s': failed to resolve size of underlying type: %d\n",
> + name, (int)sz);
> + return -EINVAL;
> + }
> + dst_var->size = sz;
Looks like a hack to me.
In the test you're using:
void *bpf_cast_to_kern_ctx(void *obj) __ksym;
but __weak is missing.
Is that the reason you're hitting this issue?
