On Wed, May 5, 2021 at 6:42 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > We can't currently allow to attach functions with variable arguments. > The problem is that we should save all the registers for arguments, > which is probably doable, but if caller uses more than 6 arguments, > we need stack data, which will be wrong, because of the extra stack > frame we do in bpf trampoline, so we could crash. > > Also currently there's malformed trampoline code generated for such > functions at the moment as described in: > https://lore.kernel.org/bpf/20210429212834.82621-1-jolsa@xxxxxxxxxx/ > > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > --- LGTM. Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > kernel/bpf/btf.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > index 0600ed325fa0..161511bb3e51 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -5206,6 +5206,13 @@ int btf_distill_func_proto(struct bpf_verifier_log *log, > m->ret_size = ret; > > for (i = 0; i < nargs; i++) { > + if (i == nargs - 1 && args[i].type == 0) { > + bpf_log(log, > + "The function %s with variable args is unsupported.\n", > + tname); > + return -EINVAL; > + > + } > ret = __get_type_size(btf, args[i].type, &t); > if (ret < 0) { > bpf_log(log, > @@ -5213,6 +5220,12 @@ int btf_distill_func_proto(struct bpf_verifier_log *log, > tname, i, btf_kind_str[BTF_INFO_KIND(t->info)]); > return -EINVAL; > } > + if (ret == 0) { > + bpf_log(log, > + "The function %s has malformed void argument.\n", > + tname); > + return -EINVAL; > + } > m->arg_size[i] = ret; > } > m->nr_args = nargs; > -- > 2.30.2 >
