On Wed, Dec 1, 2021 at 10:00 AM Andrii Nakryiko
[off-list ref] wrote:

But you emphasized an important point, that it's probably good to
allow users to distinguish errors from reading actual value 0. There
are and will be situations where argument isn't available or some
combination of conditions are not supported. So I think, while it's a
bit more verbose, these forms are generally better:

int bpf_get_func_arg(int n, u64 *value);
int bpf_get_func_ret(u64 *value);

WDYT?

Makes sense to me.
The verifier will be able to inline it just fine.
Two extra insns only compared to direct return.