On 08/22, Alexei Starovoitov wrote:
> On Thu, Aug 22, 2024 at 12:02 AM Tze-nan Wu (吳澤南)
> <Tze-nan.Wu@xxxxxxxxxxxx> wrote:
> >
> >
> > BTW, If this should be handled in kernel, modification shown below
> > could fix the issue without breaking the "static_branch" usage in both
> > macros:
> >
> >
> > +++ /include/linux/bpf-cgroup.h:
> > -#define BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen)
> > +#define BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen, compat)
> > ({
> > int __ret = 0;
> > if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT))
> > copy_from_sockptr(&__ret, optlen, sizeof(int));
> > + else
> > + *compat = true;
> > __ret;
> > })
> >
> > #define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname,
> > optval, optlen, max_optlen, retval)
> > ({
> > int __ret = retval;
> > - if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT) &&
> > - cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT))
> > + if (cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT))
> > if (!(sock)->sk_prot->bpf_bypass_getsockopt ||
> > ...
> >
> > +++ /net/socket.c:
> > int do_sock_getsockopt(struct socket *sock, bool compat, int level,
> > {
> > ...
> > ...
> > + /* The meaning of `compat` variable could be changed here
> > + * to indicate if cgroup_bpf_enabled(CGROUP_SOCK_OPS) is
> > false.
> > + */
> > if (!compat)
> > - max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen);
> > + max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen,
> > &compat);
>
> This is better, but it's still quite a hack. Let's not override it.
> We can have another bool, but the question:
> do we really need BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN ?
> copy_from_sockptr(&__ret, optlen, sizeof(int));
> should be fast enough to do it unconditionally.
> What are we saving here?
>
> Stan ?
Agreed, most likely nobody would notice :-)
