Re: some kernel hacking tasks

[Antonio Huete Jiménez <ahuete.devel@xxxxxxxxx>]

Hi Sephe,

I think I've tackled all the points you mentioned:  
http://leaf.dragonflybsd.org/~tuxillo/archive/patches/bpf_token03.diff

I've also found a place where bpf_token might be needed. Not sure either  
whether we would need to check all the bpf_tap(), bpf_mtap() and  
bpf_ptap() calls to see if they're properly protected.

diff --git a/sys/net/if_loop.c b/sys/net/if_loop.c
index e3f6724..a58d943 100644
--- a/sys/net/if_loop.c
+++ b/sys/net/if_loop.c
@@ -199,7 +199,7 @@ if_simloop(struct ifnet *ifp, struct mbuf *m, int af,  
int hlen)
         }

         if (ifp->if_bpf) {
-               get_mplock();
+               lwkt_gettoken(&bpf_token);

                 /* Re-check */
                 if (ifp->if_bpf == NULL)
@@ -212,7 +212,7 @@ if_simloop(struct ifnet *ifp, struct mbuf *m, int af,  
int hlen)
                         bpf_mtap(ifp->if_bpf, m);
                 }
  rel:
-               rel_mplock();
+               lwkt_reltoken(&bpf_token);
         }

         /* Strip away media header */

Cheers,
Antonio Huete

> I have looked at the patch.  I think there are still something missing:
> - bpf code actually assumes that mplock is held on the device node
> interfaces, so you probably need to protect them w/ the bpf token.
> - bpfattach/bpfdetach should probably be protected by bpf token
> - Macros like BPF_TAP() and ETHER_BPF_MTAP() probably will need the
> check-hold_token-recheck sequence, e.g.:
> if (ifp->if_bpf) {
>     bpf_gettoken();
>     if (ifp->if_bpf)
>         bpf_tap(...);
>     bpf_reltoken();
> }
>
> Best Regards,
> sephe