Change m_devget()'s outdated and unused `offset' argument to actually mean

something: offset into the first mbuf of the target chain before copying
the source data over.

Make drivers using m_devget() with a first argument "data - ETHER_ALIGN"
to use the offset argument to pass ETHER_ALIGN in. The way it was previously
done is potentially dangerous if the source data was at the top of a page
and the offset caused the previous page to be copied (if the
previous page has not yet been appropriately mapped).

The old `offset' argument in m_devget() is not used anywhere (it's always
0) and dates back to ~1995 (and earlier?) when support for ethernet trailers
existed. With that support gone, it was merely collecting dust.

Tested on alpha by: jlemon
Partially submitted by: jlemon
Reviewed by: jlemon
MFC after: 3 weeks

1 files changed, 2 insertions, 3 deletions

diff --git a/sys/dev/sf/if_sf.c b/sys/dev/sf/if_sf.c
index dd26fca1e7af..e0d0149cc193 100644
--- a/sys/dev/sf/if_sf.c
+++ b/sys/dev/sf/if_sf.c
@@ -989,14 +989,13 @@ static void sf_rxeof(sc)
 			continue;
 		}
 
-		m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-		    cur_rx->sf_len + ETHER_ALIGN, 0, ifp, NULL);
+		m0 = m_devget(mtod(m, char *), cur_rx->sf_len, ETHER_ALIGN,
+		    ifp, NULL);
 		sf_newbuf(sc, desc, m);
 		if (m0 == NULL) {
 			ifp->if_ierrors++;
 			continue;
 		}
-		m_adj(m0, ETHER_ALIGN);
 		m = m0;
 
 		eh = mtod(m, struct ether_header *);