Change m_devget()'s outdated and unused `offset' argument to actually mean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

15 files changed, 57 insertions, 90 deletions

diff --git a/sys/dev/dc/if_dc.c b/sys/dev/dc/if_dc.c
index 83eb65e..0ef88c3 100644
--- a/sys/dev/dc/if_dc.c
+++ b/sys/dev/dc/if_dc.c
@@ -2502,15 +2502,14 @@ static void dc_rxeof(sc)
 		/* No errors; receive the packet. */	
 		total_len -= ETHER_CRC_LEN;
 
-		m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-		    total_len + ETHER_ALIGN, 0, ifp, NULL);
+		m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN, ifp,
+		    NULL);
 		dc_newbuf(sc, i, m);
 		DC_INC(i, DC_RX_LIST_CNT);
 		if (m0 == NULL) {
 			ifp->if_ierrors++;
 			continue;
 		}
-		m_adj(m0, ETHER_ALIGN);
 		m = m0;
 
 		ifp->if_ipackets++;
diff --git a/sys/dev/lge/if_lge.c b/sys/dev/lge/if_lge.c
index d6f9e80..1558004 100644
--- a/sys/dev/lge/if_lge.c
+++ b/sys/dev/lge/if_lge.c
@@ -993,8 +993,8 @@ static void lge_rxeof(sc, cnt)
 		}
 
 		if (lge_newbuf(sc, &LGE_RXTAIL(sc), NULL) == ENOBUFS) {
-			m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-			    total_len + ETHER_ALIGN, 0, ifp, NULL);
+			m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN,
+			    ifp, NULL);
 			lge_newbuf(sc, &LGE_RXTAIL(sc), m);
 			if (m0 == NULL) {
 				printf("lge%d: no receive buffers "
@@ -1003,7 +1003,6 @@ static void lge_rxeof(sc, cnt)
 				ifp->if_ierrors++;
 				continue;
 			}
-			m_adj(m0, ETHER_ALIGN);
 			m = m0;
 		} else {
 			m->m_pkthdr.rcvif = ifp;
diff --git a/sys/dev/nge/if_nge.c b/sys/dev/nge/if_nge.c
index 9c15beb..65dd718 100644
--- a/sys/dev/nge/if_nge.c
+++ b/sys/dev/nge/if_nge.c
@@ -1278,8 +1278,8 @@ static void nge_rxeof(sc)
 		 * only gigE chip I know of with alignment constraints
 		 * on receive buffers. RX buffers must be 64-bit aligned.
 		 */
-		m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-		    total_len + ETHER_ALIGN, 0, ifp, NULL);
+		m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN, ifp,
+		    NULL);
 		nge_newbuf(sc, cur_rx, m);
 		if (m0 == NULL) {
 			printf("nge%d: no receive buffers "
@@ -1288,7 +1288,6 @@ static void nge_rxeof(sc)
 			ifp->if_ierrors++;
 			continue;
 		}
-		m_adj(m0, ETHER_ALIGN);
 		m = m0;
 
 		ifp->if_ipackets++;
diff --git a/sys/dev/sf/if_sf.c b/sys/dev/sf/if_sf.c
index dd26fca..e0d0149 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 *);
diff --git a/sys/dev/sk/if_sk.c b/sys/dev/sk/if_sk.c
index 83d5720..6c9ec6a 100644
--- a/sys/dev/sk/if_sk.c
+++ b/sys/dev/sk/if_sk.c
@@ -1579,8 +1579,8 @@ static void sk_rxeof(sc_if)
 		 */
 		if (sk_newbuf(sc_if, cur_rx, NULL) == ENOBUFS) {
 			struct mbuf		*m0;
-			m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-			    total_len + ETHER_ALIGN, 0, ifp, NULL);
+			m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN,
+			    ifp, NULL);
 			sk_newbuf(sc_if, cur_rx, m);
 			if (m0 == NULL) {
 				printf("sk%d: no receive buffers "
@@ -1589,7 +1589,6 @@ static void sk_rxeof(sc_if)
 				ifp->if_ierrors++;
 				continue;
 			}
-			m_adj(m0, ETHER_ALIGN);
 			m = m0;
 		} else {
 			m->m_pkthdr.rcvif = ifp;
diff --git a/sys/dev/vr/if_vr.c b/sys/dev/vr/if_vr.c
index 93fba3e..9ed0266 100644
--- a/sys/dev/vr/if_vr.c
+++ b/sys/dev/vr/if_vr.c
@@ -1029,14 +1029,13 @@ static void vr_rxeof(sc)
 		 */
 		total_len -= ETHER_CRC_LEN;
 
-		m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-		    total_len + ETHER_ALIGN, 0, ifp, NULL);
+		m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN, ifp,
+		    NULL);
 		vr_newbuf(sc, cur_rx, m);
 		if (m0 == NULL) {
 			ifp->if_ierrors++;
 			continue;
 		}
-		m_adj(m0, ETHER_ALIGN);
 		m = m0;
 
 		ifp->if_ipackets++;
diff --git a/sys/dev/vx/if_vx.c b/sys/dev/vx/if_vx.c
index e1fa760..f475080 100644
--- a/sys/dev/vx/if_vx.c
+++ b/sys/dev/vx/if_vx.c
@@ -691,15 +691,12 @@ again:
     {
 	struct mbuf		*m0;
 
-	m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-	    m->m_pkthdr.len + ETHER_ALIGN, 0, ifp, NULL);
-
+	m0 = m_devget(mtod(m, char *), m->m_pkthdr.len, ETHER_ALIGN, ifp, NULL);
 	if (m0 == NULL) {
 		ifp->if_ierrors++;
 		goto abort;
 	}
 
-	m_adj(m0, ETHER_ALIGN);
 	m_freem(m);
 	m = m0;
     }
diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index 4134623..a4d3674 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -1078,29 +1078,26 @@ extpacket:
 }
 /*
  * Routine to copy from device local memory into mbufs.
+ * Note that `off' argument is offset into first mbuf of target chain from
+ * which to begin copying the data to.
  */
 struct mbuf *
-m_devget(char *buf, int totlen, int off0, struct ifnet *ifp,
+m_devget(char *buf, int totlen, int off, struct ifnet *ifp,
 	 void (*copy)(char *from, caddr_t to, u_int len))
 {
 	struct mbuf *m;
 	struct mbuf *top = 0, **mp = ⊤
-	int off = off0, len;
-	char *cp;
-	char *epkt;
-
-	cp = buf;
-	epkt = cp + totlen;
-	if (off) {
-		cp += off + 2 * sizeof(u_short);
-		totlen -= 2 * sizeof(u_short);
-	}
+	int len;
+
+	if (off < 0 || off > MHLEN)
+		return (NULL);
+
 	MGETHDR(m, M_DONTWAIT, MT_DATA);
 	if (m == NULL)
 		return (NULL);
 	m->m_pkthdr.rcvif = ifp;
 	m->m_pkthdr.len = totlen;
-	m->m_len = MHLEN;
+	len = MHLEN;
 
 	while (totlen > 0) {
 		if (top) {
@@ -1109,37 +1106,35 @@ m_devget(char *buf, int totlen, int off0, struct ifnet *ifp,
 				m_freem(top);
 				return (NULL);
 			}
-			m->m_len = MLEN;
+			len = MLEN;
 		}
-		len = min(totlen, epkt - cp);
-		if (len >= MINCLSIZE) {
+		if (totlen + off >= MINCLSIZE) {
 			MCLGET(m, M_DONTWAIT);
 			if (m->m_flags & M_EXT)
-				m->m_len = len = min(len, MCLBYTES);
-			else
-				len = m->m_len;
+				len = MCLBYTES;
 		} else {
 			/*
 			 * Place initial small packet/header at end of mbuf.
 			 */
-			if (len < m->m_len) {
-				if (top == NULL && len +
-				    max_linkhdr <= m->m_len)
-					m->m_data += max_linkhdr;
-				m->m_len = len;
-			} else
-				len = m->m_len;
+			if (top == NULL && totlen + off + max_linkhdr <= len) {
+				m->m_data += max_linkhdr;
+				len -= max_linkhdr;
+			}
+		}
+		if (off) {
+			m->m_data += off;
+			len -= off;
+			off = 0;
 		}
+		m->m_len = len = min(totlen, len);
 		if (copy)
-			copy(cp, mtod(m, caddr_t), (unsigned)len);
+			copy(buf, mtod(m, caddr_t), (unsigned)len);
 		else
-			bcopy(cp, mtod(m, caddr_t), (unsigned)len);
-		cp += len;
+			bcopy(buf, mtod(m, caddr_t), (unsigned)len);
+		buf += len;
 		*mp = m;
 		mp = &m->m_next;
 		totlen -= len;
-		if (cp == epkt)
-			cp = buf;
 	}
 	return (top);
 }
diff --git a/sys/pci/if_dc.c b/sys/pci/if_dc.c
index 83eb65e..0ef88c3 100644
--- a/sys/pci/if_dc.c
+++ b/sys/pci/if_dc.c
@@ -2502,15 +2502,14 @@ static void dc_rxeof(sc)
 		/* No errors; receive the packet. */	
 		total_len -= ETHER_CRC_LEN;
 
-		m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-		    total_len + ETHER_ALIGN, 0, ifp, NULL);
+		m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN, ifp,
+		    NULL);
 		dc_newbuf(sc, i, m);
 		DC_INC(i, DC_RX_LIST_CNT);
 		if (m0 == NULL) {
 			ifp->if_ierrors++;
 			continue;
 		}
-		m_adj(m0, ETHER_ALIGN);
 		m = m0;
 
 		ifp->if_ipackets++;
diff --git a/sys/pci/if_rl.c b/sys/pci/if_rl.c
index 90dd737..269f293 100644
--- a/sys/pci/if_rl.c
+++ b/sys/pci/if_rl.c
@@ -1063,14 +1063,8 @@ static int rl_list_tx_init(sc)
  * the 'rx status register' mentioned in the datasheet.
  *
  * Note: to make the Alpha happy, the frame payload needs to be aligned
- * on a 32-bit boundary. To achieve this, we cheat a bit by copying from
- * the ring buffer starting at an address two bytes before the actual
- * data location. We can then shave off the first two bytes using m_adj().
- * The reason we do this is because m_devget() doesn't let us specify an
- * offset into the mbuf storage space, so we have to artificially create
- * one. The ring is allocated in such a way that there are a few unused
- * bytes of space preceecing it so that it will be safe for us to do the
- * 2-byte backstep even if reading from the ring at offset 0.
+ * on a 32-bit boundary. To achieve this, we pass RL_ETHER_ALIGN (2 bytes)
+ * as the offset argument to m_devget(). 
  */
 static void rl_rxeof(sc)
 	struct rl_softc		*sc;
@@ -1148,32 +1142,25 @@ static void rl_rxeof(sc)
 		wrap = (sc->rl_cdata.rl_rx_buf + RL_RXBUFLEN) - rxbufpos;
 
 		if (total_len > wrap) {
-			/*
-			 * Fool m_devget() into thinking we want to copy
-			 * the whole buffer so we don't end up fragmenting
-			 * the data.
-			 */
-			m = m_devget(rxbufpos - RL_ETHER_ALIGN,
-			    total_len + RL_ETHER_ALIGN, 0, ifp, NULL);
+			m = m_devget(rxbufpos, total_len, RL_ETHER_ALIGN, ifp,
+			    NULL);
 			if (m == NULL) {
 				ifp->if_ierrors++;
 				printf("rl%d: out of mbufs, tried to "
 				    "copy %d bytes\n", sc->rl_unit, wrap);
 			} else {
-				m_adj(m, RL_ETHER_ALIGN);
 				m_copyback(m, wrap, total_len - wrap,
 					sc->rl_cdata.rl_rx_buf);
 			}
 			cur_rx = (total_len - wrap + ETHER_CRC_LEN);
 		} else {
-			m = m_devget(rxbufpos - RL_ETHER_ALIGN,
-			    total_len + RL_ETHER_ALIGN, 0, ifp, NULL);
+			m = m_devget(rxbufpos, total_len, RL_ETHER_ALIGN, ifp,
+			    NULL);
 			if (m == NULL) {
 				ifp->if_ierrors++;
 				printf("rl%d: out of mbufs, tried to "
 				    "copy %d bytes\n", sc->rl_unit, total_len);
-			} else
-				m_adj(m, RL_ETHER_ALIGN);
+			}
 			cur_rx += total_len + 4 + ETHER_CRC_LEN;
 		}
 
diff --git a/sys/pci/if_sf.c b/sys/pci/if_sf.c
index dd26fca..e0d0149 100644
--- a/sys/pci/if_sf.c
+++ b/sys/pci/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 *);
diff --git a/sys/pci/if_sis.c b/sys/pci/if_sis.c
index 8394674..c93fba3 100644
--- a/sys/pci/if_sis.c
+++ b/sys/pci/if_sis.c
@@ -1129,14 +1129,13 @@ static void sis_rxeof(sc)
 		}
 
 		/* No errors; receive the packet. */	
-		m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-		    total_len + ETHER_ALIGN, 0, ifp, NULL);
+		m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN, ifp,
+		    NULL);
 		sis_newbuf(sc, cur_rx, m);
 		if (m0 == NULL) {
 			ifp->if_ierrors++;
 			continue;
 		}
-		m_adj(m0, ETHER_ALIGN);
 		m = m0;
 
 		ifp->if_ipackets++;
diff --git a/sys/pci/if_sk.c b/sys/pci/if_sk.c
index 83d5720..6c9ec6a 100644
--- a/sys/pci/if_sk.c
+++ b/sys/pci/if_sk.c
@@ -1579,8 +1579,8 @@ static void sk_rxeof(sc_if)
 		 */
 		if (sk_newbuf(sc_if, cur_rx, NULL) == ENOBUFS) {
 			struct mbuf		*m0;
-			m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-			    total_len + ETHER_ALIGN, 0, ifp, NULL);
+			m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN,
+			    ifp, NULL);
 			sk_newbuf(sc_if, cur_rx, m);
 			if (m0 == NULL) {
 				printf("sk%d: no receive buffers "
@@ -1589,7 +1589,6 @@ static void sk_rxeof(sc_if)
 				ifp->if_ierrors++;
 				continue;
 			}
-			m_adj(m0, ETHER_ALIGN);
 			m = m0;
 		} else {
 			m->m_pkthdr.rcvif = ifp;
diff --git a/sys/pci/if_vr.c b/sys/pci/if_vr.c
index 93fba3e..9ed0266 100644
--- a/sys/pci/if_vr.c
+++ b/sys/pci/if_vr.c
@@ -1029,14 +1029,13 @@ static void vr_rxeof(sc)
 		 */
 		total_len -= ETHER_CRC_LEN;
 
-		m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-		    total_len + ETHER_ALIGN, 0, ifp, NULL);
+		m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN, ifp,
+		    NULL);
 		vr_newbuf(sc, cur_rx, m);
 		if (m0 == NULL) {
 			ifp->if_ierrors++;
 			continue;
 		}
-		m_adj(m0, ETHER_ALIGN);
 		m = m0;
 
 		ifp->if_ipackets++;
diff --git a/sys/pci/if_wb.c b/sys/pci/if_wb.c
index 50de1fd..a03951b 100644
--- a/sys/pci/if_wb.c
+++ b/sys/pci/if_wb.c
@@ -1175,14 +1175,13 @@ static void wb_rxeof(sc)
 		 */
 		total_len -= ETHER_CRC_LEN;
 
-		m0 = m_devget(mtod(m, char *) - ETHER_ALIGN,
-		     total_len + ETHER_ALIGN, 0, ifp, NULL);
+		m0 = m_devget(mtod(m, char *), total_len, ETHER_ALIGN, ifp,
+		    NULL);
 		wb_newbuf(sc, cur_rx, m);
 		if (m0 == NULL) {
 			ifp->if_ierrors++;
 			break;
 		}
-		m_adj(m0, ETHER_ALIGN);
 		m = m0;
 
 		ifp->if_ipackets++;