[PATCH v3] sh_eth: Fix skb alloc size and alignment adjust rule.

[Yoshihiro Kaneko <ykaneko0929@gmail.com>]

From: Mitsuhiro Kimura <mitsuhiro.kimura.kc@renesas.com>

In the current driver, allocation size of skb does not care the alignment
adjust after allocation.
And also, in the current implementation, buffer alignment method by
sh_eth_set_receive_align function has a bug that this function displace
buffer start address forcedly when the alignment is corrected.
In the result, tail of the skb will exceed allocated area and kernel panic
will be occurred.
This patch fix this issue.

Signed-off-by: Mitsuhiro Kimura <mitsuhiro.kimura.kc@renesas.com>
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
---

The first version of this patch was a part of the patch series as follows:   
[PATCH 2/3] sh_eth: Fix skb alloc size and alignment adjust rule.

This patch is based on net tree.

v3 [Yoshihiro Kaneko]
* use uintptr_t instead of u32 in sh_eth_set_receive_align()

v2 [Yoshihiro Kaneko]
* Update as suggested by Sergei Shtylyov
  - Fixed the coding style
  - Corrected the comment
  - Removed {SH2_SH3|SH4}_SKB_RX_ALIGN

 drivers/net/ethernet/renesas/sh_eth.c | 32 +++++++++++++-------------------
 drivers/net/ethernet/renesas/sh_eth.h |  4 ++--
 2 files changed, 15 insertions(+), 21 deletions(-)

diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
index 60e9c2c..f9e30b8 100644
--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/drivers/net/ethernet/renesas/sh_eth.c
@@ -917,21 +917,13 @@ static int sh_eth_reset(struct net_device *ndev)
 	return ret;
 }
 
-#if defined(CONFIG_CPU_SH4) || defined(CONFIG_ARCH_SHMOBILE)
 static void sh_eth_set_receive_align(struct sk_buff *skb)
 {
-	int reserve;
+	uintptr_t reserve = (uintptr_t)skb->data & (SH_ETH_RX_ALIGN - 1);
 
-	reserve = SH4_SKB_RX_ALIGN - ((u32)skb->data & (SH4_SKB_RX_ALIGN - 1));
 	if (reserve)
-		skb_reserve(skb, reserve);
+		skb_reserve(skb, SH_ETH_RX_ALIGN - reserve);
 }
-#else
-static void sh_eth_set_receive_align(struct sk_buff *skb)
-{
-	skb_reserve(skb, SH2_SH3_SKB_RX_ALIGN);
-}
-#endif
 
 
 /* CPU <-> EDMAC endian convert */
@@ -1119,6 +1111,7 @@ static void sh_eth_ring_format(struct net_device *ndev)
 	struct sh_eth_txdesc *txdesc = NULL;
 	int rx_ringsize = sizeof(*rxdesc) * mdp->num_rx_ring;
 	int tx_ringsize = sizeof(*txdesc) * mdp->num_tx_ring;
+	int skbuff_size = mdp->rx_buf_sz + SH_ETH_RX_ALIGN - 1;
 
 	mdp->cur_rx = 0;
 	mdp->cur_tx = 0;
@@ -1131,21 +1124,21 @@ static void sh_eth_ring_format(struct net_device *ndev)
 	for (i = 0; i < mdp->num_rx_ring; i++) {
 		/* skb */
 		mdp->rx_skbuff[i] = NULL;
-		skb = netdev_alloc_skb(ndev, mdp->rx_buf_sz);
+		skb = netdev_alloc_skb(ndev, skbuff_size);
 		mdp->rx_skbuff[i] = skb;
 		if (skb = NULL)
 			break;
-		dma_map_single(&ndev->dev, skb->data, mdp->rx_buf_sz,
-			       DMA_FROM_DEVICE);
 		sh_eth_set_receive_align(skb);
 
 		/* RX descriptor */
 		rxdesc = &mdp->rx_ring[i];
+		/* The size of the buffer is a multiple of 16 bytes. */
+		rxdesc->buffer_length = ALIGN(mdp->rx_buf_sz, 16);
+		dma_map_single(&ndev->dev, skb->data, rxdesc->buffer_length,
+			       DMA_FROM_DEVICE);
 		rxdesc->addr = virt_to_phys(PTR_ALIGN(skb->data, 4));
 		rxdesc->status = cpu_to_edmac(mdp, RD_RACT | RD_RFP);
 
-		/* The size of the buffer is 16 byte boundary. */
-		rxdesc->buffer_length = ALIGN(mdp->rx_buf_sz, 16);
 		/* Rx descriptor address set */
 		if (i = 0) {
 			sh_eth_write(ndev, mdp->rx_desc_dma, RDLAR);
@@ -1397,6 +1390,7 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota)
 	struct sk_buff *skb;
 	u16 pkt_len = 0;
 	u32 desc_status;
+	int skbuff_size = mdp->rx_buf_sz + SH_ETH_RX_ALIGN - 1;
 
 	rxdesc = &mdp->rx_ring[entry];
 	while (!(rxdesc->status & cpu_to_edmac(mdp, RD_RACT))) {
@@ -1448,7 +1442,7 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota)
 			if (mdp->cd->rpadir)
 				skb_reserve(skb, NET_IP_ALIGN);
 			dma_sync_single_for_cpu(&ndev->dev, rxdesc->addr,
-						mdp->rx_buf_sz,
+						ALIGN(mdp->rx_buf_sz, 16),
 						DMA_FROM_DEVICE);
 			skb_put(skb, pkt_len);
 			skb->protocol = eth_type_trans(skb, ndev);
@@ -1468,13 +1462,13 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota)
 		rxdesc->buffer_length = ALIGN(mdp->rx_buf_sz, 16);
 
 		if (mdp->rx_skbuff[entry] = NULL) {
-			skb = netdev_alloc_skb(ndev, mdp->rx_buf_sz);
+			skb = netdev_alloc_skb(ndev, skbuff_size);
 			mdp->rx_skbuff[entry] = skb;
 			if (skb = NULL)
 				break;	/* Better luck next round. */
-			dma_map_single(&ndev->dev, skb->data, mdp->rx_buf_sz,
-				       DMA_FROM_DEVICE);
 			sh_eth_set_receive_align(skb);
+			dma_map_single(&ndev->dev, skb->data,
+				       rxdesc->buffer_length, DMA_FROM_DEVICE);
 
 			skb_checksum_none_assert(skb);
 			rxdesc->addr = virt_to_phys(PTR_ALIGN(skb->data, 4));
diff --git a/drivers/net/ethernet/renesas/sh_eth.h b/drivers/net/ethernet/renesas/sh_eth.h
index b37c427..9fa9332 100644
--- a/drivers/net/ethernet/renesas/sh_eth.h
+++ b/drivers/net/ethernet/renesas/sh_eth.h
@@ -162,9 +162,9 @@ enum {
 
 /* Driver's parameters */
 #if defined(CONFIG_CPU_SH4) || defined(CONFIG_ARCH_SHMOBILE)
-#define SH4_SKB_RX_ALIGN	32
+#define SH_ETH_RX_ALIGN		32
 #else
-#define SH2_SH3_SKB_RX_ALIGN	2
+#define SH_ETH_RX_ALIGN		2
 #endif
 
 /* Register's bits
-- 
1.9.1