net: axienet: Fix casting of pointers to u32

This driver was casting skb pointers to u32 and storing them as such in
the DMA buffer descriptor, which is obviously broken on 64-bit. The area
of the buffer descriptor being used is not accessed by the hardware and
has sufficient room for a 32 or 64-bit pointer, so just store the skb
pointer as such.
Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/xilinx/xilinx_axienet.h

@@ -356,9 +356,6 @@
  * @app2:         MM2S/S2MM User Application Field 2.
  * @app3:         MM2S/S2MM User Application Field 3.
  * @app4:         MM2S/S2MM User Application Field 4.
- * @sw_id_offset: MM2S/S2MM Sw ID
- * @reserved5:    Reserved and not used
- * @reserved6:    Reserved and not used
  */
 struct axidma_bd {
 	u32 next;	/* Physical address of next buffer descriptor */
@@ -373,11 +370,9 @@ struct axidma_bd {
 	u32 app1;	/* TX start << 16 | insert */
 	u32 app2;	/* TX csum seed */
 	u32 app3;
-	u32 app4;
-	u32 sw_id_offset;
-	u32 reserved5;
-	u32 reserved6;
-};
+	u32 app4;   /* Last field used by HW */
+	struct sk_buff *skb;
+} __aligned(XAXIDMA_BD_MINIMUM_ALIGNMENT);
 
 /**
  * struct axienet_local - axienet private per device data

drivers/net/ethernet/xilinx/xilinx_axienet_main.c

@@ -159,8 +159,7 @@ static void axienet_dma_bd_release(struct net_device *ndev)
 	for (i = 0; i < RX_BD_NUM; i++) {
 		dma_unmap_single(ndev->dev.parent, lp->rx_bd_v[i].phys,
 				 lp->max_frm_size, DMA_FROM_DEVICE);
-		dev_kfree_skb((struct sk_buff *)
-			      (lp->rx_bd_v[i].sw_id_offset));
+		dev_kfree_skb(lp->rx_bd_v[i].skb);
 	}
 
 	if (lp->rx_bd_v) {
@@ -227,7 +226,7 @@ static int axienet_dma_bd_init(struct net_device *ndev)
 		if (!skb)
 			goto out;
 
-		lp->rx_bd_v[i].sw_id_offset = (u32) skb;
+		lp->rx_bd_v[i].skb = skb;
 		lp->rx_bd_v[i].phys = dma_map_single(ndev->dev.parent,
 						     skb->data,
 						     lp->max_frm_size,
@@ -595,14 +594,15 @@ static void axienet_start_xmit_done(struct net_device *ndev)
 		dma_unmap_single(ndev->dev.parent, cur_p->phys,
 				(cur_p->cntrl & XAXIDMA_BD_CTRL_LENGTH_MASK),
 				DMA_TO_DEVICE);
-		if (cur_p->app4)
-			dev_consume_skb_irq((struct sk_buff *)cur_p->app4);
+		if (cur_p->skb)
+			dev_consume_skb_irq(cur_p->skb);
 		/*cur_p->phys = 0;*/
 		cur_p->app0 = 0;
 		cur_p->app1 = 0;
 		cur_p->app2 = 0;
 		cur_p->app4 = 0;
 		cur_p->status = 0;
+		cur_p->skb = NULL;
 
 		size += status & XAXIDMA_BD_STS_ACTUAL_LEN_MASK;
 		packets++;
@@ -707,7 +707,7 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	}
 
 	cur_p->cntrl |= XAXIDMA_BD_CTRL_TXEOF_MASK;
-	cur_p->app4 = (unsigned long)skb;
+	cur_p->skb = skb;
 
 	tail_p = lp->tx_bd_p + sizeof(*lp->tx_bd_v) * lp->tx_bd_tail;
 	/* Start the transfer */
@@ -742,13 +742,15 @@ static void axienet_recv(struct net_device *ndev)
 
 	while ((cur_p->status & XAXIDMA_BD_STS_COMPLETE_MASK)) {
 		tail_p = lp->rx_bd_p + sizeof(*lp->rx_bd_v) * lp->rx_bd_ci;
-		skb = (struct sk_buff *) (cur_p->sw_id_offset);
-		length = cur_p->app4 & 0x0000FFFF;
 
 		dma_unmap_single(ndev->dev.parent, cur_p->phys,
 				 lp->max_frm_size,
 				 DMA_FROM_DEVICE);
 
+		skb = cur_p->skb;
+		cur_p->skb = NULL;
+		length = cur_p->app4 & 0x0000FFFF;
+
 		skb_put(skb, length);
 		skb->protocol = eth_type_trans(skb, ndev);
 		/*skb_checksum_none_assert(skb);*/
@@ -783,7 +785,7 @@ static void axienet_recv(struct net_device *ndev)
 					     DMA_FROM_DEVICE);
 		cur_p->cntrl = lp->max_frm_size;
 		cur_p->status = 0;
-		cur_p->sw_id_offset = (u32) new_skb;
+		cur_p->skb = new_skb;
 
 		++lp->rx_bd_ci;
 		lp->rx_bd_ci %= RX_BD_NUM;
@@ -1343,8 +1345,8 @@ static void axienet_dma_err_handler(unsigned long data)
 					 (cur_p->cntrl &
 					  XAXIDMA_BD_CTRL_LENGTH_MASK),
 					 DMA_TO_DEVICE);
-		if (cur_p->app4)
-			dev_kfree_skb_irq((struct sk_buff *) cur_p->app4);
+		if (cur_p->skb)
+			dev_kfree_skb_irq(cur_p->skb);
 		cur_p->phys = 0;
 		cur_p->cntrl = 0;
 		cur_p->status = 0;
@@ -1353,7 +1355,7 @@ static void axienet_dma_err_handler(unsigned long data)
 		cur_p->app2 = 0;
 		cur_p->app3 = 0;
 		cur_p->app4 = 0;
-		cur_p->sw_id_offset = 0;
+		cur_p->skb = NULL;
 	}
 
 	for (i = 0; i < RX_BD_NUM; i++) {