[U-Boot] Data Abort with gcc 7.1

https://lists.denx.de/pipermail/u-boot/2017-July/298016.html

The --wno-unaligned-access option does not help because the
compiler assumes that the struct pointer is properly aligned.

This bug can be fixed by either:

  1) Always ensure proper alignment of the udp packet header
     pointers, which are passed to the net_set_ip_header() function
     and similar functions. Some further investigation is necessary.

or

  2) Just add a "packed" attribute to the ip_udp_hdr struct. In this
     case the compiler will always assume the smallest 1 byte alignment.
     It may have some performance implications though.

include/net.h

@@ -296,7 +296,7 @@ struct ethernet_hdr {
 	u8		et_dest[6];	/* Destination node		*/
 	u8		et_src[6];	/* Source node			*/
 	u16		et_protlen;	/* Protocol or length		*/
-};
+}__attribute__((__packed__));
 
 /* Ethernet header size */
 #define ETHER_HDR_SIZE	(sizeof(struct ethernet_hdr))
@@ -314,7 +314,7 @@ struct e802_hdr {
 	u8		et_snap2;
 	u8		et_snap3;
 	u16		et_prot;	/* 802 protocol			*/
-};
+}__attribute__((__packed__));
 
 /* 802 + SNAP + ethernet header size */
 #define E802_HDR_SIZE	(sizeof(struct e802_hdr))
@@ -328,7 +328,7 @@ struct vlan_ethernet_hdr {
 	u16		vet_vlan_type;	/* PROT_VLAN			*/
 	u16		vet_tag;	/* TAG of VLAN			*/
 	u16		vet_type;	/* protocol type		*/
-};
+}__attribute__((__packed__));
 
 /* VLAN Ethernet header size */
 #define VLAN_ETHER_HDR_SIZE	(sizeof(struct vlan_ethernet_hdr))
@@ -358,7 +358,7 @@ struct ip_hdr {
 	u16		ip_sum;		/* checksum			*/
 	struct in_addr	ip_src;		/* Source IP address		*/
 	struct in_addr	ip_dst;		/* Destination IP address	*/
-};
+}__attribute__((__packed__));
 
 #define IP_OFFS		0x1fff /* ip offset *= 8 */
 #define IP_FLAGS	0xe000 /* first 3 bits */
@@ -386,7 +386,7 @@ struct ip_udp_hdr {
 	u16		udp_dst;	/* UDP destination port		*/
 	u16		udp_len;	/* Length of UDP packet		*/
 	u16		udp_xsum;	/* Checksum			*/
-};
+}__attribute__((__packed__));
 
 #define IP_UDP_HDR_SIZE		(sizeof(struct ip_udp_hdr))
 #define UDP_HDR_SIZE		(IP_UDP_HDR_SIZE - IP_HDR_SIZE)
@@ -425,7 +425,7 @@ struct arp_hdr {
 	u8		ar_tha[];	/* Target hardware address	*/
 	u8		ar_tpa[];	/* Target protocol address	*/
 #endif /* 0 */
-};
+}__attribute__((__packed__));
 
 #define ARP_HDR_SIZE	(8+20)		/* Size assuming ethernet	*/
 
@@ -460,7 +460,7 @@ struct icmp_hdr {
 		} frag;
 		u8 data[0];
 	} un;
-};
+}__attribute__((__packed__));
 
 #define ICMP_HDR_SIZE		(sizeof(struct icmp_hdr))
 #define IP_ICMP_HDR_SIZE	(IP_HDR_SIZE + ICMP_HDR_SIZE)

net/bootp.h

@@ -49,7 +49,7 @@ struct bootp_hdr {
 	char		bp_sname[64];	/* Server host name		*/
 	char		bp_file[128];	/* Boot file name		*/
 	char		bp_vend[OPT_FIELD_SIZE]; /* Vendor information	*/
-};
+}__attribute__((__packed__));
 
 #define BOOTP_HDR_SIZE	sizeof(struct bootp_hdr)
 

net/sntp.h

@@ -51,7 +51,7 @@ struct sntp_pkt_t {
 	unsigned long long originate_timestamp;
 	unsigned long long receive_timestamp;
 	unsigned long long transmit_timestamp;
-};
+}__attribute__((__packed__));
 
 void sntp_start(void);	/* Begin SNTP */