Re: net: vrf: Handle ipv6 multicast and link-local addresses

Em Wed, Aug 03, 2016 at 10:27:44PM +0200, Geert Uytterhoeven escreveu:

On Wed, Aug 3, 2016 at 10:11 PM, David Ahern [off-list ref] wrote:

quoted

On 8/3/16 1:57 PM, Geert Uytterhoeven wrote:

quoted

quoted

+static void vrf_ip6_input_dst(struct sk_buff *skb, struct net_device *vrf_dev,

quoted

+                             int ifindex)
+{
+       const struct ipv6hdr *iph = ipv6_hdr(skb);
+       struct flowi6 fl6 = {
+               .daddr          = iph->daddr,
+               .saddr          = iph->saddr,
+               .flowlabel      = ip6_flowinfo(iph),

The above assignment causes the following compiler warning with
m68k-linux-gnu-gcc-4.1:

    drivers/net/vrf.c: In function ‘vrf_ip6_input_dst’:
    drivers/net/vrf.c:870: warning: initialized field with
side-effects overwritten
    drivers/net/vrf.c:870: warning: (near initialization for ‘fl6’)

Unfortunately I have no idea what it means, nor do I see what's wrong
with the code.

no idea. Fields are initialized once and left and right data types are the same.

Can you remove one line at a time? Line 870 is ".flowi6_proto   = iph->nexthdr," but all of the flowi6 macros are unique references to unique fields in flowi_common. The flowlabel line you point out is a unique field as well.

The only thing that seems to matter is assigning the result of the call to
ip6_flowinfo() to .flowlabel. Assigning a constant makes the warning go away.

Yeah, the 870 line number is funny, as it doesn't point to the offending line.

quoted

Can you run pahole on file that did compile? e.g.,

pahole -C 'flowi6' net/ipv6/route.o

and get the common struct too:

pahole -C 'flowi_common' net/ipv6/route.o

No output. Perhaps pahole doesn't play well with cross-compiling?

Can you send me this net/ipv6/route.o file? It should work as long as
CONFIG_DEBUG_INFO was used to build this cross kernel.

For instance, here cross compiling perf tools for s390 from a ubuntu
16.04 container running on a fedora 24 host, I get:

[root@jouet 14.04.4]# file /var/lib/docker/devicemapper/mnt/b7ba22999d88feebc42de2ea17fe27e94febf228439fccf2b84c0c9e1ccd8af7/rootfs/tmp/build/perf/perf
/var/lib/docker/devicemapper/mnt/b7ba22999d88feebc42de2ea17fe27e94febf228439fccf2b84c0c9e1ccd8af7/rootfs/tmp/build/perf/perf: ELF 64-bit MSB shared object, IBM S/390, version 1 (SYSV), dynamically linked, interpreter /lib/ld64.so.1, for GNU/Linux 3.2.0, BuildID[sha1]=22b27009c61130ed5727bcaf9ad0813d414b8c5a, not stripped
[root@jouet 14.04.4]#

Thus a s/390 object, that I then process from a x86_64 pahole:

[root@jouet 14.04.4]# file /home/acme/git/pahole/build/pahole
/home/acme/git/pahole/build/pahole: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=c90855d4ffa815bf0dddb3463bc45aea4855d0e2, not stripped
[root@jouet 14.04.4]# 

Giving these results:

[root@jouet 14.04.4]# pahole -C sockaddr_in6 /var/lib/docker/devicemapper/mnt/b7ba22999d88feebc42de2ea17fe27e94febf228439fccf2b84c0c9e1ccd8af7/rootfs/tmp/build/perf/perf
struct sockaddr_in6 {
	sa_family_t                sin6_family;          /*     0     2 */
	in_port_t                  sin6_port;            /*     2     2 */
	uint32_t                   sin6_flowinfo;        /*     4     4 */
	struct in6_addr            sin6_addr;            /*     8    16 */
	uint32_t                   sin6_scope_id;        /*    24     4 */

	/* size: 28, cachelines: 1, members: 5 */
	/* last cacheline: 28 bytes */
};
[root@jouet 14.04.4]#

Expanding types:

[root@jouet 14.04.4]# pahole --expand_types -C sockaddr_in6 /var/lib/docker/devicemapper/mnt/b7ba22999d88feebc42de2ea17fe27e94febf228439fccf2b84c0c9e1ccd8af7/rootfs/tmp/build/perf/perf
struct sockaddr_in6 {
	/* typedef sa_family_t */ short unsigned int         sin6_family;                /*     0     2 */
	/* typedef in_port_t -> uint16_t */ short unsigned int         sin6_port;        /*     2     2 */
	/* typedef uint32_t */ unsigned int               sin6_flowinfo;                 /*     4     4 */
	struct in6_addr {
		union {
			/* typedef uint8_t */ unsigned char __u6_addr8[16];              /*          16 */
			/* typedef uint16_t */ short unsigned int __u6_addr16[8];        /*          16 */
			/* typedef uint32_t */ unsigned int __u6_addr32[4];              /*          16 */
		} __in6_u;                                                               /*     8    16 */
	} sin6_addr; /*     8    16 */
	/* typedef uint32_t */ unsigned int               sin6_scope_id;                 /*    24     4 */

	/* size: 28, cachelines: 1, members: 5 */
	/* last cacheline: 28 bytes */
};
[root@jouet 14.04.4]#

etc.

Guess I need to put together a m68k target for building the perf tools (and
test pahole & friends on such objects)... :-)

- Arnaldo