Hello.
The following function in the BPF selftest progs/test_xdp_noinline.c:
/* don't believe your eyes!
* below function has 6 arguments whereas bpf and llvm allow maximum of 5
* but since it's _static_ llvm can optimize one argument away
*/
__attribute__ ((noinline))
static int process_l3_headers_v6(struct packet_description *pckt,
__u8 *protocol, __u64 off,
__u16 *pkt_bytes, void *data,
void *data_end)
{
struct ipv6hdr *ip6h;
__u64 iph_len;
int action;
ip6h = data + off;
if (ip6h + 1 > data_end)
return XDP_DROP;
iph_len = sizeof(struct ipv6hdr);
*protocol = ip6h->nexthdr;
pckt->flow.proto = *protocol;
*pkt_bytes = bpf_ntohs(ip6h->payload_len);
off += iph_len;
if (*protocol == 45) {
return XDP_DROP;
} else if (*protocol == 59) {
action = parse_icmpv6(data, data_end, off, pckt);
if (action >= 0)
return action;
} else {
memcpy(pckt->flow.srcv6, ip6h->saddr.in6_u.u6_addr32, 16);
memcpy(pckt->flow.dstv6, ip6h->daddr.in6_u.u6_addr32, 16);
}
return -1;
}
Relies, as acknowledged in the comment block, on LLVM optimizing out one
of the arguments. As it happens GCC doesn't optimize that argument out,
and as a result it fails at compile-time when building
tst_xdp_noinline.c.
Would it be possible to rewrite this particular test to not rely on that
particular optimization?
TIA.
