On 12/11/2018 10:49 PM, Stanislav Fomichev wrote:
> On 12/11, Stanislav Fomichev wrote:
>> We're using bpf_htons in test_progs.c to initialize some static
>> global data and I think I hit some weird case on an older compiler
>> which doesn't have __builtin_bswap16 (and __builtin_constant_p
>> expands to false).
>>
>> In this case I see:
>> error: implicit declaration of function '__builtin_bswap16'
Is that gcc < 4.8?
>> Let's explicitly use __constant_htons which should be exposed by the
>> linux/byteorder.h uapi header.
>
> Forgot to mention, that using simple htons produces the following:
> test_progs.c:54:17: error: braced-group within expression allowed only
> inside a function
> .eth.h_proto = htons(ETH_P_IP),
>
>> Signed-off-by: Stanislav Fomichev <s...@google.com>
>> ---
>> tools/testing/selftests/bpf/test_progs.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/tools/testing/selftests/bpf/test_progs.c
>> b/tools/testing/selftests/bpf/test_progs.c
>> index 26f1fdf3e2bf..61593d319c0e 100644
>> --- a/tools/testing/selftests/bpf/test_progs.c
>> +++ b/tools/testing/selftests/bpf/test_progs.c
>> @@ -51,10 +51,10 @@ static struct {
>> struct iphdr iph;
>> struct tcphdr tcp;
>> } __packed pkt_v4 = {
>> - .eth.h_proto = bpf_htons(ETH_P_IP),
>> + .eth.h_proto = __constant_htons(ETH_P_IP),
If the __builtin_constant_p() evaluated to false on the constants (?),
wouldn't using the __bpf_constant_htons() directly work as well given
it's not using a builtin either? Should be fine either way though using
the same api/header might be slightly nicer.
>> .iph.ihl = 5,
>> .iph.protocol = 6,
>> - .iph.tot_len = bpf_htons(MAGIC_BYTES),
>> + .iph.tot_len = __constant_htons(MAGIC_BYTES),
>> .tcp.urg_ptr = 123,
>> };
>>
>> @@ -64,9 +64,9 @@ static struct {
>> struct ipv6hdr iph;
>> struct tcphdr tcp;
>> } __packed pkt_v6 = {
>> - .eth.h_proto = bpf_htons(ETH_P_IPV6),
>> + .eth.h_proto = __constant_htons(ETH_P_IPV6),
>> .iph.nexthdr = 6,
>> - .iph.payload_len = bpf_htons(MAGIC_BYTES),
>> + .iph.payload_len = __constant_htons(MAGIC_BYTES),
>> .tcp.urg_ptr = 123,
>> };
>>
>> --
>> 2.20.0.rc2.403.gdbc3b29805-goog
>>
