Hi Eric,
On 02/18/2019 10:51 PM, Daniel Borkmann wrote:
> On 02/15/2019 02:07 PM, Daniel Borkmann wrote:
>> On 02/14/2019 10:37 PM, Alexei Starovoitov wrote:
>>> On Thu, Feb 14, 2019 at 10:33 AM Eric Leblond <eric@xxxxxxxxx> wrote:
>>>>
>>>> Hello,
>>>>
>>>> On Wed, 2019-02-13 at 20:46 +0100, Eric Leblond wrote:
>>>>> Hello,
>>>>>
>>>>> I've got a simple socket filter program that seems to interrupt when
>>>>> calling the load_word construct. I'm seeing the first message but
>>>>> never
>>>>> the second one.
>>>>>
>>>>> The code is the following
>>>>>
>>>>> int SEC("filter") hashfilter(struct __sk_buff *skb) {
>>>>> __u32 nhoff = BPF_LL_OFF + ETH_HLEN;
>>>>
>>>> So it seems the problem was coming from this line. Removing BPF_LL_OFF
>>>> fixes the problem for kernel starting 4.18.
>>>>
>>>> Is this a known issue ?
>>>>
>>>> Is there something that would allow a BPF file to work independently of
>>>> the kernel version ?
>>>
>>> Daniel,
>>> can this be related to removal of ld_abs legacy ?
>>
>> Hm, strange, I'll take a look.
>
> Do you have a concrete stand-alone reproducer? Works fine for me on
> latest bpf tree at least (internal code gen is same for filter and
> tc BPF) ...
>
> # pwd
> /root/iproute2/examples/bpf
> # cat foo.c
> #include <stdio.h>
> #include <linux/if_ether.h>
> #include <linux/ip.h>
> #include "../../include/bpf_api.h"
>
> __section_cls_entry
> int cls_entry(struct __sk_buff *skb)
> {
> __u32 nhoff = BPF_LL_OFF + ETH_HLEN;
> __u32 ip = 0;
> __u32 *value = NULL;
> #if 1
> char fmtrei[] = "word load\n";
> trace_printk(fmtrei, sizeof(fmtrei));
> #endif
> ip = load_word(skb, nhoff + offsetof(struct iphdr, saddr));
> #if 1
> char fmti[] = "work done\n";
> trace_printk(fmti, sizeof(fmti));
> #endif
> return TC_ACT_OK;
> }
>
> BPF_LICENSE("GPL");
> # clang -target bpf -O2 -Wall -c foo.c -o foo.o -I ../../include/uapi/
> # tc qdisc add dev bond0 clsact
> # tc filter add dev bond0 ingress bpf da obj ./foo.o
> # tc exec bpf dbg
> [...]
> <idle>-0 [005] .Ns. 21102.794996: 0: work done
> <idle>-0 [005] ..s. 21102.796023: 0: word load
> <idle>-0 [005] .Ns. 21102.796045: 0: work done
> <idle>-0 [005] ..s. 21102.807417: 0: word load
> <idle>-0 [005] .Ns. 21102.807438: 0: work done
> <idle>-0 [005] ..s. 21102.808365: 0: word load
> <idle>-0 [005] .Ns. 21102.808387: 0: work done
> <idle>-0 [005] ..s. 21102.819905: 0: word load
> <idle>-0 [005] .Ns. 21102.819923: 0: work done
> <idle>-0 [005] ..s. 21102.820626: 0: word load
> <idle>-0 [005] .Ns. 21102.820646: 0: work done
> <idle>-0 [005] ..s. 21102.832293: 0: word load
> <idle>-0 [005] .Ns. 21102.832314: 0: work done
> [...]
> # uname -a
> Linux test2 5.0.0-rc6+ #1 SMP Mon Feb 18 13:06:11 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
> # llc --version
> [...]
> LLVM version 3.8.0
> # cat /proc/sys/net/core/bpf_jit_enable
> 1
Small ping, can you confirm the same on your side? If not, do you
have a reproducer?
Thanks,
Daniel
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