On Tue, 2020-08-04 at 20:40 +0300, Yauheni Kaliuta wrote:
> Hi!
>
> I have a failure (crash) of selftests/bpf/test_kmod.sh on s390.
>
> The problem comes with loading with
>
> sysctl -w net.core.bpf_jit_harden=2
>
> In that case the program (lib/test_bpf.c):
>
> static int bpf_fill_maxinsns1(struct bpf_test *self)
> {
> unsigned int len = BPF_MAXINSNS;
> struct sock_filter *insn;
> __u32 k = ~0;
> int i;
>
> insn = kmalloc_array(len, sizeof(*insn), GFP_KERNEL);
> if (!insn)
> return -ENOMEM;
>
> for (i = 0; i < len; i++, k--)
> insn[i] = __BPF_STMT(BPF_RET | BPF_K, k);
>
> self->u.ptr.insns = insn;
> self->u.ptr.len = len;
>
> return 0;
> }
>
> after blinding and jiting is 98362 bytes for me and it does not fit
> 16bit offset for BRC 15,.. command where BPF_EXIT | BPF_JMP is
> translated.
>
> What is the easiest way to use BRCL for large offset here?
>
> Thanks!
Hi Yauheni!
Did you try bpf-next, specifically with commit 5fa6974471c5 ("s390/bpf:
Use brcl for jumping to exit_ip if necessary")? This was supposed to
fix this problem.
Best regards,
Ilya
