Hi Petar,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/Petar-Penkov/Introduce-a-BPF-helper-to-generate-SYN-cookies/20190723-235628
base:   https://kernel.googlesource.com/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: parisc-c8000_defconfig (attached as .config)
compiler: hppa64-linux-gcc (GCC) 7.4.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.4.0 make.cross ARCH=parisc 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   hppa64-linux-ld: arch/parisc/kernel/entry.o(.text.hot+0x22b8): cannot reach preempt_schedule_irq
   arch/parisc/kernel/entry.o: In function `intr_do_preempt':
   (.text.hot+0x22b8): relocation truncated to fit: R_PARISC_PCREL22F against symbol `preempt_schedule_irq' defined in .sched.text section in kernel/sched/core.o
   net/ipv4/tcp_input.o: In function `.LC240':
>> (.data.rel.ro+0x718): undefined reference to `__cookie_v6_init_sequence'

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