[MPTCP] Fwd: [martineau:kbuild-mptcp 22/38] subflow.c:undefined reference to `__crypto_memneq'

[MPTCP] Fwd: [martineau:kbuild-mptcp 22/38] subflow.c:undefined reference to `__crypto_memneq'

[Florian Westphal]

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----- Forwarded message from kbuild test robot <lkp(a)intel.com> -----

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/martineau/linux.git kbuild-mptcp
head:   c4ccdd8177fb3d8123dd294ae93ee2dac1f43f32
commit: ccd5b6ef8fd4b37a7721231a55482523b07d7ef9 [22/38] mptcp: Add handling of incoming MP_JOIN requests
config: xtensa-common_defconfig (attached as .config)
compiler: xtensa-linux-gcc (GCC) 7.5.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout ccd5b6ef8fd4b37a7721231a55482523b07d7ef9
        # save the attached .config to linux build tree
        GCC_VERSION=7.5.0 make.cross ARCH=xtensa 

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

All errors (new ones prefixed by >>):

   net/mptcp/subflow.o: In function `subflow_ulp_release':
>> subflow.c:(.text+0x41c): undefined reference to `__crypto_memneq'
   net/mptcp/subflow.o: In function `subflow_syn_recv_sock':
   subflow.c:(.text+0x53a): undefined reference to `__crypto_memneq'

Hmpf.  The .config has CONFIG_CRYPTO=n and then the symbol doesn't
exist.

So we have two choices:
- select CRYPTO from Kconfig
- use plain memcmp as before (might reveal info about key though)
- copypaste a similar function into mptcp.

What do you think?