kern/53680: libnv broke zfs

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         53680
>Category:       kern
>Synopsis:       libnv broke zfs
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Oct 23 08:30:01 +0000 2018
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2018.09.29.14.41.37
>Organization:
>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

Lots of zfs tests are now failing when running the ATF tests on real
hardware, in addition to the failures already reported in 53423.

Bisection shows that the problem started with rmind's commit of
2018.09.29.14.41.37, with the commit message:

  NPF: Major rework -- migrate NPF to the libnv library.
  - This conversion significantly simplifies the code and moves NPF to
    a binary serialisation format (replacing the XML-like format).
  - Fix some memory/reference leaks and possibly use-after-free bugs.
  - Bump NPF_VERSION as this change makes libnpf incompatible with the
    previous versions.  Also, different serialisation format means NPF
    connection/config saving and loading is not compatible with the
    previous versions either.

  Thanks to christos@ for extra testing.

Logs are at:

  http://www.gson.org/netbsd/bugs/build/amd64-baremetal/commits-2018.09.html#2018.09.29.14.41.37

The console log contains lots of messages like these:

      zfs_access_simple: [ 4783.9331055] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_size' redefined
  [ 4784.0542610] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_add_nvpair' redefined
  [ 4784.1834259] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvpair_type' redefined
  [ 4784.3063407] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_next_nvpair' redefined
  [ 4784.4365476] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_unpack' redefined
  [ 4784.5636293] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_free' redefined
  [ 4784.6844606] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvpair_name' redefined
  [ 4784.8073766] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_add_string' redefined
  [ 4784.9365423] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_add_nvlist_array' redefined
  [ 4785.0740406] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_remove_nvpair' redefined
  [ 4785.2042460] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_add_string_array' redefined
  [ 4785.3396623] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_add_nvlist' redefined
  [ 4785.4688270] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_empty' redefined
  [ 4785.5948661] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_exists' redefined
  [ 4785.7177822] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_pack' redefined
  [ 4785.8406981] kobj_checksyms, 1020: [%M/solaris/solaris.kmod]: linker error: global symbol `nvlist_prev_nvpair' redefined
  [ 4785.9709036] WARNING: module error: recursive load failed for `zfs' (`solaris' required), error 8
  [2.225602s] Failed: mount failed: Unknown error: 256

>How-To-Repeat:

Run the full ATF test suite on real amd64 hardware.

>Fix: