The problem is that libseccomp was patched at version 2.3.1-2.1ubuntu4.1, in d/p/lp-1815415-arch-update-syscalls-for-Linux-4.9.patch, to add a definition for the pkey_mprotect syscall. The systemd test case checks for the definition of this syscall, and uses it if it's defined, which with the new libseccomp library, it is.
However, the ppc64el kernel doesn't add support for the pkey_mprotect syscall until 4.16.
Either the bionic 4.15 kernel should add support for pkey_mprotect syscall (commit 3350eb2ea127978319ced883523d828046af4045, at least, possibly more), or libseccomp should remove it, at least for ppc64el builds on bionic. Adding support for it to the kernel for ppc64el is probably the best approach.
This is not a bug in systemd.
The problem is that libseccomp was patched at version 2.3.1-2.1ubuntu4.1, in d/p/lp- 1815415- arch-update- syscalls- for-Linux- 4.9.patch, to add a definition for the pkey_mprotect syscall. The systemd test case checks for the definition of this syscall, and uses it if it's defined, which with the new libseccomp library, it is.
However, the ppc64el kernel doesn't add support for the pkey_mprotect syscall until 4.16.
Either the bionic 4.15 kernel should add support for pkey_mprotect syscall (commit 3350eb2ea127978 319ced883523d82 8046af4045, at least, possibly more), or libseccomp should remove it, at least for ppc64el builds on bionic. Adding support for it to the kernel for ppc64el is probably the best approach.