[SRU Bionic, Focal 0/1] LP: #1928522 seccomp_bpf:syscall_faked from kselftests fail on s390x

[Thadeu Lima de Souza Cascardo]

[Impact]
kselftests seccomp_bpf will start failing on s390x, though due to a test
problem, not a kernel regression, thus wasting people's time doing test
review.

[Regression potential]
Though this is only changing the test, we might be missing or miss failures
in the future because some tests are not executed anymore.
ptrace_syscall_faked, ptrace_syscall_errno and syscall_errno should all
work just fine on s390x, but will be skipped as well with this change.

[Fix]
The fix is to consider that s390x cannot change syscall and errno at once
by using ptrace. It can, however, change the errno at syscall exit time,
which could even be used with seccomp SECCOMP_RET_TRACE as long as ptrace
is used to track the exit transitions. But the test is not designed to deal
with such situations.

[Test case]
seccomp_bpf was run, ptrace_faked passed and no new subtests have failed.

Sven Schnelle (1):
  selftests/seccomp: s390 shares the syscall and return value register

 tools/testing/selftests/seccomp/seccomp_bpf.c | 1 +
 1 file changed, 1 insertion(+)

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2.30.2