ubuntu_seccomp pseudo-syscall fails on s390 / PowerPC

[Thadeu Lima de Souza Cascardo]

libseccomp upstream has changed the test code for 29-sim-pseudo_syscall.c, which has broken it for s390. Perhaps s390 has been broken since forever and the test change is just uncovering it. We need to investigate if the fix would be needed in the test, libseccomp or the kernel. This seems to affect at least 4.4 and 5.4 kernels, but may affect everything.

[Thadeu Lima de Souza Cascardo (cascardo)]

The test generates a BPF with libseccomp API then runs a BPF simulator. The libseccomp commit 51c46f80c1edee863bbc4eb21b03decc44e69a45 ("all: block negative syscall numbers from the filter") seems to indicate this is fixing and testing problems on the filter (which I read as BPF filter), so this is unlikely a kernel problem.

However, it might be uncovering a libseccomp bug on s390.

Cascardo.

[Alex Murray (alexmurray)]

Adding a task against libseccomp until we know more about where the bug lies.

[Po-Hsu Lin (cypressyew)]

This issue can be found on ppc64el (openstack VM) as well, all the way from 5.4 to 6.5

[Magali Lemes do Sacramento (magalilemes)]

Upstream is tracking the same issue on aarch64 too: https://github.com/seccomp/libseccomp/issues/418