I just added in support for PPC-srop. You can see the pull request here. The doctest is skipped as the current version of qemu-user segfaults when the test is run. If you try debugging the integration test at line 162 as follows, you can see that the sigreturn system call works just fine, however, after returning from a do_syscall, qemu fails.
The files used for testing can be found here. The sigreturn call works as expected when run on a qemu-system-powerpc build.
The files used for testing can be found here. The sigreturn call works as expected when run on a qemu-system-powerpc build.