Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal

Pull assorted signal-related fixes from Al Viro:
 "uml regression fix (braino in sys_execve() patch) + a bunch of fucked
  sigaltstack-on-rt_sigreturn uses, similar to sparc64 fix that went in
  through davem's tree.  m32r horrors not included - that one's waiting
  for maintainer."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal:
  microblaze: rt_sigreturn is too trigger-happy about sigaltstack errors
  score: do_sigaltstack() expects a userland pointer...
  sh64: fix altstack switching on sigreturn
  openrisk: fix altstack switching on sigreturn
  um: get_safe_registers() should be done in flush_thread(), not start_thread()