CC      arch/um/os-Linux/skas/mem.o
arch/um/os-Linux/skas/mem.c:58:2: warning: #warning Need to look up userspace_pid by cpu
  CC      arch/um/os-Linux/skas/process.o
arch/um/os-Linux/skas/process.c: In function ‘copy_context_skas0’:
arch/um/os-Linux/skas/process.c:328: error: ‘PAGE_SHIFT’ undeclared (first use in this function)
arch/um/os-Linux/skas/process.c:328: error: (Each undeclared identifier is reported only once
arch/um/os-Linux/skas/process.c:328: error: for each function it appears in.)
arch/um/os-Linux/skas/process.c:560:2: warning: #warning need cpu pid in switch_mm_skas
make[2]: *** [arch/um/os-Linux/skas/process.o] Error 1
make[1]: *** [arch/um/os-Linux/skas] Error 2
make: *** [arch/um/os-Linux] Error 2