error: incomplete type 'struct pt_regs'

there is an error in exersize1 and exersize3:  incomplete type 'struct pt_regs'
                                                                          struct pt_regs regs
 
 it's head file problem, type.h and ptrace.h didn't include the discribe of the struct pt_regs,I want to know how to fix this error.
The exiseze2 works well.  hope your help, thanks a lot.