c3ade864d9
support PTRACE_SETREGS. In struct process, add 'unsigned long *ptrace_debugreg', instead of 'struct user *userp'. debug registers are read/written from/to ptrace_debugreg, save/restore in schedule(). most general registers are proc->uctx. fs_base is proc->thread.tlsblock_base. gs_base,ds,es,fs,gs and orig_rax are uncompleted. other members in 'struct user' are ignored, same as Linux implementation. refs #257 refs #373 refs #263