pre_execve
error = pre_execve(td, &oldvmspace);
error = pre_execve(td, &oldvmspace);
error = pre_execve(td, &oldvmspace);
error = pre_execve(td, &oldvmspace);
error = pre_execve(td, &oldvmspace);
error = pre_execve(td, &oldvmspace);
int pre_execve(struct thread *td, struct vmspace **oldvmspace);