#include<u.h>#include<libc.h>ulongtruerand(void){ulongx;staticintrandfd=-1;if(randfd<0)randfd=open("/dev/random",OREAD|OCEXEC);if(randfd<0)sysfatal("can't open /dev/random");if(read(randfd,&x,sizeof(x))!=sizeof(x))sysfatal("can't read /dev/random");returnx;}