/* kern_fork.c 6.1 83/07/29 */ #include "../machine/reg.h" #include "../machine/pte.h" #include "../machine/psl.h" #include "../h/param.h" #include "../h/systm.h" #include "../h/map.h" #include "../h/dir.h" #include "../h/user.h" #include "../h/kernel.h" #include "../h/proc.h" #include "../h/inode.h" #include "../h/seg.h" #include "../h/vm.h" #include "../h/text.h" #include "../h/file.h" #include "../h/acct.h" #include "../h/quota.h" /* * fork system call. */ fork() { u.u_cdmap = zdmap; u.u_csmap = zdmap; if (swpexpand(u.u_dsize, u.u_ssize, &u.u_cdmap, &u.u_csmap) == 0) { u.u_r.r_val2 = 0; return; } fork1(0); } vfork() { fork1(1); } fork1(isvfork) int isvfork; { register struct proc *p1, *p2; register a; a = 0; p2 = NULL; for (p1 = proc; p1 < procNPROC; p1++) { if (p1->p_stat==NULL && p2==NULL) p2 = p1; else { if (p1->p_uid==u.u_uid && p1->p_stat!=NULL) a++; } } /* * Disallow if * No processes at all; * not su and too many procs owned; or * not su and would take last slot. */ if (p2==NULL) tablefull("proc"); if (p2==NULL || (u.u_uid!=0 && (p2==procNPROC-1 || a>MAXUPRC))) { u.u_error = EAGAIN; if (!isvfork) { (void) vsexpand(0, &u.u_cdmap, 1); (void) vsexpand(0, &u.u_csmap, 1); } goto out; } p1 = u.u_procp; if (newproc(isvfork)) { u.u_r.r_val1 = p1->p_pid; u.u_r.r_val2 = 1; /* child */ u.u_start = time.tv_sec; u.u_acflag = AFORK; return; } u.u_r.r_val1 = p2->p_pid; out: u.u_r.r_val2 = 0; } /* * Create a new process-- the internal version of * sys fork. * It returns 1 in the new process, 0 in the old. */ newproc(isvfork) int isvfork; { register struct proc *p; register struct proc *rpp, *rip; register int n; register struct file *fp; p = NULL; /* * First, just locate a slot for a process * and copy the useful info from this process into it. * The panic "cannot happen" because fork has already * checked for the existence of a slot. */ retry: mpid++; if (mpid >= 30000) { mpid = 0; goto retry; } for (rpp = proc; rpp < procNPROC; rpp++) { if (rpp->p_stat == NULL && p==NULL) p = rpp; if (rpp->p_pid==mpid || rpp->p_pgrp==mpid) goto retry; } if ((rpp = p) == NULL) panic("no procs"); /* * Make a proc table entry for the new process. */ rip = u.u_procp; #ifdef QUOTA rpp->p_quota = rip->p_quota; rpp->p_quota->q_cnt++; #endif rpp->p_stat = SIDL; timerclear(&rpp->p_realtimer.it_value); rpp->p_flag = SLOAD | (rip->p_flag & (SPAGI|SOUSIG)); if (isvfork) { rpp->p_flag |= SVFORK; rpp->p_ndx = rip->p_ndx; } else rpp->p_ndx = rpp - proc; rpp->p_uid = rip->p_uid; rpp->p_pgrp = rip->p_pgrp; rpp->p_nice = rip->p_nice; rpp->p_textp = isvfork ? 0 : rip->p_textp; rpp->p_pid = mpid; rpp->p_ppid = rip->p_pid; rpp->p_pptr = rip; rpp->p_osptr = rip->p_cptr; if (rip->p_cptr) rip->p_cptr->p_ysptr = rpp; rpp->p_ysptr = NULL; rpp->p_cptr = NULL; rip->p_cptr = rpp; rpp->p_time = 0; rpp->p_cpu = 0; rpp->p_sigmask = rip->p_sigmask; rpp->p_sigcatch = rip->p_sigcatch; rpp->p_sigignore = rip->p_sigignore; /* take along any pending signals like stops? */ if (isvfork) { rpp->p_tsize = rpp->p_dsize = rpp->p_ssize = 0; rpp->p_szpt = clrnd(ctopt(UPAGES)); forkstat.cntvfork++; forkstat.sizvfork += rip->p_dsize + rip->p_ssize; } else { rpp->p_tsize = rip->p_tsize; rpp->p_dsize = rip->p_dsize; rpp->p_ssize = rip->p_ssize; rpp->p_szpt = rip->p_szpt; forkstat.cntfork++; forkstat.sizfork += rip->p_dsize + rip->p_ssize; } rpp->p_rssize = 0; rpp->p_maxrss = rip->p_maxrss; rpp->p_wchan = 0; rpp->p_slptime = 0; rpp->p_pctcpu = 0; rpp->p_cpticks = 0; n = PIDHASH(rpp->p_pid); p->p_idhash = pidhash[n]; pidhash[n] = rpp - proc; multprog++; /* * Increase reference counts on shared objects. */ for (n = 0; n < NOFILE; n++) { fp = u.u_ofile[n]; if (fp == NULL) continue; fp->f_count++; } u.u_cdir->i_count++; if (u.u_rdir) u.u_rdir->i_count++; /* * Partially simulate the environment * of the new process so that when it is actually * created (by copying) it will look right. * This begins the section where we must prevent the parent * from being swapped. */ rip->p_flag |= SKEEP; if (procdup(rpp, isvfork)) return (1); /* * Make child runnable and add to run queue. */ (void) spl6(); rpp->p_stat = SRUN; setrq(rpp); (void) spl0(); /* * Cause child to take a non-local goto as soon as it runs. * On older systems this was done with SSWAP bit in proc * table; on VAX we use u.u_pcb.pcb_sswap so don't need * to do rpp->p_flag |= SSWAP. Actually do nothing here. */ /* rpp->p_flag |= SSWAP; */ /* * Now can be swapped. */ rip->p_flag &= ~SKEEP; /* * If vfork make chain from parent process to child * (where virtal memory is temporarily). Wait for * child to finish, steal virtual memory back, * and wakeup child to let it die. */ if (isvfork) { u.u_procp->p_xlink = rpp; u.u_procp->p_flag |= SNOVM; while (rpp->p_flag & SVFORK) sleep((caddr_t)rpp, PZERO - 1); if ((rpp->p_flag & SLOAD) == 0) panic("newproc vfork"); uaccess(rpp, Vfmap, &vfutl); u.u_procp->p_xlink = 0; vpassvm(rpp, u.u_procp, &vfutl, &u, Vfmap); u.u_procp->p_flag &= ~SNOVM; rpp->p_ndx = rpp - proc; rpp->p_flag |= SVFDONE; wakeup((caddr_t)rpp); } /* * 0 return means parent. */ return (0); }