1 /* 2 * Copyright (c) 1982, 1986 Regents of the University of California. 3 * All rights reserved. The Berkeley software License Agreement 4 * specifies the terms and conditions for redistribution. 5 * 6 * @(#)kern_fork.c 7.2 (Berkeley) 11/03/86 7 */ 8 9 #include "../machine/reg.h" 10 #include "../machine/pte.h" 11 #include "../machine/psl.h" 12 13 #include "param.h" 14 #include "systm.h" 15 #include "map.h" 16 #include "dir.h" 17 #include "user.h" 18 #include "kernel.h" 19 #include "proc.h" 20 #include "inode.h" 21 #include "seg.h" 22 #include "vm.h" 23 #include "text.h" 24 #include "file.h" 25 #include "acct.h" 26 #include "quota.h" 27 28 /* 29 * fork system call. 30 */ 31 fork() 32 { 33 34 u.u_cdmap = zdmap; 35 u.u_csmap = zdmap; 36 if (swpexpand(u.u_dsize, u.u_ssize, &u.u_cdmap, &u.u_csmap) == 0) { 37 u.u_r.r_val2 = 0; 38 return; 39 } 40 fork1(0); 41 } 42 43 vfork() 44 { 45 46 fork1(1); 47 } 48 49 fork1(isvfork) 50 int isvfork; 51 { 52 register struct proc *p1, *p2; 53 register a; 54 55 a = 0; 56 if (u.u_uid != 0) { 57 for (p1 = allproc; p1; p1 = p1->p_nxt) 58 if (p1->p_uid == u.u_uid) 59 a++; 60 for (p1 = zombproc; p1; p1 = p1->p_nxt) 61 if (p1->p_uid == u.u_uid) 62 a++; 63 } 64 /* 65 * Disallow if 66 * No processes at all; 67 * not su and too many procs owned; or 68 * not su and would take last slot. 69 */ 70 p2 = freeproc; 71 if (p2==NULL) 72 tablefull("proc"); 73 if (p2==NULL || (u.u_uid!=0 && (p2->p_nxt == NULL || a>MAXUPRC))) { 74 u.u_error = EAGAIN; 75 if (!isvfork) { 76 (void) vsexpand((size_t)0, &u.u_cdmap, 1); 77 (void) vsexpand((size_t)0, &u.u_csmap, 1); 78 } 79 goto out; 80 } 81 p1 = u.u_procp; 82 if (newproc(isvfork)) { 83 u.u_r.r_val1 = p1->p_pid; 84 u.u_r.r_val2 = 1; /* child */ 85 u.u_start = time; 86 u.u_acflag = AFORK; 87 return; 88 } 89 u.u_r.r_val1 = p2->p_pid; 90 91 out: 92 u.u_r.r_val2 = 0; 93 } 94 95 /* 96 * Create a new process-- the internal version of 97 * sys fork. 98 * It returns 1 in the new process, 0 in the old. 99 */ 100 newproc(isvfork) 101 int isvfork; 102 { 103 register struct proc *rpp, *rip; 104 register int n; 105 register struct file *fp; 106 static int pidchecked = 0; 107 108 /* 109 * First, just locate a slot for a process 110 * and copy the useful info from this process into it. 111 * The panic "cannot happen" because fork has already 112 * checked for the existence of a slot. 113 */ 114 mpid++; 115 retry: 116 if (mpid >= 30000) { 117 mpid = 100; 118 pidchecked = 0; 119 } 120 if (mpid >= pidchecked) { 121 int doingzomb = 0; 122 123 pidchecked = 30000; 124 /* 125 * Scan the proc table to check whether this pid 126 * is in use. Remember the lowest pid that's greater 127 * than mpid, so we can avoid checking for a while. 128 */ 129 rpp = allproc; 130 again: 131 for (; rpp != NULL; rpp = rpp->p_nxt) { 132 if (rpp->p_pid == mpid || rpp->p_pgrp == mpid) { 133 mpid++; 134 if (mpid >= pidchecked) 135 goto retry; 136 } 137 if (rpp->p_pid > mpid && pidchecked > rpp->p_pid) 138 pidchecked = rpp->p_pid; 139 if (rpp->p_pgrp > mpid && pidchecked > rpp->p_pgrp) 140 pidchecked = rpp->p_pgrp; 141 } 142 if (!doingzomb) { 143 doingzomb = 1; 144 rpp = zombproc; 145 goto again; 146 } 147 } 148 if ((rpp = freeproc) == NULL) 149 panic("no procs"); 150 151 freeproc = rpp->p_nxt; /* off freeproc */ 152 rpp->p_nxt = allproc; /* onto allproc */ 153 rpp->p_nxt->p_prev = &rpp->p_nxt; /* (allproc is never NULL) */ 154 rpp->p_prev = &allproc; 155 allproc = rpp; 156 157 /* 158 * Make a proc table entry for the new process. 159 */ 160 rip = u.u_procp; 161 #ifdef QUOTA 162 rpp->p_quota = rip->p_quota; 163 rpp->p_quota->q_cnt++; 164 #endif 165 #if defined(tahoe) 166 rpp->p_ckey = rip->p_ckey; 167 rpp->p_dkey = 0; 168 #endif 169 rpp->p_stat = SIDL; 170 timerclear(&rpp->p_realtimer.it_value); 171 rpp->p_flag = SLOAD | (rip->p_flag & (SPAGI|SOUSIG)); 172 if (isvfork) { 173 rpp->p_flag |= SVFORK; 174 rpp->p_ndx = rip->p_ndx; 175 } else 176 rpp->p_ndx = rpp - proc; 177 rpp->p_uid = rip->p_uid; 178 rpp->p_pgrp = rip->p_pgrp; 179 rpp->p_nice = rip->p_nice; 180 rpp->p_textp = isvfork ? 0 : rip->p_textp; 181 rpp->p_pid = mpid; 182 rpp->p_ppid = rip->p_pid; 183 rpp->p_pptr = rip; 184 rpp->p_osptr = rip->p_cptr; 185 if (rip->p_cptr) 186 rip->p_cptr->p_ysptr = rpp; 187 rpp->p_ysptr = NULL; 188 rpp->p_cptr = NULL; 189 rip->p_cptr = rpp; 190 rpp->p_time = 0; 191 rpp->p_cpu = 0; 192 rpp->p_sigmask = rip->p_sigmask; 193 rpp->p_sigcatch = rip->p_sigcatch; 194 rpp->p_sigignore = rip->p_sigignore; 195 /* take along any pending signals like stops? */ 196 if (isvfork) { 197 rpp->p_tsize = rpp->p_dsize = rpp->p_ssize = 0; 198 rpp->p_szpt = clrnd(ctopt(UPAGES)); 199 forkstat.cntvfork++; 200 forkstat.sizvfork += rip->p_dsize + rip->p_ssize; 201 } else { 202 rpp->p_tsize = rip->p_tsize; 203 rpp->p_dsize = rip->p_dsize; 204 rpp->p_ssize = rip->p_ssize; 205 rpp->p_szpt = rip->p_szpt; 206 forkstat.cntfork++; 207 forkstat.sizfork += rip->p_dsize + rip->p_ssize; 208 } 209 rpp->p_rssize = 0; 210 rpp->p_maxrss = rip->p_maxrss; 211 rpp->p_wchan = 0; 212 rpp->p_slptime = 0; 213 rpp->p_pctcpu = 0; 214 rpp->p_cpticks = 0; 215 n = PIDHASH(rpp->p_pid); 216 rpp->p_idhash = pidhash[n]; 217 pidhash[n] = rpp - proc; 218 multprog++; 219 220 /* 221 * Increase reference counts on shared objects. 222 */ 223 for (n = 0; n <= u.u_lastfile; n++) { 224 fp = u.u_ofile[n]; 225 if (fp == NULL) 226 continue; 227 fp->f_count++; 228 } 229 u.u_cdir->i_count++; 230 if (u.u_rdir) 231 u.u_rdir->i_count++; 232 233 /* 234 * This begins the section where we must prevent the parent 235 * from being swapped. 236 */ 237 rip->p_flag |= SKEEP; 238 if (procdup(rpp, isvfork)) 239 return (1); 240 241 /* 242 * Make child runnable and add to run queue. 243 */ 244 (void) splclock(); 245 rpp->p_stat = SRUN; 246 setrq(rpp); 247 (void) spl0(); 248 249 /* 250 * Cause child to take a non-local goto as soon as it runs. 251 * On older systems this was done with SSWAP bit in proc 252 * table; on VAX we use u.u_pcb.pcb_sswap so don't need 253 * to do rpp->p_flag |= SSWAP. Actually do nothing here. 254 */ 255 /* rpp->p_flag |= SSWAP; */ 256 257 /* 258 * Now can be swapped. 259 */ 260 rip->p_flag &= ~SKEEP; 261 262 /* 263 * If vfork make chain from parent process to child 264 * (where virtal memory is temporarily). Wait for 265 * child to finish, steal virtual memory back, 266 * and wakeup child to let it die. 267 */ 268 if (isvfork) { 269 u.u_procp->p_xlink = rpp; 270 u.u_procp->p_flag |= SNOVM; 271 while (rpp->p_flag & SVFORK) 272 sleep((caddr_t)rpp, PZERO - 1); 273 if ((rpp->p_flag & SLOAD) == 0) 274 panic("newproc vfork"); 275 uaccess(rpp, Vfmap, &vfutl); 276 u.u_procp->p_xlink = 0; 277 vpassvm(rpp, u.u_procp, &vfutl, &u, Vfmap); 278 u.u_procp->p_flag &= ~SNOVM; 279 rpp->p_ndx = rpp - proc; 280 rpp->p_flag |= SVFDONE; 281 wakeup((caddr_t)rpp); 282 } 283 284 /* 285 * 0 return means parent. 286 */ 287 return (0); 288 } 289