1 /* 2 * Copyright (c) 1982, 1986, 1989 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that the above copyright notice and this paragraph are 7 * duplicated in all such forms and that any documentation, 8 * advertising materials, and other materials related to such 9 * distribution and use acknowledge that the software was developed 10 * by the University of California, Berkeley. The name of the 11 * University may not be used to endorse or promote products derived 12 * from this software without specific prior written permission. 13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 16 * 17 * @(#)kern_fork.c 7.10 (Berkeley) 11/20/89 18 */ 19 20 #include "param.h" 21 #include "systm.h" 22 #include "map.h" 23 #include "user.h" 24 #include "kernel.h" 25 #include "proc.h" 26 #include "vnode.h" 27 #include "seg.h" 28 #include "vm.h" 29 #include "text.h" 30 #include "file.h" 31 #include "acct.h" 32 #include "../ufs/quota.h" 33 34 #include "machine/reg.h" 35 #include "machine/pte.h" 36 #include "machine/psl.h" 37 38 /* 39 * fork system call. 40 */ 41 fork() 42 { 43 44 u.u_cdmap = zdmap; 45 u.u_csmap = zdmap; 46 if (swpexpand(u.u_dsize, u.u_ssize, &u.u_cdmap, &u.u_csmap) == 0) { 47 u.u_r.r_val2 = 0; 48 return; 49 } 50 fork1(0); 51 } 52 53 vfork() 54 { 55 56 fork1(1); 57 } 58 59 fork1(isvfork) 60 int isvfork; 61 { 62 register struct proc *p1, *p2; 63 register a; 64 65 a = 0; 66 if (u.u_uid != 0) { 67 for (p1 = allproc; p1; p1 = p1->p_nxt) 68 if (p1->p_uid == u.u_uid) 69 a++; 70 for (p1 = zombproc; p1; p1 = p1->p_nxt) 71 if (p1->p_uid == u.u_uid) 72 a++; 73 } 74 /* 75 * Disallow if 76 * No processes at all; 77 * not su and too many procs owned; or 78 * not su and would take last slot. 79 */ 80 p2 = freeproc; 81 if (p2==NULL) 82 tablefull("proc"); 83 if (p2==NULL || (u.u_uid!=0 && (p2->p_nxt == NULL || a>MAXUPRC))) { 84 u.u_error = EAGAIN; 85 if (!isvfork) { 86 (void) vsexpand((size_t)0, &u.u_cdmap, 1); 87 (void) vsexpand((size_t)0, &u.u_csmap, 1); 88 } 89 goto out; 90 } 91 p1 = u.u_procp; 92 if (newproc(isvfork)) { 93 u.u_r.r_val1 = p1->p_pid; 94 u.u_r.r_val2 = 1; /* child */ 95 u.u_start = time; 96 u.u_acflag = AFORK; 97 return; 98 } 99 u.u_r.r_val1 = p2->p_pid; 100 101 out: 102 u.u_r.r_val2 = 0; 103 } 104 105 /* 106 * Create a new process-- the internal version of 107 * sys fork. 108 * It returns 1 in the new process, 0 in the old. 109 */ 110 newproc(isvfork) 111 int isvfork; 112 { 113 register struct proc *rpp, *rip; 114 register int n; 115 register struct file *fp; 116 static int pidchecked = 0; 117 118 /* 119 * First, just locate a slot for a process 120 * and copy the useful info from this process into it. 121 * The panic "cannot happen" because fork has already 122 * checked for the existence of a slot. 123 */ 124 mpid++; 125 retry: 126 if (mpid >= 30000) { 127 mpid = 100; 128 pidchecked = 0; 129 } 130 if (mpid >= pidchecked) { 131 int doingzomb = 0; 132 133 pidchecked = 30000; 134 /* 135 * Scan the proc table to check whether this pid 136 * is in use. Remember the lowest pid that's greater 137 * than mpid, so we can avoid checking for a while. 138 */ 139 rpp = allproc; 140 again: 141 for (; rpp != NULL; rpp = rpp->p_nxt) { 142 if (rpp->p_pid == mpid || rpp->p_pgrp->pg_id == mpid) { 143 mpid++; 144 if (mpid >= pidchecked) 145 goto retry; 146 } 147 if (rpp->p_pid > mpid && pidchecked > rpp->p_pid) 148 pidchecked = rpp->p_pid; 149 if (rpp->p_pgrp->pg_id > mpid && 150 pidchecked > rpp->p_pgrp->pg_id) 151 pidchecked = rpp->p_pgrp->pg_id; 152 } 153 if (!doingzomb) { 154 doingzomb = 1; 155 rpp = zombproc; 156 goto again; 157 } 158 } 159 if ((rpp = freeproc) == NULL) 160 panic("no procs"); 161 162 freeproc = rpp->p_nxt; /* off freeproc */ 163 rpp->p_nxt = allproc; /* onto allproc */ 164 rpp->p_nxt->p_prev = &rpp->p_nxt; /* (allproc is never NULL) */ 165 rpp->p_prev = &allproc; 166 allproc = rpp; 167 168 /* 169 * Make a proc table entry for the new process. 170 */ 171 rip = u.u_procp; 172 #ifdef QUOTA 173 rpp->p_quota = rip->p_quota; 174 rpp->p_quota->q_cnt++; 175 #endif 176 #if defined(tahoe) 177 rpp->p_ckey = rip->p_ckey; 178 rpp->p_dkey = 0; 179 #endif 180 rpp->p_stat = SIDL; 181 timerclear(&rpp->p_realtimer.it_value); 182 rpp->p_flag = SLOAD | (rip->p_flag & (SPAGV|SCTTY)); 183 if (isvfork) { 184 rpp->p_flag |= SVFORK; 185 rpp->p_ndx = rip->p_ndx; 186 } else 187 rpp->p_ndx = rpp - proc; 188 rpp->p_uid = rip->p_uid; 189 rpp->p_ruid = rip->p_ruid; 190 rpp->p_rgid = rip->p_rgid; 191 rpp->p_pgrp = rip->p_pgrp; 192 rpp->p_pgrpnxt = rip->p_pgrpnxt; 193 rip->p_pgrpnxt = rpp; 194 rpp->p_nice = rip->p_nice; 195 rpp->p_textp = isvfork ? 0 : rip->p_textp; 196 rpp->p_pid = mpid; 197 rpp->p_ppid = rip->p_pid; 198 rpp->p_pptr = rip; 199 rpp->p_osptr = rip->p_cptr; 200 if (rip->p_cptr) 201 rip->p_cptr->p_ysptr = rpp; 202 rpp->p_ysptr = NULL; 203 rpp->p_cptr = NULL; 204 rip->p_cptr = rpp; 205 rpp->p_time = 0; 206 rpp->p_cpu = 0; 207 rpp->p_sigmask = rip->p_sigmask; 208 rpp->p_sigcatch = rip->p_sigcatch; 209 rpp->p_sigignore = rip->p_sigignore; 210 /* take along any pending signals like stops? */ 211 if (isvfork) { 212 rpp->p_tsize = rpp->p_dsize = rpp->p_ssize = 0; 213 rpp->p_szpt = clrnd(ctopt(UPAGES)); 214 forkstat.cntvfork++; 215 forkstat.sizvfork += rip->p_dsize + rip->p_ssize; 216 } else { 217 rpp->p_tsize = rip->p_tsize; 218 rpp->p_dsize = rip->p_dsize; 219 rpp->p_ssize = rip->p_ssize; 220 rpp->p_szpt = rip->p_szpt; 221 forkstat.cntfork++; 222 forkstat.sizfork += rip->p_dsize + rip->p_ssize; 223 } 224 #ifdef KTRACE 225 if (rip->p_flag&SKTR) { 226 rpp->p_flag |= SKTR; 227 if ((rpp->p_tracep = rip->p_tracep) != NULL) 228 VREF(rpp->p_tracep); 229 rpp->p_traceflag = rip->p_traceflag; 230 } else { 231 rpp->p_tracep = NULL; 232 rpp->p_traceflag = 0; 233 } 234 #endif 235 rpp->p_rssize = 0; 236 rpp->p_maxrss = rip->p_maxrss; 237 rpp->p_wchan = 0; 238 rpp->p_slptime = 0; 239 rpp->p_pctcpu = 0; 240 rpp->p_cpticks = 0; 241 n = PIDHASH(rpp->p_pid); 242 rpp->p_idhash = pidhash[n]; 243 pidhash[n] = rpp - proc; 244 multprog++; 245 246 /* 247 * Increase reference counts on shared objects. 248 */ 249 for (n = 0; n <= u.u_lastfile; n++) { 250 fp = u.u_ofile[n]; 251 if (fp == NULL) 252 continue; 253 fp->f_count++; 254 } 255 VREF(u.u_cdir); 256 if (u.u_rdir) 257 VREF(u.u_rdir); 258 crhold(u.u_cred); 259 260 /* 261 * This begins the section where we must prevent the parent 262 * from being swapped. 263 */ 264 rip->p_flag |= SKEEP; 265 if (procdup(rpp, isvfork)) 266 return (1); 267 268 /* 269 * Make child runnable and add to run queue. 270 */ 271 (void) splclock(); 272 rpp->p_stat = SRUN; 273 setrq(rpp); 274 (void) spl0(); 275 276 /* 277 * Cause child to take a non-local goto as soon as it runs. 278 * On older systems this was done with SSWAP bit in proc 279 * table; on VAX we use u.u_pcb.pcb_sswap so don't need 280 * to do rpp->p_flag |= SSWAP. Actually do nothing here. 281 */ 282 /* rpp->p_flag |= SSWAP; */ 283 284 /* 285 * Now can be swapped. 286 */ 287 rip->p_flag &= ~SKEEP; 288 289 /* 290 * If vfork make chain from parent process to child 291 * (where virtal memory is temporarily). Wait for 292 * child to finish, steal virtual memory back, 293 * and wakeup child to let it die. 294 */ 295 if (isvfork) { 296 u.u_procp->p_xlink = rpp; 297 u.u_procp->p_flag |= SNOVM; 298 while (rpp->p_flag & SVFORK) 299 sleep((caddr_t)rpp, PZERO - 1); 300 if ((rpp->p_flag & SLOAD) == 0) 301 panic("newproc vfork"); 302 uaccess(rpp, Vfmap, &vfutl); 303 u.u_procp->p_xlink = 0; 304 vpassvm(rpp, u.u_procp, &vfutl, &u, Vfmap); 305 u.u_procp->p_flag &= ~SNOVM; 306 rpp->p_ndx = rpp - proc; 307 rpp->p_flag |= SVFDONE; 308 wakeup((caddr_t)rpp); 309 } 310 311 /* 312 * 0 return means parent. 313 */ 314 return (0); 315 } 316