1 /* 2 * Copyright (c) 1982, 1986, 1989, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * from: @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 39 * $Id: kern_fork.c,v 1.18 1994/06/15 19:59:21 mycroft Exp $ 40 */ 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/map.h> 45 #include <sys/filedesc.h> 46 #include <sys/kernel.h> 47 #include <sys/malloc.h> 48 #include <sys/proc.h> 49 #include <sys/resourcevar.h> 50 #include <sys/vnode.h> 51 #include <sys/file.h> 52 #include <sys/acct.h> 53 #include <sys/ktrace.h> 54 55 /* ARGSUSED */ 56 fork(p, uap, retval) 57 struct proc *p; 58 void *uap; 59 int retval[]; 60 { 61 62 return (fork1(p, 0, retval)); 63 } 64 65 /* ARGSUSED */ 66 vfork(p, uap, retval) 67 struct proc *p; 68 void *uap; 69 int retval[]; 70 { 71 72 return (fork1(p, 1, retval)); 73 } 74 75 int nprocs = 1; /* process 0 */ 76 77 fork1(p1, isvfork, retval) 78 register struct proc *p1; 79 int isvfork, retval[]; 80 { 81 register struct proc *p2; 82 register uid_t uid; 83 struct proc *newproc; 84 struct proc **hash; 85 int count; 86 static int nextpid, pidchecked = 0; 87 88 /* 89 * Although process entries are dynamically created, we still keep 90 * a global limit on the maximum number we will create. Don't allow 91 * a nonprivileged user to use the last process; don't let root 92 * exceed the limit. The variable nprocs is the current number of 93 * processes, maxproc is the limit. 94 */ 95 uid = p1->p_cred->p_ruid; 96 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 97 tablefull("proc"); 98 return (EAGAIN); 99 } 100 /* 101 * Increment the count of procs running with this uid. Don't allow 102 * a nonprivileged user to exceed their current limit. 103 */ 104 count = chgproccnt(uid, 1); 105 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 106 (void)chgproccnt(uid, -1); 107 return (EAGAIN); 108 } 109 110 /* Allocate new proc. */ 111 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 112 113 /* 114 * Find an unused process ID. We remember a range of unused IDs 115 * ready to use (from nextpid+1 through pidchecked-1). 116 */ 117 nextpid++; 118 retry: 119 /* 120 * If the process ID prototype has wrapped around, 121 * restart somewhat above 0, as the low-numbered procs 122 * tend to include daemons that don't exit. 123 */ 124 if (nextpid >= PID_MAX) { 125 nextpid = 100; 126 pidchecked = 0; 127 } 128 if (nextpid >= pidchecked) { 129 int doingzomb = 0; 130 131 pidchecked = PID_MAX; 132 /* 133 * Scan the active and zombie procs to check whether this pid 134 * is in use. Remember the lowest pid that's greater 135 * than nextpid, so we can avoid checking for a while. 136 */ 137 p2 = (struct proc *)allproc; 138 again: 139 for (; p2 != NULL; p2 = p2->p_next) { 140 while (p2->p_pid == nextpid || 141 p2->p_pgrp->pg_id == nextpid) { 142 nextpid++; 143 if (nextpid >= pidchecked) 144 goto retry; 145 } 146 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 147 pidchecked = p2->p_pid; 148 if (p2->p_pgrp->pg_id > nextpid && 149 pidchecked > p2->p_pgrp->pg_id) 150 pidchecked = p2->p_pgrp->pg_id; 151 } 152 if (!doingzomb) { 153 doingzomb = 1; 154 p2 = zombproc; 155 goto again; 156 } 157 } 158 159 160 /* 161 * Link onto allproc (this should probably be delayed). 162 * Heavy use of volatile here to prevent the compiler from 163 * rearranging code. Yes, it *is* terribly ugly, but at least 164 * it works. 165 */ 166 nprocs++; 167 p2 = newproc; 168 #define Vp2 ((volatile struct proc *)p2) 169 Vp2->p_stat = SIDL; /* protect against others */ 170 Vp2->p_pid = nextpid; 171 /* 172 * This is really: 173 * p2->p_next = allproc; 174 * allproc->p_prev = &p2->p_next; 175 * p2->p_prev = &allproc; 176 * allproc = p2; 177 * The assignment via allproc is legal since it is never NULL. 178 */ 179 *(volatile struct proc **)&Vp2->p_next = allproc; 180 *(volatile struct proc ***)&allproc->p_prev = 181 (volatile struct proc **)&Vp2->p_next; 182 *(volatile struct proc ***)&Vp2->p_prev = &allproc; 183 allproc = Vp2; 184 #undef Vp2 185 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 186 187 /* Insert on the hash chain. */ 188 hash = &pidhash[PIDHASH(p2->p_pid)]; 189 p2->p_hash = *hash; 190 *hash = p2; 191 192 /* 193 * Make a proc table entry for the new process. 194 * Start by zeroing the section of proc that is zero-initialized, 195 * then copy the section that is copied directly from the parent. 196 */ 197 bzero(&p2->p_startzero, 198 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 199 bcopy(&p1->p_startcopy, &p2->p_startcopy, 200 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 201 202 /* 203 * Duplicate sub-structures as needed. 204 * Increase reference counts on shared objects. 205 * The p_stats and p_sigacts substructs are set in vm_fork. 206 */ 207 p2->p_flag = P_INMEM; 208 if (p1->p_flag & P_PROFIL) 209 startprofclock(p2); 210 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 211 M_SUBPROC, M_WAITOK); 212 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 213 p2->p_cred->p_refcnt = 1; 214 crhold(p1->p_ucred); 215 216 /* bump references to the text vnode (for procfs) */ 217 p2->p_textvp = p1->p_textvp; 218 if (p2->p_textvp) 219 VREF(p2->p_textvp); 220 221 p2->p_fd = fdcopy(p1); 222 /* 223 * If p_limit is still copy-on-write, bump refcnt, 224 * otherwise get a copy that won't be modified. 225 * (If PL_SHAREMOD is clear, the structure is shared 226 * copy-on-write.) 227 */ 228 if (p1->p_limit->p_lflags & PL_SHAREMOD) 229 p2->p_limit = limcopy(p1->p_limit); 230 else { 231 p2->p_limit = p1->p_limit; 232 p2->p_limit->p_refcnt++; 233 } 234 235 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 236 p2->p_flag |= P_CONTROLT; 237 if (isvfork) 238 p2->p_flag |= P_PPWAIT; 239 p2->p_pgrpnxt = p1->p_pgrpnxt; 240 p1->p_pgrpnxt = p2; 241 p2->p_pptr = p1; 242 p2->p_osptr = p1->p_cptr; 243 if (p1->p_cptr) 244 p1->p_cptr->p_ysptr = p2; 245 p1->p_cptr = p2; 246 #ifdef KTRACE 247 /* 248 * Copy traceflag and tracefile if enabled. 249 * If not inherited, these were zeroed above. 250 */ 251 if (p1->p_traceflag&KTRFAC_INHERIT) { 252 p2->p_traceflag = p1->p_traceflag; 253 if ((p2->p_tracep = p1->p_tracep) != NULL) 254 VREF(p2->p_tracep); 255 } 256 #endif 257 258 /* 259 * This begins the section where we must prevent the parent 260 * from being swapped. 261 */ 262 p1->p_holdcnt++; 263 /* 264 * Set return values for child before vm_fork, 265 * so they can be copied to child stack. 266 * We return parent pid, and mark as child in retval[1]. 267 * NOTE: the kernel stack may be at a different location in the child 268 * process, and thus addresses of automatic variables (including retval) 269 * may be invalid after vm_fork returns in the child process. 270 */ 271 retval[0] = p1->p_pid; 272 retval[1] = 1; 273 if (vm_fork(p1, p2, isvfork)) { 274 /* 275 * Child process. Set start time and get to work. 276 */ 277 (void) splclock(); 278 p2->p_stats->p_start = time; 279 (void) spl0(); 280 p2->p_acflag = AFORK; 281 return (0); 282 } 283 284 /* 285 * Make child runnable and add to run queue. 286 */ 287 (void) splhigh(); 288 p2->p_stat = SRUN; 289 setrunqueue(p2); 290 (void) spl0(); 291 292 /* 293 * Now can be swapped. 294 */ 295 p1->p_holdcnt--; 296 297 /* 298 * Preserve synchronization semantics of vfork. If waiting for 299 * child to exec or exit, set P_PPWAIT on child, and sleep on our 300 * proc (in case of exit). 301 */ 302 if (isvfork) 303 while (p2->p_flag & P_PPWAIT) 304 tsleep(p1, PWAIT, "ppwait", 0); 305 306 /* 307 * Return child pid to parent process, 308 * marking us as parent via retval[1]. 309 */ 310 retval[0] = p2->p_pid; 311 retval[1] = 0; 312 return (0); 313 } 314