1 /* $OpenBSD: kern_fork.c,v 1.13 1999/01/11 20:25:09 niklas Exp $ */ 2 /* $NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1989, 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * (c) UNIX System Laboratories, Inc. 8 * All or some portions of this file are derived from material licensed 9 * to the University of California by American Telephone and Telegraph 10 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 11 * the permission of UNIX System Laboratories, Inc. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 42 */ 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/map.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/malloc.h> 50 #include <sys/mount.h> 51 #include <sys/proc.h> 52 #include <sys/resourcevar.h> 53 #include <sys/vnode.h> 54 #include <sys/file.h> 55 #include <sys/acct.h> 56 #include <sys/ktrace.h> 57 #include <dev/rndvar.h> 58 59 #include <sys/syscallargs.h> 60 61 #include <vm/vm.h> 62 63 int nprocs = 1; /* process 0 */ 64 int randompid; /* when set to 1, pid's go random */ 65 pid_t lastpid; 66 67 /*ARGSUSED*/ 68 int 69 sys_fork(p, v, retval) 70 struct proc *p; 71 void *v; 72 register_t *retval; 73 { 74 return (fork1(p, ISFORK, 0, retval)); 75 } 76 77 /*ARGSUSED*/ 78 int 79 sys_vfork(p, v, retval) 80 struct proc *p; 81 void *v; 82 register_t *retval; 83 { 84 return (fork1(p, ISVFORK, 0, retval)); 85 } 86 87 int 88 sys_rfork(p, v, retval) 89 struct proc *p; 90 void *v; 91 register_t *retval; 92 { 93 struct sys_rfork_args /* { 94 syscallarg(int) flags; 95 } */ *uap = v; 96 97 return (fork1(p, ISRFORK, SCARG(uap, flags), retval)); 98 } 99 100 int 101 fork1(p1, forktype, rforkflags, retval) 102 register struct proc *p1; 103 int forktype; 104 int rforkflags; 105 register_t *retval; 106 { 107 register struct proc *p2; 108 register uid_t uid; 109 struct proc *newproc; 110 struct vmspace *vm; 111 int count; 112 static int pidchecked = 0; 113 int dupfd = 1, cleanfd = 0; 114 115 if (forktype == ISRFORK) { 116 dupfd = 0; 117 if ((rforkflags & RFPROC) == 0) 118 return (EINVAL); 119 if ((rforkflags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 120 return (EINVAL); 121 if (rforkflags & RFFDG) 122 dupfd = 1; 123 if (rforkflags & RFCFDG) 124 cleanfd = 1; 125 } 126 127 /* 128 * Although process entries are dynamically created, we still keep 129 * a global limit on the maximum number we will create. Don't allow 130 * a nonprivileged user to use the last process; don't let root 131 * exceed the limit. The variable nprocs is the current number of 132 * processes, maxproc is the limit. 133 */ 134 uid = p1->p_cred->p_ruid; 135 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 136 tablefull("proc"); 137 return (EAGAIN); 138 } 139 140 /* 141 * Increment the count of procs running with this uid. Don't allow 142 * a nonprivileged user to exceed their current limit. 143 */ 144 count = chgproccnt(uid, 1); 145 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 146 (void)chgproccnt(uid, -1); 147 return (EAGAIN); 148 } 149 150 /* Allocate new proc. */ 151 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 152 153 lastpid++; 154 if (randompid) 155 lastpid = PID_MAX; 156 retry: 157 /* 158 * If the process ID prototype has wrapped around, 159 * restart somewhat above 0, as the low-numbered procs 160 * tend to include daemons that don't exit. 161 */ 162 if (lastpid >= PID_MAX) { 163 lastpid = arc4random() % PID_MAX; 164 pidchecked = 0; 165 } 166 if (lastpid >= pidchecked) { 167 int doingzomb = 0; 168 169 pidchecked = PID_MAX; 170 /* 171 * Scan the active and zombie procs to check whether this pid 172 * is in use. Remember the lowest pid that's greater 173 * than lastpid, so we can avoid checking for a while. 174 */ 175 p2 = allproc.lh_first; 176 again: 177 for (; p2 != 0; p2 = p2->p_list.le_next) { 178 while (p2->p_pid == lastpid || 179 p2->p_pgrp->pg_id == lastpid) { 180 lastpid++; 181 if (lastpid >= pidchecked) 182 goto retry; 183 } 184 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 185 pidchecked = p2->p_pid; 186 if (p2->p_pgrp->pg_id > lastpid && 187 pidchecked > p2->p_pgrp->pg_id) 188 pidchecked = p2->p_pgrp->pg_id; 189 } 190 if (!doingzomb) { 191 doingzomb = 1; 192 p2 = zombproc.lh_first; 193 goto again; 194 } 195 } 196 197 nprocs++; 198 p2 = newproc; 199 p2->p_stat = SIDL; /* protect against others */ 200 p2->p_pid = lastpid; 201 LIST_INSERT_HEAD(&allproc, p2, p_list); 202 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 203 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 204 205 /* 206 * Make a proc table entry for the new process. 207 * Start by zeroing the section of proc that is zero-initialized, 208 * then copy the section that is copied directly from the parent. 209 */ 210 bzero(&p2->p_startzero, 211 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 212 bcopy(&p1->p_startcopy, &p2->p_startcopy, 213 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 214 215 /* 216 * Duplicate sub-structures as needed. 217 * Increase reference counts on shared objects. 218 * The p_stats and p_sigacts substructs are set in vm_fork. 219 */ 220 p2->p_flag = P_INMEM; 221 p2->p_emul = p1->p_emul; 222 if (p1->p_flag & P_PROFIL) 223 startprofclock(p2); 224 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 225 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 226 M_SUBPROC, M_WAITOK); 227 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 228 p2->p_cred->p_refcnt = 1; 229 crhold(p1->p_ucred); 230 231 /* bump references to the text vnode (for procfs) */ 232 p2->p_textvp = p1->p_textvp; 233 if (p2->p_textvp) 234 VREF(p2->p_textvp); 235 236 if (cleanfd) 237 p2->p_fd = fdinit(p1); 238 else if (dupfd) 239 p2->p_fd = fdcopy(p1); 240 else 241 p2->p_fd = fdshare(p1); 242 243 /* 244 * If p_limit is still copy-on-write, bump refcnt, 245 * otherwise get a copy that won't be modified. 246 * (If PL_SHAREMOD is clear, the structure is shared 247 * copy-on-write.) 248 */ 249 if (p1->p_limit->p_lflags & PL_SHAREMOD) 250 p2->p_limit = limcopy(p1->p_limit); 251 else { 252 p2->p_limit = p1->p_limit; 253 p2->p_limit->p_refcnt++; 254 } 255 256 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 257 p2->p_flag |= P_CONTROLT; 258 if (forktype == ISVFORK) 259 p2->p_flag |= P_PPWAIT; 260 LIST_INSERT_AFTER(p1, p2, p_pglist); 261 p2->p_pptr = p1; 262 if (forktype == ISRFORK && (rforkflags & RFNOWAIT)) { 263 p2->p_flag |= P_NOZOMBIE; 264 } else { 265 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 266 } 267 LIST_INIT(&p2->p_children); 268 269 #ifdef KTRACE 270 /* 271 * Copy traceflag and tracefile if enabled. 272 * If not inherited, these were zeroed above. 273 */ 274 if (p1->p_traceflag&KTRFAC_INHERIT) { 275 p2->p_traceflag = p1->p_traceflag; 276 if ((p2->p_tracep = p1->p_tracep) != NULL) 277 VREF(p2->p_tracep); 278 } 279 #endif 280 281 /* 282 * This begins the section where we must prevent the parent 283 * from being swapped. 284 */ 285 p1->p_holdcnt++; 286 287 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 288 /* share as much address space as possible */ 289 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 290 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 291 VM_INHERIT_SHARE); 292 } 293 294 #ifdef __FORK_BRAINDAMAGE 295 /* 296 * Set return values for child before vm_fork, 297 * so they can be copied to child stack. 298 * We return 0, rather than the traditional behaviour of modifying the 299 * return value in the system call stub. 300 * NOTE: the kernel stack may be at a different location in the child 301 * process, and thus addresses of automatic variables (including retval) 302 * may be invalid after vm_fork returns in the child process. 303 */ 304 retval[0] = 0; 305 retval[1] = 1; 306 if (vm_fork(p1, p2)) 307 return (0); 308 #else 309 /* 310 * Finish creating the child process. It will return through a 311 * different path later. 312 */ 313 vm_fork(p1, p2); 314 #endif 315 vm = p2->p_vmspace; 316 317 switch (forktype) { 318 case ISFORK: 319 forkstat.cntfork++; 320 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 321 break; 322 case ISVFORK: 323 forkstat.cntvfork++; 324 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 325 break; 326 case ISRFORK: 327 forkstat.cntrfork++; 328 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 329 break; 330 } 331 332 /* 333 * Make child runnable, set start time, and add to run queue. 334 */ 335 (void) splstatclock(); 336 p2->p_stats->p_start = time; 337 p2->p_acflag = AFORK; 338 p2->p_stat = SRUN; 339 setrunqueue(p2); 340 (void) spl0(); 341 342 /* 343 * Now can be swapped. 344 */ 345 p1->p_holdcnt--; 346 347 /* 348 * Preserve synchronization semantics of vfork. If waiting for 349 * child to exec or exit, set P_PPWAIT on child, and sleep on our 350 * proc (in case of exit). 351 */ 352 if (forktype == ISVFORK) 353 while (p2->p_flag & P_PPWAIT) 354 tsleep(p1, PWAIT, "ppwait", 0); 355 356 /* 357 * Return child pid to parent process, 358 * marking us as parent via retval[1]. 359 */ 360 retval[0] = p2->p_pid; 361 retval[1] = 0; 362 return (0); 363 } 364