1 /* $OpenBSD: kern_fork.c,v 1.11 1997/08/01 22:54:49 deraadt 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 #define ISFORK 0 68 #define ISVFORK 1 69 #define ISRFORK 2 70 71 int fork1 __P((struct proc *, int, int, register_t *)); 72 73 /*ARGSUSED*/ 74 int 75 sys_fork(p, v, retval) 76 struct proc *p; 77 void *v; 78 register_t *retval; 79 { 80 return (fork1(p, ISFORK, 0, retval)); 81 } 82 83 /*ARGSUSED*/ 84 int 85 sys_vfork(p, v, retval) 86 struct proc *p; 87 void *v; 88 register_t *retval; 89 { 90 return (fork1(p, ISVFORK, 0, retval)); 91 } 92 93 int 94 sys_rfork(p, v, retval) 95 struct proc *p; 96 void *v; 97 register_t *retval; 98 { 99 struct sys_rfork_args /* { 100 syscallarg(int) flags; 101 } */ *uap = v; 102 103 return (fork1(p, ISRFORK, SCARG(uap, flags), retval)); 104 } 105 106 int 107 fork1(p1, forktype, rforkflags, retval) 108 register struct proc *p1; 109 int forktype; 110 int rforkflags; 111 register_t *retval; 112 { 113 register struct proc *p2; 114 register uid_t uid; 115 struct proc *newproc; 116 struct vmspace *vm; 117 int count; 118 static int pidchecked = 0; 119 int dupfd = 1, cleanfd = 0; 120 121 if (forktype == ISRFORK) { 122 dupfd = 0; 123 if ((rforkflags & RFPROC) == 0) 124 return (EINVAL); 125 if ((rforkflags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 126 return (EINVAL); 127 if (rforkflags & RFFDG) 128 dupfd = 1; 129 if (rforkflags & RFNOWAIT) 130 return (EINVAL); /* XXX unimplimented */ 131 if (rforkflags & RFCFDG) 132 cleanfd = 1; 133 } 134 135 /* 136 * Although process entries are dynamically created, we still keep 137 * a global limit on the maximum number we will create. Don't allow 138 * a nonprivileged user to use the last process; don't let root 139 * exceed the limit. The variable nprocs is the current number of 140 * processes, maxproc is the limit. 141 */ 142 uid = p1->p_cred->p_ruid; 143 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 144 tablefull("proc"); 145 return (EAGAIN); 146 } 147 148 /* 149 * Increment the count of procs running with this uid. Don't allow 150 * a nonprivileged user to exceed their current limit. 151 */ 152 count = chgproccnt(uid, 1); 153 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 154 (void)chgproccnt(uid, -1); 155 return (EAGAIN); 156 } 157 158 /* Allocate new proc. */ 159 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 160 161 lastpid++; 162 if (randompid) 163 lastpid = PID_MAX; 164 retry: 165 /* 166 * If the process ID prototype has wrapped around, 167 * restart somewhat above 0, as the low-numbered procs 168 * tend to include daemons that don't exit. 169 */ 170 if (lastpid >= PID_MAX) { 171 lastpid = arc4random() % PID_MAX; 172 pidchecked = 0; 173 } 174 if (lastpid >= pidchecked) { 175 int doingzomb = 0; 176 177 pidchecked = PID_MAX; 178 /* 179 * Scan the active and zombie procs to check whether this pid 180 * is in use. Remember the lowest pid that's greater 181 * than lastpid, so we can avoid checking for a while. 182 */ 183 p2 = allproc.lh_first; 184 again: 185 for (; p2 != 0; p2 = p2->p_list.le_next) { 186 while (p2->p_pid == lastpid || 187 p2->p_pgrp->pg_id == lastpid) { 188 lastpid++; 189 if (lastpid >= pidchecked) 190 goto retry; 191 } 192 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 193 pidchecked = p2->p_pid; 194 if (p2->p_pgrp->pg_id > lastpid && 195 pidchecked > p2->p_pgrp->pg_id) 196 pidchecked = p2->p_pgrp->pg_id; 197 } 198 if (!doingzomb) { 199 doingzomb = 1; 200 p2 = zombproc.lh_first; 201 goto again; 202 } 203 } 204 205 nprocs++; 206 p2 = newproc; 207 p2->p_stat = SIDL; /* protect against others */ 208 p2->p_pid = lastpid; 209 LIST_INSERT_HEAD(&allproc, p2, p_list); 210 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 211 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 212 213 /* 214 * Make a proc table entry for the new process. 215 * Start by zeroing the section of proc that is zero-initialized, 216 * then copy the section that is copied directly from the parent. 217 */ 218 bzero(&p2->p_startzero, 219 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 220 bcopy(&p1->p_startcopy, &p2->p_startcopy, 221 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 222 223 /* 224 * Duplicate sub-structures as needed. 225 * Increase reference counts on shared objects. 226 * The p_stats and p_sigacts substructs are set in vm_fork. 227 */ 228 p2->p_flag = P_INMEM; 229 p2->p_emul = p1->p_emul; 230 if (p1->p_flag & P_PROFIL) 231 startprofclock(p2); 232 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 233 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 234 M_SUBPROC, M_WAITOK); 235 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 236 p2->p_cred->p_refcnt = 1; 237 crhold(p1->p_ucred); 238 239 /* bump references to the text vnode (for procfs) */ 240 p2->p_textvp = p1->p_textvp; 241 if (p2->p_textvp) 242 VREF(p2->p_textvp); 243 244 if (cleanfd) 245 p2->p_fd = fdinit(p1); 246 else if (dupfd) 247 p2->p_fd = fdcopy(p1); 248 else 249 p2->p_fd = fdshare(p1); 250 251 /* 252 * If p_limit is still copy-on-write, bump refcnt, 253 * otherwise get a copy that won't be modified. 254 * (If PL_SHAREMOD is clear, the structure is shared 255 * copy-on-write.) 256 */ 257 if (p1->p_limit->p_lflags & PL_SHAREMOD) 258 p2->p_limit = limcopy(p1->p_limit); 259 else { 260 p2->p_limit = p1->p_limit; 261 p2->p_limit->p_refcnt++; 262 } 263 264 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 265 p2->p_flag |= P_CONTROLT; 266 if (forktype == ISVFORK) 267 p2->p_flag |= P_PPWAIT; 268 LIST_INSERT_AFTER(p1, p2, p_pglist); 269 p2->p_pptr = p1; 270 if (rforkflags & RFNOWAIT) { 271 /* XXX should we do anything? */ 272 } else { 273 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 274 } 275 LIST_INIT(&p2->p_children); 276 277 #ifdef KTRACE 278 /* 279 * Copy traceflag and tracefile if enabled. 280 * If not inherited, these were zeroed above. 281 */ 282 if (p1->p_traceflag&KTRFAC_INHERIT) { 283 p2->p_traceflag = p1->p_traceflag; 284 if ((p2->p_tracep = p1->p_tracep) != NULL) 285 VREF(p2->p_tracep); 286 } 287 #endif 288 289 /* 290 * This begins the section where we must prevent the parent 291 * from being swapped. 292 */ 293 p1->p_holdcnt++; 294 295 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 296 /* share as much address space as possible */ 297 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 298 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 299 VM_INHERIT_SHARE); 300 } 301 302 #ifdef __FORK_BRAINDAMAGE 303 /* 304 * Set return values for child before vm_fork, 305 * so they can be copied to child stack. 306 * We return 0, rather than the traditional behaviour of modifying the 307 * return value in the system call stub. 308 * NOTE: the kernel stack may be at a different location in the child 309 * process, and thus addresses of automatic variables (including retval) 310 * may be invalid after vm_fork returns in the child process. 311 */ 312 retval[0] = 0; 313 retval[1] = 1; 314 if (vm_fork(p1, p2)) 315 return (0); 316 #else 317 /* 318 * Finish creating the child process. It will return through a 319 * different path later. 320 */ 321 vm_fork(p1, p2); 322 #endif 323 vm = p2->p_vmspace; 324 325 switch (forktype) { 326 case ISFORK: 327 forkstat.cntfork++; 328 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 329 break; 330 case ISVFORK: 331 forkstat.cntvfork++; 332 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 333 break; 334 case ISRFORK: 335 forkstat.cntrfork++; 336 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 337 break; 338 } 339 340 /* 341 * Make child runnable, set start time, and add to run queue. 342 */ 343 (void) splstatclock(); 344 p2->p_stats->p_start = time; 345 p2->p_acflag = AFORK; 346 p2->p_stat = SRUN; 347 setrunqueue(p2); 348 (void) spl0(); 349 350 /* 351 * Now can be swapped. 352 */ 353 p1->p_holdcnt--; 354 355 /* 356 * Preserve synchronization semantics of vfork. If waiting for 357 * child to exec or exit, set P_PPWAIT on child, and sleep on our 358 * proc (in case of exit). 359 */ 360 if (forktype == ISVFORK) 361 while (p2->p_flag & P_PPWAIT) 362 tsleep(p1, PWAIT, "ppwait", 0); 363 364 /* 365 * Return child pid to parent process, 366 * marking us as parent via retval[1]. 367 */ 368 retval[0] = p2->p_pid; 369 retval[1] = 0; 370 return (0); 371 } 372