1 /* $OpenBSD: kern_fork.c,v 1.10 1997/08/01 21:59:13 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 if (dupfd == 0) 134 return (EPERM); 135 } 136 137 /* 138 * Although process entries are dynamically created, we still keep 139 * a global limit on the maximum number we will create. Don't allow 140 * a nonprivileged user to use the last process; don't let root 141 * exceed the limit. The variable nprocs is the current number of 142 * processes, maxproc is the limit. 143 */ 144 uid = p1->p_cred->p_ruid; 145 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 146 tablefull("proc"); 147 return (EAGAIN); 148 } 149 150 /* 151 * Increment the count of procs running with this uid. Don't allow 152 * a nonprivileged user to exceed their current limit. 153 */ 154 count = chgproccnt(uid, 1); 155 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 156 (void)chgproccnt(uid, -1); 157 return (EAGAIN); 158 } 159 160 /* Allocate new proc. */ 161 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 162 163 lastpid++; 164 if (randompid) 165 lastpid = PID_MAX; 166 retry: 167 /* 168 * If the process ID prototype has wrapped around, 169 * restart somewhat above 0, as the low-numbered procs 170 * tend to include daemons that don't exit. 171 */ 172 if (lastpid >= PID_MAX) { 173 lastpid = arc4random() % PID_MAX; 174 pidchecked = 0; 175 } 176 if (lastpid >= pidchecked) { 177 int doingzomb = 0; 178 179 pidchecked = PID_MAX; 180 /* 181 * Scan the active and zombie procs to check whether this pid 182 * is in use. Remember the lowest pid that's greater 183 * than lastpid, so we can avoid checking for a while. 184 */ 185 p2 = allproc.lh_first; 186 again: 187 for (; p2 != 0; p2 = p2->p_list.le_next) { 188 while (p2->p_pid == lastpid || 189 p2->p_pgrp->pg_id == lastpid) { 190 lastpid++; 191 if (lastpid >= pidchecked) 192 goto retry; 193 } 194 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 195 pidchecked = p2->p_pid; 196 if (p2->p_pgrp->pg_id > lastpid && 197 pidchecked > p2->p_pgrp->pg_id) 198 pidchecked = p2->p_pgrp->pg_id; 199 } 200 if (!doingzomb) { 201 doingzomb = 1; 202 p2 = zombproc.lh_first; 203 goto again; 204 } 205 } 206 207 nprocs++; 208 p2 = newproc; 209 p2->p_stat = SIDL; /* protect against others */ 210 p2->p_pid = lastpid; 211 LIST_INSERT_HEAD(&allproc, p2, p_list); 212 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 213 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 214 215 /* 216 * Make a proc table entry for the new process. 217 * Start by zeroing the section of proc that is zero-initialized, 218 * then copy the section that is copied directly from the parent. 219 */ 220 bzero(&p2->p_startzero, 221 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 222 bcopy(&p1->p_startcopy, &p2->p_startcopy, 223 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 224 225 /* 226 * Duplicate sub-structures as needed. 227 * Increase reference counts on shared objects. 228 * The p_stats and p_sigacts substructs are set in vm_fork. 229 */ 230 p2->p_flag = P_INMEM; 231 p2->p_emul = p1->p_emul; 232 if (p1->p_flag & P_PROFIL) 233 startprofclock(p2); 234 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 235 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 236 M_SUBPROC, M_WAITOK); 237 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 238 p2->p_cred->p_refcnt = 1; 239 crhold(p1->p_ucred); 240 241 /* bump references to the text vnode (for procfs) */ 242 p2->p_textvp = p1->p_textvp; 243 if (p2->p_textvp) 244 VREF(p2->p_textvp); 245 246 if (cleanfd) 247 p2->p_fd = fdinit(p1); 248 else if (dupfd) 249 p2->p_fd = fdcopy(p1); 250 else 251 p2->p_fd = fdshare(p1); 252 253 /* 254 * If p_limit is still copy-on-write, bump refcnt, 255 * otherwise get a copy that won't be modified. 256 * (If PL_SHAREMOD is clear, the structure is shared 257 * copy-on-write.) 258 */ 259 if (p1->p_limit->p_lflags & PL_SHAREMOD) 260 p2->p_limit = limcopy(p1->p_limit); 261 else { 262 p2->p_limit = p1->p_limit; 263 p2->p_limit->p_refcnt++; 264 } 265 266 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 267 p2->p_flag |= P_CONTROLT; 268 if (forktype == ISVFORK) 269 p2->p_flag |= P_PPWAIT; 270 LIST_INSERT_AFTER(p1, p2, p_pglist); 271 p2->p_pptr = p1; 272 if (rforkflags & RFNOWAIT) { 273 /* XXX should we do anything? */ 274 } else { 275 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 276 } 277 LIST_INIT(&p2->p_children); 278 279 #ifdef KTRACE 280 /* 281 * Copy traceflag and tracefile if enabled. 282 * If not inherited, these were zeroed above. 283 */ 284 if (p1->p_traceflag&KTRFAC_INHERIT) { 285 p2->p_traceflag = p1->p_traceflag; 286 if ((p2->p_tracep = p1->p_tracep) != NULL) 287 VREF(p2->p_tracep); 288 } 289 #endif 290 291 /* 292 * This begins the section where we must prevent the parent 293 * from being swapped. 294 */ 295 p1->p_holdcnt++; 296 297 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 298 /* share as much address space as possible */ 299 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 300 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 301 VM_INHERIT_SHARE); 302 } 303 304 #ifdef __FORK_BRAINDAMAGE 305 /* 306 * Set return values for child before vm_fork, 307 * so they can be copied to child stack. 308 * We return 0, rather than the traditional behaviour of modifying the 309 * return value in the system call stub. 310 * NOTE: the kernel stack may be at a different location in the child 311 * process, and thus addresses of automatic variables (including retval) 312 * may be invalid after vm_fork returns in the child process. 313 */ 314 retval[0] = 0; 315 retval[1] = 1; 316 if (vm_fork(p1, p2)) 317 return (0); 318 #else 319 /* 320 * Finish creating the child process. It will return through a 321 * different path later. 322 */ 323 vm_fork(p1, p2); 324 #endif 325 vm = p2->p_vmspace; 326 327 switch (forktype) { 328 case ISFORK: 329 forkstat.cntfork++; 330 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 331 break; 332 case ISVFORK: 333 forkstat.cntvfork++; 334 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 335 break; 336 case ISRFORK: 337 forkstat.cntrfork++; 338 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 339 break; 340 } 341 342 /* 343 * Make child runnable, set start time, and add to run queue. 344 */ 345 (void) splstatclock(); 346 p2->p_stats->p_start = time; 347 p2->p_acflag = AFORK; 348 p2->p_stat = SRUN; 349 setrunqueue(p2); 350 (void) spl0(); 351 352 /* 353 * Now can be swapped. 354 */ 355 p1->p_holdcnt--; 356 357 /* 358 * Preserve synchronization semantics of vfork. If waiting for 359 * child to exec or exit, set P_PPWAIT on child, and sleep on our 360 * proc (in case of exit). 361 */ 362 if (forktype == ISVFORK) 363 while (p2->p_flag & P_PPWAIT) 364 tsleep(p1, PWAIT, "ppwait", 0); 365 366 /* 367 * Return child pid to parent process, 368 * marking us as parent via retval[1]. 369 */ 370 retval[0] = p2->p_pid; 371 retval[1] = 0; 372 return (0); 373 } 374