1 /* $OpenBSD: kern_fork.c,v 1.43 2001/09/19 20:50:58 mickey 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/signalvar.h> 54 #include <sys/vnode.h> 55 #include <sys/file.h> 56 #include <sys/acct.h> 57 #include <sys/ktrace.h> 58 #include <sys/sched.h> 59 #include <dev/rndvar.h> 60 #include <sys/pool.h> 61 62 #include <sys/syscallargs.h> 63 64 #include <vm/vm.h> 65 #include <uvm/uvm_extern.h> 66 #include <uvm/uvm_map.h> 67 68 int nprocs = 1; /* process 0 */ 69 int randompid; /* when set to 1, pid's go random */ 70 pid_t lastpid; 71 struct forkstat forkstat; 72 73 74 /*ARGSUSED*/ 75 int 76 sys_fork(p, v, retval) 77 struct proc *p; 78 void *v; 79 register_t *retval; 80 { 81 return (fork1(p, SIGCHLD, FORK_FORK, NULL, 0, retval)); 82 } 83 84 /*ARGSUSED*/ 85 int 86 sys_vfork(p, v, retval) 87 struct proc *p; 88 void *v; 89 register_t *retval; 90 { 91 return (fork1(p, SIGCHLD, FORK_VFORK|FORK_PPWAIT, NULL, 0, retval)); 92 } 93 94 int 95 sys_rfork(p, v, retval) 96 struct proc *p; 97 void *v; 98 register_t *retval; 99 { 100 struct sys_rfork_args /* { 101 syscallarg(int) flags; 102 } */ *uap = v; 103 104 int rforkflags; 105 int flags; 106 107 flags = FORK_RFORK; 108 rforkflags = SCARG(uap, flags); 109 110 if ((rforkflags & RFPROC) == 0) 111 return (EINVAL); 112 113 switch(rforkflags & (RFFDG|RFCFDG)) { 114 case (RFFDG|RFCFDG): 115 return EINVAL; 116 case RFCFDG: 117 flags |= FORK_CLEANFILES; 118 break; 119 case RFFDG: 120 break; 121 default: 122 flags |= FORK_SHAREFILES; 123 break; 124 } 125 126 if (rforkflags & RFNOWAIT) 127 flags |= FORK_NOZOMBIE; 128 129 if (rforkflags & RFMEM) 130 flags |= FORK_VMNOSTACK; 131 132 return (fork1(p, SIGCHLD, flags, NULL, 0, retval)); 133 } 134 135 int 136 fork1(p1, exitsig, flags, stack, stacksize, retval) 137 register struct proc *p1; 138 int exitsig; 139 int flags; 140 void *stack; 141 size_t stacksize; 142 register_t *retval; 143 { 144 struct proc *p2; 145 uid_t uid; 146 struct proc *newproc; 147 struct vmspace *vm; 148 int count; 149 static int pidchecked = 0; 150 vaddr_t uaddr; 151 int s; 152 extern void endtsleep __P((void *)); 153 extern void realitexpire __P((void *)); 154 155 /* 156 * Although process entries are dynamically created, we still keep 157 * a global limit on the maximum number we will create. We reserve 158 * the last 5 processes to root. The variable nprocs is the current 159 * number of processes, maxproc is the limit. 160 */ 161 uid = p1->p_cred->p_ruid; 162 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 163 tablefull("proc"); 164 return (EAGAIN); 165 } 166 167 /* 168 * Increment the count of procs running with this uid. Don't allow 169 * a nonprivileged user to exceed their current limit. 170 */ 171 count = chgproccnt(uid, 1); 172 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 173 (void)chgproccnt(uid, -1); 174 return (EAGAIN); 175 } 176 177 /* 178 * Allocate a pcb and kernel stack for the process 179 */ 180 uaddr = uvm_km_valloc(kernel_map, USPACE); 181 if (uaddr == 0) 182 return ENOMEM; 183 184 /* Allocate new proc. */ 185 newproc = pool_get(&proc_pool, PR_WAITOK); 186 187 lastpid++; 188 if (randompid) 189 lastpid = PID_MAX; 190 retry: 191 /* 192 * If the process ID prototype has wrapped around, 193 * restart somewhat above 0, as the low-numbered procs 194 * tend to include daemons that don't exit. 195 */ 196 if (lastpid >= PID_MAX) { 197 lastpid = arc4random() % PID_MAX; 198 pidchecked = 0; 199 } 200 if (lastpid >= pidchecked) { 201 int doingzomb = 0; 202 203 pidchecked = PID_MAX; 204 /* 205 * Scan the active and zombie procs to check whether this pid 206 * is in use. Remember the lowest pid that's greater 207 * than lastpid, so we can avoid checking for a while. 208 */ 209 p2 = LIST_FIRST(&allproc); 210 again: 211 for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) { 212 while (p2->p_pid == lastpid || 213 p2->p_pgrp->pg_id == lastpid) { 214 lastpid++; 215 if (lastpid >= pidchecked) 216 goto retry; 217 } 218 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 219 pidchecked = p2->p_pid; 220 if (p2->p_pgrp->pg_id > lastpid && 221 pidchecked > p2->p_pgrp->pg_id) 222 pidchecked = p2->p_pgrp->pg_id; 223 } 224 if (!doingzomb) { 225 doingzomb = 1; 226 p2 = LIST_FIRST(&zombproc); 227 goto again; 228 } 229 } 230 231 nprocs++; 232 p2 = newproc; 233 p2->p_stat = SIDL; /* protect against others */ 234 p2->p_pid = lastpid; 235 p2->p_exitsig = exitsig; 236 LIST_INSERT_HEAD(&allproc, p2, p_list); 237 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 238 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 239 240 /* 241 * Make a proc table entry for the new process. 242 * Start by zeroing the section of proc that is zero-initialized, 243 * then copy the section that is copied directly from the parent. 244 */ 245 bzero(&p2->p_startzero, 246 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 247 bcopy(&p1->p_startcopy, &p2->p_startcopy, 248 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 249 250 /* 251 * Initialize the timeouts. 252 */ 253 timeout_set(&p2->p_sleep_to, endtsleep, p2); 254 timeout_set(&p2->p_realit_to, realitexpire, p2); 255 256 /* 257 * Duplicate sub-structures as needed. 258 * Increase reference counts on shared objects. 259 * The p_stats and p_sigacts substructs are set in vm_fork. 260 */ 261 p2->p_flag = P_INMEM; 262 p2->p_emul = p1->p_emul; 263 if (p1->p_flag & P_PROFIL) 264 startprofclock(p2); 265 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 266 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 267 M_SUBPROC, M_WAITOK); 268 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 269 p2->p_cred->p_refcnt = 1; 270 crhold(p1->p_ucred); 271 272 /* bump references to the text vnode (for procfs) */ 273 p2->p_textvp = p1->p_textvp; 274 if (p2->p_textvp) 275 VREF(p2->p_textvp); 276 277 if (flags & FORK_CLEANFILES) 278 p2->p_fd = fdinit(p1); 279 else if (flags & FORK_SHAREFILES) 280 p2->p_fd = fdshare(p1); 281 else 282 p2->p_fd = fdcopy(p1); 283 284 /* 285 * If p_limit is still copy-on-write, bump refcnt, 286 * otherwise get a copy that won't be modified. 287 * (If PL_SHAREMOD is clear, the structure is shared 288 * copy-on-write.) 289 */ 290 if (p1->p_limit->p_lflags & PL_SHAREMOD) 291 p2->p_limit = limcopy(p1->p_limit); 292 else { 293 p2->p_limit = p1->p_limit; 294 p2->p_limit->p_refcnt++; 295 } 296 297 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 298 p2->p_flag |= P_CONTROLT; 299 if (flags & FORK_PPWAIT) 300 p2->p_flag |= P_PPWAIT; 301 LIST_INSERT_AFTER(p1, p2, p_pglist); 302 p2->p_pptr = p1; 303 if (flags & FORK_NOZOMBIE) 304 p2->p_flag |= P_NOZOMBIE; 305 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 306 LIST_INIT(&p2->p_children); 307 308 #ifdef KTRACE 309 /* 310 * Copy traceflag and tracefile if enabled. 311 * If not inherited, these were zeroed above. 312 */ 313 if (p1->p_traceflag & KTRFAC_INHERIT) { 314 p2->p_traceflag = p1->p_traceflag; 315 if ((p2->p_tracep = p1->p_tracep) != NULL) 316 VREF(p2->p_tracep); 317 } 318 #endif 319 320 /* 321 * set priority of child to be that of parent 322 * XXX should move p_estcpu into the region of struct proc which gets 323 * copied. 324 */ 325 scheduler_fork_hook(p1, p2); 326 327 /* 328 * Create signal actions for the child process. 329 */ 330 if (flags & FORK_SIGHAND) 331 sigactsshare(p1, p2); 332 else 333 p2->p_sigacts = sigactsinit(p1); 334 335 /* 336 * This begins the section where we must prevent the parent 337 * from being swapped. 338 */ 339 PHOLD(p1); 340 341 if (flags & FORK_VMNOSTACK) { 342 /* share as much address space as possible */ 343 (void) uvm_map_inherit(&p1->p_vmspace->vm_map, 344 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 345 VM_INHERIT_SHARE); 346 } 347 348 p2->p_addr = (struct user *)uaddr; 349 350 /* 351 * Finish creating the child process. It will return through a 352 * different path later. 353 */ 354 uvm_fork(p1, p2, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack, 355 stacksize); 356 357 vm = p2->p_vmspace; 358 359 if (flags & FORK_FORK) { 360 forkstat.cntfork++; 361 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 362 } else if (flags & FORK_VFORK) { 363 forkstat.cntvfork++; 364 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 365 } else if (flags & FORK_RFORK) { 366 forkstat.cntrfork++; 367 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 368 } else { 369 forkstat.cntkthread++; 370 forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize; 371 } 372 373 /* 374 * Make child runnable, set start time, and add to run queue. 375 */ 376 s = splstatclock(); 377 p2->p_stats->p_start = time; 378 p2->p_acflag = AFORK; 379 p2->p_stat = SRUN; 380 setrunqueue(p2); 381 splx(s); 382 383 /* 384 * Now can be swapped. 385 */ 386 PRELE(p1); 387 388 uvmexp.forks++; 389 if (flags & FORK_PPWAIT) 390 uvmexp.forks_ppwait++; 391 if (flags & FORK_SHAREVM) 392 uvmexp.forks_sharevm++; 393 394 /* 395 * tell any interested parties about the new process 396 */ 397 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 398 399 /* 400 * Preserve synchronization semantics of vfork. If waiting for 401 * child to exec or exit, set P_PPWAIT on child, and sleep on our 402 * proc (in case of exit). 403 */ 404 if (flags & FORK_PPWAIT) 405 while (p2->p_flag & P_PPWAIT) 406 tsleep(p1, PWAIT, "ppwait", 0); 407 408 /* 409 * Return child pid to parent process, 410 * marking us as parent via retval[1]. 411 */ 412 retval[0] = p2->p_pid; 413 retval[1] = 0; 414 return (0); 415 } 416 417