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 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 39 * $Id: kern_fork.c,v 1.60 1999/04/28 01:04:27 luoqi Exp $ 40 */ 41 42 #include "opt_ktrace.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/sysproto.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/sysctl.h> 50 #include <sys/malloc.h> 51 #include <sys/proc.h> 52 #include <sys/resourcevar.h> 53 #include <sys/vnode.h> 54 #include <sys/acct.h> 55 #include <sys/ktrace.h> 56 #include <sys/unistd.h> 57 #include <sys/jail.h> 58 59 #include <vm/vm.h> 60 #include <sys/lock.h> 61 #include <vm/pmap.h> 62 #include <vm/vm_map.h> 63 #include <vm/vm_extern.h> 64 #include <vm/vm_zone.h> 65 66 #include <machine/frame.h> 67 #include <sys/user.h> 68 69 static int fast_vfork = 1; 70 SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, ""); 71 72 /* 73 * These are the stuctures used to create a callout list for things to do 74 * when forking a process 75 */ 76 typedef struct fork_list_element { 77 struct fork_list_element *next; 78 forklist_fn function; 79 } *fle_p; 80 81 static fle_p fork_list; 82 83 #ifndef _SYS_SYSPROTO_H_ 84 struct fork_args { 85 int dummy; 86 }; 87 #endif 88 89 /* ARGSUSED */ 90 int 91 fork(p, uap) 92 struct proc *p; 93 struct fork_args *uap; 94 { 95 96 return (fork1(p, RFFDG | RFPROC)); 97 } 98 99 /* ARGSUSED */ 100 int 101 vfork(p, uap) 102 struct proc *p; 103 struct vfork_args *uap; 104 { 105 106 return (fork1(p, RFFDG | RFPROC | RFPPWAIT | (fast_vfork ? RFMEM : 0))); 107 } 108 109 /* ARGSUSED */ 110 int 111 rfork(p, uap) 112 struct proc *p; 113 struct rfork_args *uap; 114 { 115 116 return (fork1(p, uap->flags)); 117 } 118 119 120 int nprocs = 1; /* process 0 */ 121 static int nextpid = 0; 122 123 int 124 fork1(p1, flags) 125 register struct proc *p1; 126 int flags; 127 { 128 register struct proc *p2, *pptr; 129 register uid_t uid; 130 struct proc *newproc; 131 int count; 132 static int pidchecked = 0; 133 fle_p ep ; 134 135 ep = fork_list; 136 137 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 138 return (EINVAL); 139 140 /* 141 * Here we don't create a new process, but we divorce 142 * certain parts of a process from itself. 143 */ 144 if ((flags & RFPROC) == 0) { 145 146 /* 147 * Divorce the memory, if it is shared, essentially 148 * this changes shared memory amongst threads, into 149 * COW locally. 150 */ 151 if ((flags & RFMEM) == 0) { 152 if (p1->p_vmspace->vm_refcnt > 1) { 153 vmspace_unshare(p1); 154 } 155 } 156 157 /* 158 * Close all file descriptors. 159 */ 160 if (flags & RFCFDG) { 161 struct filedesc *fdtmp; 162 fdtmp = fdinit(p1); 163 fdfree(p1); 164 p1->p_fd = fdtmp; 165 } 166 167 /* 168 * Unshare file descriptors (from parent.) 169 */ 170 if (flags & RFFDG) { 171 if (p1->p_fd->fd_refcnt > 1) { 172 struct filedesc *newfd; 173 newfd = fdcopy(p1); 174 fdfree(p1); 175 p1->p_fd = newfd; 176 } 177 } 178 return (0); 179 } 180 181 /* 182 * Although process entries are dynamically created, we still keep 183 * a global limit on the maximum number we will create. Don't allow 184 * a nonprivileged user to use the last process; don't let root 185 * exceed the limit. The variable nprocs is the current number of 186 * processes, maxproc is the limit. 187 */ 188 uid = p1->p_cred->p_ruid; 189 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 190 tablefull("proc"); 191 return (EAGAIN); 192 } 193 /* 194 * Increment the nprocs resource before blocking can occur. There 195 * are hard-limits as to the number of processes that can run. 196 */ 197 nprocs++; 198 199 /* 200 * Increment the count of procs running with this uid. Don't allow 201 * a nonprivileged user to exceed their current limit. 202 */ 203 count = chgproccnt(uid, 1); 204 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 205 (void)chgproccnt(uid, -1); 206 /* 207 * Back out the process count 208 */ 209 nprocs--; 210 return (EAGAIN); 211 } 212 213 /* Allocate new proc. */ 214 newproc = zalloc(proc_zone); 215 216 /* 217 * Setup linkage for kernel based threading 218 */ 219 if((flags & RFTHREAD) != 0) { 220 newproc->p_peers = p1->p_peers; 221 p1->p_peers = newproc; 222 newproc->p_leader = p1->p_leader; 223 } else { 224 newproc->p_peers = 0; 225 newproc->p_leader = newproc; 226 } 227 228 newproc->p_wakeup = 0; 229 230 /* 231 * Find an unused process ID. We remember a range of unused IDs 232 * ready to use (from nextpid+1 through pidchecked-1). 233 */ 234 nextpid++; 235 retry: 236 /* 237 * If the process ID prototype has wrapped around, 238 * restart somewhat above 0, as the low-numbered procs 239 * tend to include daemons that don't exit. 240 */ 241 if (nextpid >= PID_MAX) { 242 nextpid = 100; 243 pidchecked = 0; 244 } 245 if (nextpid >= pidchecked) { 246 int doingzomb = 0; 247 248 pidchecked = PID_MAX; 249 /* 250 * Scan the active and zombie procs to check whether this pid 251 * is in use. Remember the lowest pid that's greater 252 * than nextpid, so we can avoid checking for a while. 253 */ 254 p2 = allproc.lh_first; 255 again: 256 for (; p2 != 0; p2 = p2->p_list.le_next) { 257 while (p2->p_pid == nextpid || 258 p2->p_pgrp->pg_id == nextpid || 259 p2->p_session->s_sid == nextpid) { 260 nextpid++; 261 if (nextpid >= pidchecked) 262 goto retry; 263 } 264 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 265 pidchecked = p2->p_pid; 266 if (p2->p_pgrp->pg_id > nextpid && 267 pidchecked > p2->p_pgrp->pg_id) 268 pidchecked = p2->p_pgrp->pg_id; 269 if (p2->p_session->s_sid > nextpid && 270 pidchecked > p2->p_session->s_sid) 271 pidchecked = p2->p_session->s_sid; 272 } 273 if (!doingzomb) { 274 doingzomb = 1; 275 p2 = zombproc.lh_first; 276 goto again; 277 } 278 } 279 280 p2 = newproc; 281 p2->p_stat = SIDL; /* protect against others */ 282 p2->p_pid = nextpid; 283 LIST_INSERT_HEAD(&allproc, p2, p_list); 284 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 285 286 /* 287 * Make a proc table entry for the new process. 288 * Start by zeroing the section of proc that is zero-initialized, 289 * then copy the section that is copied directly from the parent. 290 */ 291 bzero(&p2->p_startzero, 292 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 293 bcopy(&p1->p_startcopy, &p2->p_startcopy, 294 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 295 296 p2->p_aioinfo = NULL; 297 298 /* 299 * Duplicate sub-structures as needed. 300 * Increase reference counts on shared objects. 301 * The p_stats and p_sigacts substructs are set in vm_fork. 302 */ 303 p2->p_flag = P_INMEM; 304 if (p1->p_flag & P_PROFIL) 305 startprofclock(p2); 306 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 307 M_SUBPROC, M_WAITOK); 308 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 309 p2->p_cred->p_refcnt = 1; 310 crhold(p1->p_ucred); 311 312 if (p2->p_prison) { 313 p2->p_prison->pr_ref++; 314 p2->p_flag |= P_JAILED; 315 } 316 317 if (flags & RFSIGSHARE) { 318 p2->p_procsig = p1->p_procsig; 319 p2->p_procsig->ps_refcnt++; 320 if (p1->p_sigacts == &p1->p_addr->u_sigacts) { 321 struct sigacts *newsigacts; 322 int s; 323 324 if (p2->p_procsig->ps_refcnt != 2) 325 printf ("PID:%d Creating shared sigacts with procsig->ps_refcnt %d\n", 326 p2->p_pid, p2->p_procsig->ps_refcnt); 327 /* Create the shared sigacts structure */ 328 MALLOC (newsigacts, struct sigacts *, sizeof (struct sigacts), 329 M_SUBPROC, M_WAITOK); 330 s = splhigh(); 331 /* Set p_sigacts to the new shared structure. Note that this 332 * is updating p1->p_sigacts at the same time, since p_sigacts 333 * is just a pointer to the shared p_procsig->ps_sigacts. 334 */ 335 p2->p_sigacts = newsigacts; 336 /* Copy in the values from the u area */ 337 *p2->p_sigacts = p1->p_addr->u_sigacts; 338 splx (s); 339 } 340 } else { 341 MALLOC (p2->p_procsig, struct procsig *, sizeof(struct procsig), 342 M_SUBPROC, M_WAITOK); 343 bcopy(&p1->p_procsig->ps_begincopy, &p2->p_procsig->ps_begincopy, 344 (char *)&p1->p_procsig->ps_endcopy - 345 (char *)&p1->p_procsig->ps_begincopy); 346 p2->p_procsig->ps_refcnt = 1; 347 /* Note that we fill in the values of sigacts in vm_fork */ 348 p2->p_sigacts = NULL; 349 } 350 if (flags & RFLINUXTHPN) 351 p2->p_sigparent = SIGUSR1; 352 else 353 p2->p_sigparent = SIGCHLD; 354 355 /* bump references to the text vnode (for procfs) */ 356 p2->p_textvp = p1->p_textvp; 357 if (p2->p_textvp) 358 VREF(p2->p_textvp); 359 360 if (flags & RFCFDG) 361 p2->p_fd = fdinit(p1); 362 else if (flags & RFFDG) 363 p2->p_fd = fdcopy(p1); 364 else 365 p2->p_fd = fdshare(p1); 366 367 /* 368 * If p_limit is still copy-on-write, bump refcnt, 369 * otherwise get a copy that won't be modified. 370 * (If PL_SHAREMOD is clear, the structure is shared 371 * copy-on-write.) 372 */ 373 if (p1->p_limit->p_lflags & PL_SHAREMOD) 374 p2->p_limit = limcopy(p1->p_limit); 375 else { 376 p2->p_limit = p1->p_limit; 377 p2->p_limit->p_refcnt++; 378 } 379 380 /* 381 * Preserve some more flags in subprocess. P_PROFIL has already 382 * been preserved. 383 */ 384 p2->p_flag |= p1->p_flag & P_SUGID; 385 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 386 p2->p_flag |= P_CONTROLT; 387 if (flags & RFPPWAIT) 388 p2->p_flag |= P_PPWAIT; 389 390 LIST_INSERT_AFTER(p1, p2, p_pglist); 391 392 /* 393 * Attach the new process to its parent. 394 * 395 * If RFNOWAIT is set, the newly created process becomes a child 396 * of init. This effectively disassociates the child from the 397 * parent. 398 */ 399 if (flags & RFNOWAIT) 400 pptr = initproc; 401 else 402 pptr = p1; 403 p2->p_pptr = pptr; 404 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 405 LIST_INIT(&p2->p_children); 406 407 #ifdef KTRACE 408 /* 409 * Copy traceflag and tracefile if enabled. 410 * If not inherited, these were zeroed above. 411 */ 412 if (p1->p_traceflag&KTRFAC_INHERIT) { 413 p2->p_traceflag = p1->p_traceflag; 414 if ((p2->p_tracep = p1->p_tracep) != NULL) 415 VREF(p2->p_tracep); 416 } 417 #endif 418 419 /* 420 * set priority of child to be that of parent 421 */ 422 p2->p_estcpu = p1->p_estcpu; 423 424 /* 425 * This begins the section where we must prevent the parent 426 * from being swapped. 427 */ 428 PHOLD(p1); 429 430 /* 431 * Finish creating the child process. It will return via a different 432 * execution path later. (ie: directly into user mode) 433 */ 434 vm_fork(p1, p2, flags); 435 436 /* 437 * Both processes are set up, now check if any loadable modules want 438 * to adjust anything. 439 * What if they have an error? XXX 440 */ 441 while (ep) { 442 (*ep->function)(p1, p2, flags); 443 ep = ep->next; 444 } 445 446 /* 447 * Make child runnable and add to run queue. 448 */ 449 microtime(&(p2->p_stats->p_start)); 450 p2->p_acflag = AFORK; 451 (void) splhigh(); 452 p2->p_stat = SRUN; 453 setrunqueue(p2); 454 (void) spl0(); 455 456 /* 457 * Now can be swapped. 458 */ 459 PRELE(p1); 460 461 /* 462 * Preserve synchronization semantics of vfork. If waiting for 463 * child to exec or exit, set P_PPWAIT on child, and sleep on our 464 * proc (in case of exit). 465 */ 466 while (p2->p_flag & P_PPWAIT) 467 tsleep(p1, PWAIT, "ppwait", 0); 468 469 /* 470 * Return child pid to parent process, 471 * marking us as parent via p1->p_retval[1]. 472 */ 473 p1->p_retval[0] = p2->p_pid; 474 p1->p_retval[1] = 0; 475 return (0); 476 } 477 478 /* 479 * The next two functionms are general routines to handle adding/deleting 480 * items on the fork callout list. 481 * 482 * at_fork(): 483 * Take the arguments given and put them onto the fork callout list, 484 * However first make sure that it's not already there. 485 * Returns 0 on success or a standard error number. 486 */ 487 int 488 at_fork(function) 489 forklist_fn function; 490 { 491 fle_p ep; 492 493 /* let the programmer know if he's been stupid */ 494 if (rm_at_fork(function)) 495 printf("fork callout entry already present\n"); 496 ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT); 497 if (ep == NULL) 498 return (ENOMEM); 499 ep->next = fork_list; 500 ep->function = function; 501 fork_list = ep; 502 return (0); 503 } 504 505 /* 506 * Scan the exit callout list for the given items and remove them. 507 * Returns the number of items removed. 508 * Theoretically this value can only be 0 or 1. 509 */ 510 int 511 rm_at_fork(function) 512 forklist_fn function; 513 { 514 fle_p *epp, ep; 515 int count; 516 517 count= 0; 518 epp = &fork_list; 519 ep = *epp; 520 while (ep) { 521 if (ep->function == function) { 522 *epp = ep->next; 523 free(ep, M_TEMP); 524 count++; 525 } else { 526 epp = &ep->next; 527 } 528 ep = *epp; 529 } 530 return (count); 531 } 532