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 * $FreeBSD$ 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 <sys/user.h> 67 68 static int fast_vfork = 1; 69 SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, ""); 70 71 /* 72 * These are the stuctures used to create a callout list for things to do 73 * when forking a process 74 */ 75 typedef struct fork_list_element { 76 struct fork_list_element *next; 77 forklist_fn function; 78 } *fle_p; 79 80 static fle_p fork_list; 81 82 #ifndef _SYS_SYSPROTO_H_ 83 struct fork_args { 84 int dummy; 85 }; 86 #endif 87 88 /* ARGSUSED */ 89 int 90 fork(p, uap) 91 struct proc *p; 92 struct fork_args *uap; 93 { 94 int error; 95 struct proc *p2; 96 97 error = fork1(p, RFFDG | RFPROC, &p2); 98 if (error == 0) { 99 p->p_retval[0] = p2->p_pid; 100 p->p_retval[1] = 0; 101 } 102 return error; 103 } 104 105 /* ARGSUSED */ 106 int 107 vfork(p, uap) 108 struct proc *p; 109 struct vfork_args *uap; 110 { 111 int error; 112 struct proc *p2; 113 114 error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); 115 if (error == 0) { 116 p->p_retval[0] = p2->p_pid; 117 p->p_retval[1] = 0; 118 } 119 return error; 120 } 121 122 int 123 rfork(p, uap) 124 struct proc *p; 125 struct rfork_args *uap; 126 { 127 int error; 128 struct proc *p2; 129 130 error = fork1(p, uap->flags, &p2); 131 if (error == 0) { 132 p->p_retval[0] = p2 ? p2->p_pid : 0; 133 p->p_retval[1] = 0; 134 } 135 return error; 136 } 137 138 139 int nprocs = 1; /* process 0 */ 140 static int nextpid = 0; 141 142 int 143 fork1(p1, flags, procp) 144 struct proc *p1; 145 int flags; 146 struct proc **procp; 147 { 148 struct proc *p2, *pptr; 149 uid_t uid; 150 struct proc *newproc; 151 int count; 152 static int pidchecked = 0; 153 fle_p ep ; 154 155 ep = fork_list; 156 157 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 158 return (EINVAL); 159 160 /* 161 * Here we don't create a new process, but we divorce 162 * certain parts of a process from itself. 163 */ 164 if ((flags & RFPROC) == 0) { 165 166 /* 167 * Divorce the memory, if it is shared, essentially 168 * this changes shared memory amongst threads, into 169 * COW locally. 170 */ 171 if ((flags & RFMEM) == 0) { 172 if (p1->p_vmspace->vm_refcnt > 1) { 173 vmspace_unshare(p1); 174 } 175 } 176 177 /* 178 * Close all file descriptors. 179 */ 180 if (flags & RFCFDG) { 181 struct filedesc *fdtmp; 182 fdtmp = fdinit(p1); 183 fdfree(p1); 184 p1->p_fd = fdtmp; 185 } 186 187 /* 188 * Unshare file descriptors (from parent.) 189 */ 190 if (flags & RFFDG) { 191 if (p1->p_fd->fd_refcnt > 1) { 192 struct filedesc *newfd; 193 newfd = fdcopy(p1); 194 fdfree(p1); 195 p1->p_fd = newfd; 196 } 197 } 198 *procp = NULL; 199 return (0); 200 } 201 202 /* 203 * Although process entries are dynamically created, we still keep 204 * a global limit on the maximum number we will create. Don't allow 205 * a nonprivileged user to use the last process; don't let root 206 * exceed the limit. The variable nprocs is the current number of 207 * processes, maxproc is the limit. 208 */ 209 uid = p1->p_cred->p_ruid; 210 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 211 tablefull("proc"); 212 return (EAGAIN); 213 } 214 /* 215 * Increment the nprocs resource before blocking can occur. There 216 * are hard-limits as to the number of processes that can run. 217 */ 218 nprocs++; 219 220 /* 221 * Increment the count of procs running with this uid. Don't allow 222 * a nonprivileged user to exceed their current limit. 223 */ 224 count = chgproccnt(uid, 1); 225 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 226 (void)chgproccnt(uid, -1); 227 /* 228 * Back out the process count 229 */ 230 nprocs--; 231 return (EAGAIN); 232 } 233 234 /* Allocate new proc. */ 235 newproc = zalloc(proc_zone); 236 237 /* 238 * Setup linkage for kernel based threading 239 */ 240 if((flags & RFTHREAD) != 0) { 241 newproc->p_peers = p1->p_peers; 242 p1->p_peers = newproc; 243 newproc->p_leader = p1->p_leader; 244 } else { 245 newproc->p_peers = 0; 246 newproc->p_leader = newproc; 247 } 248 249 newproc->p_wakeup = 0; 250 251 newproc->p_vmspace = NULL; 252 253 /* 254 * Find an unused process ID. We remember a range of unused IDs 255 * ready to use (from nextpid+1 through pidchecked-1). 256 */ 257 nextpid++; 258 retry: 259 /* 260 * If the process ID prototype has wrapped around, 261 * restart somewhat above 0, as the low-numbered procs 262 * tend to include daemons that don't exit. 263 */ 264 if (nextpid >= PID_MAX) { 265 nextpid = 100; 266 pidchecked = 0; 267 } 268 if (nextpid >= pidchecked) { 269 int doingzomb = 0; 270 271 pidchecked = PID_MAX; 272 /* 273 * Scan the active and zombie procs to check whether this pid 274 * is in use. Remember the lowest pid that's greater 275 * than nextpid, so we can avoid checking for a while. 276 */ 277 p2 = allproc.lh_first; 278 again: 279 for (; p2 != 0; p2 = p2->p_list.le_next) { 280 while (p2->p_pid == nextpid || 281 p2->p_pgrp->pg_id == nextpid || 282 p2->p_session->s_sid == nextpid) { 283 nextpid++; 284 if (nextpid >= pidchecked) 285 goto retry; 286 } 287 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 288 pidchecked = p2->p_pid; 289 if (p2->p_pgrp->pg_id > nextpid && 290 pidchecked > p2->p_pgrp->pg_id) 291 pidchecked = p2->p_pgrp->pg_id; 292 if (p2->p_session->s_sid > nextpid && 293 pidchecked > p2->p_session->s_sid) 294 pidchecked = p2->p_session->s_sid; 295 } 296 if (!doingzomb) { 297 doingzomb = 1; 298 p2 = zombproc.lh_first; 299 goto again; 300 } 301 } 302 303 p2 = newproc; 304 p2->p_stat = SIDL; /* protect against others */ 305 p2->p_pid = nextpid; 306 LIST_INSERT_HEAD(&allproc, p2, p_list); 307 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 308 309 /* 310 * Make a proc table entry for the new process. 311 * Start by zeroing the section of proc that is zero-initialized, 312 * then copy the section that is copied directly from the parent. 313 */ 314 bzero(&p2->p_startzero, 315 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 316 bcopy(&p1->p_startcopy, &p2->p_startcopy, 317 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 318 319 p2->p_aioinfo = NULL; 320 321 /* 322 * Duplicate sub-structures as needed. 323 * Increase reference counts on shared objects. 324 * The p_stats and p_sigacts substructs are set in vm_fork. 325 */ 326 p2->p_flag = P_INMEM; 327 if (p1->p_flag & P_PROFIL) 328 startprofclock(p2); 329 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 330 M_SUBPROC, M_WAITOK); 331 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 332 p2->p_cred->p_refcnt = 1; 333 crhold(p1->p_ucred); 334 335 if (p2->p_prison) { 336 p2->p_prison->pr_ref++; 337 p2->p_flag |= P_JAILED; 338 } 339 340 if (flags & RFSIGSHARE) { 341 p2->p_procsig = p1->p_procsig; 342 p2->p_procsig->ps_refcnt++; 343 if (p1->p_sigacts == &p1->p_addr->u_sigacts) { 344 struct sigacts *newsigacts; 345 int s; 346 347 /* Create the shared sigacts structure */ 348 MALLOC(newsigacts, struct sigacts *, 349 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 350 s = splhigh(); 351 /* 352 * Set p_sigacts to the new shared structure. 353 * Note that this is updating p1->p_sigacts at the 354 * same time, since p_sigacts is just a pointer to 355 * the shared p_procsig->ps_sigacts. 356 */ 357 p2->p_sigacts = newsigacts; 358 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts, 359 sizeof(*p2->p_sigacts)); 360 *p2->p_sigacts = p1->p_addr->u_sigacts; 361 splx(s); 362 } 363 } else { 364 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), 365 M_SUBPROC, M_WAITOK); 366 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 367 p2->p_procsig->ps_refcnt = 1; 368 p2->p_sigacts = NULL; /* finished in vm_fork() */ 369 } 370 if (flags & RFLINUXTHPN) 371 p2->p_sigparent = SIGUSR1; 372 else 373 p2->p_sigparent = SIGCHLD; 374 375 /* bump references to the text vnode (for procfs) */ 376 p2->p_textvp = p1->p_textvp; 377 if (p2->p_textvp) 378 VREF(p2->p_textvp); 379 380 if (flags & RFCFDG) 381 p2->p_fd = fdinit(p1); 382 else if (flags & RFFDG) 383 p2->p_fd = fdcopy(p1); 384 else 385 p2->p_fd = fdshare(p1); 386 387 /* 388 * If p_limit is still copy-on-write, bump refcnt, 389 * otherwise get a copy that won't be modified. 390 * (If PL_SHAREMOD is clear, the structure is shared 391 * copy-on-write.) 392 */ 393 if (p1->p_limit->p_lflags & PL_SHAREMOD) 394 p2->p_limit = limcopy(p1->p_limit); 395 else { 396 p2->p_limit = p1->p_limit; 397 p2->p_limit->p_refcnt++; 398 } 399 400 /* 401 * Preserve some more flags in subprocess. P_PROFIL has already 402 * been preserved. 403 */ 404 p2->p_flag |= p1->p_flag & P_SUGID; 405 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 406 p2->p_flag |= P_CONTROLT; 407 if (flags & RFPPWAIT) 408 p2->p_flag |= P_PPWAIT; 409 410 LIST_INSERT_AFTER(p1, p2, p_pglist); 411 412 /* 413 * Attach the new process to its parent. 414 * 415 * If RFNOWAIT is set, the newly created process becomes a child 416 * of init. This effectively disassociates the child from the 417 * parent. 418 */ 419 if (flags & RFNOWAIT) 420 pptr = initproc; 421 else 422 pptr = p1; 423 p2->p_pptr = pptr; 424 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 425 LIST_INIT(&p2->p_children); 426 427 #ifdef KTRACE 428 /* 429 * Copy traceflag and tracefile if enabled. 430 * If not inherited, these were zeroed above. 431 */ 432 if (p1->p_traceflag&KTRFAC_INHERIT) { 433 p2->p_traceflag = p1->p_traceflag; 434 if ((p2->p_tracep = p1->p_tracep) != NULL) 435 VREF(p2->p_tracep); 436 } 437 #endif 438 439 /* 440 * set priority of child to be that of parent 441 */ 442 p2->p_estcpu = p1->p_estcpu; 443 444 /* 445 * This begins the section where we must prevent the parent 446 * from being swapped. 447 */ 448 PHOLD(p1); 449 450 /* 451 * Finish creating the child process. It will return via a different 452 * execution path later. (ie: directly into user mode) 453 */ 454 vm_fork(p1, p2, flags); 455 456 /* 457 * Both processes are set up, now check if any loadable modules want 458 * to adjust anything. 459 * What if they have an error? XXX 460 */ 461 while (ep) { 462 (*ep->function)(p1, p2, flags); 463 ep = ep->next; 464 } 465 466 /* 467 * Make child runnable and add to run queue. 468 */ 469 microtime(&(p2->p_stats->p_start)); 470 p2->p_acflag = AFORK; 471 (void) splhigh(); 472 p2->p_stat = SRUN; 473 setrunqueue(p2); 474 (void) spl0(); 475 476 /* 477 * Now can be swapped. 478 */ 479 PRELE(p1); 480 481 /* 482 * Preserve synchronization semantics of vfork. If waiting for 483 * child to exec or exit, set P_PPWAIT on child, and sleep on our 484 * proc (in case of exit). 485 */ 486 while (p2->p_flag & P_PPWAIT) 487 tsleep(p1, PWAIT, "ppwait", 0); 488 489 /* 490 * Return child proc pointer to parent. 491 */ 492 *procp = p2; 493 return (0); 494 } 495 496 /* 497 * The next two functionms are general routines to handle adding/deleting 498 * items on the fork callout list. 499 * 500 * at_fork(): 501 * Take the arguments given and put them onto the fork callout list, 502 * However first make sure that it's not already there. 503 * Returns 0 on success or a standard error number. 504 */ 505 int 506 at_fork(function) 507 forklist_fn function; 508 { 509 fle_p ep; 510 511 /* let the programmer know if he's been stupid */ 512 if (rm_at_fork(function)) 513 printf("fork callout entry already present\n"); 514 ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT); 515 if (ep == NULL) 516 return (ENOMEM); 517 ep->next = fork_list; 518 ep->function = function; 519 fork_list = ep; 520 return (0); 521 } 522 523 /* 524 * Scan the exit callout list for the given items and remove them. 525 * Returns the number of items removed. 526 * Theoretically this value can only be 0 or 1. 527 */ 528 int 529 rm_at_fork(function) 530 forklist_fn function; 531 { 532 fle_p *epp, ep; 533 int count; 534 535 count= 0; 536 epp = &fork_list; 537 ep = *epp; 538 while (ep) { 539 if (ep->function == function) { 540 *epp = ep->next; 541 free(ep, M_TEMP); 542 count++; 543 } else { 544 epp = &ep->next; 545 } 546 ep = *epp; 547 } 548 return (count); 549 } 550