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 */ 40 41 #include <sys/cdefs.h> 42 __FBSDID("$FreeBSD$"); 43 44 #include "opt_ktrace.h" 45 #include "opt_mac.h" 46 47 #include <sys/param.h> 48 #include <sys/systm.h> 49 #include <sys/sysproto.h> 50 #include <sys/eventhandler.h> 51 #include <sys/filedesc.h> 52 #include <sys/kernel.h> 53 #include <sys/kthread.h> 54 #include <sys/sysctl.h> 55 #include <sys/lock.h> 56 #include <sys/malloc.h> 57 #include <sys/mutex.h> 58 #include <sys/proc.h> 59 #include <sys/pioctl.h> 60 #include <sys/resourcevar.h> 61 #include <sys/sched.h> 62 #include <sys/syscall.h> 63 #include <sys/vmmeter.h> 64 #include <sys/vnode.h> 65 #include <sys/acct.h> 66 #include <sys/mac.h> 67 #include <sys/ktr.h> 68 #include <sys/ktrace.h> 69 #include <sys/unistd.h> 70 #include <sys/sx.h> 71 72 #include <vm/vm.h> 73 #include <vm/pmap.h> 74 #include <vm/vm_map.h> 75 #include <vm/vm_extern.h> 76 #include <vm/uma.h> 77 78 #include <sys/user.h> 79 #include <machine/critical.h> 80 81 #ifndef _SYS_SYSPROTO_H_ 82 struct fork_args { 83 int dummy; 84 }; 85 #endif 86 87 static int forksleep; /* Place for fork1() to sleep on. */ 88 89 /* 90 * MPSAFE 91 */ 92 /* ARGSUSED */ 93 int 94 fork(td, uap) 95 struct thread *td; 96 struct fork_args *uap; 97 { 98 int error; 99 struct proc *p2; 100 101 error = fork1(td, RFFDG | RFPROC, 0, &p2); 102 if (error == 0) { 103 td->td_retval[0] = p2->p_pid; 104 td->td_retval[1] = 0; 105 } 106 return (error); 107 } 108 109 /* 110 * MPSAFE 111 */ 112 /* ARGSUSED */ 113 int 114 vfork(td, uap) 115 struct thread *td; 116 struct vfork_args *uap; 117 { 118 int error; 119 struct proc *p2; 120 121 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 122 if (error == 0) { 123 td->td_retval[0] = p2->p_pid; 124 td->td_retval[1] = 0; 125 } 126 return (error); 127 } 128 129 /* 130 * MPSAFE 131 */ 132 int 133 rfork(td, uap) 134 struct thread *td; 135 struct rfork_args *uap; 136 { 137 struct proc *p2; 138 int error; 139 140 /* Don't allow kernel-only flags. */ 141 if ((uap->flags & RFKERNELONLY) != 0) 142 return (EINVAL); 143 144 error = fork1(td, uap->flags, 0, &p2); 145 if (error == 0) { 146 td->td_retval[0] = p2 ? p2->p_pid : 0; 147 td->td_retval[1] = 0; 148 } 149 return (error); 150 } 151 152 int nprocs = 1; /* process 0 */ 153 int lastpid = 0; 154 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 155 "Last used PID"); 156 157 /* 158 * Random component to lastpid generation. We mix in a random factor to make 159 * it a little harder to predict. We sanity check the modulus value to avoid 160 * doing it in critical paths. Don't let it be too small or we pointlessly 161 * waste randomness entropy, and don't let it be impossibly large. Using a 162 * modulus that is too big causes a LOT more process table scans and slows 163 * down fork processing as the pidchecked caching is defeated. 164 */ 165 static int randompid = 0; 166 167 static int 168 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 169 { 170 int error, pid; 171 172 error = sysctl_wire_old_buffer(req, sizeof(int)); 173 if (error != 0) 174 return(error); 175 sx_xlock(&allproc_lock); 176 pid = randompid; 177 error = sysctl_handle_int(oidp, &pid, 0, req); 178 if (error == 0 && req->newptr != NULL) { 179 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 180 pid = PID_MAX - 100; 181 else if (pid < 2) /* NOP */ 182 pid = 0; 183 else if (pid < 100) /* Make it reasonable */ 184 pid = 100; 185 randompid = pid; 186 } 187 sx_xunlock(&allproc_lock); 188 return (error); 189 } 190 191 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 192 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 193 194 int 195 fork1(td, flags, pages, procp) 196 struct thread *td; 197 int flags; 198 int pages; 199 struct proc **procp; 200 { 201 struct proc *p1, *p2, *pptr; 202 uid_t uid; 203 struct proc *newproc; 204 int ok, trypid; 205 static int curfail, pidchecked = 0; 206 static struct timeval lastfail; 207 struct filedesc *fd; 208 struct filedesc_to_leader *fdtol; 209 struct thread *td2; 210 struct kse *ke2; 211 struct ksegrp *kg2; 212 struct sigacts *newsigacts; 213 int error; 214 215 /* Can't copy and clear. */ 216 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 217 return (EINVAL); 218 219 p1 = td->td_proc; 220 221 /* 222 * Here we don't create a new process, but we divorce 223 * certain parts of a process from itself. 224 */ 225 if ((flags & RFPROC) == 0) { 226 mtx_lock(&Giant); 227 vm_forkproc(td, NULL, NULL, flags); 228 mtx_unlock(&Giant); 229 230 /* 231 * Close all file descriptors. 232 */ 233 if (flags & RFCFDG) { 234 struct filedesc *fdtmp; 235 FILEDESC_LOCK(td->td_proc->p_fd); 236 fdtmp = fdinit(td->td_proc->p_fd); 237 FILEDESC_UNLOCK(td->td_proc->p_fd); 238 fdfree(td); 239 p1->p_fd = fdtmp; 240 } 241 242 /* 243 * Unshare file descriptors (from parent). 244 */ 245 if (flags & RFFDG) { 246 FILEDESC_LOCK(p1->p_fd); 247 if (p1->p_fd->fd_refcnt > 1) { 248 struct filedesc *newfd; 249 250 newfd = fdcopy(td->td_proc->p_fd); 251 FILEDESC_UNLOCK(p1->p_fd); 252 fdfree(td); 253 p1->p_fd = newfd; 254 } else 255 FILEDESC_UNLOCK(p1->p_fd); 256 } 257 *procp = NULL; 258 return (0); 259 } 260 261 /* 262 * Note 1:1 allows for forking with one thread coming out on the 263 * other side with the expectation that the process is about to 264 * exec. 265 */ 266 if (p1->p_flag & P_SA) { 267 /* 268 * Idle the other threads for a second. 269 * Since the user space is copied, it must remain stable. 270 * In addition, all threads (from the user perspective) 271 * need to either be suspended or in the kernel, 272 * where they will try restart in the parent and will 273 * be aborted in the child. 274 */ 275 PROC_LOCK(p1); 276 if (thread_single(SINGLE_NO_EXIT)) { 277 /* Abort. Someone else is single threading before us. */ 278 PROC_UNLOCK(p1); 279 return (ERESTART); 280 } 281 PROC_UNLOCK(p1); 282 /* 283 * All other activity in this process 284 * is now suspended at the user boundary, 285 * (or other safe places if we think of any). 286 */ 287 } 288 289 /* Allocate new proc. */ 290 newproc = uma_zalloc(proc_zone, M_WAITOK); 291 #ifdef MAC 292 mac_init_proc(newproc); 293 #endif 294 295 /* We have to lock the process tree while we look for a pid. */ 296 sx_slock(&proctree_lock); 297 298 /* 299 * Although process entries are dynamically created, we still keep 300 * a global limit on the maximum number we will create. Don't allow 301 * a nonprivileged user to use the last ten processes; don't let root 302 * exceed the limit. The variable nprocs is the current number of 303 * processes, maxproc is the limit. 304 */ 305 sx_xlock(&allproc_lock); 306 uid = td->td_ucred->cr_ruid; 307 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 308 error = EAGAIN; 309 goto fail; 310 } 311 312 /* 313 * Increment the count of procs running with this uid. Don't allow 314 * a nonprivileged user to exceed their current limit. 315 */ 316 PROC_LOCK(p1); 317 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 318 (uid != 0) ? lim_cur(p1, RLIMIT_NPROC) : 0); 319 PROC_UNLOCK(p1); 320 if (!ok) { 321 error = EAGAIN; 322 goto fail; 323 } 324 325 /* 326 * Increment the nprocs resource before blocking can occur. There 327 * are hard-limits as to the number of processes that can run. 328 */ 329 nprocs++; 330 331 /* 332 * Find an unused process ID. We remember a range of unused IDs 333 * ready to use (from lastpid+1 through pidchecked-1). 334 * 335 * If RFHIGHPID is set (used during system boot), do not allocate 336 * low-numbered pids. 337 */ 338 trypid = lastpid + 1; 339 if (flags & RFHIGHPID) { 340 if (trypid < 10) 341 trypid = 10; 342 } else { 343 if (randompid) 344 trypid += arc4random() % randompid; 345 } 346 retry: 347 /* 348 * If the process ID prototype has wrapped around, 349 * restart somewhat above 0, as the low-numbered procs 350 * tend to include daemons that don't exit. 351 */ 352 if (trypid >= PID_MAX) { 353 trypid = trypid % PID_MAX; 354 if (trypid < 100) 355 trypid += 100; 356 pidchecked = 0; 357 } 358 if (trypid >= pidchecked) { 359 int doingzomb = 0; 360 361 pidchecked = PID_MAX; 362 /* 363 * Scan the active and zombie procs to check whether this pid 364 * is in use. Remember the lowest pid that's greater 365 * than trypid, so we can avoid checking for a while. 366 */ 367 p2 = LIST_FIRST(&allproc); 368 again: 369 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 370 PROC_LOCK(p2); 371 while (p2->p_pid == trypid || 372 (p2->p_pgrp != NULL && 373 (p2->p_pgrp->pg_id == trypid || 374 (p2->p_session != NULL && 375 p2->p_session->s_sid == trypid)))) { 376 trypid++; 377 if (trypid >= pidchecked) { 378 PROC_UNLOCK(p2); 379 goto retry; 380 } 381 } 382 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 383 pidchecked = p2->p_pid; 384 if (p2->p_pgrp != NULL) { 385 if (p2->p_pgrp->pg_id > trypid && 386 pidchecked > p2->p_pgrp->pg_id) 387 pidchecked = p2->p_pgrp->pg_id; 388 if (p2->p_session != NULL && 389 p2->p_session->s_sid > trypid && 390 pidchecked > p2->p_session->s_sid) 391 pidchecked = p2->p_session->s_sid; 392 } 393 PROC_UNLOCK(p2); 394 } 395 if (!doingzomb) { 396 doingzomb = 1; 397 p2 = LIST_FIRST(&zombproc); 398 goto again; 399 } 400 } 401 sx_sunlock(&proctree_lock); 402 403 /* 404 * RFHIGHPID does not mess with the lastpid counter during boot. 405 */ 406 if (flags & RFHIGHPID) 407 pidchecked = 0; 408 else 409 lastpid = trypid; 410 411 p2 = newproc; 412 p2->p_state = PRS_NEW; /* protect against others */ 413 p2->p_pid = trypid; 414 LIST_INSERT_HEAD(&allproc, p2, p_list); 415 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 416 sx_xunlock(&allproc_lock); 417 418 /* 419 * Malloc things while we don't hold any locks. 420 */ 421 if (flags & RFSIGSHARE) 422 newsigacts = NULL; 423 else 424 newsigacts = sigacts_alloc(); 425 426 /* 427 * Copy filedesc. 428 */ 429 if (flags & RFCFDG) { 430 FILEDESC_LOCK(td->td_proc->p_fd); 431 fd = fdinit(td->td_proc->p_fd); 432 FILEDESC_UNLOCK(td->td_proc->p_fd); 433 fdtol = NULL; 434 } else if (flags & RFFDG) { 435 FILEDESC_LOCK(p1->p_fd); 436 fd = fdcopy(td->td_proc->p_fd); 437 FILEDESC_UNLOCK(p1->p_fd); 438 fdtol = NULL; 439 } else { 440 fd = fdshare(p1->p_fd); 441 if (p1->p_fdtol == NULL) 442 p1->p_fdtol = 443 filedesc_to_leader_alloc(NULL, 444 NULL, 445 p1->p_leader); 446 if ((flags & RFTHREAD) != 0) { 447 /* 448 * Shared file descriptor table and 449 * shared process leaders. 450 */ 451 fdtol = p1->p_fdtol; 452 FILEDESC_LOCK(p1->p_fd); 453 fdtol->fdl_refcount++; 454 FILEDESC_UNLOCK(p1->p_fd); 455 } else { 456 /* 457 * Shared file descriptor table, and 458 * different process leaders 459 */ 460 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 461 p1->p_fd, 462 p2); 463 } 464 } 465 /* 466 * Make a proc table entry for the new process. 467 * Start by zeroing the section of proc that is zero-initialized, 468 * then copy the section that is copied directly from the parent. 469 */ 470 td2 = FIRST_THREAD_IN_PROC(p2); 471 kg2 = FIRST_KSEGRP_IN_PROC(p2); 472 ke2 = FIRST_KSE_IN_KSEGRP(kg2); 473 474 /* Allocate and switch to an alternate kstack if specified. */ 475 if (pages != 0) 476 vm_thread_new_altkstack(td2, pages); 477 478 PROC_LOCK(p2); 479 PROC_LOCK(p1); 480 481 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 482 483 bzero(&p2->p_startzero, 484 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 485 bzero(&ke2->ke_startzero, 486 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 487 bzero(&td2->td_startzero, 488 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 489 bzero(&kg2->kg_startzero, 490 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 491 492 bcopy(&p1->p_startcopy, &p2->p_startcopy, 493 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 494 bcopy(&td->td_startcopy, &td2->td_startcopy, 495 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 496 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 497 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 498 #undef RANGEOF 499 500 td2->td_tid = p2->p_pid; 501 td2->td_sigstk = td->td_sigstk; 502 503 /* Set up the thread as an active thread (as if runnable). */ 504 ke2->ke_state = KES_THREAD; 505 ke2->ke_thread = td2; 506 td2->td_kse = ke2; 507 508 /* 509 * Duplicate sub-structures as needed. 510 * Increase reference counts on shared objects. 511 * The p_stats substruct is set in vm_forkproc. 512 */ 513 p2->p_flag = 0; 514 if (p1->p_flag & P_PROFIL) 515 startprofclock(p2); 516 mtx_lock_spin(&sched_lock); 517 p2->p_sflag = PS_INMEM; 518 /* 519 * Allow the scheduler to adjust the priority of the child and 520 * parent while we hold the sched_lock. 521 */ 522 sched_fork(p1, p2); 523 524 mtx_unlock_spin(&sched_lock); 525 p2->p_ucred = crhold(td->td_ucred); 526 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 527 528 pargs_hold(p2->p_args); 529 530 if (flags & RFSIGSHARE) { 531 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 532 } else { 533 sigacts_copy(newsigacts, p1->p_sigacts); 534 p2->p_sigacts = newsigacts; 535 } 536 if (flags & RFLINUXTHPN) 537 p2->p_sigparent = SIGUSR1; 538 else 539 p2->p_sigparent = SIGCHLD; 540 541 p2->p_textvp = p1->p_textvp; 542 p2->p_fd = fd; 543 p2->p_fdtol = fdtol; 544 545 /* 546 * p_limit is copy-on-write. Bump its refcount. 547 */ 548 p2->p_limit = lim_hold(p1->p_limit); 549 PROC_UNLOCK(p1); 550 PROC_UNLOCK(p2); 551 552 /* Bump references to the text vnode (for procfs) */ 553 if (p2->p_textvp) 554 vref(p2->p_textvp); 555 556 /* 557 * Set up linkage for kernel based threading. 558 */ 559 if ((flags & RFTHREAD) != 0) { 560 mtx_lock(&ppeers_lock); 561 p2->p_peers = p1->p_peers; 562 p1->p_peers = p2; 563 p2->p_leader = p1->p_leader; 564 mtx_unlock(&ppeers_lock); 565 PROC_LOCK(p1->p_leader); 566 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 567 PROC_UNLOCK(p1->p_leader); 568 /* 569 * The task leader is exiting, so process p1 is 570 * going to be killed shortly. Since p1 obviously 571 * isn't dead yet, we know that the leader is either 572 * sending SIGKILL's to all the processes in this 573 * task or is sleeping waiting for all the peers to 574 * exit. We let p1 complete the fork, but we need 575 * to go ahead and kill the new process p2 since 576 * the task leader may not get a chance to send 577 * SIGKILL to it. We leave it on the list so that 578 * the task leader will wait for this new process 579 * to commit suicide. 580 */ 581 PROC_LOCK(p2); 582 psignal(p2, SIGKILL); 583 PROC_UNLOCK(p2); 584 } else 585 PROC_UNLOCK(p1->p_leader); 586 } else { 587 p2->p_peers = NULL; 588 p2->p_leader = p2; 589 } 590 591 sx_xlock(&proctree_lock); 592 PGRP_LOCK(p1->p_pgrp); 593 PROC_LOCK(p2); 594 PROC_LOCK(p1); 595 596 /* 597 * Preserve some more flags in subprocess. P_PROFIL has already 598 * been preserved. 599 */ 600 p2->p_flag |= p1->p_flag & P_SUGID; 601 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 602 SESS_LOCK(p1->p_session); 603 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 604 p2->p_flag |= P_CONTROLT; 605 SESS_UNLOCK(p1->p_session); 606 if (flags & RFPPWAIT) 607 p2->p_flag |= P_PPWAIT; 608 609 p2->p_pgrp = p1->p_pgrp; 610 LIST_INSERT_AFTER(p1, p2, p_pglist); 611 PGRP_UNLOCK(p1->p_pgrp); 612 LIST_INIT(&p2->p_children); 613 614 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 615 616 #ifdef KTRACE 617 /* 618 * Copy traceflag and tracefile if enabled. 619 */ 620 mtx_lock(&ktrace_mtx); 621 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 622 if (p1->p_traceflag & KTRFAC_INHERIT) { 623 p2->p_traceflag = p1->p_traceflag; 624 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 625 VREF(p2->p_tracevp); 626 KASSERT(p1->p_tracecred != NULL, 627 ("ktrace vnode with no cred")); 628 p2->p_tracecred = crhold(p1->p_tracecred); 629 } 630 } 631 mtx_unlock(&ktrace_mtx); 632 #endif 633 634 /* 635 * If PF_FORK is set, the child process inherits the 636 * procfs ioctl flags from its parent. 637 */ 638 if (p1->p_pfsflags & PF_FORK) { 639 p2->p_stops = p1->p_stops; 640 p2->p_pfsflags = p1->p_pfsflags; 641 } 642 643 /* 644 * This begins the section where we must prevent the parent 645 * from being swapped. 646 */ 647 _PHOLD(p1); 648 PROC_UNLOCK(p1); 649 650 /* 651 * Attach the new process to its parent. 652 * 653 * If RFNOWAIT is set, the newly created process becomes a child 654 * of init. This effectively disassociates the child from the 655 * parent. 656 */ 657 if (flags & RFNOWAIT) 658 pptr = initproc; 659 else 660 pptr = p1; 661 p2->p_pptr = pptr; 662 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 663 sx_xunlock(&proctree_lock); 664 665 /* Inform accounting that we have forked. */ 666 p2->p_acflag = AFORK; 667 PROC_UNLOCK(p2); 668 669 /* 670 * Finish creating the child process. It will return via a different 671 * execution path later. (ie: directly into user mode) 672 */ 673 mtx_lock(&Giant); 674 vm_forkproc(td, p2, td2, flags); 675 676 if (flags == (RFFDG | RFPROC)) { 677 cnt.v_forks++; 678 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 679 p2->p_vmspace->vm_ssize; 680 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 681 cnt.v_vforks++; 682 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 683 p2->p_vmspace->vm_ssize; 684 } else if (p1 == &proc0) { 685 cnt.v_kthreads++; 686 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 687 p2->p_vmspace->vm_ssize; 688 } else { 689 cnt.v_rforks++; 690 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 691 p2->p_vmspace->vm_ssize; 692 } 693 mtx_unlock(&Giant); 694 695 /* 696 * Both processes are set up, now check if any loadable modules want 697 * to adjust anything. 698 * What if they have an error? XXX 699 */ 700 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 701 702 /* 703 * Set the child start time and mark the process as being complete. 704 */ 705 microuptime(&p2->p_stats->p_start); 706 mtx_lock_spin(&sched_lock); 707 p2->p_state = PRS_NORMAL; 708 709 /* 710 * If RFSTOPPED not requested, make child runnable and add to 711 * run queue. 712 */ 713 if ((flags & RFSTOPPED) == 0) { 714 TD_SET_CAN_RUN(td2); 715 setrunqueue(td2); 716 } 717 mtx_unlock_spin(&sched_lock); 718 719 /* 720 * Now can be swapped. 721 */ 722 PROC_LOCK(p1); 723 _PRELE(p1); 724 725 /* 726 * Tell any interested parties about the new process. 727 */ 728 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 729 730 PROC_UNLOCK(p1); 731 732 /* 733 * Preserve synchronization semantics of vfork. If waiting for 734 * child to exec or exit, set P_PPWAIT on child, and sleep on our 735 * proc (in case of exit). 736 */ 737 PROC_LOCK(p2); 738 while (p2->p_flag & P_PPWAIT) 739 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 740 PROC_UNLOCK(p2); 741 742 /* 743 * If other threads are waiting, let them continue now. 744 */ 745 if (p1->p_flag & P_SA) { 746 PROC_LOCK(p1); 747 thread_single_end(); 748 PROC_UNLOCK(p1); 749 } 750 751 /* 752 * Return child proc pointer to parent. 753 */ 754 *procp = p2; 755 return (0); 756 fail: 757 sx_sunlock(&proctree_lock); 758 if (ppsratecheck(&lastfail, &curfail, 1)) 759 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 760 uid); 761 sx_xunlock(&allproc_lock); 762 #ifdef MAC 763 mac_destroy_proc(newproc); 764 #endif 765 uma_zfree(proc_zone, newproc); 766 if (p1->p_flag & P_SA) { 767 PROC_LOCK(p1); 768 thread_single_end(); 769 PROC_UNLOCK(p1); 770 } 771 tsleep(&forksleep, PUSER, "fork", hz / 2); 772 return (error); 773 } 774 775 /* 776 * Handle the return of a child process from fork1(). This function 777 * is called from the MD fork_trampoline() entry point. 778 */ 779 void 780 fork_exit(callout, arg, frame) 781 void (*callout)(void *, struct trapframe *); 782 void *arg; 783 struct trapframe *frame; 784 { 785 struct proc *p; 786 struct thread *td; 787 788 /* 789 * Processes normally resume in mi_switch() after being 790 * cpu_switch()'ed to, but when children start up they arrive here 791 * instead, so we must do much the same things as mi_switch() would. 792 */ 793 794 if ((td = PCPU_GET(deadthread))) { 795 PCPU_SET(deadthread, NULL); 796 thread_stash(td); 797 } 798 td = curthread; 799 p = td->td_proc; 800 td->td_oncpu = PCPU_GET(cpuid); 801 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 802 803 /* 804 * Finish setting up thread glue so that it begins execution in a 805 * non-nested critical section with sched_lock held but not recursed. 806 */ 807 sched_lock.mtx_lock = (uintptr_t)td; 808 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 809 cpu_critical_fork_exit(); 810 CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid, 811 p->p_comm); 812 mtx_unlock_spin(&sched_lock); 813 814 /* 815 * cpu_set_fork_handler intercepts this function call to 816 * have this call a non-return function to stay in kernel mode. 817 * initproc has its own fork handler, but it does return. 818 */ 819 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 820 callout(arg, frame); 821 822 /* 823 * Check if a kernel thread misbehaved and returned from its main 824 * function. 825 */ 826 PROC_LOCK(p); 827 if (p->p_flag & P_KTHREAD) { 828 PROC_UNLOCK(p); 829 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 830 p->p_comm, p->p_pid); 831 kthread_exit(0); 832 } 833 PROC_UNLOCK(p); 834 #ifdef DIAGNOSTIC 835 cred_free_thread(td); 836 #endif 837 mtx_assert(&Giant, MA_NOTOWNED); 838 } 839 840 /* 841 * Simplified back end of syscall(), used when returning from fork() 842 * directly into user mode. Giant is not held on entry, and must not 843 * be held on return. This function is passed in to fork_exit() as the 844 * first parameter and is called when returning to a new userland process. 845 */ 846 void 847 fork_return(td, frame) 848 struct thread *td; 849 struct trapframe *frame; 850 { 851 852 userret(td, frame, 0); 853 #ifdef KTRACE 854 if (KTRPOINT(td, KTR_SYSRET)) 855 ktrsysret(SYS_fork, 0, 0); 856 #endif 857 mtx_assert(&Giant, MA_NOTOWNED); 858 } 859