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 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD$"); 39 40 #include "opt_ktrace.h" 41 #include "opt_mac.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/sysproto.h> 46 #include <sys/eventhandler.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/kthread.h> 50 #include <sys/sysctl.h> 51 #include <sys/lock.h> 52 #include <sys/malloc.h> 53 #include <sys/mutex.h> 54 #include <sys/priv.h> 55 #include <sys/proc.h> 56 #include <sys/pioctl.h> 57 #include <sys/resourcevar.h> 58 #include <sys/sched.h> 59 #include <sys/syscall.h> 60 #include <sys/vmmeter.h> 61 #include <sys/vnode.h> 62 #include <sys/acct.h> 63 #include <sys/ktr.h> 64 #include <sys/ktrace.h> 65 #include <sys/unistd.h> 66 #include <sys/sx.h> 67 #include <sys/signalvar.h> 68 69 #include <security/audit/audit.h> 70 #include <security/mac/mac_framework.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 79 #ifndef _SYS_SYSPROTO_H_ 80 struct fork_args { 81 int dummy; 82 }; 83 #endif 84 85 /* ARGSUSED */ 86 int 87 fork(td, uap) 88 struct thread *td; 89 struct fork_args *uap; 90 { 91 int error; 92 struct proc *p2; 93 94 error = fork1(td, RFFDG | RFPROC, 0, &p2); 95 if (error == 0) { 96 td->td_retval[0] = p2->p_pid; 97 td->td_retval[1] = 0; 98 } 99 return (error); 100 } 101 102 /* ARGSUSED */ 103 int 104 vfork(td, uap) 105 struct thread *td; 106 struct vfork_args *uap; 107 { 108 int error; 109 struct proc *p2; 110 111 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 112 if (error == 0) { 113 td->td_retval[0] = p2->p_pid; 114 td->td_retval[1] = 0; 115 } 116 return (error); 117 } 118 119 int 120 rfork(td, uap) 121 struct thread *td; 122 struct rfork_args *uap; 123 { 124 struct proc *p2; 125 int error; 126 127 /* Don't allow kernel-only flags. */ 128 if ((uap->flags & RFKERNELONLY) != 0) 129 return (EINVAL); 130 131 AUDIT_ARG(fflags, uap->flags); 132 error = fork1(td, uap->flags, 0, &p2); 133 if (error == 0) { 134 td->td_retval[0] = p2 ? p2->p_pid : 0; 135 td->td_retval[1] = 0; 136 } 137 return (error); 138 } 139 140 int nprocs = 1; /* process 0 */ 141 int lastpid = 0; 142 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 143 "Last used PID"); 144 145 /* 146 * Random component to lastpid generation. We mix in a random factor to make 147 * it a little harder to predict. We sanity check the modulus value to avoid 148 * doing it in critical paths. Don't let it be too small or we pointlessly 149 * waste randomness entropy, and don't let it be impossibly large. Using a 150 * modulus that is too big causes a LOT more process table scans and slows 151 * down fork processing as the pidchecked caching is defeated. 152 */ 153 static int randompid = 0; 154 155 static int 156 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 157 { 158 int error, pid; 159 160 error = sysctl_wire_old_buffer(req, sizeof(int)); 161 if (error != 0) 162 return(error); 163 sx_xlock(&allproc_lock); 164 pid = randompid; 165 error = sysctl_handle_int(oidp, &pid, 0, req); 166 if (error == 0 && req->newptr != NULL) { 167 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 168 pid = PID_MAX - 100; 169 else if (pid < 2) /* NOP */ 170 pid = 0; 171 else if (pid < 100) /* Make it reasonable */ 172 pid = 100; 173 randompid = pid; 174 } 175 sx_xunlock(&allproc_lock); 176 return (error); 177 } 178 179 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 180 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 181 182 int 183 fork1(td, flags, pages, procp) 184 struct thread *td; 185 int flags; 186 int pages; 187 struct proc **procp; 188 { 189 struct proc *p1, *p2, *pptr; 190 struct proc *newproc; 191 int ok, trypid; 192 static int curfail, pidchecked = 0; 193 static struct timeval lastfail; 194 struct filedesc *fd; 195 struct filedesc_to_leader *fdtol; 196 struct thread *td2; 197 struct sigacts *newsigacts; 198 struct vmspace *vm2; 199 int error; 200 201 /* Can't copy and clear. */ 202 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 203 return (EINVAL); 204 205 p1 = td->td_proc; 206 207 /* 208 * Here we don't create a new process, but we divorce 209 * certain parts of a process from itself. 210 */ 211 if ((flags & RFPROC) == 0) { 212 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 213 (flags & (RFCFDG | RFFDG))) { 214 PROC_LOCK(p1); 215 if (thread_single(SINGLE_BOUNDARY)) { 216 PROC_UNLOCK(p1); 217 return (ERESTART); 218 } 219 PROC_UNLOCK(p1); 220 } 221 222 error = vm_forkproc(td, NULL, NULL, NULL, flags); 223 if (error) 224 goto norfproc_fail; 225 226 /* 227 * Close all file descriptors. 228 */ 229 if (flags & RFCFDG) { 230 struct filedesc *fdtmp; 231 fdtmp = fdinit(td->td_proc->p_fd); 232 fdfree(td); 233 p1->p_fd = fdtmp; 234 } 235 236 /* 237 * Unshare file descriptors (from parent). 238 */ 239 if (flags & RFFDG) 240 fdunshare(p1, td); 241 242 norfproc_fail: 243 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 244 (flags & (RFCFDG | RFFDG))) { 245 PROC_LOCK(p1); 246 thread_single_end(); 247 PROC_UNLOCK(p1); 248 } 249 *procp = NULL; 250 return (error); 251 } 252 253 /* 254 * XXX 255 * We did have single-threading code here 256 * however it proved un-needed and caused problems 257 */ 258 259 vm2 = NULL; 260 /* Allocate new proc. */ 261 newproc = uma_zalloc(proc_zone, M_WAITOK); 262 if (TAILQ_EMPTY(&newproc->p_threads)) { 263 td2 = thread_alloc(); 264 if (td2 == NULL) { 265 error = ENOMEM; 266 goto fail1; 267 } 268 proc_linkup(newproc, td2); 269 } else 270 td2 = FIRST_THREAD_IN_PROC(newproc); 271 272 /* Allocate and switch to an alternate kstack if specified. */ 273 if (pages != 0) { 274 if (!vm_thread_new_altkstack(td2, pages)) { 275 error = ENOMEM; 276 goto fail1; 277 } 278 } 279 if ((flags & RFMEM) == 0) { 280 vm2 = vmspace_fork(p1->p_vmspace); 281 if (vm2 == NULL) { 282 error = ENOMEM; 283 goto fail1; 284 } 285 } 286 #ifdef MAC 287 mac_proc_init(newproc); 288 #endif 289 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL); 290 STAILQ_INIT(&newproc->p_ktr); 291 292 /* We have to lock the process tree while we look for a pid. */ 293 sx_slock(&proctree_lock); 294 295 /* 296 * Although process entries are dynamically created, we still keep 297 * a global limit on the maximum number we will create. Don't allow 298 * a nonprivileged user to use the last ten processes; don't let root 299 * exceed the limit. The variable nprocs is the current number of 300 * processes, maxproc is the limit. 301 */ 302 sx_xlock(&allproc_lock); 303 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 304 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 305 error = EAGAIN; 306 goto fail; 307 } 308 309 /* 310 * Increment the count of procs running with this uid. Don't allow 311 * a nonprivileged user to exceed their current limit. 312 * 313 * XXXRW: Can we avoid privilege here if it's not needed? 314 */ 315 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 316 if (error == 0) 317 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 318 else { 319 PROC_LOCK(p1); 320 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 321 lim_cur(p1, RLIMIT_NPROC)); 322 PROC_UNLOCK(p1); 323 } 324 if (!ok) { 325 error = EAGAIN; 326 goto fail; 327 } 328 329 /* 330 * Increment the nprocs resource before blocking can occur. There 331 * are hard-limits as to the number of processes that can run. 332 */ 333 nprocs++; 334 335 /* 336 * Find an unused process ID. We remember a range of unused IDs 337 * ready to use (from lastpid+1 through pidchecked-1). 338 * 339 * If RFHIGHPID is set (used during system boot), do not allocate 340 * low-numbered pids. 341 */ 342 trypid = lastpid + 1; 343 if (flags & RFHIGHPID) { 344 if (trypid < 10) 345 trypid = 10; 346 } else { 347 if (randompid) 348 trypid += arc4random() % randompid; 349 } 350 retry: 351 /* 352 * If the process ID prototype has wrapped around, 353 * restart somewhat above 0, as the low-numbered procs 354 * tend to include daemons that don't exit. 355 */ 356 if (trypid >= PID_MAX) { 357 trypid = trypid % PID_MAX; 358 if (trypid < 100) 359 trypid += 100; 360 pidchecked = 0; 361 } 362 if (trypid >= pidchecked) { 363 int doingzomb = 0; 364 365 pidchecked = PID_MAX; 366 /* 367 * Scan the active and zombie procs to check whether this pid 368 * is in use. Remember the lowest pid that's greater 369 * than trypid, so we can avoid checking for a while. 370 */ 371 p2 = LIST_FIRST(&allproc); 372 again: 373 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 374 while (p2->p_pid == trypid || 375 (p2->p_pgrp != NULL && 376 (p2->p_pgrp->pg_id == trypid || 377 (p2->p_session != NULL && 378 p2->p_session->s_sid == trypid)))) { 379 trypid++; 380 if (trypid >= pidchecked) 381 goto retry; 382 } 383 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 384 pidchecked = p2->p_pid; 385 if (p2->p_pgrp != NULL) { 386 if (p2->p_pgrp->pg_id > trypid && 387 pidchecked > p2->p_pgrp->pg_id) 388 pidchecked = p2->p_pgrp->pg_id; 389 if (p2->p_session != NULL && 390 p2->p_session->s_sid > trypid && 391 pidchecked > p2->p_session->s_sid) 392 pidchecked = p2->p_session->s_sid; 393 } 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 /* 415 * Allow the scheduler to initialize the child. 416 */ 417 thread_lock(td); 418 sched_fork(td, td2); 419 thread_unlock(td); 420 AUDIT_ARG(pid, p2->p_pid); 421 LIST_INSERT_HEAD(&allproc, p2, p_list); 422 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 423 424 PROC_LOCK(p2); 425 PROC_LOCK(p1); 426 427 sx_xunlock(&allproc_lock); 428 429 bcopy(&p1->p_startcopy, &p2->p_startcopy, 430 __rangeof(struct proc, p_startcopy, p_endcopy)); 431 PROC_UNLOCK(p1); 432 433 bzero(&p2->p_startzero, 434 __rangeof(struct proc, p_startzero, p_endzero)); 435 436 p2->p_ucred = crhold(td->td_ucred); 437 PROC_UNLOCK(p2); 438 439 /* 440 * Malloc things while we don't hold any locks. 441 */ 442 if (flags & RFSIGSHARE) 443 newsigacts = NULL; 444 else 445 newsigacts = sigacts_alloc(); 446 447 /* 448 * Copy filedesc. 449 */ 450 if (flags & RFCFDG) { 451 fd = fdinit(p1->p_fd); 452 fdtol = NULL; 453 } else if (flags & RFFDG) { 454 fd = fdcopy(p1->p_fd); 455 fdtol = NULL; 456 } else { 457 fd = fdshare(p1->p_fd); 458 if (p1->p_fdtol == NULL) 459 p1->p_fdtol = 460 filedesc_to_leader_alloc(NULL, 461 NULL, 462 p1->p_leader); 463 if ((flags & RFTHREAD) != 0) { 464 /* 465 * Shared file descriptor table and 466 * shared process leaders. 467 */ 468 fdtol = p1->p_fdtol; 469 FILEDESC_XLOCK(p1->p_fd); 470 fdtol->fdl_refcount++; 471 FILEDESC_XUNLOCK(p1->p_fd); 472 } else { 473 /* 474 * Shared file descriptor table, and 475 * different process leaders 476 */ 477 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 478 p1->p_fd, 479 p2); 480 } 481 } 482 /* 483 * Make a proc table entry for the new process. 484 * Start by zeroing the section of proc that is zero-initialized, 485 * then copy the section that is copied directly from the parent. 486 */ 487 488 PROC_LOCK(p2); 489 PROC_LOCK(p1); 490 491 bzero(&td2->td_startzero, 492 __rangeof(struct thread, td_startzero, td_endzero)); 493 494 bcopy(&td->td_startcopy, &td2->td_startcopy, 495 __rangeof(struct thread, td_startcopy, td_endcopy)); 496 497 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 498 td2->td_sigstk = td->td_sigstk; 499 td2->td_sigmask = td->td_sigmask; 500 td2->td_flags = TDF_INMEM; 501 502 /* 503 * Duplicate sub-structures as needed. 504 * Increase reference counts on shared objects. 505 */ 506 p2->p_flag = P_INMEM; 507 p2->p_swtick = ticks; 508 if (p1->p_flag & P_PROFIL) 509 startprofclock(p2); 510 td2->td_ucred = crhold(p2->p_ucred); 511 pargs_hold(p2->p_args); 512 513 if (flags & RFSIGSHARE) { 514 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 515 } else { 516 sigacts_copy(newsigacts, p1->p_sigacts); 517 p2->p_sigacts = newsigacts; 518 } 519 if (flags & RFLINUXTHPN) 520 p2->p_sigparent = SIGUSR1; 521 else 522 p2->p_sigparent = SIGCHLD; 523 524 p2->p_textvp = p1->p_textvp; 525 p2->p_fd = fd; 526 p2->p_fdtol = fdtol; 527 528 /* 529 * p_limit is copy-on-write. Bump its refcount. 530 */ 531 lim_fork(p1, p2); 532 533 pstats_fork(p1->p_stats, p2->p_stats); 534 535 PROC_UNLOCK(p1); 536 PROC_UNLOCK(p2); 537 538 /* Bump references to the text vnode (for procfs) */ 539 if (p2->p_textvp) 540 vref(p2->p_textvp); 541 542 /* 543 * Set up linkage for kernel based threading. 544 */ 545 if ((flags & RFTHREAD) != 0) { 546 mtx_lock(&ppeers_lock); 547 p2->p_peers = p1->p_peers; 548 p1->p_peers = p2; 549 p2->p_leader = p1->p_leader; 550 mtx_unlock(&ppeers_lock); 551 PROC_LOCK(p1->p_leader); 552 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 553 PROC_UNLOCK(p1->p_leader); 554 /* 555 * The task leader is exiting, so process p1 is 556 * going to be killed shortly. Since p1 obviously 557 * isn't dead yet, we know that the leader is either 558 * sending SIGKILL's to all the processes in this 559 * task or is sleeping waiting for all the peers to 560 * exit. We let p1 complete the fork, but we need 561 * to go ahead and kill the new process p2 since 562 * the task leader may not get a chance to send 563 * SIGKILL to it. We leave it on the list so that 564 * the task leader will wait for this new process 565 * to commit suicide. 566 */ 567 PROC_LOCK(p2); 568 psignal(p2, SIGKILL); 569 PROC_UNLOCK(p2); 570 } else 571 PROC_UNLOCK(p1->p_leader); 572 } else { 573 p2->p_peers = NULL; 574 p2->p_leader = p2; 575 } 576 577 sx_xlock(&proctree_lock); 578 PGRP_LOCK(p1->p_pgrp); 579 PROC_LOCK(p2); 580 PROC_LOCK(p1); 581 582 /* 583 * Preserve some more flags in subprocess. P_PROFIL has already 584 * been preserved. 585 */ 586 p2->p_flag |= p1->p_flag & P_SUGID; 587 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 588 SESS_LOCK(p1->p_session); 589 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 590 p2->p_flag |= P_CONTROLT; 591 SESS_UNLOCK(p1->p_session); 592 if (flags & RFPPWAIT) 593 p2->p_flag |= P_PPWAIT; 594 595 p2->p_pgrp = p1->p_pgrp; 596 LIST_INSERT_AFTER(p1, p2, p_pglist); 597 PGRP_UNLOCK(p1->p_pgrp); 598 LIST_INIT(&p2->p_children); 599 600 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 601 602 #ifdef KTRACE 603 /* 604 * Copy traceflag and tracefile if enabled. 605 */ 606 mtx_lock(&ktrace_mtx); 607 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 608 if (p1->p_traceflag & KTRFAC_INHERIT) { 609 p2->p_traceflag = p1->p_traceflag; 610 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 611 VREF(p2->p_tracevp); 612 KASSERT(p1->p_tracecred != NULL, 613 ("ktrace vnode with no cred")); 614 p2->p_tracecred = crhold(p1->p_tracecred); 615 } 616 } 617 mtx_unlock(&ktrace_mtx); 618 #endif 619 620 /* 621 * If PF_FORK is set, the child process inherits the 622 * procfs ioctl flags from its parent. 623 */ 624 if (p1->p_pfsflags & PF_FORK) { 625 p2->p_stops = p1->p_stops; 626 p2->p_pfsflags = p1->p_pfsflags; 627 } 628 629 /* 630 * This begins the section where we must prevent the parent 631 * from being swapped. 632 */ 633 _PHOLD(p1); 634 PROC_UNLOCK(p1); 635 636 /* 637 * Attach the new process to its parent. 638 * 639 * If RFNOWAIT is set, the newly created process becomes a child 640 * of init. This effectively disassociates the child from the 641 * parent. 642 */ 643 if (flags & RFNOWAIT) 644 pptr = initproc; 645 else 646 pptr = p1; 647 p2->p_pptr = pptr; 648 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 649 sx_xunlock(&proctree_lock); 650 651 /* Inform accounting that we have forked. */ 652 p2->p_acflag = AFORK; 653 PROC_UNLOCK(p2); 654 655 /* 656 * Finish creating the child process. It will return via a different 657 * execution path later. (ie: directly into user mode) 658 */ 659 vm_forkproc(td, p2, td2, vm2, flags); 660 661 if (flags == (RFFDG | RFPROC)) { 662 PCPU_INC(cnt.v_forks); 663 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 664 p2->p_vmspace->vm_ssize); 665 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 666 PCPU_INC(cnt.v_vforks); 667 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 668 p2->p_vmspace->vm_ssize); 669 } else if (p1 == &proc0) { 670 PCPU_INC(cnt.v_kthreads); 671 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 672 p2->p_vmspace->vm_ssize); 673 } else { 674 PCPU_INC(cnt.v_rforks); 675 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 676 p2->p_vmspace->vm_ssize); 677 } 678 679 /* 680 * Both processes are set up, now check if any loadable modules want 681 * to adjust anything. 682 * What if they have an error? XXX 683 */ 684 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 685 686 /* 687 * Set the child start time and mark the process as being complete. 688 */ 689 microuptime(&p2->p_stats->p_start); 690 PROC_SLOCK(p2); 691 p2->p_state = PRS_NORMAL; 692 PROC_SUNLOCK(p2); 693 694 /* 695 * If RFSTOPPED not requested, make child runnable and add to 696 * run queue. 697 */ 698 if ((flags & RFSTOPPED) == 0) { 699 thread_lock(td2); 700 TD_SET_CAN_RUN(td2); 701 sched_add(td2, SRQ_BORING); 702 thread_unlock(td2); 703 } 704 705 /* 706 * Now can be swapped. 707 */ 708 PROC_LOCK(p1); 709 _PRELE(p1); 710 711 /* 712 * Tell any interested parties about the new process. 713 */ 714 KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid); 715 716 PROC_UNLOCK(p1); 717 718 /* 719 * Preserve synchronization semantics of vfork. If waiting for 720 * child to exec or exit, set P_PPWAIT on child, and sleep on our 721 * proc (in case of exit). 722 */ 723 PROC_LOCK(p2); 724 while (p2->p_flag & P_PPWAIT) 725 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 726 PROC_UNLOCK(p2); 727 728 /* 729 * Return child proc pointer to parent. 730 */ 731 *procp = p2; 732 return (0); 733 fail: 734 sx_sunlock(&proctree_lock); 735 if (ppsratecheck(&lastfail, &curfail, 1)) 736 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 737 td->td_ucred->cr_ruid); 738 sx_xunlock(&allproc_lock); 739 #ifdef MAC 740 mac_proc_destroy(newproc); 741 #endif 742 fail1: 743 if (vm2 != NULL) 744 vmspace_free(vm2); 745 uma_zfree(proc_zone, newproc); 746 pause("fork", hz / 2); 747 return (error); 748 } 749 750 /* 751 * Handle the return of a child process from fork1(). This function 752 * is called from the MD fork_trampoline() entry point. 753 */ 754 void 755 fork_exit(callout, arg, frame) 756 void (*callout)(void *, struct trapframe *); 757 void *arg; 758 struct trapframe *frame; 759 { 760 struct proc *p; 761 struct thread *td; 762 struct thread *dtd; 763 764 td = curthread; 765 p = td->td_proc; 766 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 767 768 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 769 td, td->td_sched, p->p_pid, td->td_name); 770 771 sched_fork_exit(td); 772 /* 773 * Processes normally resume in mi_switch() after being 774 * cpu_switch()'ed to, but when children start up they arrive here 775 * instead, so we must do much the same things as mi_switch() would. 776 */ 777 if ((dtd = PCPU_GET(deadthread))) { 778 PCPU_SET(deadthread, NULL); 779 thread_stash(dtd); 780 } 781 thread_unlock(td); 782 783 /* 784 * cpu_set_fork_handler intercepts this function call to 785 * have this call a non-return function to stay in kernel mode. 786 * initproc has its own fork handler, but it does return. 787 */ 788 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 789 callout(arg, frame); 790 791 /* 792 * Check if a kernel thread misbehaved and returned from its main 793 * function. 794 */ 795 if (p->p_flag & P_KTHREAD) { 796 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 797 td->td_name, p->p_pid); 798 kproc_exit(0); 799 } 800 mtx_assert(&Giant, MA_NOTOWNED); 801 802 EVENTHANDLER_INVOKE(schedtail, p); 803 } 804 805 /* 806 * Simplified back end of syscall(), used when returning from fork() 807 * directly into user mode. Giant is not held on entry, and must not 808 * be held on return. This function is passed in to fork_exit() as the 809 * first parameter and is called when returning to a new userland process. 810 */ 811 void 812 fork_return(td, frame) 813 struct thread *td; 814 struct trapframe *frame; 815 { 816 817 userret(td, frame); 818 #ifdef KTRACE 819 if (KTRPOINT(td, KTR_SYSRET)) 820 ktrsysret(SYS_fork, 0, 0); 821 #endif 822 mtx_assert(&Giant, MA_NOTOWNED); 823 } 824