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/proc.h> 55 #include <sys/pioctl.h> 56 #include <sys/resourcevar.h> 57 #include <sys/sched.h> 58 #include <sys/syscall.h> 59 #include <sys/vmmeter.h> 60 #include <sys/vnode.h> 61 #include <sys/acct.h> 62 #include <sys/mac.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 <vm/vm.h> 70 #include <vm/pmap.h> 71 #include <vm/vm_map.h> 72 #include <vm/vm_extern.h> 73 #include <vm/uma.h> 74 75 #include <machine/critical.h> 76 77 #ifndef _SYS_SYSPROTO_H_ 78 struct fork_args { 79 int dummy; 80 }; 81 #endif 82 83 static int forksleep; /* Place for fork1() to sleep on. */ 84 85 /* 86 * MPSAFE 87 */ 88 /* ARGSUSED */ 89 int 90 fork(td, uap) 91 struct thread *td; 92 struct fork_args *uap; 93 { 94 int error; 95 struct proc *p2; 96 97 error = fork1(td, RFFDG | RFPROC, 0, &p2); 98 if (error == 0) { 99 td->td_retval[0] = p2->p_pid; 100 td->td_retval[1] = 0; 101 } 102 return (error); 103 } 104 105 /* 106 * MPSAFE 107 */ 108 /* ARGSUSED */ 109 int 110 vfork(td, uap) 111 struct thread *td; 112 struct vfork_args *uap; 113 { 114 int error; 115 struct proc *p2; 116 117 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 118 if (error == 0) { 119 td->td_retval[0] = p2->p_pid; 120 td->td_retval[1] = 0; 121 } 122 return (error); 123 } 124 125 /* 126 * MPSAFE 127 */ 128 int 129 rfork(td, uap) 130 struct thread *td; 131 struct rfork_args *uap; 132 { 133 struct proc *p2; 134 int error; 135 136 /* Don't allow kernel-only flags. */ 137 if ((uap->flags & RFKERNELONLY) != 0) 138 return (EINVAL); 139 140 error = fork1(td, uap->flags, 0, &p2); 141 if (error == 0) { 142 td->td_retval[0] = p2 ? p2->p_pid : 0; 143 td->td_retval[1] = 0; 144 } 145 return (error); 146 } 147 148 int nprocs = 1; /* process 0 */ 149 int lastpid = 0; 150 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 151 "Last used PID"); 152 153 /* 154 * Random component to lastpid generation. We mix in a random factor to make 155 * it a little harder to predict. We sanity check the modulus value to avoid 156 * doing it in critical paths. Don't let it be too small or we pointlessly 157 * waste randomness entropy, and don't let it be impossibly large. Using a 158 * modulus that is too big causes a LOT more process table scans and slows 159 * down fork processing as the pidchecked caching is defeated. 160 */ 161 static int randompid = 0; 162 163 static int 164 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 165 { 166 int error, pid; 167 168 error = sysctl_wire_old_buffer(req, sizeof(int)); 169 if (error != 0) 170 return(error); 171 sx_xlock(&allproc_lock); 172 pid = randompid; 173 error = sysctl_handle_int(oidp, &pid, 0, req); 174 if (error == 0 && req->newptr != NULL) { 175 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 176 pid = PID_MAX - 100; 177 else if (pid < 2) /* NOP */ 178 pid = 0; 179 else if (pid < 100) /* Make it reasonable */ 180 pid = 100; 181 randompid = pid; 182 } 183 sx_xunlock(&allproc_lock); 184 return (error); 185 } 186 187 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 188 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 189 190 int 191 fork1(td, flags, pages, procp) 192 struct thread *td; 193 int flags; 194 int pages; 195 struct proc **procp; 196 { 197 struct proc *p1, *p2, *pptr; 198 uid_t uid; 199 struct proc *newproc; 200 int ok, trypid; 201 static int curfail, pidchecked = 0; 202 static struct timeval lastfail; 203 struct filedesc *fd; 204 struct filedesc_to_leader *fdtol; 205 struct thread *td2; 206 struct ksegrp *kg2; 207 struct sigacts *newsigacts; 208 int error; 209 210 /* Can't copy and clear. */ 211 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 212 return (EINVAL); 213 214 p1 = td->td_proc; 215 216 /* 217 * Here we don't create a new process, but we divorce 218 * certain parts of a process from itself. 219 */ 220 if ((flags & RFPROC) == 0) { 221 vm_forkproc(td, NULL, NULL, flags); 222 223 /* 224 * Close all file descriptors. 225 */ 226 if (flags & RFCFDG) { 227 struct filedesc *fdtmp; 228 fdtmp = fdinit(td->td_proc->p_fd); 229 fdfree(td); 230 p1->p_fd = fdtmp; 231 } 232 233 /* 234 * Unshare file descriptors (from parent). 235 */ 236 if (flags & RFFDG) 237 fdunshare(p1, td); 238 *procp = NULL; 239 return (0); 240 } 241 242 /* 243 * Note 1:1 allows for forking with one thread coming out on the 244 * other side with the expectation that the process is about to 245 * exec. 246 */ 247 if (p1->p_flag & P_HADTHREADS) { 248 /* 249 * Idle the other threads for a second. 250 * Since the user space is copied, it must remain stable. 251 * In addition, all threads (from the user perspective) 252 * need to either be suspended or in the kernel, 253 * where they will try restart in the parent and will 254 * be aborted in the child. 255 */ 256 PROC_LOCK(p1); 257 if (thread_single(SINGLE_NO_EXIT)) { 258 /* Abort. Someone else is single threading before us. */ 259 PROC_UNLOCK(p1); 260 return (ERESTART); 261 } 262 PROC_UNLOCK(p1); 263 /* 264 * All other activity in this process 265 * is now suspended at the user boundary, 266 * (or other safe places if we think of any). 267 */ 268 } 269 270 /* Allocate new proc. */ 271 newproc = uma_zalloc(proc_zone, M_WAITOK); 272 #ifdef MAC 273 mac_init_proc(newproc); 274 #endif 275 knlist_init(&newproc->p_klist, &newproc->p_mtx); 276 277 /* We have to lock the process tree while we look for a pid. */ 278 sx_slock(&proctree_lock); 279 280 /* 281 * Although process entries are dynamically created, we still keep 282 * a global limit on the maximum number we will create. Don't allow 283 * a nonprivileged user to use the last ten processes; don't let root 284 * exceed the limit. The variable nprocs is the current number of 285 * processes, maxproc is the limit. 286 */ 287 sx_xlock(&allproc_lock); 288 uid = td->td_ucred->cr_ruid; 289 if ((nprocs >= maxproc - 10 && 290 suser_cred(td->td_ucred, SUSER_RUID) != 0) || 291 nprocs >= maxproc) { 292 error = EAGAIN; 293 goto fail; 294 } 295 296 /* 297 * Increment the count of procs running with this uid. Don't allow 298 * a nonprivileged user to exceed their current limit. 299 */ 300 PROC_LOCK(p1); 301 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 302 (uid != 0) ? lim_cur(p1, RLIMIT_NPROC) : 0); 303 PROC_UNLOCK(p1); 304 if (!ok) { 305 error = EAGAIN; 306 goto fail; 307 } 308 309 /* 310 * Increment the nprocs resource before blocking can occur. There 311 * are hard-limits as to the number of processes that can run. 312 */ 313 nprocs++; 314 315 /* 316 * Find an unused process ID. We remember a range of unused IDs 317 * ready to use (from lastpid+1 through pidchecked-1). 318 * 319 * If RFHIGHPID is set (used during system boot), do not allocate 320 * low-numbered pids. 321 */ 322 trypid = lastpid + 1; 323 if (flags & RFHIGHPID) { 324 if (trypid < 10) 325 trypid = 10; 326 } else { 327 if (randompid) 328 trypid += arc4random() % randompid; 329 } 330 retry: 331 /* 332 * If the process ID prototype has wrapped around, 333 * restart somewhat above 0, as the low-numbered procs 334 * tend to include daemons that don't exit. 335 */ 336 if (trypid >= PID_MAX) { 337 trypid = trypid % PID_MAX; 338 if (trypid < 100) 339 trypid += 100; 340 pidchecked = 0; 341 } 342 if (trypid >= pidchecked) { 343 int doingzomb = 0; 344 345 pidchecked = PID_MAX; 346 /* 347 * Scan the active and zombie procs to check whether this pid 348 * is in use. Remember the lowest pid that's greater 349 * than trypid, so we can avoid checking for a while. 350 */ 351 p2 = LIST_FIRST(&allproc); 352 again: 353 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 354 PROC_LOCK(p2); 355 while (p2->p_pid == trypid || 356 (p2->p_pgrp != NULL && 357 (p2->p_pgrp->pg_id == trypid || 358 (p2->p_session != NULL && 359 p2->p_session->s_sid == trypid)))) { 360 trypid++; 361 if (trypid >= pidchecked) { 362 PROC_UNLOCK(p2); 363 goto retry; 364 } 365 } 366 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 367 pidchecked = p2->p_pid; 368 if (p2->p_pgrp != NULL) { 369 if (p2->p_pgrp->pg_id > trypid && 370 pidchecked > p2->p_pgrp->pg_id) 371 pidchecked = p2->p_pgrp->pg_id; 372 if (p2->p_session != NULL && 373 p2->p_session->s_sid > trypid && 374 pidchecked > p2->p_session->s_sid) 375 pidchecked = p2->p_session->s_sid; 376 } 377 PROC_UNLOCK(p2); 378 } 379 if (!doingzomb) { 380 doingzomb = 1; 381 p2 = LIST_FIRST(&zombproc); 382 goto again; 383 } 384 } 385 sx_sunlock(&proctree_lock); 386 387 /* 388 * RFHIGHPID does not mess with the lastpid counter during boot. 389 */ 390 if (flags & RFHIGHPID) 391 pidchecked = 0; 392 else 393 lastpid = trypid; 394 395 p2 = newproc; 396 p2->p_state = PRS_NEW; /* protect against others */ 397 p2->p_pid = trypid; 398 LIST_INSERT_HEAD(&allproc, p2, p_list); 399 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 400 sx_xunlock(&allproc_lock); 401 402 /* 403 * Malloc things while we don't hold any locks. 404 */ 405 if (flags & RFSIGSHARE) 406 newsigacts = NULL; 407 else 408 newsigacts = sigacts_alloc(); 409 410 /* 411 * Copy filedesc. 412 */ 413 if (flags & RFCFDG) { 414 fd = fdinit(p1->p_fd); 415 fdtol = NULL; 416 } else if (flags & RFFDG) { 417 fd = fdcopy(p1->p_fd); 418 fdtol = NULL; 419 } else { 420 fd = fdshare(p1->p_fd); 421 if (p1->p_fdtol == NULL) 422 p1->p_fdtol = 423 filedesc_to_leader_alloc(NULL, 424 NULL, 425 p1->p_leader); 426 if ((flags & RFTHREAD) != 0) { 427 /* 428 * Shared file descriptor table and 429 * shared process leaders. 430 */ 431 fdtol = p1->p_fdtol; 432 FILEDESC_LOCK_FAST(p1->p_fd); 433 fdtol->fdl_refcount++; 434 FILEDESC_UNLOCK_FAST(p1->p_fd); 435 } else { 436 /* 437 * Shared file descriptor table, and 438 * different process leaders 439 */ 440 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 441 p1->p_fd, 442 p2); 443 } 444 } 445 /* 446 * Make a proc table entry for the new process. 447 * Start by zeroing the section of proc that is zero-initialized, 448 * then copy the section that is copied directly from the parent. 449 */ 450 td2 = FIRST_THREAD_IN_PROC(p2); 451 kg2 = FIRST_KSEGRP_IN_PROC(p2); 452 453 /* Allocate and switch to an alternate kstack if specified. */ 454 if (pages != 0) 455 vm_thread_new_altkstack(td2, pages); 456 457 PROC_LOCK(p2); 458 PROC_LOCK(p1); 459 460 bzero(&p2->p_startzero, 461 __rangeof(struct proc, p_startzero, p_endzero)); 462 bzero(&td2->td_startzero, 463 __rangeof(struct thread, td_startzero, td_endzero)); 464 bzero(&kg2->kg_startzero, 465 __rangeof(struct ksegrp, kg_startzero, kg_endzero)); 466 467 bcopy(&p1->p_startcopy, &p2->p_startcopy, 468 __rangeof(struct proc, p_startcopy, p_endcopy)); 469 bcopy(&td->td_startcopy, &td2->td_startcopy, 470 __rangeof(struct thread, td_startcopy, td_endcopy)); 471 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 472 __rangeof(struct ksegrp, kg_startcopy, kg_endcopy)); 473 474 td2->td_sigstk = td->td_sigstk; 475 476 /* 477 * Duplicate sub-structures as needed. 478 * Increase reference counts on shared objects. 479 */ 480 p2->p_flag = 0; 481 if (p1->p_flag & P_PROFIL) 482 startprofclock(p2); 483 mtx_lock_spin(&sched_lock); 484 p2->p_sflag = PS_INMEM; 485 /* 486 * Allow the scheduler to adjust the priority of the child and 487 * parent while we hold the sched_lock. 488 */ 489 sched_fork(td, td2); 490 491 mtx_unlock_spin(&sched_lock); 492 p2->p_ucred = crhold(td->td_ucred); 493 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 494 495 pargs_hold(p2->p_args); 496 497 if (flags & RFSIGSHARE) { 498 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 499 } else { 500 sigacts_copy(newsigacts, p1->p_sigacts); 501 p2->p_sigacts = newsigacts; 502 } 503 if (flags & RFLINUXTHPN) 504 p2->p_sigparent = SIGUSR1; 505 else 506 p2->p_sigparent = SIGCHLD; 507 508 p2->p_textvp = p1->p_textvp; 509 p2->p_fd = fd; 510 p2->p_fdtol = fdtol; 511 512 /* 513 * p_limit is copy-on-write. Bump its refcount. 514 */ 515 p2->p_limit = lim_hold(p1->p_limit); 516 517 pstats_fork(p1->p_stats, p2->p_stats); 518 519 PROC_UNLOCK(p1); 520 PROC_UNLOCK(p2); 521 522 /* Bump references to the text vnode (for procfs) */ 523 if (p2->p_textvp) 524 vref(p2->p_textvp); 525 526 /* 527 * Set up linkage for kernel based threading. 528 */ 529 if ((flags & RFTHREAD) != 0) { 530 mtx_lock(&ppeers_lock); 531 p2->p_peers = p1->p_peers; 532 p1->p_peers = p2; 533 p2->p_leader = p1->p_leader; 534 mtx_unlock(&ppeers_lock); 535 PROC_LOCK(p1->p_leader); 536 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 537 PROC_UNLOCK(p1->p_leader); 538 /* 539 * The task leader is exiting, so process p1 is 540 * going to be killed shortly. Since p1 obviously 541 * isn't dead yet, we know that the leader is either 542 * sending SIGKILL's to all the processes in this 543 * task or is sleeping waiting for all the peers to 544 * exit. We let p1 complete the fork, but we need 545 * to go ahead and kill the new process p2 since 546 * the task leader may not get a chance to send 547 * SIGKILL to it. We leave it on the list so that 548 * the task leader will wait for this new process 549 * to commit suicide. 550 */ 551 PROC_LOCK(p2); 552 psignal(p2, SIGKILL); 553 PROC_UNLOCK(p2); 554 } else 555 PROC_UNLOCK(p1->p_leader); 556 } else { 557 p2->p_peers = NULL; 558 p2->p_leader = p2; 559 } 560 561 sx_xlock(&proctree_lock); 562 PGRP_LOCK(p1->p_pgrp); 563 PROC_LOCK(p2); 564 PROC_LOCK(p1); 565 566 /* 567 * Preserve some more flags in subprocess. P_PROFIL has already 568 * been preserved. 569 */ 570 p2->p_flag |= p1->p_flag & P_SUGID; 571 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 572 SESS_LOCK(p1->p_session); 573 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 574 p2->p_flag |= P_CONTROLT; 575 SESS_UNLOCK(p1->p_session); 576 if (flags & RFPPWAIT) 577 p2->p_flag |= P_PPWAIT; 578 579 p2->p_pgrp = p1->p_pgrp; 580 LIST_INSERT_AFTER(p1, p2, p_pglist); 581 PGRP_UNLOCK(p1->p_pgrp); 582 LIST_INIT(&p2->p_children); 583 584 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 585 586 #ifdef KTRACE 587 /* 588 * Copy traceflag and tracefile if enabled. 589 */ 590 mtx_lock(&ktrace_mtx); 591 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 592 if (p1->p_traceflag & KTRFAC_INHERIT) { 593 p2->p_traceflag = p1->p_traceflag; 594 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 595 VREF(p2->p_tracevp); 596 KASSERT(p1->p_tracecred != NULL, 597 ("ktrace vnode with no cred")); 598 p2->p_tracecred = crhold(p1->p_tracecred); 599 } 600 } 601 mtx_unlock(&ktrace_mtx); 602 #endif 603 604 /* 605 * If PF_FORK is set, the child process inherits the 606 * procfs ioctl flags from its parent. 607 */ 608 if (p1->p_pfsflags & PF_FORK) { 609 p2->p_stops = p1->p_stops; 610 p2->p_pfsflags = p1->p_pfsflags; 611 } 612 613 /* 614 * This begins the section where we must prevent the parent 615 * from being swapped. 616 */ 617 _PHOLD(p1); 618 PROC_UNLOCK(p1); 619 620 /* 621 * Attach the new process to its parent. 622 * 623 * If RFNOWAIT is set, the newly created process becomes a child 624 * of init. This effectively disassociates the child from the 625 * parent. 626 */ 627 if (flags & RFNOWAIT) 628 pptr = initproc; 629 else 630 pptr = p1; 631 p2->p_pptr = pptr; 632 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 633 sx_xunlock(&proctree_lock); 634 635 /* Inform accounting that we have forked. */ 636 p2->p_acflag = AFORK; 637 PROC_UNLOCK(p2); 638 639 /* 640 * Finish creating the child process. It will return via a different 641 * execution path later. (ie: directly into user mode) 642 */ 643 vm_forkproc(td, p2, td2, flags); 644 645 if (flags == (RFFDG | RFPROC)) { 646 atomic_add_int(&cnt.v_forks, 1); 647 atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize + 648 p2->p_vmspace->vm_ssize); 649 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 650 atomic_add_int(&cnt.v_vforks, 1); 651 atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 652 p2->p_vmspace->vm_ssize); 653 } else if (p1 == &proc0) { 654 atomic_add_int(&cnt.v_kthreads, 1); 655 atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 656 p2->p_vmspace->vm_ssize); 657 } else { 658 atomic_add_int(&cnt.v_rforks, 1); 659 atomic_add_int(&cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 660 p2->p_vmspace->vm_ssize); 661 } 662 663 /* 664 * Both processes are set up, now check if any loadable modules want 665 * to adjust anything. 666 * What if they have an error? XXX 667 */ 668 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 669 670 /* 671 * Set the child start time and mark the process as being complete. 672 */ 673 microuptime(&p2->p_stats->p_start); 674 mtx_lock_spin(&sched_lock); 675 p2->p_state = PRS_NORMAL; 676 677 /* 678 * If RFSTOPPED not requested, make child runnable and add to 679 * run queue. 680 */ 681 if ((flags & RFSTOPPED) == 0) { 682 TD_SET_CAN_RUN(td2); 683 setrunqueue(td2, SRQ_BORING); 684 } 685 mtx_unlock_spin(&sched_lock); 686 687 /* 688 * Now can be swapped. 689 */ 690 PROC_LOCK(p1); 691 _PRELE(p1); 692 693 /* 694 * Tell any interested parties about the new process. 695 */ 696 KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid); 697 698 PROC_UNLOCK(p1); 699 700 /* 701 * Preserve synchronization semantics of vfork. If waiting for 702 * child to exec or exit, set P_PPWAIT on child, and sleep on our 703 * proc (in case of exit). 704 */ 705 PROC_LOCK(p2); 706 while (p2->p_flag & P_PPWAIT) 707 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 708 PROC_UNLOCK(p2); 709 710 /* 711 * If other threads are waiting, let them continue now. 712 */ 713 if (p1->p_flag & P_HADTHREADS) { 714 PROC_LOCK(p1); 715 thread_single_end(); 716 PROC_UNLOCK(p1); 717 } 718 719 /* 720 * Return child proc pointer to parent. 721 */ 722 *procp = p2; 723 return (0); 724 fail: 725 sx_sunlock(&proctree_lock); 726 if (ppsratecheck(&lastfail, &curfail, 1)) 727 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 728 uid); 729 sx_xunlock(&allproc_lock); 730 #ifdef MAC 731 mac_destroy_proc(newproc); 732 #endif 733 uma_zfree(proc_zone, newproc); 734 if (p1->p_flag & P_HADTHREADS) { 735 PROC_LOCK(p1); 736 thread_single_end(); 737 PROC_UNLOCK(p1); 738 } 739 tsleep(&forksleep, PUSER, "fork", hz / 2); 740 return (error); 741 } 742 743 /* 744 * Handle the return of a child process from fork1(). This function 745 * is called from the MD fork_trampoline() entry point. 746 */ 747 void 748 fork_exit(callout, arg, frame) 749 void (*callout)(void *, struct trapframe *); 750 void *arg; 751 struct trapframe *frame; 752 { 753 struct proc *p; 754 struct thread *td; 755 756 /* 757 * Finish setting up thread glue so that it begins execution in a 758 * non-nested critical section with sched_lock held but not recursed. 759 */ 760 td = curthread; 761 p = td->td_proc; 762 td->td_oncpu = PCPU_GET(cpuid); 763 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 764 765 sched_lock.mtx_lock = (uintptr_t)td; 766 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 767 cpu_critical_fork_exit(); 768 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 769 td, td->td_sched, p->p_pid, p->p_comm); 770 771 /* 772 * Processes normally resume in mi_switch() after being 773 * cpu_switch()'ed to, but when children start up they arrive here 774 * instead, so we must do much the same things as mi_switch() would. 775 */ 776 777 if ((td = PCPU_GET(deadthread))) { 778 PCPU_SET(deadthread, NULL); 779 thread_stash(td); 780 } 781 td = curthread; 782 mtx_unlock_spin(&sched_lock); 783 784 /* 785 * cpu_set_fork_handler intercepts this function call to 786 * have this call a non-return function to stay in kernel mode. 787 * initproc has its own fork handler, but it does return. 788 */ 789 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 790 callout(arg, frame); 791 792 /* 793 * Check if a kernel thread misbehaved and returned from its main 794 * function. 795 */ 796 PROC_LOCK(p); 797 if (p->p_flag & P_KTHREAD) { 798 PROC_UNLOCK(p); 799 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 800 p->p_comm, p->p_pid); 801 kthread_exit(0); 802 } 803 PROC_UNLOCK(p); 804 mtx_assert(&Giant, MA_NOTOWNED); 805 } 806 807 /* 808 * Simplified back end of syscall(), used when returning from fork() 809 * directly into user mode. Giant is not held on entry, and must not 810 * be held on return. This function is passed in to fork_exit() as the 811 * first parameter and is called when returning to a new userland process. 812 */ 813 void 814 fork_return(td, frame) 815 struct thread *td; 816 struct trapframe *frame; 817 { 818 819 userret(td, frame, 0); 820 #ifdef KTRACE 821 if (KTRPOINT(td, KTR_SYSRET)) 822 ktrsysret(SYS_fork, 0, 0); 823 #endif 824 mtx_assert(&Giant, MA_NOTOWNED); 825 } 826