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 76 #ifndef _SYS_SYSPROTO_H_ 77 struct fork_args { 78 int dummy; 79 }; 80 #endif 81 82 static int forksleep; /* Place for fork1() to sleep on. */ 83 84 /* 85 * MPSAFE 86 */ 87 /* ARGSUSED */ 88 int 89 fork(td, uap) 90 struct thread *td; 91 struct fork_args *uap; 92 { 93 int error; 94 struct proc *p2; 95 96 error = fork1(td, RFFDG | RFPROC, 0, &p2); 97 if (error == 0) { 98 td->td_retval[0] = p2->p_pid; 99 td->td_retval[1] = 0; 100 } 101 return (error); 102 } 103 104 /* 105 * MPSAFE 106 */ 107 /* ARGSUSED */ 108 int 109 vfork(td, uap) 110 struct thread *td; 111 struct vfork_args *uap; 112 { 113 int error; 114 struct proc *p2; 115 116 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 117 if (error == 0) { 118 td->td_retval[0] = p2->p_pid; 119 td->td_retval[1] = 0; 120 } 121 return (error); 122 } 123 124 /* 125 * MPSAFE 126 */ 127 int 128 rfork(td, uap) 129 struct thread *td; 130 struct rfork_args *uap; 131 { 132 struct proc *p2; 133 int error; 134 135 /* Don't allow kernel-only flags. */ 136 if ((uap->flags & RFKERNELONLY) != 0) 137 return (EINVAL); 138 139 error = fork1(td, uap->flags, 0, &p2); 140 if (error == 0) { 141 td->td_retval[0] = p2 ? p2->p_pid : 0; 142 td->td_retval[1] = 0; 143 } 144 return (error); 145 } 146 147 int nprocs = 1; /* process 0 */ 148 int lastpid = 0; 149 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 150 "Last used PID"); 151 152 /* 153 * Random component to lastpid generation. We mix in a random factor to make 154 * it a little harder to predict. We sanity check the modulus value to avoid 155 * doing it in critical paths. Don't let it be too small or we pointlessly 156 * waste randomness entropy, and don't let it be impossibly large. Using a 157 * modulus that is too big causes a LOT more process table scans and slows 158 * down fork processing as the pidchecked caching is defeated. 159 */ 160 static int randompid = 0; 161 162 static int 163 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 164 { 165 int error, pid; 166 167 error = sysctl_wire_old_buffer(req, sizeof(int)); 168 if (error != 0) 169 return(error); 170 sx_xlock(&allproc_lock); 171 pid = randompid; 172 error = sysctl_handle_int(oidp, &pid, 0, req); 173 if (error == 0 && req->newptr != NULL) { 174 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 175 pid = PID_MAX - 100; 176 else if (pid < 2) /* NOP */ 177 pid = 0; 178 else if (pid < 100) /* Make it reasonable */ 179 pid = 100; 180 randompid = pid; 181 } 182 sx_xunlock(&allproc_lock); 183 return (error); 184 } 185 186 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 187 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 188 189 int 190 fork1(td, flags, pages, procp) 191 struct thread *td; 192 int flags; 193 int pages; 194 struct proc **procp; 195 { 196 struct proc *p1, *p2, *pptr; 197 uid_t uid; 198 struct proc *newproc; 199 int ok, trypid; 200 static int curfail, pidchecked = 0; 201 static struct timeval lastfail; 202 struct filedesc *fd; 203 struct filedesc_to_leader *fdtol; 204 struct thread *td2; 205 struct ksegrp *kg2; 206 struct sigacts *newsigacts; 207 int error; 208 209 /* Can't copy and clear. */ 210 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 211 return (EINVAL); 212 213 p1 = td->td_proc; 214 215 /* 216 * Here we don't create a new process, but we divorce 217 * certain parts of a process from itself. 218 */ 219 if ((flags & RFPROC) == 0) { 220 vm_forkproc(td, NULL, NULL, flags); 221 222 /* 223 * Close all file descriptors. 224 */ 225 if (flags & RFCFDG) { 226 struct filedesc *fdtmp; 227 fdtmp = fdinit(td->td_proc->p_fd); 228 fdfree(td); 229 p1->p_fd = fdtmp; 230 } 231 232 /* 233 * Unshare file descriptors (from parent). 234 */ 235 if (flags & RFFDG) 236 fdunshare(p1, td); 237 *procp = NULL; 238 return (0); 239 } 240 241 /* 242 * Note 1:1 allows for forking with one thread coming out on the 243 * other side with the expectation that the process is about to 244 * exec. 245 */ 246 if (p1->p_flag & P_HADTHREADS) { 247 /* 248 * Idle the other threads for a second. 249 * Since the user space is copied, it must remain stable. 250 * In addition, all threads (from the user perspective) 251 * need to either be suspended or in the kernel, 252 * where they will try restart in the parent and will 253 * be aborted in the child. 254 */ 255 PROC_LOCK(p1); 256 if (thread_single(SINGLE_NO_EXIT)) { 257 /* Abort. Someone else is single threading before us. */ 258 PROC_UNLOCK(p1); 259 return (ERESTART); 260 } 261 PROC_UNLOCK(p1); 262 /* 263 * All other activity in this process 264 * is now suspended at the user boundary, 265 * (or other safe places if we think of any). 266 */ 267 } 268 269 /* Allocate new proc. */ 270 newproc = uma_zalloc(proc_zone, M_WAITOK); 271 #ifdef MAC 272 mac_init_proc(newproc); 273 #endif 274 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL); 275 276 /* We have to lock the process tree while we look for a pid. */ 277 sx_slock(&proctree_lock); 278 279 /* 280 * Although process entries are dynamically created, we still keep 281 * a global limit on the maximum number we will create. Don't allow 282 * a nonprivileged user to use the last ten processes; don't let root 283 * exceed the limit. The variable nprocs is the current number of 284 * processes, maxproc is the limit. 285 */ 286 sx_xlock(&allproc_lock); 287 uid = td->td_ucred->cr_ruid; 288 if ((nprocs >= maxproc - 10 && 289 suser_cred(td->td_ucred, SUSER_RUID) != 0) || 290 nprocs >= maxproc) { 291 error = EAGAIN; 292 goto fail; 293 } 294 295 /* 296 * Increment the count of procs running with this uid. Don't allow 297 * a nonprivileged user to exceed their current limit. 298 */ 299 PROC_LOCK(p1); 300 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 301 (uid != 0) ? lim_cur(p1, RLIMIT_NPROC) : 0); 302 PROC_UNLOCK(p1); 303 if (!ok) { 304 error = EAGAIN; 305 goto fail; 306 } 307 308 /* 309 * Increment the nprocs resource before blocking can occur. There 310 * are hard-limits as to the number of processes that can run. 311 */ 312 nprocs++; 313 314 /* 315 * Find an unused process ID. We remember a range of unused IDs 316 * ready to use (from lastpid+1 through pidchecked-1). 317 * 318 * If RFHIGHPID is set (used during system boot), do not allocate 319 * low-numbered pids. 320 */ 321 trypid = lastpid + 1; 322 if (flags & RFHIGHPID) { 323 if (trypid < 10) 324 trypid = 10; 325 } else { 326 if (randompid) 327 trypid += arc4random() % randompid; 328 } 329 retry: 330 /* 331 * If the process ID prototype has wrapped around, 332 * restart somewhat above 0, as the low-numbered procs 333 * tend to include daemons that don't exit. 334 */ 335 if (trypid >= PID_MAX) { 336 trypid = trypid % PID_MAX; 337 if (trypid < 100) 338 trypid += 100; 339 pidchecked = 0; 340 } 341 if (trypid >= pidchecked) { 342 int doingzomb = 0; 343 344 pidchecked = PID_MAX; 345 /* 346 * Scan the active and zombie procs to check whether this pid 347 * is in use. Remember the lowest pid that's greater 348 * than trypid, so we can avoid checking for a while. 349 */ 350 p2 = LIST_FIRST(&allproc); 351 again: 352 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 353 PROC_LOCK(p2); 354 while (p2->p_pid == trypid || 355 (p2->p_pgrp != NULL && 356 (p2->p_pgrp->pg_id == trypid || 357 (p2->p_session != NULL && 358 p2->p_session->s_sid == trypid)))) { 359 trypid++; 360 if (trypid >= pidchecked) { 361 PROC_UNLOCK(p2); 362 goto retry; 363 } 364 } 365 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 366 pidchecked = p2->p_pid; 367 if (p2->p_pgrp != NULL) { 368 if (p2->p_pgrp->pg_id > trypid && 369 pidchecked > p2->p_pgrp->pg_id) 370 pidchecked = p2->p_pgrp->pg_id; 371 if (p2->p_session != NULL && 372 p2->p_session->s_sid > trypid && 373 pidchecked > p2->p_session->s_sid) 374 pidchecked = p2->p_session->s_sid; 375 } 376 PROC_UNLOCK(p2); 377 } 378 if (!doingzomb) { 379 doingzomb = 1; 380 p2 = LIST_FIRST(&zombproc); 381 goto again; 382 } 383 } 384 sx_sunlock(&proctree_lock); 385 386 /* 387 * RFHIGHPID does not mess with the lastpid counter during boot. 388 */ 389 if (flags & RFHIGHPID) 390 pidchecked = 0; 391 else 392 lastpid = trypid; 393 394 p2 = newproc; 395 p2->p_state = PRS_NEW; /* protect against others */ 396 p2->p_pid = trypid; 397 LIST_INSERT_HEAD(&allproc, p2, p_list); 398 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 399 sx_xunlock(&allproc_lock); 400 401 /* 402 * Malloc things while we don't hold any locks. 403 */ 404 if (flags & RFSIGSHARE) 405 newsigacts = NULL; 406 else 407 newsigacts = sigacts_alloc(); 408 409 /* 410 * Copy filedesc. 411 */ 412 if (flags & RFCFDG) { 413 fd = fdinit(p1->p_fd); 414 fdtol = NULL; 415 } else if (flags & RFFDG) { 416 fd = fdcopy(p1->p_fd); 417 fdtol = NULL; 418 } else { 419 fd = fdshare(p1->p_fd); 420 if (p1->p_fdtol == NULL) 421 p1->p_fdtol = 422 filedesc_to_leader_alloc(NULL, 423 NULL, 424 p1->p_leader); 425 if ((flags & RFTHREAD) != 0) { 426 /* 427 * Shared file descriptor table and 428 * shared process leaders. 429 */ 430 fdtol = p1->p_fdtol; 431 FILEDESC_LOCK_FAST(p1->p_fd); 432 fdtol->fdl_refcount++; 433 FILEDESC_UNLOCK_FAST(p1->p_fd); 434 } else { 435 /* 436 * Shared file descriptor table, and 437 * different process leaders 438 */ 439 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 440 p1->p_fd, 441 p2); 442 } 443 } 444 /* 445 * Make a proc table entry for the new process. 446 * Start by zeroing the section of proc that is zero-initialized, 447 * then copy the section that is copied directly from the parent. 448 */ 449 td2 = FIRST_THREAD_IN_PROC(p2); 450 kg2 = FIRST_KSEGRP_IN_PROC(p2); 451 452 /* Allocate and switch to an alternate kstack if specified. */ 453 if (pages != 0) 454 vm_thread_new_altkstack(td2, pages); 455 456 PROC_LOCK(p2); 457 PROC_LOCK(p1); 458 459 bzero(&p2->p_startzero, 460 __rangeof(struct proc, p_startzero, p_endzero)); 461 bzero(&td2->td_startzero, 462 __rangeof(struct thread, td_startzero, td_endzero)); 463 bzero(&kg2->kg_startzero, 464 __rangeof(struct ksegrp, kg_startzero, kg_endzero)); 465 466 bcopy(&p1->p_startcopy, &p2->p_startcopy, 467 __rangeof(struct proc, p_startcopy, p_endcopy)); 468 bcopy(&td->td_startcopy, &td2->td_startcopy, 469 __rangeof(struct thread, td_startcopy, td_endcopy)); 470 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 471 __rangeof(struct ksegrp, kg_startcopy, kg_endcopy)); 472 473 td2->td_sigstk = td->td_sigstk; 474 td2->td_sigmask = td->td_sigmask; 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 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 768 td, td->td_sched, p->p_pid, p->p_comm); 769 770 /* 771 * Processes normally resume in mi_switch() after being 772 * cpu_switch()'ed to, but when children start up they arrive here 773 * instead, so we must do much the same things as mi_switch() would. 774 */ 775 776 if ((td = PCPU_GET(deadthread))) { 777 PCPU_SET(deadthread, NULL); 778 thread_stash(td); 779 } 780 td = curthread; 781 mtx_unlock_spin(&sched_lock); 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 PROC_LOCK(p); 796 if (p->p_flag & P_KTHREAD) { 797 PROC_UNLOCK(p); 798 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 799 p->p_comm, p->p_pid); 800 kthread_exit(0); 801 } 802 PROC_UNLOCK(p); 803 mtx_assert(&Giant, MA_NOTOWNED); 804 } 805 806 /* 807 * Simplified back end of syscall(), used when returning from fork() 808 * directly into user mode. Giant is not held on entry, and must not 809 * be held on return. This function is passed in to fork_exit() as the 810 * first parameter and is called when returning to a new userland process. 811 */ 812 void 813 fork_return(td, frame) 814 struct thread *td; 815 struct trapframe *frame; 816 { 817 818 userret(td, frame, 0); 819 #ifdef KTRACE 820 if (KTRPOINT(td, KTR_SYSRET)) 821 ktrsysret(SYS_fork, 0, 0); 822 #endif 823 mtx_assert(&Giant, MA_NOTOWNED); 824 } 825