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 FILEDESC_LOCK_FAST(p1->p_fd); 238 if (p1->p_fd->fd_refcnt > 1) { 239 struct filedesc *newfd; 240 241 FILEDESC_UNLOCK_FAST(p1->p_fd); 242 newfd = fdcopy(p1->p_fd); 243 fdfree(td); 244 p1->p_fd = newfd; 245 } else 246 FILEDESC_UNLOCK_FAST(p1->p_fd); 247 } 248 *procp = NULL; 249 return (0); 250 } 251 252 /* 253 * Note 1:1 allows for forking with one thread coming out on the 254 * other side with the expectation that the process is about to 255 * exec. 256 */ 257 if (p1->p_flag & P_HADTHREADS) { 258 /* 259 * Idle the other threads for a second. 260 * Since the user space is copied, it must remain stable. 261 * In addition, all threads (from the user perspective) 262 * need to either be suspended or in the kernel, 263 * where they will try restart in the parent and will 264 * be aborted in the child. 265 */ 266 PROC_LOCK(p1); 267 if (thread_single(SINGLE_NO_EXIT)) { 268 /* Abort. Someone else is single threading before us. */ 269 PROC_UNLOCK(p1); 270 return (ERESTART); 271 } 272 PROC_UNLOCK(p1); 273 /* 274 * All other activity in this process 275 * is now suspended at the user boundary, 276 * (or other safe places if we think of any). 277 */ 278 } 279 280 /* Allocate new proc. */ 281 newproc = uma_zalloc(proc_zone, M_WAITOK); 282 #ifdef MAC 283 mac_init_proc(newproc); 284 #endif 285 knlist_init(&newproc->p_klist, &newproc->p_mtx); 286 287 /* We have to lock the process tree while we look for a pid. */ 288 sx_slock(&proctree_lock); 289 290 /* 291 * Although process entries are dynamically created, we still keep 292 * a global limit on the maximum number we will create. Don't allow 293 * a nonprivileged user to use the last ten processes; don't let root 294 * exceed the limit. The variable nprocs is the current number of 295 * processes, maxproc is the limit. 296 */ 297 sx_xlock(&allproc_lock); 298 uid = td->td_ucred->cr_ruid; 299 if ((nprocs >= maxproc - 10 && 300 suser_cred(td->td_ucred, SUSER_RUID) != 0) || 301 nprocs >= maxproc) { 302 error = EAGAIN; 303 goto fail; 304 } 305 306 /* 307 * Increment the count of procs running with this uid. Don't allow 308 * a nonprivileged user to exceed their current limit. 309 */ 310 PROC_LOCK(p1); 311 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 312 (uid != 0) ? lim_cur(p1, RLIMIT_NPROC) : 0); 313 PROC_UNLOCK(p1); 314 if (!ok) { 315 error = EAGAIN; 316 goto fail; 317 } 318 319 /* 320 * Increment the nprocs resource before blocking can occur. There 321 * are hard-limits as to the number of processes that can run. 322 */ 323 nprocs++; 324 325 /* 326 * Find an unused process ID. We remember a range of unused IDs 327 * ready to use (from lastpid+1 through pidchecked-1). 328 * 329 * If RFHIGHPID is set (used during system boot), do not allocate 330 * low-numbered pids. 331 */ 332 trypid = lastpid + 1; 333 if (flags & RFHIGHPID) { 334 if (trypid < 10) 335 trypid = 10; 336 } else { 337 if (randompid) 338 trypid += arc4random() % randompid; 339 } 340 retry: 341 /* 342 * If the process ID prototype has wrapped around, 343 * restart somewhat above 0, as the low-numbered procs 344 * tend to include daemons that don't exit. 345 */ 346 if (trypid >= PID_MAX) { 347 trypid = trypid % PID_MAX; 348 if (trypid < 100) 349 trypid += 100; 350 pidchecked = 0; 351 } 352 if (trypid >= pidchecked) { 353 int doingzomb = 0; 354 355 pidchecked = PID_MAX; 356 /* 357 * Scan the active and zombie procs to check whether this pid 358 * is in use. Remember the lowest pid that's greater 359 * than trypid, so we can avoid checking for a while. 360 */ 361 p2 = LIST_FIRST(&allproc); 362 again: 363 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 364 PROC_LOCK(p2); 365 while (p2->p_pid == trypid || 366 (p2->p_pgrp != NULL && 367 (p2->p_pgrp->pg_id == trypid || 368 (p2->p_session != NULL && 369 p2->p_session->s_sid == trypid)))) { 370 trypid++; 371 if (trypid >= pidchecked) { 372 PROC_UNLOCK(p2); 373 goto retry; 374 } 375 } 376 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 377 pidchecked = p2->p_pid; 378 if (p2->p_pgrp != NULL) { 379 if (p2->p_pgrp->pg_id > trypid && 380 pidchecked > p2->p_pgrp->pg_id) 381 pidchecked = p2->p_pgrp->pg_id; 382 if (p2->p_session != NULL && 383 p2->p_session->s_sid > trypid && 384 pidchecked > p2->p_session->s_sid) 385 pidchecked = p2->p_session->s_sid; 386 } 387 PROC_UNLOCK(p2); 388 } 389 if (!doingzomb) { 390 doingzomb = 1; 391 p2 = LIST_FIRST(&zombproc); 392 goto again; 393 } 394 } 395 sx_sunlock(&proctree_lock); 396 397 /* 398 * RFHIGHPID does not mess with the lastpid counter during boot. 399 */ 400 if (flags & RFHIGHPID) 401 pidchecked = 0; 402 else 403 lastpid = trypid; 404 405 p2 = newproc; 406 p2->p_state = PRS_NEW; /* protect against others */ 407 p2->p_pid = trypid; 408 LIST_INSERT_HEAD(&allproc, p2, p_list); 409 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 410 sx_xunlock(&allproc_lock); 411 412 /* 413 * Malloc things while we don't hold any locks. 414 */ 415 if (flags & RFSIGSHARE) 416 newsigacts = NULL; 417 else 418 newsigacts = sigacts_alloc(); 419 420 /* 421 * Copy filedesc. 422 */ 423 if (flags & RFCFDG) { 424 fd = fdinit(p1->p_fd); 425 fdtol = NULL; 426 } else if (flags & RFFDG) { 427 fd = fdcopy(p1->p_fd); 428 fdtol = NULL; 429 } else { 430 fd = fdshare(p1->p_fd); 431 if (p1->p_fdtol == NULL) 432 p1->p_fdtol = 433 filedesc_to_leader_alloc(NULL, 434 NULL, 435 p1->p_leader); 436 if ((flags & RFTHREAD) != 0) { 437 /* 438 * Shared file descriptor table and 439 * shared process leaders. 440 */ 441 fdtol = p1->p_fdtol; 442 FILEDESC_LOCK_FAST(p1->p_fd); 443 fdtol->fdl_refcount++; 444 FILEDESC_UNLOCK_FAST(p1->p_fd); 445 } else { 446 /* 447 * Shared file descriptor table, and 448 * different process leaders 449 */ 450 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 451 p1->p_fd, 452 p2); 453 } 454 } 455 /* 456 * Make a proc table entry for the new process. 457 * Start by zeroing the section of proc that is zero-initialized, 458 * then copy the section that is copied directly from the parent. 459 */ 460 td2 = FIRST_THREAD_IN_PROC(p2); 461 kg2 = FIRST_KSEGRP_IN_PROC(p2); 462 463 /* Allocate and switch to an alternate kstack if specified. */ 464 if (pages != 0) 465 vm_thread_new_altkstack(td2, pages); 466 467 PROC_LOCK(p2); 468 PROC_LOCK(p1); 469 470 bzero(&p2->p_startzero, 471 __rangeof(struct proc, p_startzero, p_endzero)); 472 bzero(&td2->td_startzero, 473 __rangeof(struct thread, td_startzero, td_endzero)); 474 bzero(&kg2->kg_startzero, 475 __rangeof(struct ksegrp, kg_startzero, kg_endzero)); 476 477 bcopy(&p1->p_startcopy, &p2->p_startcopy, 478 __rangeof(struct proc, p_startcopy, p_endcopy)); 479 bcopy(&td->td_startcopy, &td2->td_startcopy, 480 __rangeof(struct thread, td_startcopy, td_endcopy)); 481 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 482 __rangeof(struct ksegrp, kg_startcopy, kg_endcopy)); 483 484 td2->td_sigstk = td->td_sigstk; 485 486 /* 487 * Duplicate sub-structures as needed. 488 * Increase reference counts on shared objects. 489 */ 490 p2->p_flag = 0; 491 if (p1->p_flag & P_PROFIL) 492 startprofclock(p2); 493 mtx_lock_spin(&sched_lock); 494 p2->p_sflag = PS_INMEM; 495 /* 496 * Allow the scheduler to adjust the priority of the child and 497 * parent while we hold the sched_lock. 498 */ 499 sched_fork(td, td2); 500 501 mtx_unlock_spin(&sched_lock); 502 p2->p_ucred = crhold(td->td_ucred); 503 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 504 505 pargs_hold(p2->p_args); 506 507 if (flags & RFSIGSHARE) { 508 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 509 } else { 510 sigacts_copy(newsigacts, p1->p_sigacts); 511 p2->p_sigacts = newsigacts; 512 } 513 if (flags & RFLINUXTHPN) 514 p2->p_sigparent = SIGUSR1; 515 else 516 p2->p_sigparent = SIGCHLD; 517 518 p2->p_textvp = p1->p_textvp; 519 p2->p_fd = fd; 520 p2->p_fdtol = fdtol; 521 522 /* 523 * p_limit is copy-on-write. Bump its refcount. 524 */ 525 p2->p_limit = lim_hold(p1->p_limit); 526 527 pstats_fork(p1->p_stats, p2->p_stats); 528 529 PROC_UNLOCK(p1); 530 PROC_UNLOCK(p2); 531 532 /* Bump references to the text vnode (for procfs) */ 533 if (p2->p_textvp) 534 vref(p2->p_textvp); 535 536 /* 537 * Set up linkage for kernel based threading. 538 */ 539 if ((flags & RFTHREAD) != 0) { 540 mtx_lock(&ppeers_lock); 541 p2->p_peers = p1->p_peers; 542 p1->p_peers = p2; 543 p2->p_leader = p1->p_leader; 544 mtx_unlock(&ppeers_lock); 545 PROC_LOCK(p1->p_leader); 546 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 547 PROC_UNLOCK(p1->p_leader); 548 /* 549 * The task leader is exiting, so process p1 is 550 * going to be killed shortly. Since p1 obviously 551 * isn't dead yet, we know that the leader is either 552 * sending SIGKILL's to all the processes in this 553 * task or is sleeping waiting for all the peers to 554 * exit. We let p1 complete the fork, but we need 555 * to go ahead and kill the new process p2 since 556 * the task leader may not get a chance to send 557 * SIGKILL to it. We leave it on the list so that 558 * the task leader will wait for this new process 559 * to commit suicide. 560 */ 561 PROC_LOCK(p2); 562 psignal(p2, SIGKILL); 563 PROC_UNLOCK(p2); 564 } else 565 PROC_UNLOCK(p1->p_leader); 566 } else { 567 p2->p_peers = NULL; 568 p2->p_leader = p2; 569 } 570 571 sx_xlock(&proctree_lock); 572 PGRP_LOCK(p1->p_pgrp); 573 PROC_LOCK(p2); 574 PROC_LOCK(p1); 575 576 /* 577 * Preserve some more flags in subprocess. P_PROFIL has already 578 * been preserved. 579 */ 580 p2->p_flag |= p1->p_flag & P_SUGID; 581 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 582 SESS_LOCK(p1->p_session); 583 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 584 p2->p_flag |= P_CONTROLT; 585 SESS_UNLOCK(p1->p_session); 586 if (flags & RFPPWAIT) 587 p2->p_flag |= P_PPWAIT; 588 589 p2->p_pgrp = p1->p_pgrp; 590 LIST_INSERT_AFTER(p1, p2, p_pglist); 591 PGRP_UNLOCK(p1->p_pgrp); 592 LIST_INIT(&p2->p_children); 593 594 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 595 596 #ifdef KTRACE 597 /* 598 * Copy traceflag and tracefile if enabled. 599 */ 600 mtx_lock(&ktrace_mtx); 601 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 602 if (p1->p_traceflag & KTRFAC_INHERIT) { 603 p2->p_traceflag = p1->p_traceflag; 604 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 605 VREF(p2->p_tracevp); 606 KASSERT(p1->p_tracecred != NULL, 607 ("ktrace vnode with no cred")); 608 p2->p_tracecred = crhold(p1->p_tracecred); 609 } 610 } 611 mtx_unlock(&ktrace_mtx); 612 #endif 613 614 /* 615 * If PF_FORK is set, the child process inherits the 616 * procfs ioctl flags from its parent. 617 */ 618 if (p1->p_pfsflags & PF_FORK) { 619 p2->p_stops = p1->p_stops; 620 p2->p_pfsflags = p1->p_pfsflags; 621 } 622 623 /* 624 * This begins the section where we must prevent the parent 625 * from being swapped. 626 */ 627 _PHOLD(p1); 628 PROC_UNLOCK(p1); 629 630 /* 631 * Attach the new process to its parent. 632 * 633 * If RFNOWAIT is set, the newly created process becomes a child 634 * of init. This effectively disassociates the child from the 635 * parent. 636 */ 637 if (flags & RFNOWAIT) 638 pptr = initproc; 639 else 640 pptr = p1; 641 p2->p_pptr = pptr; 642 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 643 sx_xunlock(&proctree_lock); 644 645 /* Inform accounting that we have forked. */ 646 p2->p_acflag = AFORK; 647 PROC_UNLOCK(p2); 648 649 /* 650 * Finish creating the child process. It will return via a different 651 * execution path later. (ie: directly into user mode) 652 */ 653 vm_forkproc(td, p2, td2, flags); 654 655 if (flags == (RFFDG | RFPROC)) { 656 atomic_add_int(&cnt.v_forks, 1); 657 atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize + 658 p2->p_vmspace->vm_ssize); 659 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 660 atomic_add_int(&cnt.v_vforks, 1); 661 atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 662 p2->p_vmspace->vm_ssize); 663 } else if (p1 == &proc0) { 664 atomic_add_int(&cnt.v_kthreads, 1); 665 atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 666 p2->p_vmspace->vm_ssize); 667 } else { 668 atomic_add_int(&cnt.v_rforks, 1); 669 atomic_add_int(&cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 670 p2->p_vmspace->vm_ssize); 671 } 672 673 /* 674 * Both processes are set up, now check if any loadable modules want 675 * to adjust anything. 676 * What if they have an error? XXX 677 */ 678 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 679 680 /* 681 * Set the child start time and mark the process as being complete. 682 */ 683 microuptime(&p2->p_stats->p_start); 684 mtx_lock_spin(&sched_lock); 685 p2->p_state = PRS_NORMAL; 686 687 /* 688 * If RFSTOPPED not requested, make child runnable and add to 689 * run queue. 690 */ 691 if ((flags & RFSTOPPED) == 0) { 692 TD_SET_CAN_RUN(td2); 693 setrunqueue(td2, SRQ_BORING); 694 } 695 mtx_unlock_spin(&sched_lock); 696 697 /* 698 * Now can be swapped. 699 */ 700 PROC_LOCK(p1); 701 _PRELE(p1); 702 703 /* 704 * Tell any interested parties about the new process. 705 */ 706 KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid); 707 708 PROC_UNLOCK(p1); 709 710 /* 711 * Preserve synchronization semantics of vfork. If waiting for 712 * child to exec or exit, set P_PPWAIT on child, and sleep on our 713 * proc (in case of exit). 714 */ 715 PROC_LOCK(p2); 716 while (p2->p_flag & P_PPWAIT) 717 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 718 PROC_UNLOCK(p2); 719 720 /* 721 * If other threads are waiting, let them continue now. 722 */ 723 if (p1->p_flag & P_HADTHREADS) { 724 PROC_LOCK(p1); 725 thread_single_end(); 726 PROC_UNLOCK(p1); 727 } 728 729 /* 730 * Return child proc pointer to parent. 731 */ 732 *procp = p2; 733 return (0); 734 fail: 735 sx_sunlock(&proctree_lock); 736 if (ppsratecheck(&lastfail, &curfail, 1)) 737 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 738 uid); 739 sx_xunlock(&allproc_lock); 740 #ifdef MAC 741 mac_destroy_proc(newproc); 742 #endif 743 uma_zfree(proc_zone, newproc); 744 if (p1->p_flag & P_HADTHREADS) { 745 PROC_LOCK(p1); 746 thread_single_end(); 747 PROC_UNLOCK(p1); 748 } 749 tsleep(&forksleep, PUSER, "fork", hz / 2); 750 return (error); 751 } 752 753 /* 754 * Handle the return of a child process from fork1(). This function 755 * is called from the MD fork_trampoline() entry point. 756 */ 757 void 758 fork_exit(callout, arg, frame) 759 void (*callout)(void *, struct trapframe *); 760 void *arg; 761 struct trapframe *frame; 762 { 763 struct proc *p; 764 struct thread *td; 765 766 /* 767 * Finish setting up thread glue so that it begins execution in a 768 * non-nested critical section with sched_lock held but not recursed. 769 */ 770 td = curthread; 771 p = td->td_proc; 772 td->td_oncpu = PCPU_GET(cpuid); 773 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 774 775 sched_lock.mtx_lock = (uintptr_t)td; 776 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 777 cpu_critical_fork_exit(); 778 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 779 td, td->td_sched, p->p_pid, p->p_comm); 780 781 /* 782 * Processes normally resume in mi_switch() after being 783 * cpu_switch()'ed to, but when children start up they arrive here 784 * instead, so we must do much the same things as mi_switch() would. 785 */ 786 787 if ((td = PCPU_GET(deadthread))) { 788 PCPU_SET(deadthread, NULL); 789 thread_stash(td); 790 } 791 td = curthread; 792 mtx_unlock_spin(&sched_lock); 793 794 /* 795 * cpu_set_fork_handler intercepts this function call to 796 * have this call a non-return function to stay in kernel mode. 797 * initproc has its own fork handler, but it does return. 798 */ 799 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 800 callout(arg, frame); 801 802 /* 803 * Check if a kernel thread misbehaved and returned from its main 804 * function. 805 */ 806 PROC_LOCK(p); 807 if (p->p_flag & P_KTHREAD) { 808 PROC_UNLOCK(p); 809 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 810 p->p_comm, p->p_pid); 811 kthread_exit(0); 812 } 813 PROC_UNLOCK(p); 814 mtx_assert(&Giant, MA_NOTOWNED); 815 } 816 817 /* 818 * Simplified back end of syscall(), used when returning from fork() 819 * directly into user mode. Giant is not held on entry, and must not 820 * be held on return. This function is passed in to fork_exit() as the 821 * first parameter and is called when returning to a new userland process. 822 */ 823 void 824 fork_return(td, frame) 825 struct thread *td; 826 struct trapframe *frame; 827 { 828 829 userret(td, frame, 0); 830 #ifdef KTRACE 831 if (KTRPOINT(td, KTR_SYSRET)) 832 ktrsysret(SYS_fork, 0, 0); 833 #endif 834 mtx_assert(&Giant, MA_NOTOWNED); 835 } 836