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 <security/audit/audit.h> 70 71 #include <vm/vm.h> 72 #include <vm/pmap.h> 73 #include <vm/vm_map.h> 74 #include <vm/vm_extern.h> 75 #include <vm/uma.h> 76 77 78 #ifndef _SYS_SYSPROTO_H_ 79 struct fork_args { 80 int dummy; 81 }; 82 #endif 83 84 static int forksleep; /* Place for fork1() to sleep on. */ 85 86 /* 87 * MPSAFE 88 */ 89 /* ARGSUSED */ 90 int 91 fork(td, uap) 92 struct thread *td; 93 struct fork_args *uap; 94 { 95 int error; 96 struct proc *p2; 97 98 error = fork1(td, RFFDG | RFPROC, 0, &p2); 99 if (error == 0) { 100 td->td_retval[0] = p2->p_pid; 101 td->td_retval[1] = 0; 102 } 103 return (error); 104 } 105 106 /* 107 * MPSAFE 108 */ 109 /* ARGSUSED */ 110 int 111 vfork(td, uap) 112 struct thread *td; 113 struct vfork_args *uap; 114 { 115 int error; 116 struct proc *p2; 117 118 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 119 if (error == 0) { 120 td->td_retval[0] = p2->p_pid; 121 td->td_retval[1] = 0; 122 } 123 return (error); 124 } 125 126 /* 127 * MPSAFE 128 */ 129 int 130 rfork(td, uap) 131 struct thread *td; 132 struct rfork_args *uap; 133 { 134 struct proc *p2; 135 int error; 136 137 /* Don't allow kernel-only flags. */ 138 if ((uap->flags & RFKERNELONLY) != 0) 139 return (EINVAL); 140 141 AUDIT_ARG(fflags, uap->flags); 142 error = fork1(td, uap->flags, 0, &p2); 143 if (error == 0) { 144 td->td_retval[0] = p2 ? p2->p_pid : 0; 145 td->td_retval[1] = 0; 146 } 147 return (error); 148 } 149 150 int nprocs = 1; /* process 0 */ 151 int lastpid = 0; 152 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 153 "Last used PID"); 154 155 /* 156 * Random component to lastpid generation. We mix in a random factor to make 157 * it a little harder to predict. We sanity check the modulus value to avoid 158 * doing it in critical paths. Don't let it be too small or we pointlessly 159 * waste randomness entropy, and don't let it be impossibly large. Using a 160 * modulus that is too big causes a LOT more process table scans and slows 161 * down fork processing as the pidchecked caching is defeated. 162 */ 163 static int randompid = 0; 164 165 static int 166 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 167 { 168 int error, pid; 169 170 error = sysctl_wire_old_buffer(req, sizeof(int)); 171 if (error != 0) 172 return(error); 173 sx_xlock(&allproc_lock); 174 pid = randompid; 175 error = sysctl_handle_int(oidp, &pid, 0, req); 176 if (error == 0 && req->newptr != NULL) { 177 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 178 pid = PID_MAX - 100; 179 else if (pid < 2) /* NOP */ 180 pid = 0; 181 else if (pid < 100) /* Make it reasonable */ 182 pid = 100; 183 randompid = pid; 184 } 185 sx_xunlock(&allproc_lock); 186 return (error); 187 } 188 189 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 190 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 191 192 int 193 fork1(td, flags, pages, procp) 194 struct thread *td; 195 int flags; 196 int pages; 197 struct proc **procp; 198 { 199 struct proc *p1, *p2, *pptr; 200 struct proc *newproc; 201 int ok, trypid; 202 static int curfail, pidchecked = 0; 203 static struct timeval lastfail; 204 struct filedesc *fd; 205 struct filedesc_to_leader *fdtol; 206 struct thread *td2; 207 struct ksegrp *kg2; 208 struct sigacts *newsigacts; 209 int error; 210 211 /* Can't copy and clear. */ 212 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 213 return (EINVAL); 214 215 p1 = td->td_proc; 216 217 /* 218 * Here we don't create a new process, but we divorce 219 * certain parts of a process from itself. 220 */ 221 if ((flags & RFPROC) == 0) { 222 if ((p1->p_flag & P_HADTHREADS) && 223 (flags & (RFCFDG | RFFDG))) { 224 PROC_LOCK(p1); 225 if (thread_single(SINGLE_BOUNDARY)) { 226 PROC_UNLOCK(p1); 227 return (ERESTART); 228 } 229 PROC_UNLOCK(p1); 230 } 231 232 vm_forkproc(td, NULL, NULL, flags); 233 234 /* 235 * Close all file descriptors. 236 */ 237 if (flags & RFCFDG) { 238 struct filedesc *fdtmp; 239 fdtmp = fdinit(td->td_proc->p_fd); 240 fdfree(td); 241 p1->p_fd = fdtmp; 242 } 243 244 /* 245 * Unshare file descriptors (from parent). 246 */ 247 if (flags & RFFDG) 248 fdunshare(p1, td); 249 250 if ((p1->p_flag & P_HADTHREADS) && 251 (flags & (RFCFDG | RFFDG))) { 252 PROC_LOCK(p1); 253 thread_single_end(); 254 PROC_UNLOCK(p1); 255 } 256 *procp = NULL; 257 return (0); 258 } 259 260 /* 261 * Note 1:1 allows for forking with one thread coming out on the 262 * other side with the expectation that the process is about to 263 * exec. 264 */ 265 if (p1->p_flag & P_HADTHREADS) { 266 /* 267 * Idle the other threads for a second. 268 * Since the user space is copied, it must remain stable. 269 * In addition, all threads (from the user perspective) 270 * need to either be suspended or in the kernel, 271 * where they will try restart in the parent and will 272 * be aborted in the child. 273 */ 274 PROC_LOCK(p1); 275 if (thread_single(SINGLE_NO_EXIT)) { 276 /* Abort. Someone else is single threading before us. */ 277 PROC_UNLOCK(p1); 278 return (ERESTART); 279 } 280 PROC_UNLOCK(p1); 281 /* 282 * All other activity in this process 283 * is now suspended at the user boundary, 284 * (or other safe places if we think of any). 285 */ 286 } 287 288 /* Allocate new proc. */ 289 newproc = uma_zalloc(proc_zone, M_WAITOK); 290 #ifdef MAC 291 mac_init_proc(newproc); 292 #endif 293 #ifdef AUDIT 294 audit_proc_alloc(newproc); 295 #endif 296 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL); 297 STAILQ_INIT(&newproc->p_ktr); 298 299 /* We have to lock the process tree while we look for a pid. */ 300 sx_slock(&proctree_lock); 301 302 /* 303 * Although process entries are dynamically created, we still keep 304 * a global limit on the maximum number we will create. Don't allow 305 * a nonprivileged user to use the last ten processes; don't let root 306 * exceed the limit. The variable nprocs is the current number of 307 * processes, maxproc is the limit. 308 */ 309 sx_xlock(&allproc_lock); 310 if ((nprocs >= maxproc - 10 && 311 suser_cred(td->td_ucred, SUSER_RUID) != 0) || 312 nprocs >= maxproc) { 313 error = EAGAIN; 314 goto fail; 315 } 316 317 /* 318 * Increment the count of procs running with this uid. Don't allow 319 * a nonprivileged user to exceed their current limit. 320 */ 321 error = suser_cred(td->td_ucred, SUSER_RUID | SUSER_ALLOWJAIL); 322 if (error == 0) 323 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 324 else { 325 PROC_LOCK(p1); 326 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 327 lim_cur(p1, RLIMIT_NPROC)); 328 PROC_UNLOCK(p1); 329 } 330 if (!ok) { 331 error = EAGAIN; 332 goto fail; 333 } 334 335 /* 336 * Increment the nprocs resource before blocking can occur. There 337 * are hard-limits as to the number of processes that can run. 338 */ 339 nprocs++; 340 341 /* 342 * Find an unused process ID. We remember a range of unused IDs 343 * ready to use (from lastpid+1 through pidchecked-1). 344 * 345 * If RFHIGHPID is set (used during system boot), do not allocate 346 * low-numbered pids. 347 */ 348 trypid = lastpid + 1; 349 if (flags & RFHIGHPID) { 350 if (trypid < 10) 351 trypid = 10; 352 } else { 353 if (randompid) 354 trypid += arc4random() % randompid; 355 } 356 retry: 357 /* 358 * If the process ID prototype has wrapped around, 359 * restart somewhat above 0, as the low-numbered procs 360 * tend to include daemons that don't exit. 361 */ 362 if (trypid >= PID_MAX) { 363 trypid = trypid % PID_MAX; 364 if (trypid < 100) 365 trypid += 100; 366 pidchecked = 0; 367 } 368 if (trypid >= pidchecked) { 369 int doingzomb = 0; 370 371 pidchecked = PID_MAX; 372 /* 373 * Scan the active and zombie procs to check whether this pid 374 * is in use. Remember the lowest pid that's greater 375 * than trypid, so we can avoid checking for a while. 376 */ 377 p2 = LIST_FIRST(&allproc); 378 again: 379 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 380 while (p2->p_pid == trypid || 381 (p2->p_pgrp != NULL && 382 (p2->p_pgrp->pg_id == trypid || 383 (p2->p_session != NULL && 384 p2->p_session->s_sid == trypid)))) { 385 trypid++; 386 if (trypid >= pidchecked) 387 goto retry; 388 } 389 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 390 pidchecked = p2->p_pid; 391 if (p2->p_pgrp != NULL) { 392 if (p2->p_pgrp->pg_id > trypid && 393 pidchecked > p2->p_pgrp->pg_id) 394 pidchecked = p2->p_pgrp->pg_id; 395 if (p2->p_session != NULL && 396 p2->p_session->s_sid > trypid && 397 pidchecked > p2->p_session->s_sid) 398 pidchecked = p2->p_session->s_sid; 399 } 400 } 401 if (!doingzomb) { 402 doingzomb = 1; 403 p2 = LIST_FIRST(&zombproc); 404 goto again; 405 } 406 } 407 sx_sunlock(&proctree_lock); 408 409 /* 410 * RFHIGHPID does not mess with the lastpid counter during boot. 411 */ 412 if (flags & RFHIGHPID) 413 pidchecked = 0; 414 else 415 lastpid = trypid; 416 417 p2 = newproc; 418 p2->p_state = PRS_NEW; /* protect against others */ 419 p2->p_pid = trypid; 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 sx_xunlock(&allproc_lock); 424 425 /* 426 * Malloc things while we don't hold any locks. 427 */ 428 if (flags & RFSIGSHARE) 429 newsigacts = NULL; 430 else 431 newsigacts = sigacts_alloc(); 432 433 /* 434 * Copy filedesc. 435 */ 436 if (flags & RFCFDG) { 437 fd = fdinit(p1->p_fd); 438 fdtol = NULL; 439 } else if (flags & RFFDG) { 440 fd = fdcopy(p1->p_fd); 441 fdtol = NULL; 442 } else { 443 fd = fdshare(p1->p_fd); 444 if (p1->p_fdtol == NULL) 445 p1->p_fdtol = 446 filedesc_to_leader_alloc(NULL, 447 NULL, 448 p1->p_leader); 449 if ((flags & RFTHREAD) != 0) { 450 /* 451 * Shared file descriptor table and 452 * shared process leaders. 453 */ 454 fdtol = p1->p_fdtol; 455 FILEDESC_LOCK_FAST(p1->p_fd); 456 fdtol->fdl_refcount++; 457 FILEDESC_UNLOCK_FAST(p1->p_fd); 458 } else { 459 /* 460 * Shared file descriptor table, and 461 * different process leaders 462 */ 463 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 464 p1->p_fd, 465 p2); 466 } 467 } 468 /* 469 * Make a proc table entry for the new process. 470 * Start by zeroing the section of proc that is zero-initialized, 471 * then copy the section that is copied directly from the parent. 472 */ 473 td2 = FIRST_THREAD_IN_PROC(p2); 474 kg2 = FIRST_KSEGRP_IN_PROC(p2); 475 476 /* Allocate and switch to an alternate kstack if specified. */ 477 if (pages != 0) 478 vm_thread_new_altkstack(td2, pages); 479 480 PROC_LOCK(p2); 481 PROC_LOCK(p1); 482 483 bzero(&p2->p_startzero, 484 __rangeof(struct proc, p_startzero, p_endzero)); 485 bzero(&td2->td_startzero, 486 __rangeof(struct thread, td_startzero, td_endzero)); 487 bzero(&kg2->kg_startzero, 488 __rangeof(struct ksegrp, kg_startzero, kg_endzero)); 489 490 bcopy(&p1->p_startcopy, &p2->p_startcopy, 491 __rangeof(struct proc, p_startcopy, p_endcopy)); 492 bcopy(&td->td_startcopy, &td2->td_startcopy, 493 __rangeof(struct thread, td_startcopy, td_endcopy)); 494 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 495 __rangeof(struct ksegrp, kg_startcopy, kg_endcopy)); 496 497 td2->td_sigstk = td->td_sigstk; 498 td2->td_sigmask = td->td_sigmask; 499 500 /* 501 * Duplicate sub-structures as needed. 502 * Increase reference counts on shared objects. 503 */ 504 p2->p_flag = 0; 505 if (p1->p_flag & P_PROFIL) 506 startprofclock(p2); 507 mtx_lock_spin(&sched_lock); 508 p2->p_sflag = PS_INMEM; 509 /* 510 * Allow the scheduler to adjust the priority of the child and 511 * parent while we hold the sched_lock. 512 */ 513 sched_fork(td, td2); 514 515 mtx_unlock_spin(&sched_lock); 516 p2->p_ucred = crhold(td->td_ucred); 517 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 518 #ifdef AUDIT 519 audit_proc_fork(p1, p2); 520 #endif 521 pargs_hold(p2->p_args); 522 523 if (flags & RFSIGSHARE) { 524 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 525 } else { 526 sigacts_copy(newsigacts, p1->p_sigacts); 527 p2->p_sigacts = newsigacts; 528 } 529 if (flags & RFLINUXTHPN) 530 p2->p_sigparent = SIGUSR1; 531 else 532 p2->p_sigparent = SIGCHLD; 533 534 p2->p_textvp = p1->p_textvp; 535 p2->p_fd = fd; 536 p2->p_fdtol = fdtol; 537 538 /* 539 * p_limit is copy-on-write. Bump its refcount. 540 */ 541 p2->p_limit = lim_hold(p1->p_limit); 542 543 pstats_fork(p1->p_stats, p2->p_stats); 544 545 PROC_UNLOCK(p1); 546 PROC_UNLOCK(p2); 547 548 /* Bump references to the text vnode (for procfs) */ 549 if (p2->p_textvp) 550 vref(p2->p_textvp); 551 552 /* 553 * Set up linkage for kernel based threading. 554 */ 555 if ((flags & RFTHREAD) != 0) { 556 mtx_lock(&ppeers_lock); 557 p2->p_peers = p1->p_peers; 558 p1->p_peers = p2; 559 p2->p_leader = p1->p_leader; 560 mtx_unlock(&ppeers_lock); 561 PROC_LOCK(p1->p_leader); 562 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 563 PROC_UNLOCK(p1->p_leader); 564 /* 565 * The task leader is exiting, so process p1 is 566 * going to be killed shortly. Since p1 obviously 567 * isn't dead yet, we know that the leader is either 568 * sending SIGKILL's to all the processes in this 569 * task or is sleeping waiting for all the peers to 570 * exit. We let p1 complete the fork, but we need 571 * to go ahead and kill the new process p2 since 572 * the task leader may not get a chance to send 573 * SIGKILL to it. We leave it on the list so that 574 * the task leader will wait for this new process 575 * to commit suicide. 576 */ 577 PROC_LOCK(p2); 578 psignal(p2, SIGKILL); 579 PROC_UNLOCK(p2); 580 } else 581 PROC_UNLOCK(p1->p_leader); 582 } else { 583 p2->p_peers = NULL; 584 p2->p_leader = p2; 585 } 586 587 sx_xlock(&proctree_lock); 588 PGRP_LOCK(p1->p_pgrp); 589 PROC_LOCK(p2); 590 PROC_LOCK(p1); 591 592 /* 593 * Preserve some more flags in subprocess. P_PROFIL has already 594 * been preserved. 595 */ 596 p2->p_flag |= p1->p_flag & P_SUGID; 597 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 598 SESS_LOCK(p1->p_session); 599 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 600 p2->p_flag |= P_CONTROLT; 601 SESS_UNLOCK(p1->p_session); 602 if (flags & RFPPWAIT) 603 p2->p_flag |= P_PPWAIT; 604 605 p2->p_pgrp = p1->p_pgrp; 606 LIST_INSERT_AFTER(p1, p2, p_pglist); 607 PGRP_UNLOCK(p1->p_pgrp); 608 LIST_INIT(&p2->p_children); 609 610 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 611 612 #ifdef KTRACE 613 /* 614 * Copy traceflag and tracefile if enabled. 615 */ 616 mtx_lock(&ktrace_mtx); 617 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 618 if (p1->p_traceflag & KTRFAC_INHERIT) { 619 p2->p_traceflag = p1->p_traceflag; 620 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 621 VREF(p2->p_tracevp); 622 KASSERT(p1->p_tracecred != NULL, 623 ("ktrace vnode with no cred")); 624 p2->p_tracecred = crhold(p1->p_tracecred); 625 } 626 } 627 mtx_unlock(&ktrace_mtx); 628 #endif 629 630 /* 631 * If PF_FORK is set, the child process inherits the 632 * procfs ioctl flags from its parent. 633 */ 634 if (p1->p_pfsflags & PF_FORK) { 635 p2->p_stops = p1->p_stops; 636 p2->p_pfsflags = p1->p_pfsflags; 637 } 638 639 /* 640 * This begins the section where we must prevent the parent 641 * from being swapped. 642 */ 643 _PHOLD(p1); 644 PROC_UNLOCK(p1); 645 646 /* 647 * Attach the new process to its parent. 648 * 649 * If RFNOWAIT is set, the newly created process becomes a child 650 * of init. This effectively disassociates the child from the 651 * parent. 652 */ 653 if (flags & RFNOWAIT) 654 pptr = initproc; 655 else 656 pptr = p1; 657 p2->p_pptr = pptr; 658 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 659 sx_xunlock(&proctree_lock); 660 661 /* Inform accounting that we have forked. */ 662 p2->p_acflag = AFORK; 663 PROC_UNLOCK(p2); 664 665 /* 666 * Finish creating the child process. It will return via a different 667 * execution path later. (ie: directly into user mode) 668 */ 669 vm_forkproc(td, p2, td2, flags); 670 671 if (flags == (RFFDG | RFPROC)) { 672 atomic_add_int(&cnt.v_forks, 1); 673 atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize + 674 p2->p_vmspace->vm_ssize); 675 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 676 atomic_add_int(&cnt.v_vforks, 1); 677 atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 678 p2->p_vmspace->vm_ssize); 679 } else if (p1 == &proc0) { 680 atomic_add_int(&cnt.v_kthreads, 1); 681 atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 682 p2->p_vmspace->vm_ssize); 683 } else { 684 atomic_add_int(&cnt.v_rforks, 1); 685 atomic_add_int(&cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 686 p2->p_vmspace->vm_ssize); 687 } 688 689 /* 690 * Both processes are set up, now check if any loadable modules want 691 * to adjust anything. 692 * What if they have an error? XXX 693 */ 694 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 695 696 /* 697 * Set the child start time and mark the process as being complete. 698 */ 699 microuptime(&p2->p_stats->p_start); 700 mtx_lock_spin(&sched_lock); 701 p2->p_state = PRS_NORMAL; 702 703 /* 704 * If RFSTOPPED not requested, make child runnable and add to 705 * run queue. 706 */ 707 if ((flags & RFSTOPPED) == 0) { 708 TD_SET_CAN_RUN(td2); 709 setrunqueue(td2, SRQ_BORING); 710 } 711 mtx_unlock_spin(&sched_lock); 712 713 /* 714 * Now can be swapped. 715 */ 716 PROC_LOCK(p1); 717 _PRELE(p1); 718 719 /* 720 * Tell any interested parties about the new process. 721 */ 722 KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid); 723 724 PROC_UNLOCK(p1); 725 726 /* 727 * Preserve synchronization semantics of vfork. If waiting for 728 * child to exec or exit, set P_PPWAIT on child, and sleep on our 729 * proc (in case of exit). 730 */ 731 PROC_LOCK(p2); 732 while (p2->p_flag & P_PPWAIT) 733 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 734 PROC_UNLOCK(p2); 735 736 /* 737 * If other threads are waiting, let them continue now. 738 */ 739 if (p1->p_flag & P_HADTHREADS) { 740 PROC_LOCK(p1); 741 thread_single_end(); 742 PROC_UNLOCK(p1); 743 } 744 745 /* 746 * Return child proc pointer to parent. 747 */ 748 *procp = p2; 749 return (0); 750 fail: 751 sx_sunlock(&proctree_lock); 752 if (ppsratecheck(&lastfail, &curfail, 1)) 753 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 754 td->td_ucred->cr_ruid); 755 sx_xunlock(&allproc_lock); 756 #ifdef MAC 757 mac_destroy_proc(newproc); 758 #endif 759 #ifdef AUDIT 760 audit_proc_free(newproc); 761 #endif 762 uma_zfree(proc_zone, newproc); 763 if (p1->p_flag & P_HADTHREADS) { 764 PROC_LOCK(p1); 765 thread_single_end(); 766 PROC_UNLOCK(p1); 767 } 768 tsleep(&forksleep, PUSER, "fork", hz / 2); 769 return (error); 770 } 771 772 /* 773 * Handle the return of a child process from fork1(). This function 774 * is called from the MD fork_trampoline() entry point. 775 */ 776 void 777 fork_exit(callout, arg, frame) 778 void (*callout)(void *, struct trapframe *); 779 void *arg; 780 struct trapframe *frame; 781 { 782 struct proc *p; 783 struct thread *td; 784 785 /* 786 * Finish setting up thread glue so that it begins execution in a 787 * non-nested critical section with sched_lock held but not recursed. 788 */ 789 td = curthread; 790 p = td->td_proc; 791 td->td_oncpu = PCPU_GET(cpuid); 792 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 793 794 sched_lock.mtx_lock = (uintptr_t)td; 795 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 796 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 797 td, td->td_sched, p->p_pid, p->p_comm); 798 799 /* 800 * Processes normally resume in mi_switch() after being 801 * cpu_switch()'ed to, but when children start up they arrive here 802 * instead, so we must do much the same things as mi_switch() would. 803 */ 804 805 if ((td = PCPU_GET(deadthread))) { 806 PCPU_SET(deadthread, NULL); 807 thread_stash(td); 808 } 809 td = curthread; 810 mtx_unlock_spin(&sched_lock); 811 812 /* 813 * cpu_set_fork_handler intercepts this function call to 814 * have this call a non-return function to stay in kernel mode. 815 * initproc has its own fork handler, but it does return. 816 */ 817 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 818 callout(arg, frame); 819 820 /* 821 * Check if a kernel thread misbehaved and returned from its main 822 * function. 823 */ 824 if (p->p_flag & P_KTHREAD) { 825 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 826 p->p_comm, p->p_pid); 827 kthread_exit(0); 828 } 829 mtx_assert(&Giant, MA_NOTOWNED); 830 } 831 832 /* 833 * Simplified back end of syscall(), used when returning from fork() 834 * directly into user mode. Giant is not held on entry, and must not 835 * be held on return. This function is passed in to fork_exit() as the 836 * first parameter and is called when returning to a new userland process. 837 */ 838 void 839 fork_return(td, frame) 840 struct thread *td; 841 struct trapframe *frame; 842 { 843 844 userret(td, frame); 845 #ifdef KTRACE 846 if (KTRPOINT(td, KTR_SYSRET)) 847 ktrsysret(SYS_fork, 0, 0); 848 #endif 849 mtx_assert(&Giant, MA_NOTOWNED); 850 } 851