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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 39 */ 40 41 #include <sys/cdefs.h> 42 __FBSDID("$FreeBSD$"); 43 44 #include "opt_ktrace.h" 45 #include "opt_mac.h" 46 47 #include <sys/param.h> 48 #include <sys/systm.h> 49 #include <sys/sysproto.h> 50 #include <sys/eventhandler.h> 51 #include <sys/filedesc.h> 52 #include <sys/kernel.h> 53 #include <sys/kthread.h> 54 #include <sys/sysctl.h> 55 #include <sys/lock.h> 56 #include <sys/malloc.h> 57 #include <sys/mutex.h> 58 #include <sys/proc.h> 59 #include <sys/pioctl.h> 60 #include <sys/resourcevar.h> 61 #include <sys/sched.h> 62 #include <sys/syscall.h> 63 #include <sys/vmmeter.h> 64 #include <sys/vnode.h> 65 #include <sys/acct.h> 66 #include <sys/mac.h> 67 #include <sys/ktr.h> 68 #include <sys/ktrace.h> 69 #include <sys/unistd.h> 70 #include <sys/sx.h> 71 72 #include <vm/vm.h> 73 #include <vm/pmap.h> 74 #include <vm/vm_map.h> 75 #include <vm/vm_extern.h> 76 #include <vm/uma.h> 77 78 #include <sys/user.h> 79 #include <machine/critical.h> 80 81 #ifndef _SYS_SYSPROTO_H_ 82 struct fork_args { 83 int dummy; 84 }; 85 #endif 86 87 static int forksleep; /* Place for fork1() to sleep on. */ 88 89 /* 90 * MPSAFE 91 */ 92 /* ARGSUSED */ 93 int 94 fork(td, uap) 95 struct thread *td; 96 struct fork_args *uap; 97 { 98 int error; 99 struct proc *p2; 100 101 error = fork1(td, RFFDG | RFPROC, 0, &p2); 102 if (error == 0) { 103 td->td_retval[0] = p2->p_pid; 104 td->td_retval[1] = 0; 105 } 106 return (error); 107 } 108 109 /* 110 * MPSAFE 111 */ 112 /* ARGSUSED */ 113 int 114 vfork(td, uap) 115 struct thread *td; 116 struct vfork_args *uap; 117 { 118 int error; 119 struct proc *p2; 120 121 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 122 if (error == 0) { 123 td->td_retval[0] = p2->p_pid; 124 td->td_retval[1] = 0; 125 } 126 return (error); 127 } 128 129 /* 130 * MPSAFE 131 */ 132 int 133 rfork(td, uap) 134 struct thread *td; 135 struct rfork_args *uap; 136 { 137 int error; 138 struct proc *p2; 139 140 /* Don't allow kernel only flags. */ 141 if ((uap->flags & RFKERNELONLY) != 0) 142 return (EINVAL); 143 error = fork1(td, uap->flags, 0, &p2); 144 if (error == 0) { 145 td->td_retval[0] = p2 ? p2->p_pid : 0; 146 td->td_retval[1] = 0; 147 } 148 return (error); 149 } 150 151 int nprocs = 1; /* process 0 */ 152 int lastpid = 0; 153 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 154 "Last used PID"); 155 156 /* 157 * Random component to lastpid generation. We mix in a random factor to make 158 * it a little harder to predict. We sanity check the modulus value to avoid 159 * doing it in critical paths. Don't let it be too small or we pointlessly 160 * waste randomness entropy, and don't let it be impossibly large. Using a 161 * modulus that is too big causes a LOT more process table scans and slows 162 * down fork processing as the pidchecked caching is defeated. 163 */ 164 static int randompid = 0; 165 166 static int 167 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 168 { 169 int error, pid; 170 171 sysctl_wire_old_buffer(req, sizeof(int)); 172 sx_xlock(&allproc_lock); 173 pid = randompid; 174 error = sysctl_handle_int(oidp, &pid, 0, req); 175 if (error == 0 && req->newptr != NULL) { 176 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 177 pid = PID_MAX - 100; 178 else if (pid < 2) /* NOP */ 179 pid = 0; 180 else if (pid < 100) /* Make it reasonable */ 181 pid = 100; 182 randompid = pid; 183 } 184 sx_xunlock(&allproc_lock); 185 return (error); 186 } 187 188 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 189 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 190 191 int 192 fork1(td, flags, pages, procp) 193 struct thread *td; 194 int flags; 195 int pages; 196 struct proc **procp; 197 { 198 struct proc *p1, *p2, *pptr; 199 uid_t uid; 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 kse *ke2; 208 struct ksegrp *kg2; 209 struct sigacts *newsigacts; 210 int error; 211 212 /* Can't copy and clear. */ 213 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 214 return (EINVAL); 215 216 p1 = td->td_proc; 217 mtx_lock(&Giant); 218 219 /* 220 * Here we don't create a new process, but we divorce 221 * certain parts of a process from itself. 222 */ 223 if ((flags & RFPROC) == 0) { 224 vm_forkproc(td, NULL, NULL, flags); 225 226 /* 227 * Close all file descriptors. 228 */ 229 if (flags & RFCFDG) { 230 struct filedesc *fdtmp; 231 fdtmp = fdinit(td->td_proc->p_fd); 232 fdfree(td); 233 p1->p_fd = fdtmp; 234 } 235 236 /* 237 * Unshare file descriptors (from parent.) 238 */ 239 if (flags & RFFDG) { 240 FILEDESC_LOCK(p1->p_fd); 241 if (p1->p_fd->fd_refcnt > 1) { 242 struct filedesc *newfd; 243 244 newfd = fdcopy(td->td_proc->p_fd); 245 FILEDESC_UNLOCK(p1->p_fd); 246 fdfree(td); 247 p1->p_fd = newfd; 248 } else 249 FILEDESC_UNLOCK(p1->p_fd); 250 } 251 mtx_unlock(&Giant); 252 *procp = NULL; 253 return (0); 254 } 255 256 /* 257 * Note 1:1 allows for forking with one thread coming out on the 258 * other side with the expectation that the process is about to 259 * exec. 260 */ 261 if (p1->p_flag & P_SA) { 262 /* 263 * Idle the other threads for a second. 264 * Since the user space is copied, it must remain stable. 265 * In addition, all threads (from the user perspective) 266 * need to either be suspended or in the kernel, 267 * where they will try restart in the parent and will 268 * be aborted in the child. 269 */ 270 PROC_LOCK(p1); 271 if (thread_single(SINGLE_NO_EXIT)) { 272 /* Abort.. someone else is single threading before us */ 273 PROC_UNLOCK(p1); 274 mtx_unlock(&Giant); 275 return (ERESTART); 276 } 277 PROC_UNLOCK(p1); 278 /* 279 * All other activity in this process 280 * is now suspended at the user boundary, 281 * (or other safe places if we think of any). 282 */ 283 } 284 285 /* Allocate new proc. */ 286 newproc = uma_zalloc(proc_zone, M_WAITOK); 287 #ifdef MAC 288 mac_init_proc(newproc); 289 #endif 290 291 /* 292 * Although process entries are dynamically created, we still keep 293 * a global limit on the maximum number we will create. Don't allow 294 * a nonprivileged user to use the last ten processes; don't let root 295 * exceed the limit. The variable nprocs is the current number of 296 * processes, maxproc is the limit. 297 */ 298 sx_xlock(&allproc_lock); 299 uid = td->td_ucred->cr_ruid; 300 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 301 error = EAGAIN; 302 goto fail; 303 } 304 305 /* 306 * Increment the count of procs running with this uid. Don't allow 307 * a nonprivileged user to exceed their current limit. 308 */ 309 PROC_LOCK(p1); 310 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 311 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 312 PROC_UNLOCK(p1); 313 if (!ok) { 314 error = EAGAIN; 315 goto fail; 316 } 317 318 /* 319 * Increment the nprocs resource before blocking can occur. There 320 * are hard-limits as to the number of processes that can run. 321 */ 322 nprocs++; 323 324 /* 325 * Find an unused process ID. We remember a range of unused IDs 326 * ready to use (from lastpid+1 through pidchecked-1). 327 * 328 * If RFHIGHPID is set (used during system boot), do not allocate 329 * low-numbered pids. 330 */ 331 trypid = lastpid + 1; 332 if (flags & RFHIGHPID) { 333 if (trypid < 10) 334 trypid = 10; 335 } else { 336 if (randompid) 337 trypid += arc4random() % randompid; 338 } 339 retry: 340 /* 341 * If the process ID prototype has wrapped around, 342 * restart somewhat above 0, as the low-numbered procs 343 * tend to include daemons that don't exit. 344 */ 345 if (trypid >= PID_MAX) { 346 trypid = trypid % PID_MAX; 347 if (trypid < 100) 348 trypid += 100; 349 pidchecked = 0; 350 } 351 if (trypid >= pidchecked) { 352 int doingzomb = 0; 353 354 pidchecked = PID_MAX; 355 /* 356 * Scan the active and zombie procs to check whether this pid 357 * is in use. Remember the lowest pid that's greater 358 * than trypid, so we can avoid checking for a while. 359 */ 360 p2 = LIST_FIRST(&allproc); 361 again: 362 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 363 PROC_LOCK(p2); 364 while (p2->p_pid == trypid || 365 p2->p_pgrp->pg_id == trypid || 366 p2->p_session->s_sid == trypid) { 367 trypid++; 368 if (trypid >= pidchecked) { 369 PROC_UNLOCK(p2); 370 goto retry; 371 } 372 } 373 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 374 pidchecked = p2->p_pid; 375 if (p2->p_pgrp->pg_id > trypid && 376 pidchecked > p2->p_pgrp->pg_id) 377 pidchecked = p2->p_pgrp->pg_id; 378 if (p2->p_session->s_sid > trypid && 379 pidchecked > p2->p_session->s_sid) 380 pidchecked = p2->p_session->s_sid; 381 PROC_UNLOCK(p2); 382 } 383 if (!doingzomb) { 384 doingzomb = 1; 385 p2 = LIST_FIRST(&zombproc); 386 goto again; 387 } 388 } 389 390 /* 391 * RFHIGHPID does not mess with the lastpid counter during boot. 392 */ 393 if (flags & RFHIGHPID) 394 pidchecked = 0; 395 else 396 lastpid = trypid; 397 398 p2 = newproc; 399 p2->p_state = PRS_NEW; /* protect against others */ 400 p2->p_pid = trypid; 401 LIST_INSERT_HEAD(&allproc, p2, p_list); 402 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 403 sx_xunlock(&allproc_lock); 404 405 /* 406 * Malloc things while we don't hold any locks. 407 */ 408 if (flags & RFSIGSHARE) 409 newsigacts = NULL; 410 else 411 newsigacts = sigacts_alloc(); 412 413 /* 414 * Copy filedesc. 415 */ 416 if (flags & RFCFDG) { 417 fd = fdinit(td->td_proc->p_fd); 418 fdtol = NULL; 419 } else if (flags & RFFDG) { 420 FILEDESC_LOCK(p1->p_fd); 421 fd = fdcopy(td->td_proc->p_fd); 422 FILEDESC_UNLOCK(p1->p_fd); 423 fdtol = NULL; 424 } else { 425 fd = fdshare(p1->p_fd); 426 if (p1->p_fdtol == NULL) 427 p1->p_fdtol = 428 filedesc_to_leader_alloc(NULL, 429 NULL, 430 p1->p_leader); 431 if ((flags & RFTHREAD) != 0) { 432 /* 433 * Shared file descriptor table and 434 * shared process leaders. 435 */ 436 fdtol = p1->p_fdtol; 437 FILEDESC_LOCK(p1->p_fd); 438 fdtol->fdl_refcount++; 439 FILEDESC_UNLOCK(p1->p_fd); 440 } else { 441 /* 442 * Shared file descriptor table, and 443 * different process leaders 444 */ 445 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 446 p1->p_fd, 447 p2); 448 } 449 } 450 /* 451 * Make a proc table entry for the new process. 452 * Start by zeroing the section of proc that is zero-initialized, 453 * then copy the section that is copied directly from the parent. 454 */ 455 td2 = FIRST_THREAD_IN_PROC(p2); 456 kg2 = FIRST_KSEGRP_IN_PROC(p2); 457 ke2 = FIRST_KSE_IN_KSEGRP(kg2); 458 459 /* Allocate and switch to an alternate kstack if specified */ 460 if (pages != 0) 461 vm_thread_new_altkstack(td2, pages); 462 463 PROC_LOCK(p2); 464 PROC_LOCK(p1); 465 466 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 467 468 bzero(&p2->p_startzero, 469 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 470 bzero(&ke2->ke_startzero, 471 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 472 bzero(&td2->td_startzero, 473 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 474 bzero(&kg2->kg_startzero, 475 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 476 477 bcopy(&p1->p_startcopy, &p2->p_startcopy, 478 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 479 bcopy(&td->td_startcopy, &td2->td_startcopy, 480 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 481 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 482 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 483 #undef RANGEOF 484 485 td2->td_sigstk = td->td_sigstk; 486 487 /* Set up the thread as an active thread (as if runnable). */ 488 ke2->ke_state = KES_THREAD; 489 ke2->ke_thread = td2; 490 td2->td_kse = ke2; 491 492 /* 493 * Duplicate sub-structures as needed. 494 * Increase reference counts on shared objects. 495 * The p_stats substruct is set in vm_forkproc. 496 */ 497 p2->p_flag = 0; 498 if (p1->p_flag & P_PROFIL) 499 startprofclock(p2); 500 mtx_lock_spin(&sched_lock); 501 p2->p_sflag = PS_INMEM; 502 /* 503 * Allow the scheduler to adjust the priority of the child and 504 * parent while we hold the sched_lock. 505 */ 506 sched_fork(p1, p2); 507 508 mtx_unlock_spin(&sched_lock); 509 p2->p_ucred = crhold(td->td_ucred); 510 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 511 512 pargs_hold(p2->p_args); 513 514 if (flags & RFSIGSHARE) { 515 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 516 } else { 517 sigacts_copy(newsigacts, p1->p_sigacts); 518 p2->p_sigacts = newsigacts; 519 } 520 if (flags & RFLINUXTHPN) 521 p2->p_sigparent = SIGUSR1; 522 else 523 p2->p_sigparent = SIGCHLD; 524 525 /* Bump references to the text vnode (for procfs) */ 526 p2->p_textvp = p1->p_textvp; 527 if (p2->p_textvp) 528 VREF(p2->p_textvp); 529 p2->p_fd = fd; 530 p2->p_fdtol = fdtol; 531 PROC_UNLOCK(p1); 532 PROC_UNLOCK(p2); 533 534 /* 535 * p_limit is copy-on-write, bump refcnt, 536 */ 537 p2->p_limit = p1->p_limit; 538 p2->p_limit->p_refcnt++; 539 540 /* 541 * Setup linkage for kernel based threading 542 */ 543 if((flags & RFTHREAD) != 0) { 544 mtx_lock(&ppeers_lock); 545 p2->p_peers = p1->p_peers; 546 p1->p_peers = p2; 547 p2->p_leader = p1->p_leader; 548 mtx_unlock(&ppeers_lock); 549 PROC_LOCK(p1->p_leader); 550 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 551 PROC_UNLOCK(p1->p_leader); 552 /* 553 * The task leader is exiting, so process p1 is 554 * going to be killed shortly. Since p1 obviously 555 * isn't dead yet, we know that the leader is either 556 * sending SIGKILL's to all the processes in this 557 * task or is sleeping waiting for all the peers to 558 * exit. We let p1 complete the fork, but we need 559 * to go ahead and kill the new process p2 since 560 * the task leader may not get a chance to send 561 * SIGKILL to it. We leave it on the list so that 562 * the task leader will wait for this new process 563 * to commit suicide. 564 */ 565 PROC_LOCK(p2); 566 psignal(p2, SIGKILL); 567 PROC_UNLOCK(p2); 568 } else 569 PROC_UNLOCK(p1->p_leader); 570 } else { 571 p2->p_peers = NULL; 572 p2->p_leader = p2; 573 } 574 575 sx_xlock(&proctree_lock); 576 PGRP_LOCK(p1->p_pgrp); 577 PROC_LOCK(p2); 578 PROC_LOCK(p1); 579 580 /* 581 * Preserve some more flags in subprocess. P_PROFIL has already 582 * been preserved. 583 */ 584 p2->p_flag |= p1->p_flag & P_SUGID; 585 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 586 SESS_LOCK(p1->p_session); 587 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 588 p2->p_flag |= P_CONTROLT; 589 SESS_UNLOCK(p1->p_session); 590 if (flags & RFPPWAIT) 591 p2->p_flag |= P_PPWAIT; 592 593 p2->p_pgrp = p1->p_pgrp; 594 LIST_INSERT_AFTER(p1, p2, p_pglist); 595 PGRP_UNLOCK(p1->p_pgrp); 596 LIST_INIT(&p2->p_children); 597 598 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 599 600 #ifdef KTRACE 601 /* 602 * Copy traceflag and tracefile if enabled. 603 */ 604 mtx_lock(&ktrace_mtx); 605 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 606 if (p1->p_traceflag & KTRFAC_INHERIT) { 607 p2->p_traceflag = p1->p_traceflag; 608 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 609 VREF(p2->p_tracevp); 610 KASSERT(p1->p_tracecred != NULL, 611 ("ktrace vnode with no cred")); 612 p2->p_tracecred = crhold(p1->p_tracecred); 613 } 614 } 615 mtx_unlock(&ktrace_mtx); 616 #endif 617 618 /* 619 * If PF_FORK is set, the child process inherits the 620 * procfs ioctl flags from its parent. 621 */ 622 if (p1->p_pfsflags & PF_FORK) { 623 p2->p_stops = p1->p_stops; 624 p2->p_pfsflags = p1->p_pfsflags; 625 } 626 627 /* 628 * This begins the section where we must prevent the parent 629 * from being swapped. 630 */ 631 _PHOLD(p1); 632 PROC_UNLOCK(p1); 633 634 /* 635 * Attach the new process to its parent. 636 * 637 * If RFNOWAIT is set, the newly created process becomes a child 638 * of init. This effectively disassociates the child from the 639 * parent. 640 */ 641 if (flags & RFNOWAIT) 642 pptr = initproc; 643 else 644 pptr = p1; 645 p2->p_pptr = pptr; 646 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 647 sx_xunlock(&proctree_lock); 648 649 /* Inform accounting that we have forked. */ 650 p2->p_acflag = AFORK; 651 PROC_UNLOCK(p2); 652 653 /* 654 * Finish creating the child process. It will return via a different 655 * execution path later. (ie: directly into user mode) 656 */ 657 vm_forkproc(td, p2, td2, flags); 658 659 if (flags == (RFFDG | RFPROC)) { 660 cnt.v_forks++; 661 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 662 p2->p_vmspace->vm_ssize; 663 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 664 cnt.v_vforks++; 665 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 666 p2->p_vmspace->vm_ssize; 667 } else if (p1 == &proc0) { 668 cnt.v_kthreads++; 669 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 670 p2->p_vmspace->vm_ssize; 671 } else { 672 cnt.v_rforks++; 673 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 674 p2->p_vmspace->vm_ssize; 675 } 676 677 /* 678 * Both processes are set up, now check if any loadable modules want 679 * to adjust anything. 680 * What if they have an error? XXX 681 */ 682 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 683 684 /* 685 * If RFSTOPPED not requested, make child runnable and add to 686 * run queue. 687 */ 688 microuptime(&p2->p_stats->p_start); 689 if ((flags & RFSTOPPED) == 0) { 690 mtx_lock_spin(&sched_lock); 691 p2->p_state = PRS_NORMAL; 692 TD_SET_CAN_RUN(td2); 693 setrunqueue(td2); 694 mtx_unlock_spin(&sched_lock); 695 } 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(&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_SA) { 724 PROC_LOCK(p1); 725 thread_single_end(); 726 PROC_UNLOCK(p1); 727 } 728 729 /* 730 * Return child proc pointer to parent. 731 */ 732 mtx_unlock(&Giant); 733 *procp = p2; 734 return (0); 735 fail: 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_SA) { 745 PROC_LOCK(p1); 746 thread_single_end(); 747 PROC_UNLOCK(p1); 748 } 749 tsleep(&forksleep, PUSER, "fork", hz / 2); 750 mtx_unlock(&Giant); 751 return (error); 752 } 753 754 /* 755 * Handle the return of a child process from fork1(). This function 756 * is called from the MD fork_trampoline() entry point. 757 */ 758 void 759 fork_exit(callout, arg, frame) 760 void (*callout)(void *, struct trapframe *); 761 void *arg; 762 struct trapframe *frame; 763 { 764 struct proc *p; 765 struct thread *td; 766 767 /* 768 * Processes normally resume in mi_switch() after being 769 * cpu_switch()'ed to, but when children start up they arrive here 770 * instead, so we must do much the same things as mi_switch() would. 771 */ 772 773 if ((td = PCPU_GET(deadthread))) { 774 PCPU_SET(deadthread, NULL); 775 thread_stash(td); 776 } 777 td = curthread; 778 p = td->td_proc; 779 td->td_oncpu = PCPU_GET(cpuid); 780 p->p_state = PRS_NORMAL; 781 782 /* 783 * Finish setting up thread glue so that it begins execution in a 784 * non-nested critical section with sched_lock held but not recursed. 785 */ 786 sched_lock.mtx_lock = (uintptr_t)td; 787 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 788 cpu_critical_fork_exit(); 789 CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid, 790 p->p_comm); 791 mtx_unlock_spin(&sched_lock); 792 793 /* 794 * cpu_set_fork_handler intercepts this function call to 795 * have this call a non-return function to stay in kernel mode. 796 * initproc has its own fork handler, but it does return. 797 */ 798 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 799 callout(arg, frame); 800 801 /* 802 * Check if a kernel thread misbehaved and returned from its main 803 * function. 804 */ 805 PROC_LOCK(p); 806 if (p->p_flag & P_KTHREAD) { 807 PROC_UNLOCK(p); 808 mtx_lock(&Giant); 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 #ifdef DIAGNOSTIC 815 cred_free_thread(td); 816 #endif 817 mtx_assert(&Giant, MA_NOTOWNED); 818 } 819 820 /* 821 * Simplified back end of syscall(), used when returning from fork() 822 * directly into user mode. Giant is not held on entry, and must not 823 * be held on return. This function is passed in to fork_exit() as the 824 * first parameter and is called when returning to a new userland process. 825 */ 826 void 827 fork_return(td, frame) 828 struct thread *td; 829 struct trapframe *frame; 830 { 831 832 userret(td, frame, 0); 833 #ifdef KTRACE 834 if (KTRPOINT(td, KTR_SYSRET)) 835 ktrsysret(SYS_fork, 0, 0); 836 #endif 837 mtx_assert(&Giant, MA_NOTOWNED); 838 } 839