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/sysctl.h> 54 #include <sys/lock.h> 55 #include <sys/malloc.h> 56 #include <sys/mutex.h> 57 #include <sys/proc.h> 58 #include <sys/pioctl.h> 59 #include <sys/resourcevar.h> 60 #include <sys/sched.h> 61 #include <sys/syscall.h> 62 #include <sys/vnode.h> 63 #include <sys/acct.h> 64 #include <sys/mac.h> 65 #include <sys/ktr.h> 66 #include <sys/ktrace.h> 67 #include <sys/kthread.h> 68 #include <sys/unistd.h> 69 #include <sys/jail.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/vmmeter.h> 79 #include <sys/user.h> 80 #include <machine/critical.h> 81 82 #ifndef _SYS_SYSPROTO_H_ 83 struct fork_args { 84 int dummy; 85 }; 86 #endif 87 88 static int forksleep; /* Place for fork1() to sleep on. */ 89 90 /* 91 * MPSAFE 92 */ 93 /* ARGSUSED */ 94 int 95 fork(td, uap) 96 struct thread *td; 97 struct fork_args *uap; 98 { 99 int error; 100 struct proc *p2; 101 102 error = fork1(td, RFFDG | RFPROC, 0, &p2); 103 if (error == 0) { 104 td->td_retval[0] = p2->p_pid; 105 td->td_retval[1] = 0; 106 } 107 return error; 108 } 109 110 /* 111 * MPSAFE 112 */ 113 /* ARGSUSED */ 114 int 115 vfork(td, uap) 116 struct thread *td; 117 struct vfork_args *uap; 118 { 119 int error; 120 struct proc *p2; 121 122 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 123 if (error == 0) { 124 td->td_retval[0] = p2->p_pid; 125 td->td_retval[1] = 0; 126 } 127 return error; 128 } 129 130 /* 131 * MPSAFE 132 */ 133 int 134 rfork(td, uap) 135 struct thread *td; 136 struct rfork_args *uap; 137 { 138 int error; 139 struct proc *p2; 140 141 /* Don't allow kernel only flags. */ 142 if ((uap->flags & RFKERNELONLY) != 0) 143 return (EINVAL); 144 error = fork1(td, uap->flags, 0, &p2); 145 if (error == 0) { 146 td->td_retval[0] = p2 ? p2->p_pid : 0; 147 td->td_retval[1] = 0; 148 } 149 return error; 150 } 151 152 153 int nprocs = 1; /* process 0 */ 154 int lastpid = 0; 155 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 156 "Last used PID"); 157 158 /* 159 * Random component to lastpid generation. We mix in a random factor to make 160 * it a little harder to predict. We sanity check the modulus value to avoid 161 * doing it in critical paths. Don't let it be too small or we pointlessly 162 * waste randomness entropy, and don't let it be impossibly large. Using a 163 * modulus that is too big causes a LOT more process table scans and slows 164 * down fork processing as the pidchecked caching is defeated. 165 */ 166 static int randompid = 0; 167 168 static int 169 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 170 { 171 int error, pid; 172 173 sysctl_wire_old_buffer(req, sizeof(int)); 174 sx_xlock(&allproc_lock); 175 pid = randompid; 176 error = sysctl_handle_int(oidp, &pid, 0, req); 177 if (error == 0 && req->newptr != NULL) { 178 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 179 pid = PID_MAX - 100; 180 else if (pid < 2) /* NOP */ 181 pid = 0; 182 else if (pid < 100) /* Make it reasonable */ 183 pid = 100; 184 randompid = pid; 185 } 186 sx_xunlock(&allproc_lock); 187 return (error); 188 } 189 190 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 191 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 192 193 int 194 fork1(td, flags, pages, procp) 195 struct thread *td; /* parent proc */ 196 int flags; 197 int pages; 198 struct proc **procp; /* child proc */ 199 { 200 struct proc *p2, *pptr; 201 uid_t uid; 202 struct proc *newproc; 203 int trypid; 204 int ok; 205 static int pidchecked = 0; 206 struct filedesc *fd; 207 struct filedesc_to_leader *fdtol; 208 struct proc *p1 = td->td_proc; 209 struct thread *td2; 210 struct kse *ke2; 211 struct ksegrp *kg2; 212 struct sigacts *newsigacts; 213 int error; 214 215 /* Can't copy and clear */ 216 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 217 return (EINVAL); 218 219 mtx_lock(&Giant); 220 /* 221 * Here we don't create a new process, but we divorce 222 * certain parts of a process from itself. 223 */ 224 if ((flags & RFPROC) == 0) { 225 vm_forkproc(td, NULL, NULL, flags); 226 227 /* 228 * Close all file descriptors. 229 */ 230 if (flags & RFCFDG) { 231 struct filedesc *fdtmp; 232 fdtmp = fdinit(td->td_proc->p_fd); 233 fdfree(td); 234 p1->p_fd = fdtmp; 235 } 236 237 /* 238 * Unshare file descriptors (from parent.) 239 */ 240 if (flags & RFFDG) { 241 FILEDESC_LOCK(p1->p_fd); 242 if (p1->p_fd->fd_refcnt > 1) { 243 struct filedesc *newfd; 244 245 newfd = fdcopy(td->td_proc->p_fd); 246 FILEDESC_UNLOCK(p1->p_fd); 247 fdfree(td); 248 p1->p_fd = newfd; 249 } else 250 FILEDESC_UNLOCK(p1->p_fd); 251 } 252 mtx_unlock(&Giant); 253 *procp = NULL; 254 return (0); 255 } 256 257 /* 258 * Note 1:1 allows for forking with one thread coming out on the 259 * other side with the expectation that the process is about to 260 * exec. 261 */ 262 if (p1->p_flag & P_THREADED) { 263 /* 264 * Idle the other threads for a second. 265 * Since the user space is copied, it must remain stable. 266 * In addition, all threads (from the user perspective) 267 * need to either be suspended or in the kernel, 268 * where they will try restart in the parent and will 269 * be aborted in the child. 270 */ 271 PROC_LOCK(p1); 272 if (thread_single(SINGLE_NO_EXIT)) { 273 /* Abort.. someone else is single threading before us */ 274 PROC_UNLOCK(p1); 275 mtx_unlock(&Giant); 276 return (ERESTART); 277 } 278 PROC_UNLOCK(p1); 279 /* 280 * All other activity in this process 281 * is now suspended at the user boundary, 282 * (or other safe places if we think of any). 283 */ 284 } 285 286 /* Allocate new proc. */ 287 newproc = uma_zalloc(proc_zone, M_WAITOK); 288 #ifdef MAC 289 mac_init_proc(newproc); 290 #endif 291 292 /* 293 * Although process entries are dynamically created, we still keep 294 * a global limit on the maximum number we will create. Don't allow 295 * a nonprivileged user to use the last ten processes; don't let root 296 * exceed the limit. The variable nprocs is the current number of 297 * processes, maxproc is the limit. 298 */ 299 sx_xlock(&allproc_lock); 300 uid = td->td_ucred->cr_ruid; 301 if ((nprocs >= maxproc - 10 && uid != 0) || 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) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 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 } 337 } else { 338 if (randompid) 339 trypid += arc4random() % randompid; 340 } 341 retry: 342 /* 343 * If the process ID prototype has wrapped around, 344 * restart somewhat above 0, as the low-numbered procs 345 * tend to include daemons that don't exit. 346 */ 347 if (trypid >= PID_MAX) { 348 trypid = trypid % PID_MAX; 349 if (trypid < 100) 350 trypid += 100; 351 pidchecked = 0; 352 } 353 if (trypid >= pidchecked) { 354 int doingzomb = 0; 355 356 pidchecked = PID_MAX; 357 /* 358 * Scan the active and zombie procs to check whether this pid 359 * is in use. Remember the lowest pid that's greater 360 * than trypid, so we can avoid checking for a while. 361 */ 362 p2 = LIST_FIRST(&allproc); 363 again: 364 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 365 PROC_LOCK(p2); 366 while (p2->p_pid == trypid || 367 p2->p_pgrp->pg_id == trypid || 368 p2->p_session->s_sid == trypid) { 369 trypid++; 370 if (trypid >= pidchecked) { 371 PROC_UNLOCK(p2); 372 goto retry; 373 } 374 } 375 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 376 pidchecked = p2->p_pid; 377 if (p2->p_pgrp->pg_id > trypid && 378 pidchecked > p2->p_pgrp->pg_id) 379 pidchecked = p2->p_pgrp->pg_id; 380 if (p2->p_session->s_sid > trypid && 381 pidchecked > p2->p_session->s_sid) 382 pidchecked = p2->p_session->s_sid; 383 PROC_UNLOCK(p2); 384 } 385 if (!doingzomb) { 386 doingzomb = 1; 387 p2 = LIST_FIRST(&zombproc); 388 goto again; 389 } 390 } 391 392 /* 393 * RFHIGHPID does not mess with the lastpid counter during boot. 394 */ 395 if (flags & RFHIGHPID) 396 pidchecked = 0; 397 else 398 lastpid = trypid; 399 400 p2 = newproc; 401 p2->p_state = PRS_NEW; /* protect against others */ 402 p2->p_pid = trypid; 403 LIST_INSERT_HEAD(&allproc, p2, p_list); 404 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 405 sx_xunlock(&allproc_lock); 406 407 /* 408 * Malloc things while we don't hold any locks. 409 */ 410 if (flags & RFSIGSHARE) 411 newsigacts = NULL; 412 else 413 newsigacts = sigacts_alloc(); 414 415 /* 416 * Copy filedesc. 417 */ 418 if (flags & RFCFDG) { 419 fd = fdinit(td->td_proc->p_fd); 420 fdtol = NULL; 421 } else if (flags & RFFDG) { 422 FILEDESC_LOCK(p1->p_fd); 423 fd = fdcopy(td->td_proc->p_fd); 424 FILEDESC_UNLOCK(p1->p_fd); 425 fdtol = NULL; 426 } else { 427 fd = fdshare(p1->p_fd); 428 if (p1->p_fdtol == NULL) 429 p1->p_fdtol = 430 filedesc_to_leader_alloc(NULL, 431 NULL, 432 p1->p_leader); 433 if ((flags & RFTHREAD) != 0) { 434 /* 435 * Shared file descriptor table and 436 * shared process leaders. 437 */ 438 fdtol = p1->p_fdtol; 439 FILEDESC_LOCK(p1->p_fd); 440 fdtol->fdl_refcount++; 441 FILEDESC_UNLOCK(p1->p_fd); 442 } else { 443 /* 444 * Shared file descriptor table, and 445 * different process leaders 446 */ 447 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 448 p1->p_fd, 449 p2); 450 } 451 } 452 /* 453 * Make a proc table entry for the new process. 454 * Start by zeroing the section of proc that is zero-initialized, 455 * then copy the section that is copied directly from the parent. 456 */ 457 td2 = FIRST_THREAD_IN_PROC(p2); 458 kg2 = FIRST_KSEGRP_IN_PROC(p2); 459 ke2 = FIRST_KSE_IN_KSEGRP(kg2); 460 461 /* Allocate and switch to an alternate kstack if specified */ 462 if (pages != 0) 463 vm_thread_new_altkstack(td2, pages); 464 465 PROC_LOCK(p2); 466 PROC_LOCK(p1); 467 468 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 469 470 bzero(&p2->p_startzero, 471 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 472 bzero(&ke2->ke_startzero, 473 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 474 bzero(&td2->td_startzero, 475 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 476 bzero(&kg2->kg_startzero, 477 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 478 479 bcopy(&p1->p_startcopy, &p2->p_startcopy, 480 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 481 bcopy(&td->td_startcopy, &td2->td_startcopy, 482 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 483 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 484 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 485 #undef RANGEOF 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 | P_ALTSTACK); 585 SESS_LOCK(p1->p_session); 586 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 587 p2->p_flag |= P_CONTROLT; 588 SESS_UNLOCK(p1->p_session); 589 if (flags & RFPPWAIT) 590 p2->p_flag |= P_PPWAIT; 591 592 LIST_INSERT_AFTER(p1, p2, p_pglist); 593 PGRP_UNLOCK(p1->p_pgrp); 594 LIST_INIT(&p2->p_children); 595 596 callout_init(&p2->p_itcallout, 1); 597 598 #ifdef KTRACE 599 /* 600 * Copy traceflag and tracefile if enabled. 601 */ 602 mtx_lock(&ktrace_mtx); 603 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 604 if (p1->p_traceflag & KTRFAC_INHERIT) { 605 p2->p_traceflag = p1->p_traceflag; 606 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 607 VREF(p2->p_tracevp); 608 KASSERT(p1->p_tracecred != NULL, 609 ("ktrace vnode with no cred")); 610 p2->p_tracecred = crhold(p1->p_tracecred); 611 } 612 } 613 mtx_unlock(&ktrace_mtx); 614 #endif 615 616 /* 617 * If PF_FORK is set, the child process inherits the 618 * procfs ioctl flags from its parent. 619 */ 620 if (p1->p_pfsflags & PF_FORK) { 621 p2->p_stops = p1->p_stops; 622 p2->p_pfsflags = p1->p_pfsflags; 623 } 624 625 /* 626 * This begins the section where we must prevent the parent 627 * from being swapped. 628 */ 629 _PHOLD(p1); 630 PROC_UNLOCK(p1); 631 632 /* 633 * Attach the new process to its parent. 634 * 635 * If RFNOWAIT is set, the newly created process becomes a child 636 * of init. This effectively disassociates the child from the 637 * parent. 638 */ 639 if (flags & RFNOWAIT) 640 pptr = initproc; 641 else 642 pptr = p1; 643 p2->p_pptr = pptr; 644 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 645 sx_xunlock(&proctree_lock); 646 647 /* Inform accounting that we have forked. */ 648 p2->p_acflag = AFORK; 649 PROC_UNLOCK(p2); 650 651 /* 652 * Finish creating the child process. It will return via a different 653 * execution path later. (ie: directly into user mode) 654 */ 655 vm_forkproc(td, p2, td2, flags); 656 657 if (flags == (RFFDG | RFPROC)) { 658 cnt.v_forks++; 659 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 660 p2->p_vmspace->vm_ssize; 661 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 662 cnt.v_vforks++; 663 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 664 p2->p_vmspace->vm_ssize; 665 } else if (p1 == &proc0) { 666 cnt.v_kthreads++; 667 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 668 p2->p_vmspace->vm_ssize; 669 } else { 670 cnt.v_rforks++; 671 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 672 p2->p_vmspace->vm_ssize; 673 } 674 675 /* 676 * Both processes are set up, now check if any loadable modules want 677 * to adjust anything. 678 * What if they have an error? XXX 679 */ 680 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 681 682 /* 683 * If RFSTOPPED not requested, make child runnable and add to 684 * run queue. 685 */ 686 microuptime(&p2->p_stats->p_start); 687 if ((flags & RFSTOPPED) == 0) { 688 mtx_lock_spin(&sched_lock); 689 p2->p_state = PRS_NORMAL; 690 TD_SET_CAN_RUN(td2); 691 setrunqueue(td2); 692 mtx_unlock_spin(&sched_lock); 693 } 694 695 /* 696 * Now can be swapped. 697 */ 698 PROC_LOCK(p1); 699 _PRELE(p1); 700 701 /* 702 * tell any interested parties about the new process 703 */ 704 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 705 PROC_UNLOCK(p1); 706 707 /* 708 * Preserve synchronization semantics of vfork. If waiting for 709 * child to exec or exit, set P_PPWAIT on child, and sleep on our 710 * proc (in case of exit). 711 */ 712 PROC_LOCK(p2); 713 while (p2->p_flag & P_PPWAIT) 714 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 715 PROC_UNLOCK(p2); 716 717 /* 718 * If other threads are waiting, let them continue now 719 */ 720 if (p1->p_flag & P_THREADED) { 721 PROC_LOCK(p1); 722 thread_single_end(); 723 PROC_UNLOCK(p1); 724 } 725 726 /* 727 * Return child proc pointer to parent. 728 */ 729 mtx_unlock(&Giant); 730 *procp = p2; 731 return (0); 732 fail: 733 sx_xunlock(&allproc_lock); 734 uma_zfree(proc_zone, newproc); 735 if (p1->p_flag & P_THREADED) { 736 PROC_LOCK(p1); 737 thread_single_end(); 738 PROC_UNLOCK(p1); 739 } 740 tsleep(&forksleep, PUSER, "fork", hz / 2); 741 mtx_unlock(&Giant); 742 return (error); 743 } 744 745 /* 746 * Handle the return of a child process from fork1(). This function 747 * is called from the MD fork_trampoline() entry point. 748 */ 749 void 750 fork_exit(callout, arg, frame) 751 void (*callout)(void *, struct trapframe *); 752 void *arg; 753 struct trapframe *frame; 754 { 755 struct thread *td; 756 struct proc *p; 757 758 if ((td = PCPU_GET(deadthread))) { 759 PCPU_SET(deadthread, NULL); 760 thread_stash(td); 761 } 762 td = curthread; 763 p = td->td_proc; 764 td->td_oncpu = PCPU_GET(cpuid); 765 p->p_state = PRS_NORMAL; 766 /* 767 * Finish setting up thread glue. We need to initialize 768 * the thread into a td_critnest=1 state. Some platforms 769 * may have already partially or fully initialized td_critnest 770 * and/or td_md.md_savecrit (when applciable). 771 * 772 * see <arch>/<arch>/critical.c 773 */ 774 sched_lock.mtx_lock = (uintptr_t)td; 775 sched_lock.mtx_recurse = 0; 776 cpu_critical_fork_exit(); 777 CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid, 778 p->p_comm); 779 if (PCPU_GET(switchtime.sec) == 0) 780 binuptime(PCPU_PTR(switchtime)); 781 PCPU_SET(switchticks, ticks); 782 mtx_unlock_spin(&sched_lock); 783 784 /* 785 * cpu_set_fork_handler intercepts this function call to 786 * have this call a non-return function to stay in kernel mode. 787 * initproc has its own fork handler, but it does return. 788 */ 789 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 790 callout(arg, frame); 791 792 /* 793 * Check if a kernel thread misbehaved and returned from its main 794 * function. 795 */ 796 PROC_LOCK(p); 797 if (p->p_flag & P_KTHREAD) { 798 PROC_UNLOCK(p); 799 mtx_lock(&Giant); 800 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 801 p->p_comm, p->p_pid); 802 kthread_exit(0); 803 } 804 PROC_UNLOCK(p); 805 #ifdef DIAGNOSTIC 806 cred_free_thread(td); 807 #endif 808 mtx_assert(&Giant, MA_NOTOWNED); 809 } 810 811 /* 812 * Simplified back end of syscall(), used when returning from fork() 813 * directly into user mode. Giant is not held on entry, and must not 814 * be held on return. This function is passed in to fork_exit() as the 815 * first parameter and is called when returning to a new userland process. 816 */ 817 void 818 fork_return(td, frame) 819 struct thread *td; 820 struct trapframe *frame; 821 { 822 823 userret(td, frame, 0); 824 #ifdef KTRACE 825 if (KTRPOINT(td, KTR_SYSRET)) 826 ktrsysret(SYS_fork, 0, 0); 827 #endif 828 mtx_assert(&Giant, MA_NOTOWNED); 829 } 830