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 curfail, pidchecked = 0; 206 static struct timeval lastfail; 207 struct filedesc *fd; 208 struct filedesc_to_leader *fdtol; 209 struct proc *p1 = td->td_proc; 210 struct thread *td2; 211 struct kse *ke2; 212 struct ksegrp *kg2; 213 struct sigacts *newsigacts; 214 int error; 215 216 /* Can't copy and clear */ 217 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 218 return (EINVAL); 219 220 mtx_lock(&Giant); 221 /* 222 * Here we don't create a new process, but we divorce 223 * certain parts of a process from itself. 224 */ 225 if ((flags & RFPROC) == 0) { 226 vm_forkproc(td, NULL, NULL, flags); 227 228 /* 229 * Close all file descriptors. 230 */ 231 if (flags & RFCFDG) { 232 struct filedesc *fdtmp; 233 fdtmp = fdinit(td->td_proc->p_fd); 234 fdfree(td); 235 p1->p_fd = fdtmp; 236 } 237 238 /* 239 * Unshare file descriptors (from parent.) 240 */ 241 if (flags & RFFDG) { 242 FILEDESC_LOCK(p1->p_fd); 243 if (p1->p_fd->fd_refcnt > 1) { 244 struct filedesc *newfd; 245 246 newfd = fdcopy(td->td_proc->p_fd); 247 FILEDESC_UNLOCK(p1->p_fd); 248 fdfree(td); 249 p1->p_fd = newfd; 250 } else 251 FILEDESC_UNLOCK(p1->p_fd); 252 } 253 mtx_unlock(&Giant); 254 *procp = NULL; 255 return (0); 256 } 257 258 /* 259 * Note 1:1 allows for forking with one thread coming out on the 260 * other side with the expectation that the process is about to 261 * exec. 262 */ 263 if (p1->p_flag & P_SA) { 264 /* 265 * Idle the other threads for a second. 266 * Since the user space is copied, it must remain stable. 267 * In addition, all threads (from the user perspective) 268 * need to either be suspended or in the kernel, 269 * where they will try restart in the parent and will 270 * be aborted in the child. 271 */ 272 PROC_LOCK(p1); 273 if (thread_single(SINGLE_NO_EXIT)) { 274 /* Abort.. someone else is single threading before us */ 275 PROC_UNLOCK(p1); 276 mtx_unlock(&Giant); 277 return (ERESTART); 278 } 279 PROC_UNLOCK(p1); 280 /* 281 * All other activity in this process 282 * is now suspended at the user boundary, 283 * (or other safe places if we think of any). 284 */ 285 } 286 287 /* Allocate new proc. */ 288 newproc = uma_zalloc(proc_zone, M_WAITOK); 289 #ifdef MAC 290 mac_init_proc(newproc); 291 #endif 292 293 /* 294 * Although process entries are dynamically created, we still keep 295 * a global limit on the maximum number we will create. Don't allow 296 * a nonprivileged user to use the last ten processes; don't let root 297 * exceed the limit. The variable nprocs is the current number of 298 * processes, maxproc is the limit. 299 */ 300 sx_xlock(&allproc_lock); 301 uid = td->td_ucred->cr_ruid; 302 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 303 error = EAGAIN; 304 goto fail; 305 } 306 307 /* 308 * Increment the count of procs running with this uid. Don't allow 309 * a nonprivileged user to exceed their current limit. 310 */ 311 PROC_LOCK(p1); 312 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 313 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 314 PROC_UNLOCK(p1); 315 if (!ok) { 316 error = EAGAIN; 317 goto fail; 318 } 319 320 /* 321 * Increment the nprocs resource before blocking can occur. There 322 * are hard-limits as to the number of processes that can run. 323 */ 324 nprocs++; 325 326 /* 327 * Find an unused process ID. We remember a range of unused IDs 328 * ready to use (from lastpid+1 through pidchecked-1). 329 * 330 * If RFHIGHPID is set (used during system boot), do not allocate 331 * low-numbered pids. 332 */ 333 trypid = lastpid + 1; 334 if (flags & RFHIGHPID) { 335 if (trypid < 10) { 336 trypid = 10; 337 } 338 } else { 339 if (randompid) 340 trypid += arc4random() % randompid; 341 } 342 retry: 343 /* 344 * If the process ID prototype has wrapped around, 345 * restart somewhat above 0, as the low-numbered procs 346 * tend to include daemons that don't exit. 347 */ 348 if (trypid >= PID_MAX) { 349 trypid = trypid % PID_MAX; 350 if (trypid < 100) 351 trypid += 100; 352 pidchecked = 0; 353 } 354 if (trypid >= pidchecked) { 355 int doingzomb = 0; 356 357 pidchecked = PID_MAX; 358 /* 359 * Scan the active and zombie procs to check whether this pid 360 * is in use. Remember the lowest pid that's greater 361 * than trypid, so we can avoid checking for a while. 362 */ 363 p2 = LIST_FIRST(&allproc); 364 again: 365 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 366 PROC_LOCK(p2); 367 while (p2->p_pid == trypid || 368 p2->p_pgrp->pg_id == trypid || 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->pg_id > trypid && 379 pidchecked > p2->p_pgrp->pg_id) 380 pidchecked = p2->p_pgrp->pg_id; 381 if (p2->p_session->s_sid > trypid && 382 pidchecked > p2->p_session->s_sid) 383 pidchecked = p2->p_session->s_sid; 384 PROC_UNLOCK(p2); 385 } 386 if (!doingzomb) { 387 doingzomb = 1; 388 p2 = LIST_FIRST(&zombproc); 389 goto again; 390 } 391 } 392 393 /* 394 * RFHIGHPID does not mess with the lastpid counter during boot. 395 */ 396 if (flags & RFHIGHPID) 397 pidchecked = 0; 398 else 399 lastpid = trypid; 400 401 p2 = newproc; 402 p2->p_state = PRS_NEW; /* protect against others */ 403 p2->p_pid = trypid; 404 LIST_INSERT_HEAD(&allproc, p2, p_list); 405 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 406 sx_xunlock(&allproc_lock); 407 408 /* 409 * Malloc things while we don't hold any locks. 410 */ 411 if (flags & RFSIGSHARE) 412 newsigacts = NULL; 413 else 414 newsigacts = sigacts_alloc(); 415 416 /* 417 * Copy filedesc. 418 */ 419 if (flags & RFCFDG) { 420 fd = fdinit(td->td_proc->p_fd); 421 fdtol = NULL; 422 } else if (flags & RFFDG) { 423 FILEDESC_LOCK(p1->p_fd); 424 fd = fdcopy(td->td_proc->p_fd); 425 FILEDESC_UNLOCK(p1->p_fd); 426 fdtol = NULL; 427 } else { 428 fd = fdshare(p1->p_fd); 429 if (p1->p_fdtol == NULL) 430 p1->p_fdtol = 431 filedesc_to_leader_alloc(NULL, 432 NULL, 433 p1->p_leader); 434 if ((flags & RFTHREAD) != 0) { 435 /* 436 * Shared file descriptor table and 437 * shared process leaders. 438 */ 439 fdtol = p1->p_fdtol; 440 FILEDESC_LOCK(p1->p_fd); 441 fdtol->fdl_refcount++; 442 FILEDESC_UNLOCK(p1->p_fd); 443 } else { 444 /* 445 * Shared file descriptor table, and 446 * different process leaders 447 */ 448 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 449 p1->p_fd, 450 p2); 451 } 452 } 453 /* 454 * Make a proc table entry for the new process. 455 * Start by zeroing the section of proc that is zero-initialized, 456 * then copy the section that is copied directly from the parent. 457 */ 458 td2 = FIRST_THREAD_IN_PROC(p2); 459 kg2 = FIRST_KSEGRP_IN_PROC(p2); 460 ke2 = FIRST_KSE_IN_KSEGRP(kg2); 461 462 /* Allocate and switch to an alternate kstack if specified */ 463 if (pages != 0) 464 vm_thread_new_altkstack(td2, pages); 465 466 PROC_LOCK(p2); 467 PROC_LOCK(p1); 468 469 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 470 471 bzero(&p2->p_startzero, 472 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 473 bzero(&ke2->ke_startzero, 474 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 475 bzero(&td2->td_startzero, 476 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 477 bzero(&kg2->kg_startzero, 478 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 479 480 bcopy(&p1->p_startcopy, &p2->p_startcopy, 481 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 482 bcopy(&td->td_startcopy, &td2->td_startcopy, 483 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 484 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 485 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 486 #undef RANGEOF 487 488 /* Set up the thread as an active thread (as if runnable). */ 489 ke2->ke_state = KES_THREAD; 490 ke2->ke_thread = td2; 491 td2->td_kse = ke2; 492 493 /* 494 * Duplicate sub-structures as needed. 495 * Increase reference counts on shared objects. 496 * The p_stats substruct is set in vm_forkproc. 497 */ 498 p2->p_flag = 0; 499 if (p1->p_flag & P_PROFIL) 500 startprofclock(p2); 501 mtx_lock_spin(&sched_lock); 502 p2->p_sflag = PS_INMEM; 503 /* 504 * Allow the scheduler to adjust the priority of the child and 505 * parent while we hold the sched_lock. 506 */ 507 sched_fork(p1, p2); 508 509 mtx_unlock_spin(&sched_lock); 510 p2->p_ucred = crhold(td->td_ucred); 511 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 512 513 pargs_hold(p2->p_args); 514 515 if (flags & RFSIGSHARE) { 516 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 517 } else { 518 sigacts_copy(newsigacts, p1->p_sigacts); 519 p2->p_sigacts = newsigacts; 520 } 521 if (flags & RFLINUXTHPN) 522 p2->p_sigparent = SIGUSR1; 523 else 524 p2->p_sigparent = SIGCHLD; 525 526 /* Bump references to the text vnode (for procfs) */ 527 p2->p_textvp = p1->p_textvp; 528 if (p2->p_textvp) 529 VREF(p2->p_textvp); 530 p2->p_fd = fd; 531 p2->p_fdtol = fdtol; 532 PROC_UNLOCK(p1); 533 PROC_UNLOCK(p2); 534 535 /* 536 * p_limit is copy-on-write, bump refcnt, 537 */ 538 p2->p_limit = p1->p_limit; 539 p2->p_limit->p_refcnt++; 540 541 /* 542 * Setup linkage for kernel based threading 543 */ 544 if((flags & RFTHREAD) != 0) { 545 mtx_lock(&ppeers_lock); 546 p2->p_peers = p1->p_peers; 547 p1->p_peers = p2; 548 p2->p_leader = p1->p_leader; 549 mtx_unlock(&ppeers_lock); 550 PROC_LOCK(p1->p_leader); 551 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 552 PROC_UNLOCK(p1->p_leader); 553 /* 554 * The task leader is exiting, so process p1 is 555 * going to be killed shortly. Since p1 obviously 556 * isn't dead yet, we know that the leader is either 557 * sending SIGKILL's to all the processes in this 558 * task or is sleeping waiting for all the peers to 559 * exit. We let p1 complete the fork, but we need 560 * to go ahead and kill the new process p2 since 561 * the task leader may not get a chance to send 562 * SIGKILL to it. We leave it on the list so that 563 * the task leader will wait for this new process 564 * to commit suicide. 565 */ 566 PROC_LOCK(p2); 567 psignal(p2, SIGKILL); 568 PROC_UNLOCK(p2); 569 } else 570 PROC_UNLOCK(p1->p_leader); 571 } else { 572 p2->p_peers = NULL; 573 p2->p_leader = p2; 574 } 575 576 sx_xlock(&proctree_lock); 577 PGRP_LOCK(p1->p_pgrp); 578 PROC_LOCK(p2); 579 PROC_LOCK(p1); 580 581 /* 582 * Preserve some more flags in subprocess. P_PROFIL has already 583 * been preserved. 584 */ 585 p2->p_flag |= p1->p_flag & (P_SUGID | P_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 LIST_INSERT_AFTER(p1, p2, p_pglist); 594 PGRP_UNLOCK(p1->p_pgrp); 595 LIST_INIT(&p2->p_children); 596 597 callout_init(&p2->p_itcallout, 1); 598 599 #ifdef KTRACE 600 /* 601 * Copy traceflag and tracefile if enabled. 602 */ 603 mtx_lock(&ktrace_mtx); 604 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 605 if (p1->p_traceflag & KTRFAC_INHERIT) { 606 p2->p_traceflag = p1->p_traceflag; 607 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 608 VREF(p2->p_tracevp); 609 KASSERT(p1->p_tracecred != NULL, 610 ("ktrace vnode with no cred")); 611 p2->p_tracecred = crhold(p1->p_tracecred); 612 } 613 } 614 mtx_unlock(&ktrace_mtx); 615 #endif 616 617 /* 618 * If PF_FORK is set, the child process inherits the 619 * procfs ioctl flags from its parent. 620 */ 621 if (p1->p_pfsflags & PF_FORK) { 622 p2->p_stops = p1->p_stops; 623 p2->p_pfsflags = p1->p_pfsflags; 624 } 625 626 /* 627 * This begins the section where we must prevent the parent 628 * from being swapped. 629 */ 630 _PHOLD(p1); 631 PROC_UNLOCK(p1); 632 633 /* 634 * Attach the new process to its parent. 635 * 636 * If RFNOWAIT is set, the newly created process becomes a child 637 * of init. This effectively disassociates the child from the 638 * parent. 639 */ 640 if (flags & RFNOWAIT) 641 pptr = initproc; 642 else 643 pptr = p1; 644 p2->p_pptr = pptr; 645 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 646 sx_xunlock(&proctree_lock); 647 648 /* Inform accounting that we have forked. */ 649 p2->p_acflag = AFORK; 650 PROC_UNLOCK(p2); 651 652 /* 653 * Finish creating the child process. It will return via a different 654 * execution path later. (ie: directly into user mode) 655 */ 656 vm_forkproc(td, p2, td2, flags); 657 658 if (flags == (RFFDG | RFPROC)) { 659 cnt.v_forks++; 660 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 661 p2->p_vmspace->vm_ssize; 662 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 663 cnt.v_vforks++; 664 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 665 p2->p_vmspace->vm_ssize; 666 } else if (p1 == &proc0) { 667 cnt.v_kthreads++; 668 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 669 p2->p_vmspace->vm_ssize; 670 } else { 671 cnt.v_rforks++; 672 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 673 p2->p_vmspace->vm_ssize; 674 } 675 676 /* 677 * Both processes are set up, now check if any loadable modules want 678 * to adjust anything. 679 * What if they have an error? XXX 680 */ 681 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 682 683 /* 684 * If RFSTOPPED not requested, make child runnable and add to 685 * run queue. 686 */ 687 microuptime(&p2->p_stats->p_start); 688 if ((flags & RFSTOPPED) == 0) { 689 mtx_lock_spin(&sched_lock); 690 p2->p_state = PRS_NORMAL; 691 TD_SET_CAN_RUN(td2); 692 setrunqueue(td2); 693 mtx_unlock_spin(&sched_lock); 694 } 695 696 /* 697 * Now can be swapped. 698 */ 699 PROC_LOCK(p1); 700 _PRELE(p1); 701 702 /* 703 * tell any interested parties about the new process 704 */ 705 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 706 PROC_UNLOCK(p1); 707 708 /* 709 * Preserve synchronization semantics of vfork. If waiting for 710 * child to exec or exit, set P_PPWAIT on child, and sleep on our 711 * proc (in case of exit). 712 */ 713 PROC_LOCK(p2); 714 while (p2->p_flag & P_PPWAIT) 715 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 716 PROC_UNLOCK(p2); 717 718 /* 719 * If other threads are waiting, let them continue now 720 */ 721 if (p1->p_flag & P_SA) { 722 PROC_LOCK(p1); 723 thread_single_end(); 724 PROC_UNLOCK(p1); 725 } 726 727 /* 728 * Return child proc pointer to parent. 729 */ 730 mtx_unlock(&Giant); 731 *procp = p2; 732 return (0); 733 fail: 734 if (ppsratecheck(&lastfail, &curfail, 1)) 735 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 736 uid); 737 sx_xunlock(&allproc_lock); 738 uma_zfree(proc_zone, newproc); 739 if (p1->p_flag & P_SA) { 740 PROC_LOCK(p1); 741 thread_single_end(); 742 PROC_UNLOCK(p1); 743 } 744 tsleep(&forksleep, PUSER, "fork", hz / 2); 745 mtx_unlock(&Giant); 746 return (error); 747 } 748 749 /* 750 * Handle the return of a child process from fork1(). This function 751 * is called from the MD fork_trampoline() entry point. 752 */ 753 void 754 fork_exit(callout, arg, frame) 755 void (*callout)(void *, struct trapframe *); 756 void *arg; 757 struct trapframe *frame; 758 { 759 struct thread *td; 760 struct proc *p; 761 762 if ((td = PCPU_GET(deadthread))) { 763 PCPU_SET(deadthread, NULL); 764 thread_stash(td); 765 } 766 td = curthread; 767 p = td->td_proc; 768 td->td_oncpu = PCPU_GET(cpuid); 769 p->p_state = PRS_NORMAL; 770 /* 771 * Finish setting up thread glue. We need to initialize 772 * the thread into a td_critnest=1 state. Some platforms 773 * may have already partially or fully initialized td_critnest 774 * and/or td_md.md_savecrit (when applciable). 775 * 776 * see <arch>/<arch>/critical.c 777 */ 778 sched_lock.mtx_lock = (uintptr_t)td; 779 sched_lock.mtx_recurse = 0; 780 cpu_critical_fork_exit(); 781 CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid, 782 p->p_comm); 783 if (PCPU_GET(switchtime.sec) == 0) 784 binuptime(PCPU_PTR(switchtime)); 785 PCPU_SET(switchticks, ticks); 786 mtx_unlock_spin(&sched_lock); 787 788 /* 789 * cpu_set_fork_handler intercepts this function call to 790 * have this call a non-return function to stay in kernel mode. 791 * initproc has its own fork handler, but it does return. 792 */ 793 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 794 callout(arg, frame); 795 796 /* 797 * Check if a kernel thread misbehaved and returned from its main 798 * function. 799 */ 800 PROC_LOCK(p); 801 if (p->p_flag & P_KTHREAD) { 802 PROC_UNLOCK(p); 803 mtx_lock(&Giant); 804 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 805 p->p_comm, p->p_pid); 806 kthread_exit(0); 807 } 808 PROC_UNLOCK(p); 809 #ifdef DIAGNOSTIC 810 cred_free_thread(td); 811 #endif 812 mtx_assert(&Giant, MA_NOTOWNED); 813 } 814 815 /* 816 * Simplified back end of syscall(), used when returning from fork() 817 * directly into user mode. Giant is not held on entry, and must not 818 * be held on return. This function is passed in to fork_exit() as the 819 * first parameter and is called when returning to a new userland process. 820 */ 821 void 822 fork_return(td, frame) 823 struct thread *td; 824 struct trapframe *frame; 825 { 826 827 userret(td, frame, 0); 828 #ifdef KTRACE 829 if (KTRPOINT(td, KTR_SYSRET)) 830 ktrsysret(SYS_fork, 0, 0); 831 #endif 832 mtx_assert(&Giant, MA_NOTOWNED); 833 } 834