Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c
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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: releng/5.3/sys/kern/kern_fork.c 136588 2004-10-16 08:43:07Z cvs2svn $"); 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 68 #include <vm/vm.h> 69 #include <vm/pmap.h> 70 #include <vm/vm_map.h> 71 #include <vm/vm_extern.h> 72 #include <vm/uma.h> 73 74 #include <sys/user.h> 75 #include <machine/critical.h> 76 77 #ifndef _SYS_SYSPROTO_H_ 78 struct fork_args { 79 int dummy; 80 }; 81 #endif 82 83 static int forksleep; /* Place for fork1() to sleep on. */ 84 85 /* 86 * MPSAFE 87 */ 88 /* ARGSUSED */ 89 int 90 fork(td, uap) 91 struct thread *td; 92 struct fork_args *uap; 93 { 94 int error; 95 struct proc *p2; 96 97 error = fork1(td, RFFDG | RFPROC, 0, &p2); 98 if (error == 0) { 99 td->td_retval[0] = p2->p_pid; 100 td->td_retval[1] = 0; 101 } 102 return (error); 103 } 104 105 /* 106 * MPSAFE 107 */ 108 /* ARGSUSED */ 109 int 110 vfork(td, uap) 111 struct thread *td; 112 struct vfork_args *uap; 113 { 114 int error; 115 struct proc *p2; 116 117 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 118 if (error == 0) { 119 td->td_retval[0] = p2->p_pid; 120 td->td_retval[1] = 0; 121 } 122 return (error); 123 } 124 125 /* 126 * MPSAFE 127 */ 128 int 129 rfork(td, uap) 130 struct thread *td; 131 struct rfork_args *uap; 132 { 133 struct proc *p2; 134 int error; 135 136 /* Don't allow kernel-only flags. */ 137 if ((uap->flags & RFKERNELONLY) != 0) 138 return (EINVAL); 139 140 error = fork1(td, uap->flags, 0, &p2); 141 if (error == 0) { 142 td->td_retval[0] = p2 ? p2->p_pid : 0; 143 td->td_retval[1] = 0; 144 } 145 return (error); 146 } 147 148 int nprocs = 1; /* process 0 */ 149 int lastpid = 0; 150 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 151 "Last used PID"); 152 153 /* 154 * Random component to lastpid generation. We mix in a random factor to make 155 * it a little harder to predict. We sanity check the modulus value to avoid 156 * doing it in critical paths. Don't let it be too small or we pointlessly 157 * waste randomness entropy, and don't let it be impossibly large. Using a 158 * modulus that is too big causes a LOT more process table scans and slows 159 * down fork processing as the pidchecked caching is defeated. 160 */ 161 static int randompid = 0; 162 163 static int 164 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 165 { 166 int error, pid; 167 168 error = sysctl_wire_old_buffer(req, sizeof(int)); 169 if (error != 0) 170 return(error); 171 sx_xlock(&allproc_lock); 172 pid = randompid; 173 error = sysctl_handle_int(oidp, &pid, 0, req); 174 if (error == 0 && req->newptr != NULL) { 175 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 176 pid = PID_MAX - 100; 177 else if (pid < 2) /* NOP */ 178 pid = 0; 179 else if (pid < 100) /* Make it reasonable */ 180 pid = 100; 181 randompid = pid; 182 } 183 sx_xunlock(&allproc_lock); 184 return (error); 185 } 186 187 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 188 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 189 190 int 191 fork1(td, flags, pages, procp) 192 struct thread *td; 193 int flags; 194 int pages; 195 struct proc **procp; 196 { 197 struct proc *p1, *p2, *pptr; 198 uid_t uid; 199 struct proc *newproc; 200 int ok, trypid; 201 static int curfail, pidchecked = 0; 202 static struct timeval lastfail; 203 struct filedesc *fd; 204 struct filedesc_to_leader *fdtol; 205 struct thread *td2; 206 struct ksegrp *kg2; 207 struct sigacts *newsigacts; 208 int error; 209 210 /* Can't copy and clear. */ 211 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 212 return (EINVAL); 213 214 p1 = td->td_proc; 215 216 /* 217 * Here we don't create a new process, but we divorce 218 * certain parts of a process from itself. 219 */ 220 if ((flags & RFPROC) == 0) { 221 mtx_lock(&Giant); 222 vm_forkproc(td, NULL, NULL, flags); 223 mtx_unlock(&Giant); 224 225 /* 226 * Close all file descriptors. 227 */ 228 if (flags & RFCFDG) { 229 struct filedesc *fdtmp; 230 FILEDESC_LOCK(td->td_proc->p_fd); 231 fdtmp = fdinit(td->td_proc->p_fd); 232 FILEDESC_UNLOCK(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 *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_HADTHREADS) { 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 return (ERESTART); 275 } 276 PROC_UNLOCK(p1); 277 /* 278 * All other activity in this process 279 * is now suspended at the user boundary, 280 * (or other safe places if we think of any). 281 */ 282 } 283 284 /* Allocate new proc. */ 285 newproc = uma_zalloc(proc_zone, M_WAITOK); 286 #ifdef MAC 287 mac_init_proc(newproc); 288 #endif 289 knlist_init(&newproc->p_klist, &newproc->p_mtx); 290 291 /* We have to lock the process tree while we look for a pid. */ 292 sx_slock(&proctree_lock); 293 294 /* 295 * Although process entries are dynamically created, we still keep 296 * a global limit on the maximum number we will create. Don't allow 297 * a nonprivileged user to use the last ten processes; don't let root 298 * exceed the limit. The variable nprocs is the current number of 299 * processes, maxproc is the limit. 300 */ 301 sx_xlock(&allproc_lock); 302 uid = td->td_ucred->cr_ruid; 303 if ((nprocs >= maxproc - 10 && 304 suser_cred(td->td_ucred, SUSER_RUID) != 0) || 305 nprocs >= maxproc) { 306 error = EAGAIN; 307 goto fail; 308 } 309 310 /* 311 * Increment the count of procs running with this uid. Don't allow 312 * a nonprivileged user to exceed their current limit. 313 */ 314 PROC_LOCK(p1); 315 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 316 (uid != 0) ? lim_cur(p1, RLIMIT_NPROC) : 0); 317 PROC_UNLOCK(p1); 318 if (!ok) { 319 error = EAGAIN; 320 goto fail; 321 } 322 323 /* 324 * Increment the nprocs resource before blocking can occur. There 325 * are hard-limits as to the number of processes that can run. 326 */ 327 nprocs++; 328 329 /* 330 * Find an unused process ID. We remember a range of unused IDs 331 * ready to use (from lastpid+1 through pidchecked-1). 332 * 333 * If RFHIGHPID is set (used during system boot), do not allocate 334 * low-numbered pids. 335 */ 336 trypid = lastpid + 1; 337 if (flags & RFHIGHPID) { 338 if (trypid < 10) 339 trypid = 10; 340 } else { 341 if (randompid) 342 trypid += arc4random() % randompid; 343 } 344 retry: 345 /* 346 * If the process ID prototype has wrapped around, 347 * restart somewhat above 0, as the low-numbered procs 348 * tend to include daemons that don't exit. 349 */ 350 if (trypid >= PID_MAX) { 351 trypid = trypid % PID_MAX; 352 if (trypid < 100) 353 trypid += 100; 354 pidchecked = 0; 355 } 356 if (trypid >= pidchecked) { 357 int doingzomb = 0; 358 359 pidchecked = PID_MAX; 360 /* 361 * Scan the active and zombie procs to check whether this pid 362 * is in use. Remember the lowest pid that's greater 363 * than trypid, so we can avoid checking for a while. 364 */ 365 p2 = LIST_FIRST(&allproc); 366 again: 367 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 368 PROC_LOCK(p2); 369 while (p2->p_pid == trypid || 370 (p2->p_pgrp != NULL && 371 (p2->p_pgrp->pg_id == trypid || 372 (p2->p_session != NULL && 373 p2->p_session->s_sid == trypid)))) { 374 trypid++; 375 if (trypid >= pidchecked) { 376 PROC_UNLOCK(p2); 377 goto retry; 378 } 379 } 380 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 381 pidchecked = p2->p_pid; 382 if (p2->p_pgrp != NULL) { 383 if (p2->p_pgrp->pg_id > trypid && 384 pidchecked > p2->p_pgrp->pg_id) 385 pidchecked = p2->p_pgrp->pg_id; 386 if (p2->p_session != NULL && 387 p2->p_session->s_sid > trypid && 388 pidchecked > p2->p_session->s_sid) 389 pidchecked = p2->p_session->s_sid; 390 } 391 PROC_UNLOCK(p2); 392 } 393 if (!doingzomb) { 394 doingzomb = 1; 395 p2 = LIST_FIRST(&zombproc); 396 goto again; 397 } 398 } 399 sx_sunlock(&proctree_lock); 400 401 /* 402 * RFHIGHPID does not mess with the lastpid counter during boot. 403 */ 404 if (flags & RFHIGHPID) 405 pidchecked = 0; 406 else 407 lastpid = trypid; 408 409 p2 = newproc; 410 p2->p_state = PRS_NEW; /* protect against others */ 411 p2->p_pid = trypid; 412 LIST_INSERT_HEAD(&allproc, p2, p_list); 413 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 414 sx_xunlock(&allproc_lock); 415 416 /* 417 * Malloc things while we don't hold any locks. 418 */ 419 if (flags & RFSIGSHARE) 420 newsigacts = NULL; 421 else 422 newsigacts = sigacts_alloc(); 423 424 /* 425 * Copy filedesc. 426 */ 427 if (flags & RFCFDG) { 428 FILEDESC_LOCK(td->td_proc->p_fd); 429 fd = fdinit(td->td_proc->p_fd); 430 FILEDESC_UNLOCK(td->td_proc->p_fd); 431 fdtol = NULL; 432 } else if (flags & RFFDG) { 433 FILEDESC_LOCK(p1->p_fd); 434 fd = fdcopy(td->td_proc->p_fd); 435 FILEDESC_UNLOCK(p1->p_fd); 436 fdtol = NULL; 437 } else { 438 fd = fdshare(p1->p_fd); 439 if (p1->p_fdtol == NULL) 440 p1->p_fdtol = 441 filedesc_to_leader_alloc(NULL, 442 NULL, 443 p1->p_leader); 444 if ((flags & RFTHREAD) != 0) { 445 /* 446 * Shared file descriptor table and 447 * shared process leaders. 448 */ 449 fdtol = p1->p_fdtol; 450 FILEDESC_LOCK(p1->p_fd); 451 fdtol->fdl_refcount++; 452 FILEDESC_UNLOCK(p1->p_fd); 453 } else { 454 /* 455 * Shared file descriptor table, and 456 * different process leaders 457 */ 458 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 459 p1->p_fd, 460 p2); 461 } 462 } 463 /* 464 * Make a proc table entry for the new process. 465 * Start by zeroing the section of proc that is zero-initialized, 466 * then copy the section that is copied directly from the parent. 467 */ 468 td2 = FIRST_THREAD_IN_PROC(p2); 469 kg2 = FIRST_KSEGRP_IN_PROC(p2); 470 471 /* Allocate and switch to an alternate kstack if specified. */ 472 if (pages != 0) 473 vm_thread_new_altkstack(td2, pages); 474 475 PROC_LOCK(p2); 476 PROC_LOCK(p1); 477 478 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 479 480 bzero(&p2->p_startzero, 481 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 482 bzero(&td2->td_startzero, 483 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 484 bzero(&kg2->kg_startzero, 485 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 486 487 bcopy(&p1->p_startcopy, &p2->p_startcopy, 488 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 489 bcopy(&td->td_startcopy, &td2->td_startcopy, 490 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 491 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 492 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 493 #undef RANGEOF 494 495 td2->td_sigstk = td->td_sigstk; 496 497 /* 498 * Duplicate sub-structures as needed. 499 * Increase reference counts on shared objects. 500 * The p_stats substruct is set in vm_forkproc. 501 */ 502 p2->p_flag = 0; 503 if (p1->p_flag & P_PROFIL) 504 startprofclock(p2); 505 mtx_lock_spin(&sched_lock); 506 p2->p_sflag = PS_INMEM; 507 /* 508 * Allow the scheduler to adjust the priority of the child and 509 * parent while we hold the sched_lock. 510 */ 511 sched_fork(td, td2); 512 513 mtx_unlock_spin(&sched_lock); 514 p2->p_ucred = crhold(td->td_ucred); 515 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 516 517 pargs_hold(p2->p_args); 518 519 if (flags & RFSIGSHARE) { 520 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 521 } else { 522 sigacts_copy(newsigacts, p1->p_sigacts); 523 p2->p_sigacts = newsigacts; 524 } 525 if (flags & RFLINUXTHPN) 526 p2->p_sigparent = SIGUSR1; 527 else 528 p2->p_sigparent = SIGCHLD; 529 530 p2->p_textvp = p1->p_textvp; 531 p2->p_fd = fd; 532 p2->p_fdtol = fdtol; 533 534 /* 535 * p_limit is copy-on-write. Bump its refcount. 536 */ 537 p2->p_limit = lim_hold(p1->p_limit); 538 PROC_UNLOCK(p1); 539 PROC_UNLOCK(p2); 540 541 /* Bump references to the text vnode (for procfs) */ 542 if (p2->p_textvp) 543 vref(p2->p_textvp); 544 545 /* 546 * Set up linkage for kernel based threading. 547 */ 548 if ((flags & RFTHREAD) != 0) { 549 mtx_lock(&ppeers_lock); 550 p2->p_peers = p1->p_peers; 551 p1->p_peers = p2; 552 p2->p_leader = p1->p_leader; 553 mtx_unlock(&ppeers_lock); 554 PROC_LOCK(p1->p_leader); 555 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 556 PROC_UNLOCK(p1->p_leader); 557 /* 558 * The task leader is exiting, so process p1 is 559 * going to be killed shortly. Since p1 obviously 560 * isn't dead yet, we know that the leader is either 561 * sending SIGKILL's to all the processes in this 562 * task or is sleeping waiting for all the peers to 563 * exit. We let p1 complete the fork, but we need 564 * to go ahead and kill the new process p2 since 565 * the task leader may not get a chance to send 566 * SIGKILL to it. We leave it on the list so that 567 * the task leader will wait for this new process 568 * to commit suicide. 569 */ 570 PROC_LOCK(p2); 571 psignal(p2, SIGKILL); 572 PROC_UNLOCK(p2); 573 } else 574 PROC_UNLOCK(p1->p_leader); 575 } else { 576 p2->p_peers = NULL; 577 p2->p_leader = p2; 578 } 579 580 sx_xlock(&proctree_lock); 581 PGRP_LOCK(p1->p_pgrp); 582 PROC_LOCK(p2); 583 PROC_LOCK(p1); 584 585 /* 586 * Preserve some more flags in subprocess. P_PROFIL has already 587 * been preserved. 588 */ 589 p2->p_flag |= p1->p_flag & P_SUGID; 590 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 591 SESS_LOCK(p1->p_session); 592 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 593 p2->p_flag |= P_CONTROLT; 594 SESS_UNLOCK(p1->p_session); 595 if (flags & RFPPWAIT) 596 p2->p_flag |= P_PPWAIT; 597 598 p2->p_pgrp = p1->p_pgrp; 599 LIST_INSERT_AFTER(p1, p2, p_pglist); 600 PGRP_UNLOCK(p1->p_pgrp); 601 LIST_INIT(&p2->p_children); 602 603 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 604 605 #ifdef KTRACE 606 /* 607 * Copy traceflag and tracefile if enabled. 608 */ 609 mtx_lock(&ktrace_mtx); 610 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 611 if (p1->p_traceflag & KTRFAC_INHERIT) { 612 p2->p_traceflag = p1->p_traceflag; 613 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 614 VREF(p2->p_tracevp); 615 KASSERT(p1->p_tracecred != NULL, 616 ("ktrace vnode with no cred")); 617 p2->p_tracecred = crhold(p1->p_tracecred); 618 } 619 } 620 mtx_unlock(&ktrace_mtx); 621 #endif 622 623 /* 624 * If PF_FORK is set, the child process inherits the 625 * procfs ioctl flags from its parent. 626 */ 627 if (p1->p_pfsflags & PF_FORK) { 628 p2->p_stops = p1->p_stops; 629 p2->p_pfsflags = p1->p_pfsflags; 630 } 631 632 /* 633 * This begins the section where we must prevent the parent 634 * from being swapped. 635 */ 636 _PHOLD(p1); 637 PROC_UNLOCK(p1); 638 639 /* 640 * Attach the new process to its parent. 641 * 642 * If RFNOWAIT is set, the newly created process becomes a child 643 * of init. This effectively disassociates the child from the 644 * parent. 645 */ 646 if (flags & RFNOWAIT) 647 pptr = initproc; 648 else 649 pptr = p1; 650 p2->p_pptr = pptr; 651 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 652 sx_xunlock(&proctree_lock); 653 654 /* Inform accounting that we have forked. */ 655 p2->p_acflag = AFORK; 656 PROC_UNLOCK(p2); 657 658 /* 659 * Finish creating the child process. It will return via a different 660 * execution path later. (ie: directly into user mode) 661 */ 662 mtx_lock(&Giant); 663 vm_forkproc(td, p2, td2, flags); 664 665 if (flags == (RFFDG | RFPROC)) { 666 cnt.v_forks++; 667 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 668 p2->p_vmspace->vm_ssize; 669 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 670 cnt.v_vforks++; 671 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 672 p2->p_vmspace->vm_ssize; 673 } else if (p1 == &proc0) { 674 cnt.v_kthreads++; 675 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 676 p2->p_vmspace->vm_ssize; 677 } else { 678 cnt.v_rforks++; 679 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 680 p2->p_vmspace->vm_ssize; 681 } 682 mtx_unlock(&Giant); 683 684 /* 685 * Both processes are set up, now check if any loadable modules want 686 * to adjust anything. 687 * What if they have an error? XXX 688 */ 689 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 690 691 /* 692 * Set the child start time and mark the process as being complete. 693 */ 694 microuptime(&p2->p_stats->p_start); 695 mtx_lock_spin(&sched_lock); 696 p2->p_state = PRS_NORMAL; 697 698 /* 699 * If RFSTOPPED not requested, make child runnable and add to 700 * run queue. 701 */ 702 if ((flags & RFSTOPPED) == 0) { 703 TD_SET_CAN_RUN(td2); 704 setrunqueue(td2, SRQ_BORING); 705 } 706 mtx_unlock_spin(&sched_lock); 707 708 /* 709 * Now can be swapped. 710 */ 711 PROC_LOCK(p1); 712 _PRELE(p1); 713 714 /* 715 * Tell any interested parties about the new process. 716 */ 717 KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid); 718 719 PROC_UNLOCK(p1); 720 721 /* 722 * Preserve synchronization semantics of vfork. If waiting for 723 * child to exec or exit, set P_PPWAIT on child, and sleep on our 724 * proc (in case of exit). 725 */ 726 PROC_LOCK(p2); 727 while (p2->p_flag & P_PPWAIT) 728 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 729 PROC_UNLOCK(p2); 730 731 /* 732 * If other threads are waiting, let them continue now. 733 */ 734 if (p1->p_flag & P_HADTHREADS) { 735 PROC_LOCK(p1); 736 thread_single_end(); 737 PROC_UNLOCK(p1); 738 } 739 740 /* 741 * Return child proc pointer to parent. 742 */ 743 *procp = p2; 744 return (0); 745 fail: 746 sx_sunlock(&proctree_lock); 747 if (ppsratecheck(&lastfail, &curfail, 1)) 748 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 749 uid); 750 sx_xunlock(&allproc_lock); 751 #ifdef MAC 752 mac_destroy_proc(newproc); 753 #endif 754 uma_zfree(proc_zone, newproc); 755 if (p1->p_flag & P_HADTHREADS) { 756 PROC_LOCK(p1); 757 thread_single_end(); 758 PROC_UNLOCK(p1); 759 } 760 tsleep(&forksleep, PUSER, "fork", hz / 2); 761 return (error); 762 } 763 764 /* 765 * Handle the return of a child process from fork1(). This function 766 * is called from the MD fork_trampoline() entry point. 767 */ 768 void 769 fork_exit(callout, arg, frame) 770 void (*callout)(void *, struct trapframe *); 771 void *arg; 772 struct trapframe *frame; 773 { 774 struct proc *p; 775 struct thread *td; 776 777 /* 778 * Finish setting up thread glue so that it begins execution in a 779 * non-nested critical section with sched_lock held but not recursed. 780 */ 781 td = curthread; 782 p = td->td_proc; 783 td->td_oncpu = PCPU_GET(cpuid); 784 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 785 786 sched_lock.mtx_lock = (uintptr_t)td; 787 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 788 cpu_critical_fork_exit(); 789 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 790 td, td->td_sched, p->p_pid, p->p_comm); 791 792 /* 793 * Processes normally resume in mi_switch() after being 794 * cpu_switch()'ed to, but when children start up they arrive here 795 * instead, so we must do much the same things as mi_switch() would. 796 */ 797 798 if ((td = PCPU_GET(deadthread))) { 799 PCPU_SET(deadthread, NULL); 800 thread_stash(td); 801 } 802 td = curthread; 803 mtx_unlock_spin(&sched_lock); 804 805 /* 806 * cpu_set_fork_handler intercepts this function call to 807 * have this call a non-return function to stay in kernel mode. 808 * initproc has its own fork handler, but it does return. 809 */ 810 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 811 callout(arg, frame); 812 813 /* 814 * Check if a kernel thread misbehaved and returned from its main 815 * function. 816 */ 817 PROC_LOCK(p); 818 if (p->p_flag & P_KTHREAD) { 819 PROC_UNLOCK(p); 820 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 821 p->p_comm, p->p_pid); 822 kthread_exit(0); 823 } 824 PROC_UNLOCK(p); 825 mtx_assert(&Giant, MA_NOTOWNED); 826 } 827 828 /* 829 * Simplified back end of syscall(), used when returning from fork() 830 * directly into user mode. Giant is not held on entry, and must not 831 * be held on return. This function is passed in to fork_exit() as the 832 * first parameter and is called when returning to a new userland process. 833 */ 834 void 835 fork_return(td, frame) 836 struct thread *td; 837 struct trapframe *frame; 838 { 839 840 userret(td, frame, 0); 841 #ifdef KTRACE 842 if (KTRPOINT(td, KTR_SYSRET)) 843 ktrsysret(SYS_fork, 0, 0); 844 #endif 845 mtx_assert(&Giant, MA_NOTOWNED); 846 }
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