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("$FreeBSD$"); 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/priv.h> 55 #include <sys/proc.h> 56 #include <sys/pioctl.h> 57 #include <sys/resourcevar.h> 58 #include <sys/sched.h> 59 #include <sys/syscall.h> 60 #include <sys/vmmeter.h> 61 #include <sys/vnode.h> 62 #include <sys/acct.h> 63 #include <sys/ktr.h> 64 #include <sys/ktrace.h> 65 #include <sys/unistd.h> 66 #include <sys/sx.h> 67 #include <sys/signalvar.h> 68 69 #include <security/audit/audit.h> 70 #include <security/mac/mac_framework.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 79 #ifndef _SYS_SYSPROTO_H_ 80 struct fork_args { 81 int dummy; 82 }; 83 #endif 84 85 /* ARGSUSED */ 86 int 87 fork(td, uap) 88 struct thread *td; 89 struct fork_args *uap; 90 { 91 int error; 92 struct proc *p2; 93 94 error = fork1(td, RFFDG | RFPROC, 0, &p2); 95 if (error == 0) { 96 td->td_retval[0] = p2->p_pid; 97 td->td_retval[1] = 0; 98 } 99 return (error); 100 } 101 102 /* ARGSUSED */ 103 int 104 vfork(td, uap) 105 struct thread *td; 106 struct vfork_args *uap; 107 { 108 int error; 109 struct proc *p2; 110 111 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 112 if (error == 0) { 113 td->td_retval[0] = p2->p_pid; 114 td->td_retval[1] = 0; 115 } 116 return (error); 117 } 118 119 int 120 rfork(td, uap) 121 struct thread *td; 122 struct rfork_args *uap; 123 { 124 struct proc *p2; 125 int error; 126 127 /* Don't allow kernel-only flags. */ 128 if ((uap->flags & RFKERNELONLY) != 0) 129 return (EINVAL); 130 131 AUDIT_ARG(fflags, uap->flags); 132 error = fork1(td, uap->flags, 0, &p2); 133 if (error == 0) { 134 td->td_retval[0] = p2 ? p2->p_pid : 0; 135 td->td_retval[1] = 0; 136 } 137 return (error); 138 } 139 140 int nprocs = 1; /* process 0 */ 141 int lastpid = 0; 142 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 143 "Last used PID"); 144 145 /* 146 * Random component to lastpid generation. We mix in a random factor to make 147 * it a little harder to predict. We sanity check the modulus value to avoid 148 * doing it in critical paths. Don't let it be too small or we pointlessly 149 * waste randomness entropy, and don't let it be impossibly large. Using a 150 * modulus that is too big causes a LOT more process table scans and slows 151 * down fork processing as the pidchecked caching is defeated. 152 */ 153 static int randompid = 0; 154 155 static int 156 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 157 { 158 int error, pid; 159 160 error = sysctl_wire_old_buffer(req, sizeof(int)); 161 if (error != 0) 162 return(error); 163 sx_xlock(&allproc_lock); 164 pid = randompid; 165 error = sysctl_handle_int(oidp, &pid, 0, req); 166 if (error == 0 && req->newptr != NULL) { 167 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 168 pid = PID_MAX - 100; 169 else if (pid < 2) /* NOP */ 170 pid = 0; 171 else if (pid < 100) /* Make it reasonable */ 172 pid = 100; 173 randompid = pid; 174 } 175 sx_xunlock(&allproc_lock); 176 return (error); 177 } 178 179 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 180 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 181 182 int 183 fork1(td, flags, pages, procp) 184 struct thread *td; 185 int flags; 186 int pages; 187 struct proc **procp; 188 { 189 struct proc *p1, *p2, *pptr; 190 struct proc *newproc; 191 int ok, trypid; 192 static int curfail, pidchecked = 0; 193 static struct timeval lastfail; 194 struct filedesc *fd; 195 struct filedesc_to_leader *fdtol; 196 struct thread *td2; 197 struct sigacts *newsigacts; 198 struct vmspace *vm2; 199 int error; 200 201 /* Can't copy and clear. */ 202 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 203 return (EINVAL); 204 205 p1 = td->td_proc; 206 207 /* 208 * Here we don't create a new process, but we divorce 209 * certain parts of a process from itself. 210 */ 211 if ((flags & RFPROC) == 0) { 212 if ((p1->p_flag & P_HADTHREADS) && 213 (flags & (RFCFDG | RFFDG))) { 214 PROC_LOCK(p1); 215 if (thread_single(SINGLE_BOUNDARY)) { 216 PROC_UNLOCK(p1); 217 return (ERESTART); 218 } 219 PROC_UNLOCK(p1); 220 } 221 222 error = vm_forkproc(td, NULL, NULL, NULL, flags); 223 if (error) 224 goto norfproc_fail; 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 fdunshare(p1, td); 241 242 norfproc_fail: 243 if ((p1->p_flag & P_HADTHREADS) && 244 (flags & (RFCFDG | RFFDG))) { 245 PROC_LOCK(p1); 246 thread_single_end(); 247 PROC_UNLOCK(p1); 248 } 249 *procp = NULL; 250 return (error); 251 } 252 253 /* Allocate new proc. */ 254 newproc = uma_zalloc(proc_zone, M_WAITOK); 255 if (TAILQ_EMPTY(&newproc->p_threads)) { 256 td2 = thread_alloc(); 257 if (td2 == NULL) { 258 error = ENOMEM; 259 goto fail1; 260 } 261 proc_linkup(newproc, td2); 262 sched_newproc(newproc, td2); 263 } else 264 td2 = FIRST_THREAD_IN_PROC(newproc); 265 266 /* Allocate and switch to an alternate kstack if specified. */ 267 if (pages != 0) { 268 if (!vm_thread_new_altkstack(td2, pages)) { 269 error = ENOMEM; 270 goto fail1; 271 } 272 } 273 if ((flags & RFMEM) == 0) { 274 vm2 = vmspace_fork(p1->p_vmspace); 275 if (vm2 == NULL) { 276 error = ENOMEM; 277 goto fail1; 278 } 279 } else 280 vm2 = NULL; 281 #ifdef MAC 282 mac_init_proc(newproc); 283 #endif 284 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL); 285 STAILQ_INIT(&newproc->p_ktr); 286 287 /* We have to lock the process tree while we look for a pid. */ 288 sx_slock(&proctree_lock); 289 290 /* 291 * Although process entries are dynamically created, we still keep 292 * a global limit on the maximum number we will create. Don't allow 293 * a nonprivileged user to use the last ten processes; don't let root 294 * exceed the limit. The variable nprocs is the current number of 295 * processes, maxproc is the limit. 296 */ 297 sx_xlock(&allproc_lock); 298 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 299 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 300 error = EAGAIN; 301 goto fail; 302 } 303 304 /* 305 * Increment the count of procs running with this uid. Don't allow 306 * a nonprivileged user to exceed their current limit. 307 * 308 * XXXRW: Can we avoid privilege here if it's not needed? 309 */ 310 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 311 if (error == 0) 312 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 313 else { 314 PROC_LOCK(p1); 315 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 316 lim_cur(p1, RLIMIT_NPROC)); 317 PROC_UNLOCK(p1); 318 } 319 if (!ok) { 320 error = EAGAIN; 321 goto fail; 322 } 323 324 /* 325 * Increment the nprocs resource before blocking can occur. There 326 * are hard-limits as to the number of processes that can run. 327 */ 328 nprocs++; 329 330 /* 331 * Find an unused process ID. We remember a range of unused IDs 332 * ready to use (from lastpid+1 through pidchecked-1). 333 * 334 * If RFHIGHPID is set (used during system boot), do not allocate 335 * low-numbered pids. 336 */ 337 trypid = lastpid + 1; 338 if (flags & RFHIGHPID) { 339 if (trypid < 10) 340 trypid = 10; 341 } else { 342 if (randompid) 343 trypid += arc4random() % randompid; 344 } 345 retry: 346 /* 347 * If the process ID prototype has wrapped around, 348 * restart somewhat above 0, as the low-numbered procs 349 * tend to include daemons that don't exit. 350 */ 351 if (trypid >= PID_MAX) { 352 trypid = trypid % PID_MAX; 353 if (trypid < 100) 354 trypid += 100; 355 pidchecked = 0; 356 } 357 if (trypid >= pidchecked) { 358 int doingzomb = 0; 359 360 pidchecked = PID_MAX; 361 /* 362 * Scan the active and zombie procs to check whether this pid 363 * is in use. Remember the lowest pid that's greater 364 * than trypid, so we can avoid checking for a while. 365 */ 366 p2 = LIST_FIRST(&allproc); 367 again: 368 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 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 goto retry; 377 } 378 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 379 pidchecked = p2->p_pid; 380 if (p2->p_pgrp != NULL) { 381 if (p2->p_pgrp->pg_id > trypid && 382 pidchecked > p2->p_pgrp->pg_id) 383 pidchecked = p2->p_pgrp->pg_id; 384 if (p2->p_session != NULL && 385 p2->p_session->s_sid > trypid && 386 pidchecked > p2->p_session->s_sid) 387 pidchecked = p2->p_session->s_sid; 388 } 389 } 390 if (!doingzomb) { 391 doingzomb = 1; 392 p2 = LIST_FIRST(&zombproc); 393 goto again; 394 } 395 } 396 sx_sunlock(&proctree_lock); 397 398 /* 399 * RFHIGHPID does not mess with the lastpid counter during boot. 400 */ 401 if (flags & RFHIGHPID) 402 pidchecked = 0; 403 else 404 lastpid = trypid; 405 406 p2 = newproc; 407 p2->p_state = PRS_NEW; /* protect against others */ 408 p2->p_pid = trypid; 409 /* 410 * Allow the scheduler to initialize the child. 411 */ 412 thread_lock(td); 413 sched_fork(td, td2); 414 thread_unlock(td); 415 AUDIT_ARG(pid, p2->p_pid); 416 LIST_INSERT_HEAD(&allproc, p2, p_list); 417 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 418 419 PROC_LOCK(p2); 420 PROC_LOCK(p1); 421 422 sx_xunlock(&allproc_lock); 423 424 bcopy(&p1->p_startcopy, &p2->p_startcopy, 425 __rangeof(struct proc, p_startcopy, p_endcopy)); 426 PROC_UNLOCK(p1); 427 428 bzero(&p2->p_startzero, 429 __rangeof(struct proc, p_startzero, p_endzero)); 430 431 p2->p_ucred = crhold(td->td_ucred); 432 PROC_UNLOCK(p2); 433 434 /* 435 * Malloc things while we don't hold any locks. 436 */ 437 if (flags & RFSIGSHARE) 438 newsigacts = NULL; 439 else 440 newsigacts = sigacts_alloc(); 441 442 /* 443 * Copy filedesc. 444 */ 445 if (flags & RFCFDG) { 446 fd = fdinit(p1->p_fd); 447 fdtol = NULL; 448 } else if (flags & RFFDG) { 449 fd = fdcopy(p1->p_fd); 450 fdtol = NULL; 451 } else { 452 fd = fdshare(p1->p_fd); 453 if (p1->p_fdtol == NULL) 454 p1->p_fdtol = 455 filedesc_to_leader_alloc(NULL, 456 NULL, 457 p1->p_leader); 458 if ((flags & RFTHREAD) != 0) { 459 /* 460 * Shared file descriptor table and 461 * shared process leaders. 462 */ 463 fdtol = p1->p_fdtol; 464 FILEDESC_XLOCK(p1->p_fd); 465 fdtol->fdl_refcount++; 466 FILEDESC_XUNLOCK(p1->p_fd); 467 } else { 468 /* 469 * Shared file descriptor table, and 470 * different process leaders 471 */ 472 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 473 p1->p_fd, 474 p2); 475 } 476 } 477 /* 478 * Make a proc table entry for the new process. 479 * Start by zeroing the section of proc that is zero-initialized, 480 * then copy the section that is copied directly from the parent. 481 */ 482 483 PROC_LOCK(p2); 484 PROC_LOCK(p1); 485 486 bzero(&td2->td_startzero, 487 __rangeof(struct thread, td_startzero, td_endzero)); 488 489 bcopy(&td->td_startcopy, &td2->td_startcopy, 490 __rangeof(struct thread, td_startcopy, td_endcopy)); 491 492 td2->td_sigstk = td->td_sigstk; 493 td2->td_sigmask = td->td_sigmask; 494 td2->td_flags = TDF_INMEM; 495 496 /* 497 * Duplicate sub-structures as needed. 498 * Increase reference counts on shared objects. 499 */ 500 p2->p_flag = P_INMEM; 501 p2->p_swtick = ticks; 502 if (p1->p_flag & P_PROFIL) 503 startprofclock(p2); 504 td2->td_ucred = crhold(p2->p_ucred); 505 pargs_hold(p2->p_args); 506 507 if (flags & RFSIGSHARE) { 508 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 509 } else { 510 sigacts_copy(newsigacts, p1->p_sigacts); 511 p2->p_sigacts = newsigacts; 512 } 513 if (flags & RFLINUXTHPN) 514 p2->p_sigparent = SIGUSR1; 515 else 516 p2->p_sigparent = SIGCHLD; 517 518 p2->p_textvp = p1->p_textvp; 519 p2->p_fd = fd; 520 p2->p_fdtol = fdtol; 521 522 /* 523 * p_limit is copy-on-write. Bump its refcount. 524 */ 525 lim_fork(p1, p2); 526 527 pstats_fork(p1->p_stats, p2->p_stats); 528 529 PROC_UNLOCK(p1); 530 PROC_UNLOCK(p2); 531 532 /* Bump references to the text vnode (for procfs) */ 533 if (p2->p_textvp) 534 vref(p2->p_textvp); 535 536 /* 537 * Set up linkage for kernel based threading. 538 */ 539 if ((flags & RFTHREAD) != 0) { 540 mtx_lock(&ppeers_lock); 541 p2->p_peers = p1->p_peers; 542 p1->p_peers = p2; 543 p2->p_leader = p1->p_leader; 544 mtx_unlock(&ppeers_lock); 545 PROC_LOCK(p1->p_leader); 546 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 547 PROC_UNLOCK(p1->p_leader); 548 /* 549 * The task leader is exiting, so process p1 is 550 * going to be killed shortly. Since p1 obviously 551 * isn't dead yet, we know that the leader is either 552 * sending SIGKILL's to all the processes in this 553 * task or is sleeping waiting for all the peers to 554 * exit. We let p1 complete the fork, but we need 555 * to go ahead and kill the new process p2 since 556 * the task leader may not get a chance to send 557 * SIGKILL to it. We leave it on the list so that 558 * the task leader will wait for this new process 559 * to commit suicide. 560 */ 561 PROC_LOCK(p2); 562 psignal(p2, SIGKILL); 563 PROC_UNLOCK(p2); 564 } else 565 PROC_UNLOCK(p1->p_leader); 566 } else { 567 p2->p_peers = NULL; 568 p2->p_leader = p2; 569 } 570 571 sx_xlock(&proctree_lock); 572 PGRP_LOCK(p1->p_pgrp); 573 PROC_LOCK(p2); 574 PROC_LOCK(p1); 575 576 /* 577 * Preserve some more flags in subprocess. P_PROFIL has already 578 * been preserved. 579 */ 580 p2->p_flag |= p1->p_flag & P_SUGID; 581 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 582 SESS_LOCK(p1->p_session); 583 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 584 p2->p_flag |= P_CONTROLT; 585 SESS_UNLOCK(p1->p_session); 586 if (flags & RFPPWAIT) 587 p2->p_flag |= P_PPWAIT; 588 589 p2->p_pgrp = p1->p_pgrp; 590 LIST_INSERT_AFTER(p1, p2, p_pglist); 591 PGRP_UNLOCK(p1->p_pgrp); 592 LIST_INIT(&p2->p_children); 593 594 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 595 596 #ifdef KTRACE 597 /* 598 * Copy traceflag and tracefile if enabled. 599 */ 600 mtx_lock(&ktrace_mtx); 601 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 602 if (p1->p_traceflag & KTRFAC_INHERIT) { 603 p2->p_traceflag = p1->p_traceflag; 604 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 605 VREF(p2->p_tracevp); 606 KASSERT(p1->p_tracecred != NULL, 607 ("ktrace vnode with no cred")); 608 p2->p_tracecred = crhold(p1->p_tracecred); 609 } 610 } 611 mtx_unlock(&ktrace_mtx); 612 #endif 613 614 /* 615 * If PF_FORK is set, the child process inherits the 616 * procfs ioctl flags from its parent. 617 */ 618 if (p1->p_pfsflags & PF_FORK) { 619 p2->p_stops = p1->p_stops; 620 p2->p_pfsflags = p1->p_pfsflags; 621 } 622 623 /* 624 * This begins the section where we must prevent the parent 625 * from being swapped. 626 */ 627 _PHOLD(p1); 628 PROC_UNLOCK(p1); 629 630 /* 631 * Attach the new process to its parent. 632 * 633 * If RFNOWAIT is set, the newly created process becomes a child 634 * of init. This effectively disassociates the child from the 635 * parent. 636 */ 637 if (flags & RFNOWAIT) 638 pptr = initproc; 639 else 640 pptr = p1; 641 p2->p_pptr = pptr; 642 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 643 sx_xunlock(&proctree_lock); 644 645 /* Inform accounting that we have forked. */ 646 p2->p_acflag = AFORK; 647 PROC_UNLOCK(p2); 648 649 /* 650 * Finish creating the child process. It will return via a different 651 * execution path later. (ie: directly into user mode) 652 */ 653 vm_forkproc(td, p2, td2, vm2, flags); 654 655 if (flags == (RFFDG | RFPROC)) { 656 PCPU_INC(cnt.v_forks); 657 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 658 p2->p_vmspace->vm_ssize); 659 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 660 PCPU_INC(cnt.v_vforks); 661 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 662 p2->p_vmspace->vm_ssize); 663 } else if (p1 == &proc0) { 664 PCPU_INC(cnt.v_kthreads); 665 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 666 p2->p_vmspace->vm_ssize); 667 } else { 668 PCPU_INC(cnt.v_rforks); 669 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 670 p2->p_vmspace->vm_ssize); 671 } 672 673 /* 674 * Both processes are set up, now check if any loadable modules want 675 * to adjust anything. 676 * What if they have an error? XXX 677 */ 678 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 679 680 /* 681 * Set the child start time and mark the process as being complete. 682 */ 683 microuptime(&p2->p_stats->p_start); 684 PROC_SLOCK(p2); 685 p2->p_state = PRS_NORMAL; 686 PROC_SUNLOCK(p2); 687 688 /* 689 * If RFSTOPPED not requested, make child runnable and add to 690 * run queue. 691 */ 692 if ((flags & RFSTOPPED) == 0) { 693 thread_lock(td2); 694 TD_SET_CAN_RUN(td2); 695 sched_add(td2, SRQ_BORING); 696 thread_unlock(td2); 697 } 698 699 /* 700 * Now can be swapped. 701 */ 702 PROC_LOCK(p1); 703 _PRELE(p1); 704 705 /* 706 * Tell any interested parties about the new process. 707 */ 708 KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid); 709 710 PROC_UNLOCK(p1); 711 712 /* 713 * Preserve synchronization semantics of vfork. If waiting for 714 * child to exec or exit, set P_PPWAIT on child, and sleep on our 715 * proc (in case of exit). 716 */ 717 PROC_LOCK(p2); 718 while (p2->p_flag & P_PPWAIT) 719 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 720 PROC_UNLOCK(p2); 721 722 /* 723 * Return child proc pointer to parent. 724 */ 725 *procp = p2; 726 return (0); 727 fail: 728 sx_sunlock(&proctree_lock); 729 if (ppsratecheck(&lastfail, &curfail, 1)) 730 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 731 td->td_ucred->cr_ruid); 732 sx_xunlock(&allproc_lock); 733 #ifdef MAC 734 mac_destroy_proc(newproc); 735 #endif 736 fail1: 737 uma_zfree(proc_zone, newproc); 738 pause("fork", hz / 2); 739 return (error); 740 } 741 742 /* 743 * Handle the return of a child process from fork1(). This function 744 * is called from the MD fork_trampoline() entry point. 745 */ 746 void 747 fork_exit(callout, arg, frame) 748 void (*callout)(void *, struct trapframe *); 749 void *arg; 750 struct trapframe *frame; 751 { 752 struct proc *p; 753 struct thread *td; 754 struct thread *dtd; 755 756 td = curthread; 757 p = td->td_proc; 758 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 759 760 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 761 td, td->td_sched, p->p_pid, p->p_comm); 762 763 sched_fork_exit(td); 764 /* 765 * Processes normally resume in mi_switch() after being 766 * cpu_switch()'ed to, but when children start up they arrive here 767 * instead, so we must do much the same things as mi_switch() would. 768 */ 769 if ((dtd = PCPU_GET(deadthread))) { 770 PCPU_SET(deadthread, NULL); 771 thread_stash(dtd); 772 } 773 thread_unlock(td); 774 775 /* 776 * cpu_set_fork_handler intercepts this function call to 777 * have this call a non-return function to stay in kernel mode. 778 * initproc has its own fork handler, but it does return. 779 */ 780 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 781 callout(arg, frame); 782 783 /* 784 * Check if a kernel thread misbehaved and returned from its main 785 * function. 786 */ 787 if (p->p_flag & P_KTHREAD) { 788 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 789 p->p_comm, p->p_pid); 790 kthread_exit(0); 791 } 792 mtx_assert(&Giant, MA_NOTOWNED); 793 794 EVENTHANDLER_INVOKE(schedtail, p); 795 } 796 797 /* 798 * Simplified back end of syscall(), used when returning from fork() 799 * directly into user mode. Giant is not held on entry, and must not 800 * be held on return. This function is passed in to fork_exit() as the 801 * first parameter and is called when returning to a new userland process. 802 */ 803 void 804 fork_return(td, frame) 805 struct thread *td; 806 struct trapframe *frame; 807 { 808 809 userret(td, frame); 810 #ifdef KTRACE 811 if (KTRPOINT(td, KTR_SYSRET)) 812 ktrsysret(SYS_fork, 0, 0); 813 #endif 814 mtx_assert(&Giant, MA_NOTOWNED); 815 }
Cache object: 2ef8844e8580fb1773537e74a6def1a6
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