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_kdtrace.h" 41 #include "opt_ktrace.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/jail.h> 49 #include <sys/kernel.h> 50 #include <sys/kthread.h> 51 #include <sys/sysctl.h> 52 #include <sys/lock.h> 53 #include <sys/malloc.h> 54 #include <sys/mutex.h> 55 #include <sys/priv.h> 56 #include <sys/proc.h> 57 #include <sys/pioctl.h> 58 #include <sys/resourcevar.h> 59 #include <sys/sched.h> 60 #include <sys/syscall.h> 61 #include <sys/vmmeter.h> 62 #include <sys/vnode.h> 63 #include <sys/acct.h> 64 #include <sys/ktr.h> 65 #include <sys/ktrace.h> 66 #include <sys/unistd.h> 67 #include <sys/sdt.h> 68 #include <sys/sx.h> 69 #include <sys/signalvar.h> 70 #include <sys/vimage.h> 71 72 #include <security/audit/audit.h> 73 #include <security/mac/mac_framework.h> 74 75 #include <vm/vm.h> 76 #include <vm/pmap.h> 77 #include <vm/vm_map.h> 78 #include <vm/vm_extern.h> 79 #include <vm/uma.h> 80 81 #ifdef KDTRACE_HOOKS 82 #include <sys/dtrace_bsd.h> 83 dtrace_fork_func_t dtrace_fasttrap_fork; 84 #endif 85 86 SDT_PROVIDER_DECLARE(proc); 87 SDT_PROBE_DEFINE(proc, kernel, , create); 88 SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *"); 89 SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *"); 90 SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int"); 91 92 #ifndef _SYS_SYSPROTO_H_ 93 struct fork_args { 94 int dummy; 95 }; 96 #endif 97 98 /* ARGSUSED */ 99 int 100 fork(td, uap) 101 struct thread *td; 102 struct fork_args *uap; 103 { 104 int error; 105 struct proc *p2; 106 107 error = fork1(td, RFFDG | RFPROC, 0, &p2); 108 if (error == 0) { 109 td->td_retval[0] = p2->p_pid; 110 td->td_retval[1] = 0; 111 } 112 return (error); 113 } 114 115 /* ARGSUSED */ 116 int 117 vfork(td, uap) 118 struct thread *td; 119 struct vfork_args *uap; 120 { 121 int error, flags; 122 struct proc *p2; 123 124 #ifdef XEN 125 flags = RFFDG | RFPROC; /* validate that this is still an issue */ 126 #else 127 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 128 #endif 129 error = fork1(td, flags, 0, &p2); 130 if (error == 0) { 131 td->td_retval[0] = p2->p_pid; 132 td->td_retval[1] = 0; 133 } 134 return (error); 135 } 136 137 int 138 rfork(td, uap) 139 struct thread *td; 140 struct rfork_args *uap; 141 { 142 struct proc *p2; 143 int error; 144 145 /* Don't allow kernel-only flags. */ 146 if ((uap->flags & RFKERNELONLY) != 0) 147 return (EINVAL); 148 149 AUDIT_ARG(fflags, uap->flags); 150 error = fork1(td, uap->flags, 0, &p2); 151 if (error == 0) { 152 td->td_retval[0] = p2 ? p2->p_pid : 0; 153 td->td_retval[1] = 0; 154 } 155 return (error); 156 } 157 158 int nprocs = 1; /* process 0 */ 159 int lastpid = 0; 160 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 161 "Last used PID"); 162 163 /* 164 * Random component to lastpid generation. We mix in a random factor to make 165 * it a little harder to predict. We sanity check the modulus value to avoid 166 * doing it in critical paths. Don't let it be too small or we pointlessly 167 * waste randomness entropy, and don't let it be impossibly large. Using a 168 * modulus that is too big causes a LOT more process table scans and slows 169 * down fork processing as the pidchecked caching is defeated. 170 */ 171 static int randompid = 0; 172 173 static int 174 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 175 { 176 int error, pid; 177 178 error = sysctl_wire_old_buffer(req, sizeof(int)); 179 if (error != 0) 180 return(error); 181 sx_xlock(&allproc_lock); 182 pid = randompid; 183 error = sysctl_handle_int(oidp, &pid, 0, req); 184 if (error == 0 && req->newptr != NULL) { 185 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 186 pid = PID_MAX - 100; 187 else if (pid < 2) /* NOP */ 188 pid = 0; 189 else if (pid < 100) /* Make it reasonable */ 190 pid = 100; 191 randompid = pid; 192 } 193 sx_xunlock(&allproc_lock); 194 return (error); 195 } 196 197 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 198 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 199 200 int 201 fork1(td, flags, pages, procp) 202 struct thread *td; 203 int flags; 204 int pages; 205 struct proc **procp; 206 { 207 struct proc *p1, *p2, *pptr; 208 struct proc *newproc; 209 int ok, trypid; 210 static int curfail, pidchecked = 0; 211 static struct timeval lastfail; 212 struct filedesc *fd; 213 struct filedesc_to_leader *fdtol; 214 struct thread *td2; 215 struct sigacts *newsigacts; 216 struct vmspace *vm2; 217 int error; 218 219 /* Can't copy and clear. */ 220 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 221 return (EINVAL); 222 223 p1 = td->td_proc; 224 225 /* 226 * Here we don't create a new process, but we divorce 227 * certain parts of a process from itself. 228 */ 229 if ((flags & RFPROC) == 0) { 230 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 231 (flags & (RFCFDG | RFFDG))) { 232 PROC_LOCK(p1); 233 if (thread_single(SINGLE_BOUNDARY)) { 234 PROC_UNLOCK(p1); 235 return (ERESTART); 236 } 237 PROC_UNLOCK(p1); 238 } 239 240 error = vm_forkproc(td, NULL, NULL, NULL, flags); 241 if (error) 242 goto norfproc_fail; 243 244 /* 245 * Close all file descriptors. 246 */ 247 if (flags & RFCFDG) { 248 struct filedesc *fdtmp; 249 fdtmp = fdinit(td->td_proc->p_fd); 250 fdfree(td); 251 p1->p_fd = fdtmp; 252 } 253 254 /* 255 * Unshare file descriptors (from parent). 256 */ 257 if (flags & RFFDG) 258 fdunshare(p1, td); 259 260 norfproc_fail: 261 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 262 (flags & (RFCFDG | RFFDG))) { 263 PROC_LOCK(p1); 264 thread_single_end(); 265 PROC_UNLOCK(p1); 266 } 267 *procp = NULL; 268 return (error); 269 } 270 271 /* 272 * XXX 273 * We did have single-threading code here 274 * however it proved un-needed and caused problems 275 */ 276 277 vm2 = NULL; 278 /* Allocate new proc. */ 279 newproc = uma_zalloc(proc_zone, M_WAITOK); 280 if (TAILQ_EMPTY(&newproc->p_threads)) { 281 td2 = thread_alloc(); 282 if (td2 == NULL) { 283 error = ENOMEM; 284 goto fail1; 285 } 286 proc_linkup(newproc, td2); 287 } else 288 td2 = FIRST_THREAD_IN_PROC(newproc); 289 290 /* Allocate and switch to an alternate kstack if specified. */ 291 if (pages != 0) { 292 if (!vm_thread_new_altkstack(td2, pages)) { 293 error = ENOMEM; 294 goto fail1; 295 } 296 } 297 if ((flags & RFMEM) == 0) { 298 vm2 = vmspace_fork(p1->p_vmspace); 299 if (vm2 == NULL) { 300 error = ENOMEM; 301 goto fail1; 302 } 303 } 304 #ifdef MAC 305 mac_proc_init(newproc); 306 #endif 307 knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL); 308 STAILQ_INIT(&newproc->p_ktr); 309 310 /* We have to lock the process tree while we look for a pid. */ 311 sx_slock(&proctree_lock); 312 313 /* 314 * Although process entries are dynamically created, we still keep 315 * a global limit on the maximum number we will create. Don't allow 316 * a nonprivileged user to use the last ten processes; don't let root 317 * exceed the limit. The variable nprocs is the current number of 318 * processes, maxproc is the limit. 319 */ 320 sx_xlock(&allproc_lock); 321 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 322 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 323 error = EAGAIN; 324 goto fail; 325 } 326 327 /* 328 * Increment the count of procs running with this uid. Don't allow 329 * a nonprivileged user to exceed their current limit. 330 * 331 * XXXRW: Can we avoid privilege here if it's not needed? 332 */ 333 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 334 if (error == 0) 335 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 336 else { 337 PROC_LOCK(p1); 338 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 339 lim_cur(p1, RLIMIT_NPROC)); 340 PROC_UNLOCK(p1); 341 } 342 if (!ok) { 343 error = EAGAIN; 344 goto fail; 345 } 346 347 /* 348 * Increment the nprocs resource before blocking can occur. There 349 * are hard-limits as to the number of processes that can run. 350 */ 351 nprocs++; 352 #ifdef VIMAGE 353 P_TO_VPROCG(p1)->nprocs++; 354 #endif 355 356 /* 357 * Find an unused process ID. We remember a range of unused IDs 358 * ready to use (from lastpid+1 through pidchecked-1). 359 * 360 * If RFHIGHPID is set (used during system boot), do not allocate 361 * low-numbered pids. 362 */ 363 trypid = lastpid + 1; 364 if (flags & RFHIGHPID) { 365 if (trypid < 10) 366 trypid = 10; 367 } else { 368 if (randompid) 369 trypid += arc4random() % randompid; 370 } 371 retry: 372 /* 373 * If the process ID prototype has wrapped around, 374 * restart somewhat above 0, as the low-numbered procs 375 * tend to include daemons that don't exit. 376 */ 377 if (trypid >= PID_MAX) { 378 trypid = trypid % PID_MAX; 379 if (trypid < 100) 380 trypid += 100; 381 pidchecked = 0; 382 } 383 if (trypid >= pidchecked) { 384 int doingzomb = 0; 385 386 pidchecked = PID_MAX; 387 /* 388 * Scan the active and zombie procs to check whether this pid 389 * is in use. Remember the lowest pid that's greater 390 * than trypid, so we can avoid checking for a while. 391 */ 392 p2 = LIST_FIRST(&allproc); 393 again: 394 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 395 while (p2->p_pid == trypid || 396 (p2->p_pgrp != NULL && 397 (p2->p_pgrp->pg_id == trypid || 398 (p2->p_session != NULL && 399 p2->p_session->s_sid == trypid)))) { 400 trypid++; 401 if (trypid >= pidchecked) 402 goto retry; 403 } 404 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 405 pidchecked = p2->p_pid; 406 if (p2->p_pgrp != NULL) { 407 if (p2->p_pgrp->pg_id > trypid && 408 pidchecked > p2->p_pgrp->pg_id) 409 pidchecked = p2->p_pgrp->pg_id; 410 if (p2->p_session != NULL && 411 p2->p_session->s_sid > trypid && 412 pidchecked > p2->p_session->s_sid) 413 pidchecked = p2->p_session->s_sid; 414 } 415 } 416 if (!doingzomb) { 417 doingzomb = 1; 418 p2 = LIST_FIRST(&zombproc); 419 goto again; 420 } 421 } 422 sx_sunlock(&proctree_lock); 423 424 /* 425 * RFHIGHPID does not mess with the lastpid counter during boot. 426 */ 427 if (flags & RFHIGHPID) 428 pidchecked = 0; 429 else 430 lastpid = trypid; 431 432 p2 = newproc; 433 p2->p_state = PRS_NEW; /* protect against others */ 434 p2->p_pid = trypid; 435 /* 436 * Allow the scheduler to initialize the child. 437 */ 438 thread_lock(td); 439 sched_fork(td, td2); 440 thread_unlock(td); 441 AUDIT_ARG(pid, p2->p_pid); 442 LIST_INSERT_HEAD(&allproc, p2, p_list); 443 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 444 445 PROC_LOCK(p2); 446 PROC_LOCK(p1); 447 448 sx_xunlock(&allproc_lock); 449 450 bcopy(&p1->p_startcopy, &p2->p_startcopy, 451 __rangeof(struct proc, p_startcopy, p_endcopy)); 452 pargs_hold(p2->p_args); 453 PROC_UNLOCK(p1); 454 455 bzero(&p2->p_startzero, 456 __rangeof(struct proc, p_startzero, p_endzero)); 457 458 p2->p_ucred = crhold(td->td_ucred); 459 460 /* Tell the prison that we exist. */ 461 prison_proc_hold(p2->p_ucred->cr_prison); 462 463 PROC_UNLOCK(p2); 464 465 /* 466 * Malloc things while we don't hold any locks. 467 */ 468 if (flags & RFSIGSHARE) 469 newsigacts = NULL; 470 else 471 newsigacts = sigacts_alloc(); 472 473 /* 474 * Copy filedesc. 475 */ 476 if (flags & RFCFDG) { 477 fd = fdinit(p1->p_fd); 478 fdtol = NULL; 479 } else if (flags & RFFDG) { 480 fd = fdcopy(p1->p_fd); 481 fdtol = NULL; 482 } else { 483 fd = fdshare(p1->p_fd); 484 if (p1->p_fdtol == NULL) 485 p1->p_fdtol = 486 filedesc_to_leader_alloc(NULL, 487 NULL, 488 p1->p_leader); 489 if ((flags & RFTHREAD) != 0) { 490 /* 491 * Shared file descriptor table and 492 * shared process leaders. 493 */ 494 fdtol = p1->p_fdtol; 495 FILEDESC_XLOCK(p1->p_fd); 496 fdtol->fdl_refcount++; 497 FILEDESC_XUNLOCK(p1->p_fd); 498 } else { 499 /* 500 * Shared file descriptor table, and 501 * different process leaders 502 */ 503 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 504 p1->p_fd, 505 p2); 506 } 507 } 508 /* 509 * Make a proc table entry for the new process. 510 * Start by zeroing the section of proc that is zero-initialized, 511 * then copy the section that is copied directly from the parent. 512 */ 513 514 PROC_LOCK(p2); 515 PROC_LOCK(p1); 516 517 bzero(&td2->td_startzero, 518 __rangeof(struct thread, td_startzero, td_endzero)); 519 520 bcopy(&td->td_startcopy, &td2->td_startcopy, 521 __rangeof(struct thread, td_startcopy, td_endcopy)); 522 523 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 524 td2->td_sigstk = td->td_sigstk; 525 td2->td_sigmask = td->td_sigmask; 526 td2->td_flags = TDF_INMEM; 527 528 #ifdef VIMAGE 529 td2->td_vnet = NULL; 530 td2->td_vnet_lpush = NULL; 531 #endif 532 533 /* 534 * Duplicate sub-structures as needed. 535 * Increase reference counts on shared objects. 536 */ 537 p2->p_flag = P_INMEM; 538 p2->p_swtick = ticks; 539 if (p1->p_flag & P_PROFIL) 540 startprofclock(p2); 541 td2->td_ucred = crhold(p2->p_ucred); 542 543 if (flags & RFSIGSHARE) { 544 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 545 } else { 546 sigacts_copy(newsigacts, p1->p_sigacts); 547 p2->p_sigacts = newsigacts; 548 } 549 if (flags & RFLINUXTHPN) 550 p2->p_sigparent = SIGUSR1; 551 else 552 p2->p_sigparent = SIGCHLD; 553 554 p2->p_textvp = p1->p_textvp; 555 p2->p_fd = fd; 556 p2->p_fdtol = fdtol; 557 558 /* 559 * p_limit is copy-on-write. Bump its refcount. 560 */ 561 lim_fork(p1, p2); 562 563 pstats_fork(p1->p_stats, p2->p_stats); 564 565 PROC_UNLOCK(p1); 566 PROC_UNLOCK(p2); 567 568 /* Bump references to the text vnode (for procfs) */ 569 if (p2->p_textvp) 570 vref(p2->p_textvp); 571 572 /* 573 * Set up linkage for kernel based threading. 574 */ 575 if ((flags & RFTHREAD) != 0) { 576 mtx_lock(&ppeers_lock); 577 p2->p_peers = p1->p_peers; 578 p1->p_peers = p2; 579 p2->p_leader = p1->p_leader; 580 mtx_unlock(&ppeers_lock); 581 PROC_LOCK(p1->p_leader); 582 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 583 PROC_UNLOCK(p1->p_leader); 584 /* 585 * The task leader is exiting, so process p1 is 586 * going to be killed shortly. Since p1 obviously 587 * isn't dead yet, we know that the leader is either 588 * sending SIGKILL's to all the processes in this 589 * task or is sleeping waiting for all the peers to 590 * exit. We let p1 complete the fork, but we need 591 * to go ahead and kill the new process p2 since 592 * the task leader may not get a chance to send 593 * SIGKILL to it. We leave it on the list so that 594 * the task leader will wait for this new process 595 * to commit suicide. 596 */ 597 PROC_LOCK(p2); 598 psignal(p2, SIGKILL); 599 PROC_UNLOCK(p2); 600 } else 601 PROC_UNLOCK(p1->p_leader); 602 } else { 603 p2->p_peers = NULL; 604 p2->p_leader = p2; 605 } 606 607 sx_xlock(&proctree_lock); 608 PGRP_LOCK(p1->p_pgrp); 609 PROC_LOCK(p2); 610 PROC_LOCK(p1); 611 612 /* 613 * Preserve some more flags in subprocess. P_PROFIL has already 614 * been preserved. 615 */ 616 p2->p_flag |= p1->p_flag & P_SUGID; 617 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 618 SESS_LOCK(p1->p_session); 619 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 620 p2->p_flag |= P_CONTROLT; 621 SESS_UNLOCK(p1->p_session); 622 if (flags & RFPPWAIT) 623 p2->p_flag |= P_PPWAIT; 624 625 p2->p_pgrp = p1->p_pgrp; 626 LIST_INSERT_AFTER(p1, p2, p_pglist); 627 PGRP_UNLOCK(p1->p_pgrp); 628 LIST_INIT(&p2->p_children); 629 630 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 631 632 #ifdef KTRACE 633 /* 634 * Copy traceflag and tracefile if enabled. 635 */ 636 mtx_lock(&ktrace_mtx); 637 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 638 if (p1->p_traceflag & KTRFAC_INHERIT) { 639 p2->p_traceflag = p1->p_traceflag; 640 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 641 VREF(p2->p_tracevp); 642 KASSERT(p1->p_tracecred != NULL, 643 ("ktrace vnode with no cred")); 644 p2->p_tracecred = crhold(p1->p_tracecred); 645 } 646 } 647 mtx_unlock(&ktrace_mtx); 648 #endif 649 650 /* 651 * If PF_FORK is set, the child process inherits the 652 * procfs ioctl flags from its parent. 653 */ 654 if (p1->p_pfsflags & PF_FORK) { 655 p2->p_stops = p1->p_stops; 656 p2->p_pfsflags = p1->p_pfsflags; 657 } 658 659 #ifdef KDTRACE_HOOKS 660 /* 661 * Tell the DTrace fasttrap provider about the new process 662 * if it has registered an interest. 663 */ 664 if (dtrace_fasttrap_fork) 665 dtrace_fasttrap_fork(p1, p2); 666 #endif 667 668 /* 669 * This begins the section where we must prevent the parent 670 * from being swapped. 671 */ 672 _PHOLD(p1); 673 PROC_UNLOCK(p1); 674 675 /* 676 * Attach the new process to its parent. 677 * 678 * If RFNOWAIT is set, the newly created process becomes a child 679 * of init. This effectively disassociates the child from the 680 * parent. 681 */ 682 if (flags & RFNOWAIT) 683 pptr = initproc; 684 else 685 pptr = p1; 686 p2->p_pptr = pptr; 687 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 688 sx_xunlock(&proctree_lock); 689 690 /* Inform accounting that we have forked. */ 691 p2->p_acflag = AFORK; 692 PROC_UNLOCK(p2); 693 694 /* 695 * Finish creating the child process. It will return via a different 696 * execution path later. (ie: directly into user mode) 697 */ 698 vm_forkproc(td, p2, td2, vm2, flags); 699 700 if (flags == (RFFDG | RFPROC)) { 701 PCPU_INC(cnt.v_forks); 702 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 703 p2->p_vmspace->vm_ssize); 704 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 705 PCPU_INC(cnt.v_vforks); 706 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 707 p2->p_vmspace->vm_ssize); 708 } else if (p1 == &proc0) { 709 PCPU_INC(cnt.v_kthreads); 710 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 711 p2->p_vmspace->vm_ssize); 712 } else { 713 PCPU_INC(cnt.v_rforks); 714 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 715 p2->p_vmspace->vm_ssize); 716 } 717 718 /* 719 * Both processes are set up, now check if any loadable modules want 720 * to adjust anything. 721 * What if they have an error? XXX 722 */ 723 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 724 725 /* 726 * Set the child start time and mark the process as being complete. 727 */ 728 microuptime(&p2->p_stats->p_start); 729 PROC_SLOCK(p2); 730 p2->p_state = PRS_NORMAL; 731 PROC_SUNLOCK(p2); 732 733 /* 734 * If RFSTOPPED not requested, make child runnable and add to 735 * run queue. 736 */ 737 if ((flags & RFSTOPPED) == 0) { 738 thread_lock(td2); 739 TD_SET_CAN_RUN(td2); 740 sched_add(td2, SRQ_BORING); 741 thread_unlock(td2); 742 } 743 744 /* 745 * Now can be swapped. 746 */ 747 PROC_LOCK(p1); 748 _PRELE(p1); 749 PROC_UNLOCK(p1); 750 751 /* 752 * Tell any interested parties about the new process. 753 */ 754 knote_fork(&p1->p_klist, p2->p_pid); 755 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 756 757 /* 758 * Preserve synchronization semantics of vfork. If waiting for 759 * child to exec or exit, set P_PPWAIT on child, and sleep on our 760 * proc (in case of exit). 761 */ 762 PROC_LOCK(p2); 763 while (p2->p_flag & P_PPWAIT) 764 cv_wait(&p2->p_pwait, &p2->p_mtx); 765 PROC_UNLOCK(p2); 766 767 /* 768 * Return child proc pointer to parent. 769 */ 770 *procp = p2; 771 return (0); 772 fail: 773 sx_sunlock(&proctree_lock); 774 if (ppsratecheck(&lastfail, &curfail, 1)) 775 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 776 td->td_ucred->cr_ruid); 777 sx_xunlock(&allproc_lock); 778 #ifdef MAC 779 mac_proc_destroy(newproc); 780 #endif 781 fail1: 782 if (vm2 != NULL) 783 vmspace_free(vm2); 784 uma_zfree(proc_zone, newproc); 785 pause("fork", hz / 2); 786 return (error); 787 } 788 789 /* 790 * Handle the return of a child process from fork1(). This function 791 * is called from the MD fork_trampoline() entry point. 792 */ 793 void 794 fork_exit(callout, arg, frame) 795 void (*callout)(void *, struct trapframe *); 796 void *arg; 797 struct trapframe *frame; 798 { 799 struct proc *p; 800 struct thread *td; 801 struct thread *dtd; 802 803 td = curthread; 804 p = td->td_proc; 805 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 806 807 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 808 td, td->td_sched, p->p_pid, td->td_name); 809 810 sched_fork_exit(td); 811 /* 812 * Processes normally resume in mi_switch() after being 813 * cpu_switch()'ed to, but when children start up they arrive here 814 * instead, so we must do much the same things as mi_switch() would. 815 */ 816 if ((dtd = PCPU_GET(deadthread))) { 817 PCPU_SET(deadthread, NULL); 818 thread_stash(dtd); 819 } 820 thread_unlock(td); 821 822 /* 823 * cpu_set_fork_handler intercepts this function call to 824 * have this call a non-return function to stay in kernel mode. 825 * initproc has its own fork handler, but it does return. 826 */ 827 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 828 callout(arg, frame); 829 830 /* 831 * Check if a kernel thread misbehaved and returned from its main 832 * function. 833 */ 834 if (p->p_flag & P_KTHREAD) { 835 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 836 td->td_name, p->p_pid); 837 kproc_exit(0); 838 } 839 mtx_assert(&Giant, MA_NOTOWNED); 840 841 EVENTHANDLER_INVOKE(schedtail, p); 842 } 843 844 /* 845 * Simplified back end of syscall(), used when returning from fork() 846 * directly into user mode. Giant is not held on entry, and must not 847 * be held on return. This function is passed in to fork_exit() as the 848 * first parameter and is called when returning to a new userland process. 849 */ 850 void 851 fork_return(td, frame) 852 struct thread *td; 853 struct trapframe *frame; 854 { 855 856 userret(td, frame); 857 #ifdef KTRACE 858 if (KTRPOINT(td, KTR_SYSRET)) 859 ktrsysret(SYS_fork, 0, 0); 860 #endif 861 mtx_assert(&Giant, MA_NOTOWNED); 862 } 863