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 71 #include <security/audit/audit.h> 72 #include <security/mac/mac_framework.h> 73 74 #include <vm/vm.h> 75 #include <vm/pmap.h> 76 #include <vm/vm_map.h> 77 #include <vm/vm_extern.h> 78 #include <vm/uma.h> 79 80 #ifdef KDTRACE_HOOKS 81 #include <sys/dtrace_bsd.h> 82 dtrace_fork_func_t dtrace_fasttrap_fork; 83 #endif 84 85 SDT_PROVIDER_DECLARE(proc); 86 SDT_PROBE_DEFINE(proc, kernel, , create); 87 SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *"); 88 SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *"); 89 SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int"); 90 91 #ifndef _SYS_SYSPROTO_H_ 92 struct fork_args { 93 int dummy; 94 }; 95 #endif 96 97 /* ARGSUSED */ 98 int 99 fork(td, uap) 100 struct thread *td; 101 struct fork_args *uap; 102 { 103 int error; 104 struct proc *p2; 105 106 error = fork1(td, RFFDG | RFPROC, 0, &p2); 107 if (error == 0) { 108 td->td_retval[0] = p2->p_pid; 109 td->td_retval[1] = 0; 110 } 111 return (error); 112 } 113 114 /* ARGSUSED */ 115 int 116 vfork(td, uap) 117 struct thread *td; 118 struct vfork_args *uap; 119 { 120 int error, flags; 121 struct proc *p2; 122 123 #ifdef XEN 124 flags = RFFDG | RFPROC; /* validate that this is still an issue */ 125 #else 126 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 127 #endif 128 error = fork1(td, flags, 0, &p2); 129 if (error == 0) { 130 td->td_retval[0] = p2->p_pid; 131 td->td_retval[1] = 0; 132 } 133 return (error); 134 } 135 136 int 137 rfork(td, uap) 138 struct thread *td; 139 struct rfork_args *uap; 140 { 141 struct proc *p2; 142 int error; 143 144 /* Don't allow kernel-only flags. */ 145 if ((uap->flags & RFKERNELONLY) != 0) 146 return (EINVAL); 147 148 AUDIT_ARG_FFLAGS(uap->flags); 149 error = fork1(td, uap->flags, 0, &p2); 150 if (error == 0) { 151 td->td_retval[0] = p2 ? p2->p_pid : 0; 152 td->td_retval[1] = 0; 153 } 154 return (error); 155 } 156 157 int nprocs = 1; /* process 0 */ 158 int lastpid = 0; 159 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 160 "Last used PID"); 161 162 /* 163 * Random component to lastpid generation. We mix in a random factor to make 164 * it a little harder to predict. We sanity check the modulus value to avoid 165 * doing it in critical paths. Don't let it be too small or we pointlessly 166 * waste randomness entropy, and don't let it be impossibly large. Using a 167 * modulus that is too big causes a LOT more process table scans and slows 168 * down fork processing as the pidchecked caching is defeated. 169 */ 170 static int randompid = 0; 171 172 static int 173 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 174 { 175 int error, pid; 176 177 error = sysctl_wire_old_buffer(req, sizeof(int)); 178 if (error != 0) 179 return(error); 180 sx_xlock(&allproc_lock); 181 pid = randompid; 182 error = sysctl_handle_int(oidp, &pid, 0, req); 183 if (error == 0 && req->newptr != NULL) { 184 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 185 pid = PID_MAX - 100; 186 else if (pid < 2) /* NOP */ 187 pid = 0; 188 else if (pid < 100) /* Make it reasonable */ 189 pid = 100; 190 randompid = pid; 191 } 192 sx_xunlock(&allproc_lock); 193 return (error); 194 } 195 196 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 197 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 198 199 int 200 fork1(td, flags, pages, procp) 201 struct thread *td; 202 int flags; 203 int pages; 204 struct proc **procp; 205 { 206 struct proc *p1, *p2, *pptr; 207 struct proc *newproc; 208 int ok, trypid; 209 static int curfail, pidchecked = 0; 210 static struct timeval lastfail; 211 struct filedesc *fd; 212 struct filedesc_to_leader *fdtol; 213 struct thread *td2; 214 struct sigacts *newsigacts; 215 struct vmspace *vm2; 216 vm_ooffset_t mem_charged; 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 mem_charged = 0; 278 vm2 = NULL; 279 /* Allocate new proc. */ 280 newproc = uma_zalloc(proc_zone, M_WAITOK); 281 if (TAILQ_EMPTY(&newproc->p_threads)) { 282 td2 = thread_alloc(); 283 if (td2 == NULL) { 284 error = ENOMEM; 285 goto fail1; 286 } 287 proc_linkup(newproc, td2); 288 } else 289 td2 = FIRST_THREAD_IN_PROC(newproc); 290 291 /* Allocate and switch to an alternate kstack if specified. */ 292 if (pages != 0) { 293 if (!vm_thread_new_altkstack(td2, pages)) { 294 error = ENOMEM; 295 goto fail1; 296 } 297 } 298 if ((flags & RFMEM) == 0) { 299 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 300 if (vm2 == NULL) { 301 error = ENOMEM; 302 goto fail1; 303 } 304 if (!swap_reserve(mem_charged)) { 305 /* 306 * The swap reservation failed. The accounting 307 * from the entries of the copied vm2 will be 308 * substracted in vmspace_free(), so force the 309 * reservation there. 310 */ 311 swap_reserve_force(mem_charged); 312 error = ENOMEM; 313 goto fail1; 314 } 315 } else 316 vm2 = NULL; 317 #ifdef MAC 318 mac_proc_init(newproc); 319 #endif 320 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 321 STAILQ_INIT(&newproc->p_ktr); 322 323 /* We have to lock the process tree while we look for a pid. */ 324 sx_slock(&proctree_lock); 325 326 /* 327 * Although process entries are dynamically created, we still keep 328 * a global limit on the maximum number we will create. Don't allow 329 * a nonprivileged user to use the last ten processes; don't let root 330 * exceed the limit. The variable nprocs is the current number of 331 * processes, maxproc is the limit. 332 */ 333 sx_xlock(&allproc_lock); 334 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 335 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 336 error = EAGAIN; 337 goto fail; 338 } 339 340 /* 341 * Increment the count of procs running with this uid. Don't allow 342 * a nonprivileged user to exceed their current limit. 343 * 344 * XXXRW: Can we avoid privilege here if it's not needed? 345 */ 346 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 347 if (error == 0) 348 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 349 else { 350 PROC_LOCK(p1); 351 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 352 lim_cur(p1, RLIMIT_NPROC)); 353 PROC_UNLOCK(p1); 354 } 355 if (!ok) { 356 error = EAGAIN; 357 goto fail; 358 } 359 360 /* 361 * Increment the nprocs resource before blocking can occur. There 362 * are hard-limits as to the number of processes that can run. 363 */ 364 nprocs++; 365 366 /* 367 * Find an unused process ID. We remember a range of unused IDs 368 * ready to use (from lastpid+1 through pidchecked-1). 369 * 370 * If RFHIGHPID is set (used during system boot), do not allocate 371 * low-numbered pids. 372 */ 373 trypid = lastpid + 1; 374 if (flags & RFHIGHPID) { 375 if (trypid < 10) 376 trypid = 10; 377 } else { 378 if (randompid) 379 trypid += arc4random() % randompid; 380 } 381 retry: 382 /* 383 * If the process ID prototype has wrapped around, 384 * restart somewhat above 0, as the low-numbered procs 385 * tend to include daemons that don't exit. 386 */ 387 if (trypid >= PID_MAX) { 388 trypid = trypid % PID_MAX; 389 if (trypid < 100) 390 trypid += 100; 391 pidchecked = 0; 392 } 393 if (trypid >= pidchecked) { 394 int doingzomb = 0; 395 396 pidchecked = PID_MAX; 397 /* 398 * Scan the active and zombie procs to check whether this pid 399 * is in use. Remember the lowest pid that's greater 400 * than trypid, so we can avoid checking for a while. 401 */ 402 p2 = LIST_FIRST(&allproc); 403 again: 404 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 405 while (p2->p_pid == trypid || 406 (p2->p_pgrp != NULL && 407 (p2->p_pgrp->pg_id == trypid || 408 (p2->p_session != NULL && 409 p2->p_session->s_sid == trypid)))) { 410 trypid++; 411 if (trypid >= pidchecked) 412 goto retry; 413 } 414 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 415 pidchecked = p2->p_pid; 416 if (p2->p_pgrp != NULL) { 417 if (p2->p_pgrp->pg_id > trypid && 418 pidchecked > p2->p_pgrp->pg_id) 419 pidchecked = p2->p_pgrp->pg_id; 420 if (p2->p_session != NULL && 421 p2->p_session->s_sid > trypid && 422 pidchecked > p2->p_session->s_sid) 423 pidchecked = p2->p_session->s_sid; 424 } 425 } 426 if (!doingzomb) { 427 doingzomb = 1; 428 p2 = LIST_FIRST(&zombproc); 429 goto again; 430 } 431 } 432 sx_sunlock(&proctree_lock); 433 434 /* 435 * RFHIGHPID does not mess with the lastpid counter during boot. 436 */ 437 if (flags & RFHIGHPID) 438 pidchecked = 0; 439 else 440 lastpid = trypid; 441 442 p2 = newproc; 443 p2->p_state = PRS_NEW; /* protect against others */ 444 p2->p_pid = trypid; 445 /* 446 * Allow the scheduler to initialize the child. 447 */ 448 thread_lock(td); 449 sched_fork(td, td2); 450 thread_unlock(td); 451 AUDIT_ARG_PID(p2->p_pid); 452 LIST_INSERT_HEAD(&allproc, p2, p_list); 453 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 454 455 PROC_LOCK(p2); 456 PROC_LOCK(p1); 457 458 sx_xunlock(&allproc_lock); 459 460 bcopy(&p1->p_startcopy, &p2->p_startcopy, 461 __rangeof(struct proc, p_startcopy, p_endcopy)); 462 pargs_hold(p2->p_args); 463 PROC_UNLOCK(p1); 464 465 bzero(&p2->p_startzero, 466 __rangeof(struct proc, p_startzero, p_endzero)); 467 468 p2->p_ucred = crhold(td->td_ucred); 469 470 /* Tell the prison that we exist. */ 471 prison_proc_hold(p2->p_ucred->cr_prison); 472 473 PROC_UNLOCK(p2); 474 475 /* 476 * Malloc things while we don't hold any locks. 477 */ 478 if (flags & RFSIGSHARE) 479 newsigacts = NULL; 480 else 481 newsigacts = sigacts_alloc(); 482 483 /* 484 * Copy filedesc. 485 */ 486 if (flags & RFCFDG) { 487 fd = fdinit(p1->p_fd); 488 fdtol = NULL; 489 } else if (flags & RFFDG) { 490 fd = fdcopy(p1->p_fd); 491 fdtol = NULL; 492 } else { 493 fd = fdshare(p1->p_fd); 494 if (p1->p_fdtol == NULL) 495 p1->p_fdtol = 496 filedesc_to_leader_alloc(NULL, 497 NULL, 498 p1->p_leader); 499 if ((flags & RFTHREAD) != 0) { 500 /* 501 * Shared file descriptor table and 502 * shared process leaders. 503 */ 504 fdtol = p1->p_fdtol; 505 FILEDESC_XLOCK(p1->p_fd); 506 fdtol->fdl_refcount++; 507 FILEDESC_XUNLOCK(p1->p_fd); 508 } else { 509 /* 510 * Shared file descriptor table, and 511 * different process leaders 512 */ 513 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 514 p1->p_fd, 515 p2); 516 } 517 } 518 /* 519 * Make a proc table entry for the new process. 520 * Start by zeroing the section of proc that is zero-initialized, 521 * then copy the section that is copied directly from the parent. 522 */ 523 524 PROC_LOCK(p2); 525 PROC_LOCK(p1); 526 527 bzero(&td2->td_startzero, 528 __rangeof(struct thread, td_startzero, td_endzero)); 529 530 bcopy(&td->td_startcopy, &td2->td_startcopy, 531 __rangeof(struct thread, td_startcopy, td_endcopy)); 532 533 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 534 td2->td_sigstk = td->td_sigstk; 535 td2->td_sigmask = td->td_sigmask; 536 td2->td_flags = TDF_INMEM; 537 538 #ifdef VIMAGE 539 td2->td_vnet = NULL; 540 td2->td_vnet_lpush = NULL; 541 #endif 542 543 /* 544 * Duplicate sub-structures as needed. 545 * Increase reference counts on shared objects. 546 */ 547 p2->p_flag = P_INMEM; 548 p2->p_swtick = ticks; 549 if (p1->p_flag & P_PROFIL) 550 startprofclock(p2); 551 td2->td_ucred = crhold(p2->p_ucred); 552 553 if (flags & RFSIGSHARE) { 554 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 555 } else { 556 sigacts_copy(newsigacts, p1->p_sigacts); 557 p2->p_sigacts = newsigacts; 558 } 559 if (flags & RFLINUXTHPN) 560 p2->p_sigparent = SIGUSR1; 561 else 562 p2->p_sigparent = SIGCHLD; 563 564 p2->p_textvp = p1->p_textvp; 565 p2->p_fd = fd; 566 p2->p_fdtol = fdtol; 567 568 /* 569 * p_limit is copy-on-write. Bump its refcount. 570 */ 571 lim_fork(p1, p2); 572 573 pstats_fork(p1->p_stats, p2->p_stats); 574 575 PROC_UNLOCK(p1); 576 PROC_UNLOCK(p2); 577 578 /* Bump references to the text vnode (for procfs) */ 579 if (p2->p_textvp) 580 vref(p2->p_textvp); 581 582 /* 583 * Set up linkage for kernel based threading. 584 */ 585 if ((flags & RFTHREAD) != 0) { 586 mtx_lock(&ppeers_lock); 587 p2->p_peers = p1->p_peers; 588 p1->p_peers = p2; 589 p2->p_leader = p1->p_leader; 590 mtx_unlock(&ppeers_lock); 591 PROC_LOCK(p1->p_leader); 592 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 593 PROC_UNLOCK(p1->p_leader); 594 /* 595 * The task leader is exiting, so process p1 is 596 * going to be killed shortly. Since p1 obviously 597 * isn't dead yet, we know that the leader is either 598 * sending SIGKILL's to all the processes in this 599 * task or is sleeping waiting for all the peers to 600 * exit. We let p1 complete the fork, but we need 601 * to go ahead and kill the new process p2 since 602 * the task leader may not get a chance to send 603 * SIGKILL to it. We leave it on the list so that 604 * the task leader will wait for this new process 605 * to commit suicide. 606 */ 607 PROC_LOCK(p2); 608 psignal(p2, SIGKILL); 609 PROC_UNLOCK(p2); 610 } else 611 PROC_UNLOCK(p1->p_leader); 612 } else { 613 p2->p_peers = NULL; 614 p2->p_leader = p2; 615 } 616 617 sx_xlock(&proctree_lock); 618 PGRP_LOCK(p1->p_pgrp); 619 PROC_LOCK(p2); 620 PROC_LOCK(p1); 621 622 /* 623 * Preserve some more flags in subprocess. P_PROFIL has already 624 * been preserved. 625 */ 626 p2->p_flag |= p1->p_flag & P_SUGID; 627 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 628 SESS_LOCK(p1->p_session); 629 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 630 p2->p_flag |= P_CONTROLT; 631 SESS_UNLOCK(p1->p_session); 632 if (flags & RFPPWAIT) 633 p2->p_flag |= P_PPWAIT; 634 635 p2->p_pgrp = p1->p_pgrp; 636 LIST_INSERT_AFTER(p1, p2, p_pglist); 637 PGRP_UNLOCK(p1->p_pgrp); 638 LIST_INIT(&p2->p_children); 639 640 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 641 642 #ifdef KTRACE 643 /* 644 * Copy traceflag and tracefile if enabled. 645 */ 646 mtx_lock(&ktrace_mtx); 647 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 648 if (p1->p_traceflag & KTRFAC_INHERIT) { 649 p2->p_traceflag = p1->p_traceflag; 650 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 651 VREF(p2->p_tracevp); 652 KASSERT(p1->p_tracecred != NULL, 653 ("ktrace vnode with no cred")); 654 p2->p_tracecred = crhold(p1->p_tracecred); 655 } 656 } 657 mtx_unlock(&ktrace_mtx); 658 #endif 659 660 /* 661 * If PF_FORK is set, the child process inherits the 662 * procfs ioctl flags from its parent. 663 */ 664 if (p1->p_pfsflags & PF_FORK) { 665 p2->p_stops = p1->p_stops; 666 p2->p_pfsflags = p1->p_pfsflags; 667 } 668 669 #ifdef KDTRACE_HOOKS 670 /* 671 * Tell the DTrace fasttrap provider about the new process 672 * if it has registered an interest. 673 */ 674 if (dtrace_fasttrap_fork) 675 dtrace_fasttrap_fork(p1, p2); 676 #endif 677 678 /* 679 * This begins the section where we must prevent the parent 680 * from being swapped. 681 */ 682 _PHOLD(p1); 683 PROC_UNLOCK(p1); 684 685 /* 686 * Attach the new process to its parent. 687 * 688 * If RFNOWAIT is set, the newly created process becomes a child 689 * of init. This effectively disassociates the child from the 690 * parent. 691 */ 692 if (flags & RFNOWAIT) 693 pptr = initproc; 694 else 695 pptr = p1; 696 p2->p_pptr = pptr; 697 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 698 sx_xunlock(&proctree_lock); 699 700 /* Inform accounting that we have forked. */ 701 p2->p_acflag = AFORK; 702 PROC_UNLOCK(p2); 703 704 /* 705 * Finish creating the child process. It will return via a different 706 * execution path later. (ie: directly into user mode) 707 */ 708 vm_forkproc(td, p2, td2, vm2, flags); 709 710 if (flags == (RFFDG | RFPROC)) { 711 PCPU_INC(cnt.v_forks); 712 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 713 p2->p_vmspace->vm_ssize); 714 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 715 PCPU_INC(cnt.v_vforks); 716 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 717 p2->p_vmspace->vm_ssize); 718 } else if (p1 == &proc0) { 719 PCPU_INC(cnt.v_kthreads); 720 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 721 p2->p_vmspace->vm_ssize); 722 } else { 723 PCPU_INC(cnt.v_rforks); 724 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 725 p2->p_vmspace->vm_ssize); 726 } 727 728 /* 729 * Both processes are set up, now check if any loadable modules want 730 * to adjust anything. 731 * What if they have an error? XXX 732 */ 733 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 734 735 /* 736 * Set the child start time and mark the process as being complete. 737 */ 738 microuptime(&p2->p_stats->p_start); 739 PROC_SLOCK(p2); 740 p2->p_state = PRS_NORMAL; 741 PROC_SUNLOCK(p2); 742 743 /* 744 * If RFSTOPPED not requested, make child runnable and add to 745 * run queue. 746 */ 747 if ((flags & RFSTOPPED) == 0) { 748 thread_lock(td2); 749 TD_SET_CAN_RUN(td2); 750 sched_add(td2, SRQ_BORING); 751 thread_unlock(td2); 752 } 753 754 /* 755 * Now can be swapped. 756 */ 757 PROC_LOCK(p1); 758 _PRELE(p1); 759 PROC_UNLOCK(p1); 760 761 /* 762 * Tell any interested parties about the new process. 763 */ 764 knote_fork(&p1->p_klist, p2->p_pid); 765 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 766 767 /* 768 * Preserve synchronization semantics of vfork. If waiting for 769 * child to exec or exit, set P_PPWAIT on child, and sleep on our 770 * proc (in case of exit). 771 */ 772 PROC_LOCK(p2); 773 while (p2->p_flag & P_PPWAIT) 774 cv_wait(&p2->p_pwait, &p2->p_mtx); 775 PROC_UNLOCK(p2); 776 777 /* 778 * Return child proc pointer to parent. 779 */ 780 *procp = p2; 781 return (0); 782 fail: 783 sx_sunlock(&proctree_lock); 784 if (ppsratecheck(&lastfail, &curfail, 1)) 785 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 786 td->td_ucred->cr_ruid); 787 sx_xunlock(&allproc_lock); 788 #ifdef MAC 789 mac_proc_destroy(newproc); 790 #endif 791 fail1: 792 if (vm2 != NULL) 793 vmspace_free(vm2); 794 uma_zfree(proc_zone, newproc); 795 pause("fork", hz / 2); 796 return (error); 797 } 798 799 /* 800 * Handle the return of a child process from fork1(). This function 801 * is called from the MD fork_trampoline() entry point. 802 */ 803 void 804 fork_exit(callout, arg, frame) 805 void (*callout)(void *, struct trapframe *); 806 void *arg; 807 struct trapframe *frame; 808 { 809 struct proc *p; 810 struct thread *td; 811 struct thread *dtd; 812 813 td = curthread; 814 p = td->td_proc; 815 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 816 817 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 818 td, td->td_sched, p->p_pid, td->td_name); 819 820 sched_fork_exit(td); 821 /* 822 * Processes normally resume in mi_switch() after being 823 * cpu_switch()'ed to, but when children start up they arrive here 824 * instead, so we must do much the same things as mi_switch() would. 825 */ 826 if ((dtd = PCPU_GET(deadthread))) { 827 PCPU_SET(deadthread, NULL); 828 thread_stash(dtd); 829 } 830 thread_unlock(td); 831 832 /* 833 * cpu_set_fork_handler intercepts this function call to 834 * have this call a non-return function to stay in kernel mode. 835 * initproc has its own fork handler, but it does return. 836 */ 837 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 838 callout(arg, frame); 839 840 /* 841 * Check if a kernel thread misbehaved and returned from its main 842 * function. 843 */ 844 if (p->p_flag & P_KTHREAD) { 845 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 846 td->td_name, p->p_pid); 847 kproc_exit(0); 848 } 849 mtx_assert(&Giant, MA_NOTOWNED); 850 851 EVENTHANDLER_INVOKE(schedtail, p); 852 } 853 854 /* 855 * Simplified back end of syscall(), used when returning from fork() 856 * directly into user mode. Giant is not held on entry, and must not 857 * be held on return. This function is passed in to fork_exit() as the 858 * first parameter and is called when returning to a new userland process. 859 */ 860 void 861 fork_return(td, frame) 862 struct thread *td; 863 struct trapframe *frame; 864 { 865 866 userret(td, frame); 867 #ifdef KTRACE 868 if (KTRPOINT(td, KTR_SYSRET)) 869 ktrsysret(SYS_fork, 0, 0); 870 #endif 871 mtx_assert(&Giant, MA_NOTOWNED); 872 } 873