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_kdtrace.h" 41 #include "opt_ktrace.h" 42 #include "opt_kstack_pages.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/sysproto.h> 47 #include <sys/eventhandler.h> 48 #include <sys/filedesc.h> 49 #include <sys/jail.h> 50 #include <sys/kernel.h> 51 #include <sys/kthread.h> 52 #include <sys/sysctl.h> 53 #include <sys/lock.h> 54 #include <sys/malloc.h> 55 #include <sys/mutex.h> 56 #include <sys/priv.h> 57 #include <sys/proc.h> 58 #include <sys/pioctl.h> 59 #include <sys/resourcevar.h> 60 #include <sys/sched.h> 61 #include <sys/syscall.h> 62 #include <sys/vmmeter.h> 63 #include <sys/vnode.h> 64 #include <sys/acct.h> 65 #include <sys/ktr.h> 66 #include <sys/ktrace.h> 67 #include <sys/unistd.h> 68 #include <sys/sdt.h> 69 #include <sys/sx.h> 70 #include <sys/sysent.h> 71 #include <sys/signalvar.h> 72 73 #include <security/audit/audit.h> 74 #include <security/mac/mac_framework.h> 75 76 #include <vm/vm.h> 77 #include <vm/pmap.h> 78 #include <vm/vm_map.h> 79 #include <vm/vm_extern.h> 80 #include <vm/uma.h> 81 82 #ifdef KDTRACE_HOOKS 83 #include <sys/dtrace_bsd.h> 84 dtrace_fork_func_t dtrace_fasttrap_fork; 85 #endif 86 87 SDT_PROVIDER_DECLARE(proc); 88 SDT_PROBE_DEFINE(proc, kernel, , create, create); 89 SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *"); 90 SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *"); 91 SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int"); 92 93 #ifndef _SYS_SYSPROTO_H_ 94 struct fork_args { 95 int dummy; 96 }; 97 #endif 98 99 /* ARGSUSED */ 100 int 101 fork(td, uap) 102 struct thread *td; 103 struct fork_args *uap; 104 { 105 int error; 106 struct proc *p2; 107 108 error = fork1(td, RFFDG | RFPROC, 0, &p2); 109 if (error == 0) { 110 td->td_retval[0] = p2->p_pid; 111 td->td_retval[1] = 0; 112 } 113 return (error); 114 } 115 116 /* ARGSUSED */ 117 int 118 vfork(td, uap) 119 struct thread *td; 120 struct vfork_args *uap; 121 { 122 int error, flags; 123 struct proc *p2; 124 125 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 126 error = fork1(td, flags, 0, &p2); 127 if (error == 0) { 128 td->td_retval[0] = p2->p_pid; 129 td->td_retval[1] = 0; 130 } 131 return (error); 132 } 133 134 int 135 rfork(td, uap) 136 struct thread *td; 137 struct rfork_args *uap; 138 { 139 struct proc *p2; 140 int error; 141 142 /* Don't allow kernel-only flags. */ 143 if ((uap->flags & RFKERNELONLY) != 0) 144 return (EINVAL); 145 146 AUDIT_ARG_FFLAGS(uap->flags); 147 error = fork1(td, uap->flags, 0, &p2); 148 if (error == 0) { 149 td->td_retval[0] = p2 ? p2->p_pid : 0; 150 td->td_retval[1] = 0; 151 } 152 return (error); 153 } 154 155 int nprocs = 1; /* process 0 */ 156 int lastpid = 0; 157 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 158 "Last used PID"); 159 160 /* 161 * Random component to lastpid generation. We mix in a random factor to make 162 * it a little harder to predict. We sanity check the modulus value to avoid 163 * doing it in critical paths. Don't let it be too small or we pointlessly 164 * waste randomness entropy, and don't let it be impossibly large. Using a 165 * modulus that is too big causes a LOT more process table scans and slows 166 * down fork processing as the pidchecked caching is defeated. 167 */ 168 static int randompid = 0; 169 170 static int 171 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 172 { 173 int error, pid; 174 175 error = sysctl_wire_old_buffer(req, sizeof(int)); 176 if (error != 0) 177 return(error); 178 sx_xlock(&allproc_lock); 179 pid = randompid; 180 error = sysctl_handle_int(oidp, &pid, 0, req); 181 if (error == 0 && req->newptr != NULL) { 182 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 183 pid = PID_MAX - 100; 184 else if (pid < 2) /* NOP */ 185 pid = 0; 186 else if (pid < 100) /* Make it reasonable */ 187 pid = 100; 188 randompid = pid; 189 } 190 sx_xunlock(&allproc_lock); 191 return (error); 192 } 193 194 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 195 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 196 197 int 198 fork1(td, flags, pages, procp) 199 struct thread *td; 200 int flags; 201 int pages; 202 struct proc **procp; 203 { 204 struct proc *p1, *p2, *pptr; 205 struct proc *newproc; 206 int ok, p2_held, trypid; 207 static int curfail, pidchecked = 0; 208 static struct timeval lastfail; 209 struct filedesc *fd; 210 struct filedesc_to_leader *fdtol; 211 struct thread *td2; 212 struct sigacts *newsigacts; 213 struct vmspace *vm2; 214 vm_ooffset_t mem_charged; 215 int error; 216 217 /* Check for the undefined or unimplemented flags. */ 218 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 219 return (EINVAL); 220 221 /* Signal value requires RFTSIGZMB. */ 222 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 223 return (EINVAL); 224 225 /* Can't copy and clear. */ 226 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 227 return (EINVAL); 228 229 /* Check the validity of the signal number. */ 230 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 231 return (EINVAL); 232 233 p2_held = 0; 234 p1 = td->td_proc; 235 236 /* 237 * Here we don't create a new process, but we divorce 238 * certain parts of a process from itself. 239 */ 240 if ((flags & RFPROC) == 0) { 241 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 242 (flags & (RFCFDG | RFFDG))) { 243 PROC_LOCK(p1); 244 if (thread_single(SINGLE_BOUNDARY)) { 245 PROC_UNLOCK(p1); 246 return (ERESTART); 247 } 248 PROC_UNLOCK(p1); 249 } 250 251 error = vm_forkproc(td, NULL, NULL, NULL, flags); 252 if (error) 253 goto norfproc_fail; 254 255 /* 256 * Close all file descriptors. 257 */ 258 if (flags & RFCFDG) { 259 struct filedesc *fdtmp; 260 fdtmp = fdinit(td->td_proc->p_fd); 261 fdfree(td); 262 p1->p_fd = fdtmp; 263 } 264 265 /* 266 * Unshare file descriptors (from parent). 267 */ 268 if (flags & RFFDG) 269 fdunshare(p1, td); 270 271 norfproc_fail: 272 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 273 (flags & (RFCFDG | RFFDG))) { 274 PROC_LOCK(p1); 275 thread_single_end(); 276 PROC_UNLOCK(p1); 277 } 278 *procp = NULL; 279 return (error); 280 } 281 282 /* 283 * XXX 284 * We did have single-threading code here 285 * however it proved un-needed and caused problems 286 */ 287 288 mem_charged = 0; 289 vm2 = NULL; 290 if (pages == 0) 291 pages = KSTACK_PAGES; 292 /* Allocate new proc. */ 293 newproc = uma_zalloc(proc_zone, M_WAITOK); 294 td2 = FIRST_THREAD_IN_PROC(newproc); 295 if (td2 == NULL) { 296 td2 = thread_alloc(pages); 297 if (td2 == NULL) { 298 error = ENOMEM; 299 goto fail1; 300 } 301 proc_linkup(newproc, td2); 302 } else { 303 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 304 if (td2->td_kstack != 0) 305 vm_thread_dispose(td2); 306 if (!thread_alloc_stack(td2, pages)) { 307 error = ENOMEM; 308 goto fail1; 309 } 310 } 311 } 312 313 if ((flags & RFMEM) == 0) { 314 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 315 if (vm2 == NULL) { 316 error = ENOMEM; 317 goto fail1; 318 } 319 if (!swap_reserve(mem_charged)) { 320 /* 321 * The swap reservation failed. The accounting 322 * from the entries of the copied vm2 will be 323 * substracted in vmspace_free(), so force the 324 * reservation there. 325 */ 326 swap_reserve_force(mem_charged); 327 error = ENOMEM; 328 goto fail1; 329 } 330 } else 331 vm2 = NULL; 332 #ifdef MAC 333 mac_proc_init(newproc); 334 #endif 335 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 336 STAILQ_INIT(&newproc->p_ktr); 337 338 /* We have to lock the process tree while we look for a pid. */ 339 sx_slock(&proctree_lock); 340 341 /* 342 * Although process entries are dynamically created, we still keep 343 * a global limit on the maximum number we will create. Don't allow 344 * a nonprivileged user to use the last ten processes; don't let root 345 * exceed the limit. The variable nprocs is the current number of 346 * processes, maxproc is the limit. 347 */ 348 sx_xlock(&allproc_lock); 349 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 350 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 351 error = EAGAIN; 352 goto fail; 353 } 354 355 /* 356 * Increment the count of procs running with this uid. Don't allow 357 * a nonprivileged user to exceed their current limit. 358 * 359 * XXXRW: Can we avoid privilege here if it's not needed? 360 */ 361 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 362 if (error == 0) 363 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 364 else { 365 PROC_LOCK(p1); 366 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 367 lim_cur(p1, RLIMIT_NPROC)); 368 PROC_UNLOCK(p1); 369 } 370 if (!ok) { 371 error = EAGAIN; 372 goto fail; 373 } 374 375 /* 376 * Increment the nprocs resource before blocking can occur. There 377 * are hard-limits as to the number of processes that can run. 378 */ 379 nprocs++; 380 381 /* 382 * Find an unused process ID. We remember a range of unused IDs 383 * ready to use (from lastpid+1 through pidchecked-1). 384 * 385 * If RFHIGHPID is set (used during system boot), do not allocate 386 * low-numbered pids. 387 */ 388 trypid = lastpid + 1; 389 if (flags & RFHIGHPID) { 390 if (trypid < 10) 391 trypid = 10; 392 } else { 393 if (randompid) 394 trypid += arc4random() % randompid; 395 } 396 retry: 397 /* 398 * If the process ID prototype has wrapped around, 399 * restart somewhat above 0, as the low-numbered procs 400 * tend to include daemons that don't exit. 401 */ 402 if (trypid >= PID_MAX) { 403 trypid = trypid % PID_MAX; 404 if (trypid < 100) 405 trypid += 100; 406 pidchecked = 0; 407 } 408 if (trypid >= pidchecked) { 409 int doingzomb = 0; 410 411 pidchecked = PID_MAX; 412 /* 413 * Scan the active and zombie procs to check whether this pid 414 * is in use. Remember the lowest pid that's greater 415 * than trypid, so we can avoid checking for a while. 416 */ 417 p2 = LIST_FIRST(&allproc); 418 again: 419 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 420 while (p2->p_pid == trypid || 421 (p2->p_pgrp != NULL && 422 (p2->p_pgrp->pg_id == trypid || 423 (p2->p_session != NULL && 424 p2->p_session->s_sid == trypid)))) { 425 trypid++; 426 if (trypid >= pidchecked) 427 goto retry; 428 } 429 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 430 pidchecked = p2->p_pid; 431 if (p2->p_pgrp != NULL) { 432 if (p2->p_pgrp->pg_id > trypid && 433 pidchecked > p2->p_pgrp->pg_id) 434 pidchecked = p2->p_pgrp->pg_id; 435 if (p2->p_session != NULL && 436 p2->p_session->s_sid > trypid && 437 pidchecked > p2->p_session->s_sid) 438 pidchecked = p2->p_session->s_sid; 439 } 440 } 441 if (!doingzomb) { 442 doingzomb = 1; 443 p2 = LIST_FIRST(&zombproc); 444 goto again; 445 } 446 } 447 sx_sunlock(&proctree_lock); 448 449 /* 450 * RFHIGHPID does not mess with the lastpid counter during boot. 451 */ 452 if (flags & RFHIGHPID) 453 pidchecked = 0; 454 else 455 lastpid = trypid; 456 457 p2 = newproc; 458 p2->p_state = PRS_NEW; /* protect against others */ 459 p2->p_pid = trypid; 460 AUDIT_ARG_PID(p2->p_pid); 461 LIST_INSERT_HEAD(&allproc, p2, p_list); 462 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 463 464 PROC_LOCK(p2); 465 PROC_LOCK(p1); 466 467 sx_xunlock(&allproc_lock); 468 469 bcopy(&p1->p_startcopy, &p2->p_startcopy, 470 __rangeof(struct proc, p_startcopy, p_endcopy)); 471 pargs_hold(p2->p_args); 472 PROC_UNLOCK(p1); 473 474 bzero(&p2->p_startzero, 475 __rangeof(struct proc, p_startzero, p_endzero)); 476 477 p2->p_ucred = crhold(td->td_ucred); 478 479 /* Tell the prison that we exist. */ 480 prison_proc_hold(p2->p_ucred->cr_prison); 481 482 PROC_UNLOCK(p2); 483 484 /* 485 * Malloc things while we don't hold any locks. 486 */ 487 if (flags & RFSIGSHARE) 488 newsigacts = NULL; 489 else 490 newsigacts = sigacts_alloc(); 491 492 /* 493 * Copy filedesc. 494 */ 495 if (flags & RFCFDG) { 496 fd = fdinit(p1->p_fd); 497 fdtol = NULL; 498 } else if (flags & RFFDG) { 499 fd = fdcopy(p1->p_fd); 500 fdtol = NULL; 501 } else { 502 fd = fdshare(p1->p_fd); 503 if (p1->p_fdtol == NULL) 504 p1->p_fdtol = 505 filedesc_to_leader_alloc(NULL, 506 NULL, 507 p1->p_leader); 508 if ((flags & RFTHREAD) != 0) { 509 /* 510 * Shared file descriptor table and 511 * shared process leaders. 512 */ 513 fdtol = p1->p_fdtol; 514 FILEDESC_XLOCK(p1->p_fd); 515 fdtol->fdl_refcount++; 516 FILEDESC_XUNLOCK(p1->p_fd); 517 } else { 518 /* 519 * Shared file descriptor table, and 520 * different process leaders 521 */ 522 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 523 p1->p_fd, 524 p2); 525 } 526 } 527 /* 528 * Make a proc table entry for the new process. 529 * Start by zeroing the section of proc that is zero-initialized, 530 * then copy the section that is copied directly from the parent. 531 */ 532 533 PROC_LOCK(p2); 534 PROC_LOCK(p1); 535 536 bzero(&td2->td_startzero, 537 __rangeof(struct thread, td_startzero, td_endzero)); 538 bzero(&td2->td_rux, sizeof(td2->td_rux)); 539 td2->td_map_def_user = NULL; 540 td2->td_dbg_forked = 0; 541 542 bcopy(&td->td_startcopy, &td2->td_startcopy, 543 __rangeof(struct thread, td_startcopy, td_endcopy)); 544 545 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 546 td2->td_sigstk = td->td_sigstk; 547 td2->td_sigmask = td->td_sigmask; 548 td2->td_flags = TDF_INMEM; 549 550 #ifdef VIMAGE 551 td2->td_vnet = NULL; 552 td2->td_vnet_lpush = NULL; 553 #endif 554 555 /* 556 * Allow the scheduler to initialize the child. 557 */ 558 thread_lock(td); 559 sched_fork(td, td2); 560 thread_unlock(td); 561 562 /* 563 * Duplicate sub-structures as needed. 564 * Increase reference counts on shared objects. 565 */ 566 p2->p_flag = P_INMEM; 567 p2->p_swtick = ticks; 568 if (p1->p_flag & P_PROFIL) 569 startprofclock(p2); 570 td2->td_ucred = crhold(p2->p_ucred); 571 572 if (flags & RFSIGSHARE) { 573 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 574 } else { 575 sigacts_copy(newsigacts, p1->p_sigacts); 576 p2->p_sigacts = newsigacts; 577 } 578 579 if (flags & RFTSIGZMB) 580 p2->p_sigparent = RFTSIGNUM(flags); 581 else if (flags & RFLINUXTHPN) 582 p2->p_sigparent = SIGUSR1; 583 else 584 p2->p_sigparent = SIGCHLD; 585 586 p2->p_textvp = p1->p_textvp; 587 p2->p_fd = fd; 588 p2->p_fdtol = fdtol; 589 590 /* 591 * p_limit is copy-on-write. Bump its refcount. 592 */ 593 lim_fork(p1, p2); 594 595 pstats_fork(p1->p_stats, p2->p_stats); 596 597 PROC_UNLOCK(p1); 598 PROC_UNLOCK(p2); 599 600 /* Bump references to the text vnode (for procfs) */ 601 if (p2->p_textvp) 602 vref(p2->p_textvp); 603 604 /* 605 * Set up linkage for kernel based threading. 606 */ 607 if ((flags & RFTHREAD) != 0) { 608 mtx_lock(&ppeers_lock); 609 p2->p_peers = p1->p_peers; 610 p1->p_peers = p2; 611 p2->p_leader = p1->p_leader; 612 mtx_unlock(&ppeers_lock); 613 PROC_LOCK(p1->p_leader); 614 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 615 PROC_UNLOCK(p1->p_leader); 616 /* 617 * The task leader is exiting, so process p1 is 618 * going to be killed shortly. Since p1 obviously 619 * isn't dead yet, we know that the leader is either 620 * sending SIGKILL's to all the processes in this 621 * task or is sleeping waiting for all the peers to 622 * exit. We let p1 complete the fork, but we need 623 * to go ahead and kill the new process p2 since 624 * the task leader may not get a chance to send 625 * SIGKILL to it. We leave it on the list so that 626 * the task leader will wait for this new process 627 * to commit suicide. 628 */ 629 PROC_LOCK(p2); 630 psignal(p2, SIGKILL); 631 PROC_UNLOCK(p2); 632 } else 633 PROC_UNLOCK(p1->p_leader); 634 } else { 635 p2->p_peers = NULL; 636 p2->p_leader = p2; 637 } 638 639 sx_xlock(&proctree_lock); 640 PGRP_LOCK(p1->p_pgrp); 641 PROC_LOCK(p2); 642 PROC_LOCK(p1); 643 644 /* 645 * Preserve some more flags in subprocess. P_PROFIL has already 646 * been preserved. 647 */ 648 p2->p_flag |= p1->p_flag & P_SUGID; 649 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 650 SESS_LOCK(p1->p_session); 651 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 652 p2->p_flag |= P_CONTROLT; 653 SESS_UNLOCK(p1->p_session); 654 if (flags & RFPPWAIT) 655 p2->p_flag |= P_PPWAIT; 656 657 p2->p_pgrp = p1->p_pgrp; 658 LIST_INSERT_AFTER(p1, p2, p_pglist); 659 PGRP_UNLOCK(p1->p_pgrp); 660 LIST_INIT(&p2->p_children); 661 662 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 663 664 /* 665 * If PF_FORK is set, the child process inherits the 666 * procfs ioctl flags from its parent. 667 */ 668 if (p1->p_pfsflags & PF_FORK) { 669 p2->p_stops = p1->p_stops; 670 p2->p_pfsflags = p1->p_pfsflags; 671 } 672 673 /* 674 * This begins the section where we must prevent the parent 675 * from being swapped. 676 */ 677 _PHOLD(p1); 678 PROC_UNLOCK(p1); 679 680 /* 681 * Attach the new process to its parent. 682 * 683 * If RFNOWAIT is set, the newly created process becomes a child 684 * of init. This effectively disassociates the child from the 685 * parent. 686 */ 687 if (flags & RFNOWAIT) 688 pptr = initproc; 689 else 690 pptr = p1; 691 p2->p_pptr = pptr; 692 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 693 sx_xunlock(&proctree_lock); 694 695 /* Inform accounting that we have forked. */ 696 p2->p_acflag = AFORK; 697 PROC_UNLOCK(p2); 698 699 #ifdef KTRACE 700 ktrprocfork(p1, p2); 701 #endif 702 703 /* 704 * Finish creating the child process. It will return via a different 705 * execution path later. (ie: directly into user mode) 706 */ 707 vm_forkproc(td, p2, td2, vm2, flags); 708 709 if (flags == (RFFDG | RFPROC)) { 710 PCPU_INC(cnt.v_forks); 711 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 712 p2->p_vmspace->vm_ssize); 713 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 714 PCPU_INC(cnt.v_vforks); 715 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 716 p2->p_vmspace->vm_ssize); 717 } else if (p1 == &proc0) { 718 PCPU_INC(cnt.v_kthreads); 719 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 720 p2->p_vmspace->vm_ssize); 721 } else { 722 PCPU_INC(cnt.v_rforks); 723 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 724 p2->p_vmspace->vm_ssize); 725 } 726 727 /* 728 * Both processes are set up, now check if any loadable modules want 729 * to adjust anything. 730 * What if they have an error? XXX 731 */ 732 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 733 734 /* 735 * Set the child start time and mark the process as being complete. 736 */ 737 PROC_LOCK(p2); 738 PROC_LOCK(p1); 739 microuptime(&p2->p_stats->p_start); 740 PROC_SLOCK(p2); 741 p2->p_state = PRS_NORMAL; 742 PROC_SUNLOCK(p2); 743 744 #ifdef KDTRACE_HOOKS 745 /* 746 * Tell the DTrace fasttrap provider about the new process 747 * if it has registered an interest. We have to do this only after 748 * p_state is PRS_NORMAL since the fasttrap module will use pfind() 749 * later on. 750 */ 751 if (dtrace_fasttrap_fork) 752 dtrace_fasttrap_fork(p1, p2); 753 #endif 754 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 755 P_FOLLOWFORK)) { 756 /* 757 * Arrange for debugger to receive the fork event. 758 * 759 * We can report PL_FLAG_FORKED regardless of 760 * P_FOLLOWFORK settings, but it does not make a sense 761 * for runaway child. 762 */ 763 td->td_dbgflags |= TDB_FORK; 764 td->td_dbg_forked = p2->p_pid; 765 td2->td_dbgflags |= TDB_STOPATFORK; 766 _PHOLD(p2); 767 p2_held = 1; 768 } 769 PROC_UNLOCK(p2); 770 if ((flags & RFSTOPPED) == 0) { 771 /* 772 * If RFSTOPPED not requested, make child runnable and 773 * add to run queue. 774 */ 775 thread_lock(td2); 776 TD_SET_CAN_RUN(td2); 777 sched_add(td2, SRQ_BORING); 778 thread_unlock(td2); 779 } 780 781 /* 782 * Now can be swapped. 783 */ 784 _PRELE(p1); 785 PROC_UNLOCK(p1); 786 787 /* 788 * Tell any interested parties about the new process. 789 */ 790 knote_fork(&p1->p_klist, p2->p_pid); 791 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 792 793 /* 794 * Wait until debugger is attached to child. 795 */ 796 PROC_LOCK(p2); 797 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 798 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 799 if (p2_held) 800 _PRELE(p2); 801 802 /* 803 * Preserve synchronization semantics of vfork. If waiting for 804 * child to exec or exit, set P_PPWAIT on child, and sleep on our 805 * proc (in case of exit). 806 */ 807 while (p2->p_flag & P_PPWAIT) 808 cv_wait(&p2->p_pwait, &p2->p_mtx); 809 PROC_UNLOCK(p2); 810 811 /* 812 * Return child proc pointer to parent. 813 */ 814 *procp = p2; 815 return (0); 816 fail: 817 sx_sunlock(&proctree_lock); 818 if (ppsratecheck(&lastfail, &curfail, 1)) 819 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 820 td->td_ucred->cr_ruid); 821 sx_xunlock(&allproc_lock); 822 #ifdef MAC 823 mac_proc_destroy(newproc); 824 #endif 825 fail1: 826 if (vm2 != NULL) 827 vmspace_free(vm2); 828 uma_zfree(proc_zone, newproc); 829 pause("fork", hz / 2); 830 return (error); 831 } 832 833 /* 834 * Handle the return of a child process from fork1(). This function 835 * is called from the MD fork_trampoline() entry point. 836 */ 837 void 838 fork_exit(callout, arg, frame) 839 void (*callout)(void *, struct trapframe *); 840 void *arg; 841 struct trapframe *frame; 842 { 843 struct proc *p; 844 struct thread *td; 845 struct thread *dtd; 846 847 td = curthread; 848 p = td->td_proc; 849 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 850 851 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 852 td, td->td_sched, p->p_pid, td->td_name); 853 854 sched_fork_exit(td); 855 /* 856 * Processes normally resume in mi_switch() after being 857 * cpu_switch()'ed to, but when children start up they arrive here 858 * instead, so we must do much the same things as mi_switch() would. 859 */ 860 if ((dtd = PCPU_GET(deadthread))) { 861 PCPU_SET(deadthread, NULL); 862 thread_stash(dtd); 863 } 864 thread_unlock(td); 865 866 /* 867 * cpu_set_fork_handler intercepts this function call to 868 * have this call a non-return function to stay in kernel mode. 869 * initproc has its own fork handler, but it does return. 870 */ 871 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 872 callout(arg, frame); 873 874 /* 875 * Check if a kernel thread misbehaved and returned from its main 876 * function. 877 */ 878 if (p->p_flag & P_KTHREAD) { 879 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 880 td->td_name, p->p_pid); 881 kthread_exit(); 882 } 883 mtx_assert(&Giant, MA_NOTOWNED); 884 885 if (p->p_sysent->sv_schedtail != NULL) 886 (p->p_sysent->sv_schedtail)(td); 887 } 888 889 /* 890 * Simplified back end of syscall(), used when returning from fork() 891 * directly into user mode. Giant is not held on entry, and must not 892 * be held on return. This function is passed in to fork_exit() as the 893 * first parameter and is called when returning to a new userland process. 894 */ 895 void 896 fork_return(td, frame) 897 struct thread *td; 898 struct trapframe *frame; 899 { 900 struct proc *p, *dbg; 901 902 if (td->td_dbgflags & TDB_STOPATFORK) { 903 p = td->td_proc; 904 sx_xlock(&proctree_lock); 905 PROC_LOCK(p); 906 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 907 (P_TRACED | P_FOLLOWFORK)) { 908 /* 909 * If debugger still wants auto-attach for the 910 * parent's children, do it now. 911 */ 912 dbg = p->p_pptr->p_pptr; 913 p->p_flag |= P_TRACED; 914 p->p_oppid = p->p_pptr->p_pid; 915 proc_reparent(p, dbg); 916 sx_xunlock(&proctree_lock); 917 ptracestop(td, SIGSTOP); 918 } else { 919 /* 920 * ... otherwise clear the request. 921 */ 922 sx_xunlock(&proctree_lock); 923 td->td_dbgflags &= ~TDB_STOPATFORK; 924 cv_broadcast(&p->p_dbgwait); 925 } 926 PROC_UNLOCK(p); 927 } 928 929 userret(td, frame); 930 931 #ifdef KTRACE 932 if (KTRPOINT(td, KTR_SYSRET)) 933 ktrsysret(SYS_fork, 0, 0); 934 #endif 935 mtx_assert(&Giant, MA_NOTOWNED); 936 }
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