Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c
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1 /*- 2 * Copyright (c) 1982, 1986, 1989, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD: releng/8.3/sys/kern/kern_fork.c 224211 2011-07-19 10:41:26Z kib $"); 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 #ifdef XEN 126 flags = RFFDG | RFPROC; /* validate that this is still an issue */ 127 #else 128 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 129 #endif 130 error = fork1(td, flags, 0, &p2); 131 if (error == 0) { 132 td->td_retval[0] = p2->p_pid; 133 td->td_retval[1] = 0; 134 } 135 return (error); 136 } 137 138 int 139 rfork(td, uap) 140 struct thread *td; 141 struct rfork_args *uap; 142 { 143 struct proc *p2; 144 int error; 145 146 /* Don't allow kernel-only flags. */ 147 if ((uap->flags & RFKERNELONLY) != 0) 148 return (EINVAL); 149 150 AUDIT_ARG_FFLAGS(uap->flags); 151 error = fork1(td, uap->flags, 0, &p2); 152 if (error == 0) { 153 td->td_retval[0] = p2 ? p2->p_pid : 0; 154 td->td_retval[1] = 0; 155 } 156 return (error); 157 } 158 159 int nprocs = 1; /* process 0 */ 160 int lastpid = 0; 161 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 162 "Last used PID"); 163 164 /* 165 * Random component to lastpid generation. We mix in a random factor to make 166 * it a little harder to predict. We sanity check the modulus value to avoid 167 * doing it in critical paths. Don't let it be too small or we pointlessly 168 * waste randomness entropy, and don't let it be impossibly large. Using a 169 * modulus that is too big causes a LOT more process table scans and slows 170 * down fork processing as the pidchecked caching is defeated. 171 */ 172 static int randompid = 0; 173 174 static int 175 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 176 { 177 int error, pid; 178 179 error = sysctl_wire_old_buffer(req, sizeof(int)); 180 if (error != 0) 181 return(error); 182 sx_xlock(&allproc_lock); 183 pid = randompid; 184 error = sysctl_handle_int(oidp, &pid, 0, req); 185 if (error == 0 && req->newptr != NULL) { 186 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 187 pid = PID_MAX - 100; 188 else if (pid < 2) /* NOP */ 189 pid = 0; 190 else if (pid < 100) /* Make it reasonable */ 191 pid = 100; 192 randompid = pid; 193 } 194 sx_xunlock(&allproc_lock); 195 return (error); 196 } 197 198 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 199 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 200 201 int 202 fork1(td, flags, pages, procp) 203 struct thread *td; 204 int flags; 205 int pages; 206 struct proc **procp; 207 { 208 struct proc *p1, *p2, *pptr; 209 struct proc *newproc; 210 int ok, p2_held, trypid; 211 static int curfail, pidchecked = 0; 212 static struct timeval lastfail; 213 struct filedesc *fd; 214 struct filedesc_to_leader *fdtol; 215 struct thread *td2; 216 struct sigacts *newsigacts; 217 struct vmspace *vm2; 218 vm_ooffset_t mem_charged; 219 int error; 220 221 /* Check for the undefined or unimplemented flags. */ 222 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 223 return (EINVAL); 224 225 /* Signal value requires RFTSIGZMB. */ 226 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 227 return (EINVAL); 228 229 /* Can't copy and clear. */ 230 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 231 return (EINVAL); 232 233 /* Check the validity of the signal number. */ 234 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 235 return (EINVAL); 236 237 p2_held = 0; 238 p1 = td->td_proc; 239 240 /* 241 * Here we don't create a new process, but we divorce 242 * certain parts of a process from itself. 243 */ 244 if ((flags & RFPROC) == 0) { 245 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 246 (flags & (RFCFDG | RFFDG))) { 247 PROC_LOCK(p1); 248 if (thread_single(SINGLE_BOUNDARY)) { 249 PROC_UNLOCK(p1); 250 return (ERESTART); 251 } 252 PROC_UNLOCK(p1); 253 } 254 255 error = vm_forkproc(td, NULL, NULL, NULL, flags); 256 if (error) 257 goto norfproc_fail; 258 259 /* 260 * Close all file descriptors. 261 */ 262 if (flags & RFCFDG) { 263 struct filedesc *fdtmp; 264 fdtmp = fdinit(td->td_proc->p_fd); 265 fdfree(td); 266 p1->p_fd = fdtmp; 267 } 268 269 /* 270 * Unshare file descriptors (from parent). 271 */ 272 if (flags & RFFDG) 273 fdunshare(p1, td); 274 275 norfproc_fail: 276 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 277 (flags & (RFCFDG | RFFDG))) { 278 PROC_LOCK(p1); 279 thread_single_end(); 280 PROC_UNLOCK(p1); 281 } 282 *procp = NULL; 283 return (error); 284 } 285 286 /* 287 * XXX 288 * We did have single-threading code here 289 * however it proved un-needed and caused problems 290 */ 291 292 mem_charged = 0; 293 vm2 = NULL; 294 if (pages == 0) 295 pages = KSTACK_PAGES; 296 /* Allocate new proc. */ 297 newproc = uma_zalloc(proc_zone, M_WAITOK); 298 td2 = FIRST_THREAD_IN_PROC(newproc); 299 if (td2 == NULL) { 300 td2 = thread_alloc(pages); 301 if (td2 == NULL) { 302 error = ENOMEM; 303 goto fail1; 304 } 305 proc_linkup(newproc, td2); 306 } else { 307 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 308 if (td2->td_kstack != 0) 309 vm_thread_dispose(td2); 310 if (!thread_alloc_stack(td2, pages)) { 311 error = ENOMEM; 312 goto fail1; 313 } 314 } 315 } 316 317 if ((flags & RFMEM) == 0) { 318 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 319 if (vm2 == NULL) { 320 error = ENOMEM; 321 goto fail1; 322 } 323 if (!swap_reserve(mem_charged)) { 324 /* 325 * The swap reservation failed. The accounting 326 * from the entries of the copied vm2 will be 327 * substracted in vmspace_free(), so force the 328 * reservation there. 329 */ 330 swap_reserve_force(mem_charged); 331 error = ENOMEM; 332 goto fail1; 333 } 334 } else 335 vm2 = NULL; 336 #ifdef MAC 337 mac_proc_init(newproc); 338 #endif 339 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 340 STAILQ_INIT(&newproc->p_ktr); 341 342 /* We have to lock the process tree while we look for a pid. */ 343 sx_slock(&proctree_lock); 344 345 /* 346 * Although process entries are dynamically created, we still keep 347 * a global limit on the maximum number we will create. Don't allow 348 * a nonprivileged user to use the last ten processes; don't let root 349 * exceed the limit. The variable nprocs is the current number of 350 * processes, maxproc is the limit. 351 */ 352 sx_xlock(&allproc_lock); 353 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 354 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 355 error = EAGAIN; 356 goto fail; 357 } 358 359 /* 360 * Increment the count of procs running with this uid. Don't allow 361 * a nonprivileged user to exceed their current limit. 362 * 363 * XXXRW: Can we avoid privilege here if it's not needed? 364 */ 365 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 366 if (error == 0) 367 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 368 else { 369 PROC_LOCK(p1); 370 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 371 lim_cur(p1, RLIMIT_NPROC)); 372 PROC_UNLOCK(p1); 373 } 374 if (!ok) { 375 error = EAGAIN; 376 goto fail; 377 } 378 379 /* 380 * Increment the nprocs resource before blocking can occur. There 381 * are hard-limits as to the number of processes that can run. 382 */ 383 nprocs++; 384 385 /* 386 * Find an unused process ID. We remember a range of unused IDs 387 * ready to use (from lastpid+1 through pidchecked-1). 388 * 389 * If RFHIGHPID is set (used during system boot), do not allocate 390 * low-numbered pids. 391 */ 392 trypid = lastpid + 1; 393 if (flags & RFHIGHPID) { 394 if (trypid < 10) 395 trypid = 10; 396 } else { 397 if (randompid) 398 trypid += arc4random() % randompid; 399 } 400 retry: 401 /* 402 * If the process ID prototype has wrapped around, 403 * restart somewhat above 0, as the low-numbered procs 404 * tend to include daemons that don't exit. 405 */ 406 if (trypid >= PID_MAX) { 407 trypid = trypid % PID_MAX; 408 if (trypid < 100) 409 trypid += 100; 410 pidchecked = 0; 411 } 412 if (trypid >= pidchecked) { 413 int doingzomb = 0; 414 415 pidchecked = PID_MAX; 416 /* 417 * Scan the active and zombie procs to check whether this pid 418 * is in use. Remember the lowest pid that's greater 419 * than trypid, so we can avoid checking for a while. 420 */ 421 p2 = LIST_FIRST(&allproc); 422 again: 423 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 424 while (p2->p_pid == trypid || 425 (p2->p_pgrp != NULL && 426 (p2->p_pgrp->pg_id == trypid || 427 (p2->p_session != NULL && 428 p2->p_session->s_sid == trypid)))) { 429 trypid++; 430 if (trypid >= pidchecked) 431 goto retry; 432 } 433 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 434 pidchecked = p2->p_pid; 435 if (p2->p_pgrp != NULL) { 436 if (p2->p_pgrp->pg_id > trypid && 437 pidchecked > p2->p_pgrp->pg_id) 438 pidchecked = p2->p_pgrp->pg_id; 439 if (p2->p_session != NULL && 440 p2->p_session->s_sid > trypid && 441 pidchecked > p2->p_session->s_sid) 442 pidchecked = p2->p_session->s_sid; 443 } 444 } 445 if (!doingzomb) { 446 doingzomb = 1; 447 p2 = LIST_FIRST(&zombproc); 448 goto again; 449 } 450 } 451 sx_sunlock(&proctree_lock); 452 453 /* 454 * RFHIGHPID does not mess with the lastpid counter during boot. 455 */ 456 if (flags & RFHIGHPID) 457 pidchecked = 0; 458 else 459 lastpid = trypid; 460 461 p2 = newproc; 462 p2->p_state = PRS_NEW; /* protect against others */ 463 p2->p_pid = trypid; 464 AUDIT_ARG_PID(p2->p_pid); 465 LIST_INSERT_HEAD(&allproc, p2, p_list); 466 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 467 468 PROC_LOCK(p2); 469 PROC_LOCK(p1); 470 471 sx_xunlock(&allproc_lock); 472 473 bcopy(&p1->p_startcopy, &p2->p_startcopy, 474 __rangeof(struct proc, p_startcopy, p_endcopy)); 475 pargs_hold(p2->p_args); 476 PROC_UNLOCK(p1); 477 478 bzero(&p2->p_startzero, 479 __rangeof(struct proc, p_startzero, p_endzero)); 480 481 p2->p_ucred = crhold(td->td_ucred); 482 483 /* Tell the prison that we exist. */ 484 prison_proc_hold(p2->p_ucred->cr_prison); 485 486 PROC_UNLOCK(p2); 487 488 /* 489 * Malloc things while we don't hold any locks. 490 */ 491 if (flags & RFSIGSHARE) 492 newsigacts = NULL; 493 else 494 newsigacts = sigacts_alloc(); 495 496 /* 497 * Copy filedesc. 498 */ 499 if (flags & RFCFDG) { 500 fd = fdinit(p1->p_fd); 501 fdtol = NULL; 502 } else if (flags & RFFDG) { 503 fd = fdcopy(p1->p_fd); 504 fdtol = NULL; 505 } else { 506 fd = fdshare(p1->p_fd); 507 if (p1->p_fdtol == NULL) 508 p1->p_fdtol = 509 filedesc_to_leader_alloc(NULL, 510 NULL, 511 p1->p_leader); 512 if ((flags & RFTHREAD) != 0) { 513 /* 514 * Shared file descriptor table and 515 * shared process leaders. 516 */ 517 fdtol = p1->p_fdtol; 518 FILEDESC_XLOCK(p1->p_fd); 519 fdtol->fdl_refcount++; 520 FILEDESC_XUNLOCK(p1->p_fd); 521 } else { 522 /* 523 * Shared file descriptor table, and 524 * different process leaders 525 */ 526 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 527 p1->p_fd, 528 p2); 529 } 530 } 531 /* 532 * Make a proc table entry for the new process. 533 * Start by zeroing the section of proc that is zero-initialized, 534 * then copy the section that is copied directly from the parent. 535 */ 536 537 PROC_LOCK(p2); 538 PROC_LOCK(p1); 539 540 bzero(&td2->td_startzero, 541 __rangeof(struct thread, td_startzero, td_endzero)); 542 bzero(&td2->td_rux, sizeof(td2->td_rux)); 543 td2->td_map_def_user = NULL; 544 td2->td_dbg_forked = 0; 545 546 bcopy(&td->td_startcopy, &td2->td_startcopy, 547 __rangeof(struct thread, td_startcopy, td_endcopy)); 548 549 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 550 td2->td_sigstk = td->td_sigstk; 551 td2->td_sigmask = td->td_sigmask; 552 td2->td_flags = TDF_INMEM; 553 554 #ifdef VIMAGE 555 td2->td_vnet = NULL; 556 td2->td_vnet_lpush = NULL; 557 #endif 558 559 /* 560 * Allow the scheduler to initialize the child. 561 */ 562 thread_lock(td); 563 sched_fork(td, td2); 564 thread_unlock(td); 565 566 /* 567 * Duplicate sub-structures as needed. 568 * Increase reference counts on shared objects. 569 */ 570 p2->p_flag = P_INMEM; 571 p2->p_swtick = ticks; 572 if (p1->p_flag & P_PROFIL) 573 startprofclock(p2); 574 td2->td_ucred = crhold(p2->p_ucred); 575 576 if (flags & RFSIGSHARE) { 577 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 578 } else { 579 sigacts_copy(newsigacts, p1->p_sigacts); 580 p2->p_sigacts = newsigacts; 581 } 582 583 if (flags & RFTSIGZMB) 584 p2->p_sigparent = RFTSIGNUM(flags); 585 else if (flags & RFLINUXTHPN) 586 p2->p_sigparent = SIGUSR1; 587 else 588 p2->p_sigparent = SIGCHLD; 589 590 p2->p_textvp = p1->p_textvp; 591 p2->p_fd = fd; 592 p2->p_fdtol = fdtol; 593 594 /* 595 * p_limit is copy-on-write. Bump its refcount. 596 */ 597 lim_fork(p1, p2); 598 599 pstats_fork(p1->p_stats, p2->p_stats); 600 601 PROC_UNLOCK(p1); 602 PROC_UNLOCK(p2); 603 604 /* Bump references to the text vnode (for procfs) */ 605 if (p2->p_textvp) 606 vref(p2->p_textvp); 607 608 /* 609 * Set up linkage for kernel based threading. 610 */ 611 if ((flags & RFTHREAD) != 0) { 612 mtx_lock(&ppeers_lock); 613 p2->p_peers = p1->p_peers; 614 p1->p_peers = p2; 615 p2->p_leader = p1->p_leader; 616 mtx_unlock(&ppeers_lock); 617 PROC_LOCK(p1->p_leader); 618 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 619 PROC_UNLOCK(p1->p_leader); 620 /* 621 * The task leader is exiting, so process p1 is 622 * going to be killed shortly. Since p1 obviously 623 * isn't dead yet, we know that the leader is either 624 * sending SIGKILL's to all the processes in this 625 * task or is sleeping waiting for all the peers to 626 * exit. We let p1 complete the fork, but we need 627 * to go ahead and kill the new process p2 since 628 * the task leader may not get a chance to send 629 * SIGKILL to it. We leave it on the list so that 630 * the task leader will wait for this new process 631 * to commit suicide. 632 */ 633 PROC_LOCK(p2); 634 psignal(p2, SIGKILL); 635 PROC_UNLOCK(p2); 636 } else 637 PROC_UNLOCK(p1->p_leader); 638 } else { 639 p2->p_peers = NULL; 640 p2->p_leader = p2; 641 } 642 643 sx_xlock(&proctree_lock); 644 PGRP_LOCK(p1->p_pgrp); 645 PROC_LOCK(p2); 646 PROC_LOCK(p1); 647 648 /* 649 * Preserve some more flags in subprocess. P_PROFIL has already 650 * been preserved. 651 */ 652 p2->p_flag |= p1->p_flag & P_SUGID; 653 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 654 SESS_LOCK(p1->p_session); 655 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 656 p2->p_flag |= P_CONTROLT; 657 SESS_UNLOCK(p1->p_session); 658 if (flags & RFPPWAIT) 659 p2->p_flag |= P_PPWAIT; 660 661 p2->p_pgrp = p1->p_pgrp; 662 LIST_INSERT_AFTER(p1, p2, p_pglist); 663 PGRP_UNLOCK(p1->p_pgrp); 664 LIST_INIT(&p2->p_children); 665 666 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 667 668 /* 669 * If PF_FORK is set, the child process inherits the 670 * procfs ioctl flags from its parent. 671 */ 672 if (p1->p_pfsflags & PF_FORK) { 673 p2->p_stops = p1->p_stops; 674 p2->p_pfsflags = p1->p_pfsflags; 675 } 676 677 /* 678 * This begins the section where we must prevent the parent 679 * from being swapped. 680 */ 681 _PHOLD(p1); 682 PROC_UNLOCK(p1); 683 684 /* 685 * Attach the new process to its parent. 686 * 687 * If RFNOWAIT is set, the newly created process becomes a child 688 * of init. This effectively disassociates the child from the 689 * parent. 690 */ 691 if (flags & RFNOWAIT) 692 pptr = initproc; 693 else 694 pptr = p1; 695 p2->p_pptr = pptr; 696 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 697 sx_xunlock(&proctree_lock); 698 699 /* Inform accounting that we have forked. */ 700 p2->p_acflag = AFORK; 701 PROC_UNLOCK(p2); 702 703 #ifdef KTRACE 704 ktrprocfork(p1, p2); 705 #endif 706 707 /* 708 * Finish creating the child process. It will return via a different 709 * execution path later. (ie: directly into user mode) 710 */ 711 vm_forkproc(td, p2, td2, vm2, flags); 712 713 if (flags == (RFFDG | RFPROC)) { 714 PCPU_INC(cnt.v_forks); 715 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 716 p2->p_vmspace->vm_ssize); 717 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 718 PCPU_INC(cnt.v_vforks); 719 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 720 p2->p_vmspace->vm_ssize); 721 } else if (p1 == &proc0) { 722 PCPU_INC(cnt.v_kthreads); 723 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 724 p2->p_vmspace->vm_ssize); 725 } else { 726 PCPU_INC(cnt.v_rforks); 727 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 728 p2->p_vmspace->vm_ssize); 729 } 730 731 /* 732 * Both processes are set up, now check if any loadable modules want 733 * to adjust anything. 734 * What if they have an error? XXX 735 */ 736 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 737 738 /* 739 * Set the child start time and mark the process as being complete. 740 */ 741 PROC_LOCK(p2); 742 PROC_LOCK(p1); 743 microuptime(&p2->p_stats->p_start); 744 PROC_SLOCK(p2); 745 p2->p_state = PRS_NORMAL; 746 PROC_SUNLOCK(p2); 747 748 #ifdef KDTRACE_HOOKS 749 /* 750 * Tell the DTrace fasttrap provider about the new process 751 * if it has registered an interest. We have to do this only after 752 * p_state is PRS_NORMAL since the fasttrap module will use pfind() 753 * later on. 754 */ 755 if (dtrace_fasttrap_fork) 756 dtrace_fasttrap_fork(p1, p2); 757 #endif 758 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 759 P_FOLLOWFORK)) { 760 /* 761 * Arrange for debugger to receive the fork event. 762 * 763 * We can report PL_FLAG_FORKED regardless of 764 * P_FOLLOWFORK settings, but it does not make a sense 765 * for runaway child. 766 */ 767 td->td_dbgflags |= TDB_FORK; 768 td->td_dbg_forked = p2->p_pid; 769 td2->td_dbgflags |= TDB_STOPATFORK; 770 _PHOLD(p2); 771 p2_held = 1; 772 } 773 PROC_UNLOCK(p2); 774 if ((flags & RFSTOPPED) == 0) { 775 /* 776 * If RFSTOPPED not requested, make child runnable and 777 * add to run queue. 778 */ 779 thread_lock(td2); 780 TD_SET_CAN_RUN(td2); 781 sched_add(td2, SRQ_BORING); 782 thread_unlock(td2); 783 } 784 785 /* 786 * Now can be swapped. 787 */ 788 _PRELE(p1); 789 PROC_UNLOCK(p1); 790 791 /* 792 * Tell any interested parties about the new process. 793 */ 794 knote_fork(&p1->p_klist, p2->p_pid); 795 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 796 797 /* 798 * Wait until debugger is attached to child. 799 */ 800 PROC_LOCK(p2); 801 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 802 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 803 if (p2_held) 804 _PRELE(p2); 805 806 /* 807 * Preserve synchronization semantics of vfork. If waiting for 808 * child to exec or exit, set P_PPWAIT on child, and sleep on our 809 * proc (in case of exit). 810 */ 811 while (p2->p_flag & P_PPWAIT) 812 cv_wait(&p2->p_pwait, &p2->p_mtx); 813 PROC_UNLOCK(p2); 814 815 /* 816 * Return child proc pointer to parent. 817 */ 818 *procp = p2; 819 return (0); 820 fail: 821 sx_sunlock(&proctree_lock); 822 if (ppsratecheck(&lastfail, &curfail, 1)) 823 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 824 td->td_ucred->cr_ruid); 825 sx_xunlock(&allproc_lock); 826 #ifdef MAC 827 mac_proc_destroy(newproc); 828 #endif 829 fail1: 830 if (vm2 != NULL) 831 vmspace_free(vm2); 832 uma_zfree(proc_zone, newproc); 833 pause("fork", hz / 2); 834 return (error); 835 } 836 837 /* 838 * Handle the return of a child process from fork1(). This function 839 * is called from the MD fork_trampoline() entry point. 840 */ 841 void 842 fork_exit(callout, arg, frame) 843 void (*callout)(void *, struct trapframe *); 844 void *arg; 845 struct trapframe *frame; 846 { 847 struct proc *p; 848 struct thread *td; 849 struct thread *dtd; 850 851 td = curthread; 852 p = td->td_proc; 853 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 854 855 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 856 td, td->td_sched, p->p_pid, td->td_name); 857 858 sched_fork_exit(td); 859 /* 860 * Processes normally resume in mi_switch() after being 861 * cpu_switch()'ed to, but when children start up they arrive here 862 * instead, so we must do much the same things as mi_switch() would. 863 */ 864 if ((dtd = PCPU_GET(deadthread))) { 865 PCPU_SET(deadthread, NULL); 866 thread_stash(dtd); 867 } 868 thread_unlock(td); 869 870 /* 871 * cpu_set_fork_handler intercepts this function call to 872 * have this call a non-return function to stay in kernel mode. 873 * initproc has its own fork handler, but it does return. 874 */ 875 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 876 callout(arg, frame); 877 878 /* 879 * Check if a kernel thread misbehaved and returned from its main 880 * function. 881 */ 882 if (p->p_flag & P_KTHREAD) { 883 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 884 td->td_name, p->p_pid); 885 kproc_exit(0); 886 } 887 mtx_assert(&Giant, MA_NOTOWNED); 888 889 if (p->p_sysent->sv_schedtail != NULL) 890 (p->p_sysent->sv_schedtail)(td); 891 } 892 893 /* 894 * Simplified back end of syscall(), used when returning from fork() 895 * directly into user mode. Giant is not held on entry, and must not 896 * be held on return. This function is passed in to fork_exit() as the 897 * first parameter and is called when returning to a new userland process. 898 */ 899 void 900 fork_return(td, frame) 901 struct thread *td; 902 struct trapframe *frame; 903 { 904 struct proc *p, *dbg; 905 906 if (td->td_dbgflags & TDB_STOPATFORK) { 907 p = td->td_proc; 908 sx_xlock(&proctree_lock); 909 PROC_LOCK(p); 910 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 911 (P_TRACED | P_FOLLOWFORK)) { 912 /* 913 * If debugger still wants auto-attach for the 914 * parent's children, do it now. 915 */ 916 dbg = p->p_pptr->p_pptr; 917 p->p_flag |= P_TRACED; 918 p->p_oppid = p->p_pptr->p_pid; 919 proc_reparent(p, dbg); 920 sx_xunlock(&proctree_lock); 921 ptracestop(td, SIGSTOP); 922 } else { 923 /* 924 * ... otherwise clear the request. 925 */ 926 sx_xunlock(&proctree_lock); 927 td->td_dbgflags &= ~TDB_STOPATFORK; 928 cv_broadcast(&p->p_dbgwait); 929 } 930 PROC_UNLOCK(p); 931 } 932 933 userret(td, frame); 934 935 #ifdef KTRACE 936 if (KTRPOINT(td, KTR_SYSRET)) 937 ktrsysret(SYS_fork, 0, 0); 938 #endif 939 mtx_assert(&Giant, MA_NOTOWNED); 940 }
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