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/8.2/sys/kern/kern_fork.c 213362 2010-10-02 17:41:47Z 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/signalvar.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 vm_ooffset_t mem_charged; 218 int error; 219 220 /* Can't copy and clear. */ 221 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 222 return (EINVAL); 223 224 p1 = td->td_proc; 225 226 /* 227 * Here we don't create a new process, but we divorce 228 * certain parts of a process from itself. 229 */ 230 if ((flags & RFPROC) == 0) { 231 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 232 (flags & (RFCFDG | RFFDG))) { 233 PROC_LOCK(p1); 234 if (thread_single(SINGLE_BOUNDARY)) { 235 PROC_UNLOCK(p1); 236 return (ERESTART); 237 } 238 PROC_UNLOCK(p1); 239 } 240 241 error = vm_forkproc(td, NULL, NULL, NULL, flags); 242 if (error) 243 goto norfproc_fail; 244 245 /* 246 * Close all file descriptors. 247 */ 248 if (flags & RFCFDG) { 249 struct filedesc *fdtmp; 250 fdtmp = fdinit(td->td_proc->p_fd); 251 fdfree(td); 252 p1->p_fd = fdtmp; 253 } 254 255 /* 256 * Unshare file descriptors (from parent). 257 */ 258 if (flags & RFFDG) 259 fdunshare(p1, td); 260 261 norfproc_fail: 262 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 263 (flags & (RFCFDG | RFFDG))) { 264 PROC_LOCK(p1); 265 thread_single_end(); 266 PROC_UNLOCK(p1); 267 } 268 *procp = NULL; 269 return (error); 270 } 271 272 /* 273 * XXX 274 * We did have single-threading code here 275 * however it proved un-needed and caused problems 276 */ 277 278 mem_charged = 0; 279 vm2 = NULL; 280 if (pages == 0) 281 pages = KSTACK_PAGES; 282 /* Allocate new proc. */ 283 newproc = uma_zalloc(proc_zone, M_WAITOK); 284 td2 = FIRST_THREAD_IN_PROC(newproc); 285 if (td2 == NULL) { 286 td2 = thread_alloc(pages); 287 if (td2 == NULL) { 288 error = ENOMEM; 289 goto fail1; 290 } 291 proc_linkup(newproc, td2); 292 } else { 293 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 294 if (td2->td_kstack != 0) 295 vm_thread_dispose(td2); 296 if (!thread_alloc_stack(td2, pages)) { 297 error = ENOMEM; 298 goto fail1; 299 } 300 } 301 } 302 303 if ((flags & RFMEM) == 0) { 304 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 305 if (vm2 == NULL) { 306 error = ENOMEM; 307 goto fail1; 308 } 309 if (!swap_reserve(mem_charged)) { 310 /* 311 * The swap reservation failed. The accounting 312 * from the entries of the copied vm2 will be 313 * substracted in vmspace_free(), so force the 314 * reservation there. 315 */ 316 swap_reserve_force(mem_charged); 317 error = ENOMEM; 318 goto fail1; 319 } 320 } else 321 vm2 = NULL; 322 #ifdef MAC 323 mac_proc_init(newproc); 324 #endif 325 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 326 STAILQ_INIT(&newproc->p_ktr); 327 328 /* We have to lock the process tree while we look for a pid. */ 329 sx_slock(&proctree_lock); 330 331 /* 332 * Although process entries are dynamically created, we still keep 333 * a global limit on the maximum number we will create. Don't allow 334 * a nonprivileged user to use the last ten processes; don't let root 335 * exceed the limit. The variable nprocs is the current number of 336 * processes, maxproc is the limit. 337 */ 338 sx_xlock(&allproc_lock); 339 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 340 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 341 error = EAGAIN; 342 goto fail; 343 } 344 345 /* 346 * Increment the count of procs running with this uid. Don't allow 347 * a nonprivileged user to exceed their current limit. 348 * 349 * XXXRW: Can we avoid privilege here if it's not needed? 350 */ 351 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 352 if (error == 0) 353 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 354 else { 355 PROC_LOCK(p1); 356 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 357 lim_cur(p1, RLIMIT_NPROC)); 358 PROC_UNLOCK(p1); 359 } 360 if (!ok) { 361 error = EAGAIN; 362 goto fail; 363 } 364 365 /* 366 * Increment the nprocs resource before blocking can occur. There 367 * are hard-limits as to the number of processes that can run. 368 */ 369 nprocs++; 370 371 /* 372 * Find an unused process ID. We remember a range of unused IDs 373 * ready to use (from lastpid+1 through pidchecked-1). 374 * 375 * If RFHIGHPID is set (used during system boot), do not allocate 376 * low-numbered pids. 377 */ 378 trypid = lastpid + 1; 379 if (flags & RFHIGHPID) { 380 if (trypid < 10) 381 trypid = 10; 382 } else { 383 if (randompid) 384 trypid += arc4random() % randompid; 385 } 386 retry: 387 /* 388 * If the process ID prototype has wrapped around, 389 * restart somewhat above 0, as the low-numbered procs 390 * tend to include daemons that don't exit. 391 */ 392 if (trypid >= PID_MAX) { 393 trypid = trypid % PID_MAX; 394 if (trypid < 100) 395 trypid += 100; 396 pidchecked = 0; 397 } 398 if (trypid >= pidchecked) { 399 int doingzomb = 0; 400 401 pidchecked = PID_MAX; 402 /* 403 * Scan the active and zombie procs to check whether this pid 404 * is in use. Remember the lowest pid that's greater 405 * than trypid, so we can avoid checking for a while. 406 */ 407 p2 = LIST_FIRST(&allproc); 408 again: 409 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 410 while (p2->p_pid == trypid || 411 (p2->p_pgrp != NULL && 412 (p2->p_pgrp->pg_id == trypid || 413 (p2->p_session != NULL && 414 p2->p_session->s_sid == trypid)))) { 415 trypid++; 416 if (trypid >= pidchecked) 417 goto retry; 418 } 419 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 420 pidchecked = p2->p_pid; 421 if (p2->p_pgrp != NULL) { 422 if (p2->p_pgrp->pg_id > trypid && 423 pidchecked > p2->p_pgrp->pg_id) 424 pidchecked = p2->p_pgrp->pg_id; 425 if (p2->p_session != NULL && 426 p2->p_session->s_sid > trypid && 427 pidchecked > p2->p_session->s_sid) 428 pidchecked = p2->p_session->s_sid; 429 } 430 } 431 if (!doingzomb) { 432 doingzomb = 1; 433 p2 = LIST_FIRST(&zombproc); 434 goto again; 435 } 436 } 437 sx_sunlock(&proctree_lock); 438 439 /* 440 * RFHIGHPID does not mess with the lastpid counter during boot. 441 */ 442 if (flags & RFHIGHPID) 443 pidchecked = 0; 444 else 445 lastpid = trypid; 446 447 p2 = newproc; 448 p2->p_state = PRS_NEW; /* protect against others */ 449 p2->p_pid = trypid; 450 /* 451 * Allow the scheduler to initialize the child. 452 */ 453 thread_lock(td); 454 sched_fork(td, td2); 455 thread_unlock(td); 456 AUDIT_ARG_PID(p2->p_pid); 457 LIST_INSERT_HEAD(&allproc, p2, p_list); 458 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 459 460 PROC_LOCK(p2); 461 PROC_LOCK(p1); 462 463 sx_xunlock(&allproc_lock); 464 465 bcopy(&p1->p_startcopy, &p2->p_startcopy, 466 __rangeof(struct proc, p_startcopy, p_endcopy)); 467 pargs_hold(p2->p_args); 468 PROC_UNLOCK(p1); 469 470 bzero(&p2->p_startzero, 471 __rangeof(struct proc, p_startzero, p_endzero)); 472 473 p2->p_ucred = crhold(td->td_ucred); 474 475 /* Tell the prison that we exist. */ 476 prison_proc_hold(p2->p_ucred->cr_prison); 477 478 PROC_UNLOCK(p2); 479 480 /* 481 * Malloc things while we don't hold any locks. 482 */ 483 if (flags & RFSIGSHARE) 484 newsigacts = NULL; 485 else 486 newsigacts = sigacts_alloc(); 487 488 /* 489 * Copy filedesc. 490 */ 491 if (flags & RFCFDG) { 492 fd = fdinit(p1->p_fd); 493 fdtol = NULL; 494 } else if (flags & RFFDG) { 495 fd = fdcopy(p1->p_fd); 496 fdtol = NULL; 497 } else { 498 fd = fdshare(p1->p_fd); 499 if (p1->p_fdtol == NULL) 500 p1->p_fdtol = 501 filedesc_to_leader_alloc(NULL, 502 NULL, 503 p1->p_leader); 504 if ((flags & RFTHREAD) != 0) { 505 /* 506 * Shared file descriptor table and 507 * shared process leaders. 508 */ 509 fdtol = p1->p_fdtol; 510 FILEDESC_XLOCK(p1->p_fd); 511 fdtol->fdl_refcount++; 512 FILEDESC_XUNLOCK(p1->p_fd); 513 } else { 514 /* 515 * Shared file descriptor table, and 516 * different process leaders 517 */ 518 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 519 p1->p_fd, 520 p2); 521 } 522 } 523 /* 524 * Make a proc table entry for the new process. 525 * Start by zeroing the section of proc that is zero-initialized, 526 * then copy the section that is copied directly from the parent. 527 */ 528 529 PROC_LOCK(p2); 530 PROC_LOCK(p1); 531 532 bzero(&td2->td_startzero, 533 __rangeof(struct thread, td_startzero, td_endzero)); 534 bzero(&td2->td_rux, sizeof(td2->td_rux)); 535 td2->td_map_def_user = NULL; 536 537 bcopy(&td->td_startcopy, &td2->td_startcopy, 538 __rangeof(struct thread, td_startcopy, td_endcopy)); 539 540 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 541 td2->td_sigstk = td->td_sigstk; 542 td2->td_sigmask = td->td_sigmask; 543 td2->td_flags = TDF_INMEM; 544 545 #ifdef VIMAGE 546 td2->td_vnet = NULL; 547 td2->td_vnet_lpush = NULL; 548 #endif 549 550 /* 551 * Duplicate sub-structures as needed. 552 * Increase reference counts on shared objects. 553 */ 554 p2->p_flag = P_INMEM; 555 p2->p_swtick = ticks; 556 if (p1->p_flag & P_PROFIL) 557 startprofclock(p2); 558 td2->td_ucred = crhold(p2->p_ucred); 559 560 if (flags & RFSIGSHARE) { 561 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 562 } else { 563 sigacts_copy(newsigacts, p1->p_sigacts); 564 p2->p_sigacts = newsigacts; 565 } 566 if (flags & RFLINUXTHPN) 567 p2->p_sigparent = SIGUSR1; 568 else 569 p2->p_sigparent = SIGCHLD; 570 571 p2->p_textvp = p1->p_textvp; 572 p2->p_fd = fd; 573 p2->p_fdtol = fdtol; 574 575 /* 576 * p_limit is copy-on-write. Bump its refcount. 577 */ 578 lim_fork(p1, p2); 579 580 pstats_fork(p1->p_stats, p2->p_stats); 581 582 PROC_UNLOCK(p1); 583 PROC_UNLOCK(p2); 584 585 /* Bump references to the text vnode (for procfs) */ 586 if (p2->p_textvp) 587 vref(p2->p_textvp); 588 589 /* 590 * Set up linkage for kernel based threading. 591 */ 592 if ((flags & RFTHREAD) != 0) { 593 mtx_lock(&ppeers_lock); 594 p2->p_peers = p1->p_peers; 595 p1->p_peers = p2; 596 p2->p_leader = p1->p_leader; 597 mtx_unlock(&ppeers_lock); 598 PROC_LOCK(p1->p_leader); 599 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 600 PROC_UNLOCK(p1->p_leader); 601 /* 602 * The task leader is exiting, so process p1 is 603 * going to be killed shortly. Since p1 obviously 604 * isn't dead yet, we know that the leader is either 605 * sending SIGKILL's to all the processes in this 606 * task or is sleeping waiting for all the peers to 607 * exit. We let p1 complete the fork, but we need 608 * to go ahead and kill the new process p2 since 609 * the task leader may not get a chance to send 610 * SIGKILL to it. We leave it on the list so that 611 * the task leader will wait for this new process 612 * to commit suicide. 613 */ 614 PROC_LOCK(p2); 615 psignal(p2, SIGKILL); 616 PROC_UNLOCK(p2); 617 } else 618 PROC_UNLOCK(p1->p_leader); 619 } else { 620 p2->p_peers = NULL; 621 p2->p_leader = p2; 622 } 623 624 sx_xlock(&proctree_lock); 625 PGRP_LOCK(p1->p_pgrp); 626 PROC_LOCK(p2); 627 PROC_LOCK(p1); 628 629 /* 630 * Preserve some more flags in subprocess. P_PROFIL has already 631 * been preserved. 632 */ 633 p2->p_flag |= p1->p_flag & P_SUGID; 634 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 635 SESS_LOCK(p1->p_session); 636 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 637 p2->p_flag |= P_CONTROLT; 638 SESS_UNLOCK(p1->p_session); 639 if (flags & RFPPWAIT) 640 p2->p_flag |= P_PPWAIT; 641 642 p2->p_pgrp = p1->p_pgrp; 643 LIST_INSERT_AFTER(p1, p2, p_pglist); 644 PGRP_UNLOCK(p1->p_pgrp); 645 LIST_INIT(&p2->p_children); 646 647 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 648 649 #ifdef KTRACE 650 /* 651 * Copy traceflag and tracefile if enabled. 652 */ 653 mtx_lock(&ktrace_mtx); 654 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 655 if (p1->p_traceflag & KTRFAC_INHERIT) { 656 p2->p_traceflag = p1->p_traceflag; 657 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 658 VREF(p2->p_tracevp); 659 KASSERT(p1->p_tracecred != NULL, 660 ("ktrace vnode with no cred")); 661 p2->p_tracecred = crhold(p1->p_tracecred); 662 } 663 } 664 mtx_unlock(&ktrace_mtx); 665 #endif 666 667 /* 668 * If PF_FORK is set, the child process inherits the 669 * procfs ioctl flags from its parent. 670 */ 671 if (p1->p_pfsflags & PF_FORK) { 672 p2->p_stops = p1->p_stops; 673 p2->p_pfsflags = p1->p_pfsflags; 674 } 675 676 #ifdef KDTRACE_HOOKS 677 /* 678 * Tell the DTrace fasttrap provider about the new process 679 * if it has registered an interest. 680 */ 681 if (dtrace_fasttrap_fork) 682 dtrace_fasttrap_fork(p1, p2); 683 #endif 684 685 /* 686 * This begins the section where we must prevent the parent 687 * from being swapped. 688 */ 689 _PHOLD(p1); 690 PROC_UNLOCK(p1); 691 692 /* 693 * Attach the new process to its parent. 694 * 695 * If RFNOWAIT is set, the newly created process becomes a child 696 * of init. This effectively disassociates the child from the 697 * parent. 698 */ 699 if (flags & RFNOWAIT) 700 pptr = initproc; 701 else 702 pptr = p1; 703 p2->p_pptr = pptr; 704 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 705 sx_xunlock(&proctree_lock); 706 707 /* Inform accounting that we have forked. */ 708 p2->p_acflag = AFORK; 709 PROC_UNLOCK(p2); 710 711 /* 712 * Finish creating the child process. It will return via a different 713 * execution path later. (ie: directly into user mode) 714 */ 715 vm_forkproc(td, p2, td2, vm2, flags); 716 717 if (flags == (RFFDG | RFPROC)) { 718 PCPU_INC(cnt.v_forks); 719 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 720 p2->p_vmspace->vm_ssize); 721 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 722 PCPU_INC(cnt.v_vforks); 723 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 724 p2->p_vmspace->vm_ssize); 725 } else if (p1 == &proc0) { 726 PCPU_INC(cnt.v_kthreads); 727 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 728 p2->p_vmspace->vm_ssize); 729 } else { 730 PCPU_INC(cnt.v_rforks); 731 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 732 p2->p_vmspace->vm_ssize); 733 } 734 735 /* 736 * Both processes are set up, now check if any loadable modules want 737 * to adjust anything. 738 * What if they have an error? XXX 739 */ 740 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 741 742 /* 743 * Set the child start time and mark the process as being complete. 744 */ 745 microuptime(&p2->p_stats->p_start); 746 PROC_SLOCK(p2); 747 p2->p_state = PRS_NORMAL; 748 PROC_SUNLOCK(p2); 749 750 /* 751 * If RFSTOPPED not requested, make child runnable and add to 752 * run queue. 753 */ 754 if ((flags & RFSTOPPED) == 0) { 755 thread_lock(td2); 756 TD_SET_CAN_RUN(td2); 757 sched_add(td2, SRQ_BORING); 758 thread_unlock(td2); 759 } 760 761 /* 762 * Now can be swapped. 763 */ 764 PROC_LOCK(p1); 765 _PRELE(p1); 766 PROC_UNLOCK(p1); 767 768 /* 769 * Tell any interested parties about the new process. 770 */ 771 knote_fork(&p1->p_klist, p2->p_pid); 772 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 773 774 /* 775 * Preserve synchronization semantics of vfork. If waiting for 776 * child to exec or exit, set P_PPWAIT on child, and sleep on our 777 * proc (in case of exit). 778 */ 779 PROC_LOCK(p2); 780 while (p2->p_flag & P_PPWAIT) 781 cv_wait(&p2->p_pwait, &p2->p_mtx); 782 PROC_UNLOCK(p2); 783 784 /* 785 * Return child proc pointer to parent. 786 */ 787 *procp = p2; 788 return (0); 789 fail: 790 sx_sunlock(&proctree_lock); 791 if (ppsratecheck(&lastfail, &curfail, 1)) 792 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 793 td->td_ucred->cr_ruid); 794 sx_xunlock(&allproc_lock); 795 #ifdef MAC 796 mac_proc_destroy(newproc); 797 #endif 798 fail1: 799 if (vm2 != NULL) 800 vmspace_free(vm2); 801 uma_zfree(proc_zone, newproc); 802 pause("fork", hz / 2); 803 return (error); 804 } 805 806 /* 807 * Handle the return of a child process from fork1(). This function 808 * is called from the MD fork_trampoline() entry point. 809 */ 810 void 811 fork_exit(callout, arg, frame) 812 void (*callout)(void *, struct trapframe *); 813 void *arg; 814 struct trapframe *frame; 815 { 816 struct proc *p; 817 struct thread *td; 818 struct thread *dtd; 819 820 td = curthread; 821 p = td->td_proc; 822 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 823 824 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 825 td, td->td_sched, p->p_pid, td->td_name); 826 827 sched_fork_exit(td); 828 /* 829 * Processes normally resume in mi_switch() after being 830 * cpu_switch()'ed to, but when children start up they arrive here 831 * instead, so we must do much the same things as mi_switch() would. 832 */ 833 if ((dtd = PCPU_GET(deadthread))) { 834 PCPU_SET(deadthread, NULL); 835 thread_stash(dtd); 836 } 837 thread_unlock(td); 838 839 /* 840 * cpu_set_fork_handler intercepts this function call to 841 * have this call a non-return function to stay in kernel mode. 842 * initproc has its own fork handler, but it does return. 843 */ 844 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 845 callout(arg, frame); 846 847 /* 848 * Check if a kernel thread misbehaved and returned from its main 849 * function. 850 */ 851 if (p->p_flag & P_KTHREAD) { 852 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 853 td->td_name, p->p_pid); 854 kproc_exit(0); 855 } 856 mtx_assert(&Giant, MA_NOTOWNED); 857 858 EVENTHANDLER_INVOKE(schedtail, p); 859 } 860 861 /* 862 * Simplified back end of syscall(), used when returning from fork() 863 * directly into user mode. Giant is not held on entry, and must not 864 * be held on return. This function is passed in to fork_exit() as the 865 * first parameter and is called when returning to a new userland process. 866 */ 867 void 868 fork_return(td, frame) 869 struct thread *td; 870 struct trapframe *frame; 871 { 872 873 userret(td, frame); 874 #ifdef KTRACE 875 if (KTRPOINT(td, KTR_SYSRET)) 876 ktrsysret(SYS_fork, 0, 0); 877 #endif 878 mtx_assert(&Giant, MA_NOTOWNED); 879 }
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