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_mac.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/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/jail.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; 122 struct proc *p2; 123 124 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 125 if (error == 0) { 126 td->td_retval[0] = p2->p_pid; 127 td->td_retval[1] = 0; 128 } 129 return (error); 130 } 131 132 int 133 rfork(td, uap) 134 struct thread *td; 135 struct rfork_args *uap; 136 { 137 struct proc *p2; 138 int error; 139 140 /* Don't allow kernel-only flags. */ 141 if ((uap->flags & RFKERNELONLY) != 0) 142 return (EINVAL); 143 144 AUDIT_ARG(fflags, uap->flags); 145 error = fork1(td, uap->flags, 0, &p2); 146 if (error == 0) { 147 td->td_retval[0] = p2 ? p2->p_pid : 0; 148 td->td_retval[1] = 0; 149 } 150 return (error); 151 } 152 153 int nprocs = 1; /* process 0 */ 154 int lastpid = 0; 155 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 156 "Last used PID"); 157 158 /* 159 * Random component to lastpid generation. We mix in a random factor to make 160 * it a little harder to predict. We sanity check the modulus value to avoid 161 * doing it in critical paths. Don't let it be too small or we pointlessly 162 * waste randomness entropy, and don't let it be impossibly large. Using a 163 * modulus that is too big causes a LOT more process table scans and slows 164 * down fork processing as the pidchecked caching is defeated. 165 */ 166 static int randompid = 0; 167 168 static int 169 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 170 { 171 int error, pid; 172 173 error = sysctl_wire_old_buffer(req, sizeof(int)); 174 if (error != 0) 175 return(error); 176 sx_xlock(&allproc_lock); 177 pid = randompid; 178 error = sysctl_handle_int(oidp, &pid, 0, req); 179 if (error == 0 && req->newptr != NULL) { 180 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 181 pid = PID_MAX - 100; 182 else if (pid < 2) /* NOP */ 183 pid = 0; 184 else if (pid < 100) /* Make it reasonable */ 185 pid = 100; 186 randompid = pid; 187 } 188 sx_xunlock(&allproc_lock); 189 return (error); 190 } 191 192 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 193 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 194 195 int 196 fork1(td, flags, pages, procp) 197 struct thread *td; 198 int flags; 199 int pages; 200 struct proc **procp; 201 { 202 struct proc *p1, *p2, *pptr; 203 struct proc *newproc; 204 int ok, trypid; 205 static int curfail, pidchecked = 0; 206 static struct timeval lastfail; 207 struct filedesc *fd; 208 struct filedesc_to_leader *fdtol; 209 struct thread *td2; 210 struct sigacts *newsigacts; 211 struct vmspace *vm2; 212 int error; 213 214 /* Can't copy and clear. */ 215 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 216 return (EINVAL); 217 218 p1 = td->td_proc; 219 220 /* 221 * Here we don't create a new process, but we divorce 222 * certain parts of a process from itself. 223 */ 224 if ((flags & RFPROC) == 0) { 225 if ((p1->p_flag & P_HADTHREADS) && 226 (flags & (RFCFDG | RFFDG))) { 227 PROC_LOCK(p1); 228 if (thread_single(SINGLE_BOUNDARY)) { 229 PROC_UNLOCK(p1); 230 return (ERESTART); 231 } 232 PROC_UNLOCK(p1); 233 } 234 235 error = vm_forkproc(td, NULL, NULL, NULL, flags); 236 if (error) 237 goto norfproc_fail; 238 239 /* 240 * Close all file descriptors. 241 */ 242 if (flags & RFCFDG) { 243 struct filedesc *fdtmp; 244 fdtmp = fdinit(td->td_proc->p_fd); 245 fdfree(td); 246 p1->p_fd = fdtmp; 247 } 248 249 /* 250 * Unshare file descriptors (from parent). 251 */ 252 if (flags & RFFDG) 253 fdunshare(p1, td); 254 255 norfproc_fail: 256 if ((p1->p_flag & P_HADTHREADS) && 257 (flags & (RFCFDG | RFFDG))) { 258 PROC_LOCK(p1); 259 thread_single_end(); 260 PROC_UNLOCK(p1); 261 } 262 *procp = NULL; 263 return (error); 264 } 265 266 vm2 = NULL; 267 /* Allocate new proc. */ 268 newproc = uma_zalloc(proc_zone, M_WAITOK); 269 if (TAILQ_EMPTY(&newproc->p_threads)) { 270 td2 = thread_alloc(); 271 if (td2 == NULL) { 272 error = ENOMEM; 273 goto fail1; 274 } 275 proc_linkup(newproc, td2); 276 sched_newproc(newproc, td2); 277 } else 278 td2 = FIRST_THREAD_IN_PROC(newproc); 279 280 /* Allocate and switch to an alternate kstack if specified. */ 281 if (pages != 0) { 282 if (!vm_thread_new_altkstack(td2, pages)) { 283 error = ENOMEM; 284 goto fail1; 285 } 286 } 287 if ((flags & RFMEM) == 0) { 288 vm2 = vmspace_fork(p1->p_vmspace); 289 if (vm2 == NULL) { 290 error = ENOMEM; 291 goto fail1; 292 } 293 } 294 #ifdef MAC 295 mac_init_proc(newproc); 296 #endif 297 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 298 STAILQ_INIT(&newproc->p_ktr); 299 300 /* We have to lock the process tree while we look for a pid. */ 301 sx_slock(&proctree_lock); 302 303 /* 304 * Although process entries are dynamically created, we still keep 305 * a global limit on the maximum number we will create. Don't allow 306 * a nonprivileged user to use the last ten processes; don't let root 307 * exceed the limit. The variable nprocs is the current number of 308 * processes, maxproc is the limit. 309 */ 310 sx_xlock(&allproc_lock); 311 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 312 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 313 error = EAGAIN; 314 goto fail; 315 } 316 317 /* 318 * Increment the count of procs running with this uid. Don't allow 319 * a nonprivileged user to exceed their current limit. 320 * 321 * XXXRW: Can we avoid privilege here if it's not needed? 322 */ 323 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 324 if (error == 0) 325 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 326 else { 327 PROC_LOCK(p1); 328 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 329 lim_cur(p1, RLIMIT_NPROC)); 330 PROC_UNLOCK(p1); 331 } 332 if (!ok) { 333 error = EAGAIN; 334 goto fail; 335 } 336 337 /* 338 * Increment the nprocs resource before blocking can occur. There 339 * are hard-limits as to the number of processes that can run. 340 */ 341 nprocs++; 342 343 /* 344 * Find an unused process ID. We remember a range of unused IDs 345 * ready to use (from lastpid+1 through pidchecked-1). 346 * 347 * If RFHIGHPID is set (used during system boot), do not allocate 348 * low-numbered pids. 349 */ 350 trypid = lastpid + 1; 351 if (flags & RFHIGHPID) { 352 if (trypid < 10) 353 trypid = 10; 354 } else { 355 if (randompid) 356 trypid += arc4random() % randompid; 357 } 358 retry: 359 /* 360 * If the process ID prototype has wrapped around, 361 * restart somewhat above 0, as the low-numbered procs 362 * tend to include daemons that don't exit. 363 */ 364 if (trypid >= PID_MAX) { 365 trypid = trypid % PID_MAX; 366 if (trypid < 100) 367 trypid += 100; 368 pidchecked = 0; 369 } 370 if (trypid >= pidchecked) { 371 int doingzomb = 0; 372 373 pidchecked = PID_MAX; 374 /* 375 * Scan the active and zombie procs to check whether this pid 376 * is in use. Remember the lowest pid that's greater 377 * than trypid, so we can avoid checking for a while. 378 */ 379 p2 = LIST_FIRST(&allproc); 380 again: 381 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 382 while (p2->p_pid == trypid || 383 (p2->p_pgrp != NULL && 384 (p2->p_pgrp->pg_id == trypid || 385 (p2->p_session != NULL && 386 p2->p_session->s_sid == trypid)))) { 387 trypid++; 388 if (trypid >= pidchecked) 389 goto retry; 390 } 391 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 392 pidchecked = p2->p_pid; 393 if (p2->p_pgrp != NULL) { 394 if (p2->p_pgrp->pg_id > trypid && 395 pidchecked > p2->p_pgrp->pg_id) 396 pidchecked = p2->p_pgrp->pg_id; 397 if (p2->p_session != NULL && 398 p2->p_session->s_sid > trypid && 399 pidchecked > p2->p_session->s_sid) 400 pidchecked = p2->p_session->s_sid; 401 } 402 } 403 if (!doingzomb) { 404 doingzomb = 1; 405 p2 = LIST_FIRST(&zombproc); 406 goto again; 407 } 408 } 409 sx_sunlock(&proctree_lock); 410 411 /* 412 * RFHIGHPID does not mess with the lastpid counter during boot. 413 */ 414 if (flags & RFHIGHPID) 415 pidchecked = 0; 416 else 417 lastpid = trypid; 418 419 p2 = newproc; 420 p2->p_state = PRS_NEW; /* protect against others */ 421 p2->p_pid = trypid; 422 AUDIT_ARG(pid, p2->p_pid); 423 LIST_INSERT_HEAD(&allproc, p2, p_list); 424 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 425 426 PROC_LOCK(p2); 427 PROC_LOCK(p1); 428 429 sx_xunlock(&allproc_lock); 430 431 bcopy(&p1->p_startcopy, &p2->p_startcopy, 432 __rangeof(struct proc, p_startcopy, p_endcopy)); 433 pargs_hold(p2->p_args); 434 PROC_UNLOCK(p1); 435 436 bzero(&p2->p_startzero, 437 __rangeof(struct proc, p_startzero, p_endzero)); 438 439 p2->p_ucred = crhold(td->td_ucred); 440 441 /* In case we are jailed tell the prison that we exist. */ 442 if (jailed(p2->p_ucred)) 443 prison_proc_hold(p2->p_ucred->cr_prison); 444 445 PROC_UNLOCK(p2); 446 447 /* 448 * Malloc things while we don't hold any locks. 449 */ 450 if (flags & RFSIGSHARE) 451 newsigacts = NULL; 452 else 453 newsigacts = sigacts_alloc(); 454 455 /* 456 * Copy filedesc. 457 */ 458 if (flags & RFCFDG) { 459 fd = fdinit(p1->p_fd); 460 fdtol = NULL; 461 } else if (flags & RFFDG) { 462 fd = fdcopy(p1->p_fd); 463 fdtol = NULL; 464 } else { 465 fd = fdshare(p1->p_fd); 466 if (p1->p_fdtol == NULL) 467 p1->p_fdtol = 468 filedesc_to_leader_alloc(NULL, 469 NULL, 470 p1->p_leader); 471 if ((flags & RFTHREAD) != 0) { 472 /* 473 * Shared file descriptor table and 474 * shared process leaders. 475 */ 476 fdtol = p1->p_fdtol; 477 FILEDESC_XLOCK(p1->p_fd); 478 fdtol->fdl_refcount++; 479 FILEDESC_XUNLOCK(p1->p_fd); 480 } else { 481 /* 482 * Shared file descriptor table, and 483 * different process leaders 484 */ 485 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 486 p1->p_fd, 487 p2); 488 } 489 } 490 /* 491 * Make a proc table entry for the new process. 492 * Start by zeroing the section of proc that is zero-initialized, 493 * then copy the section that is copied directly from the parent. 494 */ 495 496 PROC_LOCK(p2); 497 PROC_LOCK(p1); 498 499 bzero(&td2->td_startzero, 500 __rangeof(struct thread, td_startzero, td_endzero)); 501 502 bcopy(&td->td_startcopy, &td2->td_startcopy, 503 __rangeof(struct thread, td_startcopy, td_endcopy)); 504 bzero(&td2->td_osd, sizeof(struct osd)); 505 506 td2->td_sigstk = td->td_sigstk; 507 td2->td_sigmask = td->td_sigmask; 508 td2->td_flags = TDF_INMEM; 509 510 /* 511 * Allow the scheduler to initialize the child. 512 */ 513 thread_lock(td); 514 sched_fork(td, td2); 515 thread_unlock(td); 516 517 /* 518 * Duplicate sub-structures as needed. 519 * Increase reference counts on shared objects. 520 */ 521 p2->p_flag = P_INMEM; 522 p2->p_swtick = ticks; 523 if (p1->p_flag & P_PROFIL) 524 startprofclock(p2); 525 td2->td_ucred = crhold(p2->p_ucred); 526 527 if (flags & RFSIGSHARE) { 528 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 529 } else { 530 sigacts_copy(newsigacts, p1->p_sigacts); 531 p2->p_sigacts = newsigacts; 532 } 533 if (flags & RFLINUXTHPN) 534 p2->p_sigparent = SIGUSR1; 535 else 536 p2->p_sigparent = SIGCHLD; 537 538 p2->p_textvp = p1->p_textvp; 539 p2->p_fd = fd; 540 p2->p_fdtol = fdtol; 541 542 /* 543 * p_limit is copy-on-write. Bump its refcount. 544 */ 545 lim_fork(p1, p2); 546 547 pstats_fork(p1->p_stats, p2->p_stats); 548 549 PROC_UNLOCK(p1); 550 PROC_UNLOCK(p2); 551 552 /* Bump references to the text vnode (for procfs) */ 553 if (p2->p_textvp) 554 vref(p2->p_textvp); 555 556 /* 557 * Set up linkage for kernel based threading. 558 */ 559 if ((flags & RFTHREAD) != 0) { 560 mtx_lock(&ppeers_lock); 561 p2->p_peers = p1->p_peers; 562 p1->p_peers = p2; 563 p2->p_leader = p1->p_leader; 564 mtx_unlock(&ppeers_lock); 565 PROC_LOCK(p1->p_leader); 566 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 567 PROC_UNLOCK(p1->p_leader); 568 /* 569 * The task leader is exiting, so process p1 is 570 * going to be killed shortly. Since p1 obviously 571 * isn't dead yet, we know that the leader is either 572 * sending SIGKILL's to all the processes in this 573 * task or is sleeping waiting for all the peers to 574 * exit. We let p1 complete the fork, but we need 575 * to go ahead and kill the new process p2 since 576 * the task leader may not get a chance to send 577 * SIGKILL to it. We leave it on the list so that 578 * the task leader will wait for this new process 579 * to commit suicide. 580 */ 581 PROC_LOCK(p2); 582 psignal(p2, SIGKILL); 583 PROC_UNLOCK(p2); 584 } else 585 PROC_UNLOCK(p1->p_leader); 586 } else { 587 p2->p_peers = NULL; 588 p2->p_leader = p2; 589 } 590 591 sx_xlock(&proctree_lock); 592 PGRP_LOCK(p1->p_pgrp); 593 PROC_LOCK(p2); 594 PROC_LOCK(p1); 595 596 /* 597 * Preserve some more flags in subprocess. P_PROFIL has already 598 * been preserved. 599 */ 600 p2->p_flag |= p1->p_flag & P_SUGID; 601 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 602 SESS_LOCK(p1->p_session); 603 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 604 p2->p_flag |= P_CONTROLT; 605 SESS_UNLOCK(p1->p_session); 606 if (flags & RFPPWAIT) 607 p2->p_flag |= P_PPWAIT; 608 609 p2->p_pgrp = p1->p_pgrp; 610 LIST_INSERT_AFTER(p1, p2, p_pglist); 611 PGRP_UNLOCK(p1->p_pgrp); 612 LIST_INIT(&p2->p_children); 613 614 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 615 616 #ifdef KTRACE 617 ktrprocfork(p1, p2); 618 #endif 619 620 /* 621 * If PF_FORK is set, the child process inherits the 622 * procfs ioctl flags from its parent. 623 */ 624 if (p1->p_pfsflags & PF_FORK) { 625 p2->p_stops = p1->p_stops; 626 p2->p_pfsflags = p1->p_pfsflags; 627 } 628 629 #ifdef KDTRACE_HOOKS 630 /* 631 * Tell the DTrace fasttrap provider about the new process 632 * if it has registered an interest. 633 */ 634 if (dtrace_fasttrap_fork) 635 dtrace_fasttrap_fork(p1, p2); 636 #endif 637 638 /* 639 * This begins the section where we must prevent the parent 640 * from being swapped. 641 */ 642 _PHOLD(p1); 643 PROC_UNLOCK(p1); 644 645 /* 646 * Attach the new process to its parent. 647 * 648 * If RFNOWAIT is set, the newly created process becomes a child 649 * of init. This effectively disassociates the child from the 650 * parent. 651 */ 652 if (flags & RFNOWAIT) 653 pptr = initproc; 654 else 655 pptr = p1; 656 p2->p_pptr = pptr; 657 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 658 sx_xunlock(&proctree_lock); 659 660 /* Inform accounting that we have forked. */ 661 p2->p_acflag = AFORK; 662 PROC_UNLOCK(p2); 663 664 /* 665 * Finish creating the child process. It will return via a different 666 * execution path later. (ie: directly into user mode) 667 */ 668 vm_forkproc(td, p2, td2, vm2, flags); 669 670 if (flags == (RFFDG | RFPROC)) { 671 PCPU_INC(cnt.v_forks); 672 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 673 p2->p_vmspace->vm_ssize); 674 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 675 PCPU_INC(cnt.v_vforks); 676 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 677 p2->p_vmspace->vm_ssize); 678 } else if (p1 == &proc0) { 679 PCPU_INC(cnt.v_kthreads); 680 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 681 p2->p_vmspace->vm_ssize); 682 } else { 683 PCPU_INC(cnt.v_rforks); 684 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 685 p2->p_vmspace->vm_ssize); 686 } 687 688 /* 689 * Both processes are set up, now check if any loadable modules want 690 * to adjust anything. 691 * What if they have an error? XXX 692 */ 693 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 694 695 /* 696 * Set the child start time and mark the process as being complete. 697 */ 698 microuptime(&p2->p_stats->p_start); 699 PROC_SLOCK(p2); 700 p2->p_state = PRS_NORMAL; 701 PROC_SUNLOCK(p2); 702 703 /* 704 * If RFSTOPPED not requested, make child runnable and add to 705 * run queue. 706 */ 707 if ((flags & RFSTOPPED) == 0) { 708 thread_lock(td2); 709 TD_SET_CAN_RUN(td2); 710 sched_add(td2, SRQ_BORING); 711 thread_unlock(td2); 712 } 713 714 /* 715 * Now can be swapped. 716 */ 717 PROC_LOCK(p1); 718 _PRELE(p1); 719 PROC_UNLOCK(p1); 720 721 /* 722 * Tell any interested parties about the new process. 723 */ 724 knote_fork(&p1->p_klist, p2->p_pid); 725 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 726 727 /* 728 * Preserve synchronization semantics of vfork. If waiting for 729 * child to exec or exit, set P_PPWAIT on child, and sleep on our 730 * proc (in case of exit). 731 */ 732 PROC_LOCK(p2); 733 while (p2->p_flag & P_PPWAIT) 734 cv_wait(&p2->p_pwait, &p2->p_mtx); 735 PROC_UNLOCK(p2); 736 737 /* 738 * Return child proc pointer to parent. 739 */ 740 *procp = p2; 741 return (0); 742 fail: 743 sx_sunlock(&proctree_lock); 744 if (ppsratecheck(&lastfail, &curfail, 1)) 745 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 746 td->td_ucred->cr_ruid); 747 sx_xunlock(&allproc_lock); 748 #ifdef MAC 749 mac_destroy_proc(newproc); 750 #endif 751 fail1: 752 if (vm2 != NULL) 753 vmspace_free(vm2); 754 uma_zfree(proc_zone, newproc); 755 pause("fork", hz / 2); 756 return (error); 757 } 758 759 /* 760 * Handle the return of a child process from fork1(). This function 761 * is called from the MD fork_trampoline() entry point. 762 */ 763 void 764 fork_exit(callout, arg, frame) 765 void (*callout)(void *, struct trapframe *); 766 void *arg; 767 struct trapframe *frame; 768 { 769 struct proc *p; 770 struct thread *td; 771 struct thread *dtd; 772 773 td = curthread; 774 p = td->td_proc; 775 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 776 777 CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)", 778 td, td->td_sched, p->p_pid, p->p_comm); 779 780 sched_fork_exit(td); 781 /* 782 * Processes normally resume in mi_switch() after being 783 * cpu_switch()'ed to, but when children start up they arrive here 784 * instead, so we must do much the same things as mi_switch() would. 785 */ 786 if ((dtd = PCPU_GET(deadthread))) { 787 PCPU_SET(deadthread, NULL); 788 thread_stash(dtd); 789 } 790 thread_unlock(td); 791 792 /* 793 * cpu_set_fork_handler intercepts this function call to 794 * have this call a non-return function to stay in kernel mode. 795 * initproc has its own fork handler, but it does return. 796 */ 797 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 798 callout(arg, frame); 799 800 /* 801 * Check if a kernel thread misbehaved and returned from its main 802 * function. 803 */ 804 if (p->p_flag & P_KTHREAD) { 805 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 806 p->p_comm, p->p_pid); 807 kthread_exit(0); 808 } 809 mtx_assert(&Giant, MA_NOTOWNED); 810 811 EVENTHANDLER_INVOKE(schedtail, p); 812 } 813 814 /* 815 * Simplified back end of syscall(), used when returning from fork() 816 * directly into user mode. Giant is not held on entry, and must not 817 * be held on return. This function is passed in to fork_exit() as the 818 * first parameter and is called when returning to a new userland process. 819 */ 820 void 821 fork_return(td, frame) 822 struct thread *td; 823 struct trapframe *frame; 824 { 825 826 userret(td, frame); 827 #ifdef KTRACE 828 if (KTRPOINT(td, KTR_SYSRET)) 829 ktrsysret(SYS_fork, 0, 0); 830 #endif 831 mtx_assert(&Giant, MA_NOTOWNED); 832 }
Cache object: c0ebce8db1f46958321bcaf1aa0bcbfb
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