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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 39 * $FreeBSD$ 40 */ 41 42 #include "opt_ktrace.h" 43 #include "opt_mac.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/sysproto.h> 48 #include <sys/filedesc.h> 49 #include <sys/kernel.h> 50 #include <sys/sysctl.h> 51 #include <sys/lock.h> 52 #include <sys/malloc.h> 53 #include <sys/mutex.h> 54 #include <sys/proc.h> 55 #include <sys/pioctl.h> 56 #include <sys/resourcevar.h> 57 #include <sys/sched.h> 58 #include <sys/syscall.h> 59 #include <sys/vnode.h> 60 #include <sys/acct.h> 61 #include <sys/mac.h> 62 #include <sys/ktr.h> 63 #include <sys/ktrace.h> 64 #include <sys/kthread.h> 65 #include <sys/unistd.h> 66 #include <sys/jail.h> 67 #include <sys/sx.h> 68 69 #include <vm/vm.h> 70 #include <vm/pmap.h> 71 #include <vm/vm_map.h> 72 #include <vm/vm_extern.h> 73 #include <vm/uma.h> 74 75 #include <sys/vmmeter.h> 76 #include <sys/user.h> 77 #include <machine/critical.h> 78 79 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); 80 81 /* 82 * These are the stuctures used to create a callout list for things to do 83 * when forking a process 84 */ 85 struct forklist { 86 forklist_fn function; 87 TAILQ_ENTRY(forklist) next; 88 }; 89 90 static struct sx fork_list_lock; 91 92 TAILQ_HEAD(forklist_head, forklist); 93 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); 94 95 #ifndef _SYS_SYSPROTO_H_ 96 struct fork_args { 97 int dummy; 98 }; 99 #endif 100 101 int forksleep; /* Place for fork1() to sleep on. */ 102 103 static void 104 init_fork_list(void *data __unused) 105 { 106 107 sx_init(&fork_list_lock, "fork list"); 108 } 109 SYSINIT(fork_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_fork_list, NULL); 110 111 /* 112 * MPSAFE 113 */ 114 /* ARGSUSED */ 115 int 116 fork(td, uap) 117 struct thread *td; 118 struct fork_args *uap; 119 { 120 int error; 121 struct proc *p2; 122 123 mtx_lock(&Giant); 124 error = fork1(td, RFFDG | RFPROC, 0, &p2); 125 if (error == 0) { 126 td->td_retval[0] = p2->p_pid; 127 td->td_retval[1] = 0; 128 } 129 mtx_unlock(&Giant); 130 return error; 131 } 132 133 /* 134 * MPSAFE 135 */ 136 /* ARGSUSED */ 137 int 138 vfork(td, uap) 139 struct thread *td; 140 struct vfork_args *uap; 141 { 142 int error; 143 struct proc *p2; 144 145 mtx_lock(&Giant); 146 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 147 if (error == 0) { 148 td->td_retval[0] = p2->p_pid; 149 td->td_retval[1] = 0; 150 } 151 mtx_unlock(&Giant); 152 return error; 153 } 154 155 /* 156 * MPSAFE 157 */ 158 int 159 rfork(td, uap) 160 struct thread *td; 161 struct rfork_args *uap; 162 { 163 int error; 164 struct proc *p2; 165 166 /* Don't allow kernel only flags. */ 167 if ((uap->flags & RFKERNELONLY) != 0) 168 return (EINVAL); 169 mtx_lock(&Giant); 170 error = fork1(td, uap->flags, 0, &p2); 171 if (error == 0) { 172 td->td_retval[0] = p2 ? p2->p_pid : 0; 173 td->td_retval[1] = 0; 174 } 175 mtx_unlock(&Giant); 176 return error; 177 } 178 179 180 int nprocs = 1; /* process 0 */ 181 int lastpid = 0; 182 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 183 "Last used PID"); 184 185 /* 186 * Random component to lastpid generation. We mix in a random factor to make 187 * it a little harder to predict. We sanity check the modulus value to avoid 188 * doing it in critical paths. Don't let it be too small or we pointlessly 189 * waste randomness entropy, and don't let it be impossibly large. Using a 190 * modulus that is too big causes a LOT more process table scans and slows 191 * down fork processing as the pidchecked caching is defeated. 192 */ 193 static int randompid = 0; 194 195 static int 196 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 197 { 198 int error, pid; 199 200 sysctl_wire_old_buffer(req, sizeof(int)); 201 sx_xlock(&allproc_lock); 202 pid = randompid; 203 error = sysctl_handle_int(oidp, &pid, 0, req); 204 if (error == 0 && req->newptr != NULL) { 205 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 206 pid = PID_MAX - 100; 207 else if (pid < 2) /* NOP */ 208 pid = 0; 209 else if (pid < 100) /* Make it reasonable */ 210 pid = 100; 211 randompid = pid; 212 } 213 sx_xunlock(&allproc_lock); 214 return (error); 215 } 216 217 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 218 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 219 220 int 221 fork1(td, flags, pages, procp) 222 struct thread *td; /* parent proc */ 223 int flags; 224 int pages; 225 struct proc **procp; /* child proc */ 226 { 227 struct proc *p2, *pptr; 228 uid_t uid; 229 struct proc *newproc; 230 int trypid; 231 int ok; 232 static int pidchecked = 0; 233 struct forklist *ep; 234 struct filedesc *fd; 235 struct proc *p1 = td->td_proc; 236 struct thread *td2; 237 struct kse *ke2; 238 struct ksegrp *kg2; 239 struct sigacts *newsigacts; 240 struct procsig *newprocsig; 241 int error; 242 243 GIANT_REQUIRED; 244 245 /* Can't copy and clear */ 246 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 247 return (EINVAL); 248 249 /* 250 * Here we don't create a new process, but we divorce 251 * certain parts of a process from itself. 252 */ 253 if ((flags & RFPROC) == 0) { 254 vm_forkproc(td, NULL, NULL, flags); 255 256 /* 257 * Close all file descriptors. 258 */ 259 if (flags & RFCFDG) { 260 struct filedesc *fdtmp; 261 fdtmp = fdinit(td); /* XXXKSE */ 262 fdfree(td); /* XXXKSE */ 263 p1->p_fd = fdtmp; 264 } 265 266 /* 267 * Unshare file descriptors (from parent.) 268 */ 269 if (flags & RFFDG) { 270 FILEDESC_LOCK(p1->p_fd); 271 if (p1->p_fd->fd_refcnt > 1) { 272 struct filedesc *newfd; 273 274 newfd = fdcopy(td); 275 FILEDESC_UNLOCK(p1->p_fd); 276 fdfree(td); 277 p1->p_fd = newfd; 278 } else 279 FILEDESC_UNLOCK(p1->p_fd); 280 } 281 *procp = NULL; 282 return (0); 283 } 284 285 if (p1->p_flag & P_KSES) { 286 /* 287 * Idle the other threads for a second. 288 * Since the user space is copied, it must remain stable. 289 * In addition, all threads (from the user perspective) 290 * need to either be suspended or in the kernel, 291 * where they will try restart in the parent and will 292 * be aborted in the child. 293 */ 294 PROC_LOCK(p1); 295 if (thread_single(SINGLE_NO_EXIT)) { 296 /* Abort.. someone else is single threading before us */ 297 PROC_UNLOCK(p1); 298 return (ERESTART); 299 } 300 PROC_UNLOCK(p1); 301 /* 302 * All other activity in this process 303 * is now suspended at the user boundary, 304 * (or other safe places if we think of any). 305 */ 306 } 307 308 /* Allocate new proc. */ 309 newproc = uma_zalloc(proc_zone, M_WAITOK); 310 #ifdef MAC 311 mac_init_proc(newproc); 312 #endif 313 314 /* 315 * Although process entries are dynamically created, we still keep 316 * a global limit on the maximum number we will create. Don't allow 317 * a nonprivileged user to use the last ten processes; don't let root 318 * exceed the limit. The variable nprocs is the current number of 319 * processes, maxproc is the limit. 320 */ 321 sx_xlock(&allproc_lock); 322 uid = td->td_ucred->cr_ruid; 323 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 324 error = EAGAIN; 325 goto fail; 326 } 327 328 /* 329 * Increment the count of procs running with this uid. Don't allow 330 * a nonprivileged user to exceed their current limit. 331 */ 332 PROC_LOCK(p1); 333 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 334 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 335 PROC_UNLOCK(p1); 336 if (!ok) { 337 error = EAGAIN; 338 goto fail; 339 } 340 341 /* 342 * Increment the nprocs resource before blocking can occur. There 343 * are hard-limits as to the number of processes that can run. 344 */ 345 nprocs++; 346 347 /* 348 * Find an unused process ID. We remember a range of unused IDs 349 * ready to use (from lastpid+1 through pidchecked-1). 350 * 351 * If RFHIGHPID is set (used during system boot), do not allocate 352 * low-numbered pids. 353 */ 354 trypid = lastpid + 1; 355 if (flags & RFHIGHPID) { 356 if (trypid < 10) { 357 trypid = 10; 358 } 359 } else { 360 if (randompid) 361 trypid += arc4random() % randompid; 362 } 363 retry: 364 /* 365 * If the process ID prototype has wrapped around, 366 * restart somewhat above 0, as the low-numbered procs 367 * tend to include daemons that don't exit. 368 */ 369 if (trypid >= PID_MAX) { 370 trypid = trypid % PID_MAX; 371 if (trypid < 100) 372 trypid += 100; 373 pidchecked = 0; 374 } 375 if (trypid >= pidchecked) { 376 int doingzomb = 0; 377 378 pidchecked = PID_MAX; 379 /* 380 * Scan the active and zombie procs to check whether this pid 381 * is in use. Remember the lowest pid that's greater 382 * than trypid, so we can avoid checking for a while. 383 */ 384 p2 = LIST_FIRST(&allproc); 385 again: 386 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 387 PROC_LOCK(p2); 388 while (p2->p_pid == trypid || 389 p2->p_pgrp->pg_id == trypid || 390 p2->p_session->s_sid == trypid) { 391 trypid++; 392 if (trypid >= pidchecked) { 393 PROC_UNLOCK(p2); 394 goto retry; 395 } 396 } 397 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 398 pidchecked = p2->p_pid; 399 if (p2->p_pgrp->pg_id > trypid && 400 pidchecked > p2->p_pgrp->pg_id) 401 pidchecked = p2->p_pgrp->pg_id; 402 if (p2->p_session->s_sid > trypid && 403 pidchecked > p2->p_session->s_sid) 404 pidchecked = p2->p_session->s_sid; 405 PROC_UNLOCK(p2); 406 } 407 if (!doingzomb) { 408 doingzomb = 1; 409 p2 = LIST_FIRST(&zombproc); 410 goto again; 411 } 412 } 413 414 /* 415 * RFHIGHPID does not mess with the lastpid counter during boot. 416 */ 417 if (flags & RFHIGHPID) 418 pidchecked = 0; 419 else 420 lastpid = trypid; 421 422 p2 = newproc; 423 p2->p_state = PRS_NEW; /* protect against others */ 424 p2->p_pid = trypid; 425 LIST_INSERT_HEAD(&allproc, p2, p_list); 426 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 427 sx_xunlock(&allproc_lock); 428 429 /* 430 * Malloc things while we don't hold any locks. 431 */ 432 if (flags & RFSIGSHARE) { 433 MALLOC(newsigacts, struct sigacts *, 434 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 435 newprocsig = NULL; 436 } else { 437 newsigacts = NULL; 438 MALLOC(newprocsig, struct procsig *, sizeof(struct procsig), 439 M_SUBPROC, M_WAITOK); 440 } 441 442 /* 443 * Copy filedesc. 444 * XXX: This is busted. fd*() need to not take proc 445 * arguments or something. 446 */ 447 if (flags & RFCFDG) 448 fd = fdinit(td); 449 else if (flags & RFFDG) { 450 FILEDESC_LOCK(p1->p_fd); 451 fd = fdcopy(td); 452 FILEDESC_UNLOCK(p1->p_fd); 453 } else 454 fd = fdshare(p1); 455 456 /* 457 * Make a proc table entry for the new process. 458 * Start by zeroing the section of proc that is zero-initialized, 459 * then copy the section that is copied directly from the parent. 460 */ 461 td2 = FIRST_THREAD_IN_PROC(p2); 462 kg2 = FIRST_KSEGRP_IN_PROC(p2); 463 ke2 = FIRST_KSE_IN_KSEGRP(kg2); 464 465 /* Allocate and switch to an alternate kstack if specified */ 466 if (pages != 0) 467 pmap_new_altkstack(td2, pages); 468 469 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 470 471 bzero(&p2->p_startzero, 472 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 473 bzero(&ke2->ke_startzero, 474 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 475 bzero(&td2->td_startzero, 476 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 477 bzero(&kg2->kg_startzero, 478 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 479 480 mtx_init(&p2->p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 481 PROC_LOCK(p2); 482 PROC_LOCK(p1); 483 484 bcopy(&p1->p_startcopy, &p2->p_startcopy, 485 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 486 bcopy(&td->td_startcopy, &td2->td_startcopy, 487 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 488 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 489 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 490 #undef RANGEOF 491 492 /* Set up the thread as an active thread (as if runnable). */ 493 ke2->ke_state = KES_THREAD; 494 ke2->ke_thread = td2; 495 td2->td_kse = ke2; 496 td2->td_flags &= ~TDF_UNBOUND; /* For the rest of this syscall. */ 497 498 /* 499 * Duplicate sub-structures as needed. 500 * Increase reference counts on shared objects. 501 * The p_stats and p_sigacts substructs are set in vm_forkproc. 502 */ 503 p2->p_flag = 0; 504 mtx_lock_spin(&sched_lock); 505 p2->p_sflag = PS_INMEM; 506 if (p1->p_sflag & PS_PROFIL) 507 startprofclock(p2); 508 /* 509 * Allow the scheduler to adjust the priority of the child and 510 * parent while we hold the sched_lock. 511 */ 512 sched_fork(td->td_ksegrp, kg2); 513 514 mtx_unlock_spin(&sched_lock); 515 p2->p_ucred = crhold(td->td_ucred); 516 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 517 518 pargs_hold(p2->p_args); 519 520 if (flags & RFSIGSHARE) { 521 p2->p_procsig = p1->p_procsig; 522 p2->p_procsig->ps_refcnt++; 523 if (p1->p_sigacts == &p1->p_uarea->u_sigacts) { 524 /* 525 * Set p_sigacts to the new shared structure. 526 * Note that this is updating p1->p_sigacts at the 527 * same time, since p_sigacts is just a pointer to 528 * the shared p_procsig->ps_sigacts. 529 */ 530 p2->p_sigacts = newsigacts; 531 newsigacts = NULL; 532 *p2->p_sigacts = p1->p_uarea->u_sigacts; 533 } 534 } else { 535 p2->p_procsig = newprocsig; 536 newprocsig = NULL; 537 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 538 p2->p_procsig->ps_refcnt = 1; 539 p2->p_sigacts = NULL; /* finished in vm_forkproc() */ 540 } 541 if (flags & RFLINUXTHPN) 542 p2->p_sigparent = SIGUSR1; 543 else 544 p2->p_sigparent = SIGCHLD; 545 546 /* Bump references to the text vnode (for procfs) */ 547 p2->p_textvp = p1->p_textvp; 548 if (p2->p_textvp) 549 VREF(p2->p_textvp); 550 p2->p_fd = fd; 551 PROC_UNLOCK(p1); 552 PROC_UNLOCK(p2); 553 554 /* 555 * If p_limit is still copy-on-write, bump refcnt, 556 * otherwise get a copy that won't be modified. 557 * (If PL_SHAREMOD is clear, the structure is shared 558 * copy-on-write.) 559 */ 560 if (p1->p_limit->p_lflags & PL_SHAREMOD) 561 p2->p_limit = limcopy(p1->p_limit); 562 else { 563 p2->p_limit = p1->p_limit; 564 p2->p_limit->p_refcnt++; 565 } 566 567 /* 568 * Setup linkage for kernel based threading 569 */ 570 if((flags & RFTHREAD) != 0) { 571 mtx_lock(&ppeers_lock); 572 p2->p_peers = p1->p_peers; 573 p1->p_peers = p2; 574 p2->p_leader = p1->p_leader; 575 mtx_unlock(&ppeers_lock); 576 PROC_LOCK(p1->p_leader); 577 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 578 PROC_UNLOCK(p1->p_leader); 579 /* 580 * The task leader is exiting, so process p1 is 581 * going to be killed shortly. Since p1 obviously 582 * isn't dead yet, we know that the leader is either 583 * sending SIGKILL's to all the processes in this 584 * task or is sleeping waiting for all the peers to 585 * exit. We let p1 complete the fork, but we need 586 * to go ahead and kill the new process p2 since 587 * the task leader may not get a chance to send 588 * SIGKILL to it. We leave it on the list so that 589 * the task leader will wait for this new process 590 * to commit suicide. 591 */ 592 PROC_LOCK(p2); 593 psignal(p2, SIGKILL); 594 PROC_UNLOCK(p2); 595 } else 596 PROC_UNLOCK(p1->p_leader); 597 } else { 598 p2->p_peers = NULL; 599 p2->p_leader = p2; 600 } 601 602 sx_xlock(&proctree_lock); 603 PGRP_LOCK(p1->p_pgrp); 604 PROC_LOCK(p2); 605 PROC_LOCK(p1); 606 607 /* 608 * Preserve some more flags in subprocess. PS_PROFIL has already 609 * been preserved. 610 */ 611 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 612 SESS_LOCK(p1->p_session); 613 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 614 p2->p_flag |= P_CONTROLT; 615 SESS_UNLOCK(p1->p_session); 616 if (flags & RFPPWAIT) 617 p2->p_flag |= P_PPWAIT; 618 619 LIST_INSERT_AFTER(p1, p2, p_pglist); 620 PGRP_UNLOCK(p1->p_pgrp); 621 LIST_INIT(&p2->p_children); 622 623 callout_init(&p2->p_itcallout, 0); 624 625 #ifdef KTRACE 626 /* 627 * Copy traceflag and tracefile if enabled. 628 */ 629 mtx_lock(&ktrace_mtx); 630 KASSERT(p2->p_tracep == NULL, ("new process has a ktrace vnode")); 631 if (p1->p_traceflag & KTRFAC_INHERIT) { 632 p2->p_traceflag = p1->p_traceflag; 633 if ((p2->p_tracep = p1->p_tracep) != NULL) 634 VREF(p2->p_tracep); 635 } 636 mtx_unlock(&ktrace_mtx); 637 #endif 638 639 /* 640 * If PF_FORK is set, the child process inherits the 641 * procfs ioctl flags from its parent. 642 */ 643 if (p1->p_pfsflags & PF_FORK) { 644 p2->p_stops = p1->p_stops; 645 p2->p_pfsflags = p1->p_pfsflags; 646 } 647 648 /* 649 * This begins the section where we must prevent the parent 650 * from being swapped. 651 */ 652 _PHOLD(p1); 653 PROC_UNLOCK(p1); 654 655 /* 656 * Attach the new process to its parent. 657 * 658 * If RFNOWAIT is set, the newly created process becomes a child 659 * of init. This effectively disassociates the child from the 660 * parent. 661 */ 662 if (flags & RFNOWAIT) 663 pptr = initproc; 664 else 665 pptr = p1; 666 p2->p_pptr = pptr; 667 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 668 PROC_UNLOCK(p2); 669 sx_xunlock(&proctree_lock); 670 671 KASSERT(newprocsig == NULL, ("unused newprocsig")); 672 if (newsigacts != NULL) 673 FREE(newsigacts, M_SUBPROC); 674 /* 675 * Finish creating the child process. It will return via a different 676 * execution path later. (ie: directly into user mode) 677 */ 678 vm_forkproc(td, p2, td2, flags); 679 680 if (flags == (RFFDG | RFPROC)) { 681 cnt.v_forks++; 682 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 683 p2->p_vmspace->vm_ssize; 684 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 685 cnt.v_vforks++; 686 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 687 p2->p_vmspace->vm_ssize; 688 } else if (p1 == &proc0) { 689 cnt.v_kthreads++; 690 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 691 p2->p_vmspace->vm_ssize; 692 } else { 693 cnt.v_rforks++; 694 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 695 p2->p_vmspace->vm_ssize; 696 } 697 698 /* 699 * Both processes are set up, now check if any loadable modules want 700 * to adjust anything. 701 * What if they have an error? XXX 702 */ 703 sx_slock(&fork_list_lock); 704 TAILQ_FOREACH(ep, &fork_list, next) { 705 (*ep->function)(p1, p2, flags); 706 } 707 sx_sunlock(&fork_list_lock); 708 709 /* 710 * If RFSTOPPED not requested, make child runnable and add to 711 * run queue. 712 */ 713 microtime(&(p2->p_stats->p_start)); 714 p2->p_acflag = AFORK; 715 if ((flags & RFSTOPPED) == 0) { 716 mtx_lock_spin(&sched_lock); 717 p2->p_state = PRS_NORMAL; 718 TD_SET_CAN_RUN(td2); 719 setrunqueue(td2); 720 mtx_unlock_spin(&sched_lock); 721 } 722 723 /* 724 * Now can be swapped. 725 */ 726 PROC_LOCK(p1); 727 _PRELE(p1); 728 729 /* 730 * tell any interested parties about the new process 731 */ 732 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 733 PROC_UNLOCK(p1); 734 735 /* 736 * Preserve synchronization semantics of vfork. If waiting for 737 * child to exec or exit, set P_PPWAIT on child, and sleep on our 738 * proc (in case of exit). 739 */ 740 PROC_LOCK(p2); 741 while (p2->p_flag & P_PPWAIT) 742 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 743 PROC_UNLOCK(p2); 744 745 /* 746 * If other threads are waiting, let them continue now 747 */ 748 if (p1->p_flag & P_KSES) { 749 PROC_LOCK(p1); 750 thread_single_end(); 751 PROC_UNLOCK(p1); 752 } 753 754 /* 755 * Return child proc pointer to parent. 756 */ 757 *procp = p2; 758 return (0); 759 fail: 760 sx_xunlock(&allproc_lock); 761 uma_zfree(proc_zone, newproc); 762 if (p1->p_flag & P_KSES) { 763 PROC_LOCK(p1); 764 thread_single_end(); 765 PROC_UNLOCK(p1); 766 } 767 tsleep(&forksleep, PUSER, "fork", hz / 2); 768 return (error); 769 } 770 771 /* 772 * The next two functionms are general routines to handle adding/deleting 773 * items on the fork callout list. 774 * 775 * at_fork(): 776 * Take the arguments given and put them onto the fork callout list, 777 * However first make sure that it's not already there. 778 * Returns 0 on success or a standard error number. 779 */ 780 781 int 782 at_fork(function) 783 forklist_fn function; 784 { 785 struct forklist *ep; 786 787 #ifdef INVARIANTS 788 /* let the programmer know if he's been stupid */ 789 if (rm_at_fork(function)) 790 printf("WARNING: fork callout entry (%p) already present\n", 791 function); 792 #endif 793 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); 794 if (ep == NULL) 795 return (ENOMEM); 796 ep->function = function; 797 sx_xlock(&fork_list_lock); 798 TAILQ_INSERT_TAIL(&fork_list, ep, next); 799 sx_xunlock(&fork_list_lock); 800 return (0); 801 } 802 803 /* 804 * Scan the exit callout list for the given item and remove it.. 805 * Returns the number of items removed (0 or 1) 806 */ 807 808 int 809 rm_at_fork(function) 810 forklist_fn function; 811 { 812 struct forklist *ep; 813 814 sx_xlock(&fork_list_lock); 815 TAILQ_FOREACH(ep, &fork_list, next) { 816 if (ep->function == function) { 817 TAILQ_REMOVE(&fork_list, ep, next); 818 sx_xunlock(&fork_list_lock); 819 free(ep, M_ATFORK); 820 return(1); 821 } 822 } 823 sx_xunlock(&fork_list_lock); 824 return (0); 825 } 826 827 /* 828 * Handle the return of a child process from fork1(). This function 829 * is called from the MD fork_trampoline() entry point. 830 */ 831 void 832 fork_exit(callout, arg, frame) 833 void (*callout)(void *, struct trapframe *); 834 void *arg; 835 struct trapframe *frame; 836 { 837 struct thread *td = curthread; 838 struct proc *p = td->td_proc; 839 840 td->td_kse->ke_oncpu = PCPU_GET(cpuid); 841 p->p_state = PRS_NORMAL; 842 /* 843 * Finish setting up thread glue. We need to initialize 844 * the thread into a td_critnest=1 state. Some platforms 845 * may have already partially or fully initialized td_critnest 846 * and/or td_md.md_savecrit (when applciable). 847 * 848 * see <arch>/<arch>/critical.c 849 */ 850 sched_lock.mtx_lock = (uintptr_t)td; 851 sched_lock.mtx_recurse = 0; 852 cpu_critical_fork_exit(); 853 CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid, 854 p->p_comm); 855 if (PCPU_GET(switchtime.sec) == 0) 856 binuptime(PCPU_PTR(switchtime)); 857 PCPU_SET(switchticks, ticks); 858 mtx_unlock_spin(&sched_lock); 859 860 /* 861 * cpu_set_fork_handler intercepts this function call to 862 * have this call a non-return function to stay in kernel mode. 863 * initproc has its own fork handler, but it does return. 864 */ 865 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 866 callout(arg, frame); 867 868 /* 869 * Check if a kernel thread misbehaved and returned from its main 870 * function. 871 */ 872 PROC_LOCK(p); 873 if (p->p_flag & P_KTHREAD) { 874 PROC_UNLOCK(p); 875 mtx_lock(&Giant); 876 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 877 p->p_comm, p->p_pid); 878 kthread_exit(0); 879 } 880 PROC_UNLOCK(p); 881 #ifdef DIAGNOSTIC 882 cred_free_thread(td); 883 #endif 884 mtx_assert(&Giant, MA_NOTOWNED); 885 } 886 887 /* 888 * Simplified back end of syscall(), used when returning from fork() 889 * directly into user mode. Giant is not held on entry, and must not 890 * be held on return. This function is passed in to fork_exit() as the 891 * first parameter and is called when returning to a new userland process. 892 */ 893 void 894 fork_return(td, frame) 895 struct thread *td; 896 struct trapframe *frame; 897 { 898 899 userret(td, frame, 0); 900 #ifdef KTRACE 901 if (KTRPOINT(td, KTR_SYSRET)) 902 ktrsysret(SYS_fork, 0, 0); 903 #endif 904 mtx_assert(&Giant, MA_NOTOWNED); 905 } 906