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 /* 170 * Don't allow sharing of file descriptor table unless 171 * RFTHREAD flag is supplied 172 */ 173 if ((uap->flags & (RFPROC | RFTHREAD | RFFDG | RFCFDG)) == 174 RFPROC) 175 return(EINVAL); 176 mtx_lock(&Giant); 177 error = fork1(td, uap->flags, 0, &p2); 178 if (error == 0) { 179 td->td_retval[0] = p2 ? p2->p_pid : 0; 180 td->td_retval[1] = 0; 181 } 182 mtx_unlock(&Giant); 183 return error; 184 } 185 186 187 int nprocs = 1; /* process 0 */ 188 int lastpid = 0; 189 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 190 "Last used PID"); 191 192 /* 193 * Random component to lastpid generation. We mix in a random factor to make 194 * it a little harder to predict. We sanity check the modulus value to avoid 195 * doing it in critical paths. Don't let it be too small or we pointlessly 196 * waste randomness entropy, and don't let it be impossibly large. Using a 197 * modulus that is too big causes a LOT more process table scans and slows 198 * down fork processing as the pidchecked caching is defeated. 199 */ 200 static int randompid = 0; 201 202 static int 203 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 204 { 205 int error, pid; 206 207 sysctl_wire_old_buffer(req, sizeof(int)); 208 sx_xlock(&allproc_lock); 209 pid = randompid; 210 error = sysctl_handle_int(oidp, &pid, 0, req); 211 if (error == 0 && req->newptr != NULL) { 212 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 213 pid = PID_MAX - 100; 214 else if (pid < 2) /* NOP */ 215 pid = 0; 216 else if (pid < 100) /* Make it reasonable */ 217 pid = 100; 218 randompid = pid; 219 } 220 sx_xunlock(&allproc_lock); 221 return (error); 222 } 223 224 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 225 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 226 227 int 228 fork1(td, flags, pages, procp) 229 struct thread *td; /* parent proc */ 230 int flags; 231 int pages; 232 struct proc **procp; /* child proc */ 233 { 234 struct proc *p2, *pptr; 235 uid_t uid; 236 struct proc *newproc; 237 int trypid; 238 int ok; 239 static int pidchecked = 0; 240 struct forklist *ep; 241 struct filedesc *fd; 242 struct proc *p1 = td->td_proc; 243 struct thread *td2; 244 struct kse *ke2; 245 struct ksegrp *kg2; 246 struct sigacts *newsigacts; 247 struct procsig *newprocsig; 248 int error; 249 250 GIANT_REQUIRED; 251 252 /* Can't copy and clear */ 253 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 254 return (EINVAL); 255 256 /* 257 * Here we don't create a new process, but we divorce 258 * certain parts of a process from itself. 259 */ 260 if ((flags & RFPROC) == 0) { 261 vm_forkproc(td, NULL, NULL, flags); 262 263 /* 264 * Close all file descriptors. 265 */ 266 if (flags & RFCFDG) { 267 struct filedesc *fdtmp; 268 fdtmp = fdinit(td->td_proc->p_fd); 269 fdfree(td); 270 p1->p_fd = fdtmp; 271 } 272 273 /* 274 * Unshare file descriptors (from parent.) 275 */ 276 if (flags & RFFDG) { 277 FILEDESC_LOCK(p1->p_fd); 278 if (p1->p_fd->fd_refcnt > 1) { 279 struct filedesc *newfd; 280 281 newfd = fdcopy(td->td_proc->p_fd); 282 FILEDESC_UNLOCK(p1->p_fd); 283 fdfree(td); 284 p1->p_fd = newfd; 285 } else 286 FILEDESC_UNLOCK(p1->p_fd); 287 } 288 *procp = NULL; 289 return (0); 290 } 291 292 if (p1->p_flag & P_THREADED) { 293 /* 294 * Idle the other threads for a second. 295 * Since the user space is copied, it must remain stable. 296 * In addition, all threads (from the user perspective) 297 * need to either be suspended or in the kernel, 298 * where they will try restart in the parent and will 299 * be aborted in the child. 300 */ 301 PROC_LOCK(p1); 302 if (thread_single(SINGLE_NO_EXIT)) { 303 /* Abort.. someone else is single threading before us */ 304 PROC_UNLOCK(p1); 305 return (ERESTART); 306 } 307 PROC_UNLOCK(p1); 308 /* 309 * All other activity in this process 310 * is now suspended at the user boundary, 311 * (or other safe places if we think of any). 312 */ 313 } 314 315 /* Allocate new proc. */ 316 newproc = uma_zalloc(proc_zone, M_WAITOK); 317 #ifdef MAC 318 mac_init_proc(newproc); 319 #endif 320 321 /* 322 * Although process entries are dynamically created, we still keep 323 * a global limit on the maximum number we will create. Don't allow 324 * a nonprivileged user to use the last ten processes; don't let root 325 * exceed the limit. The variable nprocs is the current number of 326 * processes, maxproc is the limit. 327 */ 328 sx_xlock(&allproc_lock); 329 uid = td->td_ucred->cr_ruid; 330 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 331 error = EAGAIN; 332 goto fail; 333 } 334 335 /* 336 * Increment the count of procs running with this uid. Don't allow 337 * a nonprivileged user to exceed their current limit. 338 */ 339 PROC_LOCK(p1); 340 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 341 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 342 PROC_UNLOCK(p1); 343 if (!ok) { 344 error = EAGAIN; 345 goto fail; 346 } 347 348 /* 349 * Increment the nprocs resource before blocking can occur. There 350 * are hard-limits as to the number of processes that can run. 351 */ 352 nprocs++; 353 354 /* 355 * Find an unused process ID. We remember a range of unused IDs 356 * ready to use (from lastpid+1 through pidchecked-1). 357 * 358 * If RFHIGHPID is set (used during system boot), do not allocate 359 * low-numbered pids. 360 */ 361 trypid = lastpid + 1; 362 if (flags & RFHIGHPID) { 363 if (trypid < 10) { 364 trypid = 10; 365 } 366 } else { 367 if (randompid) 368 trypid += arc4random() % randompid; 369 } 370 retry: 371 /* 372 * If the process ID prototype has wrapped around, 373 * restart somewhat above 0, as the low-numbered procs 374 * tend to include daemons that don't exit. 375 */ 376 if (trypid >= PID_MAX) { 377 trypid = trypid % PID_MAX; 378 if (trypid < 100) 379 trypid += 100; 380 pidchecked = 0; 381 } 382 if (trypid >= pidchecked) { 383 int doingzomb = 0; 384 385 pidchecked = PID_MAX; 386 /* 387 * Scan the active and zombie procs to check whether this pid 388 * is in use. Remember the lowest pid that's greater 389 * than trypid, so we can avoid checking for a while. 390 */ 391 p2 = LIST_FIRST(&allproc); 392 again: 393 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 394 PROC_LOCK(p2); 395 while (p2->p_pid == trypid || 396 p2->p_pgrp->pg_id == trypid || 397 p2->p_session->s_sid == trypid) { 398 trypid++; 399 if (trypid >= pidchecked) { 400 PROC_UNLOCK(p2); 401 goto retry; 402 } 403 } 404 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 405 pidchecked = p2->p_pid; 406 if (p2->p_pgrp->pg_id > trypid && 407 pidchecked > p2->p_pgrp->pg_id) 408 pidchecked = p2->p_pgrp->pg_id; 409 if (p2->p_session->s_sid > trypid && 410 pidchecked > p2->p_session->s_sid) 411 pidchecked = p2->p_session->s_sid; 412 PROC_UNLOCK(p2); 413 } 414 if (!doingzomb) { 415 doingzomb = 1; 416 p2 = LIST_FIRST(&zombproc); 417 goto again; 418 } 419 } 420 421 /* 422 * RFHIGHPID does not mess with the lastpid counter during boot. 423 */ 424 if (flags & RFHIGHPID) 425 pidchecked = 0; 426 else 427 lastpid = trypid; 428 429 p2 = newproc; 430 p2->p_state = PRS_NEW; /* protect against others */ 431 p2->p_pid = trypid; 432 LIST_INSERT_HEAD(&allproc, p2, p_list); 433 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 434 sx_xunlock(&allproc_lock); 435 436 /* 437 * Malloc things while we don't hold any locks. 438 */ 439 if (flags & RFSIGSHARE) { 440 MALLOC(newsigacts, struct sigacts *, 441 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 442 newprocsig = NULL; 443 } else { 444 newsigacts = NULL; 445 MALLOC(newprocsig, struct procsig *, sizeof(struct procsig), 446 M_SUBPROC, M_WAITOK); 447 } 448 449 /* 450 * Copy filedesc. 451 * XXX: This is busted. fd*() need to not take proc 452 * arguments or something. 453 */ 454 if (flags & RFCFDG) 455 fd = fdinit(td->td_proc->p_fd); 456 else if (flags & RFFDG) { 457 FILEDESC_LOCK(p1->p_fd); 458 fd = fdcopy(td->td_proc->p_fd); 459 FILEDESC_UNLOCK(p1->p_fd); 460 } else 461 fd = fdshare(p1->p_fd); 462 463 /* 464 * Make a proc table entry for the new process. 465 * Start by zeroing the section of proc that is zero-initialized, 466 * then copy the section that is copied directly from the parent. 467 */ 468 td2 = FIRST_THREAD_IN_PROC(p2); 469 kg2 = FIRST_KSEGRP_IN_PROC(p2); 470 ke2 = FIRST_KSE_IN_KSEGRP(kg2); 471 472 /* Allocate and switch to an alternate kstack if specified */ 473 if (pages != 0) 474 pmap_new_altkstack(td2, pages); 475 476 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 477 478 bzero(&p2->p_startzero, 479 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 480 bzero(&ke2->ke_startzero, 481 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 482 bzero(&td2->td_startzero, 483 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 484 bzero(&kg2->kg_startzero, 485 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 486 487 mtx_init(&p2->p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 488 PROC_LOCK(p2); 489 PROC_LOCK(p1); 490 491 bcopy(&p1->p_startcopy, &p2->p_startcopy, 492 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 493 bcopy(&td->td_startcopy, &td2->td_startcopy, 494 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 495 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 496 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 497 #undef RANGEOF 498 499 /* Set up the thread as an active thread (as if runnable). */ 500 ke2->ke_state = KES_THREAD; 501 ke2->ke_thread = td2; 502 td2->td_kse = ke2; 503 504 /* 505 * Duplicate sub-structures as needed. 506 * Increase reference counts on shared objects. 507 * The p_stats and p_sigacts substructs are set in vm_forkproc. 508 */ 509 p2->p_flag = 0; 510 mtx_lock_spin(&sched_lock); 511 p2->p_sflag = PS_INMEM; 512 if (p1->p_sflag & PS_PROFIL) 513 startprofclock(p2); 514 /* 515 * Allow the scheduler to adjust the priority of the child and 516 * parent while we hold the sched_lock. 517 */ 518 sched_fork(td->td_ksegrp, kg2); 519 520 mtx_unlock_spin(&sched_lock); 521 p2->p_ucred = crhold(td->td_ucred); 522 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 523 524 pargs_hold(p2->p_args); 525 526 if (flags & RFSIGSHARE) { 527 p2->p_procsig = p1->p_procsig; 528 p2->p_procsig->ps_refcnt++; 529 if (p1->p_sigacts == &p1->p_uarea->u_sigacts) { 530 /* 531 * Set p_sigacts to the new shared structure. 532 * Note that this is updating p1->p_sigacts at the 533 * same time, since p_sigacts is just a pointer to 534 * the shared p_procsig->ps_sigacts. 535 */ 536 p2->p_sigacts = newsigacts; 537 newsigacts = NULL; 538 *p2->p_sigacts = p1->p_uarea->u_sigacts; 539 } 540 } else { 541 p2->p_procsig = newprocsig; 542 newprocsig = NULL; 543 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 544 p2->p_procsig->ps_refcnt = 1; 545 p2->p_sigacts = NULL; /* finished in vm_forkproc() */ 546 } 547 if (flags & RFLINUXTHPN) 548 p2->p_sigparent = SIGUSR1; 549 else 550 p2->p_sigparent = SIGCHLD; 551 552 /* Bump references to the text vnode (for procfs) */ 553 p2->p_textvp = p1->p_textvp; 554 if (p2->p_textvp) 555 VREF(p2->p_textvp); 556 p2->p_fd = fd; 557 PROC_UNLOCK(p1); 558 PROC_UNLOCK(p2); 559 560 /* 561 * p_limit is copy-on-write, bump refcnt, 562 */ 563 p2->p_limit = p1->p_limit; 564 p2->p_limit->p_refcnt++; 565 566 /* 567 * Setup linkage for kernel based threading 568 */ 569 if((flags & RFTHREAD) != 0) { 570 mtx_lock(&ppeers_lock); 571 p2->p_peers = p1->p_peers; 572 p1->p_peers = p2; 573 p2->p_leader = p1->p_leader; 574 mtx_unlock(&ppeers_lock); 575 PROC_LOCK(p1->p_leader); 576 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 577 PROC_UNLOCK(p1->p_leader); 578 /* 579 * The task leader is exiting, so process p1 is 580 * going to be killed shortly. Since p1 obviously 581 * isn't dead yet, we know that the leader is either 582 * sending SIGKILL's to all the processes in this 583 * task or is sleeping waiting for all the peers to 584 * exit. We let p1 complete the fork, but we need 585 * to go ahead and kill the new process p2 since 586 * the task leader may not get a chance to send 587 * SIGKILL to it. We leave it on the list so that 588 * the task leader will wait for this new process 589 * to commit suicide. 590 */ 591 PROC_LOCK(p2); 592 psignal(p2, SIGKILL); 593 PROC_UNLOCK(p2); 594 } else 595 PROC_UNLOCK(p1->p_leader); 596 } else { 597 p2->p_peers = NULL; 598 p2->p_leader = p2; 599 } 600 601 sx_xlock(&proctree_lock); 602 PGRP_LOCK(p1->p_pgrp); 603 PROC_LOCK(p2); 604 PROC_LOCK(p1); 605 606 /* 607 * Preserve some more flags in subprocess. PS_PROFIL has already 608 * been preserved. 609 */ 610 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 611 SESS_LOCK(p1->p_session); 612 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 613 p2->p_flag |= P_CONTROLT; 614 SESS_UNLOCK(p1->p_session); 615 if (flags & RFPPWAIT) 616 p2->p_flag |= P_PPWAIT; 617 618 LIST_INSERT_AFTER(p1, p2, p_pglist); 619 PGRP_UNLOCK(p1->p_pgrp); 620 LIST_INIT(&p2->p_children); 621 622 callout_init(&p2->p_itcallout, 0); 623 624 #ifdef KTRACE 625 /* 626 * Copy traceflag and tracefile if enabled. 627 */ 628 mtx_lock(&ktrace_mtx); 629 KASSERT(p2->p_tracep == NULL, ("new process has a ktrace vnode")); 630 if (p1->p_traceflag & KTRFAC_INHERIT) { 631 p2->p_traceflag = p1->p_traceflag; 632 if ((p2->p_tracep = p1->p_tracep) != NULL) 633 VREF(p2->p_tracep); 634 } 635 mtx_unlock(&ktrace_mtx); 636 #endif 637 638 /* 639 * If PF_FORK is set, the child process inherits the 640 * procfs ioctl flags from its parent. 641 */ 642 if (p1->p_pfsflags & PF_FORK) { 643 p2->p_stops = p1->p_stops; 644 p2->p_pfsflags = p1->p_pfsflags; 645 } 646 647 /* 648 * This begins the section where we must prevent the parent 649 * from being swapped. 650 */ 651 _PHOLD(p1); 652 PROC_UNLOCK(p1); 653 654 /* 655 * Attach the new process to its parent. 656 * 657 * If RFNOWAIT is set, the newly created process becomes a child 658 * of init. This effectively disassociates the child from the 659 * parent. 660 */ 661 if (flags & RFNOWAIT) 662 pptr = initproc; 663 else 664 pptr = p1; 665 p2->p_pptr = pptr; 666 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 667 PROC_UNLOCK(p2); 668 sx_xunlock(&proctree_lock); 669 670 KASSERT(newprocsig == NULL, ("unused newprocsig")); 671 if (newsigacts != NULL) 672 FREE(newsigacts, M_SUBPROC); 673 /* 674 * Finish creating the child process. It will return via a different 675 * execution path later. (ie: directly into user mode) 676 */ 677 vm_forkproc(td, p2, td2, flags); 678 679 if (flags == (RFFDG | RFPROC)) { 680 cnt.v_forks++; 681 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 682 p2->p_vmspace->vm_ssize; 683 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 684 cnt.v_vforks++; 685 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 686 p2->p_vmspace->vm_ssize; 687 } else if (p1 == &proc0) { 688 cnt.v_kthreads++; 689 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 690 p2->p_vmspace->vm_ssize; 691 } else { 692 cnt.v_rforks++; 693 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 694 p2->p_vmspace->vm_ssize; 695 } 696 697 /* 698 * Both processes are set up, now check if any loadable modules want 699 * to adjust anything. 700 * What if they have an error? XXX 701 */ 702 sx_slock(&fork_list_lock); 703 TAILQ_FOREACH(ep, &fork_list, next) { 704 (*ep->function)(p1, p2, flags); 705 } 706 sx_sunlock(&fork_list_lock); 707 708 /* 709 * If RFSTOPPED not requested, make child runnable and add to 710 * run queue. 711 */ 712 microtime(&(p2->p_stats->p_start)); 713 p2->p_acflag = AFORK; 714 if ((flags & RFSTOPPED) == 0) { 715 mtx_lock_spin(&sched_lock); 716 p2->p_state = PRS_NORMAL; 717 TD_SET_CAN_RUN(td2); 718 setrunqueue(td2); 719 mtx_unlock_spin(&sched_lock); 720 } 721 722 /* 723 * Now can be swapped. 724 */ 725 PROC_LOCK(p1); 726 _PRELE(p1); 727 728 /* 729 * tell any interested parties about the new process 730 */ 731 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 732 PROC_UNLOCK(p1); 733 734 /* 735 * Preserve synchronization semantics of vfork. If waiting for 736 * child to exec or exit, set P_PPWAIT on child, and sleep on our 737 * proc (in case of exit). 738 */ 739 PROC_LOCK(p2); 740 while (p2->p_flag & P_PPWAIT) 741 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 742 PROC_UNLOCK(p2); 743 744 /* 745 * If other threads are waiting, let them continue now 746 */ 747 if (p1->p_flag & P_THREADED) { 748 PROC_LOCK(p1); 749 thread_single_end(); 750 PROC_UNLOCK(p1); 751 } 752 753 /* 754 * Return child proc pointer to parent. 755 */ 756 *procp = p2; 757 return (0); 758 fail: 759 sx_xunlock(&allproc_lock); 760 uma_zfree(proc_zone, newproc); 761 if (p1->p_flag & P_THREADED) { 762 PROC_LOCK(p1); 763 thread_single_end(); 764 PROC_UNLOCK(p1); 765 } 766 tsleep(&forksleep, PUSER, "fork", hz / 2); 767 return (error); 768 } 769 770 /* 771 * The next two functionms are general routines to handle adding/deleting 772 * items on the fork callout list. 773 * 774 * at_fork(): 775 * Take the arguments given and put them onto the fork callout list, 776 * However first make sure that it's not already there. 777 * Returns 0 on success or a standard error number. 778 */ 779 780 int 781 at_fork(function) 782 forklist_fn function; 783 { 784 struct forklist *ep; 785 786 #ifdef INVARIANTS 787 /* let the programmer know if he's been stupid */ 788 if (rm_at_fork(function)) 789 printf("WARNING: fork callout entry (%p) already present\n", 790 function); 791 #endif 792 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); 793 if (ep == NULL) 794 return (ENOMEM); 795 ep->function = function; 796 sx_xlock(&fork_list_lock); 797 TAILQ_INSERT_TAIL(&fork_list, ep, next); 798 sx_xunlock(&fork_list_lock); 799 return (0); 800 } 801 802 /* 803 * Scan the exit callout list for the given item and remove it.. 804 * Returns the number of items removed (0 or 1) 805 */ 806 807 int 808 rm_at_fork(function) 809 forklist_fn function; 810 { 811 struct forklist *ep; 812 813 sx_xlock(&fork_list_lock); 814 TAILQ_FOREACH(ep, &fork_list, next) { 815 if (ep->function == function) { 816 TAILQ_REMOVE(&fork_list, ep, next); 817 sx_xunlock(&fork_list_lock); 818 free(ep, M_ATFORK); 819 return(1); 820 } 821 } 822 sx_xunlock(&fork_list_lock); 823 return (0); 824 } 825 826 /* 827 * Handle the return of a child process from fork1(). This function 828 * is called from the MD fork_trampoline() entry point. 829 */ 830 void 831 fork_exit(callout, arg, frame) 832 void (*callout)(void *, struct trapframe *); 833 void *arg; 834 struct trapframe *frame; 835 { 836 struct thread *td; 837 struct proc *p; 838 839 if ((td = PCPU_GET(deadthread))) { 840 PCPU_SET(deadthread, NULL); 841 thread_stash(td); 842 } 843 td = curthread; 844 p = td->td_proc; 845 td->td_kse->ke_oncpu = PCPU_GET(cpuid); 846 p->p_state = PRS_NORMAL; 847 /* 848 * Finish setting up thread glue. We need to initialize 849 * the thread into a td_critnest=1 state. Some platforms 850 * may have already partially or fully initialized td_critnest 851 * and/or td_md.md_savecrit (when applciable). 852 * 853 * see <arch>/<arch>/critical.c 854 */ 855 sched_lock.mtx_lock = (uintptr_t)td; 856 sched_lock.mtx_recurse = 0; 857 cpu_critical_fork_exit(); 858 CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid, 859 p->p_comm); 860 if (PCPU_GET(switchtime.sec) == 0) 861 binuptime(PCPU_PTR(switchtime)); 862 PCPU_SET(switchticks, ticks); 863 mtx_unlock_spin(&sched_lock); 864 865 /* 866 * cpu_set_fork_handler intercepts this function call to 867 * have this call a non-return function to stay in kernel mode. 868 * initproc has its own fork handler, but it does return. 869 */ 870 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 871 callout(arg, frame); 872 873 /* 874 * Check if a kernel thread misbehaved and returned from its main 875 * function. 876 */ 877 PROC_LOCK(p); 878 if (p->p_flag & P_KTHREAD) { 879 PROC_UNLOCK(p); 880 mtx_lock(&Giant); 881 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 882 p->p_comm, p->p_pid); 883 kthread_exit(0); 884 } 885 PROC_UNLOCK(p); 886 #ifdef DIAGNOSTIC 887 cred_free_thread(td); 888 #endif 889 mtx_assert(&Giant, MA_NOTOWNED); 890 } 891 892 /* 893 * Simplified back end of syscall(), used when returning from fork() 894 * directly into user mode. Giant is not held on entry, and must not 895 * be held on return. This function is passed in to fork_exit() as the 896 * first parameter and is called when returning to a new userland process. 897 */ 898 void 899 fork_return(td, frame) 900 struct thread *td; 901 struct trapframe *frame; 902 { 903 904 userret(td, frame, 0); 905 #ifdef KTRACE 906 if (KTRPOINT(td, KTR_SYSRET)) 907 ktrsysret(SYS_fork, 0, 0); 908 #endif 909 mtx_assert(&Giant, MA_NOTOWNED); 910 } 911