87 88/* 89 * MPSAFE 90 */ 91/* ARGSUSED */ 92int 93fork(td, uap) 94 struct thread *td; 95 struct fork_args *uap; 96{ 97 int error; 98 struct proc *p2; 99 100 error = fork1(td, RFFDG | RFPROC, 0, &p2); 101 if (error == 0) { 102 td->td_retval[0] = p2->p_pid; 103 td->td_retval[1] = 0; 104 } 105 return error; 106} 107 108/* 109 * MPSAFE 110 */ 111/* ARGSUSED */ 112int 113vfork(td, uap) 114 struct thread *td; 115 struct vfork_args *uap; 116{ 117 int error; 118 struct proc *p2; 119 120 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 121 if (error == 0) { 122 td->td_retval[0] = p2->p_pid; 123 td->td_retval[1] = 0; 124 } 125 return error; 126} 127 128/* 129 * MPSAFE 130 */ 131int 132rfork(td, uap) 133 struct thread *td; 134 struct rfork_args *uap; 135{ 136 int error; 137 struct proc *p2; 138 139 /* Don't allow kernel only flags. */ 140 if ((uap->flags & RFKERNELONLY) != 0) 141 return (EINVAL); 142 /* 143 * Don't allow sharing of file descriptor table unless 144 * RFTHREAD flag is supplied 145 */ 146 if ((uap->flags & (RFPROC | RFTHREAD | RFFDG | RFCFDG)) == 147 RFPROC) 148 return(EINVAL); 149 error = fork1(td, uap->flags, 0, &p2); 150 if (error == 0) { 151 td->td_retval[0] = p2 ? p2->p_pid : 0; 152 td->td_retval[1] = 0; 153 } 154 return error; 155} 156 157 158int nprocs = 1; /* process 0 */ 159int lastpid = 0; 160SYSCTL_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 */ 171static int randompid = 0; 172 173static int 174sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 175{ 176 int error, pid; 177 178 sysctl_wire_old_buffer(req, sizeof(int)); 179 sx_xlock(&allproc_lock); 180 pid = randompid; 181 error = sysctl_handle_int(oidp, &pid, 0, req); 182 if (error == 0 && req->newptr != NULL) { 183 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 184 pid = PID_MAX - 100; 185 else if (pid < 2) /* NOP */ 186 pid = 0; 187 else if (pid < 100) /* Make it reasonable */ 188 pid = 100; 189 randompid = pid; 190 } 191 sx_xunlock(&allproc_lock); 192 return (error); 193} 194 195SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 196 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 197 198int 199fork1(td, flags, pages, procp) 200 struct thread *td; /* parent proc */ 201 int flags; 202 int pages; 203 struct proc **procp; /* child proc */ 204{ 205 struct proc *p2, *pptr; 206 uid_t uid; 207 struct proc *newproc; 208 int trypid; 209 int ok; 210 static int pidchecked = 0; 211 struct filedesc *fd; 212 struct proc *p1 = td->td_proc; 213 struct thread *td2; 214 struct kse *ke2; 215 struct ksegrp *kg2; 216 struct sigacts *newsigacts; 217 struct procsig *newprocsig; 218 int error; 219 220 /* Can't copy and clear */ 221 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 222 return (EINVAL); 223 224 mtx_lock(&Giant); 225 /* 226 * Here we don't create a new process, but we divorce 227 * certain parts of a process from itself. 228 */ 229 if ((flags & RFPROC) == 0) { 230 vm_forkproc(td, NULL, NULL, flags); 231 232 /* 233 * Close all file descriptors. 234 */ 235 if (flags & RFCFDG) { 236 struct filedesc *fdtmp; 237 fdtmp = fdinit(td->td_proc->p_fd); 238 fdfree(td); 239 p1->p_fd = fdtmp; 240 } 241 242 /* 243 * Unshare file descriptors (from parent.) 244 */ 245 if (flags & RFFDG) { 246 FILEDESC_LOCK(p1->p_fd); 247 if (p1->p_fd->fd_refcnt > 1) { 248 struct filedesc *newfd; 249 250 newfd = fdcopy(td->td_proc->p_fd); 251 FILEDESC_UNLOCK(p1->p_fd); 252 fdfree(td); 253 p1->p_fd = newfd; 254 } else 255 FILEDESC_UNLOCK(p1->p_fd); 256 } 257 mtx_unlock(&Giant); 258 *procp = NULL; 259 return (0); 260 } 261 262 /* 263 * Note 1:1 allows for forking with one thread coming out on the 264 * other side with the expectation that the process is about to 265 * exec. 266 */ 267 if (p1->p_flag & P_THREADED) { 268 /* 269 * Idle the other threads for a second. 270 * Since the user space is copied, it must remain stable. 271 * In addition, all threads (from the user perspective) 272 * need to either be suspended or in the kernel, 273 * where they will try restart in the parent and will 274 * be aborted in the child. 275 */ 276 PROC_LOCK(p1); 277 if (thread_single(SINGLE_NO_EXIT)) { 278 /* Abort.. someone else is single threading before us */ 279 PROC_UNLOCK(p1); 280 mtx_unlock(&Giant); 281 return (ERESTART); 282 } 283 PROC_UNLOCK(p1); 284 /* 285 * All other activity in this process 286 * is now suspended at the user boundary, 287 * (or other safe places if we think of any). 288 */ 289 } 290 291 /* Allocate new proc. */ 292 newproc = uma_zalloc(proc_zone, M_WAITOK); 293#ifdef MAC 294 mac_init_proc(newproc); 295#endif 296 297 /* 298 * Although process entries are dynamically created, we still keep 299 * a global limit on the maximum number we will create. Don't allow 300 * a nonprivileged user to use the last ten processes; don't let root 301 * exceed the limit. The variable nprocs is the current number of 302 * processes, maxproc is the limit. 303 */ 304 sx_xlock(&allproc_lock); 305 uid = td->td_ucred->cr_ruid; 306 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 307 error = EAGAIN; 308 goto fail; 309 } 310 311 /* 312 * Increment the count of procs running with this uid. Don't allow 313 * a nonprivileged user to exceed their current limit. 314 */ 315 PROC_LOCK(p1); 316 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 317 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 318 PROC_UNLOCK(p1); 319 if (!ok) { 320 error = EAGAIN; 321 goto fail; 322 } 323 324 /* 325 * Increment the nprocs resource before blocking can occur. There 326 * are hard-limits as to the number of processes that can run. 327 */ 328 nprocs++; 329 330 /* 331 * Find an unused process ID. We remember a range of unused IDs 332 * ready to use (from lastpid+1 through pidchecked-1). 333 * 334 * If RFHIGHPID is set (used during system boot), do not allocate 335 * low-numbered pids. 336 */ 337 trypid = lastpid + 1; 338 if (flags & RFHIGHPID) { 339 if (trypid < 10) { 340 trypid = 10; 341 } 342 } else { 343 if (randompid) 344 trypid += arc4random() % randompid; 345 } 346retry: 347 /* 348 * If the process ID prototype has wrapped around, 349 * restart somewhat above 0, as the low-numbered procs 350 * tend to include daemons that don't exit. 351 */ 352 if (trypid >= PID_MAX) { 353 trypid = trypid % PID_MAX; 354 if (trypid < 100) 355 trypid += 100; 356 pidchecked = 0; 357 } 358 if (trypid >= pidchecked) { 359 int doingzomb = 0; 360 361 pidchecked = PID_MAX; 362 /* 363 * Scan the active and zombie procs to check whether this pid 364 * is in use. Remember the lowest pid that's greater 365 * than trypid, so we can avoid checking for a while. 366 */ 367 p2 = LIST_FIRST(&allproc); 368again: 369 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 370 PROC_LOCK(p2); 371 while (p2->p_pid == trypid || 372 p2->p_pgrp->pg_id == trypid || 373 p2->p_session->s_sid == trypid) { 374 trypid++; 375 if (trypid >= pidchecked) { 376 PROC_UNLOCK(p2); 377 goto retry; 378 } 379 } 380 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 381 pidchecked = p2->p_pid; 382 if (p2->p_pgrp->pg_id > trypid && 383 pidchecked > p2->p_pgrp->pg_id) 384 pidchecked = p2->p_pgrp->pg_id; 385 if (p2->p_session->s_sid > trypid && 386 pidchecked > p2->p_session->s_sid) 387 pidchecked = p2->p_session->s_sid; 388 PROC_UNLOCK(p2); 389 } 390 if (!doingzomb) { 391 doingzomb = 1; 392 p2 = LIST_FIRST(&zombproc); 393 goto again; 394 } 395 } 396 397 /* 398 * RFHIGHPID does not mess with the lastpid counter during boot. 399 */ 400 if (flags & RFHIGHPID) 401 pidchecked = 0; 402 else 403 lastpid = trypid; 404 405 p2 = newproc; 406 p2->p_state = PRS_NEW; /* protect against others */ 407 p2->p_pid = trypid; 408 LIST_INSERT_HEAD(&allproc, p2, p_list); 409 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 410 sx_xunlock(&allproc_lock); 411 412 /* 413 * Malloc things while we don't hold any locks. 414 */ 415 if (flags & RFSIGSHARE) { 416 MALLOC(newsigacts, struct sigacts *, 417 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 418 newprocsig = NULL; 419 } else { 420 newsigacts = NULL; 421 MALLOC(newprocsig, struct procsig *, sizeof(struct procsig), 422 M_SUBPROC, M_WAITOK); 423 } 424 425 /* 426 * Copy filedesc. 427 * XXX: This is busted. fd*() need to not take proc 428 * arguments or something. 429 */ 430 if (flags & RFCFDG) 431 fd = fdinit(td->td_proc->p_fd); 432 else if (flags & RFFDG) { 433 FILEDESC_LOCK(p1->p_fd); 434 fd = fdcopy(td->td_proc->p_fd); 435 FILEDESC_UNLOCK(p1->p_fd); 436 } else 437 fd = fdshare(p1->p_fd); 438 439 /* 440 * Make a proc table entry for the new process. 441 * Start by zeroing the section of proc that is zero-initialized, 442 * then copy the section that is copied directly from the parent. 443 */ 444 td2 = FIRST_THREAD_IN_PROC(p2); 445 kg2 = FIRST_KSEGRP_IN_PROC(p2); 446 ke2 = FIRST_KSE_IN_KSEGRP(kg2); 447 448 /* Allocate and switch to an alternate kstack if specified */ 449 if (pages != 0) 450 pmap_new_altkstack(td2, pages); 451 452#define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 453 454 bzero(&p2->p_startzero, 455 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 456 bzero(&ke2->ke_startzero, 457 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 458 bzero(&td2->td_startzero, 459 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 460 bzero(&kg2->kg_startzero, 461 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 462 463 mtx_init(&p2->p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 464 PROC_LOCK(p2); 465 PROC_LOCK(p1); 466 467 bcopy(&p1->p_startcopy, &p2->p_startcopy, 468 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 469 bcopy(&td->td_startcopy, &td2->td_startcopy, 470 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 471 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 472 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 473#undef RANGEOF 474 475 /* Set up the thread as an active thread (as if runnable). */ 476 ke2->ke_state = KES_THREAD; 477 ke2->ke_thread = td2; 478 td2->td_kse = ke2; 479 480 /* 481 * Duplicate sub-structures as needed. 482 * Increase reference counts on shared objects. 483 * The p_stats and p_sigacts substructs are set in vm_forkproc. 484 */ 485 p2->p_flag = 0; 486 if (p1->p_flag & P_PROFIL) 487 startprofclock(p2); 488 mtx_lock_spin(&sched_lock); 489 p2->p_sflag = PS_INMEM; 490 /* 491 * Allow the scheduler to adjust the priority of the child and 492 * parent while we hold the sched_lock. 493 */ 494 sched_fork(p1, p2); 495 496 mtx_unlock_spin(&sched_lock); 497 p2->p_ucred = crhold(td->td_ucred); 498 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 499 500 pargs_hold(p2->p_args); 501 502 if (flags & RFSIGSHARE) { 503 p2->p_procsig = p1->p_procsig; 504 p2->p_procsig->ps_refcnt++; 505 if (p1->p_sigacts == &p1->p_uarea->u_sigacts) { 506 /* 507 * Set p_sigacts to the new shared structure. 508 * Note that this is updating p1->p_sigacts at the 509 * same time, since p_sigacts is just a pointer to 510 * the shared p_procsig->ps_sigacts. 511 */ 512 p2->p_sigacts = newsigacts; 513 newsigacts = NULL; 514 *p2->p_sigacts = p1->p_uarea->u_sigacts; 515 } 516 } else { 517 p2->p_procsig = newprocsig; 518 newprocsig = NULL; 519 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 520 p2->p_procsig->ps_refcnt = 1; 521 p2->p_sigacts = NULL; /* finished in vm_forkproc() */ 522 } 523 if (flags & RFLINUXTHPN) 524 p2->p_sigparent = SIGUSR1; 525 else 526 p2->p_sigparent = SIGCHLD; 527 528 /* Bump references to the text vnode (for procfs) */ 529 p2->p_textvp = p1->p_textvp; 530 if (p2->p_textvp) 531 VREF(p2->p_textvp); 532 p2->p_fd = fd; 533 PROC_UNLOCK(p1); 534 PROC_UNLOCK(p2); 535 536 /* 537 * p_limit is copy-on-write, bump refcnt, 538 */ 539 p2->p_limit = p1->p_limit; 540 p2->p_limit->p_refcnt++; 541 542 /* 543 * Setup linkage for kernel based threading 544 */ 545 if((flags & RFTHREAD) != 0) { 546 mtx_lock(&ppeers_lock); 547 p2->p_peers = p1->p_peers; 548 p1->p_peers = p2; 549 p2->p_leader = p1->p_leader; 550 mtx_unlock(&ppeers_lock); 551 PROC_LOCK(p1->p_leader); 552 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 553 PROC_UNLOCK(p1->p_leader); 554 /* 555 * The task leader is exiting, so process p1 is 556 * going to be killed shortly. Since p1 obviously 557 * isn't dead yet, we know that the leader is either 558 * sending SIGKILL's to all the processes in this 559 * task or is sleeping waiting for all the peers to 560 * exit. We let p1 complete the fork, but we need 561 * to go ahead and kill the new process p2 since 562 * the task leader may not get a chance to send 563 * SIGKILL to it. We leave it on the list so that 564 * the task leader will wait for this new process 565 * to commit suicide. 566 */ 567 PROC_LOCK(p2); 568 psignal(p2, SIGKILL); 569 PROC_UNLOCK(p2); 570 } else 571 PROC_UNLOCK(p1->p_leader); 572 } else { 573 p2->p_peers = NULL; 574 p2->p_leader = p2; 575 } 576 577 sx_xlock(&proctree_lock); 578 PGRP_LOCK(p1->p_pgrp); 579 PROC_LOCK(p2); 580 PROC_LOCK(p1); 581 582 /* 583 * Preserve some more flags in subprocess. P_PROFIL has already 584 * been preserved. 585 */ 586 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 587 SESS_LOCK(p1->p_session); 588 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 589 p2->p_flag |= P_CONTROLT; 590 SESS_UNLOCK(p1->p_session); 591 if (flags & RFPPWAIT) 592 p2->p_flag |= P_PPWAIT; 593 594 LIST_INSERT_AFTER(p1, p2, p_pglist); 595 PGRP_UNLOCK(p1->p_pgrp); 596 LIST_INIT(&p2->p_children); 597 598 callout_init(&p2->p_itcallout, 1); 599 600#ifdef KTRACE 601 /* 602 * Copy traceflag and tracefile if enabled. 603 */ 604 mtx_lock(&ktrace_mtx); 605 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 606 if (p1->p_traceflag & KTRFAC_INHERIT) { 607 p2->p_traceflag = p1->p_traceflag; 608 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 609 VREF(p2->p_tracevp); 610 KASSERT(p1->p_tracecred != NULL, 611 ("ktrace vnode with no cred")); 612 p2->p_tracecred = crhold(p1->p_tracecred); 613 } 614 } 615 mtx_unlock(&ktrace_mtx); 616#endif 617 618 /* 619 * If PF_FORK is set, the child process inherits the 620 * procfs ioctl flags from its parent. 621 */ 622 if (p1->p_pfsflags & PF_FORK) { 623 p2->p_stops = p1->p_stops; 624 p2->p_pfsflags = p1->p_pfsflags; 625 } 626 627 /* 628 * This begins the section where we must prevent the parent 629 * from being swapped. 630 */ 631 _PHOLD(p1); 632 PROC_UNLOCK(p1); 633 634 /* 635 * Attach the new process to its parent. 636 * 637 * If RFNOWAIT is set, the newly created process becomes a child 638 * of init. This effectively disassociates the child from the 639 * parent. 640 */ 641 if (flags & RFNOWAIT) 642 pptr = initproc; 643 else 644 pptr = p1; 645 p2->p_pptr = pptr; 646 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 647 sx_xunlock(&proctree_lock); 648 649 /* Inform accounting that we have forked. */ 650 p2->p_acflag = AFORK; 651 PROC_UNLOCK(p2); 652 653 KASSERT(newprocsig == NULL, ("unused newprocsig")); 654 if (newsigacts != NULL) 655 FREE(newsigacts, M_SUBPROC); 656 /* 657 * Finish creating the child process. It will return via a different 658 * execution path later. (ie: directly into user mode) 659 */ 660 vm_forkproc(td, p2, td2, flags); 661 662 if (flags == (RFFDG | RFPROC)) { 663 cnt.v_forks++; 664 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 665 p2->p_vmspace->vm_ssize; 666 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 667 cnt.v_vforks++; 668 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 669 p2->p_vmspace->vm_ssize; 670 } else if (p1 == &proc0) { 671 cnt.v_kthreads++; 672 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 673 p2->p_vmspace->vm_ssize; 674 } else { 675 cnt.v_rforks++; 676 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 677 p2->p_vmspace->vm_ssize; 678 } 679 680 /* 681 * Both processes are set up, now check if any loadable modules want 682 * to adjust anything. 683 * What if they have an error? XXX 684 */ 685 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 686 687 /* 688 * If RFSTOPPED not requested, make child runnable and add to 689 * run queue. 690 */ 691 microtime(&(p2->p_stats->p_start)); 692 if ((flags & RFSTOPPED) == 0) { 693 mtx_lock_spin(&sched_lock); 694 p2->p_state = PRS_NORMAL; 695 TD_SET_CAN_RUN(td2); 696 setrunqueue(td2); 697 mtx_unlock_spin(&sched_lock); 698 } 699 700 /* 701 * Now can be swapped. 702 */ 703 PROC_LOCK(p1); 704 _PRELE(p1); 705 706 /* 707 * tell any interested parties about the new process 708 */ 709 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 710 PROC_UNLOCK(p1); 711 712 /* 713 * Preserve synchronization semantics of vfork. If waiting for 714 * child to exec or exit, set P_PPWAIT on child, and sleep on our 715 * proc (in case of exit). 716 */ 717 PROC_LOCK(p2); 718 while (p2->p_flag & P_PPWAIT) 719 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 720 PROC_UNLOCK(p2); 721 722 /* 723 * If other threads are waiting, let them continue now 724 */ 725 if (p1->p_flag & P_THREADED) { 726 PROC_LOCK(p1); 727 thread_single_end(); 728 PROC_UNLOCK(p1); 729 } 730 731 /* 732 * Return child proc pointer to parent. 733 */ 734 mtx_unlock(&Giant); 735 *procp = p2; 736 return (0); 737fail: 738 sx_xunlock(&allproc_lock); 739 uma_zfree(proc_zone, newproc); 740 if (p1->p_flag & P_THREADED) { 741 PROC_LOCK(p1); 742 thread_single_end(); 743 PROC_UNLOCK(p1); 744 } 745 tsleep(&forksleep, PUSER, "fork", hz / 2); 746 mtx_unlock(&Giant); 747 return (error); 748} 749 750/* 751 * Handle the return of a child process from fork1(). This function 752 * is called from the MD fork_trampoline() entry point. 753 */ 754void 755fork_exit(callout, arg, frame) 756 void (*callout)(void *, struct trapframe *); 757 void *arg; 758 struct trapframe *frame; 759{ 760 struct thread *td; 761 struct proc *p; 762 763 if ((td = PCPU_GET(deadthread))) { 764 PCPU_SET(deadthread, NULL); 765 thread_stash(td); 766 } 767 td = curthread; 768 p = td->td_proc; 769 td->td_oncpu = PCPU_GET(cpuid); 770 p->p_state = PRS_NORMAL; 771 /* 772 * Finish setting up thread glue. We need to initialize 773 * the thread into a td_critnest=1 state. Some platforms 774 * may have already partially or fully initialized td_critnest 775 * and/or td_md.md_savecrit (when applciable). 776 * 777 * see <arch>/<arch>/critical.c 778 */ 779 sched_lock.mtx_lock = (uintptr_t)td; 780 sched_lock.mtx_recurse = 0; 781 cpu_critical_fork_exit(); 782 CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid, 783 p->p_comm); 784 if (PCPU_GET(switchtime.sec) == 0) 785 binuptime(PCPU_PTR(switchtime)); 786 PCPU_SET(switchticks, ticks); 787 mtx_unlock_spin(&sched_lock); 788 789 /* 790 * cpu_set_fork_handler intercepts this function call to 791 * have this call a non-return function to stay in kernel mode. 792 * initproc has its own fork handler, but it does return. 793 */ 794 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 795 callout(arg, frame); 796 797 /* 798 * Check if a kernel thread misbehaved and returned from its main 799 * function. 800 */ 801 PROC_LOCK(p); 802 if (p->p_flag & P_KTHREAD) { 803 PROC_UNLOCK(p); 804 mtx_lock(&Giant); 805 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 806 p->p_comm, p->p_pid); 807 kthread_exit(0); 808 } 809 PROC_UNLOCK(p); 810#ifdef DIAGNOSTIC 811 cred_free_thread(td); 812#endif 813 mtx_assert(&Giant, MA_NOTOWNED); 814} 815 816/* 817 * Simplified back end of syscall(), used when returning from fork() 818 * directly into user mode. Giant is not held on entry, and must not 819 * be held on return. This function is passed in to fork_exit() as the 820 * first parameter and is called when returning to a new userland process. 821 */ 822void 823fork_return(td, frame) 824 struct thread *td; 825 struct trapframe *frame; 826{ 827 828 userret(td, frame, 0); 829#ifdef KTRACE 830 if (KTRPOINT(td, KTR_SYSRET)) 831 ktrsysret(SYS_fork, 0, 0); 832#endif 833 mtx_assert(&Giant, MA_NOTOWNED); 834}
| 87 88/* 89 * MPSAFE 90 */ 91/* ARGSUSED */ 92int 93fork(td, uap) 94 struct thread *td; 95 struct fork_args *uap; 96{ 97 int error; 98 struct proc *p2; 99 100 error = fork1(td, RFFDG | RFPROC, 0, &p2); 101 if (error == 0) { 102 td->td_retval[0] = p2->p_pid; 103 td->td_retval[1] = 0; 104 } 105 return error; 106} 107 108/* 109 * MPSAFE 110 */ 111/* ARGSUSED */ 112int 113vfork(td, uap) 114 struct thread *td; 115 struct vfork_args *uap; 116{ 117 int error; 118 struct proc *p2; 119 120 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2); 121 if (error == 0) { 122 td->td_retval[0] = p2->p_pid; 123 td->td_retval[1] = 0; 124 } 125 return error; 126} 127 128/* 129 * MPSAFE 130 */ 131int 132rfork(td, uap) 133 struct thread *td; 134 struct rfork_args *uap; 135{ 136 int error; 137 struct proc *p2; 138 139 /* Don't allow kernel only flags. */ 140 if ((uap->flags & RFKERNELONLY) != 0) 141 return (EINVAL); 142 /* 143 * Don't allow sharing of file descriptor table unless 144 * RFTHREAD flag is supplied 145 */ 146 if ((uap->flags & (RFPROC | RFTHREAD | RFFDG | RFCFDG)) == 147 RFPROC) 148 return(EINVAL); 149 error = fork1(td, uap->flags, 0, &p2); 150 if (error == 0) { 151 td->td_retval[0] = p2 ? p2->p_pid : 0; 152 td->td_retval[1] = 0; 153 } 154 return error; 155} 156 157 158int nprocs = 1; /* process 0 */ 159int lastpid = 0; 160SYSCTL_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 */ 171static int randompid = 0; 172 173static int 174sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 175{ 176 int error, pid; 177 178 sysctl_wire_old_buffer(req, sizeof(int)); 179 sx_xlock(&allproc_lock); 180 pid = randompid; 181 error = sysctl_handle_int(oidp, &pid, 0, req); 182 if (error == 0 && req->newptr != NULL) { 183 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 184 pid = PID_MAX - 100; 185 else if (pid < 2) /* NOP */ 186 pid = 0; 187 else if (pid < 100) /* Make it reasonable */ 188 pid = 100; 189 randompid = pid; 190 } 191 sx_xunlock(&allproc_lock); 192 return (error); 193} 194 195SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 196 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 197 198int 199fork1(td, flags, pages, procp) 200 struct thread *td; /* parent proc */ 201 int flags; 202 int pages; 203 struct proc **procp; /* child proc */ 204{ 205 struct proc *p2, *pptr; 206 uid_t uid; 207 struct proc *newproc; 208 int trypid; 209 int ok; 210 static int pidchecked = 0; 211 struct filedesc *fd; 212 struct proc *p1 = td->td_proc; 213 struct thread *td2; 214 struct kse *ke2; 215 struct ksegrp *kg2; 216 struct sigacts *newsigacts; 217 struct procsig *newprocsig; 218 int error; 219 220 /* Can't copy and clear */ 221 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 222 return (EINVAL); 223 224 mtx_lock(&Giant); 225 /* 226 * Here we don't create a new process, but we divorce 227 * certain parts of a process from itself. 228 */ 229 if ((flags & RFPROC) == 0) { 230 vm_forkproc(td, NULL, NULL, flags); 231 232 /* 233 * Close all file descriptors. 234 */ 235 if (flags & RFCFDG) { 236 struct filedesc *fdtmp; 237 fdtmp = fdinit(td->td_proc->p_fd); 238 fdfree(td); 239 p1->p_fd = fdtmp; 240 } 241 242 /* 243 * Unshare file descriptors (from parent.) 244 */ 245 if (flags & RFFDG) { 246 FILEDESC_LOCK(p1->p_fd); 247 if (p1->p_fd->fd_refcnt > 1) { 248 struct filedesc *newfd; 249 250 newfd = fdcopy(td->td_proc->p_fd); 251 FILEDESC_UNLOCK(p1->p_fd); 252 fdfree(td); 253 p1->p_fd = newfd; 254 } else 255 FILEDESC_UNLOCK(p1->p_fd); 256 } 257 mtx_unlock(&Giant); 258 *procp = NULL; 259 return (0); 260 } 261 262 /* 263 * Note 1:1 allows for forking with one thread coming out on the 264 * other side with the expectation that the process is about to 265 * exec. 266 */ 267 if (p1->p_flag & P_THREADED) { 268 /* 269 * Idle the other threads for a second. 270 * Since the user space is copied, it must remain stable. 271 * In addition, all threads (from the user perspective) 272 * need to either be suspended or in the kernel, 273 * where they will try restart in the parent and will 274 * be aborted in the child. 275 */ 276 PROC_LOCK(p1); 277 if (thread_single(SINGLE_NO_EXIT)) { 278 /* Abort.. someone else is single threading before us */ 279 PROC_UNLOCK(p1); 280 mtx_unlock(&Giant); 281 return (ERESTART); 282 } 283 PROC_UNLOCK(p1); 284 /* 285 * All other activity in this process 286 * is now suspended at the user boundary, 287 * (or other safe places if we think of any). 288 */ 289 } 290 291 /* Allocate new proc. */ 292 newproc = uma_zalloc(proc_zone, M_WAITOK); 293#ifdef MAC 294 mac_init_proc(newproc); 295#endif 296 297 /* 298 * Although process entries are dynamically created, we still keep 299 * a global limit on the maximum number we will create. Don't allow 300 * a nonprivileged user to use the last ten processes; don't let root 301 * exceed the limit. The variable nprocs is the current number of 302 * processes, maxproc is the limit. 303 */ 304 sx_xlock(&allproc_lock); 305 uid = td->td_ucred->cr_ruid; 306 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 307 error = EAGAIN; 308 goto fail; 309 } 310 311 /* 312 * Increment the count of procs running with this uid. Don't allow 313 * a nonprivileged user to exceed their current limit. 314 */ 315 PROC_LOCK(p1); 316 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 317 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 318 PROC_UNLOCK(p1); 319 if (!ok) { 320 error = EAGAIN; 321 goto fail; 322 } 323 324 /* 325 * Increment the nprocs resource before blocking can occur. There 326 * are hard-limits as to the number of processes that can run. 327 */ 328 nprocs++; 329 330 /* 331 * Find an unused process ID. We remember a range of unused IDs 332 * ready to use (from lastpid+1 through pidchecked-1). 333 * 334 * If RFHIGHPID is set (used during system boot), do not allocate 335 * low-numbered pids. 336 */ 337 trypid = lastpid + 1; 338 if (flags & RFHIGHPID) { 339 if (trypid < 10) { 340 trypid = 10; 341 } 342 } else { 343 if (randompid) 344 trypid += arc4random() % randompid; 345 } 346retry: 347 /* 348 * If the process ID prototype has wrapped around, 349 * restart somewhat above 0, as the low-numbered procs 350 * tend to include daemons that don't exit. 351 */ 352 if (trypid >= PID_MAX) { 353 trypid = trypid % PID_MAX; 354 if (trypid < 100) 355 trypid += 100; 356 pidchecked = 0; 357 } 358 if (trypid >= pidchecked) { 359 int doingzomb = 0; 360 361 pidchecked = PID_MAX; 362 /* 363 * Scan the active and zombie procs to check whether this pid 364 * is in use. Remember the lowest pid that's greater 365 * than trypid, so we can avoid checking for a while. 366 */ 367 p2 = LIST_FIRST(&allproc); 368again: 369 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 370 PROC_LOCK(p2); 371 while (p2->p_pid == trypid || 372 p2->p_pgrp->pg_id == trypid || 373 p2->p_session->s_sid == trypid) { 374 trypid++; 375 if (trypid >= pidchecked) { 376 PROC_UNLOCK(p2); 377 goto retry; 378 } 379 } 380 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 381 pidchecked = p2->p_pid; 382 if (p2->p_pgrp->pg_id > trypid && 383 pidchecked > p2->p_pgrp->pg_id) 384 pidchecked = p2->p_pgrp->pg_id; 385 if (p2->p_session->s_sid > trypid && 386 pidchecked > p2->p_session->s_sid) 387 pidchecked = p2->p_session->s_sid; 388 PROC_UNLOCK(p2); 389 } 390 if (!doingzomb) { 391 doingzomb = 1; 392 p2 = LIST_FIRST(&zombproc); 393 goto again; 394 } 395 } 396 397 /* 398 * RFHIGHPID does not mess with the lastpid counter during boot. 399 */ 400 if (flags & RFHIGHPID) 401 pidchecked = 0; 402 else 403 lastpid = trypid; 404 405 p2 = newproc; 406 p2->p_state = PRS_NEW; /* protect against others */ 407 p2->p_pid = trypid; 408 LIST_INSERT_HEAD(&allproc, p2, p_list); 409 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 410 sx_xunlock(&allproc_lock); 411 412 /* 413 * Malloc things while we don't hold any locks. 414 */ 415 if (flags & RFSIGSHARE) { 416 MALLOC(newsigacts, struct sigacts *, 417 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 418 newprocsig = NULL; 419 } else { 420 newsigacts = NULL; 421 MALLOC(newprocsig, struct procsig *, sizeof(struct procsig), 422 M_SUBPROC, M_WAITOK); 423 } 424 425 /* 426 * Copy filedesc. 427 * XXX: This is busted. fd*() need to not take proc 428 * arguments or something. 429 */ 430 if (flags & RFCFDG) 431 fd = fdinit(td->td_proc->p_fd); 432 else if (flags & RFFDG) { 433 FILEDESC_LOCK(p1->p_fd); 434 fd = fdcopy(td->td_proc->p_fd); 435 FILEDESC_UNLOCK(p1->p_fd); 436 } else 437 fd = fdshare(p1->p_fd); 438 439 /* 440 * Make a proc table entry for the new process. 441 * Start by zeroing the section of proc that is zero-initialized, 442 * then copy the section that is copied directly from the parent. 443 */ 444 td2 = FIRST_THREAD_IN_PROC(p2); 445 kg2 = FIRST_KSEGRP_IN_PROC(p2); 446 ke2 = FIRST_KSE_IN_KSEGRP(kg2); 447 448 /* Allocate and switch to an alternate kstack if specified */ 449 if (pages != 0) 450 pmap_new_altkstack(td2, pages); 451 452#define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 453 454 bzero(&p2->p_startzero, 455 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 456 bzero(&ke2->ke_startzero, 457 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 458 bzero(&td2->td_startzero, 459 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 460 bzero(&kg2->kg_startzero, 461 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 462 463 mtx_init(&p2->p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 464 PROC_LOCK(p2); 465 PROC_LOCK(p1); 466 467 bcopy(&p1->p_startcopy, &p2->p_startcopy, 468 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 469 bcopy(&td->td_startcopy, &td2->td_startcopy, 470 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 471 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 472 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 473#undef RANGEOF 474 475 /* Set up the thread as an active thread (as if runnable). */ 476 ke2->ke_state = KES_THREAD; 477 ke2->ke_thread = td2; 478 td2->td_kse = ke2; 479 480 /* 481 * Duplicate sub-structures as needed. 482 * Increase reference counts on shared objects. 483 * The p_stats and p_sigacts substructs are set in vm_forkproc. 484 */ 485 p2->p_flag = 0; 486 if (p1->p_flag & P_PROFIL) 487 startprofclock(p2); 488 mtx_lock_spin(&sched_lock); 489 p2->p_sflag = PS_INMEM; 490 /* 491 * Allow the scheduler to adjust the priority of the child and 492 * parent while we hold the sched_lock. 493 */ 494 sched_fork(p1, p2); 495 496 mtx_unlock_spin(&sched_lock); 497 p2->p_ucred = crhold(td->td_ucred); 498 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 499 500 pargs_hold(p2->p_args); 501 502 if (flags & RFSIGSHARE) { 503 p2->p_procsig = p1->p_procsig; 504 p2->p_procsig->ps_refcnt++; 505 if (p1->p_sigacts == &p1->p_uarea->u_sigacts) { 506 /* 507 * Set p_sigacts to the new shared structure. 508 * Note that this is updating p1->p_sigacts at the 509 * same time, since p_sigacts is just a pointer to 510 * the shared p_procsig->ps_sigacts. 511 */ 512 p2->p_sigacts = newsigacts; 513 newsigacts = NULL; 514 *p2->p_sigacts = p1->p_uarea->u_sigacts; 515 } 516 } else { 517 p2->p_procsig = newprocsig; 518 newprocsig = NULL; 519 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 520 p2->p_procsig->ps_refcnt = 1; 521 p2->p_sigacts = NULL; /* finished in vm_forkproc() */ 522 } 523 if (flags & RFLINUXTHPN) 524 p2->p_sigparent = SIGUSR1; 525 else 526 p2->p_sigparent = SIGCHLD; 527 528 /* Bump references to the text vnode (for procfs) */ 529 p2->p_textvp = p1->p_textvp; 530 if (p2->p_textvp) 531 VREF(p2->p_textvp); 532 p2->p_fd = fd; 533 PROC_UNLOCK(p1); 534 PROC_UNLOCK(p2); 535 536 /* 537 * p_limit is copy-on-write, bump refcnt, 538 */ 539 p2->p_limit = p1->p_limit; 540 p2->p_limit->p_refcnt++; 541 542 /* 543 * Setup linkage for kernel based threading 544 */ 545 if((flags & RFTHREAD) != 0) { 546 mtx_lock(&ppeers_lock); 547 p2->p_peers = p1->p_peers; 548 p1->p_peers = p2; 549 p2->p_leader = p1->p_leader; 550 mtx_unlock(&ppeers_lock); 551 PROC_LOCK(p1->p_leader); 552 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 553 PROC_UNLOCK(p1->p_leader); 554 /* 555 * The task leader is exiting, so process p1 is 556 * going to be killed shortly. Since p1 obviously 557 * isn't dead yet, we know that the leader is either 558 * sending SIGKILL's to all the processes in this 559 * task or is sleeping waiting for all the peers to 560 * exit. We let p1 complete the fork, but we need 561 * to go ahead and kill the new process p2 since 562 * the task leader may not get a chance to send 563 * SIGKILL to it. We leave it on the list so that 564 * the task leader will wait for this new process 565 * to commit suicide. 566 */ 567 PROC_LOCK(p2); 568 psignal(p2, SIGKILL); 569 PROC_UNLOCK(p2); 570 } else 571 PROC_UNLOCK(p1->p_leader); 572 } else { 573 p2->p_peers = NULL; 574 p2->p_leader = p2; 575 } 576 577 sx_xlock(&proctree_lock); 578 PGRP_LOCK(p1->p_pgrp); 579 PROC_LOCK(p2); 580 PROC_LOCK(p1); 581 582 /* 583 * Preserve some more flags in subprocess. P_PROFIL has already 584 * been preserved. 585 */ 586 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 587 SESS_LOCK(p1->p_session); 588 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 589 p2->p_flag |= P_CONTROLT; 590 SESS_UNLOCK(p1->p_session); 591 if (flags & RFPPWAIT) 592 p2->p_flag |= P_PPWAIT; 593 594 LIST_INSERT_AFTER(p1, p2, p_pglist); 595 PGRP_UNLOCK(p1->p_pgrp); 596 LIST_INIT(&p2->p_children); 597 598 callout_init(&p2->p_itcallout, 1); 599 600#ifdef KTRACE 601 /* 602 * Copy traceflag and tracefile if enabled. 603 */ 604 mtx_lock(&ktrace_mtx); 605 KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); 606 if (p1->p_traceflag & KTRFAC_INHERIT) { 607 p2->p_traceflag = p1->p_traceflag; 608 if ((p2->p_tracevp = p1->p_tracevp) != NULL) { 609 VREF(p2->p_tracevp); 610 KASSERT(p1->p_tracecred != NULL, 611 ("ktrace vnode with no cred")); 612 p2->p_tracecred = crhold(p1->p_tracecred); 613 } 614 } 615 mtx_unlock(&ktrace_mtx); 616#endif 617 618 /* 619 * If PF_FORK is set, the child process inherits the 620 * procfs ioctl flags from its parent. 621 */ 622 if (p1->p_pfsflags & PF_FORK) { 623 p2->p_stops = p1->p_stops; 624 p2->p_pfsflags = p1->p_pfsflags; 625 } 626 627 /* 628 * This begins the section where we must prevent the parent 629 * from being swapped. 630 */ 631 _PHOLD(p1); 632 PROC_UNLOCK(p1); 633 634 /* 635 * Attach the new process to its parent. 636 * 637 * If RFNOWAIT is set, the newly created process becomes a child 638 * of init. This effectively disassociates the child from the 639 * parent. 640 */ 641 if (flags & RFNOWAIT) 642 pptr = initproc; 643 else 644 pptr = p1; 645 p2->p_pptr = pptr; 646 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 647 sx_xunlock(&proctree_lock); 648 649 /* Inform accounting that we have forked. */ 650 p2->p_acflag = AFORK; 651 PROC_UNLOCK(p2); 652 653 KASSERT(newprocsig == NULL, ("unused newprocsig")); 654 if (newsigacts != NULL) 655 FREE(newsigacts, M_SUBPROC); 656 /* 657 * Finish creating the child process. It will return via a different 658 * execution path later. (ie: directly into user mode) 659 */ 660 vm_forkproc(td, p2, td2, flags); 661 662 if (flags == (RFFDG | RFPROC)) { 663 cnt.v_forks++; 664 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 665 p2->p_vmspace->vm_ssize; 666 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 667 cnt.v_vforks++; 668 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 669 p2->p_vmspace->vm_ssize; 670 } else if (p1 == &proc0) { 671 cnt.v_kthreads++; 672 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 673 p2->p_vmspace->vm_ssize; 674 } else { 675 cnt.v_rforks++; 676 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 677 p2->p_vmspace->vm_ssize; 678 } 679 680 /* 681 * Both processes are set up, now check if any loadable modules want 682 * to adjust anything. 683 * What if they have an error? XXX 684 */ 685 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 686 687 /* 688 * If RFSTOPPED not requested, make child runnable and add to 689 * run queue. 690 */ 691 microtime(&(p2->p_stats->p_start)); 692 if ((flags & RFSTOPPED) == 0) { 693 mtx_lock_spin(&sched_lock); 694 p2->p_state = PRS_NORMAL; 695 TD_SET_CAN_RUN(td2); 696 setrunqueue(td2); 697 mtx_unlock_spin(&sched_lock); 698 } 699 700 /* 701 * Now can be swapped. 702 */ 703 PROC_LOCK(p1); 704 _PRELE(p1); 705 706 /* 707 * tell any interested parties about the new process 708 */ 709 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 710 PROC_UNLOCK(p1); 711 712 /* 713 * Preserve synchronization semantics of vfork. If waiting for 714 * child to exec or exit, set P_PPWAIT on child, and sleep on our 715 * proc (in case of exit). 716 */ 717 PROC_LOCK(p2); 718 while (p2->p_flag & P_PPWAIT) 719 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 720 PROC_UNLOCK(p2); 721 722 /* 723 * If other threads are waiting, let them continue now 724 */ 725 if (p1->p_flag & P_THREADED) { 726 PROC_LOCK(p1); 727 thread_single_end(); 728 PROC_UNLOCK(p1); 729 } 730 731 /* 732 * Return child proc pointer to parent. 733 */ 734 mtx_unlock(&Giant); 735 *procp = p2; 736 return (0); 737fail: 738 sx_xunlock(&allproc_lock); 739 uma_zfree(proc_zone, newproc); 740 if (p1->p_flag & P_THREADED) { 741 PROC_LOCK(p1); 742 thread_single_end(); 743 PROC_UNLOCK(p1); 744 } 745 tsleep(&forksleep, PUSER, "fork", hz / 2); 746 mtx_unlock(&Giant); 747 return (error); 748} 749 750/* 751 * Handle the return of a child process from fork1(). This function 752 * is called from the MD fork_trampoline() entry point. 753 */ 754void 755fork_exit(callout, arg, frame) 756 void (*callout)(void *, struct trapframe *); 757 void *arg; 758 struct trapframe *frame; 759{ 760 struct thread *td; 761 struct proc *p; 762 763 if ((td = PCPU_GET(deadthread))) { 764 PCPU_SET(deadthread, NULL); 765 thread_stash(td); 766 } 767 td = curthread; 768 p = td->td_proc; 769 td->td_oncpu = PCPU_GET(cpuid); 770 p->p_state = PRS_NORMAL; 771 /* 772 * Finish setting up thread glue. We need to initialize 773 * the thread into a td_critnest=1 state. Some platforms 774 * may have already partially or fully initialized td_critnest 775 * and/or td_md.md_savecrit (when applciable). 776 * 777 * see <arch>/<arch>/critical.c 778 */ 779 sched_lock.mtx_lock = (uintptr_t)td; 780 sched_lock.mtx_recurse = 0; 781 cpu_critical_fork_exit(); 782 CTR3(KTR_PROC, "fork_exit: new thread %p (pid %d, %s)", td, p->p_pid, 783 p->p_comm); 784 if (PCPU_GET(switchtime.sec) == 0) 785 binuptime(PCPU_PTR(switchtime)); 786 PCPU_SET(switchticks, ticks); 787 mtx_unlock_spin(&sched_lock); 788 789 /* 790 * cpu_set_fork_handler intercepts this function call to 791 * have this call a non-return function to stay in kernel mode. 792 * initproc has its own fork handler, but it does return. 793 */ 794 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 795 callout(arg, frame); 796 797 /* 798 * Check if a kernel thread misbehaved and returned from its main 799 * function. 800 */ 801 PROC_LOCK(p); 802 if (p->p_flag & P_KTHREAD) { 803 PROC_UNLOCK(p); 804 mtx_lock(&Giant); 805 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 806 p->p_comm, p->p_pid); 807 kthread_exit(0); 808 } 809 PROC_UNLOCK(p); 810#ifdef DIAGNOSTIC 811 cred_free_thread(td); 812#endif 813 mtx_assert(&Giant, MA_NOTOWNED); 814} 815 816/* 817 * Simplified back end of syscall(), used when returning from fork() 818 * directly into user mode. Giant is not held on entry, and must not 819 * be held on return. This function is passed in to fork_exit() as the 820 * first parameter and is called when returning to a new userland process. 821 */ 822void 823fork_return(td, frame) 824 struct thread *td; 825 struct trapframe *frame; 826{ 827 828 userret(td, frame, 0); 829#ifdef KTRACE 830 if (KTRPOINT(td, KTR_SYSRET)) 831 ktrsysret(SYS_fork, 0, 0); 832#endif 833 mtx_assert(&Giant, MA_NOTOWNED); 834}
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