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_ktrace.h" 41 #include "opt_kstack_pages.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/sysproto.h> 46 #include <sys/eventhandler.h> 47 #include <sys/fcntl.h> 48 #include <sys/filedesc.h> 49 #include <sys/jail.h> 50 #include <sys/kernel.h> 51 #include <sys/kthread.h> 52 #include <sys/sysctl.h> 53 #include <sys/lock.h> 54 #include <sys/malloc.h> 55 #include <sys/mutex.h> 56 #include <sys/priv.h> 57 #include <sys/proc.h> 58 #include <sys/procdesc.h> 59 #include <sys/pioctl.h> 60 #include <sys/racct.h> 61 #include <sys/resourcevar.h> 62 #include <sys/sched.h> 63 #include <sys/syscall.h> 64 #include <sys/vmmeter.h> 65 #include <sys/vnode.h> 66 #include <sys/acct.h> 67 #include <sys/ktr.h> 68 #include <sys/ktrace.h> 69 #include <sys/unistd.h> 70 #include <sys/sdt.h> 71 #include <sys/sx.h> 72 #include <sys/sysent.h> 73 #include <sys/signalvar.h> 74 75 #include <security/audit/audit.h> 76 #include <security/mac/mac_framework.h> 77 78 #include <vm/vm.h> 79 #include <vm/pmap.h> 80 #include <vm/vm_map.h> 81 #include <vm/vm_extern.h> 82 #include <vm/uma.h> 83 84 #ifdef KDTRACE_HOOKS 85 #include <sys/dtrace_bsd.h> 86 dtrace_fork_func_t dtrace_fasttrap_fork; 87 #endif 88 89 SDT_PROVIDER_DECLARE(proc); 90 SDT_PROBE_DEFINE3(proc, kernel, , create, "struct proc *", 91 "struct proc *", "int"); 92 93 #ifndef _SYS_SYSPROTO_H_ 94 struct fork_args { 95 int dummy; 96 }; 97 #endif 98 99 /* ARGSUSED */ 100 int 101 sys_fork(struct thread *td, struct fork_args *uap) 102 { 103 int error; 104 struct proc *p2; 105 106 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0); 107 if (error == 0) { 108 td->td_retval[0] = p2->p_pid; 109 td->td_retval[1] = 0; 110 } 111 return (error); 112 } 113 114 /* ARGUSED */ 115 int 116 sys_pdfork(td, uap) 117 struct thread *td; 118 struct pdfork_args *uap; 119 { 120 int error, fd; 121 struct proc *p2; 122 123 /* 124 * It is necessary to return fd by reference because 0 is a valid file 125 * descriptor number, and the child needs to be able to distinguish 126 * itself from the parent using the return value. 127 */ 128 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2, 129 &fd, uap->flags); 130 if (error == 0) { 131 td->td_retval[0] = p2->p_pid; 132 td->td_retval[1] = 0; 133 error = copyout(&fd, uap->fdp, sizeof(fd)); 134 } 135 return (error); 136 } 137 138 /* ARGSUSED */ 139 int 140 sys_vfork(struct thread *td, struct vfork_args *uap) 141 { 142 int error, flags; 143 struct proc *p2; 144 145 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 146 error = fork1(td, flags, 0, &p2, NULL, 0); 147 if (error == 0) { 148 td->td_retval[0] = p2->p_pid; 149 td->td_retval[1] = 0; 150 } 151 return (error); 152 } 153 154 int 155 sys_rfork(struct thread *td, struct rfork_args *uap) 156 { 157 struct proc *p2; 158 int error; 159 160 /* Don't allow kernel-only flags. */ 161 if ((uap->flags & RFKERNELONLY) != 0) 162 return (EINVAL); 163 164 AUDIT_ARG_FFLAGS(uap->flags); 165 error = fork1(td, uap->flags, 0, &p2, NULL, 0); 166 if (error == 0) { 167 td->td_retval[0] = p2 ? p2->p_pid : 0; 168 td->td_retval[1] = 0; 169 } 170 return (error); 171 } 172 173 int nprocs = 1; /* process 0 */ 174 int lastpid = 0; 175 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 176 "Last used PID"); 177 178 /* 179 * Random component to lastpid generation. We mix in a random factor to make 180 * it a little harder to predict. We sanity check the modulus value to avoid 181 * doing it in critical paths. Don't let it be too small or we pointlessly 182 * waste randomness entropy, and don't let it be impossibly large. Using a 183 * modulus that is too big causes a LOT more process table scans and slows 184 * down fork processing as the pidchecked caching is defeated. 185 */ 186 static int randompid = 0; 187 188 static int 189 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 190 { 191 int error, pid; 192 193 error = sysctl_wire_old_buffer(req, sizeof(int)); 194 if (error != 0) 195 return(error); 196 sx_xlock(&allproc_lock); 197 pid = randompid; 198 error = sysctl_handle_int(oidp, &pid, 0, req); 199 if (error == 0 && req->newptr != NULL) { 200 if (pid < 0 || pid > pid_max - 100) /* out of range */ 201 pid = pid_max - 100; 202 else if (pid < 2) /* NOP */ 203 pid = 0; 204 else if (pid < 100) /* Make it reasonable */ 205 pid = 100; 206 randompid = pid; 207 } 208 sx_xunlock(&allproc_lock); 209 return (error); 210 } 211 212 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 213 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 214 215 static int 216 fork_findpid(int flags) 217 { 218 struct proc *p; 219 int trypid; 220 static int pidchecked = 0; 221 222 /* 223 * Requires allproc_lock in order to iterate over the list 224 * of processes, and proctree_lock to access p_pgrp. 225 */ 226 sx_assert(&allproc_lock, SX_LOCKED); 227 sx_assert(&proctree_lock, SX_LOCKED); 228 229 /* 230 * Find an unused process ID. We remember a range of unused IDs 231 * ready to use (from lastpid+1 through pidchecked-1). 232 * 233 * If RFHIGHPID is set (used during system boot), do not allocate 234 * low-numbered pids. 235 */ 236 trypid = lastpid + 1; 237 if (flags & RFHIGHPID) { 238 if (trypid < 10) 239 trypid = 10; 240 } else { 241 if (randompid) 242 trypid += arc4random() % randompid; 243 } 244 retry: 245 /* 246 * If the process ID prototype has wrapped around, 247 * restart somewhat above 0, as the low-numbered procs 248 * tend to include daemons that don't exit. 249 */ 250 if (trypid >= pid_max) { 251 trypid = trypid % pid_max; 252 if (trypid < 100) 253 trypid += 100; 254 pidchecked = 0; 255 } 256 if (trypid >= pidchecked) { 257 int doingzomb = 0; 258 259 pidchecked = PID_MAX; 260 /* 261 * Scan the active and zombie procs to check whether this pid 262 * is in use. Remember the lowest pid that's greater 263 * than trypid, so we can avoid checking for a while. 264 * 265 * Avoid reuse of the process group id, session id or 266 * the reaper subtree id. Note that for process group 267 * and sessions, the amount of reserved pids is 268 * limited by process limit. For the subtree ids, the 269 * id is kept reserved only while there is a 270 * non-reaped process in the subtree, so amount of 271 * reserved pids is limited by process limit times 272 * two. 273 */ 274 p = LIST_FIRST(&allproc); 275 again: 276 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 277 while (p->p_pid == trypid || 278 p->p_reapsubtree == trypid || 279 (p->p_pgrp != NULL && 280 (p->p_pgrp->pg_id == trypid || 281 (p->p_session != NULL && 282 p->p_session->s_sid == trypid)))) { 283 trypid++; 284 if (trypid >= pidchecked) 285 goto retry; 286 } 287 if (p->p_pid > trypid && pidchecked > p->p_pid) 288 pidchecked = p->p_pid; 289 if (p->p_pgrp != NULL) { 290 if (p->p_pgrp->pg_id > trypid && 291 pidchecked > p->p_pgrp->pg_id) 292 pidchecked = p->p_pgrp->pg_id; 293 if (p->p_session != NULL && 294 p->p_session->s_sid > trypid && 295 pidchecked > p->p_session->s_sid) 296 pidchecked = p->p_session->s_sid; 297 } 298 } 299 if (!doingzomb) { 300 doingzomb = 1; 301 p = LIST_FIRST(&zombproc); 302 goto again; 303 } 304 } 305 306 /* 307 * RFHIGHPID does not mess with the lastpid counter during boot. 308 */ 309 if (flags & RFHIGHPID) 310 pidchecked = 0; 311 else 312 lastpid = trypid; 313 314 return (trypid); 315 } 316 317 static int 318 fork_norfproc(struct thread *td, int flags) 319 { 320 int error; 321 struct proc *p1; 322 323 KASSERT((flags & RFPROC) == 0, 324 ("fork_norfproc called with RFPROC set")); 325 p1 = td->td_proc; 326 327 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 328 (flags & (RFCFDG | RFFDG))) { 329 PROC_LOCK(p1); 330 if (thread_single(p1, SINGLE_BOUNDARY)) { 331 PROC_UNLOCK(p1); 332 return (ERESTART); 333 } 334 PROC_UNLOCK(p1); 335 } 336 337 error = vm_forkproc(td, NULL, NULL, NULL, flags); 338 if (error) 339 goto fail; 340 341 /* 342 * Close all file descriptors. 343 */ 344 if (flags & RFCFDG) { 345 struct filedesc *fdtmp; 346 fdtmp = fdinit(td->td_proc->p_fd, false); 347 fdescfree(td); 348 p1->p_fd = fdtmp; 349 } 350 351 /* 352 * Unshare file descriptors (from parent). 353 */ 354 if (flags & RFFDG) 355 fdunshare(td); 356 357 fail: 358 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 359 (flags & (RFCFDG | RFFDG))) { 360 PROC_LOCK(p1); 361 thread_single_end(p1, SINGLE_BOUNDARY); 362 PROC_UNLOCK(p1); 363 } 364 return (error); 365 } 366 367 static void 368 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, 369 struct vmspace *vm2, int pdflags) 370 { 371 struct proc *p1, *pptr; 372 int p2_held, trypid; 373 struct filedesc *fd; 374 struct filedesc_to_leader *fdtol; 375 struct sigacts *newsigacts; 376 377 sx_assert(&proctree_lock, SX_SLOCKED); 378 sx_assert(&allproc_lock, SX_XLOCKED); 379 380 p2_held = 0; 381 p1 = td->td_proc; 382 383 /* 384 * Increment the nprocs resource before blocking can occur. There 385 * are hard-limits as to the number of processes that can run. 386 */ 387 nprocs++; 388 389 trypid = fork_findpid(flags); 390 391 sx_sunlock(&proctree_lock); 392 393 p2->p_state = PRS_NEW; /* protect against others */ 394 p2->p_pid = trypid; 395 AUDIT_ARG_PID(p2->p_pid); 396 LIST_INSERT_HEAD(&allproc, p2, p_list); 397 allproc_gen++; 398 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 399 tidhash_add(td2); 400 PROC_LOCK(p2); 401 PROC_LOCK(p1); 402 403 sx_xunlock(&allproc_lock); 404 405 bcopy(&p1->p_startcopy, &p2->p_startcopy, 406 __rangeof(struct proc, p_startcopy, p_endcopy)); 407 pargs_hold(p2->p_args); 408 PROC_UNLOCK(p1); 409 410 bzero(&p2->p_startzero, 411 __rangeof(struct proc, p_startzero, p_endzero)); 412 413 /* Tell the prison that we exist. */ 414 prison_proc_hold(p2->p_ucred->cr_prison); 415 416 PROC_UNLOCK(p2); 417 418 /* 419 * Malloc things while we don't hold any locks. 420 */ 421 if (flags & RFSIGSHARE) 422 newsigacts = NULL; 423 else 424 newsigacts = sigacts_alloc(); 425 426 /* 427 * Copy filedesc. 428 */ 429 if (flags & RFCFDG) { 430 fd = fdinit(p1->p_fd, false); 431 fdtol = NULL; 432 } else if (flags & RFFDG) { 433 fd = fdcopy(p1->p_fd); 434 fdtol = NULL; 435 } else { 436 fd = fdshare(p1->p_fd); 437 if (p1->p_fdtol == NULL) 438 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 439 p1->p_leader); 440 if ((flags & RFTHREAD) != 0) { 441 /* 442 * Shared file descriptor table, and shared 443 * process leaders. 444 */ 445 fdtol = p1->p_fdtol; 446 FILEDESC_XLOCK(p1->p_fd); 447 fdtol->fdl_refcount++; 448 FILEDESC_XUNLOCK(p1->p_fd); 449 } else { 450 /* 451 * Shared file descriptor table, and different 452 * process leaders. 453 */ 454 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 455 p1->p_fd, p2); 456 } 457 } 458 /* 459 * Make a proc table entry for the new process. 460 * Start by zeroing the section of proc that is zero-initialized, 461 * then copy the section that is copied directly from the parent. 462 */ 463 464 PROC_LOCK(p2); 465 PROC_LOCK(p1); 466 467 bzero(&td2->td_startzero, 468 __rangeof(struct thread, td_startzero, td_endzero)); 469 470 bcopy(&td->td_startcopy, &td2->td_startcopy, 471 __rangeof(struct thread, td_startcopy, td_endcopy)); 472 473 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 474 td2->td_sigstk = td->td_sigstk; 475 td2->td_flags = TDF_INMEM; 476 td2->td_lend_user_pri = PRI_MAX; 477 478 #ifdef VIMAGE 479 td2->td_vnet = NULL; 480 td2->td_vnet_lpush = NULL; 481 #endif 482 483 /* 484 * Allow the scheduler to initialize the child. 485 */ 486 thread_lock(td); 487 sched_fork(td, td2); 488 thread_unlock(td); 489 490 /* 491 * Duplicate sub-structures as needed. 492 * Increase reference counts on shared objects. 493 */ 494 p2->p_flag = P_INMEM; 495 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC); 496 p2->p_swtick = ticks; 497 if (p1->p_flag & P_PROFIL) 498 startprofclock(p2); 499 td2->td_ucred = crhold(p2->p_ucred); 500 501 if (flags & RFSIGSHARE) { 502 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 503 } else { 504 sigacts_copy(newsigacts, p1->p_sigacts); 505 p2->p_sigacts = newsigacts; 506 } 507 508 if (flags & RFTSIGZMB) 509 p2->p_sigparent = RFTSIGNUM(flags); 510 else if (flags & RFLINUXTHPN) 511 p2->p_sigparent = SIGUSR1; 512 else 513 p2->p_sigparent = SIGCHLD; 514 515 p2->p_textvp = p1->p_textvp; 516 p2->p_fd = fd; 517 p2->p_fdtol = fdtol; 518 519 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 520 p2->p_flag |= P_PROTECTED; 521 p2->p_flag2 |= P2_INHERIT_PROTECTED; 522 } 523 524 /* 525 * p_limit is copy-on-write. Bump its refcount. 526 */ 527 lim_fork(p1, p2); 528 529 pstats_fork(p1->p_stats, p2->p_stats); 530 531 PROC_UNLOCK(p1); 532 PROC_UNLOCK(p2); 533 534 /* Bump references to the text vnode (for procfs). */ 535 if (p2->p_textvp) 536 vref(p2->p_textvp); 537 538 /* 539 * Set up linkage for kernel based threading. 540 */ 541 if ((flags & RFTHREAD) != 0) { 542 mtx_lock(&ppeers_lock); 543 p2->p_peers = p1->p_peers; 544 p1->p_peers = p2; 545 p2->p_leader = p1->p_leader; 546 mtx_unlock(&ppeers_lock); 547 PROC_LOCK(p1->p_leader); 548 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 549 PROC_UNLOCK(p1->p_leader); 550 /* 551 * The task leader is exiting, so process p1 is 552 * going to be killed shortly. Since p1 obviously 553 * isn't dead yet, we know that the leader is either 554 * sending SIGKILL's to all the processes in this 555 * task or is sleeping waiting for all the peers to 556 * exit. We let p1 complete the fork, but we need 557 * to go ahead and kill the new process p2 since 558 * the task leader may not get a chance to send 559 * SIGKILL to it. We leave it on the list so that 560 * the task leader will wait for this new process 561 * to commit suicide. 562 */ 563 PROC_LOCK(p2); 564 kern_psignal(p2, SIGKILL); 565 PROC_UNLOCK(p2); 566 } else 567 PROC_UNLOCK(p1->p_leader); 568 } else { 569 p2->p_peers = NULL; 570 p2->p_leader = p2; 571 } 572 573 sx_xlock(&proctree_lock); 574 PGRP_LOCK(p1->p_pgrp); 575 PROC_LOCK(p2); 576 PROC_LOCK(p1); 577 578 /* 579 * Preserve some more flags in subprocess. P_PROFIL has already 580 * been preserved. 581 */ 582 p2->p_flag |= p1->p_flag & P_SUGID; 583 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 584 SESS_LOCK(p1->p_session); 585 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 586 p2->p_flag |= P_CONTROLT; 587 SESS_UNLOCK(p1->p_session); 588 if (flags & RFPPWAIT) 589 p2->p_flag |= P_PPWAIT; 590 591 p2->p_pgrp = p1->p_pgrp; 592 LIST_INSERT_AFTER(p1, p2, p_pglist); 593 PGRP_UNLOCK(p1->p_pgrp); 594 LIST_INIT(&p2->p_children); 595 LIST_INIT(&p2->p_orphans); 596 597 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 598 599 /* 600 * If PF_FORK is set, the child process inherits the 601 * procfs ioctl flags from its parent. 602 */ 603 if (p1->p_pfsflags & PF_FORK) { 604 p2->p_stops = p1->p_stops; 605 p2->p_pfsflags = p1->p_pfsflags; 606 } 607 608 /* 609 * This begins the section where we must prevent the parent 610 * from being swapped. 611 */ 612 _PHOLD(p1); 613 PROC_UNLOCK(p1); 614 615 /* 616 * Attach the new process to its parent. 617 * 618 * If RFNOWAIT is set, the newly created process becomes a child 619 * of init. This effectively disassociates the child from the 620 * parent. 621 */ 622 if ((flags & RFNOWAIT) != 0) { 623 pptr = p1->p_reaper; 624 p2->p_reaper = pptr; 625 } else { 626 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 627 p1 : p1->p_reaper; 628 pptr = p1; 629 } 630 p2->p_pptr = pptr; 631 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 632 LIST_INIT(&p2->p_reaplist); 633 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 634 if (p2->p_reaper == p1) 635 p2->p_reapsubtree = p2->p_pid; 636 sx_xunlock(&proctree_lock); 637 638 /* Inform accounting that we have forked. */ 639 p2->p_acflag = AFORK; 640 PROC_UNLOCK(p2); 641 642 #ifdef KTRACE 643 ktrprocfork(p1, p2); 644 #endif 645 646 /* 647 * Finish creating the child process. It will return via a different 648 * execution path later. (ie: directly into user mode) 649 */ 650 vm_forkproc(td, p2, td2, vm2, flags); 651 652 if (flags == (RFFDG | RFPROC)) { 653 PCPU_INC(cnt.v_forks); 654 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 655 p2->p_vmspace->vm_ssize); 656 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 657 PCPU_INC(cnt.v_vforks); 658 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 659 p2->p_vmspace->vm_ssize); 660 } else if (p1 == &proc0) { 661 PCPU_INC(cnt.v_kthreads); 662 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 663 p2->p_vmspace->vm_ssize); 664 } else { 665 PCPU_INC(cnt.v_rforks); 666 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 667 p2->p_vmspace->vm_ssize); 668 } 669 670 /* 671 * Associate the process descriptor with the process before anything 672 * can happen that might cause that process to need the descriptor. 673 * However, don't do this until after fork(2) can no longer fail. 674 */ 675 if (flags & RFPROCDESC) 676 procdesc_new(p2, pdflags); 677 678 /* 679 * Both processes are set up, now check if any loadable modules want 680 * to adjust anything. 681 */ 682 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 683 684 /* 685 * Set the child start time and mark the process as being complete. 686 */ 687 PROC_LOCK(p2); 688 PROC_LOCK(p1); 689 microuptime(&p2->p_stats->p_start); 690 PROC_SLOCK(p2); 691 p2->p_state = PRS_NORMAL; 692 PROC_SUNLOCK(p2); 693 694 #ifdef KDTRACE_HOOKS 695 /* 696 * Tell the DTrace fasttrap provider about the new process so that any 697 * tracepoints inherited from the parent can be removed. We have to do 698 * this only after p_state is PRS_NORMAL since the fasttrap module will 699 * use pfind() later on. 700 */ 701 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork) 702 dtrace_fasttrap_fork(p1, p2); 703 #endif 704 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 705 P_FOLLOWFORK)) { 706 /* 707 * Arrange for debugger to receive the fork event. 708 * 709 * We can report PL_FLAG_FORKED regardless of 710 * P_FOLLOWFORK settings, but it does not make a sense 711 * for runaway child. 712 */ 713 td->td_dbgflags |= TDB_FORK; 714 td->td_dbg_forked = p2->p_pid; 715 td2->td_dbgflags |= TDB_STOPATFORK; 716 _PHOLD(p2); 717 p2_held = 1; 718 } 719 if (flags & RFPPWAIT) { 720 td->td_pflags |= TDP_RFPPWAIT; 721 td->td_rfppwait_p = p2; 722 } 723 PROC_UNLOCK(p2); 724 if ((flags & RFSTOPPED) == 0) { 725 /* 726 * If RFSTOPPED not requested, make child runnable and 727 * add to run queue. 728 */ 729 thread_lock(td2); 730 TD_SET_CAN_RUN(td2); 731 sched_add(td2, SRQ_BORING); 732 thread_unlock(td2); 733 } 734 735 /* 736 * Now can be swapped. 737 */ 738 _PRELE(p1); 739 PROC_UNLOCK(p1); 740 741 /* 742 * Tell any interested parties about the new process. 743 */ 744 knote_fork(&p1->p_klist, p2->p_pid); 745 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 746 747 /* 748 * Wait until debugger is attached to child. 749 */ 750 PROC_LOCK(p2); 751 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 752 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 753 if (p2_held) 754 _PRELE(p2); 755 PROC_UNLOCK(p2); 756 } 757 758 int 759 fork1(struct thread *td, int flags, int pages, struct proc **procp, 760 int *procdescp, int pdflags) 761 { 762 struct proc *p1; 763 struct proc *newproc; 764 int ok; 765 struct thread *td2; 766 struct vmspace *vm2; 767 vm_ooffset_t mem_charged; 768 int error; 769 static int curfail; 770 static struct timeval lastfail; 771 struct file *fp_procdesc = NULL; 772 773 /* Check for the undefined or unimplemented flags. */ 774 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 775 return (EINVAL); 776 777 /* Signal value requires RFTSIGZMB. */ 778 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 779 return (EINVAL); 780 781 /* Can't copy and clear. */ 782 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 783 return (EINVAL); 784 785 /* Check the validity of the signal number. */ 786 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 787 return (EINVAL); 788 789 if ((flags & RFPROCDESC) != 0) { 790 /* Can't not create a process yet get a process descriptor. */ 791 if ((flags & RFPROC) == 0) 792 return (EINVAL); 793 794 /* Must provide a place to put a procdesc if creating one. */ 795 if (procdescp == NULL) 796 return (EINVAL); 797 } 798 799 p1 = td->td_proc; 800 801 /* 802 * Here we don't create a new process, but we divorce 803 * certain parts of a process from itself. 804 */ 805 if ((flags & RFPROC) == 0) { 806 *procp = NULL; 807 return (fork_norfproc(td, flags)); 808 } 809 810 /* 811 * If required, create a process descriptor in the parent first; we 812 * will abandon it if something goes wrong. We don't finit() until 813 * later. 814 */ 815 if (flags & RFPROCDESC) { 816 error = falloc(td, &fp_procdesc, procdescp, 0); 817 if (error != 0) 818 return (error); 819 } 820 821 mem_charged = 0; 822 vm2 = NULL; 823 if (pages == 0) 824 pages = KSTACK_PAGES; 825 /* Allocate new proc. */ 826 newproc = uma_zalloc(proc_zone, M_WAITOK); 827 td2 = FIRST_THREAD_IN_PROC(newproc); 828 if (td2 == NULL) { 829 td2 = thread_alloc(pages); 830 if (td2 == NULL) { 831 error = ENOMEM; 832 goto fail2; 833 } 834 proc_linkup(newproc, td2); 835 } else { 836 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 837 if (td2->td_kstack != 0) 838 vm_thread_dispose(td2); 839 if (!thread_alloc_stack(td2, pages)) { 840 error = ENOMEM; 841 goto fail2; 842 } 843 } 844 } 845 846 if ((flags & RFMEM) == 0) { 847 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 848 if (vm2 == NULL) { 849 error = ENOMEM; 850 goto fail2; 851 } 852 if (!swap_reserve(mem_charged)) { 853 /* 854 * The swap reservation failed. The accounting 855 * from the entries of the copied vm2 will be 856 * substracted in vmspace_free(), so force the 857 * reservation there. 858 */ 859 swap_reserve_force(mem_charged); 860 error = ENOMEM; 861 goto fail2; 862 } 863 } else 864 vm2 = NULL; 865 866 /* 867 * XXX: This is ugly; when we copy resource usage, we need to bump 868 * per-cred resource counters. 869 */ 870 proc_set_cred_init(newproc, crhold(td->td_ucred)); 871 872 /* 873 * Initialize resource accounting for the child process. 874 */ 875 error = racct_proc_fork(p1, newproc); 876 if (error != 0) { 877 error = EAGAIN; 878 goto fail1; 879 } 880 881 #ifdef MAC 882 mac_proc_init(newproc); 883 #endif 884 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 885 STAILQ_INIT(&newproc->p_ktr); 886 887 /* We have to lock the process tree while we look for a pid. */ 888 sx_slock(&proctree_lock); 889 890 /* 891 * Although process entries are dynamically created, we still keep 892 * a global limit on the maximum number we will create. Don't allow 893 * a nonprivileged user to use the last ten processes; don't let root 894 * exceed the limit. The variable nprocs is the current number of 895 * processes, maxproc is the limit. 896 */ 897 sx_xlock(&allproc_lock); 898 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 899 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 900 error = EAGAIN; 901 goto fail; 902 } 903 904 /* 905 * Increment the count of procs running with this uid. Don't allow 906 * a nonprivileged user to exceed their current limit. 907 * 908 * XXXRW: Can we avoid privilege here if it's not needed? 909 */ 910 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 911 if (error == 0) 912 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 913 else { 914 PROC_LOCK(p1); 915 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 916 lim_cur(p1, RLIMIT_NPROC)); 917 PROC_UNLOCK(p1); 918 } 919 if (ok) { 920 do_fork(td, flags, newproc, td2, vm2, pdflags); 921 922 /* 923 * Return child proc pointer to parent. 924 */ 925 *procp = newproc; 926 if (flags & RFPROCDESC) { 927 procdesc_finit(newproc->p_procdesc, fp_procdesc); 928 fdrop(fp_procdesc, td); 929 } 930 racct_proc_fork_done(newproc); 931 return (0); 932 } 933 934 error = EAGAIN; 935 fail: 936 sx_sunlock(&proctree_lock); 937 if (ppsratecheck(&lastfail, &curfail, 1)) 938 printf("maxproc limit exceeded by uid %u (pid %d); see tuning(7) and login.conf(5)\n", 939 td->td_ucred->cr_ruid, p1->p_pid); 940 sx_xunlock(&allproc_lock); 941 #ifdef MAC 942 mac_proc_destroy(newproc); 943 #endif 944 racct_proc_exit(newproc); 945 fail1: 946 crfree(proc_set_cred(newproc, NULL)); 947 fail2: 948 if (vm2 != NULL) 949 vmspace_free(vm2); 950 uma_zfree(proc_zone, newproc); 951 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 952 fdclose(td, fp_procdesc, *procdescp); 953 fdrop(fp_procdesc, td); 954 } 955 pause("fork", hz / 2); 956 return (error); 957 } 958 959 /* 960 * Handle the return of a child process from fork1(). This function 961 * is called from the MD fork_trampoline() entry point. 962 */ 963 void 964 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 965 struct trapframe *frame) 966 { 967 struct proc *p; 968 struct thread *td; 969 struct thread *dtd; 970 971 td = curthread; 972 p = td->td_proc; 973 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 974 975 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 976 td, td->td_sched, p->p_pid, td->td_name); 977 978 sched_fork_exit(td); 979 /* 980 * Processes normally resume in mi_switch() after being 981 * cpu_switch()'ed to, but when children start up they arrive here 982 * instead, so we must do much the same things as mi_switch() would. 983 */ 984 if ((dtd = PCPU_GET(deadthread))) { 985 PCPU_SET(deadthread, NULL); 986 thread_stash(dtd); 987 } 988 thread_unlock(td); 989 990 /* 991 * cpu_set_fork_handler intercepts this function call to 992 * have this call a non-return function to stay in kernel mode. 993 * initproc has its own fork handler, but it does return. 994 */ 995 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 996 callout(arg, frame); 997 998 /* 999 * Check if a kernel thread misbehaved and returned from its main 1000 * function. 1001 */ 1002 if (p->p_flag & P_KTHREAD) { 1003 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1004 td->td_name, p->p_pid); 1005 kproc_exit(0); 1006 } 1007 mtx_assert(&Giant, MA_NOTOWNED); 1008 1009 if (p->p_sysent->sv_schedtail != NULL) 1010 (p->p_sysent->sv_schedtail)(td); 1011 } 1012 1013 /* 1014 * Simplified back end of syscall(), used when returning from fork() 1015 * directly into user mode. Giant is not held on entry, and must not 1016 * be held on return. This function is passed in to fork_exit() as the 1017 * first parameter and is called when returning to a new userland process. 1018 */ 1019 void 1020 fork_return(struct thread *td, struct trapframe *frame) 1021 { 1022 struct proc *p, *dbg; 1023 1024 if (td->td_dbgflags & TDB_STOPATFORK) { 1025 p = td->td_proc; 1026 sx_xlock(&proctree_lock); 1027 PROC_LOCK(p); 1028 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 1029 (P_TRACED | P_FOLLOWFORK)) { 1030 /* 1031 * If debugger still wants auto-attach for the 1032 * parent's children, do it now. 1033 */ 1034 dbg = p->p_pptr->p_pptr; 1035 p->p_flag |= P_TRACED; 1036 p->p_oppid = p->p_pptr->p_pid; 1037 proc_reparent(p, dbg); 1038 sx_xunlock(&proctree_lock); 1039 td->td_dbgflags |= TDB_CHILD; 1040 ptracestop(td, SIGSTOP); 1041 td->td_dbgflags &= ~TDB_CHILD; 1042 } else { 1043 /* 1044 * ... otherwise clear the request. 1045 */ 1046 sx_xunlock(&proctree_lock); 1047 td->td_dbgflags &= ~TDB_STOPATFORK; 1048 cv_broadcast(&p->p_dbgwait); 1049 } 1050 PROC_UNLOCK(p); 1051 } 1052 1053 userret(td, frame); 1054 1055 #ifdef KTRACE 1056 if (KTRPOINT(td, KTR_SYSRET)) 1057 ktrsysret(SYS_fork, 0, 0); 1058 #endif 1059 } 1060