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 #include <vm/vm_domain.h> 84 85 #ifdef KDTRACE_HOOKS 86 #include <sys/dtrace_bsd.h> 87 dtrace_fork_func_t dtrace_fasttrap_fork; 88 #endif 89 90 SDT_PROVIDER_DECLARE(proc); 91 SDT_PROBE_DEFINE3(proc, kernel, , create, "struct proc *", 92 "struct proc *", "int"); 93 94 #ifndef _SYS_SYSPROTO_H_ 95 struct fork_args { 96 int dummy; 97 }; 98 #endif 99 100 /* ARGSUSED */ 101 int 102 sys_fork(struct thread *td, struct fork_args *uap) 103 { 104 int error; 105 struct proc *p2; 106 107 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0); 108 if (error == 0) { 109 td->td_retval[0] = p2->p_pid; 110 td->td_retval[1] = 0; 111 } 112 return (error); 113 } 114 115 /* ARGUSED */ 116 int 117 sys_pdfork(td, uap) 118 struct thread *td; 119 struct pdfork_args *uap; 120 { 121 int error, fd; 122 struct proc *p2; 123 124 /* 125 * It is necessary to return fd by reference because 0 is a valid file 126 * descriptor number, and the child needs to be able to distinguish 127 * itself from the parent using the return value. 128 */ 129 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2, 130 &fd, uap->flags); 131 if (error == 0) { 132 td->td_retval[0] = p2->p_pid; 133 td->td_retval[1] = 0; 134 error = copyout(&fd, uap->fdp, sizeof(fd)); 135 } 136 return (error); 137 } 138 139 /* ARGSUSED */ 140 int 141 sys_vfork(struct thread *td, struct vfork_args *uap) 142 { 143 int error, flags; 144 struct proc *p2; 145 146 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 147 error = fork1(td, flags, 0, &p2, NULL, 0); 148 if (error == 0) { 149 td->td_retval[0] = p2->p_pid; 150 td->td_retval[1] = 0; 151 } 152 return (error); 153 } 154 155 int 156 sys_rfork(struct thread *td, struct rfork_args *uap) 157 { 158 struct proc *p2; 159 int error; 160 161 /* Don't allow kernel-only flags. */ 162 if ((uap->flags & RFKERNELONLY) != 0) 163 return (EINVAL); 164 165 AUDIT_ARG_FFLAGS(uap->flags); 166 error = fork1(td, uap->flags, 0, &p2, NULL, 0); 167 if (error == 0) { 168 td->td_retval[0] = p2 ? p2->p_pid : 0; 169 td->td_retval[1] = 0; 170 } 171 return (error); 172 } 173 174 int nprocs = 1; /* process 0 */ 175 int lastpid = 0; 176 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 177 "Last used PID"); 178 179 /* 180 * Random component to lastpid generation. We mix in a random factor to make 181 * it a little harder to predict. We sanity check the modulus value to avoid 182 * doing it in critical paths. Don't let it be too small or we pointlessly 183 * waste randomness entropy, and don't let it be impossibly large. Using a 184 * modulus that is too big causes a LOT more process table scans and slows 185 * down fork processing as the pidchecked caching is defeated. 186 */ 187 static int randompid = 0; 188 189 static int 190 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 191 { 192 int error, pid; 193 194 error = sysctl_wire_old_buffer(req, sizeof(int)); 195 if (error != 0) 196 return(error); 197 sx_xlock(&allproc_lock); 198 pid = randompid; 199 error = sysctl_handle_int(oidp, &pid, 0, req); 200 if (error == 0 && req->newptr != NULL) { 201 if (pid < 0 || pid > pid_max - 100) /* out of range */ 202 pid = pid_max - 100; 203 else if (pid < 2) /* NOP */ 204 pid = 0; 205 else if (pid < 100) /* Make it reasonable */ 206 pid = 100; 207 randompid = pid; 208 } 209 sx_xunlock(&allproc_lock); 210 return (error); 211 } 212 213 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 214 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 215 216 static int 217 fork_findpid(int flags) 218 { 219 struct proc *p; 220 int trypid; 221 static int pidchecked = 0; 222 223 /* 224 * Requires allproc_lock in order to iterate over the list 225 * of processes, and proctree_lock to access p_pgrp. 226 */ 227 sx_assert(&allproc_lock, SX_LOCKED); 228 sx_assert(&proctree_lock, SX_LOCKED); 229 230 /* 231 * Find an unused process ID. We remember a range of unused IDs 232 * ready to use (from lastpid+1 through pidchecked-1). 233 * 234 * If RFHIGHPID is set (used during system boot), do not allocate 235 * low-numbered pids. 236 */ 237 trypid = lastpid + 1; 238 if (flags & RFHIGHPID) { 239 if (trypid < 10) 240 trypid = 10; 241 } else { 242 if (randompid) 243 trypid += arc4random() % randompid; 244 } 245 retry: 246 /* 247 * If the process ID prototype has wrapped around, 248 * restart somewhat above 0, as the low-numbered procs 249 * tend to include daemons that don't exit. 250 */ 251 if (trypid >= pid_max) { 252 trypid = trypid % pid_max; 253 if (trypid < 100) 254 trypid += 100; 255 pidchecked = 0; 256 } 257 if (trypid >= pidchecked) { 258 int doingzomb = 0; 259 260 pidchecked = PID_MAX; 261 /* 262 * Scan the active and zombie procs to check whether this pid 263 * is in use. Remember the lowest pid that's greater 264 * than trypid, so we can avoid checking for a while. 265 * 266 * Avoid reuse of the process group id, session id or 267 * the reaper subtree id. Note that for process group 268 * and sessions, the amount of reserved pids is 269 * limited by process limit. For the subtree ids, the 270 * id is kept reserved only while there is a 271 * non-reaped process in the subtree, so amount of 272 * reserved pids is limited by process limit times 273 * two. 274 */ 275 p = LIST_FIRST(&allproc); 276 again: 277 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 278 while (p->p_pid == trypid || 279 p->p_reapsubtree == trypid || 280 (p->p_pgrp != NULL && 281 (p->p_pgrp->pg_id == trypid || 282 (p->p_session != NULL && 283 p->p_session->s_sid == trypid)))) { 284 trypid++; 285 if (trypid >= pidchecked) 286 goto retry; 287 } 288 if (p->p_pid > trypid && pidchecked > p->p_pid) 289 pidchecked = p->p_pid; 290 if (p->p_pgrp != NULL) { 291 if (p->p_pgrp->pg_id > trypid && 292 pidchecked > p->p_pgrp->pg_id) 293 pidchecked = p->p_pgrp->pg_id; 294 if (p->p_session != NULL && 295 p->p_session->s_sid > trypid && 296 pidchecked > p->p_session->s_sid) 297 pidchecked = p->p_session->s_sid; 298 } 299 } 300 if (!doingzomb) { 301 doingzomb = 1; 302 p = LIST_FIRST(&zombproc); 303 goto again; 304 } 305 } 306 307 /* 308 * RFHIGHPID does not mess with the lastpid counter during boot. 309 */ 310 if (flags & RFHIGHPID) 311 pidchecked = 0; 312 else 313 lastpid = trypid; 314 315 return (trypid); 316 } 317 318 static int 319 fork_norfproc(struct thread *td, int flags) 320 { 321 int error; 322 struct proc *p1; 323 324 KASSERT((flags & RFPROC) == 0, 325 ("fork_norfproc called with RFPROC set")); 326 p1 = td->td_proc; 327 328 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 329 (flags & (RFCFDG | RFFDG))) { 330 PROC_LOCK(p1); 331 if (thread_single(p1, SINGLE_BOUNDARY)) { 332 PROC_UNLOCK(p1); 333 return (ERESTART); 334 } 335 PROC_UNLOCK(p1); 336 } 337 338 error = vm_forkproc(td, NULL, NULL, NULL, flags); 339 if (error) 340 goto fail; 341 342 /* 343 * Close all file descriptors. 344 */ 345 if (flags & RFCFDG) { 346 struct filedesc *fdtmp; 347 fdtmp = fdinit(td->td_proc->p_fd, false); 348 fdescfree(td); 349 p1->p_fd = fdtmp; 350 } 351 352 /* 353 * Unshare file descriptors (from parent). 354 */ 355 if (flags & RFFDG) 356 fdunshare(td); 357 358 fail: 359 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 360 (flags & (RFCFDG | RFFDG))) { 361 PROC_LOCK(p1); 362 thread_single_end(p1, SINGLE_BOUNDARY); 363 PROC_UNLOCK(p1); 364 } 365 return (error); 366 } 367 368 static void 369 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, 370 struct vmspace *vm2, int pdflags) 371 { 372 struct proc *p1, *pptr; 373 int p2_held, trypid; 374 struct filedesc *fd; 375 struct filedesc_to_leader *fdtol; 376 struct sigacts *newsigacts; 377 378 sx_assert(&proctree_lock, SX_SLOCKED); 379 sx_assert(&allproc_lock, SX_XLOCKED); 380 381 p2_held = 0; 382 p1 = td->td_proc; 383 384 /* 385 * Increment the nprocs resource before blocking can occur. There 386 * are hard-limits as to the number of processes that can run. 387 */ 388 nprocs++; 389 390 trypid = fork_findpid(flags); 391 392 sx_sunlock(&proctree_lock); 393 394 p2->p_state = PRS_NEW; /* protect against others */ 395 p2->p_pid = trypid; 396 AUDIT_ARG_PID(p2->p_pid); 397 LIST_INSERT_HEAD(&allproc, p2, p_list); 398 allproc_gen++; 399 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 400 tidhash_add(td2); 401 PROC_LOCK(p2); 402 PROC_LOCK(p1); 403 404 sx_xunlock(&allproc_lock); 405 406 bcopy(&p1->p_startcopy, &p2->p_startcopy, 407 __rangeof(struct proc, p_startcopy, p_endcopy)); 408 pargs_hold(p2->p_args); 409 410 PROC_UNLOCK(p1); 411 412 bzero(&p2->p_startzero, 413 __rangeof(struct proc, p_startzero, p_endzero)); 414 415 /* Tell the prison that we exist. */ 416 prison_proc_hold(p2->p_ucred->cr_prison); 417 418 PROC_UNLOCK(p2); 419 420 /* 421 * Malloc things while we don't hold any locks. 422 */ 423 if (flags & RFSIGSHARE) 424 newsigacts = NULL; 425 else 426 newsigacts = sigacts_alloc(); 427 428 /* 429 * Copy filedesc. 430 */ 431 if (flags & RFCFDG) { 432 fd = fdinit(p1->p_fd, false); 433 fdtol = NULL; 434 } else if (flags & RFFDG) { 435 fd = fdcopy(p1->p_fd); 436 fdtol = NULL; 437 } else { 438 fd = fdshare(p1->p_fd); 439 if (p1->p_fdtol == NULL) 440 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 441 p1->p_leader); 442 if ((flags & RFTHREAD) != 0) { 443 /* 444 * Shared file descriptor table, and shared 445 * process leaders. 446 */ 447 fdtol = p1->p_fdtol; 448 FILEDESC_XLOCK(p1->p_fd); 449 fdtol->fdl_refcount++; 450 FILEDESC_XUNLOCK(p1->p_fd); 451 } else { 452 /* 453 * Shared file descriptor table, and different 454 * process leaders. 455 */ 456 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 457 p1->p_fd, p2); 458 } 459 } 460 /* 461 * Make a proc table entry for the new process. 462 * Start by zeroing the section of proc that is zero-initialized, 463 * then copy the section that is copied directly from the parent. 464 */ 465 466 PROC_LOCK(p2); 467 PROC_LOCK(p1); 468 469 bzero(&td2->td_startzero, 470 __rangeof(struct thread, td_startzero, td_endzero)); 471 472 bcopy(&td->td_startcopy, &td2->td_startcopy, 473 __rangeof(struct thread, td_startcopy, td_endcopy)); 474 475 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 476 td2->td_sigstk = td->td_sigstk; 477 td2->td_flags = TDF_INMEM; 478 td2->td_lend_user_pri = PRI_MAX; 479 480 #ifdef VIMAGE 481 td2->td_vnet = NULL; 482 td2->td_vnet_lpush = NULL; 483 #endif 484 485 /* 486 * Allow the scheduler to initialize the child. 487 */ 488 thread_lock(td); 489 sched_fork(td, td2); 490 thread_unlock(td); 491 492 /* 493 * Duplicate sub-structures as needed. 494 * Increase reference counts on shared objects. 495 */ 496 p2->p_flag = P_INMEM; 497 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC); 498 p2->p_swtick = ticks; 499 if (p1->p_flag & P_PROFIL) 500 startprofclock(p2); 501 502 /* 503 * Whilst the proc lock is held, copy the VM domain data out 504 * using the VM domain method. 505 */ 506 vm_domain_policy_init(&p2->p_vm_dom_policy); 507 vm_domain_policy_localcopy(&p2->p_vm_dom_policy, 508 &p1->p_vm_dom_policy); 509 510 if (flags & RFSIGSHARE) { 511 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 512 } else { 513 sigacts_copy(newsigacts, p1->p_sigacts); 514 p2->p_sigacts = newsigacts; 515 } 516 517 if (flags & RFTSIGZMB) 518 p2->p_sigparent = RFTSIGNUM(flags); 519 else if (flags & RFLINUXTHPN) 520 p2->p_sigparent = SIGUSR1; 521 else 522 p2->p_sigparent = SIGCHLD; 523 524 p2->p_textvp = p1->p_textvp; 525 p2->p_fd = fd; 526 p2->p_fdtol = fdtol; 527 528 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 529 p2->p_flag |= P_PROTECTED; 530 p2->p_flag2 |= P2_INHERIT_PROTECTED; 531 } 532 533 /* 534 * p_limit is copy-on-write. Bump its refcount. 535 */ 536 lim_fork(p1, p2); 537 538 thread_cow_get_proc(td2, p2); 539 540 pstats_fork(p1->p_stats, p2->p_stats); 541 542 PROC_UNLOCK(p1); 543 PROC_UNLOCK(p2); 544 545 /* Bump references to the text vnode (for procfs). */ 546 if (p2->p_textvp) 547 vref(p2->p_textvp); 548 549 /* 550 * Set up linkage for kernel based threading. 551 */ 552 if ((flags & RFTHREAD) != 0) { 553 mtx_lock(&ppeers_lock); 554 p2->p_peers = p1->p_peers; 555 p1->p_peers = p2; 556 p2->p_leader = p1->p_leader; 557 mtx_unlock(&ppeers_lock); 558 PROC_LOCK(p1->p_leader); 559 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 560 PROC_UNLOCK(p1->p_leader); 561 /* 562 * The task leader is exiting, so process p1 is 563 * going to be killed shortly. Since p1 obviously 564 * isn't dead yet, we know that the leader is either 565 * sending SIGKILL's to all the processes in this 566 * task or is sleeping waiting for all the peers to 567 * exit. We let p1 complete the fork, but we need 568 * to go ahead and kill the new process p2 since 569 * the task leader may not get a chance to send 570 * SIGKILL to it. We leave it on the list so that 571 * the task leader will wait for this new process 572 * to commit suicide. 573 */ 574 PROC_LOCK(p2); 575 kern_psignal(p2, SIGKILL); 576 PROC_UNLOCK(p2); 577 } else 578 PROC_UNLOCK(p1->p_leader); 579 } else { 580 p2->p_peers = NULL; 581 p2->p_leader = p2; 582 } 583 584 sx_xlock(&proctree_lock); 585 PGRP_LOCK(p1->p_pgrp); 586 PROC_LOCK(p2); 587 PROC_LOCK(p1); 588 589 /* 590 * Preserve some more flags in subprocess. P_PROFIL has already 591 * been preserved. 592 */ 593 p2->p_flag |= p1->p_flag & P_SUGID; 594 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 595 SESS_LOCK(p1->p_session); 596 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 597 p2->p_flag |= P_CONTROLT; 598 SESS_UNLOCK(p1->p_session); 599 if (flags & RFPPWAIT) 600 p2->p_flag |= P_PPWAIT; 601 602 p2->p_pgrp = p1->p_pgrp; 603 LIST_INSERT_AFTER(p1, p2, p_pglist); 604 PGRP_UNLOCK(p1->p_pgrp); 605 LIST_INIT(&p2->p_children); 606 LIST_INIT(&p2->p_orphans); 607 608 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 609 610 /* 611 * If PF_FORK is set, the child process inherits the 612 * procfs ioctl flags from its parent. 613 */ 614 if (p1->p_pfsflags & PF_FORK) { 615 p2->p_stops = p1->p_stops; 616 p2->p_pfsflags = p1->p_pfsflags; 617 } 618 619 /* 620 * This begins the section where we must prevent the parent 621 * from being swapped. 622 */ 623 _PHOLD(p1); 624 PROC_UNLOCK(p1); 625 626 /* 627 * Attach the new process to its parent. 628 * 629 * If RFNOWAIT is set, the newly created process becomes a child 630 * of init. This effectively disassociates the child from the 631 * parent. 632 */ 633 if ((flags & RFNOWAIT) != 0) { 634 pptr = p1->p_reaper; 635 p2->p_reaper = pptr; 636 } else { 637 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 638 p1 : p1->p_reaper; 639 pptr = p1; 640 } 641 p2->p_pptr = pptr; 642 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 643 LIST_INIT(&p2->p_reaplist); 644 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 645 if (p2->p_reaper == p1) 646 p2->p_reapsubtree = p2->p_pid; 647 sx_xunlock(&proctree_lock); 648 649 /* Inform accounting that we have forked. */ 650 p2->p_acflag = AFORK; 651 PROC_UNLOCK(p2); 652 653 #ifdef KTRACE 654 ktrprocfork(p1, p2); 655 #endif 656 657 /* 658 * Finish creating the child process. It will return via a different 659 * execution path later. (ie: directly into user mode) 660 */ 661 vm_forkproc(td, p2, td2, vm2, flags); 662 663 if (flags == (RFFDG | RFPROC)) { 664 PCPU_INC(cnt.v_forks); 665 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 666 p2->p_vmspace->vm_ssize); 667 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 668 PCPU_INC(cnt.v_vforks); 669 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 670 p2->p_vmspace->vm_ssize); 671 } else if (p1 == &proc0) { 672 PCPU_INC(cnt.v_kthreads); 673 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 674 p2->p_vmspace->vm_ssize); 675 } else { 676 PCPU_INC(cnt.v_rforks); 677 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 678 p2->p_vmspace->vm_ssize); 679 } 680 681 /* 682 * Associate the process descriptor with the process before anything 683 * can happen that might cause that process to need the descriptor. 684 * However, don't do this until after fork(2) can no longer fail. 685 */ 686 if (flags & RFPROCDESC) 687 procdesc_new(p2, pdflags); 688 689 /* 690 * Both processes are set up, now check if any loadable modules want 691 * to adjust anything. 692 */ 693 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 694 695 /* 696 * Set the child start time and mark the process as being complete. 697 */ 698 PROC_LOCK(p2); 699 PROC_LOCK(p1); 700 microuptime(&p2->p_stats->p_start); 701 PROC_SLOCK(p2); 702 p2->p_state = PRS_NORMAL; 703 PROC_SUNLOCK(p2); 704 705 #ifdef KDTRACE_HOOKS 706 /* 707 * Tell the DTrace fasttrap provider about the new process so that any 708 * tracepoints inherited from the parent can be removed. We have to do 709 * this only after p_state is PRS_NORMAL since the fasttrap module will 710 * use pfind() later on. 711 */ 712 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork) 713 dtrace_fasttrap_fork(p1, p2); 714 #endif 715 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 716 P_FOLLOWFORK)) { 717 /* 718 * Arrange for debugger to receive the fork event. 719 * 720 * We can report PL_FLAG_FORKED regardless of 721 * P_FOLLOWFORK settings, but it does not make a sense 722 * for runaway child. 723 */ 724 td->td_dbgflags |= TDB_FORK; 725 td->td_dbg_forked = p2->p_pid; 726 td2->td_dbgflags |= TDB_STOPATFORK; 727 _PHOLD(p2); 728 p2_held = 1; 729 } 730 if (flags & RFPPWAIT) { 731 td->td_pflags |= TDP_RFPPWAIT; 732 td->td_rfppwait_p = p2; 733 } 734 PROC_UNLOCK(p2); 735 if ((flags & RFSTOPPED) == 0) { 736 /* 737 * If RFSTOPPED not requested, make child runnable and 738 * add to run queue. 739 */ 740 thread_lock(td2); 741 TD_SET_CAN_RUN(td2); 742 sched_add(td2, SRQ_BORING); 743 thread_unlock(td2); 744 } 745 746 /* 747 * Now can be swapped. 748 */ 749 _PRELE(p1); 750 PROC_UNLOCK(p1); 751 752 /* 753 * Tell any interested parties about the new process. 754 */ 755 knote_fork(&p1->p_klist, p2->p_pid); 756 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 757 758 /* 759 * Wait until debugger is attached to child. 760 */ 761 PROC_LOCK(p2); 762 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 763 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 764 if (p2_held) 765 _PRELE(p2); 766 PROC_UNLOCK(p2); 767 } 768 769 int 770 fork1(struct thread *td, int flags, int pages, struct proc **procp, 771 int *procdescp, int pdflags) 772 { 773 struct proc *p1; 774 struct proc *newproc; 775 int ok; 776 struct thread *td2; 777 struct vmspace *vm2; 778 vm_ooffset_t mem_charged; 779 int error; 780 static int curfail; 781 static struct timeval lastfail; 782 struct file *fp_procdesc = NULL; 783 784 /* Check for the undefined or unimplemented flags. */ 785 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 786 return (EINVAL); 787 788 /* Signal value requires RFTSIGZMB. */ 789 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 790 return (EINVAL); 791 792 /* Can't copy and clear. */ 793 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 794 return (EINVAL); 795 796 /* Check the validity of the signal number. */ 797 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 798 return (EINVAL); 799 800 if ((flags & RFPROCDESC) != 0) { 801 /* Can't not create a process yet get a process descriptor. */ 802 if ((flags & RFPROC) == 0) 803 return (EINVAL); 804 805 /* Must provide a place to put a procdesc if creating one. */ 806 if (procdescp == NULL) 807 return (EINVAL); 808 } 809 810 p1 = td->td_proc; 811 812 /* 813 * Here we don't create a new process, but we divorce 814 * certain parts of a process from itself. 815 */ 816 if ((flags & RFPROC) == 0) { 817 *procp = NULL; 818 return (fork_norfproc(td, flags)); 819 } 820 821 /* 822 * If required, create a process descriptor in the parent first; we 823 * will abandon it if something goes wrong. We don't finit() until 824 * later. 825 */ 826 if (flags & RFPROCDESC) { 827 error = falloc(td, &fp_procdesc, procdescp, 0); 828 if (error != 0) 829 return (error); 830 } 831 832 mem_charged = 0; 833 vm2 = NULL; 834 if (pages == 0) 835 pages = KSTACK_PAGES; 836 /* Allocate new proc. */ 837 newproc = uma_zalloc(proc_zone, M_WAITOK); 838 td2 = FIRST_THREAD_IN_PROC(newproc); 839 if (td2 == NULL) { 840 td2 = thread_alloc(pages); 841 if (td2 == NULL) { 842 error = ENOMEM; 843 goto fail2; 844 } 845 proc_linkup(newproc, td2); 846 } else { 847 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 848 if (td2->td_kstack != 0) 849 vm_thread_dispose(td2); 850 if (!thread_alloc_stack(td2, pages)) { 851 error = ENOMEM; 852 goto fail2; 853 } 854 } 855 } 856 857 if ((flags & RFMEM) == 0) { 858 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 859 if (vm2 == NULL) { 860 error = ENOMEM; 861 goto fail2; 862 } 863 if (!swap_reserve(mem_charged)) { 864 /* 865 * The swap reservation failed. The accounting 866 * from the entries of the copied vm2 will be 867 * substracted in vmspace_free(), so force the 868 * reservation there. 869 */ 870 swap_reserve_force(mem_charged); 871 error = ENOMEM; 872 goto fail2; 873 } 874 } else 875 vm2 = NULL; 876 877 /* 878 * XXX: This is ugly; when we copy resource usage, we need to bump 879 * per-cred resource counters. 880 */ 881 proc_set_cred_init(newproc, crhold(td->td_ucred)); 882 883 /* 884 * Initialize resource accounting for the child process. 885 */ 886 error = racct_proc_fork(p1, newproc); 887 if (error != 0) { 888 error = EAGAIN; 889 goto fail1; 890 } 891 892 #ifdef MAC 893 mac_proc_init(newproc); 894 #endif 895 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 896 STAILQ_INIT(&newproc->p_ktr); 897 898 /* We have to lock the process tree while we look for a pid. */ 899 sx_slock(&proctree_lock); 900 901 /* 902 * Although process entries are dynamically created, we still keep 903 * a global limit on the maximum number we will create. Don't allow 904 * a nonprivileged user to use the last ten processes; don't let root 905 * exceed the limit. The variable nprocs is the current number of 906 * processes, maxproc is the limit. 907 */ 908 sx_xlock(&allproc_lock); 909 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 910 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 911 error = EAGAIN; 912 goto fail; 913 } 914 915 /* 916 * Increment the count of procs running with this uid. Don't allow 917 * a nonprivileged user to exceed their current limit. 918 * 919 * XXXRW: Can we avoid privilege here if it's not needed? 920 */ 921 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 922 if (error == 0) 923 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 924 else { 925 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 926 lim_cur(td, RLIMIT_NPROC)); 927 } 928 if (ok) { 929 do_fork(td, flags, newproc, td2, vm2, pdflags); 930 931 /* 932 * Return child proc pointer to parent. 933 */ 934 *procp = newproc; 935 if (flags & RFPROCDESC) { 936 procdesc_finit(newproc->p_procdesc, fp_procdesc); 937 fdrop(fp_procdesc, td); 938 } 939 racct_proc_fork_done(newproc); 940 return (0); 941 } 942 943 error = EAGAIN; 944 fail: 945 sx_sunlock(&proctree_lock); 946 if (ppsratecheck(&lastfail, &curfail, 1)) 947 printf("maxproc limit exceeded by uid %u (pid %d); see tuning(7) and login.conf(5)\n", 948 td->td_ucred->cr_ruid, p1->p_pid); 949 sx_xunlock(&allproc_lock); 950 #ifdef MAC 951 mac_proc_destroy(newproc); 952 #endif 953 racct_proc_exit(newproc); 954 fail1: 955 crfree(newproc->p_ucred); 956 newproc->p_ucred = NULL; 957 fail2: 958 if (vm2 != NULL) 959 vmspace_free(vm2); 960 uma_zfree(proc_zone, newproc); 961 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 962 fdclose(td, fp_procdesc, *procdescp); 963 fdrop(fp_procdesc, td); 964 } 965 pause("fork", hz / 2); 966 return (error); 967 } 968 969 /* 970 * Handle the return of a child process from fork1(). This function 971 * is called from the MD fork_trampoline() entry point. 972 */ 973 void 974 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 975 struct trapframe *frame) 976 { 977 struct proc *p; 978 struct thread *td; 979 struct thread *dtd; 980 981 td = curthread; 982 p = td->td_proc; 983 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 984 985 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 986 td, td->td_sched, p->p_pid, td->td_name); 987 988 sched_fork_exit(td); 989 /* 990 * Processes normally resume in mi_switch() after being 991 * cpu_switch()'ed to, but when children start up they arrive here 992 * instead, so we must do much the same things as mi_switch() would. 993 */ 994 if ((dtd = PCPU_GET(deadthread))) { 995 PCPU_SET(deadthread, NULL); 996 thread_stash(dtd); 997 } 998 thread_unlock(td); 999 1000 /* 1001 * cpu_set_fork_handler intercepts this function call to 1002 * have this call a non-return function to stay in kernel mode. 1003 * initproc has its own fork handler, but it does return. 1004 */ 1005 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1006 callout(arg, frame); 1007 1008 /* 1009 * Check if a kernel thread misbehaved and returned from its main 1010 * function. 1011 */ 1012 if (p->p_flag & P_KTHREAD) { 1013 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1014 td->td_name, p->p_pid); 1015 kproc_exit(0); 1016 } 1017 mtx_assert(&Giant, MA_NOTOWNED); 1018 1019 if (p->p_sysent->sv_schedtail != NULL) 1020 (p->p_sysent->sv_schedtail)(td); 1021 } 1022 1023 /* 1024 * Simplified back end of syscall(), used when returning from fork() 1025 * directly into user mode. Giant is not held on entry, and must not 1026 * be held on return. This function is passed in to fork_exit() as the 1027 * first parameter and is called when returning to a new userland process. 1028 */ 1029 void 1030 fork_return(struct thread *td, struct trapframe *frame) 1031 { 1032 struct proc *p, *dbg; 1033 1034 if (td->td_dbgflags & TDB_STOPATFORK) { 1035 p = td->td_proc; 1036 sx_xlock(&proctree_lock); 1037 PROC_LOCK(p); 1038 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 1039 (P_TRACED | P_FOLLOWFORK)) { 1040 /* 1041 * If debugger still wants auto-attach for the 1042 * parent's children, do it now. 1043 */ 1044 dbg = p->p_pptr->p_pptr; 1045 p->p_flag |= P_TRACED; 1046 p->p_oppid = p->p_pptr->p_pid; 1047 CTR2(KTR_PTRACE, 1048 "fork_return: attaching to new child pid %d: oppid %d", 1049 p->p_pid, p->p_oppid); 1050 proc_reparent(p, dbg); 1051 sx_xunlock(&proctree_lock); 1052 td->td_dbgflags |= TDB_CHILD; 1053 ptracestop(td, SIGSTOP); 1054 td->td_dbgflags &= ~TDB_CHILD; 1055 } else { 1056 /* 1057 * ... otherwise clear the request. 1058 */ 1059 sx_xunlock(&proctree_lock); 1060 td->td_dbgflags &= ~TDB_STOPATFORK; 1061 cv_broadcast(&p->p_dbgwait); 1062 } 1063 PROC_UNLOCK(p); 1064 } 1065 1066 userret(td, frame); 1067 1068 #ifdef KTRACE 1069 if (KTRPOINT(td, KTR_SYSRET)) 1070 ktrsysret(SYS_fork, 0, 0); 1071 #endif 1072 } 1073