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/ptrace.h> 61 #include <sys/racct.h> 62 #include <sys/resourcevar.h> 63 #include <sys/sched.h> 64 #include <sys/syscall.h> 65 #include <sys/vmmeter.h> 66 #include <sys/vnode.h> 67 #include <sys/acct.h> 68 #include <sys/ktr.h> 69 #include <sys/ktrace.h> 70 #include <sys/unistd.h> 71 #include <sys/sdt.h> 72 #include <sys/sx.h> 73 #include <sys/sysent.h> 74 #include <sys/signalvar.h> 75 76 #include <security/audit/audit.h> 77 #include <security/mac/mac_framework.h> 78 79 #include <vm/vm.h> 80 #include <vm/pmap.h> 81 #include <vm/vm_map.h> 82 #include <vm/vm_extern.h> 83 #include <vm/uma.h> 84 #include <vm/vm_domain.h> 85 86 #ifdef KDTRACE_HOOKS 87 #include <sys/dtrace_bsd.h> 88 dtrace_fork_func_t dtrace_fasttrap_fork; 89 #endif 90 91 SDT_PROVIDER_DECLARE(proc); 92 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "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, NULL); 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, NULL); 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, NULL); 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, NULL); 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 trypid = fork_findpid(flags); 385 386 sx_sunlock(&proctree_lock); 387 388 p2->p_state = PRS_NEW; /* protect against others */ 389 p2->p_pid = trypid; 390 AUDIT_ARG_PID(p2->p_pid); 391 LIST_INSERT_HEAD(&allproc, p2, p_list); 392 allproc_gen++; 393 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 394 tidhash_add(td2); 395 PROC_LOCK(p2); 396 PROC_LOCK(p1); 397 398 sx_xunlock(&allproc_lock); 399 400 bcopy(&p1->p_startcopy, &p2->p_startcopy, 401 __rangeof(struct proc, p_startcopy, p_endcopy)); 402 pargs_hold(p2->p_args); 403 404 PROC_UNLOCK(p1); 405 406 bzero(&p2->p_startzero, 407 __rangeof(struct proc, p_startzero, p_endzero)); 408 409 /* Tell the prison that we exist. */ 410 prison_proc_hold(p2->p_ucred->cr_prison); 411 412 PROC_UNLOCK(p2); 413 414 /* 415 * Malloc things while we don't hold any locks. 416 */ 417 if (flags & RFSIGSHARE) 418 newsigacts = NULL; 419 else 420 newsigacts = sigacts_alloc(); 421 422 /* 423 * Copy filedesc. 424 */ 425 if (flags & RFCFDG) { 426 fd = fdinit(p1->p_fd, false); 427 fdtol = NULL; 428 } else if (flags & RFFDG) { 429 fd = fdcopy(p1->p_fd); 430 fdtol = NULL; 431 } else { 432 fd = fdshare(p1->p_fd); 433 if (p1->p_fdtol == NULL) 434 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 435 p1->p_leader); 436 if ((flags & RFTHREAD) != 0) { 437 /* 438 * Shared file descriptor table, and shared 439 * process leaders. 440 */ 441 fdtol = p1->p_fdtol; 442 FILEDESC_XLOCK(p1->p_fd); 443 fdtol->fdl_refcount++; 444 FILEDESC_XUNLOCK(p1->p_fd); 445 } else { 446 /* 447 * Shared file descriptor table, and different 448 * process leaders. 449 */ 450 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 451 p1->p_fd, p2); 452 } 453 } 454 /* 455 * Make a proc table entry for the new process. 456 * Start by zeroing the section of proc that is zero-initialized, 457 * then copy the section that is copied directly from the parent. 458 */ 459 460 PROC_LOCK(p2); 461 PROC_LOCK(p1); 462 463 bzero(&td2->td_startzero, 464 __rangeof(struct thread, td_startzero, td_endzero)); 465 466 bcopy(&td->td_startcopy, &td2->td_startcopy, 467 __rangeof(struct thread, td_startcopy, td_endcopy)); 468 469 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 470 td2->td_sigstk = td->td_sigstk; 471 td2->td_flags = TDF_INMEM; 472 td2->td_lend_user_pri = PRI_MAX; 473 474 #ifdef VIMAGE 475 td2->td_vnet = NULL; 476 td2->td_vnet_lpush = NULL; 477 #endif 478 479 /* 480 * Allow the scheduler to initialize the child. 481 */ 482 thread_lock(td); 483 sched_fork(td, td2); 484 thread_unlock(td); 485 486 /* 487 * Duplicate sub-structures as needed. 488 * Increase reference counts on shared objects. 489 */ 490 p2->p_flag = P_INMEM; 491 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC); 492 p2->p_swtick = ticks; 493 if (p1->p_flag & P_PROFIL) 494 startprofclock(p2); 495 496 /* 497 * Whilst the proc lock is held, copy the VM domain data out 498 * using the VM domain method. 499 */ 500 vm_domain_policy_init(&p2->p_vm_dom_policy); 501 vm_domain_policy_localcopy(&p2->p_vm_dom_policy, 502 &p1->p_vm_dom_policy); 503 504 if (flags & RFSIGSHARE) { 505 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 506 } else { 507 sigacts_copy(newsigacts, p1->p_sigacts); 508 p2->p_sigacts = newsigacts; 509 } 510 511 if (flags & RFTSIGZMB) 512 p2->p_sigparent = RFTSIGNUM(flags); 513 else if (flags & RFLINUXTHPN) 514 p2->p_sigparent = SIGUSR1; 515 else 516 p2->p_sigparent = SIGCHLD; 517 518 p2->p_textvp = p1->p_textvp; 519 p2->p_fd = fd; 520 p2->p_fdtol = fdtol; 521 522 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 523 p2->p_flag |= P_PROTECTED; 524 p2->p_flag2 |= P2_INHERIT_PROTECTED; 525 } 526 527 /* 528 * p_limit is copy-on-write. Bump its refcount. 529 */ 530 lim_fork(p1, p2); 531 532 thread_cow_get_proc(td2, p2); 533 534 pstats_fork(p1->p_stats, p2->p_stats); 535 536 PROC_UNLOCK(p1); 537 PROC_UNLOCK(p2); 538 539 /* Bump references to the text vnode (for procfs). */ 540 if (p2->p_textvp) 541 vref(p2->p_textvp); 542 543 /* 544 * Set up linkage for kernel based threading. 545 */ 546 if ((flags & RFTHREAD) != 0) { 547 mtx_lock(&ppeers_lock); 548 p2->p_peers = p1->p_peers; 549 p1->p_peers = p2; 550 p2->p_leader = p1->p_leader; 551 mtx_unlock(&ppeers_lock); 552 PROC_LOCK(p1->p_leader); 553 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 554 PROC_UNLOCK(p1->p_leader); 555 /* 556 * The task leader is exiting, so process p1 is 557 * going to be killed shortly. Since p1 obviously 558 * isn't dead yet, we know that the leader is either 559 * sending SIGKILL's to all the processes in this 560 * task or is sleeping waiting for all the peers to 561 * exit. We let p1 complete the fork, but we need 562 * to go ahead and kill the new process p2 since 563 * the task leader may not get a chance to send 564 * SIGKILL to it. We leave it on the list so that 565 * the task leader will wait for this new process 566 * to commit suicide. 567 */ 568 PROC_LOCK(p2); 569 kern_psignal(p2, SIGKILL); 570 PROC_UNLOCK(p2); 571 } else 572 PROC_UNLOCK(p1->p_leader); 573 } else { 574 p2->p_peers = NULL; 575 p2->p_leader = p2; 576 } 577 578 sx_xlock(&proctree_lock); 579 PGRP_LOCK(p1->p_pgrp); 580 PROC_LOCK(p2); 581 PROC_LOCK(p1); 582 583 /* 584 * Preserve some more flags in subprocess. P_PROFIL has already 585 * been preserved. 586 */ 587 p2->p_flag |= p1->p_flag & P_SUGID; 588 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING; 589 SESS_LOCK(p1->p_session); 590 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 591 p2->p_flag |= P_CONTROLT; 592 SESS_UNLOCK(p1->p_session); 593 if (flags & RFPPWAIT) 594 p2->p_flag |= P_PPWAIT; 595 596 p2->p_pgrp = p1->p_pgrp; 597 LIST_INSERT_AFTER(p1, p2, p_pglist); 598 PGRP_UNLOCK(p1->p_pgrp); 599 LIST_INIT(&p2->p_children); 600 LIST_INIT(&p2->p_orphans); 601 602 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 603 604 /* 605 * If PF_FORK is set, the child process inherits the 606 * procfs ioctl flags from its parent. 607 */ 608 if (p1->p_pfsflags & PF_FORK) { 609 p2->p_stops = p1->p_stops; 610 p2->p_pfsflags = p1->p_pfsflags; 611 } 612 613 /* 614 * This begins the section where we must prevent the parent 615 * from being swapped. 616 */ 617 _PHOLD(p1); 618 PROC_UNLOCK(p1); 619 620 /* 621 * Attach the new process to its parent. 622 * 623 * If RFNOWAIT is set, the newly created process becomes a child 624 * of init. This effectively disassociates the child from the 625 * parent. 626 */ 627 if ((flags & RFNOWAIT) != 0) { 628 pptr = p1->p_reaper; 629 p2->p_reaper = pptr; 630 } else { 631 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 632 p1 : p1->p_reaper; 633 pptr = p1; 634 } 635 p2->p_pptr = pptr; 636 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 637 LIST_INIT(&p2->p_reaplist); 638 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 639 if (p2->p_reaper == p1) 640 p2->p_reapsubtree = p2->p_pid; 641 sx_xunlock(&proctree_lock); 642 643 /* Inform accounting that we have forked. */ 644 p2->p_acflag = AFORK; 645 PROC_UNLOCK(p2); 646 647 #ifdef KTRACE 648 ktrprocfork(p1, p2); 649 #endif 650 651 /* 652 * Finish creating the child process. It will return via a different 653 * execution path later. (ie: directly into user mode) 654 */ 655 vm_forkproc(td, p2, td2, vm2, flags); 656 657 if (flags == (RFFDG | RFPROC)) { 658 PCPU_INC(cnt.v_forks); 659 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 660 p2->p_vmspace->vm_ssize); 661 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 662 PCPU_INC(cnt.v_vforks); 663 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 664 p2->p_vmspace->vm_ssize); 665 } else if (p1 == &proc0) { 666 PCPU_INC(cnt.v_kthreads); 667 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 668 p2->p_vmspace->vm_ssize); 669 } else { 670 PCPU_INC(cnt.v_rforks); 671 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 672 p2->p_vmspace->vm_ssize); 673 } 674 675 /* 676 * Associate the process descriptor with the process before anything 677 * can happen that might cause that process to need the descriptor. 678 * However, don't do this until after fork(2) can no longer fail. 679 */ 680 if (flags & RFPROCDESC) 681 procdesc_new(p2, pdflags); 682 683 /* 684 * Both processes are set up, now check if any loadable modules want 685 * to adjust anything. 686 */ 687 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 688 689 /* 690 * Set the child start time and mark the process as being complete. 691 */ 692 PROC_LOCK(p2); 693 PROC_LOCK(p1); 694 microuptime(&p2->p_stats->p_start); 695 PROC_SLOCK(p2); 696 p2->p_state = PRS_NORMAL; 697 PROC_SUNLOCK(p2); 698 699 #ifdef KDTRACE_HOOKS 700 /* 701 * Tell the DTrace fasttrap provider about the new process so that any 702 * tracepoints inherited from the parent can be removed. We have to do 703 * this only after p_state is PRS_NORMAL since the fasttrap module will 704 * use pfind() later on. 705 */ 706 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork) 707 dtrace_fasttrap_fork(p1, p2); 708 #endif 709 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 710 P_FOLLOWFORK)) { 711 /* 712 * Arrange for debugger to receive the fork event. 713 * 714 * We can report PL_FLAG_FORKED regardless of 715 * P_FOLLOWFORK settings, but it does not make a sense 716 * for runaway child. 717 */ 718 td->td_dbgflags |= TDB_FORK; 719 td->td_dbg_forked = p2->p_pid; 720 td2->td_dbgflags |= TDB_STOPATFORK; 721 _PHOLD(p2); 722 p2_held = 1; 723 } 724 if (flags & RFPPWAIT) { 725 td->td_pflags |= TDP_RFPPWAIT; 726 td->td_rfppwait_p = p2; 727 } 728 PROC_UNLOCK(p2); 729 if ((flags & RFSTOPPED) == 0) { 730 /* 731 * If RFSTOPPED not requested, make child runnable and 732 * add to run queue. 733 */ 734 thread_lock(td2); 735 TD_SET_CAN_RUN(td2); 736 sched_add(td2, SRQ_BORING); 737 thread_unlock(td2); 738 } 739 740 /* 741 * Now can be swapped. 742 */ 743 _PRELE(p1); 744 PROC_UNLOCK(p1); 745 746 /* 747 * Tell any interested parties about the new process. 748 */ 749 knote_fork(&p1->p_klist, p2->p_pid); 750 SDT_PROBE3(proc, , , create, p2, p1, flags); 751 752 /* 753 * Wait until debugger is attached to child. 754 */ 755 PROC_LOCK(p2); 756 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 757 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 758 if (p2_held) 759 _PRELE(p2); 760 PROC_UNLOCK(p2); 761 } 762 763 int 764 fork1(struct thread *td, int flags, int pages, struct proc **procp, 765 int *procdescp, int pdflags, struct filecaps *fcaps) 766 { 767 struct proc *p1, *newproc; 768 struct thread *td2; 769 struct vmspace *vm2; 770 struct file *fp_procdesc; 771 vm_ooffset_t mem_charged; 772 int error, nprocs_new, ok; 773 static int curfail; 774 static struct timeval lastfail; 775 776 /* Check for the undefined or unimplemented flags. */ 777 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 778 return (EINVAL); 779 780 /* Signal value requires RFTSIGZMB. */ 781 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 782 return (EINVAL); 783 784 /* Can't copy and clear. */ 785 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 786 return (EINVAL); 787 788 /* Check the validity of the signal number. */ 789 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 790 return (EINVAL); 791 792 if ((flags & RFPROCDESC) != 0) { 793 /* Can't not create a process yet get a process descriptor. */ 794 if ((flags & RFPROC) == 0) 795 return (EINVAL); 796 797 /* Must provide a place to put a procdesc if creating one. */ 798 if (procdescp == NULL) 799 return (EINVAL); 800 } 801 802 p1 = td->td_proc; 803 804 /* 805 * Here we don't create a new process, but we divorce 806 * certain parts of a process from itself. 807 */ 808 if ((flags & RFPROC) == 0) { 809 *procp = NULL; 810 return (fork_norfproc(td, flags)); 811 } 812 813 fp_procdesc = NULL; 814 newproc = NULL; 815 vm2 = NULL; 816 817 /* 818 * Increment the nprocs resource before allocations occur. 819 * Although process entries are dynamically created, we still 820 * keep a global limit on the maximum number we will 821 * create. There are hard-limits as to the number of processes 822 * that can run, established by the KVA and memory usage for 823 * the process data. 824 * 825 * Don't allow a nonprivileged user to use the last ten 826 * processes; don't let root exceed the limit. 827 */ 828 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 829 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred, 830 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) { 831 error = EAGAIN; 832 sx_xlock(&allproc_lock); 833 if (ppsratecheck(&lastfail, &curfail, 1)) { 834 printf("maxproc limit exceeded by uid %u (pid %d); " 835 "see tuning(7) and login.conf(5)\n", 836 td->td_ucred->cr_ruid, p1->p_pid); 837 } 838 sx_xunlock(&allproc_lock); 839 goto fail2; 840 } 841 842 /* 843 * If required, create a process descriptor in the parent first; we 844 * will abandon it if something goes wrong. We don't finit() until 845 * later. 846 */ 847 if (flags & RFPROCDESC) { 848 error = falloc_caps(td, &fp_procdesc, procdescp, 0, fcaps); 849 if (error != 0) 850 goto fail2; 851 } 852 853 mem_charged = 0; 854 if (pages == 0) 855 pages = kstack_pages; 856 /* Allocate new proc. */ 857 newproc = uma_zalloc(proc_zone, M_WAITOK); 858 td2 = FIRST_THREAD_IN_PROC(newproc); 859 if (td2 == NULL) { 860 td2 = thread_alloc(pages); 861 if (td2 == NULL) { 862 error = ENOMEM; 863 goto fail2; 864 } 865 proc_linkup(newproc, td2); 866 } else { 867 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 868 if (td2->td_kstack != 0) 869 vm_thread_dispose(td2); 870 if (!thread_alloc_stack(td2, pages)) { 871 error = ENOMEM; 872 goto fail2; 873 } 874 } 875 } 876 877 if ((flags & RFMEM) == 0) { 878 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 879 if (vm2 == NULL) { 880 error = ENOMEM; 881 goto fail2; 882 } 883 if (!swap_reserve(mem_charged)) { 884 /* 885 * The swap reservation failed. The accounting 886 * from the entries of the copied vm2 will be 887 * substracted in vmspace_free(), so force the 888 * reservation there. 889 */ 890 swap_reserve_force(mem_charged); 891 error = ENOMEM; 892 goto fail2; 893 } 894 } else 895 vm2 = NULL; 896 897 /* 898 * XXX: This is ugly; when we copy resource usage, we need to bump 899 * per-cred resource counters. 900 */ 901 proc_set_cred_init(newproc, crhold(td->td_ucred)); 902 903 /* 904 * Initialize resource accounting for the child process. 905 */ 906 error = racct_proc_fork(p1, newproc); 907 if (error != 0) { 908 error = EAGAIN; 909 goto fail1; 910 } 911 912 #ifdef MAC 913 mac_proc_init(newproc); 914 #endif 915 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 916 STAILQ_INIT(&newproc->p_ktr); 917 918 /* We have to lock the process tree while we look for a pid. */ 919 sx_slock(&proctree_lock); 920 sx_xlock(&allproc_lock); 921 922 /* 923 * Increment the count of procs running with this uid. Don't allow 924 * a nonprivileged user to exceed their current limit. 925 * 926 * XXXRW: Can we avoid privilege here if it's not needed? 927 */ 928 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 929 if (error == 0) 930 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 931 else { 932 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 933 lim_cur(td, RLIMIT_NPROC)); 934 } 935 if (ok) { 936 do_fork(td, flags, newproc, td2, vm2, pdflags); 937 938 /* 939 * Return child proc pointer to parent. 940 */ 941 *procp = newproc; 942 if (flags & RFPROCDESC) { 943 procdesc_finit(newproc->p_procdesc, fp_procdesc); 944 fdrop(fp_procdesc, td); 945 } 946 racct_proc_fork_done(newproc); 947 return (0); 948 } 949 950 error = EAGAIN; 951 sx_sunlock(&proctree_lock); 952 sx_xunlock(&allproc_lock); 953 #ifdef MAC 954 mac_proc_destroy(newproc); 955 #endif 956 racct_proc_exit(newproc); 957 fail1: 958 crfree(newproc->p_ucred); 959 newproc->p_ucred = NULL; 960 fail2: 961 if (vm2 != NULL) 962 vmspace_free(vm2); 963 uma_zfree(proc_zone, newproc); 964 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 965 fdclose(td, fp_procdesc, *procdescp); 966 fdrop(fp_procdesc, td); 967 } 968 atomic_add_int(&nprocs, -1); 969 pause("fork", hz / 2); 970 return (error); 971 } 972 973 /* 974 * Handle the return of a child process from fork1(). This function 975 * is called from the MD fork_trampoline() entry point. 976 */ 977 void 978 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 979 struct trapframe *frame) 980 { 981 struct proc *p; 982 struct thread *td; 983 struct thread *dtd; 984 985 td = curthread; 986 p = td->td_proc; 987 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 988 989 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 990 td, td->td_sched, p->p_pid, td->td_name); 991 992 sched_fork_exit(td); 993 /* 994 * Processes normally resume in mi_switch() after being 995 * cpu_switch()'ed to, but when children start up they arrive here 996 * instead, so we must do much the same things as mi_switch() would. 997 */ 998 if ((dtd = PCPU_GET(deadthread))) { 999 PCPU_SET(deadthread, NULL); 1000 thread_stash(dtd); 1001 } 1002 thread_unlock(td); 1003 1004 /* 1005 * cpu_set_fork_handler intercepts this function call to 1006 * have this call a non-return function to stay in kernel mode. 1007 * initproc has its own fork handler, but it does return. 1008 */ 1009 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1010 callout(arg, frame); 1011 1012 /* 1013 * Check if a kernel thread misbehaved and returned from its main 1014 * function. 1015 */ 1016 if (p->p_flag & P_KTHREAD) { 1017 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1018 td->td_name, p->p_pid); 1019 kproc_exit(0); 1020 } 1021 mtx_assert(&Giant, MA_NOTOWNED); 1022 1023 if (p->p_sysent->sv_schedtail != NULL) 1024 (p->p_sysent->sv_schedtail)(td); 1025 td->td_pflags &= ~TDP_FORKING; 1026 } 1027 1028 /* 1029 * Simplified back end of syscall(), used when returning from fork() 1030 * directly into user mode. Giant is not held on entry, and must not 1031 * be held on return. This function is passed in to fork_exit() as the 1032 * first parameter and is called when returning to a new userland process. 1033 */ 1034 void 1035 fork_return(struct thread *td, struct trapframe *frame) 1036 { 1037 struct proc *p, *dbg; 1038 1039 p = td->td_proc; 1040 if (td->td_dbgflags & TDB_STOPATFORK) { 1041 sx_xlock(&proctree_lock); 1042 PROC_LOCK(p); 1043 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 1044 (P_TRACED | P_FOLLOWFORK)) { 1045 /* 1046 * If debugger still wants auto-attach for the 1047 * parent's children, do it now. 1048 */ 1049 dbg = p->p_pptr->p_pptr; 1050 p->p_flag |= P_TRACED; 1051 p->p_oppid = p->p_pptr->p_pid; 1052 CTR2(KTR_PTRACE, 1053 "fork_return: attaching to new child pid %d: oppid %d", 1054 p->p_pid, p->p_oppid); 1055 proc_reparent(p, dbg); 1056 sx_xunlock(&proctree_lock); 1057 td->td_dbgflags |= TDB_CHILD | TDB_SCX; 1058 ptracestop(td, SIGSTOP); 1059 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1060 } else { 1061 /* 1062 * ... otherwise clear the request. 1063 */ 1064 sx_xunlock(&proctree_lock); 1065 td->td_dbgflags &= ~TDB_STOPATFORK; 1066 cv_broadcast(&p->p_dbgwait); 1067 } 1068 PROC_UNLOCK(p); 1069 } else if (p->p_flag & P_TRACED) { 1070 /* 1071 * This is the start of a new thread in a traced 1072 * process. Report a system call exit event. 1073 */ 1074 PROC_LOCK(p); 1075 td->td_dbgflags |= TDB_SCX; 1076 _STOPEVENT(p, S_SCX, td->td_dbg_sc_code); 1077 if ((p->p_stops & S_PT_SCX) != 0) 1078 ptracestop(td, SIGTRAP); 1079 td->td_dbgflags &= ~TDB_SCX; 1080 PROC_UNLOCK(p); 1081 } 1082 1083 userret(td, frame); 1084 1085 #ifdef KTRACE 1086 if (KTRPOINT(td, KTR_SYSRET)) 1087 ktrsysret(SYS_fork, 0, 0); 1088 #endif 1089 } 1090