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, kernel, , create, "struct proc *", 93 "struct proc *", "int"); 94 95 #ifndef _SYS_SYSPROTO_H_ 96 struct fork_args { 97 int dummy; 98 }; 99 #endif 100 101 /* ARGSUSED */ 102 int 103 sys_fork(struct thread *td, struct fork_args *uap) 104 { 105 int error; 106 struct proc *p2; 107 108 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0, NULL); 109 if (error == 0) { 110 td->td_retval[0] = p2->p_pid; 111 td->td_retval[1] = 0; 112 } 113 return (error); 114 } 115 116 /* ARGUSED */ 117 int 118 sys_pdfork(td, uap) 119 struct thread *td; 120 struct pdfork_args *uap; 121 { 122 int error, fd; 123 struct proc *p2; 124 125 /* 126 * It is necessary to return fd by reference because 0 is a valid file 127 * descriptor number, and the child needs to be able to distinguish 128 * itself from the parent using the return value. 129 */ 130 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2, 131 &fd, uap->flags, NULL); 132 if (error == 0) { 133 td->td_retval[0] = p2->p_pid; 134 td->td_retval[1] = 0; 135 error = copyout(&fd, uap->fdp, sizeof(fd)); 136 } 137 return (error); 138 } 139 140 /* ARGSUSED */ 141 int 142 sys_vfork(struct thread *td, struct vfork_args *uap) 143 { 144 int error, flags; 145 struct proc *p2; 146 147 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 148 error = fork1(td, flags, 0, &p2, NULL, 0, NULL); 149 if (error == 0) { 150 td->td_retval[0] = p2->p_pid; 151 td->td_retval[1] = 0; 152 } 153 return (error); 154 } 155 156 int 157 sys_rfork(struct thread *td, struct rfork_args *uap) 158 { 159 struct proc *p2; 160 int error; 161 162 /* Don't allow kernel-only flags. */ 163 if ((uap->flags & RFKERNELONLY) != 0) 164 return (EINVAL); 165 166 AUDIT_ARG_FFLAGS(uap->flags); 167 error = fork1(td, uap->flags, 0, &p2, NULL, 0, NULL); 168 if (error == 0) { 169 td->td_retval[0] = p2 ? p2->p_pid : 0; 170 td->td_retval[1] = 0; 171 } 172 return (error); 173 } 174 175 int nprocs = 1; /* process 0 */ 176 int lastpid = 0; 177 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 178 "Last used PID"); 179 180 /* 181 * Random component to lastpid generation. We mix in a random factor to make 182 * it a little harder to predict. We sanity check the modulus value to avoid 183 * doing it in critical paths. Don't let it be too small or we pointlessly 184 * waste randomness entropy, and don't let it be impossibly large. Using a 185 * modulus that is too big causes a LOT more process table scans and slows 186 * down fork processing as the pidchecked caching is defeated. 187 */ 188 static int randompid = 0; 189 190 static int 191 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 192 { 193 int error, pid; 194 195 error = sysctl_wire_old_buffer(req, sizeof(int)); 196 if (error != 0) 197 return(error); 198 sx_xlock(&allproc_lock); 199 pid = randompid; 200 error = sysctl_handle_int(oidp, &pid, 0, req); 201 if (error == 0 && req->newptr != NULL) { 202 if (pid < 0 || pid > pid_max - 100) /* out of range */ 203 pid = pid_max - 100; 204 else if (pid < 2) /* NOP */ 205 pid = 0; 206 else if (pid < 100) /* Make it reasonable */ 207 pid = 100; 208 randompid = pid; 209 } 210 sx_xunlock(&allproc_lock); 211 return (error); 212 } 213 214 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 215 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 216 217 static int 218 fork_findpid(int flags) 219 { 220 struct proc *p; 221 int trypid; 222 static int pidchecked = 0; 223 224 /* 225 * Requires allproc_lock in order to iterate over the list 226 * of processes, and proctree_lock to access p_pgrp. 227 */ 228 sx_assert(&allproc_lock, SX_LOCKED); 229 sx_assert(&proctree_lock, SX_LOCKED); 230 231 /* 232 * Find an unused process ID. We remember a range of unused IDs 233 * ready to use (from lastpid+1 through pidchecked-1). 234 * 235 * If RFHIGHPID is set (used during system boot), do not allocate 236 * low-numbered pids. 237 */ 238 trypid = lastpid + 1; 239 if (flags & RFHIGHPID) { 240 if (trypid < 10) 241 trypid = 10; 242 } else { 243 if (randompid) 244 trypid += arc4random() % randompid; 245 } 246 retry: 247 /* 248 * If the process ID prototype has wrapped around, 249 * restart somewhat above 0, as the low-numbered procs 250 * tend to include daemons that don't exit. 251 */ 252 if (trypid >= pid_max) { 253 trypid = trypid % pid_max; 254 if (trypid < 100) 255 trypid += 100; 256 pidchecked = 0; 257 } 258 if (trypid >= pidchecked) { 259 int doingzomb = 0; 260 261 pidchecked = PID_MAX; 262 /* 263 * Scan the active and zombie procs to check whether this pid 264 * is in use. Remember the lowest pid that's greater 265 * than trypid, so we can avoid checking for a while. 266 * 267 * Avoid reuse of the process group id, session id or 268 * the reaper subtree id. Note that for process group 269 * and sessions, the amount of reserved pids is 270 * limited by process limit. For the subtree ids, the 271 * id is kept reserved only while there is a 272 * non-reaped process in the subtree, so amount of 273 * reserved pids is limited by process limit times 274 * two. 275 */ 276 p = LIST_FIRST(&allproc); 277 again: 278 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 279 while (p->p_pid == trypid || 280 p->p_reapsubtree == trypid || 281 (p->p_pgrp != NULL && 282 (p->p_pgrp->pg_id == trypid || 283 (p->p_session != NULL && 284 p->p_session->s_sid == trypid)))) { 285 trypid++; 286 if (trypid >= pidchecked) 287 goto retry; 288 } 289 if (p->p_pid > trypid && pidchecked > p->p_pid) 290 pidchecked = p->p_pid; 291 if (p->p_pgrp != NULL) { 292 if (p->p_pgrp->pg_id > trypid && 293 pidchecked > p->p_pgrp->pg_id) 294 pidchecked = p->p_pgrp->pg_id; 295 if (p->p_session != NULL && 296 p->p_session->s_sid > trypid && 297 pidchecked > p->p_session->s_sid) 298 pidchecked = p->p_session->s_sid; 299 } 300 } 301 if (!doingzomb) { 302 doingzomb = 1; 303 p = LIST_FIRST(&zombproc); 304 goto again; 305 } 306 } 307 308 /* 309 * RFHIGHPID does not mess with the lastpid counter during boot. 310 */ 311 if (flags & RFHIGHPID) 312 pidchecked = 0; 313 else 314 lastpid = trypid; 315 316 return (trypid); 317 } 318 319 static int 320 fork_norfproc(struct thread *td, int flags) 321 { 322 int error; 323 struct proc *p1; 324 325 KASSERT((flags & RFPROC) == 0, 326 ("fork_norfproc called with RFPROC set")); 327 p1 = td->td_proc; 328 329 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 330 (flags & (RFCFDG | RFFDG))) { 331 PROC_LOCK(p1); 332 if (thread_single(p1, SINGLE_BOUNDARY)) { 333 PROC_UNLOCK(p1); 334 return (ERESTART); 335 } 336 PROC_UNLOCK(p1); 337 } 338 339 error = vm_forkproc(td, NULL, NULL, NULL, flags); 340 if (error) 341 goto fail; 342 343 /* 344 * Close all file descriptors. 345 */ 346 if (flags & RFCFDG) { 347 struct filedesc *fdtmp; 348 fdtmp = fdinit(td->td_proc->p_fd, false); 349 fdescfree(td); 350 p1->p_fd = fdtmp; 351 } 352 353 /* 354 * Unshare file descriptors (from parent). 355 */ 356 if (flags & RFFDG) 357 fdunshare(td); 358 359 fail: 360 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 361 (flags & (RFCFDG | RFFDG))) { 362 PROC_LOCK(p1); 363 thread_single_end(p1, SINGLE_BOUNDARY); 364 PROC_UNLOCK(p1); 365 } 366 return (error); 367 } 368 369 static void 370 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, 371 struct vmspace *vm2, int pdflags) 372 { 373 struct proc *p1, *pptr; 374 int p2_held, trypid; 375 struct filedesc *fd; 376 struct filedesc_to_leader *fdtol; 377 struct sigacts *newsigacts; 378 379 sx_assert(&proctree_lock, SX_SLOCKED); 380 sx_assert(&allproc_lock, SX_XLOCKED); 381 382 p2_held = 0; 383 p1 = td->td_proc; 384 385 trypid = fork_findpid(flags); 386 387 sx_sunlock(&proctree_lock); 388 389 p2->p_state = PRS_NEW; /* protect against others */ 390 p2->p_pid = trypid; 391 AUDIT_ARG_PID(p2->p_pid); 392 LIST_INSERT_HEAD(&allproc, p2, p_list); 393 allproc_gen++; 394 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 395 tidhash_add(td2); 396 PROC_LOCK(p2); 397 PROC_LOCK(p1); 398 399 sx_xunlock(&allproc_lock); 400 401 bcopy(&p1->p_startcopy, &p2->p_startcopy, 402 __rangeof(struct proc, p_startcopy, p_endcopy)); 403 pargs_hold(p2->p_args); 404 405 PROC_UNLOCK(p1); 406 407 bzero(&p2->p_startzero, 408 __rangeof(struct proc, p_startzero, p_endzero)); 409 410 /* Tell the prison that we exist. */ 411 prison_proc_hold(p2->p_ucred->cr_prison); 412 413 PROC_UNLOCK(p2); 414 415 /* 416 * Malloc things while we don't hold any locks. 417 */ 418 if (flags & RFSIGSHARE) 419 newsigacts = NULL; 420 else 421 newsigacts = sigacts_alloc(); 422 423 /* 424 * Copy filedesc. 425 */ 426 if (flags & RFCFDG) { 427 fd = fdinit(p1->p_fd, false); 428 fdtol = NULL; 429 } else if (flags & RFFDG) { 430 fd = fdcopy(p1->p_fd); 431 fdtol = NULL; 432 } else { 433 fd = fdshare(p1->p_fd); 434 if (p1->p_fdtol == NULL) 435 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 436 p1->p_leader); 437 if ((flags & RFTHREAD) != 0) { 438 /* 439 * Shared file descriptor table, and shared 440 * process leaders. 441 */ 442 fdtol = p1->p_fdtol; 443 FILEDESC_XLOCK(p1->p_fd); 444 fdtol->fdl_refcount++; 445 FILEDESC_XUNLOCK(p1->p_fd); 446 } else { 447 /* 448 * Shared file descriptor table, and different 449 * process leaders. 450 */ 451 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 452 p1->p_fd, p2); 453 } 454 } 455 /* 456 * Make a proc table entry for the new process. 457 * Start by zeroing the section of proc that is zero-initialized, 458 * then copy the section that is copied directly from the parent. 459 */ 460 461 PROC_LOCK(p2); 462 PROC_LOCK(p1); 463 464 bzero(&td2->td_startzero, 465 __rangeof(struct thread, td_startzero, td_endzero)); 466 467 bcopy(&td->td_startcopy, &td2->td_startcopy, 468 __rangeof(struct thread, td_startcopy, td_endcopy)); 469 470 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 471 td2->td_sigstk = td->td_sigstk; 472 td2->td_flags = TDF_INMEM; 473 td2->td_lend_user_pri = PRI_MAX; 474 475 #ifdef VIMAGE 476 td2->td_vnet = NULL; 477 td2->td_vnet_lpush = NULL; 478 #endif 479 480 /* 481 * Allow the scheduler to initialize the child. 482 */ 483 thread_lock(td); 484 sched_fork(td, td2); 485 thread_unlock(td); 486 487 /* 488 * Duplicate sub-structures as needed. 489 * Increase reference counts on shared objects. 490 */ 491 p2->p_flag = P_INMEM; 492 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC); 493 p2->p_swtick = ticks; 494 if (p1->p_flag & P_PROFIL) 495 startprofclock(p2); 496 497 /* 498 * Whilst the proc lock is held, copy the VM domain data out 499 * using the VM domain method. 500 */ 501 vm_domain_policy_init(&p2->p_vm_dom_policy); 502 vm_domain_policy_localcopy(&p2->p_vm_dom_policy, 503 &p1->p_vm_dom_policy); 504 505 if (flags & RFSIGSHARE) { 506 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 507 } else { 508 sigacts_copy(newsigacts, p1->p_sigacts); 509 p2->p_sigacts = newsigacts; 510 } 511 512 if (flags & RFTSIGZMB) 513 p2->p_sigparent = RFTSIGNUM(flags); 514 else if (flags & RFLINUXTHPN) 515 p2->p_sigparent = SIGUSR1; 516 else 517 p2->p_sigparent = SIGCHLD; 518 519 p2->p_textvp = p1->p_textvp; 520 p2->p_fd = fd; 521 p2->p_fdtol = fdtol; 522 523 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 524 p2->p_flag |= P_PROTECTED; 525 p2->p_flag2 |= P2_INHERIT_PROTECTED; 526 } 527 528 /* 529 * p_limit is copy-on-write. Bump its refcount. 530 */ 531 lim_fork(p1, p2); 532 533 thread_cow_get_proc(td2, p2); 534 535 pstats_fork(p1->p_stats, p2->p_stats); 536 537 PROC_UNLOCK(p1); 538 PROC_UNLOCK(p2); 539 540 /* Bump references to the text vnode (for procfs). */ 541 if (p2->p_textvp) 542 vref(p2->p_textvp); 543 544 /* 545 * Set up linkage for kernel based threading. 546 */ 547 if ((flags & RFTHREAD) != 0) { 548 mtx_lock(&ppeers_lock); 549 p2->p_peers = p1->p_peers; 550 p1->p_peers = p2; 551 p2->p_leader = p1->p_leader; 552 mtx_unlock(&ppeers_lock); 553 PROC_LOCK(p1->p_leader); 554 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 555 PROC_UNLOCK(p1->p_leader); 556 /* 557 * The task leader is exiting, so process p1 is 558 * going to be killed shortly. Since p1 obviously 559 * isn't dead yet, we know that the leader is either 560 * sending SIGKILL's to all the processes in this 561 * task or is sleeping waiting for all the peers to 562 * exit. We let p1 complete the fork, but we need 563 * to go ahead and kill the new process p2 since 564 * the task leader may not get a chance to send 565 * SIGKILL to it. We leave it on the list so that 566 * the task leader will wait for this new process 567 * to commit suicide. 568 */ 569 PROC_LOCK(p2); 570 kern_psignal(p2, SIGKILL); 571 PROC_UNLOCK(p2); 572 } else 573 PROC_UNLOCK(p1->p_leader); 574 } else { 575 p2->p_peers = NULL; 576 p2->p_leader = p2; 577 } 578 579 sx_xlock(&proctree_lock); 580 PGRP_LOCK(p1->p_pgrp); 581 PROC_LOCK(p2); 582 PROC_LOCK(p1); 583 584 /* 585 * Preserve some more flags in subprocess. P_PROFIL has already 586 * been preserved. 587 */ 588 p2->p_flag |= p1->p_flag & P_SUGID; 589 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING; 590 SESS_LOCK(p1->p_session); 591 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 592 p2->p_flag |= P_CONTROLT; 593 SESS_UNLOCK(p1->p_session); 594 if (flags & RFPPWAIT) 595 p2->p_flag |= P_PPWAIT; 596 597 p2->p_pgrp = p1->p_pgrp; 598 LIST_INSERT_AFTER(p1, p2, p_pglist); 599 PGRP_UNLOCK(p1->p_pgrp); 600 LIST_INIT(&p2->p_children); 601 LIST_INIT(&p2->p_orphans); 602 603 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 604 605 /* 606 * If PF_FORK is set, the child process inherits the 607 * procfs ioctl flags from its parent. 608 */ 609 if (p1->p_pfsflags & PF_FORK) { 610 p2->p_stops = p1->p_stops; 611 p2->p_pfsflags = p1->p_pfsflags; 612 } 613 614 /* 615 * This begins the section where we must prevent the parent 616 * from being swapped. 617 */ 618 _PHOLD(p1); 619 PROC_UNLOCK(p1); 620 621 /* 622 * Attach the new process to its parent. 623 * 624 * If RFNOWAIT is set, the newly created process becomes a child 625 * of init. This effectively disassociates the child from the 626 * parent. 627 */ 628 if ((flags & RFNOWAIT) != 0) { 629 pptr = p1->p_reaper; 630 p2->p_reaper = pptr; 631 } else { 632 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 633 p1 : p1->p_reaper; 634 pptr = p1; 635 } 636 p2->p_pptr = pptr; 637 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 638 LIST_INIT(&p2->p_reaplist); 639 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 640 if (p2->p_reaper == p1) 641 p2->p_reapsubtree = p2->p_pid; 642 sx_xunlock(&proctree_lock); 643 644 /* Inform accounting that we have forked. */ 645 p2->p_acflag = AFORK; 646 PROC_UNLOCK(p2); 647 648 #ifdef KTRACE 649 ktrprocfork(p1, p2); 650 #endif 651 652 /* 653 * Finish creating the child process. It will return via a different 654 * execution path later. (ie: directly into user mode) 655 */ 656 vm_forkproc(td, p2, td2, vm2, flags); 657 658 if (flags == (RFFDG | RFPROC)) { 659 PCPU_INC(cnt.v_forks); 660 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 661 p2->p_vmspace->vm_ssize); 662 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 663 PCPU_INC(cnt.v_vforks); 664 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 665 p2->p_vmspace->vm_ssize); 666 } else if (p1 == &proc0) { 667 PCPU_INC(cnt.v_kthreads); 668 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 669 p2->p_vmspace->vm_ssize); 670 } else { 671 PCPU_INC(cnt.v_rforks); 672 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 673 p2->p_vmspace->vm_ssize); 674 } 675 676 /* 677 * Associate the process descriptor with the process before anything 678 * can happen that might cause that process to need the descriptor. 679 * However, don't do this until after fork(2) can no longer fail. 680 */ 681 if (flags & RFPROCDESC) 682 procdesc_new(p2, pdflags); 683 684 /* 685 * Both processes are set up, now check if any loadable modules want 686 * to adjust anything. 687 */ 688 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 689 690 /* 691 * Set the child start time and mark the process as being complete. 692 */ 693 PROC_LOCK(p2); 694 PROC_LOCK(p1); 695 microuptime(&p2->p_stats->p_start); 696 PROC_SLOCK(p2); 697 p2->p_state = PRS_NORMAL; 698 PROC_SUNLOCK(p2); 699 700 #ifdef KDTRACE_HOOKS 701 /* 702 * Tell the DTrace fasttrap provider about the new process so that any 703 * tracepoints inherited from the parent can be removed. We have to do 704 * this only after p_state is PRS_NORMAL since the fasttrap module will 705 * use pfind() later on. 706 */ 707 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork) 708 dtrace_fasttrap_fork(p1, p2); 709 #endif 710 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 711 P_FOLLOWFORK)) { 712 /* 713 * Arrange for debugger to receive the fork event. 714 * 715 * We can report PL_FLAG_FORKED regardless of 716 * P_FOLLOWFORK settings, but it does not make a sense 717 * for runaway child. 718 */ 719 td->td_dbgflags |= TDB_FORK; 720 td->td_dbg_forked = p2->p_pid; 721 td2->td_dbgflags |= TDB_STOPATFORK; 722 _PHOLD(p2); 723 p2_held = 1; 724 } 725 if (flags & RFPPWAIT) { 726 td->td_pflags |= TDP_RFPPWAIT; 727 td->td_rfppwait_p = p2; 728 } 729 PROC_UNLOCK(p2); 730 if ((flags & RFSTOPPED) == 0) { 731 /* 732 * If RFSTOPPED not requested, make child runnable and 733 * add to run queue. 734 */ 735 thread_lock(td2); 736 TD_SET_CAN_RUN(td2); 737 sched_add(td2, SRQ_BORING); 738 thread_unlock(td2); 739 } 740 741 /* 742 * Now can be swapped. 743 */ 744 _PRELE(p1); 745 PROC_UNLOCK(p1); 746 747 /* 748 * Tell any interested parties about the new process. 749 */ 750 knote_fork(&p1->p_klist, p2->p_pid); 751 SDT_PROBE3(proc, kernel, , create, p2, p1, flags); 752 753 /* 754 * Wait until debugger is attached to child. 755 */ 756 PROC_LOCK(p2); 757 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 758 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 759 if (p2_held) 760 _PRELE(p2); 761 PROC_UNLOCK(p2); 762 } 763 764 int 765 fork1(struct thread *td, int flags, int pages, struct proc **procp, 766 int *procdescp, int pdflags, struct filecaps *fcaps) 767 { 768 struct proc *p1, *newproc; 769 struct thread *td2; 770 struct vmspace *vm2; 771 struct file *fp_procdesc; 772 vm_ooffset_t mem_charged; 773 int error, nprocs_new, ok; 774 static int curfail; 775 static struct timeval lastfail; 776 777 /* Check for the undefined or unimplemented flags. */ 778 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 779 return (EINVAL); 780 781 /* Signal value requires RFTSIGZMB. */ 782 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 783 return (EINVAL); 784 785 /* Can't copy and clear. */ 786 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 787 return (EINVAL); 788 789 /* Check the validity of the signal number. */ 790 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 791 return (EINVAL); 792 793 if ((flags & RFPROCDESC) != 0) { 794 /* Can't not create a process yet get a process descriptor. */ 795 if ((flags & RFPROC) == 0) 796 return (EINVAL); 797 798 /* Must provide a place to put a procdesc if creating one. */ 799 if (procdescp == NULL) 800 return (EINVAL); 801 } 802 803 p1 = td->td_proc; 804 805 /* 806 * Here we don't create a new process, but we divorce 807 * certain parts of a process from itself. 808 */ 809 if ((flags & RFPROC) == 0) { 810 *procp = NULL; 811 return (fork_norfproc(td, flags)); 812 } 813 814 fp_procdesc = NULL; 815 newproc = NULL; 816 vm2 = NULL; 817 818 /* 819 * Increment the nprocs resource before allocations occur. 820 * Although process entries are dynamically created, we still 821 * keep a global limit on the maximum number we will 822 * create. There are hard-limits as to the number of processes 823 * that can run, established by the KVA and memory usage for 824 * the process data. 825 * 826 * Don't allow a nonprivileged user to use the last ten 827 * processes; don't let root exceed the limit. 828 */ 829 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 830 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred, 831 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) { 832 error = EAGAIN; 833 sx_xlock(&allproc_lock); 834 if (ppsratecheck(&lastfail, &curfail, 1)) { 835 printf("maxproc limit exceeded by uid %u (pid %d); " 836 "see tuning(7) and login.conf(5)\n", 837 td->td_ucred->cr_ruid, p1->p_pid); 838 } 839 sx_xunlock(&allproc_lock); 840 goto fail2; 841 } 842 843 /* 844 * If required, create a process descriptor in the parent first; we 845 * will abandon it if something goes wrong. We don't finit() until 846 * later. 847 */ 848 if (flags & RFPROCDESC) { 849 error = falloc_caps(td, &fp_procdesc, procdescp, 0, fcaps); 850 if (error != 0) 851 goto fail2; 852 } 853 854 mem_charged = 0; 855 if (pages == 0) 856 pages = kstack_pages; 857 /* Allocate new proc. */ 858 newproc = uma_zalloc(proc_zone, M_WAITOK); 859 td2 = FIRST_THREAD_IN_PROC(newproc); 860 if (td2 == NULL) { 861 td2 = thread_alloc(pages); 862 if (td2 == NULL) { 863 error = ENOMEM; 864 goto fail2; 865 } 866 proc_linkup(newproc, td2); 867 } else { 868 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 869 if (td2->td_kstack != 0) 870 vm_thread_dispose(td2); 871 if (!thread_alloc_stack(td2, pages)) { 872 error = ENOMEM; 873 goto fail2; 874 } 875 } 876 } 877 878 if ((flags & RFMEM) == 0) { 879 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 880 if (vm2 == NULL) { 881 error = ENOMEM; 882 goto fail2; 883 } 884 if (!swap_reserve(mem_charged)) { 885 /* 886 * The swap reservation failed. The accounting 887 * from the entries of the copied vm2 will be 888 * substracted in vmspace_free(), so force the 889 * reservation there. 890 */ 891 swap_reserve_force(mem_charged); 892 error = ENOMEM; 893 goto fail2; 894 } 895 } else 896 vm2 = NULL; 897 898 /* 899 * XXX: This is ugly; when we copy resource usage, we need to bump 900 * per-cred resource counters. 901 */ 902 proc_set_cred_init(newproc, crhold(td->td_ucred)); 903 904 /* 905 * Initialize resource accounting for the child process. 906 */ 907 error = racct_proc_fork(p1, newproc); 908 if (error != 0) { 909 error = EAGAIN; 910 goto fail1; 911 } 912 913 #ifdef MAC 914 mac_proc_init(newproc); 915 #endif 916 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 917 STAILQ_INIT(&newproc->p_ktr); 918 919 /* We have to lock the process tree while we look for a pid. */ 920 sx_slock(&proctree_lock); 921 sx_xlock(&allproc_lock); 922 923 /* 924 * Increment the count of procs running with this uid. Don't allow 925 * a nonprivileged user to exceed their current limit. 926 * 927 * XXXRW: Can we avoid privilege here if it's not needed? 928 */ 929 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 930 if (error == 0) 931 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 932 else { 933 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 934 lim_cur(td, RLIMIT_NPROC)); 935 } 936 if (ok) { 937 do_fork(td, flags, newproc, td2, vm2, pdflags); 938 939 /* 940 * Return child proc pointer to parent. 941 */ 942 *procp = newproc; 943 if (flags & RFPROCDESC) { 944 procdesc_finit(newproc->p_procdesc, fp_procdesc); 945 fdrop(fp_procdesc, td); 946 } 947 racct_proc_fork_done(newproc); 948 return (0); 949 } 950 951 error = EAGAIN; 952 sx_sunlock(&proctree_lock); 953 sx_xunlock(&allproc_lock); 954 #ifdef MAC 955 mac_proc_destroy(newproc); 956 #endif 957 racct_proc_exit(newproc); 958 fail1: 959 crfree(newproc->p_ucred); 960 newproc->p_ucred = NULL; 961 fail2: 962 if (vm2 != NULL) 963 vmspace_free(vm2); 964 uma_zfree(proc_zone, newproc); 965 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 966 fdclose(td, fp_procdesc, *procdescp); 967 fdrop(fp_procdesc, td); 968 } 969 atomic_add_int(&nprocs, -1); 970 pause("fork", hz / 2); 971 return (error); 972 } 973 974 /* 975 * Handle the return of a child process from fork1(). This function 976 * is called from the MD fork_trampoline() entry point. 977 */ 978 void 979 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 980 struct trapframe *frame) 981 { 982 struct proc *p; 983 struct thread *td; 984 struct thread *dtd; 985 986 td = curthread; 987 p = td->td_proc; 988 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 989 990 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 991 td, td->td_sched, p->p_pid, td->td_name); 992 993 sched_fork_exit(td); 994 /* 995 * Processes normally resume in mi_switch() after being 996 * cpu_switch()'ed to, but when children start up they arrive here 997 * instead, so we must do much the same things as mi_switch() would. 998 */ 999 if ((dtd = PCPU_GET(deadthread))) { 1000 PCPU_SET(deadthread, NULL); 1001 thread_stash(dtd); 1002 } 1003 thread_unlock(td); 1004 1005 /* 1006 * cpu_set_fork_handler intercepts this function call to 1007 * have this call a non-return function to stay in kernel mode. 1008 * initproc has its own fork handler, but it does return. 1009 */ 1010 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1011 callout(arg, frame); 1012 1013 /* 1014 * Check if a kernel thread misbehaved and returned from its main 1015 * function. 1016 */ 1017 if (p->p_flag & P_KTHREAD) { 1018 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1019 td->td_name, p->p_pid); 1020 kproc_exit(0); 1021 } 1022 mtx_assert(&Giant, MA_NOTOWNED); 1023 1024 if (p->p_sysent->sv_schedtail != NULL) 1025 (p->p_sysent->sv_schedtail)(td); 1026 td->td_pflags &= ~TDP_FORKING; 1027 } 1028 1029 /* 1030 * Simplified back end of syscall(), used when returning from fork() 1031 * directly into user mode. Giant is not held on entry, and must not 1032 * be held on return. This function is passed in to fork_exit() as the 1033 * first parameter and is called when returning to a new userland process. 1034 */ 1035 void 1036 fork_return(struct thread *td, struct trapframe *frame) 1037 { 1038 struct proc *p, *dbg; 1039 1040 p = td->td_proc; 1041 if (td->td_dbgflags & TDB_STOPATFORK) { 1042 sx_xlock(&proctree_lock); 1043 PROC_LOCK(p); 1044 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 1045 (P_TRACED | P_FOLLOWFORK)) { 1046 /* 1047 * If debugger still wants auto-attach for the 1048 * parent's children, do it now. 1049 */ 1050 dbg = p->p_pptr->p_pptr; 1051 p->p_flag |= P_TRACED; 1052 p->p_oppid = p->p_pptr->p_pid; 1053 CTR2(KTR_PTRACE, 1054 "fork_return: attaching to new child pid %d: oppid %d", 1055 p->p_pid, p->p_oppid); 1056 proc_reparent(p, dbg); 1057 sx_xunlock(&proctree_lock); 1058 td->td_dbgflags |= TDB_CHILD | TDB_SCX; 1059 ptracestop(td, SIGSTOP); 1060 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1061 } else { 1062 /* 1063 * ... otherwise clear the request. 1064 */ 1065 sx_xunlock(&proctree_lock); 1066 td->td_dbgflags &= ~TDB_STOPATFORK; 1067 cv_broadcast(&p->p_dbgwait); 1068 } 1069 PROC_UNLOCK(p); 1070 } else if (p->p_flag & P_TRACED) { 1071 /* 1072 * This is the start of a new thread in a traced 1073 * process. Report a system call exit event. 1074 */ 1075 PROC_LOCK(p); 1076 td->td_dbgflags |= TDB_SCX; 1077 _STOPEVENT(p, S_SCX, td->td_dbg_sc_code); 1078 if ((p->p_stops & S_PT_SCX) != 0) 1079 ptracestop(td, SIGTRAP); 1080 td->td_dbgflags &= ~TDB_SCX; 1081 PROC_UNLOCK(p); 1082 } 1083 1084 userret(td, frame); 1085 1086 #ifdef KTRACE 1087 if (KTRPOINT(td, KTR_SYSRET)) 1088 ktrsysret(SYS_fork, 0, 0); 1089 #endif 1090 } 1091