1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1989, 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 37 */ 38 39 #include <sys/cdefs.h> 40 __FBSDID("$FreeBSD$"); 41 42 #include "opt_ktrace.h" 43 #include "opt_kstack_pages.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/bitstring.h> 48 #include <sys/sysproto.h> 49 #include <sys/eventhandler.h> 50 #include <sys/fcntl.h> 51 #include <sys/filedesc.h> 52 #include <sys/jail.h> 53 #include <sys/kernel.h> 54 #include <sys/kthread.h> 55 #include <sys/sysctl.h> 56 #include <sys/lock.h> 57 #include <sys/malloc.h> 58 #include <sys/mutex.h> 59 #include <sys/priv.h> 60 #include <sys/proc.h> 61 #include <sys/procdesc.h> 62 #include <sys/pioctl.h> 63 #include <sys/ptrace.h> 64 #include <sys/racct.h> 65 #include <sys/resourcevar.h> 66 #include <sys/sched.h> 67 #include <sys/syscall.h> 68 #include <sys/vmmeter.h> 69 #include <sys/vnode.h> 70 #include <sys/acct.h> 71 #include <sys/ktr.h> 72 #include <sys/ktrace.h> 73 #include <sys/unistd.h> 74 #include <sys/sdt.h> 75 #include <sys/sx.h> 76 #include <sys/sysent.h> 77 #include <sys/signalvar.h> 78 79 #include <security/audit/audit.h> 80 #include <security/mac/mac_framework.h> 81 82 #include <vm/vm.h> 83 #include <vm/pmap.h> 84 #include <vm/vm_map.h> 85 #include <vm/vm_extern.h> 86 #include <vm/uma.h> 87 88 #ifdef KDTRACE_HOOKS 89 #include <sys/dtrace_bsd.h> 90 dtrace_fork_func_t dtrace_fasttrap_fork; 91 #endif 92 93 SDT_PROVIDER_DECLARE(proc); 94 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int"); 95 96 #ifndef _SYS_SYSPROTO_H_ 97 struct fork_args { 98 int dummy; 99 }; 100 #endif 101 102 EVENTHANDLER_LIST_DECLARE(process_fork); 103 104 /* ARGSUSED */ 105 int 106 sys_fork(struct thread *td, struct fork_args *uap) 107 { 108 struct fork_req fr; 109 int error, pid; 110 111 bzero(&fr, sizeof(fr)); 112 fr.fr_flags = RFFDG | RFPROC; 113 fr.fr_pidp = &pid; 114 error = fork1(td, &fr); 115 if (error == 0) { 116 td->td_retval[0] = pid; 117 td->td_retval[1] = 0; 118 } 119 return (error); 120 } 121 122 /* ARGUSED */ 123 int 124 sys_pdfork(struct thread *td, struct pdfork_args *uap) 125 { 126 struct fork_req fr; 127 int error, fd, pid; 128 129 bzero(&fr, sizeof(fr)); 130 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC; 131 fr.fr_pidp = &pid; 132 fr.fr_pd_fd = &fd; 133 fr.fr_pd_flags = uap->flags; 134 /* 135 * It is necessary to return fd by reference because 0 is a valid file 136 * descriptor number, and the child needs to be able to distinguish 137 * itself from the parent using the return value. 138 */ 139 error = fork1(td, &fr); 140 if (error == 0) { 141 td->td_retval[0] = pid; 142 td->td_retval[1] = 0; 143 error = copyout(&fd, uap->fdp, sizeof(fd)); 144 } 145 return (error); 146 } 147 148 /* ARGSUSED */ 149 int 150 sys_vfork(struct thread *td, struct vfork_args *uap) 151 { 152 struct fork_req fr; 153 int error, pid; 154 155 bzero(&fr, sizeof(fr)); 156 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 157 fr.fr_pidp = &pid; 158 error = fork1(td, &fr); 159 if (error == 0) { 160 td->td_retval[0] = pid; 161 td->td_retval[1] = 0; 162 } 163 return (error); 164 } 165 166 int 167 sys_rfork(struct thread *td, struct rfork_args *uap) 168 { 169 struct fork_req fr; 170 int error, pid; 171 172 /* Don't allow kernel-only flags. */ 173 if ((uap->flags & RFKERNELONLY) != 0) 174 return (EINVAL); 175 176 AUDIT_ARG_FFLAGS(uap->flags); 177 bzero(&fr, sizeof(fr)); 178 fr.fr_flags = uap->flags; 179 fr.fr_pidp = &pid; 180 error = fork1(td, &fr); 181 if (error == 0) { 182 td->td_retval[0] = pid; 183 td->td_retval[1] = 0; 184 } 185 return (error); 186 } 187 188 int nprocs = 1; /* process 0 */ 189 int lastpid = 0; 190 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 191 "Last used PID"); 192 193 /* 194 * Random component to lastpid generation. We mix in a random factor to make 195 * it a little harder to predict. We sanity check the modulus value to avoid 196 * doing it in critical paths. Don't let it be too small or we pointlessly 197 * waste randomness entropy, and don't let it be impossibly large. Using a 198 * modulus that is too big causes a LOT more process table scans and slows 199 * down fork processing as the pidchecked caching is defeated. 200 */ 201 static int randompid = 0; 202 203 static int 204 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 205 { 206 int error, pid; 207 208 error = sysctl_wire_old_buffer(req, sizeof(int)); 209 if (error != 0) 210 return(error); 211 sx_xlock(&allproc_lock); 212 pid = randompid; 213 error = sysctl_handle_int(oidp, &pid, 0, req); 214 if (error == 0 && req->newptr != NULL) { 215 if (pid == 0) 216 randompid = 0; 217 else if (pid == 1) 218 /* generate a random PID modulus between 100 and 1123 */ 219 randompid = 100 + arc4random() % 1024; 220 else if (pid < 0 || pid > pid_max - 100) 221 /* out of range */ 222 randompid = pid_max - 100; 223 else if (pid < 100) 224 /* Make it reasonable */ 225 randompid = 100; 226 else 227 randompid = pid; 228 } 229 sx_xunlock(&allproc_lock); 230 return (error); 231 } 232 233 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 234 0, 0, sysctl_kern_randompid, "I", "Random PID modulus. Special values: 0: disable, 1: choose random value"); 235 236 extern bitstr_t proc_id_pidmap; 237 extern bitstr_t proc_id_grpidmap; 238 extern bitstr_t proc_id_sessidmap; 239 extern bitstr_t proc_id_reapmap; 240 241 /* 242 * Find an unused process ID 243 * 244 * If RFHIGHPID is set (used during system boot), do not allocate 245 * low-numbered pids. 246 */ 247 static int 248 fork_findpid(int flags) 249 { 250 pid_t result; 251 int trypid; 252 253 trypid = lastpid + 1; 254 if (flags & RFHIGHPID) { 255 if (trypid < 10) 256 trypid = 10; 257 } else { 258 if (randompid) 259 trypid += arc4random() % randompid; 260 } 261 mtx_lock(&procid_lock); 262 retry: 263 /* 264 * If the process ID prototype has wrapped around, 265 * restart somewhat above 0, as the low-numbered procs 266 * tend to include daemons that don't exit. 267 */ 268 if (trypid >= pid_max) { 269 trypid = trypid % pid_max; 270 if (trypid < 100) 271 trypid += 100; 272 } 273 274 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result); 275 if (result == -1) { 276 trypid = 100; 277 goto retry; 278 } 279 if (bit_test(&proc_id_grpidmap, result) || 280 bit_test(&proc_id_sessidmap, result) || 281 bit_test(&proc_id_reapmap, result)) { 282 trypid = result + 1; 283 goto retry; 284 } 285 286 /* 287 * RFHIGHPID does not mess with the lastpid counter during boot. 288 */ 289 if ((flags & RFHIGHPID) == 0) 290 lastpid = result; 291 292 bit_set(&proc_id_pidmap, result); 293 mtx_unlock(&procid_lock); 294 295 return (result); 296 } 297 298 static int 299 fork_norfproc(struct thread *td, int flags) 300 { 301 int error; 302 struct proc *p1; 303 304 KASSERT((flags & RFPROC) == 0, 305 ("fork_norfproc called with RFPROC set")); 306 p1 = td->td_proc; 307 308 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 309 (flags & (RFCFDG | RFFDG))) { 310 PROC_LOCK(p1); 311 if (thread_single(p1, SINGLE_BOUNDARY)) { 312 PROC_UNLOCK(p1); 313 return (ERESTART); 314 } 315 PROC_UNLOCK(p1); 316 } 317 318 error = vm_forkproc(td, NULL, NULL, NULL, flags); 319 if (error) 320 goto fail; 321 322 /* 323 * Close all file descriptors. 324 */ 325 if (flags & RFCFDG) { 326 struct filedesc *fdtmp; 327 fdtmp = fdinit(td->td_proc->p_fd, false); 328 fdescfree(td); 329 p1->p_fd = fdtmp; 330 } 331 332 /* 333 * Unshare file descriptors (from parent). 334 */ 335 if (flags & RFFDG) 336 fdunshare(td); 337 338 fail: 339 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 340 (flags & (RFCFDG | RFFDG))) { 341 PROC_LOCK(p1); 342 thread_single_end(p1, SINGLE_BOUNDARY); 343 PROC_UNLOCK(p1); 344 } 345 return (error); 346 } 347 348 static void 349 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 350 struct vmspace *vm2, struct file *fp_procdesc) 351 { 352 struct proc *p1, *pptr; 353 int trypid; 354 struct filedesc *fd; 355 struct filedesc_to_leader *fdtol; 356 struct sigacts *newsigacts; 357 358 sx_assert(&allproc_lock, SX_XLOCKED); 359 360 p1 = td->td_proc; 361 362 trypid = fork_findpid(fr->fr_flags); 363 p2->p_state = PRS_NEW; /* protect against others */ 364 p2->p_pid = trypid; 365 AUDIT_ARG_PID(p2->p_pid); 366 LIST_INSERT_HEAD(&allproc, p2, p_list); 367 allproc_gen++; 368 sx_xlock(PIDHASHLOCK(p2->p_pid)); 369 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 370 sx_xunlock(PIDHASHLOCK(p2->p_pid)); 371 PROC_LOCK(p2); 372 PROC_LOCK(p1); 373 374 sx_xunlock(&allproc_lock); 375 376 bcopy(&p1->p_startcopy, &p2->p_startcopy, 377 __rangeof(struct proc, p_startcopy, p_endcopy)); 378 pargs_hold(p2->p_args); 379 380 PROC_UNLOCK(p1); 381 382 bzero(&p2->p_startzero, 383 __rangeof(struct proc, p_startzero, p_endzero)); 384 385 /* Tell the prison that we exist. */ 386 prison_proc_hold(p2->p_ucred->cr_prison); 387 388 PROC_UNLOCK(p2); 389 390 tidhash_add(td2); 391 392 /* 393 * Malloc things while we don't hold any locks. 394 */ 395 if (fr->fr_flags & RFSIGSHARE) 396 newsigacts = NULL; 397 else 398 newsigacts = sigacts_alloc(); 399 400 /* 401 * Copy filedesc. 402 */ 403 if (fr->fr_flags & RFCFDG) { 404 fd = fdinit(p1->p_fd, false); 405 fdtol = NULL; 406 } else if (fr->fr_flags & RFFDG) { 407 fd = fdcopy(p1->p_fd); 408 fdtol = NULL; 409 } else { 410 fd = fdshare(p1->p_fd); 411 if (p1->p_fdtol == NULL) 412 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 413 p1->p_leader); 414 if ((fr->fr_flags & RFTHREAD) != 0) { 415 /* 416 * Shared file descriptor table, and shared 417 * process leaders. 418 */ 419 fdtol = p1->p_fdtol; 420 FILEDESC_XLOCK(p1->p_fd); 421 fdtol->fdl_refcount++; 422 FILEDESC_XUNLOCK(p1->p_fd); 423 } else { 424 /* 425 * Shared file descriptor table, and different 426 * process leaders. 427 */ 428 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 429 p1->p_fd, p2); 430 } 431 } 432 /* 433 * Make a proc table entry for the new process. 434 * Start by zeroing the section of proc that is zero-initialized, 435 * then copy the section that is copied directly from the parent. 436 */ 437 438 PROC_LOCK(p2); 439 PROC_LOCK(p1); 440 441 bzero(&td2->td_startzero, 442 __rangeof(struct thread, td_startzero, td_endzero)); 443 444 bcopy(&td->td_startcopy, &td2->td_startcopy, 445 __rangeof(struct thread, td_startcopy, td_endcopy)); 446 447 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 448 td2->td_sigstk = td->td_sigstk; 449 td2->td_flags = TDF_INMEM; 450 td2->td_lend_user_pri = PRI_MAX; 451 452 #ifdef VIMAGE 453 td2->td_vnet = NULL; 454 td2->td_vnet_lpush = NULL; 455 #endif 456 457 /* 458 * Allow the scheduler to initialize the child. 459 */ 460 thread_lock(td); 461 sched_fork(td, td2); 462 thread_unlock(td); 463 464 /* 465 * Duplicate sub-structures as needed. 466 * Increase reference counts on shared objects. 467 */ 468 p2->p_flag = P_INMEM; 469 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC | P2_TRAPCAP); 470 p2->p_swtick = ticks; 471 if (p1->p_flag & P_PROFIL) 472 startprofclock(p2); 473 474 if (fr->fr_flags & RFSIGSHARE) { 475 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 476 } else { 477 sigacts_copy(newsigacts, p1->p_sigacts); 478 p2->p_sigacts = newsigacts; 479 } 480 481 if (fr->fr_flags & RFTSIGZMB) 482 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 483 else if (fr->fr_flags & RFLINUXTHPN) 484 p2->p_sigparent = SIGUSR1; 485 else 486 p2->p_sigparent = SIGCHLD; 487 488 p2->p_textvp = p1->p_textvp; 489 p2->p_fd = fd; 490 p2->p_fdtol = fdtol; 491 492 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 493 p2->p_flag |= P_PROTECTED; 494 p2->p_flag2 |= P2_INHERIT_PROTECTED; 495 } 496 497 /* 498 * p_limit is copy-on-write. Bump its refcount. 499 */ 500 lim_fork(p1, p2); 501 502 thread_cow_get_proc(td2, p2); 503 504 pstats_fork(p1->p_stats, p2->p_stats); 505 506 PROC_UNLOCK(p1); 507 PROC_UNLOCK(p2); 508 509 /* Bump references to the text vnode (for procfs). */ 510 if (p2->p_textvp) 511 vrefact(p2->p_textvp); 512 513 /* 514 * Set up linkage for kernel based threading. 515 */ 516 if ((fr->fr_flags & RFTHREAD) != 0) { 517 mtx_lock(&ppeers_lock); 518 p2->p_peers = p1->p_peers; 519 p1->p_peers = p2; 520 p2->p_leader = p1->p_leader; 521 mtx_unlock(&ppeers_lock); 522 PROC_LOCK(p1->p_leader); 523 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 524 PROC_UNLOCK(p1->p_leader); 525 /* 526 * The task leader is exiting, so process p1 is 527 * going to be killed shortly. Since p1 obviously 528 * isn't dead yet, we know that the leader is either 529 * sending SIGKILL's to all the processes in this 530 * task or is sleeping waiting for all the peers to 531 * exit. We let p1 complete the fork, but we need 532 * to go ahead and kill the new process p2 since 533 * the task leader may not get a chance to send 534 * SIGKILL to it. We leave it on the list so that 535 * the task leader will wait for this new process 536 * to commit suicide. 537 */ 538 PROC_LOCK(p2); 539 kern_psignal(p2, SIGKILL); 540 PROC_UNLOCK(p2); 541 } else 542 PROC_UNLOCK(p1->p_leader); 543 } else { 544 p2->p_peers = NULL; 545 p2->p_leader = p2; 546 } 547 548 sx_xlock(&proctree_lock); 549 PGRP_LOCK(p1->p_pgrp); 550 PROC_LOCK(p2); 551 PROC_LOCK(p1); 552 553 /* 554 * Preserve some more flags in subprocess. P_PROFIL has already 555 * been preserved. 556 */ 557 p2->p_flag |= p1->p_flag & P_SUGID; 558 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING; 559 SESS_LOCK(p1->p_session); 560 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 561 p2->p_flag |= P_CONTROLT; 562 SESS_UNLOCK(p1->p_session); 563 if (fr->fr_flags & RFPPWAIT) 564 p2->p_flag |= P_PPWAIT; 565 566 p2->p_pgrp = p1->p_pgrp; 567 LIST_INSERT_AFTER(p1, p2, p_pglist); 568 PGRP_UNLOCK(p1->p_pgrp); 569 LIST_INIT(&p2->p_children); 570 LIST_INIT(&p2->p_orphans); 571 572 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 573 574 /* 575 * If PF_FORK is set, the child process inherits the 576 * procfs ioctl flags from its parent. 577 */ 578 if (p1->p_pfsflags & PF_FORK) { 579 p2->p_stops = p1->p_stops; 580 p2->p_pfsflags = p1->p_pfsflags; 581 } 582 583 /* 584 * This begins the section where we must prevent the parent 585 * from being swapped. 586 */ 587 _PHOLD(p1); 588 PROC_UNLOCK(p1); 589 590 /* 591 * Attach the new process to its parent. 592 * 593 * If RFNOWAIT is set, the newly created process becomes a child 594 * of init. This effectively disassociates the child from the 595 * parent. 596 */ 597 if ((fr->fr_flags & RFNOWAIT) != 0) { 598 pptr = p1->p_reaper; 599 p2->p_reaper = pptr; 600 } else { 601 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 602 p1 : p1->p_reaper; 603 pptr = p1; 604 } 605 p2->p_pptr = pptr; 606 p2->p_oppid = pptr->p_pid; 607 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 608 LIST_INIT(&p2->p_reaplist); 609 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 610 if (p2->p_reaper == p1 && p1 != initproc) { 611 p2->p_reapsubtree = p2->p_pid; 612 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 613 } 614 sx_xunlock(&proctree_lock); 615 616 /* Inform accounting that we have forked. */ 617 p2->p_acflag = AFORK; 618 PROC_UNLOCK(p2); 619 620 #ifdef KTRACE 621 ktrprocfork(p1, p2); 622 #endif 623 624 /* 625 * Finish creating the child process. It will return via a different 626 * execution path later. (ie: directly into user mode) 627 */ 628 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 629 630 if (fr->fr_flags == (RFFDG | RFPROC)) { 631 VM_CNT_INC(v_forks); 632 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 633 p2->p_vmspace->vm_ssize); 634 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 635 VM_CNT_INC(v_vforks); 636 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 637 p2->p_vmspace->vm_ssize); 638 } else if (p1 == &proc0) { 639 VM_CNT_INC(v_kthreads); 640 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 641 p2->p_vmspace->vm_ssize); 642 } else { 643 VM_CNT_INC(v_rforks); 644 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 645 p2->p_vmspace->vm_ssize); 646 } 647 648 /* 649 * Associate the process descriptor with the process before anything 650 * can happen that might cause that process to need the descriptor. 651 * However, don't do this until after fork(2) can no longer fail. 652 */ 653 if (fr->fr_flags & RFPROCDESC) 654 procdesc_new(p2, fr->fr_pd_flags); 655 656 /* 657 * Both processes are set up, now check if any loadable modules want 658 * to adjust anything. 659 */ 660 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 661 662 /* 663 * Set the child start time and mark the process as being complete. 664 */ 665 PROC_LOCK(p2); 666 PROC_LOCK(p1); 667 microuptime(&p2->p_stats->p_start); 668 PROC_SLOCK(p2); 669 p2->p_state = PRS_NORMAL; 670 PROC_SUNLOCK(p2); 671 672 #ifdef KDTRACE_HOOKS 673 /* 674 * Tell the DTrace fasttrap provider about the new process so that any 675 * tracepoints inherited from the parent can be removed. We have to do 676 * this only after p_state is PRS_NORMAL since the fasttrap module will 677 * use pfind() later on. 678 */ 679 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 680 dtrace_fasttrap_fork(p1, p2); 681 #endif 682 if (fr->fr_flags & RFPPWAIT) { 683 td->td_pflags |= TDP_RFPPWAIT; 684 td->td_rfppwait_p = p2; 685 td->td_dbgflags |= TDB_VFORK; 686 } 687 PROC_UNLOCK(p2); 688 689 /* 690 * Tell any interested parties about the new process. 691 */ 692 knote_fork(p1->p_klist, p2->p_pid); 693 694 /* 695 * Now can be swapped. 696 */ 697 _PRELE(p1); 698 PROC_UNLOCK(p1); 699 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 700 701 if (fr->fr_flags & RFPROCDESC) { 702 procdesc_finit(p2->p_procdesc, fp_procdesc); 703 fdrop(fp_procdesc, td); 704 } 705 706 /* 707 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 708 * synced with forks in progress so it is OK if we miss it 709 * if being set atm. 710 */ 711 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 712 sx_xlock(&proctree_lock); 713 PROC_LOCK(p2); 714 715 /* 716 * p1->p_ptevents & p1->p_pptr are protected by both 717 * process and proctree locks for modifications, 718 * so owning proctree_lock allows the race-free read. 719 */ 720 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 721 /* 722 * Arrange for debugger to receive the fork event. 723 * 724 * We can report PL_FLAG_FORKED regardless of 725 * P_FOLLOWFORK settings, but it does not make a sense 726 * for runaway child. 727 */ 728 td->td_dbgflags |= TDB_FORK; 729 td->td_dbg_forked = p2->p_pid; 730 td2->td_dbgflags |= TDB_STOPATFORK; 731 proc_set_traced(p2, true); 732 CTR2(KTR_PTRACE, 733 "do_fork: attaching to new child pid %d: oppid %d", 734 p2->p_pid, p2->p_oppid); 735 proc_reparent(p2, p1->p_pptr, false); 736 } 737 PROC_UNLOCK(p2); 738 sx_xunlock(&proctree_lock); 739 } 740 741 racct_proc_fork_done(p2); 742 743 if ((fr->fr_flags & RFSTOPPED) == 0) { 744 if (fr->fr_pidp != NULL) 745 *fr->fr_pidp = p2->p_pid; 746 /* 747 * If RFSTOPPED not requested, make child runnable and 748 * add to run queue. 749 */ 750 thread_lock(td2); 751 TD_SET_CAN_RUN(td2); 752 sched_add(td2, SRQ_BORING); 753 thread_unlock(td2); 754 } else { 755 *fr->fr_procp = p2; 756 } 757 } 758 759 void 760 fork_rfppwait(struct thread *td) 761 { 762 struct proc *p, *p2; 763 764 MPASS(td->td_pflags & TDP_RFPPWAIT); 765 766 p = td->td_proc; 767 /* 768 * Preserve synchronization semantics of vfork. If 769 * waiting for child to exec or exit, fork set 770 * P_PPWAIT on child, and there we sleep on our proc 771 * (in case of exit). 772 * 773 * Do it after the ptracestop() above is finished, to 774 * not block our debugger until child execs or exits 775 * to finish vfork wait. 776 */ 777 td->td_pflags &= ~TDP_RFPPWAIT; 778 p2 = td->td_rfppwait_p; 779 again: 780 PROC_LOCK(p2); 781 while (p2->p_flag & P_PPWAIT) { 782 PROC_LOCK(p); 783 if (thread_suspend_check_needed()) { 784 PROC_UNLOCK(p2); 785 thread_suspend_check(0); 786 PROC_UNLOCK(p); 787 goto again; 788 } else { 789 PROC_UNLOCK(p); 790 } 791 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 792 } 793 PROC_UNLOCK(p2); 794 795 if (td->td_dbgflags & TDB_VFORK) { 796 PROC_LOCK(p); 797 if (p->p_ptevents & PTRACE_VFORK) 798 ptracestop(td, SIGTRAP, NULL); 799 td->td_dbgflags &= ~TDB_VFORK; 800 PROC_UNLOCK(p); 801 } 802 } 803 804 int 805 fork1(struct thread *td, struct fork_req *fr) 806 { 807 struct proc *p1, *newproc; 808 struct thread *td2; 809 struct vmspace *vm2; 810 struct file *fp_procdesc; 811 vm_ooffset_t mem_charged; 812 int error, nprocs_new, ok; 813 static int curfail; 814 static struct timeval lastfail; 815 int flags, pages; 816 817 flags = fr->fr_flags; 818 pages = fr->fr_pages; 819 820 if ((flags & RFSTOPPED) != 0) 821 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 822 else 823 MPASS(fr->fr_procp == NULL); 824 825 /* Check for the undefined or unimplemented flags. */ 826 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 827 return (EINVAL); 828 829 /* Signal value requires RFTSIGZMB. */ 830 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 831 return (EINVAL); 832 833 /* Can't copy and clear. */ 834 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 835 return (EINVAL); 836 837 /* Check the validity of the signal number. */ 838 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 839 return (EINVAL); 840 841 if ((flags & RFPROCDESC) != 0) { 842 /* Can't not create a process yet get a process descriptor. */ 843 if ((flags & RFPROC) == 0) 844 return (EINVAL); 845 846 /* Must provide a place to put a procdesc if creating one. */ 847 if (fr->fr_pd_fd == NULL) 848 return (EINVAL); 849 850 /* Check if we are using supported flags. */ 851 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 852 return (EINVAL); 853 } 854 855 p1 = td->td_proc; 856 857 /* 858 * Here we don't create a new process, but we divorce 859 * certain parts of a process from itself. 860 */ 861 if ((flags & RFPROC) == 0) { 862 if (fr->fr_procp != NULL) 863 *fr->fr_procp = NULL; 864 else if (fr->fr_pidp != NULL) 865 *fr->fr_pidp = 0; 866 return (fork_norfproc(td, flags)); 867 } 868 869 fp_procdesc = NULL; 870 newproc = NULL; 871 vm2 = NULL; 872 873 /* 874 * Increment the nprocs resource before allocations occur. 875 * Although process entries are dynamically created, we still 876 * keep a global limit on the maximum number we will 877 * create. There are hard-limits as to the number of processes 878 * that can run, established by the KVA and memory usage for 879 * the process data. 880 * 881 * Don't allow a nonprivileged user to use the last ten 882 * processes; don't let root exceed the limit. 883 */ 884 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 885 if ((nprocs_new >= maxproc - 10 && 886 priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0) || 887 nprocs_new >= maxproc) { 888 error = EAGAIN; 889 sx_xlock(&allproc_lock); 890 if (ppsratecheck(&lastfail, &curfail, 1)) { 891 printf("maxproc limit exceeded by uid %u (pid %d); " 892 "see tuning(7) and login.conf(5)\n", 893 td->td_ucred->cr_ruid, p1->p_pid); 894 } 895 sx_xunlock(&allproc_lock); 896 goto fail2; 897 } 898 899 /* 900 * If required, create a process descriptor in the parent first; we 901 * will abandon it if something goes wrong. We don't finit() until 902 * later. 903 */ 904 if (flags & RFPROCDESC) { 905 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 906 fr->fr_pd_flags, fr->fr_pd_fcaps); 907 if (error != 0) 908 goto fail2; 909 } 910 911 mem_charged = 0; 912 if (pages == 0) 913 pages = kstack_pages; 914 /* Allocate new proc. */ 915 newproc = uma_zalloc(proc_zone, M_WAITOK); 916 td2 = FIRST_THREAD_IN_PROC(newproc); 917 if (td2 == NULL) { 918 td2 = thread_alloc(pages); 919 if (td2 == NULL) { 920 error = ENOMEM; 921 goto fail2; 922 } 923 proc_linkup(newproc, td2); 924 } else { 925 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 926 if (td2->td_kstack != 0) 927 vm_thread_dispose(td2); 928 if (!thread_alloc_stack(td2, pages)) { 929 error = ENOMEM; 930 goto fail2; 931 } 932 } 933 } 934 935 if ((flags & RFMEM) == 0) { 936 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 937 if (vm2 == NULL) { 938 error = ENOMEM; 939 goto fail2; 940 } 941 if (!swap_reserve(mem_charged)) { 942 /* 943 * The swap reservation failed. The accounting 944 * from the entries of the copied vm2 will be 945 * subtracted in vmspace_free(), so force the 946 * reservation there. 947 */ 948 swap_reserve_force(mem_charged); 949 error = ENOMEM; 950 goto fail2; 951 } 952 } else 953 vm2 = NULL; 954 955 /* 956 * XXX: This is ugly; when we copy resource usage, we need to bump 957 * per-cred resource counters. 958 */ 959 proc_set_cred_init(newproc, crhold(td->td_ucred)); 960 961 /* 962 * Initialize resource accounting for the child process. 963 */ 964 error = racct_proc_fork(p1, newproc); 965 if (error != 0) { 966 error = EAGAIN; 967 goto fail1; 968 } 969 970 #ifdef MAC 971 mac_proc_init(newproc); 972 #endif 973 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 974 STAILQ_INIT(&newproc->p_ktr); 975 976 sx_xlock(&allproc_lock); 977 978 /* 979 * Increment the count of procs running with this uid. Don't allow 980 * a nonprivileged user to exceed their current limit. 981 * 982 * XXXRW: Can we avoid privilege here if it's not needed? 983 */ 984 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT); 985 if (error == 0) 986 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 987 else { 988 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 989 lim_cur(td, RLIMIT_NPROC)); 990 } 991 if (ok) { 992 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 993 return (0); 994 } 995 996 error = EAGAIN; 997 sx_xunlock(&allproc_lock); 998 #ifdef MAC 999 mac_proc_destroy(newproc); 1000 #endif 1001 racct_proc_exit(newproc); 1002 fail1: 1003 crfree(newproc->p_ucred); 1004 newproc->p_ucred = NULL; 1005 fail2: 1006 if (vm2 != NULL) 1007 vmspace_free(vm2); 1008 uma_zfree(proc_zone, newproc); 1009 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1010 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1011 fdrop(fp_procdesc, td); 1012 } 1013 atomic_add_int(&nprocs, -1); 1014 pause("fork", hz / 2); 1015 return (error); 1016 } 1017 1018 /* 1019 * Handle the return of a child process from fork1(). This function 1020 * is called from the MD fork_trampoline() entry point. 1021 */ 1022 void 1023 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1024 struct trapframe *frame) 1025 { 1026 struct proc *p; 1027 struct thread *td; 1028 struct thread *dtd; 1029 1030 td = curthread; 1031 p = td->td_proc; 1032 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1033 1034 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1035 td, td_get_sched(td), p->p_pid, td->td_name); 1036 1037 sched_fork_exit(td); 1038 /* 1039 * Processes normally resume in mi_switch() after being 1040 * cpu_switch()'ed to, but when children start up they arrive here 1041 * instead, so we must do much the same things as mi_switch() would. 1042 */ 1043 if ((dtd = PCPU_GET(deadthread))) { 1044 PCPU_SET(deadthread, NULL); 1045 thread_stash(dtd); 1046 } 1047 thread_unlock(td); 1048 1049 /* 1050 * cpu_fork_kthread_handler intercepts this function call to 1051 * have this call a non-return function to stay in kernel mode. 1052 * initproc has its own fork handler, but it does return. 1053 */ 1054 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1055 callout(arg, frame); 1056 1057 /* 1058 * Check if a kernel thread misbehaved and returned from its main 1059 * function. 1060 */ 1061 if (p->p_flag & P_KPROC) { 1062 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1063 td->td_name, p->p_pid); 1064 kthread_exit(); 1065 } 1066 mtx_assert(&Giant, MA_NOTOWNED); 1067 1068 if (p->p_sysent->sv_schedtail != NULL) 1069 (p->p_sysent->sv_schedtail)(td); 1070 td->td_pflags &= ~TDP_FORKING; 1071 } 1072 1073 /* 1074 * Simplified back end of syscall(), used when returning from fork() 1075 * directly into user mode. This function is passed in to fork_exit() 1076 * as the first parameter and is called when returning to a new 1077 * userland process. 1078 */ 1079 void 1080 fork_return(struct thread *td, struct trapframe *frame) 1081 { 1082 struct proc *p; 1083 1084 p = td->td_proc; 1085 if (td->td_dbgflags & TDB_STOPATFORK) { 1086 PROC_LOCK(p); 1087 if ((p->p_flag & P_TRACED) != 0) { 1088 /* 1089 * Inform the debugger if one is still present. 1090 */ 1091 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1092 ptracestop(td, SIGSTOP, NULL); 1093 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1094 } else { 1095 /* 1096 * ... otherwise clear the request. 1097 */ 1098 td->td_dbgflags &= ~TDB_STOPATFORK; 1099 } 1100 PROC_UNLOCK(p); 1101 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) { 1102 /* 1103 * This is the start of a new thread in a traced 1104 * process. Report a system call exit event. 1105 */ 1106 PROC_LOCK(p); 1107 td->td_dbgflags |= TDB_SCX; 1108 _STOPEVENT(p, S_SCX, td->td_sa.code); 1109 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1110 (td->td_dbgflags & TDB_BORN) != 0) 1111 ptracestop(td, SIGTRAP, NULL); 1112 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1113 PROC_UNLOCK(p); 1114 } 1115 1116 userret(td, frame); 1117 1118 #ifdef KTRACE 1119 if (KTRPOINT(td, KTR_SYSRET)) 1120 ktrsysret(SYS_fork, 0, 0); 1121 #endif 1122 } 1123