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/ptrace.h> 63 #include <sys/racct.h> 64 #include <sys/resourcevar.h> 65 #include <sys/sched.h> 66 #include <sys/syscall.h> 67 #include <sys/vmmeter.h> 68 #include <sys/vnode.h> 69 #include <sys/acct.h> 70 #include <sys/ktr.h> 71 #include <sys/ktrace.h> 72 #include <sys/unistd.h> 73 #include <sys/sdt.h> 74 #include <sys/sx.h> 75 #include <sys/sysent.h> 76 #include <sys/signalvar.h> 77 78 #include <security/audit/audit.h> 79 #include <security/mac/mac_framework.h> 80 81 #include <vm/vm.h> 82 #include <vm/pmap.h> 83 #include <vm/vm_map.h> 84 #include <vm/vm_extern.h> 85 #include <vm/uma.h> 86 87 #ifdef KDTRACE_HOOKS 88 #include <sys/dtrace_bsd.h> 89 dtrace_fork_func_t dtrace_fasttrap_fork; 90 #endif 91 92 SDT_PROVIDER_DECLARE(proc); 93 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "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 struct fork_req fr; 106 int error, pid; 107 108 bzero(&fr, sizeof(fr)); 109 fr.fr_flags = RFFDG | RFPROC; 110 fr.fr_pidp = &pid; 111 error = fork1(td, &fr); 112 if (error == 0) { 113 td->td_retval[0] = pid; 114 td->td_retval[1] = 0; 115 } 116 return (error); 117 } 118 119 /* ARGUSED */ 120 int 121 sys_pdfork(struct thread *td, struct pdfork_args *uap) 122 { 123 struct fork_req fr; 124 int error, fd, pid; 125 126 bzero(&fr, sizeof(fr)); 127 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC; 128 fr.fr_pidp = &pid; 129 fr.fr_pd_fd = &fd; 130 fr.fr_pd_flags = uap->flags; 131 AUDIT_ARG_FFLAGS(uap->flags); 132 /* 133 * It is necessary to return fd by reference because 0 is a valid file 134 * descriptor number, and the child needs to be able to distinguish 135 * itself from the parent using the return value. 136 */ 137 error = fork1(td, &fr); 138 if (error == 0) { 139 td->td_retval[0] = pid; 140 td->td_retval[1] = 0; 141 error = copyout(&fd, uap->fdp, sizeof(fd)); 142 } 143 return (error); 144 } 145 146 /* ARGSUSED */ 147 int 148 sys_vfork(struct thread *td, struct vfork_args *uap) 149 { 150 struct fork_req fr; 151 int error, pid; 152 153 bzero(&fr, sizeof(fr)); 154 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 155 fr.fr_pidp = &pid; 156 error = fork1(td, &fr); 157 if (error == 0) { 158 td->td_retval[0] = pid; 159 td->td_retval[1] = 0; 160 } 161 return (error); 162 } 163 164 int 165 sys_rfork(struct thread *td, struct rfork_args *uap) 166 { 167 struct fork_req fr; 168 int error, pid; 169 170 /* Don't allow kernel-only flags. */ 171 if ((uap->flags & RFKERNELONLY) != 0) 172 return (EINVAL); 173 /* RFSPAWN must not appear with others */ 174 if ((uap->flags & RFSPAWN) != 0 && uap->flags != RFSPAWN) 175 return (EINVAL); 176 177 AUDIT_ARG_FFLAGS(uap->flags); 178 bzero(&fr, sizeof(fr)); 179 if ((uap->flags & RFSPAWN) != 0) { 180 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 181 fr.fr_flags2 = FR2_DROPSIG_CAUGHT; 182 } else { 183 fr.fr_flags = uap->flags; 184 } 185 fr.fr_pidp = &pid; 186 error = fork1(td, &fr); 187 if (error == 0) { 188 td->td_retval[0] = pid; 189 td->td_retval[1] = 0; 190 } 191 return (error); 192 } 193 194 int __exclusive_cache_line nprocs = 1; /* process 0 */ 195 int lastpid = 0; 196 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 197 "Last used PID"); 198 199 /* 200 * Random component to lastpid generation. We mix in a random factor to make 201 * it a little harder to predict. We sanity check the modulus value to avoid 202 * doing it in critical paths. Don't let it be too small or we pointlessly 203 * waste randomness entropy, and don't let it be impossibly large. Using a 204 * modulus that is too big causes a LOT more process table scans and slows 205 * down fork processing as the pidchecked caching is defeated. 206 */ 207 static int randompid = 0; 208 209 static int 210 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 211 { 212 int error, pid; 213 214 error = sysctl_wire_old_buffer(req, sizeof(int)); 215 if (error != 0) 216 return(error); 217 sx_xlock(&allproc_lock); 218 pid = randompid; 219 error = sysctl_handle_int(oidp, &pid, 0, req); 220 if (error == 0 && req->newptr != NULL) { 221 if (pid == 0) 222 randompid = 0; 223 else if (pid == 1) 224 /* generate a random PID modulus between 100 and 1123 */ 225 randompid = 100 + arc4random() % 1024; 226 else if (pid < 0 || pid > pid_max - 100) 227 /* out of range */ 228 randompid = pid_max - 100; 229 else if (pid < 100) 230 /* Make it reasonable */ 231 randompid = 100; 232 else 233 randompid = pid; 234 } 235 sx_xunlock(&allproc_lock); 236 return (error); 237 } 238 239 SYSCTL_PROC(_kern, OID_AUTO, randompid, 240 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, 241 sysctl_kern_randompid, "I", 242 "Random PID modulus. Special values: 0: disable, 1: choose random value"); 243 244 extern bitstr_t proc_id_pidmap; 245 extern bitstr_t proc_id_grpidmap; 246 extern bitstr_t proc_id_sessidmap; 247 extern bitstr_t proc_id_reapmap; 248 249 /* 250 * Find an unused process ID 251 * 252 * If RFHIGHPID is set (used during system boot), do not allocate 253 * low-numbered pids. 254 */ 255 static int 256 fork_findpid(int flags) 257 { 258 pid_t result; 259 int trypid, random; 260 261 /* 262 * Avoid calling arc4random with procid_lock held. 263 */ 264 random = 0; 265 if (__predict_false(randompid)) 266 random = arc4random() % randompid; 267 268 mtx_lock(&procid_lock); 269 270 trypid = lastpid + 1; 271 if (flags & RFHIGHPID) { 272 if (trypid < 10) 273 trypid = 10; 274 } else { 275 trypid += random; 276 } 277 retry: 278 if (trypid >= pid_max) 279 trypid = 2; 280 281 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result); 282 if (result == -1) { 283 KASSERT(trypid != 2, ("unexpectedly ran out of IDs")); 284 trypid = 2; 285 goto retry; 286 } 287 if (bit_test(&proc_id_grpidmap, result) || 288 bit_test(&proc_id_sessidmap, result) || 289 bit_test(&proc_id_reapmap, result)) { 290 trypid = result + 1; 291 goto retry; 292 } 293 294 /* 295 * RFHIGHPID does not mess with the lastpid counter during boot. 296 */ 297 if ((flags & RFHIGHPID) == 0) 298 lastpid = result; 299 300 bit_set(&proc_id_pidmap, result); 301 mtx_unlock(&procid_lock); 302 303 return (result); 304 } 305 306 static int 307 fork_norfproc(struct thread *td, int flags) 308 { 309 int error; 310 struct proc *p1; 311 312 KASSERT((flags & RFPROC) == 0, 313 ("fork_norfproc called with RFPROC set")); 314 p1 = td->td_proc; 315 316 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 317 (flags & (RFCFDG | RFFDG))) { 318 PROC_LOCK(p1); 319 if (thread_single(p1, SINGLE_BOUNDARY)) { 320 PROC_UNLOCK(p1); 321 return (ERESTART); 322 } 323 PROC_UNLOCK(p1); 324 } 325 326 error = vm_forkproc(td, NULL, NULL, NULL, flags); 327 if (error) 328 goto fail; 329 330 /* 331 * Close all file descriptors. 332 */ 333 if (flags & RFCFDG) { 334 struct filedesc *fdtmp; 335 struct pwddesc *pdtmp; 336 pdtmp = pdinit(td->td_proc->p_pd, false); 337 fdtmp = fdinit(td->td_proc->p_fd, false, NULL); 338 pdescfree(td); 339 fdescfree(td); 340 p1->p_fd = fdtmp; 341 p1->p_pd = pdtmp; 342 } 343 344 /* 345 * Unshare file descriptors (from parent). 346 */ 347 if (flags & RFFDG) { 348 fdunshare(td); 349 pdunshare(td); 350 } 351 352 fail: 353 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 354 (flags & (RFCFDG | RFFDG))) { 355 PROC_LOCK(p1); 356 thread_single_end(p1, SINGLE_BOUNDARY); 357 PROC_UNLOCK(p1); 358 } 359 return (error); 360 } 361 362 static void 363 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 364 struct vmspace *vm2, struct file *fp_procdesc) 365 { 366 struct proc *p1, *pptr; 367 struct filedesc *fd; 368 struct filedesc_to_leader *fdtol; 369 struct pwddesc *pd; 370 struct sigacts *newsigacts; 371 372 p1 = td->td_proc; 373 374 PROC_LOCK(p1); 375 bcopy(&p1->p_startcopy, &p2->p_startcopy, 376 __rangeof(struct proc, p_startcopy, p_endcopy)); 377 pargs_hold(p2->p_args); 378 PROC_UNLOCK(p1); 379 380 bzero(&p2->p_startzero, 381 __rangeof(struct proc, p_startzero, p_endzero)); 382 383 /* Tell the prison that we exist. */ 384 prison_proc_hold(p2->p_ucred->cr_prison); 385 386 p2->p_state = PRS_NEW; /* protect against others */ 387 p2->p_pid = fork_findpid(fr->fr_flags); 388 AUDIT_ARG_PID(p2->p_pid); 389 390 sx_xlock(&allproc_lock); 391 LIST_INSERT_HEAD(&allproc, p2, p_list); 392 allproc_gen++; 393 sx_xunlock(&allproc_lock); 394 395 sx_xlock(PIDHASHLOCK(p2->p_pid)); 396 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 397 sx_xunlock(PIDHASHLOCK(p2->p_pid)); 398 399 tidhash_add(td2); 400 401 /* 402 * Malloc things while we don't hold any locks. 403 */ 404 if (fr->fr_flags & RFSIGSHARE) 405 newsigacts = NULL; 406 else 407 newsigacts = sigacts_alloc(); 408 409 /* 410 * Copy filedesc. 411 */ 412 if (fr->fr_flags & RFCFDG) { 413 pd = pdinit(p1->p_pd, false); 414 fd = fdinit(p1->p_fd, false, NULL); 415 fdtol = NULL; 416 } else if (fr->fr_flags & RFFDG) { 417 if (fr->fr_flags2 & FR2_SHARE_PATHS) 418 pd = pdshare(p1->p_pd); 419 else 420 pd = pdcopy(p1->p_pd); 421 fd = fdcopy(p1->p_fd); 422 fdtol = NULL; 423 } else { 424 if (fr->fr_flags2 & FR2_SHARE_PATHS) 425 pd = pdcopy(p1->p_pd); 426 else 427 pd = pdshare(p1->p_pd); 428 fd = fdshare(p1->p_fd); 429 if (p1->p_fdtol == NULL) 430 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 431 p1->p_leader); 432 if ((fr->fr_flags & RFTHREAD) != 0) { 433 /* 434 * Shared file descriptor table, and shared 435 * process leaders. 436 */ 437 fdtol = p1->p_fdtol; 438 FILEDESC_XLOCK(p1->p_fd); 439 fdtol->fdl_refcount++; 440 FILEDESC_XUNLOCK(p1->p_fd); 441 } else { 442 /* 443 * Shared file descriptor table, and different 444 * process leaders. 445 */ 446 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 447 p1->p_fd, p2); 448 } 449 } 450 /* 451 * Make a proc table entry for the new process. 452 * Start by zeroing the section of proc that is zero-initialized, 453 * then copy the section that is copied directly from the parent. 454 */ 455 456 PROC_LOCK(p2); 457 PROC_LOCK(p1); 458 459 bzero(&td2->td_startzero, 460 __rangeof(struct thread, td_startzero, td_endzero)); 461 462 bcopy(&td->td_startcopy, &td2->td_startcopy, 463 __rangeof(struct thread, td_startcopy, td_endcopy)); 464 465 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 466 td2->td_sigstk = td->td_sigstk; 467 td2->td_flags = TDF_INMEM; 468 td2->td_lend_user_pri = PRI_MAX; 469 470 #ifdef VIMAGE 471 td2->td_vnet = NULL; 472 td2->td_vnet_lpush = NULL; 473 #endif 474 475 /* 476 * Allow the scheduler to initialize the child. 477 */ 478 thread_lock(td); 479 sched_fork(td, td2); 480 thread_unlock(td); 481 482 /* 483 * Duplicate sub-structures as needed. 484 * Increase reference counts on shared objects. 485 */ 486 p2->p_flag = P_INMEM; 487 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE | 488 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC | 489 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP | 490 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC); 491 p2->p_swtick = ticks; 492 if (p1->p_flag & P_PROFIL) 493 startprofclock(p2); 494 495 if (fr->fr_flags & RFSIGSHARE) { 496 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 497 } else { 498 sigacts_copy(newsigacts, p1->p_sigacts); 499 p2->p_sigacts = newsigacts; 500 if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) { 501 mtx_lock(&p2->p_sigacts->ps_mtx); 502 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0) 503 sig_drop_caught(p2); 504 if ((fr->fr_flags2 & FR2_KPROC) != 0) 505 p2->p_sigacts->ps_flag |= PS_NOCLDWAIT; 506 mtx_unlock(&p2->p_sigacts->ps_mtx); 507 } 508 } 509 510 if (fr->fr_flags & RFTSIGZMB) 511 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 512 else if (fr->fr_flags & RFLINUXTHPN) 513 p2->p_sigparent = SIGUSR1; 514 else 515 p2->p_sigparent = SIGCHLD; 516 517 if ((fr->fr_flags2 & FR2_KPROC) != 0) { 518 p2->p_flag |= P_SYSTEM | P_KPROC; 519 td2->td_pflags |= TDP_KTHREAD; 520 } 521 522 p2->p_textvp = p1->p_textvp; 523 p2->p_fd = fd; 524 p2->p_fdtol = fdtol; 525 p2->p_pd = pd; 526 527 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 528 p2->p_flag |= P_PROTECTED; 529 p2->p_flag2 |= P2_INHERIT_PROTECTED; 530 } 531 532 /* 533 * p_limit is copy-on-write. Bump its refcount. 534 */ 535 lim_fork(p1, p2); 536 537 thread_cow_get_proc(td2, p2); 538 539 pstats_fork(p1->p_stats, p2->p_stats); 540 541 PROC_UNLOCK(p1); 542 PROC_UNLOCK(p2); 543 544 /* Bump references to the text vnode (for procfs). */ 545 if (p2->p_textvp) 546 vrefact(p2->p_textvp); 547 548 /* 549 * Set up linkage for kernel based threading. 550 */ 551 if ((fr->fr_flags & RFTHREAD) != 0) { 552 mtx_lock(&ppeers_lock); 553 p2->p_peers = p1->p_peers; 554 p1->p_peers = p2; 555 p2->p_leader = p1->p_leader; 556 mtx_unlock(&ppeers_lock); 557 PROC_LOCK(p1->p_leader); 558 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 559 PROC_UNLOCK(p1->p_leader); 560 /* 561 * The task leader is exiting, so process p1 is 562 * going to be killed shortly. Since p1 obviously 563 * isn't dead yet, we know that the leader is either 564 * sending SIGKILL's to all the processes in this 565 * task or is sleeping waiting for all the peers to 566 * exit. We let p1 complete the fork, but we need 567 * to go ahead and kill the new process p2 since 568 * the task leader may not get a chance to send 569 * SIGKILL to it. We leave it on the list so that 570 * the task leader will wait for this new process 571 * to commit suicide. 572 */ 573 PROC_LOCK(p2); 574 kern_psignal(p2, SIGKILL); 575 PROC_UNLOCK(p2); 576 } else 577 PROC_UNLOCK(p1->p_leader); 578 } else { 579 p2->p_peers = NULL; 580 p2->p_leader = p2; 581 } 582 583 sx_xlock(&proctree_lock); 584 PGRP_LOCK(p1->p_pgrp); 585 PROC_LOCK(p2); 586 PROC_LOCK(p1); 587 588 /* 589 * Preserve some more flags in subprocess. P_PROFIL has already 590 * been preserved. 591 */ 592 p2->p_flag |= p1->p_flag & P_SUGID; 593 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK | 594 TDP_SIGFASTBLOCK)) | TDP_FORKING; 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 (fr->fr_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 * This begins the section where we must prevent the parent 612 * from being swapped. 613 */ 614 _PHOLD(p1); 615 PROC_UNLOCK(p1); 616 617 /* 618 * Attach the new process to its parent. 619 * 620 * If RFNOWAIT is set, the newly created process becomes a child 621 * of init. This effectively disassociates the child from the 622 * parent. 623 */ 624 if ((fr->fr_flags & RFNOWAIT) != 0) { 625 pptr = p1->p_reaper; 626 p2->p_reaper = pptr; 627 } else { 628 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 629 p1 : p1->p_reaper; 630 pptr = p1; 631 } 632 p2->p_pptr = pptr; 633 p2->p_oppid = pptr->p_pid; 634 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 635 LIST_INIT(&p2->p_reaplist); 636 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 637 if (p2->p_reaper == p1 && p1 != initproc) { 638 p2->p_reapsubtree = p2->p_pid; 639 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 640 } 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, fr->fr_flags); 656 657 if (fr->fr_flags == (RFFDG | RFPROC)) { 658 VM_CNT_INC(v_forks); 659 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 660 p2->p_vmspace->vm_ssize); 661 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 662 VM_CNT_INC(v_vforks); 663 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 664 p2->p_vmspace->vm_ssize); 665 } else if (p1 == &proc0) { 666 VM_CNT_INC(v_kthreads); 667 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 668 p2->p_vmspace->vm_ssize); 669 } else { 670 VM_CNT_INC(v_rforks); 671 VM_CNT_ADD(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 (fr->fr_flags & RFPROCDESC) 681 procdesc_new(p2, fr->fr_pd_flags); 682 683 /* 684 * Both processes are set up, now check if any loadable modules want 685 * to adjust anything. 686 */ 687 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_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 ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 707 dtrace_fasttrap_fork(p1, p2); 708 #endif 709 if (fr->fr_flags & RFPPWAIT) { 710 td->td_pflags |= TDP_RFPPWAIT; 711 td->td_rfppwait_p = p2; 712 td->td_dbgflags |= TDB_VFORK; 713 } 714 PROC_UNLOCK(p2); 715 716 /* 717 * Tell any interested parties about the new process. 718 */ 719 knote_fork(p1->p_klist, p2->p_pid); 720 721 /* 722 * Now can be swapped. 723 */ 724 _PRELE(p1); 725 PROC_UNLOCK(p1); 726 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 727 728 if (fr->fr_flags & RFPROCDESC) { 729 procdesc_finit(p2->p_procdesc, fp_procdesc); 730 fdrop(fp_procdesc, td); 731 } 732 733 /* 734 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 735 * synced with forks in progress so it is OK if we miss it 736 * if being set atm. 737 */ 738 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 739 sx_xlock(&proctree_lock); 740 PROC_LOCK(p2); 741 742 /* 743 * p1->p_ptevents & p1->p_pptr are protected by both 744 * process and proctree locks for modifications, 745 * so owning proctree_lock allows the race-free read. 746 */ 747 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 748 /* 749 * Arrange for debugger to receive the fork event. 750 * 751 * We can report PL_FLAG_FORKED regardless of 752 * P_FOLLOWFORK settings, but it does not make a sense 753 * for runaway child. 754 */ 755 td->td_dbgflags |= TDB_FORK; 756 td->td_dbg_forked = p2->p_pid; 757 td2->td_dbgflags |= TDB_STOPATFORK; 758 proc_set_traced(p2, true); 759 CTR2(KTR_PTRACE, 760 "do_fork: attaching to new child pid %d: oppid %d", 761 p2->p_pid, p2->p_oppid); 762 proc_reparent(p2, p1->p_pptr, false); 763 } 764 PROC_UNLOCK(p2); 765 sx_xunlock(&proctree_lock); 766 } 767 768 racct_proc_fork_done(p2); 769 770 if ((fr->fr_flags & RFSTOPPED) == 0) { 771 if (fr->fr_pidp != NULL) 772 *fr->fr_pidp = p2->p_pid; 773 /* 774 * If RFSTOPPED not requested, make child runnable and 775 * add to run queue. 776 */ 777 thread_lock(td2); 778 TD_SET_CAN_RUN(td2); 779 sched_add(td2, SRQ_BORING); 780 } else { 781 *fr->fr_procp = p2; 782 } 783 } 784 785 void 786 fork_rfppwait(struct thread *td) 787 { 788 struct proc *p, *p2; 789 790 MPASS(td->td_pflags & TDP_RFPPWAIT); 791 792 p = td->td_proc; 793 /* 794 * Preserve synchronization semantics of vfork. If 795 * waiting for child to exec or exit, fork set 796 * P_PPWAIT on child, and there we sleep on our proc 797 * (in case of exit). 798 * 799 * Do it after the ptracestop() above is finished, to 800 * not block our debugger until child execs or exits 801 * to finish vfork wait. 802 */ 803 td->td_pflags &= ~TDP_RFPPWAIT; 804 p2 = td->td_rfppwait_p; 805 again: 806 PROC_LOCK(p2); 807 while (p2->p_flag & P_PPWAIT) { 808 PROC_LOCK(p); 809 if (thread_suspend_check_needed()) { 810 PROC_UNLOCK(p2); 811 thread_suspend_check(0); 812 PROC_UNLOCK(p); 813 goto again; 814 } else { 815 PROC_UNLOCK(p); 816 } 817 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 818 } 819 PROC_UNLOCK(p2); 820 821 if (td->td_dbgflags & TDB_VFORK) { 822 PROC_LOCK(p); 823 if (p->p_ptevents & PTRACE_VFORK) 824 ptracestop(td, SIGTRAP, NULL); 825 td->td_dbgflags &= ~TDB_VFORK; 826 PROC_UNLOCK(p); 827 } 828 } 829 830 int 831 fork1(struct thread *td, struct fork_req *fr) 832 { 833 struct proc *p1, *newproc; 834 struct thread *td2; 835 struct vmspace *vm2; 836 struct ucred *cred; 837 struct file *fp_procdesc; 838 vm_ooffset_t mem_charged; 839 int error, nprocs_new; 840 static int curfail; 841 static struct timeval lastfail; 842 int flags, pages; 843 844 flags = fr->fr_flags; 845 pages = fr->fr_pages; 846 847 if ((flags & RFSTOPPED) != 0) 848 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 849 else 850 MPASS(fr->fr_procp == NULL); 851 852 /* Check for the undefined or unimplemented flags. */ 853 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 854 return (EINVAL); 855 856 /* Signal value requires RFTSIGZMB. */ 857 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 858 return (EINVAL); 859 860 /* Can't copy and clear. */ 861 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 862 return (EINVAL); 863 864 /* Check the validity of the signal number. */ 865 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 866 return (EINVAL); 867 868 if ((flags & RFPROCDESC) != 0) { 869 /* Can't not create a process yet get a process descriptor. */ 870 if ((flags & RFPROC) == 0) 871 return (EINVAL); 872 873 /* Must provide a place to put a procdesc if creating one. */ 874 if (fr->fr_pd_fd == NULL) 875 return (EINVAL); 876 877 /* Check if we are using supported flags. */ 878 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 879 return (EINVAL); 880 } 881 882 p1 = td->td_proc; 883 884 /* 885 * Here we don't create a new process, but we divorce 886 * certain parts of a process from itself. 887 */ 888 if ((flags & RFPROC) == 0) { 889 if (fr->fr_procp != NULL) 890 *fr->fr_procp = NULL; 891 else if (fr->fr_pidp != NULL) 892 *fr->fr_pidp = 0; 893 return (fork_norfproc(td, flags)); 894 } 895 896 fp_procdesc = NULL; 897 newproc = NULL; 898 vm2 = NULL; 899 900 /* 901 * Increment the nprocs resource before allocations occur. 902 * Although process entries are dynamically created, we still 903 * keep a global limit on the maximum number we will 904 * create. There are hard-limits as to the number of processes 905 * that can run, established by the KVA and memory usage for 906 * the process data. 907 * 908 * Don't allow a nonprivileged user to use the last ten 909 * processes; don't let root exceed the limit. 910 */ 911 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 912 if (nprocs_new >= maxproc - 10) { 913 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 || 914 nprocs_new >= maxproc) { 915 error = EAGAIN; 916 sx_xlock(&allproc_lock); 917 if (ppsratecheck(&lastfail, &curfail, 1)) { 918 printf("maxproc limit exceeded by uid %u " 919 "(pid %d); see tuning(7) and " 920 "login.conf(5)\n", 921 td->td_ucred->cr_ruid, p1->p_pid); 922 } 923 sx_xunlock(&allproc_lock); 924 goto fail2; 925 } 926 } 927 928 /* 929 * If required, create a process descriptor in the parent first; we 930 * will abandon it if something goes wrong. We don't finit() until 931 * later. 932 */ 933 if (flags & RFPROCDESC) { 934 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 935 fr->fr_pd_flags, fr->fr_pd_fcaps); 936 if (error != 0) 937 goto fail2; 938 AUDIT_ARG_FD(*fr->fr_pd_fd); 939 } 940 941 mem_charged = 0; 942 if (pages == 0) 943 pages = kstack_pages; 944 /* Allocate new proc. */ 945 newproc = uma_zalloc(proc_zone, M_WAITOK); 946 td2 = FIRST_THREAD_IN_PROC(newproc); 947 if (td2 == NULL) { 948 td2 = thread_alloc(pages); 949 if (td2 == NULL) { 950 error = ENOMEM; 951 goto fail2; 952 } 953 proc_linkup(newproc, td2); 954 } else { 955 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 956 if (td2->td_kstack != 0) 957 vm_thread_dispose(td2); 958 if (!thread_alloc_stack(td2, pages)) { 959 error = ENOMEM; 960 goto fail2; 961 } 962 } 963 } 964 965 if ((flags & RFMEM) == 0) { 966 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 967 if (vm2 == NULL) { 968 error = ENOMEM; 969 goto fail2; 970 } 971 if (!swap_reserve(mem_charged)) { 972 /* 973 * The swap reservation failed. The accounting 974 * from the entries of the copied vm2 will be 975 * subtracted in vmspace_free(), so force the 976 * reservation there. 977 */ 978 swap_reserve_force(mem_charged); 979 error = ENOMEM; 980 goto fail2; 981 } 982 } else 983 vm2 = NULL; 984 985 /* 986 * XXX: This is ugly; when we copy resource usage, we need to bump 987 * per-cred resource counters. 988 */ 989 proc_set_cred_init(newproc, td->td_ucred); 990 991 /* 992 * Initialize resource accounting for the child process. 993 */ 994 error = racct_proc_fork(p1, newproc); 995 if (error != 0) { 996 error = EAGAIN; 997 goto fail1; 998 } 999 1000 #ifdef MAC 1001 mac_proc_init(newproc); 1002 #endif 1003 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 1004 STAILQ_INIT(&newproc->p_ktr); 1005 1006 /* 1007 * Increment the count of procs running with this uid. Don't allow 1008 * a nonprivileged user to exceed their current limit. 1009 */ 1010 cred = td->td_ucred; 1011 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) { 1012 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0) 1013 goto fail0; 1014 chgproccnt(cred->cr_ruidinfo, 1, 0); 1015 } 1016 1017 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 1018 return (0); 1019 fail0: 1020 error = EAGAIN; 1021 #ifdef MAC 1022 mac_proc_destroy(newproc); 1023 #endif 1024 racct_proc_exit(newproc); 1025 fail1: 1026 proc_unset_cred(newproc); 1027 fail2: 1028 if (vm2 != NULL) 1029 vmspace_free(vm2); 1030 uma_zfree(proc_zone, newproc); 1031 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1032 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1033 fdrop(fp_procdesc, td); 1034 } 1035 atomic_add_int(&nprocs, -1); 1036 pause("fork", hz / 2); 1037 return (error); 1038 } 1039 1040 /* 1041 * Handle the return of a child process from fork1(). This function 1042 * is called from the MD fork_trampoline() entry point. 1043 */ 1044 void 1045 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1046 struct trapframe *frame) 1047 { 1048 struct proc *p; 1049 struct thread *td; 1050 struct thread *dtd; 1051 1052 td = curthread; 1053 p = td->td_proc; 1054 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1055 1056 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1057 td, td_get_sched(td), p->p_pid, td->td_name); 1058 1059 sched_fork_exit(td); 1060 /* 1061 * Processes normally resume in mi_switch() after being 1062 * cpu_switch()'ed to, but when children start up they arrive here 1063 * instead, so we must do much the same things as mi_switch() would. 1064 */ 1065 if ((dtd = PCPU_GET(deadthread))) { 1066 PCPU_SET(deadthread, NULL); 1067 thread_stash(dtd); 1068 } 1069 thread_unlock(td); 1070 1071 /* 1072 * cpu_fork_kthread_handler intercepts this function call to 1073 * have this call a non-return function to stay in kernel mode. 1074 * initproc has its own fork handler, but it does return. 1075 */ 1076 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1077 callout(arg, frame); 1078 1079 /* 1080 * Check if a kernel thread misbehaved and returned from its main 1081 * function. 1082 */ 1083 if (p->p_flag & P_KPROC) { 1084 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1085 td->td_name, p->p_pid); 1086 kthread_exit(); 1087 } 1088 mtx_assert(&Giant, MA_NOTOWNED); 1089 1090 if (p->p_sysent->sv_schedtail != NULL) 1091 (p->p_sysent->sv_schedtail)(td); 1092 td->td_pflags &= ~TDP_FORKING; 1093 } 1094 1095 /* 1096 * Simplified back end of syscall(), used when returning from fork() 1097 * directly into user mode. This function is passed in to fork_exit() 1098 * as the first parameter and is called when returning to a new 1099 * userland process. 1100 */ 1101 void 1102 fork_return(struct thread *td, struct trapframe *frame) 1103 { 1104 struct proc *p; 1105 1106 p = td->td_proc; 1107 if (td->td_dbgflags & TDB_STOPATFORK) { 1108 PROC_LOCK(p); 1109 if ((p->p_flag & P_TRACED) != 0) { 1110 /* 1111 * Inform the debugger if one is still present. 1112 */ 1113 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1114 ptracestop(td, SIGSTOP, NULL); 1115 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1116 } else { 1117 /* 1118 * ... otherwise clear the request. 1119 */ 1120 td->td_dbgflags &= ~TDB_STOPATFORK; 1121 } 1122 PROC_UNLOCK(p); 1123 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) { 1124 /* 1125 * This is the start of a new thread in a traced 1126 * process. Report a system call exit event. 1127 */ 1128 PROC_LOCK(p); 1129 td->td_dbgflags |= TDB_SCX; 1130 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1131 (td->td_dbgflags & TDB_BORN) != 0) 1132 ptracestop(td, SIGTRAP, NULL); 1133 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1134 PROC_UNLOCK(p); 1135 } 1136 1137 /* 1138 * If the prison was killed mid-fork, die along with it. 1139 */ 1140 if (!prison_isalive(td->td_ucred->cr_prison)) 1141 exit1(td, 0, SIGKILL); 1142 1143 userret(td, frame); 1144 1145 #ifdef KTRACE 1146 if (KTRPOINT(td, KTR_SYSRET)) 1147 ktrsysret(SYS_fork, 0, 0); 1148 #endif 1149 } 1150