Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c
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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: releng/12.0/sys/kern/kern_fork.c 335504 2018-06-21 21:12:49Z kib $"); 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/sysproto.h> 48 #include <sys/eventhandler.h> 49 #include <sys/fcntl.h> 50 #include <sys/filedesc.h> 51 #include <sys/jail.h> 52 #include <sys/kernel.h> 53 #include <sys/kthread.h> 54 #include <sys/sysctl.h> 55 #include <sys/lock.h> 56 #include <sys/malloc.h> 57 #include <sys/mutex.h> 58 #include <sys/priv.h> 59 #include <sys/proc.h> 60 #include <sys/procdesc.h> 61 #include <sys/pioctl.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 EVENTHANDLER_LIST_DECLARE(process_fork); 102 103 /* ARGSUSED */ 104 int 105 sys_fork(struct thread *td, struct fork_args *uap) 106 { 107 struct fork_req fr; 108 int error, pid; 109 110 bzero(&fr, sizeof(fr)); 111 fr.fr_flags = RFFDG | RFPROC; 112 fr.fr_pidp = &pid; 113 error = fork1(td, &fr); 114 if (error == 0) { 115 td->td_retval[0] = pid; 116 td->td_retval[1] = 0; 117 } 118 return (error); 119 } 120 121 /* ARGUSED */ 122 int 123 sys_pdfork(struct thread *td, struct pdfork_args *uap) 124 { 125 struct fork_req fr; 126 int error, fd, pid; 127 128 bzero(&fr, sizeof(fr)); 129 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC; 130 fr.fr_pidp = &pid; 131 fr.fr_pd_fd = &fd; 132 fr.fr_pd_flags = uap->flags; 133 /* 134 * It is necessary to return fd by reference because 0 is a valid file 135 * descriptor number, and the child needs to be able to distinguish 136 * itself from the parent using the return value. 137 */ 138 error = fork1(td, &fr); 139 if (error == 0) { 140 td->td_retval[0] = pid; 141 td->td_retval[1] = 0; 142 error = copyout(&fd, uap->fdp, sizeof(fd)); 143 } 144 return (error); 145 } 146 147 /* ARGSUSED */ 148 int 149 sys_vfork(struct thread *td, struct vfork_args *uap) 150 { 151 struct fork_req fr; 152 int error, pid; 153 154 bzero(&fr, sizeof(fr)); 155 fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 156 fr.fr_pidp = &pid; 157 error = fork1(td, &fr); 158 if (error == 0) { 159 td->td_retval[0] = pid; 160 td->td_retval[1] = 0; 161 } 162 return (error); 163 } 164 165 int 166 sys_rfork(struct thread *td, struct rfork_args *uap) 167 { 168 struct fork_req fr; 169 int error, pid; 170 171 /* Don't allow kernel-only flags. */ 172 if ((uap->flags & RFKERNELONLY) != 0) 173 return (EINVAL); 174 175 AUDIT_ARG_FFLAGS(uap->flags); 176 bzero(&fr, sizeof(fr)); 177 fr.fr_flags = uap->flags; 178 fr.fr_pidp = &pid; 179 error = fork1(td, &fr); 180 if (error == 0) { 181 td->td_retval[0] = pid; 182 td->td_retval[1] = 0; 183 } 184 return (error); 185 } 186 187 int nprocs = 1; /* process 0 */ 188 int lastpid = 0; 189 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 190 "Last used PID"); 191 192 /* 193 * Random component to lastpid generation. We mix in a random factor to make 194 * it a little harder to predict. We sanity check the modulus value to avoid 195 * doing it in critical paths. Don't let it be too small or we pointlessly 196 * waste randomness entropy, and don't let it be impossibly large. Using a 197 * modulus that is too big causes a LOT more process table scans and slows 198 * down fork processing as the pidchecked caching is defeated. 199 */ 200 static int randompid = 0; 201 202 static int 203 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 204 { 205 int error, pid; 206 207 error = sysctl_wire_old_buffer(req, sizeof(int)); 208 if (error != 0) 209 return(error); 210 sx_xlock(&allproc_lock); 211 pid = randompid; 212 error = sysctl_handle_int(oidp, &pid, 0, req); 213 if (error == 0 && req->newptr != NULL) { 214 if (pid == 0) 215 randompid = 0; 216 else if (pid == 1) 217 /* generate a random PID modulus between 100 and 1123 */ 218 randompid = 100 + arc4random() % 1024; 219 else if (pid < 0 || pid > pid_max - 100) 220 /* out of range */ 221 randompid = pid_max - 100; 222 else if (pid < 100) 223 /* Make it reasonable */ 224 randompid = 100; 225 else 226 randompid = pid; 227 } 228 sx_xunlock(&allproc_lock); 229 return (error); 230 } 231 232 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 233 0, 0, sysctl_kern_randompid, "I", "Random PID modulus. Special values: 0: disable, 1: choose random value"); 234 235 static int 236 fork_findpid(int flags) 237 { 238 struct proc *p; 239 int trypid; 240 static int pidchecked = 0; 241 242 /* 243 * Requires allproc_lock in order to iterate over the list 244 * of processes, and proctree_lock to access p_pgrp. 245 */ 246 sx_assert(&allproc_lock, SX_LOCKED); 247 sx_assert(&proctree_lock, SX_LOCKED); 248 249 /* 250 * Find an unused process ID. We remember a range of unused IDs 251 * ready to use (from lastpid+1 through pidchecked-1). 252 * 253 * If RFHIGHPID is set (used during system boot), do not allocate 254 * low-numbered pids. 255 */ 256 trypid = lastpid + 1; 257 if (flags & RFHIGHPID) { 258 if (trypid < 10) 259 trypid = 10; 260 } else { 261 if (randompid) 262 trypid += arc4random() % randompid; 263 } 264 retry: 265 /* 266 * If the process ID prototype has wrapped around, 267 * restart somewhat above 0, as the low-numbered procs 268 * tend to include daemons that don't exit. 269 */ 270 if (trypid >= pid_max) { 271 trypid = trypid % pid_max; 272 if (trypid < 100) 273 trypid += 100; 274 pidchecked = 0; 275 } 276 if (trypid >= pidchecked) { 277 int doingzomb = 0; 278 279 pidchecked = PID_MAX; 280 /* 281 * Scan the active and zombie procs to check whether this pid 282 * is in use. Remember the lowest pid that's greater 283 * than trypid, so we can avoid checking for a while. 284 * 285 * Avoid reuse of the process group id, session id or 286 * the reaper subtree id. Note that for process group 287 * and sessions, the amount of reserved pids is 288 * limited by process limit. For the subtree ids, the 289 * id is kept reserved only while there is a 290 * non-reaped process in the subtree, so amount of 291 * reserved pids is limited by process limit times 292 * two. 293 */ 294 p = LIST_FIRST(&allproc); 295 again: 296 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 297 while (p->p_pid == trypid || 298 p->p_reapsubtree == trypid || 299 (p->p_pgrp != NULL && 300 (p->p_pgrp->pg_id == trypid || 301 (p->p_session != NULL && 302 p->p_session->s_sid == trypid)))) { 303 trypid++; 304 if (trypid >= pidchecked) 305 goto retry; 306 } 307 if (p->p_pid > trypid && pidchecked > p->p_pid) 308 pidchecked = p->p_pid; 309 if (p->p_pgrp != NULL) { 310 if (p->p_pgrp->pg_id > trypid && 311 pidchecked > p->p_pgrp->pg_id) 312 pidchecked = p->p_pgrp->pg_id; 313 if (p->p_session != NULL && 314 p->p_session->s_sid > trypid && 315 pidchecked > p->p_session->s_sid) 316 pidchecked = p->p_session->s_sid; 317 } 318 } 319 if (!doingzomb) { 320 doingzomb = 1; 321 p = LIST_FIRST(&zombproc); 322 goto again; 323 } 324 } 325 326 /* 327 * RFHIGHPID does not mess with the lastpid counter during boot. 328 */ 329 if (flags & RFHIGHPID) 330 pidchecked = 0; 331 else 332 lastpid = trypid; 333 334 return (trypid); 335 } 336 337 static int 338 fork_norfproc(struct thread *td, int flags) 339 { 340 int error; 341 struct proc *p1; 342 343 KASSERT((flags & RFPROC) == 0, 344 ("fork_norfproc called with RFPROC set")); 345 p1 = td->td_proc; 346 347 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 348 (flags & (RFCFDG | RFFDG))) { 349 PROC_LOCK(p1); 350 if (thread_single(p1, SINGLE_BOUNDARY)) { 351 PROC_UNLOCK(p1); 352 return (ERESTART); 353 } 354 PROC_UNLOCK(p1); 355 } 356 357 error = vm_forkproc(td, NULL, NULL, NULL, flags); 358 if (error) 359 goto fail; 360 361 /* 362 * Close all file descriptors. 363 */ 364 if (flags & RFCFDG) { 365 struct filedesc *fdtmp; 366 fdtmp = fdinit(td->td_proc->p_fd, false); 367 fdescfree(td); 368 p1->p_fd = fdtmp; 369 } 370 371 /* 372 * Unshare file descriptors (from parent). 373 */ 374 if (flags & RFFDG) 375 fdunshare(td); 376 377 fail: 378 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 379 (flags & (RFCFDG | RFFDG))) { 380 PROC_LOCK(p1); 381 thread_single_end(p1, SINGLE_BOUNDARY); 382 PROC_UNLOCK(p1); 383 } 384 return (error); 385 } 386 387 static void 388 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 389 struct vmspace *vm2, struct file *fp_procdesc) 390 { 391 struct proc *p1, *pptr; 392 int trypid; 393 struct filedesc *fd; 394 struct filedesc_to_leader *fdtol; 395 struct sigacts *newsigacts; 396 397 sx_assert(&proctree_lock, SX_LOCKED); 398 sx_assert(&allproc_lock, SX_XLOCKED); 399 400 p1 = td->td_proc; 401 402 trypid = fork_findpid(fr->fr_flags); 403 404 p2->p_state = PRS_NEW; /* protect against others */ 405 p2->p_pid = trypid; 406 AUDIT_ARG_PID(p2->p_pid); 407 LIST_INSERT_HEAD(&allproc, p2, p_list); 408 allproc_gen++; 409 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 410 PROC_LOCK(p2); 411 PROC_LOCK(p1); 412 413 sx_xunlock(&allproc_lock); 414 sx_xunlock(&proctree_lock); 415 416 bcopy(&p1->p_startcopy, &p2->p_startcopy, 417 __rangeof(struct proc, p_startcopy, p_endcopy)); 418 pargs_hold(p2->p_args); 419 420 PROC_UNLOCK(p1); 421 422 bzero(&p2->p_startzero, 423 __rangeof(struct proc, p_startzero, p_endzero)); 424 425 /* Tell the prison that we exist. */ 426 prison_proc_hold(p2->p_ucred->cr_prison); 427 428 PROC_UNLOCK(p2); 429 430 tidhash_add(td2); 431 432 /* 433 * Malloc things while we don't hold any locks. 434 */ 435 if (fr->fr_flags & RFSIGSHARE) 436 newsigacts = NULL; 437 else 438 newsigacts = sigacts_alloc(); 439 440 /* 441 * Copy filedesc. 442 */ 443 if (fr->fr_flags & RFCFDG) { 444 fd = fdinit(p1->p_fd, false); 445 fdtol = NULL; 446 } else if (fr->fr_flags & RFFDG) { 447 fd = fdcopy(p1->p_fd); 448 fdtol = NULL; 449 } else { 450 fd = fdshare(p1->p_fd); 451 if (p1->p_fdtol == NULL) 452 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 453 p1->p_leader); 454 if ((fr->fr_flags & RFTHREAD) != 0) { 455 /* 456 * Shared file descriptor table, and shared 457 * process leaders. 458 */ 459 fdtol = p1->p_fdtol; 460 FILEDESC_XLOCK(p1->p_fd); 461 fdtol->fdl_refcount++; 462 FILEDESC_XUNLOCK(p1->p_fd); 463 } else { 464 /* 465 * Shared file descriptor table, and different 466 * process leaders. 467 */ 468 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 469 p1->p_fd, p2); 470 } 471 } 472 /* 473 * Make a proc table entry for the new process. 474 * Start by zeroing the section of proc that is zero-initialized, 475 * then copy the section that is copied directly from the parent. 476 */ 477 478 PROC_LOCK(p2); 479 PROC_LOCK(p1); 480 481 bzero(&td2->td_startzero, 482 __rangeof(struct thread, td_startzero, td_endzero)); 483 484 bcopy(&td->td_startcopy, &td2->td_startcopy, 485 __rangeof(struct thread, td_startcopy, td_endcopy)); 486 487 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 488 td2->td_sigstk = td->td_sigstk; 489 td2->td_flags = TDF_INMEM; 490 td2->td_lend_user_pri = PRI_MAX; 491 492 #ifdef VIMAGE 493 td2->td_vnet = NULL; 494 td2->td_vnet_lpush = NULL; 495 #endif 496 497 /* 498 * Allow the scheduler to initialize the child. 499 */ 500 thread_lock(td); 501 sched_fork(td, td2); 502 thread_unlock(td); 503 504 /* 505 * Duplicate sub-structures as needed. 506 * Increase reference counts on shared objects. 507 */ 508 p2->p_flag = P_INMEM; 509 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC | P2_TRAPCAP); 510 p2->p_swtick = ticks; 511 if (p1->p_flag & P_PROFIL) 512 startprofclock(p2); 513 514 if (fr->fr_flags & RFSIGSHARE) { 515 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 516 } else { 517 sigacts_copy(newsigacts, p1->p_sigacts); 518 p2->p_sigacts = newsigacts; 519 } 520 521 if (fr->fr_flags & RFTSIGZMB) 522 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 523 else if (fr->fr_flags & RFLINUXTHPN) 524 p2->p_sigparent = SIGUSR1; 525 else 526 p2->p_sigparent = SIGCHLD; 527 528 p2->p_textvp = p1->p_textvp; 529 p2->p_fd = fd; 530 p2->p_fdtol = fdtol; 531 532 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 533 p2->p_flag |= P_PROTECTED; 534 p2->p_flag2 |= P2_INHERIT_PROTECTED; 535 } 536 537 /* 538 * p_limit is copy-on-write. Bump its refcount. 539 */ 540 lim_fork(p1, p2); 541 542 thread_cow_get_proc(td2, p2); 543 544 pstats_fork(p1->p_stats, p2->p_stats); 545 546 PROC_UNLOCK(p1); 547 PROC_UNLOCK(p2); 548 549 /* Bump references to the text vnode (for procfs). */ 550 if (p2->p_textvp) 551 vrefact(p2->p_textvp); 552 553 /* 554 * Set up linkage for kernel based threading. 555 */ 556 if ((fr->fr_flags & RFTHREAD) != 0) { 557 mtx_lock(&ppeers_lock); 558 p2->p_peers = p1->p_peers; 559 p1->p_peers = p2; 560 p2->p_leader = p1->p_leader; 561 mtx_unlock(&ppeers_lock); 562 PROC_LOCK(p1->p_leader); 563 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 564 PROC_UNLOCK(p1->p_leader); 565 /* 566 * The task leader is exiting, so process p1 is 567 * going to be killed shortly. Since p1 obviously 568 * isn't dead yet, we know that the leader is either 569 * sending SIGKILL's to all the processes in this 570 * task or is sleeping waiting for all the peers to 571 * exit. We let p1 complete the fork, but we need 572 * to go ahead and kill the new process p2 since 573 * the task leader may not get a chance to send 574 * SIGKILL to it. We leave it on the list so that 575 * the task leader will wait for this new process 576 * to commit suicide. 577 */ 578 PROC_LOCK(p2); 579 kern_psignal(p2, SIGKILL); 580 PROC_UNLOCK(p2); 581 } else 582 PROC_UNLOCK(p1->p_leader); 583 } else { 584 p2->p_peers = NULL; 585 p2->p_leader = p2; 586 } 587 588 sx_xlock(&proctree_lock); 589 PGRP_LOCK(p1->p_pgrp); 590 PROC_LOCK(p2); 591 PROC_LOCK(p1); 592 593 /* 594 * Preserve some more flags in subprocess. P_PROFIL has already 595 * been preserved. 596 */ 597 p2->p_flag |= p1->p_flag & P_SUGID; 598 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING; 599 SESS_LOCK(p1->p_session); 600 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 601 p2->p_flag |= P_CONTROLT; 602 SESS_UNLOCK(p1->p_session); 603 if (fr->fr_flags & RFPPWAIT) 604 p2->p_flag |= P_PPWAIT; 605 606 p2->p_pgrp = p1->p_pgrp; 607 LIST_INSERT_AFTER(p1, p2, p_pglist); 608 PGRP_UNLOCK(p1->p_pgrp); 609 LIST_INIT(&p2->p_children); 610 LIST_INIT(&p2->p_orphans); 611 612 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 613 614 /* 615 * If PF_FORK is set, the child process inherits the 616 * procfs ioctl flags from its parent. 617 */ 618 if (p1->p_pfsflags & PF_FORK) { 619 p2->p_stops = p1->p_stops; 620 p2->p_pfsflags = p1->p_pfsflags; 621 } 622 623 /* 624 * This begins the section where we must prevent the parent 625 * from being swapped. 626 */ 627 _PHOLD(p1); 628 PROC_UNLOCK(p1); 629 630 /* 631 * Attach the new process to its parent. 632 * 633 * If RFNOWAIT is set, the newly created process becomes a child 634 * of init. This effectively disassociates the child from the 635 * parent. 636 */ 637 if ((fr->fr_flags & RFNOWAIT) != 0) { 638 pptr = p1->p_reaper; 639 p2->p_reaper = pptr; 640 } else { 641 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 642 p1 : p1->p_reaper; 643 pptr = p1; 644 } 645 p2->p_pptr = pptr; 646 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 647 LIST_INIT(&p2->p_reaplist); 648 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 649 if (p2->p_reaper == p1) 650 p2->p_reapsubtree = p2->p_pid; 651 sx_xunlock(&proctree_lock); 652 653 /* Inform accounting that we have forked. */ 654 p2->p_acflag = AFORK; 655 PROC_UNLOCK(p2); 656 657 #ifdef KTRACE 658 ktrprocfork(p1, p2); 659 #endif 660 661 /* 662 * Finish creating the child process. It will return via a different 663 * execution path later. (ie: directly into user mode) 664 */ 665 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 666 667 if (fr->fr_flags == (RFFDG | RFPROC)) { 668 VM_CNT_INC(v_forks); 669 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 670 p2->p_vmspace->vm_ssize); 671 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 672 VM_CNT_INC(v_vforks); 673 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 674 p2->p_vmspace->vm_ssize); 675 } else if (p1 == &proc0) { 676 VM_CNT_INC(v_kthreads); 677 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 678 p2->p_vmspace->vm_ssize); 679 } else { 680 VM_CNT_INC(v_rforks); 681 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 682 p2->p_vmspace->vm_ssize); 683 } 684 685 /* 686 * Associate the process descriptor with the process before anything 687 * can happen that might cause that process to need the descriptor. 688 * However, don't do this until after fork(2) can no longer fail. 689 */ 690 if (fr->fr_flags & RFPROCDESC) 691 procdesc_new(p2, fr->fr_pd_flags); 692 693 /* 694 * Both processes are set up, now check if any loadable modules want 695 * to adjust anything. 696 */ 697 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 698 699 /* 700 * Set the child start time and mark the process as being complete. 701 */ 702 PROC_LOCK(p2); 703 PROC_LOCK(p1); 704 microuptime(&p2->p_stats->p_start); 705 PROC_SLOCK(p2); 706 p2->p_state = PRS_NORMAL; 707 PROC_SUNLOCK(p2); 708 709 #ifdef KDTRACE_HOOKS 710 /* 711 * Tell the DTrace fasttrap provider about the new process so that any 712 * tracepoints inherited from the parent can be removed. We have to do 713 * this only after p_state is PRS_NORMAL since the fasttrap module will 714 * use pfind() later on. 715 */ 716 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 717 dtrace_fasttrap_fork(p1, p2); 718 #endif 719 /* 720 * Hold the process so that it cannot exit after we make it runnable, 721 * but before we wait for the debugger. 722 */ 723 _PHOLD(p2); 724 if (fr->fr_flags & RFPPWAIT) { 725 td->td_pflags |= TDP_RFPPWAIT; 726 td->td_rfppwait_p = p2; 727 td->td_dbgflags |= TDB_VFORK; 728 } 729 PROC_UNLOCK(p2); 730 731 /* 732 * Now can be swapped. 733 */ 734 _PRELE(p1); 735 PROC_UNLOCK(p1); 736 737 /* 738 * Tell any interested parties about the new process. 739 */ 740 knote_fork(p1->p_klist, p2->p_pid); 741 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 742 743 if (fr->fr_flags & RFPROCDESC) { 744 procdesc_finit(p2->p_procdesc, fp_procdesc); 745 fdrop(fp_procdesc, td); 746 } 747 748 /* 749 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 750 * synced with forks in progress so it is OK if we miss it 751 * if being set atm. 752 */ 753 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 754 sx_xlock(&proctree_lock); 755 PROC_LOCK(p2); 756 757 /* 758 * p1->p_ptevents & p1->p_pptr are protected by both 759 * process and proctree locks for modifications, 760 * so owning proctree_lock allows the race-free read. 761 */ 762 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 763 /* 764 * Arrange for debugger to receive the fork event. 765 * 766 * We can report PL_FLAG_FORKED regardless of 767 * P_FOLLOWFORK settings, but it does not make a sense 768 * for runaway child. 769 */ 770 td->td_dbgflags |= TDB_FORK; 771 td->td_dbg_forked = p2->p_pid; 772 td2->td_dbgflags |= TDB_STOPATFORK; 773 proc_set_traced(p2, true); 774 CTR2(KTR_PTRACE, 775 "do_fork: attaching to new child pid %d: oppid %d", 776 p2->p_pid, p2->p_oppid); 777 proc_reparent(p2, p1->p_pptr); 778 } 779 PROC_UNLOCK(p2); 780 sx_xunlock(&proctree_lock); 781 } 782 783 if ((fr->fr_flags & RFSTOPPED) == 0) { 784 /* 785 * If RFSTOPPED not requested, make child runnable and 786 * add to run queue. 787 */ 788 thread_lock(td2); 789 TD_SET_CAN_RUN(td2); 790 sched_add(td2, SRQ_BORING); 791 thread_unlock(td2); 792 if (fr->fr_pidp != NULL) 793 *fr->fr_pidp = p2->p_pid; 794 } else { 795 *fr->fr_procp = p2; 796 } 797 798 PROC_LOCK(p2); 799 _PRELE(p2); 800 racct_proc_fork_done(p2); 801 PROC_UNLOCK(p2); 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 && priv_check_cred(td->td_ucred, 886 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) { 887 error = EAGAIN; 888 sx_xlock(&allproc_lock); 889 if (ppsratecheck(&lastfail, &curfail, 1)) { 890 printf("maxproc limit exceeded by uid %u (pid %d); " 891 "see tuning(7) and login.conf(5)\n", 892 td->td_ucred->cr_ruid, p1->p_pid); 893 } 894 sx_xunlock(&allproc_lock); 895 goto fail2; 896 } 897 898 /* 899 * If required, create a process descriptor in the parent first; we 900 * will abandon it if something goes wrong. We don't finit() until 901 * later. 902 */ 903 if (flags & RFPROCDESC) { 904 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 905 fr->fr_pd_flags, fr->fr_pd_fcaps); 906 if (error != 0) 907 goto fail2; 908 } 909 910 mem_charged = 0; 911 if (pages == 0) 912 pages = kstack_pages; 913 /* Allocate new proc. */ 914 newproc = uma_zalloc(proc_zone, M_WAITOK); 915 td2 = FIRST_THREAD_IN_PROC(newproc); 916 if (td2 == NULL) { 917 td2 = thread_alloc(pages); 918 if (td2 == NULL) { 919 error = ENOMEM; 920 goto fail2; 921 } 922 proc_linkup(newproc, td2); 923 } else { 924 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 925 if (td2->td_kstack != 0) 926 vm_thread_dispose(td2); 927 if (!thread_alloc_stack(td2, pages)) { 928 error = ENOMEM; 929 goto fail2; 930 } 931 } 932 } 933 934 if ((flags & RFMEM) == 0) { 935 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 936 if (vm2 == NULL) { 937 error = ENOMEM; 938 goto fail2; 939 } 940 if (!swap_reserve(mem_charged)) { 941 /* 942 * The swap reservation failed. The accounting 943 * from the entries of the copied vm2 will be 944 * subtracted in vmspace_free(), so force the 945 * reservation there. 946 */ 947 swap_reserve_force(mem_charged); 948 error = ENOMEM; 949 goto fail2; 950 } 951 } else 952 vm2 = NULL; 953 954 /* 955 * XXX: This is ugly; when we copy resource usage, we need to bump 956 * per-cred resource counters. 957 */ 958 proc_set_cred_init(newproc, crhold(td->td_ucred)); 959 960 /* 961 * Initialize resource accounting for the child process. 962 */ 963 error = racct_proc_fork(p1, newproc); 964 if (error != 0) { 965 error = EAGAIN; 966 goto fail1; 967 } 968 969 #ifdef MAC 970 mac_proc_init(newproc); 971 #endif 972 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 973 STAILQ_INIT(&newproc->p_ktr); 974 975 /* We have to lock the process tree while we look for a pid. */ 976 sx_xlock(&proctree_lock); 977 sx_xlock(&allproc_lock); 978 979 /* 980 * Increment the count of procs running with this uid. Don't allow 981 * a nonprivileged user to exceed their current limit. 982 * 983 * XXXRW: Can we avoid privilege here if it's not needed? 984 */ 985 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 986 if (error == 0) 987 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 988 else { 989 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 990 lim_cur(td, RLIMIT_NPROC)); 991 } 992 if (ok) { 993 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 994 return (0); 995 } 996 997 error = EAGAIN; 998 sx_xunlock(&allproc_lock); 999 sx_xunlock(&proctree_lock); 1000 #ifdef MAC 1001 mac_proc_destroy(newproc); 1002 #endif 1003 racct_proc_exit(newproc); 1004 fail1: 1005 crfree(newproc->p_ucred); 1006 newproc->p_ucred = NULL; 1007 fail2: 1008 if (vm2 != NULL) 1009 vmspace_free(vm2); 1010 uma_zfree(proc_zone, newproc); 1011 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1012 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1013 fdrop(fp_procdesc, td); 1014 } 1015 atomic_add_int(&nprocs, -1); 1016 pause("fork", hz / 2); 1017 return (error); 1018 } 1019 1020 /* 1021 * Handle the return of a child process from fork1(). This function 1022 * is called from the MD fork_trampoline() entry point. 1023 */ 1024 void 1025 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1026 struct trapframe *frame) 1027 { 1028 struct proc *p; 1029 struct thread *td; 1030 struct thread *dtd; 1031 1032 td = curthread; 1033 p = td->td_proc; 1034 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1035 1036 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1037 td, td_get_sched(td), p->p_pid, td->td_name); 1038 1039 sched_fork_exit(td); 1040 /* 1041 * Processes normally resume in mi_switch() after being 1042 * cpu_switch()'ed to, but when children start up they arrive here 1043 * instead, so we must do much the same things as mi_switch() would. 1044 */ 1045 if ((dtd = PCPU_GET(deadthread))) { 1046 PCPU_SET(deadthread, NULL); 1047 thread_stash(dtd); 1048 } 1049 thread_unlock(td); 1050 1051 /* 1052 * cpu_fork_kthread_handler intercepts this function call to 1053 * have this call a non-return function to stay in kernel mode. 1054 * initproc has its own fork handler, but it does return. 1055 */ 1056 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1057 callout(arg, frame); 1058 1059 /* 1060 * Check if a kernel thread misbehaved and returned from its main 1061 * function. 1062 */ 1063 if (p->p_flag & P_KPROC) { 1064 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1065 td->td_name, p->p_pid); 1066 kthread_exit(); 1067 } 1068 mtx_assert(&Giant, MA_NOTOWNED); 1069 1070 if (p->p_sysent->sv_schedtail != NULL) 1071 (p->p_sysent->sv_schedtail)(td); 1072 td->td_pflags &= ~TDP_FORKING; 1073 } 1074 1075 /* 1076 * Simplified back end of syscall(), used when returning from fork() 1077 * directly into user mode. This function is passed in to fork_exit() 1078 * as the first parameter and is called when returning to a new 1079 * userland process. 1080 */ 1081 void 1082 fork_return(struct thread *td, struct trapframe *frame) 1083 { 1084 struct proc *p; 1085 1086 p = td->td_proc; 1087 if (td->td_dbgflags & TDB_STOPATFORK) { 1088 PROC_LOCK(p); 1089 if ((p->p_flag & P_TRACED) != 0) { 1090 /* 1091 * Inform the debugger if one is still present. 1092 */ 1093 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1094 ptracestop(td, SIGSTOP, NULL); 1095 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1096 } else { 1097 /* 1098 * ... otherwise clear the request. 1099 */ 1100 td->td_dbgflags &= ~TDB_STOPATFORK; 1101 } 1102 PROC_UNLOCK(p); 1103 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) { 1104 /* 1105 * This is the start of a new thread in a traced 1106 * process. Report a system call exit event. 1107 */ 1108 PROC_LOCK(p); 1109 td->td_dbgflags |= TDB_SCX; 1110 _STOPEVENT(p, S_SCX, td->td_sa.code); 1111 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1112 (td->td_dbgflags & TDB_BORN) != 0) 1113 ptracestop(td, SIGTRAP, NULL); 1114 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1115 PROC_UNLOCK(p); 1116 } 1117 1118 userret(td, frame); 1119 1120 #ifdef KTRACE 1121 if (KTRPOINT(td, KTR_SYSRET)) 1122 ktrsysret(SYS_fork, 0, 0); 1123 #endif 1124 }
Cache object: 7ab95262dba275bdc5c763970fa50c1d
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