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("$FreeBSD$"); 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) != 0) { 501 mtx_lock(&p2->p_sigacts->ps_mtx); 502 sig_drop_caught(p2); 503 mtx_unlock(&p2->p_sigacts->ps_mtx); 504 } 505 } 506 507 if (fr->fr_flags & RFTSIGZMB) 508 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 509 else if (fr->fr_flags & RFLINUXTHPN) 510 p2->p_sigparent = SIGUSR1; 511 else 512 p2->p_sigparent = SIGCHLD; 513 514 p2->p_textvp = p1->p_textvp; 515 p2->p_fd = fd; 516 p2->p_fdtol = fdtol; 517 p2->p_pd = pd; 518 519 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 520 p2->p_flag |= P_PROTECTED; 521 p2->p_flag2 |= P2_INHERIT_PROTECTED; 522 } 523 524 /* 525 * p_limit is copy-on-write. Bump its refcount. 526 */ 527 lim_fork(p1, p2); 528 529 thread_cow_get_proc(td2, p2); 530 531 pstats_fork(p1->p_stats, p2->p_stats); 532 533 PROC_UNLOCK(p1); 534 PROC_UNLOCK(p2); 535 536 /* Bump references to the text vnode (for procfs). */ 537 if (p2->p_textvp) 538 vrefact(p2->p_textvp); 539 540 /* 541 * Set up linkage for kernel based threading. 542 */ 543 if ((fr->fr_flags & RFTHREAD) != 0) { 544 mtx_lock(&ppeers_lock); 545 p2->p_peers = p1->p_peers; 546 p1->p_peers = p2; 547 p2->p_leader = p1->p_leader; 548 mtx_unlock(&ppeers_lock); 549 PROC_LOCK(p1->p_leader); 550 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 551 PROC_UNLOCK(p1->p_leader); 552 /* 553 * The task leader is exiting, so process p1 is 554 * going to be killed shortly. Since p1 obviously 555 * isn't dead yet, we know that the leader is either 556 * sending SIGKILL's to all the processes in this 557 * task or is sleeping waiting for all the peers to 558 * exit. We let p1 complete the fork, but we need 559 * to go ahead and kill the new process p2 since 560 * the task leader may not get a chance to send 561 * SIGKILL to it. We leave it on the list so that 562 * the task leader will wait for this new process 563 * to commit suicide. 564 */ 565 PROC_LOCK(p2); 566 kern_psignal(p2, SIGKILL); 567 PROC_UNLOCK(p2); 568 } else 569 PROC_UNLOCK(p1->p_leader); 570 } else { 571 p2->p_peers = NULL; 572 p2->p_leader = p2; 573 } 574 575 sx_xlock(&proctree_lock); 576 PGRP_LOCK(p1->p_pgrp); 577 PROC_LOCK(p2); 578 PROC_LOCK(p1); 579 580 /* 581 * Preserve some more flags in subprocess. P_PROFIL has already 582 * been preserved. 583 */ 584 p2->p_flag |= p1->p_flag & P_SUGID; 585 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK | 586 TDP_SIGFASTBLOCK)) | TDP_FORKING; 587 SESS_LOCK(p1->p_session); 588 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 589 p2->p_flag |= P_CONTROLT; 590 SESS_UNLOCK(p1->p_session); 591 if (fr->fr_flags & RFPPWAIT) 592 p2->p_flag |= P_PPWAIT; 593 594 p2->p_pgrp = p1->p_pgrp; 595 LIST_INSERT_AFTER(p1, p2, p_pglist); 596 PGRP_UNLOCK(p1->p_pgrp); 597 LIST_INIT(&p2->p_children); 598 LIST_INIT(&p2->p_orphans); 599 600 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 601 602 /* 603 * This begins the section where we must prevent the parent 604 * from being swapped. 605 */ 606 _PHOLD(p1); 607 PROC_UNLOCK(p1); 608 609 /* 610 * Attach the new process to its parent. 611 * 612 * If RFNOWAIT is set, the newly created process becomes a child 613 * of init. This effectively disassociates the child from the 614 * parent. 615 */ 616 if ((fr->fr_flags & RFNOWAIT) != 0) { 617 pptr = p1->p_reaper; 618 p2->p_reaper = pptr; 619 } else { 620 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 621 p1 : p1->p_reaper; 622 pptr = p1; 623 } 624 p2->p_pptr = pptr; 625 p2->p_oppid = pptr->p_pid; 626 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 627 LIST_INIT(&p2->p_reaplist); 628 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 629 if (p2->p_reaper == p1 && p1 != initproc) { 630 p2->p_reapsubtree = p2->p_pid; 631 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 632 } 633 sx_xunlock(&proctree_lock); 634 635 /* Inform accounting that we have forked. */ 636 p2->p_acflag = AFORK; 637 PROC_UNLOCK(p2); 638 639 #ifdef KTRACE 640 ktrprocfork(p1, p2); 641 #endif 642 643 /* 644 * Finish creating the child process. It will return via a different 645 * execution path later. (ie: directly into user mode) 646 */ 647 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 648 649 if (fr->fr_flags == (RFFDG | RFPROC)) { 650 VM_CNT_INC(v_forks); 651 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 652 p2->p_vmspace->vm_ssize); 653 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 654 VM_CNT_INC(v_vforks); 655 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 656 p2->p_vmspace->vm_ssize); 657 } else if (p1 == &proc0) { 658 VM_CNT_INC(v_kthreads); 659 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 660 p2->p_vmspace->vm_ssize); 661 } else { 662 VM_CNT_INC(v_rforks); 663 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 664 p2->p_vmspace->vm_ssize); 665 } 666 667 /* 668 * Associate the process descriptor with the process before anything 669 * can happen that might cause that process to need the descriptor. 670 * However, don't do this until after fork(2) can no longer fail. 671 */ 672 if (fr->fr_flags & RFPROCDESC) 673 procdesc_new(p2, fr->fr_pd_flags); 674 675 /* 676 * Both processes are set up, now check if any loadable modules want 677 * to adjust anything. 678 */ 679 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 680 681 /* 682 * Set the child start time and mark the process as being complete. 683 */ 684 PROC_LOCK(p2); 685 PROC_LOCK(p1); 686 microuptime(&p2->p_stats->p_start); 687 PROC_SLOCK(p2); 688 p2->p_state = PRS_NORMAL; 689 PROC_SUNLOCK(p2); 690 691 #ifdef KDTRACE_HOOKS 692 /* 693 * Tell the DTrace fasttrap provider about the new process so that any 694 * tracepoints inherited from the parent can be removed. We have to do 695 * this only after p_state is PRS_NORMAL since the fasttrap module will 696 * use pfind() later on. 697 */ 698 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 699 dtrace_fasttrap_fork(p1, p2); 700 #endif 701 if (fr->fr_flags & RFPPWAIT) { 702 td->td_pflags |= TDP_RFPPWAIT; 703 td->td_rfppwait_p = p2; 704 td->td_dbgflags |= TDB_VFORK; 705 } 706 PROC_UNLOCK(p2); 707 708 /* 709 * Tell any interested parties about the new process. 710 */ 711 knote_fork(p1->p_klist, p2->p_pid); 712 713 /* 714 * Now can be swapped. 715 */ 716 _PRELE(p1); 717 PROC_UNLOCK(p1); 718 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 719 720 if (fr->fr_flags & RFPROCDESC) { 721 procdesc_finit(p2->p_procdesc, fp_procdesc); 722 fdrop(fp_procdesc, td); 723 } 724 725 /* 726 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 727 * synced with forks in progress so it is OK if we miss it 728 * if being set atm. 729 */ 730 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 731 sx_xlock(&proctree_lock); 732 PROC_LOCK(p2); 733 734 /* 735 * p1->p_ptevents & p1->p_pptr are protected by both 736 * process and proctree locks for modifications, 737 * so owning proctree_lock allows the race-free read. 738 */ 739 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 740 /* 741 * Arrange for debugger to receive the fork event. 742 * 743 * We can report PL_FLAG_FORKED regardless of 744 * P_FOLLOWFORK settings, but it does not make a sense 745 * for runaway child. 746 */ 747 td->td_dbgflags |= TDB_FORK; 748 td->td_dbg_forked = p2->p_pid; 749 td2->td_dbgflags |= TDB_STOPATFORK; 750 proc_set_traced(p2, true); 751 CTR2(KTR_PTRACE, 752 "do_fork: attaching to new child pid %d: oppid %d", 753 p2->p_pid, p2->p_oppid); 754 proc_reparent(p2, p1->p_pptr, false); 755 } 756 PROC_UNLOCK(p2); 757 sx_xunlock(&proctree_lock); 758 } 759 760 racct_proc_fork_done(p2); 761 762 if ((fr->fr_flags & RFSTOPPED) == 0) { 763 if (fr->fr_pidp != NULL) 764 *fr->fr_pidp = p2->p_pid; 765 /* 766 * If RFSTOPPED not requested, make child runnable and 767 * add to run queue. 768 */ 769 thread_lock(td2); 770 TD_SET_CAN_RUN(td2); 771 sched_add(td2, SRQ_BORING); 772 } else { 773 *fr->fr_procp = p2; 774 } 775 } 776 777 void 778 fork_rfppwait(struct thread *td) 779 { 780 struct proc *p, *p2; 781 782 MPASS(td->td_pflags & TDP_RFPPWAIT); 783 784 p = td->td_proc; 785 /* 786 * Preserve synchronization semantics of vfork. If 787 * waiting for child to exec or exit, fork set 788 * P_PPWAIT on child, and there we sleep on our proc 789 * (in case of exit). 790 * 791 * Do it after the ptracestop() above is finished, to 792 * not block our debugger until child execs or exits 793 * to finish vfork wait. 794 */ 795 td->td_pflags &= ~TDP_RFPPWAIT; 796 p2 = td->td_rfppwait_p; 797 again: 798 PROC_LOCK(p2); 799 while (p2->p_flag & P_PPWAIT) { 800 PROC_LOCK(p); 801 if (thread_suspend_check_needed()) { 802 PROC_UNLOCK(p2); 803 thread_suspend_check(0); 804 PROC_UNLOCK(p); 805 goto again; 806 } else { 807 PROC_UNLOCK(p); 808 } 809 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 810 } 811 PROC_UNLOCK(p2); 812 813 if (td->td_dbgflags & TDB_VFORK) { 814 PROC_LOCK(p); 815 if (p->p_ptevents & PTRACE_VFORK) 816 ptracestop(td, SIGTRAP, NULL); 817 td->td_dbgflags &= ~TDB_VFORK; 818 PROC_UNLOCK(p); 819 } 820 } 821 822 int 823 fork1(struct thread *td, struct fork_req *fr) 824 { 825 struct proc *p1, *newproc; 826 struct thread *td2; 827 struct vmspace *vm2; 828 struct ucred *cred; 829 struct file *fp_procdesc; 830 vm_ooffset_t mem_charged; 831 int error, nprocs_new; 832 static int curfail; 833 static struct timeval lastfail; 834 int flags, pages; 835 836 flags = fr->fr_flags; 837 pages = fr->fr_pages; 838 839 if ((flags & RFSTOPPED) != 0) 840 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 841 else 842 MPASS(fr->fr_procp == NULL); 843 844 /* Check for the undefined or unimplemented flags. */ 845 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 846 return (EINVAL); 847 848 /* Signal value requires RFTSIGZMB. */ 849 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 850 return (EINVAL); 851 852 /* Can't copy and clear. */ 853 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 854 return (EINVAL); 855 856 /* Check the validity of the signal number. */ 857 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 858 return (EINVAL); 859 860 if ((flags & RFPROCDESC) != 0) { 861 /* Can't not create a process yet get a process descriptor. */ 862 if ((flags & RFPROC) == 0) 863 return (EINVAL); 864 865 /* Must provide a place to put a procdesc if creating one. */ 866 if (fr->fr_pd_fd == NULL) 867 return (EINVAL); 868 869 /* Check if we are using supported flags. */ 870 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 871 return (EINVAL); 872 } 873 874 p1 = td->td_proc; 875 876 /* 877 * Here we don't create a new process, but we divorce 878 * certain parts of a process from itself. 879 */ 880 if ((flags & RFPROC) == 0) { 881 if (fr->fr_procp != NULL) 882 *fr->fr_procp = NULL; 883 else if (fr->fr_pidp != NULL) 884 *fr->fr_pidp = 0; 885 return (fork_norfproc(td, flags)); 886 } 887 888 fp_procdesc = NULL; 889 newproc = NULL; 890 vm2 = NULL; 891 892 /* 893 * Increment the nprocs resource before allocations occur. 894 * Although process entries are dynamically created, we still 895 * keep a global limit on the maximum number we will 896 * create. There are hard-limits as to the number of processes 897 * that can run, established by the KVA and memory usage for 898 * the process data. 899 * 900 * Don't allow a nonprivileged user to use the last ten 901 * processes; don't let root exceed the limit. 902 */ 903 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 904 if (nprocs_new >= maxproc - 10) { 905 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 || 906 nprocs_new >= maxproc) { 907 error = EAGAIN; 908 sx_xlock(&allproc_lock); 909 if (ppsratecheck(&lastfail, &curfail, 1)) { 910 printf("maxproc limit exceeded by uid %u " 911 "(pid %d); see tuning(7) and " 912 "login.conf(5)\n", 913 td->td_ucred->cr_ruid, p1->p_pid); 914 } 915 sx_xunlock(&allproc_lock); 916 goto fail2; 917 } 918 } 919 920 /* 921 * If required, create a process descriptor in the parent first; we 922 * will abandon it if something goes wrong. We don't finit() until 923 * later. 924 */ 925 if (flags & RFPROCDESC) { 926 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 927 fr->fr_pd_flags, fr->fr_pd_fcaps); 928 if (error != 0) 929 goto fail2; 930 AUDIT_ARG_FD(*fr->fr_pd_fd); 931 } 932 933 mem_charged = 0; 934 if (pages == 0) 935 pages = kstack_pages; 936 /* Allocate new proc. */ 937 newproc = uma_zalloc(proc_zone, M_WAITOK); 938 td2 = FIRST_THREAD_IN_PROC(newproc); 939 if (td2 == NULL) { 940 td2 = thread_alloc(pages); 941 if (td2 == NULL) { 942 error = ENOMEM; 943 goto fail2; 944 } 945 proc_linkup(newproc, td2); 946 } else { 947 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 948 if (td2->td_kstack != 0) 949 vm_thread_dispose(td2); 950 if (!thread_alloc_stack(td2, pages)) { 951 error = ENOMEM; 952 goto fail2; 953 } 954 } 955 } 956 957 if ((flags & RFMEM) == 0) { 958 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 959 if (vm2 == NULL) { 960 error = ENOMEM; 961 goto fail2; 962 } 963 if (!swap_reserve(mem_charged)) { 964 /* 965 * The swap reservation failed. The accounting 966 * from the entries of the copied vm2 will be 967 * subtracted in vmspace_free(), so force the 968 * reservation there. 969 */ 970 swap_reserve_force(mem_charged); 971 error = ENOMEM; 972 goto fail2; 973 } 974 } else 975 vm2 = NULL; 976 977 /* 978 * XXX: This is ugly; when we copy resource usage, we need to bump 979 * per-cred resource counters. 980 */ 981 proc_set_cred_init(newproc, td->td_ucred); 982 983 /* 984 * Initialize resource accounting for the child process. 985 */ 986 error = racct_proc_fork(p1, newproc); 987 if (error != 0) { 988 error = EAGAIN; 989 goto fail1; 990 } 991 992 #ifdef MAC 993 mac_proc_init(newproc); 994 #endif 995 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 996 STAILQ_INIT(&newproc->p_ktr); 997 998 /* 999 * Increment the count of procs running with this uid. Don't allow 1000 * a nonprivileged user to exceed their current limit. 1001 */ 1002 cred = td->td_ucred; 1003 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) { 1004 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0) 1005 goto fail0; 1006 chgproccnt(cred->cr_ruidinfo, 1, 0); 1007 } 1008 1009 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 1010 return (0); 1011 fail0: 1012 error = EAGAIN; 1013 #ifdef MAC 1014 mac_proc_destroy(newproc); 1015 #endif 1016 racct_proc_exit(newproc); 1017 fail1: 1018 proc_unset_cred(newproc); 1019 fail2: 1020 if (vm2 != NULL) 1021 vmspace_free(vm2); 1022 uma_zfree(proc_zone, newproc); 1023 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1024 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1025 fdrop(fp_procdesc, td); 1026 } 1027 atomic_add_int(&nprocs, -1); 1028 pause("fork", hz / 2); 1029 return (error); 1030 } 1031 1032 /* 1033 * Handle the return of a child process from fork1(). This function 1034 * is called from the MD fork_trampoline() entry point. 1035 */ 1036 void 1037 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1038 struct trapframe *frame) 1039 { 1040 struct proc *p; 1041 struct thread *td; 1042 struct thread *dtd; 1043 1044 td = curthread; 1045 p = td->td_proc; 1046 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1047 1048 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1049 td, td_get_sched(td), p->p_pid, td->td_name); 1050 1051 sched_fork_exit(td); 1052 /* 1053 * Processes normally resume in mi_switch() after being 1054 * cpu_switch()'ed to, but when children start up they arrive here 1055 * instead, so we must do much the same things as mi_switch() would. 1056 */ 1057 if ((dtd = PCPU_GET(deadthread))) { 1058 PCPU_SET(deadthread, NULL); 1059 thread_stash(dtd); 1060 } 1061 thread_unlock(td); 1062 1063 /* 1064 * cpu_fork_kthread_handler intercepts this function call to 1065 * have this call a non-return function to stay in kernel mode. 1066 * initproc has its own fork handler, but it does return. 1067 */ 1068 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1069 callout(arg, frame); 1070 1071 /* 1072 * Check if a kernel thread misbehaved and returned from its main 1073 * function. 1074 */ 1075 if (p->p_flag & P_KPROC) { 1076 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1077 td->td_name, p->p_pid); 1078 kthread_exit(); 1079 } 1080 mtx_assert(&Giant, MA_NOTOWNED); 1081 1082 if (p->p_sysent->sv_schedtail != NULL) 1083 (p->p_sysent->sv_schedtail)(td); 1084 td->td_pflags &= ~TDP_FORKING; 1085 } 1086 1087 /* 1088 * Simplified back end of syscall(), used when returning from fork() 1089 * directly into user mode. This function is passed in to fork_exit() 1090 * as the first parameter and is called when returning to a new 1091 * userland process. 1092 */ 1093 void 1094 fork_return(struct thread *td, struct trapframe *frame) 1095 { 1096 struct proc *p; 1097 1098 p = td->td_proc; 1099 if (td->td_dbgflags & TDB_STOPATFORK) { 1100 PROC_LOCK(p); 1101 if ((p->p_flag & P_TRACED) != 0) { 1102 /* 1103 * Inform the debugger if one is still present. 1104 */ 1105 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1106 ptracestop(td, SIGSTOP, NULL); 1107 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1108 } else { 1109 /* 1110 * ... otherwise clear the request. 1111 */ 1112 td->td_dbgflags &= ~TDB_STOPATFORK; 1113 } 1114 PROC_UNLOCK(p); 1115 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) { 1116 /* 1117 * This is the start of a new thread in a traced 1118 * process. Report a system call exit event. 1119 */ 1120 PROC_LOCK(p); 1121 td->td_dbgflags |= TDB_SCX; 1122 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1123 (td->td_dbgflags & TDB_BORN) != 0) 1124 ptracestop(td, SIGTRAP, NULL); 1125 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1126 PROC_UNLOCK(p); 1127 } 1128 1129 /* 1130 * If the prison was killed mid-fork, die along with it. 1131 */ 1132 if (!prison_isalive(td->td_ucred->cr_prison)) 1133 exit1(td, 0, SIGKILL); 1134 1135 userret(td, frame); 1136 1137 #ifdef KTRACE 1138 if (KTRPOINT(td, KTR_SYSRET)) 1139 ktrsysret(SYS_fork, 0, 0); 1140 #endif 1141 }
Cache object: f1efc48cc3b616829974d0843dfc8b4a
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