Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c
Version:
- FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
SearchContext: - none - 3 - 10
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 struct proc *p1; 310 int error; 311 312 KASSERT((flags & RFPROC) == 0, 313 ("fork_norfproc called with RFPROC set")); 314 p1 = td->td_proc; 315 316 /* 317 * Quiesce other threads if necessary. If RFMEM is not specified we 318 * must ensure that other threads do not concurrently create a second 319 * process sharing the vmspace, see vmspace_unshare(). 320 */ 321 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 322 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 323 PROC_LOCK(p1); 324 if (thread_single(p1, SINGLE_BOUNDARY)) { 325 PROC_UNLOCK(p1); 326 return (ERESTART); 327 } 328 PROC_UNLOCK(p1); 329 } 330 331 error = vm_forkproc(td, NULL, NULL, NULL, flags); 332 if (error != 0) 333 goto fail; 334 335 /* 336 * Close all file descriptors. 337 */ 338 if ((flags & RFCFDG) != 0) { 339 struct filedesc *fdtmp; 340 struct pwddesc *pdtmp; 341 342 pdtmp = pdinit(td->td_proc->p_pd, false); 343 fdtmp = fdinit(td->td_proc->p_fd, false, NULL); 344 pdescfree(td); 345 fdescfree(td); 346 p1->p_fd = fdtmp; 347 p1->p_pd = pdtmp; 348 } 349 350 /* 351 * Unshare file descriptors (from parent). 352 */ 353 if ((flags & RFFDG) != 0) { 354 fdunshare(td); 355 pdunshare(td); 356 } 357 358 fail: 359 if ((p1->p_flag & (P_HADTHREADS | P_SYSTEM)) == P_HADTHREADS && 360 ((flags & (RFCFDG | RFFDG)) != 0 || (flags & RFMEM) == 0)) { 361 PROC_LOCK(p1); 362 thread_single_end(p1, SINGLE_BOUNDARY); 363 PROC_UNLOCK(p1); 364 } 365 return (error); 366 } 367 368 static void 369 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 370 struct vmspace *vm2, struct file *fp_procdesc) 371 { 372 struct proc *p1, *pptr; 373 struct filedesc *fd; 374 struct filedesc_to_leader *fdtol; 375 struct pwddesc *pd; 376 struct sigacts *newsigacts; 377 378 p1 = td->td_proc; 379 380 PROC_LOCK(p1); 381 bcopy(&p1->p_startcopy, &p2->p_startcopy, 382 __rangeof(struct proc, p_startcopy, p_endcopy)); 383 pargs_hold(p2->p_args); 384 PROC_UNLOCK(p1); 385 386 bzero(&p2->p_startzero, 387 __rangeof(struct proc, p_startzero, p_endzero)); 388 389 /* Tell the prison that we exist. */ 390 prison_proc_hold(p2->p_ucred->cr_prison); 391 392 p2->p_state = PRS_NEW; /* protect against others */ 393 p2->p_pid = fork_findpid(fr->fr_flags); 394 AUDIT_ARG_PID(p2->p_pid); 395 TSFORK(p2->p_pid, p1->p_pid); 396 397 sx_xlock(&allproc_lock); 398 LIST_INSERT_HEAD(&allproc, p2, p_list); 399 allproc_gen++; 400 sx_xunlock(&allproc_lock); 401 402 sx_xlock(PIDHASHLOCK(p2->p_pid)); 403 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 404 sx_xunlock(PIDHASHLOCK(p2->p_pid)); 405 406 tidhash_add(td2); 407 408 /* 409 * Malloc things while we don't hold any locks. 410 */ 411 if (fr->fr_flags & RFSIGSHARE) 412 newsigacts = NULL; 413 else 414 newsigacts = sigacts_alloc(); 415 416 /* 417 * Copy filedesc. 418 */ 419 if (fr->fr_flags & RFCFDG) { 420 pd = pdinit(p1->p_pd, false); 421 fd = fdinit(p1->p_fd, false, NULL); 422 fdtol = NULL; 423 } else if (fr->fr_flags & RFFDG) { 424 if (fr->fr_flags2 & FR2_SHARE_PATHS) 425 pd = pdshare(p1->p_pd); 426 else 427 pd = pdcopy(p1->p_pd); 428 fd = fdcopy(p1->p_fd); 429 fdtol = NULL; 430 } else { 431 if (fr->fr_flags2 & FR2_SHARE_PATHS) 432 pd = pdcopy(p1->p_pd); 433 else 434 pd = pdshare(p1->p_pd); 435 fd = fdshare(p1->p_fd); 436 if (p1->p_fdtol == NULL) 437 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 438 p1->p_leader); 439 if ((fr->fr_flags & RFTHREAD) != 0) { 440 /* 441 * Shared file descriptor table, and shared 442 * process leaders. 443 */ 444 fdtol = filedesc_to_leader_share(p1->p_fdtol, p1->p_fd); 445 } else { 446 /* 447 * Shared file descriptor table, and different 448 * process leaders. 449 */ 450 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 451 p1->p_fd, p2); 452 } 453 } 454 /* 455 * Make a proc table entry for the new process. 456 * Start by zeroing the section of proc that is zero-initialized, 457 * then copy the section that is copied directly from the parent. 458 */ 459 460 PROC_LOCK(p2); 461 PROC_LOCK(p1); 462 463 bzero(&td2->td_startzero, 464 __rangeof(struct thread, td_startzero, td_endzero)); 465 466 bcopy(&td->td_startcopy, &td2->td_startcopy, 467 __rangeof(struct thread, td_startcopy, td_endcopy)); 468 469 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 470 td2->td_sigstk = td->td_sigstk; 471 td2->td_flags = TDF_INMEM; 472 td2->td_lend_user_pri = PRI_MAX; 473 474 #ifdef VIMAGE 475 td2->td_vnet = NULL; 476 td2->td_vnet_lpush = NULL; 477 #endif 478 479 /* 480 * Allow the scheduler to initialize the child. 481 */ 482 thread_lock(td); 483 sched_fork(td, td2); 484 thread_unlock(td); 485 486 /* 487 * Duplicate sub-structures as needed. 488 * Increase reference counts on shared objects. 489 */ 490 p2->p_flag = P_INMEM; 491 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE | 492 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC | 493 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP | 494 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC | P2_NO_NEW_PRIVS | 495 P2_WXORX_DISABLE | P2_WXORX_ENABLE_EXEC); 496 p2->p_swtick = ticks; 497 if (p1->p_flag & P_PROFIL) 498 startprofclock(p2); 499 500 if (fr->fr_flags & RFSIGSHARE) { 501 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 502 } else { 503 sigacts_copy(newsigacts, p1->p_sigacts); 504 p2->p_sigacts = newsigacts; 505 if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) { 506 mtx_lock(&p2->p_sigacts->ps_mtx); 507 if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0) 508 sig_drop_caught(p2); 509 if ((fr->fr_flags2 & FR2_KPROC) != 0) 510 p2->p_sigacts->ps_flag |= PS_NOCLDWAIT; 511 mtx_unlock(&p2->p_sigacts->ps_mtx); 512 } 513 } 514 515 if (fr->fr_flags & RFTSIGZMB) 516 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 517 else if (fr->fr_flags & RFLINUXTHPN) 518 p2->p_sigparent = SIGUSR1; 519 else 520 p2->p_sigparent = SIGCHLD; 521 522 if ((fr->fr_flags2 & FR2_KPROC) != 0) { 523 p2->p_flag |= P_SYSTEM | P_KPROC; 524 td2->td_pflags |= TDP_KTHREAD; 525 } 526 527 p2->p_textvp = p1->p_textvp; 528 p2->p_textdvp = p1->p_textdvp; 529 p2->p_fd = fd; 530 p2->p_fdtol = fdtol; 531 p2->p_pd = pd; 532 p2->p_elf_brandinfo = p1->p_elf_brandinfo; 533 534 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 535 p2->p_flag |= P_PROTECTED; 536 p2->p_flag2 |= P2_INHERIT_PROTECTED; 537 } 538 539 /* 540 * p_limit is copy-on-write. Bump its refcount. 541 */ 542 lim_fork(p1, p2); 543 544 thread_cow_get_proc(td2, p2); 545 546 pstats_fork(p1->p_stats, p2->p_stats); 547 548 PROC_UNLOCK(p1); 549 PROC_UNLOCK(p2); 550 551 /* 552 * Bump references to the text vnode and directory, and copy 553 * the hardlink name. 554 */ 555 if (p2->p_textvp != NULL) 556 vrefact(p2->p_textvp); 557 if (p2->p_textdvp != NULL) 558 vrefact(p2->p_textdvp); 559 p2->p_binname = p1->p_binname == NULL ? NULL : 560 strdup(p1->p_binname, M_PARGS); 561 562 /* 563 * Set up linkage for kernel based threading. 564 */ 565 if ((fr->fr_flags & RFTHREAD) != 0) { 566 mtx_lock(&ppeers_lock); 567 p2->p_peers = p1->p_peers; 568 p1->p_peers = p2; 569 p2->p_leader = p1->p_leader; 570 mtx_unlock(&ppeers_lock); 571 PROC_LOCK(p1->p_leader); 572 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 573 PROC_UNLOCK(p1->p_leader); 574 /* 575 * The task leader is exiting, so process p1 is 576 * going to be killed shortly. Since p1 obviously 577 * isn't dead yet, we know that the leader is either 578 * sending SIGKILL's to all the processes in this 579 * task or is sleeping waiting for all the peers to 580 * exit. We let p1 complete the fork, but we need 581 * to go ahead and kill the new process p2 since 582 * the task leader may not get a chance to send 583 * SIGKILL to it. We leave it on the list so that 584 * the task leader will wait for this new process 585 * to commit suicide. 586 */ 587 PROC_LOCK(p2); 588 kern_psignal(p2, SIGKILL); 589 PROC_UNLOCK(p2); 590 } else 591 PROC_UNLOCK(p1->p_leader); 592 } else { 593 p2->p_peers = NULL; 594 p2->p_leader = p2; 595 } 596 597 sx_xlock(&proctree_lock); 598 PGRP_LOCK(p1->p_pgrp); 599 PROC_LOCK(p2); 600 PROC_LOCK(p1); 601 602 /* 603 * Preserve some more flags in subprocess. P_PROFIL has already 604 * been preserved. 605 */ 606 p2->p_flag |= p1->p_flag & P_SUGID; 607 td2->td_pflags |= (td->td_pflags & (TDP_ALTSTACK | 608 TDP_SIGFASTBLOCK)) | TDP_FORKING; 609 SESS_LOCK(p1->p_session); 610 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 611 p2->p_flag |= P_CONTROLT; 612 SESS_UNLOCK(p1->p_session); 613 if (fr->fr_flags & RFPPWAIT) 614 p2->p_flag |= P_PPWAIT; 615 616 p2->p_pgrp = p1->p_pgrp; 617 LIST_INSERT_AFTER(p1, p2, p_pglist); 618 PGRP_UNLOCK(p1->p_pgrp); 619 LIST_INIT(&p2->p_children); 620 LIST_INIT(&p2->p_orphans); 621 622 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 623 TAILQ_INIT(&p2->p_kqtim_stop); 624 625 /* 626 * This begins the section where we must prevent the parent 627 * from being swapped. 628 */ 629 _PHOLD(p1); 630 PROC_UNLOCK(p1); 631 632 /* 633 * Attach the new process to its parent. 634 * 635 * If RFNOWAIT is set, the newly created process becomes a child 636 * of init. This effectively disassociates the child from the 637 * parent. 638 */ 639 if ((fr->fr_flags & RFNOWAIT) != 0) { 640 pptr = p1->p_reaper; 641 p2->p_reaper = pptr; 642 } else { 643 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 644 p1 : p1->p_reaper; 645 pptr = p1; 646 } 647 p2->p_pptr = pptr; 648 p2->p_oppid = pptr->p_pid; 649 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 650 LIST_INIT(&p2->p_reaplist); 651 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 652 if (p2->p_reaper == p1 && p1 != initproc) { 653 p2->p_reapsubtree = p2->p_pid; 654 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 655 } 656 sx_xunlock(&proctree_lock); 657 658 /* Inform accounting that we have forked. */ 659 p2->p_acflag = AFORK; 660 PROC_UNLOCK(p2); 661 662 #ifdef KTRACE 663 ktrprocfork(p1, p2); 664 #endif 665 666 /* 667 * Finish creating the child process. It will return via a different 668 * execution path later. (ie: directly into user mode) 669 */ 670 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 671 672 if (fr->fr_flags == (RFFDG | RFPROC)) { 673 VM_CNT_INC(v_forks); 674 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 675 p2->p_vmspace->vm_ssize); 676 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 677 VM_CNT_INC(v_vforks); 678 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 679 p2->p_vmspace->vm_ssize); 680 } else if (p1 == &proc0) { 681 VM_CNT_INC(v_kthreads); 682 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 683 p2->p_vmspace->vm_ssize); 684 } else { 685 VM_CNT_INC(v_rforks); 686 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 687 p2->p_vmspace->vm_ssize); 688 } 689 690 /* 691 * Associate the process descriptor with the process before anything 692 * can happen that might cause that process to need the descriptor. 693 * However, don't do this until after fork(2) can no longer fail. 694 */ 695 if (fr->fr_flags & RFPROCDESC) 696 procdesc_new(p2, fr->fr_pd_flags); 697 698 /* 699 * Both processes are set up, now check if any loadable modules want 700 * to adjust anything. 701 */ 702 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 703 704 /* 705 * Set the child start time and mark the process as being complete. 706 */ 707 PROC_LOCK(p2); 708 PROC_LOCK(p1); 709 microuptime(&p2->p_stats->p_start); 710 PROC_SLOCK(p2); 711 p2->p_state = PRS_NORMAL; 712 PROC_SUNLOCK(p2); 713 714 #ifdef KDTRACE_HOOKS 715 /* 716 * Tell the DTrace fasttrap provider about the new process so that any 717 * tracepoints inherited from the parent can be removed. We have to do 718 * this only after p_state is PRS_NORMAL since the fasttrap module will 719 * use pfind() later on. 720 */ 721 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 722 dtrace_fasttrap_fork(p1, p2); 723 #endif 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 * Tell any interested parties about the new process. 733 */ 734 knote_fork(p1->p_klist, p2->p_pid); 735 736 /* 737 * Now can be swapped. 738 */ 739 _PRELE(p1); 740 PROC_UNLOCK(p1); 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, false); 778 } 779 PROC_UNLOCK(p2); 780 sx_xunlock(&proctree_lock); 781 } 782 783 racct_proc_fork_done(p2); 784 785 if ((fr->fr_flags & RFSTOPPED) == 0) { 786 if (fr->fr_pidp != NULL) 787 *fr->fr_pidp = p2->p_pid; 788 /* 789 * If RFSTOPPED not requested, make child runnable and 790 * add to run queue. 791 */ 792 thread_lock(td2); 793 TD_SET_CAN_RUN(td2); 794 sched_add(td2, SRQ_BORING); 795 } else { 796 *fr->fr_procp = p2; 797 } 798 } 799 800 void 801 fork_rfppwait(struct thread *td) 802 { 803 struct proc *p, *p2; 804 805 MPASS(td->td_pflags & TDP_RFPPWAIT); 806 807 p = td->td_proc; 808 /* 809 * Preserve synchronization semantics of vfork. If 810 * waiting for child to exec or exit, fork set 811 * P_PPWAIT on child, and there we sleep on our proc 812 * (in case of exit). 813 * 814 * Do it after the ptracestop() above is finished, to 815 * not block our debugger until child execs or exits 816 * to finish vfork wait. 817 */ 818 td->td_pflags &= ~TDP_RFPPWAIT; 819 p2 = td->td_rfppwait_p; 820 again: 821 PROC_LOCK(p2); 822 while (p2->p_flag & P_PPWAIT) { 823 PROC_LOCK(p); 824 if (thread_suspend_check_needed()) { 825 PROC_UNLOCK(p2); 826 thread_suspend_check(0); 827 PROC_UNLOCK(p); 828 goto again; 829 } else { 830 PROC_UNLOCK(p); 831 } 832 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 833 } 834 PROC_UNLOCK(p2); 835 836 if (td->td_dbgflags & TDB_VFORK) { 837 PROC_LOCK(p); 838 if (p->p_ptevents & PTRACE_VFORK) 839 ptracestop(td, SIGTRAP, NULL); 840 td->td_dbgflags &= ~TDB_VFORK; 841 PROC_UNLOCK(p); 842 } 843 } 844 845 int 846 fork1(struct thread *td, struct fork_req *fr) 847 { 848 struct proc *p1, *newproc; 849 struct thread *td2; 850 struct vmspace *vm2; 851 struct ucred *cred; 852 struct file *fp_procdesc; 853 vm_ooffset_t mem_charged; 854 int error, nprocs_new; 855 static int curfail; 856 static struct timeval lastfail; 857 int flags, pages; 858 859 flags = fr->fr_flags; 860 pages = fr->fr_pages; 861 862 if ((flags & RFSTOPPED) != 0) 863 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 864 else 865 MPASS(fr->fr_procp == NULL); 866 867 /* Check for the undefined or unimplemented flags. */ 868 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 869 return (EINVAL); 870 871 /* Signal value requires RFTSIGZMB. */ 872 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 873 return (EINVAL); 874 875 /* Can't copy and clear. */ 876 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 877 return (EINVAL); 878 879 /* Check the validity of the signal number. */ 880 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 881 return (EINVAL); 882 883 if ((flags & RFPROCDESC) != 0) { 884 /* Can't not create a process yet get a process descriptor. */ 885 if ((flags & RFPROC) == 0) 886 return (EINVAL); 887 888 /* Must provide a place to put a procdesc if creating one. */ 889 if (fr->fr_pd_fd == NULL) 890 return (EINVAL); 891 892 /* Check if we are using supported flags. */ 893 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 894 return (EINVAL); 895 } 896 897 p1 = td->td_proc; 898 899 /* 900 * Here we don't create a new process, but we divorce 901 * certain parts of a process from itself. 902 */ 903 if ((flags & RFPROC) == 0) { 904 if (fr->fr_procp != NULL) 905 *fr->fr_procp = NULL; 906 else if (fr->fr_pidp != NULL) 907 *fr->fr_pidp = 0; 908 return (fork_norfproc(td, flags)); 909 } 910 911 fp_procdesc = NULL; 912 newproc = NULL; 913 vm2 = NULL; 914 915 /* 916 * Increment the nprocs resource before allocations occur. 917 * Although process entries are dynamically created, we still 918 * keep a global limit on the maximum number we will 919 * create. There are hard-limits as to the number of processes 920 * that can run, established by the KVA and memory usage for 921 * the process data. 922 * 923 * Don't allow a nonprivileged user to use the last ten 924 * processes; don't let root exceed the limit. 925 */ 926 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 927 if (nprocs_new >= maxproc - 10) { 928 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 || 929 nprocs_new >= maxproc) { 930 error = EAGAIN; 931 sx_xlock(&allproc_lock); 932 if (ppsratecheck(&lastfail, &curfail, 1)) { 933 printf("maxproc limit exceeded by uid %u " 934 "(pid %d); see tuning(7) and " 935 "login.conf(5)\n", 936 td->td_ucred->cr_ruid, p1->p_pid); 937 } 938 sx_xunlock(&allproc_lock); 939 goto fail2; 940 } 941 } 942 943 /* 944 * If required, create a process descriptor in the parent first; we 945 * will abandon it if something goes wrong. We don't finit() until 946 * later. 947 */ 948 if (flags & RFPROCDESC) { 949 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 950 fr->fr_pd_flags, fr->fr_pd_fcaps); 951 if (error != 0) 952 goto fail2; 953 AUDIT_ARG_FD(*fr->fr_pd_fd); 954 } 955 956 mem_charged = 0; 957 if (pages == 0) 958 pages = kstack_pages; 959 /* Allocate new proc. */ 960 newproc = uma_zalloc(proc_zone, M_WAITOK); 961 td2 = FIRST_THREAD_IN_PROC(newproc); 962 if (td2 == NULL) { 963 td2 = thread_alloc(pages); 964 if (td2 == NULL) { 965 error = ENOMEM; 966 goto fail2; 967 } 968 proc_linkup(newproc, td2); 969 } else { 970 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 971 if (td2->td_kstack != 0) 972 vm_thread_dispose(td2); 973 if (!thread_alloc_stack(td2, pages)) { 974 error = ENOMEM; 975 goto fail2; 976 } 977 } 978 } 979 980 if ((flags & RFMEM) == 0) { 981 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 982 if (vm2 == NULL) { 983 error = ENOMEM; 984 goto fail2; 985 } 986 if (!swap_reserve(mem_charged)) { 987 /* 988 * The swap reservation failed. The accounting 989 * from the entries of the copied vm2 will be 990 * subtracted in vmspace_free(), so force the 991 * reservation there. 992 */ 993 swap_reserve_force(mem_charged); 994 error = ENOMEM; 995 goto fail2; 996 } 997 } else 998 vm2 = NULL; 999 1000 /* 1001 * XXX: This is ugly; when we copy resource usage, we need to bump 1002 * per-cred resource counters. 1003 */ 1004 proc_set_cred_init(newproc, td->td_ucred); 1005 1006 /* 1007 * Initialize resource accounting for the child process. 1008 */ 1009 error = racct_proc_fork(p1, newproc); 1010 if (error != 0) { 1011 error = EAGAIN; 1012 goto fail1; 1013 } 1014 1015 #ifdef MAC 1016 mac_proc_init(newproc); 1017 #endif 1018 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 1019 STAILQ_INIT(&newproc->p_ktr); 1020 1021 /* 1022 * Increment the count of procs running with this uid. Don't allow 1023 * a nonprivileged user to exceed their current limit. 1024 */ 1025 cred = td->td_ucred; 1026 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) { 1027 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0) 1028 goto fail0; 1029 chgproccnt(cred->cr_ruidinfo, 1, 0); 1030 } 1031 1032 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 1033 return (0); 1034 fail0: 1035 error = EAGAIN; 1036 #ifdef MAC 1037 mac_proc_destroy(newproc); 1038 #endif 1039 racct_proc_exit(newproc); 1040 fail1: 1041 proc_unset_cred(newproc); 1042 fail2: 1043 if (vm2 != NULL) 1044 vmspace_free(vm2); 1045 uma_zfree(proc_zone, newproc); 1046 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1047 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1048 fdrop(fp_procdesc, td); 1049 } 1050 atomic_add_int(&nprocs, -1); 1051 pause("fork", hz / 2); 1052 return (error); 1053 } 1054 1055 /* 1056 * Handle the return of a child process from fork1(). This function 1057 * is called from the MD fork_trampoline() entry point. 1058 */ 1059 void 1060 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1061 struct trapframe *frame) 1062 { 1063 struct proc *p; 1064 struct thread *td; 1065 struct thread *dtd; 1066 1067 td = curthread; 1068 p = td->td_proc; 1069 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1070 1071 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1072 td, td_get_sched(td), p->p_pid, td->td_name); 1073 1074 sched_fork_exit(td); 1075 1076 /* 1077 * Processes normally resume in mi_switch() after being 1078 * cpu_switch()'ed to, but when children start up they arrive here 1079 * instead, so we must do much the same things as mi_switch() would. 1080 */ 1081 if ((dtd = PCPU_GET(deadthread))) { 1082 PCPU_SET(deadthread, NULL); 1083 thread_stash(dtd); 1084 } 1085 thread_unlock(td); 1086 1087 /* 1088 * cpu_fork_kthread_handler intercepts this function call to 1089 * have this call a non-return function to stay in kernel mode. 1090 * initproc has its own fork handler, but it does return. 1091 */ 1092 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1093 callout(arg, frame); 1094 1095 /* 1096 * Check if a kernel thread misbehaved and returned from its main 1097 * function. 1098 */ 1099 if (p->p_flag & P_KPROC) { 1100 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1101 td->td_name, p->p_pid); 1102 kthread_exit(); 1103 } 1104 mtx_assert(&Giant, MA_NOTOWNED); 1105 1106 if (p->p_sysent->sv_schedtail != NULL) 1107 (p->p_sysent->sv_schedtail)(td); 1108 td->td_pflags &= ~TDP_FORKING; 1109 } 1110 1111 /* 1112 * Simplified back end of syscall(), used when returning from fork() 1113 * directly into user mode. This function is passed in to fork_exit() 1114 * as the first parameter and is called when returning to a new 1115 * userland process. 1116 */ 1117 void 1118 fork_return(struct thread *td, struct trapframe *frame) 1119 { 1120 struct proc *p; 1121 1122 p = td->td_proc; 1123 if (td->td_dbgflags & TDB_STOPATFORK) { 1124 PROC_LOCK(p); 1125 if ((p->p_flag & P_TRACED) != 0) { 1126 /* 1127 * Inform the debugger if one is still present. 1128 */ 1129 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1130 ptracestop(td, SIGSTOP, NULL); 1131 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1132 } else { 1133 /* 1134 * ... otherwise clear the request. 1135 */ 1136 td->td_dbgflags &= ~TDB_STOPATFORK; 1137 } 1138 PROC_UNLOCK(p); 1139 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) { 1140 /* 1141 * This is the start of a new thread in a traced 1142 * process. Report a system call exit event. 1143 */ 1144 PROC_LOCK(p); 1145 td->td_dbgflags |= TDB_SCX; 1146 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1147 (td->td_dbgflags & TDB_BORN) != 0) 1148 ptracestop(td, SIGTRAP, NULL); 1149 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1150 PROC_UNLOCK(p); 1151 } 1152 1153 /* 1154 * If the prison was killed mid-fork, die along with it. 1155 */ 1156 if (!prison_isalive(td->td_ucred->cr_prison)) 1157 exit1(td, 0, SIGKILL); 1158 1159 userret(td, frame); 1160 1161 #ifdef KTRACE 1162 if (KTRPOINT(td, KTR_SYSRET)) 1163 ktrsysret(SYS_fork, 0, 0); 1164 #endif 1165 }
Cache object: 9a3b1d2f3a8f728fc2f2fe349c797dae
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]