1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1989, 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 37 */ 38 39 #include <sys/cdefs.h> 40 __FBSDID("$FreeBSD$"); 41 42 #include "opt_ktrace.h" 43 #include "opt_kstack_pages.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/bitstring.h> 48 #include <sys/sysproto.h> 49 #include <sys/eventhandler.h> 50 #include <sys/fcntl.h> 51 #include <sys/filedesc.h> 52 #include <sys/jail.h> 53 #include <sys/kernel.h> 54 #include <sys/kthread.h> 55 #include <sys/sysctl.h> 56 #include <sys/lock.h> 57 #include <sys/malloc.h> 58 #include <sys/mutex.h> 59 #include <sys/priv.h> 60 #include <sys/proc.h> 61 #include <sys/procdesc.h> 62 #include <sys/pioctl.h> 63 #include <sys/ptrace.h> 64 #include <sys/racct.h> 65 #include <sys/resourcevar.h> 66 #include <sys/sched.h> 67 #include <sys/syscall.h> 68 #include <sys/vmmeter.h> 69 #include <sys/vnode.h> 70 #include <sys/acct.h> 71 #include <sys/ktr.h> 72 #include <sys/ktrace.h> 73 #include <sys/unistd.h> 74 #include <sys/sdt.h> 75 #include <sys/sx.h> 76 #include <sys/sysent.h> 77 #include <sys/signalvar.h> 78 79 #include <security/audit/audit.h> 80 #include <security/mac/mac_framework.h> 81 82 #include <vm/vm.h> 83 #include <vm/pmap.h> 84 #include <vm/vm_map.h> 85 #include <vm/vm_extern.h> 86 #include <vm/uma.h> 87 88 #ifdef KDTRACE_HOOKS 89 #include <sys/dtrace_bsd.h> 90 dtrace_fork_func_t dtrace_fasttrap_fork; 91 #endif 92 93 SDT_PROVIDER_DECLARE(proc); 94 SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int"); 95 96 #ifndef _SYS_SYSPROTO_H_ 97 struct fork_args { 98 int dummy; 99 }; 100 #endif 101 102 /* ARGSUSED */ 103 int 104 sys_fork(struct thread *td, struct fork_args *uap) 105 { 106 struct fork_req fr; 107 int error, pid; 108 109 bzero(&fr, sizeof(fr)); 110 fr.fr_flags = RFFDG | RFPROC; 111 fr.fr_pidp = &pid; 112 error = fork1(td, &fr); 113 if (error == 0) { 114 td->td_retval[0] = pid; 115 td->td_retval[1] = 0; 116 } 117 return (error); 118 } 119 120 /* ARGUSED */ 121 int 122 sys_pdfork(struct thread *td, struct pdfork_args *uap) 123 { 124 struct fork_req fr; 125 int error, fd, pid; 126 127 bzero(&fr, sizeof(fr)); 128 fr.fr_flags = RFFDG | RFPROC | RFPROCDESC; 129 fr.fr_pidp = &pid; 130 fr.fr_pd_fd = &fd; 131 fr.fr_pd_flags = 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); 173 174 AUDIT_ARG_FFLAGS(uap->flags); 175 bzero(&fr, sizeof(fr)); 176 fr.fr_flags = uap->flags; 177 fr.fr_pidp = &pid; 178 error = fork1(td, &fr); 179 if (error == 0) { 180 td->td_retval[0] = pid; 181 td->td_retval[1] = 0; 182 } 183 return (error); 184 } 185 186 int __exclusive_cache_line nprocs = 1; /* process 0 */ 187 int lastpid = 0; 188 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 189 "Last used PID"); 190 191 /* 192 * Random component to lastpid generation. We mix in a random factor to make 193 * it a little harder to predict. We sanity check the modulus value to avoid 194 * doing it in critical paths. Don't let it be too small or we pointlessly 195 * waste randomness entropy, and don't let it be impossibly large. Using a 196 * modulus that is too big causes a LOT more process table scans and slows 197 * down fork processing as the pidchecked caching is defeated. 198 */ 199 static int randompid = 0; 200 201 static int 202 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 203 { 204 int error, pid; 205 206 error = sysctl_wire_old_buffer(req, sizeof(int)); 207 if (error != 0) 208 return(error); 209 sx_xlock(&allproc_lock); 210 pid = randompid; 211 error = sysctl_handle_int(oidp, &pid, 0, req); 212 if (error == 0 && req->newptr != NULL) { 213 if (pid == 0) 214 randompid = 0; 215 else if (pid == 1) 216 /* generate a random PID modulus between 100 and 1123 */ 217 randompid = 100 + arc4random() % 1024; 218 else if (pid < 0 || pid > pid_max - 100) 219 /* out of range */ 220 randompid = pid_max - 100; 221 else if (pid < 100) 222 /* Make it reasonable */ 223 randompid = 100; 224 else 225 randompid = pid; 226 } 227 sx_xunlock(&allproc_lock); 228 return (error); 229 } 230 231 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 232 0, 0, sysctl_kern_randompid, "I", "Random PID modulus. Special values: 0: disable, 1: choose random value"); 233 234 extern bitstr_t proc_id_pidmap; 235 extern bitstr_t proc_id_grpidmap; 236 extern bitstr_t proc_id_sessidmap; 237 extern bitstr_t proc_id_reapmap; 238 239 /* 240 * Find an unused process ID 241 * 242 * If RFHIGHPID is set (used during system boot), do not allocate 243 * low-numbered pids. 244 */ 245 static int 246 fork_findpid(int flags) 247 { 248 pid_t result; 249 int trypid, random; 250 251 /* 252 * Avoid calling arc4random with procid_lock held. 253 */ 254 random = 0; 255 if (__predict_false(randompid)) 256 random = arc4random() % randompid; 257 258 mtx_lock(&procid_lock); 259 260 trypid = lastpid + 1; 261 if (flags & RFHIGHPID) { 262 if (trypid < 10) 263 trypid = 10; 264 } else { 265 trypid += random; 266 } 267 retry: 268 if (trypid >= pid_max) 269 trypid = 2; 270 271 bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result); 272 if (result == -1) { 273 KASSERT(trypid != 2, ("unexpectedly ran out of IDs")); 274 trypid = 2; 275 goto retry; 276 } 277 if (bit_test(&proc_id_grpidmap, result) || 278 bit_test(&proc_id_sessidmap, result) || 279 bit_test(&proc_id_reapmap, result)) { 280 trypid = result + 1; 281 goto retry; 282 } 283 284 /* 285 * RFHIGHPID does not mess with the lastpid counter during boot. 286 */ 287 if ((flags & RFHIGHPID) == 0) 288 lastpid = result; 289 290 bit_set(&proc_id_pidmap, result); 291 mtx_unlock(&procid_lock); 292 293 return (result); 294 } 295 296 static int 297 fork_norfproc(struct thread *td, int flags) 298 { 299 int error; 300 struct proc *p1; 301 302 KASSERT((flags & RFPROC) == 0, 303 ("fork_norfproc called with RFPROC set")); 304 p1 = td->td_proc; 305 306 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 307 (flags & (RFCFDG | RFFDG))) { 308 PROC_LOCK(p1); 309 if (thread_single(p1, SINGLE_BOUNDARY)) { 310 PROC_UNLOCK(p1); 311 return (ERESTART); 312 } 313 PROC_UNLOCK(p1); 314 } 315 316 error = vm_forkproc(td, NULL, NULL, NULL, flags); 317 if (error) 318 goto fail; 319 320 /* 321 * Close all file descriptors. 322 */ 323 if (flags & RFCFDG) { 324 struct filedesc *fdtmp; 325 fdtmp = fdinit(td->td_proc->p_fd, false); 326 fdescfree(td); 327 p1->p_fd = fdtmp; 328 } 329 330 /* 331 * Unshare file descriptors (from parent). 332 */ 333 if (flags & RFFDG) 334 fdunshare(td); 335 336 fail: 337 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 338 (flags & (RFCFDG | RFFDG))) { 339 PROC_LOCK(p1); 340 thread_single_end(p1, SINGLE_BOUNDARY); 341 PROC_UNLOCK(p1); 342 } 343 return (error); 344 } 345 346 static void 347 do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *td2, 348 struct vmspace *vm2, struct file *fp_procdesc) 349 { 350 struct proc *p1, *pptr; 351 struct filedesc *fd; 352 struct filedesc_to_leader *fdtol; 353 struct sigacts *newsigacts; 354 355 p1 = td->td_proc; 356 357 PROC_LOCK(p1); 358 bcopy(&p1->p_startcopy, &p2->p_startcopy, 359 __rangeof(struct proc, p_startcopy, p_endcopy)); 360 pargs_hold(p2->p_args); 361 PROC_UNLOCK(p1); 362 363 bzero(&p2->p_startzero, 364 __rangeof(struct proc, p_startzero, p_endzero)); 365 366 /* Tell the prison that we exist. */ 367 prison_proc_hold(p2->p_ucred->cr_prison); 368 369 p2->p_state = PRS_NEW; /* protect against others */ 370 p2->p_pid = fork_findpid(fr->fr_flags); 371 AUDIT_ARG_PID(p2->p_pid); 372 373 sx_xlock(&allproc_lock); 374 LIST_INSERT_HEAD(&allproc, p2, p_list); 375 allproc_gen++; 376 sx_xunlock(&allproc_lock); 377 378 sx_xlock(PIDHASHLOCK(p2->p_pid)); 379 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 380 sx_xunlock(PIDHASHLOCK(p2->p_pid)); 381 382 tidhash_add(td2); 383 384 /* 385 * Malloc things while we don't hold any locks. 386 */ 387 if (fr->fr_flags & RFSIGSHARE) 388 newsigacts = NULL; 389 else 390 newsigacts = sigacts_alloc(); 391 392 /* 393 * Copy filedesc. 394 */ 395 if (fr->fr_flags & RFCFDG) { 396 fd = fdinit(p1->p_fd, false); 397 fdtol = NULL; 398 } else if (fr->fr_flags & RFFDG) { 399 fd = fdcopy(p1->p_fd); 400 fdtol = NULL; 401 } else { 402 fd = fdshare(p1->p_fd); 403 if (p1->p_fdtol == NULL) 404 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 405 p1->p_leader); 406 if ((fr->fr_flags & RFTHREAD) != 0) { 407 /* 408 * Shared file descriptor table, and shared 409 * process leaders. 410 */ 411 fdtol = p1->p_fdtol; 412 FILEDESC_XLOCK(p1->p_fd); 413 fdtol->fdl_refcount++; 414 FILEDESC_XUNLOCK(p1->p_fd); 415 } else { 416 /* 417 * Shared file descriptor table, and different 418 * process leaders. 419 */ 420 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 421 p1->p_fd, p2); 422 } 423 } 424 /* 425 * Make a proc table entry for the new process. 426 * Start by zeroing the section of proc that is zero-initialized, 427 * then copy the section that is copied directly from the parent. 428 */ 429 430 PROC_LOCK(p2); 431 PROC_LOCK(p1); 432 433 bzero(&td2->td_startzero, 434 __rangeof(struct thread, td_startzero, td_endzero)); 435 436 bcopy(&td->td_startcopy, &td2->td_startcopy, 437 __rangeof(struct thread, td_startcopy, td_endcopy)); 438 439 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 440 td2->td_sigstk = td->td_sigstk; 441 td2->td_flags = TDF_INMEM; 442 td2->td_lend_user_pri = PRI_MAX; 443 444 #ifdef VIMAGE 445 td2->td_vnet = NULL; 446 td2->td_vnet_lpush = NULL; 447 #endif 448 449 /* 450 * Allow the scheduler to initialize the child. 451 */ 452 thread_lock(td); 453 sched_fork(td, td2); 454 thread_unlock(td); 455 456 /* 457 * Duplicate sub-structures as needed. 458 * Increase reference counts on shared objects. 459 */ 460 p2->p_flag = P_INMEM; 461 p2->p_flag2 = p1->p_flag2 & (P2_ASLR_DISABLE | P2_ASLR_ENABLE | 462 P2_ASLR_IGNSTART | P2_NOTRACE | P2_NOTRACE_EXEC | 463 P2_PROTMAX_ENABLE | P2_PROTMAX_DISABLE | P2_TRAPCAP | 464 P2_STKGAP_DISABLE | P2_STKGAP_DISABLE_EXEC); 465 p2->p_swtick = ticks; 466 if (p1->p_flag & P_PROFIL) 467 startprofclock(p2); 468 469 if (fr->fr_flags & RFSIGSHARE) { 470 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 471 } else { 472 sigacts_copy(newsigacts, p1->p_sigacts); 473 p2->p_sigacts = newsigacts; 474 } 475 476 if (fr->fr_flags & RFTSIGZMB) 477 p2->p_sigparent = RFTSIGNUM(fr->fr_flags); 478 else if (fr->fr_flags & RFLINUXTHPN) 479 p2->p_sigparent = SIGUSR1; 480 else 481 p2->p_sigparent = SIGCHLD; 482 483 p2->p_textvp = p1->p_textvp; 484 p2->p_fd = fd; 485 p2->p_fdtol = fdtol; 486 487 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 488 p2->p_flag |= P_PROTECTED; 489 p2->p_flag2 |= P2_INHERIT_PROTECTED; 490 } 491 492 /* 493 * p_limit is copy-on-write. Bump its refcount. 494 */ 495 lim_fork(p1, p2); 496 497 thread_cow_get_proc(td2, p2); 498 499 pstats_fork(p1->p_stats, p2->p_stats); 500 501 PROC_UNLOCK(p1); 502 PROC_UNLOCK(p2); 503 504 /* Bump references to the text vnode (for procfs). */ 505 if (p2->p_textvp) 506 vrefact(p2->p_textvp); 507 508 /* 509 * Set up linkage for kernel based threading. 510 */ 511 if ((fr->fr_flags & RFTHREAD) != 0) { 512 mtx_lock(&ppeers_lock); 513 p2->p_peers = p1->p_peers; 514 p1->p_peers = p2; 515 p2->p_leader = p1->p_leader; 516 mtx_unlock(&ppeers_lock); 517 PROC_LOCK(p1->p_leader); 518 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 519 PROC_UNLOCK(p1->p_leader); 520 /* 521 * The task leader is exiting, so process p1 is 522 * going to be killed shortly. Since p1 obviously 523 * isn't dead yet, we know that the leader is either 524 * sending SIGKILL's to all the processes in this 525 * task or is sleeping waiting for all the peers to 526 * exit. We let p1 complete the fork, but we need 527 * to go ahead and kill the new process p2 since 528 * the task leader may not get a chance to send 529 * SIGKILL to it. We leave it on the list so that 530 * the task leader will wait for this new process 531 * to commit suicide. 532 */ 533 PROC_LOCK(p2); 534 kern_psignal(p2, SIGKILL); 535 PROC_UNLOCK(p2); 536 } else 537 PROC_UNLOCK(p1->p_leader); 538 } else { 539 p2->p_peers = NULL; 540 p2->p_leader = p2; 541 } 542 543 sx_xlock(&proctree_lock); 544 PGRP_LOCK(p1->p_pgrp); 545 PROC_LOCK(p2); 546 PROC_LOCK(p1); 547 548 /* 549 * Preserve some more flags in subprocess. P_PROFIL has already 550 * been preserved. 551 */ 552 p2->p_flag |= p1->p_flag & P_SUGID; 553 td2->td_pflags |= (td->td_pflags & TDP_ALTSTACK) | TDP_FORKING; 554 SESS_LOCK(p1->p_session); 555 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 556 p2->p_flag |= P_CONTROLT; 557 SESS_UNLOCK(p1->p_session); 558 if (fr->fr_flags & RFPPWAIT) 559 p2->p_flag |= P_PPWAIT; 560 561 p2->p_pgrp = p1->p_pgrp; 562 LIST_INSERT_AFTER(p1, p2, p_pglist); 563 PGRP_UNLOCK(p1->p_pgrp); 564 LIST_INIT(&p2->p_children); 565 LIST_INIT(&p2->p_orphans); 566 567 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 568 569 /* 570 * If PF_FORK is set, the child process inherits the 571 * procfs ioctl flags from its parent. 572 */ 573 if (p1->p_pfsflags & PF_FORK) { 574 p2->p_stops = p1->p_stops; 575 p2->p_pfsflags = p1->p_pfsflags; 576 } 577 578 /* 579 * This begins the section where we must prevent the parent 580 * from being swapped. 581 */ 582 _PHOLD(p1); 583 PROC_UNLOCK(p1); 584 585 /* 586 * Attach the new process to its parent. 587 * 588 * If RFNOWAIT is set, the newly created process becomes a child 589 * of init. This effectively disassociates the child from the 590 * parent. 591 */ 592 if ((fr->fr_flags & RFNOWAIT) != 0) { 593 pptr = p1->p_reaper; 594 p2->p_reaper = pptr; 595 } else { 596 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 597 p1 : p1->p_reaper; 598 pptr = p1; 599 } 600 p2->p_pptr = pptr; 601 p2->p_oppid = pptr->p_pid; 602 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 603 LIST_INIT(&p2->p_reaplist); 604 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 605 if (p2->p_reaper == p1 && p1 != initproc) { 606 p2->p_reapsubtree = p2->p_pid; 607 proc_id_set_cond(PROC_ID_REAP, p2->p_pid); 608 } 609 sx_xunlock(&proctree_lock); 610 611 /* Inform accounting that we have forked. */ 612 p2->p_acflag = AFORK; 613 PROC_UNLOCK(p2); 614 615 #ifdef KTRACE 616 ktrprocfork(p1, p2); 617 #endif 618 619 /* 620 * Finish creating the child process. It will return via a different 621 * execution path later. (ie: directly into user mode) 622 */ 623 vm_forkproc(td, p2, td2, vm2, fr->fr_flags); 624 625 if (fr->fr_flags == (RFFDG | RFPROC)) { 626 VM_CNT_INC(v_forks); 627 VM_CNT_ADD(v_forkpages, p2->p_vmspace->vm_dsize + 628 p2->p_vmspace->vm_ssize); 629 } else if (fr->fr_flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 630 VM_CNT_INC(v_vforks); 631 VM_CNT_ADD(v_vforkpages, p2->p_vmspace->vm_dsize + 632 p2->p_vmspace->vm_ssize); 633 } else if (p1 == &proc0) { 634 VM_CNT_INC(v_kthreads); 635 VM_CNT_ADD(v_kthreadpages, p2->p_vmspace->vm_dsize + 636 p2->p_vmspace->vm_ssize); 637 } else { 638 VM_CNT_INC(v_rforks); 639 VM_CNT_ADD(v_rforkpages, p2->p_vmspace->vm_dsize + 640 p2->p_vmspace->vm_ssize); 641 } 642 643 /* 644 * Associate the process descriptor with the process before anything 645 * can happen that might cause that process to need the descriptor. 646 * However, don't do this until after fork(2) can no longer fail. 647 */ 648 if (fr->fr_flags & RFPROCDESC) 649 procdesc_new(p2, fr->fr_pd_flags); 650 651 /* 652 * Both processes are set up, now check if any loadable modules want 653 * to adjust anything. 654 */ 655 EVENTHANDLER_DIRECT_INVOKE(process_fork, p1, p2, fr->fr_flags); 656 657 /* 658 * Set the child start time and mark the process as being complete. 659 */ 660 PROC_LOCK(p2); 661 PROC_LOCK(p1); 662 microuptime(&p2->p_stats->p_start); 663 PROC_SLOCK(p2); 664 p2->p_state = PRS_NORMAL; 665 PROC_SUNLOCK(p2); 666 667 #ifdef KDTRACE_HOOKS 668 /* 669 * Tell the DTrace fasttrap provider about the new process so that any 670 * tracepoints inherited from the parent can be removed. We have to do 671 * this only after p_state is PRS_NORMAL since the fasttrap module will 672 * use pfind() later on. 673 */ 674 if ((fr->fr_flags & RFMEM) == 0 && dtrace_fasttrap_fork) 675 dtrace_fasttrap_fork(p1, p2); 676 #endif 677 if (fr->fr_flags & RFPPWAIT) { 678 td->td_pflags |= TDP_RFPPWAIT; 679 td->td_rfppwait_p = p2; 680 td->td_dbgflags |= TDB_VFORK; 681 } 682 PROC_UNLOCK(p2); 683 684 /* 685 * Tell any interested parties about the new process. 686 */ 687 knote_fork(p1->p_klist, p2->p_pid); 688 689 /* 690 * Now can be swapped. 691 */ 692 _PRELE(p1); 693 PROC_UNLOCK(p1); 694 SDT_PROBE3(proc, , , create, p2, p1, fr->fr_flags); 695 696 if (fr->fr_flags & RFPROCDESC) { 697 procdesc_finit(p2->p_procdesc, fp_procdesc); 698 fdrop(fp_procdesc, td); 699 } 700 701 /* 702 * Speculative check for PTRACE_FORK. PTRACE_FORK is not 703 * synced with forks in progress so it is OK if we miss it 704 * if being set atm. 705 */ 706 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 707 sx_xlock(&proctree_lock); 708 PROC_LOCK(p2); 709 710 /* 711 * p1->p_ptevents & p1->p_pptr are protected by both 712 * process and proctree locks for modifications, 713 * so owning proctree_lock allows the race-free read. 714 */ 715 if ((p1->p_ptevents & PTRACE_FORK) != 0) { 716 /* 717 * Arrange for debugger to receive the fork event. 718 * 719 * We can report PL_FLAG_FORKED regardless of 720 * P_FOLLOWFORK settings, but it does not make a sense 721 * for runaway child. 722 */ 723 td->td_dbgflags |= TDB_FORK; 724 td->td_dbg_forked = p2->p_pid; 725 td2->td_dbgflags |= TDB_STOPATFORK; 726 proc_set_traced(p2, true); 727 CTR2(KTR_PTRACE, 728 "do_fork: attaching to new child pid %d: oppid %d", 729 p2->p_pid, p2->p_oppid); 730 proc_reparent(p2, p1->p_pptr, false); 731 } 732 PROC_UNLOCK(p2); 733 sx_xunlock(&proctree_lock); 734 } 735 736 racct_proc_fork_done(p2); 737 738 if ((fr->fr_flags & RFSTOPPED) == 0) { 739 if (fr->fr_pidp != NULL) 740 *fr->fr_pidp = p2->p_pid; 741 /* 742 * If RFSTOPPED not requested, make child runnable and 743 * add to run queue. 744 */ 745 thread_lock(td2); 746 TD_SET_CAN_RUN(td2); 747 sched_add(td2, SRQ_BORING); 748 thread_unlock(td2); 749 } else { 750 *fr->fr_procp = p2; 751 } 752 } 753 754 void 755 fork_rfppwait(struct thread *td) 756 { 757 struct proc *p, *p2; 758 759 MPASS(td->td_pflags & TDP_RFPPWAIT); 760 761 p = td->td_proc; 762 /* 763 * Preserve synchronization semantics of vfork. If 764 * waiting for child to exec or exit, fork set 765 * P_PPWAIT on child, and there we sleep on our proc 766 * (in case of exit). 767 * 768 * Do it after the ptracestop() above is finished, to 769 * not block our debugger until child execs or exits 770 * to finish vfork wait. 771 */ 772 td->td_pflags &= ~TDP_RFPPWAIT; 773 p2 = td->td_rfppwait_p; 774 again: 775 PROC_LOCK(p2); 776 while (p2->p_flag & P_PPWAIT) { 777 PROC_LOCK(p); 778 if (thread_suspend_check_needed()) { 779 PROC_UNLOCK(p2); 780 thread_suspend_check(0); 781 PROC_UNLOCK(p); 782 goto again; 783 } else { 784 PROC_UNLOCK(p); 785 } 786 cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); 787 } 788 PROC_UNLOCK(p2); 789 790 if (td->td_dbgflags & TDB_VFORK) { 791 PROC_LOCK(p); 792 if (p->p_ptevents & PTRACE_VFORK) 793 ptracestop(td, SIGTRAP, NULL); 794 td->td_dbgflags &= ~TDB_VFORK; 795 PROC_UNLOCK(p); 796 } 797 } 798 799 int 800 fork1(struct thread *td, struct fork_req *fr) 801 { 802 struct proc *p1, *newproc; 803 struct thread *td2; 804 struct vmspace *vm2; 805 struct ucred *cred; 806 struct file *fp_procdesc; 807 vm_ooffset_t mem_charged; 808 int error, nprocs_new; 809 static int curfail; 810 static struct timeval lastfail; 811 int flags, pages; 812 813 flags = fr->fr_flags; 814 pages = fr->fr_pages; 815 816 if ((flags & RFSTOPPED) != 0) 817 MPASS(fr->fr_procp != NULL && fr->fr_pidp == NULL); 818 else 819 MPASS(fr->fr_procp == NULL); 820 821 /* Check for the undefined or unimplemented flags. */ 822 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 823 return (EINVAL); 824 825 /* Signal value requires RFTSIGZMB. */ 826 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 827 return (EINVAL); 828 829 /* Can't copy and clear. */ 830 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 831 return (EINVAL); 832 833 /* Check the validity of the signal number. */ 834 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 835 return (EINVAL); 836 837 if ((flags & RFPROCDESC) != 0) { 838 /* Can't not create a process yet get a process descriptor. */ 839 if ((flags & RFPROC) == 0) 840 return (EINVAL); 841 842 /* Must provide a place to put a procdesc if creating one. */ 843 if (fr->fr_pd_fd == NULL) 844 return (EINVAL); 845 846 /* Check if we are using supported flags. */ 847 if ((fr->fr_pd_flags & ~PD_ALLOWED_AT_FORK) != 0) 848 return (EINVAL); 849 } 850 851 p1 = td->td_proc; 852 853 /* 854 * Here we don't create a new process, but we divorce 855 * certain parts of a process from itself. 856 */ 857 if ((flags & RFPROC) == 0) { 858 if (fr->fr_procp != NULL) 859 *fr->fr_procp = NULL; 860 else if (fr->fr_pidp != NULL) 861 *fr->fr_pidp = 0; 862 return (fork_norfproc(td, flags)); 863 } 864 865 fp_procdesc = NULL; 866 newproc = NULL; 867 vm2 = NULL; 868 869 /* 870 * Increment the nprocs resource before allocations occur. 871 * Although process entries are dynamically created, we still 872 * keep a global limit on the maximum number we will 873 * create. There are hard-limits as to the number of processes 874 * that can run, established by the KVA and memory usage for 875 * the process data. 876 * 877 * Don't allow a nonprivileged user to use the last ten 878 * processes; don't let root exceed the limit. 879 */ 880 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 881 if (nprocs_new >= maxproc - 10) { 882 if (priv_check_cred(td->td_ucred, PRIV_MAXPROC) != 0 || 883 nprocs_new >= maxproc) { 884 error = EAGAIN; 885 sx_xlock(&allproc_lock); 886 if (ppsratecheck(&lastfail, &curfail, 1)) { 887 printf("maxproc limit exceeded by uid %u " 888 "(pid %d); see tuning(7) and " 889 "login.conf(5)\n", 890 td->td_ucred->cr_ruid, p1->p_pid); 891 } 892 sx_xunlock(&allproc_lock); 893 goto fail2; 894 } 895 } 896 897 /* 898 * If required, create a process descriptor in the parent first; we 899 * will abandon it if something goes wrong. We don't finit() until 900 * later. 901 */ 902 if (flags & RFPROCDESC) { 903 error = procdesc_falloc(td, &fp_procdesc, fr->fr_pd_fd, 904 fr->fr_pd_flags, fr->fr_pd_fcaps); 905 if (error != 0) 906 goto fail2; 907 } 908 909 mem_charged = 0; 910 if (pages == 0) 911 pages = kstack_pages; 912 /* Allocate new proc. */ 913 newproc = uma_zalloc(proc_zone, M_WAITOK); 914 td2 = FIRST_THREAD_IN_PROC(newproc); 915 if (td2 == NULL) { 916 td2 = thread_alloc(pages); 917 if (td2 == NULL) { 918 error = ENOMEM; 919 goto fail2; 920 } 921 proc_linkup(newproc, td2); 922 } else { 923 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 924 if (td2->td_kstack != 0) 925 vm_thread_dispose(td2); 926 if (!thread_alloc_stack(td2, pages)) { 927 error = ENOMEM; 928 goto fail2; 929 } 930 } 931 } 932 933 if ((flags & RFMEM) == 0) { 934 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 935 if (vm2 == NULL) { 936 error = ENOMEM; 937 goto fail2; 938 } 939 if (!swap_reserve(mem_charged)) { 940 /* 941 * The swap reservation failed. The accounting 942 * from the entries of the copied vm2 will be 943 * subtracted in vmspace_free(), so force the 944 * reservation there. 945 */ 946 swap_reserve_force(mem_charged); 947 error = ENOMEM; 948 goto fail2; 949 } 950 } else 951 vm2 = NULL; 952 953 /* 954 * XXX: This is ugly; when we copy resource usage, we need to bump 955 * per-cred resource counters. 956 */ 957 proc_set_cred_init(newproc, crhold(td->td_ucred)); 958 959 /* 960 * Initialize resource accounting for the child process. 961 */ 962 error = racct_proc_fork(p1, newproc); 963 if (error != 0) { 964 error = EAGAIN; 965 goto fail1; 966 } 967 968 #ifdef MAC 969 mac_proc_init(newproc); 970 #endif 971 newproc->p_klist = knlist_alloc(&newproc->p_mtx); 972 STAILQ_INIT(&newproc->p_ktr); 973 974 /* 975 * Increment the count of procs running with this uid. Don't allow 976 * a nonprivileged user to exceed their current limit. 977 */ 978 cred = td->td_ucred; 979 if (!chgproccnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_NPROC))) { 980 if (priv_check_cred(cred, PRIV_PROC_LIMIT) != 0) 981 goto fail0; 982 chgproccnt(cred->cr_ruidinfo, 1, 0); 983 } 984 985 do_fork(td, fr, newproc, td2, vm2, fp_procdesc); 986 return (0); 987 fail0: 988 error = EAGAIN; 989 #ifdef MAC 990 mac_proc_destroy(newproc); 991 #endif 992 racct_proc_exit(newproc); 993 fail1: 994 crfree(newproc->p_ucred); 995 newproc->p_ucred = NULL; 996 fail2: 997 if (vm2 != NULL) 998 vmspace_free(vm2); 999 uma_zfree(proc_zone, newproc); 1000 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 1001 fdclose(td, fp_procdesc, *fr->fr_pd_fd); 1002 fdrop(fp_procdesc, td); 1003 } 1004 atomic_add_int(&nprocs, -1); 1005 pause("fork", hz / 2); 1006 return (error); 1007 } 1008 1009 /* 1010 * Handle the return of a child process from fork1(). This function 1011 * is called from the MD fork_trampoline() entry point. 1012 */ 1013 void 1014 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 1015 struct trapframe *frame) 1016 { 1017 struct proc *p; 1018 struct thread *td; 1019 struct thread *dtd; 1020 1021 td = curthread; 1022 p = td->td_proc; 1023 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1024 1025 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1026 td, td_get_sched(td), p->p_pid, td->td_name); 1027 1028 sched_fork_exit(td); 1029 /* 1030 * Processes normally resume in mi_switch() after being 1031 * cpu_switch()'ed to, but when children start up they arrive here 1032 * instead, so we must do much the same things as mi_switch() would. 1033 */ 1034 if ((dtd = PCPU_GET(deadthread))) { 1035 PCPU_SET(deadthread, NULL); 1036 thread_stash(dtd); 1037 } 1038 thread_unlock(td); 1039 1040 /* 1041 * cpu_fork_kthread_handler intercepts this function call to 1042 * have this call a non-return function to stay in kernel mode. 1043 * initproc has its own fork handler, but it does return. 1044 */ 1045 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1046 callout(arg, frame); 1047 1048 /* 1049 * Check if a kernel thread misbehaved and returned from its main 1050 * function. 1051 */ 1052 if (p->p_flag & P_KPROC) { 1053 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1054 td->td_name, p->p_pid); 1055 kthread_exit(); 1056 } 1057 mtx_assert(&Giant, MA_NOTOWNED); 1058 1059 if (p->p_sysent->sv_schedtail != NULL) 1060 (p->p_sysent->sv_schedtail)(td); 1061 td->td_pflags &= ~TDP_FORKING; 1062 } 1063 1064 /* 1065 * Simplified back end of syscall(), used when returning from fork() 1066 * directly into user mode. This function is passed in to fork_exit() 1067 * as the first parameter and is called when returning to a new 1068 * userland process. 1069 */ 1070 void 1071 fork_return(struct thread *td, struct trapframe *frame) 1072 { 1073 struct proc *p; 1074 1075 p = td->td_proc; 1076 if (td->td_dbgflags & TDB_STOPATFORK) { 1077 PROC_LOCK(p); 1078 if ((p->p_flag & P_TRACED) != 0) { 1079 /* 1080 * Inform the debugger if one is still present. 1081 */ 1082 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1083 ptracestop(td, SIGSTOP, NULL); 1084 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1085 } else { 1086 /* 1087 * ... otherwise clear the request. 1088 */ 1089 td->td_dbgflags &= ~TDB_STOPATFORK; 1090 } 1091 PROC_UNLOCK(p); 1092 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) { 1093 /* 1094 * This is the start of a new thread in a traced 1095 * process. Report a system call exit event. 1096 */ 1097 PROC_LOCK(p); 1098 td->td_dbgflags |= TDB_SCX; 1099 _STOPEVENT(p, S_SCX, td->td_sa.code); 1100 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1101 (td->td_dbgflags & TDB_BORN) != 0) 1102 ptracestop(td, SIGTRAP, NULL); 1103 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1104 PROC_UNLOCK(p); 1105 } 1106 1107 userret(td, frame); 1108 1109 #ifdef KTRACE 1110 if (KTRPOINT(td, KTR_SYSRET)) 1111 ktrsysret(SYS_fork, 0, 0); 1112 #endif 1113 } 1114