1 /*- 2 * Copyright (c) 1982, 1986, 1989, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD$"); 39 40 #include "opt_kdtrace.h" 41 #include "opt_ktrace.h" 42 #include "opt_kstack_pages.h" 43 #include "opt_procdesc.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/sysproto.h> 48 #include <sys/eventhandler.h> 49 #include <sys/fcntl.h> 50 #include <sys/filedesc.h> 51 #include <sys/jail.h> 52 #include <sys/kernel.h> 53 #include <sys/kthread.h> 54 #include <sys/sysctl.h> 55 #include <sys/lock.h> 56 #include <sys/malloc.h> 57 #include <sys/mutex.h> 58 #include <sys/priv.h> 59 #include <sys/proc.h> 60 #include <sys/procdesc.h> 61 #include <sys/pioctl.h> 62 #include <sys/racct.h> 63 #include <sys/resourcevar.h> 64 #include <sys/sched.h> 65 #include <sys/syscall.h> 66 #include <sys/vmmeter.h> 67 #include <sys/vnode.h> 68 #include <sys/acct.h> 69 #include <sys/ktr.h> 70 #include <sys/ktrace.h> 71 #include <sys/unistd.h> 72 #include <sys/sdt.h> 73 #include <sys/sx.h> 74 #include <sys/sysent.h> 75 #include <sys/signalvar.h> 76 77 #include <security/audit/audit.h> 78 #include <security/mac/mac_framework.h> 79 80 #include <vm/vm.h> 81 #include <vm/pmap.h> 82 #include <vm/vm_map.h> 83 #include <vm/vm_extern.h> 84 #include <vm/uma.h> 85 86 #ifdef KDTRACE_HOOKS 87 #include <sys/dtrace_bsd.h> 88 dtrace_fork_func_t dtrace_fasttrap_fork; 89 #endif 90 91 SDT_PROVIDER_DECLARE(proc); 92 SDT_PROBE_DEFINE(proc, kernel, , create, create); 93 SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *"); 94 SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *"); 95 SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int"); 96 97 #ifndef _SYS_SYSPROTO_H_ 98 struct fork_args { 99 int dummy; 100 }; 101 #endif 102 103 /* ARGSUSED */ 104 int 105 sys_fork(struct thread *td, struct fork_args *uap) 106 { 107 int error; 108 struct proc *p2; 109 110 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0); 111 if (error == 0) { 112 td->td_retval[0] = p2->p_pid; 113 td->td_retval[1] = 0; 114 } 115 return (error); 116 } 117 118 /* ARGUSED */ 119 int 120 sys_pdfork(td, uap) 121 struct thread *td; 122 struct pdfork_args *uap; 123 { 124 #ifdef PROCDESC 125 int error, fd; 126 struct proc *p2; 127 128 /* 129 * It is necessary to return fd by reference because 0 is a valid file 130 * descriptor number, and the child needs to be able to distinguish 131 * itself from the parent using the return value. 132 */ 133 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2, 134 &fd, uap->flags); 135 if (error == 0) { 136 td->td_retval[0] = p2->p_pid; 137 td->td_retval[1] = 0; 138 error = copyout(&fd, uap->fdp, sizeof(fd)); 139 } 140 return (error); 141 #else 142 return (ENOSYS); 143 #endif 144 } 145 146 /* ARGSUSED */ 147 int 148 sys_vfork(struct thread *td, struct vfork_args *uap) 149 { 150 int error, flags; 151 struct proc *p2; 152 153 #ifdef XEN 154 flags = RFFDG | RFPROC; /* validate that this is still an issue */ 155 #else 156 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 157 #endif 158 error = fork1(td, flags, 0, &p2, NULL, 0); 159 if (error == 0) { 160 td->td_retval[0] = p2->p_pid; 161 td->td_retval[1] = 0; 162 } 163 return (error); 164 } 165 166 int 167 sys_rfork(struct thread *td, struct rfork_args *uap) 168 { 169 struct proc *p2; 170 int error; 171 172 /* Don't allow kernel-only flags. */ 173 if ((uap->flags & RFKERNELONLY) != 0) 174 return (EINVAL); 175 176 AUDIT_ARG_FFLAGS(uap->flags); 177 error = fork1(td, uap->flags, 0, &p2, NULL, 0); 178 if (error == 0) { 179 td->td_retval[0] = p2 ? p2->p_pid : 0; 180 td->td_retval[1] = 0; 181 } 182 return (error); 183 } 184 185 int nprocs = 1; /* process 0 */ 186 int lastpid = 0; 187 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 188 "Last used PID"); 189 190 /* 191 * Random component to lastpid generation. We mix in a random factor to make 192 * it a little harder to predict. We sanity check the modulus value to avoid 193 * doing it in critical paths. Don't let it be too small or we pointlessly 194 * waste randomness entropy, and don't let it be impossibly large. Using a 195 * modulus that is too big causes a LOT more process table scans and slows 196 * down fork processing as the pidchecked caching is defeated. 197 */ 198 static int randompid = 0; 199 200 static int 201 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 202 { 203 int error, pid; 204 205 error = sysctl_wire_old_buffer(req, sizeof(int)); 206 if (error != 0) 207 return(error); 208 sx_xlock(&allproc_lock); 209 pid = randompid; 210 error = sysctl_handle_int(oidp, &pid, 0, req); 211 if (error == 0 && req->newptr != NULL) { 212 if (pid < 0 || pid > pid_max - 100) /* out of range */ 213 pid = pid_max - 100; 214 else if (pid < 2) /* NOP */ 215 pid = 0; 216 else if (pid < 100) /* Make it reasonable */ 217 pid = 100; 218 randompid = pid; 219 } 220 sx_xunlock(&allproc_lock); 221 return (error); 222 } 223 224 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 225 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 226 227 static int 228 fork_findpid(int flags) 229 { 230 struct proc *p; 231 int trypid; 232 static int pidchecked = 0; 233 234 /* 235 * Requires allproc_lock in order to iterate over the list 236 * of processes, and proctree_lock to access p_pgrp. 237 */ 238 sx_assert(&allproc_lock, SX_LOCKED); 239 sx_assert(&proctree_lock, SX_LOCKED); 240 241 /* 242 * Find an unused process ID. We remember a range of unused IDs 243 * ready to use (from lastpid+1 through pidchecked-1). 244 * 245 * If RFHIGHPID is set (used during system boot), do not allocate 246 * low-numbered pids. 247 */ 248 trypid = lastpid + 1; 249 if (flags & RFHIGHPID) { 250 if (trypid < 10) 251 trypid = 10; 252 } else { 253 if (randompid) 254 trypid += arc4random() % randompid; 255 } 256 retry: 257 /* 258 * If the process ID prototype has wrapped around, 259 * restart somewhat above 0, as the low-numbered procs 260 * tend to include daemons that don't exit. 261 */ 262 if (trypid >= pid_max) { 263 trypid = trypid % pid_max; 264 if (trypid < 100) 265 trypid += 100; 266 pidchecked = 0; 267 } 268 if (trypid >= pidchecked) { 269 int doingzomb = 0; 270 271 pidchecked = PID_MAX; 272 /* 273 * Scan the active and zombie procs to check whether this pid 274 * is in use. Remember the lowest pid that's greater 275 * than trypid, so we can avoid checking for a while. 276 */ 277 p = LIST_FIRST(&allproc); 278 again: 279 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 280 while (p->p_pid == trypid || 281 (p->p_pgrp != NULL && 282 (p->p_pgrp->pg_id == trypid || 283 (p->p_session != NULL && 284 p->p_session->s_sid == trypid)))) { 285 trypid++; 286 if (trypid >= pidchecked) 287 goto retry; 288 } 289 if (p->p_pid > trypid && pidchecked > p->p_pid) 290 pidchecked = p->p_pid; 291 if (p->p_pgrp != NULL) { 292 if (p->p_pgrp->pg_id > trypid && 293 pidchecked > p->p_pgrp->pg_id) 294 pidchecked = p->p_pgrp->pg_id; 295 if (p->p_session != NULL && 296 p->p_session->s_sid > trypid && 297 pidchecked > p->p_session->s_sid) 298 pidchecked = p->p_session->s_sid; 299 } 300 } 301 if (!doingzomb) { 302 doingzomb = 1; 303 p = LIST_FIRST(&zombproc); 304 goto again; 305 } 306 } 307 308 /* 309 * RFHIGHPID does not mess with the lastpid counter during boot. 310 */ 311 if (flags & RFHIGHPID) 312 pidchecked = 0; 313 else 314 lastpid = trypid; 315 316 return (trypid); 317 } 318 319 static int 320 fork_norfproc(struct thread *td, int flags) 321 { 322 int error; 323 struct proc *p1; 324 325 KASSERT((flags & RFPROC) == 0, 326 ("fork_norfproc called with RFPROC set")); 327 p1 = td->td_proc; 328 329 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 330 (flags & (RFCFDG | RFFDG))) { 331 PROC_LOCK(p1); 332 if (thread_single(SINGLE_BOUNDARY)) { 333 PROC_UNLOCK(p1); 334 return (ERESTART); 335 } 336 PROC_UNLOCK(p1); 337 } 338 339 error = vm_forkproc(td, NULL, NULL, NULL, flags); 340 if (error) 341 goto fail; 342 343 /* 344 * Close all file descriptors. 345 */ 346 if (flags & RFCFDG) { 347 struct filedesc *fdtmp; 348 fdtmp = fdinit(td->td_proc->p_fd); 349 fdfree(td); 350 p1->p_fd = fdtmp; 351 } 352 353 /* 354 * Unshare file descriptors (from parent). 355 */ 356 if (flags & RFFDG) 357 fdunshare(p1, td); 358 359 fail: 360 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 361 (flags & (RFCFDG | RFFDG))) { 362 PROC_LOCK(p1); 363 thread_single_end(); 364 PROC_UNLOCK(p1); 365 } 366 return (error); 367 } 368 369 static void 370 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, 371 struct vmspace *vm2, int pdflags) 372 { 373 struct proc *p1, *pptr; 374 int p2_held, trypid; 375 struct filedesc *fd; 376 struct filedesc_to_leader *fdtol; 377 struct sigacts *newsigacts; 378 379 sx_assert(&proctree_lock, SX_SLOCKED); 380 sx_assert(&allproc_lock, SX_XLOCKED); 381 382 p2_held = 0; 383 p1 = td->td_proc; 384 385 /* 386 * Increment the nprocs resource before blocking can occur. There 387 * are hard-limits as to the number of processes that can run. 388 */ 389 nprocs++; 390 391 trypid = fork_findpid(flags); 392 393 sx_sunlock(&proctree_lock); 394 395 p2->p_state = PRS_NEW; /* protect against others */ 396 p2->p_pid = trypid; 397 AUDIT_ARG_PID(p2->p_pid); 398 LIST_INSERT_HEAD(&allproc, p2, p_list); 399 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 400 tidhash_add(td2); 401 PROC_LOCK(p2); 402 PROC_LOCK(p1); 403 404 sx_xunlock(&allproc_lock); 405 406 bcopy(&p1->p_startcopy, &p2->p_startcopy, 407 __rangeof(struct proc, p_startcopy, p_endcopy)); 408 pargs_hold(p2->p_args); 409 PROC_UNLOCK(p1); 410 411 bzero(&p2->p_startzero, 412 __rangeof(struct proc, p_startzero, p_endzero)); 413 414 p2->p_ucred = crhold(td->td_ucred); 415 416 /* Tell the prison that we exist. */ 417 prison_proc_hold(p2->p_ucred->cr_prison); 418 419 PROC_UNLOCK(p2); 420 421 /* 422 * Malloc things while we don't hold any locks. 423 */ 424 if (flags & RFSIGSHARE) 425 newsigacts = NULL; 426 else 427 newsigacts = sigacts_alloc(); 428 429 /* 430 * Copy filedesc. 431 */ 432 if (flags & RFCFDG) { 433 fd = fdinit(p1->p_fd); 434 fdtol = NULL; 435 } else if (flags & RFFDG) { 436 fd = fdcopy(p1->p_fd); 437 fdtol = NULL; 438 } else { 439 fd = fdshare(p1->p_fd); 440 if (p1->p_fdtol == NULL) 441 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 442 p1->p_leader); 443 if ((flags & RFTHREAD) != 0) { 444 /* 445 * Shared file descriptor table, and shared 446 * process leaders. 447 */ 448 fdtol = p1->p_fdtol; 449 FILEDESC_XLOCK(p1->p_fd); 450 fdtol->fdl_refcount++; 451 FILEDESC_XUNLOCK(p1->p_fd); 452 } else { 453 /* 454 * Shared file descriptor table, and different 455 * process leaders. 456 */ 457 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 458 p1->p_fd, p2); 459 } 460 } 461 /* 462 * Make a proc table entry for the new process. 463 * Start by zeroing the section of proc that is zero-initialized, 464 * then copy the section that is copied directly from the parent. 465 */ 466 467 PROC_LOCK(p2); 468 PROC_LOCK(p1); 469 470 bzero(&td2->td_startzero, 471 __rangeof(struct thread, td_startzero, td_endzero)); 472 473 bcopy(&td->td_startcopy, &td2->td_startcopy, 474 __rangeof(struct thread, td_startcopy, td_endcopy)); 475 476 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 477 td2->td_sigstk = td->td_sigstk; 478 td2->td_flags = TDF_INMEM; 479 td2->td_lend_user_pri = PRI_MAX; 480 481 #ifdef VIMAGE 482 td2->td_vnet = NULL; 483 td2->td_vnet_lpush = NULL; 484 #endif 485 486 /* 487 * Allow the scheduler to initialize the child. 488 */ 489 thread_lock(td); 490 sched_fork(td, td2); 491 thread_unlock(td); 492 493 /* 494 * Duplicate sub-structures as needed. 495 * Increase reference counts on shared objects. 496 */ 497 p2->p_flag = P_INMEM; 498 p2->p_swtick = ticks; 499 if (p1->p_flag & P_PROFIL) 500 startprofclock(p2); 501 td2->td_ucred = crhold(p2->p_ucred); 502 503 if (flags & RFSIGSHARE) { 504 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 505 } else { 506 sigacts_copy(newsigacts, p1->p_sigacts); 507 p2->p_sigacts = newsigacts; 508 } 509 510 if (flags & RFTSIGZMB) 511 p2->p_sigparent = RFTSIGNUM(flags); 512 else if (flags & RFLINUXTHPN) 513 p2->p_sigparent = SIGUSR1; 514 else 515 p2->p_sigparent = SIGCHLD; 516 517 p2->p_textvp = p1->p_textvp; 518 p2->p_fd = fd; 519 p2->p_fdtol = fdtol; 520 521 /* 522 * p_limit is copy-on-write. Bump its refcount. 523 */ 524 lim_fork(p1, p2); 525 526 pstats_fork(p1->p_stats, p2->p_stats); 527 528 PROC_UNLOCK(p1); 529 PROC_UNLOCK(p2); 530 531 /* Bump references to the text vnode (for procfs). */ 532 if (p2->p_textvp) 533 vref(p2->p_textvp); 534 535 /* 536 * Set up linkage for kernel based threading. 537 */ 538 if ((flags & RFTHREAD) != 0) { 539 mtx_lock(&ppeers_lock); 540 p2->p_peers = p1->p_peers; 541 p1->p_peers = p2; 542 p2->p_leader = p1->p_leader; 543 mtx_unlock(&ppeers_lock); 544 PROC_LOCK(p1->p_leader); 545 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 546 PROC_UNLOCK(p1->p_leader); 547 /* 548 * The task leader is exiting, so process p1 is 549 * going to be killed shortly. Since p1 obviously 550 * isn't dead yet, we know that the leader is either 551 * sending SIGKILL's to all the processes in this 552 * task or is sleeping waiting for all the peers to 553 * exit. We let p1 complete the fork, but we need 554 * to go ahead and kill the new process p2 since 555 * the task leader may not get a chance to send 556 * SIGKILL to it. We leave it on the list so that 557 * the task leader will wait for this new process 558 * to commit suicide. 559 */ 560 PROC_LOCK(p2); 561 kern_psignal(p2, SIGKILL); 562 PROC_UNLOCK(p2); 563 } else 564 PROC_UNLOCK(p1->p_leader); 565 } else { 566 p2->p_peers = NULL; 567 p2->p_leader = p2; 568 } 569 570 sx_xlock(&proctree_lock); 571 PGRP_LOCK(p1->p_pgrp); 572 PROC_LOCK(p2); 573 PROC_LOCK(p1); 574 575 /* 576 * Preserve some more flags in subprocess. P_PROFIL has already 577 * been preserved. 578 */ 579 p2->p_flag |= p1->p_flag & P_SUGID; 580 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 581 SESS_LOCK(p1->p_session); 582 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 583 p2->p_flag |= P_CONTROLT; 584 SESS_UNLOCK(p1->p_session); 585 if (flags & RFPPWAIT) 586 p2->p_flag |= P_PPWAIT; 587 588 p2->p_pgrp = p1->p_pgrp; 589 LIST_INSERT_AFTER(p1, p2, p_pglist); 590 PGRP_UNLOCK(p1->p_pgrp); 591 LIST_INIT(&p2->p_children); 592 LIST_INIT(&p2->p_orphans); 593 594 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 595 596 /* 597 * If PF_FORK is set, the child process inherits the 598 * procfs ioctl flags from its parent. 599 */ 600 if (p1->p_pfsflags & PF_FORK) { 601 p2->p_stops = p1->p_stops; 602 p2->p_pfsflags = p1->p_pfsflags; 603 } 604 605 /* 606 * This begins the section where we must prevent the parent 607 * from being swapped. 608 */ 609 _PHOLD(p1); 610 PROC_UNLOCK(p1); 611 612 /* 613 * Attach the new process to its parent. 614 * 615 * If RFNOWAIT is set, the newly created process becomes a child 616 * of init. This effectively disassociates the child from the 617 * parent. 618 */ 619 if (flags & RFNOWAIT) 620 pptr = initproc; 621 else 622 pptr = p1; 623 p2->p_pptr = pptr; 624 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 625 sx_xunlock(&proctree_lock); 626 627 /* Inform accounting that we have forked. */ 628 p2->p_acflag = AFORK; 629 PROC_UNLOCK(p2); 630 631 #ifdef KTRACE 632 ktrprocfork(p1, p2); 633 #endif 634 635 /* 636 * Finish creating the child process. It will return via a different 637 * execution path later. (ie: directly into user mode) 638 */ 639 vm_forkproc(td, p2, td2, vm2, flags); 640 641 if (flags == (RFFDG | RFPROC)) { 642 PCPU_INC(cnt.v_forks); 643 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 644 p2->p_vmspace->vm_ssize); 645 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 646 PCPU_INC(cnt.v_vforks); 647 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 648 p2->p_vmspace->vm_ssize); 649 } else if (p1 == &proc0) { 650 PCPU_INC(cnt.v_kthreads); 651 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 652 p2->p_vmspace->vm_ssize); 653 } else { 654 PCPU_INC(cnt.v_rforks); 655 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 656 p2->p_vmspace->vm_ssize); 657 } 658 659 #ifdef PROCDESC 660 /* 661 * Associate the process descriptor with the process before anything 662 * can happen that might cause that process to need the descriptor. 663 * However, don't do this until after fork(2) can no longer fail. 664 */ 665 if (flags & RFPROCDESC) 666 procdesc_new(p2, pdflags); 667 #endif 668 669 /* 670 * Both processes are set up, now check if any loadable modules want 671 * to adjust anything. 672 */ 673 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 674 675 /* 676 * Set the child start time and mark the process as being complete. 677 */ 678 PROC_LOCK(p2); 679 PROC_LOCK(p1); 680 microuptime(&p2->p_stats->p_start); 681 PROC_SLOCK(p2); 682 p2->p_state = PRS_NORMAL; 683 PROC_SUNLOCK(p2); 684 685 #ifdef KDTRACE_HOOKS 686 /* 687 * Tell the DTrace fasttrap provider about the new process 688 * if it has registered an interest. We have to do this only after 689 * p_state is PRS_NORMAL since the fasttrap module will use pfind() 690 * later on. 691 */ 692 if (dtrace_fasttrap_fork) 693 dtrace_fasttrap_fork(p1, p2); 694 #endif 695 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 696 P_FOLLOWFORK)) { 697 /* 698 * Arrange for debugger to receive the fork event. 699 * 700 * We can report PL_FLAG_FORKED regardless of 701 * P_FOLLOWFORK settings, but it does not make a sense 702 * for runaway child. 703 */ 704 td->td_dbgflags |= TDB_FORK; 705 td->td_dbg_forked = p2->p_pid; 706 td2->td_dbgflags |= TDB_STOPATFORK; 707 _PHOLD(p2); 708 p2_held = 1; 709 } 710 if (flags & RFPPWAIT) { 711 td->td_pflags |= TDP_RFPPWAIT; 712 td->td_rfppwait_p = p2; 713 } 714 PROC_UNLOCK(p2); 715 if ((flags & RFSTOPPED) == 0) { 716 /* 717 * If RFSTOPPED not requested, make child runnable and 718 * add to run queue. 719 */ 720 thread_lock(td2); 721 TD_SET_CAN_RUN(td2); 722 sched_add(td2, SRQ_BORING); 723 thread_unlock(td2); 724 } 725 726 /* 727 * Now can be swapped. 728 */ 729 _PRELE(p1); 730 PROC_UNLOCK(p1); 731 732 /* 733 * Tell any interested parties about the new process. 734 */ 735 knote_fork(&p1->p_klist, p2->p_pid); 736 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 737 738 /* 739 * Wait until debugger is attached to child. 740 */ 741 PROC_LOCK(p2); 742 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 743 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 744 if (p2_held) 745 _PRELE(p2); 746 PROC_UNLOCK(p2); 747 } 748 749 int 750 fork1(struct thread *td, int flags, int pages, struct proc **procp, 751 int *procdescp, int pdflags) 752 { 753 struct proc *p1; 754 struct proc *newproc; 755 int ok; 756 struct thread *td2; 757 struct vmspace *vm2; 758 vm_ooffset_t mem_charged; 759 int error; 760 static int curfail; 761 static struct timeval lastfail; 762 #ifdef PROCDESC 763 struct file *fp_procdesc = NULL; 764 #endif 765 766 /* Check for the undefined or unimplemented flags. */ 767 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 768 return (EINVAL); 769 770 /* Signal value requires RFTSIGZMB. */ 771 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 772 return (EINVAL); 773 774 /* Can't copy and clear. */ 775 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 776 return (EINVAL); 777 778 /* Check the validity of the signal number. */ 779 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 780 return (EINVAL); 781 782 #ifdef PROCDESC 783 if ((flags & RFPROCDESC) != 0) { 784 /* Can't not create a process yet get a process descriptor. */ 785 if ((flags & RFPROC) == 0) 786 return (EINVAL); 787 788 /* Must provide a place to put a procdesc if creating one. */ 789 if (procdescp == NULL) 790 return (EINVAL); 791 } 792 #endif 793 794 p1 = td->td_proc; 795 796 /* 797 * Here we don't create a new process, but we divorce 798 * certain parts of a process from itself. 799 */ 800 if ((flags & RFPROC) == 0) { 801 *procp = NULL; 802 return (fork_norfproc(td, flags)); 803 } 804 805 #ifdef PROCDESC 806 /* 807 * If required, create a process descriptor in the parent first; we 808 * will abandon it if something goes wrong. We don't finit() until 809 * later. 810 */ 811 if (flags & RFPROCDESC) { 812 error = falloc(td, &fp_procdesc, procdescp, 0); 813 if (error != 0) 814 return (error); 815 } 816 #endif 817 818 mem_charged = 0; 819 vm2 = NULL; 820 if (pages == 0) 821 pages = KSTACK_PAGES; 822 /* Allocate new proc. */ 823 newproc = uma_zalloc(proc_zone, M_WAITOK); 824 td2 = FIRST_THREAD_IN_PROC(newproc); 825 if (td2 == NULL) { 826 td2 = thread_alloc(pages); 827 if (td2 == NULL) { 828 error = ENOMEM; 829 goto fail1; 830 } 831 proc_linkup(newproc, td2); 832 } else { 833 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 834 if (td2->td_kstack != 0) 835 vm_thread_dispose(td2); 836 if (!thread_alloc_stack(td2, pages)) { 837 error = ENOMEM; 838 goto fail1; 839 } 840 } 841 } 842 843 if ((flags & RFMEM) == 0) { 844 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 845 if (vm2 == NULL) { 846 error = ENOMEM; 847 goto fail1; 848 } 849 if (!swap_reserve(mem_charged)) { 850 /* 851 * The swap reservation failed. The accounting 852 * from the entries of the copied vm2 will be 853 * substracted in vmspace_free(), so force the 854 * reservation there. 855 */ 856 swap_reserve_force(mem_charged); 857 error = ENOMEM; 858 goto fail1; 859 } 860 } else 861 vm2 = NULL; 862 863 /* 864 * XXX: This is ugly; when we copy resource usage, we need to bump 865 * per-cred resource counters. 866 */ 867 newproc->p_ucred = p1->p_ucred; 868 869 /* 870 * Initialize resource accounting for the child process. 871 */ 872 error = racct_proc_fork(p1, newproc); 873 if (error != 0) { 874 error = EAGAIN; 875 goto fail1; 876 } 877 878 #ifdef MAC 879 mac_proc_init(newproc); 880 #endif 881 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 882 STAILQ_INIT(&newproc->p_ktr); 883 884 /* We have to lock the process tree while we look for a pid. */ 885 sx_slock(&proctree_lock); 886 887 /* 888 * Although process entries are dynamically created, we still keep 889 * a global limit on the maximum number we will create. Don't allow 890 * a nonprivileged user to use the last ten processes; don't let root 891 * exceed the limit. The variable nprocs is the current number of 892 * processes, maxproc is the limit. 893 */ 894 sx_xlock(&allproc_lock); 895 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 896 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 897 error = EAGAIN; 898 goto fail; 899 } 900 901 /* 902 * Increment the count of procs running with this uid. Don't allow 903 * a nonprivileged user to exceed their current limit. 904 * 905 * XXXRW: Can we avoid privilege here if it's not needed? 906 */ 907 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 908 if (error == 0) 909 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 910 else { 911 PROC_LOCK(p1); 912 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 913 lim_cur(p1, RLIMIT_NPROC)); 914 PROC_UNLOCK(p1); 915 } 916 if (ok) { 917 do_fork(td, flags, newproc, td2, vm2, pdflags); 918 919 /* 920 * Return child proc pointer to parent. 921 */ 922 *procp = newproc; 923 #ifdef PROCDESC 924 if (flags & RFPROCDESC) { 925 procdesc_finit(newproc->p_procdesc, fp_procdesc); 926 fdrop(fp_procdesc, td); 927 } 928 #endif 929 racct_proc_fork_done(newproc); 930 return (0); 931 } 932 933 error = EAGAIN; 934 fail: 935 sx_sunlock(&proctree_lock); 936 if (ppsratecheck(&lastfail, &curfail, 1)) 937 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 938 td->td_ucred->cr_ruid); 939 sx_xunlock(&allproc_lock); 940 #ifdef MAC 941 mac_proc_destroy(newproc); 942 #endif 943 racct_proc_exit(newproc); 944 fail1: 945 if (vm2 != NULL) 946 vmspace_free(vm2); 947 uma_zfree(proc_zone, newproc); 948 #ifdef PROCDESC 949 if (((flags & RFPROCDESC) != 0) && (fp_procdesc != NULL)) { 950 fdclose(td->td_proc->p_fd, fp_procdesc, *procdescp, td); 951 fdrop(fp_procdesc, td); 952 } 953 #endif 954 pause("fork", hz / 2); 955 return (error); 956 } 957 958 /* 959 * Handle the return of a child process from fork1(). This function 960 * is called from the MD fork_trampoline() entry point. 961 */ 962 void 963 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 964 struct trapframe *frame) 965 { 966 struct proc *p; 967 struct thread *td; 968 struct thread *dtd; 969 970 td = curthread; 971 p = td->td_proc; 972 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 973 974 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 975 td, td->td_sched, p->p_pid, td->td_name); 976 977 sched_fork_exit(td); 978 /* 979 * Processes normally resume in mi_switch() after being 980 * cpu_switch()'ed to, but when children start up they arrive here 981 * instead, so we must do much the same things as mi_switch() would. 982 */ 983 if ((dtd = PCPU_GET(deadthread))) { 984 PCPU_SET(deadthread, NULL); 985 thread_stash(dtd); 986 } 987 thread_unlock(td); 988 989 /* 990 * cpu_set_fork_handler intercepts this function call to 991 * have this call a non-return function to stay in kernel mode. 992 * initproc has its own fork handler, but it does return. 993 */ 994 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 995 callout(arg, frame); 996 997 /* 998 * Check if a kernel thread misbehaved and returned from its main 999 * function. 1000 */ 1001 if (p->p_flag & P_KTHREAD) { 1002 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1003 td->td_name, p->p_pid); 1004 kproc_exit(0); 1005 } 1006 mtx_assert(&Giant, MA_NOTOWNED); 1007 1008 if (p->p_sysent->sv_schedtail != NULL) 1009 (p->p_sysent->sv_schedtail)(td); 1010 } 1011 1012 /* 1013 * Simplified back end of syscall(), used when returning from fork() 1014 * directly into user mode. Giant is not held on entry, and must not 1015 * be held on return. This function is passed in to fork_exit() as the 1016 * first parameter and is called when returning to a new userland process. 1017 */ 1018 void 1019 fork_return(struct thread *td, struct trapframe *frame) 1020 { 1021 struct proc *p, *dbg; 1022 1023 if (td->td_dbgflags & TDB_STOPATFORK) { 1024 p = td->td_proc; 1025 sx_xlock(&proctree_lock); 1026 PROC_LOCK(p); 1027 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 1028 (P_TRACED | P_FOLLOWFORK)) { 1029 /* 1030 * If debugger still wants auto-attach for the 1031 * parent's children, do it now. 1032 */ 1033 dbg = p->p_pptr->p_pptr; 1034 p->p_flag |= P_TRACED; 1035 p->p_oppid = p->p_pptr->p_pid; 1036 proc_reparent(p, dbg); 1037 sx_xunlock(&proctree_lock); 1038 td->td_dbgflags |= TDB_CHILD; 1039 ptracestop(td, SIGSTOP); 1040 td->td_dbgflags &= ~TDB_CHILD; 1041 } else { 1042 /* 1043 * ... otherwise clear the request. 1044 */ 1045 sx_xunlock(&proctree_lock); 1046 td->td_dbgflags &= ~TDB_STOPATFORK; 1047 cv_broadcast(&p->p_dbgwait); 1048 } 1049 PROC_UNLOCK(p); 1050 } 1051 1052 userret(td, frame); 1053 1054 #ifdef KTRACE 1055 if (KTRPOINT(td, KTR_SYSRET)) 1056 ktrsysret(SYS_fork, 0, 0); 1057 #endif 1058 } 1059