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