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 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/sysproto.h> 47 #include <sys/eventhandler.h> 48 #include <sys/filedesc.h> 49 #include <sys/jail.h> 50 #include <sys/kernel.h> 51 #include <sys/kthread.h> 52 #include <sys/sysctl.h> 53 #include <sys/lock.h> 54 #include <sys/malloc.h> 55 #include <sys/mutex.h> 56 #include <sys/priv.h> 57 #include <sys/proc.h> 58 #include <sys/pioctl.h> 59 #include <sys/resourcevar.h> 60 #include <sys/sched.h> 61 #include <sys/syscall.h> 62 #include <sys/vmmeter.h> 63 #include <sys/vnode.h> 64 #include <sys/acct.h> 65 #include <sys/ktr.h> 66 #include <sys/ktrace.h> 67 #include <sys/unistd.h> 68 #include <sys/sdt.h> 69 #include <sys/sx.h> 70 #include <sys/signalvar.h> 71 72 #include <security/audit/audit.h> 73 #include <security/mac/mac_framework.h> 74 75 #include <vm/vm.h> 76 #include <vm/pmap.h> 77 #include <vm/vm_map.h> 78 #include <vm/vm_extern.h> 79 #include <vm/uma.h> 80 81 #ifdef KDTRACE_HOOKS 82 #include <sys/dtrace_bsd.h> 83 dtrace_fork_func_t dtrace_fasttrap_fork; 84 #endif 85 86 SDT_PROVIDER_DECLARE(proc); 87 SDT_PROBE_DEFINE(proc, kernel, , create, create); 88 SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *"); 89 SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *"); 90 SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int"); 91 92 #ifndef _SYS_SYSPROTO_H_ 93 struct fork_args { 94 int dummy; 95 }; 96 #endif 97 98 /* ARGSUSED */ 99 int 100 fork(struct thread *td, struct fork_args *uap) 101 { 102 int error; 103 struct proc *p2; 104 105 error = fork1(td, RFFDG | RFPROC, 0, &p2); 106 if (error == 0) { 107 td->td_retval[0] = p2->p_pid; 108 td->td_retval[1] = 0; 109 } 110 return (error); 111 } 112 113 /* ARGSUSED */ 114 int 115 vfork(td, uap) 116 struct thread *td; 117 struct vfork_args *uap; 118 { 119 int error, flags; 120 struct proc *p2; 121 122 #ifdef XEN 123 flags = RFFDG | RFPROC; /* validate that this is still an issue */ 124 #else 125 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 126 #endif 127 error = fork1(td, flags, 0, &p2); 128 if (error == 0) { 129 td->td_retval[0] = p2->p_pid; 130 td->td_retval[1] = 0; 131 } 132 return (error); 133 } 134 135 int 136 rfork(struct thread *td, struct rfork_args *uap) 137 { 138 struct proc *p2; 139 int error; 140 141 /* Don't allow kernel-only flags. */ 142 if ((uap->flags & RFKERNELONLY) != 0) 143 return (EINVAL); 144 145 AUDIT_ARG_FFLAGS(uap->flags); 146 error = fork1(td, uap->flags, 0, &p2); 147 if (error == 0) { 148 td->td_retval[0] = p2 ? p2->p_pid : 0; 149 td->td_retval[1] = 0; 150 } 151 return (error); 152 } 153 154 int nprocs = 1; /* process 0 */ 155 int lastpid = 0; 156 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 157 "Last used PID"); 158 159 /* 160 * Random component to lastpid generation. We mix in a random factor to make 161 * it a little harder to predict. We sanity check the modulus value to avoid 162 * doing it in critical paths. Don't let it be too small or we pointlessly 163 * waste randomness entropy, and don't let it be impossibly large. Using a 164 * modulus that is too big causes a LOT more process table scans and slows 165 * down fork processing as the pidchecked caching is defeated. 166 */ 167 static int randompid = 0; 168 169 static int 170 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 171 { 172 int error, pid; 173 174 error = sysctl_wire_old_buffer(req, sizeof(int)); 175 if (error != 0) 176 return(error); 177 sx_xlock(&allproc_lock); 178 pid = randompid; 179 error = sysctl_handle_int(oidp, &pid, 0, req); 180 if (error == 0 && req->newptr != NULL) { 181 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 182 pid = PID_MAX - 100; 183 else if (pid < 2) /* NOP */ 184 pid = 0; 185 else if (pid < 100) /* Make it reasonable */ 186 pid = 100; 187 randompid = pid; 188 } 189 sx_xunlock(&allproc_lock); 190 return (error); 191 } 192 193 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 194 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 195 196 static int 197 fork_findpid(int flags) 198 { 199 struct proc *p; 200 int trypid; 201 static int pidchecked = 0; 202 203 sx_assert(&allproc_lock, SX_XLOCKED); 204 205 /* 206 * Find an unused process ID. We remember a range of unused IDs 207 * ready to use (from lastpid+1 through pidchecked-1). 208 * 209 * If RFHIGHPID is set (used during system boot), do not allocate 210 * low-numbered pids. 211 */ 212 trypid = lastpid + 1; 213 if (flags & RFHIGHPID) { 214 if (trypid < 10) 215 trypid = 10; 216 } else { 217 if (randompid) 218 trypid += arc4random() % randompid; 219 } 220 retry: 221 /* 222 * If the process ID prototype has wrapped around, 223 * restart somewhat above 0, as the low-numbered procs 224 * tend to include daemons that don't exit. 225 */ 226 if (trypid >= PID_MAX) { 227 trypid = trypid % PID_MAX; 228 if (trypid < 100) 229 trypid += 100; 230 pidchecked = 0; 231 } 232 if (trypid >= pidchecked) { 233 int doingzomb = 0; 234 235 pidchecked = PID_MAX; 236 /* 237 * Scan the active and zombie procs to check whether this pid 238 * is in use. Remember the lowest pid that's greater 239 * than trypid, so we can avoid checking for a while. 240 */ 241 p = LIST_FIRST(&allproc); 242 again: 243 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 244 while (p->p_pid == trypid || 245 (p->p_pgrp != NULL && 246 (p->p_pgrp->pg_id == trypid || 247 (p->p_session != NULL && 248 p->p_session->s_sid == trypid)))) { 249 trypid++; 250 if (trypid >= pidchecked) 251 goto retry; 252 } 253 if (p->p_pid > trypid && pidchecked > p->p_pid) 254 pidchecked = p->p_pid; 255 if (p->p_pgrp != NULL) { 256 if (p->p_pgrp->pg_id > trypid && 257 pidchecked > p->p_pgrp->pg_id) 258 pidchecked = p->p_pgrp->pg_id; 259 if (p->p_session != NULL && 260 p->p_session->s_sid > trypid && 261 pidchecked > p->p_session->s_sid) 262 pidchecked = p->p_session->s_sid; 263 } 264 } 265 if (!doingzomb) { 266 doingzomb = 1; 267 p = LIST_FIRST(&zombproc); 268 goto again; 269 } 270 } 271 272 /* 273 * RFHIGHPID does not mess with the lastpid counter during boot. 274 */ 275 if (flags & RFHIGHPID) 276 pidchecked = 0; 277 else 278 lastpid = trypid; 279 280 return (trypid); 281 } 282 283 static int 284 fork_norfproc(struct thread *td, int flags, struct proc **procp) 285 { 286 int error; 287 struct proc *p1; 288 289 KASSERT((flags & RFPROC) == 0, 290 ("fork_norfproc called with RFPROC set")); 291 p1 = td->td_proc; 292 *procp = NULL; 293 294 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 295 (flags & (RFCFDG | RFFDG))) { 296 PROC_LOCK(p1); 297 if (thread_single(SINGLE_BOUNDARY)) { 298 PROC_UNLOCK(p1); 299 return (ERESTART); 300 } 301 PROC_UNLOCK(p1); 302 } 303 304 error = vm_forkproc(td, NULL, NULL, NULL, flags); 305 if (error) 306 goto fail; 307 308 /* 309 * Close all file descriptors. 310 */ 311 if (flags & RFCFDG) { 312 struct filedesc *fdtmp; 313 fdtmp = fdinit(td->td_proc->p_fd); 314 fdfree(td); 315 p1->p_fd = fdtmp; 316 } 317 318 /* 319 * Unshare file descriptors (from parent). 320 */ 321 if (flags & RFFDG) 322 fdunshare(p1, td); 323 324 fail: 325 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 326 (flags & (RFCFDG | RFFDG))) { 327 PROC_LOCK(p1); 328 thread_single_end(); 329 PROC_UNLOCK(p1); 330 } 331 return (error); 332 } 333 334 static void 335 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, 336 struct vmspace *vm2) 337 { 338 struct proc *p1, *pptr; 339 int trypid; 340 struct filedesc *fd; 341 struct filedesc_to_leader *fdtol; 342 struct sigacts *newsigacts; 343 344 sx_assert(&proctree_lock, SX_SLOCKED); 345 sx_assert(&allproc_lock, SX_XLOCKED); 346 347 p1 = td->td_proc; 348 349 /* 350 * Increment the nprocs resource before blocking can occur. There 351 * are hard-limits as to the number of processes that can run. 352 */ 353 nprocs++; 354 355 trypid = fork_findpid(flags); 356 357 sx_sunlock(&proctree_lock); 358 359 p2->p_state = PRS_NEW; /* protect against others */ 360 p2->p_pid = trypid; 361 /* 362 * Allow the scheduler to initialize the child. 363 */ 364 thread_lock(td); 365 sched_fork(td, td2); 366 thread_unlock(td); 367 AUDIT_ARG_PID(p2->p_pid); 368 LIST_INSERT_HEAD(&allproc, p2, p_list); 369 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 370 tidhash_add(td2); 371 PROC_LOCK(p2); 372 PROC_LOCK(p1); 373 374 sx_xunlock(&allproc_lock); 375 376 bcopy(&p1->p_startcopy, &p2->p_startcopy, 377 __rangeof(struct proc, p_startcopy, p_endcopy)); 378 pargs_hold(p2->p_args); 379 PROC_UNLOCK(p1); 380 381 bzero(&p2->p_startzero, 382 __rangeof(struct proc, p_startzero, p_endzero)); 383 384 p2->p_ucred = crhold(td->td_ucred); 385 386 /* Tell the prison that we exist. */ 387 prison_proc_hold(p2->p_ucred->cr_prison); 388 389 PROC_UNLOCK(p2); 390 391 /* 392 * Malloc things while we don't hold any locks. 393 */ 394 if (flags & RFSIGSHARE) 395 newsigacts = NULL; 396 else 397 newsigacts = sigacts_alloc(); 398 399 /* 400 * Copy filedesc. 401 */ 402 if (flags & RFCFDG) { 403 fd = fdinit(p1->p_fd); 404 fdtol = NULL; 405 } else if (flags & RFFDG) { 406 fd = fdcopy(p1->p_fd); 407 fdtol = NULL; 408 } else { 409 fd = fdshare(p1->p_fd); 410 if (p1->p_fdtol == NULL) 411 p1->p_fdtol = 412 filedesc_to_leader_alloc(NULL, 413 NULL, 414 p1->p_leader); 415 if ((flags & RFTHREAD) != 0) { 416 /* 417 * Shared file descriptor table and 418 * shared process leaders. 419 */ 420 fdtol = p1->p_fdtol; 421 FILEDESC_XLOCK(p1->p_fd); 422 fdtol->fdl_refcount++; 423 FILEDESC_XUNLOCK(p1->p_fd); 424 } else { 425 /* 426 * Shared file descriptor table, and 427 * different process leaders 428 */ 429 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 430 p1->p_fd, 431 p2); 432 } 433 } 434 /* 435 * Make a proc table entry for the new process. 436 * Start by zeroing the section of proc that is zero-initialized, 437 * then copy the section that is copied directly from the parent. 438 */ 439 440 PROC_LOCK(p2); 441 PROC_LOCK(p1); 442 443 bzero(&td2->td_startzero, 444 __rangeof(struct thread, td_startzero, td_endzero)); 445 446 bcopy(&td->td_startcopy, &td2->td_startcopy, 447 __rangeof(struct thread, td_startcopy, td_endcopy)); 448 449 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 450 td2->td_sigstk = td->td_sigstk; 451 td2->td_sigmask = td->td_sigmask; 452 td2->td_flags = TDF_INMEM; 453 td2->td_lend_user_pri = PRI_MAX; 454 455 #ifdef VIMAGE 456 td2->td_vnet = NULL; 457 td2->td_vnet_lpush = NULL; 458 #endif 459 460 /* 461 * Duplicate sub-structures as needed. 462 * Increase reference counts on shared objects. 463 */ 464 p2->p_flag = P_INMEM; 465 p2->p_swtick = ticks; 466 if (p1->p_flag & P_PROFIL) 467 startprofclock(p2); 468 td2->td_ucred = crhold(p2->p_ucred); 469 470 if (flags & RFSIGSHARE) { 471 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 472 } else { 473 sigacts_copy(newsigacts, p1->p_sigacts); 474 p2->p_sigacts = newsigacts; 475 } 476 if (flags & RFLINUXTHPN) 477 p2->p_sigparent = SIGUSR1; 478 else 479 p2->p_sigparent = SIGCHLD; 480 481 p2->p_textvp = p1->p_textvp; 482 p2->p_fd = fd; 483 p2->p_fdtol = fdtol; 484 485 /* 486 * p_limit is copy-on-write. Bump its refcount. 487 */ 488 lim_fork(p1, p2); 489 490 pstats_fork(p1->p_stats, p2->p_stats); 491 492 PROC_UNLOCK(p1); 493 PROC_UNLOCK(p2); 494 495 /* Bump references to the text vnode (for procfs) */ 496 if (p2->p_textvp) 497 vref(p2->p_textvp); 498 499 /* 500 * Set up linkage for kernel based threading. 501 */ 502 if ((flags & RFTHREAD) != 0) { 503 mtx_lock(&ppeers_lock); 504 p2->p_peers = p1->p_peers; 505 p1->p_peers = p2; 506 p2->p_leader = p1->p_leader; 507 mtx_unlock(&ppeers_lock); 508 PROC_LOCK(p1->p_leader); 509 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 510 PROC_UNLOCK(p1->p_leader); 511 /* 512 * The task leader is exiting, so process p1 is 513 * going to be killed shortly. Since p1 obviously 514 * isn't dead yet, we know that the leader is either 515 * sending SIGKILL's to all the processes in this 516 * task or is sleeping waiting for all the peers to 517 * exit. We let p1 complete the fork, but we need 518 * to go ahead and kill the new process p2 since 519 * the task leader may not get a chance to send 520 * SIGKILL to it. We leave it on the list so that 521 * the task leader will wait for this new process 522 * to commit suicide. 523 */ 524 PROC_LOCK(p2); 525 psignal(p2, SIGKILL); 526 PROC_UNLOCK(p2); 527 } else 528 PROC_UNLOCK(p1->p_leader); 529 } else { 530 p2->p_peers = NULL; 531 p2->p_leader = p2; 532 } 533 534 sx_xlock(&proctree_lock); 535 PGRP_LOCK(p1->p_pgrp); 536 PROC_LOCK(p2); 537 PROC_LOCK(p1); 538 539 /* 540 * Preserve some more flags in subprocess. P_PROFIL has already 541 * been preserved. 542 */ 543 p2->p_flag |= p1->p_flag & P_SUGID; 544 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 545 SESS_LOCK(p1->p_session); 546 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 547 p2->p_flag |= P_CONTROLT; 548 SESS_UNLOCK(p1->p_session); 549 if (flags & RFPPWAIT) 550 p2->p_flag |= P_PPWAIT; 551 552 p2->p_pgrp = p1->p_pgrp; 553 LIST_INSERT_AFTER(p1, p2, p_pglist); 554 PGRP_UNLOCK(p1->p_pgrp); 555 LIST_INIT(&p2->p_children); 556 557 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 558 559 #ifdef KTRACE 560 ktrprocfork(p1, p2); 561 #endif 562 563 /* 564 * If PF_FORK is set, the child process inherits the 565 * procfs ioctl flags from its parent. 566 */ 567 if (p1->p_pfsflags & PF_FORK) { 568 p2->p_stops = p1->p_stops; 569 p2->p_pfsflags = p1->p_pfsflags; 570 } 571 572 /* 573 * This begins the section where we must prevent the parent 574 * from being swapped. 575 */ 576 _PHOLD(p1); 577 PROC_UNLOCK(p1); 578 579 /* 580 * Attach the new process to its parent. 581 * 582 * If RFNOWAIT is set, the newly created process becomes a child 583 * of init. This effectively disassociates the child from the 584 * parent. 585 */ 586 if (flags & RFNOWAIT) 587 pptr = initproc; 588 else 589 pptr = p1; 590 p2->p_pptr = pptr; 591 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 592 sx_xunlock(&proctree_lock); 593 594 /* Inform accounting that we have forked. */ 595 p2->p_acflag = AFORK; 596 PROC_UNLOCK(p2); 597 598 /* 599 * Finish creating the child process. It will return via a different 600 * execution path later. (ie: directly into user mode) 601 */ 602 vm_forkproc(td, p2, td2, vm2, flags); 603 604 if (flags == (RFFDG | RFPROC)) { 605 PCPU_INC(cnt.v_forks); 606 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 607 p2->p_vmspace->vm_ssize); 608 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 609 PCPU_INC(cnt.v_vforks); 610 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 611 p2->p_vmspace->vm_ssize); 612 } else if (p1 == &proc0) { 613 PCPU_INC(cnt.v_kthreads); 614 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 615 p2->p_vmspace->vm_ssize); 616 } else { 617 PCPU_INC(cnt.v_rforks); 618 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 619 p2->p_vmspace->vm_ssize); 620 } 621 622 /* 623 * Both processes are set up, now check if any loadable modules want 624 * to adjust anything. 625 * What if they have an error? XXX 626 */ 627 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 628 629 /* 630 * Set the child start time and mark the process as being complete. 631 */ 632 microuptime(&p2->p_stats->p_start); 633 PROC_SLOCK(p2); 634 p2->p_state = PRS_NORMAL; 635 PROC_SUNLOCK(p2); 636 #ifdef KDTRACE_HOOKS 637 /* 638 * Tell the DTrace fasttrap provider about the new process 639 * if it has registered an interest. We have to do this only after 640 * p_state is PRS_NORMAL since the fasttrap module will use pfind() 641 * later on. 642 */ 643 if (dtrace_fasttrap_fork) { 644 PROC_LOCK(p1); 645 PROC_LOCK(p2); 646 dtrace_fasttrap_fork(p1, p2); 647 PROC_UNLOCK(p2); 648 PROC_UNLOCK(p1); 649 } 650 #endif 651 652 /* 653 * If RFSTOPPED not requested, make child runnable and add to 654 * run queue. 655 */ 656 if ((flags & RFSTOPPED) == 0) { 657 thread_lock(td2); 658 TD_SET_CAN_RUN(td2); 659 sched_add(td2, SRQ_BORING); 660 thread_unlock(td2); 661 } 662 663 /* 664 * Now can be swapped. 665 */ 666 PROC_LOCK(p1); 667 _PRELE(p1); 668 PROC_UNLOCK(p1); 669 670 /* 671 * Tell any interested parties about the new process. 672 */ 673 knote_fork(&p1->p_klist, p2->p_pid); 674 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 675 676 /* 677 * Preserve synchronization semantics of vfork. If waiting for 678 * child to exec or exit, set P_PPWAIT on child, and sleep on our 679 * proc (in case of exit). 680 */ 681 PROC_LOCK(p2); 682 while (p2->p_flag & P_PPWAIT) 683 cv_wait(&p2->p_pwait, &p2->p_mtx); 684 PROC_UNLOCK(p2); 685 686 } 687 688 int 689 fork1(struct thread *td, int flags, int pages, struct proc **procp) 690 { 691 struct proc *p1; 692 struct proc *newproc; 693 int ok; 694 struct thread *td2; 695 struct vmspace *vm2; 696 vm_ooffset_t mem_charged; 697 int error; 698 static int curfail; 699 static struct timeval lastfail; 700 701 /* Can't copy and clear. */ 702 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 703 return (EINVAL); 704 705 p1 = td->td_proc; 706 707 /* 708 * Here we don't create a new process, but we divorce 709 * certain parts of a process from itself. 710 */ 711 if ((flags & RFPROC) == 0) 712 return (fork_norfproc(td, flags, procp)); 713 714 /* 715 * XXX 716 * We did have single-threading code here 717 * however it proved un-needed and caused problems 718 */ 719 720 mem_charged = 0; 721 vm2 = NULL; 722 if (pages == 0) 723 pages = KSTACK_PAGES; 724 /* Allocate new proc. */ 725 newproc = uma_zalloc(proc_zone, M_WAITOK); 726 td2 = FIRST_THREAD_IN_PROC(newproc); 727 if (td2 == NULL) { 728 td2 = thread_alloc(pages); 729 if (td2 == NULL) { 730 error = ENOMEM; 731 goto fail1; 732 } 733 proc_linkup(newproc, td2); 734 } else { 735 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 736 if (td2->td_kstack != 0) 737 vm_thread_dispose(td2); 738 if (!thread_alloc_stack(td2, pages)) { 739 error = ENOMEM; 740 goto fail1; 741 } 742 } 743 } 744 745 if ((flags & RFMEM) == 0) { 746 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 747 if (vm2 == NULL) { 748 error = ENOMEM; 749 goto fail1; 750 } 751 if (!swap_reserve(mem_charged)) { 752 /* 753 * The swap reservation failed. The accounting 754 * from the entries of the copied vm2 will be 755 * substracted in vmspace_free(), so force the 756 * reservation there. 757 */ 758 swap_reserve_force(mem_charged); 759 error = ENOMEM; 760 goto fail1; 761 } 762 } else 763 vm2 = NULL; 764 #ifdef MAC 765 mac_proc_init(newproc); 766 #endif 767 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 768 STAILQ_INIT(&newproc->p_ktr); 769 770 /* We have to lock the process tree while we look for a pid. */ 771 sx_slock(&proctree_lock); 772 773 /* 774 * Although process entries are dynamically created, we still keep 775 * a global limit on the maximum number we will create. Don't allow 776 * a nonprivileged user to use the last ten processes; don't let root 777 * exceed the limit. The variable nprocs is the current number of 778 * processes, maxproc is the limit. 779 */ 780 sx_xlock(&allproc_lock); 781 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 782 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 783 error = EAGAIN; 784 goto fail; 785 } 786 787 /* 788 * Increment the count of procs running with this uid. Don't allow 789 * a nonprivileged user to exceed their current limit. 790 * 791 * XXXRW: Can we avoid privilege here if it's not needed? 792 */ 793 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 794 if (error == 0) 795 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 796 else { 797 PROC_LOCK(p1); 798 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 799 lim_cur(p1, RLIMIT_NPROC)); 800 PROC_UNLOCK(p1); 801 } 802 if (ok) { 803 do_fork(td, flags, newproc, td2, vm2); 804 805 /* 806 * Return child proc pointer to parent. 807 */ 808 *procp = newproc; 809 return (0); 810 } 811 812 error = EAGAIN; 813 fail: 814 sx_sunlock(&proctree_lock); 815 if (ppsratecheck(&lastfail, &curfail, 1)) 816 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 817 td->td_ucred->cr_ruid); 818 sx_xunlock(&allproc_lock); 819 #ifdef MAC 820 mac_proc_destroy(newproc); 821 #endif 822 fail1: 823 if (vm2 != NULL) 824 vmspace_free(vm2); 825 uma_zfree(proc_zone, newproc); 826 pause("fork", hz / 2); 827 return (error); 828 } 829 830 /* 831 * Handle the return of a child process from fork1(). This function 832 * is called from the MD fork_trampoline() entry point. 833 */ 834 void 835 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 836 struct trapframe *frame) 837 { 838 struct proc *p; 839 struct thread *td; 840 struct thread *dtd; 841 842 td = curthread; 843 p = td->td_proc; 844 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 845 846 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 847 td, td->td_sched, p->p_pid, td->td_name); 848 849 sched_fork_exit(td); 850 /* 851 * Processes normally resume in mi_switch() after being 852 * cpu_switch()'ed to, but when children start up they arrive here 853 * instead, so we must do much the same things as mi_switch() would. 854 */ 855 if ((dtd = PCPU_GET(deadthread))) { 856 PCPU_SET(deadthread, NULL); 857 thread_stash(dtd); 858 } 859 thread_unlock(td); 860 861 /* 862 * cpu_set_fork_handler intercepts this function call to 863 * have this call a non-return function to stay in kernel mode. 864 * initproc has its own fork handler, but it does return. 865 */ 866 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 867 callout(arg, frame); 868 869 /* 870 * Check if a kernel thread misbehaved and returned from its main 871 * function. 872 */ 873 if (p->p_flag & P_KTHREAD) { 874 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 875 td->td_name, p->p_pid); 876 kproc_exit(0); 877 } 878 mtx_assert(&Giant, MA_NOTOWNED); 879 880 EVENTHANDLER_INVOKE(schedtail, p); 881 } 882 883 /* 884 * Simplified back end of syscall(), used when returning from fork() 885 * directly into user mode. Giant is not held on entry, and must not 886 * be held on return. This function is passed in to fork_exit() as the 887 * first parameter and is called when returning to a new userland process. 888 */ 889 void 890 fork_return(struct thread *td, struct trapframe *frame) 891 { 892 893 userret(td, frame); 894 #ifdef KTRACE 895 if (KTRPOINT(td, KTR_SYSRET)) 896 ktrsysret(SYS_fork, 0, 0); 897 #endif 898 mtx_assert(&Giant, MA_NOTOWNED); 899 } 900