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(struct thread *td, struct vfork_args *uap) 116 { 117 int error, flags; 118 struct proc *p2; 119 120 #ifdef XEN 121 flags = RFFDG | RFPROC; /* validate that this is still an issue */ 122 #else 123 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 124 #endif 125 error = fork1(td, flags, 0, &p2); 126 if (error == 0) { 127 td->td_retval[0] = p2->p_pid; 128 td->td_retval[1] = 0; 129 } 130 return (error); 131 } 132 133 int 134 rfork(struct thread *td, struct rfork_args *uap) 135 { 136 struct proc *p2; 137 int error; 138 139 /* Don't allow kernel-only flags. */ 140 if ((uap->flags & RFKERNELONLY) != 0) 141 return (EINVAL); 142 143 AUDIT_ARG_FFLAGS(uap->flags); 144 error = fork1(td, uap->flags, 0, &p2); 145 if (error == 0) { 146 td->td_retval[0] = p2 ? p2->p_pid : 0; 147 td->td_retval[1] = 0; 148 } 149 return (error); 150 } 151 152 int nprocs = 1; /* process 0 */ 153 int lastpid = 0; 154 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 155 "Last used PID"); 156 157 /* 158 * Random component to lastpid generation. We mix in a random factor to make 159 * it a little harder to predict. We sanity check the modulus value to avoid 160 * doing it in critical paths. Don't let it be too small or we pointlessly 161 * waste randomness entropy, and don't let it be impossibly large. Using a 162 * modulus that is too big causes a LOT more process table scans and slows 163 * down fork processing as the pidchecked caching is defeated. 164 */ 165 static int randompid = 0; 166 167 static int 168 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 169 { 170 int error, pid; 171 172 error = sysctl_wire_old_buffer(req, sizeof(int)); 173 if (error != 0) 174 return(error); 175 sx_xlock(&allproc_lock); 176 pid = randompid; 177 error = sysctl_handle_int(oidp, &pid, 0, req); 178 if (error == 0 && req->newptr != NULL) { 179 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 180 pid = PID_MAX - 100; 181 else if (pid < 2) /* NOP */ 182 pid = 0; 183 else if (pid < 100) /* Make it reasonable */ 184 pid = 100; 185 randompid = pid; 186 } 187 sx_xunlock(&allproc_lock); 188 return (error); 189 } 190 191 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 192 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 193 194 static int 195 fork_findpid(int flags) 196 { 197 struct proc *p; 198 int trypid; 199 static int pidchecked = 0; 200 201 /* 202 * Requires allproc_lock in order to iterate over the list 203 * of processes, and proctree_lock to access p_pgrp. 204 */ 205 sx_assert(&allproc_lock, SX_LOCKED); 206 sx_assert(&proctree_lock, SX_LOCKED); 207 208 /* 209 * Find an unused process ID. We remember a range of unused IDs 210 * ready to use (from lastpid+1 through pidchecked-1). 211 * 212 * If RFHIGHPID is set (used during system boot), do not allocate 213 * low-numbered pids. 214 */ 215 trypid = lastpid + 1; 216 if (flags & RFHIGHPID) { 217 if (trypid < 10) 218 trypid = 10; 219 } else { 220 if (randompid) 221 trypid += arc4random() % randompid; 222 } 223 retry: 224 /* 225 * If the process ID prototype has wrapped around, 226 * restart somewhat above 0, as the low-numbered procs 227 * tend to include daemons that don't exit. 228 */ 229 if (trypid >= PID_MAX) { 230 trypid = trypid % PID_MAX; 231 if (trypid < 100) 232 trypid += 100; 233 pidchecked = 0; 234 } 235 if (trypid >= pidchecked) { 236 int doingzomb = 0; 237 238 pidchecked = PID_MAX; 239 /* 240 * Scan the active and zombie procs to check whether this pid 241 * is in use. Remember the lowest pid that's greater 242 * than trypid, so we can avoid checking for a while. 243 */ 244 p = LIST_FIRST(&allproc); 245 again: 246 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 247 while (p->p_pid == trypid || 248 (p->p_pgrp != NULL && 249 (p->p_pgrp->pg_id == trypid || 250 (p->p_session != NULL && 251 p->p_session->s_sid == trypid)))) { 252 trypid++; 253 if (trypid >= pidchecked) 254 goto retry; 255 } 256 if (p->p_pid > trypid && pidchecked > p->p_pid) 257 pidchecked = p->p_pid; 258 if (p->p_pgrp != NULL) { 259 if (p->p_pgrp->pg_id > trypid && 260 pidchecked > p->p_pgrp->pg_id) 261 pidchecked = p->p_pgrp->pg_id; 262 if (p->p_session != NULL && 263 p->p_session->s_sid > trypid && 264 pidchecked > p->p_session->s_sid) 265 pidchecked = p->p_session->s_sid; 266 } 267 } 268 if (!doingzomb) { 269 doingzomb = 1; 270 p = LIST_FIRST(&zombproc); 271 goto again; 272 } 273 } 274 275 /* 276 * RFHIGHPID does not mess with the lastpid counter during boot. 277 */ 278 if (flags & RFHIGHPID) 279 pidchecked = 0; 280 else 281 lastpid = trypid; 282 283 return (trypid); 284 } 285 286 static int 287 fork_norfproc(struct thread *td, int flags) 288 { 289 int error; 290 struct proc *p1; 291 292 KASSERT((flags & RFPROC) == 0, 293 ("fork_norfproc called with RFPROC set")); 294 p1 = td->td_proc; 295 296 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 297 (flags & (RFCFDG | RFFDG))) { 298 PROC_LOCK(p1); 299 if (thread_single(SINGLE_BOUNDARY)) { 300 PROC_UNLOCK(p1); 301 return (ERESTART); 302 } 303 PROC_UNLOCK(p1); 304 } 305 306 error = vm_forkproc(td, NULL, NULL, NULL, flags); 307 if (error) 308 goto fail; 309 310 /* 311 * Close all file descriptors. 312 */ 313 if (flags & RFCFDG) { 314 struct filedesc *fdtmp; 315 fdtmp = fdinit(td->td_proc->p_fd); 316 fdfree(td); 317 p1->p_fd = fdtmp; 318 } 319 320 /* 321 * Unshare file descriptors (from parent). 322 */ 323 if (flags & RFFDG) 324 fdunshare(p1, td); 325 326 fail: 327 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 328 (flags & (RFCFDG | RFFDG))) { 329 PROC_LOCK(p1); 330 thread_single_end(); 331 PROC_UNLOCK(p1); 332 } 333 return (error); 334 } 335 336 static void 337 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, 338 struct vmspace *vm2) 339 { 340 struct proc *p1, *pptr; 341 int trypid; 342 struct filedesc *fd; 343 struct filedesc_to_leader *fdtol; 344 struct sigacts *newsigacts; 345 346 sx_assert(&proctree_lock, SX_SLOCKED); 347 sx_assert(&allproc_lock, SX_XLOCKED); 348 349 p1 = td->td_proc; 350 351 /* 352 * Increment the nprocs resource before blocking can occur. There 353 * are hard-limits as to the number of processes that can run. 354 */ 355 nprocs++; 356 357 trypid = fork_findpid(flags); 358 359 sx_sunlock(&proctree_lock); 360 361 p2->p_state = PRS_NEW; /* protect against others */ 362 p2->p_pid = trypid; 363 AUDIT_ARG_PID(p2->p_pid); 364 LIST_INSERT_HEAD(&allproc, p2, p_list); 365 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 366 tidhash_add(td2); 367 PROC_LOCK(p2); 368 PROC_LOCK(p1); 369 370 sx_xunlock(&allproc_lock); 371 372 bcopy(&p1->p_startcopy, &p2->p_startcopy, 373 __rangeof(struct proc, p_startcopy, p_endcopy)); 374 pargs_hold(p2->p_args); 375 PROC_UNLOCK(p1); 376 377 bzero(&p2->p_startzero, 378 __rangeof(struct proc, p_startzero, p_endzero)); 379 380 p2->p_ucred = crhold(td->td_ucred); 381 382 /* Tell the prison that we exist. */ 383 prison_proc_hold(p2->p_ucred->cr_prison); 384 385 PROC_UNLOCK(p2); 386 387 /* 388 * Malloc things while we don't hold any locks. 389 */ 390 if (flags & RFSIGSHARE) 391 newsigacts = NULL; 392 else 393 newsigacts = sigacts_alloc(); 394 395 /* 396 * Copy filedesc. 397 */ 398 if (flags & RFCFDG) { 399 fd = fdinit(p1->p_fd); 400 fdtol = NULL; 401 } else if (flags & RFFDG) { 402 fd = fdcopy(p1->p_fd); 403 fdtol = NULL; 404 } else { 405 fd = fdshare(p1->p_fd); 406 if (p1->p_fdtol == NULL) 407 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 408 p1->p_leader); 409 if ((flags & RFTHREAD) != 0) { 410 /* 411 * Shared file descriptor table, and shared 412 * process leaders. 413 */ 414 fdtol = p1->p_fdtol; 415 FILEDESC_XLOCK(p1->p_fd); 416 fdtol->fdl_refcount++; 417 FILEDESC_XUNLOCK(p1->p_fd); 418 } else { 419 /* 420 * Shared file descriptor table, and different 421 * process leaders. 422 */ 423 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 424 p1->p_fd, p2); 425 } 426 } 427 /* 428 * Make a proc table entry for the new process. 429 * Start by zeroing the section of proc that is zero-initialized, 430 * then copy the section that is copied directly from the parent. 431 */ 432 433 PROC_LOCK(p2); 434 PROC_LOCK(p1); 435 436 bzero(&td2->td_startzero, 437 __rangeof(struct thread, td_startzero, td_endzero)); 438 439 bcopy(&td->td_startcopy, &td2->td_startcopy, 440 __rangeof(struct thread, td_startcopy, td_endcopy)); 441 442 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 443 td2->td_sigstk = td->td_sigstk; 444 td2->td_sigmask = td->td_sigmask; 445 td2->td_flags = TDF_INMEM; 446 td2->td_lend_user_pri = PRI_MAX; 447 448 #ifdef VIMAGE 449 td2->td_vnet = NULL; 450 td2->td_vnet_lpush = NULL; 451 #endif 452 453 /* 454 * Allow the scheduler to initialize the child. 455 */ 456 thread_lock(td); 457 sched_fork(td, td2); 458 thread_unlock(td); 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 */ 626 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 627 628 /* 629 * Set the child start time and mark the process as being complete. 630 */ 631 microuptime(&p2->p_stats->p_start); 632 PROC_SLOCK(p2); 633 p2->p_state = PRS_NORMAL; 634 PROC_SUNLOCK(p2); 635 #ifdef KDTRACE_HOOKS 636 /* 637 * Tell the DTrace fasttrap provider about the new process 638 * if it has registered an interest. We have to do this only after 639 * p_state is PRS_NORMAL since the fasttrap module will use pfind() 640 * later on. 641 */ 642 if (dtrace_fasttrap_fork) { 643 PROC_LOCK(p1); 644 PROC_LOCK(p2); 645 dtrace_fasttrap_fork(p1, p2); 646 PROC_UNLOCK(p2); 647 PROC_UNLOCK(p1); 648 } 649 #endif 650 651 /* 652 * If RFSTOPPED not requested, make child runnable and add to 653 * run queue. 654 */ 655 if ((flags & RFSTOPPED) == 0) { 656 thread_lock(td2); 657 TD_SET_CAN_RUN(td2); 658 sched_add(td2, SRQ_BORING); 659 thread_unlock(td2); 660 } 661 662 /* 663 * Now can be swapped. 664 */ 665 PROC_LOCK(p1); 666 _PRELE(p1); 667 PROC_UNLOCK(p1); 668 669 /* 670 * Tell any interested parties about the new process. 671 */ 672 knote_fork(&p1->p_klist, p2->p_pid); 673 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 674 675 /* 676 * Preserve synchronization semantics of vfork. If waiting for 677 * child to exec or exit, set P_PPWAIT on child, and sleep on our 678 * proc (in case of exit). 679 */ 680 PROC_LOCK(p2); 681 while (p2->p_flag & P_PPWAIT) 682 cv_wait(&p2->p_pwait, &p2->p_mtx); 683 PROC_UNLOCK(p2); 684 } 685 686 int 687 fork1(struct thread *td, int flags, int pages, struct proc **procp) 688 { 689 struct proc *p1; 690 struct proc *newproc; 691 int ok; 692 struct thread *td2; 693 struct vmspace *vm2; 694 vm_ooffset_t mem_charged; 695 int error; 696 static int curfail; 697 static struct timeval lastfail; 698 699 /* Can't copy and clear. */ 700 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 701 return (EINVAL); 702 703 p1 = td->td_proc; 704 705 /* 706 * Here we don't create a new process, but we divorce 707 * certain parts of a process from itself. 708 */ 709 if ((flags & RFPROC) == 0) { 710 *procp = NULL; 711 return (fork_norfproc(td, flags)); 712 } 713 714 mem_charged = 0; 715 vm2 = NULL; 716 if (pages == 0) 717 pages = KSTACK_PAGES; 718 /* Allocate new proc. */ 719 newproc = uma_zalloc(proc_zone, M_WAITOK); 720 td2 = FIRST_THREAD_IN_PROC(newproc); 721 if (td2 == NULL) { 722 td2 = thread_alloc(pages); 723 if (td2 == NULL) { 724 error = ENOMEM; 725 goto fail1; 726 } 727 proc_linkup(newproc, td2); 728 } else { 729 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 730 if (td2->td_kstack != 0) 731 vm_thread_dispose(td2); 732 if (!thread_alloc_stack(td2, pages)) { 733 error = ENOMEM; 734 goto fail1; 735 } 736 } 737 } 738 739 if ((flags & RFMEM) == 0) { 740 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 741 if (vm2 == NULL) { 742 error = ENOMEM; 743 goto fail1; 744 } 745 if (!swap_reserve(mem_charged)) { 746 /* 747 * The swap reservation failed. The accounting 748 * from the entries of the copied vm2 will be 749 * substracted in vmspace_free(), so force the 750 * reservation there. 751 */ 752 swap_reserve_force(mem_charged); 753 error = ENOMEM; 754 goto fail1; 755 } 756 } else 757 vm2 = NULL; 758 #ifdef MAC 759 mac_proc_init(newproc); 760 #endif 761 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 762 STAILQ_INIT(&newproc->p_ktr); 763 764 /* We have to lock the process tree while we look for a pid. */ 765 sx_slock(&proctree_lock); 766 767 /* 768 * Although process entries are dynamically created, we still keep 769 * a global limit on the maximum number we will create. Don't allow 770 * a nonprivileged user to use the last ten processes; don't let root 771 * exceed the limit. The variable nprocs is the current number of 772 * processes, maxproc is the limit. 773 */ 774 sx_xlock(&allproc_lock); 775 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 776 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 777 error = EAGAIN; 778 goto fail; 779 } 780 781 /* 782 * Increment the count of procs running with this uid. Don't allow 783 * a nonprivileged user to exceed their current limit. 784 * 785 * XXXRW: Can we avoid privilege here if it's not needed? 786 */ 787 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 788 if (error == 0) 789 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 790 else { 791 PROC_LOCK(p1); 792 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 793 lim_cur(p1, RLIMIT_NPROC)); 794 PROC_UNLOCK(p1); 795 } 796 if (ok) { 797 do_fork(td, flags, newproc, td2, vm2); 798 799 /* 800 * Return child proc pointer to parent. 801 */ 802 *procp = newproc; 803 return (0); 804 } 805 806 error = EAGAIN; 807 fail: 808 sx_sunlock(&proctree_lock); 809 if (ppsratecheck(&lastfail, &curfail, 1)) 810 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 811 td->td_ucred->cr_ruid); 812 sx_xunlock(&allproc_lock); 813 #ifdef MAC 814 mac_proc_destroy(newproc); 815 #endif 816 fail1: 817 if (vm2 != NULL) 818 vmspace_free(vm2); 819 uma_zfree(proc_zone, newproc); 820 pause("fork", hz / 2); 821 return (error); 822 } 823 824 /* 825 * Handle the return of a child process from fork1(). This function 826 * is called from the MD fork_trampoline() entry point. 827 */ 828 void 829 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 830 struct trapframe *frame) 831 { 832 struct proc *p; 833 struct thread *td; 834 struct thread *dtd; 835 836 td = curthread; 837 p = td->td_proc; 838 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 839 840 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 841 td, td->td_sched, p->p_pid, td->td_name); 842 843 sched_fork_exit(td); 844 /* 845 * Processes normally resume in mi_switch() after being 846 * cpu_switch()'ed to, but when children start up they arrive here 847 * instead, so we must do much the same things as mi_switch() would. 848 */ 849 if ((dtd = PCPU_GET(deadthread))) { 850 PCPU_SET(deadthread, NULL); 851 thread_stash(dtd); 852 } 853 thread_unlock(td); 854 855 /* 856 * cpu_set_fork_handler intercepts this function call to 857 * have this call a non-return function to stay in kernel mode. 858 * initproc has its own fork handler, but it does return. 859 */ 860 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 861 callout(arg, frame); 862 863 /* 864 * Check if a kernel thread misbehaved and returned from its main 865 * function. 866 */ 867 if (p->p_flag & P_KTHREAD) { 868 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 869 td->td_name, p->p_pid); 870 kproc_exit(0); 871 } 872 mtx_assert(&Giant, MA_NOTOWNED); 873 874 EVENTHANDLER_INVOKE(schedtail, p); 875 } 876 877 /* 878 * Simplified back end of syscall(), used when returning from fork() 879 * directly into user mode. Giant is not held on entry, and must not 880 * be held on return. This function is passed in to fork_exit() as the 881 * first parameter and is called when returning to a new userland process. 882 */ 883 void 884 fork_return(struct thread *td, struct trapframe *frame) 885 { 886 887 userret(td, frame); 888 #ifdef KTRACE 889 if (KTRPOINT(td, KTR_SYSRET)) 890 ktrsysret(SYS_fork, 0, 0); 891 #endif 892 mtx_assert(&Giant, MA_NOTOWNED); 893 } 894