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/sysent.h> 71 #include <sys/signalvar.h> 72 73 #include <security/audit/audit.h> 74 #include <security/mac/mac_framework.h> 75 76 #include <vm/vm.h> 77 #include <vm/pmap.h> 78 #include <vm/vm_map.h> 79 #include <vm/vm_extern.h> 80 #include <vm/uma.h> 81 82 #ifdef KDTRACE_HOOKS 83 #include <sys/dtrace_bsd.h> 84 dtrace_fork_func_t dtrace_fasttrap_fork; 85 #endif 86 87 SDT_PROVIDER_DECLARE(proc); 88 SDT_PROBE_DEFINE(proc, kernel, , create, create); 89 SDT_PROBE_ARGTYPE(proc, kernel, , create, 0, "struct proc *"); 90 SDT_PROBE_ARGTYPE(proc, kernel, , create, 1, "struct proc *"); 91 SDT_PROBE_ARGTYPE(proc, kernel, , create, 2, "int"); 92 93 #ifndef _SYS_SYSPROTO_H_ 94 struct fork_args { 95 int dummy; 96 }; 97 #endif 98 99 /* ARGSUSED */ 100 int 101 fork(struct thread *td, struct fork_args *uap) 102 { 103 int error; 104 struct proc *p2; 105 106 error = fork1(td, RFFDG | RFPROC, 0, &p2); 107 if (error == 0) { 108 td->td_retval[0] = p2->p_pid; 109 td->td_retval[1] = 0; 110 } 111 return (error); 112 } 113 114 /* ARGSUSED */ 115 int 116 vfork(struct thread *td, struct vfork_args *uap) 117 { 118 int error, flags; 119 struct proc *p2; 120 121 #ifdef XEN 122 flags = RFFDG | RFPROC; /* validate that this is still an issue */ 123 #else 124 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 125 #endif 126 error = fork1(td, flags, 0, &p2); 127 if (error == 0) { 128 td->td_retval[0] = p2->p_pid; 129 td->td_retval[1] = 0; 130 } 131 return (error); 132 } 133 134 int 135 rfork(struct thread *td, struct rfork_args *uap) 136 { 137 struct proc *p2; 138 int error; 139 140 /* Don't allow kernel-only flags. */ 141 if ((uap->flags & RFKERNELONLY) != 0) 142 return (EINVAL); 143 144 AUDIT_ARG_FFLAGS(uap->flags); 145 error = fork1(td, uap->flags, 0, &p2); 146 if (error == 0) { 147 td->td_retval[0] = p2 ? p2->p_pid : 0; 148 td->td_retval[1] = 0; 149 } 150 return (error); 151 } 152 153 int nprocs = 1; /* process 0 */ 154 int lastpid = 0; 155 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 156 "Last used PID"); 157 158 /* 159 * Random component to lastpid generation. We mix in a random factor to make 160 * it a little harder to predict. We sanity check the modulus value to avoid 161 * doing it in critical paths. Don't let it be too small or we pointlessly 162 * waste randomness entropy, and don't let it be impossibly large. Using a 163 * modulus that is too big causes a LOT more process table scans and slows 164 * down fork processing as the pidchecked caching is defeated. 165 */ 166 static int randompid = 0; 167 168 static int 169 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 170 { 171 int error, pid; 172 173 error = sysctl_wire_old_buffer(req, sizeof(int)); 174 if (error != 0) 175 return(error); 176 sx_xlock(&allproc_lock); 177 pid = randompid; 178 error = sysctl_handle_int(oidp, &pid, 0, req); 179 if (error == 0 && req->newptr != NULL) { 180 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 181 pid = PID_MAX - 100; 182 else if (pid < 2) /* NOP */ 183 pid = 0; 184 else if (pid < 100) /* Make it reasonable */ 185 pid = 100; 186 randompid = pid; 187 } 188 sx_xunlock(&allproc_lock); 189 return (error); 190 } 191 192 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 193 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 194 195 static int 196 fork_findpid(int flags) 197 { 198 struct proc *p; 199 int trypid; 200 static int pidchecked = 0; 201 202 /* 203 * Requires allproc_lock in order to iterate over the list 204 * of processes, and proctree_lock to access p_pgrp. 205 */ 206 sx_assert(&allproc_lock, SX_LOCKED); 207 sx_assert(&proctree_lock, SX_LOCKED); 208 209 /* 210 * Find an unused process ID. We remember a range of unused IDs 211 * ready to use (from lastpid+1 through pidchecked-1). 212 * 213 * If RFHIGHPID is set (used during system boot), do not allocate 214 * low-numbered pids. 215 */ 216 trypid = lastpid + 1; 217 if (flags & RFHIGHPID) { 218 if (trypid < 10) 219 trypid = 10; 220 } else { 221 if (randompid) 222 trypid += arc4random() % randompid; 223 } 224 retry: 225 /* 226 * If the process ID prototype has wrapped around, 227 * restart somewhat above 0, as the low-numbered procs 228 * tend to include daemons that don't exit. 229 */ 230 if (trypid >= PID_MAX) { 231 trypid = trypid % PID_MAX; 232 if (trypid < 100) 233 trypid += 100; 234 pidchecked = 0; 235 } 236 if (trypid >= pidchecked) { 237 int doingzomb = 0; 238 239 pidchecked = PID_MAX; 240 /* 241 * Scan the active and zombie procs to check whether this pid 242 * is in use. Remember the lowest pid that's greater 243 * than trypid, so we can avoid checking for a while. 244 */ 245 p = LIST_FIRST(&allproc); 246 again: 247 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 248 while (p->p_pid == trypid || 249 (p->p_pgrp != NULL && 250 (p->p_pgrp->pg_id == trypid || 251 (p->p_session != NULL && 252 p->p_session->s_sid == trypid)))) { 253 trypid++; 254 if (trypid >= pidchecked) 255 goto retry; 256 } 257 if (p->p_pid > trypid && pidchecked > p->p_pid) 258 pidchecked = p->p_pid; 259 if (p->p_pgrp != NULL) { 260 if (p->p_pgrp->pg_id > trypid && 261 pidchecked > p->p_pgrp->pg_id) 262 pidchecked = p->p_pgrp->pg_id; 263 if (p->p_session != NULL && 264 p->p_session->s_sid > trypid && 265 pidchecked > p->p_session->s_sid) 266 pidchecked = p->p_session->s_sid; 267 } 268 } 269 if (!doingzomb) { 270 doingzomb = 1; 271 p = LIST_FIRST(&zombproc); 272 goto again; 273 } 274 } 275 276 /* 277 * RFHIGHPID does not mess with the lastpid counter during boot. 278 */ 279 if (flags & RFHIGHPID) 280 pidchecked = 0; 281 else 282 lastpid = trypid; 283 284 return (trypid); 285 } 286 287 static int 288 fork_norfproc(struct thread *td, int flags) 289 { 290 int error; 291 struct proc *p1; 292 293 KASSERT((flags & RFPROC) == 0, 294 ("fork_norfproc called with RFPROC set")); 295 p1 = td->td_proc; 296 297 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 298 (flags & (RFCFDG | RFFDG))) { 299 PROC_LOCK(p1); 300 if (thread_single(SINGLE_BOUNDARY)) { 301 PROC_UNLOCK(p1); 302 return (ERESTART); 303 } 304 PROC_UNLOCK(p1); 305 } 306 307 error = vm_forkproc(td, NULL, NULL, NULL, flags); 308 if (error) 309 goto fail; 310 311 /* 312 * Close all file descriptors. 313 */ 314 if (flags & RFCFDG) { 315 struct filedesc *fdtmp; 316 fdtmp = fdinit(td->td_proc->p_fd); 317 fdfree(td); 318 p1->p_fd = fdtmp; 319 } 320 321 /* 322 * Unshare file descriptors (from parent). 323 */ 324 if (flags & RFFDG) 325 fdunshare(p1, td); 326 327 fail: 328 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 329 (flags & (RFCFDG | RFFDG))) { 330 PROC_LOCK(p1); 331 thread_single_end(); 332 PROC_UNLOCK(p1); 333 } 334 return (error); 335 } 336 337 static void 338 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, 339 struct vmspace *vm2) 340 { 341 struct proc *p1, *pptr; 342 int p2_held, trypid; 343 struct filedesc *fd; 344 struct filedesc_to_leader *fdtol; 345 struct sigacts *newsigacts; 346 347 sx_assert(&proctree_lock, SX_SLOCKED); 348 sx_assert(&allproc_lock, SX_XLOCKED); 349 350 p2_held = 0; 351 p1 = td->td_proc; 352 353 /* 354 * Increment the nprocs resource before blocking can occur. There 355 * are hard-limits as to the number of processes that can run. 356 */ 357 nprocs++; 358 359 trypid = fork_findpid(flags); 360 361 sx_sunlock(&proctree_lock); 362 363 p2->p_state = PRS_NEW; /* protect against others */ 364 p2->p_pid = trypid; 365 AUDIT_ARG_PID(p2->p_pid); 366 LIST_INSERT_HEAD(&allproc, p2, p_list); 367 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 368 tidhash_add(td2); 369 PROC_LOCK(p2); 370 PROC_LOCK(p1); 371 372 sx_xunlock(&allproc_lock); 373 374 bcopy(&p1->p_startcopy, &p2->p_startcopy, 375 __rangeof(struct proc, p_startcopy, p_endcopy)); 376 pargs_hold(p2->p_args); 377 PROC_UNLOCK(p1); 378 379 bzero(&p2->p_startzero, 380 __rangeof(struct proc, p_startzero, p_endzero)); 381 382 p2->p_ucred = crhold(td->td_ucred); 383 384 /* Tell the prison that we exist. */ 385 prison_proc_hold(p2->p_ucred->cr_prison); 386 387 PROC_UNLOCK(p2); 388 389 /* 390 * Malloc things while we don't hold any locks. 391 */ 392 if (flags & RFSIGSHARE) 393 newsigacts = NULL; 394 else 395 newsigacts = sigacts_alloc(); 396 397 /* 398 * Copy filedesc. 399 */ 400 if (flags & RFCFDG) { 401 fd = fdinit(p1->p_fd); 402 fdtol = NULL; 403 } else if (flags & RFFDG) { 404 fd = fdcopy(p1->p_fd); 405 fdtol = NULL; 406 } else { 407 fd = fdshare(p1->p_fd); 408 if (p1->p_fdtol == NULL) 409 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 410 p1->p_leader); 411 if ((flags & RFTHREAD) != 0) { 412 /* 413 * Shared file descriptor table, and shared 414 * process leaders. 415 */ 416 fdtol = p1->p_fdtol; 417 FILEDESC_XLOCK(p1->p_fd); 418 fdtol->fdl_refcount++; 419 FILEDESC_XUNLOCK(p1->p_fd); 420 } else { 421 /* 422 * Shared file descriptor table, and different 423 * process leaders. 424 */ 425 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 426 p1->p_fd, p2); 427 } 428 } 429 /* 430 * Make a proc table entry for the new process. 431 * Start by zeroing the section of proc that is zero-initialized, 432 * then copy the section that is copied directly from the parent. 433 */ 434 435 PROC_LOCK(p2); 436 PROC_LOCK(p1); 437 438 bzero(&td2->td_startzero, 439 __rangeof(struct thread, td_startzero, td_endzero)); 440 441 bcopy(&td->td_startcopy, &td2->td_startcopy, 442 __rangeof(struct thread, td_startcopy, td_endcopy)); 443 444 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 445 td2->td_sigstk = td->td_sigstk; 446 td2->td_sigmask = td->td_sigmask; 447 td2->td_flags = TDF_INMEM; 448 td2->td_lend_user_pri = PRI_MAX; 449 450 #ifdef VIMAGE 451 td2->td_vnet = NULL; 452 td2->td_vnet_lpush = NULL; 453 #endif 454 455 /* 456 * Allow the scheduler to initialize the child. 457 */ 458 thread_lock(td); 459 sched_fork(td, td2); 460 thread_unlock(td); 461 462 /* 463 * Duplicate sub-structures as needed. 464 * Increase reference counts on shared objects. 465 */ 466 p2->p_flag = P_INMEM; 467 p2->p_swtick = ticks; 468 if (p1->p_flag & P_PROFIL) 469 startprofclock(p2); 470 td2->td_ucred = crhold(p2->p_ucred); 471 472 if (flags & RFSIGSHARE) { 473 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 474 } else { 475 sigacts_copy(newsigacts, p1->p_sigacts); 476 p2->p_sigacts = newsigacts; 477 } 478 if (flags & RFLINUXTHPN) 479 p2->p_sigparent = SIGUSR1; 480 else 481 p2->p_sigparent = SIGCHLD; 482 483 p2->p_textvp = p1->p_textvp; 484 p2->p_fd = fd; 485 p2->p_fdtol = fdtol; 486 487 /* 488 * p_limit is copy-on-write. Bump its refcount. 489 */ 490 lim_fork(p1, p2); 491 492 pstats_fork(p1->p_stats, p2->p_stats); 493 494 PROC_UNLOCK(p1); 495 PROC_UNLOCK(p2); 496 497 /* Bump references to the text vnode (for procfs). */ 498 if (p2->p_textvp) 499 vref(p2->p_textvp); 500 501 /* 502 * Set up linkage for kernel based threading. 503 */ 504 if ((flags & RFTHREAD) != 0) { 505 mtx_lock(&ppeers_lock); 506 p2->p_peers = p1->p_peers; 507 p1->p_peers = p2; 508 p2->p_leader = p1->p_leader; 509 mtx_unlock(&ppeers_lock); 510 PROC_LOCK(p1->p_leader); 511 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 512 PROC_UNLOCK(p1->p_leader); 513 /* 514 * The task leader is exiting, so process p1 is 515 * going to be killed shortly. Since p1 obviously 516 * isn't dead yet, we know that the leader is either 517 * sending SIGKILL's to all the processes in this 518 * task or is sleeping waiting for all the peers to 519 * exit. We let p1 complete the fork, but we need 520 * to go ahead and kill the new process p2 since 521 * the task leader may not get a chance to send 522 * SIGKILL to it. We leave it on the list so that 523 * the task leader will wait for this new process 524 * to commit suicide. 525 */ 526 PROC_LOCK(p2); 527 psignal(p2, SIGKILL); 528 PROC_UNLOCK(p2); 529 } else 530 PROC_UNLOCK(p1->p_leader); 531 } else { 532 p2->p_peers = NULL; 533 p2->p_leader = p2; 534 } 535 536 sx_xlock(&proctree_lock); 537 PGRP_LOCK(p1->p_pgrp); 538 PROC_LOCK(p2); 539 PROC_LOCK(p1); 540 541 /* 542 * Preserve some more flags in subprocess. P_PROFIL has already 543 * been preserved. 544 */ 545 p2->p_flag |= p1->p_flag & P_SUGID; 546 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 547 SESS_LOCK(p1->p_session); 548 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 549 p2->p_flag |= P_CONTROLT; 550 SESS_UNLOCK(p1->p_session); 551 if (flags & RFPPWAIT) 552 p2->p_flag |= P_PPWAIT; 553 554 p2->p_pgrp = p1->p_pgrp; 555 LIST_INSERT_AFTER(p1, p2, p_pglist); 556 PGRP_UNLOCK(p1->p_pgrp); 557 LIST_INIT(&p2->p_children); 558 559 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 560 561 /* 562 * If PF_FORK is set, the child process inherits the 563 * procfs ioctl flags from its parent. 564 */ 565 if (p1->p_pfsflags & PF_FORK) { 566 p2->p_stops = p1->p_stops; 567 p2->p_pfsflags = p1->p_pfsflags; 568 } 569 570 /* 571 * This begins the section where we must prevent the parent 572 * from being swapped. 573 */ 574 _PHOLD(p1); 575 PROC_UNLOCK(p1); 576 577 /* 578 * Attach the new process to its parent. 579 * 580 * If RFNOWAIT is set, the newly created process becomes a child 581 * of init. This effectively disassociates the child from the 582 * parent. 583 */ 584 if (flags & RFNOWAIT) 585 pptr = initproc; 586 else 587 pptr = p1; 588 p2->p_pptr = pptr; 589 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 590 sx_xunlock(&proctree_lock); 591 592 /* Inform accounting that we have forked. */ 593 p2->p_acflag = AFORK; 594 PROC_UNLOCK(p2); 595 596 #ifdef KTRACE 597 ktrprocfork(p1, p2); 598 #endif 599 600 /* 601 * Finish creating the child process. It will return via a different 602 * execution path later. (ie: directly into user mode) 603 */ 604 vm_forkproc(td, p2, td2, vm2, flags); 605 606 if (flags == (RFFDG | RFPROC)) { 607 PCPU_INC(cnt.v_forks); 608 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 609 p2->p_vmspace->vm_ssize); 610 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 611 PCPU_INC(cnt.v_vforks); 612 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 613 p2->p_vmspace->vm_ssize); 614 } else if (p1 == &proc0) { 615 PCPU_INC(cnt.v_kthreads); 616 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 617 p2->p_vmspace->vm_ssize); 618 } else { 619 PCPU_INC(cnt.v_rforks); 620 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 621 p2->p_vmspace->vm_ssize); 622 } 623 624 /* 625 * Both processes are set up, now check if any loadable modules want 626 * to adjust anything. 627 */ 628 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 629 630 /* 631 * Set the child start time and mark the process as being complete. 632 */ 633 microuptime(&p2->p_stats->p_start); 634 PROC_SLOCK(p2); 635 p2->p_state = PRS_NORMAL; 636 PROC_SUNLOCK(p2); 637 638 PROC_LOCK(p1); 639 #ifdef KDTRACE_HOOKS 640 /* 641 * Tell the DTrace fasttrap provider about the new process 642 * if it has registered an interest. We have to do this only after 643 * p_state is PRS_NORMAL since the fasttrap module will use pfind() 644 * later on. 645 */ 646 if (dtrace_fasttrap_fork) { 647 PROC_LOCK(p2); 648 dtrace_fasttrap_fork(p1, p2); 649 PROC_UNLOCK(p2); 650 } 651 #endif 652 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 653 P_FOLLOWFORK)) { 654 /* 655 * Arrange for debugger to receive the fork event. 656 * 657 * We can report PL_FLAG_FORKED regardless of 658 * P_FOLLOWFORK settings, but it does not make a sense 659 * for runaway child. 660 */ 661 td->td_dbgflags |= TDB_FORK; 662 td->td_dbg_forked = p2->p_pid; 663 PROC_LOCK(p2); 664 td2->td_dbgflags |= TDB_STOPATFORK; 665 _PHOLD(p2); 666 p2_held = 1; 667 PROC_UNLOCK(p2); 668 } 669 if ((flags & RFSTOPPED) == 0) { 670 /* 671 * If RFSTOPPED not requested, make child runnable and 672 * add to run queue. 673 */ 674 thread_lock(td2); 675 TD_SET_CAN_RUN(td2); 676 sched_add(td2, SRQ_BORING); 677 thread_unlock(td2); 678 } 679 680 /* 681 * Now can be swapped. 682 */ 683 _PRELE(p1); 684 PROC_UNLOCK(p1); 685 686 /* 687 * Tell any interested parties about the new process. 688 */ 689 knote_fork(&p1->p_klist, p2->p_pid); 690 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 691 692 /* 693 * Wait until debugger is attached to child. 694 */ 695 PROC_LOCK(p2); 696 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 697 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 698 if (p2_held) 699 _PRELE(p2); 700 701 /* 702 * Preserve synchronization semantics of vfork. If waiting for 703 * child to exec or exit, set P_PPWAIT on child, and sleep on our 704 * proc (in case of exit). 705 */ 706 while (p2->p_flag & P_PPWAIT) 707 cv_wait(&p2->p_pwait, &p2->p_mtx); 708 PROC_UNLOCK(p2); 709 } 710 711 int 712 fork1(struct thread *td, int flags, int pages, struct proc **procp) 713 { 714 struct proc *p1; 715 struct proc *newproc; 716 int ok; 717 struct thread *td2; 718 struct vmspace *vm2; 719 vm_ooffset_t mem_charged; 720 int error; 721 static int curfail; 722 static struct timeval lastfail; 723 724 /* Can't copy and clear. */ 725 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 726 return (EINVAL); 727 728 p1 = td->td_proc; 729 730 /* 731 * Here we don't create a new process, but we divorce 732 * certain parts of a process from itself. 733 */ 734 if ((flags & RFPROC) == 0) { 735 *procp = NULL; 736 return (fork_norfproc(td, flags)); 737 } 738 739 mem_charged = 0; 740 vm2 = NULL; 741 if (pages == 0) 742 pages = KSTACK_PAGES; 743 /* Allocate new proc. */ 744 newproc = uma_zalloc(proc_zone, M_WAITOK); 745 td2 = FIRST_THREAD_IN_PROC(newproc); 746 if (td2 == NULL) { 747 td2 = thread_alloc(pages); 748 if (td2 == NULL) { 749 error = ENOMEM; 750 goto fail1; 751 } 752 proc_linkup(newproc, td2); 753 } else { 754 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 755 if (td2->td_kstack != 0) 756 vm_thread_dispose(td2); 757 if (!thread_alloc_stack(td2, pages)) { 758 error = ENOMEM; 759 goto fail1; 760 } 761 } 762 } 763 764 if ((flags & RFMEM) == 0) { 765 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 766 if (vm2 == NULL) { 767 error = ENOMEM; 768 goto fail1; 769 } 770 if (!swap_reserve(mem_charged)) { 771 /* 772 * The swap reservation failed. The accounting 773 * from the entries of the copied vm2 will be 774 * substracted in vmspace_free(), so force the 775 * reservation there. 776 */ 777 swap_reserve_force(mem_charged); 778 error = ENOMEM; 779 goto fail1; 780 } 781 } else 782 vm2 = NULL; 783 #ifdef MAC 784 mac_proc_init(newproc); 785 #endif 786 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 787 STAILQ_INIT(&newproc->p_ktr); 788 789 /* We have to lock the process tree while we look for a pid. */ 790 sx_slock(&proctree_lock); 791 792 /* 793 * Although process entries are dynamically created, we still keep 794 * a global limit on the maximum number we will create. Don't allow 795 * a nonprivileged user to use the last ten processes; don't let root 796 * exceed the limit. The variable nprocs is the current number of 797 * processes, maxproc is the limit. 798 */ 799 sx_xlock(&allproc_lock); 800 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 801 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 802 error = EAGAIN; 803 goto fail; 804 } 805 806 /* 807 * Increment the count of procs running with this uid. Don't allow 808 * a nonprivileged user to exceed their current limit. 809 * 810 * XXXRW: Can we avoid privilege here if it's not needed? 811 */ 812 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 813 if (error == 0) 814 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 815 else { 816 PROC_LOCK(p1); 817 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 818 lim_cur(p1, RLIMIT_NPROC)); 819 PROC_UNLOCK(p1); 820 } 821 if (ok) { 822 do_fork(td, flags, newproc, td2, vm2); 823 824 /* 825 * Return child proc pointer to parent. 826 */ 827 *procp = newproc; 828 return (0); 829 } 830 831 error = EAGAIN; 832 fail: 833 sx_sunlock(&proctree_lock); 834 if (ppsratecheck(&lastfail, &curfail, 1)) 835 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 836 td->td_ucred->cr_ruid); 837 sx_xunlock(&allproc_lock); 838 #ifdef MAC 839 mac_proc_destroy(newproc); 840 #endif 841 fail1: 842 if (vm2 != NULL) 843 vmspace_free(vm2); 844 uma_zfree(proc_zone, newproc); 845 pause("fork", hz / 2); 846 return (error); 847 } 848 849 /* 850 * Handle the return of a child process from fork1(). This function 851 * is called from the MD fork_trampoline() entry point. 852 */ 853 void 854 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 855 struct trapframe *frame) 856 { 857 struct proc *p; 858 struct thread *td; 859 struct thread *dtd; 860 861 td = curthread; 862 p = td->td_proc; 863 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 864 865 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 866 td, td->td_sched, p->p_pid, td->td_name); 867 868 sched_fork_exit(td); 869 /* 870 * Processes normally resume in mi_switch() after being 871 * cpu_switch()'ed to, but when children start up they arrive here 872 * instead, so we must do much the same things as mi_switch() would. 873 */ 874 if ((dtd = PCPU_GET(deadthread))) { 875 PCPU_SET(deadthread, NULL); 876 thread_stash(dtd); 877 } 878 thread_unlock(td); 879 880 /* 881 * cpu_set_fork_handler intercepts this function call to 882 * have this call a non-return function to stay in kernel mode. 883 * initproc has its own fork handler, but it does return. 884 */ 885 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 886 callout(arg, frame); 887 888 /* 889 * Check if a kernel thread misbehaved and returned from its main 890 * function. 891 */ 892 if (p->p_flag & P_KTHREAD) { 893 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 894 td->td_name, p->p_pid); 895 kproc_exit(0); 896 } 897 mtx_assert(&Giant, MA_NOTOWNED); 898 899 if (p->p_sysent->sv_schedtail != NULL) 900 (p->p_sysent->sv_schedtail)(td); 901 } 902 903 /* 904 * Simplified back end of syscall(), used when returning from fork() 905 * directly into user mode. Giant is not held on entry, and must not 906 * be held on return. This function is passed in to fork_exit() as the 907 * first parameter and is called when returning to a new userland process. 908 */ 909 void 910 fork_return(struct thread *td, struct trapframe *frame) 911 { 912 struct proc *p, *dbg; 913 914 if (td->td_dbgflags & TDB_STOPATFORK) { 915 p = td->td_proc; 916 sx_xlock(&proctree_lock); 917 PROC_LOCK(p); 918 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 919 (P_TRACED | P_FOLLOWFORK)) { 920 /* 921 * If debugger still wants auto-attach for the 922 * parent's children, do it now. 923 */ 924 dbg = p->p_pptr->p_pptr; 925 p->p_flag |= P_TRACED; 926 p->p_oppid = p->p_pptr->p_pid; 927 proc_reparent(p, dbg); 928 sx_xunlock(&proctree_lock); 929 ptracestop(td, SIGSTOP); 930 } else { 931 /* 932 * ... otherwise clear the request. 933 */ 934 sx_xunlock(&proctree_lock); 935 td->td_dbgflags &= ~TDB_STOPATFORK; 936 cv_broadcast(&p->p_dbgwait); 937 } 938 PROC_UNLOCK(p); 939 } 940 941 userret(td, frame); 942 943 #ifdef KTRACE 944 if (KTRPOINT(td, KTR_SYSRET)) 945 ktrsysret(SYS_fork, 0, 0); 946 #endif 947 mtx_assert(&Giant, MA_NOTOWNED); 948 } 949