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 p2_held, 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 p2_held = 0; 350 p1 = td->td_proc; 351 352 /* 353 * Increment the nprocs resource before blocking can occur. There 354 * are hard-limits as to the number of processes that can run. 355 */ 356 nprocs++; 357 358 trypid = fork_findpid(flags); 359 360 sx_sunlock(&proctree_lock); 361 362 p2->p_state = PRS_NEW; /* protect against others */ 363 p2->p_pid = trypid; 364 AUDIT_ARG_PID(p2->p_pid); 365 LIST_INSERT_HEAD(&allproc, p2, p_list); 366 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 367 tidhash_add(td2); 368 PROC_LOCK(p2); 369 PROC_LOCK(p1); 370 371 sx_xunlock(&allproc_lock); 372 373 bcopy(&p1->p_startcopy, &p2->p_startcopy, 374 __rangeof(struct proc, p_startcopy, p_endcopy)); 375 pargs_hold(p2->p_args); 376 PROC_UNLOCK(p1); 377 378 bzero(&p2->p_startzero, 379 __rangeof(struct proc, p_startzero, p_endzero)); 380 381 p2->p_ucred = crhold(td->td_ucred); 382 383 /* Tell the prison that we exist. */ 384 prison_proc_hold(p2->p_ucred->cr_prison); 385 386 PROC_UNLOCK(p2); 387 388 /* 389 * Malloc things while we don't hold any locks. 390 */ 391 if (flags & RFSIGSHARE) 392 newsigacts = NULL; 393 else 394 newsigacts = sigacts_alloc(); 395 396 /* 397 * Copy filedesc. 398 */ 399 if (flags & RFCFDG) { 400 fd = fdinit(p1->p_fd); 401 fdtol = NULL; 402 } else if (flags & RFFDG) { 403 fd = fdcopy(p1->p_fd); 404 fdtol = NULL; 405 } else { 406 fd = fdshare(p1->p_fd); 407 if (p1->p_fdtol == NULL) 408 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 409 p1->p_leader); 410 if ((flags & RFTHREAD) != 0) { 411 /* 412 * Shared file descriptor table, and shared 413 * process leaders. 414 */ 415 fdtol = p1->p_fdtol; 416 FILEDESC_XLOCK(p1->p_fd); 417 fdtol->fdl_refcount++; 418 FILEDESC_XUNLOCK(p1->p_fd); 419 } else { 420 /* 421 * Shared file descriptor table, and different 422 * process leaders. 423 */ 424 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 425 p1->p_fd, p2); 426 } 427 } 428 /* 429 * Make a proc table entry for the new process. 430 * Start by zeroing the section of proc that is zero-initialized, 431 * then copy the section that is copied directly from the parent. 432 */ 433 434 PROC_LOCK(p2); 435 PROC_LOCK(p1); 436 437 bzero(&td2->td_startzero, 438 __rangeof(struct thread, td_startzero, td_endzero)); 439 440 bcopy(&td->td_startcopy, &td2->td_startcopy, 441 __rangeof(struct thread, td_startcopy, td_endcopy)); 442 443 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 444 td2->td_sigstk = td->td_sigstk; 445 td2->td_sigmask = td->td_sigmask; 446 td2->td_flags = TDF_INMEM; 447 td2->td_lend_user_pri = PRI_MAX; 448 449 #ifdef VIMAGE 450 td2->td_vnet = NULL; 451 td2->td_vnet_lpush = NULL; 452 #endif 453 454 /* 455 * Allow the scheduler to initialize the child. 456 */ 457 thread_lock(td); 458 sched_fork(td, td2); 459 thread_unlock(td); 460 461 /* 462 * Duplicate sub-structures as needed. 463 * Increase reference counts on shared objects. 464 */ 465 p2->p_flag = P_INMEM; 466 p2->p_swtick = ticks; 467 if (p1->p_flag & P_PROFIL) 468 startprofclock(p2); 469 td2->td_ucred = crhold(p2->p_ucred); 470 471 if (flags & RFSIGSHARE) { 472 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 473 } else { 474 sigacts_copy(newsigacts, p1->p_sigacts); 475 p2->p_sigacts = newsigacts; 476 } 477 if (flags & RFLINUXTHPN) 478 p2->p_sigparent = SIGUSR1; 479 else 480 p2->p_sigparent = SIGCHLD; 481 482 p2->p_textvp = p1->p_textvp; 483 p2->p_fd = fd; 484 p2->p_fdtol = fdtol; 485 486 /* 487 * p_limit is copy-on-write. Bump its refcount. 488 */ 489 lim_fork(p1, p2); 490 491 pstats_fork(p1->p_stats, p2->p_stats); 492 493 PROC_UNLOCK(p1); 494 PROC_UNLOCK(p2); 495 496 /* Bump references to the text vnode (for procfs). */ 497 if (p2->p_textvp) 498 vref(p2->p_textvp); 499 500 /* 501 * Set up linkage for kernel based threading. 502 */ 503 if ((flags & RFTHREAD) != 0) { 504 mtx_lock(&ppeers_lock); 505 p2->p_peers = p1->p_peers; 506 p1->p_peers = p2; 507 p2->p_leader = p1->p_leader; 508 mtx_unlock(&ppeers_lock); 509 PROC_LOCK(p1->p_leader); 510 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 511 PROC_UNLOCK(p1->p_leader); 512 /* 513 * The task leader is exiting, so process p1 is 514 * going to be killed shortly. Since p1 obviously 515 * isn't dead yet, we know that the leader is either 516 * sending SIGKILL's to all the processes in this 517 * task or is sleeping waiting for all the peers to 518 * exit. We let p1 complete the fork, but we need 519 * to go ahead and kill the new process p2 since 520 * the task leader may not get a chance to send 521 * SIGKILL to it. We leave it on the list so that 522 * the task leader will wait for this new process 523 * to commit suicide. 524 */ 525 PROC_LOCK(p2); 526 psignal(p2, SIGKILL); 527 PROC_UNLOCK(p2); 528 } else 529 PROC_UNLOCK(p1->p_leader); 530 } else { 531 p2->p_peers = NULL; 532 p2->p_leader = p2; 533 } 534 535 sx_xlock(&proctree_lock); 536 PGRP_LOCK(p1->p_pgrp); 537 PROC_LOCK(p2); 538 PROC_LOCK(p1); 539 540 /* 541 * Preserve some more flags in subprocess. P_PROFIL has already 542 * been preserved. 543 */ 544 p2->p_flag |= p1->p_flag & P_SUGID; 545 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 546 SESS_LOCK(p1->p_session); 547 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 548 p2->p_flag |= P_CONTROLT; 549 SESS_UNLOCK(p1->p_session); 550 if (flags & RFPPWAIT) 551 p2->p_flag |= P_PPWAIT; 552 553 p2->p_pgrp = p1->p_pgrp; 554 LIST_INSERT_AFTER(p1, p2, p_pglist); 555 PGRP_UNLOCK(p1->p_pgrp); 556 LIST_INIT(&p2->p_children); 557 558 callout_init(&p2->p_itcallout, CALLOUT_MPSAFE); 559 560 /* 561 * If PF_FORK is set, the child process inherits the 562 * procfs ioctl flags from its parent. 563 */ 564 if (p1->p_pfsflags & PF_FORK) { 565 p2->p_stops = p1->p_stops; 566 p2->p_pfsflags = p1->p_pfsflags; 567 } 568 569 /* 570 * This begins the section where we must prevent the parent 571 * from being swapped. 572 */ 573 _PHOLD(p1); 574 PROC_UNLOCK(p1); 575 576 /* 577 * Attach the new process to its parent. 578 * 579 * If RFNOWAIT is set, the newly created process becomes a child 580 * of init. This effectively disassociates the child from the 581 * parent. 582 */ 583 if (flags & RFNOWAIT) 584 pptr = initproc; 585 else 586 pptr = p1; 587 p2->p_pptr = pptr; 588 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 589 sx_xunlock(&proctree_lock); 590 591 /* Inform accounting that we have forked. */ 592 p2->p_acflag = AFORK; 593 PROC_UNLOCK(p2); 594 595 #ifdef KTRACE 596 ktrprocfork(p1, p2); 597 #endif 598 599 /* 600 * Finish creating the child process. It will return via a different 601 * execution path later. (ie: directly into user mode) 602 */ 603 vm_forkproc(td, p2, td2, vm2, flags); 604 605 if (flags == (RFFDG | RFPROC)) { 606 PCPU_INC(cnt.v_forks); 607 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 608 p2->p_vmspace->vm_ssize); 609 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 610 PCPU_INC(cnt.v_vforks); 611 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 612 p2->p_vmspace->vm_ssize); 613 } else if (p1 == &proc0) { 614 PCPU_INC(cnt.v_kthreads); 615 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 616 p2->p_vmspace->vm_ssize); 617 } else { 618 PCPU_INC(cnt.v_rforks); 619 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 620 p2->p_vmspace->vm_ssize); 621 } 622 623 /* 624 * Both processes are set up, now check if any loadable modules want 625 * to adjust anything. 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); 636 637 PROC_LOCK(p1); 638 #ifdef KDTRACE_HOOKS 639 /* 640 * Tell the DTrace fasttrap provider about the new process 641 * if it has registered an interest. We have to do this only after 642 * p_state is PRS_NORMAL since the fasttrap module will use pfind() 643 * later on. 644 */ 645 if (dtrace_fasttrap_fork) { 646 PROC_LOCK(p2); 647 dtrace_fasttrap_fork(p1, p2); 648 PROC_UNLOCK(p2); 649 } 650 #endif 651 if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED | 652 P_FOLLOWFORK)) { 653 /* 654 * Arrange for debugger to receive the fork event. 655 * 656 * We can report PL_FLAG_FORKED regardless of 657 * P_FOLLOWFORK settings, but it does not make a sense 658 * for runaway child. 659 */ 660 td->td_dbgflags |= TDB_FORK; 661 td->td_dbg_forked = p2->p_pid; 662 PROC_LOCK(p2); 663 td2->td_dbgflags |= TDB_STOPATFORK; 664 _PHOLD(p2); 665 p2_held = 1; 666 PROC_UNLOCK(p2); 667 } 668 if ((flags & RFSTOPPED) == 0) { 669 /* 670 * If RFSTOPPED not requested, make child runnable and 671 * add to run queue. 672 */ 673 thread_lock(td2); 674 TD_SET_CAN_RUN(td2); 675 sched_add(td2, SRQ_BORING); 676 thread_unlock(td2); 677 } 678 679 /* 680 * Now can be swapped. 681 */ 682 _PRELE(p1); 683 PROC_UNLOCK(p1); 684 685 /* 686 * Tell any interested parties about the new process. 687 */ 688 knote_fork(&p1->p_klist, p2->p_pid); 689 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 690 691 /* 692 * Wait until debugger is attached to child. 693 */ 694 PROC_LOCK(p2); 695 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 696 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 697 if (p2_held) 698 _PRELE(p2); 699 700 /* 701 * Preserve synchronization semantics of vfork. If waiting for 702 * child to exec or exit, set P_PPWAIT on child, and sleep on our 703 * proc (in case of exit). 704 */ 705 while (p2->p_flag & P_PPWAIT) 706 cv_wait(&p2->p_pwait, &p2->p_mtx); 707 PROC_UNLOCK(p2); 708 } 709 710 int 711 fork1(struct thread *td, int flags, int pages, struct proc **procp) 712 { 713 struct proc *p1; 714 struct proc *newproc; 715 int ok; 716 struct thread *td2; 717 struct vmspace *vm2; 718 vm_ooffset_t mem_charged; 719 int error; 720 static int curfail; 721 static struct timeval lastfail; 722 723 /* Can't copy and clear. */ 724 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 725 return (EINVAL); 726 727 p1 = td->td_proc; 728 729 /* 730 * Here we don't create a new process, but we divorce 731 * certain parts of a process from itself. 732 */ 733 if ((flags & RFPROC) == 0) { 734 *procp = NULL; 735 return (fork_norfproc(td, flags)); 736 } 737 738 mem_charged = 0; 739 vm2 = NULL; 740 if (pages == 0) 741 pages = KSTACK_PAGES; 742 /* Allocate new proc. */ 743 newproc = uma_zalloc(proc_zone, M_WAITOK); 744 td2 = FIRST_THREAD_IN_PROC(newproc); 745 if (td2 == NULL) { 746 td2 = thread_alloc(pages); 747 if (td2 == NULL) { 748 error = ENOMEM; 749 goto fail1; 750 } 751 proc_linkup(newproc, td2); 752 } else { 753 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 754 if (td2->td_kstack != 0) 755 vm_thread_dispose(td2); 756 if (!thread_alloc_stack(td2, pages)) { 757 error = ENOMEM; 758 goto fail1; 759 } 760 } 761 } 762 763 if ((flags & RFMEM) == 0) { 764 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 765 if (vm2 == NULL) { 766 error = ENOMEM; 767 goto fail1; 768 } 769 if (!swap_reserve(mem_charged)) { 770 /* 771 * The swap reservation failed. The accounting 772 * from the entries of the copied vm2 will be 773 * substracted in vmspace_free(), so force the 774 * reservation there. 775 */ 776 swap_reserve_force(mem_charged); 777 error = ENOMEM; 778 goto fail1; 779 } 780 } else 781 vm2 = NULL; 782 #ifdef MAC 783 mac_proc_init(newproc); 784 #endif 785 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 786 STAILQ_INIT(&newproc->p_ktr); 787 788 /* We have to lock the process tree while we look for a pid. */ 789 sx_slock(&proctree_lock); 790 791 /* 792 * Although process entries are dynamically created, we still keep 793 * a global limit on the maximum number we will create. Don't allow 794 * a nonprivileged user to use the last ten processes; don't let root 795 * exceed the limit. The variable nprocs is the current number of 796 * processes, maxproc is the limit. 797 */ 798 sx_xlock(&allproc_lock); 799 if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred, 800 PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) { 801 error = EAGAIN; 802 goto fail; 803 } 804 805 /* 806 * Increment the count of procs running with this uid. Don't allow 807 * a nonprivileged user to exceed their current limit. 808 * 809 * XXXRW: Can we avoid privilege here if it's not needed? 810 */ 811 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 812 if (error == 0) 813 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 814 else { 815 PROC_LOCK(p1); 816 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 817 lim_cur(p1, RLIMIT_NPROC)); 818 PROC_UNLOCK(p1); 819 } 820 if (ok) { 821 do_fork(td, flags, newproc, td2, vm2); 822 823 /* 824 * Return child proc pointer to parent. 825 */ 826 *procp = newproc; 827 return (0); 828 } 829 830 error = EAGAIN; 831 fail: 832 sx_sunlock(&proctree_lock); 833 if (ppsratecheck(&lastfail, &curfail, 1)) 834 printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n", 835 td->td_ucred->cr_ruid); 836 sx_xunlock(&allproc_lock); 837 #ifdef MAC 838 mac_proc_destroy(newproc); 839 #endif 840 fail1: 841 if (vm2 != NULL) 842 vmspace_free(vm2); 843 uma_zfree(proc_zone, newproc); 844 pause("fork", hz / 2); 845 return (error); 846 } 847 848 /* 849 * Handle the return of a child process from fork1(). This function 850 * is called from the MD fork_trampoline() entry point. 851 */ 852 void 853 fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 854 struct trapframe *frame) 855 { 856 struct proc *p; 857 struct thread *td; 858 struct thread *dtd; 859 860 td = curthread; 861 p = td->td_proc; 862 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 863 864 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 865 td, td->td_sched, p->p_pid, td->td_name); 866 867 sched_fork_exit(td); 868 /* 869 * Processes normally resume in mi_switch() after being 870 * cpu_switch()'ed to, but when children start up they arrive here 871 * instead, so we must do much the same things as mi_switch() would. 872 */ 873 if ((dtd = PCPU_GET(deadthread))) { 874 PCPU_SET(deadthread, NULL); 875 thread_stash(dtd); 876 } 877 thread_unlock(td); 878 879 /* 880 * cpu_set_fork_handler intercepts this function call to 881 * have this call a non-return function to stay in kernel mode. 882 * initproc has its own fork handler, but it does return. 883 */ 884 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 885 callout(arg, frame); 886 887 /* 888 * Check if a kernel thread misbehaved and returned from its main 889 * function. 890 */ 891 if (p->p_flag & P_KTHREAD) { 892 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 893 td->td_name, p->p_pid); 894 kproc_exit(0); 895 } 896 mtx_assert(&Giant, MA_NOTOWNED); 897 898 EVENTHANDLER_INVOKE(schedtail, p); 899 } 900 901 /* 902 * Simplified back end of syscall(), used when returning from fork() 903 * directly into user mode. Giant is not held on entry, and must not 904 * be held on return. This function is passed in to fork_exit() as the 905 * first parameter and is called when returning to a new userland process. 906 */ 907 void 908 fork_return(struct thread *td, struct trapframe *frame) 909 { 910 struct proc *p, *dbg; 911 912 if (td->td_dbgflags & TDB_STOPATFORK) { 913 p = td->td_proc; 914 sx_xlock(&proctree_lock); 915 PROC_LOCK(p); 916 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) == 917 (P_TRACED | P_FOLLOWFORK)) { 918 /* 919 * If debugger still wants auto-attach for the 920 * parent's children, do it now. 921 */ 922 dbg = p->p_pptr->p_pptr; 923 p->p_flag |= P_TRACED; 924 p->p_oppid = p->p_pptr->p_pid; 925 proc_reparent(p, dbg); 926 sx_xunlock(&proctree_lock); 927 ptracestop(td, SIGSTOP); 928 } else { 929 /* 930 * ... otherwise clear the request. 931 */ 932 sx_xunlock(&proctree_lock); 933 td->td_dbgflags &= ~TDB_STOPATFORK; 934 cv_broadcast(&p->p_dbgwait); 935 } 936 PROC_UNLOCK(p); 937 } 938 939 userret(td, frame); 940 941 #ifdef KTRACE 942 if (KTRPOINT(td, KTR_SYSRET)) 943 ktrsysret(SYS_fork, 0, 0); 944 #endif 945 mtx_assert(&Giant, MA_NOTOWNED); 946 } 947