kern_fork.c revision 304499
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: stable/10/sys/kern/kern_fork.c 304499 2016-08-19 20:17:57Z jhb $"); 39 40#include "opt_kdtrace.h" 41#include "opt_ktrace.h" 42#include "opt_kstack_pages.h" 43#include "opt_procdesc.h" 44 45#include <sys/param.h> 46#include <sys/systm.h> 47#include <sys/sysproto.h> 48#include <sys/eventhandler.h> 49#include <sys/fcntl.h> 50#include <sys/filedesc.h> 51#include <sys/jail.h> 52#include <sys/kernel.h> 53#include <sys/kthread.h> 54#include <sys/sysctl.h> 55#include <sys/lock.h> 56#include <sys/malloc.h> 57#include <sys/mutex.h> 58#include <sys/priv.h> 59#include <sys/proc.h> 60#include <sys/procdesc.h> 61#include <sys/pioctl.h> 62#include <sys/ptrace.h> 63#include <sys/racct.h> 64#include <sys/resourcevar.h> 65#include <sys/sched.h> 66#include <sys/syscall.h> 67#include <sys/vmmeter.h> 68#include <sys/vnode.h> 69#include <sys/acct.h> 70#include <sys/ktr.h> 71#include <sys/ktrace.h> 72#include <sys/unistd.h> 73#include <sys/sdt.h> 74#include <sys/sx.h> 75#include <sys/sysent.h> 76#include <sys/signalvar.h> 77 78#include <security/audit/audit.h> 79#include <security/mac/mac_framework.h> 80 81#include <vm/vm.h> 82#include <vm/pmap.h> 83#include <vm/vm_map.h> 84#include <vm/vm_extern.h> 85#include <vm/uma.h> 86 87#ifdef KDTRACE_HOOKS 88#include <sys/dtrace_bsd.h> 89dtrace_fork_func_t dtrace_fasttrap_fork; 90#endif 91 92SDT_PROVIDER_DECLARE(proc); 93SDT_PROBE_DEFINE3(proc, , , create, "struct proc *", "struct proc *", "int"); 94 95#ifndef _SYS_SYSPROTO_H_ 96struct fork_args { 97 int dummy; 98}; 99#endif 100 101/* ARGSUSED */ 102int 103sys_fork(struct thread *td, struct fork_args *uap) 104{ 105 int error; 106 struct proc *p2; 107 108 error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0); 109 if (error == 0) { 110 td->td_retval[0] = p2->p_pid; 111 td->td_retval[1] = 0; 112 } 113 return (error); 114} 115 116/* ARGUSED */ 117int 118sys_pdfork(td, uap) 119 struct thread *td; 120 struct pdfork_args *uap; 121{ 122#ifdef PROCDESC 123 int error, fd; 124 struct proc *p2; 125 126 /* 127 * It is necessary to return fd by reference because 0 is a valid file 128 * descriptor number, and the child needs to be able to distinguish 129 * itself from the parent using the return value. 130 */ 131 error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2, 132 &fd, uap->flags); 133 if (error == 0) { 134 td->td_retval[0] = p2->p_pid; 135 td->td_retval[1] = 0; 136 error = copyout(&fd, uap->fdp, sizeof(fd)); 137 } 138 return (error); 139#else 140 return (ENOSYS); 141#endif 142} 143 144/* ARGSUSED */ 145int 146sys_vfork(struct thread *td, struct vfork_args *uap) 147{ 148 int error, flags; 149 struct proc *p2; 150 151 flags = RFFDG | RFPROC | RFPPWAIT | RFMEM; 152 error = fork1(td, flags, 0, &p2, NULL, 0); 153 if (error == 0) { 154 td->td_retval[0] = p2->p_pid; 155 td->td_retval[1] = 0; 156 } 157 return (error); 158} 159 160int 161sys_rfork(struct thread *td, struct rfork_args *uap) 162{ 163 struct proc *p2; 164 int error; 165 166 /* Don't allow kernel-only flags. */ 167 if ((uap->flags & RFKERNELONLY) != 0) 168 return (EINVAL); 169 170 AUDIT_ARG_FFLAGS(uap->flags); 171 error = fork1(td, uap->flags, 0, &p2, NULL, 0); 172 if (error == 0) { 173 td->td_retval[0] = p2 ? p2->p_pid : 0; 174 td->td_retval[1] = 0; 175 } 176 return (error); 177} 178 179int nprocs = 1; /* process 0 */ 180int lastpid = 0; 181SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 182 "Last used PID"); 183 184/* 185 * Random component to lastpid generation. We mix in a random factor to make 186 * it a little harder to predict. We sanity check the modulus value to avoid 187 * doing it in critical paths. Don't let it be too small or we pointlessly 188 * waste randomness entropy, and don't let it be impossibly large. Using a 189 * modulus that is too big causes a LOT more process table scans and slows 190 * down fork processing as the pidchecked caching is defeated. 191 */ 192static int randompid = 0; 193 194static int 195sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 196{ 197 int error, pid; 198 199 error = sysctl_wire_old_buffer(req, sizeof(int)); 200 if (error != 0) 201 return(error); 202 sx_xlock(&allproc_lock); 203 pid = randompid; 204 error = sysctl_handle_int(oidp, &pid, 0, req); 205 if (error == 0 && req->newptr != NULL) { 206 if (pid < 0 || pid > pid_max - 100) /* out of range */ 207 pid = pid_max - 100; 208 else if (pid < 2) /* NOP */ 209 pid = 0; 210 else if (pid < 100) /* Make it reasonable */ 211 pid = 100; 212 randompid = pid; 213 } 214 sx_xunlock(&allproc_lock); 215 return (error); 216} 217 218SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 219 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 220 221static int 222fork_findpid(int flags) 223{ 224 struct proc *p; 225 int trypid; 226 static int pidchecked = 0; 227 228 /* 229 * Requires allproc_lock in order to iterate over the list 230 * of processes, and proctree_lock to access p_pgrp. 231 */ 232 sx_assert(&allproc_lock, SX_LOCKED); 233 sx_assert(&proctree_lock, SX_LOCKED); 234 235 /* 236 * Find an unused process ID. We remember a range of unused IDs 237 * ready to use (from lastpid+1 through pidchecked-1). 238 * 239 * If RFHIGHPID is set (used during system boot), do not allocate 240 * low-numbered pids. 241 */ 242 trypid = lastpid + 1; 243 if (flags & RFHIGHPID) { 244 if (trypid < 10) 245 trypid = 10; 246 } else { 247 if (randompid) 248 trypid += arc4random() % randompid; 249 } 250retry: 251 /* 252 * If the process ID prototype has wrapped around, 253 * restart somewhat above 0, as the low-numbered procs 254 * tend to include daemons that don't exit. 255 */ 256 if (trypid >= pid_max) { 257 trypid = trypid % pid_max; 258 if (trypid < 100) 259 trypid += 100; 260 pidchecked = 0; 261 } 262 if (trypid >= pidchecked) { 263 int doingzomb = 0; 264 265 pidchecked = PID_MAX; 266 /* 267 * Scan the active and zombie procs to check whether this pid 268 * is in use. Remember the lowest pid that's greater 269 * than trypid, so we can avoid checking for a while. 270 * 271 * Avoid reuse of the process group id, session id or 272 * the reaper subtree id. Note that for process group 273 * and sessions, the amount of reserved pids is 274 * limited by process limit. For the subtree ids, the 275 * id is kept reserved only while there is a 276 * non-reaped process in the subtree, so amount of 277 * reserved pids is limited by process limit times 278 * two. 279 */ 280 p = LIST_FIRST(&allproc); 281again: 282 for (; p != NULL; p = LIST_NEXT(p, p_list)) { 283 while (p->p_pid == trypid || 284 p->p_reapsubtree == trypid || 285 (p->p_pgrp != NULL && 286 (p->p_pgrp->pg_id == trypid || 287 (p->p_session != NULL && 288 p->p_session->s_sid == trypid)))) { 289 trypid++; 290 if (trypid >= pidchecked) 291 goto retry; 292 } 293 if (p->p_pid > trypid && pidchecked > p->p_pid) 294 pidchecked = p->p_pid; 295 if (p->p_pgrp != NULL) { 296 if (p->p_pgrp->pg_id > trypid && 297 pidchecked > p->p_pgrp->pg_id) 298 pidchecked = p->p_pgrp->pg_id; 299 if (p->p_session != NULL && 300 p->p_session->s_sid > trypid && 301 pidchecked > p->p_session->s_sid) 302 pidchecked = p->p_session->s_sid; 303 } 304 } 305 if (!doingzomb) { 306 doingzomb = 1; 307 p = LIST_FIRST(&zombproc); 308 goto again; 309 } 310 } 311 312 /* 313 * RFHIGHPID does not mess with the lastpid counter during boot. 314 */ 315 if (flags & RFHIGHPID) 316 pidchecked = 0; 317 else 318 lastpid = trypid; 319 320 return (trypid); 321} 322 323static int 324fork_norfproc(struct thread *td, int flags) 325{ 326 int error; 327 struct proc *p1; 328 329 KASSERT((flags & RFPROC) == 0, 330 ("fork_norfproc called with RFPROC set")); 331 p1 = td->td_proc; 332 333 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 334 (flags & (RFCFDG | RFFDG))) { 335 PROC_LOCK(p1); 336 if (thread_single(p1, SINGLE_BOUNDARY)) { 337 PROC_UNLOCK(p1); 338 return (ERESTART); 339 } 340 PROC_UNLOCK(p1); 341 } 342 343 error = vm_forkproc(td, NULL, NULL, NULL, flags); 344 if (error) 345 goto fail; 346 347 /* 348 * Close all file descriptors. 349 */ 350 if (flags & RFCFDG) { 351 struct filedesc *fdtmp; 352 fdtmp = fdinit(td->td_proc->p_fd); 353 fdescfree(td); 354 p1->p_fd = fdtmp; 355 } 356 357 /* 358 * Unshare file descriptors (from parent). 359 */ 360 if (flags & RFFDG) 361 fdunshare(td); 362 363fail: 364 if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) && 365 (flags & (RFCFDG | RFFDG))) { 366 PROC_LOCK(p1); 367 thread_single_end(p1, SINGLE_BOUNDARY); 368 PROC_UNLOCK(p1); 369 } 370 return (error); 371} 372 373static void 374do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, 375 struct vmspace *vm2, int pdflags) 376{ 377 struct proc *p1, *pptr; 378 int p2_held, trypid; 379 struct filedesc *fd; 380 struct filedesc_to_leader *fdtol; 381 struct sigacts *newsigacts; 382 383 sx_assert(&proctree_lock, SX_SLOCKED); 384 sx_assert(&allproc_lock, SX_XLOCKED); 385 386 p2_held = 0; 387 p1 = td->td_proc; 388 389 trypid = fork_findpid(flags); 390 391 sx_sunlock(&proctree_lock); 392 393 p2->p_state = PRS_NEW; /* protect against others */ 394 p2->p_pid = trypid; 395 AUDIT_ARG_PID(p2->p_pid); 396 LIST_INSERT_HEAD(&allproc, p2, p_list); 397 allproc_gen++; 398 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 399 tidhash_add(td2); 400 PROC_LOCK(p2); 401 PROC_LOCK(p1); 402 403 sx_xunlock(&allproc_lock); 404 405 bcopy(&p1->p_startcopy, &p2->p_startcopy, 406 __rangeof(struct proc, p_startcopy, p_endcopy)); 407 pargs_hold(p2->p_args); 408 PROC_UNLOCK(p1); 409 410 bzero(&p2->p_startzero, 411 __rangeof(struct proc, p_startzero, p_endzero)); 412 p2->p_treeflag = 0; 413 p2->p_filemon = NULL; 414 p2->p_ptevents = 0; 415 416 /* Tell the prison that we exist. */ 417 prison_proc_hold(p2->p_ucred->cr_prison); 418 419 PROC_UNLOCK(p2); 420 421 /* 422 * Malloc things while we don't hold any locks. 423 */ 424 if (flags & RFSIGSHARE) 425 newsigacts = NULL; 426 else 427 newsigacts = sigacts_alloc(); 428 429 /* 430 * Copy filedesc. 431 */ 432 if (flags & RFCFDG) { 433 fd = fdinit(p1->p_fd); 434 fdtol = NULL; 435 } else if (flags & RFFDG) { 436 fd = fdcopy(p1->p_fd); 437 fdtol = NULL; 438 } else { 439 fd = fdshare(p1->p_fd); 440 if (p1->p_fdtol == NULL) 441 p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL, 442 p1->p_leader); 443 if ((flags & RFTHREAD) != 0) { 444 /* 445 * Shared file descriptor table, and shared 446 * process leaders. 447 */ 448 fdtol = p1->p_fdtol; 449 FILEDESC_XLOCK(p1->p_fd); 450 fdtol->fdl_refcount++; 451 FILEDESC_XUNLOCK(p1->p_fd); 452 } else { 453 /* 454 * Shared file descriptor table, and different 455 * process leaders. 456 */ 457 fdtol = filedesc_to_leader_alloc(p1->p_fdtol, 458 p1->p_fd, p2); 459 } 460 } 461 /* 462 * Make a proc table entry for the new process. 463 * Start by zeroing the section of proc that is zero-initialized, 464 * then copy the section that is copied directly from the parent. 465 */ 466 467 PROC_LOCK(p2); 468 PROC_LOCK(p1); 469 470 bzero(&td2->td_startzero, 471 __rangeof(struct thread, td_startzero, td_endzero)); 472 td2->td_su = NULL; 473 474 bcopy(&td->td_startcopy, &td2->td_startcopy, 475 __rangeof(struct thread, td_startcopy, td_endcopy)); 476 477 bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name)); 478 td2->td_sigstk = td->td_sigstk; 479 td2->td_flags = TDF_INMEM; 480 td2->td_lend_user_pri = PRI_MAX; 481 td2->td_dbg_sc_code = td->td_dbg_sc_code; 482 td2->td_dbg_sc_narg = td->td_dbg_sc_narg; 483 484#ifdef VIMAGE 485 td2->td_vnet = NULL; 486 td2->td_vnet_lpush = NULL; 487#endif 488 489 /* 490 * Allow the scheduler to initialize the child. 491 */ 492 thread_lock(td); 493 sched_fork(td, td2); 494 thread_unlock(td); 495 496 /* 497 * Duplicate sub-structures as needed. 498 * Increase reference counts on shared objects. 499 */ 500 p2->p_flag = P_INMEM; 501 p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC); 502 p2->p_swtick = ticks; 503 if (p1->p_flag & P_PROFIL) 504 startprofclock(p2); 505 td2->td_ucred = crhold(p2->p_ucred); 506 507 if (flags & RFSIGSHARE) { 508 p2->p_sigacts = sigacts_hold(p1->p_sigacts); 509 } else { 510 sigacts_copy(newsigacts, p1->p_sigacts); 511 p2->p_sigacts = newsigacts; 512 } 513 514 if (flags & RFTSIGZMB) 515 p2->p_sigparent = RFTSIGNUM(flags); 516 else if (flags & RFLINUXTHPN) 517 p2->p_sigparent = SIGUSR1; 518 else 519 p2->p_sigparent = SIGCHLD; 520 521 p2->p_textvp = p1->p_textvp; 522 p2->p_fd = fd; 523 p2->p_fdtol = fdtol; 524 525 if (p1->p_flag2 & P2_INHERIT_PROTECTED) { 526 p2->p_flag |= P_PROTECTED; 527 p2->p_flag2 |= P2_INHERIT_PROTECTED; 528 } 529 530 /* 531 * p_limit is copy-on-write. Bump its refcount. 532 */ 533 lim_fork(p1, p2); 534 535 pstats_fork(p1->p_stats, p2->p_stats); 536 537 PROC_UNLOCK(p1); 538 PROC_UNLOCK(p2); 539 540 /* Bump references to the text vnode (for procfs). */ 541 if (p2->p_textvp) 542 vref(p2->p_textvp); 543 544 /* 545 * Set up linkage for kernel based threading. 546 */ 547 if ((flags & RFTHREAD) != 0) { 548 mtx_lock(&ppeers_lock); 549 p2->p_peers = p1->p_peers; 550 p1->p_peers = p2; 551 p2->p_leader = p1->p_leader; 552 mtx_unlock(&ppeers_lock); 553 PROC_LOCK(p1->p_leader); 554 if ((p1->p_leader->p_flag & P_WEXIT) != 0) { 555 PROC_UNLOCK(p1->p_leader); 556 /* 557 * The task leader is exiting, so process p1 is 558 * going to be killed shortly. Since p1 obviously 559 * isn't dead yet, we know that the leader is either 560 * sending SIGKILL's to all the processes in this 561 * task or is sleeping waiting for all the peers to 562 * exit. We let p1 complete the fork, but we need 563 * to go ahead and kill the new process p2 since 564 * the task leader may not get a chance to send 565 * SIGKILL to it. We leave it on the list so that 566 * the task leader will wait for this new process 567 * to commit suicide. 568 */ 569 PROC_LOCK(p2); 570 kern_psignal(p2, SIGKILL); 571 PROC_UNLOCK(p2); 572 } else 573 PROC_UNLOCK(p1->p_leader); 574 } else { 575 p2->p_peers = NULL; 576 p2->p_leader = p2; 577 } 578 579 sx_xlock(&proctree_lock); 580 PGRP_LOCK(p1->p_pgrp); 581 PROC_LOCK(p2); 582 PROC_LOCK(p1); 583 584 /* 585 * Preserve some more flags in subprocess. P_PROFIL has already 586 * been preserved. 587 */ 588 p2->p_flag |= p1->p_flag & P_SUGID; 589 td2->td_pflags |= td->td_pflags & TDP_ALTSTACK; 590 SESS_LOCK(p1->p_session); 591 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 592 p2->p_flag |= P_CONTROLT; 593 SESS_UNLOCK(p1->p_session); 594 if (flags & RFPPWAIT) 595 p2->p_flag |= P_PPWAIT; 596 597 p2->p_pgrp = p1->p_pgrp; 598 LIST_INSERT_AFTER(p1, p2, p_pglist); 599 PGRP_UNLOCK(p1->p_pgrp); 600 LIST_INIT(&p2->p_children); 601 LIST_INIT(&p2->p_orphans); 602 603 callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0); 604 605 /* 606 * If PF_FORK is set, the child process inherits the 607 * procfs ioctl flags from its parent. 608 */ 609 if (p1->p_pfsflags & PF_FORK) { 610 p2->p_stops = p1->p_stops; 611 p2->p_pfsflags = p1->p_pfsflags; 612 } 613 614 /* 615 * This begins the section where we must prevent the parent 616 * from being swapped. 617 */ 618 _PHOLD(p1); 619 PROC_UNLOCK(p1); 620 621 /* 622 * Attach the new process to its parent. 623 * 624 * If RFNOWAIT is set, the newly created process becomes a child 625 * of init. This effectively disassociates the child from the 626 * parent. 627 */ 628 if ((flags & RFNOWAIT) != 0) { 629 pptr = p1->p_reaper; 630 p2->p_reaper = pptr; 631 } else { 632 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ? 633 p1 : p1->p_reaper; 634 pptr = p1; 635 } 636 p2->p_pptr = pptr; 637 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 638 LIST_INIT(&p2->p_reaplist); 639 LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling); 640 if (p2->p_reaper == p1) 641 p2->p_reapsubtree = p2->p_pid; 642 else 643 p2->p_reapsubtree = p1->p_reapsubtree; 644 sx_xunlock(&proctree_lock); 645 646 /* Inform accounting that we have forked. */ 647 p2->p_acflag = AFORK; 648 PROC_UNLOCK(p2); 649 650#ifdef KTRACE 651 ktrprocfork(p1, p2); 652#endif 653 654 /* 655 * Finish creating the child process. It will return via a different 656 * execution path later. (ie: directly into user mode) 657 */ 658 vm_forkproc(td, p2, td2, vm2, flags); 659 660 if (flags == (RFFDG | RFPROC)) { 661 PCPU_INC(cnt.v_forks); 662 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize + 663 p2->p_vmspace->vm_ssize); 664 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 665 PCPU_INC(cnt.v_vforks); 666 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize + 667 p2->p_vmspace->vm_ssize); 668 } else if (p1 == &proc0) { 669 PCPU_INC(cnt.v_kthreads); 670 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize + 671 p2->p_vmspace->vm_ssize); 672 } else { 673 PCPU_INC(cnt.v_rforks); 674 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize + 675 p2->p_vmspace->vm_ssize); 676 } 677 678#ifdef PROCDESC 679 /* 680 * Associate the process descriptor with the process before anything 681 * can happen that might cause that process to need the descriptor. 682 * However, don't do this until after fork(2) can no longer fail. 683 */ 684 if (flags & RFPROCDESC) 685 procdesc_new(p2, pdflags); 686#endif 687 688 /* 689 * Both processes are set up, now check if any loadable modules want 690 * to adjust anything. 691 */ 692 EVENTHANDLER_INVOKE(process_fork, p1, p2, flags); 693 694 /* 695 * Set the child start time and mark the process as being complete. 696 */ 697 PROC_LOCK(p2); 698 PROC_LOCK(p1); 699 microuptime(&p2->p_stats->p_start); 700 PROC_SLOCK(p2); 701 p2->p_state = PRS_NORMAL; 702 PROC_SUNLOCK(p2); 703 704#ifdef KDTRACE_HOOKS 705 /* 706 * Tell the DTrace fasttrap provider about the new process so that any 707 * tracepoints inherited from the parent can be removed. We have to do 708 * this only after p_state is PRS_NORMAL since the fasttrap module will 709 * use pfind() later on. 710 */ 711 if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork) 712 dtrace_fasttrap_fork(p1, p2); 713#endif 714 if (p1->p_ptevents & PTRACE_FORK) { 715 /* 716 * Arrange for debugger to receive the fork event. 717 * 718 * We can report PL_FLAG_FORKED regardless of 719 * P_FOLLOWFORK settings, but it does not make a sense 720 * for runaway child. 721 */ 722 td->td_dbgflags |= TDB_FORK; 723 td->td_dbg_forked = p2->p_pid; 724 td2->td_dbgflags |= TDB_STOPATFORK; 725 _PHOLD(p2); 726 p2_held = 1; 727 } 728 if (flags & RFPPWAIT) { 729 td->td_pflags |= TDP_RFPPWAIT; 730 td->td_rfppwait_p = p2; 731 td->td_dbgflags |= TDB_VFORK; 732 } 733 PROC_UNLOCK(p2); 734 if ((flags & RFSTOPPED) == 0) { 735 /* 736 * If RFSTOPPED not requested, make child runnable and 737 * add to run queue. 738 */ 739 thread_lock(td2); 740 TD_SET_CAN_RUN(td2); 741 sched_add(td2, SRQ_BORING); 742 thread_unlock(td2); 743 } 744 745 /* 746 * Now can be swapped. 747 */ 748 _PRELE(p1); 749 PROC_UNLOCK(p1); 750 751 /* 752 * Tell any interested parties about the new process. 753 */ 754 knote_fork(&p1->p_klist, p2->p_pid); 755 SDT_PROBE3(proc, , , create, p2, p1, flags); 756 757 /* 758 * Wait until debugger is attached to child. 759 */ 760 PROC_LOCK(p2); 761 while ((td2->td_dbgflags & TDB_STOPATFORK) != 0) 762 cv_wait(&p2->p_dbgwait, &p2->p_mtx); 763 if (p2_held) 764 _PRELE(p2); 765 PROC_UNLOCK(p2); 766} 767 768int 769fork1(struct thread *td, int flags, int pages, struct proc **procp, 770 int *procdescp, int pdflags) 771{ 772 struct proc *p1, *newproc; 773 struct thread *td2; 774 struct vmspace *vm2; 775#ifdef PROCDESC 776 struct file *fp_procdesc; 777#endif 778 vm_ooffset_t mem_charged; 779 int error, nprocs_new, ok; 780 static int curfail; 781 static struct timeval lastfail; 782 783 /* Check for the undefined or unimplemented flags. */ 784 if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0) 785 return (EINVAL); 786 787 /* Signal value requires RFTSIGZMB. */ 788 if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0) 789 return (EINVAL); 790 791 /* Can't copy and clear. */ 792 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 793 return (EINVAL); 794 795 /* Check the validity of the signal number. */ 796 if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG) 797 return (EINVAL); 798 799#ifdef PROCDESC 800 if ((flags & RFPROCDESC) != 0) { 801 /* Can't not create a process yet get a process descriptor. */ 802 if ((flags & RFPROC) == 0) 803 return (EINVAL); 804 805 /* Must provide a place to put a procdesc if creating one. */ 806 if (procdescp == NULL) 807 return (EINVAL); 808 } 809#endif 810 811 p1 = td->td_proc; 812 813 /* 814 * Here we don't create a new process, but we divorce 815 * certain parts of a process from itself. 816 */ 817 if ((flags & RFPROC) == 0) { 818 *procp = NULL; 819 return (fork_norfproc(td, flags)); 820 } 821 822#ifdef PROCDESC 823 fp_procdesc = NULL; 824#endif 825 newproc = NULL; 826 vm2 = NULL; 827 828 /* 829 * Increment the nprocs resource before allocations occur. 830 * Although process entries are dynamically created, we still 831 * keep a global limit on the maximum number we will 832 * create. There are hard-limits as to the number of processes 833 * that can run, established by the KVA and memory usage for 834 * the process data. 835 * 836 * Don't allow a nonprivileged user to use the last ten 837 * processes; don't let root exceed the limit. 838 */ 839 nprocs_new = atomic_fetchadd_int(&nprocs, 1) + 1; 840 if ((nprocs_new >= maxproc - 10 && priv_check_cred(td->td_ucred, 841 PRIV_MAXPROC, 0) != 0) || nprocs_new >= maxproc) { 842 sx_xlock(&allproc_lock); 843 if (ppsratecheck(&lastfail, &curfail, 1)) { 844 printf("maxproc limit exceeded by uid %u (pid %d); " 845 "see tuning(7) and login.conf(5)\n", 846 td->td_ucred->cr_ruid, p1->p_pid); 847 } 848 sx_xunlock(&allproc_lock); 849 error = EAGAIN; 850 goto fail1; 851 } 852 853#ifdef PROCDESC 854 /* 855 * If required, create a process descriptor in the parent first; we 856 * will abandon it if something goes wrong. We don't finit() until 857 * later. 858 */ 859 if (flags & RFPROCDESC) { 860 error = falloc(td, &fp_procdesc, procdescp, 0); 861 if (error != 0) 862 goto fail1; 863 } 864#endif 865 866 mem_charged = 0; 867 if (pages == 0) 868 pages = KSTACK_PAGES; 869 /* Allocate new proc. */ 870 newproc = uma_zalloc(proc_zone, M_WAITOK); 871 td2 = FIRST_THREAD_IN_PROC(newproc); 872 if (td2 == NULL) { 873 td2 = thread_alloc(pages); 874 if (td2 == NULL) { 875 error = ENOMEM; 876 goto fail2; 877 } 878 proc_linkup(newproc, td2); 879 } else { 880 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) { 881 if (td2->td_kstack != 0) 882 vm_thread_dispose(td2); 883 if (!thread_alloc_stack(td2, pages)) { 884 error = ENOMEM; 885 goto fail2; 886 } 887 } 888 } 889 890 if ((flags & RFMEM) == 0) { 891 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged); 892 if (vm2 == NULL) { 893 error = ENOMEM; 894 goto fail2; 895 } 896 if (!swap_reserve(mem_charged)) { 897 /* 898 * The swap reservation failed. The accounting 899 * from the entries of the copied vm2 will be 900 * subtracted in vmspace_free(), so force the 901 * reservation there. 902 */ 903 swap_reserve_force(mem_charged); 904 error = ENOMEM; 905 goto fail2; 906 } 907 } else 908 vm2 = NULL; 909 910 /* 911 * XXX: This is ugly; when we copy resource usage, we need to bump 912 * per-cred resource counters. 913 */ 914 proc_set_cred_init(newproc, crhold(td->td_ucred)); 915 916 /* 917 * Initialize resource accounting for the child process. 918 */ 919 error = racct_proc_fork(p1, newproc); 920 if (error != 0) { 921 error = EAGAIN; 922 goto fail1; 923 } 924 925#ifdef MAC 926 mac_proc_init(newproc); 927#endif 928 knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx); 929 STAILQ_INIT(&newproc->p_ktr); 930 931 /* We have to lock the process tree while we look for a pid. */ 932 sx_slock(&proctree_lock); 933 sx_xlock(&allproc_lock); 934 935 /* 936 * Increment the count of procs running with this uid. Don't allow 937 * a nonprivileged user to exceed their current limit. 938 * 939 * XXXRW: Can we avoid privilege here if it's not needed? 940 */ 941 error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0); 942 if (error == 0) 943 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0); 944 else { 945 PROC_LOCK(p1); 946 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 947 lim_cur(p1, RLIMIT_NPROC)); 948 PROC_UNLOCK(p1); 949 } 950 if (ok) { 951 do_fork(td, flags, newproc, td2, vm2, pdflags); 952 953 /* 954 * Return child proc pointer to parent. 955 */ 956 *procp = newproc; 957#ifdef PROCDESC 958 if (flags & RFPROCDESC) { 959 procdesc_finit(newproc->p_procdesc, fp_procdesc); 960 fdrop(fp_procdesc, td); 961 } 962#endif 963 racct_proc_fork_done(newproc); 964 return (0); 965 } 966 967 error = EAGAIN; 968 sx_sunlock(&proctree_lock); 969 sx_xunlock(&allproc_lock); 970#ifdef MAC 971 mac_proc_destroy(newproc); 972#endif 973 racct_proc_exit(newproc); 974fail1: 975 crfree(newproc->p_ucred); 976 newproc->p_ucred = NULL; 977fail2: 978 if (vm2 != NULL) 979 vmspace_free(vm2); 980 uma_zfree(proc_zone, newproc); 981#ifdef PROCDESC 982 if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) { 983 fdclose(td->td_proc->p_fd, fp_procdesc, *procdescp, td); 984 fdrop(fp_procdesc, td); 985 } 986#endif 987 atomic_add_int(&nprocs, -1); 988 pause("fork", hz / 2); 989 return (error); 990} 991 992/* 993 * Handle the return of a child process from fork1(). This function 994 * is called from the MD fork_trampoline() entry point. 995 */ 996void 997fork_exit(void (*callout)(void *, struct trapframe *), void *arg, 998 struct trapframe *frame) 999{ 1000 struct proc *p; 1001 struct thread *td; 1002 struct thread *dtd; 1003 1004 td = curthread; 1005 p = td->td_proc; 1006 KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new")); 1007 1008 CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)", 1009 td, td->td_sched, p->p_pid, td->td_name); 1010 1011 sched_fork_exit(td); 1012 /* 1013 * Processes normally resume in mi_switch() after being 1014 * cpu_switch()'ed to, but when children start up they arrive here 1015 * instead, so we must do much the same things as mi_switch() would. 1016 */ 1017 if ((dtd = PCPU_GET(deadthread))) { 1018 PCPU_SET(deadthread, NULL); 1019 thread_stash(dtd); 1020 } 1021 thread_unlock(td); 1022 1023 /* 1024 * cpu_set_fork_handler intercepts this function call to 1025 * have this call a non-return function to stay in kernel mode. 1026 * initproc has its own fork handler, but it does return. 1027 */ 1028 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 1029 callout(arg, frame); 1030 1031 /* 1032 * Check if a kernel thread misbehaved and returned from its main 1033 * function. 1034 */ 1035 if (p->p_flag & P_KTHREAD) { 1036 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 1037 td->td_name, p->p_pid); 1038 kthread_exit(); 1039 } 1040 mtx_assert(&Giant, MA_NOTOWNED); 1041 1042 if (p->p_sysent->sv_schedtail != NULL) 1043 (p->p_sysent->sv_schedtail)(td); 1044} 1045 1046/* 1047 * Simplified back end of syscall(), used when returning from fork() 1048 * directly into user mode. This function is passed in to fork_exit() 1049 * as the first parameter and is called when returning to a new 1050 * userland process. 1051 */ 1052void 1053fork_return(struct thread *td, struct trapframe *frame) 1054{ 1055 struct proc *p, *dbg; 1056 1057 p = td->td_proc; 1058 if (td->td_dbgflags & TDB_STOPATFORK) { 1059 sx_xlock(&proctree_lock); 1060 PROC_LOCK(p); 1061 if (p->p_pptr->p_ptevents & PTRACE_FORK) { 1062 /* 1063 * If debugger still wants auto-attach for the 1064 * parent's children, do it now. 1065 */ 1066 dbg = p->p_pptr->p_pptr; 1067 proc_set_traced(p); 1068 CTR2(KTR_PTRACE, 1069 "fork_return: attaching to new child pid %d: oppid %d", 1070 p->p_pid, p->p_oppid); 1071 proc_reparent(p, dbg); 1072 sx_xunlock(&proctree_lock); 1073 td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP; 1074 ptracestop(td, SIGSTOP); 1075 td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX); 1076 } else { 1077 /* 1078 * ... otherwise clear the request. 1079 */ 1080 sx_xunlock(&proctree_lock); 1081 td->td_dbgflags &= ~TDB_STOPATFORK; 1082 cv_broadcast(&p->p_dbgwait); 1083 } 1084 PROC_UNLOCK(p); 1085 } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) { 1086 /* 1087 * This is the start of a new thread in a traced 1088 * process. Report a system call exit event. 1089 */ 1090 PROC_LOCK(p); 1091 td->td_dbgflags |= TDB_SCX; 1092 _STOPEVENT(p, S_SCX, td->td_dbg_sc_code); 1093 if ((p->p_ptevents & PTRACE_SCX) != 0 || 1094 (td->td_dbgflags & TDB_BORN) != 0) 1095 ptracestop(td, SIGTRAP); 1096 td->td_dbgflags &= ~(TDB_SCX | TDB_BORN); 1097 PROC_UNLOCK(p); 1098 } 1099 1100 userret(td, frame); 1101 1102#ifdef KTRACE 1103 if (KTRPOINT(td, KTR_SYSRET)) 1104 ktrsysret(SYS_fork, 0, 0); 1105#endif 1106} 1107