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