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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 39 * $FreeBSD$ 40 */ 41 42 #include "opt_ktrace.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/sysproto.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/sysctl.h> 50 #include <sys/lock.h> 51 #include <sys/malloc.h> 52 #include <sys/mutex.h> 53 #include <sys/proc.h> 54 #include <sys/resourcevar.h> 55 #include <sys/syscall.h> 56 #include <sys/vnode.h> 57 #include <sys/acct.h> 58 #include <sys/ktr.h> 59 #include <sys/ktrace.h> 60 #include <sys/kthread.h> 61 #include <sys/unistd.h> 62 #include <sys/jail.h> 63 #include <sys/sx.h> 64 65 #include <vm/vm.h> 66 #include <vm/pmap.h> 67 #include <vm/vm_map.h> 68 #include <vm/vm_extern.h> 69 #include <vm/vm_zone.h> 70 71 #include <sys/vmmeter.h> 72 #include <sys/user.h> 73 74 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); 75 76 static int fast_vfork = 1; 77 SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, 78 "flag to indicate whether we have a fast vfork()"); 79 80 /* 81 * These are the stuctures used to create a callout list for things to do 82 * when forking a process 83 */ 84 struct forklist { 85 forklist_fn function; 86 TAILQ_ENTRY(forklist) next; 87 }; 88 89 static struct sx fork_list_lock; 90 91 TAILQ_HEAD(forklist_head, forklist); 92 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); 93 94 #ifndef _SYS_SYSPROTO_H_ 95 struct fork_args { 96 int dummy; 97 }; 98 #endif 99 100 static void 101 init_fork_list(void *data __unused) 102 { 103 104 sx_init(&fork_list_lock, "fork list"); 105 } 106 SYSINIT(fork_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_fork_list, NULL); 107 108 /* 109 * MPSAFE 110 */ 111 /* ARGSUSED */ 112 int 113 fork(td, uap) 114 struct thread *td; 115 struct fork_args *uap; 116 { 117 int error; 118 struct proc *p2; 119 120 mtx_lock(&Giant); 121 error = fork1(td, RFFDG | RFPROC, &p2); 122 if (error == 0) { 123 td->td_retval[0] = p2->p_pid; 124 td->td_retval[1] = 0; 125 } 126 mtx_unlock(&Giant); 127 return error; 128 } 129 130 /* 131 * MPSAFE 132 */ 133 /* ARGSUSED */ 134 int 135 vfork(td, uap) 136 struct thread *td; 137 struct vfork_args *uap; 138 { 139 int error; 140 struct proc *p2; 141 142 mtx_lock(&Giant); 143 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); 144 if (error == 0) { 145 td->td_retval[0] = p2->p_pid; 146 td->td_retval[1] = 0; 147 } 148 mtx_unlock(&Giant); 149 return error; 150 } 151 152 /* 153 * MPSAFE 154 */ 155 int 156 rfork(td, uap) 157 struct thread *td; 158 struct rfork_args *uap; 159 { 160 int error; 161 struct proc *p2; 162 163 /* Don't allow kernel only flags. */ 164 if ((uap->flags & RFKERNELONLY) != 0) 165 return (EINVAL); 166 mtx_lock(&Giant); 167 error = fork1(td, uap->flags, &p2); 168 if (error == 0) { 169 td->td_retval[0] = p2 ? p2->p_pid : 0; 170 td->td_retval[1] = 0; 171 } 172 mtx_unlock(&Giant); 173 return error; 174 } 175 176 177 int nprocs = 1; /* process 0 */ 178 int lastpid = 0; 179 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 180 "Last used PID"); 181 182 /* 183 * Random component to lastpid generation. We mix in a random factor to make 184 * it a little harder to predict. We sanity check the modulus value to avoid 185 * doing it in critical paths. Don't let it be too small or we pointlessly 186 * waste randomness entropy, and don't let it be impossibly large. Using a 187 * modulus that is too big causes a LOT more process table scans and slows 188 * down fork processing as the pidchecked caching is defeated. 189 */ 190 static int randompid = 0; 191 192 static int 193 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 194 { 195 int error, pid; 196 197 pid = randompid; 198 error = sysctl_handle_int(oidp, &pid, 0, req); 199 if (error || !req->newptr) 200 return (error); 201 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 202 pid = PID_MAX - 100; 203 else if (pid < 2) /* NOP */ 204 pid = 0; 205 else if (pid < 100) /* Make it reasonable */ 206 pid = 100; 207 randompid = pid; 208 return (error); 209 } 210 211 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 212 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 213 214 #if 0 215 void 216 kse_init(struct kse *kse1, struct kse *kse2) 217 { 218 } 219 220 void 221 thread_init(struct thread *thread1, struct thread *thread2) 222 { 223 } 224 225 void 226 ksegrp_init(struct ksegrp *ksegrp1, struct ksegrp *ksegrp2) 227 { 228 } 229 #endif 230 231 int 232 fork1(td, flags, procp) 233 struct thread *td; /* parent proc */ 234 int flags; 235 struct proc **procp; /* child proc */ 236 { 237 struct proc *p2, *pptr; 238 uid_t uid; 239 struct proc *newproc; 240 int trypid; 241 int ok; 242 static int pidchecked = 0; 243 struct forklist *ep; 244 struct filedesc *fd; 245 struct proc *p1 = td->td_proc; 246 247 GIANT_REQUIRED; 248 249 /* Can't copy and clear */ 250 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 251 return (EINVAL); 252 253 /* 254 * Here we don't create a new process, but we divorce 255 * certain parts of a process from itself. 256 */ 257 if ((flags & RFPROC) == 0) { 258 vm_forkproc(td, 0, flags); 259 260 /* 261 * Close all file descriptors. 262 */ 263 if (flags & RFCFDG) { 264 struct filedesc *fdtmp; 265 fdtmp = fdinit(td); /* XXXKSE */ 266 PROC_LOCK(p1); 267 fdfree(td); /* XXXKSE */ 268 p1->p_fd = fdtmp; 269 PROC_UNLOCK(p1); 270 } 271 272 /* 273 * Unshare file descriptors (from parent.) 274 */ 275 if (flags & RFFDG) { 276 if (p1->p_fd->fd_refcnt > 1) { 277 struct filedesc *newfd; 278 newfd = fdcopy(td); 279 PROC_LOCK(p1); 280 fdfree(td); 281 p1->p_fd = newfd; 282 PROC_UNLOCK(p1); 283 } 284 } 285 *procp = NULL; 286 return (0); 287 } 288 289 /* 290 * Although process entries are dynamically created, we still keep 291 * a global limit on the maximum number we will create. Don't allow 292 * a nonprivileged user to use the last process; don't let root 293 * exceed the limit. The variable nprocs is the current number of 294 * processes, maxproc is the limit. 295 */ 296 uid = p1->p_ucred->cr_ruid; 297 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 298 tablefull("proc"); 299 return (EAGAIN); 300 } 301 /* 302 * Increment the nprocs resource before blocking can occur. There 303 * are hard-limits as to the number of processes that can run. 304 */ 305 nprocs++; 306 307 /* 308 * Increment the count of procs running with this uid. Don't allow 309 * a nonprivileged user to exceed their current limit. 310 */ 311 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1, 312 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 313 if (!ok) { 314 /* 315 * Back out the process count 316 */ 317 nprocs--; 318 return (EAGAIN); 319 } 320 321 /* Allocate new proc. */ 322 newproc = zalloc(proc_zone); 323 324 /* 325 * Setup linkage for kernel based threading 326 */ 327 if((flags & RFTHREAD) != 0) { 328 newproc->p_peers = p1->p_peers; 329 p1->p_peers = newproc; 330 newproc->p_leader = p1->p_leader; 331 } else { 332 newproc->p_peers = NULL; 333 newproc->p_leader = newproc; 334 } 335 336 newproc->p_vmspace = NULL; 337 338 /* 339 * Find an unused process ID. We remember a range of unused IDs 340 * ready to use (from lastpid+1 through pidchecked-1). 341 * 342 * If RFHIGHPID is set (used during system boot), do not allocate 343 * low-numbered pids. 344 */ 345 sx_xlock(&allproc_lock); 346 trypid = lastpid + 1; 347 if (flags & RFHIGHPID) { 348 if (trypid < 10) { 349 trypid = 10; 350 } 351 } else { 352 if (randompid) 353 trypid += arc4random() % randompid; 354 } 355 retry: 356 /* 357 * If the process ID prototype has wrapped around, 358 * restart somewhat above 0, as the low-numbered procs 359 * tend to include daemons that don't exit. 360 */ 361 if (trypid >= PID_MAX) { 362 trypid = trypid % PID_MAX; 363 if (trypid < 100) 364 trypid += 100; 365 pidchecked = 0; 366 } 367 if (trypid >= pidchecked) { 368 int doingzomb = 0; 369 370 pidchecked = PID_MAX; 371 /* 372 * Scan the active and zombie procs to check whether this pid 373 * is in use. Remember the lowest pid that's greater 374 * than trypid, so we can avoid checking for a while. 375 */ 376 p2 = LIST_FIRST(&allproc); 377 again: 378 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 379 while (p2->p_pid == trypid || 380 p2->p_pgrp->pg_id == trypid || 381 p2->p_session->s_sid == trypid) { 382 trypid++; 383 if (trypid >= pidchecked) 384 goto retry; 385 } 386 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 387 pidchecked = p2->p_pid; 388 if (p2->p_pgrp->pg_id > trypid && 389 pidchecked > p2->p_pgrp->pg_id) 390 pidchecked = p2->p_pgrp->pg_id; 391 if (p2->p_session->s_sid > trypid && 392 pidchecked > p2->p_session->s_sid) 393 pidchecked = p2->p_session->s_sid; 394 } 395 if (!doingzomb) { 396 doingzomb = 1; 397 p2 = LIST_FIRST(&zombproc); 398 goto again; 399 } 400 } 401 402 /* 403 * RFHIGHPID does not mess with the lastpid counter during boot. 404 */ 405 if (flags & RFHIGHPID) 406 pidchecked = 0; 407 else 408 lastpid = trypid; 409 410 p2 = newproc; 411 p2->p_stat = SIDL; /* protect against others */ 412 p2->p_pid = trypid; 413 LIST_INSERT_HEAD(&allproc, p2, p_list); 414 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 415 sx_xunlock(&allproc_lock); 416 417 /* 418 * Make a proc table entry for the new process. 419 * Start by zeroing the section of proc that is zero-initialized, 420 * then copy the section that is copied directly from the parent. 421 */ 422 bzero(&p2->p_startzero, 423 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 424 bzero(&p2->p_kse.ke_startzero, 425 (unsigned) ((caddr_t)&p2->p_kse.ke_endzero 426 - (caddr_t)&p2->p_kse.ke_startzero)); 427 bzero(&p2->p_thread.td_startzero, 428 (unsigned) ((caddr_t)&p2->p_thread.td_endzero 429 - (caddr_t)&p2->p_thread.td_startzero)); 430 bzero(&p2->p_ksegrp.kg_startzero, 431 (unsigned) ((caddr_t)&p2->p_ksegrp.kg_endzero 432 - (caddr_t)&p2->p_ksegrp.kg_startzero)); 433 PROC_LOCK(p1); 434 bcopy(&p1->p_startcopy, &p2->p_startcopy, 435 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 436 437 bcopy(&p1->p_kse.ke_startcopy, &p2->p_kse.ke_startcopy, 438 (unsigned) ((caddr_t)&p2->p_kse.ke_endcopy 439 - (caddr_t)&p2->p_kse.ke_startcopy)); 440 441 bcopy(&p1->p_thread.td_startcopy, &p2->p_thread.td_startcopy, 442 (unsigned) ((caddr_t)&p2->p_thread.td_endcopy 443 - (caddr_t)&p2->p_thread.td_startcopy)); 444 445 bcopy(&p1->p_ksegrp.kg_startcopy, &p2->p_ksegrp.kg_startcopy, 446 (unsigned) ((caddr_t)&p2->p_ksegrp.kg_endcopy 447 - (caddr_t)&p2->p_ksegrp.kg_startcopy)); 448 PROC_UNLOCK(p1); 449 450 /* 451 * XXXKSE Theoretically only the running thread would get copied 452 * Others in the kernel would be 'aborted' in the child. 453 * i.e return E*something* 454 */ 455 proc_linkup(p2); 456 457 mtx_init(&p2->p_mtx, "process lock", MTX_DEF); 458 PROC_LOCK(p2); 459 /* note.. XXXKSE no pcb or u-area yet */ 460 461 /* 462 * Duplicate sub-structures as needed. 463 * Increase reference counts on shared objects. 464 * The p_stats and p_sigacts substructs are set in vm_forkproc. 465 */ 466 p2->p_flag = 0; 467 mtx_lock_spin(&sched_lock); 468 p2->p_sflag = PS_INMEM; 469 if (p1->p_sflag & PS_PROFIL) 470 startprofclock(p2); 471 mtx_unlock_spin(&sched_lock); 472 PROC_LOCK(p1); 473 p2->p_ucred = crhold(p1->p_ucred); 474 p2->p_thread.td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 475 476 if (p2->p_args) 477 p2->p_args->ar_ref++; 478 479 if (flags & RFSIGSHARE) { 480 p2->p_procsig = p1->p_procsig; 481 p2->p_procsig->ps_refcnt++; 482 if (p1->p_sigacts == &p1->p_uarea->u_sigacts) { 483 struct sigacts *newsigacts; 484 485 PROC_UNLOCK(p1); 486 PROC_UNLOCK(p2); 487 /* Create the shared sigacts structure */ 488 MALLOC(newsigacts, struct sigacts *, 489 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 490 PROC_LOCK(p2); 491 PROC_LOCK(p1); 492 /* 493 * Set p_sigacts to the new shared structure. 494 * Note that this is updating p1->p_sigacts at the 495 * same time, since p_sigacts is just a pointer to 496 * the shared p_procsig->ps_sigacts. 497 */ 498 p2->p_sigacts = newsigacts; 499 *p2->p_sigacts = p1->p_uarea->u_sigacts; 500 } 501 } else { 502 PROC_UNLOCK(p1); 503 PROC_UNLOCK(p2); 504 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), 505 M_SUBPROC, M_WAITOK); 506 PROC_LOCK(p2); 507 PROC_LOCK(p1); 508 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 509 p2->p_procsig->ps_refcnt = 1; 510 p2->p_sigacts = NULL; /* finished in vm_forkproc() */ 511 } 512 if (flags & RFLINUXTHPN) 513 p2->p_sigparent = SIGUSR1; 514 else 515 p2->p_sigparent = SIGCHLD; 516 517 /* bump references to the text vnode (for procfs) */ 518 p2->p_textvp = p1->p_textvp; 519 PROC_UNLOCK(p1); 520 PROC_UNLOCK(p2); 521 if (p2->p_textvp) 522 VREF(p2->p_textvp); 523 524 if (flags & RFCFDG) 525 fd = fdinit(td); 526 else if (flags & RFFDG) 527 fd = fdcopy(td); 528 else 529 fd = fdshare(p1); 530 PROC_LOCK(p2); 531 p2->p_fd = fd; 532 533 /* 534 * If p_limit is still copy-on-write, bump refcnt, 535 * otherwise get a copy that won't be modified. 536 * (If PL_SHAREMOD is clear, the structure is shared 537 * copy-on-write.) 538 */ 539 PROC_LOCK(p1); 540 if (p1->p_limit->p_lflags & PL_SHAREMOD) 541 p2->p_limit = limcopy(p1->p_limit); 542 else { 543 p2->p_limit = p1->p_limit; 544 p2->p_limit->p_refcnt++; 545 } 546 547 /* 548 * Preserve some more flags in subprocess. PS_PROFIL has already 549 * been preserved. 550 */ 551 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 552 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 553 p2->p_flag |= P_CONTROLT; 554 if (flags & RFPPWAIT) 555 p2->p_flag |= P_PPWAIT; 556 557 LIST_INSERT_AFTER(p1, p2, p_pglist); 558 PROC_UNLOCK(p1); 559 PROC_UNLOCK(p2); 560 561 /* 562 * Attach the new process to its parent. 563 * 564 * If RFNOWAIT is set, the newly created process becomes a child 565 * of init. This effectively disassociates the child from the 566 * parent. 567 */ 568 if (flags & RFNOWAIT) 569 pptr = initproc; 570 else 571 pptr = p1; 572 sx_xlock(&proctree_lock); 573 PROC_LOCK(p2); 574 p2->p_pptr = pptr; 575 PROC_UNLOCK(p2); 576 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 577 sx_xunlock(&proctree_lock); 578 PROC_LOCK(p2); 579 LIST_INIT(&p2->p_children); 580 LIST_INIT(&p2->p_thread.td_contested); /* XXXKSE only 1 thread? */ 581 582 callout_init(&p2->p_itcallout, 0); 583 callout_init(&p2->p_thread.td_slpcallout, 1); /* XXXKSE */ 584 585 PROC_LOCK(p1); 586 #ifdef KTRACE 587 /* 588 * Copy traceflag and tracefile if enabled. If not inherited, 589 * these were zeroed above but we still could have a trace race 590 * so make sure p2's p_tracep is NULL. 591 */ 592 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) { 593 p2->p_traceflag = p1->p_traceflag; 594 if ((p2->p_tracep = p1->p_tracep) != NULL) { 595 PROC_UNLOCK(p1); 596 PROC_UNLOCK(p2); 597 VREF(p2->p_tracep); 598 PROC_LOCK(p2); 599 PROC_LOCK(p1); 600 } 601 } 602 #endif 603 604 /* 605 * set priority of child to be that of parent 606 * XXXKSE hey! copying the estcpu seems dodgy.. should split it.. 607 */ 608 mtx_lock_spin(&sched_lock); 609 p2->p_ksegrp.kg_estcpu = p1->p_ksegrp.kg_estcpu; 610 mtx_unlock_spin(&sched_lock); 611 612 /* 613 * This begins the section where we must prevent the parent 614 * from being swapped. 615 */ 616 _PHOLD(p1); 617 PROC_UNLOCK(p1); 618 PROC_UNLOCK(p2); 619 620 /* 621 * Finish creating the child process. It will return via a different 622 * execution path later. (ie: directly into user mode) 623 */ 624 vm_forkproc(td, p2, flags); 625 626 if (flags == (RFFDG | RFPROC)) { 627 cnt.v_forks++; 628 cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 629 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 630 cnt.v_vforks++; 631 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 632 } else if (p1 == &proc0) { 633 cnt.v_kthreads++; 634 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 635 } else { 636 cnt.v_rforks++; 637 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 638 } 639 640 /* 641 * Both processes are set up, now check if any loadable modules want 642 * to adjust anything. 643 * What if they have an error? XXX 644 */ 645 sx_slock(&fork_list_lock); 646 TAILQ_FOREACH(ep, &fork_list, next) { 647 (*ep->function)(p1, p2, flags); 648 } 649 sx_sunlock(&fork_list_lock); 650 651 /* 652 * If RFSTOPPED not requested, make child runnable and add to 653 * run queue. 654 */ 655 microtime(&(p2->p_stats->p_start)); 656 p2->p_acflag = AFORK; 657 if ((flags & RFSTOPPED) == 0) { 658 mtx_lock_spin(&sched_lock); 659 p2->p_stat = SRUN; 660 setrunqueue(&p2->p_thread); 661 mtx_unlock_spin(&sched_lock); 662 } 663 664 /* 665 * Now can be swapped. 666 */ 667 PROC_LOCK(p1); 668 _PRELE(p1); 669 670 /* 671 * tell any interested parties about the new process 672 */ 673 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 674 PROC_UNLOCK(p1); 675 676 /* 677 * Preserve synchronization semantics of vfork. If waiting for 678 * child to exec or exit, set P_PPWAIT on child, and sleep on our 679 * proc (in case of exit). 680 */ 681 PROC_LOCK(p2); 682 while (p2->p_flag & P_PPWAIT) 683 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 684 PROC_UNLOCK(p2); 685 686 /* 687 * Return child proc pointer to parent. 688 */ 689 *procp = p2; 690 return (0); 691 } 692 693 /* 694 * The next two functionms are general routines to handle adding/deleting 695 * items on the fork callout list. 696 * 697 * at_fork(): 698 * Take the arguments given and put them onto the fork callout list, 699 * However first make sure that it's not already there. 700 * Returns 0 on success or a standard error number. 701 */ 702 703 int 704 at_fork(function) 705 forklist_fn function; 706 { 707 struct forklist *ep; 708 709 #ifdef INVARIANTS 710 /* let the programmer know if he's been stupid */ 711 if (rm_at_fork(function)) 712 printf("WARNING: fork callout entry (%p) already present\n", 713 function); 714 #endif 715 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); 716 if (ep == NULL) 717 return (ENOMEM); 718 ep->function = function; 719 sx_xlock(&fork_list_lock); 720 TAILQ_INSERT_TAIL(&fork_list, ep, next); 721 sx_xunlock(&fork_list_lock); 722 return (0); 723 } 724 725 /* 726 * Scan the exit callout list for the given item and remove it.. 727 * Returns the number of items removed (0 or 1) 728 */ 729 730 int 731 rm_at_fork(function) 732 forklist_fn function; 733 { 734 struct forklist *ep; 735 736 sx_xlock(&fork_list_lock); 737 TAILQ_FOREACH(ep, &fork_list, next) { 738 if (ep->function == function) { 739 TAILQ_REMOVE(&fork_list, ep, next); 740 sx_xunlock(&fork_list_lock); 741 free(ep, M_ATFORK); 742 return(1); 743 } 744 } 745 sx_xunlock(&fork_list_lock); 746 return (0); 747 } 748 749 /* 750 * Handle the return of a child process from fork1(). This function 751 * is called from the MD fork_trampoline() entry point. 752 */ 753 void 754 fork_exit(callout, arg, frame) 755 void (*callout)(void *, struct trapframe *); 756 void *arg; 757 struct trapframe *frame; 758 { 759 struct thread *td = curthread; 760 struct proc *p = td->td_proc; 761 762 td->td_kse->ke_oncpu = PCPU_GET(cpuid); 763 /* 764 * Setup the sched_lock state so that we can release it. 765 */ 766 sched_lock.mtx_lock = (uintptr_t)td; 767 sched_lock.mtx_recurse = 0; 768 td->td_critnest = 1; 769 td->td_savecrit = CRITICAL_FORK; 770 CTR3(KTR_PROC, "fork_exit: new proc %p (pid %d, %s)", p, p->p_pid, 771 p->p_comm); 772 if (PCPU_GET(switchtime.tv_sec) == 0) 773 microuptime(PCPU_PTR(switchtime)); 774 PCPU_SET(switchticks, ticks); 775 mtx_unlock_spin(&sched_lock); 776 777 /* 778 * cpu_set_fork_handler intercepts this function call to 779 * have this call a non-return function to stay in kernel mode. 780 * initproc has its own fork handler, but it does return. 781 */ 782 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 783 callout(arg, frame); 784 785 /* 786 * Check if a kernel thread misbehaved and returned from its main 787 * function. 788 */ 789 PROC_LOCK(p); 790 if (p->p_flag & P_KTHREAD) { 791 PROC_UNLOCK(p); 792 mtx_lock(&Giant); 793 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 794 p->p_comm, p->p_pid); 795 kthread_exit(0); 796 } 797 PROC_UNLOCK(p); 798 mtx_lock(&Giant); 799 crfree(td->td_ucred); 800 mtx_unlock(&Giant); 801 td->td_ucred = NULL; 802 mtx_assert(&Giant, MA_NOTOWNED); 803 } 804 805 /* 806 * Simplified back end of syscall(), used when returning from fork() 807 * directly into user mode. Giant is not held on entry, and must not 808 * be held on return. This function is passed in to fork_exit() as the 809 * first parameter and is called when returning to a new userland process. 810 */ 811 void 812 fork_return(td, frame) 813 struct thread *td; 814 struct trapframe *frame; 815 { 816 817 userret(td, frame, 0); 818 #ifdef KTRACE 819 if (KTRPOINT(td->td_proc, KTR_SYSRET)) { 820 ktrsysret(td->td_proc->p_tracep, SYS_fork, 0, 0); 821 } 822 #endif 823 mtx_assert(&Giant, MA_NOTOWNED); 824 } 825