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 /* ARGSUSED */ 109 int 110 fork(p, uap) 111 struct proc *p; 112 struct fork_args *uap; 113 { 114 int error; 115 struct proc *p2; 116 117 error = fork1(p, RFFDG | RFPROC, &p2); 118 if (error == 0) { 119 p->p_retval[0] = p2->p_pid; 120 p->p_retval[1] = 0; 121 } 122 return error; 123 } 124 125 /* ARGSUSED */ 126 int 127 vfork(p, uap) 128 struct proc *p; 129 struct vfork_args *uap; 130 { 131 int error; 132 struct proc *p2; 133 134 error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); 135 if (error == 0) { 136 p->p_retval[0] = p2->p_pid; 137 p->p_retval[1] = 0; 138 } 139 return error; 140 } 141 142 int 143 rfork(p, uap) 144 struct proc *p; 145 struct rfork_args *uap; 146 { 147 int error; 148 struct proc *p2; 149 150 /* mask kernel only flags out of the user flags */ 151 error = fork1(p, uap->flags & ~RFKERNELONLY, &p2); 152 if (error == 0) { 153 p->p_retval[0] = p2 ? p2->p_pid : 0; 154 p->p_retval[1] = 0; 155 } 156 return error; 157 } 158 159 160 int nprocs = 1; /* process 0 */ 161 int lastpid = 0; 162 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 163 "Last used PID"); 164 165 /* 166 * Random component to lastpid generation. We mix in a random factor to make 167 * it a little harder to predict. We sanity check the modulus value to avoid 168 * doing it in critical paths. Don't let it be too small or we pointlessly 169 * waste randomness entropy, and don't let it be impossibly large. Using a 170 * modulus that is too big causes a LOT more process table scans and slows 171 * down fork processing as the pidchecked caching is defeated. 172 */ 173 static int randompid = 0; 174 175 static int 176 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 177 { 178 int error, pid; 179 180 pid = randompid; 181 error = sysctl_handle_int(oidp, &pid, 0, req); 182 if (error || !req->newptr) 183 return (error); 184 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 185 pid = PID_MAX - 100; 186 else if (pid < 2) /* NOP */ 187 pid = 0; 188 else if (pid < 100) /* Make it reasonable */ 189 pid = 100; 190 randompid = pid; 191 return (error); 192 } 193 194 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 195 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 196 197 int 198 fork1(p1, flags, procp) 199 struct proc *p1; /* parent proc */ 200 int flags; 201 struct proc **procp; /* child proc */ 202 { 203 struct proc *p2, *pptr; 204 uid_t uid; 205 struct proc *newproc; 206 int trypid; 207 int ok; 208 static int pidchecked = 0; 209 struct forklist *ep; 210 struct filedesc *fd; 211 212 /* Can't copy and clear */ 213 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 214 return (EINVAL); 215 216 /* 217 * Here we don't create a new process, but we divorce 218 * certain parts of a process from itself. 219 */ 220 if ((flags & RFPROC) == 0) { 221 222 vm_fork(p1, 0, flags); 223 mtx_assert(&vm_mtx, MA_NOTOWNED); 224 225 /* 226 * Close all file descriptors. 227 */ 228 if (flags & RFCFDG) { 229 struct filedesc *fdtmp; 230 fdtmp = fdinit(p1); 231 PROC_LOCK(p1); 232 fdfree(p1); 233 p1->p_fd = fdtmp; 234 PROC_UNLOCK(p1); 235 } 236 237 /* 238 * Unshare file descriptors (from parent.) 239 */ 240 if (flags & RFFDG) { 241 if (p1->p_fd->fd_refcnt > 1) { 242 struct filedesc *newfd; 243 newfd = fdcopy(p1); 244 PROC_LOCK(p1); 245 fdfree(p1); 246 p1->p_fd = newfd; 247 PROC_UNLOCK(p1); 248 } 249 } 250 *procp = NULL; 251 return (0); 252 } 253 254 /* 255 * Although process entries are dynamically created, we still keep 256 * a global limit on the maximum number we will create. Don't allow 257 * a nonprivileged user to use the last process; don't let root 258 * exceed the limit. The variable nprocs is the current number of 259 * processes, maxproc is the limit. 260 */ 261 uid = p1->p_ucred->cr_ruid; 262 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 263 tablefull("proc"); 264 return (EAGAIN); 265 } 266 /* 267 * Increment the nprocs resource before blocking can occur. There 268 * are hard-limits as to the number of processes that can run. 269 */ 270 nprocs++; 271 272 /* 273 * Increment the count of procs running with this uid. Don't allow 274 * a nonprivileged user to exceed their current limit. 275 */ 276 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1, 277 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 278 if (!ok) { 279 /* 280 * Back out the process count 281 */ 282 nprocs--; 283 return (EAGAIN); 284 } 285 286 /* Allocate new proc. */ 287 newproc = zalloc(proc_zone); 288 289 /* 290 * Setup linkage for kernel based threading 291 */ 292 if((flags & RFTHREAD) != 0) { 293 newproc->p_peers = p1->p_peers; 294 p1->p_peers = newproc; 295 newproc->p_leader = p1->p_leader; 296 } else { 297 newproc->p_peers = NULL; 298 newproc->p_leader = newproc; 299 } 300 301 newproc->p_vmspace = NULL; 302 303 /* 304 * Find an unused process ID. We remember a range of unused IDs 305 * ready to use (from lastpid+1 through pidchecked-1). 306 * 307 * If RFHIGHPID is set (used during system boot), do not allocate 308 * low-numbered pids. 309 */ 310 sx_xlock(&allproc_lock); 311 trypid = lastpid + 1; 312 if (flags & RFHIGHPID) { 313 if (trypid < 10) { 314 trypid = 10; 315 } 316 } else { 317 if (randompid) 318 trypid += arc4random() % randompid; 319 } 320 retry: 321 /* 322 * If the process ID prototype has wrapped around, 323 * restart somewhat above 0, as the low-numbered procs 324 * tend to include daemons that don't exit. 325 */ 326 if (trypid >= PID_MAX) { 327 trypid = trypid % PID_MAX; 328 if (trypid < 100) 329 trypid += 100; 330 pidchecked = 0; 331 } 332 if (trypid >= pidchecked) { 333 int doingzomb = 0; 334 335 pidchecked = PID_MAX; 336 /* 337 * Scan the active and zombie procs to check whether this pid 338 * is in use. Remember the lowest pid that's greater 339 * than trypid, so we can avoid checking for a while. 340 */ 341 p2 = LIST_FIRST(&allproc); 342 again: 343 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 344 while (p2->p_pid == trypid || 345 p2->p_pgrp->pg_id == trypid || 346 p2->p_session->s_sid == trypid) { 347 trypid++; 348 if (trypid >= pidchecked) 349 goto retry; 350 } 351 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 352 pidchecked = p2->p_pid; 353 if (p2->p_pgrp->pg_id > trypid && 354 pidchecked > p2->p_pgrp->pg_id) 355 pidchecked = p2->p_pgrp->pg_id; 356 if (p2->p_session->s_sid > trypid && 357 pidchecked > p2->p_session->s_sid) 358 pidchecked = p2->p_session->s_sid; 359 } 360 if (!doingzomb) { 361 doingzomb = 1; 362 p2 = LIST_FIRST(&zombproc); 363 goto again; 364 } 365 } 366 367 /* 368 * RFHIGHPID does not mess with the lastpid counter during boot. 369 */ 370 if (flags & RFHIGHPID) 371 pidchecked = 0; 372 else 373 lastpid = trypid; 374 375 p2 = newproc; 376 p2->p_stat = SIDL; /* protect against others */ 377 p2->p_pid = trypid; 378 LIST_INSERT_HEAD(&allproc, p2, p_list); 379 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 380 sx_xunlock(&allproc_lock); 381 382 /* 383 * Make a proc table entry for the new process. 384 * Start by zeroing the section of proc that is zero-initialized, 385 * then copy the section that is copied directly from the parent. 386 */ 387 bzero(&p2->p_startzero, 388 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 389 PROC_LOCK(p1); 390 bcopy(&p1->p_startcopy, &p2->p_startcopy, 391 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 392 PROC_UNLOCK(p1); 393 394 mtx_init(&p2->p_mtx, "process lock", MTX_DEF); 395 PROC_LOCK(p2); 396 397 /* 398 * Duplicate sub-structures as needed. 399 * Increase reference counts on shared objects. 400 * The p_stats and p_sigacts substructs are set in vm_fork. 401 */ 402 p2->p_flag = 0; 403 mtx_lock_spin(&sched_lock); 404 p2->p_sflag = PS_INMEM; 405 if (p1->p_sflag & PS_PROFIL) 406 startprofclock(p2); 407 mtx_unlock_spin(&sched_lock); 408 /* 409 * We start off holding one spinlock after fork: sched_lock. 410 */ 411 PROC_LOCK(p1); 412 crhold(p1->p_ucred); 413 p2->p_ucred = p1->p_ucred; 414 415 if (p2->p_args) 416 p2->p_args->ar_ref++; 417 418 if (flags & RFSIGSHARE) { 419 p2->p_procsig = p1->p_procsig; 420 p2->p_procsig->ps_refcnt++; 421 if (p1->p_sigacts == &p1->p_addr->u_sigacts) { 422 struct sigacts *newsigacts; 423 424 PROC_UNLOCK(p1); 425 PROC_UNLOCK(p2); 426 /* Create the shared sigacts structure */ 427 MALLOC(newsigacts, struct sigacts *, 428 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 429 PROC_LOCK(p2); 430 PROC_LOCK(p1); 431 /* 432 * Set p_sigacts to the new shared structure. 433 * Note that this is updating p1->p_sigacts at the 434 * same time, since p_sigacts is just a pointer to 435 * the shared p_procsig->ps_sigacts. 436 */ 437 p2->p_sigacts = newsigacts; 438 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts, 439 sizeof(*p2->p_sigacts)); 440 *p2->p_sigacts = p1->p_addr->u_sigacts; 441 } 442 } else { 443 PROC_UNLOCK(p1); 444 PROC_UNLOCK(p2); 445 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), 446 M_SUBPROC, M_WAITOK); 447 PROC_LOCK(p2); 448 PROC_LOCK(p1); 449 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 450 p2->p_procsig->ps_refcnt = 1; 451 p2->p_sigacts = NULL; /* finished in vm_fork() */ 452 } 453 if (flags & RFLINUXTHPN) 454 p2->p_sigparent = SIGUSR1; 455 else 456 p2->p_sigparent = SIGCHLD; 457 458 /* bump references to the text vnode (for procfs) */ 459 p2->p_textvp = p1->p_textvp; 460 PROC_UNLOCK(p1); 461 PROC_UNLOCK(p2); 462 if (p2->p_textvp) 463 VREF(p2->p_textvp); 464 465 if (flags & RFCFDG) 466 fd = fdinit(p1); 467 else if (flags & RFFDG) 468 fd = fdcopy(p1); 469 else 470 fd = fdshare(p1); 471 PROC_LOCK(p2); 472 p2->p_fd = fd; 473 474 /* 475 * If p_limit is still copy-on-write, bump refcnt, 476 * otherwise get a copy that won't be modified. 477 * (If PL_SHAREMOD is clear, the structure is shared 478 * copy-on-write.) 479 */ 480 PROC_LOCK(p1); 481 if (p1->p_limit->p_lflags & PL_SHAREMOD) 482 p2->p_limit = limcopy(p1->p_limit); 483 else { 484 p2->p_limit = p1->p_limit; 485 p2->p_limit->p_refcnt++; 486 } 487 488 /* 489 * Preserve some more flags in subprocess. PS_PROFIL has already 490 * been preserved. 491 */ 492 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 493 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 494 p2->p_flag |= P_CONTROLT; 495 if (flags & RFPPWAIT) 496 p2->p_flag |= P_PPWAIT; 497 498 LIST_INSERT_AFTER(p1, p2, p_pglist); 499 PROC_UNLOCK(p1); 500 PROC_UNLOCK(p2); 501 502 /* 503 * Attach the new process to its parent. 504 * 505 * If RFNOWAIT is set, the newly created process becomes a child 506 * of init. This effectively disassociates the child from the 507 * parent. 508 */ 509 if (flags & RFNOWAIT) 510 pptr = initproc; 511 else 512 pptr = p1; 513 sx_xlock(&proctree_lock); 514 PROC_LOCK(p2); 515 p2->p_pptr = pptr; 516 PROC_UNLOCK(p2); 517 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 518 sx_xunlock(&proctree_lock); 519 PROC_LOCK(p2); 520 LIST_INIT(&p2->p_children); 521 LIST_INIT(&p2->p_contested); 522 523 callout_init(&p2->p_itcallout, 0); 524 callout_init(&p2->p_slpcallout, 1); 525 526 PROC_LOCK(p1); 527 #ifdef KTRACE 528 /* 529 * Copy traceflag and tracefile if enabled. 530 * If not inherited, these were zeroed above. 531 */ 532 if (p1->p_traceflag & KTRFAC_INHERIT) { 533 p2->p_traceflag = p1->p_traceflag; 534 if ((p2->p_tracep = p1->p_tracep) != NULL) { 535 PROC_UNLOCK(p1); 536 PROC_UNLOCK(p2); 537 VREF(p2->p_tracep); 538 PROC_LOCK(p2); 539 PROC_LOCK(p1); 540 } 541 } 542 #endif 543 544 /* 545 * set priority of child to be that of parent 546 */ 547 mtx_lock_spin(&sched_lock); 548 p2->p_estcpu = p1->p_estcpu; 549 mtx_unlock_spin(&sched_lock); 550 551 /* 552 * This begins the section where we must prevent the parent 553 * from being swapped. 554 */ 555 _PHOLD(p1); 556 PROC_UNLOCK(p1); 557 PROC_UNLOCK(p2); 558 559 /* 560 * Finish creating the child process. It will return via a different 561 * execution path later. (ie: directly into user mode) 562 */ 563 vm_fork(p1, p2, flags); 564 mtx_assert(&vm_mtx, MA_NOTOWNED); 565 566 if (flags == (RFFDG | RFPROC)) { 567 cnt.v_forks++; 568 cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 569 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 570 cnt.v_vforks++; 571 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 572 } else if (p1 == &proc0) { 573 cnt.v_kthreads++; 574 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 575 } else { 576 cnt.v_rforks++; 577 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 578 } 579 580 /* 581 * Both processes are set up, now check if any loadable modules want 582 * to adjust anything. 583 * What if they have an error? XXX 584 */ 585 sx_slock(&fork_list_lock); 586 TAILQ_FOREACH(ep, &fork_list, next) { 587 (*ep->function)(p1, p2, flags); 588 } 589 sx_sunlock(&fork_list_lock); 590 591 /* 592 * If RFSTOPPED not requested, make child runnable and add to 593 * run queue. 594 */ 595 microtime(&(p2->p_stats->p_start)); 596 p2->p_acflag = AFORK; 597 if ((flags & RFSTOPPED) == 0) { 598 mtx_lock_spin(&sched_lock); 599 p2->p_stat = SRUN; 600 setrunqueue(p2); 601 mtx_unlock_spin(&sched_lock); 602 } 603 604 /* 605 * Now can be swapped. 606 */ 607 PROC_LOCK(p1); 608 _PRELE(p1); 609 610 /* 611 * tell any interested parties about the new process 612 */ 613 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 614 PROC_UNLOCK(p1); 615 616 /* 617 * Preserve synchronization semantics of vfork. If waiting for 618 * child to exec or exit, set P_PPWAIT on child, and sleep on our 619 * proc (in case of exit). 620 */ 621 PROC_LOCK(p2); 622 while (p2->p_flag & P_PPWAIT) 623 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 624 PROC_UNLOCK(p2); 625 626 /* 627 * Return child proc pointer to parent. 628 */ 629 *procp = p2; 630 return (0); 631 } 632 633 /* 634 * The next two functionms are general routines to handle adding/deleting 635 * items on the fork callout list. 636 * 637 * at_fork(): 638 * Take the arguments given and put them onto the fork callout list, 639 * However first make sure that it's not already there. 640 * Returns 0 on success or a standard error number. 641 */ 642 643 int 644 at_fork(function) 645 forklist_fn function; 646 { 647 struct forklist *ep; 648 649 #ifdef INVARIANTS 650 /* let the programmer know if he's been stupid */ 651 if (rm_at_fork(function)) 652 printf("WARNING: fork callout entry (%p) already present\n", 653 function); 654 #endif 655 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); 656 if (ep == NULL) 657 return (ENOMEM); 658 ep->function = function; 659 sx_xlock(&fork_list_lock); 660 TAILQ_INSERT_TAIL(&fork_list, ep, next); 661 sx_xunlock(&fork_list_lock); 662 return (0); 663 } 664 665 /* 666 * Scan the exit callout list for the given item and remove it.. 667 * Returns the number of items removed (0 or 1) 668 */ 669 670 int 671 rm_at_fork(function) 672 forklist_fn function; 673 { 674 struct forklist *ep; 675 676 sx_xlock(&fork_list_lock); 677 TAILQ_FOREACH(ep, &fork_list, next) { 678 if (ep->function == function) { 679 TAILQ_REMOVE(&fork_list, ep, next); 680 sx_xunlock(&fork_list_lock); 681 free(ep, M_ATFORK); 682 return(1); 683 } 684 } 685 sx_xunlock(&fork_list_lock); 686 return (0); 687 } 688 689 /* 690 * Handle the return of a child process from fork1(). This function 691 * is called from the MD fork_trampoline() entry point. 692 */ 693 void 694 fork_exit(callout, arg, frame) 695 void (*callout)(void *, struct trapframe *); 696 void *arg; 697 struct trapframe *frame; 698 { 699 struct proc *p; 700 701 p = curproc; 702 703 /* 704 * Setup the sched_lock state so that we can release it. 705 */ 706 sched_lock.mtx_lock = (uintptr_t)p; 707 sched_lock.mtx_recurse = 0; 708 /* 709 * XXX: We really shouldn't have to do this. 710 */ 711 mtx_intr_enable(&sched_lock); 712 mtx_unlock_spin(&sched_lock); 713 714 #ifdef SMP 715 if (PCPU_GET(switchtime.tv_sec) == 0) 716 microuptime(PCPU_PTR(switchtime)); 717 PCPU_SET(switchticks, ticks); 718 #endif 719 720 /* 721 * cpu_set_fork_handler intercepts this function call to 722 * have this call a non-return function to stay in kernel mode. 723 * initproc has its own fork handler, but it does return. 724 */ 725 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 726 callout(arg, frame); 727 728 /* 729 * Check if a kernel thread misbehaved and returned from its main 730 * function. 731 */ 732 PROC_LOCK(p); 733 if (p->p_flag & P_KTHREAD) { 734 PROC_UNLOCK(p); 735 mtx_lock(&Giant); 736 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 737 p->p_comm, p->p_pid); 738 kthread_exit(0); 739 } 740 PROC_UNLOCK(p); 741 mtx_assert(&Giant, MA_NOTOWNED); 742 } 743 744 /* 745 * Simplified back end of syscall(), used when returning from fork() 746 * directly into user mode. Giant is not held on entry, and must not 747 * be held on return. This function is passed in to fork_exit() as the 748 * first parameter and is called when returning to a new userland process. 749 */ 750 void 751 fork_return(p, frame) 752 struct proc *p; 753 struct trapframe *frame; 754 { 755 756 userret(p, frame, 0); 757 #ifdef KTRACE 758 if (KTRPOINT(p, KTR_SYSRET)) { 759 if (!mtx_owned(&Giant)) 760 mtx_lock(&Giant); 761 ktrsysret(p->p_tracep, SYS_fork, 0, 0); 762 } 763 #endif 764 if (mtx_owned(&Giant)) 765 mtx_unlock(&Giant); 766 mtx_assert(&Giant, MA_NOTOWNED); 767 } 768