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 /* mask kernel only flags out of the user flags */ 164 mtx_lock(&Giant); 165 error = fork1(td, uap->flags & ~RFKERNELONLY, &p2); 166 if (error == 0) { 167 td->td_retval[0] = p2 ? p2->p_pid : 0; 168 td->td_retval[1] = 0; 169 } 170 mtx_unlock(&Giant); 171 return error; 172 } 173 174 175 int nprocs = 1; /* process 0 */ 176 int lastpid = 0; 177 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 178 "Last used PID"); 179 180 /* 181 * Random component to lastpid generation. We mix in a random factor to make 182 * it a little harder to predict. We sanity check the modulus value to avoid 183 * doing it in critical paths. Don't let it be too small or we pointlessly 184 * waste randomness entropy, and don't let it be impossibly large. Using a 185 * modulus that is too big causes a LOT more process table scans and slows 186 * down fork processing as the pidchecked caching is defeated. 187 */ 188 static int randompid = 0; 189 190 static int 191 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 192 { 193 int error, pid; 194 195 pid = randompid; 196 error = sysctl_handle_int(oidp, &pid, 0, req); 197 if (error || !req->newptr) 198 return (error); 199 if (pid < 0 || pid > PID_MAX - 100) /* out of range */ 200 pid = PID_MAX - 100; 201 else if (pid < 2) /* NOP */ 202 pid = 0; 203 else if (pid < 100) /* Make it reasonable */ 204 pid = 100; 205 randompid = pid; 206 return (error); 207 } 208 209 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 210 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 211 212 #if 0 213 void 214 kse_init(struct kse *kse1, struct kse *kse2) 215 { 216 } 217 218 void 219 thread_init(struct thread *thread1, struct thread *thread2) 220 { 221 } 222 223 void 224 ksegrp_init(struct ksegrp *ksegrp1, struct ksegrp *ksegrp2) 225 { 226 } 227 #endif 228 229 int 230 fork1(td, flags, procp) 231 struct thread *td; /* parent proc */ 232 int flags; 233 struct proc **procp; /* child proc */ 234 { 235 struct proc *p2, *pptr; 236 uid_t uid; 237 struct proc *newproc; 238 int trypid; 239 int ok; 240 static int pidchecked = 0; 241 struct forklist *ep; 242 struct filedesc *fd; 243 struct proc *p1 = td->td_proc; 244 245 GIANT_REQUIRED; 246 247 /* Can't copy and clear */ 248 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 249 return (EINVAL); 250 251 /* 252 * Here we don't create a new process, but we divorce 253 * certain parts of a process from itself. 254 */ 255 if ((flags & RFPROC) == 0) { 256 vm_forkproc(td, 0, flags); 257 258 /* 259 * Close all file descriptors. 260 */ 261 if (flags & RFCFDG) { 262 struct filedesc *fdtmp; 263 fdtmp = fdinit(td); /* XXXKSE */ 264 PROC_LOCK(p1); 265 fdfree(td); /* XXXKSE */ 266 p1->p_fd = fdtmp; 267 PROC_UNLOCK(p1); 268 } 269 270 /* 271 * Unshare file descriptors (from parent.) 272 */ 273 if (flags & RFFDG) { 274 if (p1->p_fd->fd_refcnt > 1) { 275 struct filedesc *newfd; 276 newfd = fdcopy(td); 277 PROC_LOCK(p1); 278 fdfree(td); 279 p1->p_fd = newfd; 280 PROC_UNLOCK(p1); 281 } 282 } 283 *procp = NULL; 284 return (0); 285 } 286 287 /* 288 * Although process entries are dynamically created, we still keep 289 * a global limit on the maximum number we will create. Don't allow 290 * a nonprivileged user to use the last process; don't let root 291 * exceed the limit. The variable nprocs is the current number of 292 * processes, maxproc is the limit. 293 */ 294 uid = p1->p_ucred->cr_ruid; 295 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 296 tablefull("proc"); 297 return (EAGAIN); 298 } 299 /* 300 * Increment the nprocs resource before blocking can occur. There 301 * are hard-limits as to the number of processes that can run. 302 */ 303 nprocs++; 304 305 /* 306 * Increment the count of procs running with this uid. Don't allow 307 * a nonprivileged user to exceed their current limit. 308 */ 309 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1, 310 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 311 if (!ok) { 312 /* 313 * Back out the process count 314 */ 315 nprocs--; 316 return (EAGAIN); 317 } 318 319 /* Allocate new proc. */ 320 newproc = zalloc(proc_zone); 321 322 /* 323 * Setup linkage for kernel based threading 324 */ 325 if((flags & RFTHREAD) != 0) { 326 newproc->p_peers = p1->p_peers; 327 p1->p_peers = newproc; 328 newproc->p_leader = p1->p_leader; 329 } else { 330 newproc->p_peers = NULL; 331 newproc->p_leader = newproc; 332 } 333 334 newproc->p_vmspace = NULL; 335 336 /* 337 * Find an unused process ID. We remember a range of unused IDs 338 * ready to use (from lastpid+1 through pidchecked-1). 339 * 340 * If RFHIGHPID is set (used during system boot), do not allocate 341 * low-numbered pids. 342 */ 343 sx_xlock(&allproc_lock); 344 trypid = lastpid + 1; 345 if (flags & RFHIGHPID) { 346 if (trypid < 10) { 347 trypid = 10; 348 } 349 } else { 350 if (randompid) 351 trypid += arc4random() % randompid; 352 } 353 retry: 354 /* 355 * If the process ID prototype has wrapped around, 356 * restart somewhat above 0, as the low-numbered procs 357 * tend to include daemons that don't exit. 358 */ 359 if (trypid >= PID_MAX) { 360 trypid = trypid % PID_MAX; 361 if (trypid < 100) 362 trypid += 100; 363 pidchecked = 0; 364 } 365 if (trypid >= pidchecked) { 366 int doingzomb = 0; 367 368 pidchecked = PID_MAX; 369 /* 370 * Scan the active and zombie procs to check whether this pid 371 * is in use. Remember the lowest pid that's greater 372 * than trypid, so we can avoid checking for a while. 373 */ 374 p2 = LIST_FIRST(&allproc); 375 again: 376 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 377 while (p2->p_pid == trypid || 378 p2->p_pgrp->pg_id == trypid || 379 p2->p_session->s_sid == trypid) { 380 trypid++; 381 if (trypid >= pidchecked) 382 goto retry; 383 } 384 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 385 pidchecked = p2->p_pid; 386 if (p2->p_pgrp->pg_id > trypid && 387 pidchecked > p2->p_pgrp->pg_id) 388 pidchecked = p2->p_pgrp->pg_id; 389 if (p2->p_session->s_sid > trypid && 390 pidchecked > p2->p_session->s_sid) 391 pidchecked = p2->p_session->s_sid; 392 } 393 if (!doingzomb) { 394 doingzomb = 1; 395 p2 = LIST_FIRST(&zombproc); 396 goto again; 397 } 398 } 399 400 /* 401 * RFHIGHPID does not mess with the lastpid counter during boot. 402 */ 403 if (flags & RFHIGHPID) 404 pidchecked = 0; 405 else 406 lastpid = trypid; 407 408 p2 = newproc; 409 p2->p_stat = SIDL; /* protect against others */ 410 p2->p_pid = trypid; 411 LIST_INSERT_HEAD(&allproc, p2, p_list); 412 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 413 sx_xunlock(&allproc_lock); 414 415 /* 416 * Make a proc table entry for the new process. 417 * Start by zeroing the section of proc that is zero-initialized, 418 * then copy the section that is copied directly from the parent. 419 */ 420 bzero(&p2->p_startzero, 421 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 422 bzero(&p2->p_kse.ke_startzero, 423 (unsigned) ((caddr_t)&p2->p_kse.ke_endzero 424 - (caddr_t)&p2->p_kse.ke_startzero)); 425 bzero(&p2->p_thread.td_startzero, 426 (unsigned) ((caddr_t)&p2->p_thread.td_endzero 427 - (caddr_t)&p2->p_thread.td_startzero)); 428 bzero(&p2->p_ksegrp.kg_startzero, 429 (unsigned) ((caddr_t)&p2->p_ksegrp.kg_endzero 430 - (caddr_t)&p2->p_ksegrp.kg_startzero)); 431 PROC_LOCK(p1); 432 bcopy(&p1->p_startcopy, &p2->p_startcopy, 433 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 434 435 bcopy(&p1->p_kse.ke_startcopy, &p2->p_kse.ke_startcopy, 436 (unsigned) ((caddr_t)&p2->p_kse.ke_endcopy 437 - (caddr_t)&p2->p_kse.ke_startcopy)); 438 439 bcopy(&p1->p_thread.td_startcopy, &p2->p_thread.td_startcopy, 440 (unsigned) ((caddr_t)&p2->p_thread.td_endcopy 441 - (caddr_t)&p2->p_thread.td_startcopy)); 442 443 bcopy(&p1->p_ksegrp.kg_startcopy, &p2->p_ksegrp.kg_startcopy, 444 (unsigned) ((caddr_t)&p2->p_ksegrp.kg_endcopy 445 - (caddr_t)&p2->p_ksegrp.kg_startcopy)); 446 PROC_UNLOCK(p1); 447 448 /* 449 * XXXKSE Theoretically only the running thread would get copied 450 * Others in the kernel would be 'aborted' in the child. 451 * i.e return E*something* 452 */ 453 proc_linkup(p2); 454 455 mtx_init(&p2->p_mtx, "process lock", MTX_DEF); 456 PROC_LOCK(p2); 457 /* note.. XXXKSE no pcb or u-area yet */ 458 459 /* 460 * Duplicate sub-structures as needed. 461 * Increase reference counts on shared objects. 462 * The p_stats and p_sigacts substructs are set in vm_forkproc. 463 */ 464 p2->p_flag = 0; 465 mtx_lock_spin(&sched_lock); 466 p2->p_sflag = PS_INMEM; 467 if (p1->p_sflag & PS_PROFIL) 468 startprofclock(p2); 469 mtx_unlock_spin(&sched_lock); 470 /* 471 * We start off holding one spinlock after fork: sched_lock. 472 */ 473 PROC_LOCK(p1); 474 p2->p_ucred = crhold(p1->p_ucred); 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. 589 * If not inherited, these were zeroed above. 590 */ 591 if (p1->p_traceflag & KTRFAC_INHERIT) { 592 p2->p_traceflag = p1->p_traceflag; 593 if ((p2->p_tracep = p1->p_tracep) != NULL) { 594 PROC_UNLOCK(p1); 595 PROC_UNLOCK(p2); 596 VREF(p2->p_tracep); 597 PROC_LOCK(p2); 598 PROC_LOCK(p1); 599 } 600 } 601 #endif 602 603 /* 604 * set priority of child to be that of parent 605 * XXXKSE hey! copying the estcpu seems dodgy.. should split it.. 606 */ 607 mtx_lock_spin(&sched_lock); 608 p2->p_ksegrp.kg_estcpu = p1->p_ksegrp.kg_estcpu; 609 mtx_unlock_spin(&sched_lock); 610 611 /* 612 * This begins the section where we must prevent the parent 613 * from being swapped. 614 */ 615 _PHOLD(p1); 616 PROC_UNLOCK(p1); 617 PROC_UNLOCK(p2); 618 619 /* 620 * Finish creating the child process. It will return via a different 621 * execution path later. (ie: directly into user mode) 622 */ 623 vm_forkproc(td, p2, flags); 624 625 if (flags == (RFFDG | RFPROC)) { 626 cnt.v_forks++; 627 cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 628 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 629 cnt.v_vforks++; 630 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 631 } else if (p1 == &proc0) { 632 cnt.v_kthreads++; 633 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 634 } else { 635 cnt.v_rforks++; 636 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 637 } 638 639 /* 640 * Both processes are set up, now check if any loadable modules want 641 * to adjust anything. 642 * What if they have an error? XXX 643 */ 644 sx_slock(&fork_list_lock); 645 TAILQ_FOREACH(ep, &fork_list, next) { 646 (*ep->function)(p1, p2, flags); 647 } 648 sx_sunlock(&fork_list_lock); 649 650 /* 651 * If RFSTOPPED not requested, make child runnable and add to 652 * run queue. 653 */ 654 microtime(&(p2->p_stats->p_start)); 655 p2->p_acflag = AFORK; 656 if ((flags & RFSTOPPED) == 0) { 657 mtx_lock_spin(&sched_lock); 658 p2->p_stat = SRUN; 659 setrunqueue(&p2->p_thread); 660 mtx_unlock_spin(&sched_lock); 661 } 662 663 /* 664 * Now can be swapped. 665 */ 666 PROC_LOCK(p1); 667 _PRELE(p1); 668 669 /* 670 * tell any interested parties about the new process 671 */ 672 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 673 PROC_UNLOCK(p1); 674 675 /* 676 * Preserve synchronization semantics of vfork. If waiting for 677 * child to exec or exit, set P_PPWAIT on child, and sleep on our 678 * proc (in case of exit). 679 */ 680 PROC_LOCK(p2); 681 while (p2->p_flag & P_PPWAIT) 682 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 683 PROC_UNLOCK(p2); 684 685 /* 686 * Return child proc pointer to parent. 687 */ 688 *procp = p2; 689 return (0); 690 } 691 692 /* 693 * The next two functionms are general routines to handle adding/deleting 694 * items on the fork callout list. 695 * 696 * at_fork(): 697 * Take the arguments given and put them onto the fork callout list, 698 * However first make sure that it's not already there. 699 * Returns 0 on success or a standard error number. 700 */ 701 702 int 703 at_fork(function) 704 forklist_fn function; 705 { 706 struct forklist *ep; 707 708 #ifdef INVARIANTS 709 /* let the programmer know if he's been stupid */ 710 if (rm_at_fork(function)) 711 printf("WARNING: fork callout entry (%p) already present\n", 712 function); 713 #endif 714 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); 715 if (ep == NULL) 716 return (ENOMEM); 717 ep->function = function; 718 sx_xlock(&fork_list_lock); 719 TAILQ_INSERT_TAIL(&fork_list, ep, next); 720 sx_xunlock(&fork_list_lock); 721 return (0); 722 } 723 724 /* 725 * Scan the exit callout list for the given item and remove it.. 726 * Returns the number of items removed (0 or 1) 727 */ 728 729 int 730 rm_at_fork(function) 731 forklist_fn function; 732 { 733 struct forklist *ep; 734 735 sx_xlock(&fork_list_lock); 736 TAILQ_FOREACH(ep, &fork_list, next) { 737 if (ep->function == function) { 738 TAILQ_REMOVE(&fork_list, ep, next); 739 sx_xunlock(&fork_list_lock); 740 free(ep, M_ATFORK); 741 return(1); 742 } 743 } 744 sx_xunlock(&fork_list_lock); 745 return (0); 746 } 747 748 /* 749 * Handle the return of a child process from fork1(). This function 750 * is called from the MD fork_trampoline() entry point. 751 */ 752 void 753 fork_exit(callout, arg, frame) 754 void (*callout)(void *, struct trapframe *); 755 void *arg; 756 struct trapframe *frame; 757 { 758 struct thread *td = curthread; 759 struct proc *p = td->td_proc; 760 761 /* 762 * Setup the sched_lock state so that we can release it. 763 */ 764 sched_lock.mtx_lock = (uintptr_t)td; 765 sched_lock.mtx_recurse = 0; 766 /* 767 * XXX: We really shouldn't have to do this. 768 */ 769 mtx_intr_enable(&sched_lock); 770 mtx_unlock_spin(&sched_lock); 771 772 #ifdef SMP 773 if (PCPU_GET(switchtime.tv_sec) == 0) 774 microuptime(PCPU_PTR(switchtime)); 775 PCPU_SET(switchticks, ticks); 776 #endif 777 778 /* 779 * cpu_set_fork_handler intercepts this function call to 780 * have this call a non-return function to stay in kernel mode. 781 * initproc has its own fork handler, but it does return. 782 */ 783 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 784 callout(arg, frame); 785 786 /* 787 * Check if a kernel thread misbehaved and returned from its main 788 * function. 789 */ 790 PROC_LOCK(p); 791 if (p->p_flag & P_KTHREAD) { 792 PROC_UNLOCK(p); 793 mtx_lock(&Giant); 794 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 795 p->p_comm, p->p_pid); 796 kthread_exit(0); 797 } 798 PROC_UNLOCK(p); 799 mtx_assert(&Giant, MA_NOTOWNED); 800 } 801 802 /* 803 * Simplified back end of syscall(), used when returning from fork() 804 * directly into user mode. Giant is not held on entry, and must not 805 * be held on return. This function is passed in to fork_exit() as the 806 * first parameter and is called when returning to a new userland process. 807 */ 808 void 809 fork_return(td, frame) 810 struct thread *td; 811 struct trapframe *frame; 812 { 813 814 userret(td, frame, 0); 815 #ifdef KTRACE 816 if (KTRPOINT(td->td_proc, KTR_SYSRET)) { 817 ktrsysret(td->td_proc->p_tracep, SYS_fork, 0, 0); 818 } 819 #endif 820 mtx_assert(&Giant, MA_NOTOWNED); 821 } 822