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/uma.h> 70 71 #include <sys/vmmeter.h> 72 #include <sys/user.h> 73 #include <machine/critical.h> 74 75 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback"); 76 77 /* 78 * These are the stuctures used to create a callout list for things to do 79 * when forking a process 80 */ 81 struct forklist { 82 forklist_fn function; 83 TAILQ_ENTRY(forklist) next; 84 }; 85 86 static struct sx fork_list_lock; 87 88 TAILQ_HEAD(forklist_head, forklist); 89 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list); 90 91 #ifndef _SYS_SYSPROTO_H_ 92 struct fork_args { 93 int dummy; 94 }; 95 #endif 96 97 int forksleep; /* Place for fork1() to sleep on. */ 98 99 static void 100 init_fork_list(void *data __unused) 101 { 102 103 sx_init(&fork_list_lock, "fork list"); 104 } 105 SYSINIT(fork_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_fork_list, NULL); 106 107 /* 108 * MPSAFE 109 */ 110 /* ARGSUSED */ 111 int 112 fork(td, uap) 113 struct thread *td; 114 struct fork_args *uap; 115 { 116 int error; 117 struct proc *p2; 118 119 mtx_lock(&Giant); 120 error = fork1(td, RFFDG | RFPROC, &p2); 121 if (error == 0) { 122 td->td_retval[0] = p2->p_pid; 123 td->td_retval[1] = 0; 124 } 125 mtx_unlock(&Giant); 126 return error; 127 } 128 129 /* 130 * MPSAFE 131 */ 132 /* ARGSUSED */ 133 int 134 vfork(td, uap) 135 struct thread *td; 136 struct vfork_args *uap; 137 { 138 int error; 139 struct proc *p2; 140 141 mtx_lock(&Giant); 142 error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); 143 if (error == 0) { 144 td->td_retval[0] = p2->p_pid; 145 td->td_retval[1] = 0; 146 } 147 mtx_unlock(&Giant); 148 return error; 149 } 150 151 /* 152 * MPSAFE 153 */ 154 int 155 rfork(td, uap) 156 struct thread *td; 157 struct rfork_args *uap; 158 { 159 int error; 160 struct proc *p2; 161 162 /* Don't allow kernel only flags. */ 163 if ((uap->flags & RFKERNELONLY) != 0) 164 return (EINVAL); 165 mtx_lock(&Giant); 166 error = fork1(td, uap->flags, &p2); 167 if (error == 0) { 168 td->td_retval[0] = p2 ? p2->p_pid : 0; 169 td->td_retval[1] = 0; 170 } 171 mtx_unlock(&Giant); 172 return error; 173 } 174 175 176 int nprocs = 1; /* process 0 */ 177 int lastpid = 0; 178 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 179 "Last used PID"); 180 181 /* 182 * Random component to lastpid generation. We mix in a random factor to make 183 * it a little harder to predict. We sanity check the modulus value to avoid 184 * doing it in critical paths. Don't let it be too small or we pointlessly 185 * waste randomness entropy, and don't let it be impossibly large. Using a 186 * modulus that is too big causes a LOT more process table scans and slows 187 * down fork processing as the pidchecked caching is defeated. 188 */ 189 static int randompid = 0; 190 191 static int 192 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS) 193 { 194 int error, pid; 195 196 pid = randompid; 197 error = sysctl_handle_int(oidp, &pid, 0, req); 198 if (error || !req->newptr) 199 return (error); 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 return (error); 208 } 209 210 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW, 211 0, 0, sysctl_kern_randompid, "I", "Random PID modulus"); 212 213 #if 0 214 void 215 kse_init(struct kse *kse1, struct kse *kse2) 216 { 217 } 218 219 void 220 thread_init(struct thread *thread1, struct thread *thread2) 221 { 222 } 223 224 void 225 ksegrp_init(struct ksegrp *ksegrp1, struct ksegrp *ksegrp2) 226 { 227 } 228 #endif 229 230 int 231 fork1(td, flags, procp) 232 struct thread *td; /* parent proc */ 233 int flags; 234 struct proc **procp; /* child proc */ 235 { 236 struct proc *p2, *pptr; 237 uid_t uid; 238 struct proc *newproc; 239 int trypid; 240 int ok; 241 static int pidchecked = 0; 242 struct forklist *ep; 243 struct filedesc *fd; 244 struct proc *p1 = td->td_proc; 245 struct thread *td2; 246 struct kse *ke2; 247 struct ksegrp *kg2; 248 249 GIANT_REQUIRED; 250 251 /* Can't copy and clear */ 252 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 253 return (EINVAL); 254 255 /* 256 * Here we don't create a new process, but we divorce 257 * certain parts of a process from itself. 258 */ 259 if ((flags & RFPROC) == 0) { 260 vm_forkproc(td, NULL, NULL, flags); 261 262 /* 263 * Close all file descriptors. 264 */ 265 if (flags & RFCFDG) { 266 struct filedesc *fdtmp; 267 fdtmp = fdinit(td); /* XXXKSE */ 268 PROC_LOCK(p1); 269 fdfree(td); /* XXXKSE */ 270 p1->p_fd = fdtmp; 271 PROC_UNLOCK(p1); 272 } 273 274 /* 275 * Unshare file descriptors (from parent.) 276 */ 277 if (flags & RFFDG) { 278 FILEDESC_LOCK(p1->p_fd); 279 if (p1->p_fd->fd_refcnt > 1) { 280 struct filedesc *newfd; 281 282 newfd = fdcopy(td); 283 FILEDESC_UNLOCK(p1->p_fd); 284 PROC_LOCK(p1); 285 fdfree(td); 286 p1->p_fd = newfd; 287 PROC_UNLOCK(p1); 288 } else 289 FILEDESC_UNLOCK(p1->p_fd); 290 } 291 *procp = NULL; 292 return (0); 293 } 294 295 /* 296 * Although process entries are dynamically created, we still keep 297 * a global limit on the maximum number we will create. Don't allow 298 * a nonprivileged user to use the last process; don't let root 299 * exceed the limit. The variable nprocs is the current number of 300 * processes, maxproc is the limit. 301 */ 302 uid = p1->p_ucred->cr_ruid; 303 if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { 304 tsleep(&forksleep, PUSER, "fork", hz / 2); 305 return (EAGAIN); 306 } 307 /* 308 * Increment the nprocs resource before blocking can occur. There 309 * are hard-limits as to the number of processes that can run. 310 */ 311 nprocs++; 312 313 /* 314 * Increment the count of procs running with this uid. Don't allow 315 * a nonprivileged user to exceed their current limit. 316 */ 317 ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1, 318 (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0); 319 if (!ok) { 320 /* 321 * Back out the process count 322 */ 323 nprocs--; 324 tsleep(&forksleep, PUSER, "fork", hz / 2); 325 return (EAGAIN); 326 } 327 328 /* Allocate new proc. */ 329 newproc = uma_zalloc(proc_zone, M_WAITOK); 330 331 /* 332 * Setup linkage for kernel based threading 333 */ 334 if((flags & RFTHREAD) != 0) { 335 newproc->p_peers = p1->p_peers; 336 p1->p_peers = newproc; 337 newproc->p_leader = p1->p_leader; 338 } else { 339 newproc->p_peers = NULL; 340 newproc->p_leader = newproc; 341 } 342 343 newproc->p_vmspace = NULL; 344 345 /* 346 * Find an unused process ID. We remember a range of unused IDs 347 * ready to use (from lastpid+1 through pidchecked-1). 348 * 349 * If RFHIGHPID is set (used during system boot), do not allocate 350 * low-numbered pids. 351 */ 352 sx_xlock(&allproc_lock); 353 trypid = lastpid + 1; 354 if (flags & RFHIGHPID) { 355 if (trypid < 10) { 356 trypid = 10; 357 } 358 } else { 359 if (randompid) 360 trypid += arc4random() % randompid; 361 } 362 retry: 363 /* 364 * If the process ID prototype has wrapped around, 365 * restart somewhat above 0, as the low-numbered procs 366 * tend to include daemons that don't exit. 367 */ 368 if (trypid >= PID_MAX) { 369 trypid = trypid % PID_MAX; 370 if (trypid < 100) 371 trypid += 100; 372 pidchecked = 0; 373 } 374 if (trypid >= pidchecked) { 375 int doingzomb = 0; 376 377 pidchecked = PID_MAX; 378 /* 379 * Scan the active and zombie procs to check whether this pid 380 * is in use. Remember the lowest pid that's greater 381 * than trypid, so we can avoid checking for a while. 382 */ 383 p2 = LIST_FIRST(&allproc); 384 again: 385 for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) { 386 PROC_LOCK(p2); 387 while (p2->p_pid == trypid || 388 p2->p_pgrp->pg_id == trypid || 389 p2->p_session->s_sid == trypid) { 390 trypid++; 391 if (trypid >= pidchecked) { 392 PROC_UNLOCK(p2); 393 goto retry; 394 } 395 } 396 if (p2->p_pid > trypid && pidchecked > p2->p_pid) 397 pidchecked = p2->p_pid; 398 if (p2->p_pgrp->pg_id > trypid && 399 pidchecked > p2->p_pgrp->pg_id) 400 pidchecked = p2->p_pgrp->pg_id; 401 if (p2->p_session->s_sid > trypid && 402 pidchecked > p2->p_session->s_sid) 403 pidchecked = p2->p_session->s_sid; 404 PROC_UNLOCK(p2); 405 } 406 if (!doingzomb) { 407 doingzomb = 1; 408 p2 = LIST_FIRST(&zombproc); 409 goto again; 410 } 411 } 412 413 /* 414 * RFHIGHPID does not mess with the lastpid counter during boot. 415 */ 416 if (flags & RFHIGHPID) 417 pidchecked = 0; 418 else 419 lastpid = trypid; 420 421 p2 = newproc; 422 p2->p_stat = SIDL; /* protect against others */ 423 p2->p_pid = trypid; 424 LIST_INSERT_HEAD(&allproc, p2, p_list); 425 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 426 sx_xunlock(&allproc_lock); 427 428 /* 429 * Make a proc table entry for the new process. 430 * Start by zeroing the section of proc that is zero-initialized, 431 * then copy the section that is copied directly from the parent. 432 */ 433 td2 = thread_get(p2); 434 ke2 = &p2->p_kse; 435 kg2 = &p2->p_ksegrp; 436 437 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 438 439 bzero(&p2->p_startzero, 440 (unsigned) RANGEOF(struct proc, p_startzero, p_endzero)); 441 bzero(&ke2->ke_startzero, 442 (unsigned) RANGEOF(struct kse, ke_startzero, ke_endzero)); 443 bzero(&td2->td_startzero, 444 (unsigned) RANGEOF(struct thread, td_startzero, td_endzero)); 445 bzero(&kg2->kg_startzero, 446 (unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero)); 447 448 PROC_LOCK(p1); 449 bcopy(&p1->p_startcopy, &p2->p_startcopy, 450 (unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy)); 451 bcopy(&td->td_kse->ke_startcopy, &ke2->ke_startcopy, 452 (unsigned) RANGEOF(struct kse, ke_startcopy, ke_endcopy)); 453 bcopy(&td->td_startcopy, &td2->td_startcopy, 454 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 455 bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy, 456 (unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy)); 457 #undef RANGEOF 458 PROC_UNLOCK(p1); 459 460 /* 461 * XXXKSE Theoretically only the running thread would get copied 462 * Others in the kernel would be 'aborted' in the child. 463 * i.e return E*something* 464 */ 465 proc_linkup(p2, kg2, ke2, td2); 466 467 mtx_init(&p2->p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK); 468 PROC_LOCK(p2); 469 /* note.. XXXKSE no pcb or u-area yet */ 470 471 /* 472 * Duplicate sub-structures as needed. 473 * Increase reference counts on shared objects. 474 * The p_stats and p_sigacts substructs are set in vm_forkproc. 475 */ 476 p2->p_flag = 0; 477 mtx_lock_spin(&sched_lock); 478 p2->p_sflag = PS_INMEM; 479 if (p1->p_sflag & PS_PROFIL) 480 startprofclock(p2); 481 mtx_unlock_spin(&sched_lock); 482 PROC_LOCK(p1); 483 p2->p_ucred = crhold(p1->p_ucred); 484 td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */ 485 486 pargs_hold(p2->p_args); 487 488 if (flags & RFSIGSHARE) { 489 p2->p_procsig = p1->p_procsig; 490 p2->p_procsig->ps_refcnt++; 491 if (p1->p_sigacts == &p1->p_uarea->u_sigacts) { 492 struct sigacts *newsigacts; 493 494 PROC_UNLOCK(p1); 495 PROC_UNLOCK(p2); 496 /* Create the shared sigacts structure */ 497 MALLOC(newsigacts, struct sigacts *, 498 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 499 PROC_LOCK(p2); 500 PROC_LOCK(p1); 501 /* 502 * Set p_sigacts to the new shared structure. 503 * Note that this is updating p1->p_sigacts at the 504 * same time, since p_sigacts is just a pointer to 505 * the shared p_procsig->ps_sigacts. 506 */ 507 p2->p_sigacts = newsigacts; 508 *p2->p_sigacts = p1->p_uarea->u_sigacts; 509 } 510 } else { 511 PROC_UNLOCK(p1); 512 PROC_UNLOCK(p2); 513 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), 514 M_SUBPROC, M_WAITOK); 515 PROC_LOCK(p2); 516 PROC_LOCK(p1); 517 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 518 p2->p_procsig->ps_refcnt = 1; 519 p2->p_sigacts = NULL; /* finished in vm_forkproc() */ 520 } 521 if (flags & RFLINUXTHPN) 522 p2->p_sigparent = SIGUSR1; 523 else 524 p2->p_sigparent = SIGCHLD; 525 526 /* bump references to the text vnode (for procfs) */ 527 p2->p_textvp = p1->p_textvp; 528 PROC_UNLOCK(p1); 529 PROC_UNLOCK(p2); 530 if (p2->p_textvp) 531 VREF(p2->p_textvp); 532 533 if (flags & RFCFDG) 534 fd = fdinit(td); 535 else if (flags & RFFDG) { 536 FILEDESC_LOCK(p1->p_fd); 537 fd = fdcopy(td); 538 FILEDESC_UNLOCK(p1->p_fd); 539 } else 540 fd = fdshare(p1); 541 sx_xlock(&proctree_lock); 542 PGRP_LOCK(p1->p_pgrp); 543 PROC_LOCK(p2); 544 p2->p_fd = fd; 545 546 /* 547 * If p_limit is still copy-on-write, bump refcnt, 548 * otherwise get a copy that won't be modified. 549 * (If PL_SHAREMOD is clear, the structure is shared 550 * copy-on-write.) 551 */ 552 PROC_LOCK(p1); 553 if (p1->p_limit->p_lflags & PL_SHAREMOD) 554 p2->p_limit = limcopy(p1->p_limit); 555 else { 556 p2->p_limit = p1->p_limit; 557 p2->p_limit->p_refcnt++; 558 } 559 560 /* 561 * Preserve some more flags in subprocess. PS_PROFIL has already 562 * been preserved. 563 */ 564 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 565 SESS_LOCK(p1->p_session); 566 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 567 p2->p_flag |= P_CONTROLT; 568 SESS_UNLOCK(p1->p_session); 569 if (flags & RFPPWAIT) 570 p2->p_flag |= P_PPWAIT; 571 572 LIST_INSERT_AFTER(p1, p2, p_pglist); 573 PROC_UNLOCK(p1); 574 PROC_UNLOCK(p2); 575 PGRP_UNLOCK(p1->p_pgrp); 576 sx_xunlock(&proctree_lock); 577 578 /* 579 * Attach the new process to its parent. 580 * 581 * If RFNOWAIT is set, the newly created process becomes a child 582 * of init. This effectively disassociates the child from the 583 * parent. 584 */ 585 if (flags & RFNOWAIT) 586 pptr = initproc; 587 else 588 pptr = p1; 589 sx_xlock(&proctree_lock); 590 PROC_LOCK(p2); 591 p2->p_pptr = pptr; 592 PROC_UNLOCK(p2); 593 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 594 sx_xunlock(&proctree_lock); 595 PROC_LOCK(p2); 596 LIST_INIT(&p2->p_children); 597 LIST_INIT(&td2->td_contested); /* XXXKSE only 1 thread? */ 598 599 callout_init(&p2->p_itcallout, 0); 600 callout_init(&td2->td_slpcallout, 1); /* XXXKSE */ 601 602 PROC_LOCK(p1); 603 #ifdef KTRACE 604 /* 605 * Copy traceflag and tracefile if enabled. If not inherited, 606 * these were zeroed above but we still could have a trace race 607 * so make sure p2's p_tracep is NULL. 608 */ 609 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) { 610 p2->p_traceflag = p1->p_traceflag; 611 if ((p2->p_tracep = p1->p_tracep) != NULL) { 612 PROC_UNLOCK(p1); 613 PROC_UNLOCK(p2); 614 VREF(p2->p_tracep); 615 PROC_LOCK(p2); 616 PROC_LOCK(p1); 617 } 618 } 619 #endif 620 621 /* 622 * set priority of child to be that of parent 623 * XXXKSE hey! copying the estcpu seems dodgy.. should split it.. 624 */ 625 mtx_lock_spin(&sched_lock); 626 p2->p_ksegrp.kg_estcpu = p1->p_ksegrp.kg_estcpu; 627 mtx_unlock_spin(&sched_lock); 628 629 /* 630 * This begins the section where we must prevent the parent 631 * from being swapped. 632 */ 633 _PHOLD(p1); 634 PROC_UNLOCK(p1); 635 PROC_UNLOCK(p2); 636 637 /* 638 * Finish creating the child process. It will return via a different 639 * execution path later. (ie: directly into user mode) 640 */ 641 vm_forkproc(td, p2, td2, flags); 642 643 if (flags == (RFFDG | RFPROC)) { 644 cnt.v_forks++; 645 cnt.v_forkpages += p2->p_vmspace->vm_dsize + 646 p2->p_vmspace->vm_ssize; 647 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 648 cnt.v_vforks++; 649 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + 650 p2->p_vmspace->vm_ssize; 651 } else if (p1 == &proc0) { 652 cnt.v_kthreads++; 653 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + 654 p2->p_vmspace->vm_ssize; 655 } else { 656 cnt.v_rforks++; 657 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + 658 p2->p_vmspace->vm_ssize; 659 } 660 661 /* 662 * Both processes are set up, now check if any loadable modules want 663 * to adjust anything. 664 * What if they have an error? XXX 665 */ 666 sx_slock(&fork_list_lock); 667 TAILQ_FOREACH(ep, &fork_list, next) { 668 (*ep->function)(p1, p2, flags); 669 } 670 sx_sunlock(&fork_list_lock); 671 672 /* 673 * If RFSTOPPED not requested, make child runnable and add to 674 * run queue. 675 */ 676 microtime(&(p2->p_stats->p_start)); 677 p2->p_acflag = AFORK; 678 if ((flags & RFSTOPPED) == 0) { 679 mtx_lock_spin(&sched_lock); 680 p2->p_stat = SRUN; 681 setrunqueue(td2); 682 mtx_unlock_spin(&sched_lock); 683 } 684 685 /* 686 * Now can be swapped. 687 */ 688 PROC_LOCK(p1); 689 _PRELE(p1); 690 691 /* 692 * tell any interested parties about the new process 693 */ 694 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 695 PROC_UNLOCK(p1); 696 697 /* 698 * Preserve synchronization semantics of vfork. If waiting for 699 * child to exec or exit, set P_PPWAIT on child, and sleep on our 700 * proc (in case of exit). 701 */ 702 PROC_LOCK(p2); 703 while (p2->p_flag & P_PPWAIT) 704 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 705 PROC_UNLOCK(p2); 706 707 /* 708 * Return child proc pointer to parent. 709 */ 710 *procp = p2; 711 return (0); 712 } 713 714 /* 715 * The next two functionms are general routines to handle adding/deleting 716 * items on the fork callout list. 717 * 718 * at_fork(): 719 * Take the arguments given and put them onto the fork callout list, 720 * However first make sure that it's not already there. 721 * Returns 0 on success or a standard error number. 722 */ 723 724 int 725 at_fork(function) 726 forklist_fn function; 727 { 728 struct forklist *ep; 729 730 #ifdef INVARIANTS 731 /* let the programmer know if he's been stupid */ 732 if (rm_at_fork(function)) 733 printf("WARNING: fork callout entry (%p) already present\n", 734 function); 735 #endif 736 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); 737 if (ep == NULL) 738 return (ENOMEM); 739 ep->function = function; 740 sx_xlock(&fork_list_lock); 741 TAILQ_INSERT_TAIL(&fork_list, ep, next); 742 sx_xunlock(&fork_list_lock); 743 return (0); 744 } 745 746 /* 747 * Scan the exit callout list for the given item and remove it.. 748 * Returns the number of items removed (0 or 1) 749 */ 750 751 int 752 rm_at_fork(function) 753 forklist_fn function; 754 { 755 struct forklist *ep; 756 757 sx_xlock(&fork_list_lock); 758 TAILQ_FOREACH(ep, &fork_list, next) { 759 if (ep->function == function) { 760 TAILQ_REMOVE(&fork_list, ep, next); 761 sx_xunlock(&fork_list_lock); 762 free(ep, M_ATFORK); 763 return(1); 764 } 765 } 766 sx_xunlock(&fork_list_lock); 767 return (0); 768 } 769 770 /* 771 * Handle the return of a child process from fork1(). This function 772 * is called from the MD fork_trampoline() entry point. 773 */ 774 void 775 fork_exit(callout, arg, frame) 776 void (*callout)(void *, struct trapframe *); 777 void *arg; 778 struct trapframe *frame; 779 { 780 struct thread *td = curthread; 781 struct proc *p = td->td_proc; 782 783 td->td_kse->ke_oncpu = PCPU_GET(cpuid); 784 /* 785 * Finish setting up thread glue. We need to initialize 786 * the thread into a td_critnest=1 state. Some platforms 787 * may have already partially or fully initialized td_critnest 788 * and/or td_md.md_savecrit (when applciable). 789 * 790 * see <arch>/<arch>/critical.c 791 */ 792 sched_lock.mtx_lock = (uintptr_t)td; 793 sched_lock.mtx_recurse = 0; 794 cpu_critical_fork_exit(); 795 CTR3(KTR_PROC, "fork_exit: new proc %p (pid %d, %s)", p, p->p_pid, 796 p->p_comm); 797 if (PCPU_GET(switchtime.sec) == 0) 798 binuptime(PCPU_PTR(switchtime)); 799 PCPU_SET(switchticks, ticks); 800 mtx_unlock_spin(&sched_lock); 801 802 /* 803 * cpu_set_fork_handler intercepts this function call to 804 * have this call a non-return function to stay in kernel mode. 805 * initproc has its own fork handler, but it does return. 806 */ 807 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 808 callout(arg, frame); 809 810 /* 811 * Check if a kernel thread misbehaved and returned from its main 812 * function. 813 */ 814 PROC_LOCK(p); 815 if (p->p_flag & P_KTHREAD) { 816 PROC_UNLOCK(p); 817 mtx_lock(&Giant); 818 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 819 p->p_comm, p->p_pid); 820 kthread_exit(0); 821 } 822 PROC_UNLOCK(p); 823 #ifdef DIAGNOSTIC 824 cred_free_thread(td); 825 #endif 826 mtx_assert(&Giant, MA_NOTOWNED); 827 } 828 829 /* 830 * Simplified back end of syscall(), used when returning from fork() 831 * directly into user mode. Giant is not held on entry, and must not 832 * be held on return. This function is passed in to fork_exit() as the 833 * first parameter and is called when returning to a new userland process. 834 */ 835 void 836 fork_return(td, frame) 837 struct thread *td; 838 struct trapframe *frame; 839 { 840 841 userret(td, frame, 0); 842 #ifdef KTRACE 843 if (KTRPOINT(td->td_proc, KTR_SYSRET)) { 844 ktrsysret(td->td_proc->p_tracep, SYS_fork, 0, 0); 845 } 846 #endif 847 mtx_assert(&Giant, MA_NOTOWNED); 848 } 849