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