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|MTX_DUPOK); 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 pargs_hold(p2->p_args); 486 487 if (flags & RFSIGSHARE) { 488 p2->p_procsig = p1->p_procsig; 489 p2->p_procsig->ps_refcnt++; 490 if (p1->p_sigacts == &p1->p_uarea->u_sigacts) { 491 struct sigacts *newsigacts; 492 493 PROC_UNLOCK(p1); 494 PROC_UNLOCK(p2); 495 /* Create the shared sigacts structure */ 496 MALLOC(newsigacts, struct sigacts *, 497 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 498 PROC_LOCK(p2); 499 PROC_LOCK(p1); 500 /* 501 * Set p_sigacts to the new shared structure. 502 * Note that this is updating p1->p_sigacts at the 503 * same time, since p_sigacts is just a pointer to 504 * the shared p_procsig->ps_sigacts. 505 */ 506 p2->p_sigacts = newsigacts; 507 *p2->p_sigacts = p1->p_uarea->u_sigacts; 508 } 509 } else { 510 PROC_UNLOCK(p1); 511 PROC_UNLOCK(p2); 512 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), 513 M_SUBPROC, M_WAITOK); 514 PROC_LOCK(p2); 515 PROC_LOCK(p1); 516 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 517 p2->p_procsig->ps_refcnt = 1; 518 p2->p_sigacts = NULL; /* finished in vm_forkproc() */ 519 } 520 if (flags & RFLINUXTHPN) 521 p2->p_sigparent = SIGUSR1; 522 else 523 p2->p_sigparent = SIGCHLD; 524 525 /* bump references to the text vnode (for procfs) */ 526 p2->p_textvp = p1->p_textvp; 527 PROC_UNLOCK(p1); 528 PROC_UNLOCK(p2); 529 if (p2->p_textvp) 530 VREF(p2->p_textvp); 531 532 if (flags & RFCFDG) 533 fd = fdinit(td); 534 else if (flags & RFFDG) { 535 FILEDESC_LOCK(p1->p_fd); 536 fd = fdcopy(td); 537 FILEDESC_UNLOCK(p1->p_fd); 538 } else 539 fd = fdshare(p1); 540 PROC_LOCK(p2); 541 p2->p_fd = fd; 542 543 /* 544 * If p_limit is still copy-on-write, bump refcnt, 545 * otherwise get a copy that won't be modified. 546 * (If PL_SHAREMOD is clear, the structure is shared 547 * copy-on-write.) 548 */ 549 PROC_LOCK(p1); 550 if (p1->p_limit->p_lflags & PL_SHAREMOD) 551 p2->p_limit = limcopy(p1->p_limit); 552 else { 553 p2->p_limit = p1->p_limit; 554 p2->p_limit->p_refcnt++; 555 } 556 557 /* 558 * Preserve some more flags in subprocess. PS_PROFIL has already 559 * been preserved. 560 */ 561 p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK); 562 SESS_LOCK(p1->p_session); 563 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 564 p2->p_flag |= P_CONTROLT; 565 SESS_UNLOCK(p1->p_session); 566 if (flags & RFPPWAIT) 567 p2->p_flag |= P_PPWAIT; 568 569 LIST_INSERT_AFTER(p1, p2, p_pglist); 570 PROC_UNLOCK(p1); 571 PROC_UNLOCK(p2); 572 573 /* 574 * Attach the new process to its parent. 575 * 576 * If RFNOWAIT is set, the newly created process becomes a child 577 * of init. This effectively disassociates the child from the 578 * parent. 579 */ 580 if (flags & RFNOWAIT) 581 pptr = initproc; 582 else 583 pptr = p1; 584 sx_xlock(&proctree_lock); 585 PROC_LOCK(p2); 586 p2->p_pptr = pptr; 587 PROC_UNLOCK(p2); 588 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 589 sx_xunlock(&proctree_lock); 590 PROC_LOCK(p2); 591 LIST_INIT(&p2->p_children); 592 LIST_INIT(&td2->td_contested); /* XXXKSE only 1 thread? */ 593 594 callout_init(&p2->p_itcallout, 0); 595 callout_init(&td2->td_slpcallout, 1); /* XXXKSE */ 596 597 PROC_LOCK(p1); 598 #ifdef KTRACE 599 /* 600 * Copy traceflag and tracefile if enabled. If not inherited, 601 * these were zeroed above but we still could have a trace race 602 * so make sure p2's p_tracep is NULL. 603 */ 604 if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) { 605 p2->p_traceflag = p1->p_traceflag; 606 if ((p2->p_tracep = p1->p_tracep) != NULL) { 607 PROC_UNLOCK(p1); 608 PROC_UNLOCK(p2); 609 VREF(p2->p_tracep); 610 PROC_LOCK(p2); 611 PROC_LOCK(p1); 612 } 613 } 614 #endif 615 616 /* 617 * set priority of child to be that of parent 618 * XXXKSE hey! copying the estcpu seems dodgy.. should split it.. 619 */ 620 mtx_lock_spin(&sched_lock); 621 p2->p_ksegrp.kg_estcpu = p1->p_ksegrp.kg_estcpu; 622 mtx_unlock_spin(&sched_lock); 623 624 /* 625 * This begins the section where we must prevent the parent 626 * from being swapped. 627 */ 628 _PHOLD(p1); 629 PROC_UNLOCK(p1); 630 PROC_UNLOCK(p2); 631 632 /* 633 * Finish creating the child process. It will return via a different 634 * execution path later. (ie: directly into user mode) 635 */ 636 vm_forkproc(td, p2, td2, flags); 637 638 if (flags == (RFFDG | RFPROC)) { 639 cnt.v_forks++; 640 cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 641 } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) { 642 cnt.v_vforks++; 643 cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 644 } else if (p1 == &proc0) { 645 cnt.v_kthreads++; 646 cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 647 } else { 648 cnt.v_rforks++; 649 cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize; 650 } 651 652 /* 653 * Both processes are set up, now check if any loadable modules want 654 * to adjust anything. 655 * What if they have an error? XXX 656 */ 657 sx_slock(&fork_list_lock); 658 TAILQ_FOREACH(ep, &fork_list, next) { 659 (*ep->function)(p1, p2, flags); 660 } 661 sx_sunlock(&fork_list_lock); 662 663 /* 664 * If RFSTOPPED not requested, make child runnable and add to 665 * run queue. 666 */ 667 microtime(&(p2->p_stats->p_start)); 668 p2->p_acflag = AFORK; 669 if ((flags & RFSTOPPED) == 0) { 670 mtx_lock_spin(&sched_lock); 671 p2->p_stat = SRUN; 672 setrunqueue(td2); 673 mtx_unlock_spin(&sched_lock); 674 } 675 676 /* 677 * Now can be swapped. 678 */ 679 PROC_LOCK(p1); 680 _PRELE(p1); 681 682 /* 683 * tell any interested parties about the new process 684 */ 685 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 686 PROC_UNLOCK(p1); 687 688 /* 689 * Preserve synchronization semantics of vfork. If waiting for 690 * child to exec or exit, set P_PPWAIT on child, and sleep on our 691 * proc (in case of exit). 692 */ 693 PROC_LOCK(p2); 694 while (p2->p_flag & P_PPWAIT) 695 msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0); 696 PROC_UNLOCK(p2); 697 698 /* 699 * Return child proc pointer to parent. 700 */ 701 *procp = p2; 702 return (0); 703 } 704 705 /* 706 * The next two functionms are general routines to handle adding/deleting 707 * items on the fork callout list. 708 * 709 * at_fork(): 710 * Take the arguments given and put them onto the fork callout list, 711 * However first make sure that it's not already there. 712 * Returns 0 on success or a standard error number. 713 */ 714 715 int 716 at_fork(function) 717 forklist_fn function; 718 { 719 struct forklist *ep; 720 721 #ifdef INVARIANTS 722 /* let the programmer know if he's been stupid */ 723 if (rm_at_fork(function)) 724 printf("WARNING: fork callout entry (%p) already present\n", 725 function); 726 #endif 727 ep = malloc(sizeof(*ep), M_ATFORK, M_NOWAIT); 728 if (ep == NULL) 729 return (ENOMEM); 730 ep->function = function; 731 sx_xlock(&fork_list_lock); 732 TAILQ_INSERT_TAIL(&fork_list, ep, next); 733 sx_xunlock(&fork_list_lock); 734 return (0); 735 } 736 737 /* 738 * Scan the exit callout list for the given item and remove it.. 739 * Returns the number of items removed (0 or 1) 740 */ 741 742 int 743 rm_at_fork(function) 744 forklist_fn function; 745 { 746 struct forklist *ep; 747 748 sx_xlock(&fork_list_lock); 749 TAILQ_FOREACH(ep, &fork_list, next) { 750 if (ep->function == function) { 751 TAILQ_REMOVE(&fork_list, ep, next); 752 sx_xunlock(&fork_list_lock); 753 free(ep, M_ATFORK); 754 return(1); 755 } 756 } 757 sx_xunlock(&fork_list_lock); 758 return (0); 759 } 760 761 /* 762 * Handle the return of a child process from fork1(). This function 763 * is called from the MD fork_trampoline() entry point. 764 */ 765 void 766 fork_exit(callout, arg, frame) 767 void (*callout)(void *, struct trapframe *); 768 void *arg; 769 struct trapframe *frame; 770 { 771 struct thread *td = curthread; 772 struct proc *p = td->td_proc; 773 774 td->td_kse->ke_oncpu = PCPU_GET(cpuid); 775 /* 776 * Finish setting up thread glue. We need to initialize 777 * the thread into a td_critnest=1 state. Some platforms 778 * may have already partially or fully initialized td_critnest 779 * and/or td_md.md_savecrit (when applciable). 780 * 781 * see <arch>/<arch>/critical.c 782 */ 783 sched_lock.mtx_lock = (uintptr_t)td; 784 sched_lock.mtx_recurse = 0; 785 cpu_critical_fork_exit(); 786 CTR3(KTR_PROC, "fork_exit: new proc %p (pid %d, %s)", p, p->p_pid, 787 p->p_comm); 788 if (PCPU_GET(switchtime.sec) == 0) 789 binuptime(PCPU_PTR(switchtime)); 790 PCPU_SET(switchticks, ticks); 791 mtx_unlock_spin(&sched_lock); 792 793 /* 794 * cpu_set_fork_handler intercepts this function call to 795 * have this call a non-return function to stay in kernel mode. 796 * initproc has its own fork handler, but it does return. 797 */ 798 KASSERT(callout != NULL, ("NULL callout in fork_exit")); 799 callout(arg, frame); 800 801 /* 802 * Check if a kernel thread misbehaved and returned from its main 803 * function. 804 */ 805 PROC_LOCK(p); 806 if (p->p_flag & P_KTHREAD) { 807 PROC_UNLOCK(p); 808 mtx_lock(&Giant); 809 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n", 810 p->p_comm, p->p_pid); 811 kthread_exit(0); 812 } 813 PROC_UNLOCK(p); 814 #ifdef DIAGNOSTIC 815 cred_free_thread(td); 816 #endif 817 mtx_assert(&Giant, MA_NOTOWNED); 818 } 819 820 /* 821 * Simplified back end of syscall(), used when returning from fork() 822 * directly into user mode. Giant is not held on entry, and must not 823 * be held on return. This function is passed in to fork_exit() as the 824 * first parameter and is called when returning to a new userland process. 825 */ 826 void 827 fork_return(td, frame) 828 struct thread *td; 829 struct trapframe *frame; 830 { 831 832 userret(td, frame, 0); 833 #ifdef KTRACE 834 if (KTRPOINT(td->td_proc, KTR_SYSRET)) { 835 ktrsysret(td->td_proc->p_tracep, SYS_fork, 0, 0); 836 } 837 #endif 838 mtx_assert(&Giant, MA_NOTOWNED); 839 } 840