kern_fork.c revision 1.84.2.22
1 /* $NetBSD: kern_fork.c,v 1.84.2.22 2002/12/15 23:32:00 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 1999, 2001 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 9 * NASA Ames Research Center. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 /* 41 * Copyright (c) 1982, 1986, 1989, 1991, 1993 42 * The Regents of the University of California. All rights reserved. 43 * (c) UNIX System Laboratories, Inc. 44 * All or some portions of this file are derived from material licensed 45 * to the University of California by American Telephone and Telegraph 46 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 47 * the permission of UNIX System Laboratories, Inc. 48 * 49 * Redistribution and use in source and binary forms, with or without 50 * modification, are permitted provided that the following conditions 51 * are met: 52 * 1. Redistributions of source code must retain the above copyright 53 * notice, this list of conditions and the following disclaimer. 54 * 2. Redistributions in binary form must reproduce the above copyright 55 * notice, this list of conditions and the following disclaimer in the 56 * documentation and/or other materials provided with the distribution. 57 * 3. All advertising materials mentioning features or use of this software 58 * must display the following acknowledgement: 59 * This product includes software developed by the University of 60 * California, Berkeley and its contributors. 61 * 4. Neither the name of the University nor the names of its contributors 62 * may be used to endorse or promote products derived from this software 63 * without specific prior written permission. 64 * 65 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 66 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 67 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 68 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 69 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 70 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 71 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 72 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 73 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 74 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 75 * SUCH DAMAGE. 76 * 77 * @(#)kern_fork.c 8.8 (Berkeley) 2/14/95 78 */ 79 80 #include <sys/cdefs.h> 81 __KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.84.2.22 2002/12/15 23:32:00 thorpej Exp $"); 82 83 #include "opt_ktrace.h" 84 #include "opt_systrace.h" 85 #include "opt_multiprocessor.h" 86 87 #include <sys/param.h> 88 #include <sys/systm.h> 89 #include <sys/filedesc.h> 90 #include <sys/kernel.h> 91 #include <sys/malloc.h> 92 #include <sys/pool.h> 93 #include <sys/mount.h> 94 #include <sys/proc.h> 95 #include <sys/ras.h> 96 #include <sys/resourcevar.h> 97 #include <sys/vnode.h> 98 #include <sys/file.h> 99 #include <sys/acct.h> 100 #include <sys/ktrace.h> 101 #include <sys/vmmeter.h> 102 #include <sys/sched.h> 103 #include <sys/signalvar.h> 104 #include <sys/systrace.h> 105 106 #include <sys/sa.h> 107 #include <sys/syscallargs.h> 108 109 #include <uvm/uvm_extern.h> 110 111 112 int nprocs = 1; /* process 0 */ 113 114 /*ARGSUSED*/ 115 int 116 sys_fork(struct lwp *l, void *v, register_t *retval) 117 { 118 119 return (fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); 120 } 121 122 /* 123 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 124 * Address space is not shared, but parent is blocked until child exit. 125 */ 126 /*ARGSUSED*/ 127 int 128 sys_vfork(struct lwp *l, void *v, register_t *retval) 129 { 130 131 return (fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 132 retval, NULL)); 133 } 134 135 /* 136 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 137 * semantics. Address space is shared, and parent is blocked until child exit. 138 */ 139 /*ARGSUSED*/ 140 int 141 sys___vfork14(struct lwp *l, void *v, register_t *retval) 142 { 143 144 return (fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 145 NULL, NULL, retval, NULL)); 146 } 147 148 /* 149 * Linux-compatible __clone(2) system call. 150 */ 151 int 152 sys___clone(struct lwp *l, void *v, register_t *retval) 153 { 154 struct sys___clone_args /* { 155 syscallarg(int) flags; 156 syscallarg(void *) stack; 157 } */ *uap = v; 158 int flags, sig; 159 160 /* 161 * We don't support the CLONE_PID or CLONE_PTRACE flags. 162 */ 163 if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) 164 return (EINVAL); 165 166 flags = 0; 167 168 if (SCARG(uap, flags) & CLONE_VM) 169 flags |= FORK_SHAREVM; 170 if (SCARG(uap, flags) & CLONE_FS) 171 flags |= FORK_SHARECWD; 172 if (SCARG(uap, flags) & CLONE_FILES) 173 flags |= FORK_SHAREFILES; 174 if (SCARG(uap, flags) & CLONE_SIGHAND) 175 flags |= FORK_SHARESIGS; 176 if (SCARG(uap, flags) & CLONE_VFORK) 177 flags |= FORK_PPWAIT; 178 179 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 180 if (sig < 0 || sig >= _NSIG) 181 return (EINVAL); 182 183 /* 184 * Note that the Linux API does not provide a portable way of 185 * specifying the stack area; the caller must know if the stack 186 * grows up or down. So, we pass a stack size of 0, so that the 187 * code that makes this adjustment is a noop. 188 */ 189 return (fork1(l, flags, sig, SCARG(uap, stack), 0, 190 NULL, NULL, retval, NULL)); 191 } 192 193 /* print the 'table full' message once per 10 seconds */ 194 struct timeval fork_tfmrate = { 10, 0 }; 195 196 int 197 fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, 198 void (*func)(void *), void *arg, register_t *retval, 199 struct proc **rnewprocp) 200 { 201 struct proc *p1, *p2, *tp; 202 uid_t uid; 203 struct lwp *l2; 204 int count, s; 205 vaddr_t uaddr; 206 boolean_t inmem; 207 static int nextpid, pidchecked; 208 209 /* 210 * Although process entries are dynamically created, we still keep 211 * a global limit on the maximum number we will create. Don't allow 212 * a nonprivileged user to use the last few processes; don't let root 213 * exceed the limit. The variable nprocs is the current number of 214 * processes, maxproc is the limit. 215 */ 216 p1 = l1->l_proc; 217 uid = p1->p_cred->p_ruid; 218 if (__predict_false((nprocs >= maxproc - 5 && uid != 0) || 219 nprocs >= maxproc)) { 220 static struct timeval lasttfm; 221 222 if (ratecheck(&lasttfm, &fork_tfmrate)) 223 tablefull("proc", "increase kern.maxproc or NPROC"); 224 return (EAGAIN); 225 } 226 nprocs++; 227 228 /* 229 * Increment the count of procs running with this uid. Don't allow 230 * a nonprivileged user to exceed their current limit. 231 */ 232 count = chgproccnt(uid, 1); 233 if (__predict_false(uid != 0 && count > 234 p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 235 (void)chgproccnt(uid, -1); 236 nprocs--; 237 return (EAGAIN); 238 } 239 240 /* 241 * Allocate virtual address space for the U-area now, while it 242 * is still easy to abort the fork operation if we're out of 243 * kernel virtual address space. The actual U-area pages will 244 * be allocated and wired in uvm_fork() if needed. 245 */ 246 247 inmem = uvm_uarea_alloc(&uaddr); 248 if (__predict_false(uaddr == 0)) { 249 (void)chgproccnt(uid, -1); 250 nprocs--; 251 return (ENOMEM); 252 } 253 254 /* 255 * We are now committed to the fork. From here on, we may 256 * block on resources, but resource allocation may NOT fail. 257 */ 258 259 /* Allocate new proc. */ 260 p2 = pool_get(&proc_pool, PR_WAITOK); 261 262 /* 263 * Make a proc table entry for the new process. 264 * Start by zeroing the section of proc that is zero-initialized, 265 * then copy the section that is copied directly from the parent. 266 */ 267 memset(&p2->p_startzero, 0, 268 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 269 memcpy(&p2->p_startcopy, &p1->p_startcopy, 270 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 271 272 simple_lock_init(&p2->p_lwplock); 273 LIST_INIT(&p2->p_lwps); 274 275 /* 276 * Duplicate sub-structures as needed. 277 * Increase reference counts on shared objects. 278 * The p_stats and p_sigacts substructs are set in uvm_fork(). 279 */ 280 p2->p_flag = (p1->p_flag & P_SUGID); 281 p2->p_emul = p1->p_emul; 282 p2->p_execsw = p1->p_execsw; 283 284 if (p1->p_flag & P_PROFIL) 285 startprofclock(p2); 286 p2->p_cred = pool_get(&pcred_pool, PR_WAITOK); 287 memcpy(p2->p_cred, p1->p_cred, sizeof(*p2->p_cred)); 288 p2->p_cred->p_refcnt = 1; 289 crhold(p1->p_ucred); 290 291 LIST_INIT(&p2->p_raslist); 292 p2->p_nras = 0; 293 simple_lock_init(&p2->p_raslock); 294 #if defined(__HAVE_RAS) 295 ras_fork(p1, p2); 296 #endif 297 298 /* bump references to the text vnode (for procfs) */ 299 p2->p_textvp = p1->p_textvp; 300 if (p2->p_textvp) 301 VREF(p2->p_textvp); 302 303 if (flags & FORK_SHAREFILES) 304 fdshare(p1, p2); 305 else if (flags & FORK_CLEANFILES) 306 p2->p_fd = fdinit(p1); 307 else 308 p2->p_fd = fdcopy(p1); 309 310 if (flags & FORK_SHARECWD) 311 cwdshare(p1, p2); 312 else 313 p2->p_cwdi = cwdinit(p1); 314 315 /* 316 * If p_limit is still copy-on-write, bump refcnt, 317 * otherwise get a copy that won't be modified. 318 * (If PL_SHAREMOD is clear, the structure is shared 319 * copy-on-write.) 320 */ 321 if (p1->p_limit->p_lflags & PL_SHAREMOD) 322 p2->p_limit = limcopy(p1->p_limit); 323 else { 324 p2->p_limit = p1->p_limit; 325 p2->p_limit->p_refcnt++; 326 } 327 328 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 329 p2->p_flag |= P_CONTROLT; 330 if (flags & FORK_PPWAIT) 331 p2->p_flag |= P_PPWAIT; 332 LIST_INSERT_AFTER(p1, p2, p_pglist); 333 p2->p_pptr = (flags & FORK_NOWAIT) ? initproc : p1; 334 LIST_INSERT_HEAD(&p2->p_pptr->p_children, p2, p_sibling); 335 LIST_INIT(&p2->p_children); 336 337 #ifdef KTRACE 338 /* 339 * Copy traceflag and tracefile if enabled. 340 * If not inherited, these were zeroed above. 341 */ 342 if (p1->p_traceflag & KTRFAC_INHERIT) { 343 p2->p_traceflag = p1->p_traceflag; 344 if ((p2->p_tracep = p1->p_tracep) != NULL) 345 ktradref(p2); 346 } 347 #endif 348 349 scheduler_fork_hook(p1, p2); 350 351 /* 352 * Create signal actions for the child process. 353 */ 354 sigactsinit(p2, p1, flags & FORK_SHARESIGS); 355 356 /* 357 * p_stats. 358 * Copy parts of p_stats, and zero out the rest. 359 */ 360 p2->p_stats = pstatscopy(p1->p_stats); 361 362 /* 363 * If emulation has process fork hook, call it now. 364 */ 365 if (p2->p_emul->e_proc_fork) 366 (*p2->p_emul->e_proc_fork)(p2, p1); 367 368 /* 369 * This begins the section where we must prevent the parent 370 * from being swapped. 371 */ 372 PHOLD(l1); 373 374 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 375 376 /* 377 * Finish creating the child process. It will return through a 378 * different path later. 379 */ 380 newlwp(l1, p2, uaddr, inmem, 0, stack, stacksize, 381 (func != NULL) ? func : child_return, 382 arg, &l2); 383 384 /* 385 * BEGIN PID ALLOCATION. 386 */ 387 s = proclist_lock_write(); 388 389 /* 390 * Find an unused process ID. We remember a range of unused IDs 391 * ready to use (from nextpid+1 through pidchecked-1). 392 */ 393 nextpid++; 394 retry: 395 /* 396 * If the process ID prototype has wrapped around, 397 * restart somewhat above 0, as the low-numbered procs 398 * tend to include daemons that don't exit. 399 */ 400 if (nextpid >= PID_MAX) { 401 nextpid = 500; 402 pidchecked = 0; 403 } 404 if (nextpid >= pidchecked) { 405 const struct proclist_desc *pd; 406 407 pidchecked = PID_MAX; 408 /* 409 * Scan the process lists to check whether this pid 410 * is in use. Remember the lowest pid that's greater 411 * than nextpid, so we can avoid checking for a while. 412 */ 413 pd = proclists; 414 again: 415 LIST_FOREACH(tp, pd->pd_list, p_list) { 416 while (tp->p_pid == nextpid || 417 tp->p_pgrp->pg_id == nextpid || 418 tp->p_session->s_sid == nextpid) { 419 nextpid++; 420 if (nextpid >= pidchecked) 421 goto retry; 422 } 423 if (tp->p_pid > nextpid && pidchecked > tp->p_pid) 424 pidchecked = tp->p_pid; 425 426 if (tp->p_pgrp->pg_id > nextpid && 427 pidchecked > tp->p_pgrp->pg_id) 428 pidchecked = tp->p_pgrp->pg_id; 429 430 if (tp->p_session->s_sid > nextpid && 431 pidchecked > tp->p_session->s_sid) 432 pidchecked = tp->p_session->s_sid; 433 } 434 435 /* 436 * If there's another list, scan it. If we have checked 437 * them all, we've found one! 438 */ 439 pd++; 440 if (pd->pd_list != NULL) 441 goto again; 442 } 443 444 /* 445 * Put the proc on allproc before unlocking PID allocation 446 * so that waiters won't grab it as soon as we unlock. 447 */ 448 449 p2->p_stat = SIDL; /* protect against others */ 450 p2->p_pid = nextpid; 451 p2->p_exitsig = exitsig; /* signal for parent on exit */ 452 453 LIST_INSERT_HEAD(&allproc, p2, p_list); 454 455 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 456 457 /* 458 * END PID ALLOCATION. 459 */ 460 proclist_unlock_write(s); 461 462 #ifdef SYSTRACE 463 /* Tell systrace what's happening. */ 464 if (ISSET(p1->p_flag, P_SYSTRACE)) 465 systrace_sys_fork(p1, p2); 466 #endif 467 468 #ifdef __HAVE_SYSCALL_INTERN 469 (*p2->p_emul->e_syscall_intern)(p2); 470 #endif 471 472 /* 473 * Make child runnable, set start time, and add to run queue 474 * except if the parent requested the child to start in SSTOP state. 475 */ 476 SCHED_LOCK(s); 477 p2->p_stats->p_start = time; 478 p2->p_acflag = AFORK; 479 p2->p_nrlwps = 1; 480 if (p1->p_flag & P_STOPFORK) { 481 p2->p_stat = SSTOP; 482 l2->l_stat = LSSTOP; 483 } else { 484 p2->p_stat = SACTIVE; 485 l2->l_stat = LSRUN; 486 setrunqueue(l2); 487 } 488 SCHED_UNLOCK(s); 489 490 /* 491 * Inherit STOPFORK and STOPEXEC flags 492 */ 493 if (p1->p_flag & P_STOPFORK) 494 p2->p_flag |= P_STOPFORK; 495 if (p1->p_flag & P_STOPEXEC) 496 p2->p_flag |= P_STOPEXEC; 497 498 /* 499 * Now can be swapped. 500 */ 501 PRELE(l1); 502 503 /* 504 * Notify any interested parties about the new process. 505 */ 506 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 507 508 /* 509 * Update stats now that we know the fork was successful. 510 */ 511 uvmexp.forks++; 512 if (flags & FORK_PPWAIT) 513 uvmexp.forks_ppwait++; 514 if (flags & FORK_SHAREVM) 515 uvmexp.forks_sharevm++; 516 517 /* 518 * Pass a pointer to the new process to the caller. 519 */ 520 if (rnewprocp != NULL) 521 *rnewprocp = p2; 522 523 #ifdef KTRACE 524 if (KTRPOINT(p2, KTR_EMUL)) 525 ktremul(p2); 526 #endif 527 528 /* 529 * Preserve synchronization semantics of vfork. If waiting for 530 * child to exec or exit, set P_PPWAIT on child, and sleep on our 531 * proc (in case of exit). 532 */ 533 if (flags & FORK_PPWAIT) 534 while (p2->p_flag & P_PPWAIT) 535 tsleep(p1, PWAIT, "ppwait", 0); 536 537 /* 538 * Return child pid to parent process, 539 * marking us as parent via retval[1]. 540 */ 541 if (retval != NULL) { 542 retval[0] = p2->p_pid; 543 retval[1] = 0; 544 } 545 546 return (0); 547 } 548 549 #if defined(MULTIPROCESSOR) 550 /* 551 * XXX This is a slight hack to get newly-formed processes to 552 * XXX acquire the kernel lock as soon as they run. 553 */ 554 void 555 proc_trampoline_mp(void) 556 { 557 struct lwp *l; 558 559 l = curlwp; 560 561 SCHED_ASSERT_UNLOCKED(); 562 KERNEL_PROC_LOCK(l); 563 } 564 #endif 565
Indexes created Thu Sep 25 16:09:42 GMT 2025