kern_fork.c revision 1.162
1 /* $NetBSD: kern_fork.c,v 1.162 2008/04/24 18:39:24 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 1999, 2001, 2004, 2006, 2007, 2008 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, by Charles M. Hannum, and by Andrew Doran. 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. Neither the name of the University nor the names of its contributors 58 * may be used to endorse or promote products derived from this software 59 * without specific prior written permission. 60 * 61 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 62 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 63 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 64 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 65 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 66 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 67 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 68 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 69 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 70 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 71 * SUCH DAMAGE. 72 * 73 * @(#)kern_fork.c 8.8 (Berkeley) 2/14/95 74 */ 75 76 #include <sys/cdefs.h> 77 __KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.162 2008/04/24 18:39:24 ad Exp $"); 78 79 #include "opt_ktrace.h" 80 #include "opt_multiprocessor.h" 81 82 #include <sys/param.h> 83 #include <sys/systm.h> 84 #include <sys/filedesc.h> 85 #include <sys/kernel.h> 86 #include <sys/malloc.h> 87 #include <sys/pool.h> 88 #include <sys/mount.h> 89 #include <sys/proc.h> 90 #include <sys/ras.h> 91 #include <sys/resourcevar.h> 92 #include <sys/vnode.h> 93 #include <sys/file.h> 94 #include <sys/acct.h> 95 #include <sys/ktrace.h> 96 #include <sys/vmmeter.h> 97 #include <sys/sched.h> 98 #include <sys/signalvar.h> 99 #include <sys/kauth.h> 100 #include <sys/atomic.h> 101 #include <sys/syscallargs.h> 102 103 #include <uvm/uvm_extern.h> 104 105 u_int nprocs = 1; /* process 0 */ 106 107 /* 108 * Number of ticks to sleep if fork() would fail due to process hitting 109 * limits. Exported in miliseconds to userland via sysctl. 110 */ 111 int forkfsleep = 0; 112 113 /*ARGSUSED*/ 114 int 115 sys_fork(struct lwp *l, const void *v, register_t *retval) 116 { 117 118 return (fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); 119 } 120 121 /* 122 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 123 * Address space is not shared, but parent is blocked until child exit. 124 */ 125 /*ARGSUSED*/ 126 int 127 sys_vfork(struct lwp *l, const void *v, register_t *retval) 128 { 129 130 return (fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 131 retval, NULL)); 132 } 133 134 /* 135 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 136 * semantics. Address space is shared, and parent is blocked until child exit. 137 */ 138 /*ARGSUSED*/ 139 int 140 sys___vfork14(struct lwp *l, const void *v, register_t *retval) 141 { 142 143 return (fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 144 NULL, NULL, retval, NULL)); 145 } 146 147 /* 148 * Linux-compatible __clone(2) system call. 149 */ 150 int 151 sys___clone(struct lwp *l, const struct sys___clone_args *uap, register_t *retval) 152 { 153 /* { 154 syscallarg(int) flags; 155 syscallarg(void *) stack; 156 } */ 157 int flags, sig; 158 159 /* 160 * We don't support the CLONE_PID or CLONE_PTRACE flags. 161 */ 162 if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) 163 return (EINVAL); 164 165 /* 166 * Linux enforces CLONE_VM with CLONE_SIGHAND, do same. 167 */ 168 if (SCARG(uap, flags) & CLONE_SIGHAND 169 && (SCARG(uap, flags) & CLONE_VM) == 0) 170 return (EINVAL); 171 172 flags = 0; 173 174 if (SCARG(uap, flags) & CLONE_VM) 175 flags |= FORK_SHAREVM; 176 if (SCARG(uap, flags) & CLONE_FS) 177 flags |= FORK_SHARECWD; 178 if (SCARG(uap, flags) & CLONE_FILES) 179 flags |= FORK_SHAREFILES; 180 if (SCARG(uap, flags) & CLONE_SIGHAND) 181 flags |= FORK_SHARESIGS; 182 if (SCARG(uap, flags) & CLONE_VFORK) 183 flags |= FORK_PPWAIT; 184 185 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 186 if (sig < 0 || sig >= _NSIG) 187 return (EINVAL); 188 189 /* 190 * Note that the Linux API does not provide a portable way of 191 * specifying the stack area; the caller must know if the stack 192 * grows up or down. So, we pass a stack size of 0, so that the 193 * code that makes this adjustment is a noop. 194 */ 195 return (fork1(l, flags, sig, SCARG(uap, stack), 0, 196 NULL, NULL, retval, NULL)); 197 } 198 199 /* print the 'table full' message once per 10 seconds */ 200 struct timeval fork_tfmrate = { 10, 0 }; 201 202 /* 203 * General fork call. Note that another LWP in the process may call exec() 204 * or exit() while we are forking. It's safe to continue here, because 205 * neither operation will complete until all LWPs have exited the process. 206 */ 207 int 208 fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, 209 void (*func)(void *), void *arg, register_t *retval, 210 struct proc **rnewprocp) 211 { 212 struct proc *p1, *p2, *parent; 213 struct plimit *p1_lim; 214 uid_t uid; 215 struct lwp *l2; 216 int count; 217 vaddr_t uaddr; 218 bool inmem; 219 int tmp; 220 int tnprocs; 221 int error = 0; 222 223 p1 = l1->l_proc; 224 uid = kauth_cred_getuid(l1->l_cred); 225 tnprocs = atomic_inc_uint_nv(&nprocs); 226 227 /* 228 * Although process entries are dynamically created, we still keep 229 * a global limit on the maximum number we will create. 230 */ 231 if (__predict_false(tnprocs >= maxproc)) 232 error = -1; 233 else 234 error = kauth_authorize_process(l1->l_cred, 235 KAUTH_PROCESS_FORK, p1, KAUTH_ARG(tnprocs), NULL, NULL); 236 237 if (error) { 238 static struct timeval lasttfm; 239 atomic_dec_uint(&nprocs); 240 if (ratecheck(&lasttfm, &fork_tfmrate)) 241 tablefull("proc", "increase kern.maxproc or NPROC"); 242 if (forkfsleep) 243 (void)tsleep(&nprocs, PUSER, "forkmx", forkfsleep); 244 return (EAGAIN); 245 } 246 247 /* 248 * Enforce limits. 249 */ 250 count = chgproccnt(uid, 1); 251 if (uid != 0 && 252 __predict_false(count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 253 (void)chgproccnt(uid, -1); 254 atomic_dec_uint(&nprocs); 255 if (forkfsleep) 256 (void)tsleep(&nprocs, PUSER, "forkulim", forkfsleep); 257 return (EAGAIN); 258 } 259 260 /* 261 * Allocate virtual address space for the U-area now, while it 262 * is still easy to abort the fork operation if we're out of 263 * kernel virtual address space. The actual U-area pages will 264 * be allocated and wired in uvm_fork() if needed. 265 */ 266 267 inmem = uvm_uarea_alloc(&uaddr); 268 if (__predict_false(uaddr == 0)) { 269 (void)chgproccnt(uid, -1); 270 atomic_dec_uint(&nprocs); 271 return (ENOMEM); 272 } 273 274 /* 275 * We are now committed to the fork. From here on, we may 276 * block on resources, but resource allocation may NOT fail. 277 */ 278 279 /* Allocate new proc. */ 280 p2 = proc_alloc(); 281 282 /* 283 * Make a proc table entry for the new process. 284 * Start by zeroing the section of proc that is zero-initialized, 285 * then copy the section that is copied directly from the parent. 286 */ 287 memset(&p2->p_startzero, 0, 288 (unsigned) ((char *)&p2->p_endzero - (char *)&p2->p_startzero)); 289 memcpy(&p2->p_startcopy, &p1->p_startcopy, 290 (unsigned) ((char *)&p2->p_endcopy - (char *)&p2->p_startcopy)); 291 292 CIRCLEQ_INIT(&p2->p_sigpend.sp_info); 293 294 LIST_INIT(&p2->p_lwps); 295 LIST_INIT(&p2->p_sigwaiters); 296 297 /* 298 * Duplicate sub-structures as needed. 299 * Increase reference counts on shared objects. 300 * The p_stats and p_sigacts substructs are set in uvm_fork(). 301 * Inherit flags we want to keep. The flags related to SIGCHLD 302 * handling are important in order to keep a consistent behaviour 303 * for the child after the fork. 304 */ 305 p2->p_flag = p1->p_flag & (PK_SUGID | PK_NOCLDWAIT | PK_CLDSIGIGN); 306 p2->p_emul = p1->p_emul; 307 p2->p_execsw = p1->p_execsw; 308 309 if (flags & FORK_SYSTEM) { 310 /* 311 * Mark it as a system process. Set P_NOCLDWAIT so that 312 * children are reparented to init(8) when they exit. 313 * init(8) can easily wait them out for us. 314 */ 315 p2->p_flag |= (PK_SYSTEM | PK_NOCLDWAIT); 316 } 317 318 mutex_init(&p2->p_stmutex, MUTEX_DEFAULT, IPL_HIGH); 319 mutex_init(&p2->p_auxlock, MUTEX_DEFAULT, IPL_NONE); 320 rw_init(&p2->p_reflock); 321 cv_init(&p2->p_waitcv, "wait"); 322 cv_init(&p2->p_lwpcv, "lwpwait"); 323 324 /* 325 * Share a lock between the processes if they are to share signal 326 * state: we must synchronize access to it. 327 */ 328 if (flags & FORK_SHARESIGS) { 329 p2->p_lock = p1->p_lock; 330 mutex_obj_hold(p1->p_lock); 331 } else 332 p2->p_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE); 333 334 kauth_proc_fork(p1, p2); 335 336 p2->p_raslist = NULL; 337 #if defined(__HAVE_RAS) 338 ras_fork(p1, p2); 339 #endif 340 341 /* bump references to the text vnode (for procfs) */ 342 p2->p_textvp = p1->p_textvp; 343 if (p2->p_textvp) 344 VREF(p2->p_textvp); 345 346 if (flags & FORK_SHAREFILES) 347 fd_share(p2); 348 else if (flags & FORK_CLEANFILES) 349 p2->p_fd = fd_init(NULL); 350 else 351 p2->p_fd = fd_copy(); 352 353 if (flags & FORK_SHARECWD) 354 cwdshare(p2); 355 else 356 p2->p_cwdi = cwdinit(); 357 358 /* 359 * p_limit (rlimit stuff) is usually copy-on-write, so we just need 360 * to bump pl_refcnt. 361 * However in some cases (see compat irix, and plausibly from clone) 362 * the parent and child share limits - in which case nothing else 363 * must have a copy of the limits (PL_SHAREMOD is set). 364 */ 365 if (__predict_false(flags & FORK_SHARELIMIT)) 366 lim_privatise(p1, 1); 367 p1_lim = p1->p_limit; 368 if (p1_lim->pl_flags & PL_WRITEABLE && !(flags & FORK_SHARELIMIT)) 369 p2->p_limit = lim_copy(p1_lim); 370 else { 371 lim_addref(p1_lim); 372 p2->p_limit = p1_lim; 373 } 374 375 p2->p_sflag = ((flags & FORK_PPWAIT) ? PS_PPWAIT : 0); 376 p2->p_lflag = 0; 377 p2->p_slflag = 0; 378 parent = (flags & FORK_NOWAIT) ? initproc : p1; 379 p2->p_pptr = parent; 380 LIST_INIT(&p2->p_children); 381 382 p2->p_aio = NULL; 383 384 #ifdef KTRACE 385 /* 386 * Copy traceflag and tracefile if enabled. 387 * If not inherited, these were zeroed above. 388 */ 389 if (p1->p_traceflag & KTRFAC_INHERIT) { 390 mutex_enter(&ktrace_lock); 391 p2->p_traceflag = p1->p_traceflag; 392 if ((p2->p_tracep = p1->p_tracep) != NULL) 393 ktradref(p2); 394 mutex_exit(&ktrace_lock); 395 } 396 #endif 397 398 /* 399 * Create signal actions for the child process. 400 */ 401 p2->p_sigacts = sigactsinit(p1, flags & FORK_SHARESIGS); 402 mutex_enter(p1->p_lock); 403 p2->p_sflag |= 404 (p1->p_sflag & (PS_STOPFORK | PS_STOPEXEC | PS_NOCLDSTOP)); 405 sched_proc_fork(p1, p2); 406 mutex_exit(p1->p_lock); 407 408 p2->p_stflag = p1->p_stflag; 409 410 /* 411 * p_stats. 412 * Copy parts of p_stats, and zero out the rest. 413 */ 414 p2->p_stats = pstatscopy(p1->p_stats); 415 416 /* 417 * If emulation has process fork hook, call it now. 418 */ 419 if (p2->p_emul->e_proc_fork) 420 (*p2->p_emul->e_proc_fork)(p2, p1, flags); 421 422 /* 423 * ...and finally, any other random fork hooks that subsystems 424 * might have registered. 425 */ 426 doforkhooks(p2, p1); 427 428 /* 429 * This begins the section where we must prevent the parent 430 * from being swapped. 431 */ 432 uvm_lwp_hold(l1); 433 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? true : false); 434 435 /* 436 * Finish creating the child process. 437 * It will return through a different path later. 438 */ 439 lwp_create(l1, p2, uaddr, inmem, 0, stack, stacksize, 440 (func != NULL) ? func : child_return, arg, &l2, 441 l1->l_class); 442 443 /* 444 * It's now safe for the scheduler and other processes to see the 445 * child process. 446 */ 447 mutex_enter(proc_lock); 448 449 if (p1->p_session->s_ttyvp != NULL && p1->p_lflag & PL_CONTROLT) 450 p2->p_lflag |= PL_CONTROLT; 451 452 LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling); 453 p2->p_exitsig = exitsig; /* signal for parent on exit */ 454 455 LIST_INSERT_AFTER(p1, p2, p_pglist); 456 LIST_INSERT_HEAD(&allproc, p2, p_list); 457 458 p2->p_trace_enabled = trace_is_enabled(p2); 459 #ifdef __HAVE_SYSCALL_INTERN 460 (*p2->p_emul->e_syscall_intern)(p2); 461 #endif 462 463 /* 464 * Update stats now that we know the fork was successful. 465 */ 466 uvmexp.forks++; 467 if (flags & FORK_PPWAIT) 468 uvmexp.forks_ppwait++; 469 if (flags & FORK_SHAREVM) 470 uvmexp.forks_sharevm++; 471 472 /* 473 * Pass a pointer to the new process to the caller. 474 */ 475 if (rnewprocp != NULL) 476 *rnewprocp = p2; 477 478 if (ktrpoint(KTR_EMUL)) 479 p2->p_traceflag |= KTRFAC_TRC_EMUL; 480 481 /* 482 * Now can be swapped. 483 */ 484 uvm_lwp_rele(l1); 485 486 /* 487 * Notify any interested parties about the new process. 488 */ 489 if (!SLIST_EMPTY(&p1->p_klist)) { 490 mutex_exit(proc_lock); 491 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 492 mutex_enter(proc_lock); 493 } 494 495 /* 496 * Make child runnable, set start time, and add to run queue except 497 * if the parent requested the child to start in SSTOP state. 498 */ 499 tmp = (p2->p_userret != NULL ? LW_WUSERRET : 0); 500 mutex_enter(p2->p_lock); 501 502 getmicrotime(&p2->p_stats->p_start); 503 p2->p_acflag = AFORK; 504 if (p2->p_sflag & PS_STOPFORK) { 505 lwp_lock(l2); 506 p2->p_nrlwps = 0; 507 p2->p_stat = SSTOP; 508 p2->p_waited = 0; 509 p1->p_nstopchild++; 510 l2->l_stat = LSSTOP; 511 l2->l_flag |= tmp; 512 lwp_unlock(l2); 513 } else { 514 p2->p_nrlwps = 1; 515 p2->p_stat = SACTIVE; 516 lwp_lock(l2); 517 l2->l_stat = LSRUN; 518 l2->l_flag |= tmp; 519 sched_enqueue(l2, false); 520 lwp_unlock(l2); 521 } 522 523 mutex_exit(proc_lock); 524 525 /* 526 * Start profiling. 527 */ 528 if ((p2->p_stflag & PST_PROFIL) != 0) { 529 mutex_spin_enter(&p2->p_stmutex); 530 startprofclock(p2); 531 mutex_spin_exit(&p2->p_stmutex); 532 } 533 534 535 /* 536 * Preserve synchronization semantics of vfork. If waiting for 537 * child to exec or exit, set PS_PPWAIT on child, and sleep on our 538 * proc (in case of exit). 539 */ 540 if (flags & FORK_PPWAIT) 541 while (p2->p_sflag & PS_PPWAIT) 542 cv_wait(&p1->p_waitcv, p2->p_lock); 543 544 mutex_exit(p2->p_lock); 545 546 /* 547 * Return child pid to parent process, 548 * marking us as parent via retval[1]. 549 */ 550 if (retval != NULL) { 551 retval[0] = p2->p_pid; 552 retval[1] = 0; 553 } 554 555 return (0); 556 } 557
Indexes created Mon Sep 22 13:09:51 GMT 2025