kern_fork.c revision 1.152
1 /* $NetBSD: kern_fork.c,v 1.152 2007/12/05 07:06:52 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 1999, 2001, 2004, 2006, 2007 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 1.152 2007/12/05 07:06:52 ad Exp $"); 78 79 #include "opt_ktrace.h" 80 #include "opt_systrace.h" 81 #include "opt_multiprocessor.h" 82 83 #include <sys/param.h> 84 #include <sys/systm.h> 85 #include <sys/filedesc.h> 86 #include <sys/kernel.h> 87 #include <sys/malloc.h> 88 #include <sys/pool.h> 89 #include <sys/mount.h> 90 #include <sys/proc.h> 91 #include <sys/ras.h> 92 #include <sys/resourcevar.h> 93 #include <sys/vnode.h> 94 #include <sys/file.h> 95 #include <sys/acct.h> 96 #include <sys/ktrace.h> 97 #include <sys/vmmeter.h> 98 #include <sys/sched.h> 99 #include <sys/signalvar.h> 100 #include <sys/systrace.h> 101 #include <sys/kauth.h> 102 #include <sys/atomic.h> 103 #include <sys/syscallargs.h> 104 105 #include <uvm/uvm_extern.h> 106 107 u_int nprocs = 1; /* process 0 */ 108 109 /* 110 * Number of ticks to sleep if fork() would fail due to process hitting 111 * limits. Exported in miliseconds to userland via sysctl. 112 */ 113 int forkfsleep = 0; 114 115 /*ARGSUSED*/ 116 int 117 sys_fork(struct lwp *l, void *v, register_t *retval) 118 { 119 120 return (fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); 121 } 122 123 /* 124 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 125 * Address space is not shared, but parent is blocked until child exit. 126 */ 127 /*ARGSUSED*/ 128 int 129 sys_vfork(struct lwp *l, void *v, register_t *retval) 130 { 131 132 return (fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 133 retval, NULL)); 134 } 135 136 /* 137 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 138 * semantics. Address space is shared, and parent is blocked until child exit. 139 */ 140 /*ARGSUSED*/ 141 int 142 sys___vfork14(struct lwp *l, void *v, register_t *retval) 143 { 144 145 return (fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 146 NULL, NULL, retval, NULL)); 147 } 148 149 /* 150 * Linux-compatible __clone(2) system call. 151 */ 152 int 153 sys___clone(struct lwp *l, void *v, register_t *retval) 154 { 155 struct sys___clone_args /* { 156 syscallarg(int) flags; 157 syscallarg(void *) stack; 158 } */ *uap = v; 159 int flags, sig; 160 161 /* 162 * We don't support the CLONE_PID or CLONE_PTRACE flags. 163 */ 164 if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) 165 return (EINVAL); 166 167 /* 168 * Linux enforces CLONE_VM with CLONE_SIGHAND, do same. 169 */ 170 if (SCARG(uap, flags) & CLONE_SIGHAND 171 && (SCARG(uap, flags) & CLONE_VM) == 0) 172 return (EINVAL); 173 174 flags = 0; 175 176 if (SCARG(uap, flags) & CLONE_VM) 177 flags |= FORK_SHAREVM; 178 if (SCARG(uap, flags) & CLONE_FS) 179 flags |= FORK_SHARECWD; 180 if (SCARG(uap, flags) & CLONE_FILES) 181 flags |= FORK_SHAREFILES; 182 if (SCARG(uap, flags) & CLONE_SIGHAND) 183 flags |= FORK_SHARESIGS; 184 if (SCARG(uap, flags) & CLONE_VFORK) 185 flags |= FORK_PPWAIT; 186 187 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 188 if (sig < 0 || sig >= _NSIG) 189 return (EINVAL); 190 191 /* 192 * Note that the Linux API does not provide a portable way of 193 * specifying the stack area; the caller must know if the stack 194 * grows up or down. So, we pass a stack size of 0, so that the 195 * code that makes this adjustment is a noop. 196 */ 197 return (fork1(l, flags, sig, SCARG(uap, stack), 0, 198 NULL, NULL, retval, NULL)); 199 } 200 201 /* print the 'table full' message once per 10 seconds */ 202 struct timeval fork_tfmrate = { 10, 0 }; 203 204 /* 205 * General fork call. Note that another LWP in the process may call exec() 206 * or exit() while we are forking. It's safe to continue here, because 207 * neither operation will complete until all LWPs have exited the process. 208 */ 209 int 210 fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, 211 void (*func)(void *), void *arg, register_t *retval, 212 struct proc **rnewprocp) 213 { 214 struct proc *p1, *p2, *parent; 215 struct plimit *p1_lim; 216 uid_t uid; 217 struct lwp *l2; 218 int count; 219 vaddr_t uaddr; 220 bool inmem; 221 int tmp; 222 int tnprocs; 223 224 /* 225 * Although process entries are dynamically created, we still keep 226 * a global limit on the maximum number we will create. Don't allow 227 * a nonprivileged user to use the last few processes; don't let root 228 * exceed the limit. The variable nprocs is the current number of 229 * processes, maxproc is the limit. 230 */ 231 p1 = l1->l_proc; 232 mutex_enter(&p1->p_mutex); 233 uid = kauth_cred_getuid(p1->p_cred); 234 mutex_exit(&p1->p_mutex); 235 tnprocs = atomic_inc_uint_nv(&nprocs); 236 if (__predict_false((tnprocs >= maxproc - 5 && uid != 0) || 237 tnprocs >= maxproc)) { 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 (__predict_false(count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 252 (void)chgproccnt(uid, -1); 253 atomic_dec_uint(&nprocs); 254 if (forkfsleep) 255 (void)tsleep(&nprocs, PUSER, "forkulim", forkfsleep); 256 return (EAGAIN); 257 } 258 259 /* 260 * Allocate virtual address space for the U-area now, while it 261 * is still easy to abort the fork operation if we're out of 262 * kernel virtual address space. The actual U-area pages will 263 * be allocated and wired in uvm_fork() if needed. 264 */ 265 266 inmem = uvm_uarea_alloc(&uaddr); 267 if (__predict_false(uaddr == 0)) { 268 (void)chgproccnt(uid, -1); 269 atomic_dec_uint(&nprocs); 270 return (ENOMEM); 271 } 272 273 /* 274 * We are now committed to the fork. From here on, we may 275 * block on resources, but resource allocation may NOT fail. 276 */ 277 278 /* Allocate new proc. */ 279 p2 = proc_alloc(); 280 281 /* 282 * Make a proc table entry for the new process. 283 * Start by zeroing the section of proc that is zero-initialized, 284 * then copy the section that is copied directly from the parent. 285 */ 286 memset(&p2->p_startzero, 0, 287 (unsigned) ((char *)&p2->p_endzero - (char *)&p2->p_startzero)); 288 memcpy(&p2->p_startcopy, &p1->p_startcopy, 289 (unsigned) ((char *)&p2->p_endcopy - (char *)&p2->p_startcopy)); 290 291 CIRCLEQ_INIT(&p2->p_sigpend.sp_info); 292 293 LIST_INIT(&p2->p_lwps); 294 LIST_INIT(&p2->p_sigwaiters); 295 296 /* 297 * Duplicate sub-structures as needed. 298 * Increase reference counts on shared objects. 299 * The p_stats and p_sigacts substructs are set in uvm_fork(). 300 * Inherit flags we want to keep. The flags related to SIGCHLD 301 * handling are important in order to keep a consistent behaviour 302 * for the child after the fork. 303 */ 304 p2->p_flag = p1->p_flag & (PK_SUGID | PK_NOCLDWAIT | PK_CLDSIGIGN); 305 p2->p_emul = p1->p_emul; 306 p2->p_execsw = p1->p_execsw; 307 308 if (flags & FORK_SYSTEM) { 309 /* 310 * Mark it as a system process. Set P_NOCLDWAIT so that 311 * children are reparented to init(8) when they exit. 312 * init(8) can easily wait them out for us. 313 */ 314 p2->p_flag |= (PK_SYSTEM | PK_NOCLDWAIT); 315 } 316 317 /* XXX p_smutex can be IPL_VM except for audio drivers */ 318 mutex_init(&p2->p_smutex, MUTEX_DEFAULT, IPL_SCHED); 319 mutex_init(&p2->p_stmutex, MUTEX_DEFAULT, IPL_HIGH); 320 mutex_init(&p2->p_raslock, MUTEX_DEFAULT, IPL_NONE); 321 mutex_init(&p2->p_mutex, MUTEX_DEFAULT, IPL_NONE); 322 rw_init(&p2->p_reflock); 323 cv_init(&p2->p_waitcv, "wait"); 324 cv_init(&p2->p_lwpcv, "lwpwait"); 325 326 kauth_proc_fork(p1, p2); 327 328 p2->p_raslist = NULL; 329 #if defined(__HAVE_RAS) 330 ras_fork(p1, p2); 331 #endif 332 333 /* bump references to the text vnode (for procfs) */ 334 p2->p_textvp = p1->p_textvp; 335 if (p2->p_textvp) 336 VREF(p2->p_textvp); 337 338 if (flags & FORK_SHAREFILES) 339 fdshare(p1, p2); 340 else if (flags & FORK_CLEANFILES) 341 p2->p_fd = fdinit(p1); 342 else 343 p2->p_fd = fdcopy(p1); 344 345 if (flags & FORK_SHARECWD) 346 cwdshare(p1, p2); 347 else 348 p2->p_cwdi = cwdinit(p1); 349 350 /* 351 * p_limit (rlimit stuff) is usually copy-on-write, so we just need 352 * to bump pl_refcnt. 353 * However in some cases (see compat irix, and plausibly from clone) 354 * the parent and child share limits - in which case nothing else 355 * must have a copy of the limits (PL_SHAREMOD is set). 356 */ 357 if (__predict_false(flags & FORK_SHARELIMIT)) 358 lim_privatise(p1, 1); 359 p1_lim = p1->p_limit; 360 if (p1_lim->pl_flags & PL_WRITEABLE && !(flags & FORK_SHARELIMIT)) 361 p2->p_limit = lim_copy(p1_lim); 362 else { 363 lim_addref(p1_lim); 364 p2->p_limit = p1_lim; 365 } 366 367 p2->p_sflag = ((flags & FORK_PPWAIT) ? PS_PPWAIT : 0); 368 p2->p_lflag = 0; 369 p2->p_slflag = 0; 370 parent = (flags & FORK_NOWAIT) ? initproc : p1; 371 p2->p_pptr = parent; 372 LIST_INIT(&p2->p_children); 373 374 p2->p_aio = NULL; 375 376 #ifdef KTRACE 377 /* 378 * Copy traceflag and tracefile if enabled. 379 * If not inherited, these were zeroed above. 380 */ 381 if (p1->p_traceflag & KTRFAC_INHERIT) { 382 mutex_enter(&ktrace_lock); 383 p2->p_traceflag = p1->p_traceflag; 384 if ((p2->p_tracep = p1->p_tracep) != NULL) 385 ktradref(p2); 386 mutex_exit(&ktrace_lock); 387 } 388 #endif 389 390 /* 391 * Create signal actions for the child process. 392 */ 393 p2->p_sigacts = sigactsinit(p1, flags & FORK_SHARESIGS); 394 mutex_enter(&p1->p_smutex); 395 p2->p_sflag |= 396 (p1->p_sflag & (PS_STOPFORK | PS_STOPEXEC | PS_NOCLDSTOP)); 397 sched_proc_fork(p1, p2); 398 mutex_exit(&p1->p_smutex); 399 400 p2->p_stflag = p1->p_stflag; 401 402 /* 403 * p_stats. 404 * Copy parts of p_stats, and zero out the rest. 405 */ 406 p2->p_stats = pstatscopy(p1->p_stats); 407 408 /* 409 * If emulation has process fork hook, call it now. 410 */ 411 if (p2->p_emul->e_proc_fork) 412 (*p2->p_emul->e_proc_fork)(p2, p1, flags); 413 414 /* 415 * ...and finally, any other random fork hooks that subsystems 416 * might have registered. 417 */ 418 doforkhooks(p2, p1); 419 420 /* 421 * This begins the section where we must prevent the parent 422 * from being swapped. 423 */ 424 uvm_lwp_hold(l1); 425 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? true : false); 426 427 /* 428 * Finish creating the child process. 429 * It will return through a different path later. 430 */ 431 lwp_create(l1, p2, uaddr, inmem, 0, stack, stacksize, 432 (func != NULL) ? func : child_return, arg, &l2, 433 l1->l_class); 434 435 /* 436 * It's now safe for the scheduler and other processes to see the 437 * child process. 438 */ 439 mutex_enter(&proclist_lock); 440 441 if (p1->p_session->s_ttyvp != NULL && p1->p_lflag & PL_CONTROLT) 442 p2->p_lflag |= PL_CONTROLT; 443 444 LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling); 445 p2->p_exitsig = exitsig; /* signal for parent on exit */ 446 447 mutex_enter(&proclist_mutex); 448 LIST_INSERT_AFTER(p1, p2, p_pglist); 449 mutex_exit(&proclist_mutex); 450 LIST_INSERT_HEAD(&allproc, p2, p_list); 451 452 mutex_exit(&proclist_lock); 453 454 #ifdef SYSTRACE 455 /* Tell systrace what's happening. */ 456 if (ISSET(p1->p_flag, PK_SYSTRACE)) 457 systrace_sys_fork(p1, p2); 458 #endif 459 460 #ifdef __HAVE_SYSCALL_INTERN 461 (*p2->p_emul->e_syscall_intern)(p2); 462 #endif 463 464 /* 465 * Now can be swapped. 466 */ 467 uvm_lwp_rele(l1); 468 469 /* 470 * Notify any interested parties about the new process. 471 */ 472 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 473 474 /* 475 * Update stats now that we know the fork was successful. 476 */ 477 uvmexp.forks++; 478 if (flags & FORK_PPWAIT) 479 uvmexp.forks_ppwait++; 480 if (flags & FORK_SHAREVM) 481 uvmexp.forks_sharevm++; 482 483 /* 484 * Pass a pointer to the new process to the caller. 485 */ 486 if (rnewprocp != NULL) 487 *rnewprocp = p2; 488 489 if (ktrpoint(KTR_EMUL)) 490 p2->p_traceflag |= KTRFAC_TRC_EMUL; 491 492 /* 493 * Make child runnable, set start time, and add to run queue except 494 * if the parent requested the child to start in SSTOP state. 495 */ 496 tmp = (p2->p_userret != NULL ? LW_WUSERRET : 0); 497 mutex_enter(&proclist_mutex); 498 mutex_enter(&p2->p_smutex); 499 500 getmicrotime(&p2->p_stats->p_start); 501 p2->p_acflag = AFORK; 502 if (p2->p_sflag & PS_STOPFORK) { 503 lwp_lock(l2); 504 p2->p_nrlwps = 0; 505 p2->p_stat = SSTOP; 506 p2->p_waited = 0; 507 p1->p_nstopchild++; 508 l2->l_stat = LSSTOP; 509 l2->l_flag |= tmp; 510 lwp_unlock(l2); 511 } else { 512 p2->p_nrlwps = 1; 513 p2->p_stat = SACTIVE; 514 lwp_lock(l2); 515 l2->l_stat = LSRUN; 516 l2->l_flag |= tmp; 517 sched_enqueue(l2, false); 518 lwp_unlock(l2); 519 } 520 521 mutex_exit(&proclist_mutex); 522 523 /* 524 * Start profiling. 525 */ 526 if ((p2->p_stflag & PST_PROFIL) != 0) { 527 mutex_spin_enter(&p2->p_stmutex); 528 startprofclock(p2); 529 mutex_spin_exit(&p2->p_stmutex); 530 } 531 532 /* 533 * Preserve synchronization semantics of vfork. If waiting for 534 * child to exec or exit, set PS_PPWAIT on child, and sleep on our 535 * proc (in case of exit). 536 */ 537 if (flags & FORK_PPWAIT) 538 while (p2->p_sflag & PS_PPWAIT) 539 cv_wait(&p1->p_waitcv, &p2->p_smutex); 540 541 mutex_exit(&p2->p_smutex); 542 543 /* 544 * Return child pid to parent process, 545 * marking us as parent via retval[1]. 546 */ 547 if (retval != NULL) { 548 retval[0] = p2->p_pid; 549 retval[1] = 0; 550 } 551 552 return (0); 553 } 554
Indexes created Mon Sep 22 10:09:38 GMT 2025