kern_fork.c revision 1.177
1 /* $NetBSD: kern_fork.c,v 1.177 2010/06/13 04:13:31 yamt 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 * 20 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 22 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 23 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 24 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 30 * POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 /* 34 * Copyright (c) 1982, 1986, 1989, 1991, 1993 35 * The Regents of the University of California. All rights reserved. 36 * (c) UNIX System Laboratories, Inc. 37 * All or some portions of this file are derived from material licensed 38 * to the University of California by American Telephone and Telegraph 39 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 40 * the permission of UNIX System Laboratories, Inc. 41 * 42 * Redistribution and use in source and binary forms, with or without 43 * modification, are permitted provided that the following conditions 44 * are met: 45 * 1. Redistributions of source code must retain the above copyright 46 * notice, this list of conditions and the following disclaimer. 47 * 2. Redistributions in binary form must reproduce the above copyright 48 * notice, this list of conditions and the following disclaimer in the 49 * documentation and/or other materials provided with the distribution. 50 * 3. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)kern_fork.c 8.8 (Berkeley) 2/14/95 67 */ 68 69 #include <sys/cdefs.h> 70 __KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.177 2010/06/13 04:13:31 yamt Exp $"); 71 72 #include "opt_ktrace.h" 73 74 #include <sys/param.h> 75 #include <sys/systm.h> 76 #include <sys/filedesc.h> 77 #include <sys/kernel.h> 78 #include <sys/pool.h> 79 #include <sys/mount.h> 80 #include <sys/proc.h> 81 #include <sys/ras.h> 82 #include <sys/resourcevar.h> 83 #include <sys/vnode.h> 84 #include <sys/file.h> 85 #include <sys/acct.h> 86 #include <sys/ktrace.h> 87 #include <sys/vmmeter.h> 88 #include <sys/sched.h> 89 #include <sys/signalvar.h> 90 #include <sys/kauth.h> 91 #include <sys/atomic.h> 92 #include <sys/syscallargs.h> 93 #include <sys/uidinfo.h> 94 #include <sys/sdt.h> 95 96 #include <uvm/uvm_extern.h> 97 98 /* 99 * DTrace SDT provider definitions 100 */ 101 SDT_PROBE_DEFINE(proc,,,create, 102 "struct proc *", NULL, /* new process */ 103 "struct proc *", NULL, /* parent process */ 104 "int", NULL, /* flags */ 105 NULL, NULL, NULL, NULL); 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, const 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, const 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, const 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, const struct sys___clone_args *uap, register_t *retval) 154 { 155 /* { 156 syscallarg(int) flags; 157 syscallarg(void *) stack; 158 } */ 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 int tmp; 221 int tnprocs; 222 int error = 0; 223 224 p1 = l1->l_proc; 225 uid = kauth_cred_getuid(l1->l_cred); 226 tnprocs = atomic_inc_uint_nv(&nprocs); 227 228 /* 229 * Although process entries are dynamically created, we still keep 230 * a global limit on the maximum number we will create. 231 */ 232 if (__predict_false(tnprocs >= maxproc)) 233 error = -1; 234 else 235 error = kauth_authorize_process(l1->l_cred, 236 KAUTH_PROCESS_FORK, p1, KAUTH_ARG(tnprocs), NULL, NULL); 237 238 if (error) { 239 static struct timeval lasttfm; 240 atomic_dec_uint(&nprocs); 241 if (ratecheck(&lasttfm, &fork_tfmrate)) 242 tablefull("proc", "increase kern.maxproc or NPROC"); 243 if (forkfsleep) 244 kpause("forkmx", false, forkfsleep, NULL); 245 return (EAGAIN); 246 } 247 248 /* 249 * Enforce limits. 250 */ 251 count = chgproccnt(uid, 1); 252 if (kauth_authorize_generic(l1->l_cred, KAUTH_GENERIC_ISSUSER, NULL) != 253 0 && __predict_false(count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 254 (void)chgproccnt(uid, -1); 255 atomic_dec_uint(&nprocs); 256 if (forkfsleep) 257 kpause("forkulim", false, forkfsleep, NULL); 258 return (EAGAIN); 259 } 260 261 /* 262 * Allocate virtual address space for the U-area now, while it 263 * is still easy to abort the fork operation if we're out of 264 * kernel virtual address space. 265 */ 266 uaddr = uvm_uarea_alloc(); 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 * Inherit flags we want to keep. The flags related to SIGCHLD 300 * handling are important in order to keep a consistent behaviour 301 * for the child after the fork. 302 */ 303 p2->p_flag = p1->p_flag & (PK_SUGID | PK_NOCLDWAIT | PK_CLDSIGIGN); 304 p2->p_emul = p1->p_emul; 305 p2->p_execsw = p1->p_execsw; 306 307 if (flags & FORK_SYSTEM) { 308 /* 309 * Mark it as a system process. Set P_NOCLDWAIT so that 310 * children are reparented to init(8) when they exit. 311 * init(8) can easily wait them out for us. 312 */ 313 p2->p_flag |= (PK_SYSTEM | PK_NOCLDWAIT); 314 } 315 316 mutex_init(&p2->p_stmutex, MUTEX_DEFAULT, IPL_HIGH); 317 mutex_init(&p2->p_auxlock, MUTEX_DEFAULT, IPL_NONE); 318 rw_init(&p2->p_reflock); 319 cv_init(&p2->p_waitcv, "wait"); 320 cv_init(&p2->p_lwpcv, "lwpwait"); 321 322 /* 323 * Share a lock between the processes if they are to share signal 324 * state: we must synchronize access to it. 325 */ 326 if (flags & FORK_SHARESIGS) { 327 p2->p_lock = p1->p_lock; 328 mutex_obj_hold(p1->p_lock); 329 } else 330 p2->p_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE); 331 332 kauth_proc_fork(p1, p2); 333 334 p2->p_raslist = NULL; 335 #if defined(__HAVE_RAS) 336 ras_fork(p1, p2); 337 #endif 338 339 /* bump references to the text vnode (for procfs) */ 340 p2->p_textvp = p1->p_textvp; 341 if (p2->p_textvp) 342 vref(p2->p_textvp); 343 344 if (flags & FORK_SHAREFILES) 345 fd_share(p2); 346 else if (flags & FORK_CLEANFILES) 347 p2->p_fd = fd_init(NULL); 348 else 349 p2->p_fd = fd_copy(); 350 351 if (flags & FORK_SHARECWD) 352 cwdshare(p2); 353 else 354 p2->p_cwdi = cwdinit(); 355 356 /* 357 * p_limit (rlimit stuff) is usually copy-on-write, so we just need 358 * to bump pl_refcnt. 359 * However in some cases (see compat irix, and plausibly from clone) 360 * the parent and child share limits - in which case nothing else 361 * must have a copy of the limits (PL_SHAREMOD is set). 362 */ 363 if (__predict_false(flags & FORK_SHARELIMIT)) 364 lim_privatise(p1, 1); 365 p1_lim = p1->p_limit; 366 if (p1_lim->pl_flags & PL_WRITEABLE && !(flags & FORK_SHARELIMIT)) 367 p2->p_limit = lim_copy(p1_lim); 368 else { 369 lim_addref(p1_lim); 370 p2->p_limit = p1_lim; 371 } 372 373 p2->p_lflag = ((flags & FORK_PPWAIT) ? PL_PPWAIT : 0); 374 p2->p_sflag = 0; 375 p2->p_slflag = 0; 376 parent = (flags & FORK_NOWAIT) ? initproc : p1; 377 p2->p_pptr = parent; 378 p2->p_ppid = parent->p_pid; 379 LIST_INIT(&p2->p_children); 380 381 p2->p_aio = NULL; 382 383 #ifdef KTRACE 384 /* 385 * Copy traceflag and tracefile if enabled. 386 * If not inherited, these were zeroed above. 387 */ 388 if (p1->p_traceflag & KTRFAC_INHERIT) { 389 mutex_enter(&ktrace_lock); 390 p2->p_traceflag = p1->p_traceflag; 391 if ((p2->p_tracep = p1->p_tracep) != NULL) 392 ktradref(p2); 393 mutex_exit(&ktrace_lock); 394 } 395 #endif 396 397 /* 398 * Create signal actions for the child process. 399 */ 400 p2->p_sigacts = sigactsinit(p1, flags & FORK_SHARESIGS); 401 mutex_enter(p1->p_lock); 402 p2->p_sflag |= 403 (p1->p_sflag & (PS_STOPFORK | PS_STOPEXEC | PS_NOCLDSTOP)); 404 sched_proc_fork(p1, p2); 405 mutex_exit(p1->p_lock); 406 407 p2->p_stflag = p1->p_stflag; 408 409 /* 410 * p_stats. 411 * Copy parts of p_stats, and zero out the rest. 412 */ 413 p2->p_stats = pstatscopy(p1->p_stats); 414 415 /* 416 * If emulation has process fork hook, call it now. 417 */ 418 if (p2->p_emul->e_proc_fork) 419 (*p2->p_emul->e_proc_fork)(p2, p1, flags); 420 421 /* 422 * ...and finally, any other random fork hooks that subsystems 423 * might have registered. 424 */ 425 doforkhooks(p2, p1); 426 427 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? true : false); 428 429 SDT_PROBE(proc,,,create, p2, p1, flags, 0, 0); 430 431 /* 432 * Finish creating the child process. 433 * It will return through a different path later. 434 */ 435 lwp_create(l1, p2, uaddr, (flags & FORK_PPWAIT) ? LWP_VFORK : 0, 436 stack, stacksize, (func != NULL) ? func : child_return, arg, &l2, 437 l1->l_class); 438 439 /* 440 * It's now safe for the scheduler and other processes to see the 441 * child process. 442 */ 443 mutex_enter(proc_lock); 444 445 if (p1->p_session->s_ttyvp != NULL && p1->p_lflag & PL_CONTROLT) 446 p2->p_lflag |= PL_CONTROLT; 447 448 LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling); 449 p2->p_exitsig = exitsig; /* signal for parent on exit */ 450 451 LIST_INSERT_AFTER(p1, p2, p_pglist); 452 LIST_INSERT_HEAD(&allproc, p2, p_list); 453 454 p2->p_trace_enabled = trace_is_enabled(p2); 455 #ifdef __HAVE_SYSCALL_INTERN 456 (*p2->p_emul->e_syscall_intern)(p2); 457 #endif 458 459 /* 460 * Update stats now that we know the fork was successful. 461 */ 462 uvmexp.forks++; 463 if (flags & FORK_PPWAIT) 464 uvmexp.forks_ppwait++; 465 if (flags & FORK_SHAREVM) 466 uvmexp.forks_sharevm++; 467 468 /* 469 * Pass a pointer to the new process to the caller. 470 */ 471 if (rnewprocp != NULL) 472 *rnewprocp = p2; 473 474 if (ktrpoint(KTR_EMUL)) 475 p2->p_traceflag |= KTRFAC_TRC_EMUL; 476 477 /* 478 * Notify any interested parties about the new process. 479 */ 480 if (!SLIST_EMPTY(&p1->p_klist)) { 481 mutex_exit(proc_lock); 482 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 483 mutex_enter(proc_lock); 484 } 485 486 /* 487 * Make child runnable, set start time, and add to run queue except 488 * if the parent requested the child to start in SSTOP state. 489 */ 490 tmp = (p2->p_userret != NULL ? LW_WUSERRET : 0); 491 mutex_enter(p2->p_lock); 492 493 /* 494 * Start profiling. 495 */ 496 if ((p2->p_stflag & PST_PROFIL) != 0) { 497 mutex_spin_enter(&p2->p_stmutex); 498 startprofclock(p2); 499 mutex_spin_exit(&p2->p_stmutex); 500 } 501 502 getmicrotime(&p2->p_stats->p_start); 503 p2->p_acflag = AFORK; 504 lwp_lock(l2); 505 KASSERT(p2->p_nrlwps == 1); 506 if (p2->p_sflag & PS_STOPFORK) { 507 p2->p_nrlwps = 0; 508 p2->p_stat = SSTOP; 509 p2->p_waited = 0; 510 p1->p_nstopchild++; 511 l2->l_stat = LSSTOP; 512 l2->l_flag |= tmp; 513 lwp_unlock(l2); 514 } else { 515 p2->p_nrlwps = 1; 516 p2->p_stat = SACTIVE; 517 l2->l_stat = LSRUN; 518 l2->l_flag |= tmp; 519 sched_enqueue(l2, false); 520 lwp_unlock(l2); 521 } 522 523 mutex_exit(p2->p_lock); 524 525 /* 526 * Preserve synchronization semantics of vfork. If waiting for 527 * child to exec or exit, set PL_PPWAIT on child, and sleep on our 528 * proc (in case of exit). 529 */ 530 while (p2->p_lflag & PL_PPWAIT) 531 cv_wait(&p1->p_waitcv, proc_lock); 532 533 mutex_exit(proc_lock); 534 535 /* 536 * Return child pid to parent process, 537 * marking us as parent via retval[1]. 538 */ 539 if (retval != NULL) { 540 retval[0] = p2->p_pid; 541 retval[1] = 0; 542 } 543 544 return (0); 545 } 546
Indexes created Mon Sep 22 13:09:51 GMT 2025