1 /* $NetBSD: kern_fork.c,v 1.179 2011/01/18 23:56:49 matt 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 1.179 2011/01/18 23:56:49 matt 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 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 kpause("forkmx", false, forkfsleep, NULL); 244 return (EAGAIN); 245 } 246 247 /* 248 * Enforce limits. 249 */ 250 count = chgproccnt(uid, 1); 251 if (kauth_authorize_generic(l1->l_cred, KAUTH_GENERIC_ISSUSER, NULL) != 252 0 && __predict_false(count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 253 (void)chgproccnt(uid, -1); 254 atomic_dec_uint(&nprocs); 255 if (forkfsleep) 256 kpause("forkulim", false, forkfsleep, NULL); 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. 264 */ 265 uaddr = uvm_uarea_alloc(); 266 if (__predict_false(uaddr == 0)) { 267 (void)chgproccnt(uid, -1); 268 atomic_dec_uint(&nprocs); 269 return (ENOMEM); 270 } 271 272 /* 273 * We are now committed to the fork. From here on, we may 274 * block on resources, but resource allocation may NOT fail. 275 */ 276 277 /* Allocate new proc. */ 278 p2 = proc_alloc(); 279 280 /* 281 * Make a proc table entry for the new process. 282 * Start by zeroing the section of proc that is zero-initialized, 283 * then copy the section that is copied directly from the parent. 284 */ 285 memset(&p2->p_startzero, 0, 286 (unsigned) ((char *)&p2->p_endzero - (char *)&p2->p_startzero)); 287 memcpy(&p2->p_startcopy, &p1->p_startcopy, 288 (unsigned) ((char *)&p2->p_endcopy - (char *)&p2->p_startcopy)); 289 290 CIRCLEQ_INIT(&p2->p_sigpend.sp_info); 291 292 LIST_INIT(&p2->p_lwps); 293 LIST_INIT(&p2->p_sigwaiters); 294 295 /* 296 * Duplicate sub-structures as needed. 297 * Increase reference counts on shared objects. 298 * Inherit flags we want to keep. The flags related to SIGCHLD 299 * handling are important in order to keep a consistent behaviour 300 * for the child after the fork. If we are a 32-bit process, the 301 * child will be too. 302 */ 303 p2->p_flag = 304 p1->p_flag & (PK_SUGID | PK_NOCLDWAIT | PK_CLDSIGIGN | PK_32); 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 mutex_init(&p2->p_stmutex, MUTEX_DEFAULT, IPL_HIGH); 318 mutex_init(&p2->p_auxlock, MUTEX_DEFAULT, IPL_NONE); 319 rw_init(&p2->p_reflock); 320 cv_init(&p2->p_waitcv, "wait"); 321 cv_init(&p2->p_lwpcv, "lwpwait"); 322 323 /* 324 * Share a lock between the processes if they are to share signal 325 * state: we must synchronize access to it. 326 */ 327 if (flags & FORK_SHARESIGS) { 328 p2->p_lock = p1->p_lock; 329 mutex_obj_hold(p1->p_lock); 330 } else 331 p2->p_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE); 332 333 kauth_proc_fork(p1, p2); 334 335 p2->p_raslist = NULL; 336 #if defined(__HAVE_RAS) 337 ras_fork(p1, p2); 338 #endif 339 340 /* bump references to the text vnode (for procfs) */ 341 p2->p_textvp = p1->p_textvp; 342 if (p2->p_textvp) 343 vref(p2->p_textvp); 344 345 if (flags & FORK_SHAREFILES) 346 fd_share(p2); 347 else if (flags & FORK_CLEANFILES) 348 p2->p_fd = fd_init(NULL); 349 else 350 p2->p_fd = fd_copy(); 351 352 if (flags & FORK_SHARECWD) 353 cwdshare(p2); 354 else 355 p2->p_cwdi = cwdinit(); 356 357 /* 358 * p_limit (rlimit stuff) is usually copy-on-write, so we just need 359 * to bump pl_refcnt. 360 * However in some cases (see compat irix, and plausibly from clone) 361 * the parent and child share limits - in which case nothing else 362 * must have a copy of the limits (PL_SHAREMOD is set). 363 */ 364 if (__predict_false(flags & FORK_SHARELIMIT)) 365 lim_privatise(p1, 1); 366 p1_lim = p1->p_limit; 367 if (p1_lim->pl_flags & PL_WRITEABLE && !(flags & FORK_SHARELIMIT)) 368 p2->p_limit = lim_copy(p1_lim); 369 else { 370 lim_addref(p1_lim); 371 p2->p_limit = p1_lim; 372 } 373 374 p2->p_lflag = ((flags & FORK_PPWAIT) ? PL_PPWAIT : 0); 375 p2->p_sflag = 0; 376 p2->p_slflag = 0; 377 parent = (flags & FORK_NOWAIT) ? initproc : p1; 378 p2->p_pptr = parent; 379 p2->p_ppid = parent->p_pid; 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 * Set up the new process address space. 418 */ 419 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? true : false); 420 421 /* 422 * Finish creating the child process. 423 * It will return through a different path later. 424 */ 425 lwp_create(l1, p2, uaddr, (flags & FORK_PPWAIT) ? LWP_VFORK : 0, 426 stack, stacksize, (func != NULL) ? func : child_return, arg, &l2, 427 l1->l_class); 428 429 /* 430 * If emulation has a process fork hook, call it now. 431 */ 432 if (p2->p_emul->e_proc_fork) 433 (*p2->p_emul->e_proc_fork)(p2, l1, flags); 434 435 /* 436 * ...and finally, any other random fork hooks that subsystems 437 * might have registered. 438 */ 439 doforkhooks(p2, p1); 440 441 SDT_PROBE(proc,,,create, p2, p1, flags, 0, 0); 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 * Notify any interested parties about the new process. 483 */ 484 if (!SLIST_EMPTY(&p1->p_klist)) { 485 mutex_exit(proc_lock); 486 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 487 mutex_enter(proc_lock); 488 } 489 490 /* 491 * Make child runnable, set start time, and add to run queue except 492 * if the parent requested the child to start in SSTOP state. 493 */ 494 mutex_enter(p2->p_lock); 495 496 /* 497 * Start profiling. 498 */ 499 if ((p2->p_stflag & PST_PROFIL) != 0) { 500 mutex_spin_enter(&p2->p_stmutex); 501 startprofclock(p2); 502 mutex_spin_exit(&p2->p_stmutex); 503 } 504 505 getmicrotime(&p2->p_stats->p_start); 506 p2->p_acflag = AFORK; 507 lwp_lock(l2); 508 KASSERT(p2->p_nrlwps == 1); 509 if (p2->p_sflag & PS_STOPFORK) { 510 p2->p_nrlwps = 0; 511 p2->p_stat = SSTOP; 512 p2->p_waited = 0; 513 p1->p_nstopchild++; 514 l2->l_stat = LSSTOP; 515 lwp_unlock(l2); 516 } else { 517 p2->p_nrlwps = 1; 518 p2->p_stat = SACTIVE; 519 l2->l_stat = LSRUN; 520 sched_enqueue(l2, false); 521 lwp_unlock(l2); 522 } 523 524 mutex_exit(p2->p_lock); 525 526 /* 527 * Preserve synchronization semantics of vfork. If waiting for 528 * child to exec or exit, set PL_PPWAIT on child, and sleep on our 529 * proc (in case of exit). 530 */ 531 while (p2->p_lflag & PL_PPWAIT) 532 cv_wait(&p1->p_waitcv, proc_lock); 533 534 mutex_exit(proc_lock); 535 536 /* 537 * Return child pid to parent process, 538 * marking us as parent via retval[1]. 539 */ 540 if (retval != NULL) { 541 retval[0] = p2->p_pid; 542 retval[1] = 0; 543 } 544 545 return (0); 546 } 547