1 /* $NetBSD: kern_fork.c,v 1.173 2009/03/24 21:00:06 christos 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 1.173 2009/03/24 21:00:06 christos 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 95 #include <uvm/uvm_extern.h> 96 97 u_int nprocs = 1; /* process 0 */ 98 99 /* 100 * Number of ticks to sleep if fork() would fail due to process hitting 101 * limits. Exported in miliseconds to userland via sysctl. 102 */ 103 int forkfsleep = 0; 104 105 /*ARGSUSED*/ 106 int 107 sys_fork(struct lwp *l, const void *v, register_t *retval) 108 { 109 110 return (fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); 111 } 112 113 /* 114 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 115 * Address space is not shared, but parent is blocked until child exit. 116 */ 117 /*ARGSUSED*/ 118 int 119 sys_vfork(struct lwp *l, const void *v, register_t *retval) 120 { 121 122 return (fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 123 retval, NULL)); 124 } 125 126 /* 127 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 128 * semantics. Address space is shared, and parent is blocked until child exit. 129 */ 130 /*ARGSUSED*/ 131 int 132 sys___vfork14(struct lwp *l, const void *v, register_t *retval) 133 { 134 135 return (fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 136 NULL, NULL, retval, NULL)); 137 } 138 139 /* 140 * Linux-compatible __clone(2) system call. 141 */ 142 int 143 sys___clone(struct lwp *l, const struct sys___clone_args *uap, register_t *retval) 144 { 145 /* { 146 syscallarg(int) flags; 147 syscallarg(void *) stack; 148 } */ 149 int flags, sig; 150 151 /* 152 * We don't support the CLONE_PID or CLONE_PTRACE flags. 153 */ 154 if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) 155 return (EINVAL); 156 157 /* 158 * Linux enforces CLONE_VM with CLONE_SIGHAND, do same. 159 */ 160 if (SCARG(uap, flags) & CLONE_SIGHAND 161 && (SCARG(uap, flags) & CLONE_VM) == 0) 162 return (EINVAL); 163 164 flags = 0; 165 166 if (SCARG(uap, flags) & CLONE_VM) 167 flags |= FORK_SHAREVM; 168 if (SCARG(uap, flags) & CLONE_FS) 169 flags |= FORK_SHARECWD; 170 if (SCARG(uap, flags) & CLONE_FILES) 171 flags |= FORK_SHAREFILES; 172 if (SCARG(uap, flags) & CLONE_SIGHAND) 173 flags |= FORK_SHARESIGS; 174 if (SCARG(uap, flags) & CLONE_VFORK) 175 flags |= FORK_PPWAIT; 176 177 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 178 if (sig < 0 || sig >= _NSIG) 179 return (EINVAL); 180 181 /* 182 * Note that the Linux API does not provide a portable way of 183 * specifying the stack area; the caller must know if the stack 184 * grows up or down. So, we pass a stack size of 0, so that the 185 * code that makes this adjustment is a noop. 186 */ 187 return (fork1(l, flags, sig, SCARG(uap, stack), 0, 188 NULL, NULL, retval, NULL)); 189 } 190 191 /* print the 'table full' message once per 10 seconds */ 192 struct timeval fork_tfmrate = { 10, 0 }; 193 194 /* 195 * General fork call. Note that another LWP in the process may call exec() 196 * or exit() while we are forking. It's safe to continue here, because 197 * neither operation will complete until all LWPs have exited the process. 198 */ 199 int 200 fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, 201 void (*func)(void *), void *arg, register_t *retval, 202 struct proc **rnewprocp) 203 { 204 struct proc *p1, *p2, *parent; 205 struct plimit *p1_lim; 206 uid_t uid; 207 struct lwp *l2; 208 int count; 209 vaddr_t uaddr; 210 bool inmem; 211 int tmp; 212 int tnprocs; 213 int error = 0; 214 215 p1 = l1->l_proc; 216 uid = kauth_cred_getuid(l1->l_cred); 217 tnprocs = atomic_inc_uint_nv(&nprocs); 218 219 /* 220 * Although process entries are dynamically created, we still keep 221 * a global limit on the maximum number we will create. 222 */ 223 if (__predict_false(tnprocs >= maxproc)) 224 error = -1; 225 else 226 error = kauth_authorize_process(l1->l_cred, 227 KAUTH_PROCESS_FORK, p1, KAUTH_ARG(tnprocs), NULL, NULL); 228 229 if (error) { 230 static struct timeval lasttfm; 231 atomic_dec_uint(&nprocs); 232 if (ratecheck(&lasttfm, &fork_tfmrate)) 233 tablefull("proc", "increase kern.maxproc or NPROC"); 234 if (forkfsleep) 235 kpause("forkmx", false, forkfsleep, NULL); 236 return (EAGAIN); 237 } 238 239 /* 240 * Enforce limits. 241 */ 242 count = chgproccnt(uid, 1); 243 if (kauth_authorize_generic(l1->l_cred, KAUTH_GENERIC_ISSUSER, NULL) != 244 0 && __predict_false(count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 245 (void)chgproccnt(uid, -1); 246 atomic_dec_uint(&nprocs); 247 if (forkfsleep) 248 kpause("forkulim", false, forkfsleep, NULL); 249 return (EAGAIN); 250 } 251 252 /* 253 * Allocate virtual address space for the U-area now, while it 254 * is still easy to abort the fork operation if we're out of 255 * kernel virtual address space. The actual U-area pages will 256 * be allocated and wired in uvm_fork() if needed. 257 */ 258 259 inmem = uvm_uarea_alloc(&uaddr); 260 if (__predict_false(uaddr == 0)) { 261 (void)chgproccnt(uid, -1); 262 atomic_dec_uint(&nprocs); 263 return (ENOMEM); 264 } 265 266 /* 267 * We are now committed to the fork. From here on, we may 268 * block on resources, but resource allocation may NOT fail. 269 */ 270 271 /* Allocate new proc. */ 272 p2 = proc_alloc(); 273 274 /* 275 * Make a proc table entry for the new process. 276 * Start by zeroing the section of proc that is zero-initialized, 277 * then copy the section that is copied directly from the parent. 278 */ 279 memset(&p2->p_startzero, 0, 280 (unsigned) ((char *)&p2->p_endzero - (char *)&p2->p_startzero)); 281 memcpy(&p2->p_startcopy, &p1->p_startcopy, 282 (unsigned) ((char *)&p2->p_endcopy - (char *)&p2->p_startcopy)); 283 284 CIRCLEQ_INIT(&p2->p_sigpend.sp_info); 285 286 LIST_INIT(&p2->p_lwps); 287 LIST_INIT(&p2->p_sigwaiters); 288 289 /* 290 * Duplicate sub-structures as needed. 291 * Increase reference counts on shared objects. 292 * The p_stats and p_sigacts substructs are set in uvm_fork(). 293 * Inherit flags we want to keep. The flags related to SIGCHLD 294 * handling are important in order to keep a consistent behaviour 295 * for the child after the fork. 296 */ 297 p2->p_flag = p1->p_flag & (PK_SUGID | PK_NOCLDWAIT | PK_CLDSIGIGN); 298 p2->p_emul = p1->p_emul; 299 p2->p_execsw = p1->p_execsw; 300 301 if (flags & FORK_SYSTEM) { 302 /* 303 * Mark it as a system process. Set P_NOCLDWAIT so that 304 * children are reparented to init(8) when they exit. 305 * init(8) can easily wait them out for us. 306 */ 307 p2->p_flag |= (PK_SYSTEM | PK_NOCLDWAIT); 308 } 309 310 mutex_init(&p2->p_stmutex, MUTEX_DEFAULT, IPL_HIGH); 311 mutex_init(&p2->p_auxlock, MUTEX_DEFAULT, IPL_NONE); 312 rw_init(&p2->p_reflock); 313 cv_init(&p2->p_waitcv, "wait"); 314 cv_init(&p2->p_lwpcv, "lwpwait"); 315 316 /* 317 * Share a lock between the processes if they are to share signal 318 * state: we must synchronize access to it. 319 */ 320 if (flags & FORK_SHARESIGS) { 321 p2->p_lock = p1->p_lock; 322 mutex_obj_hold(p1->p_lock); 323 } else 324 p2->p_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE); 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 fd_share(p2); 340 else if (flags & FORK_CLEANFILES) 341 p2->p_fd = fd_init(NULL); 342 else 343 p2->p_fd = fd_copy(); 344 345 if (flags & FORK_SHARECWD) 346 cwdshare(p2); 347 else 348 p2->p_cwdi = cwdinit(); 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_lflag = ((flags & FORK_PPWAIT) ? PL_PPWAIT : 0); 368 p2->p_sflag = 0; 369 p2->p_slflag = 0; 370 parent = (flags & FORK_NOWAIT) ? initproc : p1; 371 p2->p_pptr = parent; 372 p2->p_ppid = parent->p_pid; 373 LIST_INIT(&p2->p_children); 374 375 p2->p_aio = NULL; 376 377 #ifdef KTRACE 378 /* 379 * Copy traceflag and tracefile if enabled. 380 * If not inherited, these were zeroed above. 381 */ 382 if (p1->p_traceflag & KTRFAC_INHERIT) { 383 mutex_enter(&ktrace_lock); 384 p2->p_traceflag = p1->p_traceflag; 385 if ((p2->p_tracep = p1->p_tracep) != NULL) 386 ktradref(p2); 387 mutex_exit(&ktrace_lock); 388 } 389 #endif 390 391 /* 392 * Create signal actions for the child process. 393 */ 394 p2->p_sigacts = sigactsinit(p1, flags & FORK_SHARESIGS); 395 mutex_enter(p1->p_lock); 396 p2->p_sflag |= 397 (p1->p_sflag & (PS_STOPFORK | PS_STOPEXEC | PS_NOCLDSTOP)); 398 sched_proc_fork(p1, p2); 399 mutex_exit(p1->p_lock); 400 401 p2->p_stflag = p1->p_stflag; 402 403 /* 404 * p_stats. 405 * Copy parts of p_stats, and zero out the rest. 406 */ 407 p2->p_stats = pstatscopy(p1->p_stats); 408 409 /* 410 * If emulation has process fork hook, call it now. 411 */ 412 if (p2->p_emul->e_proc_fork) 413 (*p2->p_emul->e_proc_fork)(p2, p1, flags); 414 415 /* 416 * ...and finally, any other random fork hooks that subsystems 417 * might have registered. 418 */ 419 doforkhooks(p2, p1); 420 421 /* 422 * This begins the section where we must prevent the parent 423 * from being swapped. 424 */ 425 uvm_lwp_hold(l1); 426 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? true : false); 427 428 /* 429 * Finish creating the child process. 430 * It will return through a different path later. 431 */ 432 lwp_create(l1, p2, uaddr, inmem, (flags & FORK_PPWAIT) ? LWP_VFORK : 0, 433 stack, stacksize, (func != NULL) ? func : child_return, arg, &l2, 434 l1->l_class); 435 436 /* 437 * It's now safe for the scheduler and other processes to see the 438 * child process. 439 */ 440 mutex_enter(proc_lock); 441 442 if (p1->p_session->s_ttyvp != NULL && p1->p_lflag & PL_CONTROLT) 443 p2->p_lflag |= PL_CONTROLT; 444 445 LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling); 446 p2->p_exitsig = exitsig; /* signal for parent on exit */ 447 448 LIST_INSERT_AFTER(p1, p2, p_pglist); 449 LIST_INSERT_HEAD(&allproc, p2, p_list); 450 451 p2->p_trace_enabled = trace_is_enabled(p2); 452 #ifdef __HAVE_SYSCALL_INTERN 453 (*p2->p_emul->e_syscall_intern)(p2); 454 #endif 455 456 /* 457 * Update stats now that we know the fork was successful. 458 */ 459 uvmexp.forks++; 460 if (flags & FORK_PPWAIT) 461 uvmexp.forks_ppwait++; 462 if (flags & FORK_SHAREVM) 463 uvmexp.forks_sharevm++; 464 465 /* 466 * Pass a pointer to the new process to the caller. 467 */ 468 if (rnewprocp != NULL) 469 *rnewprocp = p2; 470 471 if (ktrpoint(KTR_EMUL)) 472 p2->p_traceflag |= KTRFAC_TRC_EMUL; 473 474 /* 475 * Now can be swapped. 476 */ 477 uvm_lwp_rele(l1); 478 479 /* 480 * Notify any interested parties about the new process. 481 */ 482 if (!SLIST_EMPTY(&p1->p_klist)) { 483 mutex_exit(proc_lock); 484 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 485 mutex_enter(proc_lock); 486 } 487 488 /* 489 * Make child runnable, set start time, and add to run queue except 490 * if the parent requested the child to start in SSTOP state. 491 */ 492 tmp = (p2->p_userret != NULL ? LW_WUSERRET : 0); 493 mutex_enter(p2->p_lock); 494 495 /* 496 * Start profiling. 497 */ 498 if ((p2->p_stflag & PST_PROFIL) != 0) { 499 mutex_spin_enter(&p2->p_stmutex); 500 startprofclock(p2); 501 mutex_spin_exit(&p2->p_stmutex); 502 } 503 504 getmicrotime(&p2->p_stats->p_start); 505 p2->p_acflag = AFORK; 506 lwp_lock(l2); 507 if (p2->p_sflag & PS_STOPFORK) { 508 p2->p_nrlwps = 0; 509 p2->p_stat = SSTOP; 510 p2->p_waited = 0; 511 p1->p_nstopchild++; 512 l2->l_stat = LSSTOP; 513 l2->l_flag |= tmp; 514 lwp_unlock(l2); 515 } else { 516 p2->p_nrlwps = 1; 517 p2->p_stat = SACTIVE; 518 l2->l_stat = LSRUN; 519 l2->l_flag |= tmp; 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