1 /* $NetBSD: kern_fork.c,v 1.148 2007/11/27 01:27:30 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 1999, 2001, 2004 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. 10 * This code is derived from software contributed to The NetBSD Foundation 11 * by Charles M. Hannum. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the NetBSD 24 * Foundation, Inc. and its contributors. 25 * 4. Neither the name of The NetBSD Foundation nor the names of its 26 * contributors may be used to endorse or promote products derived 27 * from this software without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 30 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 31 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 32 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 33 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 34 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 35 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 36 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 37 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 38 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 39 * POSSIBILITY OF SUCH DAMAGE. 40 */ 41 42 /* 43 * Copyright (c) 1982, 1986, 1989, 1991, 1993 44 * The Regents of the University of California. All rights reserved. 45 * (c) UNIX System Laboratories, Inc. 46 * All or some portions of this file are derived from material licensed 47 * to the University of California by American Telephone and Telegraph 48 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 49 * the permission of UNIX System Laboratories, Inc. 50 * 51 * Redistribution and use in source and binary forms, with or without 52 * modification, are permitted provided that the following conditions 53 * are met: 54 * 1. Redistributions of source code must retain the above copyright 55 * notice, this list of conditions and the following disclaimer. 56 * 2. Redistributions in binary form must reproduce the above copyright 57 * notice, this list of conditions and the following disclaimer in the 58 * documentation and/or other materials provided with the distribution. 59 * 3. Neither the name of the University nor the names of its contributors 60 * may be used to endorse or promote products derived from this software 61 * without specific prior written permission. 62 * 63 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 64 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 65 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 66 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 67 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 68 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 69 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 70 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 71 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 72 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 73 * SUCH DAMAGE. 74 * 75 * @(#)kern_fork.c 8.8 (Berkeley) 2/14/95 76 */ 77 78 #include <sys/cdefs.h> 79 __KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.148 2007/11/27 01:27:30 ad Exp $"); 80 81 #include "opt_ktrace.h" 82 #include "opt_systrace.h" 83 #include "opt_multiprocessor.h" 84 85 #include <sys/param.h> 86 #include <sys/systm.h> 87 #include <sys/filedesc.h> 88 #include <sys/kernel.h> 89 #include <sys/malloc.h> 90 #include <sys/pool.h> 91 #include <sys/mount.h> 92 #include <sys/proc.h> 93 #include <sys/ras.h> 94 #include <sys/resourcevar.h> 95 #include <sys/vnode.h> 96 #include <sys/file.h> 97 #include <sys/acct.h> 98 #include <sys/ktrace.h> 99 #include <sys/vmmeter.h> 100 #include <sys/sched.h> 101 #include <sys/signalvar.h> 102 #include <sys/systrace.h> 103 #include <sys/kauth.h> 104 105 #include <sys/syscallargs.h> 106 107 #include <uvm/uvm_extern.h> 108 109 110 int nprocs = 1; /* process 0 */ 111 112 /* 113 * Number of ticks to sleep if fork() would fail due to process hitting 114 * limits. Exported in miliseconds to userland via sysctl. 115 */ 116 int forkfsleep = 0; 117 118 /*ARGSUSED*/ 119 int 120 sys_fork(struct lwp *l, void *v, register_t *retval) 121 { 122 123 return (fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); 124 } 125 126 /* 127 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 128 * Address space is not shared, but parent is blocked until child exit. 129 */ 130 /*ARGSUSED*/ 131 int 132 sys_vfork(struct lwp *l, void *v, register_t *retval) 133 { 134 135 return (fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 136 retval, NULL)); 137 } 138 139 /* 140 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 141 * semantics. Address space is shared, and parent is blocked until child exit. 142 */ 143 /*ARGSUSED*/ 144 int 145 sys___vfork14(struct lwp *l, void *v, register_t *retval) 146 { 147 148 return (fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 149 NULL, NULL, retval, NULL)); 150 } 151 152 /* 153 * Linux-compatible __clone(2) system call. 154 */ 155 int 156 sys___clone(struct lwp *l, void *v, register_t *retval) 157 { 158 struct sys___clone_args /* { 159 syscallarg(int) flags; 160 syscallarg(void *) stack; 161 } */ *uap = v; 162 int flags, sig; 163 164 /* 165 * We don't support the CLONE_PID or CLONE_PTRACE flags. 166 */ 167 if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) 168 return (EINVAL); 169 170 /* 171 * Linux enforces CLONE_VM with CLONE_SIGHAND, do same. 172 */ 173 if (SCARG(uap, flags) & CLONE_SIGHAND 174 && (SCARG(uap, flags) & CLONE_VM) == 0) 175 return (EINVAL); 176 177 flags = 0; 178 179 if (SCARG(uap, flags) & CLONE_VM) 180 flags |= FORK_SHAREVM; 181 if (SCARG(uap, flags) & CLONE_FS) 182 flags |= FORK_SHARECWD; 183 if (SCARG(uap, flags) & CLONE_FILES) 184 flags |= FORK_SHAREFILES; 185 if (SCARG(uap, flags) & CLONE_SIGHAND) 186 flags |= FORK_SHARESIGS; 187 if (SCARG(uap, flags) & CLONE_VFORK) 188 flags |= FORK_PPWAIT; 189 190 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 191 if (sig < 0 || sig >= _NSIG) 192 return (EINVAL); 193 194 /* 195 * Note that the Linux API does not provide a portable way of 196 * specifying the stack area; the caller must know if the stack 197 * grows up or down. So, we pass a stack size of 0, so that the 198 * code that makes this adjustment is a noop. 199 */ 200 return (fork1(l, flags, sig, SCARG(uap, stack), 0, 201 NULL, NULL, retval, NULL)); 202 } 203 204 /* print the 'table full' message once per 10 seconds */ 205 struct timeval fork_tfmrate = { 10, 0 }; 206 207 /* 208 * General fork call. Note that another LWP in the process may call exec() 209 * or exit() while we are forking. It's safe to continue here, because 210 * neither operation will complete until all LWPs have exited the process. 211 */ 212 int 213 fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, 214 void (*func)(void *), void *arg, register_t *retval, 215 struct proc **rnewprocp) 216 { 217 struct proc *p1, *p2, *parent; 218 struct plimit *p1_lim; 219 uid_t uid; 220 struct lwp *l2; 221 int count; 222 vaddr_t uaddr; 223 bool inmem; 224 int tmp; 225 226 /* 227 * Although process entries are dynamically created, we still keep 228 * a global limit on the maximum number we will create. Don't allow 229 * a nonprivileged user to use the last few processes; don't let root 230 * exceed the limit. The variable nprocs is the current number of 231 * processes, maxproc is the limit. 232 */ 233 p1 = l1->l_proc; 234 mutex_enter(&p1->p_mutex); 235 uid = kauth_cred_getuid(p1->p_cred); 236 mutex_exit(&p1->p_mutex); 237 if (__predict_false((nprocs >= maxproc - 5 && uid != 0) || 238 nprocs >= maxproc)) { 239 static struct timeval lasttfm; 240 241 if (ratecheck(&lasttfm, &fork_tfmrate)) 242 tablefull("proc", "increase kern.maxproc or NPROC"); 243 if (forkfsleep) 244 (void)tsleep(&nprocs, PUSER, "forkmx", forkfsleep); 245 return (EAGAIN); 246 } 247 nprocs++; 248 249 /* 250 * Increment the count of procs running with this uid. Don't allow 251 * a nonprivileged user to exceed their current limit. 252 */ 253 count = chgproccnt(uid, 1); 254 if (__predict_false(uid != 0 && count > 255 p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 256 (void)chgproccnt(uid, -1); 257 nprocs--; 258 if (forkfsleep) 259 (void)tsleep(&nprocs, PUSER, "forkulim", forkfsleep); 260 return (EAGAIN); 261 } 262 263 /* 264 * Allocate virtual address space for the U-area now, while it 265 * is still easy to abort the fork operation if we're out of 266 * kernel virtual address space. The actual U-area pages will 267 * be allocated and wired in uvm_fork() if needed. 268 */ 269 270 inmem = uvm_uarea_alloc(&uaddr); 271 if (__predict_false(uaddr == 0)) { 272 (void)chgproccnt(uid, -1); 273 nprocs--; 274 return (ENOMEM); 275 } 276 277 /* 278 * We are now committed to the fork. From here on, we may 279 * block on resources, but resource allocation may NOT fail. 280 */ 281 282 /* Allocate new proc. */ 283 p2 = proc_alloc(); 284 285 /* 286 * Make a proc table entry for the new process. 287 * Start by zeroing the section of proc that is zero-initialized, 288 * then copy the section that is copied directly from the parent. 289 */ 290 memset(&p2->p_startzero, 0, 291 (unsigned) ((char *)&p2->p_endzero - (char *)&p2->p_startzero)); 292 memcpy(&p2->p_startcopy, &p1->p_startcopy, 293 (unsigned) ((char *)&p2->p_endcopy - (char *)&p2->p_startcopy)); 294 295 CIRCLEQ_INIT(&p2->p_sigpend.sp_info); 296 297 LIST_INIT(&p2->p_lwps); 298 LIST_INIT(&p2->p_sigwaiters); 299 300 /* 301 * Duplicate sub-structures as needed. 302 * Increase reference counts on shared objects. 303 * The p_stats and p_sigacts substructs are set in uvm_fork(). 304 * Inherit flags we want to keep. The flags related to SIGCHLD 305 * handling are important in order to keep a consistent behaviour 306 * for the child after the fork. 307 */ 308 p2->p_flag = p1->p_flag & (PK_SUGID | PK_NOCLDWAIT | PK_CLDSIGIGN); 309 p2->p_emul = p1->p_emul; 310 p2->p_execsw = p1->p_execsw; 311 312 if (flags & FORK_SYSTEM) { 313 /* 314 * Mark it as a system process. Set P_NOCLDWAIT so that 315 * children are reparented to init(8) when they exit. 316 * init(8) can easily wait them out for us. 317 */ 318 p2->p_flag |= (PK_SYSTEM | PK_NOCLDWAIT); 319 } 320 321 /* XXX p_smutex can be IPL_VM except for audio drivers */ 322 mutex_init(&p2->p_smutex, MUTEX_SPIN, IPL_SCHED); 323 mutex_init(&p2->p_stmutex, MUTEX_SPIN, IPL_HIGH); 324 mutex_init(&p2->p_raslock, MUTEX_DEFAULT, IPL_NONE); 325 mutex_init(&p2->p_mutex, MUTEX_DEFAULT, IPL_NONE); 326 rw_init(&p2->p_reflock); 327 cv_init(&p2->p_waitcv, "wait"); 328 cv_init(&p2->p_lwpcv, "lwpwait"); 329 330 kauth_proc_fork(p1, p2); 331 332 p2->p_raslist = NULL; 333 #if defined(__HAVE_RAS) 334 ras_fork(p1, p2); 335 #endif 336 337 /* bump references to the text vnode (for procfs) */ 338 p2->p_textvp = p1->p_textvp; 339 if (p2->p_textvp) 340 VREF(p2->p_textvp); 341 342 if (flags & FORK_SHAREFILES) 343 fdshare(p1, p2); 344 else if (flags & FORK_CLEANFILES) 345 p2->p_fd = fdinit(p1); 346 else 347 p2->p_fd = fdcopy(p1); 348 349 if (flags & FORK_SHARECWD) 350 cwdshare(p1, p2); 351 else 352 p2->p_cwdi = cwdinit(p1); 353 354 /* 355 * p_limit (rlimit stuff) is usually copy-on-write, so we just need 356 * to bump pl_refcnt. 357 * However in some cases (see compat irix, and plausibly from clone) 358 * the parent and child share limits - in which case nothing else 359 * must have a copy of the limits (PL_SHAREMOD is set). 360 */ 361 if (__predict_false(flags & FORK_SHARELIMIT)) 362 lim_privatise(p1, 1); 363 p1_lim = p1->p_limit; 364 if (p1_lim->pl_flags & PL_WRITEABLE && !(flags & FORK_SHARELIMIT)) 365 p2->p_limit = lim_copy(p1_lim); 366 else { 367 lim_addref(p1_lim); 368 p2->p_limit = p1_lim; 369 } 370 371 p2->p_sflag = ((flags & FORK_PPWAIT) ? PS_PPWAIT : 0); 372 p2->p_lflag = 0; 373 p2->p_slflag = 0; 374 parent = (flags & FORK_NOWAIT) ? initproc : p1; 375 p2->p_pptr = parent; 376 LIST_INIT(&p2->p_children); 377 378 p2->p_aio = NULL; 379 380 #ifdef KTRACE 381 /* 382 * Copy traceflag and tracefile if enabled. 383 * If not inherited, these were zeroed above. 384 */ 385 if (p1->p_traceflag & KTRFAC_INHERIT) { 386 mutex_enter(&ktrace_lock); 387 p2->p_traceflag = p1->p_traceflag; 388 if ((p2->p_tracep = p1->p_tracep) != NULL) 389 ktradref(p2); 390 mutex_exit(&ktrace_lock); 391 } 392 #endif 393 394 /* 395 * Create signal actions for the child process. 396 */ 397 p2->p_sigacts = sigactsinit(p1, flags & FORK_SHARESIGS); 398 mutex_enter(&p1->p_smutex); 399 p2->p_sflag |= 400 (p1->p_sflag & (PS_STOPFORK | PS_STOPEXEC | PS_NOCLDSTOP)); 401 sched_proc_fork(p1, p2); 402 mutex_exit(&p1->p_smutex); 403 404 p2->p_stflag = p1->p_stflag; 405 406 /* 407 * p_stats. 408 * Copy parts of p_stats, and zero out the rest. 409 */ 410 p2->p_stats = pstatscopy(p1->p_stats); 411 412 /* 413 * If emulation has process fork hook, call it now. 414 */ 415 if (p2->p_emul->e_proc_fork) 416 (*p2->p_emul->e_proc_fork)(p2, p1, flags); 417 418 /* 419 * ...and finally, any other random fork hooks that subsystems 420 * might have registered. 421 */ 422 doforkhooks(p2, p1); 423 424 /* 425 * This begins the section where we must prevent the parent 426 * from being swapped. 427 */ 428 uvm_lwp_hold(l1); 429 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? true : false); 430 431 /* 432 * Finish creating the child process. 433 * It will return through a different path later. 434 */ 435 lwp_create(l1, p2, uaddr, inmem, 0, stack, stacksize, 436 (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(&proclist_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 mutex_enter(&proclist_mutex); 452 LIST_INSERT_AFTER(p1, p2, p_pglist); 453 LIST_INSERT_HEAD(&allproc, p2, p_list); 454 mutex_exit(&proclist_mutex); 455 456 mutex_exit(&proclist_lock); 457 458 #ifdef SYSTRACE 459 /* Tell systrace what's happening. */ 460 if (ISSET(p1->p_flag, PK_SYSTRACE)) 461 systrace_sys_fork(p1, p2); 462 #endif 463 464 #ifdef __HAVE_SYSCALL_INTERN 465 (*p2->p_emul->e_syscall_intern)(p2); 466 #endif 467 468 /* 469 * Now can be swapped. 470 */ 471 uvm_lwp_rele(l1); 472 473 /* 474 * Notify any interested parties about the new process. 475 */ 476 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 477 478 /* 479 * Update stats now that we know the fork was successful. 480 */ 481 uvmexp.forks++; 482 if (flags & FORK_PPWAIT) 483 uvmexp.forks_ppwait++; 484 if (flags & FORK_SHAREVM) 485 uvmexp.forks_sharevm++; 486 487 /* 488 * Pass a pointer to the new process to the caller. 489 */ 490 if (rnewprocp != NULL) 491 *rnewprocp = p2; 492 493 if (ktrpoint(KTR_EMUL)) 494 p2->p_traceflag |= KTRFAC_TRC_EMUL; 495 496 /* 497 * Make child runnable, set start time, and add to run queue except 498 * if the parent requested the child to start in SSTOP state. 499 */ 500 tmp = (p2->p_userret != NULL ? LW_WUSERRET : 0); 501 mutex_enter(&proclist_mutex); 502 mutex_enter(&p2->p_smutex); 503 504 getmicrotime(&p2->p_stats->p_start); 505 p2->p_acflag = AFORK; 506 if (p2->p_sflag & PS_STOPFORK) { 507 lwp_lock(l2); 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 lwp_lock(l2); 519 l2->l_stat = LSRUN; 520 l2->l_flag |= tmp; 521 sched_enqueue(l2, false); 522 lwp_unlock(l2); 523 } 524 525 mutex_exit(&proclist_mutex); 526 527 /* 528 * Start profiling. 529 */ 530 if ((p2->p_stflag & PST_PROFIL) != 0) { 531 mutex_spin_enter(&p2->p_stmutex); 532 startprofclock(p2); 533 mutex_spin_exit(&p2->p_stmutex); 534 } 535 536 /* 537 * Preserve synchronization semantics of vfork. If waiting for 538 * child to exec or exit, set PS_PPWAIT on child, and sleep on our 539 * proc (in case of exit). 540 */ 541 if (flags & FORK_PPWAIT) 542 while (p2->p_sflag & PS_PPWAIT) 543 cv_wait(&p1->p_waitcv, &p2->p_smutex); 544 545 mutex_exit(&p2->p_smutex); 546 547 /* 548 * Return child pid to parent process, 549 * marking us as parent via retval[1]. 550 */ 551 if (retval != NULL) { 552 retval[0] = p2->p_pid; 553 retval[1] = 0; 554 } 555 556 return (0); 557 } 558