1 /* $NetBSD: kern_fork.c,v 1.188 2012/03/02 21:23:05 rmind 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 1.188 2012/03/02 21:23:05 rmind 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/sched.h> 88 #include <sys/signalvar.h> 89 #include <sys/kauth.h> 90 #include <sys/atomic.h> 91 #include <sys/syscallargs.h> 92 #include <sys/uidinfo.h> 93 #include <sys/sdt.h> 94 #include <sys/ptrace.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 __cacheline_aligned = 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 int 116 sys_fork(struct lwp *l, const void *v, register_t *retval) 117 { 118 119 return fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL); 120 } 121 122 /* 123 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 124 * Address space is not shared, but parent is blocked until child exit. 125 */ 126 int 127 sys_vfork(struct lwp *l, const void *v, register_t *retval) 128 { 129 130 return fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 131 retval, NULL); 132 } 133 134 /* 135 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 136 * semantics. Address space is shared, and parent is blocked until child exit. 137 */ 138 int 139 sys___vfork14(struct lwp *l, const void *v, register_t *retval) 140 { 141 142 return fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 143 NULL, NULL, retval, NULL); 144 } 145 146 /* 147 * Linux-compatible __clone(2) system call. 148 */ 149 int 150 sys___clone(struct lwp *l, const struct sys___clone_args *uap, 151 register_t *retval) 152 { 153 /* { 154 syscallarg(int) flags; 155 syscallarg(void *) stack; 156 } */ 157 int flags, sig; 158 159 /* 160 * We don't support the CLONE_PID or CLONE_PTRACE flags. 161 */ 162 if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) 163 return EINVAL; 164 165 /* 166 * Linux enforces CLONE_VM with CLONE_SIGHAND, do same. 167 */ 168 if (SCARG(uap, flags) & CLONE_SIGHAND 169 && (SCARG(uap, flags) & CLONE_VM) == 0) 170 return EINVAL; 171 172 flags = 0; 173 174 if (SCARG(uap, flags) & CLONE_VM) 175 flags |= FORK_SHAREVM; 176 if (SCARG(uap, flags) & CLONE_FS) 177 flags |= FORK_SHARECWD; 178 if (SCARG(uap, flags) & CLONE_FILES) 179 flags |= FORK_SHAREFILES; 180 if (SCARG(uap, flags) & CLONE_SIGHAND) 181 flags |= FORK_SHARESIGS; 182 if (SCARG(uap, flags) & CLONE_VFORK) 183 flags |= FORK_PPWAIT; 184 185 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 186 if (sig < 0 || sig >= _NSIG) 187 return EINVAL; 188 189 /* 190 * Note that the Linux API does not provide a portable way of 191 * specifying the stack area; the caller must know if the stack 192 * grows up or down. So, we pass a stack size of 0, so that the 193 * code that makes this adjustment is a noop. 194 */ 195 return fork1(l, flags, sig, SCARG(uap, stack), 0, 196 NULL, NULL, retval, NULL); 197 } 198 199 /* 200 * Print the 'table full' message once per 10 seconds. 201 */ 202 static 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 tracefork; 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. If we are a 32-bit process, the 302 * child will be too. 303 */ 304 p2->p_flag = 305 p1->p_flag & (PK_SUGID | PK_NOCLDWAIT | PK_CLDSIGIGN | PK_32); 306 p2->p_emul = p1->p_emul; 307 p2->p_execsw = p1->p_execsw; 308 309 if (flags & FORK_SYSTEM) { 310 /* 311 * Mark it as a system process. Set P_NOCLDWAIT so that 312 * children are reparented to init(8) when they exit. 313 * init(8) can easily wait them out for us. 314 */ 315 p2->p_flag |= (PK_SYSTEM | PK_NOCLDWAIT); 316 } 317 318 mutex_init(&p2->p_stmutex, MUTEX_DEFAULT, IPL_HIGH); 319 mutex_init(&p2->p_auxlock, MUTEX_DEFAULT, IPL_NONE); 320 rw_init(&p2->p_reflock); 321 cv_init(&p2->p_waitcv, "wait"); 322 cv_init(&p2->p_lwpcv, "lwpwait"); 323 324 /* 325 * Share a lock between the processes if they are to share signal 326 * state: we must synchronize access to it. 327 */ 328 if (flags & FORK_SHARESIGS) { 329 p2->p_lock = p1->p_lock; 330 mutex_obj_hold(p1->p_lock); 331 } else 332 p2->p_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE); 333 334 kauth_proc_fork(p1, p2); 335 336 p2->p_raslist = NULL; 337 #if defined(__HAVE_RAS) 338 ras_fork(p1, p2); 339 #endif 340 341 /* bump references to the text vnode (for procfs) */ 342 p2->p_textvp = p1->p_textvp; 343 if (p2->p_textvp) 344 vref(p2->p_textvp); 345 346 if (flags & FORK_SHAREFILES) 347 fd_share(p2); 348 else if (flags & FORK_CLEANFILES) 349 p2->p_fd = fd_init(NULL); 350 else 351 p2->p_fd = fd_copy(); 352 353 /* XXX racy */ 354 p2->p_mqueue_cnt = p1->p_mqueue_cnt; 355 356 if (flags & FORK_SHARECWD) 357 cwdshare(p2); 358 else 359 p2->p_cwdi = cwdinit(); 360 361 /* 362 * Note: p_limit (rlimit stuff) is copy-on-write, so normally 363 * we just need increase pl_refcnt. 364 */ 365 p1_lim = p1->p_limit; 366 if (!p1_lim->pl_writeable) { 367 lim_addref(p1_lim); 368 p2->p_limit = p1_lim; 369 } else { 370 p2->p_limit = lim_copy(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 * Set up the new process address space. 417 */ 418 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? true : false); 419 420 /* 421 * Finish creating the child process. 422 * It will return through a different path later. 423 */ 424 lwp_create(l1, p2, uaddr, (flags & FORK_PPWAIT) ? LWP_VFORK : 0, 425 stack, stacksize, (func != NULL) ? func : child_return, arg, &l2, 426 l1->l_class); 427 428 /* 429 * Inherit l_private from the parent. 430 * Note that we cannot use lwp_setprivate() here since that 431 * also sets the CPU TLS register, which is incorrect if the 432 * process has changed that without letting the kernel know. 433 */ 434 l2->l_private = l1->l_private; 435 436 /* 437 * If emulation has a process fork hook, call it now. 438 */ 439 if (p2->p_emul->e_proc_fork) 440 (*p2->p_emul->e_proc_fork)(p2, l1, flags); 441 442 /* 443 * ...and finally, any other random fork hooks that subsystems 444 * might have registered. 445 */ 446 doforkhooks(p2, p1); 447 448 SDT_PROBE(proc,,,create, p2, p1, flags, 0, 0); 449 450 /* 451 * It's now safe for the scheduler and other processes to see the 452 * child process. 453 */ 454 mutex_enter(proc_lock); 455 456 if (p1->p_session->s_ttyvp != NULL && p1->p_lflag & PL_CONTROLT) 457 p2->p_lflag |= PL_CONTROLT; 458 459 LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling); 460 p2->p_exitsig = exitsig; /* signal for parent on exit */ 461 462 /* 463 * We don't want to tracefork vfork()ed processes because they 464 * will not receive the SIGTRAP until it is too late. 465 */ 466 tracefork = (p1->p_slflag & (PSL_TRACEFORK|PSL_TRACED)) == 467 (PSL_TRACEFORK|PSL_TRACED) && (flags && FORK_PPWAIT) == 0; 468 if (tracefork) { 469 p2->p_slflag |= PSL_TRACED; 470 p2->p_opptr = p2->p_pptr; 471 if (p2->p_pptr != p1->p_pptr) { 472 struct proc *parent1 = p2->p_pptr; 473 474 if (parent1->p_lock < p2->p_lock) { 475 if (!mutex_tryenter(parent1->p_lock)) { 476 mutex_exit(p2->p_lock); 477 mutex_enter(parent1->p_lock); 478 } 479 } else if (parent1->p_lock > p2->p_lock) { 480 mutex_enter(parent1->p_lock); 481 } 482 parent1->p_slflag |= PSL_CHTRACED; 483 proc_reparent(p2, p1->p_pptr); 484 if (parent1->p_lock != p2->p_lock) 485 mutex_exit(parent1->p_lock); 486 } 487 488 /* 489 * Set ptrace status. 490 */ 491 p1->p_fpid = p2->p_pid; 492 p2->p_fpid = p1->p_pid; 493 } 494 495 LIST_INSERT_AFTER(p1, p2, p_pglist); 496 LIST_INSERT_HEAD(&allproc, p2, p_list); 497 498 p2->p_trace_enabled = trace_is_enabled(p2); 499 #ifdef __HAVE_SYSCALL_INTERN 500 (*p2->p_emul->e_syscall_intern)(p2); 501 #endif 502 503 /* 504 * Update stats now that we know the fork was successful. 505 */ 506 uvmexp.forks++; 507 if (flags & FORK_PPWAIT) 508 uvmexp.forks_ppwait++; 509 if (flags & FORK_SHAREVM) 510 uvmexp.forks_sharevm++; 511 512 /* 513 * Pass a pointer to the new process to the caller. 514 */ 515 if (rnewprocp != NULL) 516 *rnewprocp = p2; 517 518 if (ktrpoint(KTR_EMUL)) 519 p2->p_traceflag |= KTRFAC_TRC_EMUL; 520 521 /* 522 * Notify any interested parties about the new process. 523 */ 524 if (!SLIST_EMPTY(&p1->p_klist)) { 525 mutex_exit(proc_lock); 526 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 527 mutex_enter(proc_lock); 528 } 529 530 /* 531 * Make child runnable, set start time, and add to run queue except 532 * if the parent requested the child to start in SSTOP state. 533 */ 534 mutex_enter(p2->p_lock); 535 536 /* 537 * Start profiling. 538 */ 539 if ((p2->p_stflag & PST_PROFIL) != 0) { 540 mutex_spin_enter(&p2->p_stmutex); 541 startprofclock(p2); 542 mutex_spin_exit(&p2->p_stmutex); 543 } 544 545 getmicrotime(&p2->p_stats->p_start); 546 p2->p_acflag = AFORK; 547 lwp_lock(l2); 548 KASSERT(p2->p_nrlwps == 1); 549 if (p2->p_sflag & PS_STOPFORK) { 550 struct schedstate_percpu *spc = &l2->l_cpu->ci_schedstate; 551 p2->p_nrlwps = 0; 552 p2->p_stat = SSTOP; 553 p2->p_waited = 0; 554 p1->p_nstopchild++; 555 l2->l_stat = LSSTOP; 556 KASSERT(l2->l_wchan == NULL); 557 lwp_unlock_to(l2, spc->spc_lwplock); 558 } else { 559 p2->p_nrlwps = 1; 560 p2->p_stat = SACTIVE; 561 l2->l_stat = LSRUN; 562 sched_enqueue(l2, false); 563 lwp_unlock(l2); 564 } 565 mutex_exit(p2->p_lock); 566 567 /* 568 * Preserve synchronization semantics of vfork. If waiting for 569 * child to exec or exit, set PL_PPWAIT on child, and sleep on our 570 * proc (in case of exit). 571 */ 572 while (p2->p_lflag & PL_PPWAIT) 573 cv_wait(&p1->p_waitcv, proc_lock); 574 575 /* 576 * Let the parent know that we are tracing its child. 577 */ 578 if (tracefork) { 579 ksiginfo_t ksi; 580 581 KSI_INIT_EMPTY(&ksi); 582 ksi.ksi_signo = SIGTRAP; 583 ksi.ksi_lid = l1->l_lid; 584 kpsignal(p1, &ksi, NULL); 585 } 586 587 mutex_exit(proc_lock); 588 589 /* 590 * Return child pid to parent process, 591 * marking us as parent via retval[1]. 592 */ 593 if (retval != NULL) { 594 retval[0] = p2->p_pid; 595 retval[1] = 0; 596 } 597 598 return 0; 599 } 600