1 /* $NetBSD: kern_fork.c,v 1.94 2002/09/25 22:21:42 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 1999, 2001 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 * 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 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 /* 41 * Copyright (c) 1982, 1986, 1989, 1991, 1993 42 * The Regents of the University of California. All rights reserved. 43 * (c) UNIX System Laboratories, Inc. 44 * All or some portions of this file are derived from material licensed 45 * to the University of California by American Telephone and Telegraph 46 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 47 * the permission of UNIX System Laboratories, Inc. 48 * 49 * Redistribution and use in source and binary forms, with or without 50 * modification, are permitted provided that the following conditions 51 * are met: 52 * 1. Redistributions of source code must retain the above copyright 53 * notice, this list of conditions and the following disclaimer. 54 * 2. Redistributions in binary form must reproduce the above copyright 55 * notice, this list of conditions and the following disclaimer in the 56 * documentation and/or other materials provided with the distribution. 57 * 3. All advertising materials mentioning features or use of this software 58 * must display the following acknowledgement: 59 * This product includes software developed by the University of 60 * California, Berkeley and its contributors. 61 * 4. Neither the name of the University nor the names of its contributors 62 * may be used to endorse or promote products derived from this software 63 * without specific prior written permission. 64 * 65 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 66 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 67 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 68 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 69 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 70 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 71 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 72 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 73 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 74 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 75 * SUCH DAMAGE. 76 * 77 * @(#)kern_fork.c 8.8 (Berkeley) 2/14/95 78 */ 79 80 #include <sys/cdefs.h> 81 __KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.94 2002/09/25 22:21:42 thorpej Exp $"); 82 83 #include "opt_ktrace.h" 84 #include "opt_systrace.h" 85 #include "opt_multiprocessor.h" 86 87 #include <sys/param.h> 88 #include <sys/systm.h> 89 #include <sys/filedesc.h> 90 #include <sys/kernel.h> 91 #include <sys/malloc.h> 92 #include <sys/pool.h> 93 #include <sys/mount.h> 94 #include <sys/proc.h> 95 #include <sys/ras.h> 96 #include <sys/resourcevar.h> 97 #include <sys/vnode.h> 98 #include <sys/file.h> 99 #include <sys/acct.h> 100 #include <sys/ktrace.h> 101 #include <sys/vmmeter.h> 102 #include <sys/sched.h> 103 #include <sys/signalvar.h> 104 #include <sys/systrace.h> 105 106 #include <sys/syscallargs.h> 107 108 #include <uvm/uvm_extern.h> 109 110 111 int nprocs = 1; /* process 0 */ 112 113 /*ARGSUSED*/ 114 int 115 sys_fork(struct proc *p, void *v, register_t *retval) 116 { 117 118 return (fork1(p, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); 119 } 120 121 /* 122 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 123 * Address space is not shared, but parent is blocked until child exit. 124 */ 125 /*ARGSUSED*/ 126 int 127 sys_vfork(struct proc *p, void *v, register_t *retval) 128 { 129 130 return (fork1(p, 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 /*ARGSUSED*/ 139 int 140 sys___vfork14(struct proc *p, void *v, register_t *retval) 141 { 142 143 return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 144 NULL, NULL, retval, NULL)); 145 } 146 147 /* 148 * Linux-compatible __clone(2) system call. 149 */ 150 int 151 sys___clone(struct proc *p, void *v, register_t *retval) 152 { 153 struct sys___clone_args /* { 154 syscallarg(int) flags; 155 syscallarg(void *) stack; 156 } */ *uap = v; 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 flags = 0; 166 167 if (SCARG(uap, flags) & CLONE_VM) 168 flags |= FORK_SHAREVM; 169 if (SCARG(uap, flags) & CLONE_FS) 170 flags |= FORK_SHARECWD; 171 if (SCARG(uap, flags) & CLONE_FILES) 172 flags |= FORK_SHAREFILES; 173 if (SCARG(uap, flags) & CLONE_SIGHAND) 174 flags |= FORK_SHARESIGS; 175 if (SCARG(uap, flags) & CLONE_VFORK) 176 flags |= FORK_PPWAIT; 177 178 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 179 if (sig < 0 || sig >= _NSIG) 180 return (EINVAL); 181 182 /* 183 * Note that the Linux API does not provide a portable way of 184 * specifying the stack area; the caller must know if the stack 185 * grows up or down. So, we pass a stack size of 0, so that the 186 * code that makes this adjustment is a noop. 187 */ 188 return (fork1(p, flags, sig, SCARG(uap, stack), 0, 189 NULL, NULL, retval, NULL)); 190 } 191 192 int 193 fork1(struct proc *p1, int flags, int exitsig, void *stack, size_t stacksize, 194 void (*func)(void *), void *arg, register_t *retval, 195 struct proc **rnewprocp) 196 { 197 struct proc *p2, *tp; 198 uid_t uid; 199 int count, s; 200 vaddr_t uaddr; 201 static int nextpid, pidchecked; 202 203 /* 204 * Although process entries are dynamically created, we still keep 205 * a global limit on the maximum number we will create. Don't allow 206 * a nonprivileged user to use the last process; don't let root 207 * exceed the limit. The variable nprocs is the current number of 208 * processes, maxproc is the limit. 209 */ 210 uid = p1->p_cred->p_ruid; 211 if (__predict_false((nprocs >= maxproc - 1 && uid != 0) || 212 nprocs >= maxproc)) { 213 tablefull("proc", "increase kern.maxproc or NPROC"); 214 return (EAGAIN); 215 } 216 nprocs++; 217 218 /* 219 * Increment the count of procs running with this uid. Don't allow 220 * a nonprivileged user to exceed their current limit. 221 */ 222 count = chgproccnt(uid, 1); 223 if (__predict_false(uid != 0 && count > 224 p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 225 (void)chgproccnt(uid, -1); 226 nprocs--; 227 return (EAGAIN); 228 } 229 230 /* 231 * Allocate virtual address space for the U-area now, while it 232 * is still easy to abort the fork operation if we're out of 233 * kernel virtual address space. The actual U-area pages will 234 * be allocated and wired in uvm_fork(). 235 */ 236 237 uaddr = uvm_uarea_alloc(); 238 if (__predict_false(uaddr == 0)) { 239 (void)chgproccnt(uid, -1); 240 nprocs--; 241 return (ENOMEM); 242 } 243 244 /* 245 * We are now committed to the fork. From here on, we may 246 * block on resources, but resource allocation may NOT fail. 247 */ 248 249 /* Allocate new proc. */ 250 p2 = pool_get(&proc_pool, PR_WAITOK); 251 252 /* 253 * BEGIN PID ALLOCATION. 254 */ 255 s = proclist_lock_write(); 256 257 /* 258 * Find an unused process ID. We remember a range of unused IDs 259 * ready to use (from nextpid+1 through pidchecked-1). 260 */ 261 nextpid++; 262 retry: 263 /* 264 * If the process ID prototype has wrapped around, 265 * restart somewhat above 0, as the low-numbered procs 266 * tend to include daemons that don't exit. 267 */ 268 if (nextpid >= PID_MAX) { 269 nextpid = 500; 270 pidchecked = 0; 271 } 272 if (nextpid >= pidchecked) { 273 const struct proclist_desc *pd; 274 275 pidchecked = PID_MAX; 276 /* 277 * Scan the process lists to check whether this pid 278 * is in use. Remember the lowest pid that's greater 279 * than nextpid, so we can avoid checking for a while. 280 */ 281 pd = proclists; 282 again: 283 LIST_FOREACH(tp, pd->pd_list, p_list) { 284 while (tp->p_pid == nextpid || 285 tp->p_pgrp->pg_id == nextpid || 286 tp->p_session->s_sid == nextpid) { 287 nextpid++; 288 if (nextpid >= pidchecked) 289 goto retry; 290 } 291 if (tp->p_pid > nextpid && pidchecked > tp->p_pid) 292 pidchecked = tp->p_pid; 293 294 if (tp->p_pgrp->pg_id > nextpid && 295 pidchecked > tp->p_pgrp->pg_id) 296 pidchecked = tp->p_pgrp->pg_id; 297 298 if (tp->p_session->s_sid > nextpid && 299 pidchecked > tp->p_session->s_sid) 300 pidchecked = tp->p_session->s_sid; 301 } 302 303 /* 304 * If there's another list, scan it. If we have checked 305 * them all, we've found one! 306 */ 307 pd++; 308 if (pd->pd_list != NULL) 309 goto again; 310 } 311 312 /* 313 * Put the proc on allproc before unlocking PID allocation 314 * so that waiters won't grab it as soon as we unlock. 315 */ 316 317 p2->p_stat = SIDL; /* protect against others */ 318 p2->p_pid = nextpid; 319 p2->p_exitsig = exitsig; /* signal for parent on exit */ 320 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 321 322 LIST_INSERT_HEAD(&allproc, p2, p_list); 323 324 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 325 326 /* 327 * END PID ALLOCATION. 328 */ 329 proclist_unlock_write(s); 330 331 /* 332 * Make a proc table entry for the new process. 333 * Start by zeroing the section of proc that is zero-initialized, 334 * then copy the section that is copied directly from the parent. 335 */ 336 memset(&p2->p_startzero, 0, 337 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 338 memcpy(&p2->p_startcopy, &p1->p_startcopy, 339 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 340 341 #if !defined(MULTIPROCESSOR) 342 /* 343 * In the single-processor case, all processes will always run 344 * on the same CPU. So, initialize the child's CPU to the parent's 345 * now. In the multiprocessor case, the child's CPU will be 346 * initialized in the low-level context switch code when the 347 * process runs. 348 */ 349 p2->p_cpu = p1->p_cpu; 350 #else 351 /* 352 * zero child's cpu pointer so we don't get trash. 353 */ 354 p2->p_cpu = NULL; 355 #endif /* ! MULTIPROCESSOR */ 356 357 /* 358 * Duplicate sub-structures as needed. 359 * Increase reference counts on shared objects. 360 * The p_stats and p_sigacts substructs are set in uvm_fork(). 361 */ 362 p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID); 363 p2->p_emul = p1->p_emul; 364 p2->p_execsw = p1->p_execsw; 365 366 if (p1->p_flag & P_PROFIL) 367 startprofclock(p2); 368 p2->p_cred = pool_get(&pcred_pool, PR_WAITOK); 369 memcpy(p2->p_cred, p1->p_cred, sizeof(*p2->p_cred)); 370 p2->p_cred->p_refcnt = 1; 371 crhold(p1->p_ucred); 372 373 LIST_INIT(&p2->p_raslist); 374 p2->p_nras = 0; 375 simple_lock_init(&p2->p_raslock); 376 #if defined(__HAVE_RAS) 377 ras_fork(p1, p2); 378 #endif 379 380 /* bump references to the text vnode (for procfs) */ 381 p2->p_textvp = p1->p_textvp; 382 if (p2->p_textvp) 383 VREF(p2->p_textvp); 384 385 if (flags & FORK_SHAREFILES) 386 fdshare(p1, p2); 387 else if (flags & FORK_CLEANFILES) 388 p2->p_fd = fdinit(p1); 389 else 390 p2->p_fd = fdcopy(p1); 391 392 if (flags & FORK_SHARECWD) 393 cwdshare(p1, p2); 394 else 395 p2->p_cwdi = cwdinit(p1); 396 397 /* 398 * If p_limit is still copy-on-write, bump refcnt, 399 * otherwise get a copy that won't be modified. 400 * (If PL_SHAREMOD is clear, the structure is shared 401 * copy-on-write.) 402 */ 403 if (p1->p_limit->p_lflags & PL_SHAREMOD) 404 p2->p_limit = limcopy(p1->p_limit); 405 else { 406 p2->p_limit = p1->p_limit; 407 p2->p_limit->p_refcnt++; 408 } 409 410 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 411 p2->p_flag |= P_CONTROLT; 412 if (flags & FORK_PPWAIT) 413 p2->p_flag |= P_PPWAIT; 414 LIST_INSERT_AFTER(p1, p2, p_pglist); 415 p2->p_pptr = (flags & FORK_NOWAIT) ? initproc : p1; 416 LIST_INSERT_HEAD(&p2->p_pptr->p_children, p2, p_sibling); 417 LIST_INIT(&p2->p_children); 418 419 callout_init(&p2->p_realit_ch); 420 callout_init(&p2->p_tsleep_ch); 421 422 #ifdef KTRACE 423 /* 424 * Copy traceflag and tracefile if enabled. 425 * If not inherited, these were zeroed above. 426 */ 427 if (p1->p_traceflag & KTRFAC_INHERIT) { 428 p2->p_traceflag = p1->p_traceflag; 429 if ((p2->p_tracep = p1->p_tracep) != NULL) 430 ktradref(p2); 431 } 432 #endif 433 #ifdef SYSTRACE 434 /* Tell systrace what's happening. */ 435 if (ISSET(p1->p_flag, P_SYSTRACE)) 436 systrace_sys_fork(p1, p2); 437 #endif 438 439 440 #ifdef __HAVE_SYSCALL_INTERN 441 (*p2->p_emul->e_syscall_intern)(p2); 442 #endif 443 444 scheduler_fork_hook(p1, p2); 445 446 /* 447 * Create signal actions for the child process. 448 */ 449 sigactsinit(p2, p1, flags & FORK_SHARESIGS); 450 451 /* 452 * If emulation has process fork hook, call it now. 453 */ 454 if (p2->p_emul->e_proc_fork) 455 (*p2->p_emul->e_proc_fork)(p2, p1); 456 457 /* 458 * This begins the section where we must prevent the parent 459 * from being swapped. 460 */ 461 PHOLD(p1); 462 463 /* 464 * Finish creating the child process. It will return through a 465 * different path later. 466 */ 467 p2->p_addr = (struct user *)uaddr; 468 uvm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE, 469 stack, stacksize, 470 (func != NULL) ? func : child_return, 471 (arg != NULL) ? arg : p2); 472 473 /* 474 * Make child runnable, set start time, and add to run queue. 475 */ 476 SCHED_LOCK(s); 477 p2->p_stats->p_start = time; 478 p2->p_acflag = AFORK; 479 p2->p_stat = SRUN; 480 setrunqueue(p2); 481 SCHED_UNLOCK(s); 482 483 /* 484 * Now can be swapped. 485 */ 486 PRELE(p1); 487 488 /* 489 * Update stats now that we know the fork was successful. 490 */ 491 uvmexp.forks++; 492 if (flags & FORK_PPWAIT) 493 uvmexp.forks_ppwait++; 494 if (flags & FORK_SHAREVM) 495 uvmexp.forks_sharevm++; 496 497 /* 498 * Pass a pointer to the new process to the caller. 499 */ 500 if (rnewprocp != NULL) 501 *rnewprocp = p2; 502 503 #ifdef KTRACE 504 if (KTRPOINT(p2, KTR_EMUL)) 505 ktremul(p2); 506 #endif 507 508 /* 509 * Preserve synchronization semantics of vfork. If waiting for 510 * child to exec or exit, set P_PPWAIT on child, and sleep on our 511 * proc (in case of exit). 512 */ 513 if (flags & FORK_PPWAIT) 514 while (p2->p_flag & P_PPWAIT) 515 tsleep(p1, PWAIT, "ppwait", 0); 516 517 /* 518 * Return child pid to parent process, 519 * marking us as parent via retval[1]. 520 */ 521 if (retval != NULL) { 522 retval[0] = p2->p_pid; 523 retval[1] = 0; 524 } 525 526 return (0); 527 } 528 529 #if defined(MULTIPROCESSOR) 530 /* 531 * XXX This is a slight hack to get newly-formed processes to 532 * XXX acquire the kernel lock as soon as they run. 533 */ 534 void 535 proc_trampoline_mp(void) 536 { 537 struct proc *p; 538 539 p = curproc; 540 541 SCHED_ASSERT_UNLOCKED(); 542 KERNEL_PROC_LOCK(p); 543 } 544 #endif 545