kern_fork.c revision 1.120
1 /* $NetBSD: kern_fork.c,v 1.120 2005/02/26 21:34:55 perry 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. Neither the name of the University nor the names of its contributors 58 * may be used to endorse or promote products derived from this software 59 * without specific prior written permission. 60 * 61 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 62 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 63 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 64 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 65 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 66 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 67 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 68 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 69 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 70 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 71 * SUCH DAMAGE. 72 * 73 * @(#)kern_fork.c 8.8 (Berkeley) 2/14/95 74 */ 75 76 #include <sys/cdefs.h> 77 __KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.120 2005/02/26 21:34:55 perry Exp $"); 78 79 #include "opt_ktrace.h" 80 #include "opt_systrace.h" 81 #include "opt_multiprocessor.h" 82 83 #include <sys/param.h> 84 #include <sys/systm.h> 85 #include <sys/filedesc.h> 86 #include <sys/kernel.h> 87 #include <sys/malloc.h> 88 #include <sys/pool.h> 89 #include <sys/mount.h> 90 #include <sys/proc.h> 91 #include <sys/ras.h> 92 #include <sys/resourcevar.h> 93 #include <sys/vnode.h> 94 #include <sys/file.h> 95 #include <sys/acct.h> 96 #include <sys/ktrace.h> 97 #include <sys/vmmeter.h> 98 #include <sys/sched.h> 99 #include <sys/signalvar.h> 100 #include <sys/systrace.h> 101 102 #include <sys/sa.h> 103 #include <sys/syscallargs.h> 104 105 #include <uvm/uvm_extern.h> 106 107 108 int nprocs = 1; /* process 0 */ 109 110 /* 111 * Number of ticks to sleep if fork() would fail due to process hitting 112 * limits. Exported in miliseconds to userland via sysctl. 113 */ 114 int forkfsleep = 0; 115 116 /*ARGSUSED*/ 117 int 118 sys_fork(struct lwp *l, void *v, register_t *retval) 119 { 120 121 return (fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); 122 } 123 124 /* 125 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 126 * Address space is not shared, but parent is blocked until child exit. 127 */ 128 /*ARGSUSED*/ 129 int 130 sys_vfork(struct lwp *l, void *v, register_t *retval) 131 { 132 133 return (fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 134 retval, NULL)); 135 } 136 137 /* 138 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 139 * semantics. Address space is shared, and parent is blocked until child exit. 140 */ 141 /*ARGSUSED*/ 142 int 143 sys___vfork14(struct lwp *l, void *v, register_t *retval) 144 { 145 146 return (fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 147 NULL, NULL, retval, NULL)); 148 } 149 150 /* 151 * Linux-compatible __clone(2) system call. 152 */ 153 int 154 sys___clone(struct lwp *l, void *v, register_t *retval) 155 { 156 struct sys___clone_args /* { 157 syscallarg(int) flags; 158 syscallarg(void *) stack; 159 } */ *uap = v; 160 int flags, sig; 161 162 /* 163 * We don't support the CLONE_PID or CLONE_PTRACE flags. 164 */ 165 if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) 166 return (EINVAL); 167 168 /* 169 * Linux enforces CLONE_VM with CLONE_SIGHAND, do same. 170 */ 171 if (SCARG(uap, flags) & CLONE_SIGHAND 172 && (SCARG(uap, flags) & CLONE_VM) == 0) 173 return (EINVAL); 174 175 flags = 0; 176 177 if (SCARG(uap, flags) & CLONE_VM) 178 flags |= FORK_SHAREVM; 179 if (SCARG(uap, flags) & CLONE_FS) 180 flags |= FORK_SHARECWD; 181 if (SCARG(uap, flags) & CLONE_FILES) 182 flags |= FORK_SHAREFILES; 183 if (SCARG(uap, flags) & CLONE_SIGHAND) 184 flags |= FORK_SHARESIGS; 185 if (SCARG(uap, flags) & CLONE_VFORK) 186 flags |= FORK_PPWAIT; 187 188 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 189 if (sig < 0 || sig >= _NSIG) 190 return (EINVAL); 191 192 /* 193 * Note that the Linux API does not provide a portable way of 194 * specifying the stack area; the caller must know if the stack 195 * grows up or down. So, we pass a stack size of 0, so that the 196 * code that makes this adjustment is a noop. 197 */ 198 return (fork1(l, flags, sig, SCARG(uap, stack), 0, 199 NULL, NULL, retval, NULL)); 200 } 201 202 /* print the 'table full' message once per 10 seconds */ 203 struct timeval fork_tfmrate = { 10, 0 }; 204 205 int 206 fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, 207 void (*func)(void *), void *arg, register_t *retval, 208 struct proc **rnewprocp) 209 { 210 struct proc *p1, *p2, *parent; 211 uid_t uid; 212 struct lwp *l2; 213 int count, s; 214 vaddr_t uaddr; 215 boolean_t inmem; 216 217 /* 218 * Although process entries are dynamically created, we still keep 219 * a global limit on the maximum number we will create. Don't allow 220 * a nonprivileged user to use the last few processes; don't let root 221 * exceed the limit. The variable nprocs is the current number of 222 * processes, maxproc is the limit. 223 */ 224 p1 = l1->l_proc; 225 uid = p1->p_cred->p_ruid; 226 if (__predict_false((nprocs >= maxproc - 5 && uid != 0) || 227 nprocs >= maxproc)) { 228 static struct timeval lasttfm; 229 230 if (ratecheck(&lasttfm, &fork_tfmrate)) 231 tablefull("proc", "increase kern.maxproc or NPROC"); 232 if (forkfsleep) 233 (void)tsleep(&nprocs, PUSER, "forkmx", forkfsleep); 234 return (EAGAIN); 235 } 236 nprocs++; 237 238 /* 239 * Increment the count of procs running with this uid. Don't allow 240 * a nonprivileged user to exceed their current limit. 241 */ 242 count = chgproccnt(uid, 1); 243 if (__predict_false(uid != 0 && count > 244 p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 245 (void)chgproccnt(uid, -1); 246 nprocs--; 247 if (forkfsleep) 248 (void)tsleep(&nprocs, PUSER, "forkulim", forkfsleep); 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 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) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 281 memcpy(&p2->p_startcopy, &p1->p_startcopy, 282 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 283 284 simple_lock_init(&p2->p_sigctx.ps_silock); 285 CIRCLEQ_INIT(&p2->p_sigctx.ps_siginfo); 286 simple_lock_init(&p2->p_lock); 287 LIST_INIT(&p2->p_lwps); 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 SUGID, STOPFORK and STOPEXEC flags. 294 */ 295 p2->p_flag = p1->p_flag & (P_SUGID | P_STOPFORK | P_STOPEXEC); 296 p2->p_emul = p1->p_emul; 297 p2->p_execsw = p1->p_execsw; 298 299 if (p1->p_flag & P_PROFIL) 300 startprofclock(p2); 301 p2->p_cred = pool_get(&pcred_pool, PR_WAITOK); 302 memcpy(p2->p_cred, p1->p_cred, sizeof(*p2->p_cred)); 303 p2->p_cred->p_refcnt = 1; 304 crhold(p1->p_ucred); 305 306 LIST_INIT(&p2->p_raslist); 307 #if defined(__HAVE_RAS) 308 ras_fork(p1, p2); 309 #endif 310 311 /* bump references to the text vnode (for procfs) */ 312 p2->p_textvp = p1->p_textvp; 313 if (p2->p_textvp) 314 VREF(p2->p_textvp); 315 316 if (flags & FORK_SHAREFILES) 317 fdshare(p1, p2); 318 else if (flags & FORK_CLEANFILES) 319 p2->p_fd = fdinit(p1); 320 else 321 p2->p_fd = fdcopy(p1); 322 323 if (flags & FORK_SHARECWD) 324 cwdshare(p1, p2); 325 else 326 p2->p_cwdi = cwdinit(p1); 327 328 /* 329 * If p_limit is still copy-on-write, bump refcnt, 330 * otherwise get a copy that won't be modified. 331 * (If PL_SHAREMOD is clear, the structure is shared 332 * copy-on-write.) 333 */ 334 if (p1->p_limit->p_lflags & PL_SHAREMOD) 335 p2->p_limit = limcopy(p1->p_limit); 336 else { 337 simple_lock(&p1->p_limit->p_slock); 338 p1->p_limit->p_refcnt++; 339 simple_unlock(&p1->p_limit->p_slock); 340 p2->p_limit = p1->p_limit; 341 } 342 343 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 344 p2->p_flag |= P_CONTROLT; 345 if (flags & FORK_PPWAIT) 346 p2->p_flag |= P_PPWAIT; 347 parent = (flags & FORK_NOWAIT) ? initproc : p1; 348 p2->p_pptr = parent; 349 LIST_INIT(&p2->p_children); 350 351 s = proclist_lock_write(); 352 LIST_INSERT_AFTER(p1, p2, p_pglist); 353 LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling); 354 proclist_unlock_write(s); 355 356 #ifdef KTRACE 357 /* 358 * Copy traceflag and tracefile if enabled. 359 * If not inherited, these were zeroed above. 360 */ 361 if (p1->p_traceflag & KTRFAC_INHERIT) { 362 p2->p_traceflag = p1->p_traceflag; 363 if ((p2->p_tracep = p1->p_tracep) != NULL) 364 ktradref(p2); 365 } 366 #endif 367 368 scheduler_fork_hook(p1, p2); 369 370 /* 371 * Create signal actions for the child process. 372 */ 373 sigactsinit(p2, p1, flags & FORK_SHARESIGS); 374 375 /* 376 * p_stats. 377 * Copy parts of p_stats, and zero out the rest. 378 */ 379 p2->p_stats = pstatscopy(p1->p_stats); 380 381 /* 382 * If emulation has process fork hook, call it now. 383 */ 384 if (p2->p_emul->e_proc_fork) 385 (*p2->p_emul->e_proc_fork)(p2, p1, flags); 386 387 /* 388 * ...and finally, any other random fork hooks that subsystems 389 * might have registered. 390 */ 391 doforkhooks(p2, p1); 392 393 /* 394 * This begins the section where we must prevent the parent 395 * from being swapped. 396 */ 397 PHOLD(l1); 398 399 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 400 401 /* 402 * Finish creating the child process. 403 * It will return through a different path later. 404 */ 405 newlwp(l1, p2, uaddr, inmem, 0, stack, stacksize, 406 (func != NULL) ? func : child_return, 407 arg, &l2); 408 409 /* Now safe for scheduler to see child process */ 410 s = proclist_lock_write(); 411 p2->p_exitsig = exitsig; /* signal for parent on exit */ 412 LIST_INSERT_HEAD(&allproc, p2, p_list); 413 proclist_unlock_write(s); 414 415 #ifdef SYSTRACE 416 /* Tell systrace what's happening. */ 417 if (ISSET(p1->p_flag, P_SYSTRACE)) 418 systrace_sys_fork(p1, p2); 419 #endif 420 421 #ifdef __HAVE_SYSCALL_INTERN 422 (*p2->p_emul->e_syscall_intern)(p2); 423 #endif 424 425 /* 426 * Make child runnable, set start time, and add to run queue 427 * except if the parent requested the child to start in SSTOP state. 428 */ 429 SCHED_LOCK(s); 430 p2->p_stats->p_start = time; 431 p2->p_acflag = AFORK; 432 if (p1->p_flag & P_STOPFORK) { 433 p2->p_nrlwps = 0; 434 p1->p_nstopchild++; 435 p2->p_stat = SSTOP; 436 l2->l_stat = LSSTOP; 437 } else { 438 p2->p_nrlwps = 1; 439 p2->p_stat = SACTIVE; 440 l2->l_stat = LSRUN; 441 setrunqueue(l2); 442 } 443 SCHED_UNLOCK(s); 444 445 /* 446 * Now can be swapped. 447 */ 448 PRELE(l1); 449 450 /* 451 * Notify any interested parties about the new process. 452 */ 453 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 454 455 /* 456 * Update stats now that we know the fork was successful. 457 */ 458 uvmexp.forks++; 459 if (flags & FORK_PPWAIT) 460 uvmexp.forks_ppwait++; 461 if (flags & FORK_SHAREVM) 462 uvmexp.forks_sharevm++; 463 464 /* 465 * Pass a pointer to the new process to the caller. 466 */ 467 if (rnewprocp != NULL) 468 *rnewprocp = p2; 469 470 #ifdef KTRACE 471 if (KTRPOINT(p2, KTR_EMUL)) 472 p2->p_traceflag |= KTRFAC_TRC_EMUL; 473 #endif 474 475 /* 476 * Preserve synchronization semantics of vfork. If waiting for 477 * child to exec or exit, set P_PPWAIT on child, and sleep on our 478 * proc (in case of exit). 479 */ 480 if (flags & FORK_PPWAIT) 481 while (p2->p_flag & P_PPWAIT) 482 tsleep(p1, PWAIT, "ppwait", 0); 483 484 /* 485 * Return child pid to parent process, 486 * marking us as parent via retval[1]. 487 */ 488 if (retval != NULL) { 489 retval[0] = p2->p_pid; 490 retval[1] = 0; 491 } 492 493 return (0); 494 } 495 496 #if defined(MULTIPROCESSOR) 497 /* 498 * XXX This is a slight hack to get newly-formed processes to 499 * XXX acquire the kernel lock as soon as they run. 500 */ 501 void 502 proc_trampoline_mp(void) 503 { 504 struct lwp *l; 505 506 l = curlwp; 507 508 SCHED_ASSERT_UNLOCKED(); 509 KERNEL_PROC_LOCK(l); 510 } 511 #endif 512
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