1 /* $NetBSD: kern_fork.c,v 1.111 2003/09/16 12:06:07 christos 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 1.111 2003/09/16 12:06:07 christos 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 flags = 0; 169 170 if (SCARG(uap, flags) & CLONE_VM) 171 flags |= FORK_SHAREVM; 172 if (SCARG(uap, flags) & CLONE_FS) 173 flags |= FORK_SHARECWD; 174 if (SCARG(uap, flags) & CLONE_FILES) 175 flags |= FORK_SHAREFILES; 176 if (SCARG(uap, flags) & CLONE_SIGHAND) 177 flags |= FORK_SHARESIGS; 178 if (SCARG(uap, flags) & CLONE_VFORK) 179 flags |= FORK_PPWAIT; 180 181 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 182 if (sig < 0 || sig >= _NSIG) 183 return (EINVAL); 184 185 /* 186 * Note that the Linux API does not provide a portable way of 187 * specifying the stack area; the caller must know if the stack 188 * grows up or down. So, we pass a stack size of 0, so that the 189 * code that makes this adjustment is a noop. 190 */ 191 return (fork1(l, flags, sig, SCARG(uap, stack), 0, 192 NULL, NULL, retval, NULL)); 193 } 194 195 /* print the 'table full' message once per 10 seconds */ 196 struct timeval fork_tfmrate = { 10, 0 }; 197 198 int 199 fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, 200 void (*func)(void *), void *arg, register_t *retval, 201 struct proc **rnewprocp) 202 { 203 struct proc *p1, *p2; 204 uid_t uid; 205 struct lwp *l2; 206 int count, s; 207 vaddr_t uaddr; 208 boolean_t inmem; 209 210 /* 211 * Although process entries are dynamically created, we still keep 212 * a global limit on the maximum number we will create. Don't allow 213 * a nonprivileged user to use the last few processes; don't let root 214 * exceed the limit. The variable nprocs is the current number of 215 * processes, maxproc is the limit. 216 */ 217 p1 = l1->l_proc; 218 uid = p1->p_cred->p_ruid; 219 if (__predict_false((nprocs >= maxproc - 5 && uid != 0) || 220 nprocs >= maxproc)) { 221 static struct timeval lasttfm; 222 223 if (ratecheck(&lasttfm, &fork_tfmrate)) 224 tablefull("proc", "increase kern.maxproc or NPROC"); 225 if (forkfsleep) 226 (void)tsleep(&nprocs, PUSER, "forkmx", forkfsleep); 227 return (EAGAIN); 228 } 229 nprocs++; 230 231 /* 232 * Increment the count of procs running with this uid. Don't allow 233 * a nonprivileged user to exceed their current limit. 234 */ 235 count = chgproccnt(uid, 1); 236 if (__predict_false(uid != 0 && count > 237 p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 238 (void)chgproccnt(uid, -1); 239 nprocs--; 240 if (forkfsleep) 241 (void)tsleep(&nprocs, PUSER, "forkulim", forkfsleep); 242 return (EAGAIN); 243 } 244 245 /* 246 * Allocate virtual address space for the U-area now, while it 247 * is still easy to abort the fork operation if we're out of 248 * kernel virtual address space. The actual U-area pages will 249 * be allocated and wired in uvm_fork() if needed. 250 */ 251 252 inmem = uvm_uarea_alloc(&uaddr); 253 if (__predict_false(uaddr == 0)) { 254 (void)chgproccnt(uid, -1); 255 nprocs--; 256 return (ENOMEM); 257 } 258 259 /* 260 * We are now committed to the fork. From here on, we may 261 * block on resources, but resource allocation may NOT fail. 262 */ 263 264 /* Allocate new proc. */ 265 p2 = proc_alloc(); 266 267 /* 268 * Make a proc table entry for the new process. 269 * Start by zeroing the section of proc that is zero-initialized, 270 * then copy the section that is copied directly from the parent. 271 */ 272 memset(&p2->p_startzero, 0, 273 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 274 memcpy(&p2->p_startcopy, &p1->p_startcopy, 275 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 276 277 simple_lock_init(&p2->p_sigctx.ps_silock); 278 CIRCLEQ_INIT(&p2->p_sigctx.ps_siginfo); 279 simple_lock_init(&p2->p_lwplock); 280 LIST_INIT(&p2->p_lwps); 281 282 /* 283 * Duplicate sub-structures as needed. 284 * Increase reference counts on shared objects. 285 * The p_stats and p_sigacts substructs are set in uvm_fork(). 286 */ 287 p2->p_flag = (p1->p_flag & P_SUGID); 288 p2->p_emul = p1->p_emul; 289 p2->p_execsw = p1->p_execsw; 290 291 if (p1->p_flag & P_PROFIL) 292 startprofclock(p2); 293 p2->p_cred = pool_get(&pcred_pool, PR_WAITOK); 294 memcpy(p2->p_cred, p1->p_cred, sizeof(*p2->p_cred)); 295 p2->p_cred->p_refcnt = 1; 296 crhold(p1->p_ucred); 297 298 LIST_INIT(&p2->p_raslist); 299 p2->p_nras = 0; 300 simple_lock_init(&p2->p_raslock); 301 #if defined(__HAVE_RAS) 302 ras_fork(p1, p2); 303 #endif 304 305 /* bump references to the text vnode (for procfs) */ 306 p2->p_textvp = p1->p_textvp; 307 if (p2->p_textvp) 308 VREF(p2->p_textvp); 309 310 if (flags & FORK_SHAREFILES) 311 fdshare(p1, p2); 312 else if (flags & FORK_CLEANFILES) 313 p2->p_fd = fdinit(p1); 314 else 315 p2->p_fd = fdcopy(p1); 316 317 if (flags & FORK_SHARECWD) 318 cwdshare(p1, p2); 319 else 320 p2->p_cwdi = cwdinit(p1); 321 322 /* 323 * If p_limit is still copy-on-write, bump refcnt, 324 * otherwise get a copy that won't be modified. 325 * (If PL_SHAREMOD is clear, the structure is shared 326 * copy-on-write.) 327 */ 328 if (p1->p_limit->p_lflags & PL_SHAREMOD) 329 p2->p_limit = limcopy(p1->p_limit); 330 else { 331 p2->p_limit = p1->p_limit; 332 p2->p_limit->p_refcnt++; 333 } 334 335 /* Inherit STOPFORK and STOPEXEC flags */ 336 p2->p_flag |= p1->p_flag & (P_STOPFORK | P_STOPEXEC); 337 338 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 339 p2->p_flag |= P_CONTROLT; 340 if (flags & FORK_PPWAIT) 341 p2->p_flag |= P_PPWAIT; 342 p2->p_pptr = (flags & FORK_NOWAIT) ? initproc : p1; 343 LIST_INIT(&p2->p_children); 344 345 s = proclist_lock_write(); 346 LIST_INSERT_AFTER(p1, p2, p_pglist); 347 LIST_INSERT_HEAD(&p2->p_pptr->p_children, p2, p_sibling); 348 proclist_unlock_write(s); 349 350 #ifdef KTRACE 351 /* 352 * Copy traceflag and tracefile if enabled. 353 * If not inherited, these were zeroed above. 354 */ 355 if (p1->p_traceflag & KTRFAC_INHERIT) { 356 p2->p_traceflag = p1->p_traceflag; 357 if ((p2->p_tracep = p1->p_tracep) != NULL) 358 ktradref(p2); 359 } 360 #endif 361 362 scheduler_fork_hook(p1, p2); 363 364 /* 365 * Create signal actions for the child process. 366 */ 367 sigactsinit(p2, p1, flags & FORK_SHARESIGS); 368 369 /* 370 * p_stats. 371 * Copy parts of p_stats, and zero out the rest. 372 */ 373 p2->p_stats = pstatscopy(p1->p_stats); 374 375 /* 376 * If emulation has process fork hook, call it now. 377 */ 378 if (p2->p_emul->e_proc_fork) 379 (*p2->p_emul->e_proc_fork)(p2, p1); 380 381 /* 382 * ...and finally, any other random fork hooks that subsystems 383 * might have registered. 384 */ 385 doforkhooks(p2, p1); 386 387 /* 388 * This begins the section where we must prevent the parent 389 * from being swapped. 390 */ 391 PHOLD(l1); 392 393 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 394 395 /* 396 * Finish creating the child process. 397 * It will return through a different path later. 398 */ 399 newlwp(l1, p2, uaddr, inmem, 0, stack, stacksize, 400 (func != NULL) ? func : child_return, 401 arg, &l2); 402 403 /* Now safe for scheduler to see child process */ 404 s = proclist_lock_write(); 405 p2->p_stat = SIDL; /* protect against others */ 406 p2->p_exitsig = exitsig; /* signal for parent on exit */ 407 LIST_INSERT_HEAD(&allproc, p2, p_list); 408 proclist_unlock_write(s); 409 410 #ifdef SYSTRACE 411 /* Tell systrace what's happening. */ 412 if (ISSET(p1->p_flag, P_SYSTRACE)) 413 systrace_sys_fork(p1, p2); 414 #endif 415 416 #ifdef __HAVE_SYSCALL_INTERN 417 (*p2->p_emul->e_syscall_intern)(p2); 418 #endif 419 420 /* 421 * Make child runnable, set start time, and add to run queue 422 * except if the parent requested the child to start in SSTOP state. 423 */ 424 SCHED_LOCK(s); 425 p2->p_stats->p_start = time; 426 p2->p_acflag = AFORK; 427 p2->p_nrlwps = 1; 428 if (p1->p_flag & P_STOPFORK) { 429 p2->p_stat = SSTOP; 430 l2->l_stat = LSSTOP; 431 } else { 432 p2->p_stat = SACTIVE; 433 l2->l_stat = LSRUN; 434 setrunqueue(l2); 435 } 436 SCHED_UNLOCK(s); 437 438 /* 439 * Now can be swapped. 440 */ 441 PRELE(l1); 442 443 /* 444 * Notify any interested parties about the new process. 445 */ 446 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 447 448 /* 449 * Update stats now that we know the fork was successful. 450 */ 451 uvmexp.forks++; 452 if (flags & FORK_PPWAIT) 453 uvmexp.forks_ppwait++; 454 if (flags & FORK_SHAREVM) 455 uvmexp.forks_sharevm++; 456 457 /* 458 * Pass a pointer to the new process to the caller. 459 */ 460 if (rnewprocp != NULL) 461 *rnewprocp = p2; 462 463 #ifdef KTRACE 464 if (KTRPOINT(p2, KTR_EMUL)) 465 ktremul(p2); 466 #endif 467 468 /* 469 * Preserve synchronization semantics of vfork. If waiting for 470 * child to exec or exit, set P_PPWAIT on child, and sleep on our 471 * proc (in case of exit). 472 */ 473 if (flags & FORK_PPWAIT) 474 while (p2->p_flag & P_PPWAIT) 475 tsleep(p1, PWAIT, "ppwait", 0); 476 477 /* 478 * Return child pid to parent process, 479 * marking us as parent via retval[1]. 480 */ 481 if (retval != NULL) { 482 retval[0] = p2->p_pid; 483 retval[1] = 0; 484 } 485 486 return (0); 487 } 488 489 #if defined(MULTIPROCESSOR) 490 /* 491 * XXX This is a slight hack to get newly-formed processes to 492 * XXX acquire the kernel lock as soon as they run. 493 */ 494 void 495 proc_trampoline_mp(void) 496 { 497 struct lwp *l; 498 499 l = curlwp; 500 501 SCHED_ASSERT_UNLOCKED(); 502 KERNEL_PROC_LOCK(l); 503 } 504 #endif 505