kern_fork.c revision 1.86
1 /* $NetBSD: kern_fork.c,v 1.86 2001/07/07 23:33:54 fvdl 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 "opt_ktrace.h" 81 #include "opt_multiprocessor.h" 82 83 #include <sys/param.h> 84 #include <sys/systm.h> 85 #include <sys/map.h> 86 #include <sys/filedesc.h> 87 #include <sys/kernel.h> 88 #include <sys/malloc.h> 89 #include <sys/pool.h> 90 #include <sys/mount.h> 91 #include <sys/proc.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> 100 101 #include <sys/syscallargs.h> 102 103 #include <uvm/uvm_extern.h> 104 105 int nprocs = 1; /* process 0 */ 106 107 /*ARGSUSED*/ 108 int 109 sys_fork(struct proc *p, void *v, register_t *retval) 110 { 111 112 return (fork1(p, 0, SIGCHLD, NULL, 0, NULL, NULL, retval, NULL)); 113 } 114 115 /* 116 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 117 * Address space is not shared, but parent is blocked until child exit. 118 */ 119 /*ARGSUSED*/ 120 int 121 sys_vfork(struct proc *p, void *v, register_t *retval) 122 { 123 124 return (fork1(p, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 125 retval, NULL)); 126 } 127 128 /* 129 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 130 * semantics. Address space is shared, and parent is blocked until child exit. 131 */ 132 /*ARGSUSED*/ 133 int 134 sys___vfork14(struct proc *p, void *v, register_t *retval) 135 { 136 137 return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 138 NULL, NULL, retval, NULL)); 139 } 140 141 /* 142 * Linux-compatible __clone(2) system call. 143 */ 144 int 145 sys___clone(struct proc *p, void *v, register_t *retval) 146 { 147 struct sys___clone_args /* { 148 syscallarg(int) flags; 149 syscallarg(void *) stack; 150 } */ *uap = v; 151 int flags, sig; 152 153 /* 154 * We don't support the CLONE_PID or CLONE_PTRACE flags. 155 */ 156 if (SCARG(uap, flags) & (CLONE_PID|CLONE_PTRACE)) 157 return (EINVAL); 158 159 flags = 0; 160 161 if (SCARG(uap, flags) & CLONE_VM) 162 flags |= FORK_SHAREVM; 163 if (SCARG(uap, flags) & CLONE_FS) 164 flags |= FORK_SHARECWD; 165 if (SCARG(uap, flags) & CLONE_FILES) 166 flags |= FORK_SHAREFILES; 167 if (SCARG(uap, flags) & CLONE_SIGHAND) 168 flags |= FORK_SHARESIGS; 169 if (SCARG(uap, flags) & CLONE_VFORK) 170 flags |= FORK_PPWAIT; 171 172 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 173 if (sig < 0 || sig >= _NSIG) 174 return (EINVAL); 175 176 /* 177 * Note that the Linux API does not provide a portable way of 178 * specifying the stack area; the caller must know if the stack 179 * grows up or down. So, we pass a stack size of 0, so that the 180 * code that makes this adjustment is a noop. 181 */ 182 return (fork1(p, flags, sig, SCARG(uap, stack), 0, 183 NULL, NULL, retval, NULL)); 184 } 185 186 int 187 fork1(struct proc *p1, int flags, int exitsig, void *stack, size_t stacksize, 188 void (*func)(void *), void *arg, register_t *retval, 189 struct proc **rnewprocp) 190 { 191 struct proc *p2, *tp; 192 uid_t uid; 193 int count, s; 194 vaddr_t uaddr; 195 static int nextpid, pidchecked; 196 197 /* 198 * Although process entries are dynamically created, we still keep 199 * a global limit on the maximum number we will create. Don't allow 200 * a nonprivileged user to use the last process; don't let root 201 * exceed the limit. The variable nprocs is the current number of 202 * processes, maxproc is the limit. 203 */ 204 uid = p1->p_cred->p_ruid; 205 if (__predict_false((nprocs >= maxproc - 1 && uid != 0) || 206 nprocs >= maxproc)) { 207 tablefull("proc", "increase kern.maxproc or NPROC"); 208 return (EAGAIN); 209 } 210 nprocs++; 211 212 /* 213 * Increment the count of procs running with this uid. Don't allow 214 * a nonprivileged user to exceed their current limit. 215 */ 216 count = chgproccnt(uid, 1); 217 if (__predict_false(uid != 0 && count > 218 p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 219 (void)chgproccnt(uid, -1); 220 nprocs--; 221 return (EAGAIN); 222 } 223 224 /* 225 * Allocate virtual address space for the U-area now, while it 226 * is still easy to abort the fork operation if we're out of 227 * kernel virtual address space. The actual U-area pages will 228 * be allocated and wired in vm_fork(). 229 */ 230 231 #ifndef USPACE_ALIGN 232 #define USPACE_ALIGN 0 233 #endif 234 235 uaddr = uvm_km_valloc_align(kernel_map, USPACE, USPACE_ALIGN); 236 if (__predict_false(uaddr == 0)) { 237 (void)chgproccnt(uid, -1); 238 nprocs--; 239 return (ENOMEM); 240 } 241 242 /* 243 * We are now committed to the fork. From here on, we may 244 * block on resources, but resource allocation may NOT fail. 245 */ 246 247 /* Allocate new proc. */ 248 p2 = pool_get(&proc_pool, PR_WAITOK); 249 250 /* 251 * Make a proc table entry for the new process. 252 * Start by zeroing the section of proc that is zero-initialized, 253 * then copy the section that is copied directly from the parent. 254 */ 255 memset(&p2->p_startzero, 0, 256 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 257 memcpy(&p2->p_startcopy, &p1->p_startcopy, 258 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 259 260 #if !defined(MULTIPROCESSOR) 261 /* 262 * In the single-processor case, all processes will always run 263 * on the same CPU. So, initialize the child's CPU to the parent's 264 * now. In the multiprocessor case, the child's CPU will be 265 * initialized in the low-level context switch code when the 266 * process runs. 267 */ 268 p2->p_cpu = p1->p_cpu; 269 #else 270 /* 271 * zero child's cpu pointer so we don't get trash. 272 */ 273 p2->p_cpu = NULL; 274 #endif /* ! MULTIPROCESSOR */ 275 276 /* 277 * Duplicate sub-structures as needed. 278 * Increase reference counts on shared objects. 279 * The p_stats and p_sigacts substructs are set in uvm_fork(). 280 */ 281 p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID); 282 p2->p_emul = p1->p_emul; 283 284 if (p1->p_flag & P_PROFIL) 285 startprofclock(p2); 286 p2->p_cred = pool_get(&pcred_pool, PR_WAITOK); 287 memcpy(p2->p_cred, p1->p_cred, sizeof(*p2->p_cred)); 288 p2->p_cred->p_refcnt = 1; 289 crhold(p1->p_ucred); 290 291 /* bump references to the text vnode (for procfs) */ 292 p2->p_textvp = p1->p_textvp; 293 if (p2->p_textvp) 294 VREF(p2->p_textvp); 295 296 if (flags & FORK_SHAREFILES) 297 fdshare(p1, p2); 298 else 299 p2->p_fd = fdcopy(p1); 300 301 if (flags & FORK_SHARECWD) 302 cwdshare(p1, p2); 303 else 304 p2->p_cwdi = cwdinit(p1); 305 306 /* 307 * If p_limit is still copy-on-write, bump refcnt, 308 * otherwise get a copy that won't be modified. 309 * (If PL_SHAREMOD is clear, the structure is shared 310 * copy-on-write.) 311 */ 312 if (p1->p_limit->p_lflags & PL_SHAREMOD) 313 p2->p_limit = limcopy(p1->p_limit); 314 else { 315 p2->p_limit = p1->p_limit; 316 p2->p_limit->p_refcnt++; 317 } 318 319 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 320 p2->p_flag |= P_CONTROLT; 321 if (flags & FORK_PPWAIT) 322 p2->p_flag |= P_PPWAIT; 323 LIST_INSERT_AFTER(p1, p2, p_pglist); 324 p2->p_pptr = p1; 325 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 326 LIST_INIT(&p2->p_children); 327 328 callout_init(&p2->p_realit_ch); 329 callout_init(&p2->p_tsleep_ch); 330 331 #ifdef KTRACE 332 /* 333 * Copy traceflag and tracefile if enabled. 334 * If not inherited, these were zeroed above. 335 */ 336 if (p1->p_traceflag & KTRFAC_INHERIT) { 337 p2->p_traceflag = p1->p_traceflag; 338 if ((p2->p_tracep = p1->p_tracep) != NULL) 339 ktradref(p2); 340 } 341 #endif 342 343 #ifdef __HAVE_SYSCALL_INTERN 344 (*p2->p_emul->e_syscall_intern)(p2); 345 #endif 346 347 scheduler_fork_hook(p1, p2); 348 349 /* 350 * Create signal actions for the child process. 351 */ 352 sigactsinit(p2, p1, flags & FORK_SHARESIGS); 353 354 /* 355 * If emulation has process fork hook, call it now. 356 */ 357 if (p2->p_emul->e_proc_fork) 358 (*p2->p_emul->e_proc_fork)(p2, p1); 359 360 /* 361 * This begins the section where we must prevent the parent 362 * from being swapped. 363 */ 364 PHOLD(p1); 365 366 /* 367 * Finish creating the child process. It will return through a 368 * different path later. 369 */ 370 p2->p_addr = (struct user *)uaddr; 371 uvm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE, 372 stack, stacksize, 373 (func != NULL) ? func : child_return, 374 (arg != NULL) ? arg : p2); 375 376 /* 377 * BEGIN PID ALLOCATION. 378 */ 379 s = proclist_lock_write(); 380 381 /* 382 * Find an unused process ID. We remember a range of unused IDs 383 * ready to use (from nextpid+1 through pidchecked-1). 384 */ 385 nextpid++; 386 retry: 387 /* 388 * If the process ID prototype has wrapped around, 389 * restart somewhat above 0, as the low-numbered procs 390 * tend to include daemons that don't exit. 391 */ 392 if (nextpid >= PID_MAX) { 393 nextpid = 500; 394 pidchecked = 0; 395 } 396 if (nextpid >= pidchecked) { 397 const struct proclist_desc *pd; 398 399 pidchecked = PID_MAX; 400 /* 401 * Scan the process lists to check whether this pid 402 * is in use. Remember the lowest pid that's greater 403 * than nextpid, so we can avoid checking for a while. 404 */ 405 pd = proclists; 406 again: 407 LIST_FOREACH(tp, pd->pd_list, p_list) { 408 while (tp->p_pid == nextpid || 409 tp->p_pgrp->pg_id == nextpid || 410 tp->p_session->s_sid == nextpid) { 411 nextpid++; 412 if (nextpid >= pidchecked) 413 goto retry; 414 } 415 if (tp->p_pid > nextpid && pidchecked > tp->p_pid) 416 pidchecked = tp->p_pid; 417 418 if (tp->p_pgrp->pg_id > nextpid && 419 pidchecked > tp->p_pgrp->pg_id) 420 pidchecked = tp->p_pgrp->pg_id; 421 422 if (tp->p_session->s_sid > nextpid && 423 pidchecked > tp->p_session->s_sid) 424 pidchecked = tp->p_session->s_sid; 425 } 426 427 /* 428 * If there's another list, scan it. If we have checked 429 * them all, we've found one! 430 */ 431 pd++; 432 if (pd->pd_list != NULL) 433 goto again; 434 } 435 436 /* Record the pid we've allocated. */ 437 p2->p_pid = nextpid; 438 439 /* Record the signal to be delivered to the parent on exit. */ 440 p2->p_exitsig = exitsig; 441 442 /* 443 * Put the proc on allproc before unlocking PID allocation 444 * so that waiters won't grab it as soon as we unlock. 445 */ 446 447 p2->p_stat = SIDL; /* protect against others */ 448 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 449 450 LIST_INSERT_HEAD(&allproc, p2, p_list); 451 452 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 453 454 /* 455 * END PID ALLOCATION. 456 */ 457 proclist_unlock_write(s); 458 459 /* 460 * Make child runnable, set start time, and add to run queue. 461 */ 462 SCHED_LOCK(s); 463 p2->p_stats->p_start = time; 464 p2->p_acflag = AFORK; 465 p2->p_stat = SRUN; 466 setrunqueue(p2); 467 SCHED_UNLOCK(s); 468 469 /* 470 * Now can be swapped. 471 */ 472 PRELE(p1); 473 474 /* 475 * Update stats now that we know the fork was successful. 476 */ 477 uvmexp.forks++; 478 if (flags & FORK_PPWAIT) 479 uvmexp.forks_ppwait++; 480 if (flags & FORK_SHAREVM) 481 uvmexp.forks_sharevm++; 482 483 /* 484 * Pass a pointer to the new process to the caller. 485 */ 486 if (rnewprocp != NULL) 487 *rnewprocp = p2; 488 489 #ifdef KTRACE 490 if (KTRPOINT(p2, KTR_EMUL)) 491 ktremul(p2); 492 #endif 493 494 /* 495 * Preserve synchronization semantics of vfork. If waiting for 496 * child to exec or exit, set P_PPWAIT on child, and sleep on our 497 * proc (in case of exit). 498 */ 499 if (flags & FORK_PPWAIT) 500 while (p2->p_flag & P_PPWAIT) 501 tsleep(p1, PWAIT, "ppwait", 0); 502 503 /* 504 * Return child pid to parent process, 505 * marking us as parent via retval[1]. 506 */ 507 if (retval != NULL) { 508 retval[0] = p2->p_pid; 509 retval[1] = 0; 510 } 511 512 return (0); 513 } 514 515 #if defined(MULTIPROCESSOR) 516 /* 517 * XXX This is a slight hack to get newly-formed processes to 518 * XXX acquire the kernel lock as soon as they run. 519 */ 520 void 521 proc_trampoline_mp(void) 522 { 523 struct proc *p; 524 525 p = curproc; 526 527 SCHED_ASSERT_UNLOCKED(); 528 KERNEL_PROC_LOCK(p); 529 } 530 #endif 531
Indexes created Tue Sep 23 23:09:58 GMT 2025