1 /* 2 * Copyright (c) 1982, 1986, 1989, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 39 * $Id: kern_fork.c,v 1.46 1997/08/22 15:10:00 peter Exp $ 40 */ 41 42 #include "opt_ktrace.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/sysproto.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/sysctl.h> 50 #include <sys/malloc.h> 51 #include <sys/proc.h> 52 #include <sys/resourcevar.h> 53 #include <sys/vnode.h> 54 #include <sys/acct.h> 55 #include <sys/ktrace.h> 56 #include <sys/unistd.h> 57 58 #include <vm/vm.h> 59 #include <vm/vm_param.h> 60 #include <sys/lock.h> 61 #include <vm/pmap.h> 62 #include <vm/vm_map.h> 63 #include <vm/vm_extern.h> 64 #include <vm/vm_inherit.h> 65 66 #ifdef SMP 67 int fast_vfork = 0; /* Doesn't work on SMP yet */ 68 #else 69 int fast_vfork = 1; 70 #endif 71 SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, ""); 72 73 static int fork1 __P((struct proc *p, int flags, int *retval)); 74 75 /* 76 * These are the stuctures used to create a callout list for things to do 77 * when forking a process 78 */ 79 typedef struct fork_list_element { 80 struct fork_list_element *next; 81 forklist_fn function; 82 } *fle_p; 83 84 static fle_p fork_list; 85 86 #ifndef _SYS_SYSPROTO_H_ 87 struct fork_args { 88 int dummy; 89 }; 90 #endif 91 92 /* ARGSUSED */ 93 int 94 fork(p, uap, retval) 95 struct proc *p; 96 struct fork_args *uap; 97 int retval[]; 98 { 99 return (fork1(p, (RFFDG|RFPROC), retval)); 100 } 101 102 /* ARGSUSED */ 103 int 104 vfork(p, uap, retval) 105 struct proc *p; 106 struct vfork_args *uap; 107 int retval[]; 108 { 109 return (fork1(p, (RFFDG|RFPROC|RFPPWAIT|(fast_vfork ? RFMEM : 0)), 110 retval)); 111 } 112 113 /* ARGSUSED */ 114 int 115 rfork(p, uap, retval) 116 struct proc *p; 117 struct rfork_args *uap; 118 int retval[]; 119 { 120 return (fork1(p, uap->flags, retval)); 121 } 122 123 124 int nprocs = 1; /* process 0 */ 125 static int nextpid = 0; 126 127 static int 128 fork1(p1, flags, retval) 129 register struct proc *p1; 130 int flags; 131 int retval[]; 132 { 133 register struct proc *p2, *pptr; 134 register uid_t uid; 135 struct proc *newproc; 136 int count; 137 static int pidchecked = 0; 138 fle_p ep ; 139 140 ep = fork_list; 141 142 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 143 return (EINVAL); 144 145 #ifdef SMP 146 /* 147 * FATAL now, we cannot have the same PTD on both cpus, the PTD 148 * needs to move out of PTmap and be per-process, even for shared 149 * page table processes. Unfortunately, this means either removing 150 * PTD[] as a fixed virtual address, or move it to the per-cpu map 151 * area for SMP mode. Both cases require seperate management of 152 * the per-process-even-if-PTmap-is-shared PTD. 153 */ 154 if (flags & RFMEM) { 155 printf("shared address space fork attempted: pid: %d\n", 156 p1->p_pid); 157 return (EOPNOTSUPP); 158 } 159 #endif 160 161 /* 162 * Here we don't create a new process, but we divorce 163 * certain parts of a process from itself. 164 */ 165 if ((flags & RFPROC) == 0) { 166 167 /* 168 * Divorce the memory, if it is shared, essentially 169 * this changes shared memory amongst threads, into 170 * COW locally. 171 */ 172 if ((flags & RFMEM) == 0) { 173 if (p1->p_vmspace->vm_refcnt > 1) { 174 vmspace_unshare(p1); 175 } 176 } 177 178 /* 179 * Close all file descriptors. 180 */ 181 if (flags & RFCFDG) { 182 struct filedesc *fdtmp; 183 fdtmp = fdinit(p1); 184 fdfree(p1); 185 p1->p_fd = fdtmp; 186 } 187 188 /* 189 * Unshare file descriptors (from parent.) 190 */ 191 if (flags & RFFDG) { 192 if (p1->p_fd->fd_refcnt > 1) { 193 struct filedesc *newfd; 194 newfd = fdcopy(p1); 195 fdfree(p1); 196 p1->p_fd = newfd; 197 } 198 } 199 return (0); 200 } 201 202 /* 203 * Although process entries are dynamically created, we still keep 204 * a global limit on the maximum number we will create. Don't allow 205 * a nonprivileged user to use the last process; don't let root 206 * exceed the limit. The variable nprocs is the current number of 207 * processes, maxproc is the limit. 208 */ 209 uid = p1->p_cred->p_ruid; 210 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 211 tablefull("proc"); 212 return (EAGAIN); 213 } 214 /* 215 * Increment the nprocs resource before blocking can occur. There 216 * are hard-limits as to the number of processes that can run. 217 */ 218 nprocs++; 219 220 /* 221 * Increment the count of procs running with this uid. Don't allow 222 * a nonprivileged user to exceed their current limit. 223 */ 224 count = chgproccnt(uid, 1); 225 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 226 (void)chgproccnt(uid, -1); 227 /* 228 * Back out the process count 229 */ 230 nprocs--; 231 return (EAGAIN); 232 } 233 234 /* Allocate new proc. */ 235 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 236 237 /* 238 * Setup linkage for kernel based threading 239 */ 240 if((flags & RFTHREAD) != 0) { 241 newproc->p_peers = p1->p_peers; 242 p1->p_peers = newproc; 243 newproc->p_leader = p1->p_leader; 244 } else { 245 newproc->p_peers = 0; 246 newproc->p_leader = newproc; 247 } 248 249 newproc->p_wakeup = 0; 250 251 /* 252 * Find an unused process ID. We remember a range of unused IDs 253 * ready to use (from nextpid+1 through pidchecked-1). 254 */ 255 nextpid++; 256 retry: 257 /* 258 * If the process ID prototype has wrapped around, 259 * restart somewhat above 0, as the low-numbered procs 260 * tend to include daemons that don't exit. 261 */ 262 if (nextpid >= PID_MAX) { 263 nextpid = 100; 264 pidchecked = 0; 265 } 266 if (nextpid >= pidchecked) { 267 int doingzomb = 0; 268 269 pidchecked = PID_MAX; 270 /* 271 * Scan the active and zombie procs to check whether this pid 272 * is in use. Remember the lowest pid that's greater 273 * than nextpid, so we can avoid checking for a while. 274 */ 275 p2 = allproc.lh_first; 276 again: 277 for (; p2 != 0; p2 = p2->p_list.le_next) { 278 while (p2->p_pid == nextpid || 279 p2->p_pgrp->pg_id == nextpid) { 280 nextpid++; 281 if (nextpid >= pidchecked) 282 goto retry; 283 } 284 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 285 pidchecked = p2->p_pid; 286 if (p2->p_pgrp->pg_id > nextpid && 287 pidchecked > p2->p_pgrp->pg_id) 288 pidchecked = p2->p_pgrp->pg_id; 289 } 290 if (!doingzomb) { 291 doingzomb = 1; 292 p2 = zombproc.lh_first; 293 goto again; 294 } 295 } 296 297 p2 = newproc; 298 p2->p_stat = SIDL; /* protect against others */ 299 p2->p_pid = nextpid; 300 LIST_INSERT_HEAD(&allproc, p2, p_list); 301 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 302 303 /* 304 * Make a proc table entry for the new process. 305 * Start by zeroing the section of proc that is zero-initialized, 306 * then copy the section that is copied directly from the parent. 307 */ 308 bzero(&p2->p_startzero, 309 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 310 bcopy(&p1->p_startcopy, &p2->p_startcopy, 311 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 312 313 p2->p_aioinfo = NULL; 314 315 /* 316 * Duplicate sub-structures as needed. 317 * Increase reference counts on shared objects. 318 * The p_stats and p_sigacts substructs are set in vm_fork. 319 */ 320 p2->p_flag = P_INMEM; 321 if (p1->p_flag & P_PROFIL) 322 startprofclock(p2); 323 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 324 M_SUBPROC, M_WAITOK); 325 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 326 p2->p_cred->p_refcnt = 1; 327 crhold(p1->p_ucred); 328 329 /* bump references to the text vnode (for procfs) */ 330 p2->p_textvp = p1->p_textvp; 331 if (p2->p_textvp) 332 VREF(p2->p_textvp); 333 334 if (flags & RFCFDG) 335 p2->p_fd = fdinit(p1); 336 else if (flags & RFFDG) 337 p2->p_fd = fdcopy(p1); 338 else 339 p2->p_fd = fdshare(p1); 340 341 /* 342 * If p_limit is still copy-on-write, bump refcnt, 343 * otherwise get a copy that won't be modified. 344 * (If PL_SHAREMOD is clear, the structure is shared 345 * copy-on-write.) 346 */ 347 if (p1->p_limit->p_lflags & PL_SHAREMOD) 348 p2->p_limit = limcopy(p1->p_limit); 349 else { 350 p2->p_limit = p1->p_limit; 351 p2->p_limit->p_refcnt++; 352 } 353 354 /* 355 * Preserve some flags in subprocess. 356 */ 357 p2->p_flag |= p1->p_flag & P_SUGID; 358 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 359 p2->p_flag |= P_CONTROLT; 360 if (flags & RFPPWAIT) 361 p2->p_flag |= P_PPWAIT; 362 LIST_INSERT_AFTER(p1, p2, p_pglist); 363 364 /* 365 * Attach the new process to its parent. 366 * 367 * If RFNOWAIT is set, the newly created process becomes a child 368 * of init. This effectively disassociates the child from the 369 * parent. 370 */ 371 if (flags & RFNOWAIT) 372 pptr = initproc; 373 else 374 pptr = p1; 375 p2->p_pptr = pptr; 376 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 377 LIST_INIT(&p2->p_children); 378 379 #ifdef KTRACE 380 /* 381 * Copy traceflag and tracefile if enabled. 382 * If not inherited, these were zeroed above. 383 */ 384 if (p1->p_traceflag&KTRFAC_INHERIT) { 385 p2->p_traceflag = p1->p_traceflag; 386 if ((p2->p_tracep = p1->p_tracep) != NULL) 387 VREF(p2->p_tracep); 388 } 389 #endif 390 391 /* 392 * set priority of child to be that of parent 393 */ 394 p2->p_estcpu = p1->p_estcpu; 395 396 /* 397 * This begins the section where we must prevent the parent 398 * from being swapped. 399 */ 400 p1->p_flag |= P_NOSWAP; 401 402 /* 403 * Finish creating the child process. It will return via a different 404 * execution path later. (ie: directly into user mode) 405 */ 406 vm_fork(p1, p2, flags); 407 408 /* 409 * Both processes are set up, now check if any LKMs want 410 * to adjust anything. 411 * What if they have an error? XXX 412 */ 413 while (ep) { 414 (*ep->function)(p1, p2, flags); 415 ep = ep->next; 416 } 417 418 /* 419 * Make child runnable and add to run queue. 420 */ 421 microtime(&(p2->p_stats->p_start)); 422 p2->p_acflag = AFORK; 423 (void) splhigh(); 424 p2->p_stat = SRUN; 425 setrunqueue(p2); 426 (void) spl0(); 427 428 /* 429 * Now can be swapped. 430 */ 431 p1->p_flag &= ~P_NOSWAP; 432 433 /* 434 * Preserve synchronization semantics of vfork. If waiting for 435 * child to exec or exit, set P_PPWAIT on child, and sleep on our 436 * proc (in case of exit). 437 */ 438 while (p2->p_flag & P_PPWAIT) 439 tsleep(p1, PWAIT, "ppwait", 0); 440 441 /* 442 * Return child pid to parent process, 443 * marking us as parent via retval[1]. 444 */ 445 retval[0] = p2->p_pid; 446 retval[1] = 0; 447 return (0); 448 } 449 450 /* 451 * The next two functionms are general routines to handle adding/deleting 452 * items on the fork callout list. 453 * 454 * at_fork(): 455 * Take the arguments given and put them onto the fork callout list, 456 * However first make sure that it's not already there. 457 * Returns 0 on success or a standard error number. 458 */ 459 int 460 at_fork(function) 461 forklist_fn function; 462 { 463 fle_p ep; 464 465 /* let the programmer know if he's been stupid */ 466 if (rm_at_fork(function)) 467 printf("fork callout entry already present\n"); 468 ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT); 469 if (ep == NULL) 470 return (ENOMEM); 471 ep->next = fork_list; 472 ep->function = function; 473 fork_list = ep; 474 return (0); 475 } 476 477 /* 478 * Scan the exit callout list for the given items and remove them. 479 * Returns the number of items removed. 480 * Theoretically this value can only be 0 or 1. 481 */ 482 int 483 rm_at_fork(function) 484 forklist_fn function; 485 { 486 fle_p *epp, ep; 487 int count; 488 489 count= 0; 490 epp = &fork_list; 491 ep = *epp; 492 while (ep) { 493 if (ep->function == function) { 494 *epp = ep->next; 495 free(ep, M_TEMP); 496 count++; 497 } else { 498 epp = &ep->next; 499 } 500 ep = *epp; 501 } 502 return (count); 503 } 504