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 * $FreeBSD$ 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 #include <sys/jail.h> 58 59 #include <vm/vm.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_zone.h> 65 66 #include <machine/frame.h> 67 #include <sys/user.h> 68 69 static int fast_vfork = 1; 70 SYSCTL_INT(_kern, OID_AUTO, fast_vfork, CTLFLAG_RW, &fast_vfork, 0, ""); 71 72 /* 73 * These are the stuctures used to create a callout list for things to do 74 * when forking a process 75 */ 76 typedef struct fork_list_element { 77 struct fork_list_element *next; 78 forklist_fn function; 79 } *fle_p; 80 81 static fle_p fork_list; 82 83 #ifndef _SYS_SYSPROTO_H_ 84 struct fork_args { 85 int dummy; 86 }; 87 #endif 88 89 /* ARGSUSED */ 90 int 91 fork(p, uap) 92 struct proc *p; 93 struct fork_args *uap; 94 { 95 int error; 96 struct proc *p2; 97 98 error = fork1(p, RFFDG | RFPROC, &p2); 99 if (error == 0) { 100 p->p_retval[0] = p2->p_pid; 101 p->p_retval[1] = 0; 102 } 103 return error; 104 } 105 106 /* ARGSUSED */ 107 int 108 vfork(p, uap) 109 struct proc *p; 110 struct vfork_args *uap; 111 { 112 int error; 113 struct proc *p2; 114 115 error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2); 116 if (error == 0) { 117 p->p_retval[0] = p2->p_pid; 118 p->p_retval[1] = 0; 119 } 120 return error; 121 } 122 123 int 124 rfork(p, uap) 125 struct proc *p; 126 struct rfork_args *uap; 127 { 128 int error; 129 struct proc *p2; 130 131 error = fork1(p, uap->flags, &p2); 132 if (error == 0) { 133 p->p_retval[0] = p2 ? p2->p_pid : 0; 134 p->p_retval[1] = 0; 135 } 136 return error; 137 } 138 139 140 int nprocs = 1; /* process 0 */ 141 static int nextpid = 0; 142 143 int 144 fork1(p1, flags, procp) 145 struct proc *p1; 146 int flags; 147 struct proc **procp; 148 { 149 struct proc *p2, *pptr; 150 uid_t uid; 151 struct proc *newproc; 152 int count; 153 static int pidchecked = 0; 154 fle_p ep ; 155 156 ep = fork_list; 157 158 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 159 return (EINVAL); 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 *procp = NULL; 200 return (0); 201 } 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 ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 212 tablefull("proc"); 213 return (EAGAIN); 214 } 215 /* 216 * Increment the nprocs resource before blocking can occur. There 217 * are hard-limits as to the number of processes that can run. 218 */ 219 nprocs++; 220 221 /* 222 * Increment the count of procs running with this uid. Don't allow 223 * a nonprivileged user to exceed their current limit. 224 */ 225 count = chgproccnt(uid, 1); 226 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 227 (void)chgproccnt(uid, -1); 228 /* 229 * Back out the process count 230 */ 231 nprocs--; 232 return (EAGAIN); 233 } 234 235 /* Allocate new proc. */ 236 newproc = zalloc(proc_zone); 237 238 /* 239 * Setup linkage for kernel based threading 240 */ 241 if((flags & RFTHREAD) != 0) { 242 newproc->p_peers = p1->p_peers; 243 p1->p_peers = newproc; 244 newproc->p_leader = p1->p_leader; 245 } else { 246 newproc->p_peers = 0; 247 newproc->p_leader = newproc; 248 } 249 250 newproc->p_wakeup = 0; 251 252 newproc->p_vmspace = NULL; 253 254 /* 255 * Find an unused process ID. We remember a range of unused IDs 256 * ready to use (from nextpid+1 through pidchecked-1). 257 */ 258 nextpid++; 259 retry: 260 /* 261 * If the process ID prototype has wrapped around, 262 * restart somewhat above 0, as the low-numbered procs 263 * tend to include daemons that don't exit. 264 */ 265 if (nextpid >= PID_MAX) { 266 nextpid = 100; 267 pidchecked = 0; 268 } 269 if (nextpid >= pidchecked) { 270 int doingzomb = 0; 271 272 pidchecked = PID_MAX; 273 /* 274 * Scan the active and zombie procs to check whether this pid 275 * is in use. Remember the lowest pid that's greater 276 * than nextpid, so we can avoid checking for a while. 277 */ 278 p2 = allproc.lh_first; 279 again: 280 for (; p2 != 0; p2 = p2->p_list.le_next) { 281 while (p2->p_pid == nextpid || 282 p2->p_pgrp->pg_id == nextpid || 283 p2->p_session->s_sid == nextpid) { 284 nextpid++; 285 if (nextpid >= pidchecked) 286 goto retry; 287 } 288 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 289 pidchecked = p2->p_pid; 290 if (p2->p_pgrp->pg_id > nextpid && 291 pidchecked > p2->p_pgrp->pg_id) 292 pidchecked = p2->p_pgrp->pg_id; 293 if (p2->p_session->s_sid > nextpid && 294 pidchecked > p2->p_session->s_sid) 295 pidchecked = p2->p_session->s_sid; 296 } 297 if (!doingzomb) { 298 doingzomb = 1; 299 p2 = zombproc.lh_first; 300 goto again; 301 } 302 } 303 304 p2 = newproc; 305 p2->p_stat = SIDL; /* protect against others */ 306 p2->p_pid = nextpid; 307 LIST_INSERT_HEAD(&allproc, p2, p_list); 308 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 309 310 /* 311 * Make a proc table entry for the new process. 312 * Start by zeroing the section of proc that is zero-initialized, 313 * then copy the section that is copied directly from the parent. 314 */ 315 bzero(&p2->p_startzero, 316 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 317 bcopy(&p1->p_startcopy, &p2->p_startcopy, 318 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 319 320 p2->p_aioinfo = NULL; 321 322 /* 323 * Duplicate sub-structures as needed. 324 * Increase reference counts on shared objects. 325 * The p_stats and p_sigacts substructs are set in vm_fork. 326 */ 327 p2->p_flag = P_INMEM; 328 if (p1->p_flag & P_PROFIL) 329 startprofclock(p2); 330 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 331 M_SUBPROC, M_WAITOK); 332 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 333 p2->p_cred->p_refcnt = 1; 334 crhold(p1->p_ucred); 335 336 if (p2->p_prison) { 337 p2->p_prison->pr_ref++; 338 p2->p_flag |= P_JAILED; 339 } 340 341 if (flags & RFSIGSHARE) { 342 p2->p_procsig = p1->p_procsig; 343 p2->p_procsig->ps_refcnt++; 344 if (p1->p_sigacts == &p1->p_addr->u_sigacts) { 345 struct sigacts *newsigacts; 346 int s; 347 348 /* Create the shared sigacts structure */ 349 MALLOC(newsigacts, struct sigacts *, 350 sizeof(struct sigacts), M_SUBPROC, M_WAITOK); 351 s = splhigh(); 352 /* 353 * Set p_sigacts to the new shared structure. 354 * Note that this is updating p1->p_sigacts at the 355 * same time, since p_sigacts is just a pointer to 356 * the shared p_procsig->ps_sigacts. 357 */ 358 p2->p_sigacts = newsigacts; 359 bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts, 360 sizeof(*p2->p_sigacts)); 361 *p2->p_sigacts = p1->p_addr->u_sigacts; 362 splx(s); 363 } 364 } else { 365 MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig), 366 M_SUBPROC, M_WAITOK); 367 bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig)); 368 p2->p_procsig->ps_refcnt = 1; 369 p2->p_sigacts = NULL; /* finished in vm_fork() */ 370 } 371 if (flags & RFLINUXTHPN) 372 p2->p_sigparent = SIGUSR1; 373 else 374 p2->p_sigparent = SIGCHLD; 375 376 /* bump references to the text vnode (for procfs) */ 377 p2->p_textvp = p1->p_textvp; 378 if (p2->p_textvp) 379 VREF(p2->p_textvp); 380 381 if (flags & RFCFDG) 382 p2->p_fd = fdinit(p1); 383 else if (flags & RFFDG) 384 p2->p_fd = fdcopy(p1); 385 else 386 p2->p_fd = fdshare(p1); 387 388 /* 389 * If p_limit is still copy-on-write, bump refcnt, 390 * otherwise get a copy that won't be modified. 391 * (If PL_SHAREMOD is clear, the structure is shared 392 * copy-on-write.) 393 */ 394 if (p1->p_limit->p_lflags & PL_SHAREMOD) 395 p2->p_limit = limcopy(p1->p_limit); 396 else { 397 p2->p_limit = p1->p_limit; 398 p2->p_limit->p_refcnt++; 399 } 400 401 /* 402 * Preserve some more flags in subprocess. P_PROFIL has already 403 * been preserved. 404 */ 405 p2->p_flag |= p1->p_flag & P_SUGID; 406 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 407 p2->p_flag |= P_CONTROLT; 408 if (flags & RFPPWAIT) 409 p2->p_flag |= P_PPWAIT; 410 411 LIST_INSERT_AFTER(p1, p2, p_pglist); 412 413 /* 414 * Attach the new process to its parent. 415 * 416 * If RFNOWAIT is set, the newly created process becomes a child 417 * of init. This effectively disassociates the child from the 418 * parent. 419 */ 420 if (flags & RFNOWAIT) 421 pptr = initproc; 422 else 423 pptr = p1; 424 p2->p_pptr = pptr; 425 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 426 LIST_INIT(&p2->p_children); 427 428 #ifdef KTRACE 429 /* 430 * Copy traceflag and tracefile if enabled. 431 * If not inherited, these were zeroed above. 432 */ 433 if (p1->p_traceflag&KTRFAC_INHERIT) { 434 p2->p_traceflag = p1->p_traceflag; 435 if ((p2->p_tracep = p1->p_tracep) != NULL) 436 VREF(p2->p_tracep); 437 } 438 #endif 439 440 /* 441 * set priority of child to be that of parent 442 */ 443 p2->p_estcpu = p1->p_estcpu; 444 445 /* 446 * This begins the section where we must prevent the parent 447 * from being swapped. 448 */ 449 PHOLD(p1); 450 451 /* 452 * Finish creating the child process. It will return via a different 453 * execution path later. (ie: directly into user mode) 454 */ 455 vm_fork(p1, p2, flags); 456 457 /* 458 * Both processes are set up, now check if any loadable modules want 459 * to adjust anything. 460 * What if they have an error? XXX 461 */ 462 while (ep) { 463 (*ep->function)(p1, p2, flags); 464 ep = ep->next; 465 } 466 467 /* 468 * Make child runnable and add to run queue. 469 */ 470 microtime(&(p2->p_stats->p_start)); 471 p2->p_acflag = AFORK; 472 (void) splhigh(); 473 p2->p_stat = SRUN; 474 setrunqueue(p2); 475 (void) spl0(); 476 477 /* 478 * Now can be swapped. 479 */ 480 PRELE(p1); 481 482 /* 483 * Preserve synchronization semantics of vfork. If waiting for 484 * child to exec or exit, set P_PPWAIT on child, and sleep on our 485 * proc (in case of exit). 486 */ 487 while (p2->p_flag & P_PPWAIT) 488 tsleep(p1, PWAIT, "ppwait", 0); 489 490 /* 491 * Return child proc pointer to parent. 492 */ 493 *procp = p2; 494 return (0); 495 } 496 497 /* 498 * The next two functionms are general routines to handle adding/deleting 499 * items on the fork callout list. 500 * 501 * at_fork(): 502 * Take the arguments given and put them onto the fork callout list, 503 * However first make sure that it's not already there. 504 * Returns 0 on success or a standard error number. 505 */ 506 int 507 at_fork(function) 508 forklist_fn function; 509 { 510 fle_p ep; 511 512 /* let the programmer know if he's been stupid */ 513 if (rm_at_fork(function)) 514 printf("fork callout entry already present\n"); 515 ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT); 516 if (ep == NULL) 517 return (ENOMEM); 518 ep->next = fork_list; 519 ep->function = function; 520 fork_list = ep; 521 return (0); 522 } 523 524 /* 525 * Scan the exit callout list for the given items and remove them. 526 * Returns the number of items removed. 527 * Theoretically this value can only be 0 or 1. 528 */ 529 int 530 rm_at_fork(function) 531 forklist_fn function; 532 { 533 fle_p *epp, ep; 534 int count; 535 536 count= 0; 537 epp = &fork_list; 538 ep = *epp; 539 while (ep) { 540 if (ep->function == function) { 541 *epp = ep->next; 542 free(ep, M_TEMP); 543 count++; 544 } else { 545 epp = &ep->next; 546 } 547 ep = *epp; 548 } 549 return (count); 550 } 551