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 1.25 1996/08/22 03:50:18 julian 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/malloc.h> 50 #include <sys/proc.h> 51 #include <sys/resourcevar.h> 52 #include <sys/vnode.h> 53 #include <sys/acct.h> 54 #include <sys/ktrace.h> 55 #include <sys/unistd.h> 56 57 #include <vm/vm.h> 58 #include <vm/vm_param.h> 59 #include <vm/lock.h> 60 #include <vm/pmap.h> 61 #include <vm/vm_map.h> 62 #include <vm/vm_extern.h> 63 #include <vm/vm_inherit.h> 64 65 static int fork1 __P((struct proc *p, int flags, int *retval)); 66 67 /* 68 * These are the stuctures used to create a callout list for things to do 69 * when forking a process 70 */ 71 typedef struct fork_list_element { 72 struct fork_list_element *next; 73 forklist_fn function; 74 } *fle_p; 75 76 static fle_p fork_list; 77 78 #ifndef _SYS_SYSPROTO_H_ 79 struct fork_args { 80 int dummy; 81 }; 82 #endif 83 84 /* ARGSUSED */ 85 int 86 fork(p, uap, retval) 87 struct proc *p; 88 struct fork_args *uap; 89 int retval[]; 90 { 91 return (fork1(p, (RFFDG|RFPROC), retval)); 92 } 93 94 /* ARGSUSED */ 95 int 96 vfork(p, uap, retval) 97 struct proc *p; 98 struct vfork_args *uap; 99 int retval[]; 100 { 101 return (fork1(p, (RFFDG|RFPROC|RFPPWAIT), retval)); 102 } 103 104 /* ARGSUSED */ 105 int 106 rfork(p, uap, retval) 107 struct proc *p; 108 struct rfork_args *uap; 109 int retval[]; 110 { 111 return (fork1(p, uap->flags, retval)); 112 } 113 114 115 int nprocs = 1; /* process 0 */ 116 117 static int 118 fork1(p1, flags, retval) 119 register struct proc *p1; 120 int flags; 121 int retval[]; 122 { 123 register struct proc *p2, *pptr; 124 register uid_t uid; 125 struct proc *newproc; 126 int count; 127 static int nextpid, pidchecked = 0; 128 fle_p ep ; 129 130 ep = fork_list; 131 if ((flags & RFPROC) == 0) 132 return (EINVAL); 133 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 134 return (EINVAL); 135 136 /* 137 * Although process entries are dynamically created, we still keep 138 * a global limit on the maximum number we will create. Don't allow 139 * a nonprivileged user to use the last process; don't let root 140 * exceed the limit. The variable nprocs is the current number of 141 * processes, maxproc is the limit. 142 */ 143 uid = p1->p_cred->p_ruid; 144 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 145 tablefull("proc"); 146 return (EAGAIN); 147 } 148 /* 149 * Increment the nprocs resource before blocking can occur. There 150 * are hard-limits as to the number of processes that can run. 151 */ 152 nprocs++; 153 154 /* 155 * Increment the count of procs running with this uid. Don't allow 156 * a nonprivileged user to exceed their current limit. 157 */ 158 count = chgproccnt(uid, 1); 159 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 160 (void)chgproccnt(uid, -1); 161 /* 162 * Back out the process count 163 */ 164 nprocs--; 165 return (EAGAIN); 166 } 167 168 /* Allocate new proc. */ 169 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 170 171 /* 172 * Find an unused process ID. We remember a range of unused IDs 173 * ready to use (from nextpid+1 through pidchecked-1). 174 */ 175 nextpid++; 176 retry: 177 /* 178 * If the process ID prototype has wrapped around, 179 * restart somewhat above 0, as the low-numbered procs 180 * tend to include daemons that don't exit. 181 */ 182 if (nextpid >= PID_MAX) { 183 nextpid = 100; 184 pidchecked = 0; 185 } 186 if (nextpid >= pidchecked) { 187 int doingzomb = 0; 188 189 pidchecked = PID_MAX; 190 /* 191 * Scan the active and zombie procs to check whether this pid 192 * is in use. Remember the lowest pid that's greater 193 * than nextpid, so we can avoid checking for a while. 194 */ 195 p2 = allproc.lh_first; 196 again: 197 for (; p2 != 0; p2 = p2->p_list.le_next) { 198 while (p2->p_pid == nextpid || 199 p2->p_pgrp->pg_id == nextpid) { 200 nextpid++; 201 if (nextpid >= pidchecked) 202 goto retry; 203 } 204 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 205 pidchecked = p2->p_pid; 206 if (p2->p_pgrp->pg_id > nextpid && 207 pidchecked > p2->p_pgrp->pg_id) 208 pidchecked = p2->p_pgrp->pg_id; 209 } 210 if (!doingzomb) { 211 doingzomb = 1; 212 p2 = zombproc.lh_first; 213 goto again; 214 } 215 } 216 217 p2 = newproc; 218 p2->p_stat = SIDL; /* protect against others */ 219 p2->p_pid = nextpid; 220 LIST_INSERT_HEAD(&allproc, p2, p_list); 221 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 222 223 /* 224 * Make a proc table entry for the new process. 225 * Start by zeroing the section of proc that is zero-initialized, 226 * then copy the section that is copied directly from the parent. 227 */ 228 bzero(&p2->p_startzero, 229 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 230 bcopy(&p1->p_startcopy, &p2->p_startcopy, 231 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 232 233 /* 234 * XXX: this should be done as part of the startzero above 235 */ 236 p2->p_vmspace = 0; /* XXX */ 237 238 /* 239 * Duplicate sub-structures as needed. 240 * Increase reference counts on shared objects. 241 * The p_stats and p_sigacts substructs are set in vm_fork. 242 */ 243 p2->p_flag = P_INMEM; 244 if (p1->p_flag & P_PROFIL) 245 startprofclock(p2); 246 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 247 M_SUBPROC, M_WAITOK); 248 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 249 p2->p_cred->p_refcnt = 1; 250 crhold(p1->p_ucred); 251 252 /* bump references to the text vnode (for procfs) */ 253 p2->p_textvp = p1->p_textvp; 254 if (p2->p_textvp) 255 VREF(p2->p_textvp); 256 257 if (flags & RFCFDG) 258 p2->p_fd = fdinit(p1); 259 else if (flags & RFFDG) 260 p2->p_fd = fdcopy(p1); 261 else 262 p2->p_fd = fdshare(p1); 263 264 /* 265 * If p_limit is still copy-on-write, bump refcnt, 266 * otherwise get a copy that won't be modified. 267 * (If PL_SHAREMOD is clear, the structure is shared 268 * copy-on-write.) 269 */ 270 if (p1->p_limit->p_lflags & PL_SHAREMOD) 271 p2->p_limit = limcopy(p1->p_limit); 272 else { 273 p2->p_limit = p1->p_limit; 274 p2->p_limit->p_refcnt++; 275 } 276 277 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 278 p2->p_flag |= P_CONTROLT; 279 if (flags & RFPPWAIT) 280 p2->p_flag |= P_PPWAIT; 281 LIST_INSERT_AFTER(p1, p2, p_pglist); 282 283 /* 284 * Attach the new process to its parent. 285 * 286 * If RFNOWAIT is set, the newly created process becomes a child 287 * of init. This effectively disassociates the child from the 288 * parent. 289 */ 290 if (flags & RFNOWAIT) 291 pptr = initproc; 292 else 293 pptr = p1; 294 p2->p_pptr = pptr; 295 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 296 LIST_INIT(&p2->p_children); 297 298 #ifdef KTRACE 299 /* 300 * Copy traceflag and tracefile if enabled. 301 * If not inherited, these were zeroed above. 302 */ 303 if (p1->p_traceflag&KTRFAC_INHERIT) { 304 p2->p_traceflag = p1->p_traceflag; 305 if ((p2->p_tracep = p1->p_tracep) != NULL) 306 VREF(p2->p_tracep); 307 } 308 #endif 309 310 /* 311 * set priority of child to be that of parent 312 */ 313 p2->p_estcpu = p1->p_estcpu; 314 315 /* 316 * This begins the section where we must prevent the parent 317 * from being swapped. 318 */ 319 p1->p_flag |= P_NOSWAP; 320 321 /* 322 * share as much address space as possible 323 * XXX this should probably go in vm_fork() 324 */ 325 if (flags & RFMEM) 326 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 327 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 328 VM_INHERIT_SHARE); 329 330 /* 331 * Set return values for child before vm_fork, 332 * so they can be copied to child stack. 333 * We return parent pid, and mark as child in retval[1]. 334 * NOTE: the kernel stack may be at a different location in the child 335 * process, and thus addresses of automatic variables (including retval) 336 * may be invalid after vm_fork returns in the child process. 337 */ 338 retval[0] = p1->p_pid; 339 retval[1] = 1; 340 if (vm_fork(p1, p2)) { 341 /* 342 * Child process. Set start time and get to work. 343 */ 344 microtime(&runtime); 345 p2->p_stats->p_start = runtime; 346 p2->p_acflag = AFORK; 347 return (0); 348 } 349 350 /* 351 * Both processes are set up, now check if any LKMs want 352 * to adjust anything. 353 * What if they have an error? XXX 354 */ 355 while (ep) { 356 (*ep->function)(p1, p2, flags); 357 ep = ep->next; 358 } 359 360 /* 361 * Make child runnable and add to run queue. 362 */ 363 (void) splhigh(); 364 p2->p_stat = SRUN; 365 setrunqueue(p2); 366 (void) spl0(); 367 368 /* 369 * Now can be swapped. 370 */ 371 p1->p_flag &= ~P_NOSWAP; 372 373 /* 374 * Preserve synchronization semantics of vfork. If waiting for 375 * child to exec or exit, set P_PPWAIT on child, and sleep on our 376 * proc (in case of exit). 377 */ 378 while (p2->p_flag & P_PPWAIT) 379 tsleep(p1, PWAIT, "ppwait", 0); 380 381 /* 382 * Return child pid to parent process, 383 * marking us as parent via retval[1]. 384 */ 385 retval[0] = p2->p_pid; 386 retval[1] = 0; 387 return (0); 388 } 389 390 /* 391 * The next two functionms are general routines to handle adding/deleting 392 * items on the fork callout list. 393 * 394 * at_fork(): 395 * Take the arguments given and put them onto the fork callout list, 396 * However first make sure that it's not already there. 397 * Returns 0 on success or a standard error number. 398 */ 399 int 400 at_fork(forklist_fn function) 401 { 402 fle_p ep; 403 404 /* let the programmer know if he's been stupid */ 405 if (rm_at_fork(function)) 406 printf("fork callout entry already present\n"); 407 ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT); 408 if (ep == NULL) 409 return (ENOMEM); 410 ep->next = fork_list; 411 ep->function = function; 412 fork_list = ep; 413 return (0); 414 } 415 416 /* 417 * Scan the exit callout list for the given items and remove them. 418 * Returns the number of items removed. 419 * Theoretically this value can only be 0 or 1. 420 */ 421 int 422 rm_at_fork(forklist_fn function) 423 { 424 fle_p *epp, ep; 425 int count; 426 427 count= 0; 428 epp = &fork_list; 429 ep = *epp; 430 while (ep) { 431 if (ep->function == function) { 432 *epp = ep->next; 433 free(ep, M_TEMP); 434 count++; 435 } else { 436 epp = &ep->next; 437 } 438 ep = *epp; 439 } 440 return (count); 441 } 442 443 444