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/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 <sys/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 static int nextpid = 0; 117 118 static int 119 fork1(p1, flags, retval) 120 register struct proc *p1; 121 int flags; 122 int retval[]; 123 { 124 register struct proc *p2, *pptr; 125 register uid_t uid; 126 struct proc *newproc; 127 int count; 128 static int pidchecked = 0; 129 fle_p ep ; 130 131 ep = fork_list; 132 if ((flags & RFPROC) == 0) 133 return (EINVAL); 134 if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 135 return (EINVAL); 136 137 /* 138 * Although process entries are dynamically created, we still keep 139 * a global limit on the maximum number we will create. Don't allow 140 * a nonprivileged user to use the last process; don't let root 141 * exceed the limit. The variable nprocs is the current number of 142 * processes, maxproc is the limit. 143 */ 144 uid = p1->p_cred->p_ruid; 145 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 146 tablefull("proc"); 147 return (EAGAIN); 148 } 149 /* 150 * Increment the nprocs resource before blocking can occur. There 151 * are hard-limits as to the number of processes that can run. 152 */ 153 nprocs++; 154 155 /* 156 * Increment the count of procs running with this uid. Don't allow 157 * a nonprivileged user to exceed their current limit. 158 */ 159 count = chgproccnt(uid, 1); 160 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 161 (void)chgproccnt(uid, -1); 162 /* 163 * Back out the process count 164 */ 165 nprocs--; 166 return (EAGAIN); 167 } 168 169 /* Allocate new proc. */ 170 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 171 172 /* 173 * Find an unused process ID. We remember a range of unused IDs 174 * ready to use (from nextpid+1 through pidchecked-1). 175 */ 176 nextpid++; 177 retry: 178 /* 179 * If the process ID prototype has wrapped around, 180 * restart somewhat above 0, as the low-numbered procs 181 * tend to include daemons that don't exit. 182 */ 183 if (nextpid >= PID_MAX) { 184 nextpid = 100; 185 pidchecked = 0; 186 } 187 if (nextpid >= pidchecked) { 188 int doingzomb = 0; 189 190 pidchecked = PID_MAX; 191 /* 192 * Scan the active and zombie procs to check whether this pid 193 * is in use. Remember the lowest pid that's greater 194 * than nextpid, so we can avoid checking for a while. 195 */ 196 p2 = allproc.lh_first; 197 again: 198 for (; p2 != 0; p2 = p2->p_list.le_next) { 199 while (p2->p_pid == nextpid || 200 p2->p_pgrp->pg_id == nextpid) { 201 nextpid++; 202 if (nextpid >= pidchecked) 203 goto retry; 204 } 205 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 206 pidchecked = p2->p_pid; 207 if (p2->p_pgrp->pg_id > nextpid && 208 pidchecked > p2->p_pgrp->pg_id) 209 pidchecked = p2->p_pgrp->pg_id; 210 } 211 if (!doingzomb) { 212 doingzomb = 1; 213 p2 = zombproc.lh_first; 214 goto again; 215 } 216 } 217 218 p2 = newproc; 219 p2->p_stat = SIDL; /* protect against others */ 220 p2->p_pid = nextpid; 221 LIST_INSERT_HEAD(&allproc, p2, p_list); 222 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 223 224 /* 225 * Make a proc table entry for the new process. 226 * Start by zeroing the section of proc that is zero-initialized, 227 * then copy the section that is copied directly from the parent. 228 */ 229 bzero(&p2->p_startzero, 230 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 231 bcopy(&p1->p_startcopy, &p2->p_startcopy, 232 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 233 234 /* 235 * XXX: this should be done as part of the startzero above 236 */ 237 p2->p_vmspace = 0; /* XXX */ 238 239 /* 240 * Duplicate sub-structures as needed. 241 * Increase reference counts on shared objects. 242 * The p_stats and p_sigacts substructs are set in vm_fork. 243 */ 244 p2->p_flag = P_INMEM; 245 if (p1->p_flag & P_PROFIL) 246 startprofclock(p2); 247 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 248 M_SUBPROC, M_WAITOK); 249 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 250 p2->p_cred->p_refcnt = 1; 251 crhold(p1->p_ucred); 252 253 /* bump references to the text vnode (for procfs) */ 254 p2->p_textvp = p1->p_textvp; 255 if (p2->p_textvp) 256 VREF(p2->p_textvp); 257 258 if (flags & RFCFDG) 259 p2->p_fd = fdinit(p1); 260 else if (flags & RFFDG) 261 p2->p_fd = fdcopy(p1); 262 else 263 p2->p_fd = fdshare(p1); 264 265 /* 266 * If p_limit is still copy-on-write, bump refcnt, 267 * otherwise get a copy that won't be modified. 268 * (If PL_SHAREMOD is clear, the structure is shared 269 * copy-on-write.) 270 */ 271 if (p1->p_limit->p_lflags & PL_SHAREMOD) 272 p2->p_limit = limcopy(p1->p_limit); 273 else { 274 p2->p_limit = p1->p_limit; 275 p2->p_limit->p_refcnt++; 276 } 277 278 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 279 p2->p_flag |= P_CONTROLT; 280 if (flags & RFPPWAIT) 281 p2->p_flag |= P_PPWAIT; 282 LIST_INSERT_AFTER(p1, p2, p_pglist); 283 284 /* 285 * Attach the new process to its parent. 286 * 287 * If RFNOWAIT is set, the newly created process becomes a child 288 * of init. This effectively disassociates the child from the 289 * parent. 290 */ 291 if (flags & RFNOWAIT) 292 pptr = initproc; 293 else 294 pptr = p1; 295 p2->p_pptr = pptr; 296 LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling); 297 LIST_INIT(&p2->p_children); 298 299 #ifdef KTRACE 300 /* 301 * Copy traceflag and tracefile if enabled. 302 * If not inherited, these were zeroed above. 303 */ 304 if (p1->p_traceflag&KTRFAC_INHERIT) { 305 p2->p_traceflag = p1->p_traceflag; 306 if ((p2->p_tracep = p1->p_tracep) != NULL) 307 VREF(p2->p_tracep); 308 } 309 #endif 310 311 /* 312 * set priority of child to be that of parent 313 */ 314 p2->p_estcpu = p1->p_estcpu; 315 316 /* 317 * This begins the section where we must prevent the parent 318 * from being swapped. 319 */ 320 p1->p_flag |= P_NOSWAP; 321 322 /* 323 * share as much address space as possible 324 * XXX this should probably go in vm_fork() 325 */ 326 if (flags & RFMEM) 327 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 328 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 329 VM_INHERIT_SHARE); 330 331 /* 332 * Set return values for child before vm_fork, 333 * so they can be copied to child stack. 334 * We return parent pid, and mark as child in retval[1]. 335 * NOTE: the kernel stack may be at a different location in the child 336 * process, and thus addresses of automatic variables (including retval) 337 * may be invalid after vm_fork returns in the child process. 338 */ 339 retval[0] = p1->p_pid; 340 retval[1] = 1; 341 if (vm_fork(p1, p2)) { 342 /* 343 * Child process. Set start time and get to work. 344 */ 345 microtime(&runtime); 346 (void) spl0(); 347 p2->p_stats->p_start = runtime; 348 p2->p_acflag = AFORK; 349 return (0); 350 } 351 352 /* 353 * Both processes are set up, now check if any LKMs want 354 * to adjust anything. 355 * What if they have an error? XXX 356 */ 357 while (ep) { 358 (*ep->function)(p1, p2, flags); 359 ep = ep->next; 360 } 361 362 /* 363 * Make child runnable and add to run queue. 364 */ 365 (void) splhigh(); 366 p2->p_stat = SRUN; 367 setrunqueue(p2); 368 (void) spl0(); 369 370 /* 371 * Now can be swapped. 372 */ 373 p1->p_flag &= ~P_NOSWAP; 374 375 /* 376 * Preserve synchronization semantics of vfork. If waiting for 377 * child to exec or exit, set P_PPWAIT on child, and sleep on our 378 * proc (in case of exit). 379 */ 380 while (p2->p_flag & P_PPWAIT) 381 tsleep(p1, PWAIT, "ppwait", 0); 382 383 /* 384 * Return child pid to parent process, 385 * marking us as parent via retval[1]. 386 */ 387 retval[0] = p2->p_pid; 388 retval[1] = 0; 389 return (0); 390 } 391 392 /* 393 * The next two functionms are general routines to handle adding/deleting 394 * items on the fork callout list. 395 * 396 * at_fork(): 397 * Take the arguments given and put them onto the fork callout list, 398 * However first make sure that it's not already there. 399 * Returns 0 on success or a standard error number. 400 */ 401 int 402 at_fork(forklist_fn function) 403 { 404 fle_p ep; 405 406 /* let the programmer know if he's been stupid */ 407 if (rm_at_fork(function)) 408 printf("fork callout entry already present\n"); 409 ep = malloc(sizeof(*ep), M_TEMP, M_NOWAIT); 410 if (ep == NULL) 411 return (ENOMEM); 412 ep->next = fork_list; 413 ep->function = function; 414 fork_list = ep; 415 return (0); 416 } 417 418 /* 419 * Scan the exit callout list for the given items and remove them. 420 * Returns the number of items removed. 421 * Theoretically this value can only be 0 or 1. 422 */ 423 int 424 rm_at_fork(forklist_fn function) 425 { 426 fle_p *epp, ep; 427 int count; 428 429 count= 0; 430 epp = &fork_list; 431 ep = *epp; 432 while (ep) { 433 if (ep->function == function) { 434 *epp = ep->next; 435 free(ep, M_TEMP); 436 count++; 437 } else { 438 epp = &ep->next; 439 } 440 ep = *epp; 441 } 442 return (count); 443 } 444 445 446