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 1.16 1996/01/03 21:42:02 wollman 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/file.h> 54 #include <sys/acct.h> 55 #include <sys/ktrace.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(struct proc *p, int forktype, int rforkflags, int *retval); 66 67 #define ISFORK 0 68 #define ISVFORK 1 69 #define ISRFORK 2 70 71 #ifndef _SYS_SYSPROTO_H_ 72 struct fork_args { 73 int dummy; 74 }; 75 #endif 76 77 /* ARGSUSED */ 78 int 79 fork(p, uap, retval) 80 struct proc *p; 81 struct fork_args *uap; 82 int retval[]; 83 { 84 return (fork1(p, ISFORK, 0, retval)); 85 } 86 87 /* ARGSUSED */ 88 int 89 vfork(p, uap, retval) 90 struct proc *p; 91 struct vfork_args *uap; 92 int retval[]; 93 { 94 return (fork1(p, ISVFORK, 0, retval)); 95 } 96 97 /* ARGSUSED */ 98 int 99 rfork(p, uap, retval) 100 struct proc *p; 101 struct rfork_args *uap; 102 int retval[]; 103 { 104 return (fork1(p, ISRFORK, uap->flags, retval)); 105 } 106 107 108 int nprocs = 1; /* process 0 */ 109 110 static int 111 fork1(p1, forktype, rforkflags, retval) 112 register struct proc *p1; 113 int forktype; 114 int rforkflags; 115 int retval[]; 116 { 117 register struct proc *p2; 118 register uid_t uid; 119 struct proc *newproc; 120 struct proc **hash; 121 int count; 122 static int nextpid, pidchecked = 0; 123 int dupfd = 1, cleanfd = 0; 124 125 if (forktype == ISRFORK) { 126 dupfd = 0; 127 if ((rforkflags & RFPROC) == 0) 128 return (EINVAL); 129 if ((rforkflags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 130 return (EINVAL); 131 if (rforkflags & RFFDG) 132 dupfd = 1; 133 if (rforkflags & RFNOWAIT) 134 return (EINVAL); /* XXX unimplimented */ 135 if (rforkflags & RFCFDG) 136 cleanfd = 1; 137 } 138 139 /* 140 * Although process entries are dynamically created, we still keep 141 * a global limit on the maximum number we will create. Don't allow 142 * a nonprivileged user to use the last process; don't let root 143 * exceed the limit. The variable nprocs is the current number of 144 * processes, maxproc is the limit. 145 */ 146 uid = p1->p_cred->p_ruid; 147 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 148 tablefull("proc"); 149 return (EAGAIN); 150 } 151 /* 152 * Increment the count of procs running with this uid. Don't allow 153 * a nonprivileged user to exceed their current limit. 154 */ 155 count = chgproccnt(uid, 1); 156 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 157 (void)chgproccnt(uid, -1); 158 return (EAGAIN); 159 } 160 161 /* Allocate new proc. */ 162 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 163 164 /* 165 * Find an unused process ID. We remember a range of unused IDs 166 * ready to use (from nextpid+1 through pidchecked-1). 167 */ 168 nextpid++; 169 retry: 170 /* 171 * If the process ID prototype has wrapped around, 172 * restart somewhat above 0, as the low-numbered procs 173 * tend to include daemons that don't exit. 174 */ 175 if (nextpid >= PID_MAX) { 176 nextpid = 100; 177 pidchecked = 0; 178 } 179 if (nextpid >= pidchecked) { 180 int doingzomb = 0; 181 182 pidchecked = PID_MAX; 183 /* 184 * Scan the active and zombie procs to check whether this pid 185 * is in use. Remember the lowest pid that's greater 186 * than nextpid, so we can avoid checking for a while. 187 */ 188 p2 = (struct proc *)allproc; 189 again: 190 for (; p2 != NULL; p2 = p2->p_next) { 191 while (p2->p_pid == nextpid || 192 p2->p_pgrp->pg_id == nextpid) { 193 nextpid++; 194 if (nextpid >= pidchecked) 195 goto retry; 196 } 197 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 198 pidchecked = p2->p_pid; 199 if (p2->p_pgrp->pg_id > nextpid && 200 pidchecked > p2->p_pgrp->pg_id) 201 pidchecked = p2->p_pgrp->pg_id; 202 } 203 if (!doingzomb) { 204 doingzomb = 1; 205 p2 = zombproc; 206 goto again; 207 } 208 } 209 210 211 /* 212 * Link onto allproc (this should probably be delayed). 213 * Heavy use of volatile here to prevent the compiler from 214 * rearranging code. Yes, it *is* terribly ugly, but at least 215 * it works. 216 */ 217 nprocs++; 218 p2 = newproc; 219 #define Vp2 ((volatile struct proc *)p2) 220 Vp2->p_stat = SIDL; /* protect against others */ 221 Vp2->p_pid = nextpid; 222 /* 223 * This is really: 224 * p2->p_next = allproc; 225 * allproc->p_prev = &p2->p_next; 226 * p2->p_prev = &allproc; 227 * allproc = p2; 228 * The assignment via allproc is legal since it is never NULL. 229 */ 230 *(volatile struct proc **)&Vp2->p_next = allproc; 231 *(volatile struct proc ***)&allproc->p_prev = 232 (volatile struct proc **)&Vp2->p_next; 233 *(volatile struct proc ***)&Vp2->p_prev = &allproc; 234 allproc = Vp2; 235 #undef Vp2 236 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 237 238 /* Insert on the hash chain. */ 239 hash = &pidhash[PIDHASH(p2->p_pid)]; 240 p2->p_hash = *hash; 241 *hash = p2; 242 243 /* 244 * Make a proc table entry for the new process. 245 * Start by zeroing the section of proc that is zero-initialized, 246 * then copy the section that is copied directly from the parent. 247 */ 248 bzero(&p2->p_startzero, 249 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 250 bcopy(&p1->p_startcopy, &p2->p_startcopy, 251 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 252 253 /* 254 * Duplicate sub-structures as needed. 255 * Increase reference counts on shared objects. 256 * The p_stats and p_sigacts substructs are set in vm_fork. 257 */ 258 p2->p_flag = P_INMEM; 259 if (p1->p_flag & P_PROFIL) 260 startprofclock(p2); 261 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 262 M_SUBPROC, M_WAITOK); 263 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 264 p2->p_cred->p_refcnt = 1; 265 crhold(p1->p_ucred); 266 267 /* bump references to the text vnode (for procfs) */ 268 p2->p_textvp = p1->p_textvp; 269 if (p2->p_textvp) 270 VREF(p2->p_textvp); 271 272 if (cleanfd) 273 p2->p_fd = fdinit(p1); 274 else if (dupfd) 275 p2->p_fd = fdcopy(p1); 276 else 277 p2->p_fd = fdshare(p1); 278 279 /* 280 * If p_limit is still copy-on-write, bump refcnt, 281 * otherwise get a copy that won't be modified. 282 * (If PL_SHAREMOD is clear, the structure is shared 283 * copy-on-write.) 284 */ 285 if (p1->p_limit->p_lflags & PL_SHAREMOD) 286 p2->p_limit = limcopy(p1->p_limit); 287 else { 288 p2->p_limit = p1->p_limit; 289 p2->p_limit->p_refcnt++; 290 } 291 292 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 293 p2->p_flag |= P_CONTROLT; 294 if (forktype == ISVFORK) 295 p2->p_flag |= P_PPWAIT; 296 p2->p_pgrpnxt = p1->p_pgrpnxt; 297 p1->p_pgrpnxt = p2; 298 p2->p_pptr = p1; 299 p2->p_osptr = p1->p_cptr; 300 if (p1->p_cptr) 301 p1->p_cptr->p_ysptr = p2; 302 p1->p_cptr = p2; 303 #ifdef KTRACE 304 /* 305 * Copy traceflag and tracefile if enabled. 306 * If not inherited, these were zeroed above. 307 */ 308 if (p1->p_traceflag&KTRFAC_INHERIT) { 309 p2->p_traceflag = p1->p_traceflag; 310 if ((p2->p_tracep = p1->p_tracep) != NULL) 311 VREF(p2->p_tracep); 312 } 313 #endif 314 315 /* 316 * set priority of child to be that of parent 317 */ 318 p2->p_estcpu = p1->p_estcpu; 319 320 /* 321 * This begins the section where we must prevent the parent 322 * from being swapped. 323 */ 324 p1->p_flag |= P_NOSWAP; 325 326 /* 327 * share as much address space as possible 328 */ 329 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 330 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 331 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 332 VM_INHERIT_SHARE); 333 } 334 335 /* 336 * Set return values for child before vm_fork, 337 * so they can be copied to child stack. 338 * We return parent pid, and mark as child in retval[1]. 339 * NOTE: the kernel stack may be at a different location in the child 340 * process, and thus addresses of automatic variables (including retval) 341 * may be invalid after vm_fork returns in the child process. 342 */ 343 retval[0] = p1->p_pid; 344 retval[1] = 1; 345 if (vm_fork(p1, p2)) { 346 /* 347 * Child process. Set start time and get to work. 348 */ 349 microtime(&runtime); 350 p2->p_stats->p_start = runtime; 351 p2->p_acflag = AFORK; 352 return (0); 353 } 354 355 /* 356 * Make child runnable and add to run queue. 357 */ 358 (void) splhigh(); 359 p2->p_stat = SRUN; 360 setrunqueue(p2); 361 (void) spl0(); 362 363 /* 364 * Now can be swapped. 365 */ 366 p1->p_flag &= ~P_NOSWAP; 367 368 /* 369 * Preserve synchronization semantics of vfork. If waiting for 370 * child to exec or exit, set P_PPWAIT on child, and sleep on our 371 * proc (in case of exit). 372 */ 373 if (forktype == ISVFORK) 374 while (p2->p_flag & P_PPWAIT) 375 tsleep(p1, PWAIT, "ppwait", 0); 376 377 /* 378 * Return child pid to parent process, 379 * marking us as parent via retval[1]. 380 */ 381 retval[0] = p2->p_pid; 382 retval[1] = 0; 383 return (0); 384 } 385