1 /* $OpenBSD: kern_fork.c,v 1.6 1996/09/02 01:22:05 tholo Exp $ */ 2 /* $NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1989, 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * (c) UNIX System Laboratories, Inc. 8 * All or some portions of this file are derived from material licensed 9 * to the University of California by American Telephone and Telegraph 10 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 11 * the permission of UNIX System Laboratories, Inc. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 42 */ 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/map.h> 47 #include <sys/filedesc.h> 48 #include <sys/kernel.h> 49 #include <sys/malloc.h> 50 #include <sys/mount.h> 51 #include <sys/proc.h> 52 #include <sys/resourcevar.h> 53 #include <sys/vnode.h> 54 #include <sys/file.h> 55 #include <sys/acct.h> 56 #include <sys/ktrace.h> 57 58 #include <sys/syscallargs.h> 59 60 #include <vm/vm.h> 61 62 int nprocs = 1; /* process 0 */ 63 pid_t lastpid; 64 65 #define ISFORK 0 66 #define ISVFORK 1 67 #define ISRFORK 2 68 69 int fork1 __P((struct proc *, int, int, register_t *)); 70 71 /*ARGSUSED*/ 72 int 73 sys_fork(p, v, retval) 74 struct proc *p; 75 void *v; 76 register_t *retval; 77 { 78 return (fork1(p, ISFORK, 0, retval)); 79 } 80 81 /*ARGSUSED*/ 82 int 83 sys_vfork(p, v, retval) 84 struct proc *p; 85 void *v; 86 register_t *retval; 87 { 88 return (fork1(p, ISVFORK, 0, retval)); 89 } 90 91 int 92 sys_rfork(p, v, retval) 93 struct proc *p; 94 void *v; 95 register_t *retval; 96 { 97 struct sys_rfork_args /* { 98 syscallarg(int) flags; 99 } */ *uap = v; 100 101 return (fork1(p, ISRFORK, SCARG(uap, flags), retval)); 102 } 103 104 int 105 fork1(p1, forktype, rforkflags, retval) 106 register struct proc *p1; 107 int forktype; 108 int rforkflags; 109 register_t *retval; 110 { 111 register struct proc *p2; 112 register uid_t uid; 113 struct proc *newproc; 114 int count; 115 static int pidchecked = 0; 116 int dupfd = 1, cleanfd = 0; 117 118 if (forktype == ISRFORK) { 119 dupfd = 0; 120 if ((rforkflags & RFPROC) == 0) 121 return (EINVAL); 122 if ((rforkflags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 123 return (EINVAL); 124 if (rforkflags & RFFDG) 125 dupfd = 1; 126 if (rforkflags & RFNOWAIT) 127 return (EINVAL); /* XXX unimplimented */ 128 if (rforkflags & RFCFDG) 129 cleanfd = 1; 130 } 131 132 /* 133 * Although process entries are dynamically created, we still keep 134 * a global limit on the maximum number we will create. Don't allow 135 * a nonprivileged user to use the last process; don't let root 136 * exceed the limit. The variable nprocs is the current number of 137 * processes, maxproc is the limit. 138 */ 139 uid = p1->p_cred->p_ruid; 140 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 141 tablefull("proc"); 142 return (EAGAIN); 143 } 144 145 /* 146 * Increment the count of procs running with this uid. Don't allow 147 * a nonprivileged user to exceed their current limit. 148 */ 149 count = chgproccnt(uid, 1); 150 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 151 (void)chgproccnt(uid, -1); 152 return (EAGAIN); 153 } 154 155 /* Allocate new proc. */ 156 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 157 158 /* 159 * Find an unused process ID. We remember a range of unused IDs 160 * ready to use (from lastpid+1 through pidchecked-1). 161 */ 162 lastpid++; 163 retry: 164 /* 165 * If the process ID prototype has wrapped around, 166 * restart somewhat above 0, as the low-numbered procs 167 * tend to include daemons that don't exit. 168 */ 169 if (lastpid >= PID_MAX) { 170 lastpid = 100; 171 pidchecked = 0; 172 } 173 if (lastpid >= pidchecked) { 174 int doingzomb = 0; 175 176 pidchecked = PID_MAX; 177 /* 178 * Scan the active and zombie procs to check whether this pid 179 * is in use. Remember the lowest pid that's greater 180 * than lastpid, so we can avoid checking for a while. 181 */ 182 p2 = allproc.lh_first; 183 again: 184 for (; p2 != 0; p2 = p2->p_list.le_next) { 185 while (p2->p_pid == lastpid || 186 p2->p_pgrp->pg_id == lastpid) { 187 lastpid++; 188 if (lastpid >= pidchecked) 189 goto retry; 190 } 191 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 192 pidchecked = p2->p_pid; 193 if (p2->p_pgrp->pg_id > lastpid && 194 pidchecked > p2->p_pgrp->pg_id) 195 pidchecked = p2->p_pgrp->pg_id; 196 } 197 if (!doingzomb) { 198 doingzomb = 1; 199 p2 = zombproc.lh_first; 200 goto again; 201 } 202 } 203 204 nprocs++; 205 p2 = newproc; 206 p2->p_stat = SIDL; /* protect against others */ 207 p2->p_pid = lastpid; 208 LIST_INSERT_HEAD(&allproc, p2, p_list); 209 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 210 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 211 212 /* 213 * Make a proc table entry for the new process. 214 * Start by zeroing the section of proc that is zero-initialized, 215 * then copy the section that is copied directly from the parent. 216 */ 217 bzero(&p2->p_startzero, 218 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 219 bcopy(&p1->p_startcopy, &p2->p_startcopy, 220 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 221 222 /* 223 * Duplicate sub-structures as needed. 224 * Increase reference counts on shared objects. 225 * The p_stats and p_sigacts substructs are set in vm_fork. 226 */ 227 p2->p_flag = P_INMEM; 228 p2->p_emul = p1->p_emul; 229 if (p1->p_flag & P_PROFIL) 230 startprofclock(p2); 231 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 232 M_SUBPROC, M_WAITOK); 233 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 234 p2->p_cred->p_refcnt = 1; 235 crhold(p1->p_ucred); 236 237 /* bump references to the text vnode (for procfs) */ 238 p2->p_textvp = p1->p_textvp; 239 if (p2->p_textvp) 240 VREF(p2->p_textvp); 241 242 if (cleanfd) 243 p2->p_fd = fdinit(p1); 244 else if (dupfd) 245 p2->p_fd = fdcopy(p1); 246 else 247 p2->p_fd = fdshare(p1); 248 249 /* 250 * If p_limit is still copy-on-write, bump refcnt, 251 * otherwise get a copy that won't be modified. 252 * (If PL_SHAREMOD is clear, the structure is shared 253 * copy-on-write.) 254 */ 255 if (p1->p_limit->p_lflags & PL_SHAREMOD) 256 p2->p_limit = limcopy(p1->p_limit); 257 else { 258 p2->p_limit = p1->p_limit; 259 p2->p_limit->p_refcnt++; 260 } 261 262 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 263 p2->p_flag |= P_CONTROLT; 264 if (forktype == ISVFORK) 265 p2->p_flag |= P_PPWAIT; 266 LIST_INSERT_AFTER(p1, p2, p_pglist); 267 p2->p_pptr = p1; 268 if (rforkflags & RFNOWAIT) { 269 /* XXX should we do anything? */ 270 } else { 271 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 272 } 273 LIST_INIT(&p2->p_children); 274 275 #ifdef KTRACE 276 /* 277 * Copy traceflag and tracefile if enabled. 278 * If not inherited, these were zeroed above. 279 */ 280 if (p1->p_traceflag&KTRFAC_INHERIT) { 281 p2->p_traceflag = p1->p_traceflag; 282 if ((p2->p_tracep = p1->p_tracep) != NULL) 283 VREF(p2->p_tracep); 284 } 285 #endif 286 287 /* 288 * This begins the section where we must prevent the parent 289 * from being swapped. 290 */ 291 p1->p_holdcnt++; 292 293 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 294 /* share as much address space as possible */ 295 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 296 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 297 VM_INHERIT_SHARE); 298 } 299 300 #ifdef __FORK_BRAINDAMAGE 301 /* 302 * Set return values for child before vm_fork, 303 * so they can be copied to child stack. 304 * We return 0, rather than the traditional behaviour of modifying the 305 * return value in the system call stub. 306 * NOTE: the kernel stack may be at a different location in the child 307 * process, and thus addresses of automatic variables (including retval) 308 * may be invalid after vm_fork returns in the child process. 309 */ 310 retval[0] = 0; 311 retval[1] = 1; 312 if (vm_fork(p1, p2)) 313 return (0); 314 #else 315 /* 316 * Finish creating the child process. It will return through a 317 * different path later. 318 */ 319 vm_fork(p1, p2); 320 #endif 321 322 switch (forktype) { 323 case ISFORK: 324 forkstat.cntfork++; 325 break; 326 case ISVFORK: 327 forkstat.cntvfork++; 328 break; 329 case ISRFORK: 330 forkstat.cntrfork++; 331 break; 332 } 333 334 /* 335 * Make child runnable, set start time, and add to run queue. 336 */ 337 (void) splstatclock(); 338 p2->p_stats->p_start = time; 339 p2->p_acflag = AFORK; 340 p2->p_stat = SRUN; 341 setrunqueue(p2); 342 (void) spl0(); 343 344 /* 345 * Now can be swapped. 346 */ 347 p1->p_holdcnt--; 348 349 /* 350 * Preserve synchronization semantics of vfork. If waiting for 351 * child to exec or exit, set P_PPWAIT on child, and sleep on our 352 * proc (in case of exit). 353 */ 354 if (forktype == ISVFORK) 355 while (p2->p_flag & P_PPWAIT) 356 tsleep(p1, PWAIT, "ppwait", 0); 357 358 /* 359 * Return child pid to parent process, 360 * marking us as parent via retval[1]. 361 */ 362 retval[0] = p2->p_pid; 363 retval[1] = 0; 364 return (0); 365 } 366