1 /* $OpenBSD: kern_fork.c,v 1.5 1996/03/03 17:19:45 niklas 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 64 #define ISFORK 0 65 #define ISVFORK 1 66 #define ISRFORK 2 67 68 int fork1 __P((struct proc *, int, int, register_t *)); 69 70 /*ARGSUSED*/ 71 int 72 sys_fork(p, v, retval) 73 struct proc *p; 74 void *v; 75 register_t *retval; 76 { 77 return (fork1(p, ISFORK, 0, retval)); 78 } 79 80 /*ARGSUSED*/ 81 int 82 sys_vfork(p, v, retval) 83 struct proc *p; 84 void *v; 85 register_t *retval; 86 { 87 return (fork1(p, ISVFORK, 0, retval)); 88 } 89 90 int 91 sys_rfork(p, v, retval) 92 struct proc *p; 93 void *v; 94 register_t *retval; 95 { 96 struct sys_rfork_args /* { 97 syscallarg(int) flags; 98 } */ *uap = v; 99 100 return (fork1(p, ISRFORK, SCARG(uap, flags), retval)); 101 } 102 103 int 104 fork1(p1, forktype, rforkflags, retval) 105 register struct proc *p1; 106 int forktype; 107 int rforkflags; 108 register_t *retval; 109 { 110 register struct proc *p2; 111 register uid_t uid; 112 struct proc *newproc; 113 int count; 114 static int nextpid, pidchecked = 0; 115 int dupfd = 1, cleanfd = 0; 116 117 if (forktype == ISRFORK) { 118 dupfd = 0; 119 if ((rforkflags & RFPROC) == 0) 120 return (EINVAL); 121 if ((rforkflags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 122 return (EINVAL); 123 if (rforkflags & RFFDG) 124 dupfd = 1; 125 if (rforkflags & RFNOWAIT) 126 return (EINVAL); /* XXX unimplimented */ 127 if (rforkflags & RFCFDG) 128 cleanfd = 1; 129 } 130 131 /* 132 * Although process entries are dynamically created, we still keep 133 * a global limit on the maximum number we will create. Don't allow 134 * a nonprivileged user to use the last process; don't let root 135 * exceed the limit. The variable nprocs is the current number of 136 * processes, maxproc is the limit. 137 */ 138 uid = p1->p_cred->p_ruid; 139 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 140 tablefull("proc"); 141 return (EAGAIN); 142 } 143 144 /* 145 * Increment the count of procs running with this uid. Don't allow 146 * a nonprivileged user to exceed their current limit. 147 */ 148 count = chgproccnt(uid, 1); 149 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 150 (void)chgproccnt(uid, -1); 151 return (EAGAIN); 152 } 153 154 /* Allocate new proc. */ 155 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 156 157 /* 158 * Find an unused process ID. We remember a range of unused IDs 159 * ready to use (from nextpid+1 through pidchecked-1). 160 */ 161 nextpid++; 162 retry: 163 /* 164 * If the process ID prototype has wrapped around, 165 * restart somewhat above 0, as the low-numbered procs 166 * tend to include daemons that don't exit. 167 */ 168 if (nextpid >= PID_MAX) { 169 nextpid = 100; 170 pidchecked = 0; 171 } 172 if (nextpid >= pidchecked) { 173 int doingzomb = 0; 174 175 pidchecked = PID_MAX; 176 /* 177 * Scan the active and zombie procs to check whether this pid 178 * is in use. Remember the lowest pid that's greater 179 * than nextpid, so we can avoid checking for a while. 180 */ 181 p2 = allproc.lh_first; 182 again: 183 for (; p2 != 0; p2 = p2->p_list.le_next) { 184 while (p2->p_pid == nextpid || 185 p2->p_pgrp->pg_id == nextpid) { 186 nextpid++; 187 if (nextpid >= pidchecked) 188 goto retry; 189 } 190 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 191 pidchecked = p2->p_pid; 192 if (p2->p_pgrp->pg_id > nextpid && 193 pidchecked > p2->p_pgrp->pg_id) 194 pidchecked = p2->p_pgrp->pg_id; 195 } 196 if (!doingzomb) { 197 doingzomb = 1; 198 p2 = zombproc.lh_first; 199 goto again; 200 } 201 } 202 203 nprocs++; 204 p2 = newproc; 205 p2->p_stat = SIDL; /* protect against others */ 206 p2->p_pid = nextpid; 207 LIST_INSERT_HEAD(&allproc, p2, p_list); 208 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 209 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 210 211 /* 212 * Make a proc table entry for the new process. 213 * Start by zeroing the section of proc that is zero-initialized, 214 * then copy the section that is copied directly from the parent. 215 */ 216 bzero(&p2->p_startzero, 217 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 218 bcopy(&p1->p_startcopy, &p2->p_startcopy, 219 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 220 221 /* 222 * Duplicate sub-structures as needed. 223 * Increase reference counts on shared objects. 224 * The p_stats and p_sigacts substructs are set in vm_fork. 225 */ 226 p2->p_flag = P_INMEM; 227 p2->p_emul = p1->p_emul; 228 if (p1->p_flag & P_PROFIL) 229 startprofclock(p2); 230 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 231 M_SUBPROC, M_WAITOK); 232 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 233 p2->p_cred->p_refcnt = 1; 234 crhold(p1->p_ucred); 235 236 /* bump references to the text vnode (for procfs) */ 237 p2->p_textvp = p1->p_textvp; 238 if (p2->p_textvp) 239 VREF(p2->p_textvp); 240 241 if (cleanfd) 242 p2->p_fd = fdinit(p1); 243 else if (dupfd) 244 p2->p_fd = fdcopy(p1); 245 else 246 p2->p_fd = fdshare(p1); 247 248 /* 249 * If p_limit is still copy-on-write, bump refcnt, 250 * otherwise get a copy that won't be modified. 251 * (If PL_SHAREMOD is clear, the structure is shared 252 * copy-on-write.) 253 */ 254 if (p1->p_limit->p_lflags & PL_SHAREMOD) 255 p2->p_limit = limcopy(p1->p_limit); 256 else { 257 p2->p_limit = p1->p_limit; 258 p2->p_limit->p_refcnt++; 259 } 260 261 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 262 p2->p_flag |= P_CONTROLT; 263 if (forktype == ISVFORK) 264 p2->p_flag |= P_PPWAIT; 265 LIST_INSERT_AFTER(p1, p2, p_pglist); 266 p2->p_pptr = p1; 267 if (rforkflags & RFNOWAIT) { 268 /* XXX should we do anything? */ 269 } else { 270 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 271 } 272 LIST_INIT(&p2->p_children); 273 274 #ifdef KTRACE 275 /* 276 * Copy traceflag and tracefile if enabled. 277 * If not inherited, these were zeroed above. 278 */ 279 if (p1->p_traceflag&KTRFAC_INHERIT) { 280 p2->p_traceflag = p1->p_traceflag; 281 if ((p2->p_tracep = p1->p_tracep) != NULL) 282 VREF(p2->p_tracep); 283 } 284 #endif 285 286 /* 287 * This begins the section where we must prevent the parent 288 * from being swapped. 289 */ 290 p1->p_holdcnt++; 291 292 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 293 /* share as much address space as possible */ 294 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 295 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 296 VM_INHERIT_SHARE); 297 } 298 299 #ifdef __FORK_BRAINDAMAGE 300 /* 301 * Set return values for child before vm_fork, 302 * so they can be copied to child stack. 303 * We return 0, rather than the traditional behaviour of modifying the 304 * return value in the system call stub. 305 * NOTE: the kernel stack may be at a different location in the child 306 * process, and thus addresses of automatic variables (including retval) 307 * may be invalid after vm_fork returns in the child process. 308 */ 309 retval[0] = 0; 310 retval[1] = 1; 311 if (vm_fork(p1, p2)) 312 return (0); 313 #else 314 /* 315 * Finish creating the child process. It will return through a 316 * different path later. 317 */ 318 vm_fork(p1, p2); 319 #endif 320 321 switch (forktype) { 322 case ISFORK: 323 forkstat.cntfork++; 324 break; 325 case ISVFORK: 326 forkstat.cntvfork++; 327 break; 328 case ISRFORK: 329 forkstat.cntrfork++; 330 break; 331 } 332 333 /* 334 * Make child runnable, set start time, and add to run queue. 335 */ 336 (void) splstatclock(); 337 p2->p_stats->p_start = time; 338 p2->p_acflag = AFORK; 339 p2->p_stat = SRUN; 340 setrunqueue(p2); 341 (void) spl0(); 342 343 /* 344 * Now can be swapped. 345 */ 346 p1->p_holdcnt--; 347 348 /* 349 * Preserve synchronization semantics of vfork. If waiting for 350 * child to exec or exit, set P_PPWAIT on child, and sleep on our 351 * proc (in case of exit). 352 */ 353 if (forktype == ISVFORK) 354 while (p2->p_flag & P_PPWAIT) 355 tsleep(p1, PWAIT, "ppwait", 0); 356 357 /* 358 * Return child pid to parent process, 359 * marking us as parent via retval[1]. 360 */ 361 retval[0] = p2->p_pid; 362 retval[1] = 0; 363 return (0); 364 } 365