1 /* $NetBSD: kern_fork.c,v 1.27 1995/12/10 08:26:02 mycroft Exp $ */ 2 3 /* 4 * Copyright (c) 1982, 1986, 1989, 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 41 */ 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/map.h> 46 #include <sys/filedesc.h> 47 #include <sys/kernel.h> 48 #include <sys/malloc.h> 49 #include <sys/proc.h> 50 #include <sys/resourcevar.h> 51 #include <sys/vnode.h> 52 #include <sys/file.h> 53 #include <sys/acct.h> 54 #include <sys/ktrace.h> 55 56 #include <vm/vm.h> 57 58 #include <sys/mount.h> 59 #include <sys/syscallargs.h> 60 61 int nprocs = 1; /* process 0 */ 62 63 #define ISFORK 0 64 #define ISVFORK 1 65 #define ISRFORK 2 66 67 int 68 sys_fork(p, v, retval) 69 struct proc *p; 70 void *v; 71 register_t *retval; 72 { 73 return (fork1(p, ISFORK, 0, retval)); 74 } 75 76 int 77 sys_vfork(p, v, retval) 78 struct proc *p; 79 void *v; 80 register_t *retval; 81 { 82 return (fork1(p, ISVFORK, 0, retval)); 83 } 84 85 int 86 sys_rfork(p, v, retval) 87 struct proc *p; 88 void *v; 89 register_t *retval; 90 { 91 struct sys_rfork_args /* { 92 syscallarg(int) flags; 93 } */ *uap = v; 94 95 return (fork1(p, ISRFORK, SCARG(uap, flags), retval)); 96 } 97 98 int 99 fork1(p1, forktype, rforkflags, retval) 100 register struct proc *p1; 101 int forktype; 102 int rforkflags; 103 register_t *retval; 104 { 105 register struct proc *p2; 106 register uid_t uid; 107 struct proc *newproc; 108 struct proc **hash; 109 int count; 110 static int nextpid, pidchecked = 0; 111 int dupfd = 1, cleanfd = 0; 112 113 if (forktype == ISRFORK) { 114 dupfd = 0; 115 if ((rforkflags & RFPROC) == 0) 116 return (EINVAL); 117 if ((rforkflags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 118 return (EINVAL); 119 if (rforkflags & RFFDG) 120 dupfd = 1; 121 if (rforkflags & RFNOWAIT) 122 return (EINVAL); /* XXX unimplimented */ 123 if (rforkflags & RFCFDG) 124 cleanfd = 1; 125 } 126 127 /* 128 * Although process entries are dynamically created, we still keep 129 * a global limit on the maximum number we will create. Don't allow 130 * a nonprivileged user to use the last process; don't let root 131 * exceed the limit. The variable nprocs is the current number of 132 * processes, maxproc is the limit. 133 */ 134 uid = p1->p_cred->p_ruid; 135 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 136 tablefull("proc"); 137 return (EAGAIN); 138 } 139 140 /* 141 * Increment the count of procs running with this uid. Don't allow 142 * a nonprivileged user to exceed their current limit. 143 */ 144 count = chgproccnt(uid, 1); 145 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 146 (void)chgproccnt(uid, -1); 147 return (EAGAIN); 148 } 149 150 /* Allocate new proc. */ 151 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 152 153 /* 154 * Find an unused process ID. We remember a range of unused IDs 155 * ready to use (from nextpid+1 through pidchecked-1). 156 */ 157 nextpid++; 158 retry: 159 /* 160 * If the process ID prototype has wrapped around, 161 * restart somewhat above 0, as the low-numbered procs 162 * tend to include daemons that don't exit. 163 */ 164 if (nextpid >= PID_MAX) { 165 nextpid = 100; 166 pidchecked = 0; 167 } 168 if (nextpid >= pidchecked) { 169 int doingzomb = 0; 170 171 pidchecked = PID_MAX; 172 /* 173 * Scan the active and zombie procs to check whether this pid 174 * is in use. Remember the lowest pid that's greater 175 * than nextpid, so we can avoid checking for a while. 176 */ 177 p2 = allproc.lh_first; 178 again: 179 for (; p2 != 0; p2 = p2->p_list.le_next) { 180 while (p2->p_pid == nextpid || 181 p2->p_pgrp->pg_id == nextpid) { 182 nextpid++; 183 if (nextpid >= pidchecked) 184 goto retry; 185 } 186 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 187 pidchecked = p2->p_pid; 188 if (p2->p_pgrp->pg_id > nextpid && 189 pidchecked > p2->p_pgrp->pg_id) 190 pidchecked = p2->p_pgrp->pg_id; 191 } 192 if (!doingzomb) { 193 doingzomb = 1; 194 p2 = zombproc.lh_first; 195 goto again; 196 } 197 } 198 199 nprocs++; 200 p2 = newproc; 201 p2->p_stat = SIDL; /* protect against others */ 202 p2->p_pid = nextpid; 203 LIST_INSERT_HEAD(&allproc, p2, p_list); 204 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 205 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 206 207 /* 208 * Make a proc table entry for the new process. 209 * Start by zeroing the section of proc that is zero-initialized, 210 * then copy the section that is copied directly from the parent. 211 */ 212 bzero(&p2->p_startzero, 213 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 214 bcopy(&p1->p_startcopy, &p2->p_startcopy, 215 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 216 217 /* 218 * Duplicate sub-structures as needed. 219 * Increase reference counts on shared objects. 220 * The p_stats and p_sigacts substructs are set in vm_fork. 221 */ 222 p2->p_flag = P_INMEM; 223 p2->p_emul = p1->p_emul; 224 if (p1->p_flag & P_PROFIL) 225 startprofclock(p2); 226 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 227 M_SUBPROC, M_WAITOK); 228 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 229 p2->p_cred->p_refcnt = 1; 230 crhold(p1->p_ucred); 231 232 /* bump references to the text vnode (for procfs) */ 233 p2->p_textvp = p1->p_textvp; 234 if (p2->p_textvp) 235 VREF(p2->p_textvp); 236 237 if (cleanfd) 238 p2->p_fd = fdinit(p1); 239 else if (dupfd) 240 p2->p_fd = fdcopy(p1); 241 else 242 p2->p_fd = fdshare(p1); 243 244 /* 245 * If p_limit is still copy-on-write, bump refcnt, 246 * otherwise get a copy that won't be modified. 247 * (If PL_SHAREMOD is clear, the structure is shared 248 * copy-on-write.) 249 */ 250 if (p1->p_limit->p_lflags & PL_SHAREMOD) 251 p2->p_limit = limcopy(p1->p_limit); 252 else { 253 p2->p_limit = p1->p_limit; 254 p2->p_limit->p_refcnt++; 255 } 256 257 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 258 p2->p_flag |= P_CONTROLT; 259 if (forktype == ISVFORK) 260 p2->p_flag |= P_PPWAIT; 261 LIST_INSERT_AFTER(p1, p2, p_pglist); 262 p2->p_pptr = p1; 263 if (rforkflags & RFNOWAIT) { 264 /* XXX should we do anything? */ 265 } else { 266 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 267 } 268 LIST_INIT(&p2->p_children); 269 270 #ifdef KTRACE 271 /* 272 * Copy traceflag and tracefile if enabled. 273 * If not inherited, these were zeroed above. 274 */ 275 if (p1->p_traceflag&KTRFAC_INHERIT) { 276 p2->p_traceflag = p1->p_traceflag; 277 if ((p2->p_tracep = p1->p_tracep) != NULL) 278 VREF(p2->p_tracep); 279 } 280 #endif 281 282 /* 283 * This begins the section where we must prevent the parent 284 * from being swapped. 285 */ 286 p1->p_holdcnt++; 287 288 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 289 /* share as much address space as possible */ 290 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 291 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 292 VM_INHERIT_SHARE); 293 } 294 295 #ifdef __FORK_BRAINDAMAGE 296 /* 297 * Set return values for child before vm_fork, 298 * so they can be copied to child stack. 299 * We return 0, rather than the traditional behaviour of modifying the 300 * return value in the system call stub. 301 * NOTE: the kernel stack may be at a different location in the child 302 * process, and thus addresses of automatic variables (including retval) 303 * may be invalid after vm_fork returns in the child process. 304 */ 305 retval[0] = 0; 306 retval[1] = 1; 307 if (vm_fork(p1, p2)) 308 return (0); 309 #else 310 /* 311 * Finish creating the child process. It will return through a 312 * different path later. 313 */ 314 vm_fork(p1, p2); 315 #endif 316 317 switch (forktype) { 318 case ISFORK: 319 forkstat.cntfork++; 320 break; 321 case ISVFORK: 322 forkstat.cntvfork++; 323 break; 324 case ISRFORK: 325 forkstat.cntrfork++; 326 break; 327 } 328 329 /* 330 * Make child runnable, set start time, and add to run queue. 331 */ 332 (void) splstatclock(); 333 p2->p_stats->p_start = time; 334 p2->p_acflag = AFORK; 335 p2->p_stat = SRUN; 336 setrunqueue(p2); 337 (void) spl0(); 338 339 /* 340 * Now can be swapped. 341 */ 342 p1->p_holdcnt--; 343 344 /* 345 * Preserve synchronization semantics of vfork. If waiting for 346 * child to exec or exit, set P_PPWAIT on child, and sleep on our 347 * proc (in case of exit). 348 */ 349 if (forktype == ISVFORK) 350 while (p2->p_flag & P_PPWAIT) 351 tsleep(p1, PWAIT, "ppwait", 0); 352 353 /* 354 * Return child pid to parent process, 355 * marking us as parent via retval[1]. 356 */ 357 retval[0] = p2->p_pid; 358 retval[1] = 0; 359 return (0); 360 } 361