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