1 /* $OpenBSD: kern_fork.c,v 1.17 1999/02/23 18:55:09 art 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 #include <dev/rndvar.h> 58 59 #include <sys/syscallargs.h> 60 61 #include <vm/vm.h> 62 #include <vm/vm_kern.h> 63 64 int nprocs = 1; /* process 0 */ 65 int randompid; /* when set to 1, pid's go random */ 66 pid_t lastpid; 67 68 /*ARGSUSED*/ 69 int 70 sys_fork(p, v, retval) 71 struct proc *p; 72 void *v; 73 register_t *retval; 74 { 75 return (fork1(p, ISFORK, 0, retval)); 76 } 77 78 /*ARGSUSED*/ 79 int 80 sys_vfork(p, v, retval) 81 struct proc *p; 82 void *v; 83 register_t *retval; 84 { 85 return (fork1(p, ISVFORK, 0, retval)); 86 } 87 88 int 89 sys_rfork(p, v, retval) 90 struct proc *p; 91 void *v; 92 register_t *retval; 93 { 94 struct sys_rfork_args /* { 95 syscallarg(int) flags; 96 } */ *uap = v; 97 98 return (fork1(p, ISRFORK, SCARG(uap, flags), retval)); 99 } 100 101 int 102 fork1(p1, forktype, rforkflags, retval) 103 register struct proc *p1; 104 int forktype; 105 int rforkflags; 106 register_t *retval; 107 { 108 register struct proc *p2; 109 register uid_t uid; 110 struct proc *newproc; 111 struct vmspace *vm; 112 int count; 113 static int pidchecked = 0; 114 int dupfd = 1, cleanfd = 0; 115 vm_offset_t uaddr; 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 & 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. We reserve 132 * the last 5 processes to root. The variable nprocs is the current 133 * number of processes, maxproc is the limit. 134 */ 135 uid = p1->p_cred->p_ruid; 136 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 137 tablefull("proc"); 138 return (EAGAIN); 139 } 140 141 /* 142 * Increment the count of procs running with this uid. Don't allow 143 * a nonprivileged user to exceed their current limit. 144 */ 145 count = chgproccnt(uid, 1); 146 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 147 (void)chgproccnt(uid, -1); 148 return (EAGAIN); 149 } 150 151 /* 152 * Allocate a pcb and kernel stack for the process 153 */ 154 #if defined(arc) || defined(mips_cachealias) 155 uaddr = kmem_alloc_upage(kernel_map, USPACE); 156 #else 157 uaddr = kmem_alloc_pageable(kernel_map, USPACE); 158 #endif 159 if (uaddr == 0) 160 return ENOMEM; 161 162 /* Allocate new proc. */ 163 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 164 165 lastpid++; 166 if (randompid) 167 lastpid = PID_MAX; 168 retry: 169 /* 170 * If the process ID prototype has wrapped around, 171 * restart somewhat above 0, as the low-numbered procs 172 * tend to include daemons that don't exit. 173 */ 174 if (lastpid >= PID_MAX) { 175 lastpid = arc4random() % PID_MAX; 176 pidchecked = 0; 177 } 178 if (lastpid >= pidchecked) { 179 int doingzomb = 0; 180 181 pidchecked = PID_MAX; 182 /* 183 * Scan the active and zombie procs to check whether this pid 184 * is in use. Remember the lowest pid that's greater 185 * than lastpid, so we can avoid checking for a while. 186 */ 187 p2 = allproc.lh_first; 188 again: 189 for (; p2 != 0; p2 = p2->p_list.le_next) { 190 while (p2->p_pid == lastpid || 191 p2->p_pgrp->pg_id == lastpid) { 192 lastpid++; 193 if (lastpid >= pidchecked) 194 goto retry; 195 } 196 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 197 pidchecked = p2->p_pid; 198 if (p2->p_pgrp->pg_id > lastpid && 199 pidchecked > p2->p_pgrp->pg_id) 200 pidchecked = p2->p_pgrp->pg_id; 201 } 202 if (!doingzomb) { 203 doingzomb = 1; 204 p2 = zombproc.lh_first; 205 goto again; 206 } 207 } 208 209 nprocs++; 210 p2 = newproc; 211 p2->p_stat = SIDL; /* protect against others */ 212 p2->p_pid = lastpid; 213 LIST_INSERT_HEAD(&allproc, p2, p_list); 214 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 215 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 216 217 /* 218 * Make a proc table entry for the new process. 219 * Start by zeroing the section of proc that is zero-initialized, 220 * then copy the section that is copied directly from the parent. 221 */ 222 bzero(&p2->p_startzero, 223 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 224 bcopy(&p1->p_startcopy, &p2->p_startcopy, 225 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 226 227 /* 228 * Duplicate sub-structures as needed. 229 * Increase reference counts on shared objects. 230 * The p_stats and p_sigacts substructs are set in vm_fork. 231 */ 232 p2->p_flag = P_INMEM; 233 p2->p_emul = p1->p_emul; 234 if (p1->p_flag & P_PROFIL) 235 startprofclock(p2); 236 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 237 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 238 M_SUBPROC, M_WAITOK); 239 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 240 p2->p_cred->p_refcnt = 1; 241 crhold(p1->p_ucred); 242 243 /* bump references to the text vnode (for procfs) */ 244 p2->p_textvp = p1->p_textvp; 245 if (p2->p_textvp) 246 VREF(p2->p_textvp); 247 248 if (cleanfd) 249 p2->p_fd = fdinit(p1); 250 else if (dupfd) 251 p2->p_fd = fdcopy(p1); 252 else 253 p2->p_fd = fdshare(p1); 254 255 /* 256 * If p_limit is still copy-on-write, bump refcnt, 257 * otherwise get a copy that won't be modified. 258 * (If PL_SHAREMOD is clear, the structure is shared 259 * copy-on-write.) 260 */ 261 if (p1->p_limit->p_lflags & PL_SHAREMOD) 262 p2->p_limit = limcopy(p1->p_limit); 263 else { 264 p2->p_limit = p1->p_limit; 265 p2->p_limit->p_refcnt++; 266 } 267 268 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 269 p2->p_flag |= P_CONTROLT; 270 if (forktype == ISVFORK) 271 p2->p_flag |= P_PPWAIT; 272 LIST_INSERT_AFTER(p1, p2, p_pglist); 273 p2->p_pptr = p1; 274 if (forktype == ISRFORK && (rforkflags & RFNOWAIT)) { 275 p2->p_flag |= P_NOZOMBIE; 276 } else { 277 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 278 } 279 LIST_INIT(&p2->p_children); 280 281 #ifdef KTRACE 282 /* 283 * Copy traceflag and tracefile if enabled. 284 * If not inherited, these were zeroed above. 285 */ 286 if (p1->p_traceflag&KTRFAC_INHERIT) { 287 p2->p_traceflag = p1->p_traceflag; 288 if ((p2->p_tracep = p1->p_tracep) != NULL) 289 VREF(p2->p_tracep); 290 } 291 #endif 292 293 /* 294 * This begins the section where we must prevent the parent 295 * from being swapped. 296 */ 297 p1->p_holdcnt++; 298 299 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 300 /* share as much address space as possible */ 301 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 302 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 303 VM_INHERIT_SHARE); 304 } 305 306 p2->p_addr = (struct user *)uaddr; 307 308 #ifdef __FORK_BRAINDAMAGE 309 /* 310 * Set return values for child before vm_fork, 311 * so they can be copied to child stack. 312 * We return 0, rather than the traditional behaviour of modifying the 313 * return value in the system call stub. 314 * NOTE: the kernel stack may be at a different location in the child 315 * process, and thus addresses of automatic variables (including retval) 316 * may be invalid after vm_fork returns in the child process. 317 */ 318 retval[0] = 0; 319 retval[1] = 1; 320 if (vm_fork(p1, p2)) 321 return (0); 322 #else 323 /* 324 * Finish creating the child process. It will return through a 325 * different path later. 326 */ 327 vm_fork(p1, p2); 328 #endif 329 vm = p2->p_vmspace; 330 331 switch (forktype) { 332 case ISFORK: 333 forkstat.cntfork++; 334 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 335 break; 336 case ISVFORK: 337 forkstat.cntvfork++; 338 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 339 break; 340 case ISRFORK: 341 forkstat.cntrfork++; 342 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 343 break; 344 } 345 346 /* 347 * Make child runnable, set start time, and add to run queue. 348 */ 349 (void) splstatclock(); 350 p2->p_stats->p_start = time; 351 p2->p_acflag = AFORK; 352 p2->p_stat = SRUN; 353 setrunqueue(p2); 354 (void) spl0(); 355 356 /* 357 * Now can be swapped. 358 */ 359 p1->p_holdcnt--; 360 361 /* 362 * Preserve synchronization semantics of vfork. If waiting for 363 * child to exec or exit, set P_PPWAIT on child, and sleep on our 364 * proc (in case of exit). 365 */ 366 if (forktype == ISVFORK) 367 while (p2->p_flag & P_PPWAIT) 368 tsleep(p1, PWAIT, "ppwait", 0); 369 370 /* 371 * Return child pid to parent process, 372 * marking us as parent via retval[1]. 373 */ 374 retval[0] = p2->p_pid; 375 retval[1] = 0; 376 return (0); 377 } 378