1 /* $OpenBSD: kern_fork.c,v 1.63 2003/09/23 20:26:18 millert 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. Neither the name of the University nor the names of its contributors 22 * may be used to endorse or promote products derived from this software 23 * without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 * 37 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 38 */ 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/filedesc.h> 43 #include <sys/kernel.h> 44 #include <sys/malloc.h> 45 #include <sys/mount.h> 46 #include <sys/proc.h> 47 #include <sys/resourcevar.h> 48 #include <sys/signalvar.h> 49 #include <sys/vnode.h> 50 #include <sys/file.h> 51 #include <sys/acct.h> 52 #include <sys/ktrace.h> 53 #include <sys/sched.h> 54 #include <dev/rndvar.h> 55 #include <sys/pool.h> 56 #include <sys/mman.h> 57 58 #include <sys/syscallargs.h> 59 60 #include "systrace.h" 61 #include <dev/systrace.h> 62 63 #include <uvm/uvm_extern.h> 64 #include <uvm/uvm_map.h> 65 66 int nprocs = 1; /* process 0 */ 67 int randompid; /* when set to 1, pid's go random */ 68 pid_t lastpid; 69 struct forkstat forkstat; 70 71 int pidtaken(pid_t); 72 73 /*ARGSUSED*/ 74 int 75 sys_fork(struct proc *p, void *v, register_t *retval) 76 { 77 return (fork1(p, SIGCHLD, FORK_FORK, NULL, 0, NULL, NULL, retval)); 78 } 79 80 /*ARGSUSED*/ 81 int 82 sys_vfork(struct proc *p, void *v, register_t *retval) 83 { 84 return (fork1(p, SIGCHLD, FORK_VFORK|FORK_PPWAIT, NULL, 0, NULL, 85 NULL, retval)); 86 } 87 88 int 89 sys_rfork(struct proc *p, void *v, register_t *retval) 90 { 91 struct sys_rfork_args /* { 92 syscallarg(int) flags; 93 } */ *uap = v; 94 95 int rforkflags; 96 int flags; 97 98 flags = FORK_RFORK; 99 rforkflags = SCARG(uap, flags); 100 101 if ((rforkflags & RFPROC) == 0) 102 return (EINVAL); 103 104 switch(rforkflags & (RFFDG|RFCFDG)) { 105 case (RFFDG|RFCFDG): 106 return EINVAL; 107 case RFCFDG: 108 flags |= FORK_CLEANFILES; 109 break; 110 case RFFDG: 111 break; 112 default: 113 flags |= FORK_SHAREFILES; 114 break; 115 } 116 117 if (rforkflags & RFNOWAIT) 118 flags |= FORK_NOZOMBIE; 119 120 if (rforkflags & RFMEM) 121 flags |= FORK_VMNOSTACK; 122 123 return (fork1(p, SIGCHLD, flags, NULL, 0, NULL, NULL, retval)); 124 } 125 126 /* print the 'table full' message once per 10 seconds */ 127 struct timeval fork_tfmrate = { 10, 0 }; 128 129 int 130 fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize, 131 void (*func)(void *), void *arg, register_t *retval) 132 { 133 struct proc *p2; 134 uid_t uid; 135 struct vmspace *vm; 136 int count; 137 vaddr_t uaddr; 138 int s; 139 extern void endtsleep(void *); 140 extern void realitexpire(void *); 141 142 /* 143 * Although process entries are dynamically created, we still keep 144 * a global limit on the maximum number we will create. We reserve 145 * the last 5 processes to root. The variable nprocs is the current 146 * number of processes, maxproc is the limit. 147 */ 148 uid = p1->p_cred->p_ruid; 149 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 150 static struct timeval lasttfm; 151 152 if (ratecheck(&lasttfm, &fork_tfmrate)) 153 tablefull("proc"); 154 return (EAGAIN); 155 } 156 nprocs++; 157 158 /* 159 * Increment the count of procs running with this uid. Don't allow 160 * a nonprivileged user to exceed their current limit. 161 */ 162 count = chgproccnt(uid, 1); 163 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 164 (void)chgproccnt(uid, -1); 165 nprocs--; 166 return (EAGAIN); 167 } 168 169 /* 170 * Allocate a pcb and kernel stack for the process 171 */ 172 uaddr = uvm_km_valloc(kernel_map, USPACE); 173 if (uaddr == 0) { 174 chgproccnt(uid, -1); 175 nprocs--; 176 return (ENOMEM); 177 } 178 179 /* 180 * From now on, we're committed to the fork and cannot fail. 181 */ 182 183 /* Allocate new proc. */ 184 p2 = pool_get(&proc_pool, PR_WAITOK); 185 186 p2->p_stat = SIDL; /* protect against others */ 187 p2->p_exitsig = exitsig; 188 p2->p_forw = p2->p_back = NULL; 189 190 /* 191 * Make a proc table entry for the new process. 192 * Start by zeroing the section of proc that is zero-initialized, 193 * then copy the section that is copied directly from the parent. 194 */ 195 bzero(&p2->p_startzero, 196 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 197 bcopy(&p1->p_startcopy, &p2->p_startcopy, 198 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 199 200 /* 201 * Initialize the timeouts. 202 */ 203 timeout_set(&p2->p_sleep_to, endtsleep, p2); 204 timeout_set(&p2->p_realit_to, realitexpire, p2); 205 206 /* 207 * Duplicate sub-structures as needed. 208 * Increase reference counts on shared objects. 209 * The p_stats and p_sigacts substructs are set in vm_fork. 210 */ 211 p2->p_flag = P_INMEM; 212 p2->p_emul = p1->p_emul; 213 if (p1->p_flag & P_PROFIL) 214 startprofclock(p2); 215 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 216 p2->p_cred = pool_get(&pcred_pool, PR_WAITOK); 217 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 218 p2->p_cred->p_refcnt = 1; 219 crhold(p1->p_ucred); 220 221 /* bump references to the text vnode (for procfs) */ 222 p2->p_textvp = p1->p_textvp; 223 if (p2->p_textvp) 224 VREF(p2->p_textvp); 225 226 if (flags & FORK_CLEANFILES) 227 p2->p_fd = fdinit(p1); 228 else if (flags & FORK_SHAREFILES) 229 p2->p_fd = fdshare(p1); 230 else 231 p2->p_fd = fdcopy(p1); 232 233 /* 234 * If p_limit is still copy-on-write, bump refcnt, 235 * otherwise get a copy that won't be modified. 236 * (If PL_SHAREMOD is clear, the structure is shared 237 * copy-on-write.) 238 */ 239 if (p1->p_limit->p_lflags & PL_SHAREMOD) 240 p2->p_limit = limcopy(p1->p_limit); 241 else { 242 p2->p_limit = p1->p_limit; 243 p2->p_limit->p_refcnt++; 244 } 245 246 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 247 p2->p_flag |= P_CONTROLT; 248 if (flags & FORK_PPWAIT) 249 p2->p_flag |= P_PPWAIT; 250 LIST_INSERT_AFTER(p1, p2, p_pglist); 251 p2->p_pptr = p1; 252 if (flags & FORK_NOZOMBIE) 253 p2->p_flag |= P_NOZOMBIE; 254 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 255 LIST_INIT(&p2->p_children); 256 257 #ifdef KTRACE 258 /* 259 * Copy traceflag and tracefile if enabled. 260 * If not inherited, these were zeroed above. 261 */ 262 if (p1->p_traceflag & KTRFAC_INHERIT) { 263 p2->p_traceflag = p1->p_traceflag; 264 if ((p2->p_tracep = p1->p_tracep) != NULL) 265 VREF(p2->p_tracep); 266 } 267 #endif 268 269 /* 270 * set priority of child to be that of parent 271 * XXX should move p_estcpu into the region of struct proc which gets 272 * copied. 273 */ 274 scheduler_fork_hook(p1, p2); 275 276 /* 277 * Create signal actions for the child process. 278 */ 279 if (flags & FORK_SIGHAND) 280 sigactsshare(p1, p2); 281 else 282 p2->p_sigacts = sigactsinit(p1); 283 284 /* 285 * If emulation has process fork hook, call it now. 286 */ 287 if (p2->p_emul->e_proc_fork) 288 (*p2->p_emul->e_proc_fork)(p2, p1); 289 /* 290 * This begins the section where we must prevent the parent 291 * from being swapped. 292 */ 293 PHOLD(p1); 294 295 if (flags & FORK_VMNOSTACK) { 296 /* share everything, but ... */ 297 uvm_map_inherit(&p1->p_vmspace->vm_map, 298 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS, 299 MAP_INHERIT_SHARE); 300 /* ... don't share stack */ 301 #ifdef MACHINE_STACK_GROWS_UP 302 uvm_map_inherit(&p1->p_vmspace->vm_map, 303 USRSTACK, USRSTACK + MAXSSIZ, 304 MAP_INHERIT_COPY); 305 #else 306 uvm_map_inherit(&p1->p_vmspace->vm_map, 307 USRSTACK - MAXSSIZ, USRSTACK, 308 MAP_INHERIT_COPY); 309 #endif 310 } 311 312 p2->p_addr = (struct user *)uaddr; 313 314 /* 315 * Finish creating the child process. It will return through a 316 * different path later. 317 */ 318 uvm_fork(p1, p2, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack, 319 stacksize, func ? func : child_return, arg ? arg : p2); 320 321 vm = p2->p_vmspace; 322 323 if (flags & FORK_FORK) { 324 forkstat.cntfork++; 325 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 326 } else if (flags & FORK_VFORK) { 327 forkstat.cntvfork++; 328 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 329 } else if (flags & FORK_RFORK) { 330 forkstat.cntrfork++; 331 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 332 } else { 333 forkstat.cntkthread++; 334 forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize; 335 } 336 337 /* Find an unused pid satisfying 1 <= lastpid <= PID_MAX */ 338 do { 339 lastpid = 1 + (randompid ? arc4random() : lastpid) % PID_MAX; 340 } while (pidtaken(lastpid)); 341 p2->p_pid = lastpid; 342 343 LIST_INSERT_HEAD(&allproc, p2, p_list); 344 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 345 346 #if NSYSTRACE > 0 347 if (ISSET(p1->p_flag, P_SYSTRACE)) 348 systrace_fork(p1, p2); 349 #endif 350 351 /* 352 * Make child runnable, set start time, and add to run queue. 353 */ 354 s = splstatclock(); 355 p2->p_stats->p_start = time; 356 p2->p_acflag = AFORK; 357 p2->p_stat = SRUN; 358 setrunqueue(p2); 359 splx(s); 360 361 /* 362 * Now can be swapped. 363 */ 364 PRELE(p1); 365 366 uvmexp.forks++; 367 if (flags & FORK_PPWAIT) 368 uvmexp.forks_ppwait++; 369 if (flags & FORK_SHAREVM) 370 uvmexp.forks_sharevm++; 371 372 /* 373 * tell any interested parties about the new process 374 */ 375 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 376 377 /* 378 * Preserve synchronization semantics of vfork. If waiting for 379 * child to exec or exit, set P_PPWAIT on child, and sleep on our 380 * proc (in case of exit). 381 */ 382 if (flags & FORK_PPWAIT) 383 while (p2->p_flag & P_PPWAIT) 384 tsleep(p1, PWAIT, "ppwait", 0); 385 386 /* 387 * Return child pid to parent process, 388 * marking us as parent via retval[1]. 389 */ 390 retval[0] = p2->p_pid; 391 retval[1] = 0; 392 return (0); 393 } 394 395 /* 396 * Checks for current use of a pid, either as a pid or pgid. 397 */ 398 int 399 pidtaken(pid_t pid) 400 { 401 struct proc *p; 402 403 if (pfind(pid) != NULL) 404 return (1); 405 if (pgfind(pid) != NULL) 406 return (1); 407 LIST_FOREACH(p, &zombproc, p_list) 408 if (p->p_pid == pid || p->p_pgid == pid) 409 return (1); 410 return (0); 411 } 412