1 /* $OpenBSD: kern_fork.c,v 1.62 2003/07/02 00:07:42 avsm 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 int 127 fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize, 128 void (*func)(void *), void *arg, register_t *retval) 129 { 130 struct proc *p2; 131 uid_t uid; 132 struct vmspace *vm; 133 int count; 134 vaddr_t uaddr; 135 int s; 136 extern void endtsleep(void *); 137 extern void realitexpire(void *); 138 139 /* 140 * Although process entries are dynamically created, we still keep 141 * a global limit on the maximum number we will create. We reserve 142 * the last 5 processes to root. The variable nprocs is the current 143 * number of processes, maxproc is the limit. 144 */ 145 uid = p1->p_cred->p_ruid; 146 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 147 tablefull("proc"); 148 return (EAGAIN); 149 } 150 nprocs++; 151 152 /* 153 * Increment the count of procs running with this uid. Don't allow 154 * a nonprivileged user to exceed their current limit. 155 */ 156 count = chgproccnt(uid, 1); 157 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 158 (void)chgproccnt(uid, -1); 159 nprocs--; 160 return (EAGAIN); 161 } 162 163 /* 164 * Allocate a pcb and kernel stack for the process 165 */ 166 uaddr = uvm_km_valloc(kernel_map, USPACE); 167 if (uaddr == 0) { 168 chgproccnt(uid, -1); 169 nprocs--; 170 return (ENOMEM); 171 } 172 173 /* 174 * From now on, we're committed to the fork and cannot fail. 175 */ 176 177 /* Allocate new proc. */ 178 p2 = pool_get(&proc_pool, PR_WAITOK); 179 180 p2->p_stat = SIDL; /* protect against others */ 181 p2->p_exitsig = exitsig; 182 p2->p_forw = p2->p_back = NULL; 183 184 /* 185 * Make a proc table entry for the new process. 186 * Start by zeroing the section of proc that is zero-initialized, 187 * then copy the section that is copied directly from the parent. 188 */ 189 bzero(&p2->p_startzero, 190 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 191 bcopy(&p1->p_startcopy, &p2->p_startcopy, 192 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 193 194 /* 195 * Initialize the timeouts. 196 */ 197 timeout_set(&p2->p_sleep_to, endtsleep, p2); 198 timeout_set(&p2->p_realit_to, realitexpire, p2); 199 200 /* 201 * Duplicate sub-structures as needed. 202 * Increase reference counts on shared objects. 203 * The p_stats and p_sigacts substructs are set in vm_fork. 204 */ 205 p2->p_flag = P_INMEM; 206 p2->p_emul = p1->p_emul; 207 if (p1->p_flag & P_PROFIL) 208 startprofclock(p2); 209 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 210 p2->p_cred = pool_get(&pcred_pool, PR_WAITOK); 211 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 212 p2->p_cred->p_refcnt = 1; 213 crhold(p1->p_ucred); 214 215 /* bump references to the text vnode (for procfs) */ 216 p2->p_textvp = p1->p_textvp; 217 if (p2->p_textvp) 218 VREF(p2->p_textvp); 219 220 if (flags & FORK_CLEANFILES) 221 p2->p_fd = fdinit(p1); 222 else if (flags & FORK_SHAREFILES) 223 p2->p_fd = fdshare(p1); 224 else 225 p2->p_fd = fdcopy(p1); 226 227 /* 228 * If p_limit is still copy-on-write, bump refcnt, 229 * otherwise get a copy that won't be modified. 230 * (If PL_SHAREMOD is clear, the structure is shared 231 * copy-on-write.) 232 */ 233 if (p1->p_limit->p_lflags & PL_SHAREMOD) 234 p2->p_limit = limcopy(p1->p_limit); 235 else { 236 p2->p_limit = p1->p_limit; 237 p2->p_limit->p_refcnt++; 238 } 239 240 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 241 p2->p_flag |= P_CONTROLT; 242 if (flags & FORK_PPWAIT) 243 p2->p_flag |= P_PPWAIT; 244 LIST_INSERT_AFTER(p1, p2, p_pglist); 245 p2->p_pptr = p1; 246 if (flags & FORK_NOZOMBIE) 247 p2->p_flag |= P_NOZOMBIE; 248 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 249 LIST_INIT(&p2->p_children); 250 251 #ifdef KTRACE 252 /* 253 * Copy traceflag and tracefile if enabled. 254 * If not inherited, these were zeroed above. 255 */ 256 if (p1->p_traceflag & KTRFAC_INHERIT) { 257 p2->p_traceflag = p1->p_traceflag; 258 if ((p2->p_tracep = p1->p_tracep) != NULL) 259 VREF(p2->p_tracep); 260 } 261 #endif 262 263 /* 264 * set priority of child to be that of parent 265 * XXX should move p_estcpu into the region of struct proc which gets 266 * copied. 267 */ 268 scheduler_fork_hook(p1, p2); 269 270 /* 271 * Create signal actions for the child process. 272 */ 273 if (flags & FORK_SIGHAND) 274 sigactsshare(p1, p2); 275 else 276 p2->p_sigacts = sigactsinit(p1); 277 278 /* 279 * If emulation has process fork hook, call it now. 280 */ 281 if (p2->p_emul->e_proc_fork) 282 (*p2->p_emul->e_proc_fork)(p2, p1); 283 /* 284 * This begins the section where we must prevent the parent 285 * from being swapped. 286 */ 287 PHOLD(p1); 288 289 if (flags & FORK_VMNOSTACK) { 290 /* share everything, but ... */ 291 uvm_map_inherit(&p1->p_vmspace->vm_map, 292 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS, 293 MAP_INHERIT_SHARE); 294 /* ... don't share stack */ 295 #ifdef MACHINE_STACK_GROWS_UP 296 uvm_map_inherit(&p1->p_vmspace->vm_map, 297 USRSTACK, USRSTACK + MAXSSIZ, 298 MAP_INHERIT_COPY); 299 #else 300 uvm_map_inherit(&p1->p_vmspace->vm_map, 301 USRSTACK - MAXSSIZ, USRSTACK, 302 MAP_INHERIT_COPY); 303 #endif 304 } 305 306 p2->p_addr = (struct user *)uaddr; 307 308 /* 309 * Finish creating the child process. It will return through a 310 * different path later. 311 */ 312 uvm_fork(p1, p2, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack, 313 stacksize, func ? func : child_return, arg ? arg : p2); 314 315 vm = p2->p_vmspace; 316 317 if (flags & FORK_FORK) { 318 forkstat.cntfork++; 319 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 320 } else if (flags & FORK_VFORK) { 321 forkstat.cntvfork++; 322 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 323 } else if (flags & FORK_RFORK) { 324 forkstat.cntrfork++; 325 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 326 } else { 327 forkstat.cntkthread++; 328 forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize; 329 } 330 331 /* Find an unused pid satisfying 1 <= lastpid <= PID_MAX */ 332 do { 333 lastpid = 1 + (randompid ? arc4random() : lastpid) % PID_MAX; 334 } while (pidtaken(lastpid)); 335 p2->p_pid = lastpid; 336 337 LIST_INSERT_HEAD(&allproc, p2, p_list); 338 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 339 340 #if NSYSTRACE > 0 341 if (ISSET(p1->p_flag, P_SYSTRACE)) 342 systrace_fork(p1, p2); 343 #endif 344 345 /* 346 * Make child runnable, set start time, and add to run queue. 347 */ 348 s = splstatclock(); 349 p2->p_stats->p_start = time; 350 p2->p_acflag = AFORK; 351 p2->p_stat = SRUN; 352 setrunqueue(p2); 353 splx(s); 354 355 /* 356 * Now can be swapped. 357 */ 358 PRELE(p1); 359 360 uvmexp.forks++; 361 if (flags & FORK_PPWAIT) 362 uvmexp.forks_ppwait++; 363 if (flags & FORK_SHAREVM) 364 uvmexp.forks_sharevm++; 365 366 /* 367 * tell any interested parties about the new process 368 */ 369 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 370 371 /* 372 * Preserve synchronization semantics of vfork. If waiting for 373 * child to exec or exit, set P_PPWAIT on child, and sleep on our 374 * proc (in case of exit). 375 */ 376 if (flags & FORK_PPWAIT) 377 while (p2->p_flag & P_PPWAIT) 378 tsleep(p1, PWAIT, "ppwait", 0); 379 380 /* 381 * Return child pid to parent process, 382 * marking us as parent via retval[1]. 383 */ 384 retval[0] = p2->p_pid; 385 retval[1] = 0; 386 return (0); 387 } 388 389 /* 390 * Checks for current use of a pid, either as a pid or pgid. 391 */ 392 int 393 pidtaken(pid_t pid) 394 { 395 struct proc *p; 396 397 if (pfind(pid) != NULL) 398 return (1); 399 if (pgfind(pid) != NULL) 400 return (1); 401 LIST_FOREACH(p, &zombproc, p_list) 402 if (p->p_pid == pid || p->p_pgid == pid) 403 return (1); 404 return (0); 405 } 406