1 /* $OpenBSD: kern_fork.c,v 1.38 2001/03/23 18:42:06 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 <sys/sched.h> 58 #include <dev/rndvar.h> 59 #include <sys/pool.h> 60 61 #include <sys/syscallargs.h> 62 63 #include <vm/vm.h> 64 #include <vm/vm_kern.h> 65 66 #if defined(UVM) 67 #include <uvm/uvm_extern.h> 68 #include <uvm/uvm_map.h> 69 #endif 70 71 int nprocs = 1; /* process 0 */ 72 int randompid; /* when set to 1, pid's go random */ 73 pid_t lastpid; 74 struct forkstat forkstat; 75 76 77 /*ARGSUSED*/ 78 int 79 sys_fork(p, v, retval) 80 struct proc *p; 81 void *v; 82 register_t *retval; 83 { 84 return (fork1(p, FORK_FORK, NULL, 0, retval)); 85 } 86 87 /*ARGSUSED*/ 88 int 89 sys_vfork(p, v, retval) 90 struct proc *p; 91 void *v; 92 register_t *retval; 93 { 94 return (fork1(p, FORK_VFORK|FORK_PPWAIT, NULL, 0, retval)); 95 } 96 97 int 98 sys_rfork(p, v, retval) 99 struct proc *p; 100 void *v; 101 register_t *retval; 102 { 103 struct sys_rfork_args /* { 104 syscallarg(int) flags; 105 } */ *uap = v; 106 int rforkflags; 107 int flags; 108 109 flags = FORK_RFORK; 110 rforkflags = SCARG(uap, flags); 111 112 if ((rforkflags & RFPROC) == 0) 113 return (EINVAL); 114 115 switch(rforkflags & (RFFDG|RFCFDG)) { 116 case (RFFDG|RFCFDG): 117 return EINVAL; 118 case RFCFDG: 119 flags |= FORK_CLEANFILES; 120 break; 121 case RFFDG: 122 break; 123 default: 124 flags |= FORK_SHAREFILES; 125 break; 126 } 127 128 if (rforkflags & RFNOWAIT) 129 flags |= FORK_NOZOMBIE; 130 131 if (rforkflags & RFMEM) 132 flags |= FORK_VMNOSTACK; 133 134 return (fork1(p, flags, NULL, 0, retval)); 135 } 136 137 int 138 fork1(p1, flags, stack, stacksize, retval) 139 register struct proc *p1; 140 int flags; 141 void *stack; 142 size_t stacksize; 143 register_t *retval; 144 { 145 struct proc *p2; 146 uid_t uid; 147 struct proc *newproc; 148 struct vmspace *vm; 149 int count; 150 static int pidchecked = 0; 151 vaddr_t uaddr; 152 int s; 153 extern void endtsleep __P((void *)); 154 extern void realitexpire __P((void *)); 155 156 /* 157 * Although process entries are dynamically created, we still keep 158 * a global limit on the maximum number we will create. We reserve 159 * the last 5 processes to root. The variable nprocs is the current 160 * number of processes, maxproc is the limit. 161 */ 162 uid = p1->p_cred->p_ruid; 163 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 164 tablefull("proc"); 165 return (EAGAIN); 166 } 167 168 #if !defined(UVM) 169 if (flags & FORK_SHAREVM) 170 return (EINVAL); 171 #endif 172 173 /* 174 * Increment the count of procs running with this uid. Don't allow 175 * a nonprivileged user to exceed their current limit. 176 */ 177 count = chgproccnt(uid, 1); 178 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 179 (void)chgproccnt(uid, -1); 180 return (EAGAIN); 181 } 182 183 /* 184 * Allocate a pcb and kernel stack for the process 185 */ 186 #if defined(arc) || defined(mips_cachealias) 187 uaddr = kmem_alloc_upage(kernel_map, USPACE); 188 #else 189 #if defined(UVM) 190 uaddr = uvm_km_valloc(kernel_map, USPACE); 191 #else 192 uaddr = kmem_alloc_pageable(kernel_map, USPACE); 193 #endif 194 #endif 195 if (uaddr == 0) 196 return ENOMEM; 197 198 /* Allocate new proc. */ 199 newproc = pool_get(&proc_pool, PR_WAITOK); 200 201 lastpid++; 202 if (randompid) 203 lastpid = PID_MAX; 204 retry: 205 /* 206 * If the process ID prototype has wrapped around, 207 * restart somewhat above 0, as the low-numbered procs 208 * tend to include daemons that don't exit. 209 */ 210 if (lastpid >= PID_MAX) { 211 lastpid = arc4random() % PID_MAX; 212 pidchecked = 0; 213 } 214 if (lastpid >= pidchecked) { 215 int doingzomb = 0; 216 217 pidchecked = PID_MAX; 218 /* 219 * Scan the active and zombie procs to check whether this pid 220 * is in use. Remember the lowest pid that's greater 221 * than lastpid, so we can avoid checking for a while. 222 */ 223 p2 = LIST_FIRST(&allproc); 224 again: 225 for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) { 226 while (p2->p_pid == lastpid || 227 p2->p_pgrp->pg_id == lastpid) { 228 lastpid++; 229 if (lastpid >= pidchecked) 230 goto retry; 231 } 232 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 233 pidchecked = p2->p_pid; 234 if (p2->p_pgrp->pg_id > lastpid && 235 pidchecked > p2->p_pgrp->pg_id) 236 pidchecked = p2->p_pgrp->pg_id; 237 } 238 if (!doingzomb) { 239 doingzomb = 1; 240 p2 = LIST_FIRST(&zombproc); 241 goto again; 242 } 243 } 244 245 nprocs++; 246 p2 = newproc; 247 p2->p_stat = SIDL; /* protect against others */ 248 p2->p_pid = lastpid; 249 LIST_INSERT_HEAD(&allproc, p2, p_list); 250 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 251 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 252 253 /* 254 * Make a proc table entry for the new process. 255 * Start by zeroing the section of proc that is zero-initialized, 256 * then copy the section that is copied directly from the parent. 257 */ 258 bzero(&p2->p_startzero, 259 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 260 bcopy(&p1->p_startcopy, &p2->p_startcopy, 261 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 262 263 /* 264 * Initialize the timeouts. 265 */ 266 timeout_set(&p2->p_sleep_to, endtsleep, p2); 267 timeout_set(&p2->p_realit_to, realitexpire, p2); 268 269 /* 270 * Duplicate sub-structures as needed. 271 * Increase reference counts on shared objects. 272 * The p_stats and p_sigacts substructs are set in vm_fork. 273 */ 274 p2->p_flag = P_INMEM; 275 p2->p_emul = p1->p_emul; 276 if (p1->p_flag & P_PROFIL) 277 startprofclock(p2); 278 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 279 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 280 M_SUBPROC, M_WAITOK); 281 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 282 p2->p_cred->p_refcnt = 1; 283 crhold(p1->p_ucred); 284 285 /* bump references to the text vnode (for procfs) */ 286 p2->p_textvp = p1->p_textvp; 287 if (p2->p_textvp) 288 VREF(p2->p_textvp); 289 290 if (flags & FORK_CLEANFILES) 291 p2->p_fd = fdinit(p1); 292 else if (flags & FORK_SHAREFILES) 293 p2->p_fd = fdshare(p1); 294 else 295 p2->p_fd = fdcopy(p1); 296 297 /* 298 * If p_limit is still copy-on-write, bump refcnt, 299 * otherwise get a copy that won't be modified. 300 * (If PL_SHAREMOD is clear, the structure is shared 301 * copy-on-write.) 302 */ 303 if (p1->p_limit->p_lflags & PL_SHAREMOD) 304 p2->p_limit = limcopy(p1->p_limit); 305 else { 306 p2->p_limit = p1->p_limit; 307 p2->p_limit->p_refcnt++; 308 } 309 310 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 311 p2->p_flag |= P_CONTROLT; 312 if (flags & FORK_PPWAIT) 313 p2->p_flag |= P_PPWAIT; 314 LIST_INSERT_AFTER(p1, p2, p_pglist); 315 p2->p_pptr = p1; 316 if (flags & FORK_NOZOMBIE) 317 p2->p_flag |= P_NOZOMBIE; 318 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 319 LIST_INIT(&p2->p_children); 320 321 #ifdef KTRACE 322 /* 323 * Copy traceflag and tracefile if enabled. 324 * If not inherited, these were zeroed above. 325 */ 326 if (p1->p_traceflag & KTRFAC_INHERIT) { 327 p2->p_traceflag = p1->p_traceflag; 328 if ((p2->p_tracep = p1->p_tracep) != NULL) 329 VREF(p2->p_tracep); 330 } 331 #endif 332 333 /* 334 * set priority of child to be that of parent 335 * XXX should move p_estcpu into the region of struct proc which gets 336 * copied. 337 */ 338 scheduler_fork_hook(p1, p2); 339 340 /* 341 * This begins the section where we must prevent the parent 342 * from being swapped. 343 */ 344 PHOLD(p1); 345 346 #if defined(UVM) 347 if (flags & FORK_VMNOSTACK) { 348 /* share as much address space as possible */ 349 (void) uvm_map_inherit(&p1->p_vmspace->vm_map, 350 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 351 VM_INHERIT_SHARE); 352 } 353 #else 354 if (flags & FORK_VMNOSTACK) { 355 /* share as much address space as possible */ 356 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 357 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 358 VM_INHERIT_SHARE); 359 } 360 #endif 361 362 p2->p_addr = (struct user *)uaddr; 363 364 #ifdef __FORK_BRAINDAMAGE 365 /* 366 * Set return values for child before vm_fork, 367 * so they can be copied to child stack. 368 * We return 0, rather than the traditional behaviour of modifying the 369 * return value in the system call stub. 370 * NOTE: the kernel stack may be at a different location in the child 371 * process, and thus addresses of automatic variables (including retval) 372 * may be invalid after vm_fork returns in the child process. 373 */ 374 retval[0] = 0; 375 retval[1] = 1; 376 if (vm_fork(p1, p2, stack, stacksize)) 377 return (0); 378 #else 379 /* 380 * Finish creating the child process. It will return through a 381 * different path later. 382 */ 383 #if defined(UVM) 384 uvm_fork(p1, p2, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack, 385 stacksize); 386 #else /* UVM */ 387 vm_fork(p1, p2, stack, stacksize); 388 #endif /* UVM */ 389 #endif 390 vm = p2->p_vmspace; 391 392 if (flags & FORK_FORK) { 393 forkstat.cntfork++; 394 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 395 } else if (flags & FORK_VFORK) { 396 forkstat.cntvfork++; 397 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 398 } else if (flags & FORK_RFORK) { 399 forkstat.cntrfork++; 400 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 401 } else { 402 forkstat.cntkthread++; 403 forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize; 404 } 405 406 /* 407 * Make child runnable, set start time, and add to run queue. 408 */ 409 s = splstatclock(); 410 p2->p_stats->p_start = time; 411 p2->p_acflag = AFORK; 412 p2->p_stat = SRUN; 413 setrunqueue(p2); 414 splx(s); 415 416 /* 417 * Now can be swapped. 418 */ 419 PRELE(p1); 420 421 #if defined(UVM) 422 uvmexp.forks++; 423 if (flags & FORK_PPWAIT) 424 uvmexp.forks_ppwait++; 425 if (flags & FORK_SHAREVM) 426 uvmexp.forks_sharevm++; 427 #endif 428 429 /* 430 * tell any interested parties about the new process 431 */ 432 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 433 434 /* 435 * Preserve synchronization semantics of vfork. If waiting for 436 * child to exec or exit, set P_PPWAIT on child, and sleep on our 437 * proc (in case of exit). 438 */ 439 if (flags & FORK_PPWAIT) 440 while (p2->p_flag & P_PPWAIT) 441 tsleep(p1, PWAIT, "ppwait", 0); 442 443 /* 444 * Return child pid to parent process, 445 * marking us as parent via retval[1]. 446 */ 447 retval[0] = p2->p_pid; 448 retval[1] = 0; 449 return (0); 450 } 451 452