1 /* $OpenBSD: kern_fork.c,v 1.36 2000/11/16 20:02:17 provos 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 60 #include <sys/syscallargs.h> 61 62 #include <vm/vm.h> 63 #include <vm/vm_kern.h> 64 65 #if defined(UVM) 66 #include <uvm/uvm_extern.h> 67 #include <uvm/uvm_map.h> 68 #endif 69 70 int nprocs = 1; /* process 0 */ 71 int randompid; /* when set to 1, pid's go random */ 72 pid_t lastpid; 73 struct forkstat forkstat; 74 75 76 /*ARGSUSED*/ 77 int 78 sys_fork(p, v, retval) 79 struct proc *p; 80 void *v; 81 register_t *retval; 82 { 83 return (fork1(p, FORK_FORK, NULL, 0, retval)); 84 } 85 86 /*ARGSUSED*/ 87 int 88 sys_vfork(p, v, retval) 89 struct proc *p; 90 void *v; 91 register_t *retval; 92 { 93 return (fork1(p, FORK_VFORK|FORK_PPWAIT, NULL, 0, retval)); 94 } 95 96 int 97 sys_rfork(p, v, retval) 98 struct proc *p; 99 void *v; 100 register_t *retval; 101 { 102 struct sys_rfork_args /* { 103 syscallarg(int) flags; 104 } */ *uap = v; 105 int rforkflags; 106 int flags; 107 108 flags = FORK_RFORK; 109 rforkflags = SCARG(uap, flags); 110 111 if ((rforkflags & RFPROC) == 0) 112 return (EINVAL); 113 114 switch(rforkflags & (RFFDG|RFCFDG)) { 115 case (RFFDG|RFCFDG): 116 return EINVAL; 117 case RFCFDG: 118 flags |= FORK_CLEANFILES; 119 break; 120 case RFFDG: 121 break; 122 default: 123 flags |= FORK_SHAREFILES; 124 break; 125 } 126 127 if (rforkflags & RFNOWAIT) 128 flags |= FORK_NOZOMBIE; 129 130 if (rforkflags & RFMEM) 131 flags |= FORK_VMNOSTACK; 132 133 return (fork1(p, flags, NULL, 0, retval)); 134 } 135 136 int 137 fork1(p1, flags, stack, stacksize, retval) 138 register struct proc *p1; 139 int flags; 140 void *stack; 141 size_t stacksize; 142 register_t *retval; 143 { 144 struct proc *p2; 145 uid_t uid; 146 struct proc *newproc; 147 struct vmspace *vm; 148 int count; 149 static int pidchecked = 0; 150 vaddr_t uaddr; 151 extern void endtsleep __P((void *)); 152 extern void realitexpire __P((void *)); 153 154 /* 155 * Although process entries are dynamically created, we still keep 156 * a global limit on the maximum number we will create. We reserve 157 * the last 5 processes to root. The variable nprocs is the current 158 * number of processes, maxproc is the limit. 159 */ 160 uid = p1->p_cred->p_ruid; 161 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 162 tablefull("proc"); 163 return (EAGAIN); 164 } 165 166 #if !defined(UVM) 167 if (flags & FORK_SHAREVM) 168 return (EINVAL); 169 #endif 170 171 /* 172 * Increment the count of procs running with this uid. Don't allow 173 * a nonprivileged user to exceed their current limit. 174 */ 175 count = chgproccnt(uid, 1); 176 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 177 (void)chgproccnt(uid, -1); 178 return (EAGAIN); 179 } 180 181 /* 182 * Allocate a pcb and kernel stack for the process 183 */ 184 #if defined(arc) || defined(mips_cachealias) 185 uaddr = kmem_alloc_upage(kernel_map, USPACE); 186 #else 187 #if defined(UVM) 188 uaddr = uvm_km_valloc(kernel_map, USPACE); 189 #else 190 uaddr = kmem_alloc_pageable(kernel_map, USPACE); 191 #endif 192 #endif 193 if (uaddr == 0) 194 return ENOMEM; 195 196 /* Allocate new proc. */ 197 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 198 199 lastpid++; 200 if (randompid) 201 lastpid = PID_MAX; 202 retry: 203 /* 204 * If the process ID prototype has wrapped around, 205 * restart somewhat above 0, as the low-numbered procs 206 * tend to include daemons that don't exit. 207 */ 208 if (lastpid >= PID_MAX) { 209 lastpid = arc4random() % PID_MAX; 210 pidchecked = 0; 211 } 212 if (lastpid >= pidchecked) { 213 int doingzomb = 0; 214 215 pidchecked = PID_MAX; 216 /* 217 * Scan the active and zombie procs to check whether this pid 218 * is in use. Remember the lowest pid that's greater 219 * than lastpid, so we can avoid checking for a while. 220 */ 221 p2 = LIST_FIRST(&allproc); 222 again: 223 for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) { 224 while (p2->p_pid == lastpid || 225 p2->p_pgrp->pg_id == lastpid) { 226 lastpid++; 227 if (lastpid >= pidchecked) 228 goto retry; 229 } 230 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 231 pidchecked = p2->p_pid; 232 if (p2->p_pgrp->pg_id > lastpid && 233 pidchecked > p2->p_pgrp->pg_id) 234 pidchecked = p2->p_pgrp->pg_id; 235 } 236 if (!doingzomb) { 237 doingzomb = 1; 238 p2 = LIST_FIRST(&zombproc); 239 goto again; 240 } 241 } 242 243 nprocs++; 244 p2 = newproc; 245 p2->p_stat = SIDL; /* protect against others */ 246 p2->p_pid = lastpid; 247 LIST_INSERT_HEAD(&allproc, p2, p_list); 248 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 249 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 250 251 /* 252 * Make a proc table entry for the new process. 253 * Start by zeroing the section of proc that is zero-initialized, 254 * then copy the section that is copied directly from the parent. 255 */ 256 bzero(&p2->p_startzero, 257 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 258 bcopy(&p1->p_startcopy, &p2->p_startcopy, 259 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 260 261 /* 262 * Initialize the timeouts. 263 */ 264 timeout_set(&p2->p_sleep_to, endtsleep, p2); 265 timeout_set(&p2->p_realit_to, realitexpire, p2); 266 267 /* 268 * Duplicate sub-structures as needed. 269 * Increase reference counts on shared objects. 270 * The p_stats and p_sigacts substructs are set in vm_fork. 271 */ 272 p2->p_flag = P_INMEM; 273 p2->p_emul = p1->p_emul; 274 if (p1->p_flag & P_PROFIL) 275 startprofclock(p2); 276 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 277 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 278 M_SUBPROC, M_WAITOK); 279 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 280 p2->p_cred->p_refcnt = 1; 281 crhold(p1->p_ucred); 282 283 /* bump references to the text vnode (for procfs) */ 284 p2->p_textvp = p1->p_textvp; 285 if (p2->p_textvp) 286 VREF(p2->p_textvp); 287 288 if (flags & FORK_CLEANFILES) 289 p2->p_fd = fdinit(p1); 290 else if (flags & FORK_SHAREFILES) 291 p2->p_fd = fdshare(p1); 292 else 293 p2->p_fd = fdcopy(p1); 294 295 /* 296 * If p_limit is still copy-on-write, bump refcnt, 297 * otherwise get a copy that won't be modified. 298 * (If PL_SHAREMOD is clear, the structure is shared 299 * copy-on-write.) 300 */ 301 if (p1->p_limit->p_lflags & PL_SHAREMOD) 302 p2->p_limit = limcopy(p1->p_limit); 303 else { 304 p2->p_limit = p1->p_limit; 305 p2->p_limit->p_refcnt++; 306 } 307 308 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 309 p2->p_flag |= P_CONTROLT; 310 if (flags & FORK_PPWAIT) 311 p2->p_flag |= P_PPWAIT; 312 LIST_INSERT_AFTER(p1, p2, p_pglist); 313 p2->p_pptr = p1; 314 if (flags & FORK_NOZOMBIE) 315 p2->p_flag |= P_NOZOMBIE; 316 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 317 LIST_INIT(&p2->p_children); 318 319 #ifdef KTRACE 320 /* 321 * Copy traceflag and tracefile if enabled. 322 * If not inherited, these were zeroed above. 323 */ 324 if (p1->p_traceflag & KTRFAC_INHERIT) { 325 p2->p_traceflag = p1->p_traceflag; 326 if ((p2->p_tracep = p1->p_tracep) != NULL) 327 VREF(p2->p_tracep); 328 } 329 #endif 330 331 /* 332 * set priority of child to be that of parent 333 * XXX should move p_estcpu into the region of struct proc which gets 334 * copied. 335 */ 336 scheduler_fork_hook(p1, p2); 337 338 /* 339 * This begins the section where we must prevent the parent 340 * from being swapped. 341 */ 342 PHOLD(p1); 343 344 #if defined(UVM) 345 if (flags & FORK_VMNOSTACK) { 346 /* share as much address space as possible */ 347 (void) uvm_map_inherit(&p1->p_vmspace->vm_map, 348 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 349 VM_INHERIT_SHARE); 350 } 351 #else 352 if (flags & FORK_VMNOSTACK) { 353 /* share as much address space as possible */ 354 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 355 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 356 VM_INHERIT_SHARE); 357 } 358 #endif 359 360 p2->p_addr = (struct user *)uaddr; 361 362 #ifdef __FORK_BRAINDAMAGE 363 /* 364 * Set return values for child before vm_fork, 365 * so they can be copied to child stack. 366 * We return 0, rather than the traditional behaviour of modifying the 367 * return value in the system call stub. 368 * NOTE: the kernel stack may be at a different location in the child 369 * process, and thus addresses of automatic variables (including retval) 370 * may be invalid after vm_fork returns in the child process. 371 */ 372 retval[0] = 0; 373 retval[1] = 1; 374 if (vm_fork(p1, p2, stack, stacksize)) 375 return (0); 376 #else 377 /* 378 * Finish creating the child process. It will return through a 379 * different path later. 380 */ 381 #if defined(UVM) 382 uvm_fork(p1, p2, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack, 383 stacksize); 384 #else /* UVM */ 385 vm_fork(p1, p2, stack, stacksize); 386 #endif /* UVM */ 387 #endif 388 vm = p2->p_vmspace; 389 390 if (flags & FORK_FORK) { 391 forkstat.cntfork++; 392 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 393 } else if (flags & FORK_VFORK) { 394 forkstat.cntvfork++; 395 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 396 } else if (flags & FORK_RFORK) { 397 forkstat.cntrfork++; 398 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 399 } else { 400 forkstat.cntkthread++; 401 forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize; 402 } 403 404 /* 405 * Make child runnable, set start time, and add to run queue. 406 */ 407 (void) splstatclock(); 408 p2->p_stats->p_start = time; 409 p2->p_acflag = AFORK; 410 p2->p_stat = SRUN; 411 setrunqueue(p2); 412 (void) spl0(); 413 414 /* 415 * Now can be swapped. 416 */ 417 PRELE(p1); 418 419 #if defined(UVM) 420 uvmexp.forks++; 421 if (flags & FORK_PPWAIT) 422 uvmexp.forks_ppwait++; 423 if (flags & FORK_SHAREVM) 424 uvmexp.forks_sharevm++; 425 #endif 426 427 /* 428 * tell any interested parties about the new process 429 */ 430 KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid); 431 432 /* 433 * Preserve synchronization semantics of vfork. If waiting for 434 * child to exec or exit, set P_PPWAIT on child, and sleep on our 435 * proc (in case of exit). 436 */ 437 if (flags & FORK_PPWAIT) 438 while (p2->p_flag & P_PPWAIT) 439 tsleep(p1, PWAIT, "ppwait", 0); 440 441 /* 442 * Return child pid to parent process, 443 * marking us as parent via retval[1]. 444 */ 445 retval[0] = p2->p_pid; 446 retval[1] = 0; 447 return (0); 448 } 449 450