1 /* $OpenBSD: kern_fork.c,v 1.27 2000/01/31 19:57:18 deraadt 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 74 /*ARGSUSED*/ 75 int 76 sys_fork(p, v, retval) 77 struct proc *p; 78 void *v; 79 register_t *retval; 80 { 81 return (fork1(p, FORK_FORK, NULL, 0, retval)); 82 } 83 84 /*ARGSUSED*/ 85 int 86 sys_vfork(p, v, retval) 87 struct proc *p; 88 void *v; 89 register_t *retval; 90 { 91 return (fork1(p, FORK_VFORK|FORK_PPWAIT, NULL, 0, retval)); 92 } 93 94 int 95 sys_rfork(p, v, retval) 96 struct proc *p; 97 void *v; 98 register_t *retval; 99 { 100 struct sys_rfork_args /* { 101 syscallarg(int) flags; 102 } */ *uap = v; 103 int rforkflags; 104 int flags; 105 106 flags = FORK_RFORK; 107 rforkflags = SCARG(uap, flags); 108 109 if ((rforkflags & RFPROC) == 0) 110 return (EINVAL); 111 112 switch(rforkflags & (RFFDG|RFCFDG)) { 113 case (RFFDG|RFCFDG): 114 return EINVAL; 115 case RFCFDG: 116 flags |= FORK_CLEANFILES; 117 break; 118 case RFFDG: 119 break; 120 default: 121 flags |= FORK_SHAREFILES; 122 break; 123 } 124 125 if (rforkflags & RFNOWAIT) 126 flags |= FORK_NOZOMBIE; 127 128 if (rforkflags & RFMEM) 129 flags |= FORK_SHAREVM; 130 131 return (fork1(p, flags, NULL, 0, retval)); 132 } 133 134 int 135 fork1(p1, flags, stack, stacksize, retval) 136 register struct proc *p1; 137 int flags; 138 void *stack; 139 size_t stacksize; 140 register_t *retval; 141 { 142 register struct proc *p2; 143 register uid_t uid; 144 struct proc *newproc; 145 struct vmspace *vm; 146 int count; 147 static int pidchecked = 0; 148 vaddr_t uaddr; 149 150 /* 151 * Although process entries are dynamically created, we still keep 152 * a global limit on the maximum number we will create. We reserve 153 * the last 5 processes to root. The variable nprocs is the current 154 * number of processes, maxproc is the limit. 155 */ 156 uid = p1->p_cred->p_ruid; 157 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 158 tablefull("proc"); 159 return (EAGAIN); 160 } 161 162 /* 163 * Increment the count of procs running with this uid. Don't allow 164 * a nonprivileged user to exceed their current limit. 165 */ 166 count = chgproccnt(uid, 1); 167 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 168 (void)chgproccnt(uid, -1); 169 return (EAGAIN); 170 } 171 172 /* 173 * Allocate a pcb and kernel stack for the process 174 */ 175 #if defined(arc) || defined(mips_cachealias) 176 uaddr = kmem_alloc_upage(kernel_map, USPACE); 177 #else 178 #if defined(UVM) 179 uaddr = uvm_km_valloc(kernel_map, USPACE); 180 #else 181 uaddr = kmem_alloc_pageable(kernel_map, USPACE); 182 #endif 183 #endif 184 if (uaddr == 0) 185 return ENOMEM; 186 187 /* Allocate new proc. */ 188 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 189 190 lastpid++; 191 if (randompid) 192 lastpid = PID_MAX; 193 retry: 194 /* 195 * If the process ID prototype has wrapped around, 196 * restart somewhat above 0, as the low-numbered procs 197 * tend to include daemons that don't exit. 198 */ 199 if (lastpid >= PID_MAX) { 200 lastpid = arc4random() % PID_MAX; 201 pidchecked = 0; 202 } 203 if (lastpid >= pidchecked) { 204 int doingzomb = 0; 205 206 pidchecked = PID_MAX; 207 /* 208 * Scan the active and zombie procs to check whether this pid 209 * is in use. Remember the lowest pid that's greater 210 * than lastpid, so we can avoid checking for a while. 211 */ 212 p2 = allproc.lh_first; 213 again: 214 for (; p2 != 0; p2 = p2->p_list.le_next) { 215 while (p2->p_pid == lastpid || 216 p2->p_pgrp->pg_id == lastpid) { 217 lastpid++; 218 if (lastpid >= pidchecked) 219 goto retry; 220 } 221 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 222 pidchecked = p2->p_pid; 223 if (p2->p_pgrp->pg_id > lastpid && 224 pidchecked > p2->p_pgrp->pg_id) 225 pidchecked = p2->p_pgrp->pg_id; 226 } 227 if (!doingzomb) { 228 doingzomb = 1; 229 p2 = zombproc.lh_first; 230 goto again; 231 } 232 } 233 234 nprocs++; 235 p2 = newproc; 236 p2->p_stat = SIDL; /* protect against others */ 237 p2->p_pid = lastpid; 238 LIST_INSERT_HEAD(&allproc, p2, p_list); 239 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 240 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 241 242 /* 243 * Make a proc table entry for the new process. 244 * Start by zeroing the section of proc that is zero-initialized, 245 * then copy the section that is copied directly from the parent. 246 */ 247 bzero(&p2->p_startzero, 248 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 249 bcopy(&p1->p_startcopy, &p2->p_startcopy, 250 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 251 252 /* 253 * Duplicate sub-structures as needed. 254 * Increase reference counts on shared objects. 255 * The p_stats and p_sigacts substructs are set in vm_fork. 256 */ 257 p2->p_flag = P_INMEM; 258 p2->p_emul = p1->p_emul; 259 if (p1->p_flag & P_PROFIL) 260 startprofclock(p2); 261 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 262 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 263 M_SUBPROC, M_WAITOK); 264 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 265 p2->p_cred->p_refcnt = 1; 266 crhold(p1->p_ucred); 267 268 /* bump references to the text vnode (for procfs) */ 269 p2->p_textvp = p1->p_textvp; 270 if (p2->p_textvp) 271 VREF(p2->p_textvp); 272 273 if (flags & FORK_CLEANFILES) 274 p2->p_fd = fdinit(p1); 275 else if (flags & FORK_SHAREFILES) 276 p2->p_fd = fdshare(p1); 277 else 278 p2->p_fd = fdcopy(p1); 279 280 /* 281 * If p_limit is still copy-on-write, bump refcnt, 282 * otherwise get a copy that won't be modified. 283 * (If PL_SHAREMOD is clear, the structure is shared 284 * copy-on-write.) 285 */ 286 if (p1->p_limit->p_lflags & PL_SHAREMOD) 287 p2->p_limit = limcopy(p1->p_limit); 288 else { 289 p2->p_limit = p1->p_limit; 290 p2->p_limit->p_refcnt++; 291 } 292 293 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 294 p2->p_flag |= P_CONTROLT; 295 if (flags & FORK_PPWAIT) 296 p2->p_flag |= P_PPWAIT; 297 LIST_INSERT_AFTER(p1, p2, p_pglist); 298 p2->p_pptr = p1; 299 if (flags & FORK_NOZOMBIE) 300 p2->p_flag |= P_NOZOMBIE; 301 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 302 LIST_INIT(&p2->p_children); 303 304 #ifdef KTRACE 305 /* 306 * Copy traceflag and tracefile if enabled. 307 * If not inherited, these were zeroed above. 308 */ 309 if (p1->p_traceflag & KTRFAC_INHERIT) { 310 p2->p_traceflag = p1->p_traceflag; 311 if ((p2->p_tracep = p1->p_tracep) != NULL) 312 VREF(p2->p_tracep); 313 } 314 #endif 315 316 /* 317 * set priority of child to be that of parent 318 * XXX should move p_estcpu into the region of struct proc which gets 319 * copied. 320 */ 321 scheduler_fork_hook(p1, p2); 322 323 /* 324 * This begins the section where we must prevent the parent 325 * from being swapped. 326 */ 327 p1->p_holdcnt++; 328 329 #if !defined(UVM) /* We do this later for UVM */ 330 if (flags & FORK_SHAREVM) { 331 /* share as much address space as possible */ 332 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 333 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 334 VM_INHERIT_SHARE); 335 } 336 #endif 337 338 p2->p_addr = (struct user *)uaddr; 339 340 #ifdef __FORK_BRAINDAMAGE 341 /* 342 * Set return values for child before vm_fork, 343 * so they can be copied to child stack. 344 * We return 0, rather than the traditional behaviour of modifying the 345 * return value in the system call stub. 346 * NOTE: the kernel stack may be at a different location in the child 347 * process, and thus addresses of automatic variables (including retval) 348 * may be invalid after vm_fork returns in the child process. 349 */ 350 retval[0] = 0; 351 retval[1] = 1; 352 if (vm_fork(p1, p2, stack, stacksize)) 353 return (0); 354 #else 355 /* 356 * Finish creating the child process. It will return through a 357 * different path later. 358 */ 359 #if defined(UVM) 360 uvm_fork(p1, p2, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack, 361 stacksize); 362 #else /* UVM */ 363 vm_fork(p1, p2, stack, stacksize); 364 #endif /* UVM */ 365 #endif 366 vm = p2->p_vmspace; 367 368 if (flags & FORK_FORK) { 369 forkstat.cntfork++; 370 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 371 } else if (flags & FORK_VFORK) { 372 forkstat.cntvfork++; 373 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 374 } else if (flags & FORK_RFORK) { 375 forkstat.cntrfork++; 376 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 377 } 378 379 /* 380 * Make child runnable, set start time, and add to run queue. 381 */ 382 (void) splstatclock(); 383 p2->p_stats->p_start = time; 384 p2->p_acflag = AFORK; 385 p2->p_stat = SRUN; 386 setrunqueue(p2); 387 (void) spl0(); 388 389 /* 390 * Now can be swapped. 391 */ 392 p1->p_holdcnt--; 393 394 #if defined(UVM) 395 uvmexp.forks++; 396 if (flags & FORK_PPWAIT) 397 uvmexp.forks_ppwait++; 398 if (flags & FORK_SHAREVM) 399 uvmexp.forks_sharevm++; 400 #endif 401 402 /* 403 * Preserve synchronization semantics of vfork. If waiting for 404 * child to exec or exit, set P_PPWAIT on child, and sleep on our 405 * proc (in case of exit). 406 */ 407 if (flags & FORK_PPWAIT) 408 while (p2->p_flag & P_PPWAIT) 409 tsleep(p1, PWAIT, "ppwait", 0); 410 411 /* 412 * Return child pid to parent process, 413 * marking us as parent via retval[1]. 414 */ 415 retval[0] = p2->p_pid; 416 retval[1] = 0; 417 return (0); 418 } 419 420