1 /* $OpenBSD: kern_fork.c,v 1.24 1999/08/17 10:32:18 niklas 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, ISFORK, 0, 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, ISVFORK, 0, 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; 103 104 return (fork1(p, ISRFORK, SCARG(uap, flags), NULL, 0, retval)); 105 } 106 107 int 108 fork1(p1, forktype, rforkflags, stack, stacksize, retval) 109 register struct proc *p1; 110 int forktype; 111 int rforkflags; 112 void *stack; 113 size_t stacksize; 114 register_t *retval; 115 { 116 register struct proc *p2; 117 register uid_t uid; 118 struct proc *newproc; 119 struct vmspace *vm; 120 int count; 121 static int pidchecked = 0; 122 int dupfd = 1, cleanfd = 0; 123 vaddr_t uaddr; 124 125 if (forktype == ISRFORK) { 126 dupfd = 0; 127 if ((rforkflags & RFPROC) == 0) 128 return (EINVAL); 129 if ((rforkflags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 130 return (EINVAL); 131 if (rforkflags & RFFDG) 132 dupfd = 1; 133 if (rforkflags & RFCFDG) 134 cleanfd = 1; 135 } 136 137 /* 138 * Although process entries are dynamically created, we still keep 139 * a global limit on the maximum number we will create. We reserve 140 * the last 5 processes to root. The variable nprocs is the current 141 * number of processes, maxproc is the limit. 142 */ 143 uid = p1->p_cred->p_ruid; 144 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 145 tablefull("proc"); 146 return (EAGAIN); 147 } 148 149 /* 150 * Increment the count of procs running with this uid. Don't allow 151 * a nonprivileged user to exceed their current limit. 152 */ 153 count = chgproccnt(uid, 1); 154 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 155 (void)chgproccnt(uid, -1); 156 return (EAGAIN); 157 } 158 159 /* 160 * Allocate a pcb and kernel stack for the process 161 */ 162 #if defined(arc) || defined(mips_cachealias) 163 uaddr = kmem_alloc_upage(kernel_map, USPACE); 164 #else 165 #if defined(UVM) 166 uaddr = uvm_km_valloc(kernel_map, USPACE); 167 #else 168 uaddr = kmem_alloc_pageable(kernel_map, USPACE); 169 #endif 170 #endif 171 if (uaddr == 0) 172 return ENOMEM; 173 174 /* Allocate new proc. */ 175 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 176 177 lastpid++; 178 if (randompid) 179 lastpid = PID_MAX; 180 retry: 181 /* 182 * If the process ID prototype has wrapped around, 183 * restart somewhat above 0, as the low-numbered procs 184 * tend to include daemons that don't exit. 185 */ 186 if (lastpid >= PID_MAX) { 187 lastpid = arc4random() % PID_MAX; 188 pidchecked = 0; 189 } 190 if (lastpid >= pidchecked) { 191 int doingzomb = 0; 192 193 pidchecked = PID_MAX; 194 /* 195 * Scan the active and zombie procs to check whether this pid 196 * is in use. Remember the lowest pid that's greater 197 * than lastpid, so we can avoid checking for a while. 198 */ 199 p2 = allproc.lh_first; 200 again: 201 for (; p2 != 0; p2 = p2->p_list.le_next) { 202 while (p2->p_pid == lastpid || 203 p2->p_pgrp->pg_id == lastpid) { 204 lastpid++; 205 if (lastpid >= pidchecked) 206 goto retry; 207 } 208 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 209 pidchecked = p2->p_pid; 210 if (p2->p_pgrp->pg_id > lastpid && 211 pidchecked > p2->p_pgrp->pg_id) 212 pidchecked = p2->p_pgrp->pg_id; 213 } 214 if (!doingzomb) { 215 doingzomb = 1; 216 p2 = zombproc.lh_first; 217 goto again; 218 } 219 } 220 221 nprocs++; 222 p2 = newproc; 223 p2->p_stat = SIDL; /* protect against others */ 224 p2->p_pid = lastpid; 225 LIST_INSERT_HEAD(&allproc, p2, p_list); 226 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 227 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 228 229 /* 230 * Make a proc table entry for the new process. 231 * Start by zeroing the section of proc that is zero-initialized, 232 * then copy the section that is copied directly from the parent. 233 */ 234 bzero(&p2->p_startzero, 235 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 236 bcopy(&p1->p_startcopy, &p2->p_startcopy, 237 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 238 239 /* 240 * Duplicate sub-structures as needed. 241 * Increase reference counts on shared objects. 242 * The p_stats and p_sigacts substructs are set in vm_fork. 243 */ 244 p2->p_flag = P_INMEM; 245 p2->p_emul = p1->p_emul; 246 if (p1->p_flag & P_PROFIL) 247 startprofclock(p2); 248 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 249 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 250 M_SUBPROC, M_WAITOK); 251 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 252 p2->p_cred->p_refcnt = 1; 253 crhold(p1->p_ucred); 254 255 /* bump references to the text vnode (for procfs) */ 256 p2->p_textvp = p1->p_textvp; 257 if (p2->p_textvp) 258 VREF(p2->p_textvp); 259 260 if (cleanfd) 261 p2->p_fd = fdinit(p1); 262 else if (dupfd) 263 p2->p_fd = fdcopy(p1); 264 else 265 p2->p_fd = fdshare(p1); 266 267 /* 268 * If p_limit is still copy-on-write, bump refcnt, 269 * otherwise get a copy that won't be modified. 270 * (If PL_SHAREMOD is clear, the structure is shared 271 * copy-on-write.) 272 */ 273 if (p1->p_limit->p_lflags & PL_SHAREMOD) 274 p2->p_limit = limcopy(p1->p_limit); 275 else { 276 p2->p_limit = p1->p_limit; 277 p2->p_limit->p_refcnt++; 278 } 279 280 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 281 p2->p_flag |= P_CONTROLT; 282 if (forktype == ISVFORK) 283 p2->p_flag |= P_PPWAIT; 284 LIST_INSERT_AFTER(p1, p2, p_pglist); 285 p2->p_pptr = p1; 286 if (forktype == ISRFORK && (rforkflags & RFNOWAIT)) 287 p2->p_flag |= P_NOZOMBIE; 288 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 289 LIST_INIT(&p2->p_children); 290 291 #ifdef KTRACE 292 /* 293 * Copy traceflag and tracefile if enabled. 294 * If not inherited, these were zeroed above. 295 */ 296 if (p1->p_traceflag&KTRFAC_INHERIT) { 297 p2->p_traceflag = p1->p_traceflag; 298 if ((p2->p_tracep = p1->p_tracep) != NULL) 299 VREF(p2->p_tracep); 300 } 301 #endif 302 303 /* 304 * set priority of child to be that of parent 305 * XXX should move p_estcpu into the region of struct proc which gets 306 * copied. 307 */ 308 scheduler_fork_hook(p1, p2); 309 310 /* 311 * This begins the section where we must prevent the parent 312 * from being swapped. 313 */ 314 p1->p_holdcnt++; 315 316 #if !defined(UVM) /* We do this later for UVM */ 317 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 318 /* share as much address space as possible */ 319 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 320 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 321 VM_INHERIT_SHARE); 322 } 323 #endif 324 325 p2->p_addr = (struct user *)uaddr; 326 327 #ifdef __FORK_BRAINDAMAGE 328 /* 329 * Set return values for child before vm_fork, 330 * so they can be copied to child stack. 331 * We return 0, rather than the traditional behaviour of modifying the 332 * return value in the system call stub. 333 * NOTE: the kernel stack may be at a different location in the child 334 * process, and thus addresses of automatic variables (including retval) 335 * may be invalid after vm_fork returns in the child process. 336 */ 337 retval[0] = 0; 338 retval[1] = 1; 339 if (vm_fork(p1, p2, stack, stacksize)) 340 return (0); 341 #else 342 /* 343 * Finish creating the child process. It will return through a 344 * different path later. 345 */ 346 #if defined(UVM) 347 uvm_fork(p1, p2, 348 (forktype == ISRFORK && (rforkflags & RFMEM)) ? TRUE : FALSE, 349 stack, stacksize); 350 #else /* UVM */ 351 vm_fork(p1, p2, stack, stacksize); 352 #endif /* UVM */ 353 #endif 354 vm = p2->p_vmspace; 355 356 switch (forktype) { 357 case ISFORK: 358 forkstat.cntfork++; 359 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 360 break; 361 case ISVFORK: 362 forkstat.cntvfork++; 363 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 364 break; 365 case ISRFORK: 366 forkstat.cntrfork++; 367 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 368 break; 369 } 370 371 /* 372 * Make child runnable, set start time, and add to run queue. 373 */ 374 (void) splstatclock(); 375 p2->p_stats->p_start = time; 376 p2->p_acflag = AFORK; 377 p2->p_stat = SRUN; 378 setrunqueue(p2); 379 (void) spl0(); 380 381 /* 382 * Now can be swapped. 383 */ 384 p1->p_holdcnt--; 385 386 #if defined(UVM) 387 uvmexp.forks++; 388 if (forktype == ISVFORK) 389 uvmexp.forks_ppwait++; 390 if (forktype == ISRFORK && (rforkflags & RFMEM)) 391 uvmexp.forks_sharevm++; 392 #endif 393 394 /* 395 * Preserve synchronization semantics of vfork. If waiting for 396 * child to exec or exit, set P_PPWAIT on child, and sleep on our 397 * proc (in case of exit). 398 */ 399 if (forktype == ISVFORK) 400 while (p2->p_flag & P_PPWAIT) 401 tsleep(p1, PWAIT, "ppwait", 0); 402 403 /* 404 * Return child pid to parent process, 405 * marking us as parent via retval[1]. 406 */ 407 retval[0] = p2->p_pid; 408 retval[1] = 0; 409 return (0); 410 } 411 412