1 /* $OpenBSD: kern_fork.c,v 1.18 1999/02/26 04:59:39 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 <dev/rndvar.h> 58 59 #include <sys/syscallargs.h> 60 61 #include <vm/vm.h> 62 #include <vm/vm_kern.h> 63 64 #if defined(UVM) 65 #include <uvm/uvm_extern.h> 66 #include <uvm/uvm_map.h> 67 #endif 68 69 int nprocs = 1; /* process 0 */ 70 int randompid; /* when set to 1, pid's go random */ 71 pid_t lastpid; 72 73 /*ARGSUSED*/ 74 int 75 sys_fork(p, v, retval) 76 struct proc *p; 77 void *v; 78 register_t *retval; 79 { 80 return (fork1(p, ISFORK, 0, retval)); 81 } 82 83 /*ARGSUSED*/ 84 int 85 sys_vfork(p, v, retval) 86 struct proc *p; 87 void *v; 88 register_t *retval; 89 { 90 return (fork1(p, ISVFORK, 0, retval)); 91 } 92 93 int 94 sys_rfork(p, v, retval) 95 struct proc *p; 96 void *v; 97 register_t *retval; 98 { 99 struct sys_rfork_args /* { 100 syscallarg(int) flags; 101 } */ *uap = v; 102 103 return (fork1(p, ISRFORK, SCARG(uap, flags), retval)); 104 } 105 106 int 107 fork1(p1, forktype, rforkflags, retval) 108 register struct proc *p1; 109 int forktype; 110 int rforkflags; 111 register_t *retval; 112 { 113 register struct proc *p2; 114 register uid_t uid; 115 struct proc *newproc; 116 struct vmspace *vm; 117 int count; 118 static int pidchecked = 0; 119 int dupfd = 1, cleanfd = 0; 120 vm_offset_t uaddr; 121 122 if (forktype == ISRFORK) { 123 dupfd = 0; 124 if ((rforkflags & RFPROC) == 0) 125 return (EINVAL); 126 if ((rforkflags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG)) 127 return (EINVAL); 128 if (rforkflags & RFFDG) 129 dupfd = 1; 130 if (rforkflags & RFCFDG) 131 cleanfd = 1; 132 } 133 134 /* 135 * Although process entries are dynamically created, we still keep 136 * a global limit on the maximum number we will create. We reserve 137 * the last 5 processes to root. The variable nprocs is the current 138 * number of processes, maxproc is the limit. 139 */ 140 uid = p1->p_cred->p_ruid; 141 if ((nprocs >= maxproc - 5 && uid != 0) || nprocs >= maxproc) { 142 tablefull("proc"); 143 return (EAGAIN); 144 } 145 146 /* 147 * Increment the count of procs running with this uid. Don't allow 148 * a nonprivileged user to exceed their current limit. 149 */ 150 count = chgproccnt(uid, 1); 151 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 152 (void)chgproccnt(uid, -1); 153 return (EAGAIN); 154 } 155 156 /* 157 * Allocate a pcb and kernel stack for the process 158 */ 159 #if defined(arc) || defined(mips_cachealias) 160 uaddr = kmem_alloc_upage(kernel_map, USPACE); 161 #else 162 #if defined(UVM) 163 uaddr = uvm_km_valloc(kernel_map, USPACE); 164 #else 165 uaddr = kmem_alloc_pageable(kernel_map, USPACE); 166 #endif 167 #endif 168 if (uaddr == 0) 169 return ENOMEM; 170 171 /* Allocate new proc. */ 172 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 173 174 lastpid++; 175 if (randompid) 176 lastpid = PID_MAX; 177 retry: 178 /* 179 * If the process ID prototype has wrapped around, 180 * restart somewhat above 0, as the low-numbered procs 181 * tend to include daemons that don't exit. 182 */ 183 if (lastpid >= PID_MAX) { 184 lastpid = arc4random() % PID_MAX; 185 pidchecked = 0; 186 } 187 if (lastpid >= pidchecked) { 188 int doingzomb = 0; 189 190 pidchecked = PID_MAX; 191 /* 192 * Scan the active and zombie procs to check whether this pid 193 * is in use. Remember the lowest pid that's greater 194 * than lastpid, so we can avoid checking for a while. 195 */ 196 p2 = allproc.lh_first; 197 again: 198 for (; p2 != 0; p2 = p2->p_list.le_next) { 199 while (p2->p_pid == lastpid || 200 p2->p_pgrp->pg_id == lastpid) { 201 lastpid++; 202 if (lastpid >= pidchecked) 203 goto retry; 204 } 205 if (p2->p_pid > lastpid && pidchecked > p2->p_pid) 206 pidchecked = p2->p_pid; 207 if (p2->p_pgrp->pg_id > lastpid && 208 pidchecked > p2->p_pgrp->pg_id) 209 pidchecked = p2->p_pgrp->pg_id; 210 } 211 if (!doingzomb) { 212 doingzomb = 1; 213 p2 = zombproc.lh_first; 214 goto again; 215 } 216 } 217 218 nprocs++; 219 p2 = newproc; 220 p2->p_stat = SIDL; /* protect against others */ 221 p2->p_pid = lastpid; 222 LIST_INSERT_HEAD(&allproc, p2, p_list); 223 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 224 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 225 226 /* 227 * Make a proc table entry for the new process. 228 * Start by zeroing the section of proc that is zero-initialized, 229 * then copy the section that is copied directly from the parent. 230 */ 231 bzero(&p2->p_startzero, 232 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 233 bcopy(&p1->p_startcopy, &p2->p_startcopy, 234 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 235 236 /* 237 * Duplicate sub-structures as needed. 238 * Increase reference counts on shared objects. 239 * The p_stats and p_sigacts substructs are set in vm_fork. 240 */ 241 p2->p_flag = P_INMEM; 242 p2->p_emul = p1->p_emul; 243 if (p1->p_flag & P_PROFIL) 244 startprofclock(p2); 245 p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC)); 246 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 247 M_SUBPROC, M_WAITOK); 248 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 249 p2->p_cred->p_refcnt = 1; 250 crhold(p1->p_ucred); 251 252 /* bump references to the text vnode (for procfs) */ 253 p2->p_textvp = p1->p_textvp; 254 if (p2->p_textvp) 255 VREF(p2->p_textvp); 256 257 if (cleanfd) 258 p2->p_fd = fdinit(p1); 259 else if (dupfd) 260 p2->p_fd = fdcopy(p1); 261 else 262 p2->p_fd = fdshare(p1); 263 264 /* 265 * If p_limit is still copy-on-write, bump refcnt, 266 * otherwise get a copy that won't be modified. 267 * (If PL_SHAREMOD is clear, the structure is shared 268 * copy-on-write.) 269 */ 270 if (p1->p_limit->p_lflags & PL_SHAREMOD) 271 p2->p_limit = limcopy(p1->p_limit); 272 else { 273 p2->p_limit = p1->p_limit; 274 p2->p_limit->p_refcnt++; 275 } 276 277 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 278 p2->p_flag |= P_CONTROLT; 279 if (forktype == ISVFORK) 280 p2->p_flag |= P_PPWAIT; 281 LIST_INSERT_AFTER(p1, p2, p_pglist); 282 p2->p_pptr = p1; 283 if (forktype == ISRFORK && (rforkflags & RFNOWAIT)) { 284 p2->p_flag |= P_NOZOMBIE; 285 } else { 286 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 287 } 288 LIST_INIT(&p2->p_children); 289 290 #ifdef KTRACE 291 /* 292 * Copy traceflag and tracefile if enabled. 293 * If not inherited, these were zeroed above. 294 */ 295 if (p1->p_traceflag&KTRFAC_INHERIT) { 296 p2->p_traceflag = p1->p_traceflag; 297 if ((p2->p_tracep = p1->p_tracep) != NULL) 298 VREF(p2->p_tracep); 299 } 300 #endif 301 302 /* 303 * This begins the section where we must prevent the parent 304 * from being swapped. 305 */ 306 p1->p_holdcnt++; 307 308 #if !defined(UVM) /* We do this later for UVM */ 309 if (forktype == ISRFORK && (rforkflags & RFMEM)) { 310 /* share as much address space as possible */ 311 (void) vm_map_inherit(&p1->p_vmspace->vm_map, 312 VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS - MAXSSIZ, 313 VM_INHERIT_SHARE); 314 } 315 #endif 316 317 p2->p_addr = (struct user *)uaddr; 318 319 #ifdef __FORK_BRAINDAMAGE 320 /* 321 * Set return values for child before vm_fork, 322 * so they can be copied to child stack. 323 * We return 0, rather than the traditional behaviour of modifying the 324 * return value in the system call stub. 325 * NOTE: the kernel stack may be at a different location in the child 326 * process, and thus addresses of automatic variables (including retval) 327 * may be invalid after vm_fork returns in the child process. 328 */ 329 retval[0] = 0; 330 retval[1] = 1; 331 if (vm_fork(p1, p2)) 332 return (0); 333 #else 334 /* 335 * Finish creating the child process. It will return through a 336 * different path later. 337 */ 338 #if defined(UVM) 339 uvm_fork(p1, p2, (forktype == ISRFORK && (rforkflags & RFMEM)) ? TRUE : FALSE); 340 #else /* UVM */ 341 vm_fork(p1, p2); 342 #endif /* UVM */ 343 #endif 344 vm = p2->p_vmspace; 345 346 switch (forktype) { 347 case ISFORK: 348 forkstat.cntfork++; 349 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 350 break; 351 case ISVFORK: 352 forkstat.cntvfork++; 353 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 354 break; 355 case ISRFORK: 356 forkstat.cntrfork++; 357 forkstat.sizrfork += vm->vm_dsize + vm->vm_ssize; 358 break; 359 } 360 361 /* 362 * Make child runnable, set start time, and add to run queue. 363 */ 364 (void) splstatclock(); 365 p2->p_stats->p_start = time; 366 p2->p_acflag = AFORK; 367 p2->p_stat = SRUN; 368 setrunqueue(p2); 369 (void) spl0(); 370 371 /* 372 * Now can be swapped. 373 */ 374 p1->p_holdcnt--; 375 376 #if defined(UVM) /* ART_UVM_XXX */ 377 uvmexp.forks++; 378 #ifdef notyet 379 if (rforkflags & FORK_PPWAIT) 380 uvmexp.forks_ppwait++; 381 #endif 382 if (rforkflags & RFMEM) 383 uvmexp.forks_sharevm++; 384 #endif 385 386 /* 387 * Preserve synchronization semantics of vfork. If waiting for 388 * child to exec or exit, set P_PPWAIT on child, and sleep on our 389 * proc (in case of exit). 390 */ 391 if (forktype == ISVFORK) 392 while (p2->p_flag & P_PPWAIT) 393 tsleep(p1, PWAIT, "ppwait", 0); 394 395 /* 396 * Return child pid to parent process, 397 * marking us as parent via retval[1]. 398 */ 399 retval[0] = p2->p_pid; 400 retval[1] = 0; 401 return (0); 402 } 403 404