kern_fork.c revision 1.46
1 /* $NetBSD: kern_fork.c,v 1.46 1998/08/13 02:10:57 eeh Exp $ */ 2 3 /* 4 * Copyright (c) 1982, 1986, 1989, 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * @(#)kern_fork.c 8.8 (Berkeley) 2/14/95 41 */ 42 43 #include "opt_ktrace.h" 44 #include "opt_uvm.h" 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/map.h> 49 #include <sys/filedesc.h> 50 #include <sys/kernel.h> 51 #include <sys/malloc.h> 52 #include <sys/pool.h> 53 #include <sys/mount.h> 54 #include <sys/proc.h> 55 #include <sys/resourcevar.h> 56 #include <sys/vnode.h> 57 #include <sys/file.h> 58 #include <sys/acct.h> 59 #include <sys/ktrace.h> 60 #include <sys/vmmeter.h> 61 62 #include <sys/syscallargs.h> 63 64 #include <vm/vm.h> 65 #include <vm/vm_kern.h> 66 67 #if defined(UVM) 68 #include <uvm/uvm_extern.h> 69 #endif 70 71 int nprocs = 1; /* process 0 */ 72 73 /*ARGSUSED*/ 74 int 75 sys_fork(p, v, retval) 76 struct proc *p; 77 void *v; 78 register_t *retval; 79 { 80 81 return (fork1(p, 0, retval, NULL)); 82 } 83 84 /* 85 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 86 * Address space is not shared, but parent is blocked until child exit. 87 */ 88 /*ARGSUSED*/ 89 int 90 sys_vfork(p, v, retval) 91 struct proc *p; 92 void *v; 93 register_t *retval; 94 { 95 96 return (fork1(p, FORK_PPWAIT, retval, NULL)); 97 } 98 99 /* 100 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 101 * semantics. Address space is shared, and parent is blocked until child exit. 102 */ 103 /*ARGSUSED*/ 104 int 105 sys___vfork14(p, v, retval) 106 struct proc *p; 107 void *v; 108 register_t *retval; 109 { 110 111 return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, retval, NULL)); 112 } 113 114 int 115 fork1(p1, flags, retval, rnewprocp) 116 register struct proc *p1; 117 int flags; 118 register_t *retval; 119 struct proc **rnewprocp; 120 { 121 register struct proc *p2; 122 register uid_t uid; 123 struct proc *newproc; 124 int count; 125 vaddr_t uaddr; 126 static int nextpid, pidchecked = 0; 127 128 /* 129 * Although process entries are dynamically created, we still keep 130 * a global limit on the maximum number we will create. Don't allow 131 * a nonprivileged user to use the last process; don't let root 132 * exceed the limit. The variable nprocs is the current number of 133 * processes, maxproc is the limit. 134 */ 135 uid = p1->p_cred->p_ruid; 136 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 137 tablefull("proc"); 138 return (EAGAIN); 139 } 140 141 /* 142 * Increment the count of procs running with this uid. Don't allow 143 * a nonprivileged user to exceed their current limit. 144 */ 145 count = chgproccnt(uid, 1); 146 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 147 (void)chgproccnt(uid, -1); 148 return (EAGAIN); 149 } 150 151 /* 152 * Allocate virtual address space for the U-area now, while it 153 * is still easy to abort the fork operation if we're out of 154 * kernel virtual address space. The actual U-area pages will 155 * be allocated and wired in vm_fork(). 156 */ 157 #if defined(UVM) 158 uaddr = uvm_km_valloc(kernel_map, USPACE); 159 #else 160 uaddr = kmem_alloc_pageable(kernel_map, USPACE); 161 #endif 162 if (uaddr == 0) { 163 (void)chgproccnt(uid, -1); 164 return (ENOMEM); 165 } 166 167 /* 168 * We are now committed to the fork. From here on, we may 169 * block on resources, but resource allocation may NOT fail. 170 */ 171 172 /* Allocate new proc. */ 173 newproc = pool_get(&proc_pool, PR_WAITOK); 174 175 /* 176 * Find an unused process ID. We remember a range of unused IDs 177 * ready to use (from nextpid+1 through pidchecked-1). 178 */ 179 nextpid++; 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 (nextpid >= PID_MAX) { 187 nextpid = 100; 188 pidchecked = 0; 189 } 190 if (nextpid >= 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 nextpid, 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 == nextpid || 203 p2->p_pgrp->pg_id == nextpid || 204 p2->p_session->s_sid == nextpid) { 205 nextpid++; 206 if (nextpid >= pidchecked) 207 goto retry; 208 } 209 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 210 pidchecked = p2->p_pid; 211 212 if (p2->p_pgrp->pg_id > nextpid && 213 pidchecked > p2->p_pgrp->pg_id) 214 pidchecked = p2->p_pgrp->pg_id; 215 216 if (p2->p_session->s_sid > nextpid && 217 pidchecked > p2->p_session->s_sid) 218 pidchecked = p2->p_session->s_sid; 219 } 220 if (!doingzomb) { 221 doingzomb = 1; 222 p2 = zombproc.lh_first; 223 goto again; 224 } 225 } 226 227 nprocs++; 228 p2 = newproc; 229 p2->p_stat = SIDL; /* protect against others */ 230 p2->p_pid = nextpid; 231 LIST_INSERT_HEAD(&allproc, p2, p_list); 232 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 233 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 234 235 /* 236 * Make a proc table entry for the new process. 237 * Start by zeroing the section of proc that is zero-initialized, 238 * then copy the section that is copied directly from the parent. 239 */ 240 memset(&p2->p_startzero, 0, 241 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 242 memcpy(&p2->p_startcopy, &p1->p_startcopy, 243 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 244 245 /* 246 * Duplicate sub-structures as needed. 247 * Increase reference counts on shared objects. 248 * The p_stats and p_sigacts substructs are set in vm_fork. 249 */ 250 p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID); 251 p2->p_emul = p1->p_emul; 252 if (p1->p_flag & P_PROFIL) 253 startprofclock(p2); 254 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 255 M_SUBPROC, M_WAITOK); 256 memcpy(p2->p_cred, p1->p_cred, sizeof(*p2->p_cred)); 257 p2->p_cred->p_refcnt = 1; 258 crhold(p1->p_ucred); 259 260 /* bump references to the text vnode (for procfs) */ 261 p2->p_textvp = p1->p_textvp; 262 if (p2->p_textvp) 263 VREF(p2->p_textvp); 264 265 p2->p_fd = fdcopy(p1); 266 /* 267 * If p_limit is still copy-on-write, bump refcnt, 268 * otherwise get a copy that won't be modified. 269 * (If PL_SHAREMOD is clear, the structure is shared 270 * copy-on-write.) 271 */ 272 if (p1->p_limit->p_lflags & PL_SHAREMOD) 273 p2->p_limit = limcopy(p1->p_limit); 274 else { 275 p2->p_limit = p1->p_limit; 276 p2->p_limit->p_refcnt++; 277 } 278 279 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 280 p2->p_flag |= P_CONTROLT; 281 if (flags & FORK_PPWAIT) 282 p2->p_flag |= P_PPWAIT; 283 LIST_INSERT_AFTER(p1, p2, p_pglist); 284 p2->p_pptr = p1; 285 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 286 LIST_INIT(&p2->p_children); 287 288 #ifdef KTRACE 289 /* 290 * Copy traceflag and tracefile if enabled. 291 * If not inherited, these were zeroed above. 292 */ 293 if (p1->p_traceflag&KTRFAC_INHERIT) { 294 p2->p_traceflag = p1->p_traceflag; 295 if ((p2->p_tracep = p1->p_tracep) != NULL) 296 ktradref(p2); 297 } 298 #endif 299 300 /* 301 * This begins the section where we must prevent the parent 302 * from being swapped. 303 */ 304 PHOLD(p1); 305 306 /* 307 * Finish creating the child process. It will return through a 308 * different path later. 309 */ 310 p2->p_addr = (struct user *)uaddr; 311 #if defined(UVM) 312 uvm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 313 #else 314 vm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 315 #endif 316 317 /* 318 * Make child runnable, set start time, and add to run queue. 319 */ 320 (void) splstatclock(); 321 p2->p_stats->p_start = time; 322 p2->p_acflag = AFORK; 323 p2->p_stat = SRUN; 324 setrunqueue(p2); 325 (void) spl0(); 326 327 /* 328 * Now can be swapped. 329 */ 330 PRELE(p1); 331 332 /* 333 * Update stats now that we know the fork was successful. 334 */ 335 #if defined(UVM) 336 uvmexp.forks++; 337 if (flags & FORK_PPWAIT) 338 uvmexp.forks_ppwait++; 339 if (flags & FORK_SHAREVM) 340 uvmexp.forks_sharevm++; 341 #else 342 cnt.v_forks++; 343 if (flags & FORK_PPWAIT) 344 cnt.v_forks_ppwait++; 345 if (flags & FORK_SHAREVM) 346 cnt.v_forks_sharevm++; 347 #endif 348 349 /* 350 * Pass a pointer to the new process to the caller. 351 */ 352 if (rnewprocp != NULL) 353 *rnewprocp = p2; 354 355 /* 356 * Preserve synchronization semantics of vfork. If waiting for 357 * child to exec or exit, set P_PPWAIT on child, and sleep on our 358 * proc (in case of exit). 359 */ 360 if (flags & FORK_PPWAIT) 361 while (p2->p_flag & P_PPWAIT) 362 tsleep(p1, PWAIT, "ppwait", 0); 363 364 /* 365 * Return child pid to parent process, 366 * marking us as parent via retval[1]. 367 */ 368 if (retval != NULL) { 369 retval[0] = p2->p_pid; 370 retval[1] = 0; 371 } 372 return (0); 373 } 374
Indexes created Mon Sep 22 13:09:51 GMT 2025