1 /* $OpenBSD: kern_fork.c,v 1.155 2014/01/20 03:23:42 guenther 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. Neither the name of the University nor the names of its contributors 22 * may be used to endorse or promote products derived from this software 23 * without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 * 37 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 38 */ 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/filedesc.h> 43 #include <sys/kernel.h> 44 #include <sys/malloc.h> 45 #include <sys/mount.h> 46 #include <sys/proc.h> 47 #include <sys/exec.h> 48 #include <sys/resourcevar.h> 49 #include <sys/signalvar.h> 50 #include <sys/vnode.h> 51 #include <sys/file.h> 52 #include <sys/acct.h> 53 #include <sys/ktrace.h> 54 #include <sys/sched.h> 55 #include <dev/rndvar.h> 56 #include <sys/pool.h> 57 #include <sys/mman.h> 58 #include <sys/ptrace.h> 59 60 #include <sys/syscallargs.h> 61 62 #include "systrace.h" 63 #include <dev/systrace.h> 64 65 #include <uvm/uvm_extern.h> 66 #include <uvm/uvm_map.h> 67 68 #ifdef __HAVE_MD_TCB 69 # include <machine/tcb.h> 70 #endif 71 72 int nprocesses = 1; /* process 0 */ 73 int nthreads = 1; /* proc 0 */ 74 int randompid; /* when set to 1, pid's go random */ 75 struct forkstat forkstat; 76 77 void fork_return(void *); 78 void tfork_child_return(void *); 79 int pidtaken(pid_t); 80 81 void process_new(struct proc *, struct process *); 82 83 void 84 fork_return(void *arg) 85 { 86 struct proc *p = (struct proc *)arg; 87 88 if (p->p_p->ps_flags & PS_TRACED) 89 psignal(p, SIGTRAP); 90 91 child_return(p); 92 } 93 94 /*ARGSUSED*/ 95 int 96 sys_fork(struct proc *p, void *v, register_t *retval) 97 { 98 int flags; 99 100 flags = FORK_FORK; 101 if (p->p_p->ps_ptmask & PTRACE_FORK) 102 flags |= FORK_PTRACE; 103 return (fork1(p, SIGCHLD, flags, NULL, 0, 104 fork_return, NULL, retval, NULL)); 105 } 106 107 /*ARGSUSED*/ 108 int 109 sys_vfork(struct proc *p, void *v, register_t *retval) 110 { 111 return (fork1(p, SIGCHLD, FORK_VFORK|FORK_PPWAIT, NULL, 0, NULL, 112 NULL, retval, NULL)); 113 } 114 115 int 116 sys___tfork(struct proc *p, void *v, register_t *retval) 117 { 118 struct sys___tfork_args /* { 119 syscallarg(const struct __tfork) *param; 120 syscallarg(size_t) psize; 121 } */ *uap = v; 122 size_t psize = SCARG(uap, psize); 123 struct __tfork param = { 0 }; 124 int flags; 125 int error; 126 127 if (psize == 0 || psize > sizeof(param)) 128 return (EINVAL); 129 if ((error = copyin(SCARG(uap, param), ¶m, psize))) 130 return (error); 131 #ifdef KTRACE 132 if (KTRPOINT(p, KTR_STRUCT)) 133 ktrstruct(p, "tfork", ¶m, sizeof(param)); 134 #endif 135 136 flags = FORK_TFORK | FORK_THREAD | FORK_SIGHAND | FORK_SHAREVM 137 | FORK_NOZOMBIE | FORK_SHAREFILES; 138 139 return (fork1(p, 0, flags, param.tf_stack, param.tf_tid, 140 tfork_child_return, param.tf_tcb, retval, NULL)); 141 } 142 143 void 144 tfork_child_return(void *arg) 145 { 146 struct proc *p = curproc; 147 148 TCB_SET(p, arg); 149 child_return(p); 150 } 151 152 /* 153 * Allocate and initialize a new process. 154 */ 155 void 156 process_new(struct proc *p, struct process *parent) 157 { 158 struct process *pr; 159 160 pr = pool_get(&process_pool, PR_WAITOK); 161 pr->ps_mainproc = p; 162 163 TAILQ_INIT(&pr->ps_threads); 164 TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); 165 pr->ps_pptr = parent; 166 LIST_INIT(&pr->ps_children); 167 pr->ps_refcnt = 1; 168 169 /* 170 * Make a process structure for the new process. 171 * Start by zeroing the section of proc that is zero-initialized, 172 * then copy the section that is copied directly from the parent. 173 */ 174 memset(&pr->ps_startzero, 0, 175 (caddr_t)&pr->ps_endzero - (caddr_t)&pr->ps_startzero); 176 memcpy(&pr->ps_startcopy, &parent->ps_startcopy, 177 (caddr_t)&pr->ps_endcopy - (caddr_t)&pr->ps_startcopy); 178 179 /* post-copy fixups */ 180 pr->ps_cred = pool_get(&pcred_pool, PR_WAITOK); 181 memcpy(pr->ps_cred, parent->ps_cred, sizeof(*pr->ps_cred)); 182 crhold(parent->ps_cred->pc_ucred); 183 pr->ps_limit->p_refcnt++; 184 185 /* bump references to the text vnode (for procfs) */ 186 pr->ps_textvp = parent->ps_textvp; 187 if (pr->ps_textvp) 188 vref(pr->ps_textvp); 189 190 timeout_set(&pr->ps_realit_to, realitexpire, pr); 191 192 pr->ps_flags = parent->ps_flags & (PS_SUGID | PS_SUGIDEXEC); 193 if (parent->ps_session->s_ttyvp != NULL && 194 parent->ps_flags & PS_CONTROLT) 195 atomic_setbits_int(&pr->ps_flags, PS_CONTROLT); 196 197 p->p_p = pr; 198 } 199 200 /* print the 'table full' message once per 10 seconds */ 201 struct timeval fork_tfmrate = { 10, 0 }; 202 203 int 204 fork1(struct proc *curp, int exitsig, int flags, void *stack, pid_t *tidptr, 205 void (*func)(void *), void *arg, register_t *retval, 206 struct proc **rnewprocp) 207 { 208 struct process *curpr = curp->p_p; 209 struct process *pr; 210 struct proc *p; 211 uid_t uid; 212 struct vmspace *vm; 213 int count; 214 vaddr_t uaddr; 215 int s; 216 struct ptrace_state *newptstat = NULL; 217 #if NSYSTRACE > 0 218 void *newstrp = NULL; 219 #endif 220 221 /* sanity check some flag combinations */ 222 if (flags & FORK_THREAD) { 223 if ((flags & (FORK_SIGHAND | FORK_NOZOMBIE)) != 224 (FORK_SIGHAND | FORK_NOZOMBIE)) 225 return (EINVAL); 226 } 227 if (flags & FORK_SIGHAND && (flags & FORK_SHAREVM) == 0) 228 return (EINVAL); 229 230 /* 231 * Although process entries are dynamically created, we still keep 232 * a global limit on the maximum number we will create. We reserve 233 * the last 5 processes to root. The variable nprocesses is the 234 * current number of processes, maxprocess is the limit. Similar 235 * rules for threads (struct proc): we reserve the last 5 to root; 236 * the variable nthreads is the current number of procs, maxthread is 237 * the limit. 238 */ 239 uid = curp->p_cred->p_ruid; 240 if ((nthreads >= maxthread - 5 && uid != 0) || nthreads >= maxthread) { 241 static struct timeval lasttfm; 242 243 if (ratecheck(&lasttfm, &fork_tfmrate)) 244 tablefull("proc"); 245 return (EAGAIN); 246 } 247 nthreads++; 248 249 if ((flags & FORK_THREAD) == 0) { 250 if ((nprocesses >= maxprocess - 5 && uid != 0) || 251 nprocesses >= maxprocess) { 252 static struct timeval lasttfm; 253 254 if (ratecheck(&lasttfm, &fork_tfmrate)) 255 tablefull("process"); 256 nthreads--; 257 return (EAGAIN); 258 } 259 nprocesses++; 260 261 /* 262 * Increment the count of processes running with 263 * this uid. Don't allow a nonprivileged user to 264 * exceed their current limit. 265 */ 266 count = chgproccnt(uid, 1); 267 if (uid != 0 && count > curp->p_rlimit[RLIMIT_NPROC].rlim_cur) { 268 (void)chgproccnt(uid, -1); 269 nprocesses--; 270 nthreads--; 271 return (EAGAIN); 272 } 273 } 274 275 uaddr = uvm_km_kmemalloc_pla(kernel_map, uvm.kernel_object, USPACE, 276 USPACE_ALIGN, UVM_KMF_ZERO, 277 no_constraint.ucr_low, no_constraint.ucr_high, 278 0, 0, USPACE/PAGE_SIZE); 279 if (uaddr == 0) { 280 if ((flags & FORK_THREAD) == 0) { 281 (void)chgproccnt(uid, -1); 282 nprocesses--; 283 } 284 nthreads--; 285 return (ENOMEM); 286 } 287 288 /* 289 * From now on, we're committed to the fork and cannot fail. 290 */ 291 292 /* Allocate new proc. */ 293 p = pool_get(&proc_pool, PR_WAITOK); 294 295 p->p_stat = SIDL; /* protect against others */ 296 p->p_exitsig = exitsig; 297 p->p_flag = 0; 298 p->p_xstat = 0; 299 300 if (flags & FORK_THREAD) { 301 atomic_setbits_int(&p->p_flag, P_THREAD); 302 p->p_p = pr = curpr; 303 pr->ps_refcnt++; 304 } else { 305 process_new(p, curpr); 306 pr = p->p_p; 307 } 308 309 /* 310 * Make a proc table entry for the new process. 311 * Start by zeroing the section of proc that is zero-initialized, 312 * then copy the section that is copied directly from the parent. 313 */ 314 memset(&p->p_startzero, 0, 315 (caddr_t)&p->p_endzero - (caddr_t)&p->p_startzero); 316 memcpy(&p->p_startcopy, &curp->p_startcopy, 317 (caddr_t)&p->p_endcopy - (caddr_t)&p->p_startcopy); 318 319 /* 320 * Initialize the timeouts. 321 */ 322 timeout_set(&p->p_sleep_to, endtsleep, p); 323 324 /* 325 * Duplicate sub-structures as needed. 326 * Increase reference counts on shared objects. 327 */ 328 if ((flags & FORK_THREAD) == 0) { 329 if (curpr->ps_flags & PS_PROFIL) 330 startprofclock(pr); 331 if ((flags & FORK_PTRACE) && (curpr->ps_flags & PS_TRACED)) 332 atomic_setbits_int(&pr->ps_flags, PS_TRACED); 333 } 334 335 if (flags & FORK_SHAREFILES) 336 p->p_fd = fdshare(curp); 337 else 338 p->p_fd = fdcopy(curp); 339 340 if (flags & FORK_PPWAIT) { 341 atomic_setbits_int(&pr->ps_flags, PS_PPWAIT); 342 atomic_setbits_int(&curpr->ps_flags, PS_ISPWAIT); 343 } 344 if (flags & FORK_NOZOMBIE) 345 atomic_setbits_int(&p->p_flag, P_NOZOMBIE); 346 347 #ifdef KTRACE 348 /* 349 * Copy traceflag and tracefile if enabled. 350 * If not inherited, these were zeroed above. 351 */ 352 if ((flags & FORK_THREAD) == 0 && curpr->ps_traceflag & KTRFAC_INHERIT) 353 ktrsettrace(pr, curpr->ps_traceflag, curpr->ps_tracevp, 354 curpr->ps_tracecred); 355 #endif 356 357 /* 358 * set priority of child to be that of parent 359 * XXX should move p_estcpu into the region of struct proc which gets 360 * copied. 361 */ 362 scheduler_fork_hook(curp, p); 363 364 /* 365 * Create signal actions for the child process. 366 */ 367 if (flags & FORK_SIGHAND) 368 p->p_sigacts = sigactsshare(curp); 369 else 370 p->p_sigacts = sigactsinit(curp); 371 if (flags & FORK_THREAD) 372 sigstkinit(&p->p_sigstk); 373 374 /* 375 * If emulation has process fork hook, call it now. 376 */ 377 if (p->p_emul->e_proc_fork) 378 (*p->p_emul->e_proc_fork)(p, curp); 379 380 p->p_addr = (struct user *)uaddr; 381 382 /* 383 * Finish creating the child process. It will return through a 384 * different path later. 385 */ 386 uvm_fork(curp, p, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack, 387 0, func ? func : child_return, arg ? arg : p); 388 389 vm = p->p_vmspace; 390 391 if (flags & FORK_FORK) { 392 forkstat.cntfork++; 393 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 394 } else if (flags & FORK_VFORK) { 395 forkstat.cntvfork++; 396 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 397 } else if (flags & FORK_TFORK) { 398 forkstat.cnttfork++; 399 } else { 400 forkstat.cntkthread++; 401 forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize; 402 } 403 404 if (pr->ps_flags & PS_TRACED && flags & FORK_FORK) 405 newptstat = malloc(sizeof(*newptstat), M_SUBPROC, M_WAITOK); 406 #if NSYSTRACE > 0 407 if (ISSET(curp->p_flag, P_SYSTRACE)) 408 newstrp = systrace_getproc(); 409 #endif 410 411 p->p_pid = allocpid(); 412 413 LIST_INSERT_HEAD(&allproc, p, p_list); 414 LIST_INSERT_HEAD(PIDHASH(p->p_pid), p, p_hash); 415 if ((flags & FORK_THREAD) == 0) { 416 LIST_INSERT_AFTER(curpr, pr, ps_pglist); 417 LIST_INSERT_HEAD(&curpr->ps_children, pr, ps_sibling); 418 419 if (pr->ps_flags & PS_TRACED) { 420 pr->ps_oppid = curpr->ps_pid; 421 if (pr->ps_pptr != curpr->ps_pptr) 422 proc_reparent(pr, curpr->ps_pptr); 423 424 /* 425 * Set ptrace status. 426 */ 427 if (flags & FORK_FORK) { 428 pr->ps_ptstat = newptstat; 429 newptstat = NULL; 430 curpr->ps_ptstat->pe_report_event = PTRACE_FORK; 431 pr->ps_ptstat->pe_report_event = PTRACE_FORK; 432 curpr->ps_ptstat->pe_other_pid = pr->ps_pid; 433 pr->ps_ptstat->pe_other_pid = curpr->ps_pid; 434 } 435 } 436 } else { 437 TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); 438 /* 439 * if somebody else wants to take us to single threaded mode, 440 * count ourselves in. 441 */ 442 if (pr->ps_single) { 443 curpr->ps_singlecount++; 444 atomic_setbits_int(&p->p_flag, P_SUSPSINGLE); 445 } 446 } 447 448 #if NSYSTRACE > 0 449 if (newstrp) 450 systrace_fork(curp, p, newstrp); 451 #endif 452 453 if (tidptr != NULL) { 454 pid_t pid = p->p_pid + THREAD_PID_OFFSET; 455 456 if (copyout(&pid, tidptr, sizeof(pid))) 457 psignal(curp, SIGSEGV); 458 } 459 460 /* 461 * For new processes, set accounting bits 462 */ 463 if ((flags & FORK_THREAD) == 0) { 464 getnanotime(&pr->ps_start); 465 pr->ps_acflag = AFORK; 466 } 467 468 /* 469 * Make child runnable and add to run queue. 470 */ 471 if ((flags & FORK_IDLE) == 0) { 472 SCHED_LOCK(s); 473 p->p_stat = SRUN; 474 p->p_cpu = sched_choosecpu_fork(curp, flags); 475 setrunqueue(p); 476 SCHED_UNLOCK(s); 477 } else 478 p->p_cpu = arg; 479 480 if (newptstat) 481 free(newptstat, M_SUBPROC); 482 483 /* 484 * Notify any interested parties about the new process. 485 */ 486 if ((flags & FORK_THREAD) == 0) 487 KNOTE(&curpr->ps_klist, NOTE_FORK | p->p_pid); 488 489 /* 490 * Update stats now that we know the fork was successful. 491 */ 492 uvmexp.forks++; 493 if (flags & FORK_PPWAIT) 494 uvmexp.forks_ppwait++; 495 if (flags & FORK_SHAREVM) 496 uvmexp.forks_sharevm++; 497 498 /* 499 * Pass a pointer to the new process to the caller. 500 */ 501 if (rnewprocp != NULL) 502 *rnewprocp = p; 503 504 /* 505 * Preserve synchronization semantics of vfork. If waiting for 506 * child to exec or exit, set PS_PPWAIT on child and PS_ISPWAIT 507 * on ourselves, and sleep on our process for the latter flag 508 * to go away. 509 * XXX Need to stop other rthreads in the parent 510 */ 511 if (flags & FORK_PPWAIT) 512 while (curpr->ps_flags & PS_ISPWAIT) 513 tsleep(curpr, PWAIT, "ppwait", 0); 514 515 /* 516 * If we're tracing the child, alert the parent too. 517 */ 518 if ((flags & FORK_PTRACE) && (curpr->ps_flags & PS_TRACED)) 519 psignal(curp, SIGTRAP); 520 521 /* 522 * Return child pid to parent process, 523 * marking us as parent via retval[1]. 524 */ 525 if (retval != NULL) { 526 retval[0] = p->p_pid + 527 (flags & FORK_THREAD ? THREAD_PID_OFFSET : 0); 528 retval[1] = 0; 529 } 530 return (0); 531 } 532 533 /* 534 * Checks for current use of a pid, either as a pid or pgid. 535 */ 536 pid_t oldpids[100]; 537 int 538 ispidtaken(pid_t pid) 539 { 540 uint32_t i; 541 struct proc *p; 542 543 for (i = 0; i < nitems(oldpids); i++) 544 if (pid == oldpids[i]) 545 return (1); 546 547 if (pfind(pid) != NULL) 548 return (1); 549 if (pgfind(pid) != NULL) 550 return (1); 551 LIST_FOREACH(p, &zombproc, p_list) { 552 if (p->p_pid == pid || 553 (p->p_p->ps_pgrp && p->p_p->ps_pgrp->pg_id == pid)) 554 return (1); 555 } 556 return (0); 557 } 558 559 /* Find an unused pid satisfying 1 <= lastpid <= PID_MAX */ 560 pid_t 561 allocpid(void) 562 { 563 static pid_t lastpid; 564 pid_t pid; 565 566 if (!randompid) { 567 /* only used early on for system processes */ 568 pid = ++lastpid; 569 } else { 570 do { 571 pid = 1 + arc4random_uniform(PID_MAX - 1); 572 } while (ispidtaken(pid)); 573 } 574 575 return pid; 576 } 577 578 void 579 freepid(pid_t pid) 580 { 581 static uint32_t idx; 582 583 oldpids[idx++ % nitems(oldpids)] = pid; 584 } 585 586 #if defined(MULTIPROCESSOR) 587 /* 588 * XXX This is a slight hack to get newly-formed processes to 589 * XXX acquire the kernel lock as soon as they run. 590 */ 591 void 592 proc_trampoline_mp(void) 593 { 594 struct proc *p; 595 596 p = curproc; 597 598 SCHED_ASSERT_LOCKED(); 599 __mp_unlock(&sched_lock); 600 spl0(); 601 SCHED_ASSERT_UNLOCKED(); 602 KASSERT(__mp_lock_held(&kernel_lock) == 0); 603 604 KERNEL_LOCK(); 605 } 606 #endif 607