1 /* $OpenBSD: kern_fork.c,v 1.265 2024/08/21 03:07:45 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. 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/malloc.h> 44 #include <sys/mount.h> 45 #include <sys/proc.h> 46 #include <sys/resourcevar.h> 47 #include <sys/signalvar.h> 48 #include <sys/vnode.h> 49 #include <sys/vmmeter.h> 50 #include <sys/acct.h> 51 #include <sys/ktrace.h> 52 #include <sys/sched.h> 53 #include <sys/smr.h> 54 #include <sys/sysctl.h> 55 #include <sys/pool.h> 56 #include <sys/mman.h> 57 #include <sys/ptrace.h> 58 #include <sys/atomic.h> 59 #include <sys/unistd.h> 60 #include <sys/tracepoint.h> 61 62 #include <sys/syscallargs.h> 63 64 #include <uvm/uvm.h> 65 #include <machine/tcb.h> 66 67 int nprocesses = 1; /* process 0 */ 68 int nthreads = 1; /* [a] proc 0 */ 69 struct forkstat forkstat; 70 71 void fork_return(void *); 72 pid_t alloctid(void); 73 pid_t allocpid(void); 74 int ispidtaken(pid_t); 75 76 void unveil_copy(struct process *parent, struct process *child); 77 78 struct proc *thread_new(struct proc *_parent, vaddr_t _uaddr); 79 struct process *process_new(struct proc *, struct process *, int); 80 int fork_check_maxthread(uid_t _uid); 81 82 void 83 fork_return(void *arg) 84 { 85 struct proc *p = (struct proc *)arg; 86 87 if (p->p_p->ps_flags & PS_TRACED) 88 psignal(p, SIGTRAP); 89 90 child_return(p); 91 } 92 93 int 94 sys_fork(struct proc *p, void *v, register_t *retval) 95 { 96 void (*func)(void *) = child_return; 97 int flags; 98 99 flags = FORK_FORK; 100 if (p->p_p->ps_ptmask & PTRACE_FORK) { 101 flags |= FORK_PTRACE; 102 func = fork_return; 103 } 104 return fork1(p, flags, func, NULL, retval, NULL); 105 } 106 107 int 108 sys_vfork(struct proc *p, void *v, register_t *retval) 109 { 110 return fork1(p, FORK_VFORK|FORK_PPWAIT, child_return, NULL, 111 retval, NULL); 112 } 113 114 int 115 sys___tfork(struct proc *p, void *v, register_t *retval) 116 { 117 struct sys___tfork_args /* { 118 syscallarg(const struct __tfork) *param; 119 syscallarg(size_t) psize; 120 } */ *uap = v; 121 size_t psize = SCARG(uap, psize); 122 struct __tfork param = { 0 }; 123 int error; 124 125 if (psize == 0 || psize > sizeof(param)) 126 return EINVAL; 127 if ((error = copyin(SCARG(uap, param), ¶m, psize))) 128 return error; 129 #ifdef KTRACE 130 if (KTRPOINT(p, KTR_STRUCT)) 131 ktrstruct(p, "tfork", ¶m, sizeof(param)); 132 #endif 133 #ifdef TCB_INVALID 134 if (TCB_INVALID(param.tf_tcb)) 135 return EINVAL; 136 #endif /* TCB_INVALID */ 137 138 return thread_fork(p, param.tf_stack, param.tf_tcb, param.tf_tid, 139 retval); 140 } 141 142 /* 143 * Allocate and initialize a thread (proc) structure, given the parent thread. 144 */ 145 struct proc * 146 thread_new(struct proc *parent, vaddr_t uaddr) 147 { 148 struct proc *p; 149 150 p = pool_get(&proc_pool, PR_WAITOK); 151 p->p_stat = SIDL; /* protect against others */ 152 p->p_runpri = 0; 153 p->p_flag = 0; 154 155 /* 156 * Make a proc table entry for the new process. 157 * Start by zeroing the section of proc that is zero-initialized, 158 * then copy the section that is copied directly from the parent. 159 */ 160 memset(&p->p_startzero, 0, 161 (caddr_t)&p->p_endzero - (caddr_t)&p->p_startzero); 162 memcpy(&p->p_startcopy, &parent->p_startcopy, 163 (caddr_t)&p->p_endcopy - (caddr_t)&p->p_startcopy); 164 crhold(p->p_ucred); 165 p->p_addr = (struct user *)uaddr; 166 167 /* 168 * Initialize the timeouts. 169 */ 170 timeout_set(&p->p_sleep_to, endtsleep, p); 171 172 return p; 173 } 174 175 /* 176 * Initialize common bits of a process structure, given the initial thread. 177 */ 178 void 179 process_initialize(struct process *pr, struct proc *p) 180 { 181 refcnt_init(&pr->ps_refcnt); 182 183 /* initialize the thread links */ 184 pr->ps_mainproc = p; 185 TAILQ_INIT(&pr->ps_threads); 186 TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); 187 pr->ps_threadcnt = 1; 188 p->p_p = pr; 189 190 /* give the process the same creds as the initial thread */ 191 pr->ps_ucred = p->p_ucred; 192 crhold(pr->ps_ucred); 193 /* new thread and new process */ 194 KASSERT(p->p_ucred->cr_refcnt.r_refs >= 2); 195 196 LIST_INIT(&pr->ps_children); 197 LIST_INIT(&pr->ps_orphans); 198 LIST_INIT(&pr->ps_ftlist); 199 LIST_INIT(&pr->ps_sigiolst); 200 TAILQ_INIT(&pr->ps_tslpqueue); 201 202 rw_init(&pr->ps_lock, "pslock"); 203 mtx_init(&pr->ps_mtx, IPL_HIGH); 204 klist_init_mutex(&pr->ps_klist, &pr->ps_mtx); 205 206 timeout_set_flags(&pr->ps_realit_to, realitexpire, pr, 207 KCLOCK_UPTIME, 0); 208 timeout_set(&pr->ps_rucheck_to, rucheck, pr); 209 } 210 211 212 /* 213 * Allocate and initialize a new process. 214 */ 215 struct process * 216 process_new(struct proc *p, struct process *parent, int flags) 217 { 218 struct process *pr; 219 220 pr = pool_get(&process_pool, PR_WAITOK); 221 222 /* 223 * Make a process structure for the new process. 224 * Start by zeroing the section of proc that is zero-initialized, 225 * then copy the section that is copied directly from the parent. 226 */ 227 memset(&pr->ps_startzero, 0, 228 (caddr_t)&pr->ps_endzero - (caddr_t)&pr->ps_startzero); 229 memcpy(&pr->ps_startcopy, &parent->ps_startcopy, 230 (caddr_t)&pr->ps_endcopy - (caddr_t)&pr->ps_startcopy); 231 232 process_initialize(pr, p); 233 pr->ps_pid = allocpid(); 234 lim_fork(parent, pr); 235 236 /* post-copy fixups */ 237 pr->ps_pptr = parent; 238 pr->ps_ppid = parent->ps_pid; 239 240 /* bump references to the text vnode (for sysctl) */ 241 pr->ps_textvp = parent->ps_textvp; 242 if (pr->ps_textvp) 243 vref(pr->ps_textvp); 244 245 /* copy unveil if unveil is active */ 246 unveil_copy(parent, pr); 247 248 pr->ps_flags = parent->ps_flags & 249 (PS_SUGID | PS_SUGIDEXEC | PS_PLEDGE | PS_EXECPLEDGE | 250 PS_WXNEEDED | PS_CHROOT); 251 if (parent->ps_session->s_ttyvp != NULL) 252 pr->ps_flags |= parent->ps_flags & PS_CONTROLT; 253 254 if (parent->ps_pin.pn_pins) { 255 pr->ps_pin.pn_pins = mallocarray(parent->ps_pin.pn_npins, 256 sizeof(u_int), M_PINSYSCALL, M_WAITOK); 257 memcpy(pr->ps_pin.pn_pins, parent->ps_pin.pn_pins, 258 parent->ps_pin.pn_npins * sizeof(u_int)); 259 } 260 if (parent->ps_libcpin.pn_pins) { 261 pr->ps_libcpin.pn_pins = mallocarray(parent->ps_libcpin.pn_npins, 262 sizeof(u_int), M_PINSYSCALL, M_WAITOK); 263 memcpy(pr->ps_libcpin.pn_pins, parent->ps_libcpin.pn_pins, 264 parent->ps_libcpin.pn_npins * sizeof(u_int)); 265 } 266 267 /* 268 * Duplicate sub-structures as needed. 269 * Increase reference counts on shared objects. 270 */ 271 if (flags & FORK_SHAREFILES) 272 pr->ps_fd = fdshare(parent); 273 else 274 pr->ps_fd = fdcopy(parent); 275 pr->ps_sigacts = sigactsinit(parent); 276 if (flags & FORK_SHAREVM) 277 pr->ps_vmspace = uvmspace_share(parent); 278 else 279 pr->ps_vmspace = uvmspace_fork(parent); 280 281 if (parent->ps_flags & PS_PROFIL) 282 startprofclock(pr); 283 if (flags & FORK_PTRACE) 284 pr->ps_flags |= parent->ps_flags & PS_TRACED; 285 if (flags & FORK_NOZOMBIE) 286 pr->ps_flags |= PS_NOZOMBIE; 287 if (flags & FORK_SYSTEM) 288 pr->ps_flags |= PS_SYSTEM; 289 290 /* mark as embryo to protect against others */ 291 pr->ps_flags |= PS_EMBRYO; 292 293 /* Force visibility of all of the above changes */ 294 membar_producer(); 295 296 /* it's sufficiently inited to be globally visible */ 297 LIST_INSERT_HEAD(&allprocess, pr, ps_list); 298 299 return pr; 300 } 301 302 /* print the 'table full' message once per 10 seconds */ 303 struct timeval fork_tfmrate = { 10, 0 }; 304 305 int 306 fork_check_maxthread(uid_t uid) 307 { 308 int maxthread_local, val; 309 310 /* 311 * Although process entries are dynamically created, we still keep 312 * a global limit on the maximum number we will create. We reserve 313 * the last 5 processes to root. The variable nprocesses is the 314 * current number of processes, maxprocess is the limit. Similar 315 * rules for threads (struct proc): we reserve the last 5 to root; 316 * the variable nthreads is the current number of procs, maxthread is 317 * the limit. 318 */ 319 maxthread_local = atomic_load_int(&maxthread); 320 val = atomic_inc_int_nv(&nthreads); 321 if ((val > maxthread_local - 5 && uid != 0) || 322 val > maxthread_local) { 323 static struct timeval lasttfm; 324 325 if (ratecheck(&lasttfm, &fork_tfmrate)) 326 tablefull("thread"); 327 atomic_dec_int(&nthreads); 328 return EAGAIN; 329 } 330 331 return 0; 332 } 333 334 static inline void 335 fork_thread_start(struct proc *p, struct proc *parent, int flags) 336 { 337 struct cpu_info *ci; 338 339 SCHED_LOCK(); 340 ci = sched_choosecpu_fork(parent, flags); 341 TRACEPOINT(sched, fork, p->p_tid + THREAD_PID_OFFSET, 342 p->p_p->ps_pid, CPU_INFO_UNIT(ci)); 343 setrunqueue(ci, p, p->p_usrpri); 344 SCHED_UNLOCK(); 345 } 346 347 int 348 fork1(struct proc *curp, int flags, void (*func)(void *), void *arg, 349 register_t *retval, struct proc **rnewprocp) 350 { 351 struct process *curpr = curp->p_p; 352 struct process *pr; 353 struct proc *p; 354 uid_t uid = curp->p_ucred->cr_ruid; 355 struct vmspace *vm; 356 int count, maxprocess_local; 357 vaddr_t uaddr; 358 int error; 359 struct ptrace_state *newptstat = NULL; 360 361 KASSERT((flags & ~(FORK_FORK | FORK_VFORK | FORK_PPWAIT | FORK_PTRACE 362 | FORK_IDLE | FORK_SHAREVM | FORK_SHAREFILES | FORK_NOZOMBIE 363 | FORK_SYSTEM)) == 0); 364 KASSERT(func != NULL); 365 366 if ((error = fork_check_maxthread(uid))) 367 return error; 368 369 maxprocess_local = atomic_load_int(&maxprocess); 370 if ((nprocesses >= maxprocess_local - 5 && uid != 0) || 371 nprocesses >= maxprocess_local) { 372 static struct timeval lasttfm; 373 374 if (ratecheck(&lasttfm, &fork_tfmrate)) 375 tablefull("process"); 376 atomic_dec_int(&nthreads); 377 return EAGAIN; 378 } 379 nprocesses++; 380 381 /* 382 * Increment the count of processes running with this uid. 383 * Don't allow a nonprivileged user to exceed their current limit. 384 */ 385 count = chgproccnt(uid, 1); 386 if (uid != 0 && count > lim_cur(RLIMIT_NPROC)) { 387 (void)chgproccnt(uid, -1); 388 nprocesses--; 389 atomic_dec_int(&nthreads); 390 return EAGAIN; 391 } 392 393 uaddr = uvm_uarea_alloc(); 394 if (uaddr == 0) { 395 (void)chgproccnt(uid, -1); 396 nprocesses--; 397 atomic_dec_int(&nthreads); 398 return (ENOMEM); 399 } 400 401 /* 402 * From now on, we're committed to the fork and cannot fail. 403 */ 404 p = thread_new(curp, uaddr); 405 pr = process_new(p, curpr, flags); 406 407 p->p_fd = pr->ps_fd; 408 p->p_vmspace = pr->ps_vmspace; 409 if (pr->ps_flags & PS_SYSTEM) 410 atomic_setbits_int(&p->p_flag, P_SYSTEM); 411 412 if (flags & FORK_PPWAIT) { 413 atomic_setbits_int(&pr->ps_flags, PS_PPWAIT); 414 atomic_setbits_int(&curpr->ps_flags, PS_ISPWAIT); 415 } 416 417 #ifdef KTRACE 418 /* 419 * Copy traceflag and tracefile if enabled. 420 * If not inherited, these were zeroed above. 421 */ 422 if (curpr->ps_traceflag & KTRFAC_INHERIT) 423 ktrsettrace(pr, curpr->ps_traceflag, curpr->ps_tracevp, 424 curpr->ps_tracecred); 425 #endif 426 427 /* 428 * Finish creating the child thread. cpu_fork() will copy 429 * and update the pcb and make the child ready to run. If 430 * this is a normal user fork, the child will exit directly 431 * to user mode via child_return() on its first time slice 432 * and will not return here. If this is a kernel thread, 433 * the specified entry point will be executed. 434 */ 435 cpu_fork(curp, p, NULL, NULL, func, arg ? arg : p); 436 437 vm = pr->ps_vmspace; 438 439 if (flags & FORK_FORK) { 440 forkstat.cntfork++; 441 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 442 } else if (flags & FORK_VFORK) { 443 forkstat.cntvfork++; 444 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 445 } else { 446 forkstat.cntkthread++; 447 } 448 449 if (pr->ps_flags & PS_TRACED && flags & FORK_FORK) 450 newptstat = malloc(sizeof(*newptstat), M_SUBPROC, M_WAITOK); 451 452 p->p_tid = alloctid(); 453 454 LIST_INSERT_HEAD(&allproc, p, p_list); 455 LIST_INSERT_HEAD(TIDHASH(p->p_tid), p, p_hash); 456 LIST_INSERT_HEAD(PIDHASH(pr->ps_pid), pr, ps_hash); 457 LIST_INSERT_AFTER(curpr, pr, ps_pglist); 458 LIST_INSERT_HEAD(&curpr->ps_children, pr, ps_sibling); 459 460 if (pr->ps_flags & PS_TRACED) { 461 pr->ps_oppid = curpr->ps_pid; 462 process_reparent(pr, curpr->ps_pptr); 463 464 /* 465 * Set ptrace status. 466 */ 467 if (newptstat != NULL) { 468 pr->ps_ptstat = newptstat; 469 newptstat = NULL; 470 curpr->ps_ptstat->pe_report_event = PTRACE_FORK; 471 pr->ps_ptstat->pe_report_event = PTRACE_FORK; 472 curpr->ps_ptstat->pe_other_pid = pr->ps_pid; 473 pr->ps_ptstat->pe_other_pid = curpr->ps_pid; 474 } 475 } 476 477 /* 478 * For new processes, set accounting bits and mark as complete. 479 */ 480 nanouptime(&pr->ps_start); 481 pr->ps_acflag = AFORK; 482 atomic_clearbits_int(&pr->ps_flags, PS_EMBRYO); 483 484 if ((flags & FORK_IDLE) == 0) 485 fork_thread_start(p, curp, flags); 486 else 487 p->p_cpu = arg; 488 489 free(newptstat, M_SUBPROC, sizeof(*newptstat)); 490 491 /* 492 * Notify any interested parties about the new process. 493 */ 494 knote_processfork(curpr, pr->ps_pid); 495 496 /* 497 * Update stats now that we know the fork was successful. 498 */ 499 uvmexp.forks++; 500 if (flags & FORK_PPWAIT) 501 uvmexp.forks_ppwait++; 502 if (flags & FORK_SHAREVM) 503 uvmexp.forks_sharevm++; 504 505 /* 506 * Pass a pointer to the new process to the caller. 507 */ 508 if (rnewprocp != NULL) 509 *rnewprocp = p; 510 511 /* 512 * Preserve synchronization semantics of vfork. If waiting for 513 * child to exec or exit, set PS_PPWAIT on child and PS_ISPWAIT 514 * on ourselves, and sleep on our process for the latter flag 515 * to go away. 516 * XXX Need to stop other rthreads in the parent 517 */ 518 if (flags & FORK_PPWAIT) 519 while (curpr->ps_flags & PS_ISPWAIT) 520 tsleep_nsec(curpr, PWAIT, "ppwait", INFSLP); 521 522 /* 523 * If we're tracing the child, alert the parent too. 524 */ 525 if ((flags & FORK_PTRACE) && (curpr->ps_flags & PS_TRACED)) 526 psignal(curp, SIGTRAP); 527 528 /* 529 * Return child pid to parent process 530 */ 531 if (retval != NULL) 532 *retval = pr->ps_pid; 533 return (0); 534 } 535 536 int 537 thread_fork(struct proc *curp, void *stack, void *tcb, pid_t *tidptr, 538 register_t *retval) 539 { 540 struct process *pr = curp->p_p; 541 struct proc *p; 542 pid_t tid; 543 vaddr_t uaddr; 544 int error; 545 546 if (stack == NULL) 547 return EINVAL; 548 549 if ((error = fork_check_maxthread(curp->p_ucred->cr_ruid))) 550 return error; 551 552 uaddr = uvm_uarea_alloc(); 553 if (uaddr == 0) { 554 atomic_dec_int(&nthreads); 555 return ENOMEM; 556 } 557 558 /* 559 * From now on, we're committed to the fork and cannot fail. 560 */ 561 p = thread_new(curp, uaddr); 562 atomic_setbits_int(&p->p_flag, P_THREAD); 563 sigstkinit(&p->p_sigstk); 564 memset(p->p_name, 0, sizeof p->p_name); 565 566 /* other links */ 567 p->p_p = pr; 568 569 /* local copies */ 570 p->p_fd = pr->ps_fd; 571 p->p_vmspace = pr->ps_vmspace; 572 573 /* 574 * Finish creating the child thread. cpu_fork() will copy 575 * and update the pcb and make the child ready to run. The 576 * child will exit directly to user mode via child_return() 577 * on its first time slice and will not return here. 578 */ 579 cpu_fork(curp, p, stack, tcb, child_return, p); 580 581 p->p_tid = alloctid(); 582 583 LIST_INSERT_HEAD(&allproc, p, p_list); 584 LIST_INSERT_HEAD(TIDHASH(p->p_tid), p, p_hash); 585 586 mtx_enter(&pr->ps_mtx); 587 TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); 588 pr->ps_threadcnt++; 589 590 /* 591 * if somebody else wants to take us to single threaded mode, 592 * count ourselves in. 593 */ 594 if (pr->ps_single) { 595 pr->ps_singlecnt++; 596 atomic_setbits_int(&p->p_flag, P_SUSPSINGLE); 597 } 598 mtx_leave(&pr->ps_mtx); 599 600 /* 601 * Return tid to parent thread and copy it out to userspace 602 */ 603 *retval = tid = p->p_tid + THREAD_PID_OFFSET; 604 if (tidptr != NULL) { 605 if (copyout(&tid, tidptr, sizeof(tid))) 606 psignal(curp, SIGSEGV); 607 } 608 609 fork_thread_start(p, curp, 0); 610 611 /* 612 * Update stats now that we know the fork was successful. 613 */ 614 forkstat.cnttfork++; 615 uvmexp.forks++; 616 uvmexp.forks_sharevm++; 617 618 return 0; 619 } 620 621 622 /* Find an unused tid */ 623 pid_t 624 alloctid(void) 625 { 626 pid_t tid; 627 628 do { 629 /* (0 .. TID_MASK+1] */ 630 tid = 1 + (arc4random() & TID_MASK); 631 } while (tfind(tid) != NULL); 632 633 return (tid); 634 } 635 636 /* 637 * Checks for current use of a pid, either as a pid or pgid. 638 */ 639 pid_t oldpids[128]; 640 int 641 ispidtaken(pid_t pid) 642 { 643 uint32_t i; 644 645 for (i = 0; i < nitems(oldpids); i++) 646 if (pid == oldpids[i]) 647 return (1); 648 649 if (prfind(pid) != NULL) 650 return (1); 651 if (pgfind(pid) != NULL) 652 return (1); 653 if (zombiefind(pid) != NULL) 654 return (1); 655 return (0); 656 } 657 658 /* Find an unused pid */ 659 pid_t 660 allocpid(void) 661 { 662 static int first = 1; 663 pid_t pid; 664 665 /* The first PID allocated is always 1. */ 666 if (first) { 667 first = 0; 668 return 1; 669 } 670 671 /* 672 * All subsequent PIDs are chosen randomly. We need to 673 * find an unused PID in the range [2, PID_MAX]. 674 */ 675 do { 676 pid = 2 + arc4random_uniform(PID_MAX - 1); 677 } while (ispidtaken(pid)); 678 return pid; 679 } 680 681 void 682 freepid(pid_t pid) 683 { 684 static uint32_t idx; 685 686 oldpids[idx++ % nitems(oldpids)] = pid; 687 } 688 689 /* Do machine independent parts of switching to a new process */ 690 void 691 proc_trampoline_mi(void) 692 { 693 struct schedstate_percpu *spc = &curcpu()->ci_schedstate; 694 struct proc *p = curproc; 695 696 SCHED_ASSERT_LOCKED(); 697 clear_resched(curcpu()); 698 mtx_leave(&sched_lock); 699 spl0(); 700 701 SCHED_ASSERT_UNLOCKED(); 702 KERNEL_ASSERT_UNLOCKED(); 703 assertwaitok(); 704 smr_idle(); 705 706 /* Start any optional clock interrupts needed by the thread. */ 707 if (ISSET(p->p_p->ps_flags, PS_ITIMER)) { 708 atomic_setbits_int(&spc->spc_schedflags, SPCF_ITIMER); 709 clockintr_advance(&spc->spc_itimer, hardclock_period); 710 } 711 if (ISSET(p->p_p->ps_flags, PS_PROFIL)) { 712 atomic_setbits_int(&spc->spc_schedflags, SPCF_PROFCLOCK); 713 clockintr_advance(&spc->spc_profclock, profclock_period); 714 } 715 716 nanouptime(&spc->spc_runtime); 717 KERNEL_LOCK(); 718 } 719