1 /* 2 * linux/init/main.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 * 6 * GK 2/5/95 - Changed to support mounting root fs via NFS 7 * Added initrd & change_root: Werner Almesberger & Hans Lermen, Feb '96 8 * Moan early if gcc is old, avoiding bogus kernels - Paul Gortmaker, May '96 9 * Simplified starting of init: Michael A. Griffith <grif@acm.org> 10 */ 11 12 #include <linux/types.h> 13 #include <linux/module.h> 14 #include <linux/proc_fs.h> 15 #include <linux/kernel.h> 16 #include <linux/syscalls.h> 17 #include <linux/string.h> 18 #include <linux/ctype.h> 19 #include <linux/delay.h> 20 #include <linux/utsname.h> 21 #include <linux/ioport.h> 22 #include <linux/init.h> 23 #include <linux/smp_lock.h> 24 #include <linux/initrd.h> 25 #include <linux/hdreg.h> 26 #include <linux/bootmem.h> 27 #include <linux/tty.h> 28 #include <linux/gfp.h> 29 #include <linux/percpu.h> 30 #include <linux/kmod.h> 31 #include <linux/kernel_stat.h> 32 #include <linux/start_kernel.h> 33 #include <linux/security.h> 34 #include <linux/workqueue.h> 35 #include <linux/profile.h> 36 #include <linux/rcupdate.h> 37 #include <linux/moduleparam.h> 38 #include <linux/kallsyms.h> 39 #include <linux/writeback.h> 40 #include <linux/cpu.h> 41 #include <linux/cpuset.h> 42 #include <linux/efi.h> 43 #include <linux/tick.h> 44 #include <linux/interrupt.h> 45 #include <linux/taskstats_kern.h> 46 #include <linux/delayacct.h> 47 #include <linux/unistd.h> 48 #include <linux/rmap.h> 49 #include <linux/mempolicy.h> 50 #include <linux/key.h> 51 #include <linux/unwind.h> 52 #include <linux/buffer_head.h> 53 #include <linux/debug_locks.h> 54 #include <linux/lockdep.h> 55 #include <linux/pid_namespace.h> 56 #include <linux/device.h> 57 #include <linux/kthread.h> 58 59 #include <asm/io.h> 60 #include <asm/bugs.h> 61 #include <asm/setup.h> 62 #include <asm/sections.h> 63 #include <asm/cacheflush.h> 64 65 #ifdef CONFIG_X86_LOCAL_APIC 66 #include <asm/smp.h> 67 #endif 68 69 /* 70 * This is one of the first .c files built. Error out early if we have compiler 71 * trouble. 72 * 73 * Versions of gcc older than that listed below may actually compile and link 74 * okay, but the end product can have subtle run time bugs. To avoid associated 75 * bogus bug reports, we flatly refuse to compile with a gcc that is known to be 76 * too old from the very beginning. 77 */ 78 #if (__GNUC__ < 3) || (__GNUC__ == 3 && __GNUC_MINOR__ < 2) 79 #error Sorry, your GCC is too old. It builds incorrect kernels. 80 #endif 81 82 #if __GNUC__ == 4 && __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ == 0 83 #warning gcc-4.1.0 is known to miscompile the kernel. A different compiler version is recommended. 84 #endif 85 86 static int kernel_init(void *); 87 88 extern void init_IRQ(void); 89 extern void fork_init(unsigned long); 90 extern void mca_init(void); 91 extern void sbus_init(void); 92 extern void signals_init(void); 93 extern void pidhash_init(void); 94 extern void pidmap_init(void); 95 extern void prio_tree_init(void); 96 extern void radix_tree_init(void); 97 extern void free_initmem(void); 98 #ifdef CONFIG_ACPI 99 extern void acpi_early_init(void); 100 #else 101 static inline void acpi_early_init(void) { } 102 #endif 103 #ifndef CONFIG_DEBUG_RODATA 104 static inline void mark_rodata_ro(void) { } 105 #endif 106 107 #ifdef CONFIG_TC 108 extern void tc_init(void); 109 #endif 110 111 enum system_states system_state; 112 EXPORT_SYMBOL(system_state); 113 114 /* 115 * Boot command-line arguments 116 */ 117 #define MAX_INIT_ARGS CONFIG_INIT_ENV_ARG_LIMIT 118 #define MAX_INIT_ENVS CONFIG_INIT_ENV_ARG_LIMIT 119 120 extern void time_init(void); 121 /* Default late time init is NULL. archs can override this later. */ 122 void (*late_time_init)(void); 123 extern void softirq_init(void); 124 125 /* Untouched command line saved by arch-specific code. */ 126 char __initdata boot_command_line[COMMAND_LINE_SIZE]; 127 /* Untouched saved command line (eg. for /proc) */ 128 char *saved_command_line; 129 /* Command line for parameter parsing */ 130 static char *static_command_line; 131 132 static char *execute_command; 133 static char *ramdisk_execute_command; 134 135 /* Setup configured maximum number of CPUs to activate */ 136 static unsigned int max_cpus = NR_CPUS; 137 138 /* 139 * If set, this is an indication to the drivers that reset the underlying 140 * device before going ahead with the initialization otherwise driver might 141 * rely on the BIOS and skip the reset operation. 142 * 143 * This is useful if kernel is booting in an unreliable environment. 144 * For ex. kdump situaiton where previous kernel has crashed, BIOS has been 145 * skipped and devices will be in unknown state. 146 */ 147 unsigned int reset_devices; 148 EXPORT_SYMBOL(reset_devices); 149 150 /* 151 * Setup routine for controlling SMP activation 152 * 153 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP 154 * activation entirely (the MPS table probe still happens, though). 155 * 156 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer 157 * greater than 0, limits the maximum number of CPUs activated in 158 * SMP mode to <NUM>. 159 */ 160 static int __init nosmp(char *str) 161 { 162 max_cpus = 0; 163 return 1; 164 } 165 166 __setup("nosmp", nosmp); 167 168 static int __init maxcpus(char *str) 169 { 170 get_option(&str, &max_cpus); 171 return 1; 172 } 173 174 __setup("maxcpus=", maxcpus); 175 176 static int __init set_reset_devices(char *str) 177 { 178 reset_devices = 1; 179 return 1; 180 } 181 182 __setup("reset_devices", set_reset_devices); 183 184 static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, }; 185 char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, }; 186 static const char *panic_later, *panic_param; 187 188 extern struct obs_kernel_param __setup_start[], __setup_end[]; 189 190 static int __init obsolete_checksetup(char *line) 191 { 192 struct obs_kernel_param *p; 193 int had_early_param = 0; 194 195 p = __setup_start; 196 do { 197 int n = strlen(p->str); 198 if (!strncmp(line, p->str, n)) { 199 if (p->early) { 200 /* Already done in parse_early_param? 201 * (Needs exact match on param part). 202 * Keep iterating, as we can have early 203 * params and __setups of same names 8( */ 204 if (line[n] == '\0' || line[n] == '=') 205 had_early_param = 1; 206 } else if (!p->setup_func) { 207 printk(KERN_WARNING "Parameter %s is obsolete," 208 " ignored\n", p->str); 209 return 1; 210 } else if (p->setup_func(line + n)) 211 return 1; 212 } 213 p++; 214 } while (p < __setup_end); 215 216 return had_early_param; 217 } 218 219 /* 220 * This should be approx 2 Bo*oMips to start (note initial shift), and will 221 * still work even if initially too large, it will just take slightly longer 222 */ 223 unsigned long loops_per_jiffy = (1<<12); 224 225 EXPORT_SYMBOL(loops_per_jiffy); 226 227 static int __init debug_kernel(char *str) 228 { 229 if (*str) 230 return 0; 231 console_loglevel = 10; 232 return 1; 233 } 234 235 static int __init quiet_kernel(char *str) 236 { 237 if (*str) 238 return 0; 239 console_loglevel = 4; 240 return 1; 241 } 242 243 __setup("debug", debug_kernel); 244 __setup("quiet", quiet_kernel); 245 246 static int __init loglevel(char *str) 247 { 248 get_option(&str, &console_loglevel); 249 return 1; 250 } 251 252 __setup("loglevel=", loglevel); 253 254 /* 255 * Unknown boot options get handed to init, unless they look like 256 * failed parameters 257 */ 258 static int __init unknown_bootoption(char *param, char *val) 259 { 260 /* Change NUL term back to "=", to make "param" the whole string. */ 261 if (val) { 262 /* param=val or param="val"? */ 263 if (val == param+strlen(param)+1) 264 val[-1] = '='; 265 else if (val == param+strlen(param)+2) { 266 val[-2] = '='; 267 memmove(val-1, val, strlen(val)+1); 268 val--; 269 } else 270 BUG(); 271 } 272 273 /* Handle obsolete-style parameters */ 274 if (obsolete_checksetup(param)) 275 return 0; 276 277 /* 278 * Preemptive maintenance for "why didn't my mispelled command 279 * line work?" 280 */ 281 if (strchr(param, '.') && (!val || strchr(param, '.') < val)) { 282 printk(KERN_ERR "Unknown boot option `%s': ignoring\n", param); 283 return 0; 284 } 285 286 if (panic_later) 287 return 0; 288 289 if (val) { 290 /* Environment option */ 291 unsigned int i; 292 for (i = 0; envp_init[i]; i++) { 293 if (i == MAX_INIT_ENVS) { 294 panic_later = "Too many boot env vars at `%s'"; 295 panic_param = param; 296 } 297 if (!strncmp(param, envp_init[i], val - param)) 298 break; 299 } 300 envp_init[i] = param; 301 } else { 302 /* Command line option */ 303 unsigned int i; 304 for (i = 0; argv_init[i]; i++) { 305 if (i == MAX_INIT_ARGS) { 306 panic_later = "Too many boot init vars at `%s'"; 307 panic_param = param; 308 } 309 } 310 argv_init[i] = param; 311 } 312 return 0; 313 } 314 315 static int __init init_setup(char *str) 316 { 317 unsigned int i; 318 319 execute_command = str; 320 /* 321 * In case LILO is going to boot us with default command line, 322 * it prepends "auto" before the whole cmdline which makes 323 * the shell think it should execute a script with such name. 324 * So we ignore all arguments entered _before_ init=... [MJ] 325 */ 326 for (i = 1; i < MAX_INIT_ARGS; i++) 327 argv_init[i] = NULL; 328 return 1; 329 } 330 __setup("init=", init_setup); 331 332 static int __init rdinit_setup(char *str) 333 { 334 unsigned int i; 335 336 ramdisk_execute_command = str; 337 /* See "auto" comment in init_setup */ 338 for (i = 1; i < MAX_INIT_ARGS; i++) 339 argv_init[i] = NULL; 340 return 1; 341 } 342 __setup("rdinit=", rdinit_setup); 343 344 #ifndef CONFIG_SMP 345 346 #ifdef CONFIG_X86_LOCAL_APIC 347 static void __init smp_init(void) 348 { 349 APIC_init_uniprocessor(); 350 } 351 #else 352 #define smp_init() do { } while (0) 353 #endif 354 355 static inline void setup_per_cpu_areas(void) { } 356 static inline void smp_prepare_cpus(unsigned int maxcpus) { } 357 358 #else 359 360 #ifdef __GENERIC_PER_CPU 361 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly; 362 363 EXPORT_SYMBOL(__per_cpu_offset); 364 365 static void __init setup_per_cpu_areas(void) 366 { 367 unsigned long size, i; 368 char *ptr; 369 unsigned long nr_possible_cpus = num_possible_cpus(); 370 371 /* Copy section for each CPU (we discard the original) */ 372 size = ALIGN(PERCPU_ENOUGH_ROOM, PAGE_SIZE); 373 ptr = alloc_bootmem_pages(size * nr_possible_cpus); 374 375 for_each_possible_cpu(i) { 376 __per_cpu_offset[i] = ptr - __per_cpu_start; 377 memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start); 378 ptr += size; 379 } 380 } 381 #endif /* !__GENERIC_PER_CPU */ 382 383 /* Called by boot processor to activate the rest. */ 384 static void __init smp_init(void) 385 { 386 unsigned int cpu; 387 388 /* FIXME: This should be done in userspace --RR */ 389 for_each_present_cpu(cpu) { 390 if (num_online_cpus() >= max_cpus) 391 break; 392 if (!cpu_online(cpu)) 393 cpu_up(cpu); 394 } 395 396 /* Any cleanup work */ 397 printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus()); 398 smp_cpus_done(max_cpus); 399 } 400 401 #endif 402 403 /* 404 * We need to store the untouched command line for future reference. 405 * We also need to store the touched command line since the parameter 406 * parsing is performed in place, and we should allow a component to 407 * store reference of name/value for future reference. 408 */ 409 static void __init setup_command_line(char *command_line) 410 { 411 saved_command_line = alloc_bootmem(strlen (boot_command_line)+1); 412 static_command_line = alloc_bootmem(strlen (command_line)+1); 413 strcpy (saved_command_line, boot_command_line); 414 strcpy (static_command_line, command_line); 415 } 416 417 /* 418 * We need to finalize in a non-__init function or else race conditions 419 * between the root thread and the init thread may cause start_kernel to 420 * be reaped by free_initmem before the root thread has proceeded to 421 * cpu_idle. 422 * 423 * gcc-3.4 accidentally inlines this function, so use noinline. 424 */ 425 426 static void noinline rest_init(void) 427 __releases(kernel_lock) 428 { 429 int pid; 430 431 kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND); 432 numa_default_policy(); 433 pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES); 434 kthreadd_task = find_task_by_pid(pid); 435 unlock_kernel(); 436 437 /* 438 * The boot idle thread must execute schedule() 439 * at least one to get things moving: 440 */ 441 preempt_enable_no_resched(); 442 schedule(); 443 preempt_disable(); 444 445 /* Call into cpu_idle with preempt disabled */ 446 cpu_idle(); 447 } 448 449 /* Check for early params. */ 450 static int __init do_early_param(char *param, char *val) 451 { 452 struct obs_kernel_param *p; 453 454 for (p = __setup_start; p < __setup_end; p++) { 455 if (p->early && strcmp(param, p->str) == 0) { 456 if (p->setup_func(val) != 0) 457 printk(KERN_WARNING 458 "Malformed early option '%s'\n", param); 459 } 460 } 461 /* We accept everything at this stage. */ 462 return 0; 463 } 464 465 /* Arch code calls this early on, or if not, just before other parsing. */ 466 void __init parse_early_param(void) 467 { 468 static __initdata int done = 0; 469 static __initdata char tmp_cmdline[COMMAND_LINE_SIZE]; 470 471 if (done) 472 return; 473 474 /* All fall through to do_early_param. */ 475 strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE); 476 parse_args("early options", tmp_cmdline, NULL, 0, do_early_param); 477 done = 1; 478 } 479 480 /* 481 * Activate the first processor. 482 */ 483 484 static void __init boot_cpu_init(void) 485 { 486 int cpu = smp_processor_id(); 487 /* Mark the boot cpu "present", "online" etc for SMP and UP case */ 488 cpu_set(cpu, cpu_online_map); 489 cpu_set(cpu, cpu_present_map); 490 cpu_set(cpu, cpu_possible_map); 491 } 492 493 void __init __attribute__((weak)) smp_setup_processor_id(void) 494 { 495 } 496 497 asmlinkage void __init start_kernel(void) 498 { 499 char * command_line; 500 extern struct kernel_param __start___param[], __stop___param[]; 501 502 smp_setup_processor_id(); 503 504 /* 505 * Need to run as early as possible, to initialize the 506 * lockdep hash: 507 */ 508 unwind_init(); 509 lockdep_init(); 510 511 local_irq_disable(); 512 early_boot_irqs_off(); 513 early_init_irq_lock_class(); 514 515 /* 516 * Interrupts are still disabled. Do necessary setups, then 517 * enable them 518 */ 519 lock_kernel(); 520 tick_init(); 521 boot_cpu_init(); 522 page_address_init(); 523 printk(KERN_NOTICE); 524 printk(linux_banner); 525 setup_arch(&command_line); 526 setup_command_line(command_line); 527 unwind_setup(); 528 setup_per_cpu_areas(); 529 smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */ 530 531 /* 532 * Set up the scheduler prior starting any interrupts (such as the 533 * timer interrupt). Full topology setup happens at smp_init() 534 * time - but meanwhile we still have a functioning scheduler. 535 */ 536 sched_init(); 537 /* 538 * Disable preemption - early bootup scheduling is extremely 539 * fragile until we cpu_idle() for the first time. 540 */ 541 preempt_disable(); 542 build_all_zonelists(); 543 page_alloc_init(); 544 printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line); 545 parse_early_param(); 546 parse_args("Booting kernel", static_command_line, __start___param, 547 __stop___param - __start___param, 548 &unknown_bootoption); 549 if (!irqs_disabled()) { 550 printk(KERN_WARNING "start_kernel(): bug: interrupts were " 551 "enabled *very* early, fixing it\n"); 552 local_irq_disable(); 553 } 554 sort_main_extable(); 555 trap_init(); 556 rcu_init(); 557 init_IRQ(); 558 pidhash_init(); 559 init_timers(); 560 hrtimers_init(); 561 softirq_init(); 562 timekeeping_init(); 563 time_init(); 564 profile_init(); 565 if (!irqs_disabled()) 566 printk("start_kernel(): bug: interrupts were enabled early\n"); 567 early_boot_irqs_on(); 568 local_irq_enable(); 569 570 /* 571 * HACK ALERT! This is early. We're enabling the console before 572 * we've done PCI setups etc, and console_init() must be aware of 573 * this. But we do want output early, in case something goes wrong. 574 */ 575 console_init(); 576 if (panic_later) 577 panic(panic_later, panic_param); 578 579 lockdep_info(); 580 581 /* 582 * Need to run this when irqs are enabled, because it wants 583 * to self-test [hard/soft]-irqs on/off lock inversion bugs 584 * too: 585 */ 586 locking_selftest(); 587 588 #ifdef CONFIG_BLK_DEV_INITRD 589 if (initrd_start && !initrd_below_start_ok && 590 initrd_start < min_low_pfn << PAGE_SHIFT) { 591 printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - " 592 "disabling it.\n",initrd_start,min_low_pfn << PAGE_SHIFT); 593 initrd_start = 0; 594 } 595 #endif 596 vfs_caches_init_early(); 597 cpuset_init_early(); 598 mem_init(); 599 kmem_cache_init(); 600 setup_per_cpu_pageset(); 601 numa_policy_init(); 602 if (late_time_init) 603 late_time_init(); 604 calibrate_delay(); 605 pidmap_init(); 606 pgtable_cache_init(); 607 prio_tree_init(); 608 anon_vma_init(); 609 #ifdef CONFIG_X86 610 if (efi_enabled) 611 efi_enter_virtual_mode(); 612 #endif 613 fork_init(num_physpages); 614 proc_caches_init(); 615 buffer_init(); 616 unnamed_dev_init(); 617 key_init(); 618 security_init(); 619 vfs_caches_init(num_physpages); 620 radix_tree_init(); 621 signals_init(); 622 /* rootfs populating might need page-writeback */ 623 page_writeback_init(); 624 #ifdef CONFIG_PROC_FS 625 proc_root_init(); 626 #endif 627 cpuset_init(); 628 taskstats_init_early(); 629 delayacct_init(); 630 631 check_bugs(); 632 633 acpi_early_init(); /* before LAPIC and SMP init */ 634 635 /* Do the rest non-__init'ed, we're now alive */ 636 rest_init(); 637 } 638 639 static int __initdata initcall_debug; 640 641 static int __init initcall_debug_setup(char *str) 642 { 643 initcall_debug = 1; 644 return 1; 645 } 646 __setup("initcall_debug", initcall_debug_setup); 647 648 extern initcall_t __initcall_start[], __initcall_end[]; 649 650 static void __init do_initcalls(void) 651 { 652 initcall_t *call; 653 int count = preempt_count(); 654 655 for (call = __initcall_start; call < __initcall_end; call++) { 656 ktime_t t0, t1, delta; 657 char *msg = NULL; 658 char msgbuf[40]; 659 int result; 660 661 if (initcall_debug) { 662 printk("Calling initcall 0x%p", *call); 663 print_fn_descriptor_symbol(": %s()", 664 (unsigned long) *call); 665 printk("\n"); 666 t0 = ktime_get(); 667 } 668 669 result = (*call)(); 670 671 if (initcall_debug) { 672 t1 = ktime_get(); 673 delta = ktime_sub(t1, t0); 674 675 printk("initcall 0x%p", *call); 676 print_fn_descriptor_symbol(": %s()", 677 (unsigned long) *call); 678 printk(" returned %d.\n", result); 679 680 printk("initcall 0x%p ran for %Ld msecs: ", 681 *call, (unsigned long long)delta.tv64 >> 20); 682 print_fn_descriptor_symbol("%s()\n", 683 (unsigned long) *call); 684 } 685 686 if (result && result != -ENODEV && initcall_debug) { 687 sprintf(msgbuf, "error code %d", result); 688 msg = msgbuf; 689 } 690 if (preempt_count() != count) { 691 msg = "preemption imbalance"; 692 preempt_count() = count; 693 } 694 if (irqs_disabled()) { 695 msg = "disabled interrupts"; 696 local_irq_enable(); 697 } 698 if (msg) { 699 printk(KERN_WARNING "initcall at 0x%p", *call); 700 print_fn_descriptor_symbol(": %s()", 701 (unsigned long) *call); 702 printk(": returned with %s\n", msg); 703 } 704 } 705 706 /* Make sure there is no pending stuff from the initcall sequence */ 707 flush_scheduled_work(); 708 } 709 710 /* 711 * Ok, the machine is now initialized. None of the devices 712 * have been touched yet, but the CPU subsystem is up and 713 * running, and memory and process management works. 714 * 715 * Now we can finally start doing some real work.. 716 */ 717 static void __init do_basic_setup(void) 718 { 719 /* drivers will send hotplug events */ 720 init_workqueues(); 721 usermodehelper_init(); 722 driver_init(); 723 init_irq_proc(); 724 do_initcalls(); 725 } 726 727 static void __init do_pre_smp_initcalls(void) 728 { 729 extern int spawn_ksoftirqd(void); 730 #ifdef CONFIG_SMP 731 extern int migration_init(void); 732 733 migration_init(); 734 #endif 735 spawn_ksoftirqd(); 736 spawn_softlockup_task(); 737 } 738 739 static void run_init_process(char *init_filename) 740 { 741 argv_init[0] = init_filename; 742 kernel_execve(init_filename, argv_init, envp_init); 743 } 744 745 /* This is a non __init function. Force it to be noinline otherwise gcc 746 * makes it inline to init() and it becomes part of init.text section 747 */ 748 static int noinline init_post(void) 749 { 750 free_initmem(); 751 unlock_kernel(); 752 mark_rodata_ro(); 753 system_state = SYSTEM_RUNNING; 754 numa_default_policy(); 755 756 if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0) 757 printk(KERN_WARNING "Warning: unable to open an initial console.\n"); 758 759 (void) sys_dup(0); 760 (void) sys_dup(0); 761 762 if (ramdisk_execute_command) { 763 run_init_process(ramdisk_execute_command); 764 printk(KERN_WARNING "Failed to execute %s\n", 765 ramdisk_execute_command); 766 } 767 768 /* 769 * We try each of these until one succeeds. 770 * 771 * The Bourne shell can be used instead of init if we are 772 * trying to recover a really broken machine. 773 */ 774 if (execute_command) { 775 run_init_process(execute_command); 776 printk(KERN_WARNING "Failed to execute %s. Attempting " 777 "defaults...\n", execute_command); 778 } 779 run_init_process("/sbin/init"); 780 run_init_process("/etc/init"); 781 run_init_process("/bin/init"); 782 run_init_process("/bin/sh"); 783 784 panic("No init found. Try passing init= option to kernel."); 785 } 786 787 static int __init kernel_init(void * unused) 788 { 789 lock_kernel(); 790 /* 791 * init can run on any cpu. 792 */ 793 set_cpus_allowed(current, CPU_MASK_ALL); 794 /* 795 * Tell the world that we're going to be the grim 796 * reaper of innocent orphaned children. 797 * 798 * We don't want people to have to make incorrect 799 * assumptions about where in the task array this 800 * can be found. 801 */ 802 init_pid_ns.child_reaper = current; 803 804 __set_special_pids(1, 1); 805 cad_pid = task_pid(current); 806 807 smp_prepare_cpus(max_cpus); 808 809 do_pre_smp_initcalls(); 810 811 smp_init(); 812 sched_init_smp(); 813 814 cpuset_init_smp(); 815 816 do_basic_setup(); 817 818 /* 819 * check if there is an early userspace init. If yes, let it do all 820 * the work 821 */ 822 823 if (!ramdisk_execute_command) 824 ramdisk_execute_command = "/init"; 825 826 if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) { 827 ramdisk_execute_command = NULL; 828 prepare_namespace(); 829 } 830 831 /* 832 * Ok, we have completed the initial bootup, and 833 * we're essentially up and running. Get rid of the 834 * initmem segments and start the user-mode stuff.. 835 */ 836 init_post(); 837 return 0; 838 } 839