init/main.c

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