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