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