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