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