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 179                                 printk(KERN_WARNING "Parameter %s is obsolete,"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