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 #if __GNUC__ == 4 && __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ == 0
  77 #warning gcc-4.1.0 is known to miscompile the kernel.  A different compiler version is recommended.
  78 #endif
  79
  80 static int init(void *);
  81
  82 extern void init_IRQ(void);
  83 extern void fork_init(unsigned long);
  84 extern void mca_init(void);
  85 extern void sbus_init(void);
  86 extern void sysctl_init(void);
  87 extern void signals_init(void);
  88 extern void pidhash_init(void);
  89 extern void pidmap_init(void);
  90 extern void prio_tree_init(void);
  91 extern void radix_tree_init(void);
  92 extern void free_initmem(void);
  93 extern void populate_rootfs(void);
  94 extern void driver_init(void);
  95 extern void prepare_namespace(void);
  96 #ifdef  CONFIG_ACPI
  97 extern void acpi_early_init(void);
  98 #else
  99 static inline void acpi_early_init(void) { }
 100 #endif
 101 #ifndef CONFIG_DEBUG_RODATA
 102 static inline void mark_rodata_ro(void) { }
 103 #endif
 104
 105 #ifdef CONFIG_TC
 106 extern void tc_init(void);
 107 #endif
 108
 109 enum system_states system_state;
 110 EXPORT_SYMBOL(system_state);
 111
 112 /*
 113  * Boot command-line arguments
 114  */
 115 #define MAX_INIT_ARGS CONFIG_INIT_ENV_ARG_LIMIT
 116 #define MAX_INIT_ENVS CONFIG_INIT_ENV_ARG_LIMIT
 117
 118 extern void time_init(void);
 119 /* Default late time init is NULL. archs can override this later. */
 120 void (*late_time_init)(void);
 121 extern void softirq_init(void);
 122
 123 /* Untouched command line (eg. for /proc) saved by arch-specific code. */
 124 char saved_command_line[COMMAND_LINE_SIZE];
 125
 126 static char *execute_command;
 127 static char *ramdisk_execute_command;
 128
 129 /* Setup configured maximum number of CPUs to activate */
 130 static unsigned int max_cpus = NR_CPUS;
 131
 132 /*
 133  * If set, this is an indication to the drivers that reset the underlying
 134  * device before going ahead with the initialization otherwise driver might
 135  * rely on the BIOS and skip the reset operation.
 136  *
 137  * This is useful if kernel is booting in an unreliable environment.
 138  * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
 139  * skipped and devices will be in unknown state.
 140  */
 141 unsigned int reset_devices;
 142 EXPORT_SYMBOL(reset_devices);
 143
 144 /*
 145  * Setup routine for controlling SMP activation
 146  *
 147  * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
 148  * activation entirely (the MPS table probe still happens, though).
 149  *
 150  * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
 151  * greater than 0, limits the maximum number of CPUs activated in
 152  * SMP mode to <NUM>.
 153  */
 154 static int __init nosmp(char *str)
 155 {
 156         max_cpus = 0;
 157         return 1;
 158 }
 159
 160 __setup("nosmp", nosmp);
 161
 162 static int __init maxcpus(char *str)
 163 {
 164         get_option(&str, &max_cpus);
 165         return 1;
 166 }
 167
 168 __setup("maxcpus=", maxcpus);
 169
 170 static int __init set_reset_devices(char *str)
 171 {
 172         reset_devices = 1;
 173         return 1;
 174 }
 175
 176 __setup("reset_devices", set_reset_devices);
 177
 178 static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
 179 char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
 180 static const char *panic_later, *panic_param;
 181
 182 extern struct obs_kernel_param __setup_start[], __setup_end[];
 183
 184 static int __init obsolete_checksetup(char *line)
 185 {
 186         struct obs_kernel_param *p;
 187         int had_early_param = 0;
 188
 189         p = __setup_start;
 190         do {
 191                 int n = strlen(p->str);
 192                 if (!strncmp(line, p->str, n)) {
 193                         if (p->early) {
 194                                 /* Already done in parse_early_param?
 195                                  * (Needs exact match on param part).
 196                                  * Keep iterating, as we can have early
 197                                  * params and __setups of same names 8( */
 198                                 if (line[n] == '\0' || line[n] == '=')
 199                                         had_early_param = 1;
 200                         } else if (!p->setup_func) {
 201                                 printk(KERN_WARNING "Parameter %s is obsolete,"
 202                                        " ignored\n", p->str);
 203                                 return 1;
 204                         } else if (p->setup_func(line + n))
 205                                 return 1;
 206                 }
 207                 p++;
 208         } while (p < __setup_end);
 209
 210         return had_early_param;
 211 }
 212
 213 /*
 214  * This should be approx 2 Bo*oMips to start (note initial shift), and will
 215  * still work even if initially too large, it will just take slightly longer
 216  */
 217 unsigned long loops_per_jiffy = (1<<12);
 218
 219 EXPORT_SYMBOL(loops_per_jiffy);
 220
 221 static int __init debug_kernel(char *str)
 222 {
 223         if (*str)
 224                 return 0;
 225         console_loglevel = 10;
 226         return 1;
 227 }
 228
 229 static int __init quiet_kernel(char *str)
 230 {
 231         if (*str)
 232                 return 0;
 233         console_loglevel = 4;
 234         return 1;
 235 }
 236
 237 __setup("debug", debug_kernel);
 238 __setup("quiet", quiet_kernel);
 239
 240 static int __init loglevel(char *str)
 241 {
 242         get_option(&str, &console_loglevel);
 243         return 1;
 244 }
 245
 246 __setup("loglevel=", loglevel);
 247
 248 /*
 249  * Unknown boot options get handed to init, unless they look like
 250  * failed parameters
 251  */
 252 static int __init unknown_bootoption(char *param, char *val)
 253 {
 254         /* Change NUL term back to "=", to make "param" the whole string. */
 255         if (val) {
 256                 /* param=val or param="val"? */
 257                 if (val == param+strlen(param)+1)
 258                         val[-1] = '=';
 259                 else if (val == param+strlen(param)+2) {
 260                         val[-2] = '=';
 261                         memmove(val-1, val, strlen(val)+1);
 262                         val--;
 263                 } else
 264                         BUG();
 265         }
 266
 267         /* Handle obsolete-style parameters */
 268         if (obsolete_checksetup(param))
 269                 return 0;
 270
 271         /*
 272          * Preemptive maintenance for "why didn't my mispelled command
 273          * line work?"
 274          */
 275         if (strchr(param, '.') && (!val || strchr(param, '.') < val)) {
 276                 printk(KERN_ERR "Unknown boot option `%s': ignoring\n", param);
 277                 return 0;
 278         }
 279
 280         if (panic_later)
 281                 return 0;
 282
 283         if (val) {
 284                 /* Environment option */
 285                 unsigned int i;
 286                 for (i = 0; envp_init[i]; i++) {
 287                         if (i == MAX_INIT_ENVS) {
 288                                 panic_later = "Too many boot env vars at `%s'";
 289                                 panic_param = param;
 290                         }
 291                         if (!strncmp(param, envp_init[i], val - param))
 292                                 break;
 293                 }
 294                 envp_init[i] = param;
 295         } else {
 296                 /* Command line option */
 297                 unsigned int i;
 298                 for (i = 0; argv_init[i]; i++) {
 299                         if (i == MAX_INIT_ARGS) {
 300                                 panic_later = "Too many boot init vars at `%s'";
 301                                 panic_param = param;
 302                         }
 303                 }
 304                 argv_init[i] = param;
 305         }
 306         return 0;
 307 }
 308
 309 static int __init init_setup(char *str)
 310 {
 311         unsigned int i;
 312
 313         execute_command = str;
 314         /*
 315          * In case LILO is going to boot us with default command line,
 316          * it prepends "auto" before the whole cmdline which makes
 317          * the shell think it should execute a script with such name.
 318          * So we ignore all arguments entered _before_ init=... [MJ]
 319          */
 320         for (i = 1; i < MAX_INIT_ARGS; i++)
 321                 argv_init[i] = NULL;
 322         return 1;
 323 }
 324 __setup("init=", init_setup);
 325
 326 static int __init rdinit_setup(char *str)
 327 {
 328         unsigned int i;
 329
 330         ramdisk_execute_command = str;
 331         /* See "auto" comment in init_setup */
 332         for (i = 1; i < MAX_INIT_ARGS; i++)
 333                 argv_init[i] = NULL;
 334         return 1;
 335 }
 336 __setup("rdinit=", rdinit_setup);
 337
 338 #ifndef CONFIG_SMP
 339
 340 #ifdef CONFIG_X86_LOCAL_APIC
 341 static void __init smp_init(void)
 342 {
 343         APIC_init_uniprocessor();
 344 }
 345 #else
 346 #define smp_init()      do { } while (0)
 347 #endif
 348
 349 static inline void setup_per_cpu_areas(void) { }
 350 static inline void smp_prepare_cpus(unsigned int maxcpus) { }
 351
 352 #else
 353
 354 #ifdef __GENERIC_PER_CPU
 355 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
 356
 357 EXPORT_SYMBOL(__per_cpu_offset);
 358
 359 static void __init setup_per_cpu_areas(void)
 360 {
 361         unsigned long size, i;
 362         char *ptr;
 363         unsigned long nr_possible_cpus = num_possible_cpus();
 364
 365         /* Copy section for each CPU (we discard the original) */
 366         size = ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES);
 367 #ifdef CONFIG_MODULES
 368         if (size < PERCPU_ENOUGH_ROOM)
 369                 size = PERCPU_ENOUGH_ROOM;
 370 #endif
 371         ptr = alloc_bootmem(size * nr_possible_cpus);
 372
 373         for_each_possible_cpu(i) {
 374                 __per_cpu_offset[i] = ptr - __per_cpu_start;
 375                 memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
 376                 ptr += size;
 377         }
 378 }
 379 #endif /* !__GENERIC_PER_CPU */
 380
 381 /* Called by boot processor to activate the rest. */
 382 static void __init smp_init(void)
 383 {
 384         unsigned int i;
 385
 386         /* FIXME: This should be done in userspace --RR */
 387         for_each_present_cpu(i) {
 388                 if (num_online_cpus() >= max_cpus)
 389                         break;
 390                 if (!cpu_online(i))
 391                         cpu_up(i);
 392         }
 393
 394         /* Any cleanup work */
 395         printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
 396         smp_cpus_done(max_cpus);
 397 #if 0
 398         /* Get other processors into their bootup holding patterns. */
 399
 400         smp_commence();
 401 #endif
 402 }
 403
 404 #endif
 405
 406 /*
 407  * We need to finalize in a non-__init function or else race conditions
 408  * between the root thread and the init thread may cause start_kernel to
 409  * be reaped by free_initmem before the root thread has proceeded to
 410  * cpu_idle.
 411  *
 412  * gcc-3.4 accidentally inlines this function, so use noinline.
 413  */
 414
 415 static void noinline rest_init(void)
 416         __releases(kernel_lock)
 417 {
 418         kernel_thread(init, NULL, CLONE_FS | CLONE_SIGHAND);
 419         numa_default_policy();
 420         unlock_kernel();
 421
 422         /*
 423          * The boot idle thread must execute schedule()
 424          * at least one to get things moving:
 425          */
 426         preempt_enable_no_resched();
 427         schedule();
 428         preempt_disable();
 429
 430         /* Call into cpu_idle with preempt disabled */
 431         cpu_idle();
 432 }
 433
 434 /* Check for early params. */
 435 static int __init do_early_param(char *param, char *val)
 436 {
 437         struct obs_kernel_param *p;
 438
 439         for (p = __setup_start; p < __setup_end; p++) {
 440                 if (p->early && strcmp(param, p->str) == 0) {
 441                         if (p->setup_func(val) != 0)
 442                                 printk(KERN_WARNING
 443                                        "Malformed early option '%s'\n", param);
 444                 }
 445         }
 446         /* We accept everything at this stage. */
 447         return 0;
 448 }
 449
 450 /* Arch code calls this early on, or if not, just before other parsing. */
 451 void __init parse_early_param(void)
 452 {
 453         static __initdata int done = 0;
 454         static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];
 455
 456         if (done)
 457                 return;
 458
 459         /* All fall through to do_early_param. */
 460         strlcpy(tmp_cmdline, saved_command_line, COMMAND_LINE_SIZE);
 461         parse_args("early options", tmp_cmdline, NULL, 0, do_early_param);
 462         done = 1;
 463 }
 464
 465 /*
 466  *      Activate the first processor.
 467  */
 468
 469 static void __init boot_cpu_init(void)
 470 {
 471         int cpu = smp_processor_id();
 472         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
 473         cpu_set(cpu, cpu_online_map);
 474         cpu_set(cpu, cpu_present_map);
 475         cpu_set(cpu, cpu_possible_map);
 476 }
 477
 478 void __init __attribute__((weak)) smp_setup_processor_id(void)
 479 {
 480 }
 481
 482 asmlinkage void __init start_kernel(void)
 483 {
 484         char * command_line;
 485         extern struct kernel_param __start___param[], __stop___param[];
 486
 487         smp_setup_processor_id();
 488
 489         /*
 490          * Need to run as early as possible, to initialize the
 491          * lockdep hash:
 492          */
 493         unwind_init();
 494         lockdep_init();
 495
 496         local_irq_disable();
 497         early_boot_irqs_off();
 498         early_init_irq_lock_class();
 499
 500 /*
 501  * Interrupts are still disabled. Do necessary setups, then
 502  * enable them
 503  */
 504         lock_kernel();
 505         boot_cpu_init();
 506         page_address_init();
 507         printk(KERN_NOTICE);
 508         printk(linux_banner);
 509         setup_arch(&command_line);
 510         unwind_setup();
 511         setup_per_cpu_areas();
 512         smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
 513
 514         /*
 515          * Set up the scheduler prior starting any interrupts (such as the
 516          * timer interrupt). Full topology setup happens at smp_init()
 517          * time - but meanwhile we still have a functioning scheduler.
 518          */
 519         sched_init();
 520         /*
 521          * Disable preemption - early bootup scheduling is extremely
 522          * fragile until we cpu_idle() for the first time.
 523          */
 524         preempt_disable();
 525         build_all_zonelists();
 526         page_alloc_init();
 527         printk(KERN_NOTICE "Kernel command line: %s\n", saved_command_line);
 528         parse_early_param();
 529         parse_args("Booting kernel", command_line, __start___param,
 530                    __stop___param - __start___param,
 531                    &unknown_bootoption);
 532         sort_main_extable();
 533         trap_init();
 534         rcu_init();
 535         init_IRQ();
 536         pidhash_init();
 537         init_timers();
 538         hrtimers_init();
 539         softirq_init();
 540         timekeeping_init();
 541         time_init();
 542         profile_init();
 543         if (!irqs_disabled())
 544                 printk("start_kernel(): bug: interrupts were enabled early\n");
 545         early_boot_irqs_on();
 546         local_irq_enable();
 547
 548         /*
 549          * HACK ALERT! This is early. We're enabling the console before
 550          * we've done PCI setups etc, and console_init() must be aware of
 551          * this. But we do want output early, in case something goes wrong.
 552          */
 553         console_init();
 554         if (panic_later)
 555                 panic(panic_later, panic_param);
 556
 557         lockdep_info();
 558
 559         /*
 560          * Need to run this when irqs are enabled, because it wants
 561          * to self-test [hard/soft]-irqs on/off lock inversion bugs
 562          * too:
 563          */
 564         locking_selftest();
 565
 566 #ifdef CONFIG_BLK_DEV_INITRD
 567         if (initrd_start && !initrd_below_start_ok &&
 568                         initrd_start < min_low_pfn << PAGE_SHIFT) {
 569                 printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
 570                     "disabling it.\n",initrd_start,min_low_pfn << PAGE_SHIFT);
 571                 initrd_start = 0;
 572         }
 573 #endif
 574         vfs_caches_init_early();
 575         cpuset_init_early();
 576         mem_init();
 577         kmem_cache_init();
 578         setup_per_cpu_pageset();
 579         numa_policy_init();
 580         if (late_time_init)
 581                 late_time_init();
 582         calibrate_delay();
 583         pidmap_init();
 584         pgtable_cache_init();
 585         prio_tree_init();
 586         anon_vma_init();
 587 #ifdef CONFIG_X86
 588         if (efi_enabled)
 589                 efi_enter_virtual_mode();
 590 #endif
 591         fork_init(num_physpages);
 592         proc_caches_init();
 593         buffer_init();
 594         unnamed_dev_init();
 595         key_init();
 596         security_init();
 597         vfs_caches_init(num_physpages);
 598         radix_tree_init();
 599         signals_init();
 600         /* rootfs populating might need page-writeback */
 601         page_writeback_init();
 602 #ifdef CONFIG_PROC_FS
 603         proc_root_init();
 604 #endif
 605         cpuset_init();
 606         taskstats_init_early();
 607         delayacct_init();
 608
 609         check_bugs();
 610
 611         acpi_early_init(); /* before LAPIC and SMP init */
 612
 613         /* Do the rest non-__init'ed, we're now alive */
 614         rest_init();
 615 }
 616
 617 static int __initdata initcall_debug;
 618
 619 static int __init initcall_debug_setup(char *str)
 620 {
 621         initcall_debug = 1;
 622         return 1;
 623 }
 624 __setup("initcall_debug", initcall_debug_setup);
 625
 626 struct task_struct *child_reaper = &init_task;
 627
 628 extern initcall_t __initcall_start[], __initcall_end[];
 629
 630 static void __init do_initcalls(void)
 631 {
 632         initcall_t *call;
 633         int count = preempt_count();
 634
 635         for (call = __initcall_start; call < __initcall_end; call++) {
 636                 char *msg = NULL;
 637                 char msgbuf[40];
 638                 int result;
 639
 640                 if (initcall_debug) {
 641                         printk("Calling initcall 0x%p", *call);
 642                         print_fn_descriptor_symbol(": %s()",
 643                                         (unsigned long) *call);
 644                         printk("\n");
 645                 }
 646
 647                 result = (*call)();
 648
 649                 if (result && result != -ENODEV && initcall_debug) {
 650                         sprintf(msgbuf, "error code %d", result);
 651                         msg = msgbuf;
 652                 }
 653                 if (preempt_count() != count) {
 654                         msg = "preemption imbalance";
 655                         preempt_count() = count;
 656                 }
 657                 if (irqs_disabled()) {
 658                         msg = "disabled interrupts";
 659                         local_irq_enable();
 660                 }
 661                 if (msg) {
 662                         printk(KERN_WARNING "initcall at 0x%p", *call);
 663                         print_fn_descriptor_symbol(": %s()",
 664                                         (unsigned long) *call);
 665                         printk(": returned with %s\n", msg);
 666                 }
 667         }
 668
 669         /* Make sure there is no pending stuff from the initcall sequence */
 670         flush_scheduled_work();
 671 }
 672
 673 /*
 674  * Ok, the machine is now initialized. None of the devices
 675  * have been touched yet, but the CPU subsystem is up and
 676  * running, and memory and process management works.
 677  *
 678  * Now we can finally start doing some real work..
 679  */
 680 static void __init do_basic_setup(void)
 681 {
 682         /* drivers will send hotplug events */
 683         init_workqueues();
 684         usermodehelper_init();
 685         driver_init();
 686
 687 #ifdef CONFIG_SYSCTL
 688         sysctl_init();
 689 #endif
 690
 691         do_initcalls();
 692 }
 693
 694 static void do_pre_smp_initcalls(void)
 695 {
 696         extern int spawn_ksoftirqd(void);
 697 #ifdef CONFIG_SMP
 698         extern int migration_init(void);
 699
 700         migration_init();
 701 #endif
 702         spawn_ksoftirqd();
 703         spawn_softlockup_task();
 704 }
 705
 706 static void run_init_process(char *init_filename)
 707 {
 708         argv_init[0] = init_filename;
 709         kernel_execve(init_filename, argv_init, envp_init);
 710 }
 711
 712 static int init(void * unused)
 713 {
 714         lock_kernel();
 715         /*
 716          * init can run on any cpu.
 717          */
 718         set_cpus_allowed(current, CPU_MASK_ALL);
 719         /*
 720          * Tell the world that we're going to be the grim
 721          * reaper of innocent orphaned children.
 722          *
 723          * We don't want people to have to make incorrect
 724          * assumptions about where in the task array this
 725          * can be found.
 726          */
 727         child_reaper = current;
 728
 729         cad_pid = task_pid(current);
 730
 731         smp_prepare_cpus(max_cpus);
 732
 733         do_pre_smp_initcalls();
 734
 735         smp_init();
 736         sched_init_smp();
 737
 738         cpuset_init_smp();
 739
 740         /*
 741          * Do this before initcalls, because some drivers want to access
 742          * firmware files.
 743          */
 744         populate_rootfs();
 745
 746         do_basic_setup();
 747
 748         /*
 749          * check if there is an early userspace init.  If yes, let it do all
 750          * the work
 751          */
 752
 753         if (!ramdisk_execute_command)
 754                 ramdisk_execute_command = "/init";
 755
 756         if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
 757                 ramdisk_execute_command = NULL;
 758                 prepare_namespace();
 759         }
 760
 761         /*
 762          * Ok, we have completed the initial bootup, and
 763          * we're essentially up and running. Get rid of the
 764          * initmem segments and start the user-mode stuff..
 765          */
 766         free_initmem();
 767         unlock_kernel();
 768         mark_rodata_ro();
 769         system_state = SYSTEM_RUNNING;
 770         numa_default_policy();
 771
 772         if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
 773                 printk(KERN_WARNING "Warning: unable to open an initial console.\n");
 774
 775         (void) sys_dup(0);
 776         (void) sys_dup(0);
 777
 778         if (ramdisk_execute_command) {
 779                 run_init_process(ramdisk_execute_command);
 780                 printk(KERN_WARNING "Failed to execute %s\n",
 781                                 ramdisk_execute_command);
 782         }
 783
 784         /*
 785          * We try each of these until one succeeds.
 786          *
 787          * The Bourne shell can be used instead of init if we are
 788          * trying to recover a really broken machine.
 789          */
 790         if (execute_command) {
 791                 run_init_process(execute_command);
 792                 printk(KERN_WARNING "Failed to execute %s.  Attempting "
 793                                         "defaults...\n", execute_command);
 794         }
 795         run_init_process("/sbin/init");
 796         run_init_process("/etc/init");
 797         run_init_process("/bin/init");
 798         run_init_process("/bin/sh");
 799
 800         panic("No init found.  Try passing init= option to kernel.");
 801 }