Root/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 DEBUG /* Enable initcall_debug */
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/stackprotector.h>
20#include <linux/string.h>
21#include <linux/ctype.h>
22#include <linux/delay.h>
23#include <linux/ioport.h>
24#include <linux/init.h>
25#include <linux/initrd.h>
26#include <linux/bootmem.h>
27#include <linux/acpi.h>
28#include <linux/tty.h>
29#include <linux/percpu.h>
30#include <linux/kmod.h>
31#include <linux/vmalloc.h>
32#include <linux/kernel_stat.h>
33#include <linux/start_kernel.h>
34#include <linux/security.h>
35#include <linux/smp.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/cgroup.h>
44#include <linux/efi.h>
45#include <linux/tick.h>
46#include <linux/interrupt.h>
47#include <linux/taskstats_kern.h>
48#include <linux/delayacct.h>
49#include <linux/unistd.h>
50#include <linux/rmap.h>
51#include <linux/mempolicy.h>
52#include <linux/key.h>
53#include <linux/buffer_head.h>
54#include <linux/page_cgroup.h>
55#include <linux/debug_locks.h>
56#include <linux/debugobjects.h>
57#include <linux/lockdep.h>
58#include <linux/kmemleak.h>
59#include <linux/pid_namespace.h>
60#include <linux/device.h>
61#include <linux/kthread.h>
62#include <linux/sched.h>
63#include <linux/signal.h>
64#include <linux/idr.h>
65#include <linux/kgdb.h>
66#include <linux/ftrace.h>
67#include <linux/async.h>
68#include <linux/kmemcheck.h>
69#include <linux/sfi.h>
70#include <linux/shmem_fs.h>
71#include <linux/slab.h>
72#include <linux/perf_event.h>
73#include <linux/file.h>
74#include <linux/ptrace.h>
75#include <linux/blkdev.h>
76#include <linux/elevator.h>
77#include <linux/sched_clock.h>
78
79#include <asm/io.h>
80#include <asm/bugs.h>
81#include <asm/setup.h>
82#include <asm/sections.h>
83#include <asm/cacheflush.h>
84
85#ifdef CONFIG_X86_LOCAL_APIC
86#include <asm/smp.h>
87#endif
88
89static int kernel_init(void *);
90
91extern void init_IRQ(void);
92extern void fork_init(unsigned long);
93extern void mca_init(void);
94extern void sbus_init(void);
95extern void radix_tree_init(void);
96#ifndef CONFIG_DEBUG_RODATA
97static inline void mark_rodata_ro(void) { }
98#endif
99
100#ifdef CONFIG_TC
101extern void tc_init(void);
102#endif
103
104/*
105 * Debug helper: via this flag we know that we are in 'early bootup code'
106 * where only the boot processor is running with IRQ disabled. This means
107 * two things - IRQ must not be enabled before the flag is cleared and some
108 * operations which are not allowed with IRQ disabled are allowed while the
109 * flag is set.
110 */
111bool early_boot_irqs_disabled __read_mostly;
112
113enum system_states system_state __read_mostly;
114EXPORT_SYMBOL(system_state);
115
116/*
117 * Boot command-line arguments
118 */
119#define MAX_INIT_ARGS CONFIG_INIT_ENV_ARG_LIMIT
120#define MAX_INIT_ENVS CONFIG_INIT_ENV_ARG_LIMIT
121
122extern void time_init(void);
123/* Default late time init is NULL. archs can override this later. */
124void (*__initdata late_time_init)(void);
125extern void softirq_init(void);
126
127/* Untouched command line saved by arch-specific code. */
128char __initdata boot_command_line[COMMAND_LINE_SIZE];
129/* Untouched saved command line (eg. for /proc) */
130char *saved_command_line;
131/* Command line for parameter parsing */
132static char *static_command_line;
133
134static char *execute_command;
135static char *ramdisk_execute_command;
136
137/*
138 * If set, this is an indication to the drivers that reset the underlying
139 * device before going ahead with the initialization otherwise driver might
140 * rely on the BIOS and skip the reset operation.
141 *
142 * This is useful if kernel is booting in an unreliable environment.
143 * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
144 * skipped and devices will be in unknown state.
145 */
146unsigned int reset_devices;
147EXPORT_SYMBOL(reset_devices);
148
149static int __init set_reset_devices(char *str)
150{
151    reset_devices = 1;
152    return 1;
153}
154
155__setup("reset_devices", set_reset_devices);
156
157static const char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
158const char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
159static const char *panic_later, *panic_param;
160
161extern const struct obs_kernel_param __setup_start[], __setup_end[];
162
163static int __init obsolete_checksetup(char *line)
164{
165    const struct obs_kernel_param *p;
166    int had_early_param = 0;
167
168    p = __setup_start;
169    do {
170        int n = strlen(p->str);
171        if (parameqn(line, p->str, n)) {
172            if (p->early) {
173                /* Already done in parse_early_param?
174                 * (Needs exact match on param part).
175                 * Keep iterating, as we can have early
176                 * params and __setups of same names 8( */
177                if (line[n] == '\0' || line[n] == '=')
178                    had_early_param = 1;
179            } else if (!p->setup_func) {
180                pr_warn("Parameter %s is obsolete, ignored\n",
181                    p->str);
182                return 1;
183            } else if (p->setup_func(line + n))
184                return 1;
185        }
186        p++;
187    } while (p < __setup_end);
188
189    return had_early_param;
190}
191
192/*
193 * This should be approx 2 Bo*oMips to start (note initial shift), and will
194 * still work even if initially too large, it will just take slightly longer
195 */
196unsigned long loops_per_jiffy = (1<<12);
197
198EXPORT_SYMBOL(loops_per_jiffy);
199
200static int __init debug_kernel(char *str)
201{
202    console_loglevel = 10;
203    return 0;
204}
205
206static int __init quiet_kernel(char *str)
207{
208    console_loglevel = 4;
209    return 0;
210}
211
212early_param("debug", debug_kernel);
213early_param("quiet", quiet_kernel);
214
215static int __init loglevel(char *str)
216{
217    int newlevel;
218
219    /*
220     * Only update loglevel value when a correct setting was passed,
221     * to prevent blind crashes (when loglevel being set to 0) that
222     * are quite hard to debug
223     */
224    if (get_option(&str, &newlevel)) {
225        console_loglevel = newlevel;
226        return 0;
227    }
228
229    return -EINVAL;
230}
231
232early_param("loglevel", loglevel);
233
234/* Change NUL term back to "=", to make "param" the whole string. */
235static int __init repair_env_string(char *param, char *val, const char *unused)
236{
237    if (val) {
238        /* param=val or param="val"? */
239        if (val == param+strlen(param)+1)
240            val[-1] = '=';
241        else if (val == param+strlen(param)+2) {
242            val[-2] = '=';
243            memmove(val-1, val, strlen(val)+1);
244            val--;
245        } else
246            BUG();
247    }
248    return 0;
249}
250
251/*
252 * Unknown boot options get handed to init, unless they look like
253 * unused parameters (modprobe will find them in /proc/cmdline).
254 */
255static int __init unknown_bootoption(char *param, char *val, const char *unused)
256{
257    repair_env_string(param, val, unused);
258
259    /* Handle obsolete-style parameters */
260    if (obsolete_checksetup(param))
261        return 0;
262
263    /* Unused module parameter. */
264    if (strchr(param, '.') && (!val || strchr(param, '.') < val))
265        return 0;
266
267    if (panic_later)
268        return 0;
269
270    if (val) {
271        /* Environment option */
272        unsigned int i;
273        for (i = 0; envp_init[i]; i++) {
274            if (i == MAX_INIT_ENVS) {
275                panic_later = "Too many boot env vars at `%s'";
276                panic_param = param;
277            }
278            if (!strncmp(param, envp_init[i], val - param))
279                break;
280        }
281        envp_init[i] = param;
282    } else {
283        /* Command line option */
284        unsigned int i;
285        for (i = 0; argv_init[i]; i++) {
286            if (i == MAX_INIT_ARGS) {
287                panic_later = "Too many boot init vars at `%s'";
288                panic_param = param;
289            }
290        }
291        argv_init[i] = param;
292    }
293    return 0;
294}
295
296static int __init init_setup(char *str)
297{
298    unsigned int i;
299
300    execute_command = str;
301    /*
302     * In case LILO is going to boot us with default command line,
303     * it prepends "auto" before the whole cmdline which makes
304     * the shell think it should execute a script with such name.
305     * So we ignore all arguments entered _before_ init=... [MJ]
306     */
307    for (i = 1; i < MAX_INIT_ARGS; i++)
308        argv_init[i] = NULL;
309    return 1;
310}
311__setup("init=", init_setup);
312
313static int __init rdinit_setup(char *str)
314{
315    unsigned int i;
316
317    ramdisk_execute_command = str;
318    /* See "auto" comment in init_setup */
319    for (i = 1; i < MAX_INIT_ARGS; i++)
320        argv_init[i] = NULL;
321    return 1;
322}
323__setup("rdinit=", rdinit_setup);
324
325#ifndef CONFIG_SMP
326static const unsigned int setup_max_cpus = NR_CPUS;
327#ifdef CONFIG_X86_LOCAL_APIC
328static void __init smp_init(void)
329{
330    APIC_init_uniprocessor();
331}
332#else
333#define smp_init() do { } while (0)
334#endif
335
336static inline void setup_nr_cpu_ids(void) { }
337static inline void smp_prepare_cpus(unsigned int maxcpus) { }
338#endif
339
340/*
341 * We need to store the untouched command line for future reference.
342 * We also need to store the touched command line since the parameter
343 * parsing is performed in place, and we should allow a component to
344 * store reference of name/value for future reference.
345 */
346static void __init setup_command_line(char *command_line)
347{
348    saved_command_line = alloc_bootmem(strlen (boot_command_line)+1);
349    static_command_line = alloc_bootmem(strlen (command_line)+1);
350    strcpy (saved_command_line, boot_command_line);
351    strcpy (static_command_line, command_line);
352}
353
354/*
355 * We need to finalize in a non-__init function or else race conditions
356 * between the root thread and the init thread may cause start_kernel to
357 * be reaped by free_initmem before the root thread has proceeded to
358 * cpu_idle.
359 *
360 * gcc-3.4 accidentally inlines this function, so use noinline.
361 */
362
363static __initdata DECLARE_COMPLETION(kthreadd_done);
364
365static noinline void __init_refok rest_init(void)
366{
367    int pid;
368
369    rcu_scheduler_starting();
370    /*
371     * We need to spawn init first so that it obtains pid 1, however
372     * the init task will end up wanting to create kthreads, which, if
373     * we schedule it before we create kthreadd, will OOPS.
374     */
375    kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
376    numa_default_policy();
377    pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
378    rcu_read_lock();
379    kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
380    rcu_read_unlock();
381    complete(&kthreadd_done);
382
383    /*
384     * The boot idle thread must execute schedule()
385     * at least once to get things moving:
386     */
387    init_idle_bootup_task(current);
388    schedule_preempt_disabled();
389    /* Call into cpu_idle with preempt disabled */
390    cpu_startup_entry(CPUHP_ONLINE);
391}
392
393/* Check for early params. */
394static int __init do_early_param(char *param, char *val, const char *unused)
395{
396    const struct obs_kernel_param *p;
397
398    for (p = __setup_start; p < __setup_end; p++) {
399        if ((p->early && parameq(param, p->str)) ||
400            (strcmp(param, "console") == 0 &&
401             strcmp(p->str, "earlycon") == 0)
402        ) {
403            if (p->setup_func(val) != 0)
404                pr_warn("Malformed early option '%s'\n", param);
405        }
406    }
407    /* We accept everything at this stage. */
408    return 0;
409}
410
411void __init parse_early_options(char *cmdline)
412{
413    parse_args("early options", cmdline, NULL, 0, 0, 0, do_early_param);
414}
415
416/* Arch code calls this early on, or if not, just before other parsing. */
417void __init parse_early_param(void)
418{
419    static __initdata int done = 0;
420    static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];
421
422    if (done)
423        return;
424
425    /* All fall through to do_early_param. */
426    strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
427    parse_early_options(tmp_cmdline);
428    done = 1;
429}
430
431/*
432 * Activate the first processor.
433 */
434
435static void __init boot_cpu_init(void)
436{
437    int cpu = smp_processor_id();
438    /* Mark the boot cpu "present", "online" etc for SMP and UP case */
439    set_cpu_online(cpu, true);
440    set_cpu_active(cpu, true);
441    set_cpu_present(cpu, true);
442    set_cpu_possible(cpu, true);
443}
444
445void __init __weak smp_setup_processor_id(void)
446{
447}
448
449# if THREAD_SIZE >= PAGE_SIZE
450void __init __weak thread_info_cache_init(void)
451{
452}
453#endif
454
455/*
456 * Set up kernel memory allocators
457 */
458static void __init mm_init(void)
459{
460    /*
461     * page_cgroup requires contiguous pages,
462     * bigger than MAX_ORDER unless SPARSEMEM.
463     */
464    page_cgroup_init_flatmem();
465    mem_init();
466    kmem_cache_init();
467    percpu_init_late();
468    pgtable_cache_init();
469    vmalloc_init();
470}
471
472asmlinkage void __init start_kernel(void)
473{
474    char * command_line;
475    extern const struct kernel_param __start___param[], __stop___param[];
476
477    /*
478     * Need to run as early as possible, to initialize the
479     * lockdep hash:
480     */
481    lockdep_init();
482    smp_setup_processor_id();
483    debug_objects_early_init();
484
485    /*
486     * Set up the the initial canary ASAP:
487     */
488    boot_init_stack_canary();
489
490    cgroup_init_early();
491
492    local_irq_disable();
493    early_boot_irqs_disabled = true;
494
495/*
496 * Interrupts are still disabled. Do necessary setups, then
497 * enable them
498 */
499    boot_cpu_init();
500    page_address_init();
501    pr_notice("%s", linux_banner);
502    setup_arch(&command_line);
503    mm_init_owner(&init_mm, &init_task);
504    mm_init_cpumask(&init_mm);
505    setup_command_line(command_line);
506    setup_nr_cpu_ids();
507    setup_per_cpu_areas();
508    smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
509
510    build_all_zonelists(NULL, NULL);
511    page_alloc_init();
512
513    pr_notice("Kernel command line: %s\n", boot_command_line);
514    parse_early_param();
515    parse_args("Booting kernel", static_command_line, __start___param,
516           __stop___param - __start___param,
517           -1, -1, &unknown_bootoption);
518
519    jump_label_init();
520
521    /*
522     * These use large bootmem allocations and must precede
523     * kmem_cache_init()
524     */
525    setup_log_buf(0);
526    pidhash_init();
527    vfs_caches_init_early();
528    sort_main_extable();
529    trap_init();
530    mm_init();
531
532    /*
533     * Set up the scheduler prior starting any interrupts (such as the
534     * timer interrupt). Full topology setup happens at smp_init()
535     * time - but meanwhile we still have a functioning scheduler.
536     */
537    sched_init();
538    /*
539     * Disable preemption - early bootup scheduling is extremely
540     * fragile until we cpu_idle() for the first time.
541     */
542    preempt_disable();
543    if (WARN(!irqs_disabled(), "Interrupts were enabled *very* early, fixing it\n"))
544        local_irq_disable();
545    idr_init_cache();
546    rcu_init();
547    tick_nohz_init();
548    radix_tree_init();
549    /* init some links before init_ISA_irqs() */
550    early_irq_init();
551    init_IRQ();
552    tick_init();
553    init_timers();
554    hrtimers_init();
555    softirq_init();
556    timekeeping_init();
557    time_init();
558    sched_clock_postinit();
559    perf_event_init();
560    profile_init();
561    call_function_init();
562    WARN(!irqs_disabled(), "Interrupts were enabled early\n");
563    early_boot_irqs_disabled = false;
564    local_irq_enable();
565
566    kmem_cache_init_late();
567
568    /*
569     * HACK ALERT! This is early. We're enabling the console before
570     * we've done PCI setups etc, and console_init() must be aware of
571     * this. But we do want output early, in case something goes wrong.
572     */
573    console_init();
574    if (panic_later)
575        panic(panic_later, panic_param);
576
577    lockdep_info();
578
579    /*
580     * Need to run this when irqs are enabled, because it wants
581     * to self-test [hard/soft]-irqs on/off lock inversion bugs
582     * too:
583     */
584    locking_selftest();
585
586#ifdef CONFIG_BLK_DEV_INITRD
587    if (initrd_start && !initrd_below_start_ok &&
588        page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
589        pr_crit("initrd overwritten (0x%08lx < 0x%08lx) - disabling it.\n",
590            page_to_pfn(virt_to_page((void *)initrd_start)),
591            min_low_pfn);
592        initrd_start = 0;
593    }
594#endif
595    page_cgroup_init();
596    debug_objects_mem_init();
597    kmemleak_init();
598    setup_per_cpu_pageset();
599    numa_policy_init();
600    if (late_time_init)
601        late_time_init();
602    sched_clock_init();
603    calibrate_delay();
604    pidmap_init();
605    anon_vma_init();
606#ifdef CONFIG_X86
607    if (efi_enabled(EFI_RUNTIME_SERVICES))
608        efi_enter_virtual_mode();
609#endif
610    thread_info_cache_init();
611    cred_init();
612    fork_init(totalram_pages);
613    proc_caches_init();
614    buffer_init();
615    key_init();
616    security_init();
617    dbg_late_init();
618    vfs_caches_init(totalram_pages);
619    signals_init();
620    /* rootfs populating might need page-writeback */
621    page_writeback_init();
622#ifdef CONFIG_PROC_FS
623    proc_root_init();
624#endif
625    cgroup_init();
626    cpuset_init();
627    taskstats_init_early();
628    delayacct_init();
629
630    check_bugs();
631
632    acpi_early_init(); /* before LAPIC and SMP init */
633    sfi_init_late();
634
635    if (efi_enabled(EFI_RUNTIME_SERVICES)) {
636        efi_late_init();
637        efi_free_boot_services();
638    }
639
640    ftrace_init();
641
642    /* Do the rest non-__init'ed, we're now alive */
643    rest_init();
644}
645
646/* Call all constructor functions linked into the kernel. */
647static void __init do_ctors(void)
648{
649#ifdef CONFIG_CONSTRUCTORS
650    ctor_fn_t *fn = (ctor_fn_t *) __ctors_start;
651
652    for (; fn < (ctor_fn_t *) __ctors_end; fn++)
653        (*fn)();
654#endif
655}
656
657bool initcall_debug;
658core_param(initcall_debug, initcall_debug, bool, 0644);
659
660static int __init_or_module do_one_initcall_debug(initcall_t fn)
661{
662    ktime_t calltime, delta, rettime;
663    unsigned long long duration;
664    int ret;
665
666    pr_debug("calling %pF @ %i\n", fn, task_pid_nr(current));
667    calltime = ktime_get();
668    ret = fn();
669    rettime = ktime_get();
670    delta = ktime_sub(rettime, calltime);
671    duration = (unsigned long long) ktime_to_ns(delta) >> 10;
672    pr_debug("initcall %pF returned %d after %lld usecs\n",
673         fn, ret, duration);
674
675    return ret;
676}
677
678int __init_or_module do_one_initcall(initcall_t fn)
679{
680    int count = preempt_count();
681    int ret;
682    char msgbuf[64];
683
684    if (initcall_debug)
685        ret = do_one_initcall_debug(fn);
686    else
687        ret = fn();
688
689    msgbuf[0] = 0;
690
691    if (preempt_count() != count) {
692        sprintf(msgbuf, "preemption imbalance ");
693        preempt_count() = count;
694    }
695    if (irqs_disabled()) {
696        strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));
697        local_irq_enable();
698    }
699    WARN(msgbuf[0], "initcall %pF returned with %s\n", fn, msgbuf);
700
701    return ret;
702}
703
704
705extern initcall_t __initcall_start[];
706extern initcall_t __initcall0_start[];
707extern initcall_t __initcall1_start[];
708extern initcall_t __initcall2_start[];
709extern initcall_t __initcall3_start[];
710extern initcall_t __initcall4_start[];
711extern initcall_t __initcall5_start[];
712extern initcall_t __initcall6_start[];
713extern initcall_t __initcall7_start[];
714extern initcall_t __initcall_end[];
715
716static initcall_t *initcall_levels[] __initdata = {
717    __initcall0_start,
718    __initcall1_start,
719    __initcall2_start,
720    __initcall3_start,
721    __initcall4_start,
722    __initcall5_start,
723    __initcall6_start,
724    __initcall7_start,
725    __initcall_end,
726};
727
728/* Keep these in sync with initcalls in include/linux/init.h */
729static char *initcall_level_names[] __initdata = {
730    "early",
731    "core",
732    "postcore",
733    "arch",
734    "subsys",
735    "fs",
736    "device",
737    "late",
738};
739
740static void __init do_initcall_level(int level)
741{
742    extern const struct kernel_param __start___param[], __stop___param[];
743    initcall_t *fn;
744
745    strcpy(static_command_line, saved_command_line);
746    parse_args(initcall_level_names[level],
747           static_command_line, __start___param,
748           __stop___param - __start___param,
749           level, level,
750           &repair_env_string);
751
752    for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)
753        do_one_initcall(*fn);
754}
755
756static void __init do_initcalls(void)
757{
758    int level;
759
760    for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)
761        do_initcall_level(level);
762}
763
764/*
765 * Ok, the machine is now initialized. None of the devices
766 * have been touched yet, but the CPU subsystem is up and
767 * running, and memory and process management works.
768 *
769 * Now we can finally start doing some real work..
770 */
771static void __init do_basic_setup(void)
772{
773    cpuset_init_smp();
774    usermodehelper_init();
775    shmem_init();
776    driver_init();
777    init_irq_proc();
778    do_ctors();
779    usermodehelper_enable();
780    do_initcalls();
781}
782
783static void __init do_pre_smp_initcalls(void)
784{
785    initcall_t *fn;
786
787    for (fn = __initcall_start; fn < __initcall0_start; fn++)
788        do_one_initcall(*fn);
789}
790
791/*
792 * This function requests modules which should be loaded by default and is
793 * called twice right after initrd is mounted and right before init is
794 * exec'd. If such modules are on either initrd or rootfs, they will be
795 * loaded before control is passed to userland.
796 */
797void __init load_default_modules(void)
798{
799    load_default_elevator_module();
800}
801
802static int run_init_process(const char *init_filename)
803{
804    argv_init[0] = init_filename;
805    return do_execve(init_filename,
806        (const char __user *const __user *)argv_init,
807        (const char __user *const __user *)envp_init);
808}
809
810static noinline void __init kernel_init_freeable(void);
811
812static int __ref kernel_init(void *unused)
813{
814    kernel_init_freeable();
815    /* need to finish all async __init code before freeing the memory */
816    async_synchronize_full();
817    free_initmem();
818    mark_rodata_ro();
819    system_state = SYSTEM_RUNNING;
820    numa_default_policy();
821
822    flush_delayed_fput();
823
824    if (ramdisk_execute_command) {
825        if (!run_init_process(ramdisk_execute_command))
826            return 0;
827        pr_err("Failed to execute %s\n", ramdisk_execute_command);
828    }
829
830    /*
831     * We try each of these until one succeeds.
832     *
833     * The Bourne shell can be used instead of init if we are
834     * trying to recover a really broken machine.
835     */
836    if (execute_command) {
837        if (!run_init_process(execute_command))
838            return 0;
839        pr_err("Failed to execute %s. Attempting defaults...\n",
840            execute_command);
841    }
842    if (!run_init_process("/sbin/init") ||
843        !run_init_process("/etc/init") ||
844        !run_init_process("/bin/init") ||
845        !run_init_process("/bin/sh"))
846        return 0;
847
848    panic("No init found. Try passing init= option to kernel. "
849          "See Linux Documentation/init.txt for guidance.");
850}
851
852static noinline void __init kernel_init_freeable(void)
853{
854    /*
855     * Wait until kthreadd is all set-up.
856     */
857    wait_for_completion(&kthreadd_done);
858
859    /* Now the scheduler is fully set up and can do blocking allocations */
860    gfp_allowed_mask = __GFP_BITS_MASK;
861
862    /*
863     * init can allocate pages on any node
864     */
865    set_mems_allowed(node_states[N_MEMORY]);
866    /*
867     * init can run on any cpu.
868     */
869    set_cpus_allowed_ptr(current, cpu_all_mask);
870
871    cad_pid = task_pid(current);
872
873    smp_prepare_cpus(setup_max_cpus);
874
875    do_pre_smp_initcalls();
876    lockup_detector_init();
877
878    smp_init();
879    sched_init_smp();
880
881    do_basic_setup();
882
883    /* Open the /dev/console on the rootfs, this should never fail */
884    if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
885        pr_err("Warning: unable to open an initial console.\n");
886
887    (void) sys_dup(0);
888    (void) sys_dup(0);
889    /*
890     * check if there is an early userspace init. If yes, let it do all
891     * the work
892     */
893
894    if (!ramdisk_execute_command)
895        ramdisk_execute_command = "/init";
896
897    if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
898        ramdisk_execute_command = NULL;
899        prepare_namespace();
900    }
901
902    /*
903     * Ok, we have completed the initial bootup, and
904     * we're essentially up and running. Get rid of the
905     * initmem segments and start the user-mode stuff..
906     */
907
908    /* rootfs is available now, try loading default modules */
909    load_default_modules();
910}
911

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