/*
 *  linux/init/main.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  GK 2/5/95  -  Changed to support mounting root fs via NFS
 *  Added initrd & change_root: Werner Almesberger & Hans Lermen, Feb '96
 *  Moan early if gcc is old, avoiding bogus kernels - Paul Gortmaker, May '96
 *  Simplified starting of init:  Michael A. Griffith <grif@acm.org> 
 */

#include <linux/types.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/stackprotector.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/initrd.h>
#include <linux/bootmem.h>
#include <linux/acpi.h>
#include <linux/tty.h>
#include <linux/percpu.h>
#include <linux/kmod.h>
#include <linux/vmalloc.h>
#include <linux/kernel_stat.h>
#include <linux/start_kernel.h>
#include <linux/security.h>
#include <linux/smp.h>
#include <linux/profile.h>
#include <linux/rcupdate.h>
#include <linux/moduleparam.h>
#include <linux/kallsyms.h>
#include <linux/writeback.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/cgroup.h>
#include <linux/efi.h>
#include <linux/tick.h>
#include <linux/interrupt.h>
#include <linux/taskstats_kern.h>
#include <linux/delayacct.h>
#include <linux/unistd.h>
#include <linux/rmap.h>
#include <linux/mempolicy.h>
#include <linux/key.h>
#include <linux/buffer_head.h>
#include <linux/page_cgroup.h>
#include <linux/debug_locks.h>
#include <linux/debugobjects.h>
#include <linux/lockdep.h>
#include <linux/kmemleak.h>
#include <linux/pid_namespace.h>
#include <linux/device.h>
#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/idr.h>
#include <linux/kgdb.h>
#include <linux/ftrace.h>
#include <linux/async.h>
#include <linux/kmemcheck.h>
#include <linux/sfi.h>
#include <linux/shmem_fs.h>
#include <linux/slab.h>

#include <asm/io.h>
#include <asm/bugs.h>
#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/cacheflush.h>

#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/smp.h>
#endif

static int kernel_init(void *);

extern void init_IRQ(void);
extern void fork_init(unsigned long);
extern void mca_init(void);
extern void sbus_init(void);
extern void prio_tree_init(void);
extern void radix_tree_init(void);
extern void free_initmem(void);
#ifndef CONFIG_DEBUG_RODATA
static inline void mark_rodata_ro(void) { }
#endif

#ifdef CONFIG_TC
extern void tc_init(void);
#endif

enum system_states system_state __read_mostly;
EXPORT_SYMBOL(system_state);

/*
 * Boot command-line arguments
 */
#define MAX_INIT_ARGS CONFIG_INIT_ENV_ARG_LIMIT
#define MAX_INIT_ENVS CONFIG_INIT_ENV_ARG_LIMIT

extern void time_init(void);
/* Default late time init is NULL. archs can override this later. */
void (*__initdata late_time_init)(void);
extern void softirq_init(void);

/* Untouched command line saved by arch-specific code. */
char __initdata boot_command_line[COMMAND_LINE_SIZE];
/* Untouched saved command line (eg. for /proc) */
char *saved_command_line;
/* Command line for parameter parsing */
static char *static_command_line;

static char *execute_command;
static char *ramdisk_execute_command;

#ifdef CONFIG_SMP
/* Setup configured maximum number of CPUs to activate */
unsigned int setup_max_cpus = NR_CPUS;
EXPORT_SYMBOL(setup_max_cpus);


/*
 * Setup routine for controlling SMP activation
 *
 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
 * activation entirely (the MPS table probe still happens, though).
 *
 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
 * greater than 0, limits the maximum number of CPUs activated in
 * SMP mode to <NUM>.
 */

void __weak arch_disable_smp_support(void) { }

static int __init nosmp(char *str)
{
        setup_max_cpus = 0;
        arch_disable_smp_support();

        return 0;
}

early_param("nosmp", nosmp);

/* this is hard limit */
static int __init nrcpus(char *str)
{
        int nr_cpus;

        get_option(&str, &nr_cpus);
        if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
                nr_cpu_ids = nr_cpus;

        return 0;
}

early_param("nr_cpus", nrcpus);

static int __init maxcpus(char *str)
{
        get_option(&str, &setup_max_cpus);
        if (setup_max_cpus == 0)
                arch_disable_smp_support();

        return 0;
}

early_param("maxcpus", maxcpus);
#else
static const unsigned int setup_max_cpus = NR_CPUS;
#endif

/*
 * If set, this is an indication to the drivers that reset the underlying
 * device before going ahead with the initialization otherwise driver might
 * rely on the BIOS and skip the reset operation.
 *
 * This is useful if kernel is booting in an unreliable environment.
 * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
 * skipped and devices will be in unknown state.
 */
unsigned int reset_devices;
EXPORT_SYMBOL(reset_devices);

static int __init set_reset_devices(char *str)
{
        reset_devices = 1;
        return 1;
}

__setup("reset_devices", set_reset_devices);

static const char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
const char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
static const char *panic_later, *panic_param;

extern const struct obs_kernel_param __setup_start[], __setup_end[];

static int __init obsolete_checksetup(char *line)
{
        const struct obs_kernel_param *p;
        int had_early_param = 0;

        p = __setup_start;
        do {
                int n = strlen(p->str);
                if (!strncmp(line, p->str, n)) {
                        if (p->early) {
                                /* Already done in parse_early_param?
                                 * (Needs exact match on param part).
                                 * Keep iterating, as we can have early
                                 * params and __setups of same names 8( */
                                if (line[n] == '\0' || line[n] == '=')
                                        had_early_param = 1;
                        } else if (!p->setup_func) {
                                printk(KERN_WARNING "Parameter %s is obsolete,"
                                       " ignored\n", p->str);
                                return 1;
                        } else if (p->setup_func(line + n))
                                return 1;
                }
                p++;
        } while (p < __setup_end);

        return had_early_param;
}

/*
 * This should be approx 2 Bo*oMips to start (note initial shift), and will
 * still work even if initially too large, it will just take slightly longer
 */
unsigned long loops_per_jiffy = (1<<12);

EXPORT_SYMBOL(loops_per_jiffy);

static int __init debug_kernel(char *str)
{
        console_loglevel = 10;
        return 0;
}

static int __init quiet_kernel(char *str)
{
        console_loglevel = 4;
        return 0;
}

early_param("debug", debug_kernel);
early_param("quiet", quiet_kernel);

static int __init loglevel(char *str)
{
        get_option(&str, &console_loglevel);
        return 0;
}

early_param("loglevel", loglevel);

/*
 * Unknown boot options get handed to init, unless they look like
 * unused parameters (modprobe will find them in /proc/cmdline).
 */
static int __init unknown_bootoption(char *param, char *val)
{
        /* Change NUL term back to "=", to make "param" the whole string. */
        if (val) {
                /* param=val or param="val"? */
                if (val == param+strlen(param)+1)
                        val[-1] = '=';
                else if (val == param+strlen(param)+2) {
                        val[-2] = '=';
                        memmove(val-1, val, strlen(val)+1);
                        val--;
                } else
                        BUG();
        }

        /* Handle obsolete-style parameters */
        if (obsolete_checksetup(param))
                return 0;

        /* Unused module parameter. */
        if (strchr(param, '.') && (!val || strchr(param, '.') < val))
                return 0;

        if (panic_later)
                return 0;

        if (val) {
                /* Environment option */
                unsigned int i;
                for (i = 0; envp_init[i]; i++) {
                        if (i == MAX_INIT_ENVS) {
                                panic_later = "Too many boot env vars at `%s'";
                                panic_param = param;
                        }
                        if (!strncmp(param, envp_init[i], val - param))
                                break;
                }
                envp_init[i] = param;
        } else {
                /* Command line option */
                unsigned int i;
                for (i = 0; argv_init[i]; i++) {
                        if (i == MAX_INIT_ARGS) {
                                panic_later = "Too many boot init vars at `%s'";
                                panic_param = param;
                        }
                }
                argv_init[i] = param;
        }
        return 0;
}

#ifdef CONFIG_DEBUG_PAGEALLOC
int __read_mostly debug_pagealloc_enabled = 0;
#endif

static int __init init_setup(char *str)
{
        unsigned int i;

        execute_command = str;
        /*
         * In case LILO is going to boot us with default command line,
         * it prepends "auto" before the whole cmdline which makes
         * the shell think it should execute a script with such name.
         * So we ignore all arguments entered _before_ init=... [MJ]
         */
        for (i = 1; i < MAX_INIT_ARGS; i++)
                argv_init[i] = NULL;
        return 1;
}
__setup("init=", init_setup);

static int __init rdinit_setup(char *str)
{
        unsigned int i;

        ramdisk_execute_command = str;
        /* See "auto" comment in init_setup */
        for (i = 1; i < MAX_INIT_ARGS; i++)
                argv_init[i] = NULL;
        return 1;
}
__setup("rdinit=", rdinit_setup);

#ifndef CONFIG_SMP

#ifdef CONFIG_X86_LOCAL_APIC
static void __init smp_init(void)
{
        APIC_init_uniprocessor();
}
#else
#define smp_init()      do { } while (0)
#endif

static inline void setup_nr_cpu_ids(void) { }
static inline void smp_prepare_cpus(unsigned int maxcpus) { }

#else

/* Setup number of possible processor ids */
int nr_cpu_ids __read_mostly = NR_CPUS;
EXPORT_SYMBOL(nr_cpu_ids);

/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
static void __init setup_nr_cpu_ids(void)
{
        nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
}

/* Called by boot processor to activate the rest. */
static void __init smp_init(void)
{
        unsigned int cpu;

        /* FIXME: This should be done in userspace --RR */
        for_each_present_cpu(cpu) {
                if (num_online_cpus() >= setup_max_cpus)
                        break;
                if (!cpu_online(cpu))
                        cpu_up(cpu);
        }

        /* Any cleanup work */
        printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
        smp_cpus_done(setup_max_cpus);
}

#endif

/*
 * We need to store the untouched command line for future reference.
 * We also need to store the touched command line since the parameter
 * parsing is performed in place, and we should allow a component to
 * store reference of name/value for future reference.
 */
static void __init setup_command_line(char *command_line)
{
        saved_command_line = alloc_bootmem(strlen (boot_command_line)+1);
        static_command_line = alloc_bootmem(strlen (command_line)+1);
        strcpy (saved_command_line, boot_command_line);
        strcpy (static_command_line, command_line);
}

/*
 * We need to finalize in a non-__init function or else race conditions
 * between the root thread and the init thread may cause start_kernel to
 * be reaped by free_initmem before the root thread has proceeded to
 * cpu_idle.
 *
 * gcc-3.4 accidentally inlines this function, so use noinline.
 */

static __initdata DECLARE_COMPLETION(kthreadd_done);

static noinline void __init_refok rest_init(void)
        __releases(kernel_lock)
{
        int pid;

        rcu_scheduler_starting();
        /*
         * We need to spawn init first so that it obtains pid 1, however
         * the init task will end up wanting to create kthreads, which, if
         * we schedule it before we create kthreadd, will OOPS.
         */
        kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
        numa_default_policy();
        pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
        rcu_read_lock();
        kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
        rcu_read_unlock();
        complete(&kthreadd_done);

        /*
         * The boot idle thread must execute schedule()
         * at least once to get things moving:
         */
        init_idle_bootup_task(current);
        preempt_enable_no_resched();
        schedule();
        preempt_disable();

        /* Call into cpu_idle with preempt disabled */
        cpu_idle();
}

/* Check for early params. */
static int __init do_early_param(char *param, char *val)
{
        const struct obs_kernel_param *p;

        for (p = __setup_start; p < __setup_end; p++) {
                if ((p->early && strcmp(param, p->str) == 0) ||
                    (strcmp(param, "console") == 0 &&
                     strcmp(p->str, "earlycon") == 0)
                ) {
                        if (p->setup_func(val) != 0)
                                printk(KERN_WARNING
                                       "Malformed early option '%s'\n", param);
                }
        }
        /* We accept everything at this stage. */
        return 0;
}

void __init parse_early_options(char *cmdline)
{
        parse_args("early options", cmdline, NULL, 0, do_early_param);
}

/* Arch code calls this early on, or if not, just before other parsing. */
void __init parse_early_param(void)
{
        static __initdata int done = 0;
        static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];

        if (done)
                return;

        /* All fall through to do_early_param. */
        strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
        parse_early_options(tmp_cmdline);
        done = 1;
}

/*
 *      Activate the first processor.
 */

static void __init boot_cpu_init(void)
{
        int cpu = smp_processor_id();
        /* Mark the boot cpu "present", "online" etc for SMP and UP case */
        set_cpu_online(cpu, true);
        set_cpu_active(cpu, true);
        set_cpu_present(cpu, true);
        set_cpu_possible(cpu, true);
}

void __init __weak smp_setup_processor_id(void)
{
}

void __init __weak thread_info_cache_init(void)
{
}

/*
 * Set up kernel memory allocators
 */
static void __init mm_init(void)
{
        /*
         * page_cgroup requires countinous pages as memmap
         * and it's bigger than MAX_ORDER unless SPARSEMEM.
         */
        page_cgroup_init_flatmem();
        mem_init();
        kmem_cache_init();
        percpu_init_late();
        pgtable_cache_init();
        vmalloc_init();
}

asmlinkage void __init start_kernel(void)
{
        char * command_line;
        extern const struct kernel_param __start___param[], __stop___param[];

        smp_setup_processor_id();

        /*
         * Need to run as early as possible, to initialize the
         * lockdep hash:
         */
        lockdep_init();
        debug_objects_early_init();

        /*
         * Set up the the initial canary ASAP:
         */
        boot_init_stack_canary();

        cgroup_init_early();

        local_irq_disable();
        early_boot_irqs_off();
        early_init_irq_lock_class();

/*
 * Interrupts are still disabled. Do necessary setups, then
 * enable them
 */
        tick_init();
        boot_cpu_init();
        page_address_init();
        printk(KERN_NOTICE "%s", linux_banner);
        setup_arch(&command_line);
        mm_init_owner(&init_mm, &init_task);
        setup_command_line(command_line);
        setup_nr_cpu_ids();
        setup_per_cpu_areas();
        smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */

        build_all_zonelists(NULL);
        page_alloc_init();

        printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
        parse_early_param();
        parse_args("Booting kernel", static_command_line, __start___param,
                   __stop___param - __start___param,
                   &unknown_bootoption);
        /*
         * These use large bootmem allocations and must precede
         * kmem_cache_init()
         */
        pidhash_init();
        vfs_caches_init_early();
        sort_main_extable();
        trap_init();
        mm_init();
        /*
         * Set up the scheduler prior starting any interrupts (such as the
         * timer interrupt). Full topology setup happens at smp_init()
         * time - but meanwhile we still have a functioning scheduler.
         */
        sched_init();
        /*
         * Disable preemption - early bootup scheduling is extremely
         * fragile until we cpu_idle() for the first time.
         */
        preempt_disable();
        if (!irqs_disabled()) {
                printk(KERN_WARNING "start_kernel(): bug: interrupts were "
                                "enabled *very* early, fixing it\n");
                local_irq_disable();
        }
        rcu_init();
        radix_tree_init();
        /* init some links before init_ISA_irqs() */
        early_irq_init();
        init_IRQ();
        prio_tree_init();
        init_timers();
        hrtimers_init();
        softirq_init();
        timekeeping_init();
        time_init();
        profile_init();
        if (!irqs_disabled())
                printk(KERN_CRIT "start_kernel(): bug: interrupts were "
                                 "enabled early\n");
        early_boot_irqs_on();
        local_irq_enable();

        /* Interrupts are enabled now so all GFP allocations are safe. */
        gfp_allowed_mask = __GFP_BITS_MASK;

        kmem_cache_init_late();

        /*
         * HACK ALERT! This is early. We're enabling the console before
         * we've done PCI setups etc, and console_init() must be aware of
         * this. But we do want output early, in case something goes wrong.
         */
        console_init();
        if (panic_later)
                panic(panic_later, panic_param);

        lockdep_info();

        /*
         * Need to run this when irqs are enabled, because it wants
         * to self-test [hard/soft]-irqs on/off lock inversion bugs
         * too:
         */
        locking_selftest();

#ifdef CONFIG_BLK_DEV_INITRD
        if (initrd_start && !initrd_below_start_ok &&
            page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
                printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
                    "disabling it.\n",
                    page_to_pfn(virt_to_page((void *)initrd_start)),
                    min_low_pfn);
                initrd_start = 0;
        }
#endif
        page_cgroup_init();
        enable_debug_pagealloc();
        kmemleak_init();
        debug_objects_mem_init();
        idr_init_cache();
        setup_per_cpu_pageset();
        numa_policy_init();
        if (late_time_init)
                late_time_init();
        sched_clock_init();
        calibrate_delay();
        pidmap_init();
        anon_vma_init();
#ifdef CONFIG_X86
        if (efi_enabled)
                efi_enter_virtual_mode();
#endif
        thread_info_cache_init();
        cred_init();
        fork_init(totalram_pages);
        proc_caches_init();
        buffer_init();
        key_init();
        security_init();
        dbg_late_init();
        vfs_caches_init(totalram_pages);
        signals_init();
        /* rootfs populating might need page-writeback */
        page_writeback_init();
#ifdef CONFIG_PROC_FS
        proc_root_init();
#endif
        cgroup_init();
        cpuset_init();
        taskstats_init_early();
        delayacct_init();

        check_bugs();

        acpi_early_init(); /* before LAPIC and SMP init */
        sfi_init_late();

        ftrace_init();

        /* Do the rest non-__init'ed, we're now alive */
        rest_init();
}

/* Call all constructor functions linked into the kernel. */
static void __init do_ctors(void)
{
#ifdef CONFIG_CONSTRUCTORS
        ctor_fn_t *fn = (ctor_fn_t *) __ctors_start;

        for (; fn < (ctor_fn_t *) __ctors_end; fn++)
                (*fn)();
#endif
}

int initcall_debug;
core_param(initcall_debug, initcall_debug, bool, 0644);

static char msgbuf[64];

static int __init_or_module do_one_initcall_debug(initcall_t fn)
{
        ktime_t calltime, delta, rettime;
        unsigned long long duration;
        int ret;

        printk(KERN_DEBUG "calling  %pF @ %i\n", fn, task_pid_nr(current));
        calltime = ktime_get();
        ret = fn();
        rettime = ktime_get();
        delta = ktime_sub(rettime, calltime);
        duration = (unsigned long long) ktime_to_ns(delta) >> 10;
        printk(KERN_DEBUG "initcall %pF returned %d after %lld usecs\n", fn,
                ret, duration);

        return ret;
}

int __init_or_module do_one_initcall(initcall_t fn)
{
        int count = preempt_count();
        int ret;

        if (initcall_debug)
                ret = do_one_initcall_debug(fn);
        else
                ret = fn();

        msgbuf[0] = 0;

        if (ret && ret != -ENODEV && initcall_debug)
                sprintf(msgbuf, "error code %d ", ret);

        if (preempt_count() != count) {
                strlcat(msgbuf, "preemption imbalance ", sizeof(msgbuf));
                preempt_count() = count;
        }
        if (irqs_disabled()) {
                strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));
                local_irq_enable();
        }
        if (msgbuf[0]) {
                printk("initcall %pF returned with %s\n", fn, msgbuf);
        }

        return ret;
}


extern initcall_t __initcall_start[], __initcall_end[], __early_initcall_end[];

static void __init do_initcalls(void)
{
        initcall_t *fn;

        for (fn = __early_initcall_end; fn < __initcall_end; fn++)
                do_one_initcall(*fn);

        /* Make sure there is no pending stuff from the initcall sequence */
        flush_scheduled_work();
}

/*
 * Ok, the machine is now initialized. None of the devices
 * have been touched yet, but the CPU subsystem is up and
 * running, and memory and process management works.
 *
 * Now we can finally start doing some real work..
 */
static void __init do_basic_setup(void)
{
        cpuset_init_smp();
        usermodehelper_init();
        init_tmpfs();
        driver_init();
        init_irq_proc();
        do_ctors();
        do_initcalls();
}

static void __init do_pre_smp_initcalls(void)
{
        initcall_t *fn;

        for (fn = __initcall_start; fn < __early_initcall_end; fn++)
                do_one_initcall(*fn);
}

static void run_init_process(const char *init_filename)
{
        argv_init[0] = init_filename;
        kernel_execve(init_filename, argv_init, envp_init);
}

/* This is a non __init function. Force it to be noinline otherwise gcc
 * makes it inline to init() and it becomes part of init.text section
 */
static noinline int init_post(void)
        __releases(kernel_lock)
{
        /* need to finish all async __init code before freeing the memory */
        async_synchronize_full();
        free_initmem();
        mark_rodata_ro();
        system_state = SYSTEM_RUNNING;
        numa_default_policy();


        current->signal->flags |= SIGNAL_UNKILLABLE;

        if (ramdisk_execute_command) {
                run_init_process(ramdisk_execute_command);
                printk(KERN_WARNING "Failed to execute %s\n",
                                ramdisk_execute_command);
        }

        /*
         * We try each of these until one succeeds.
         *
         * The Bourne shell can be used instead of init if we are
         * trying to recover a really broken machine.
         */
        if (execute_command) {
                run_init_process(execute_command);
                printk(KERN_WARNING "Failed to execute %s.  Attempting "
                                        "defaults...\n", execute_command);
        }
        run_init_process("/sbin/init");
        run_init_process("/etc/init");
        run_init_process("/bin/init");
        run_init_process("/bin/sh");

        panic("No init found.  Try passing init= option to kernel. "
              "See Linux Documentation/init.txt for guidance.");
}

static int __init kernel_init(void * unused)
{
        /*
         * Wait until kthreadd is all set-up.
         */
        wait_for_completion(&kthreadd_done);
        /*
         * init can allocate pages on any node
         */
        set_mems_allowed(node_states[N_HIGH_MEMORY]);
        /*
         * init can run on any cpu.
         */
        set_cpus_allowed_ptr(current, cpu_all_mask);
        /*
         * Tell the world that we're going to be the grim
         * reaper of innocent orphaned children.
         *
         * We don't want people to have to make incorrect
         * assumptions about where in the task array this
         * can be found.
         */
        init_pid_ns.child_reaper = current;

        cad_pid = task_pid(current);

        smp_prepare_cpus(setup_max_cpus);

        do_pre_smp_initcalls();

        smp_init();
        sched_init_smp();

        do_basic_setup();

        /* Open the /dev/console on the rootfs, this should never fail */
        if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
                printk(KERN_WARNING "Warning: unable to open an initial console.\n");

        (void) sys_dup(0);
        (void) sys_dup(0);
        /*
         * check if there is an early userspace init.  If yes, let it do all
         * the work
         */

        if (!ramdisk_execute_command)
                ramdisk_execute_command = "/init";

        if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
                ramdisk_execute_command = NULL;
                prepare_namespace();
        }

        /*
         * Ok, we have completed the initial bootup, and
         * we're essentially up and running. Get rid of the
         * initmem segments and start the user-mode stuff..
         */

        init_post();
        return 0;
}