linux/init/main.c at master · hometudo/linux

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10BC8

* linux/init/main.c

* 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>

#define DEBUG /* Enable initcall_debug */

#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/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_ext.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 <linux/perf_event.h>

#include <linux/file.h>

#include <linux/ptrace.h>

#include <linux/blkdev.h>

#include <linux/elevator.h>

#include <linux/sched_clock.h>

#include <linux/context_tracking.h>

#include <linux/random.h>

#include <linux/list.h>

#include <linux/integrity.h>

#include <linux/proc_ns.h>

#include <linux/io.h>

#include <linux/cache.h>

#include <asm/io.h>

#include <asm/bugs.h>

#include <asm/setup.h>

#include <asm/sections.h>

#include <asm/cacheflush.h>

static int kernel_init(void *);

extern void init_IRQ(void);

extern void fork_init(void);

extern void radix_tree_init(void);

* Debug helper: via this flag we know that we are in 'early bootup code'

* where only the boot processor is running with IRQ disabled. This means

* two things - IRQ must not be enabled before the flag is cleared and some

* operations which are not allowed with IRQ disabled are allowed while the

* flag is set.

bool early_boot_irqs_disabled __read_mostly;

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);

/* 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;

/* Command line for per-initcall parameter parsing */

static char *initcall_command_line;

static char *execute_command;

static char *ramdisk_execute_command;

* Used to generate warnings if static_key manipulation functions are used

* before jump_label_init is called.

bool static_key_initialized __read_mostly;

EXPORT_SYMBOL_GPL(static_key_initialized);

* 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 situation 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 bool __init obsolete_checksetup(char *line)

{

const struct obs_kernel_param *p;

bool had_early_param = false;

p = __setup_start;

do {

int n = strlen(p->str);

if (parameqn(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 = true;

} else if (!p->setup_func) {

pr_warn("Parameter %s is obsolete, ignored\n",

p->str);

return true;

} else if (p->setup_func(line + n))

return true;

}

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 = CONSOLE_LOGLEVEL_DEBUG;

return 0;

}

static int __init quiet_kernel(char *str)

{

console_loglevel = CONSOLE_LOGLEVEL_QUIET;

return 0;

}

early_param("debug", debug_kernel);

early_param("quiet", quiet_kernel);

static int __init loglevel(char *str)

{

int newlevel;

* Only update loglevel value when a correct setting was passed,

* to prevent blind crashes (when loglevel being set to 0) that

* are quite hard to debug

if (get_option(&str, &newlevel)) {

console_loglevel = newlevel;

return 0;

}

return -EINVAL;

}

early_param("loglevel", loglevel);

/* Change NUL term back to "=", to make "param" the whole string. */

static int __init repair_env_string(char *param, char *val,

const char *unused, void *arg)

{

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();

}

return 0;

}

/* Anything after -- gets handed straight to init. */

static int __init set_init_arg(char *param, char *val,

const char *unused, void *arg)

{

unsigned int i;

if (panic_later)

return 0;

repair_env_string(param, val, unused, NULL);

for (i = 0; argv_init[i]; i++) {

if (i == MAX_INIT_ARGS) {

panic_later = "init";

panic_param = param;

return 0;

}

argv_init[i] = param;

return 0;

}

* 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,

const char *unused, void *arg)

{

repair_env_string(param, val, unused, NULL);

/* 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 = "env";

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 = "init";

panic_param = param;

}

argv_init[i] = param;

}

return 0;

}

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

static const unsigned int setup_max_cpus = NR_CPUS;

static inline void setup_nr_cpu_ids(void) { }

static inline void smp_prepare_cpus(unsigned int maxcpus) { }

#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 =

memblock_virt_alloc(strlen(boot_command_line) + 1, 0);

initcall_command_line =

memblock_virt_alloc(strlen(boot_command_line) + 1, 0);

static_command_line = memblock_virt_alloc(strlen(command_line) + 1, 0);

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 __ref rest_init(void)

{

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);

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);

schedule_preempt_disabled();

/* Call into cpu_idle with preempt disabled */

cpu_startup_entry(CPUHP_ONLINE);

}

/* Check for early params. */

static int __init do_early_param(char *param, char *val,

const char *unused, void *arg)

{

const struct obs_kernel_param *p;

for (p = __setup_start; p < __setup_end; p++) {

if ((p->early && parameq(param, p->str)) ||

(strcmp(param, "console") == 0 &&

strcmp(p->str, "earlycon") == 0)

) {

if (p->setup_func(val) != 0)

pr_warn("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, 0, 0, NULL,

do_early_param);

}

/* Arch code calls this early on, or if not, just before other parsing. */

void __init parse_early_param(void)

{

static int done __initdata;

static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;

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;

}

void __init __weak arch_post_acpi_subsys_init(void) { }

void __init __weak smp_setup_processor_id(void)

{

}

# if THREAD_SIZE >= PAGE_SIZE

void __init __weak thread_stack_cache_init(void)

{

}

#endif

* Set up kernel memory allocators

static void __init mm_init(void)

{

* page_ext requires contiguous pages,

* bigger than MAX_ORDER unless SPARSEMEM.

page_ext_init_flatmem();

mem_init();

kmem_cache_init();

percpu_init_late();

pgtable_init();

vmalloc_init();

ioremap_huge_init();

}

asmlinkage __visible void __init start_kernel(void)

{

char *command_line;

char *after_dashes;

set_task_stack_end_magic(&init_task);

smp_setup_processor_id();

debug_objects_early_init();

* Set up the the initial canary ASAP:

boot_init_stack_canary();

cgroup_init_early();

local_irq_disable();

early_boot_irqs_disabled = true;

* Interrupts are still disabled. Do necessary setups, then

* enable them

boot_cpu_init();

page_address_init();

pr_notice("%s", linux_banner);

setup_arch(&command_line);

mm_init_cpumask(&init_mm);

setup_command_line(command_line);

setup_nr_cpu_ids();

setup_per_cpu_areas();

boot_cpu_state_init();

smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */

build_all_zonelists(NULL, NULL);

page_alloc_init();

pr_notice("Kernel command line: %s\n", boot_command_line);

parse_early_param();

after_dashes = parse_args("Booting kernel",

static_command_line, __start___param,

__stop___param - __start___param,

-1, -1, NULL, &unknown_bootoption);

if (!IS_ERR_OR_NULL(after_dashes))

parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,

NULL, set_init_arg);

jump_label_init();

* These use large bootmem allocations and must precede

* kmem_cache_init()

setup_log_buf(0);

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 (WARN(!irqs_disabled(),

"Interrupts were enabled *very* early, fixing it\n"))

local_irq_disable();

idr_init_cache();

* Allow workqueue creation and work item queueing/cancelling

* early. Work item execution depends on kthreads and starts after

* workqueue_init().

workqueue_init_early();

rcu_init();

/* trace_printk() and trace points may be used after this */

trace_init();

context_tracking_init();

radix_tree_init();

/* init some links before init_ISA_irqs() */

early_irq_init();

init_IRQ();

tick_init();

rcu_init_nohz();

init_timers();

hrtimers_init();

softirq_init();

timekeeping_init();

time_init();

sched_clock_postinit();

printk_nmi_init();

perf_event_init();

profile_init();

call_function_init();

WARN(!irqs_disabled(), "Interrupts were enabled early\n");

early_boot_irqs_disabled = false;

local_irq_enable();

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("Too many boot %s vars at `%s'", 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) {

pr_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_ext_init();

debug_objects_mem_init();

kmemleak_init();

setup_per_cpu_pageset();

numa_policy_init();

if (late_time_init)

late_time_init();

sched_clock_init();

calibrate_delay();

pidmap_init();

anon_vma_init();

acpi_early_init();

#ifdef CONFIG_X86

if (efi_enabled(EFI_RUNTIME_SERVICES))

efi_enter_virtual_mode();

#endif

#ifdef CONFIG_X86_ESPFIX64

/* Should be run before the first non-init thread is created */

init_espfix_bsp();

#endif

thread_stack_cache_init();

cred_init();

fork_init();

proc_caches_init();

buffer_init();

key_init();

security_init();

dbg_late_init();

vfs_caches_init();

pagecache_init();

signals_init();

proc_root_init();

nsfs_init();

cpuset_init();

cgroup_init();

taskstats_init_early();

delayacct_init();

check_bugs();

acpi_subsystem_init();

arch_post_acpi_subsys_init();

sfi_init_late();

if (efi_enabled(EFI_RUNTIME_SERVICES)) {

efi_late_init();

efi_free_boot_services();

}

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

}

bool initcall_debug;

core_param(initcall_debug, initcall_debug, bool, 0644);

#ifdef CONFIG_KALLSYMS

struct blacklist_entry {

struct list_head next;

char *buf;

};

static __initdata_or_module LIST_HEAD(blacklisted_initcalls);

static int __init initcall_blacklist(char *str)

{

char *str_entry;

struct blacklist_entry *entry;

/* str argument is a comma-separated list of functions */

do {

str_entry = strsep(&str, ",");

if (str_entry) {

pr_debug("blacklisting initcall %s\n", str_entry);

entry = alloc_bootmem(sizeof(*entry));

entry->buf = alloc_bootmem(strlen(str_entry) + 1);

strcpy(entry->buf, str_entry);

list_add(&entry->next, &blacklisted_initcalls);

}

} while (str_entry);

return 0;

}

static bool __init_or_module initcall_blacklisted(initcall_t fn)

{

struct blacklist_entry *entry;

char fn_name[KSYM_SYMBOL_LEN];

unsigned long addr;

if (list_empty(&blacklisted_initcalls))

return false;

addr = (unsigned long) dereference_function_descriptor(fn);

sprint_symbol_no_offset(fn_name, addr);

* fn will be "function_name [module_name]" where [module_name] is not

* displayed for built-in init functions. Strip off the [module_name].

strreplace(fn_name, ' ', '\0');

list_for_each_entry(entry, &blacklisted_initcalls, next) {

if (!strcmp(fn_name, entry->buf)) {

pr_debug("initcall %s blacklisted\n", fn_name);

return true;

}

return false;

}

#else

static int __init initcall_blacklist(char *str)

{

pr_warn("initcall_blacklist requires CONFIG_KALLSYMS\n");

return 0;

}

static bool __init_or_module initcall_blacklisted(initcall_t fn)

{

return false;

}

#endif

__setup("initcall_blacklist=", initcall_blacklist);

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;

char msgbuf[64];

if (initcall_blacklisted(fn))

return -EPERM;

if (initcall_debug)

ret = do_one_initcall_debug(fn);

else

ret = fn();

msgbuf[0] = 0;

if (preempt_count() != count) {

sprintf(msgbuf, "preemption imbalance ");

preempt_count_set(count);

}

if (irqs_disabled()) {

strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));

local_irq_enable();

}

WARN(msgbuf[0], "initcall %pF returned with %s\n", fn, msgbuf);

add_latent_entropy();

return ret;

}

extern initcall_t __initcall_start[];

extern initcall_t __initcall0_start[];

extern initcall_t __initcall1_start[];

extern initcall_t __initcall2_start[];

extern initcall_t __initcall3_start[];

extern initcall_t __initcall4_start[];

extern initcall_t __initcall5_start[];

extern initcall_t __initcall6_start[];

extern initcall_t __initcall7_start[];

extern initcall_t __initcall_end[];

static initcall_t *initcall_levels[] __initdata = {

__initcall0_start,

__initcall1_start,

__initcall2_start,

__initcall3_start,

__initcall4_start,

__initcall5_start,

__initcall6_start,

__initcall7_start,

__initcall_end,

};

/* Keep these in sync with initcalls in include/linux/init.h */

static char *initcall_level_names[] __initdata = {

"early",

"core",

"postcore",

"arch",

"subsys",

"fs",

"device",

"late",

};

static void __init do_initcall_level(int level)

{

initcall_t *fn;

strcpy(initcall_command_line, saved_command_line);

parse_args(initcall_level_names[level],

initcall_command_line, __start___param,

__stop___param - __start___param,

level, level,

NULL, &repair_env_string);

for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)

do_one_initcall(*fn);

}

static void __init do_initcalls(void)

{

int level;

for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)

do_initcall_level(level);

}

* 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();

shmem_init();

driver_init();

init_irq_proc();

do_ctors();

usermodehelper_enable();

do_initcalls();

random_int_secret_init();

}

static void __init do_pre_smp_initcalls(void)

{

initcall_t *fn;

for (fn = __initcall_start; fn < __initcall0_start; fn++)

do_one_initcall(*fn);

}

* This function requests modules which should be loaded by default and is

* called twice right after initrd is mounted and right before init is

* exec'd. If such modules are on either initrd or rootfs, they will be

* loaded before control is passed to userland.

void __init load_default_modules(void)

{

load_default_elevator_module();

}

static int run_init_process(const char *init_filename)

{

argv_init[0] = init_filename;

return do_execve(getname_kernel(init_filename),

(const char __user *const __user *)argv_init,

(const char __user *const __user *)envp_init);

}

static int try_to_run_init_process(const char *init_filename)

{

int ret;

ret = run_init_process(init_filename);

if (ret && ret != -ENOENT) {

pr_err("Starting init: %s exists but couldn't execute it (error %d)\n",

init_filename, ret);

}

return ret;

}

static noinline void __init kernel_init_freeable(void);

#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX)

bool rodata_enabled __ro_after_init = true;

static int __init set_debug_rodata(char *str)

{

return strtobool(str, &rodata_enabled);

}

__setup("rodata=", set_debug_rodata);

#endif

#ifdef CONFIG_DEBUG_RODATA

static void mark_readonly(void)

{

if (rodata_enabled)

mark_rodata_ro();

else

pr_info("Kernel memory protection disabled.\n");

}

#else

static inline void mark_readonly(void)

{

pr_warn("This architecture does not have kernel memory protection.\n");

}

#endif

static int __ref kernel_init(void *unused)

{

int ret;

kernel_init_freeable();

/* need to finish all async __init code before freeing the memory */

async_synchronize_full();

free_initmem();

mark_readonly();

system_state = SYSTEM_RUNNING;

numa_default_policy();

flush_delayed_fput();

rcu_end_inkernel_boot();

if (ramdisk_execute_command) {

ret = run_init_process(ramdisk_execute_command);

if (!ret)

return 0;

pr_err("Failed to execute %s (error %d)\n",

ramdisk_execute_command, ret);

}

* 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) {

ret = run_init_process(execute_command);

if (!ret)

return 0;

panic("Requested init %s failed (error %d).",

execute_command, ret);

}

if (!try_to_run_init_process("/sbin/init") ||

!try_to_run_init_process("/etc/init") ||

!try_to_run_init_process("/bin/init") ||

!try_to_run_init_process("/bin/sh"))

return 0;

panic("No working init found. Try passing init= option to kernel. "

"See Linux Documentation/admin-guide/init.rst for guidance.");

}

static noinline void __init kernel_init_freeable(void)

{

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