main(init)

/*
 *  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  
 */


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#ifdef CONFIG_X86_LOCAL_APIC
#include
#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 __initdata setup_max_cpus = NR_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=", where is an integer
 * greater than 0, limits the maximum number of CPUs activated in
 * SMP mode to .
 */


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);


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


extern struct obs_kernel_param __setup_start[], __setup_end[];


static int __init obsolete_checksetup(char *line)
{
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;


/*
* Set up the current CPU as possible to migrate to.
* The other ones will be done by cpu_up/cpu_down()
*/
set_cpu_active(smp_processor_id(), true);


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


rcu_scheduler_starting();
kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);  /*3    启动init 线程 */
numa_default_policy();
pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
unlock_kernel();


/*
* 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)
{
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_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();
pgtable_cache_init();
vmalloc_init();
}
/* C 代码的入口 */


asmlinkage void __init start_kernel(void)
{
char * command_line;
extern 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
 */
lock_kernel();
tick_init();
boot_cpu_init();
page_address_init();
printk(KERN_NOTICE "%s", linux_banner);
setup_arch(&command_line);    /* 1   激活处理器 */
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();
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();
/* 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. */
set_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();
kmemtrace_init();
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();
vfs_caches_init(totalram_pages);
radix_tree_init();
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();                /* 2    调用此函数，启动 init 线程*/
}


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


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


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


static char msgbuf[64];
static struct boot_trace_call call;
static struct boot_trace_ret ret;


int do_one_initcall(initcall_t fn)
{
int count = preempt_count();
ktime_t calltime, delta, rettime;


if (initcall_debug) {
call.caller = task_pid_nr(current);
printk("calling  %pF @ %i\n", fn, call.caller);
calltime = ktime_get();
trace_boot_call(&call, fn);
enable_boot_trace();
}


ret.result = fn();


if (initcall_debug) {
disable_boot_trace();
rettime = ktime_get();
delta = ktime_sub(rettime, calltime);
ret.duration = (unsigned long long) ktime_to_ns(delta) >> 10;
trace_boot_ret(&ret, fn);
printk("initcall %pF returned %d after %Ld usecs\n", fn,
ret.result, ret.duration);
}


msgbuf[0] = 0;


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


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.result;
}




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


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


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


/* 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)
{
init_workqueues();
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 *call;


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


//内核首先检查在命令行参数中有没有指定内核执行的第一个应用程序；
static void run_init_process(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();
unlock_kernel();
mark_rodata_ro();
system_state = SYSTEM_RUNNING;
numa_default_policy();


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);


current->signal->flags |= SIGNAL_UNKILLABLE;


if (ramdisk_execute_command) {  //执行rdinit=  的文件
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) {   //执行init=  的文件
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.");
}


static int __init kernel_init(void * unused)
{
lock_kernel();


/*
* init can allocate pages on any node
*/
set_mems_allowed(node_possible_map);
/*
* 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();
start_boot_trace();


smp_init();
sched_init_smp();


do_basic_setup();   /*   4     初始化设备驱动*/


/*
* 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();   /* 5    挂载根文件系统*/
}


/*
* 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;
}