main.c

Linux的初始化源代码

/*
 *  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 <[e-mail]> 
 */

#define __KERNEL_SYSCALLS__

#include <linux/config.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/utsname.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/initrd.h>
#include <linux/hdreg.h>
#include <linux/bootmem.h>
#include <linux/tty.h>
#include <linux/gfp.h>
#include <linux/percpu.h>
#include <linux/kernel_stat.h>
#include <linux/security.h>
#include <linux/workqueue.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/efi.h>
#include <linux/unistd.h>
#include <linux/rmap.h>
#include <linux/mempolicy.h>

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

/*
 * This is one of the first .c files built. Error out early
 * if we have compiler trouble..
 */
#if __GNUC__ == 2 && __GNUC_MINOR__ == 96
#ifdef CONFIG_FRAME_POINTER
#error This compiler cannot compile correctly with frame pointers enabled
#endif
#endif

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

/*
 * Versions of gcc older than that listed below may actually compile
 * and link okay, but the end product can have subtle run time bugs.
 * To avoid associated bogus bug reports, we flatly refuse to compile
 * with a gcc that is known to be too old from the very beginning.
 */
#if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 95)
#error Sorry, your GCC is too old. It builds incorrect kernels.
#endif

extern char *linux_banner;

static int init(void *);

extern void init_IRQ(void);
extern void sock_init(void);
extern void fork_init(unsigned long);
extern void mca_init(void);
extern void sbus_init(void);
extern void sysctl_init(void);
extern void signals_init(void);
extern void buffer_init(void);
extern void pidhash_init(void);
extern void pidmap_init(void);
extern void prio_tree_init(void);
extern void radix_tree_init(void);
extern void free_initmem(void);
extern void populate_rootfs(void);
extern void driver_init(void);
extern void prepare_namespace(void);

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

enum system_states system_state;
EXPORT_SYMBOL(system_state);

/*
 * Boot command-line arguments
 */
#define MAX_INIT_ARGS 8
#define MAX_INIT_ENVS 8

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

/* Untouched command line (eg. for /proc) saved by arch-specific code. */
char saved_command_line[COMMAND_LINE_SIZE];

static char *execute_command;

/* Setup configured maximum number of CPUs to activate */
static unsigned int 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=<NUM>", where <NUM> is an integer
 * greater than 0, limits the maximum number of CPUs activated in
 * SMP mode to <NUM>.
 */
static int __init nosmp(char *str)
{
	max_cpus = 0;
	return 1;
}

__setup("nosmp", nosmp);

static int __init maxcpus(char *str)
{
	get_option(&str, &max_cpus);
	return 1;
}

__setup("maxcpus=", maxcpus);

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;

__setup("profile=", profile_setup);

static int __init obsolete_checksetup(char *line)
{
	struct obs_kernel_param *p;
	extern struct obs_kernel_param __setup_start, __setup_end;

	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) */
				if (line[n] == '\0' || line[n] == '=')
					return 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 0;
}

/* 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);

/* This is the number of bits of precision for the loops_per_jiffy.  Each
   bit takes on average 1.5/HZ seconds.  This (like the original) is a little
   better than 1% */
#define LPS_PREC 8

void __devinit calibrate_delay(void)
{
	unsigned long ticks, loopbit;
	int lps_precision = LPS_PREC;

	loops_per_jiffy = (1<<12);

	printk("Calibrating delay loop... ");
	while ((loops_per_jiffy <<= 1) != 0) {
		/* wait for "start of" clock tick */
		ticks = jiffies;
		while (ticks == jiffies)
			/* nothing */;
		/* Go .. */
		ticks = jiffies;
		__delay(loops_per_jiffy);
		ticks = jiffies - ticks;
		if (ticks)
			break;
	}

/* Do a binary approximation to get loops_per_jiffy set to equal one clock
   (up to lps_precision bits) */
	loops_per_jiffy >>= 1;
	loopbit = loops_per_jiffy;
	while ( lps_precision-- && (loopbit >>= 1) ) {
		loops_per_jiffy |= loopbit;
		ticks = jiffies;
		while (ticks == jiffies);
		ticks = jiffies;
		__delay(loops_per_jiffy);
		if (jiffies != ticks)	/* longer than 1 tick */
			loops_per_jiffy &= ~loopbit;
	}

/* Round the value and print it */	
	printk("%lu.%02lu BogoMIPS\n",
		loops_per_jiffy/(500000/HZ),
		(loops_per_jiffy/(5000/HZ)) % 100);
}

static int __init debug_kernel(char *str)
{
	if (*str)
		return 0;
	console_loglevel = 10;
	return 1;
}

static int __init quiet_kernel(char *str)
{
	if (*str)
		return 0;
	console_loglevel = 4;
	return 1;
}

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

/* Unknown boot options get handed to init, unless they look like
   failed parameters */
static int __init unknown_bootoption(char *param, char *val)
{
	/* Change NUL term back to "=", to make "param" the whole string. */
	if (val)
		val[-1] = '=';

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

	/* Preemptive maintenance for "why didn't my mispelled command
           line work?" */
	if (strchr(param, '.') && (!val || strchr(param, '.') < val)) {
		printk(KERN_ERR "Unknown boot option `%s': ignoring\n", param);
		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;
}

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);

extern void setup_arch(char **);
extern void cpu_idle(void);

#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_per_cpu_areas(void) { }
static inline void smp_prepare_cpus(unsigned int maxcpus) { }

#else

#ifdef __GENERIC_PER_CPU
unsigned long __per_cpu_offset[NR_CPUS];

EXPORT_SYMBOL(__per_cpu_offset);

static void __init setup_per_cpu_areas(void)
{
	unsigned long size, i;
	char *ptr;
	/* Created by linker magic */
	extern char __per_cpu_start[], __per_cpu_end[];

	/* Copy section for each CPU (we discard the original) */
	size = ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES);
#ifdef CONFIG_MODULES
	if (size < PERCPU_ENOUGH_ROOM)
		size = PERCPU_ENOUGH_ROOM;
#endif

	ptr = alloc_bootmem(size * NR_CPUS);

	for (i = 0; i < NR_CPUS; i++, ptr += size) {
		__per_cpu_offset[i] = ptr - __per_cpu_start;
		memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
	}
}
#endif /* !__GENERIC_PER_CPU */

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

	/* FIXME: This should be done in userspace --RR */