main.c

linux1.1源代码

/*
 *  linux/init/main.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <stdarg.h>

#include <asm/system.h>
#include <asm/io.h>

#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/config.h>
#include <linux/sched.h>
#include <linux/tty.h>
#include <linux/head.h>
#include <linux/unistd.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/fs.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/utsname.h>
#include <linux/ioport.h>

extern unsigned long * prof_buffer;
extern unsigned long prof_len;
extern char edata, end;
extern char *linux_banner;
asmlinkage void lcall7(void);
struct desc_struct default_ldt;

/*
 * we need this inline - forking from kernel space will result
 * in NO COPY ON WRITE (!!!), until an execve is executed. This
 * is no problem, but for the stack. This is handled by not letting
 * main() use the stack at all after fork(). Thus, no function
 * calls - which means inline code for fork too, as otherwise we
 * would use the stack upon exit from 'fork()'.
 *
 * Actually only pause and fork are needed inline, so that there
 * won't be any messing with the stack from main(), but we define
 * some others too.
 */
#define __NR__exit __NR_exit
static inline _syscall0(int,idle)
static inline _syscall0(int,fork)
static inline _syscall0(int,pause)
static inline _syscall1(int,setup,void *,BIOS)
static inline _syscall0(int,sync)
static inline _syscall0(pid_t,setsid)
static inline _syscall3(int,write,int,fd,const char *,buf,off_t,count)
static inline _syscall1(int,dup,int,fd)
static inline _syscall3(int,execve,const char *,file,char **,argv,char **,envp)
static inline _syscall3(int,open,const char *,file,int,flag,int,mode)
static inline _syscall1(int,close,int,fd)
static inline _syscall1(int,_exit,int,exitcode)
static inline _syscall3(pid_t,waitpid,pid_t,pid,int *,wait_stat,int,options)

static inline pid_t wait(int * wait_stat)
{
	return waitpid(-1,wait_stat,0);
}

static char printbuf[1024];

extern int console_loglevel;

extern char empty_zero_page[PAGE_SIZE];
extern int vsprintf(char *,const char *,va_list);
extern void init(void);
extern void init_IRQ(void);
extern long kmalloc_init (long,long);
extern long blk_dev_init(long,long);
extern long chr_dev_init(long,long);
extern void floppy_init(void);
extern void sock_init(void);
extern long rd_init(long mem_start, int length);
unsigned long net_dev_init(unsigned long, unsigned long);
extern unsigned long simple_strtoul(const char *,char **,unsigned int);

extern void hd_setup(char *str, int *ints);
extern void bmouse_setup(char *str, int *ints);
extern void eth_setup(char *str, int *ints);
extern void xd_setup(char *str, int *ints);
extern void mcd_setup(char *str, int *ints);
extern void st0x_setup(char *str, int *ints);
extern void tmc8xx_setup(char *str, int *ints);
extern void t128_setup(char *str, int *ints);
extern void generic_NCR5380_setup(char *str, int *intr);
extern void aha152x_setup(char *str, int *ints);
extern void sound_setup(char *str, int *ints);
#ifdef CONFIG_SBPCD
extern void sbpcd_setup(char *str, int *ints);
#endif CONFIG_SBPCD

#ifdef CONFIG_SYSVIPC
extern void ipc_init(void);
#endif
#ifdef CONFIG_SCSI
extern unsigned long scsi_dev_init(unsigned long, unsigned long);
#endif

/*
 * This is set up by the setup-routine at boot-time
 */
#define PARAM	empty_zero_page
#define EXT_MEM_K (*(unsigned short *) (PARAM+2))
#define DRIVE_INFO (*(struct drive_info_struct *) (PARAM+0x80))
#define SCREEN_INFO (*(struct screen_info *) (PARAM+0))
#define MOUNT_ROOT_RDONLY (*(unsigned short *) (PARAM+0x1F2))
#define RAMDISK_SIZE (*(unsigned short *) (PARAM+0x1F8))
#define ORIG_ROOT_DEV (*(unsigned short *) (PARAM+0x1FC))
#define AUX_DEVICE_INFO (*(unsigned char *) (PARAM+0x1FF))

/*
 * Boot command-line arguments
 */
#define MAX_INIT_ARGS 8
#define MAX_INIT_ENVS 8
#define COMMAND_LINE ((char *) (PARAM+2048))

extern void time_init(void);

static unsigned long memory_start = 0;	/* After mem_init, stores the */
					/* amount of free user memory */
static unsigned long memory_end = 0;
static unsigned long low_memory_start = 0;

static char term[21];
int rows, cols;

static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
static char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", term, NULL, };

static char * argv_rc[] = { "/bin/sh", NULL };
static char * envp_rc[] = { "HOME=/", term, NULL };

static char * argv[] = { "-/bin/sh",NULL };
static char * envp[] = { "HOME=/usr/root", term, NULL };

struct drive_info_struct { char dummy[32]; } drive_info;
struct screen_info screen_info;

unsigned char aux_device_present;
int ramdisk_size;
int root_mountflags = 0;

static char fpu_error = 0;

static char command_line[80] = { 0, };

char *get_options(char *str, int *ints) 
{
	char *cur = str;
	int i=1;

	while (cur && isdigit(*cur) && i <= 10) {
		ints[i++] = simple_strtoul(cur,NULL,0);
		if ((cur = strchr(cur,',')) != NULL)
			cur++;
	}
	ints[0] = i-1;
	return(cur);
}

struct {
	char *str;
	void (*setup_func)(char *, int *);
} bootsetups[] = {
	{ "reserve=", reserve_setup },
#ifdef CONFIG_INET
	{ "ether=", eth_setup },
#endif
#ifdef CONFIG_BLK_DEV_HD
	{ "hd=", hd_setup },
#endif
#ifdef CONFIG_BUSMOUSE
	{ "bmouse=", bmouse_setup },
#endif
#ifdef CONFIG_SCSI_SEAGATE
	{ "st0x=", st0x_setup },
	{ "tmc8xx=", tmc8xx_setup },
#endif
#ifdef CONFIG_SCSI_T128
	{ "t128=", t128_setup },
#endif
#ifdef CONFIG_SCSI_GENERIC_NCR5380
	{ "ncr5380=", generic_NCR5380_setup },
#endif
#ifdef CONFIG_SCSI_AHA152X
        { "aha152x=", aha152x_setup},
#endif
#ifdef CONFIG_BLK_DEV_XD
	{ "xd=", xd_setup },
#endif
#ifdef CONFIG_MCD
	{ "mcd=", mcd_setup },
#endif
#ifdef CONFIG_SOUND
	{ "sound=", sound_setup },
#endif
#ifdef CONFIG_SBPCD
	{ "sbpcd=", sbpcd_setup },
#endif CONFIG_SBPCD
	{ 0, 0 }
};

int checksetup(char *line)
{
	int i = 0;
	int ints[11];

	while (bootsetups[i].str) {
		int n = strlen(bootsetups[i].str);
		if (!strncmp(line,bootsetups[i].str,n)) {
			bootsetups[i].setup_func(get_options(line+n,ints), ints);
			return(0);
		}
		i++;
	}
	return(1);
}

unsigned long loops_per_sec = 1;

static void calibrate_delay(void)
{
	int ticks;

	printk("Calibrating delay loop.. ");
	while (loops_per_sec <<= 1) {
		ticks = jiffies;
		__delay(loops_per_sec);
		ticks = jiffies - ticks;
		if (ticks >= HZ) {
			__asm__("mull %1 ; divl %2"
				:"=a" (loops_per_sec)
				:"d" (HZ),
				 "r" (ticks),
				 "0" (loops_per_sec)
				:"dx");
			printk("ok - %lu.%02lu BogoMips\n",
				loops_per_sec/500000,
				(loops_per_sec/5000) % 100);
			return;
		}
	}
	printk("failed\n");
}
	

/*
 * This is a simple kernel command line parsing function: it parses
 * the command line, and fills in the arguments/environment to init
 * as appropriate. Any cmd-line option is taken to be an environment
 * variable if it contains the character '='.
 *
 *
 * This routine also checks for options meant for the kernel - currently
 * only the "root=XXXX" option is recognized. These options are not given
 * to init - they are for internal kernel use only.
 */
static void parse_options(char *line)
{
	char *next;
	char *devnames[] = { "hda", "hdb", "sda", "sdb", "sdc", "sdd", "sde", "fd", "xda", "xdb", NULL };
	int devnums[]    = { 0x300, 0x340, 0x800, 0x810, 0x820, 0x830, 0x840, 0x200, 0xC00, 0xC40, 0};
	int args, envs;

	if (!*line)
		return;
	args = 0;
	envs = 1;	/* TERM is set to 'console' by default */
	next = line;
	while ((line = next) != NULL) {
		if ((next = strchr(line,' ')) != NULL)
			*next++ = 0;
		/*
		 * check for kernel options first..
		 */
		if (!strncmp(line,"root=",5)) {
			int n;
			line += 5;
			if (strncmp(line,"/dev/",5)) {
				ROOT_DEV = simple_strtoul(line,NULL,16);
				continue;
			}
			line += 5;
			for (n = 0 ; devnames[n] ; n++) {
				int len = strlen(devnames[n]);
				if (!strncmp(line,devnames[n],len)) {
					ROOT_DEV = devnums[n]+simple_strtoul(line+len,NULL,16);
					break;
				}
			}
		} else if (!strcmp(line,"ro"))
			root_mountflags |= MS_RDONLY;
		else if (!strcmp(line,"rw"))
			root_mountflags &= ~MS_RDONLY;
		else if (!strcmp(line,"debug"))
			console_loglevel = 10;
		else if (!strcmp(line,"no387")) {
			hard_math = 0;
			__asm__("movl %%cr0,%%eax\n\t"
				"orl $0xE,%%eax\n\t"
				"movl %%eax,%%cr0\n\t" : : : "ax");
		} else
			checksetup(line);
		/*
		 * Then check if it's an environment variable or
		 * an option.
		 */	
		if (strchr(line,'=')) {
			if (envs >= MAX_INIT_ENVS)
				break;
			envp_init[++envs] = line;
		} else {
			if (args >= MAX_INIT_ARGS)
				break;
			argv_init[++args] = line;
		}
	}
	argv_init[args+1] = NULL;
	envp_init[envs+1] = NULL;
}

static void copy_options(char * to, char * from)
{
	char c = ' ';

	do {
		if (c == ' ' && !memcmp("mem=", from, 4))
			memory_end = simple_strtoul(from+4, &from, 0);
		c = *(to++) = *(from++);
	} while (c);
}

static void copro_timeout(void)
{
	fpu_error = 1;
	timer_table[COPRO_TIMER].expires = jiffies+100;
	timer_active |= 1<<COPRO_TIMER;
	printk("387 failed: trying to reset\n");
	send_sig(SIGFPE, last_task_used_math, 1);
	outb_p(0,0xf1);
	outb_p(0,0xf0);
}

asmlinkage void start_kernel(void)
{
/*
 * Interrupts are still disabled. Do necessary setups, then
 * enable them
 */
	set_call_gate(&default_ldt,lcall7);
 	ROOT_DEV = ORIG_ROOT_DEV;
 	drive_info = DRIVE_INFO;
 	screen_info = SCREEN_INFO;
	aux_device_present = AUX_DEVICE_INFO;
	memory_end = (1<<20) + (EXT_MEM_K<<10);
	memory_end &= PAGE_MASK;
	ramdisk_size = RAMDISK_SIZE;
	copy_options(command_line,COMMAND_LINE);
#ifdef CONFIG_MAX_16M
	if (memory_end > 16*1024*1024)
		memory_end = 16*1024*1024;
#endif
	if (MOUNT_ROOT_RDONLY)
		root_mountflags |= MS_RDONLY;
	if ((unsigned long)&end >= (1024*1024)) {
		memory_start = (unsigned long) &end;
		low_memory_start = PAGE_SIZE;
	} else {
		memory_start = 1024*1024;
		low_memory_start = (unsigned long) &end;
	}
	low_memory_start = PAGE_ALIGN(low_memory_start);
	memory_start = paging_init(memory_start,memory_end);
	if (strncmp((char*)0x0FFFD9, "EISA", 4) == 0)
		EISA_bus = 1;
	trap_init();
	init_IRQ();
	sched_init();
	parse_options(command_line);
#ifdef CONFIG_PROFILE
	prof_buffer = (unsigned long *) memory_start;
	prof_len = (unsigned long) &end;
	prof_len >>= 2;
	memory_start += prof_len * sizeof(unsigned long);
#endif
	memory_start = kmalloc_init(memory_start,memory_end);
	memory_start = chr_dev_init(memory_start,memory_end);
	memory_start = blk_dev_init(memory_start,memory_end);
	sti();
	calibrate_delay();
#ifdef CONFIG_INET
	memory_start = net_dev_init(memory_start,memory_end);
#endif
#ifdef CONFIG_SCSI
	memory_start = scsi_dev_init(memory_start,memory_end);
#endif
	memory_start = inode_init(memory_start,memory_end);
	memory_start = file_table_init(memory_start,memory_end);
	mem_init(low_memory_start,memory_start,memory_end);
	buffer_init();
	time_init();
	floppy_init();
	sock_init();
#ifdef CONFIG_SYSVIPC
	ipc_init();
#endif
	sti();
	
	/*
	 * check if exception 16 works correctly.. This is truly evil
	 * code: it disables the high 8 interrupts to make sure that
	 * the irq13 doesn't happen. But as this will lead to a lockup
	 * if no exception16 arrives, it depends on the fact that the
	 * high 8 interrupts will be re-enabled by the next timer tick.
	 * So the irq13 will happen eventually, but the exception 16
	 * should get there first..
	 */
	if (hard_math) {
		unsigned short control_word;

		printk("Checking 386/387 coupling... ");
		timer_table[COPRO_TIMER].expires = jiffies+50;
		timer_table[COPRO_TIMER].fn = copro_timeout;
		timer_active |= 1<<COPRO_TIMER;
		__asm__("clts ; fninit ; fnstcw %0 ; fwait":"=m" (*&control_word));
		control_word &= 0xffc0;
		__asm__("fldcw %0 ; fwait": :"m" (*&control_word));
		outb_p(inb_p(0x21) | (1 << 2), 0x21);
		__asm__("fldz ; fld1 ; fdiv %st,%st(1) ; fwait");
		timer_active &= ~(1<<COPRO_TIMER);
		if (!fpu_error)
			printk("Ok, fpu using %s error reporting.\n",
				ignore_irq13?"exception 16":"irq13");
	}
#ifndef CONFIG_MATH_EMULATION
	else {
		printk("No coprocessor found and no math emulation present.\n");
		printk("Giving up.\n");
		for (;;) ;
	}
#endif

	system_utsname.machine[1] = '0' + x86;
	printk(linux_banner);

	move_to_user_mode();
	if (!fork())		/* we count on this going ok */
		init();
/*
 * task[0] is meant to be used as an "idle" task: it may not sleep, but
 * it might do some general things like count free pages or it could be
 * used to implement a reasonable LRU algorithm for the paging routines:
 * anything that can be useful, but shouldn't take time from the real
 * processes.
 *
 * Right now task[0] just does a infinite idle loop.
 */
	for(;;)
		idle();
}

static int printf(const char *fmt, ...)
{
	va_list args;
	int i;

	va_start(args, fmt);
	write(1,printbuf,i=vsprintf(printbuf, fmt, args));
	va_end(args);
	return i;
}

void init(void)
{
	int pid,i;

	setup((void *) &drive_info);
	sprintf(term, "TERM=con%dx%d", ORIG_VIDEO_COLS, ORIG_VIDEO_LINES);
	(void) open("/dev/tty1",O_RDWR,0);
	(void) dup(0);
	(void) dup(0);

	execve("/etc/init",argv_init,envp_init);
	execve("/bin/init",argv_init,envp_init);
	execve("/sbin/init",argv_init,envp_init);
	/* if this fails, fall through to original stuff */

	if (!(pid=fork())) {
		close(0);
		if (open("/etc/rc",O_RDONLY,0))
			_exit(1);
		execve("/bin/sh",argv_rc,envp_rc);
		_exit(2);
	}
	if (pid>0)
		while (pid != wait(&i))
			/* nothing */;
	while (1) {
		if ((pid = fork()) < 0) {
			printf("Fork failed in init\n\r");
			continue;
		}
		if (!pid) {
			close(0);close(1);close(2);
			setsid();
			(void) open("/dev/tty1",O_RDWR,0);
			(void) dup(0);
			(void) dup(0);
			_exit(execve("/bin/sh",argv,envp));
		}
		while (1)
			if (pid == wait(&i))
				break;
		printf("\n\rchild %d died with code %04x\n\r",pid,i);
		sync();
	}
	_exit(0);
}