/*
       *  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> 
       */
      
      #define __KERNEL_SYSCALLS__
      
      #include <linux/config.h>
      #include <linux/proc_fs.h>
      #include <linux/devfs_fs_kernel.h>
      #include <linux/unistd.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/raid/md.h>
      #include <linux/smp_lock.h>
      #include <linux/blk.h>
      #include <linux/hdreg.h>
      #include <linux/iobuf.h>
      #include <linux/bootmem.h>
      
      #include <asm/io.h>
      #include <asm/bugs.h>
      
      #ifdef CONFIG_PCI
      #include <linux/pci.h>
      #endif
      
      #ifdef CONFIG_DIO
      #include <linux/dio.h>
      #endif
      
      #ifdef CONFIG_ZORRO
      #include <linux/zorro.h>
      #endif
      
      #ifdef CONFIG_MTRR
      #  include <asm/mtrr.h>
      #endif
      
      #ifdef CONFIG_3215_CONSOLE
      extern int con3215_activate(void);
      #endif
      
      #ifdef CONFIG_NUBUS
      #include <linux/nubus.h>
      #endif
      
      #ifdef CONFIG_ISAPNP
      #include <linux/isapnp.h>
      #endif
      
      #ifdef CONFIG_IRDA
      #include <net/irda/irda_device.h>
      #endif
      
      #ifdef CONFIG_X86_IO_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__ < 91)
      #error Sorry, your GCC is too old. It builds incorrect kernels.
      #endif
      
      extern char _stext, _etext;
      extern char *linux_banner;
      
      static int init(void *);
      
      extern void init_IRQ(void);
      extern void init_modules(void);
      extern void sock_init(void);
      extern void fork_init(unsigned long);
      extern void mca_init(void);
      extern void sbus_init(void);
      extern void ppc_init(void);
      extern void sysctl_init(void);
      extern void signals_init(void);
      extern void bdev_init(void);
      extern int init_pcmcia_ds(void);
      extern void net_notifier_init(void);
      
      extern void free_initmem(void);
      extern void filesystem_setup(void);
      
      #ifdef CONFIG_TC
      extern void tc_init(void);
      #endif
      
      extern void ecard_init(void);
      
      #if defined(CONFIG_SYSVIPC)
      extern void ipc_init(void);
      #endif
      #if defined(CONFIG_QUOTA)
      extern void dquot_init_hash(void);
      #endif
      
      /*
       * Boot command-line arguments
       */
      #define MAX_INIT_ARGS 8
      #define MAX_INIT_ENVS 8
      
      extern void time_init(void);
      extern void softirq_init(void);
      
      int rows, cols;
      
      #ifdef CONFIG_BLK_DEV_INITRD
      kdev_t real_root_dev;
      #endif
      
      int root_mountflags = MS_RDONLY;
      char *execute_command;
      char root_device_name[64];
      
      
      static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
      static char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
      
 137  static int __init profile_setup(char *str)
      {
          int par;
 140      if (get_option(&str,&par)) prof_shift = par;
 141  	return 1;
      }
      
      __setup("profile=", profile_setup);
      
      
      static struct dev_name_struct {
      	const char *name;
      	const int num;
      } root_dev_names[] __initdata = {
      	{ "nfs",     0x00ff },
      	{ "hda",     0x0300 },
      	{ "hdb",     0x0340 },
      	{ "hdc",     0x1600 },
      	{ "hdd",     0x1640 },
      	{ "hde",     0x2100 },
      	{ "hdf",     0x2140 },
      	{ "hdg",     0x2200 },
      	{ "hdh",     0x2240 },
      	{ "hdi",     0x3800 },
      	{ "hdj",     0x3840 },
      	{ "hdk",     0x3900 },
      	{ "hdl",     0x3940 },
      	{ "hdm",     0x5800 },
      	{ "hdn",     0x5840 },
      	{ "hdo",     0x5900 },
      	{ "hdp",     0x5940 },
      	{ "hdq",     0x5A00 },
      	{ "hdr",     0x5A40 },
      	{ "hds",     0x5B00 },
      	{ "hdt",     0x5B40 },
      	{ "sda",     0x0800 },
      	{ "sdb",     0x0810 },
      	{ "sdc",     0x0820 },
      	{ "sdd",     0x0830 },
      	{ "sde",     0x0840 },
      	{ "sdf",     0x0850 },
      	{ "sdg",     0x0860 },
      	{ "sdh",     0x0870 },
      	{ "sdi",     0x0880 },
      	{ "sdj",     0x0890 },
      	{ "sdk",     0x08a0 },
      	{ "sdl",     0x08b0 },
      	{ "sdm",     0x08c0 },
      	{ "sdn",     0x08d0 },
      	{ "sdo",     0x08e0 },
      	{ "sdp",     0x08f0 },
      	{ "ada",     0x1c00 },
      	{ "adb",     0x1c10 },
      	{ "adc",     0x1c20 },
      	{ "add",     0x1c30 },
      	{ "ade",     0x1c40 },
      	{ "fd",      0x0200 },
      	{ "md",      0x0900 },	     
      	{ "xda",     0x0d00 },
      	{ "xdb",     0x0d40 },
      	{ "ram",     0x0100 },
      	{ "scd",     0x0b00 },
      	{ "mcd",     0x1700 },
      	{ "cdu535",  0x1800 },
      	{ "sonycd",  0x1800 },
      	{ "aztcd",   0x1d00 },
      	{ "cm206cd", 0x2000 },
      	{ "gscd",    0x1000 },
      	{ "sbpcd",   0x1900 },
      	{ "eda",     0x2400 },
      	{ "edb",     0x2440 },
      	{ "pda",	0x2d00 },
      	{ "pdb",	0x2d10 },
      	{ "pdc",	0x2d20 },
      	{ "pdd",	0x2d30 },
      	{ "pcd",	0x2e00 },
      	{ "pf",		0x2f00 },
      	{ "apblock", APBLOCK_MAJOR << 8},
      	{ "ddv", DDV_MAJOR << 8},
      	{ "jsfd",    JSFD_MAJOR << 8},
      #ifdef CONFIG_MDISK
              { "mnda", (MDISK_MAJOR << MINORBITS)},
              { "mndb", (MDISK_MAJOR << MINORBITS) + 1},
              { "mndc", (MDISK_MAJOR << MINORBITS) + 2},
              { "mndd", (MDISK_MAJOR << MINORBITS) + 3},
              { "mnde", (MDISK_MAJOR << MINORBITS) + 4},
              { "mndf", (MDISK_MAJOR << MINORBITS) + 5},
              { "mndg", (MDISK_MAJOR << MINORBITS) + 6},
              { "mndh", (MDISK_MAJOR << MINORBITS) + 7},
      #endif
      #ifdef CONFIG_DASD
      	{ "dasda", (DASD_MAJOR << MINORBITS) },
      	{ "dasdb", (DASD_MAJOR << MINORBITS) + (1 << 2) },
      	{ "dasdc", (DASD_MAJOR << MINORBITS) + (2 << 2) },
      	{ "dasdd", (DASD_MAJOR << MINORBITS) + (3 << 2) },
      	{ "dasde", (DASD_MAJOR << MINORBITS) + (4 << 2) },
      	{ "dasdf", (DASD_MAJOR << MINORBITS) + (5 << 2) },
      	{ "dasdg", (DASD_MAJOR << MINORBITS) + (6 << 2) },
      	{ "dasdh", (DASD_MAJOR << MINORBITS) + (7 << 2) },
      #endif
      #if defined(CONFIG_BLK_CPQ_DA) || defined(CONFIG_BLK_CPQ_DA_MODULE)
      	{ "ida/c0d0p",0x4800 },
      	{ "ida/c0d1p",0x4810 },
      	{ "ida/c0d2p",0x4820 },
      	{ "ida/c0d3p",0x4830 },
      	{ "ida/c0d4p",0x4840 },
      	{ "ida/c0d5p",0x4850 },
      	{ "ida/c0d6p",0x4860 },
      	{ "ida/c0d7p",0x4870 },
      	{ "ida/c0d8p",0x4880 },
      	{ "ida/c0d9p",0x4890 },
      	{ "ida/c0d10p",0x48A0 },
      	{ "ida/c0d11p",0x48B0 },
      	{ "ida/c0d12p",0x48C0 },
      	{ "ida/c0d13p",0x48D0 },
      	{ "ida/c0d14p",0x48E0 },
      	{ "ida/c0d15p",0x48F0 },
      #endif
      #if defined(CONFIG_BLK_CPQ_CISS_DA) || defined(CONFIG_BLK_CPQ_CISS_DA_MODULE)
      	{ "cciss/c0d0p",0x6800 },
      	{ "cciss/c0d1p",0x6810 },
      	{ "cciss/c0d2p",0x6820 },
      	{ "cciss/c0d3p",0x6830 },
      	{ "cciss/c0d4p",0x6840 },
      	{ "cciss/c0d5p",0x6850 },
      	{ "cciss/c0d6p",0x6860 },
      	{ "cciss/c0d7p",0x6870 },
      	{ "cciss/c0d8p",0x6880 },
      	{ "cciss/c0d9p",0x6890 },
      	{ "cciss/c0d10p",0x68A0 },
      	{ "cciss/c0d11p",0x68B0 },
      	{ "cciss/c0d12p",0x68C0 },
      	{ "cciss/c0d13p",0x68D0 },
      	{ "cciss/c0d14p",0x68E0 },
      	{ "cciss/c0d15p",0x68F0 },
      #endif
      #ifdef CONFIG_NFTL
      	{ "nftla", 0x5d00 },
      #endif
      	{ NULL, 0 }
      };
      
 279  kdev_t __init name_to_kdev_t(char *line)
      {
      	int base = 0;
      
 283  	if (strncmp(line,"/dev/",5) == 0) {
      		struct dev_name_struct *dev = root_dev_names;
      		line += 5;
 286  		do {
      			int len = strlen(dev->name);
 288  			if (strncmp(line,dev->name,len) == 0) {
      				line += len;
      				base = dev->num;
 291  				break;
      			}
      			dev++;
 294  		} while (dev->name);
      	}
 296  	return to_kdev_t(base + simple_strtoul(line,NULL,base?10:16));
      }
      
 299  static int __init root_dev_setup(char *line)
      {
      	int i;
      	char ch;
      
      	ROOT_DEV = name_to_kdev_t(line);
      	memset (root_device_name, 0, sizeof root_device_name);
 306  	if (strncmp (line, "/dev/", 5) == 0) line += 5;
 307  	for (i = 0; i < sizeof root_device_name - 1; ++i)
      	{
      	    ch = line[i];
 310  	    if ( isspace (ch) || (ch == ',') || (ch == '\0') ) break;
      	    root_device_name[i] = ch;
      	}
 313  	return 1;
      }
      
      __setup("root=", root_dev_setup);
      
 318  static int __init checksetup(char *line)
      {
      	struct kernel_param *p;
      
      	p = &__setup_start;
 323  	do {
      		int n = strlen(p->str);
 325  		if (!strncmp(line,p->str,n)) {
 326  			if (p->setup_func(line+n))
 327  				return 1;
      		}
      		p++;
 330  	} while (p < &__setup_end);
 331  	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);
      
      /* 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
      
 343  void __init calibrate_delay(void)
      {
      	unsigned long ticks, loopbit;
      	int lps_precision = LPS_PREC;
      
      	loops_per_jiffy = (1<<12);
      
      	printk("Calibrating delay loop... ");
 351  	while (loops_per_jiffy <<= 1) {
      		/* wait for "start of" clock tick */
      		ticks = jiffies;
 354  		while (ticks == jiffies)
      			/* nothing */;
      		/* Go .. */
      		ticks = jiffies;
      		__delay(loops_per_jiffy);
      		ticks = jiffies - ticks;
 360  		if (ticks)
 361  			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;
 368  	while ( lps_precision-- && (loopbit >>= 1) ) {
      		loops_per_jiffy |= loopbit;
      		ticks = jiffies;
 371  		while (ticks == jiffies);
      		ticks = jiffies;
      		__delay(loops_per_jiffy);
 374  		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);
      }
      
 384  static int __init readonly(char *str)
      {
 386  	if (*str)
 387  		return 0;
      	root_mountflags |= MS_RDONLY;
 389  	return 1;
      }
      
 392  static int __init readwrite(char *str)
      {
 394  	if (*str)
 395  		return 0;
      	root_mountflags &= ~MS_RDONLY;
 397  	return 1;
      }
      
 400  static int __init debug_kernel(char *str)
      {
 402  	if (*str)
 403  		return 0;
      	console_loglevel = 10;
 405  	return 1;
      }
      
 408  static int __init quiet_kernel(char *str)
      {
 410  	if (*str)
 411  		return 0;
      	console_loglevel = 4;
 413  	return 1;
      }
      
      __setup("ro", readonly);
      __setup("rw", readwrite);
      __setup("debug", debug_kernel);
      __setup("quiet", quiet_kernel);
      
      /*
       * 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.
       * These options are not given to init - they are for internal kernel use only.
       */
 430  static void __init parse_options(char *line)
      {
      	char *next,*quote;
      	int args, envs;
      
 435  	if (!*line)
 436  		return;
      	args = 0;
      	envs = 1;	/* TERM is set to 'linux' by default */
      	next = line;
 440  	while ((line = next) != NULL) {
                      quote = strchr(line,'"');
                      next = strchr(line, ' ');
 443                  while (next != NULL && quote != NULL && quote < next) {
                              /* we found a left quote before the next blank
                               * now we have to find the matching right quote
                               */
                              next = strchr(quote+1, '"');
 448                          if (next != NULL) {
                                      quote = strchr(next+1, '"');
                                      next = strchr(next+1, ' ');
                              }
                      }
 453                  if (next != NULL)
                              *next++ = 0;
 455  		if (!strncmp(line,"init=",5)) {
      			line += 5;
      			execute_command = line;
      			/* 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]
      			 */
      			args = 0;
 464  			continue;
      		}
 466  		if (checksetup(line))
 467  			continue;
      		
      		/*
      		 * Then check if it's an environment variable or
      		 * an option.
      		 */
 473  		if (strchr(line,'=')) {
 474  			if (envs >= MAX_INIT_ENVS)
 475  				break;
      			envp_init[++envs] = line;
 477  		} else {
 478  			if (args >= MAX_INIT_ARGS)
 479  				break;
 480  			if (*line)
      				argv_init[++args] = line;
      		}
      	}
      	argv_init[args+1] = NULL;
      	envp_init[envs+1] = NULL;
      }
      
      
      extern void setup_arch(char **);
      extern void cpu_idle(void);
      
      #ifndef CONFIG_SMP
      
      #ifdef CONFIG_X86_IO_APIC
      static void __init smp_init(void)
      {
      	IO_APIC_init_uniprocessor();
      }
      #else
      #define smp_init()	do { } while (0)
      #endif
      
      #else
      
      /* Called by boot processor to activate the rest. */
      static void __init smp_init(void)
      {
      	/* Get other processors into their bootup holding patterns. */
      	smp_boot_cpus();
      	smp_threads_ready=1;
      	smp_commence();
      }		
      
      #endif
      
      /*
       *	Activate the first processor.
       */
       
 520  asmlinkage void __init start_kernel(void)
      {
      	char * command_line;
      	unsigned long mempages;
      	extern char saved_command_line[];
      /*
       * Interrupts are still disabled. Do necessary setups, then
       * enable them
       */
 529  	lock_kernel();
      	printk(linux_banner);
      	setup_arch(&command_line);
      	printk("Kernel command line: %s\n", saved_command_line);
      	parse_options(command_line);
      	trap_init();
      	init_IRQ();
      	sched_init();
      	time_init();
      	softirq_init();
      
      	/*
      	 * 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();
      #ifdef CONFIG_MODULES
      	init_modules();
      #endif
 549  	if (prof_shift) {
      		unsigned int size;
      		/* only text is profiled */
      		prof_len = (unsigned long) &_etext - (unsigned long) &_stext;
      		prof_len >>= prof_shift;
      		
      		size = prof_len * sizeof(unsigned int) + PAGE_SIZE-1;
      		prof_buffer = (unsigned int *) alloc_bootmem(size);
      	}
      
      	kmem_cache_init();
      	sti();
      	calibrate_delay();
      #ifdef CONFIG_BLK_DEV_INITRD
      	if (initrd_start && !initrd_below_start_ok &&
      			initrd_start < min_low_pfn << PAGE_SHIFT) {
      		printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
      		    "disabling it.\n",initrd_start,min_low_pfn << PAGE_SHIFT);
      		initrd_start = 0;
      	}
      #endif
      	mem_init();
      	kmem_cache_sizes_init();
      #ifdef CONFIG_3215_CONSOLE
              con3215_activate();
      #endif
      #ifdef CONFIG_PROC_FS
      	proc_root_init();
      #endif
      	mempages = num_physpages;
      
      	fork_init(mempages);
      	proc_caches_init();
      	vfs_caches_init(mempages);
      	buffer_init(mempages);
      	page_cache_init(mempages);
      	kiobuf_setup();
      	signals_init();
      	bdev_init();
      	inode_init(mempages);
      #if defined(CONFIG_SYSVIPC)
      	ipc_init();
      #endif
      #if defined(CONFIG_QUOTA)
      	dquot_init_hash();
      #endif
      	check_bugs();
      	printk("POSIX conformance testing by UNIFIX\n");
      
      	/* 
      	 *	We count on the initial thread going ok 
      	 *	Like idlers init is an unlocked kernel thread, which will
      	 *	make syscalls (and thus be locked).
      	 */
 603  	smp_init();
      	kernel_thread(init, NULL, CLONE_FS | CLONE_FILES | CLONE_SIGNAL);
 605  	unlock_kernel();
      	current->need_resched = 1;
       	cpu_idle();
      }
      
      #ifdef CONFIG_BLK_DEV_INITRD
      static int do_linuxrc(void * shell)
      {
      	static char *argv[] = { "linuxrc", NULL, };
      
      	close(0);close(1);close(2);
      	setsid();
      	(void) open("/dev/console",O_RDWR,0);
      	(void) dup(0);
      	(void) dup(0);
      	return execve(shell, argv, envp_init);
      }
      
      #endif
      
      struct task_struct *child_reaper = &init_task;
      
 627  static void __init do_initcalls(void)
      {
      	initcall_t *call;
      
      	call = &__initcall_start;
 632  	do {
      		(*call)();
      		call++;
 635  	} while (call < &__initcall_end);
      
      	/* Make sure there is no pending stuff from the initcall sequence */
      	flush_scheduled_tasks();
      }
      
      /*
       * 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..
       */
 648  static void __init do_basic_setup(void)
      {
      #ifdef CONFIG_BLK_DEV_INITRD
      	int real_root_mountflags;
      #endif
      
      	/*
      	 * 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.
      	 */
      	child_reaper = current;
      
      #if defined(CONFIG_MTRR)	/* Do this after SMP initialization */
      /*
       * We should probably create some architecture-dependent "fixup after
       * everything is up" style function where this would belong better
       * than in init/main.c..
       */
      	mtrr_init();
      #endif
      
      #ifdef CONFIG_SYSCTL
      	sysctl_init();
      #endif
      
      	/*
      	 * Ok, at this point all CPU's should be initialized, so
      	 * we can start looking into devices..
      	 */
      #ifdef CONFIG_PCI
      	pci_init();
      #endif
      #ifdef CONFIG_SBUS
      	sbus_init();
      #endif
      #if defined(CONFIG_PPC)
      	ppc_init();
      #endif
      #ifdef CONFIG_MCA
      	mca_init();
      #endif
      #ifdef CONFIG_ARCH_ACORN
      	ecard_init();
      #endif
      #ifdef CONFIG_ZORRO
      	zorro_init();
      #endif
      #ifdef CONFIG_DIO
      	dio_init();
      #endif
      #ifdef CONFIG_NUBUS
      	nubus_init();
      #endif
      #ifdef CONFIG_ISAPNP
      	isapnp_init();
      #endif
      #ifdef CONFIG_TC
      	tc_init();
      #endif
      
      	/* Networking initialization needs a process context */ 
      	sock_init();
      
      #ifdef CONFIG_BLK_DEV_INITRD
      	real_root_dev = ROOT_DEV;
      	real_root_mountflags = root_mountflags;
      	if (initrd_start && mount_initrd) root_mountflags &= ~MS_RDONLY;
      	else mount_initrd =0;
      #endif
      
      	start_context_thread();
      	do_initcalls();
      
      	/* .. filesystems .. */
      	filesystem_setup();
      
      #ifdef CONFIG_IRDA
      	irda_device_init(); /* Must be done after protocol initialization */
      #endif
      #ifdef CONFIG_PCMCIA
      	init_pcmcia_ds();		/* Do this last */
      #endif
      
      	/* Mount the root filesystem.. */
      	mount_root();
      
      	mount_devfs_fs ();
      
      #ifdef CONFIG_BLK_DEV_INITRD
      	root_mountflags = real_root_mountflags;
      	if (mount_initrd && ROOT_DEV != real_root_dev
      	    && MAJOR(ROOT_DEV) == RAMDISK_MAJOR && MINOR(ROOT_DEV) == 0) {
      		int error;
      		int i, pid;
      
      		pid = kernel_thread(do_linuxrc, "/linuxrc", SIGCHLD);
      		if (pid>0)
      			while (pid != wait(&i));
      		if (MAJOR(real_root_dev) != RAMDISK_MAJOR
      		     || MINOR(real_root_dev) != 0) {
      			error = change_root(real_root_dev,"/initrd");
      			if (error)
      				printk(KERN_ERR "Change root to /initrd: "
      				    "error %d\n",error);
      		}
      	}
      #endif
      }
      
 761  static int init(void * unused)
      {
 763  	lock_kernel();
      	do_basic_setup();
      
      	/*
      	 * 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..
      	 */
      	free_initmem();
 772  	unlock_kernel();
      
 774  	if (open("/dev/console", O_RDWR, 0) < 0)
      		printk("Warning: unable to open an initial console.\n");
      
      	(void) dup(0);
      	(void) dup(0);
      	
      	/*
      	 * 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.
      	 */
      
 787  	if (execute_command)
      		execve(execute_command,argv_init,envp_init);
      	execve("/sbin/init",argv_init,envp_init);
      	execve("/etc/init",argv_init,envp_init);
      	execve("/bin/init",argv_init,envp_init);
      	execve("/bin/sh",argv_init,envp_init);
      	panic("No init found.  Try passing init= option to kernel.");
      }