xref: /openbmc/linux/init/main.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  *  linux/init/main.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  *
6  *  GK 2/5/95  -  Changed to support mounting root fs via NFS
7  *  Added initrd & change_root: Werner Almesberger & Hans Lermen, Feb '96
8  *  Moan early if gcc is old, avoiding bogus kernels - Paul Gortmaker, May '96
9  *  Simplified starting of init:  Michael A. Griffith <grif@acm.org>
10  */
11 
12 #include <linux/types.h>
13 #include <linux/module.h>
14 #include <linux/proc_fs.h>
15 #include <linux/kernel.h>
16 #include <linux/syscalls.h>
17 #include <linux/string.h>
18 #include <linux/ctype.h>
19 #include <linux/delay.h>
20 #include <linux/utsname.h>
21 #include <linux/ioport.h>
22 #include <linux/init.h>
23 #include <linux/smp_lock.h>
24 #include <linux/initrd.h>
25 #include <linux/hdreg.h>
26 #include <linux/bootmem.h>
27 #include <linux/tty.h>
28 #include <linux/gfp.h>
29 #include <linux/percpu.h>
30 #include <linux/kmod.h>
31 #include <linux/kernel_stat.h>
32 #include <linux/start_kernel.h>
33 #include <linux/security.h>
34 #include <linux/workqueue.h>
35 #include <linux/profile.h>
36 #include <linux/rcupdate.h>
37 #include <linux/moduleparam.h>
38 #include <linux/kallsyms.h>
39 #include <linux/writeback.h>
40 #include <linux/cpu.h>
41 #include <linux/cpuset.h>
42 #include <linux/efi.h>
43 #include <linux/tick.h>
44 #include <linux/interrupt.h>
45 #include <linux/taskstats_kern.h>
46 #include <linux/delayacct.h>
47 #include <linux/unistd.h>
48 #include <linux/rmap.h>
49 #include <linux/mempolicy.h>
50 #include <linux/key.h>
51 #include <linux/unwind.h>
52 #include <linux/buffer_head.h>
53 #include <linux/debug_locks.h>
54 #include <linux/lockdep.h>
55 #include <linux/pid_namespace.h>
56 #include <linux/device.h>
57 #include <linux/kthread.h>
58 
59 #include <asm/io.h>
60 #include <asm/bugs.h>
61 #include <asm/setup.h>
62 #include <asm/sections.h>
63 #include <asm/cacheflush.h>
64 
65 #ifdef CONFIG_X86_LOCAL_APIC
66 #include <asm/smp.h>
67 #endif
68 
69 /*
70  * This is one of the first .c files built. Error out early if we have compiler
71  * trouble.
72  *
73  * Versions of gcc older than that listed below may actually compile and link
74  * okay, but the end product can have subtle run time bugs.  To avoid associated
75  * bogus bug reports, we flatly refuse to compile with a gcc that is known to be
76  * too old from the very beginning.
77  */
78 #if (__GNUC__ < 3) || (__GNUC__ == 3 && __GNUC_MINOR__ < 2)
79 #error Sorry, your GCC is too old. It builds incorrect kernels.
80 #endif
81 
82 #if __GNUC__ == 4 && __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ == 0
83 #warning gcc-4.1.0 is known to miscompile the kernel.  A different compiler version is recommended.
84 #endif
85 
86 static int kernel_init(void *);
87 
88 extern void init_IRQ(void);
89 extern void fork_init(unsigned long);
90 extern void mca_init(void);
91 extern void sbus_init(void);
92 extern void signals_init(void);
93 extern void pidhash_init(void);
94 extern void pidmap_init(void);
95 extern void prio_tree_init(void);
96 extern void radix_tree_init(void);
97 extern void free_initmem(void);
98 #ifdef	CONFIG_ACPI
99 extern void acpi_early_init(void);
100 #else
101 static inline void acpi_early_init(void) { }
102 #endif
103 #ifndef CONFIG_DEBUG_RODATA
104 static inline void mark_rodata_ro(void) { }
105 #endif
106 
107 #ifdef CONFIG_TC
108 extern void tc_init(void);
109 #endif
110 
111 enum system_states system_state;
112 EXPORT_SYMBOL(system_state);
113 
114 /*
115  * Boot command-line arguments
116  */
117 #define MAX_INIT_ARGS CONFIG_INIT_ENV_ARG_LIMIT
118 #define MAX_INIT_ENVS CONFIG_INIT_ENV_ARG_LIMIT
119 
120 extern void time_init(void);
121 /* Default late time init is NULL. archs can override this later. */
122 void (*late_time_init)(void);
123 extern void softirq_init(void);
124 
125 /* Untouched command line saved by arch-specific code. */
126 char __initdata boot_command_line[COMMAND_LINE_SIZE];
127 /* Untouched saved command line (eg. for /proc) */
128 char *saved_command_line;
129 /* Command line for parameter parsing */
130 static char *static_command_line;
131 
132 static char *execute_command;
133 static char *ramdisk_execute_command;
134 
135 /* Setup configured maximum number of CPUs to activate */
136 static unsigned int max_cpus = NR_CPUS;
137 
138 /*
139  * If set, this is an indication to the drivers that reset the underlying
140  * device before going ahead with the initialization otherwise driver might
141  * rely on the BIOS and skip the reset operation.
142  *
143  * This is useful if kernel is booting in an unreliable environment.
144  * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
145  * skipped and devices will be in unknown state.
146  */
147 unsigned int reset_devices;
148 EXPORT_SYMBOL(reset_devices);
149 
150 /*
151  * Setup routine for controlling SMP activation
152  *
153  * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
154  * activation entirely (the MPS table probe still happens, though).
155  *
156  * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
157  * greater than 0, limits the maximum number of CPUs activated in
158  * SMP mode to <NUM>.
159  */
160 static int __init nosmp(char *str)
161 {
162 	max_cpus = 0;
163 	return 1;
164 }
165 
166 __setup("nosmp", nosmp);
167 
168 static int __init maxcpus(char *str)
169 {
170 	get_option(&str, &max_cpus);
171 	return 1;
172 }
173 
174 __setup("maxcpus=", maxcpus);
175 
176 static int __init set_reset_devices(char *str)
177 {
178 	reset_devices = 1;
179 	return 1;
180 }
181 
182 __setup("reset_devices", set_reset_devices);
183 
184 static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
185 char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
186 static const char *panic_later, *panic_param;
187 
188 extern struct obs_kernel_param __setup_start[], __setup_end[];
189 
190 static int __init obsolete_checksetup(char *line)
191 {
192 	struct obs_kernel_param *p;
193 	int had_early_param = 0;
194 
195 	p = __setup_start;
196 	do {
197 		int n = strlen(p->str);
198 		if (!strncmp(line, p->str, n)) {
199 			if (p->early) {
200 				/* Already done in parse_early_param?
201 				 * (Needs exact match on param part).
202 				 * Keep iterating, as we can have early
203 				 * params and __setups of same names 8( */
204 				if (line[n] == '\0' || line[n] == '=')
205 					had_early_param = 1;
206 			} else if (!p->setup_func) {
207 				printk(KERN_WARNING "Parameter %s is obsolete,"
208 				       " ignored\n", p->str);
209 				return 1;
210 			} else if (p->setup_func(line + n))
211 				return 1;
212 		}
213 		p++;
214 	} while (p < __setup_end);
215 
216 	return had_early_param;
217 }
218 
219 /*
220  * This should be approx 2 Bo*oMips to start (note initial shift), and will
221  * still work even if initially too large, it will just take slightly longer
222  */
223 unsigned long loops_per_jiffy = (1<<12);
224 
225 EXPORT_SYMBOL(loops_per_jiffy);
226 
227 static int __init debug_kernel(char *str)
228 {
229 	if (*str)
230 		return 0;
231 	console_loglevel = 10;
232 	return 1;
233 }
234 
235 static int __init quiet_kernel(char *str)
236 {
237 	if (*str)
238 		return 0;
239 	console_loglevel = 4;
240 	return 1;
241 }
242 
243 __setup("debug", debug_kernel);
244 __setup("quiet", quiet_kernel);
245 
246 static int __init loglevel(char *str)
247 {
248 	get_option(&str, &console_loglevel);
249 	return 1;
250 }
251 
252 __setup("loglevel=", loglevel);
253 
254 /*
255  * Unknown boot options get handed to init, unless they look like
256  * failed parameters
257  */
258 static int __init unknown_bootoption(char *param, char *val)
259 {
260 	/* Change NUL term back to "=", to make "param" the whole string. */
261 	if (val) {
262 		/* param=val or param="val"? */
263 		if (val == param+strlen(param)+1)
264 			val[-1] = '=';
265 		else if (val == param+strlen(param)+2) {
266 			val[-2] = '=';
267 			memmove(val-1, val, strlen(val)+1);
268 			val--;
269 		} else
270 			BUG();
271 	}
272 
273 	/* Handle obsolete-style parameters */
274 	if (obsolete_checksetup(param))
275 		return 0;
276 
277 	/*
278 	 * Preemptive maintenance for "why didn't my mispelled command
279 	 * line work?"
280 	 */
281 	if (strchr(param, '.') && (!val || strchr(param, '.') < val)) {
282 		printk(KERN_ERR "Unknown boot option `%s': ignoring\n", param);
283 		return 0;
284 	}
285 
286 	if (panic_later)
287 		return 0;
288 
289 	if (val) {
290 		/* Environment option */
291 		unsigned int i;
292 		for (i = 0; envp_init[i]; i++) {
293 			if (i == MAX_INIT_ENVS) {
294 				panic_later = "Too many boot env vars at `%s'";
295 				panic_param = param;
296 			}
297 			if (!strncmp(param, envp_init[i], val - param))
298 				break;
299 		}
300 		envp_init[i] = param;
301 	} else {
302 		/* Command line option */
303 		unsigned int i;
304 		for (i = 0; argv_init[i]; i++) {
305 			if (i == MAX_INIT_ARGS) {
306 				panic_later = "Too many boot init vars at `%s'";
307 				panic_param = param;
308 			}
309 		}
310 		argv_init[i] = param;
311 	}
312 	return 0;
313 }
314 
315 static int __init init_setup(char *str)
316 {
317 	unsigned int i;
318 
319 	execute_command = str;
320 	/*
321 	 * In case LILO is going to boot us with default command line,
322 	 * it prepends "auto" before the whole cmdline which makes
323 	 * the shell think it should execute a script with such name.
324 	 * So we ignore all arguments entered _before_ init=... [MJ]
325 	 */
326 	for (i = 1; i < MAX_INIT_ARGS; i++)
327 		argv_init[i] = NULL;
328 	return 1;
329 }
330 __setup("init=", init_setup);
331 
332 static int __init rdinit_setup(char *str)
333 {
334 	unsigned int i;
335 
336 	ramdisk_execute_command = str;
337 	/* See "auto" comment in init_setup */
338 	for (i = 1; i < MAX_INIT_ARGS; i++)
339 		argv_init[i] = NULL;
340 	return 1;
341 }
342 __setup("rdinit=", rdinit_setup);
343 
344 #ifndef CONFIG_SMP
345 
346 #ifdef CONFIG_X86_LOCAL_APIC
347 static void __init smp_init(void)
348 {
349 	APIC_init_uniprocessor();
350 }
351 #else
352 #define smp_init()	do { } while (0)
353 #endif
354 
355 static inline void setup_per_cpu_areas(void) { }
356 static inline void smp_prepare_cpus(unsigned int maxcpus) { }
357 
358 #else
359 
360 #ifdef __GENERIC_PER_CPU
361 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
362 
363 EXPORT_SYMBOL(__per_cpu_offset);
364 
365 static void __init setup_per_cpu_areas(void)
366 {
367 	unsigned long size, i;
368 	char *ptr;
369 	unsigned long nr_possible_cpus = num_possible_cpus();
370 
371 	/* Copy section for each CPU (we discard the original) */
372 	size = ALIGN(PERCPU_ENOUGH_ROOM, PAGE_SIZE);
373 	ptr = alloc_bootmem_pages(size * nr_possible_cpus);
374 
375 	for_each_possible_cpu(i) {
376 		__per_cpu_offset[i] = ptr - __per_cpu_start;
377 		memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
378 		ptr += size;
379 	}
380 }
381 #endif /* !__GENERIC_PER_CPU */
382 
383 /* Called by boot processor to activate the rest. */
384 static void __init smp_init(void)
385 {
386 	unsigned int cpu;
387 
388 	/* FIXME: This should be done in userspace --RR */
389 	for_each_present_cpu(cpu) {
390 		if (num_online_cpus() >= max_cpus)
391 			break;
392 		if (!cpu_online(cpu))
393 			cpu_up(cpu);
394 	}
395 
396 	/* Any cleanup work */
397 	printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
398 	smp_cpus_done(max_cpus);
399 }
400 
401 #endif
402 
403 /*
404  * We need to store the untouched command line for future reference.
405  * We also need to store the touched command line since the parameter
406  * parsing is performed in place, and we should allow a component to
407  * store reference of name/value for future reference.
408  */
409 static void __init setup_command_line(char *command_line)
410 {
411 	saved_command_line = alloc_bootmem(strlen (boot_command_line)+1);
412 	static_command_line = alloc_bootmem(strlen (command_line)+1);
413 	strcpy (saved_command_line, boot_command_line);
414 	strcpy (static_command_line, command_line);
415 }
416 
417 /*
418  * We need to finalize in a non-__init function or else race conditions
419  * between the root thread and the init thread may cause start_kernel to
420  * be reaped by free_initmem before the root thread has proceeded to
421  * cpu_idle.
422  *
423  * gcc-3.4 accidentally inlines this function, so use noinline.
424  */
425 
426 static void noinline rest_init(void)
427 	__releases(kernel_lock)
428 {
429 	int pid;
430 
431 	kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
432 	numa_default_policy();
433 	pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
434 	kthreadd_task = find_task_by_pid(pid);
435 	unlock_kernel();
436 
437 	/*
438 	 * The boot idle thread must execute schedule()
439 	 * at least one to get things moving:
440 	 */
441 	preempt_enable_no_resched();
442 	schedule();
443 	preempt_disable();
444 
445 	/* Call into cpu_idle with preempt disabled */
446 	cpu_idle();
447 }
448 
449 /* Check for early params. */
450 static int __init do_early_param(char *param, char *val)
451 {
452 	struct obs_kernel_param *p;
453 
454 	for (p = __setup_start; p < __setup_end; p++) {
455 		if (p->early && strcmp(param, p->str) == 0) {
456 			if (p->setup_func(val) != 0)
457 				printk(KERN_WARNING
458 				       "Malformed early option '%s'\n", param);
459 		}
460 	}
461 	/* We accept everything at this stage. */
462 	return 0;
463 }
464 
465 /* Arch code calls this early on, or if not, just before other parsing. */
466 void __init parse_early_param(void)
467 {
468 	static __initdata int done = 0;
469 	static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];
470 
471 	if (done)
472 		return;
473 
474 	/* All fall through to do_early_param. */
475 	strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
476 	parse_args("early options", tmp_cmdline, NULL, 0, do_early_param);
477 	done = 1;
478 }
479 
480 /*
481  *	Activate the first processor.
482  */
483 
484 static void __init boot_cpu_init(void)
485 {
486 	int cpu = smp_processor_id();
487 	/* Mark the boot cpu "present", "online" etc for SMP and UP case */
488 	cpu_set(cpu, cpu_online_map);
489 	cpu_set(cpu, cpu_present_map);
490 	cpu_set(cpu, cpu_possible_map);
491 }
492 
493 void __init __attribute__((weak)) smp_setup_processor_id(void)
494 {
495 }
496 
497 asmlinkage void __init start_kernel(void)
498 {
499 	char * command_line;
500 	extern struct kernel_param __start___param[], __stop___param[];
501 
502 	smp_setup_processor_id();
503 
504 	/*
505 	 * Need to run as early as possible, to initialize the
506 	 * lockdep hash:
507 	 */
508 	unwind_init();
509 	lockdep_init();
510 
511 	local_irq_disable();
512 	early_boot_irqs_off();
513 	early_init_irq_lock_class();
514 
515 /*
516  * Interrupts are still disabled. Do necessary setups, then
517  * enable them
518  */
519 	lock_kernel();
520 	tick_init();
521 	boot_cpu_init();
522 	page_address_init();
523 	printk(KERN_NOTICE);
524 	printk(linux_banner);
525 	setup_arch(&command_line);
526 	setup_command_line(command_line);
527 	unwind_setup();
528 	setup_per_cpu_areas();
529 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */
530 
531 	/*
532 	 * Set up the scheduler prior starting any interrupts (such as the
533 	 * timer interrupt). Full topology setup happens at smp_init()
534 	 * time - but meanwhile we still have a functioning scheduler.
535 	 */
536 	sched_init();
537 	/*
538 	 * Disable preemption - early bootup scheduling is extremely
539 	 * fragile until we cpu_idle() for the first time.
540 	 */
541 	preempt_disable();
542 	build_all_zonelists();
543 	page_alloc_init();
544 	printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
545 	parse_early_param();
546 	parse_args("Booting kernel", static_command_line, __start___param,
547 		   __stop___param - __start___param,
548 		   &unknown_bootoption);
549 	if (!irqs_disabled()) {
550 		printk(KERN_WARNING "start_kernel(): bug: interrupts were "
551 				"enabled *very* early, fixing it\n");
552 		local_irq_disable();
553 	}
554 	sort_main_extable();
555 	trap_init();
556 	rcu_init();
557 	init_IRQ();
558 	pidhash_init();
559 	init_timers();
560 	hrtimers_init();
561 	softirq_init();
562 	timekeeping_init();
563 	time_init();
564 	profile_init();
565 	if (!irqs_disabled())
566 		printk("start_kernel(): bug: interrupts were enabled early\n");
567 	early_boot_irqs_on();
568 	local_irq_enable();
569 
570 	/*
571 	 * HACK ALERT! This is early. We're enabling the console before
572 	 * we've done PCI setups etc, and console_init() must be aware of
573 	 * this. But we do want output early, in case something goes wrong.
574 	 */
575 	console_init();
576 	if (panic_later)
577 		panic(panic_later, panic_param);
578 
579 	lockdep_info();
580 
581 	/*
582 	 * Need to run this when irqs are enabled, because it wants
583 	 * to self-test [hard/soft]-irqs on/off lock inversion bugs
584 	 * too:
585 	 */
586 	locking_selftest();
587 
588 #ifdef CONFIG_BLK_DEV_INITRD
589 	if (initrd_start && !initrd_below_start_ok &&
590 			initrd_start < min_low_pfn << PAGE_SHIFT) {
591 		printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
592 		    "disabling it.\n",initrd_start,min_low_pfn << PAGE_SHIFT);
593 		initrd_start = 0;
594 	}
595 #endif
596 	vfs_caches_init_early();
597 	cpuset_init_early();
598 	mem_init();
599 	kmem_cache_init();
600 	setup_per_cpu_pageset();
601 	numa_policy_init();
602 	if (late_time_init)
603 		late_time_init();
604 	calibrate_delay();
605 	pidmap_init();
606 	pgtable_cache_init();
607 	prio_tree_init();
608 	anon_vma_init();
609 #ifdef CONFIG_X86
610 	if (efi_enabled)
611 		efi_enter_virtual_mode();
612 #endif
613 	fork_init(num_physpages);
614 	proc_caches_init();
615 	buffer_init();
616 	unnamed_dev_init();
617 	key_init();
618 	security_init();
619 	vfs_caches_init(num_physpages);
620 	radix_tree_init();
621 	signals_init();
622 	/* rootfs populating might need page-writeback */
623 	page_writeback_init();
624 #ifdef CONFIG_PROC_FS
625 	proc_root_init();
626 #endif
627 	cpuset_init();
628 	taskstats_init_early();
629 	delayacct_init();
630 
631 	check_bugs();
632 
633 	acpi_early_init(); /* before LAPIC and SMP init */
634 
635 	/* Do the rest non-__init'ed, we're now alive */
636 	rest_init();
637 }
638 
639 static int __initdata initcall_debug;
640 
641 static int __init initcall_debug_setup(char *str)
642 {
643 	initcall_debug = 1;
644 	return 1;
645 }
646 __setup("initcall_debug", initcall_debug_setup);
647 
648 extern initcall_t __initcall_start[], __initcall_end[];
649 
650 static void __init do_initcalls(void)
651 {
652 	initcall_t *call;
653 	int count = preempt_count();
654 
655 	for (call = __initcall_start; call < __initcall_end; call++) {
656 		ktime_t t0, t1, delta;
657 		char *msg = NULL;
658 		char msgbuf[40];
659 		int result;
660 
661 		if (initcall_debug) {
662 			printk("Calling initcall 0x%p", *call);
663 			print_fn_descriptor_symbol(": %s()",
664 					(unsigned long) *call);
665 			printk("\n");
666 			t0 = ktime_get();
667 		}
668 
669 		result = (*call)();
670 
671 		if (initcall_debug) {
672 			t1 = ktime_get();
673 			delta = ktime_sub(t1, t0);
674 
675 			printk("initcall 0x%p", *call);
676 			print_fn_descriptor_symbol(": %s()",
677 					(unsigned long) *call);
678 			printk(" returned %d.\n", result);
679 
680 			printk("initcall 0x%p ran for %Ld msecs: ",
681 				*call, (unsigned long long)delta.tv64 >> 20);
682 			print_fn_descriptor_symbol("%s()\n",
683 				(unsigned long) *call);
684 		}
685 
686 		if (result && result != -ENODEV && initcall_debug) {
687 			sprintf(msgbuf, "error code %d", result);
688 			msg = msgbuf;
689 		}
690 		if (preempt_count() != count) {
691 			msg = "preemption imbalance";
692 			preempt_count() = count;
693 		}
694 		if (irqs_disabled()) {
695 			msg = "disabled interrupts";
696 			local_irq_enable();
697 		}
698 		if (msg) {
699 			printk(KERN_WARNING "initcall at 0x%p", *call);
700 			print_fn_descriptor_symbol(": %s()",
701 					(unsigned long) *call);
702 			printk(": returned with %s\n", msg);
703 		}
704 	}
705 
706 	/* Make sure there is no pending stuff from the initcall sequence */
707 	flush_scheduled_work();
708 }
709 
710 /*
711  * Ok, the machine is now initialized. None of the devices
712  * have been touched yet, but the CPU subsystem is up and
713  * running, and memory and process management works.
714  *
715  * Now we can finally start doing some real work..
716  */
717 static void __init do_basic_setup(void)
718 {
719 	/* drivers will send hotplug events */
720 	init_workqueues();
721 	usermodehelper_init();
722 	driver_init();
723 	init_irq_proc();
724 	do_initcalls();
725 }
726 
727 static void __init do_pre_smp_initcalls(void)
728 {
729 	extern int spawn_ksoftirqd(void);
730 #ifdef CONFIG_SMP
731 	extern int migration_init(void);
732 
733 	migration_init();
734 #endif
735 	spawn_ksoftirqd();
736 	spawn_softlockup_task();
737 }
738 
739 static void run_init_process(char *init_filename)
740 {
741 	argv_init[0] = init_filename;
742 	kernel_execve(init_filename, argv_init, envp_init);
743 }
744 
745 /* This is a non __init function. Force it to be noinline otherwise gcc
746  * makes it inline to init() and it becomes part of init.text section
747  */
748 static int noinline init_post(void)
749 {
750 	free_initmem();
751 	unlock_kernel();
752 	mark_rodata_ro();
753 	system_state = SYSTEM_RUNNING;
754 	numa_default_policy();
755 
756 	if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
757 		printk(KERN_WARNING "Warning: unable to open an initial console.\n");
758 
759 	(void) sys_dup(0);
760 	(void) sys_dup(0);
761 
762 	if (ramdisk_execute_command) {
763 		run_init_process(ramdisk_execute_command);
764 		printk(KERN_WARNING "Failed to execute %s\n",
765 				ramdisk_execute_command);
766 	}
767 
768 	/*
769 	 * We try each of these until one succeeds.
770 	 *
771 	 * The Bourne shell can be used instead of init if we are
772 	 * trying to recover a really broken machine.
773 	 */
774 	if (execute_command) {
775 		run_init_process(execute_command);
776 		printk(KERN_WARNING "Failed to execute %s.  Attempting "
777 					"defaults...\n", execute_command);
778 	}
779 	run_init_process("/sbin/init");
780 	run_init_process("/etc/init");
781 	run_init_process("/bin/init");
782 	run_init_process("/bin/sh");
783 
784 	panic("No init found.  Try passing init= option to kernel.");
785 }
786 
787 static int __init kernel_init(void * unused)
788 {
789 	lock_kernel();
790 	/*
791 	 * init can run on any cpu.
792 	 */
793 	set_cpus_allowed(current, CPU_MASK_ALL);
794 	/*
795 	 * Tell the world that we're going to be the grim
796 	 * reaper of innocent orphaned children.
797 	 *
798 	 * We don't want people to have to make incorrect
799 	 * assumptions about where in the task array this
800 	 * can be found.
801 	 */
802 	init_pid_ns.child_reaper = current;
803 
804 	__set_special_pids(1, 1);
805 	cad_pid = task_pid(current);
806 
807 	smp_prepare_cpus(max_cpus);
808 
809 	do_pre_smp_initcalls();
810 
811 	smp_init();
812 	sched_init_smp();
813 
814 	cpuset_init_smp();
815 
816 	do_basic_setup();
817 
818 	/*
819 	 * check if there is an early userspace init.  If yes, let it do all
820 	 * the work
821 	 */
822 
823 	if (!ramdisk_execute_command)
824 		ramdisk_execute_command = "/init";
825 
826 	if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
827 		ramdisk_execute_command = NULL;
828 		prepare_namespace();
829 	}
830 
831 	/*
832 	 * Ok, we have completed the initial bootup, and
833 	 * we're essentially up and running. Get rid of the
834 	 * initmem segments and start the user-mode stuff..
835 	 */
836 	init_post();
837 	return 0;
838 }
839