xref: /openbmc/linux/init/main.c (revision 803f6914)
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/stackprotector.h>
18 #include <linux/string.h>
19 #include <linux/ctype.h>
20 #include <linux/delay.h>
21 #include <linux/ioport.h>
22 #include <linux/init.h>
23 #include <linux/initrd.h>
24 #include <linux/bootmem.h>
25 #include <linux/acpi.h>
26 #include <linux/tty.h>
27 #include <linux/percpu.h>
28 #include <linux/kmod.h>
29 #include <linux/vmalloc.h>
30 #include <linux/kernel_stat.h>
31 #include <linux/start_kernel.h>
32 #include <linux/security.h>
33 #include <linux/smp.h>
34 #include <linux/profile.h>
35 #include <linux/rcupdate.h>
36 #include <linux/moduleparam.h>
37 #include <linux/kallsyms.h>
38 #include <linux/writeback.h>
39 #include <linux/cpu.h>
40 #include <linux/cpuset.h>
41 #include <linux/cgroup.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/buffer_head.h>
52 #include <linux/page_cgroup.h>
53 #include <linux/debug_locks.h>
54 #include <linux/debugobjects.h>
55 #include <linux/lockdep.h>
56 #include <linux/kmemleak.h>
57 #include <linux/pid_namespace.h>
58 #include <linux/device.h>
59 #include <linux/kthread.h>
60 #include <linux/sched.h>
61 #include <linux/signal.h>
62 #include <linux/idr.h>
63 #include <linux/kgdb.h>
64 #include <linux/ftrace.h>
65 #include <linux/async.h>
66 #include <linux/kmemcheck.h>
67 #include <linux/sfi.h>
68 #include <linux/shmem_fs.h>
69 #include <linux/slab.h>
70 #include <linux/perf_event.h>
71 
72 #include <asm/io.h>
73 #include <asm/bugs.h>
74 #include <asm/setup.h>
75 #include <asm/sections.h>
76 #include <asm/cacheflush.h>
77 
78 #ifdef CONFIG_X86_LOCAL_APIC
79 #include <asm/smp.h>
80 #endif
81 
82 static int kernel_init(void *);
83 
84 extern void init_IRQ(void);
85 extern void fork_init(unsigned long);
86 extern void mca_init(void);
87 extern void sbus_init(void);
88 extern void prio_tree_init(void);
89 extern void radix_tree_init(void);
90 extern void free_initmem(void);
91 #ifndef CONFIG_DEBUG_RODATA
92 static inline void mark_rodata_ro(void) { }
93 #endif
94 
95 #ifdef CONFIG_TC
96 extern void tc_init(void);
97 #endif
98 
99 /*
100  * Debug helper: via this flag we know that we are in 'early bootup code'
101  * where only the boot processor is running with IRQ disabled.  This means
102  * two things - IRQ must not be enabled before the flag is cleared and some
103  * operations which are not allowed with IRQ disabled are allowed while the
104  * flag is set.
105  */
106 bool early_boot_irqs_disabled __read_mostly;
107 
108 enum system_states system_state __read_mostly;
109 EXPORT_SYMBOL(system_state);
110 
111 /*
112  * Boot command-line arguments
113  */
114 #define MAX_INIT_ARGS CONFIG_INIT_ENV_ARG_LIMIT
115 #define MAX_INIT_ENVS CONFIG_INIT_ENV_ARG_LIMIT
116 
117 extern void time_init(void);
118 /* Default late time init is NULL. archs can override this later. */
119 void (*__initdata late_time_init)(void);
120 extern void softirq_init(void);
121 
122 /* Untouched command line saved by arch-specific code. */
123 char __initdata boot_command_line[COMMAND_LINE_SIZE];
124 /* Untouched saved command line (eg. for /proc) */
125 char *saved_command_line;
126 /* Command line for parameter parsing */
127 static char *static_command_line;
128 
129 static char *execute_command;
130 static char *ramdisk_execute_command;
131 
132 /*
133  * If set, this is an indication to the drivers that reset the underlying
134  * device before going ahead with the initialization otherwise driver might
135  * rely on the BIOS and skip the reset operation.
136  *
137  * This is useful if kernel is booting in an unreliable environment.
138  * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
139  * skipped and devices will be in unknown state.
140  */
141 unsigned int reset_devices;
142 EXPORT_SYMBOL(reset_devices);
143 
144 static int __init set_reset_devices(char *str)
145 {
146 	reset_devices = 1;
147 	return 1;
148 }
149 
150 __setup("reset_devices", set_reset_devices);
151 
152 static const char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
153 const char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
154 static const char *panic_later, *panic_param;
155 
156 extern const struct obs_kernel_param __setup_start[], __setup_end[];
157 
158 static int __init obsolete_checksetup(char *line)
159 {
160 	const struct obs_kernel_param *p;
161 	int had_early_param = 0;
162 
163 	p = __setup_start;
164 	do {
165 		int n = strlen(p->str);
166 		if (parameqn(line, p->str, n)) {
167 			if (p->early) {
168 				/* Already done in parse_early_param?
169 				 * (Needs exact match on param part).
170 				 * Keep iterating, as we can have early
171 				 * params and __setups of same names 8( */
172 				if (line[n] == '\0' || line[n] == '=')
173 					had_early_param = 1;
174 			} else if (!p->setup_func) {
175 				printk(KERN_WARNING "Parameter %s is obsolete,"
176 				       " ignored\n", p->str);
177 				return 1;
178 			} else if (p->setup_func(line + n))
179 				return 1;
180 		}
181 		p++;
182 	} while (p < __setup_end);
183 
184 	return had_early_param;
185 }
186 
187 /*
188  * This should be approx 2 Bo*oMips to start (note initial shift), and will
189  * still work even if initially too large, it will just take slightly longer
190  */
191 unsigned long loops_per_jiffy = (1<<12);
192 
193 EXPORT_SYMBOL(loops_per_jiffy);
194 
195 static int __init debug_kernel(char *str)
196 {
197 	console_loglevel = 10;
198 	return 0;
199 }
200 
201 static int __init quiet_kernel(char *str)
202 {
203 	console_loglevel = 4;
204 	return 0;
205 }
206 
207 early_param("debug", debug_kernel);
208 early_param("quiet", quiet_kernel);
209 
210 static int __init loglevel(char *str)
211 {
212 	int newlevel;
213 
214 	/*
215 	 * Only update loglevel value when a correct setting was passed,
216 	 * to prevent blind crashes (when loglevel being set to 0) that
217 	 * are quite hard to debug
218 	 */
219 	if (get_option(&str, &newlevel)) {
220 		console_loglevel = newlevel;
221 		return 0;
222 	}
223 
224 	return -EINVAL;
225 }
226 
227 early_param("loglevel", loglevel);
228 
229 /*
230  * Unknown boot options get handed to init, unless they look like
231  * unused parameters (modprobe will find them in /proc/cmdline).
232  */
233 static int __init unknown_bootoption(char *param, char *val)
234 {
235 	/* Change NUL term back to "=", to make "param" the whole string. */
236 	if (val) {
237 		/* param=val or param="val"? */
238 		if (val == param+strlen(param)+1)
239 			val[-1] = '=';
240 		else if (val == param+strlen(param)+2) {
241 			val[-2] = '=';
242 			memmove(val-1, val, strlen(val)+1);
243 			val--;
244 		} else
245 			BUG();
246 	}
247 
248 	/* Handle obsolete-style parameters */
249 	if (obsolete_checksetup(param))
250 		return 0;
251 
252 	/* Unused module parameter. */
253 	if (strchr(param, '.') && (!val || strchr(param, '.') < val))
254 		return 0;
255 
256 	if (panic_later)
257 		return 0;
258 
259 	if (val) {
260 		/* Environment option */
261 		unsigned int i;
262 		for (i = 0; envp_init[i]; i++) {
263 			if (i == MAX_INIT_ENVS) {
264 				panic_later = "Too many boot env vars at `%s'";
265 				panic_param = param;
266 			}
267 			if (!strncmp(param, envp_init[i], val - param))
268 				break;
269 		}
270 		envp_init[i] = param;
271 	} else {
272 		/* Command line option */
273 		unsigned int i;
274 		for (i = 0; argv_init[i]; i++) {
275 			if (i == MAX_INIT_ARGS) {
276 				panic_later = "Too many boot init vars at `%s'";
277 				panic_param = param;
278 			}
279 		}
280 		argv_init[i] = param;
281 	}
282 	return 0;
283 }
284 
285 static int __init init_setup(char *str)
286 {
287 	unsigned int i;
288 
289 	execute_command = str;
290 	/*
291 	 * In case LILO is going to boot us with default command line,
292 	 * it prepends "auto" before the whole cmdline which makes
293 	 * the shell think it should execute a script with such name.
294 	 * So we ignore all arguments entered _before_ init=... [MJ]
295 	 */
296 	for (i = 1; i < MAX_INIT_ARGS; i++)
297 		argv_init[i] = NULL;
298 	return 1;
299 }
300 __setup("init=", init_setup);
301 
302 static int __init rdinit_setup(char *str)
303 {
304 	unsigned int i;
305 
306 	ramdisk_execute_command = str;
307 	/* See "auto" comment in init_setup */
308 	for (i = 1; i < MAX_INIT_ARGS; i++)
309 		argv_init[i] = NULL;
310 	return 1;
311 }
312 __setup("rdinit=", rdinit_setup);
313 
314 #ifndef CONFIG_SMP
315 static const unsigned int setup_max_cpus = NR_CPUS;
316 #ifdef CONFIG_X86_LOCAL_APIC
317 static void __init smp_init(void)
318 {
319 	APIC_init_uniprocessor();
320 }
321 #else
322 #define smp_init()	do { } while (0)
323 #endif
324 
325 static inline void setup_nr_cpu_ids(void) { }
326 static inline void smp_prepare_cpus(unsigned int maxcpus) { }
327 #endif
328 
329 /*
330  * We need to store the untouched command line for future reference.
331  * We also need to store the touched command line since the parameter
332  * parsing is performed in place, and we should allow a component to
333  * store reference of name/value for future reference.
334  */
335 static void __init setup_command_line(char *command_line)
336 {
337 	saved_command_line = alloc_bootmem(strlen (boot_command_line)+1);
338 	static_command_line = alloc_bootmem(strlen (command_line)+1);
339 	strcpy (saved_command_line, boot_command_line);
340 	strcpy (static_command_line, command_line);
341 }
342 
343 /*
344  * We need to finalize in a non-__init function or else race conditions
345  * between the root thread and the init thread may cause start_kernel to
346  * be reaped by free_initmem before the root thread has proceeded to
347  * cpu_idle.
348  *
349  * gcc-3.4 accidentally inlines this function, so use noinline.
350  */
351 
352 static __initdata DECLARE_COMPLETION(kthreadd_done);
353 
354 static noinline void __init_refok rest_init(void)
355 {
356 	int pid;
357 
358 	rcu_scheduler_starting();
359 	/*
360 	 * We need to spawn init first so that it obtains pid 1, however
361 	 * the init task will end up wanting to create kthreads, which, if
362 	 * we schedule it before we create kthreadd, will OOPS.
363 	 */
364 	kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
365 	numa_default_policy();
366 	pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
367 	rcu_read_lock();
368 	kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
369 	rcu_read_unlock();
370 	complete(&kthreadd_done);
371 
372 	/*
373 	 * The boot idle thread must execute schedule()
374 	 * at least once to get things moving:
375 	 */
376 	init_idle_bootup_task(current);
377 	schedule_preempt_disabled();
378 	/* Call into cpu_idle with preempt disabled */
379 	cpu_idle();
380 }
381 
382 /* Check for early params. */
383 static int __init do_early_param(char *param, char *val)
384 {
385 	const struct obs_kernel_param *p;
386 
387 	for (p = __setup_start; p < __setup_end; p++) {
388 		if ((p->early && parameq(param, p->str)) ||
389 		    (strcmp(param, "console") == 0 &&
390 		     strcmp(p->str, "earlycon") == 0)
391 		) {
392 			if (p->setup_func(val) != 0)
393 				printk(KERN_WARNING
394 				       "Malformed early option '%s'\n", param);
395 		}
396 	}
397 	/* We accept everything at this stage. */
398 	return 0;
399 }
400 
401 void __init parse_early_options(char *cmdline)
402 {
403 	parse_args("early options", cmdline, NULL, 0, do_early_param);
404 }
405 
406 /* Arch code calls this early on, or if not, just before other parsing. */
407 void __init parse_early_param(void)
408 {
409 	static __initdata int done = 0;
410 	static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];
411 
412 	if (done)
413 		return;
414 
415 	/* All fall through to do_early_param. */
416 	strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
417 	parse_early_options(tmp_cmdline);
418 	done = 1;
419 }
420 
421 /*
422  *	Activate the first processor.
423  */
424 
425 static void __init boot_cpu_init(void)
426 {
427 	int cpu = smp_processor_id();
428 	/* Mark the boot cpu "present", "online" etc for SMP and UP case */
429 	set_cpu_online(cpu, true);
430 	set_cpu_active(cpu, true);
431 	set_cpu_present(cpu, true);
432 	set_cpu_possible(cpu, true);
433 }
434 
435 void __init __weak smp_setup_processor_id(void)
436 {
437 }
438 
439 void __init __weak thread_info_cache_init(void)
440 {
441 }
442 
443 /*
444  * Set up kernel memory allocators
445  */
446 static void __init mm_init(void)
447 {
448 	/*
449 	 * page_cgroup requires contiguous pages,
450 	 * bigger than MAX_ORDER unless SPARSEMEM.
451 	 */
452 	page_cgroup_init_flatmem();
453 	mem_init();
454 	kmem_cache_init();
455 	percpu_init_late();
456 	pgtable_cache_init();
457 	vmalloc_init();
458 }
459 
460 asmlinkage void __init start_kernel(void)
461 {
462 	char * command_line;
463 	extern const struct kernel_param __start___param[], __stop___param[];
464 
465 	/*
466 	 * Need to run as early as possible, to initialize the
467 	 * lockdep hash:
468 	 */
469 	lockdep_init();
470 	smp_setup_processor_id();
471 	debug_objects_early_init();
472 
473 	/*
474 	 * Set up the the initial canary ASAP:
475 	 */
476 	boot_init_stack_canary();
477 
478 	cgroup_init_early();
479 
480 	local_irq_disable();
481 	early_boot_irqs_disabled = true;
482 
483 /*
484  * Interrupts are still disabled. Do necessary setups, then
485  * enable them
486  */
487 	tick_init();
488 	boot_cpu_init();
489 	page_address_init();
490 	printk(KERN_NOTICE "%s", linux_banner);
491 	setup_arch(&command_line);
492 	mm_init_owner(&init_mm, &init_task);
493 	mm_init_cpumask(&init_mm);
494 	setup_command_line(command_line);
495 	setup_nr_cpu_ids();
496 	setup_per_cpu_areas();
497 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */
498 
499 	build_all_zonelists(NULL);
500 	page_alloc_init();
501 
502 	printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
503 	parse_early_param();
504 	parse_args("Booting kernel", static_command_line, __start___param,
505 		   __stop___param - __start___param,
506 		   &unknown_bootoption);
507 
508 	jump_label_init();
509 
510 	/*
511 	 * These use large bootmem allocations and must precede
512 	 * kmem_cache_init()
513 	 */
514 	setup_log_buf(0);
515 	pidhash_init();
516 	vfs_caches_init_early();
517 	sort_main_extable();
518 	trap_init();
519 	mm_init();
520 
521 	/*
522 	 * Set up the scheduler prior starting any interrupts (such as the
523 	 * timer interrupt). Full topology setup happens at smp_init()
524 	 * time - but meanwhile we still have a functioning scheduler.
525 	 */
526 	sched_init();
527 	/*
528 	 * Disable preemption - early bootup scheduling is extremely
529 	 * fragile until we cpu_idle() for the first time.
530 	 */
531 	preempt_disable();
532 	if (!irqs_disabled()) {
533 		printk(KERN_WARNING "start_kernel(): bug: interrupts were "
534 				"enabled *very* early, fixing it\n");
535 		local_irq_disable();
536 	}
537 	idr_init_cache();
538 	perf_event_init();
539 	rcu_init();
540 	radix_tree_init();
541 	/* init some links before init_ISA_irqs() */
542 	early_irq_init();
543 	init_IRQ();
544 	prio_tree_init();
545 	init_timers();
546 	hrtimers_init();
547 	softirq_init();
548 	timekeeping_init();
549 	time_init();
550 	profile_init();
551 	call_function_init();
552 	if (!irqs_disabled())
553 		printk(KERN_CRIT "start_kernel(): bug: interrupts were "
554 				 "enabled early\n");
555 	early_boot_irqs_disabled = false;
556 	local_irq_enable();
557 
558 	/* Interrupts are enabled now so all GFP allocations are safe. */
559 	gfp_allowed_mask = __GFP_BITS_MASK;
560 
561 	kmem_cache_init_late();
562 
563 	/*
564 	 * HACK ALERT! This is early. We're enabling the console before
565 	 * we've done PCI setups etc, and console_init() must be aware of
566 	 * this. But we do want output early, in case something goes wrong.
567 	 */
568 	console_init();
569 	if (panic_later)
570 		panic(panic_later, panic_param);
571 
572 	lockdep_info();
573 
574 	/*
575 	 * Need to run this when irqs are enabled, because it wants
576 	 * to self-test [hard/soft]-irqs on/off lock inversion bugs
577 	 * too:
578 	 */
579 	locking_selftest();
580 
581 #ifdef CONFIG_BLK_DEV_INITRD
582 	if (initrd_start && !initrd_below_start_ok &&
583 	    page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
584 		printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
585 		    "disabling it.\n",
586 		    page_to_pfn(virt_to_page((void *)initrd_start)),
587 		    min_low_pfn);
588 		initrd_start = 0;
589 	}
590 #endif
591 	page_cgroup_init();
592 	debug_objects_mem_init();
593 	kmemleak_init();
594 	setup_per_cpu_pageset();
595 	numa_policy_init();
596 	if (late_time_init)
597 		late_time_init();
598 	sched_clock_init();
599 	calibrate_delay();
600 	pidmap_init();
601 	anon_vma_init();
602 #ifdef CONFIG_X86
603 	if (efi_enabled)
604 		efi_enter_virtual_mode();
605 #endif
606 	thread_info_cache_init();
607 	cred_init();
608 	fork_init(totalram_pages);
609 	proc_caches_init();
610 	buffer_init();
611 	key_init();
612 	security_init();
613 	dbg_late_init();
614 	vfs_caches_init(totalram_pages);
615 	signals_init();
616 	/* rootfs populating might need page-writeback */
617 	page_writeback_init();
618 #ifdef CONFIG_PROC_FS
619 	proc_root_init();
620 #endif
621 	cgroup_init();
622 	cpuset_init();
623 	taskstats_init_early();
624 	delayacct_init();
625 
626 	check_bugs();
627 
628 	acpi_early_init(); /* before LAPIC and SMP init */
629 	sfi_init_late();
630 
631 	ftrace_init();
632 
633 	/* Do the rest non-__init'ed, we're now alive */
634 	rest_init();
635 }
636 
637 /* Call all constructor functions linked into the kernel. */
638 static void __init do_ctors(void)
639 {
640 #ifdef CONFIG_CONSTRUCTORS
641 	ctor_fn_t *fn = (ctor_fn_t *) __ctors_start;
642 
643 	for (; fn < (ctor_fn_t *) __ctors_end; fn++)
644 		(*fn)();
645 #endif
646 }
647 
648 bool initcall_debug;
649 core_param(initcall_debug, initcall_debug, bool, 0644);
650 
651 static char msgbuf[64];
652 
653 static int __init_or_module do_one_initcall_debug(initcall_t fn)
654 {
655 	ktime_t calltime, delta, rettime;
656 	unsigned long long duration;
657 	int ret;
658 
659 	printk(KERN_DEBUG "calling  %pF @ %i\n", fn, task_pid_nr(current));
660 	calltime = ktime_get();
661 	ret = fn();
662 	rettime = ktime_get();
663 	delta = ktime_sub(rettime, calltime);
664 	duration = (unsigned long long) ktime_to_ns(delta) >> 10;
665 	printk(KERN_DEBUG "initcall %pF returned %d after %lld usecs\n", fn,
666 		ret, duration);
667 
668 	return ret;
669 }
670 
671 int __init_or_module do_one_initcall(initcall_t fn)
672 {
673 	int count = preempt_count();
674 	int ret;
675 
676 	if (initcall_debug)
677 		ret = do_one_initcall_debug(fn);
678 	else
679 		ret = fn();
680 
681 	msgbuf[0] = 0;
682 
683 	if (ret && ret != -ENODEV && initcall_debug)
684 		sprintf(msgbuf, "error code %d ", ret);
685 
686 	if (preempt_count() != count) {
687 		strlcat(msgbuf, "preemption imbalance ", sizeof(msgbuf));
688 		preempt_count() = count;
689 	}
690 	if (irqs_disabled()) {
691 		strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));
692 		local_irq_enable();
693 	}
694 	if (msgbuf[0]) {
695 		printk("initcall %pF returned with %s\n", fn, msgbuf);
696 	}
697 
698 	return ret;
699 }
700 
701 
702 extern initcall_t __initcall_start[], __initcall_end[], __early_initcall_end[];
703 
704 static void __init do_initcalls(void)
705 {
706 	initcall_t *fn;
707 
708 	for (fn = __early_initcall_end; fn < __initcall_end; fn++)
709 		do_one_initcall(*fn);
710 }
711 
712 /*
713  * Ok, the machine is now initialized. None of the devices
714  * have been touched yet, but the CPU subsystem is up and
715  * running, and memory and process management works.
716  *
717  * Now we can finally start doing some real work..
718  */
719 static void __init do_basic_setup(void)
720 {
721 	cpuset_init_smp();
722 	usermodehelper_init();
723 	shmem_init();
724 	driver_init();
725 	init_irq_proc();
726 	do_ctors();
727 	usermodehelper_enable();
728 	do_initcalls();
729 }
730 
731 static void __init do_pre_smp_initcalls(void)
732 {
733 	initcall_t *fn;
734 
735 	for (fn = __initcall_start; fn < __early_initcall_end; fn++)
736 		do_one_initcall(*fn);
737 }
738 
739 static void run_init_process(const 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 noinline int init_post(void)
749 {
750 	/* need to finish all async __init code before freeing the memory */
751 	async_synchronize_full();
752 	free_initmem();
753 	mark_rodata_ro();
754 	system_state = SYSTEM_RUNNING;
755 	numa_default_policy();
756 
757 
758 	current->signal->flags |= SIGNAL_UNKILLABLE;
759 
760 	if (ramdisk_execute_command) {
761 		run_init_process(ramdisk_execute_command);
762 		printk(KERN_WARNING "Failed to execute %s\n",
763 				ramdisk_execute_command);
764 	}
765 
766 	/*
767 	 * We try each of these until one succeeds.
768 	 *
769 	 * The Bourne shell can be used instead of init if we are
770 	 * trying to recover a really broken machine.
771 	 */
772 	if (execute_command) {
773 		run_init_process(execute_command);
774 		printk(KERN_WARNING "Failed to execute %s.  Attempting "
775 					"defaults...\n", execute_command);
776 	}
777 	run_init_process("/sbin/init");
778 	run_init_process("/etc/init");
779 	run_init_process("/bin/init");
780 	run_init_process("/bin/sh");
781 
782 	panic("No init found.  Try passing init= option to kernel. "
783 	      "See Linux Documentation/init.txt for guidance.");
784 }
785 
786 static int __init kernel_init(void * unused)
787 {
788 	/*
789 	 * Wait until kthreadd is all set-up.
790 	 */
791 	wait_for_completion(&kthreadd_done);
792 	/*
793 	 * init can allocate pages on any node
794 	 */
795 	set_mems_allowed(node_states[N_HIGH_MEMORY]);
796 	/*
797 	 * init can run on any cpu.
798 	 */
799 	set_cpus_allowed_ptr(current, cpu_all_mask);
800 
801 	cad_pid = task_pid(current);
802 
803 	smp_prepare_cpus(setup_max_cpus);
804 
805 	do_pre_smp_initcalls();
806 	lockup_detector_init();
807 
808 	smp_init();
809 	sched_init_smp();
810 
811 	do_basic_setup();
812 
813 	/* Open the /dev/console on the rootfs, this should never fail */
814 	if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
815 		printk(KERN_WARNING "Warning: unable to open an initial console.\n");
816 
817 	(void) sys_dup(0);
818 	(void) sys_dup(0);
819 	/*
820 	 * check if there is an early userspace init.  If yes, let it do all
821 	 * the work
822 	 */
823 
824 	if (!ramdisk_execute_command)
825 		ramdisk_execute_command = "/init";
826 
827 	if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
828 		ramdisk_execute_command = NULL;
829 		prepare_namespace();
830 	}
831 
832 	/*
833 	 * Ok, we have completed the initial bootup, and
834 	 * we're essentially up and running. Get rid of the
835 	 * initmem segments and start the user-mode stuff..
836 	 */
837 
838 	init_post();
839 	return 0;
840 }
841