xref: /openbmc/linux/init/main.c (revision 643d1f7f)
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/cgroup.h>
43 #include <linux/efi.h>
44 #include <linux/tick.h>
45 #include <linux/interrupt.h>
46 #include <linux/taskstats_kern.h>
47 #include <linux/delayacct.h>
48 #include <linux/unistd.h>
49 #include <linux/rmap.h>
50 #include <linux/mempolicy.h>
51 #include <linux/key.h>
52 #include <linux/unwind.h>
53 #include <linux/buffer_head.h>
54 #include <linux/debug_locks.h>
55 #include <linux/lockdep.h>
56 #include <linux/pid_namespace.h>
57 #include <linux/device.h>
58 #include <linux/kthread.h>
59 #include <linux/sched.h>
60 
61 #include <asm/io.h>
62 #include <asm/bugs.h>
63 #include <asm/setup.h>
64 #include <asm/sections.h>
65 #include <asm/cacheflush.h>
66 
67 #ifdef CONFIG_X86_LOCAL_APIC
68 #include <asm/smp.h>
69 #endif
70 
71 /*
72  * This is one of the first .c files built. Error out early if we have compiler
73  * trouble.
74  */
75 
76 #if __GNUC__ == 4 && __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ == 0
77 #warning gcc-4.1.0 is known to miscompile the kernel.  A different compiler version is recommended.
78 #endif
79 
80 static int kernel_init(void *);
81 
82 extern void init_IRQ(void);
83 extern void fork_init(unsigned long);
84 extern void mca_init(void);
85 extern void sbus_init(void);
86 extern void signals_init(void);
87 extern void pidhash_init(void);
88 extern void pidmap_init(void);
89 extern void prio_tree_init(void);
90 extern void radix_tree_init(void);
91 extern void free_initmem(void);
92 #ifdef	CONFIG_ACPI
93 extern void acpi_early_init(void);
94 #else
95 static inline void acpi_early_init(void) { }
96 #endif
97 #ifndef CONFIG_DEBUG_RODATA
98 static inline void mark_rodata_ro(void) { }
99 #endif
100 
101 #ifdef CONFIG_TC
102 extern void tc_init(void);
103 #endif
104 
105 enum system_states system_state;
106 EXPORT_SYMBOL(system_state);
107 
108 /*
109  * Boot command-line arguments
110  */
111 #define MAX_INIT_ARGS CONFIG_INIT_ENV_ARG_LIMIT
112 #define MAX_INIT_ENVS CONFIG_INIT_ENV_ARG_LIMIT
113 
114 extern void time_init(void);
115 /* Default late time init is NULL. archs can override this later. */
116 void (*late_time_init)(void);
117 extern void softirq_init(void);
118 
119 /* Untouched command line saved by arch-specific code. */
120 char __initdata boot_command_line[COMMAND_LINE_SIZE];
121 /* Untouched saved command line (eg. for /proc) */
122 char *saved_command_line;
123 /* Command line for parameter parsing */
124 static char *static_command_line;
125 
126 static char *execute_command;
127 static char *ramdisk_execute_command;
128 
129 #ifdef CONFIG_SMP
130 /* Setup configured maximum number of CPUs to activate */
131 unsigned int __initdata setup_max_cpus = NR_CPUS;
132 
133 /*
134  * Setup routine for controlling SMP activation
135  *
136  * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
137  * activation entirely (the MPS table probe still happens, though).
138  *
139  * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
140  * greater than 0, limits the maximum number of CPUs activated in
141  * SMP mode to <NUM>.
142  */
143 #ifndef CONFIG_X86_IO_APIC
144 static inline void disable_ioapic_setup(void) {};
145 #endif
146 
147 static int __init nosmp(char *str)
148 {
149 	setup_max_cpus = 0;
150 	disable_ioapic_setup();
151 	return 0;
152 }
153 
154 early_param("nosmp", nosmp);
155 
156 static int __init maxcpus(char *str)
157 {
158 	get_option(&str, &setup_max_cpus);
159 	if (setup_max_cpus == 0)
160 		disable_ioapic_setup();
161 
162 	return 0;
163 }
164 
165 early_param("maxcpus", maxcpus);
166 #else
167 #define setup_max_cpus NR_CPUS
168 #endif
169 
170 /*
171  * If set, this is an indication to the drivers that reset the underlying
172  * device before going ahead with the initialization otherwise driver might
173  * rely on the BIOS and skip the reset operation.
174  *
175  * This is useful if kernel is booting in an unreliable environment.
176  * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
177  * skipped and devices will be in unknown state.
178  */
179 unsigned int reset_devices;
180 EXPORT_SYMBOL(reset_devices);
181 
182 static int __init set_reset_devices(char *str)
183 {
184 	reset_devices = 1;
185 	return 1;
186 }
187 
188 __setup("reset_devices", set_reset_devices);
189 
190 static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
191 char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
192 static const char *panic_later, *panic_param;
193 
194 extern struct obs_kernel_param __setup_start[], __setup_end[];
195 
196 static int __init obsolete_checksetup(char *line)
197 {
198 	struct obs_kernel_param *p;
199 	int had_early_param = 0;
200 
201 	p = __setup_start;
202 	do {
203 		int n = strlen(p->str);
204 		if (!strncmp(line, p->str, n)) {
205 			if (p->early) {
206 				/* Already done in parse_early_param?
207 				 * (Needs exact match on param part).
208 				 * Keep iterating, as we can have early
209 				 * params and __setups of same names 8( */
210 				if (line[n] == '\0' || line[n] == '=')
211 					had_early_param = 1;
212 			} else if (!p->setup_func) {
213 				printk(KERN_WARNING "Parameter %s is obsolete,"
214 				       " ignored\n", p->str);
215 				return 1;
216 			} else if (p->setup_func(line + n))
217 				return 1;
218 		}
219 		p++;
220 	} while (p < __setup_end);
221 
222 	return had_early_param;
223 }
224 
225 /*
226  * This should be approx 2 Bo*oMips to start (note initial shift), and will
227  * still work even if initially too large, it will just take slightly longer
228  */
229 unsigned long loops_per_jiffy = (1<<12);
230 
231 EXPORT_SYMBOL(loops_per_jiffy);
232 
233 static int __init debug_kernel(char *str)
234 {
235 	if (*str)
236 		return 0;
237 	console_loglevel = 10;
238 	return 1;
239 }
240 
241 static int __init quiet_kernel(char *str)
242 {
243 	if (*str)
244 		return 0;
245 	console_loglevel = 4;
246 	return 1;
247 }
248 
249 __setup("debug", debug_kernel);
250 __setup("quiet", quiet_kernel);
251 
252 static int __init loglevel(char *str)
253 {
254 	get_option(&str, &console_loglevel);
255 	return 1;
256 }
257 
258 __setup("loglevel=", loglevel);
259 
260 /*
261  * Unknown boot options get handed to init, unless they look like
262  * failed parameters
263  */
264 static int __init unknown_bootoption(char *param, char *val)
265 {
266 	/* Change NUL term back to "=", to make "param" the whole string. */
267 	if (val) {
268 		/* param=val or param="val"? */
269 		if (val == param+strlen(param)+1)
270 			val[-1] = '=';
271 		else if (val == param+strlen(param)+2) {
272 			val[-2] = '=';
273 			memmove(val-1, val, strlen(val)+1);
274 			val--;
275 		} else
276 			BUG();
277 	}
278 
279 	/* Handle obsolete-style parameters */
280 	if (obsolete_checksetup(param))
281 		return 0;
282 
283 	/*
284 	 * Preemptive maintenance for "why didn't my misspelled command
285 	 * line work?"
286 	 */
287 	if (strchr(param, '.') && (!val || strchr(param, '.') < val)) {
288 		printk(KERN_ERR "Unknown boot option `%s': ignoring\n", param);
289 		return 0;
290 	}
291 
292 	if (panic_later)
293 		return 0;
294 
295 	if (val) {
296 		/* Environment option */
297 		unsigned int i;
298 		for (i = 0; envp_init[i]; i++) {
299 			if (i == MAX_INIT_ENVS) {
300 				panic_later = "Too many boot env vars at `%s'";
301 				panic_param = param;
302 			}
303 			if (!strncmp(param, envp_init[i], val - param))
304 				break;
305 		}
306 		envp_init[i] = param;
307 	} else {
308 		/* Command line option */
309 		unsigned int i;
310 		for (i = 0; argv_init[i]; i++) {
311 			if (i == MAX_INIT_ARGS) {
312 				panic_later = "Too many boot init vars at `%s'";
313 				panic_param = param;
314 			}
315 		}
316 		argv_init[i] = param;
317 	}
318 	return 0;
319 }
320 
321 #ifdef CONFIG_DEBUG_PAGEALLOC
322 int __read_mostly debug_pagealloc_enabled = 0;
323 #endif
324 
325 static int __init init_setup(char *str)
326 {
327 	unsigned int i;
328 
329 	execute_command = str;
330 	/*
331 	 * In case LILO is going to boot us with default command line,
332 	 * it prepends "auto" before the whole cmdline which makes
333 	 * the shell think it should execute a script with such name.
334 	 * So we ignore all arguments entered _before_ init=... [MJ]
335 	 */
336 	for (i = 1; i < MAX_INIT_ARGS; i++)
337 		argv_init[i] = NULL;
338 	return 1;
339 }
340 __setup("init=", init_setup);
341 
342 static int __init rdinit_setup(char *str)
343 {
344 	unsigned int i;
345 
346 	ramdisk_execute_command = str;
347 	/* See "auto" comment in init_setup */
348 	for (i = 1; i < MAX_INIT_ARGS; i++)
349 		argv_init[i] = NULL;
350 	return 1;
351 }
352 __setup("rdinit=", rdinit_setup);
353 
354 #ifndef CONFIG_SMP
355 
356 #ifdef CONFIG_X86_LOCAL_APIC
357 static void __init smp_init(void)
358 {
359 	APIC_init_uniprocessor();
360 }
361 #else
362 #define smp_init()	do { } while (0)
363 #endif
364 
365 static inline void setup_per_cpu_areas(void) { }
366 static inline void smp_prepare_cpus(unsigned int maxcpus) { }
367 
368 #else
369 
370 #ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
371 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
372 
373 EXPORT_SYMBOL(__per_cpu_offset);
374 
375 static void __init setup_per_cpu_areas(void)
376 {
377 	unsigned long size, i;
378 	char *ptr;
379 	unsigned long nr_possible_cpus = num_possible_cpus();
380 
381 	/* Copy section for each CPU (we discard the original) */
382 	size = ALIGN(PERCPU_ENOUGH_ROOM, PAGE_SIZE);
383 	ptr = alloc_bootmem_pages(size * nr_possible_cpus);
384 
385 	for_each_possible_cpu(i) {
386 		__per_cpu_offset[i] = ptr - __per_cpu_start;
387 		memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
388 		ptr += size;
389 	}
390 }
391 #endif /* CONFIG_HAVE_SETUP_PER_CPU_AREA */
392 
393 /* Called by boot processor to activate the rest. */
394 static void __init smp_init(void)
395 {
396 	unsigned int cpu;
397 
398 	/* FIXME: This should be done in userspace --RR */
399 	for_each_present_cpu(cpu) {
400 		if (num_online_cpus() >= setup_max_cpus)
401 			break;
402 		if (!cpu_online(cpu))
403 			cpu_up(cpu);
404 	}
405 
406 	/* Any cleanup work */
407 	printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
408 	smp_cpus_done(setup_max_cpus);
409 }
410 
411 #endif
412 
413 /*
414  * We need to store the untouched command line for future reference.
415  * We also need to store the touched command line since the parameter
416  * parsing is performed in place, and we should allow a component to
417  * store reference of name/value for future reference.
418  */
419 static void __init setup_command_line(char *command_line)
420 {
421 	saved_command_line = alloc_bootmem(strlen (boot_command_line)+1);
422 	static_command_line = alloc_bootmem(strlen (command_line)+1);
423 	strcpy (saved_command_line, boot_command_line);
424 	strcpy (static_command_line, command_line);
425 }
426 
427 /*
428  * We need to finalize in a non-__init function or else race conditions
429  * between the root thread and the init thread may cause start_kernel to
430  * be reaped by free_initmem before the root thread has proceeded to
431  * cpu_idle.
432  *
433  * gcc-3.4 accidentally inlines this function, so use noinline.
434  */
435 
436 static void noinline __init_refok rest_init(void)
437 	__releases(kernel_lock)
438 {
439 	int pid;
440 
441 	kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
442 	numa_default_policy();
443 	pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
444 	kthreadd_task = find_task_by_pid(pid);
445 	unlock_kernel();
446 
447 	/*
448 	 * The boot idle thread must execute schedule()
449 	 * at least once to get things moving:
450 	 */
451 	init_idle_bootup_task(current);
452 	preempt_enable_no_resched();
453 	schedule();
454 	preempt_disable();
455 
456 	/* Call into cpu_idle with preempt disabled */
457 	cpu_idle();
458 }
459 
460 /* Check for early params. */
461 static int __init do_early_param(char *param, char *val)
462 {
463 	struct obs_kernel_param *p;
464 
465 	for (p = __setup_start; p < __setup_end; p++) {
466 		if ((p->early && strcmp(param, p->str) == 0) ||
467 		    (strcmp(param, "console") == 0 &&
468 		     strcmp(p->str, "earlycon") == 0)
469 		) {
470 			if (p->setup_func(val) != 0)
471 				printk(KERN_WARNING
472 				       "Malformed early option '%s'\n", param);
473 		}
474 	}
475 	/* We accept everything at this stage. */
476 	return 0;
477 }
478 
479 /* Arch code calls this early on, or if not, just before other parsing. */
480 void __init parse_early_param(void)
481 {
482 	static __initdata int done = 0;
483 	static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];
484 
485 	if (done)
486 		return;
487 
488 	/* All fall through to do_early_param. */
489 	strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
490 	parse_args("early options", tmp_cmdline, NULL, 0, do_early_param);
491 	done = 1;
492 }
493 
494 /*
495  *	Activate the first processor.
496  */
497 
498 static void __init boot_cpu_init(void)
499 {
500 	int cpu = smp_processor_id();
501 	/* Mark the boot cpu "present", "online" etc for SMP and UP case */
502 	cpu_set(cpu, cpu_online_map);
503 	cpu_set(cpu, cpu_present_map);
504 	cpu_set(cpu, cpu_possible_map);
505 }
506 
507 void __init __attribute__((weak)) smp_setup_processor_id(void)
508 {
509 }
510 
511 asmlinkage void __init start_kernel(void)
512 {
513 	char * command_line;
514 	extern struct kernel_param __start___param[], __stop___param[];
515 
516 	smp_setup_processor_id();
517 
518 	/*
519 	 * Need to run as early as possible, to initialize the
520 	 * lockdep hash:
521 	 */
522 	unwind_init();
523 	lockdep_init();
524 	cgroup_init_early();
525 
526 	local_irq_disable();
527 	early_boot_irqs_off();
528 	early_init_irq_lock_class();
529 
530 /*
531  * Interrupts are still disabled. Do necessary setups, then
532  * enable them
533  */
534 	lock_kernel();
535 	tick_init();
536 	boot_cpu_init();
537 	page_address_init();
538 	printk(KERN_NOTICE);
539 	printk(linux_banner);
540 	setup_arch(&command_line);
541 	setup_command_line(command_line);
542 	unwind_setup();
543 	setup_per_cpu_areas();
544 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */
545 
546 	/*
547 	 * Set up the scheduler prior starting any interrupts (such as the
548 	 * timer interrupt). Full topology setup happens at smp_init()
549 	 * time - but meanwhile we still have a functioning scheduler.
550 	 */
551 	sched_init();
552 	/*
553 	 * Disable preemption - early bootup scheduling is extremely
554 	 * fragile until we cpu_idle() for the first time.
555 	 */
556 	preempt_disable();
557 	build_all_zonelists();
558 	page_alloc_init();
559 	enable_debug_pagealloc();
560 	printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
561 	parse_early_param();
562 	parse_args("Booting kernel", static_command_line, __start___param,
563 		   __stop___param - __start___param,
564 		   &unknown_bootoption);
565 	if (!irqs_disabled()) {
566 		printk(KERN_WARNING "start_kernel(): bug: interrupts were "
567 				"enabled *very* early, fixing it\n");
568 		local_irq_disable();
569 	}
570 	sort_main_extable();
571 	trap_init();
572 	rcu_init();
573 	init_IRQ();
574 	pidhash_init();
575 	init_timers();
576 	hrtimers_init();
577 	softirq_init();
578 	timekeeping_init();
579 	time_init();
580 	profile_init();
581 	if (!irqs_disabled())
582 		printk("start_kernel(): bug: interrupts were enabled early\n");
583 	early_boot_irqs_on();
584 	local_irq_enable();
585 
586 	/*
587 	 * HACK ALERT! This is early. We're enabling the console before
588 	 * we've done PCI setups etc, and console_init() must be aware of
589 	 * this. But we do want output early, in case something goes wrong.
590 	 */
591 	console_init();
592 	if (panic_later)
593 		panic(panic_later, panic_param);
594 
595 	lockdep_info();
596 
597 	/*
598 	 * Need to run this when irqs are enabled, because it wants
599 	 * to self-test [hard/soft]-irqs on/off lock inversion bugs
600 	 * too:
601 	 */
602 	locking_selftest();
603 
604 #ifdef CONFIG_BLK_DEV_INITRD
605 	if (initrd_start && !initrd_below_start_ok &&
606 			initrd_start < min_low_pfn << PAGE_SHIFT) {
607 		printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
608 		    "disabling it.\n",initrd_start,min_low_pfn << PAGE_SHIFT);
609 		initrd_start = 0;
610 	}
611 #endif
612 	vfs_caches_init_early();
613 	cpuset_init_early();
614 	mem_init();
615 	cpu_hotplug_init();
616 	kmem_cache_init();
617 	setup_per_cpu_pageset();
618 	numa_policy_init();
619 	if (late_time_init)
620 		late_time_init();
621 	calibrate_delay();
622 	pidmap_init();
623 	pgtable_cache_init();
624 	prio_tree_init();
625 	anon_vma_init();
626 #ifdef CONFIG_X86
627 	if (efi_enabled)
628 		efi_enter_virtual_mode();
629 #endif
630 	fork_init(num_physpages);
631 	proc_caches_init();
632 	buffer_init();
633 	unnamed_dev_init();
634 	key_init();
635 	security_init();
636 	vfs_caches_init(num_physpages);
637 	radix_tree_init();
638 	signals_init();
639 	/* rootfs populating might need page-writeback */
640 	page_writeback_init();
641 #ifdef CONFIG_PROC_FS
642 	proc_root_init();
643 #endif
644 	cgroup_init();
645 	cpuset_init();
646 	taskstats_init_early();
647 	delayacct_init();
648 
649 	check_bugs();
650 
651 	acpi_early_init(); /* before LAPIC and SMP init */
652 
653 	/* Do the rest non-__init'ed, we're now alive */
654 	rest_init();
655 }
656 
657 static int __initdata initcall_debug;
658 
659 static int __init initcall_debug_setup(char *str)
660 {
661 	initcall_debug = 1;
662 	return 1;
663 }
664 __setup("initcall_debug", initcall_debug_setup);
665 
666 extern initcall_t __initcall_start[], __initcall_end[];
667 
668 static void __init do_initcalls(void)
669 {
670 	initcall_t *call;
671 	int count = preempt_count();
672 
673 	for (call = __initcall_start; call < __initcall_end; call++) {
674 		ktime_t t0, t1, delta;
675 		char *msg = NULL;
676 		char msgbuf[40];
677 		int result;
678 
679 		if (initcall_debug) {
680 			printk("Calling initcall 0x%p", *call);
681 			print_fn_descriptor_symbol(": %s()",
682 					(unsigned long) *call);
683 			printk("\n");
684 			t0 = ktime_get();
685 		}
686 
687 		result = (*call)();
688 
689 		if (initcall_debug) {
690 			t1 = ktime_get();
691 			delta = ktime_sub(t1, t0);
692 
693 			printk("initcall 0x%p", *call);
694 			print_fn_descriptor_symbol(": %s()",
695 					(unsigned long) *call);
696 			printk(" returned %d.\n", result);
697 
698 			printk("initcall 0x%p ran for %Ld msecs: ",
699 				*call, (unsigned long long)delta.tv64 >> 20);
700 			print_fn_descriptor_symbol("%s()\n",
701 				(unsigned long) *call);
702 		}
703 
704 		if (result && result != -ENODEV && initcall_debug) {
705 			sprintf(msgbuf, "error code %d", result);
706 			msg = msgbuf;
707 		}
708 		if (preempt_count() != count) {
709 			msg = "preemption imbalance";
710 			preempt_count() = count;
711 		}
712 		if (irqs_disabled()) {
713 			msg = "disabled interrupts";
714 			local_irq_enable();
715 		}
716 		if (msg) {
717 			printk(KERN_WARNING "initcall at 0x%p", *call);
718 			print_fn_descriptor_symbol(": %s()",
719 					(unsigned long) *call);
720 			printk(": returned with %s\n", msg);
721 		}
722 	}
723 
724 	/* Make sure there is no pending stuff from the initcall sequence */
725 	flush_scheduled_work();
726 }
727 
728 /*
729  * Ok, the machine is now initialized. None of the devices
730  * have been touched yet, but the CPU subsystem is up and
731  * running, and memory and process management works.
732  *
733  * Now we can finally start doing some real work..
734  */
735 static void __init do_basic_setup(void)
736 {
737 	/* drivers will send hotplug events */
738 	init_workqueues();
739 	usermodehelper_init();
740 	driver_init();
741 	init_irq_proc();
742 	do_initcalls();
743 }
744 
745 static int __initdata nosoftlockup;
746 
747 static int __init nosoftlockup_setup(char *str)
748 {
749 	nosoftlockup = 1;
750 	return 1;
751 }
752 __setup("nosoftlockup", nosoftlockup_setup);
753 
754 static void __init do_pre_smp_initcalls(void)
755 {
756 	extern int spawn_ksoftirqd(void);
757 
758 	migration_init();
759 	spawn_ksoftirqd();
760 	if (!nosoftlockup)
761 		spawn_softlockup_task();
762 }
763 
764 static void run_init_process(char *init_filename)
765 {
766 	argv_init[0] = init_filename;
767 	kernel_execve(init_filename, argv_init, envp_init);
768 }
769 
770 /* This is a non __init function. Force it to be noinline otherwise gcc
771  * makes it inline to init() and it becomes part of init.text section
772  */
773 static int noinline init_post(void)
774 {
775 	free_initmem();
776 	unlock_kernel();
777 	mark_rodata_ro();
778 	system_state = SYSTEM_RUNNING;
779 	numa_default_policy();
780 
781 	if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
782 		printk(KERN_WARNING "Warning: unable to open an initial console.\n");
783 
784 	(void) sys_dup(0);
785 	(void) sys_dup(0);
786 
787 	if (ramdisk_execute_command) {
788 		run_init_process(ramdisk_execute_command);
789 		printk(KERN_WARNING "Failed to execute %s\n",
790 				ramdisk_execute_command);
791 	}
792 
793 	/*
794 	 * We try each of these until one succeeds.
795 	 *
796 	 * The Bourne shell can be used instead of init if we are
797 	 * trying to recover a really broken machine.
798 	 */
799 	if (execute_command) {
800 		run_init_process(execute_command);
801 		printk(KERN_WARNING "Failed to execute %s.  Attempting "
802 					"defaults...\n", execute_command);
803 	}
804 	run_init_process("/sbin/init");
805 	run_init_process("/etc/init");
806 	run_init_process("/bin/init");
807 	run_init_process("/bin/sh");
808 
809 	panic("No init found.  Try passing init= option to kernel.");
810 }
811 
812 static int __init kernel_init(void * unused)
813 {
814 	lock_kernel();
815 	/*
816 	 * init can run on any cpu.
817 	 */
818 	set_cpus_allowed(current, CPU_MASK_ALL);
819 	/*
820 	 * Tell the world that we're going to be the grim
821 	 * reaper of innocent orphaned children.
822 	 *
823 	 * We don't want people to have to make incorrect
824 	 * assumptions about where in the task array this
825 	 * can be found.
826 	 */
827 	init_pid_ns.child_reaper = current;
828 
829 	__set_special_pids(1, 1);
830 	cad_pid = task_pid(current);
831 
832 	smp_prepare_cpus(setup_max_cpus);
833 
834 	do_pre_smp_initcalls();
835 
836 	smp_init();
837 	sched_init_smp();
838 
839 	cpuset_init_smp();
840 
841 	do_basic_setup();
842 
843 	/*
844 	 * check if there is an early userspace init.  If yes, let it do all
845 	 * the work
846 	 */
847 
848 	if (!ramdisk_execute_command)
849 		ramdisk_execute_command = "/init";
850 
851 	if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
852 		ramdisk_execute_command = NULL;
853 		prepare_namespace();
854 	}
855 
856 	/*
857 	 * Ok, we have completed the initial bootup, and
858 	 * we're essentially up and running. Get rid of the
859 	 * initmem segments and start the user-mode stuff..
860 	 */
861 	init_post();
862 	return 0;
863 }
864