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Linux/init/main.c

  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 #define DEBUG           /* Enable initcall_debug */
 13 
 14 #include <linux/types.h>
 15 #include <linux/module.h>
 16 #include <linux/proc_fs.h>
 17 #include <linux/kernel.h>
 18 #include <linux/syscalls.h>
 19 #include <linux/stackprotector.h>
 20 #include <linux/string.h>
 21 #include <linux/ctype.h>
 22 #include <linux/delay.h>
 23 #include <linux/ioport.h>
 24 #include <linux/init.h>
 25 #include <linux/initrd.h>
 26 #include <linux/bootmem.h>
 27 #include <linux/acpi.h>
 28 #include <linux/tty.h>
 29 #include <linux/percpu.h>
 30 #include <linux/kmod.h>
 31 #include <linux/vmalloc.h>
 32 #include <linux/kernel_stat.h>
 33 #include <linux/start_kernel.h>
 34 #include <linux/security.h>
 35 #include <linux/smp.h>
 36 #include <linux/profile.h>
 37 #include <linux/rcupdate.h>
 38 #include <linux/moduleparam.h>
 39 #include <linux/kallsyms.h>
 40 #include <linux/writeback.h>
 41 #include <linux/cpu.h>
 42 #include <linux/cpuset.h>
 43 #include <linux/cgroup.h>
 44 #include <linux/efi.h>
 45 #include <linux/tick.h>
 46 #include <linux/interrupt.h>
 47 #include <linux/taskstats_kern.h>
 48 #include <linux/delayacct.h>
 49 #include <linux/unistd.h>
 50 #include <linux/rmap.h>
 51 #include <linux/mempolicy.h>
 52 #include <linux/key.h>
 53 #include <linux/buffer_head.h>
 54 #include <linux/page_cgroup.h>
 55 #include <linux/debug_locks.h>
 56 #include <linux/debugobjects.h>
 57 #include <linux/lockdep.h>
 58 #include <linux/kmemleak.h>
 59 #include <linux/pid_namespace.h>
 60 #include <linux/device.h>
 61 #include <linux/kthread.h>
 62 #include <linux/sched.h>
 63 #include <linux/signal.h>
 64 #include <linux/idr.h>
 65 #include <linux/kgdb.h>
 66 #include <linux/ftrace.h>
 67 #include <linux/async.h>
 68 #include <linux/kmemcheck.h>
 69 #include <linux/sfi.h>
 70 #include <linux/shmem_fs.h>
 71 #include <linux/slab.h>
 72 #include <linux/perf_event.h>
 73 #include <linux/file.h>
 74 #include <linux/ptrace.h>
 75 #include <linux/blkdev.h>
 76 #include <linux/elevator.h>
 77 #include <linux/sched_clock.h>
 78 #include <linux/context_tracking.h>
 79 #include <linux/random.h>
 80 
 81 #include <asm/io.h>
 82 #include <asm/bugs.h>
 83 #include <asm/setup.h>
 84 #include <asm/sections.h>
 85 #include <asm/cacheflush.h>
 86 
 87 #ifdef CONFIG_X86_LOCAL_APIC
 88 #include <asm/smp.h>
 89 #endif
 90 
 91 static int kernel_init(void *);
 92 
 93 extern void init_IRQ(void);
 94 extern void fork_init(unsigned long);
 95 extern void radix_tree_init(void);
 96 #ifndef CONFIG_DEBUG_RODATA
 97 static inline void mark_rodata_ro(void) { }
 98 #endif
 99 
100 /*
101  * Debug helper: via this flag we know that we are in 'early bootup code'
102  * where only the boot processor is running with IRQ disabled.  This means
103  * two things - IRQ must not be enabled before the flag is cleared and some
104  * operations which are not allowed with IRQ disabled are allowed while the
105  * flag is set.
106  */
107 bool early_boot_irqs_disabled __read_mostly;
108 
109 enum system_states system_state __read_mostly;
110 EXPORT_SYMBOL(system_state);
111 
112 /*
113  * Boot command-line arguments
114  */
115 #define MAX_INIT_ARGS CONFIG_INIT_ENV_ARG_LIMIT
116 #define MAX_INIT_ENVS CONFIG_INIT_ENV_ARG_LIMIT
117 
118 extern void time_init(void);
119 /* Default late time init is NULL. archs can override this later. */
120 void (*__initdata late_time_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 /* Command line for per-initcall parameter parsing */
129 static char *initcall_command_line;
130 
131 static char *execute_command;
132 static char *ramdisk_execute_command;
133 
134 /*
135  * Used to generate warnings if static_key manipulation functions are used
136  * before jump_label_init is called.
137  */
138 bool static_key_initialized __read_mostly = false;
139 EXPORT_SYMBOL_GPL(static_key_initialized);
140 
141 /*
142  * If set, this is an indication to the drivers that reset the underlying
143  * device before going ahead with the initialization otherwise driver might
144  * rely on the BIOS and skip the reset operation.
145  *
146  * This is useful if kernel is booting in an unreliable environment.
147  * For ex. kdump situaiton where previous kernel has crashed, BIOS has been
148  * skipped and devices will be in unknown state.
149  */
150 unsigned int reset_devices;
151 EXPORT_SYMBOL(reset_devices);
152 
153 static int __init set_reset_devices(char *str)
154 {
155         reset_devices = 1;
156         return 1;
157 }
158 
159 __setup("reset_devices", set_reset_devices);
160 
161 static const char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
162 const char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
163 static const char *panic_later, *panic_param;
164 
165 extern const struct obs_kernel_param __setup_start[], __setup_end[];
166 
167 static int __init obsolete_checksetup(char *line)
168 {
169         const struct obs_kernel_param *p;
170         int had_early_param = 0;
171 
172         p = __setup_start;
173         do {
174                 int n = strlen(p->str);
175                 if (parameqn(line, p->str, n)) {
176                         if (p->early) {
177                                 /* Already done in parse_early_param?
178                                  * (Needs exact match on param part).
179                                  * Keep iterating, as we can have early
180                                  * params and __setups of same names 8( */
181                                 if (line[n] == '\0' || line[n] == '=')
182                                         had_early_param = 1;
183                         } else if (!p->setup_func) {
184                                 pr_warn("Parameter %s is obsolete, ignored\n",
185                                         p->str);
186                                 return 1;
187                         } else if (p->setup_func(line + n))
188                                 return 1;
189                 }
190                 p++;
191         } while (p < __setup_end);
192 
193         return had_early_param;
194 }
195 
196 /*
197  * This should be approx 2 Bo*oMips to start (note initial shift), and will
198  * still work even if initially too large, it will just take slightly longer
199  */
200 unsigned long loops_per_jiffy = (1<<12);
201 
202 EXPORT_SYMBOL(loops_per_jiffy);
203 
204 static int __init debug_kernel(char *str)
205 {
206         console_loglevel = 10;
207         return 0;
208 }
209 
210 static int __init quiet_kernel(char *str)
211 {
212         console_loglevel = 4;
213         return 0;
214 }
215 
216 early_param("debug", debug_kernel);
217 early_param("quiet", quiet_kernel);
218 
219 static int __init loglevel(char *str)
220 {
221         int newlevel;
222 
223         /*
224          * Only update loglevel value when a correct setting was passed,
225          * to prevent blind crashes (when loglevel being set to 0) that
226          * are quite hard to debug
227          */
228         if (get_option(&str, &newlevel)) {
229                 console_loglevel = newlevel;
230                 return 0;
231         }
232 
233         return -EINVAL;
234 }
235 
236 early_param("loglevel", loglevel);
237 
238 /* Change NUL term back to "=", to make "param" the whole string. */
239 static int __init repair_env_string(char *param, char *val, const char *unused)
240 {
241         if (val) {
242                 /* param=val or param="val"? */
243                 if (val == param+strlen(param)+1)
244                         val[-1] = '=';
245                 else if (val == param+strlen(param)+2) {
246                         val[-2] = '=';
247                         memmove(val-1, val, strlen(val)+1);
248                         val--;
249                 } else
250                         BUG();
251         }
252         return 0;
253 }
254 
255 /*
256  * Unknown boot options get handed to init, unless they look like
257  * unused parameters (modprobe will find them in /proc/cmdline).
258  */
259 static int __init unknown_bootoption(char *param, char *val, const char *unused)
260 {
261         repair_env_string(param, val, unused);
262 
263         /* Handle obsolete-style parameters */
264         if (obsolete_checksetup(param))
265                 return 0;
266 
267         /* Unused module parameter. */
268         if (strchr(param, '.') && (!val || strchr(param, '.') < val))
269                 return 0;
270 
271         if (panic_later)
272                 return 0;
273 
274         if (val) {
275                 /* Environment option */
276                 unsigned int i;
277                 for (i = 0; envp_init[i]; i++) {
278                         if (i == MAX_INIT_ENVS) {
279                                 panic_later = "env";
280                                 panic_param = param;
281                         }
282                         if (!strncmp(param, envp_init[i], val - param))
283                                 break;
284                 }
285                 envp_init[i] = param;
286         } else {
287                 /* Command line option */
288                 unsigned int i;
289                 for (i = 0; argv_init[i]; i++) {
290                         if (i == MAX_INIT_ARGS) {
291                                 panic_later = "init";
292                                 panic_param = param;
293                         }
294                 }
295                 argv_init[i] = param;
296         }
297         return 0;
298 }
299 
300 static int __init init_setup(char *str)
301 {
302         unsigned int i;
303 
304         execute_command = str;
305         /*
306          * In case LILO is going to boot us with default command line,
307          * it prepends "auto" before the whole cmdline which makes
308          * the shell think it should execute a script with such name.
309          * So we ignore all arguments entered _before_ init=... [MJ]
310          */
311         for (i = 1; i < MAX_INIT_ARGS; i++)
312                 argv_init[i] = NULL;
313         return 1;
314 }
315 __setup("init=", init_setup);
316 
317 static int __init rdinit_setup(char *str)
318 {
319         unsigned int i;
320 
321         ramdisk_execute_command = str;
322         /* See "auto" comment in init_setup */
323         for (i = 1; i < MAX_INIT_ARGS; i++)
324                 argv_init[i] = NULL;
325         return 1;
326 }
327 __setup("rdinit=", rdinit_setup);
328 
329 #ifndef CONFIG_SMP
330 static const unsigned int setup_max_cpus = NR_CPUS;
331 #ifdef CONFIG_X86_LOCAL_APIC
332 static void __init smp_init(void)
333 {
334         APIC_init_uniprocessor();
335 }
336 #else
337 #define smp_init()      do { } while (0)
338 #endif
339 
340 static inline void setup_nr_cpu_ids(void) { }
341 static inline void smp_prepare_cpus(unsigned int maxcpus) { }
342 #endif
343 
344 /*
345  * We need to store the untouched command line for future reference.
346  * We also need to store the touched command line since the parameter
347  * parsing is performed in place, and we should allow a component to
348  * store reference of name/value for future reference.
349  */
350 static void __init setup_command_line(char *command_line)
351 {
352         saved_command_line =
353                 memblock_virt_alloc(strlen(boot_command_line) + 1, 0);
354         initcall_command_line =
355                 memblock_virt_alloc(strlen(boot_command_line) + 1, 0);
356         static_command_line = memblock_virt_alloc(strlen(command_line) + 1, 0);
357         strcpy (saved_command_line, boot_command_line);
358         strcpy (static_command_line, command_line);
359 }
360 
361 /*
362  * We need to finalize in a non-__init function or else race conditions
363  * between the root thread and the init thread may cause start_kernel to
364  * be reaped by free_initmem before the root thread has proceeded to
365  * cpu_idle.
366  *
367  * gcc-3.4 accidentally inlines this function, so use noinline.
368  */
369 
370 static __initdata DECLARE_COMPLETION(kthreadd_done);
371 
372 static noinline void __init_refok rest_init(void)
373 {
374         int pid;
375 
376         rcu_scheduler_starting();
377         /*
378          * We need to spawn init first so that it obtains pid 1, however
379          * the init task will end up wanting to create kthreads, which, if
380          * we schedule it before we create kthreadd, will OOPS.
381          */
382         kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
383         numa_default_policy();
384         pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
385         rcu_read_lock();
386         kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
387         rcu_read_unlock();
388         complete(&kthreadd_done);
389 
390         /*
391          * The boot idle thread must execute schedule()
392          * at least once to get things moving:
393          */
394         init_idle_bootup_task(current);
395         schedule_preempt_disabled();
396         /* Call into cpu_idle with preempt disabled */
397         cpu_startup_entry(CPUHP_ONLINE);
398 }
399 
400 /* Check for early params. */
401 static int __init do_early_param(char *param, char *val, const char *unused)
402 {
403         const struct obs_kernel_param *p;
404 
405         for (p = __setup_start; p < __setup_end; p++) {
406                 if ((p->early && parameq(param, p->str)) ||
407                     (strcmp(param, "console") == 0 &&
408                      strcmp(p->str, "earlycon") == 0)
409                 ) {
410                         if (p->setup_func(val) != 0)
411                                 pr_warn("Malformed early option '%s'\n", param);
412                 }
413         }
414         /* We accept everything at this stage. */
415         return 0;
416 }
417 
418 void __init parse_early_options(char *cmdline)
419 {
420         parse_args("early options", cmdline, NULL, 0, 0, 0, do_early_param);
421 }
422 
423 /* Arch code calls this early on, or if not, just before other parsing. */
424 void __init parse_early_param(void)
425 {
426         static __initdata int done = 0;
427         static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];
428 
429         if (done)
430                 return;
431 
432         /* All fall through to do_early_param. */
433         strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
434         parse_early_options(tmp_cmdline);
435         done = 1;
436 }
437 
438 /*
439  *      Activate the first processor.
440  */
441 
442 static void __init boot_cpu_init(void)
443 {
444         int cpu = smp_processor_id();
445         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
446         set_cpu_online(cpu, true);
447         set_cpu_active(cpu, true);
448         set_cpu_present(cpu, true);
449         set_cpu_possible(cpu, true);
450 }
451 
452 void __init __weak smp_setup_processor_id(void)
453 {
454 }
455 
456 # if THREAD_SIZE >= PAGE_SIZE
457 void __init __weak thread_info_cache_init(void)
458 {
459 }
460 #endif
461 
462 /*
463  * Set up kernel memory allocators
464  */
465 static void __init mm_init(void)
466 {
467         /*
468          * page_cgroup requires contiguous pages,
469          * bigger than MAX_ORDER unless SPARSEMEM.
470          */
471         page_cgroup_init_flatmem();
472         mem_init();
473         kmem_cache_init();
474         percpu_init_late();
475         pgtable_init();
476         vmalloc_init();
477 }
478 
479 asmlinkage __visible void __init start_kernel(void)
480 {
481         char * command_line;
482         extern const struct kernel_param __start___param[], __stop___param[];
483 
484         /*
485          * Need to run as early as possible, to initialize the
486          * lockdep hash:
487          */
488         lockdep_init();
489         smp_setup_processor_id();
490         debug_objects_early_init();
491 
492         /*
493          * Set up the the initial canary ASAP:
494          */
495         boot_init_stack_canary();
496 
497         cgroup_init_early();
498 
499         local_irq_disable();
500         early_boot_irqs_disabled = true;
501 
502 /*
503  * Interrupts are still disabled. Do necessary setups, then
504  * enable them
505  */
506         boot_cpu_init();
507         page_address_init();
508         pr_notice("%s", linux_banner);
509         setup_arch(&command_line);
510         mm_init_owner(&init_mm, &init_task);
511         mm_init_cpumask(&init_mm);
512         setup_command_line(command_line);
513         setup_nr_cpu_ids();
514         setup_per_cpu_areas();
515         smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
516 
517         build_all_zonelists(NULL, NULL);
518         page_alloc_init();
519 
520         pr_notice("Kernel command line: %s\n", boot_command_line);
521         parse_early_param();
522         parse_args("Booting kernel", static_command_line, __start___param,
523                    __stop___param - __start___param,
524                    -1, -1, &unknown_bootoption);
525 
526         jump_label_init();
527 
528         /*
529          * These use large bootmem allocations and must precede
530          * kmem_cache_init()
531          */
532         setup_log_buf(0);
533         pidhash_init();
534         vfs_caches_init_early();
535         sort_main_extable();
536         trap_init();
537         mm_init();
538 
539         /*
540          * Set up the scheduler prior starting any interrupts (such as the
541          * timer interrupt). Full topology setup happens at smp_init()
542          * time - but meanwhile we still have a functioning scheduler.
543          */
544         sched_init();
545         /*
546          * Disable preemption - early bootup scheduling is extremely
547          * fragile until we cpu_idle() for the first time.
548          */
549         preempt_disable();
550         if (WARN(!irqs_disabled(), "Interrupts were enabled *very* early, fixing it\n"))
551                 local_irq_disable();
552         idr_init_cache();
553         rcu_init();
554         tick_nohz_init();
555         context_tracking_init();
556         radix_tree_init();
557         /* init some links before init_ISA_irqs() */
558         early_irq_init();
559         init_IRQ();
560         tick_init();
561         init_timers();
562         hrtimers_init();
563         softirq_init();
564         timekeeping_init();
565         time_init();
566         sched_clock_postinit();
567         perf_event_init();
568         profile_init();
569         call_function_init();
570         WARN(!irqs_disabled(), "Interrupts were enabled early\n");
571         early_boot_irqs_disabled = false;
572         local_irq_enable();
573 
574         kmem_cache_init_late();
575 
576         /*
577          * HACK ALERT! This is early. We're enabling the console before
578          * we've done PCI setups etc, and console_init() must be aware of
579          * this. But we do want output early, in case something goes wrong.
580          */
581         console_init();
582         if (panic_later)
583                 panic("Too many boot %s vars at `%s'", panic_later,
584                       panic_param);
585 
586         lockdep_info();
587 
588         /*
589          * Need to run this when irqs are enabled, because it wants
590          * to self-test [hard/soft]-irqs on/off lock inversion bugs
591          * too:
592          */
593         locking_selftest();
594 
595 #ifdef CONFIG_BLK_DEV_INITRD
596         if (initrd_start && !initrd_below_start_ok &&
597             page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
598                 pr_crit("initrd overwritten (0x%08lx < 0x%08lx) - disabling it.\n",
599                     page_to_pfn(virt_to_page((void *)initrd_start)),
600                     min_low_pfn);
601                 initrd_start = 0;
602         }
603 #endif
604         page_cgroup_init();
605         debug_objects_mem_init();
606         kmemleak_init();
607         setup_per_cpu_pageset();
608         numa_policy_init();
609         if (late_time_init)
610                 late_time_init();
611         sched_clock_init();
612         calibrate_delay();
613         pidmap_init();
614         anon_vma_init();
615         acpi_early_init();
616 #ifdef CONFIG_X86
617         if (efi_enabled(EFI_RUNTIME_SERVICES))
618                 efi_enter_virtual_mode();
619 #endif
620         thread_info_cache_init();
621         cred_init();
622         fork_init(totalram_pages);
623         proc_caches_init();
624         buffer_init();
625         key_init();
626         security_init();
627         dbg_late_init();
628         vfs_caches_init(totalram_pages);
629         signals_init();
630         /* rootfs populating might need page-writeback */
631         page_writeback_init();
632 #ifdef CONFIG_PROC_FS
633         proc_root_init();
634 #endif
635         cgroup_init();
636         cpuset_init();
637         taskstats_init_early();
638         delayacct_init();
639 
640         check_bugs();
641 
642         sfi_init_late();
643 
644         if (efi_enabled(EFI_RUNTIME_SERVICES)) {
645                 efi_late_init();
646                 efi_free_boot_services();
647         }
648 
649         ftrace_init();
650 
651         /* Do the rest non-__init'ed, we're now alive */
652         rest_init();
653 }
654 
655 /* Call all constructor functions linked into the kernel. */
656 static void __init do_ctors(void)
657 {
658 #ifdef CONFIG_CONSTRUCTORS
659         ctor_fn_t *fn = (ctor_fn_t *) __ctors_start;
660 
661         for (; fn < (ctor_fn_t *) __ctors_end; fn++)
662                 (*fn)();
663 #endif
664 }
665 
666 bool initcall_debug;
667 core_param(initcall_debug, initcall_debug, bool, 0644);
668 
669 static int __init_or_module do_one_initcall_debug(initcall_t fn)
670 {
671         ktime_t calltime, delta, rettime;
672         unsigned long long duration;
673         int ret;
674 
675         pr_debug("calling  %pF @ %i\n", fn, task_pid_nr(current));
676         calltime = ktime_get();
677         ret = fn();
678         rettime = ktime_get();
679         delta = ktime_sub(rettime, calltime);
680         duration = (unsigned long long) ktime_to_ns(delta) >> 10;
681         pr_debug("initcall %pF returned %d after %lld usecs\n",
682                  fn, ret, duration);
683 
684         return ret;
685 }
686 
687 int __init_or_module do_one_initcall(initcall_t fn)
688 {
689         int count = preempt_count();
690         int ret;
691         char msgbuf[64];
692 
693         if (initcall_debug)
694                 ret = do_one_initcall_debug(fn);
695         else
696                 ret = fn();
697 
698         msgbuf[0] = 0;
699 
700         if (preempt_count() != count) {
701                 sprintf(msgbuf, "preemption imbalance ");
702                 preempt_count_set(count);
703         }
704         if (irqs_disabled()) {
705                 strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));
706                 local_irq_enable();
707         }
708         WARN(msgbuf[0], "initcall %pF returned with %s\n", fn, msgbuf);
709 
710         return ret;
711 }
712 
713 
714 extern initcall_t __initcall_start[];
715 extern initcall_t __initcall0_start[];
716 extern initcall_t __initcall1_start[];
717 extern initcall_t __initcall2_start[];
718 extern initcall_t __initcall3_start[];
719 extern initcall_t __initcall4_start[];
720 extern initcall_t __initcall5_start[];
721 extern initcall_t __initcall6_start[];
722 extern initcall_t __initcall7_start[];
723 extern initcall_t __initcall_end[];
724 
725 static initcall_t *initcall_levels[] __initdata = {
726         __initcall0_start,
727         __initcall1_start,
728         __initcall2_start,
729         __initcall3_start,
730         __initcall4_start,
731         __initcall5_start,
732         __initcall6_start,
733         __initcall7_start,
734         __initcall_end,
735 };
736 
737 /* Keep these in sync with initcalls in include/linux/init.h */
738 static char *initcall_level_names[] __initdata = {
739         "early",
740         "core",
741         "postcore",
742         "arch",
743         "subsys",
744         "fs",
745         "device",
746         "late",
747 };
748 
749 static void __init do_initcall_level(int level)
750 {
751         extern const struct kernel_param __start___param[], __stop___param[];
752         initcall_t *fn;
753 
754         strcpy(initcall_command_line, saved_command_line);
755         parse_args(initcall_level_names[level],
756                    initcall_command_line, __start___param,
757                    __stop___param - __start___param,
758                    level, level,
759                    &repair_env_string);
760 
761         for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)
762                 do_one_initcall(*fn);
763 }
764 
765 static void __init do_initcalls(void)
766 {
767         int level;
768 
769         for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)
770                 do_initcall_level(level);
771 }
772 
773 /*
774  * Ok, the machine is now initialized. None of the devices
775  * have been touched yet, but the CPU subsystem is up and
776  * running, and memory and process management works.
777  *
778  * Now we can finally start doing some real work..
779  */
780 static void __init do_basic_setup(void)
781 {
782         cpuset_init_smp();
783         usermodehelper_init();
784         shmem_init();
785         driver_init();
786         init_irq_proc();
787         do_ctors();
788         usermodehelper_enable();
789         do_initcalls();
790         random_int_secret_init();
791 }
792 
793 static void __init do_pre_smp_initcalls(void)
794 {
795         initcall_t *fn;
796 
797         for (fn = __initcall_start; fn < __initcall0_start; fn++)
798                 do_one_initcall(*fn);
799 }
800 
801 /*
802  * This function requests modules which should be loaded by default and is
803  * called twice right after initrd is mounted and right before init is
804  * exec'd.  If such modules are on either initrd or rootfs, they will be
805  * loaded before control is passed to userland.
806  */
807 void __init load_default_modules(void)
808 {
809         load_default_elevator_module();
810 }
811 
812 static int run_init_process(const char *init_filename)
813 {
814         argv_init[0] = init_filename;
815         return do_execve(getname_kernel(init_filename),
816                 (const char __user *const __user *)argv_init,
817                 (const char __user *const __user *)envp_init);
818 }
819 
820 static int try_to_run_init_process(const char *init_filename)
821 {
822         int ret;
823 
824         ret = run_init_process(init_filename);
825 
826         if (ret && ret != -ENOENT) {
827                 pr_err("Starting init: %s exists but couldn't execute it (error %d)\n",
828                        init_filename, ret);
829         }
830 
831         return ret;
832 }
833 
834 static noinline void __init kernel_init_freeable(void);
835 
836 static int __ref kernel_init(void *unused)
837 {
838         int ret;
839 
840         kernel_init_freeable();
841         /* need to finish all async __init code before freeing the memory */
842         async_synchronize_full();
843         free_initmem();
844         mark_rodata_ro();
845         system_state = SYSTEM_RUNNING;
846         numa_default_policy();
847 
848         flush_delayed_fput();
849 
850         if (ramdisk_execute_command) {
851                 ret = run_init_process(ramdisk_execute_command);
852                 if (!ret)
853                         return 0;
854                 pr_err("Failed to execute %s (error %d)\n",
855                        ramdisk_execute_command, ret);
856         }
857 
858         /*
859          * We try each of these until one succeeds.
860          *
861          * The Bourne shell can be used instead of init if we are
862          * trying to recover a really broken machine.
863          */
864         if (execute_command) {
865                 ret = run_init_process(execute_command);
866                 if (!ret)
867                         return 0;
868                 pr_err("Failed to execute %s (error %d).  Attempting defaults...\n",
869                         execute_command, ret);
870         }
871         if (!try_to_run_init_process("/sbin/init") ||
872             !try_to_run_init_process("/etc/init") ||
873             !try_to_run_init_process("/bin/init") ||
874             !try_to_run_init_process("/bin/sh"))
875                 return 0;
876 
877         panic("No working init found.  Try passing init= option to kernel. "
878               "See Linux Documentation/init.txt for guidance.");
879 }
880 
881 static noinline void __init kernel_init_freeable(void)
882 {
883         /*
884          * Wait until kthreadd is all set-up.
885          */
886         wait_for_completion(&kthreadd_done);
887 
888         /* Now the scheduler is fully set up and can do blocking allocations */
889         gfp_allowed_mask = __GFP_BITS_MASK;
890 
891         /*
892          * init can allocate pages on any node
893          */
894         set_mems_allowed(node_states[N_MEMORY]);
895         /*
896          * init can run on any cpu.
897          */
898         set_cpus_allowed_ptr(current, cpu_all_mask);
899 
900         cad_pid = task_pid(current);
901 
902         smp_prepare_cpus(setup_max_cpus);
903 
904         do_pre_smp_initcalls();
905         lockup_detector_init();
906 
907         smp_init();
908         sched_init_smp();
909 
910         do_basic_setup();
911 
912         /* Open the /dev/console on the rootfs, this should never fail */
913         if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
914                 pr_err("Warning: unable to open an initial console.\n");
915 
916         (void) sys_dup(0);
917         (void) sys_dup(0);
918         /*
919          * check if there is an early userspace init.  If yes, let it do all
920          * the work
921          */
922 
923         if (!ramdisk_execute_command)
924                 ramdisk_execute_command = "/init";
925 
926         if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
927                 ramdisk_execute_command = NULL;
928                 prepare_namespace();
929         }
930 
931         /*
932          * Ok, we have completed the initial bootup, and
933          * we're essentially up and running. Get rid of the
934          * initmem segments and start the user-mode stuff..
935          */
936 
937         /* rootfs is available now, try loading default modules */
938         load_default_modules();
939 }
940 

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