linux专题：嵌入式linux系统启动流程基础分析

asmlinkage __visible void __init start_kernel(void)
{
 char *command_line;
 char *after_dashes;
 set_task_stack_end_magic(&init_task);
 smp_setup_processor_id();
 debug_objects_early_init();
 cgroup_init_early();
 local_irq_disable();
 early_boot_irqs_disabled = true;
 /*
  * Interrupts are still disabled. Do necessary setups, then
  * enable them.
  */
 boot_cpu_init();
 page_address_init();
 pr_notice("%s", linux_banner);
 setup_arch(&command_line);
 /*
  * Set up the the initial canary and entropy after arch
  * and after adding latent and command line entropy.
  */
 add_latent_entropy();
 add_device_randomness(command_line, strlen(command_line));
 boot_init_stack_canary();
 mm_init_cpumask(&init_mm);
 setup_command_line(command_line);
 setup_nr_cpu_ids();
 setup_per_cpu_areas();
 smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
 boot_cpu_hotplug_init();
 build_all_zonelists(NULL);
 page_alloc_init();
 pr_notice("Kernel command line: %s\n", boot_command_line);
 /* parameters may set static keys */
 jump_label_init();
 parse_early_param();
 after_dashes = parse_args("Booting kernel",
      static_command_line, __start___param,
      __stop___param - __start___param,
      -1, -1, NULL, &unknown_bootoption);
 if (!IS_ERR_OR_NULL(after_dashes))
  parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,
      NULL, set_init_arg);
 /*
  * These use large bootmem allocations and must precede
  * kmem_cache_init()
  */
 setup_log_buf(0);
 pidhash_init();
 vfs_caches_init_early();
 sort_main_extable();
 trap_init();
 mm_init();
 ftrace_init();
 /* trace_printk can be enabled here */
 early_trace_init();
 /*
  * Set up the scheduler prior starting any interrupts (such as the
  * timer interrupt). Full topology setup happens at smp_init()
  * time - but meanwhile we still have a functioning scheduler.
  */
 sched_init();
 /*
  * Disable preemption - early bootup scheduling is extremely
  * fragile until we cpu_idle() for the first time.
  */
 preempt_disable();
 if (WARN(!irqs_disabled(),
   "Interrupts were enabled *very* early, fixing it\n"))
  local_irq_disable();
 radix_tree_init();
 /*
  * Allow workqueue creation and work item queueing/cancelling
  * early.  Work item execution depends on kthreads and starts after
  * workqueue_init().
  */
 workqueue_init_early();
 rcu_init();
 /* Trace events are available after this */
 trace_init();
 context_tracking_init();
 /* init some links before init_ISA_irqs() */
 early_irq_init();
 init_IRQ();
 tick_init();
 rcu_init_nohz();
 init_timers();
 hrtimers_init();
 softirq_init();
 timekeeping_init();
 time_init();
 sched_clock_postinit();
 printk_safe_init();
 perf_event_init();
 profile_init();
 call_function_init();
 WARN(!irqs_disabled(), "Interrupts were enabled early\n");
 early_boot_irqs_disabled = false;
 local_irq_enable();
 kmem_cache_init_late();
 /*
  * HACK ALERT! This is early. We're enabling the console before
  * we've done PCI setups etc, and console_init() must be aware of
  * this. But we do want output early, in case something goes wrong.
  */
 console_init();
 if (panic_later)
  panic("Too many boot %s vars at `%s'", panic_later,
        panic_param);
 lockdep_info();
 /*
  * Need to run this when irqs are enabled, because it wants
  * to self-test [hard/soft]-irqs on/off lock inversion bugs
  * too:
  */
 locking_selftest();
 /*
  * This needs to be called before any devices perform DMA
  * operations that might use the SWIOTLB bounce buffers. It will
  * mark the bounce buffers as decrypted so that their usage will
  * not cause "plain-text" data to be decrypted when accessed.
  */
 mem_encrypt_init();
#ifdef CONFIG_BLK_DEV_INITRD
 if (initrd_start && !initrd_below_start_ok &&
     page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
  pr_crit("initrd overwritten (0x%08lx < 0x%08lx) - disabling it.\n",
      page_to_pfn(virt_to_page((void *)initrd_start)),
      min_low_pfn);
  initrd_start = 0;
 }
#endif
 kmemleak_init();
 debug_objects_mem_init();
 setup_per_cpu_pageset();
 numa_policy_init();
 if (late_time_init)
  late_time_init();
 calibrate_delay();
 pidmap_init();
 anon_vma_init();
 acpi_early_init();
#ifdef CONFIG_X86
 if (efi_enabled(EFI_RUNTIME_SERVICES))
  efi_enter_virtual_mode();
#endif
 thread_stack_cache_init();
 cred_init();
 fork_init();
 proc_caches_init();
 buffer_init();
 key_init();
 security_init();
 dbg_late_init();
 vfs_caches_init();
 pagecache_init();
 signals_init();
 proc_root_init();
 nsfs_init();
 cpuset_init();
 cgroup_init();
 taskstats_init_early();
 delayacct_init();
 check_bugs();
 acpi_subsystem_init();
 arch_post_acpi_subsys_init();
 sfi_init_late();
 if (efi_enabled(EFI_RUNTIME_SERVICES)) {
  efi_free_boot_services();
 }
 /* Do the rest non-__init'ed, we're now alive */
 rest_init();
 prevent_tail_call_optimization();
}