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start_kernel是linux内核的入口函数，，定义在init/main.c里面。

start_kernel里面包含了一系列的初始化代码。

asmlinkage void __init start_kernel(void){char * command_line;extern const struct kernel_param __start___param[], __stop___param[];smp_setup_processor_id(); //确定SMP系统中每个CPU的id/** Need to run as early as possible, to initialize the* lockdep hash:*/lockdep_init(); //初始化互斥锁的dependency。debug_objects_early_init(); //初始化debug kernel相关/** Set up the the initial canary ASAP:*/boot_init_stack_canary(); //stack_canary的是带防止栈溢出攻击保护的堆栈。cgroup_init_early();local_irq_disable(); //这个太直白了。early_boot_irqs_off(); //这个也很直白。/* * Interrupts are still disabled. Do necessary setups, then * enable them */tick_init(); //初始化time ticket，时钟boot_cpu_init(); //用以启动的CPU进行初始化。也就是初始化CPU0page_address_init();//初始化页面printk(KERN_NOTICE "%s", linux_banner);setup_arch(&command_line); //CPU架构相关的初始化mm_init_owner(&init_mm, &init_task); //初始化内存管理setup_command_line(command_line); //处理启动命令行setup_nr_cpu_ids();setup_per_cpu_areas();smp_prepare_boot_cpu();//准备boot_cpu. /* arch-specific boot-cpu hooks */build_all_zonelists(NULL); //建立什么样的zone??page_alloc_init(); //初始化page allocation相关结构printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);parse_early_param();parse_args("Booting kernel", static_command_line, __start___param,__stop___param – __start___param,&unknown_bootoption);//解析启动参数/** These use large bootmem allocations and must precede* kmem_cache_init()*/pidhash_init();//初始化process ID hash表vfs_caches_init_early(); //文件系统caches预初始化sort_main_extable(); //初始化exception tabletrap_init(); //初始化trap，用以处理错误执行代码mm_init(); //初始化内存管理/** 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(); //进程调度初始化/** Disable preemption – early bootup scheduling is extremely* fragile until we cpu_idle() for the first time.*/preempt_disable();if (!irqs_disabled()) {printk(KERN_WARNING "start_kernel(): bug: interrupts were ""enabled *very* early, fixing it\n");local_irq_disable();}rcu_init(); //Read_Copy_Update机制初始radix_tree_init();/* init some links before init_ISA_irqs() */early_irq_init();init_IRQ(); //初始化中断prio_tree_init(); //这是啥？以后要弄懂init_timers(); //初始化时钟hrtimers_init();//初始化高精时钟softirq_init();//初始化软中断timekeeping_init();//初始化时钟源time_init();//初始化时间例程profile_init(); //Profile?这是什么profile?if (!irqs_disabled())printk(KERN_CRIT "start_kernel(): bug: interrupts were ""enabled early\n");early_boot_irqs_on();local_irq_enable();/* Interrupts are enabled now so all GFP allocations are safe. */gfp_allowed_mask = __GFP_BITS_MASK;kmem_cache_init_late();//初始化CPU Cache/** 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(); //初始化consoleif (panic_later)panic(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(); //自测试锁#ifdef CONFIG_BLK_DEV_INITRDif (initrd_start && !initrd_below_start_ok &&page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {printk(KERN_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;}#endifpage_cgroup_init(); //页面初始enable_debug_pagealloc(); //页面分配debug启用kmemleak_init(); //memory leak 侦测初始化debug_objects_mem_init();idr_init_cache();setup_per_cpu_pageset(); //设置每个CPU的页面集合numa_policy_init();if (late_time_init)late_time_init();sched_clock_init();//初始化调度时钟calibrate_delay(); //协同不同CPU的时钟pidmap_init();//pid是process id还是processor id?anon_vma_init();//anonymous page?什么意思？#ifdef CONFIG_X86if (efi_enabled)efi_enter_virtual_mode();#endifthread_info_cache_init(); //初始化thread infocred_init(); //credentialfork_init(totalram_pages); //初始化forkproc_caches_init(); //初始化/proc的cache?buffer_init(); // bufferkey_init(); //keysecurity_init();//securitydbg_late_init();//debugvfs_caches_init(totalram_pages);//文件系统cache初始化signals_init();//signal/* rootfs populating might need page-writeback */page_writeback_init();page_writeback#ifdef CONFIG_PROC_FSproc_root_init();#endifcgroup_init();cpuset_init(); //cpusettaskstats_init_early(); //taskdelayacct_init();check_bugs();acpi_early_init();//acpi /* before LAPIC and SMP init */sfi_init_late(); //simple firmware interfaceftrace_init();/* Do the rest non-__init'ed, we're now alive */ rest_init();}

将这些函数归归类，以后就按照类型来读：

CPU初始化

smp_setup_processor_id()

boot_cpu_init()

setup_arch(&command_line);

setup_nr_cpu_ids()

setup_per_cpu_areas()

smp_prepare_boot_cpu()

setup_per_cpu_pageset();

calibrate_delay();

cpuset_init();

内存管理初始化

boot_init_stack_canary()

page_address_init();

mm_init_owner();

page_alloc_init();

mm_init();

rcu_init();

kmem_cache_init_late();

page_cgroup_init();

kmemleak_init();

numa_policy_init();

anon_vma_init();

page_writeback_init();

进程管理

pidhash_init();

sched_init();

sched_clock_init()

pidmap_init();

fork_init(totalram_pages);

taskstats_init_early();

文件系统

vfs_caches_init_early();

thread_info_cache_init();

vfs_caches_init(totalram_pages);

中断

early_irq_init();

init_IRQ();

softirq_init();

同步互斥

lockdep_init();

lockdep_info();

locking_selftest();

时钟

tick_init();

init_timers();

hrtimers_init();

timekeeping_init();

time_init();

调试

debug_objects_early_init();

console_init();

enable_debug_pagealloc();

debug_objects_mem_init();

dbg_late_init();

其他

sort_main_extable();

trap_init();

efi_enter_virtual_mode();

cred_init();

proc_caches_init();

buffer_init();

key_init();

security_init();

signals_init();

proc_root_init();

delayacct_init();

check_bugs();

acpi_early_init();

sfi_init_late();

未知

cgroup_init_early();

build_all_zonelists(NULL);

preempt_disable();

radix_tree_init();

prio_tree_init();

profile_init();

idr_init_cache();

cgroup_init();

ftrace_init();

用敬业的精神去面对每一份挑战，

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