Linux内核start_kernel()函数
Linux内核start_kernel()函数
Linux内核start_kernel()函数- asmlinkage void __init start_kernel(void)
- {
- char * command_line;
- extern struct kernel_param __start___param[], __stop___param[];
- smp_setup_processor_id();
- //空函数
- /*
- * Need to run as early as possible, to initialize the
- * lockdep hash:
- */
- lockdep_init();/*初始化一些数据*/
- debug_objects_early_init();
- cgroup_init_early();
- local_irq_disable(); /*关闭中断*/
- early_boot_irqs_off();
- /*
- * 每一个中断都有一个中断描述符(struct irq_desc)来进行描述,这个函数的
- * 作用就是设置所有中断描述符的锁
- */
- early_init_irq_lock_class();
- /*
- * Interrupts are still disabled. Do necessary setups, then
- * enable them
- */
- lock_kernel(); /*锁上内核,Linux是支持抢占CPU,放弃启动被中断(针对多处理器)*/
- tick_init(); /*初始化时钟*/
- boot_cpu_init();/*//这个实际上是在多CPU环境下选择CPU,这里直接CPUID选择的是0号cpu*/
- page_address_init(); /* 初始化页地址,使用链表将其链接起来 */
- printk(KERN_NOTICE);
- printk(linux_banner); /*打印Linux版本*/
- setup_arch(&command_line); /* 这是一个重量级的函数了,会比较仔细地分析一下,主要完成了4个方面的工作,一个就是取得MACHINE和PROCESSOR的信息然或将他们赋值给kernel相应的全局变量,然后呢是对boot_command_line和tags接行解析,再然后呢就是memory、cach的初始化,最后是为kernel的后续运行请求资源。 */
- /*初始化内存*/
- mm_init_owner(&init_mm, &init_task);
- setup_command_line(command_line); /*保存命令行参数*/
- setup_per_cpu_areas();/* 为每个cpu申请内存空间 */
- setup_nr_cpu_ids();
- smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks//设置启动的CPU为在线状态.在多CPU架构下 */
- /*
- * 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();/*初始化进程调度器*/
- /*
- * Disable preemption - early bootup scheduling is extremely
- * fragile until we cpu_idle() for the first time.
- */
- preempt_disable(); /*禁止系统调用,即禁止抢占*/
- build_all_zonelists(); /*建立内存区域链表*/
- page_alloc_init();/*内存页初始化*/
- printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);/*打印Linux命令行启动参数*/
- parse_early_param();/*解析参数*/
- parse_args("Booting kernel", static_command_line, __start___param,
- __stop___param - __start___param,
- &unknown_bootoption); //执行命令行解析,若参数不存在,则调用unknown_bootoption
- if (!irqs_disabled()) {
- printk(KERN_WARNING "start_kernel(): bug: interrupts were "
- "enabled *very* early, fixing it\n");
- local_irq_disable();
- }/*判断中断是否关闭,若打开则关闭中断*/
- sort_main_extable(); /*对异常处理函数排序*/
- trap_init();/*空函数*/
- rcu_init();/*初始化互斥机制*/
- /* init some links before init_ISA_irqs() */
- early_irq_init();/*中断向量的初始化*/
- init_IRQ();/*完成其余中断向量的初始化*/
- pidhash_init();/*进程Hash table的初始化*/
- init_timers();/*初始化定时器*/
- hrtimers_init();/*高精度时钟初始化*/
- softirq_init();/*软中断初始化*/
- timekeeping_init();/*共用时钟的初始化*/
- time_init();/*初始化系统时钟*/
- sched_clock_init();/*进程调度时钟初始化*/
- profile_init(); /* 对内核的profile(一个内核性能调式工具)功能进行初始化 */
- if (!irqs_disabled())
- printk(KERN_CRIT "start_kernel(): bug: interrupts were "
- "enabled early\n");
- early_boot_irqs_on(); /*打开IRQ中断*/
- local_irq_enable();
- /*
- * 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();/*打印中断的初始化*/
- if (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();
- #ifdef CONFIG_BLK_DEV_INITRD
- if (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;
- }
- #endif
- vmalloc_init(); /*内存池的初始化*/
- vfs_caches_init_early();/*虚拟文件系统的初始化*/
- cpuset_init_early();/*空函数*/
- page_cgroup_init();/**/
- mem_init();/*对全局的物理页变量初始化,对没有分配的页面初始化*/
- enable_debug_pagealloc();
- cpu_hotplug_init();/*空函数*/
- kmem_cache_init();/*内核内存缓冲池的初始化*/
- debug_objects_mem_init();
- idr_init_cache();/*idr初始化缓冲*/
- setup_per_cpu_pageset();/*空函数*/
- numa_policy_init();/*空函数*/
- if (late_time_init)
- late_time_init();
- calibrate_delay(); /*校验延时函数的精确度*/
- pidmap_init();/*进程号位图初始化,一般用一个page来只是所有的进程PID占用情况*/
- pgtable_cache_init();/*空函数*/
- prio_tree_init();/*初始化优先级数组*/
- anon_vma_init();/*空函数*/
- #ifdef CONFIG_X86
- if (efi_enabled)
- efi_enter_virtual_mode();
- #endif
- thread_info_cache_init();/*空函数*/
- cred_init();
- fork_init(num_physpages);/*初始化fork()环境*/
- proc_caches_init();/*为proc文件系统创建高速缓存*/
- buffer_init();/*空函数*/
- key_init();/*没有键盘为空,有键盘初始化一个高速缓存*/
- security_init();/*空函数*/
- vfs_caches_init(num_physpages); /*虚拟文件系统挂载*/
- radix_tree_init();/*radix树的初始化,供页面查找*/
- signals_init();/*初始化信号量*/
- /* rootfs populating might need page-writeback */
- page_writeback_init();/*CPU在内存中开辟高速缓存,CPU直接访问高速缓存提以高速度。当cpu更新了高速缓存的数据后,需要定期将高速缓存的数据写回到存储介质中,比如磁盘和flash等。这个函数初始化写回的周期*/
- #ifdef CONFIG_PROC_FS
- proc_root_init();/*如果配置了proc文件系统,则需初始化并加载proc文件系统。在根目录的proc文件夹就是proc文件系统,这个文件系统是ram类型的,记录系统的临时数据,系统关机后不会写回到flash中*/
- #endif
- cgroup_init();/*空函数*/
- cpuset_init();/*空函数*/
- taskstats_init_early();/*进程状态初始化,实际上就是分配了一个存储线程状态的高速缓存*/
- delayacct_init();/*空函数*/
- check_bugs();/*测试CPU的缺陷,记录检测的缺陷,便于内核其他部分工作的需要*/
- acpi_early_init(); /* before LAPIC and SMP init */
- ftrace_init();
- /* Do the rest non-__init'ed, we're now alive */
- rest_init(); /* 创建init进程 */
- }
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