原创作品转载请注明出处《Linux内核分析》MOOC课程http://mooc.study.163.com/course/USTC-1000029000
如果我写的不好或者有误的地方请留言
- 题目自拟，内容围绕Linux内核的启动过程，即从start_kernel到init进程启动；
- 博客中需要使用实验截图
- 博客内容中需要仔细分析start_kernel函数的执行过程
- 总结部分需要阐明自己对“Linux系统启动过程”的理解，尤其是idle进程、1号进程是怎么来的。
实验报告：
在实验楼里跑了一下gdb 没有多大印象 印象就是卡 这是卡吗 下面分析换自己的虚拟机
先来个宏观认识：
从start_kernel()中可以看到最后一条语句是rest_init();
asmlinkage __visible void __init start_kernel(void)
{
char *command_line;
char *after_dashes; /*
* Need to run as early as possible, to initialize the
* lockdep hash:
*/
lockdep_init();
set_task_stack_end_magic(&init_task);
smp_setup_processor_id();
debug_objects_early_init(); /*
* Set up the the initial canary ASAP:
*/
boot_init_stack_canary(); 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);
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 */ build_all_zonelists(NULL, NULL);
page_alloc_init(); pr_notice("Kernel command line: %s\n", boot_command_line);
parse_early_param();
after_dashes = parse_args("Booting kernel",
static_command_line, __start___param,
__stop___param - __start___param,
-, -, &unknown_bootoption);
if (!IS_ERR_OR_NULL(after_dashes))
parse_args("Setting init args", after_dashes, NULL, , -, -,
set_init_arg); jump_label_init(); /*
* These use large bootmem allocations and must precede
* kmem_cache_init()
*/
setup_log_buf();
pidhash_init();
vfs_caches_init_early();
sort_main_extable();
trap_init();
mm_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();
idr_init_cache();
rcu_init();
context_tracking_init();
radix_tree_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();
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(); #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 = ;
}
#endif
page_cgroup_init();
debug_objects_mem_init();
kmemleak_init();
setup_per_cpu_pageset();
numa_policy_init();
if (late_time_init)
late_time_init();
sched_clock_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
#ifdef CONFIG_X86_ESPFIX64
/* Should be run before the first non-init thread is created */
init_espfix_bsp();
#endif
thread_info_cache_init();
cred_init();
fork_init(totalram_pages);
proc_caches_init();
buffer_init();
key_init();
security_init();
dbg_late_init();
vfs_caches_init(totalram_pages);
signals_init();
/* rootfs populating might need page-writeback */
page_writeback_init();
proc_root_init();
cgroup_init();
cpuset_init();
taskstats_init_early();
delayacct_init(); check_bugs(); sfi_init_late(); if (efi_enabled(EFI_RUNTIME_SERVICES)) {
efi_late_init();
efi_free_boot_services();
} ftrace_init(); /* Do the rest non-__init'ed, we're now alive */
rest_init();
}
start_kernel
static noinline void __init_refok rest_init(void)
{
int pid; rcu_scheduler_starting();
/*
* We need to spawn init first so that it obtains pid 1, however
* the init task will end up wanting to create kthreads, which, if
* we schedule it before we create kthreadd, will OOPS.
*/
kernel_thread(kernel_init, NULL, CLONE_FS);
numa_default_policy();
pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
rcu_read_lock();
kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
rcu_read_unlock();
complete(&kthreadd_done); /*
* The boot idle thread must execute schedule()
* at least once to get things moving:
*/
init_idle_bootup_task(current);
schedule_preempt_disabled();
/* Call into cpu_idle with preempt disabled */
cpu_startup_entry(CPUHP_ONLINE);
}
rest_init
咱们需要知道的东西如下：
在start_kernel中：
init_task:手工创建的PCB 0号进程即最终的idle进程
trap_init:初始化中断管理模块
mm_init:初始化内存管理模块
sched_init:初始化调度模块
在rest_init中：
run_init_process:linux系统中的1号进程 第一个用户态进程
注意：
1.我们需要首先初始化获得pid=1的进程 如果初始化最终创建了ktheads
我们在创建kthreadd之前调度它 Linux系统将会OOPS
2.启动空闲线程必须至少执行一次schedule()