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目錄

• • • • 1、編譯android的ini程序
      • 2、kernel中執行/init程序的流程
      • 3、run_init_process()程序介紹

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1、編譯android的ini程序

2、kernel中執行/init程序的流程

在start_kernel的末尾處, 調用了reset_init()

asmlinkage __visible void __init start_kernel(void) {......rest_init(); }

reset_init()啟了一個kernel線程kernel_init
kernel_thread(kernel_init, NULL, CLONE_FS);

static noinline void __init_refok rest_init(void) {int pid;rcu_scheduler_starting();smpboot_thread_init();/** 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); }

在kernel_init()中執行"/init"程序, 也就是第一個user程序
ret = run_init_process(execute_command), 其中execute_command是“/init”

static int __ref kernel_init(void *unused) {int ret;kernel_init_freeable();/* need to finish all async __init code before freeing the memory */async_synchronize_full();free_initmem();mark_readonly();system_state = SYSTEM_RUNNING;numa_default_policy();flush_delayed_fput();if (ramdisk_execute_command) {ret = run_init_process(ramdisk_execute_command);if (!ret)return 0;pr_err("Failed to execute %s (error %d)\n",ramdisk_execute_command, ret);}/** We try each of these until one succeeds.** The Bourne shell can be used instead of init if we are* trying to recover a really broken machine.*/if (execute_command) {ret = run_init_process(execute_command);if (!ret)return 0;panic("Requested init %s failed (error %d).",execute_command, ret);}if (!try_to_run_init_process("/sbin/init") ||!try_to_run_init_process("/etc/init") ||!try_to_run_init_process("/bin/init") ||!try_to_run_init_process("/bin/sh"))return 0;panic("No working init found. Try passing init= option to kernel. ""See Linux Documentation/init.txt for guidance."); }

在setup_up階段, 從cmdline中讀取init=xxxx，將xxx字符串寫入到了變量execute_command中

static int __init init_setup(char *str) {unsigned int i;execute_command = str;/** In case LILO is going to boot us with default command line,* it prepends "auto" before the whole cmdline which makes* the shell think it should execute a script with such name.* So we ignore all arguments entered _before_ init=... [MJ]*/for (i = 1; i < MAX_INIT_ARGS; i++)argv_init[i] = NULL;return 1; } __setup("init=", init_setup);

3、run_init_process()程序介紹

run_init_process()

總結

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