Linux kernel main function analysis and analysis

Linux kernel main function analysis and analysis

Linux kernel is a large and complex system, in which the main function plays a vital role. It is the entire The entry point of the system is responsible for initializing various subsystems, drivers and kernel modules, and finally starting the entire operating system. This article will analyze and analyze the main function of the Linux kernel, and demonstrate its key functions and execution flow through specific code examples.

In the Linux kernel, the entry point of the main function is located in the start_kernel() function in the init/main.c file. This function is the starting point of the entire kernel. It will be responsible for scheduling and performing various initialization tasks to ensure that the system can start normally. The following is a simplified version of the start_kernel() function:

asmlinkage void __init start_kernel(void)
{
    // 初始化内核调度器
    sched_init();
    
    // 初始化内存管理子系统
    mm_init();
    
    // 初始化文件系统
    fs_init();
    
    // 启动核心子系统
    kernel_init();
    
    // 进入系统的主循环
    kernel_loop();
}

In the above code, we can see that the start_kernel() function calls several important functions in sequence Initialization functions, including sched_init(), mm_init(), fs_init() and kernel_init(). Next, we briefly introduce the functions of these functions:

1. sched_init(): Initialize the kernel scheduler, including setting process scheduling policies, creating idle processes, etc.
2. mm_init(): Initialize the memory management subsystem, including establishing page tables, page table mapping, etc.
3. fs_init(): Initialize the file system, including mounting the file system, establishing the initialization process, etc.
4. kernel_init(): Start the core subsystem, including initializing device drivers, registering system calls, etc.

After calling the above function, the start_kernel() function will enter the kernel_loop() function to start the main loop of the system. In the main loop, the kernel will continuously detect and handle various interrupts, system calls and external events to maintain the operation of the system.

Below we give a simple sample code to show the execution process of the start_kernel() function:

#include <linux/kernel.h>

asmlinkage void __init start_kernel(void)
{
    // 输出内核启动信息
    printk("Starting kernel...
");
    
    // 初始化内核调度器
    printk("Initializing scheduler...
");
    sched_init();
    
    // 初始化内存管理子系统
    printk("Initializing memory management...
");
    mm_init();
    
    // 初始化文件系统
    printk("Initializing file system...
");
    fs_init();
    
    // 启动核心子系统
    printk("Starting core subsystem...
");
    kernel_init();
    
    // 进入系统的主循环
    printk("Entering kernel loop...
");
    kernel_loop();
}

Through the above code example, we can seestart_kernel()The basic execution process of the function and the initialization process of each subsystem. An in-depth understanding of the function and execution process of the Linux kernel's main function can help us better understand the operating mechanism of the entire system, which is helpful for kernel debugging and development.

In general, the Linux kernel main function is the core part of the entire system. It undertakes the important tasks of starting and managing the system. Through in-depth analysis and understanding of the function and execution process of the main function, we can better grasp the operating mechanism of the kernel and provide important reference for system optimization and expansion.

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