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Linux Kernel: main.c

Updated: Mar 24


Each box in the main.c [1] diagram [2] represents a critical aspect of the kernel's initialization process, ensuring the system is ready to execute processes, manage resources, and interact with hardware effectively.



- Purpose: The entry point for the Linux kernel initialization.

- Key Activities:

- Initialize kernel data structures.

- Parse kernel command-line arguments.

- Set up the kernel's running environment, including memory, processor, and early hardware initialization.

init functions

- Purpose: Call various initialization functions to set up different kernel subsystems.

- Key Activities:

- Sequentially invokes specific initialization routines for subsystems such as memory management, device drivers, filesystems, and networking.


- Purpose: Handle early kernel setup tasks.

- Key Activities:

- Detect and configure the CPU and its features.

- Identify available RAM and set up memory zones.

- Initialize kernel data structures and prepare the environment for further subsystem initialization.


- Purpose: Initialize the process scheduler.

- Key Activities:

- Set up the scheduler data structures and algorithms (like CFS - Completely Fair Scheduler).

- Initialize the idle task for each CPU.

- Prepare task management structures for process execution.

Memory Management

- Purpose: Set up the memory management subsystem.

- Key Activities:

- Initialize the virtual memory system, including creating the initial memory mappings for the kernel space.

- Set up page tables and allocate memory for essential kernel structures.

- Initialize slab allocators and the buddy system for efficient memory allocation.

Driver Initialization

- Purpose: Load and initialize device drivers.

- Key Activities:

- Detect and initialize essential hardware drivers like disk, network, and input/output devices.

- Set up interrupt handling mechanisms for device drivers.

- Register device drivers with the kernel's device model.


- Purpose: Establish the kernel's filesystem infrastructure.

- Key Activities:

- Initialize the Virtual File System (VFS) layer to provide a common interface for filesystem operations.

- Mount the root filesystem and prepare it for use.

- Load filesystem drivers for supported filesystem types (e.g., ext4, NFS).


- Purpose: Set up the kernel's networking stack.

- Key Activities:

- Initialize networking data structures and protocols (IP, TCP, UDP, etc.).

- Configure networking interfaces and set up routing tables.

- Prepare the network stack to handle incoming and outgoing network packets.

Virtual FS

- Purpose: Initialize the Virtual File System (VFS), an abstraction layer over actual filesystems.

- Key Activities:

- Provide a uniform interface for filesystem operations, allowing the kernel to interact with different filesystems transparently.

- Manage file descriptors, file objects, and inode objects.

- Handle filesystem mount points and namespace management.

Memory Manager

- Purpose: Manage all memory allocation and usage aspects within the kernel.

- Key Activities:

- Handle page allocation, page fault handling, and memory paging.

- Manage kernel and user-space memory separation and protection.

- Implement memory policies like overcommit handling and memory compaction.


[1] main.c

[2] Diagram generated with ChatGPT Diagrams: Show Me main.c


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