Diagram
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.
Detail
main
- 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.
Setup
- 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.
Scheduling
- 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.
Filesystem
- 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).
Networking
- 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.
References
[1] main.c
[2] Diagram generated with ChatGPT Diagrams: Show Me main.c
