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Linux Kernel Programming - Second Edition

You're reading from  Linux Kernel Programming - Second Edition

Product type Book
Published in Feb 2024
Publisher Packt
ISBN-13 9781803232225
Pages 826 pages
Edition 2nd Edition
Languages
Author (1):
Kaiwan N. Billimoria Kaiwan N. Billimoria
Profile icon Kaiwan N. Billimoria

Table of Contents (16) Chapters

Preface 1. Linux Kernel Programming – A Quick Introduction 2. Building the 6.x Linux Kernel from Source – Part 1 3. Building the 6.x Linux Kernel from Source – Part 2 4. Writing Your First Kernel Module – Part 1 5. Writing Your First Kernel Module – Part 2 6. Kernel Internals Essentials – Processes and Threads 7. Memory Management Internals – Essentials 8. Kernel Memory Allocation for Module Authors – Part 1 9. Kernel Memory Allocation for Module Authors – Part 2 10. The CPU Scheduler – Part 1 11. The CPU Scheduler – Part 2 12. Kernel Synchronization – Part 1 13. Kernel Synchronization – Part 2 14. Other Books You May Enjoy
15. Index

Understanding kernel logging and printk

There is still a lot to cover regarding the logging of kernel messages via the printk kernel API. This section delves into some of the details. It’s important for a budding kernel/driver developer like you to clearly understand these topics.

We saw earlier, in the A quick first look at the kernel printk() section, the essentials of using the kernel printk API’s functionality (have another look at it if you wish to). Here, we will explore a lot more with respect to the printk() API’s usage. Let’s get going!

Using the kernel memory ring buffer

The kernel log buffer is simply a memory buffer within the kernel virtual address space where the printk output is saved (logged). More technically, it’s the global __log_buf[] variable. Its definition in the kernel source is as follows:

kernel/printk/printk.c
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
#define LOG_BUF_LEN_MAX (u32)(1 <<...
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