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Linux Kernel Programming

You're reading from   Linux Kernel Programming A comprehensive guide to kernel internals, writing kernel modules, and kernel synchronization

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Product type Paperback
Published in Mar 2021
Publisher Packt
ISBN-13 9781789953435
Length 754 pages
Edition 1st Edition
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Author (1):
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Kaiwan N. Billimoria Kaiwan N. Billimoria
Author Profile Icon Kaiwan N. Billimoria
Kaiwan N. Billimoria
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Table of Contents (19) Chapters Close

Preface 1. Section 1: The Basics
2. Kernel Workspace Setup FREE CHAPTER 3. Building the 5.x Linux Kernel from Source - Part 1 4. Building the 5.x Linux Kernel from Source - Part 2 5. Writing Your First Kernel Module - LKMs Part 1 6. Writing Your First Kernel Module - LKMs Part 2 7. Section 2: Understanding and Working with the Kernel
8. Kernel Internals Essentials - Processes and Threads 9. Memory Management Internals - Essentials 10. Kernel Memory Allocation for Module Authors - Part 1 11. Kernel Memory Allocation for Module Authors - Part 2 12. The CPU Scheduler - Part 1 13. The CPU Scheduler - Part 2 14. Section 3: Delving Deeper
15. Kernel Synchronization - Part 1 16. Kernel Synchronization - Part 2 17. About Packt 18. Other Books You May Enjoy

Disabling kernel modules altogether

Paranoid folks might want to completely disable the loading (and unloading) of kernel modules. Rather drastic, but hey, this way you can completely lock down the kernel space of a system (as well as render any rootkits pretty much harmless). This can be achieved in two broad ways:

  • First, by setting the CONFIG_MODULES kernel config to off (it's on, of course, by default) during kernel config prior to building. Doing this is pretty drastic – it makes the decision a permanent one!
  • Second, assuming CONFIG_MODULES is turned on, module loading can be dynamically turned off at runtime via the modules_disabled sysctl tunable; take a look at this:
$ cat /proc/sys/kernel/modules_disabled
0

It's off (0) by default, of course. As usual, the man page on proc(5) tells us the story:

/proc/sys/kernel/modules_disabled (since Linux 2.6.31)
A toggle value indicating if modules are allowed...
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