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You're reading from Linux Kernel Programming

Product type Book

Published in Mar 2021

Publisher Packt

ISBN-13 9781789953435

Pages 754 pages

Edition 1st Edition

Languages

Concepts

System Administration

Author (1):

Kaiwan N. Billimoria

Table of Contents (19) Chapters

Preface

1. Section 1: The Basics

2. Kernel Workspace Setup

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

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18. Other Books You May Enjoy

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Proc filesystem tunables affecting the system log

We directly refer you to the man page on proc(5) – very valuable! – to glean information on these two security-related tunables:

dmesg_restrict
kptr_restrict

First, dmesg_restrict:

dmesg_restrict
/proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
 The value in this file determines who can see kernel syslog contents. A  value of 0 in this file imposes no restrictions. If the value is 1, only privileged users can read the kernel syslog. (See syslog(2) for more details.) Since Linux 3.4, only users with the CAP_SYS_ADMIN capability may change the value in this file.

The default (on both our Ubuntu and Fedora platforms) is 0:

$ cat /proc/sys/kernel/dmesg_restrict
0

Linux kernels use the powerful fine-granularity POSIX capabilities model. The CAP_SYS_ADMIN capability essentially is a catch-all for what is traditionally root (superuser/sysadmin) access. The CAP_SYSLOG capability gives the...

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Authors (1)

Kaiwan N. Billimoria

Kaiwan N. Billimoria taught himself BASIC programming on his dad's IBM PC back in 1983. He was programming in C and Assembly on DOS until he discovered the joys of Unix, and by around 1997, Linux! Kaiwan has worked on many aspects of the Linux system programming stack, including Bash scripting, system programming in C, kernel internals, device drivers, and embedded Linux work. He has actively worked on several commercial/FOSS projects. His contributions include drivers to the mainline Linux OS and many smaller projects hosted on GitHub. His Linux passion feeds well into his passion for teaching these topics to engineers, which he has done for well over two decades now. He's also the author of Hands-On System Programming with Linux, Linux Kernel Programming (and its Part 2 book) and Linux Kernel Debugging. It doesn't hurt that he is a recreational ultrarunner too.

See other products by Kaiwan N. Billimoria