Linux System Calls

A modification to the Linux 4.14 kernel that adds system calls for controlling and writing to a system-wide process log.

Features

• Retrieves the current process log threshold.
• Allows privileged users to change the system-wide threshold.
• Logs messages at severity levels 0–7 through the Linux kernel.
• Includes the calling process name and PID in each message.
• Limits messages to 128 characters and validates user-space memory.
• Provides a small C library for calling the new system calls from user programs.

System Calls

Number	System Call	Purpose
548	get_proc_log_level	Returns the current logging threshold
549	set_proc_log_level	Updates the threshold when called with administrator privileges
550	proc_log_message	Sends a process message to the kernel log

Messages are written only when their severity level is within the active logging threshold.

Repository Structure

• kernel/process_log.patch — Kernel modifications
• process_log/process_log.c — User-space library implementation
• process_log/process_log.h — Library interface and system call definitions
• process_log/Makefile — Builds the process logging library

Building the Library

cd process_log
make

Programs can link against the resulting library with:

gcc -o program program.c -L./process_log -lprocess_log

For C++ programs:

g++ -std=c++17 -o program program.cpp -L./process_log -lprocess_log

Applying the Kernel Patch

From the root of a clean Linux 4.14 kernel source tree:

patch -p1 < /path/to/process_log.patch

Rebuild and install the kernel after applying the patch.

Compatibility

This project was developed for the x86-64 Linux 4.14 kernel. It uses system call numbers 548–550 and may require changes for other kernel versions or architectures.