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MPU Debug Configuration Guide

Overview

The print_pids function is used to print debug information for process ID conversion. By default, this debug output is disabled and can be controlled through module parameters to enable or disable it.

Configuration Method

Runtime Parameter Control

Set debug parameters when loading the module:

# Load module and enable debug
sudo insmod mpu.ko debug_enabled=1

# Or if module is already loaded, dynamically modify
echo 1 | sudo tee /sys/module/mpu/parameters/debug_enabled

# Disable debug
echo 0 | sudo tee /sys/module/mpu/parameters/debug_enabled

# Check current status
cat /sys/module/mpu/parameters/debug_enabled

Complete Operation Example

# 1. Confirm module is not loaded
lsmod | grep mpu

# 2. Load module and enable debug
sudo insmod mpu.ko debug_enabled=1

# 3. Confirm debug is enabled
cat /sys/module/mpu/parameters/debug_enabled
# Should output: Y

# 4. View debug logs
dmesg | grep "mpu:" | tail -10

# 5. If need to disable debug
echo 0 | sudo tee /sys/module/mpu/parameters/debug_enabled

# 6. Unload module
sudo rmmod mpu

Log Viewing

Debug information is output to kernel logs, which can be viewed with the following commands:

# View kernel logs
dmesg | grep "mpu:"

# View logs in real-time
dmesg -w | grep "mpu:"

# View /var/log/kern.log
tail -f /var/log/kern.log | grep "mpu:"

Log Format

The debug log format is:

mpu: [tag] dump process pid [pid_number]

Example:

mpu: before: u32 dump process pid 1234
mpu: after: u32 dump process pid 5678

Important Notes

  1. Permission Requirements: Root privileges are required to load/unload modules and modify parameters
  2. Module Path: Ensure the mpu.ko file is in the current directory or specify the correct path
  3. Log Level: Ensure kernel log level allows displaying KERN_DEBUG level information
  4. Real-time Effect: Parameter changes take effect immediately without needing to reload the module
  5. Default Disabled: Debug functionality is disabled by default to avoid unnecessary log output