Event Tracing for Windows (ETW)

Introduction to Event Tracing for Windows (ETW)

Event Tracing for Windows (ETW) is a high-performance, low-overhead tracing facility built into the Windows operating system. It enables you to collect detailed diagnostic information about the behavior of the operating system and applications. ETW is crucial for performance analysis, debugging, and troubleshooting complex issues in Windows environments, particularly for driver development.

Key Features and Benefits

• High Performance: Designed to have minimal impact on system performance, even under heavy tracing loads.
• Low Overhead: Efficient data collection and buffering minimize resource consumption.
• Rich Data: Capable of capturing a wide range of events, from kernel activity to user-mode application events.
• Scalability: Supports tracing on single systems as well as large-scale deployments.
• Standardization: Provides a consistent mechanism for event generation and consumption across the Windows ecosystem.

Core Components of ETW

ETW involves several key components:

• Event Providers: These are the sources that generate trace events. They can be built-in Windows components (like the kernel, registry, file system) or custom providers implemented by applications and drivers.
• Event Consumers: These components receive and process the trace events. Examples include the Event Viewer, Logman, PerfView, and custom applications.
• Trace Sessions: A trace session is a logical grouping of a provider and a consumer, defining what events are collected and how they are processed.

Using ETW for Driver Development

For Windows driver developers, ETW is an indispensable tool for understanding driver behavior, identifying performance bottlenecks, and debugging issues.

Implementing a Custom ETW Provider in a Driver

You can instrument your driver with custom ETW events to gain insights into its operation. This typically involves:

1. Defining Event Manifests: Using the Message Compiler (mc.exe) to define event IDs, levels, opcodes, and message strings in an XML manifest file.
2. Generating Header Files: The mc.exe tool generates C/C++ header files that provide macros for logging events.
3. Registering the Provider: In your driver's entry point (e.g., `DriverEntry`), you register your custom ETW provider GUID.
4. Logging Events: Use the generated macros to log events at various points in your driver code, specifying the event level, opcode, and any relevant data.

Example of Event Logging (Conceptual)

// Assuming 'MyDriverEtwProvider' is the name generated from your manifest
// and 'MyDriverHandle' is your registered provider handle.

// Example: Logging an informational event
TraceEvent(MyDriverEtwProvider, &MyDriverHandle, WINEVENT_LEVEL_INFO, MYDRIVER_EVENT_MYFUNCTIONSTART, "Entering MyFunction");

// Example: Logging an event with data
ULONG_PTR data1 = 0x12345678;
ULONG data2 = 42;
TraceEventWithData(MyDriverEtwProvider, &MyDriverHandle, WINEVENT_LEVEL_WARNING, MYDRIVER_EVENT_ERRORCONDITION, 2, data1, data2);
            

Consuming ETW Events from Drivers

Several tools can be used to collect and analyze ETW data from drivers:

• PerfView: A free tool from Microsoft that is highly recommended for capturing and analyzing ETW traces. It provides powerful visualization and analysis capabilities.
• Logman: A command-line utility for managing trace sessions.
• Event Viewer: Can display some ETW events if they are configured to be forwarded to the Windows Event Log.

Capturing a Trace with PerfView

1. Download and run PerfView.

2. Click "Collect" -> "Collect".

3. Ensure "Kernel:" is checked (for kernel events, including driver activity) and select any relevant user-mode providers if needed.

4. Click "Start Collection".

5. Perform the actions in your system that you want to trace (e.g., load/unload your driver, trigger specific functionality).

6. Click "Stop Collection" in PerfView.

7. Analyze the generated .etl file in PerfView.

ETW Concepts and Best Practices

Further Resources

• PerfView Tutorial
• Microsoft Docs: About Event Tracing
• Microsoft Docs: Tracing APIs