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NVBit Tutorial: Comprehensive Guide to GPU Binary Instrumentation

Tutorial Github repo: https://github.com/eunomia-bpf/nvbit-tutorial

Official NVBit repo: https://github.com/NVlabs/NVBit

This repository provides a comprehensive, blog-style tutorial (Unofficial) for learning NVIDIA Binary Instrumentation Tool (NVBit). It offers detailed, step-by-step guidance with in-depth explanations of code to help you understand GPU binary instrumentation concepts and techniques.

NVBit is covered by the same End User License Agreement as that of the NVIDIA CUDA Toolkit. By using NVBit you agree to End User License Agreement described in the EULA.txt file.

Table of Contents

Quick Start (5 Minutes)

Get started with NVBit in just a few minutes:

# Ensure CUDA toolkit is installed and nvdisasm is in PATH
export PATH=/usr/local/cuda/bin:$PATH

# Clone this repository (if you haven't already)
cd nvbit-tutorial

# Build all tools
cd tools && make && cd ..

# Build test applications
cd test-apps && make && cd ..

# Run your first instrumentation (instruction counting)
LD_PRELOAD=./tools/instr_count/instr_count.so ./test-apps/vectoradd/vectoradd

# You should see output like:
# kernel 0 - vecAdd(...) - #thread-blocks 98, kernel instructions 50077, total instructions 50077

Next Steps: Read the instr_count tutorial, try opcode_hist to analyze instruction mix, or see FAQ if you encounter issues.

About This Tutorial Repository

This tutorial repository goes beyond basic examples with detailed blog-style documentation for each tool with comprehensive code explanations, step-by-step implementation guides showing how each tool is built, visual diagrams and examples to illustrate key concepts, best practices and performance considerations, and extension ideas for developing your own custom tools.

The repository contains the core NVBit library (core/) with the main library and header files, example tools (tools/) with practical instrumentation tools and detailed explanations, and test applications (test-apps/) with simple CUDA applications to demonstrate the tools.

Each tool in the tools/ directory includes a comprehensive tutorial README that walks through the code line-by-line, explains the build process, and describes how to interpret the output.

Prerequisites

Required Software

CUDA Toolkit (>= 12.0) - Download from NVIDIA CUDA Toolkit. Verify installation: nvcc --version

nvdisasm (included with CUDA Toolkit) 

# Add CUDA bin directory to PATH
export PATH=/usr/local/cuda/bin:$PATH
# Or for specific version:
export PATH=/usr/local/cuda-12.8/bin:$PATH

# Verify nvdisasm is accessible
which nvdisasm
⚠️ IMPORTANT: NVBit requires nvdisasm to be in your PATH. Without it, tools will fail to run.

GCC (>= 8.5.0 for x86_64; >= 8.5.0 for aarch64) - Verify: gcc --version

Make - Verify: make --version

Supported Hardware

  • GPU Compute Capability: SM 3.5 to SM 12.1
  • Architecture: x86_64, aarch64 (ARM64)

Environment Setup

Add these to your ~/.bashrc or ~/.zshrc:

# CUDA paths
export PATH=/usr/local/cuda/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/cuda/lib64:$LD_LIBRARY_PATH

Then reload: source ~/.bashrc

Introduction to NVBit

NVBit (NVIDIA Binary Instrumentation Tool) is a research prototype of a dynamic binary instrumentation library for NVIDIA GPUs.

NVBit provides a set of simple APIs that enable writing a variety of instrumentation tools. Example of instrumentation tools are: dynamic instruction counters, instruction tracers, memory reference tracers, profiling tools, etc.

NVBit allows writing instrumentation tools (which we call NVBit tools) that can inspect and modify the assembly code (SASS) of a GPU application without requiring recompilation, thus dynamic. NVBit allows instrumentation tools to inspect the SASS instructions of each function (__global__ or __device__) as it is loaded for the first time in the GPU. During this phase is possible to inject one or more instrumentation calls to arbitrary device functions before (or after) a SASS instruction. It is also possible to remove SASS instructions, although in this case NVBit does not guarantee that the application will continue to work correctly.

NVBit tries to be as low overhead as possible, although any injection of instrumentation function has an associated cost due to saving and restoring application state before and after jumping to/from the instrumentation function.

Because NVBit does not require application source code, any pre-compiled GPU application should work regardless of which compiler (or version) has been used (i.e. nvcc, pgicc, etc).

Requirements

Minimum Requirements

  • SM compute capability: >= 3.5 && <= 12.1
  • Host CPU: x86_64, aarch64
  • OS: Linux
  • GCC version: >= 8.5.0 for x86_64; >= 8.5.0 for aarch64
  • CUDA version: >= 12.0
  • CUDA driver version: <= 575.xx

Supported Platform Range

Component Supported Range Tested Version
SM Architecture 3.5 - 12.1 12.0 (RTX 5090)
CUDA Toolkit 12.0+ 12.8
NVIDIA Driver 520.xx - 575.xx 575.57.08
GCC 8.5.0 - 14.x 14.2.0
Operating System Linux (Ubuntu 20.04+, RHEL 8+, etc.) Ubuntu 24.04.3 LTS

Tested Platform

This repository has been successfully tested on the following configuration:

Component Version/Details
GPU NVIDIA GeForce RTX 5090 (SM 12.0)
CUDA Toolkit 12.8 (V12.8.93)
NVIDIA Driver 575.57.08
NVBit Version 1.7.6
Operating System Ubuntu 24.04.3 LTS
Kernel Linux 6.14.0-1007-intel
GCC 14.2.0
Architecture x86_64

Build Configuration: - Tools linked with g++ (not nvcc) to avoid CUDA 12.8+ device linking issues - Test applications compiled with -cudart shared flag - All 8 example tools compile successfully - 7 out of 8 tools tested and working (mem_printf2 has known device function issue - see FAQ)

Getting Started with NVBit

This repository uses NVBit v1.7.6 which includes support for newer CUDA versions and SM architectures up to SM_120.

NVBit is provided in this repository with the core folder containing the main static library libnvbit.a and header files (including nvbit.h with all main NVBit APIs declarations), the tools folder with various source code examples and detailed tutorial documentation, and the test-apps folder with simple applications to test NVBit tools (like a vector addition program). After learning from these examples, you can copy and modify one to create your own tool.

Building the Tools and Test Applications

Building All Tools

cd tools
make

This compiles all 8 NVBit tools into shared libraries (.so files).

Building Test Applications

cd test-apps
make

This compiles the test applications that you can use to try out the tools.

Building Individual Tools

cd tools/instr_count
make

Cleaning Build Artifacts

# Clean all tools
cd tools && make clean

# Clean test apps
cd test-apps && make clean

Important Build Notes for CUDA 12.x+

Why we use g++ instead of nvcc for linking:

CUDA 12.8+ introduced stricter device code linking requirements. To avoid "undefined reference to device functions" errors, we: - Compile device code with nvcc -dc (device code compilation) - Link the final shared library with g++ (not nvcc) - Include necessary CUDA libraries explicitly: -lcuda -lcudart_static -lpthread -ldl

Makefile Pattern: 

# Compile device functions
$(NVCC) -dc inject_funcs.cu -o inject_funcs.o

# Link with g++ (NOT nvcc)
g++ -shared -o tool.so $(OBJECTS) -L$(CUDA_LIB) -lcuda -lcudart_static

The provided Makefiles handle this automatically, but if you create your own tool, follow this pattern.

Test Application Compilation: - Use -cudart shared flag: nvcc -cudart shared your_app.cu -o your_app - This ensures the CUDA runtime is dynamically linked

Rebuilding After Changes

If you modify device code (inject_funcs.cu), you must rebuild the entire tool:

cd tools/your_tool
make clean
make

Using an NVBit Tool

Before running an NVBit tool, make sure nvdisasm is in your PATH. In Ubuntu distributions, this is typically done by adding /usr/local/cuda/bin or /usr/local/cuda-"version"/bin to the PATH environment variable.

To use an NVBit tool, either LD_PRELOAD the tool before the application command: 

LD_PRELOAD=./tools/instr_count/instr_count.so ./test-apps/vectoradd/vectoradd

Or use CUDA_INJECTION64_PATH: 

CUDA_INJECTION64_PATH=./tools/instr_count/instr_count.so ./test-apps/vectoradd/vectoradd

NOTE: NVBit uses the same mechanism as nvprof, nsight system, and nsight compute, thus they cannot be used together.

Key Concepts Covered in This Tutorial

Throughout the tutorial, you'll learn important concepts in GPU binary instrumentation: SASS instruction analysis (understanding GPU assembly), function instrumentation (adding code to existing GPU functions), basic block analysis (working with control flow graphs), memory access tracking (capturing and analyzing memory patterns), efficient GPU-CPU communication, register manipulation (reading and writing GPU registers directly), instruction replacement (modifying GPU code behavior), and performance optimization (minimizing instrumentation overhead).

Creating Your Own Tools

After working through the examples, you'll be ready to create your own custom instrumentation tools. The repository includes templates and guidance for tool structure (understanding host/device code organization), build systems (setting up Makefiles), common patterns (reusing code for frequently needed functionality), and debugging techniques (troubleshooting instrumentation issues).

Frequently Asked Questions

General Questions

What is NVBit? NVBit is a research tool that lets you analyze and modify GPU code at the binary level without recompiling.

Do I need source code? No! NVBit works on compiled CUDA binaries.

Can I use NVBit with nvprof or Nsight? No. They use the same injection mechanism and cannot run simultaneously.

Which GPUs are supported? SM 3.5 to SM 12.1 (Kepler to Blackwell architecture).

Using the Tools

Which tool should I start with? Start with instr_count, then try opcode_hist.

The tool produces too much output. How do I reduce it? 

# Instrument only first kernel
KERNEL_BEGIN=0 KERNEL_END=1 LD_PRELOAD=./tools/instr_count/instr_count.so ./app

# Instrument only first 100 instructions
INSTR_END=100 LD_PRELOAD=./tools/instr_count/instr_count.so ./app

My application runs 100x slower with instrumentation Normal for instruction-level tools. Use instr_count_bb for lower overhead, or instrument selectively.

What's the overhead of each tool? - instr_count_bb: 2-5x - instr_count_cuda_graph: 5-20x - instr_count/opcode_hist: 20-100x - mem_trace/mov_replace/record_reg_vals: 100-1000x

Can I use these tools in production? Only instr_count_bb and instr_count_cuda_graph have low enough overhead.

Specific Tool Questions

mem_printf2 doesn't work - why? Known device function call issue. It's included as an educational example.

What's the difference between warp-level and thread-level counting? - Warp-level (default): Counts 1 per warp (32 threads) - Thread-level: Counts each thread separately (32x higher) Set via COUNT_WARP_LEVEL=0 for thread-level.

How do I create my own tool? 1. Copy existing tool directory (e.g., instr_count) 2. Modify host code and device code (inject_funcs.cu) 3. Update Makefile 4. Rebuild with make

Troubleshooting

Common Issues and Solutions

1. "nvdisasm: command not found"

Problem: NVBit cannot find the nvdisasm tool.

Solution: 

# Add CUDA bin to PATH
export PATH=/usr/local/cuda/bin:$PATH

# Verify it works
which nvdisasm

Add this to your ~/.bashrc to make it permanent.

2. "undefined reference to device functions" during linking

Problem: CUDA 12.8+ linking error when building tools.

Solution: Make sure you're using g++ for linking (not nvcc). Our Makefiles already handle this, but if you're creating a custom tool: 

# Use g++ for linking, NOT nvcc
g++ -shared -o mytool.so $(OBJECTS) -L$(CUDA_LIB) -lcuda -lcudart_static

3. Tool loads but produces no output

Possible Causes: Check if nvdisasm is in PATH, verify the tool compiled successfully (check for .so file), or try with TOOL_VERBOSE=1: 

TOOL_VERBOSE=1 LD_PRELOAD=./tools/instr_count/instr_count.so ./your_app

4. "CUDA_ERROR_INVALID_VALUE" or segmentation fault

Possible Causes: GPU compute capability not supported (need SM 3.5+), driver version too old or too new (need <= 575.xx), or concurrent use with nvprof/nsight (NVBit cannot run with these tools).

Solution: 

# Check GPU compute capability
nvidia-smi --query-gpu=compute_cap --format=csv

# Check driver version
nvidia-smi

5. Build errors with "cannot find -lcuda"

Solution: 

# Add CUDA library path
export LD_LIBRARY_PATH=/usr/local/cuda/lib64:$LD_LIBRARY_PATH

6. Application crashes with instrumentation

Debugging Steps: Verify the app works without instrumentation (./your_app), test with the simplest tool (LD_PRELOAD=./tools/instr_count/instr_count.so ./your_app), or use selective instrumentation: 

KERNEL_BEGIN=0 KERNEL_END=1 LD_PRELOAD=./tools/instr_count/instr_count.so ./your_app

Getting More Help

Read tool-specific READMEs in tools/TOOLNAME/README.md, examine core/nvbit.h for API documentation, or report issues at the GitHub repository.

Before asking for help, try with TOOL_VERBOSE=1 to get diagnostic output, verify your setup meets all requirements in Prerequisites, and test with provided test applications first.

Contributing

We welcome contributions to improve the tutorial! If you find issues or have suggestions, open an issue describing the problem or enhancement, submit a pull request with your proposed changes, and follow the coding style of the existing examples.

Further Resources

For more details on the NVBit APIs, see the comments in core/nvbit.h.

You may also find these resources helpful: - NVIDIA Developer Blog - CUDA Documentation - CUDA GPU Binary Utilities

Happy learning!

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