# DynamoRIO: a runtime code manipulation platform for building your own binary tools > DynamoRIO rewrites a running program's instructions, not just its function calls, and ships the tooling to build profilers, tracers and simulators on top. Here is what it does, how to get a first run out of it, and where it stops being the right choice. **DynamoRIO/dynamorio** — Dynamic Instrumentation Tool Platform - Repository: https://github.com/DynamoRIO/dynamorio - Stars: 3,170 · Forks: 632 - Language: C - License: NOASSERTION - Published: 2026-09-24 · Updated: 2026-09-24 · Language: en - Canonical page: https://hysenlabs.com/projects/dynamorio-dynamorio ## What DynamoRIO solves, and who ends up using it Most instrumentation sits at a boundary the programmer chose: a function entry, a syscall, a library call. DynamoRIO sits somewhere else entirely. The README describes it as a runtime code manipulation system that supports code transformations on any part of a program while it executes, and it draws a line between itself and systems limited to inserting callouts or trampolines. That distinction matters. A trampoline system can tell you a function was entered; DynamoRIO's instruction manipulation library lets you rewrite the instructions themselves on IA-32, AMD64, ARM and AArch64. The audience follows from that capability. You are building a tool, not using one. The README lists the tools already built on the platform: WinAFL uses it as an instrumentation and code coverage engine, ArmIE uses it as an instruction emulator, and drmemtrace, Dr. Memory, drcov and drstrace all ship as clients. If you want a profiler, you can probably download one. If you want a profiler that answers a question nobody has asked yet, you write a client against the DynamoRIO API. The constraint that shapes everything is that the target runs unmodified. The README states the platform manipulates unmodified applications running on stock operating systems: Windows, Linux or Android, on commodity hardware. No recompilation, no source, no cooperation from the program being observed. ## How the code transformation actually happens DynamoRIO intercepts execution and rewrites it before the CPU sees it. The README frames the API as abstracting away the underlying infrastructure so the tool builder can concentrate on analyzing or modifying the application's runtime code stream. That is the architecture in one sentence: a core that takes over the instruction stream, and a client that decides what to do with it. The repository layout reflects the split. The top level carries core/, clients/, api/, ext/, libutil/, common/, suite/ and tools/ alongside third_party/. Core holds the runtime that takes control of the process. Clients holds the shipped tools, the ones the README enumerates as part of the release package. Api holds the interface you compile against, and the README points to api/samples/ for concrete starting points, naming files like memtrace_x86.c, instrace_x86.c, bbbuf.c and inscount.cpp. The data flow for the tracing tools is worth separating out, because there are two modes. drmemtrace can operate online, with multi-process support, or offline on instruction and memory address traces. The offline path is what feeds drcachesim and its family of analysis tools: cache simulation, TLB simulation, reuse distance, reuse time, opcode mix and function call tracing. The README is explicit that the simpler memtrace and instrace samples are slower than drmemtrace's offline traces, which have more surrounding infrastructure. If you are choosing a starting point, that sentence is the whole trade-off: the samples are easier to read, drmemtrace is the path that was built for volume. ## Downloading a package and finding your first client The README does not walk through a build from source, and it does not print a drrun invocation. It points to a binary package for both Windows and Linux, available free of charge from the download page at dynamorio.org/page_download.html, and to the source repository for building yourself, with API documentation included in the release package. The repository uses CMake at the top level (CMakeLists.txt, CTestConfig.cmake), which is the build system you would be working with if you go the source route. Because the README gives no command line, this article will not invent one. The launcher is named drrun and appears in the search terms people use around this project, but its flags, its client selector and its path inside an unpacked release are documented in the release package rather than in the README. Read that documentation before running anything, and treat any invocation you find elsewhere as unverified against this version. The same applies to the shipped clients. The README lists drcov as a code coverage tool and drltrace as a library tracing tool, both included in the release package, and drmemtrace as the tracing and analysis framework behind drcachesim. It does not show how to select them from the command line. If you want to write your own logic instead, api/samples/inscount.cpp is the smallest thing to read before starting a file of your own. ## Where DynamoRIO is the wrong tool The first limitation is stated plainly in the README: Mac OSX support is in progress. If your target is a macOS binary, this is not a supported platform, and no amount of API familiarity changes that. Windows, Linux and Android are the stated targets. The second is the cost of the abstraction. DynamoRIO gives you arbitrary instruction modification, and in exchange you write C against an instruction manipulation library with per-architecture concerns. The README's own framing, that the API abstracts away the details of the underlying infrastructure, is accurate but also a warning: there is a substantial infrastructure underneath, and the samples exist because nobody starts from a blank file productively. If your actual problem is hooking three functions in a Python process, this is several orders of magnitude more machinery than the problem deserves. The third is that transparency is a claim you have to verify per target, not a property you get for free. The README calls the manipulation efficient, transparent and comprehensive, but the platform is rewriting instructions under a running program. Anything that inspects its own code, relies on precise timing, or is itself an instrumentation or anti-debugging layer is a case where you should expect to spend time on the interaction rather than on your analysis. The README does not document a rollback or detachment procedure, and it does not list per-target compatibility caveats, so treat those as questions for the discussion list rather than as documented guarantees. ## DynamoRIO versus Pin and Frida The two comparisons people search for are the right ones, and they split along different axes. Against Pin, the difference is philosophical rather than functional. Both are dynamic binary instrumentation frameworks that take over an application's instruction stream and expose an API for building tools. DynamoRIO's distinguishing claim, in its own words, is that it is not limited to inserting callouts or trampolines and allows arbitrary modification of application instructions. The practical consequence is that DynamoRIO is also a platform you can build an emulator on, which is exactly what ArmIE does and what the legacy drcpusim did. If you want callout-based analysis, either framework will do; if you want to change what the instructions mean, that is the axis DynamoRIO emphasizes. Against Frida, the difference is the level of the interface. Frida is an injection and hooking toolkit: you attach to a process and script behavior from JavaScript, and the unit of work is a function or a memory address. DynamoRIO's unit of work is the instruction, and its client is compiled C linked against an API. For reverse engineering a mobile app or poking at a running service, Frida's scripting loop is dramatically shorter. For building a cache simulator, a TLB simulator or a reuse-distance analyzer, which is what drcachesim's tool family actually is, Frida has no equivalent because the analysis needs the instruction and memory address stream, not a set of hooks. ## Maintenance cadence, licensing and the upgrade question The last push to the repository was on 2026-09-23, and the most recent release listed is cronbuild-11.91.20715 from 2026-09-19. The release names are the tell: these are cron builds, produced on a weekly schedule, with the previous two dated 2026-09-12 and 2026-09-05. That is a project shipping continuously rather than tagging occasional stable versions, and it has a direct consequence for anyone building on it. You are not choosing between named releases with migration notes; you are choosing a point in a stream. Pinning a specific cron build for a production tool is the only way to make an upgrade a decision rather than an event. The licensing picture needs care. The README states the source is available primarily under a BSD license and links to a license page, but the repository metadata reports the license as NOASSERTION, meaning no standard license identifier was detected from the files. Those two statements are not in conflict, but they are not the same statement either. License.txt sits at the top level, and if you plan to redistribute a tool built on the API, that file and the license page are what you read. This is not legal advice, and the gap between "primarily under a BSD license" and a machine-detected NOASSERTION is exactly the kind of thing to resolve before shipping. Upgrade cost is mostly your own code. The core is maintained upstream; your client is not. Each weekly build can move the API surface, and the README offers no deprecation policy or compatibility guarantee, so budget for rebuilding clients against new releases rather than assuming they carry forward. ## Conclusion Adopt DynamoRIO if you need instruction-level control over a program you did not write and cannot recompile, and you are willing to write C against its API. Do not adopt it if you only need to hook a handful of functions in a managed runtime, where Frida's JavaScript injection is far less work, or if you need an officially supported macOS build, since the README states Mac support is in progress. Before committing, verify three things: which binary package matches your OS and architecture on the download page, whether the drrun launcher and the drmemtrace client cover your tracing needs before you write a custom client, and what the license page says about redistribution if you intend to ship a tool built on the API. ## FAQ ### How do you use DynamoRIO? You start from a release package, use the drrun launcher to run a client against a program, and either pick a client that ships with the package, such as drcov or drltrace, or write your own in C against the DynamoRIO API using api/samples/ as a starting point. The README does not print the exact command line, so the release package documentation is where the invocation is defined. ### What is the difference between DynamoRIO and Pin? Both are dynamic binary instrumentation frameworks that take over a running program's instruction stream. DynamoRIO's own description emphasizes that it is not limited to inserting callouts or trampolines and permits arbitrary modification of application instructions, which is why emulators such as ArmIE are built on it. ### Which operating systems does DynamoRIO support? The README states Windows, Linux and Android on IA-32, AMD64, ARM and AArch64 hardware, with Mac OSX support described as in progress. Binary packages are offered for Windows and Linux. ### Do I need the source code of the program I want to instrument? No. The README describes DynamoRIO as manipulating unmodified applications running on stock operating systems, so the target binary is instrumented as it executes without recompilation. ### What tools come with the DynamoRIO release package? The README lists Dr. Memory, the drmemtrace tracing and analysis framework with drcachesim and its cache, TLB, reuse distance, reuse time, opcode mix and function call tracing tools, plus drcpusim, drstrace, drcov, drltrace, memtrace, memval, instrace, bbbuf, inscount and Dr. Fuzz. ## Sources - [DynamoRIO/dynamorio on GitHub](https://github.com/DynamoRIO/dynamorio) - [Issues](https://github.com/DynamoRIO/dynamorio/issues) - [README](https://github.com/DynamoRIO/dynamorio/blob/master/README.md) - [Releases](https://github.com/DynamoRIO/dynamorio/releases) --- Hysen Labs editorial analysis, written from the project's own repository and release notes. Cite the canonical page: https://hysenlabs.com/projects/dynamorio-dynamorio