# GTIRB

The GrammaTech Intermediate Representation for Binaries (GTIRB) is a
machine code analysis and rewriting data structure.  It is intended to
facilitate the communication of binary IR between programs performing
binary disassembly, analysis, transformation, and pretty printing.
GTIRB is modeled on LLVM-IR, and seeks to serve a similar
functionality of encouraging communication and interoperability
between tools.

The remainder of this file describes various aspects of GTIRB:
- [Structure](#structure)
- [Installing](#installing)
- [Building](#building)
- [Usage](#usage)

# Structure

GTIRB has the following structure.  Solid lines denote inheritance.
Dotted lines denote reference by UUID.

![GTIRB Data Structure](.gtirb.svg)

## IR

An instance of GTIRB may include multiple modules (`Module`) which
represent loadable objects such as executables or libraries, an
inter-procedural control flow graph (`IPCFG`), and Auxiliary Data tables
(`AuxData`) which can hold arbitrary analysis results in user-defined
formats which can easily reference other elements of the IR.  Each
module holds information such as symbols (`Symbol`) and sections which
themselves hold the actual bytes and data and code blocks of the
module.  The CFG consists of basic blocks (`Block`) and control flow
edges between these blocks.  Each data or code block references a
range of bytes in a byte interval (`ByteInterval`).  A section may
hold one large byte interval holding all blocks---if the relative
positions of blocks in that section are defined---or may hold one byte
interval per block---if the relative positions of blocks is not
defined, e.g. for the code blocks in the `.text` section during
program rewriting.  Each symbol holds a pointer to the block or datum
it references.


## Instructions

GTIRB explicitly does NOT represent instructions or instruction
semantics but does provide symbolic operand information and access to
the bytes.  There are many *intermediate languages* (IL)s for
representation of instruction semantics (e.g.,
[BAP](https://github.com/BinaryAnalysisPlatform/bap)'s
[BIL](https://github.com/BinaryAnalysisPlatform/bil/releases/download/v0.1/bil.pdf),
[Angr](http://angr.io)'s [Vex](https://github.com/angr/pyvex), or
[Ghidra](https://www.nsa.gov/resources/everyone/ghidra/)'s P-code).
GTIRB works with these or any other IL by storing instructions
generally and efficiently as *raw machine-code bytes* and separately
storing the symbolic and control flow information.  The popular
[Capstone](https://www.capstone-engine.org)/[Keystone](https://www.keystone-engine.org)
decoder/encoder provide an excellent option to read and write
instructions from/to GTIRB's machine-code byte representation without
committing to any particular semantic IL.  By supporting multiple ILs
and separate storage of analysis results in auxiliary data tables
GTIRB enables collaboration between independent binary analysis and
rewriting teams and tools.


## Auxiliary Data

GTIRB provides for the sharing of additional information,
e.g. analysis results, in the form of `AuxData` objects.  These can
store maps and vectors of basic GTIRB types in a portable way. The
[GTIRB manual](https://grammatech.github.io/gtirb/) describes the
structure for common types of auxiliary data such as function boundary
information, type information, or results of common analyses in
[Standard AuxData Schemata](https://grammatech.github.io/gtirb/md__aux_data.html).


## UUIDs

Every element of GTIRB---e.g., modules (`Module`), symbols (`Symbol`),
and blocks (`Block`)---has a universally unique identifier (UUID).
UUIDs allow both first-class IR components and AuxData tables to
reference elements of the IR.

Instructions and symbolic operands can be addressed by the class
`Offset` which encapsulates a UUID (that refers to the instruction's
block) and an offset.

# Installing
Packages currently existing for easily installing GTIRB (and attendant
tooling including the [ddisasm](https://github.com/GrammaTech/ddisasm)
disassembler and
[gtirb-pprinter](https://github.com/GrammaTech/gtirb-pprinter) pretty
printer) on Windows, Ubuntu, and Arch Linux.  See below for
instructions.  GTIRB is versioned with Major.Minor.Patch versioning
where Major version increments will require significant source changes
but should be very rare, Minor version increments may require small
source changes, and Patch version increments shouldn't break any
downstream builds.  We do not yet provide ABI compatibility across any
version changes.

## Windows
Pre-built debug and release binaries are available for Windows at:
[windows-debug/](https://grammatech.github.io/gtirb/pkgs/windows-debug/),
and
[windows-release/](https://grammatech.github.io/gtirb/pkgs/windows-release/).
A symbol server for the debugging symbols for both the release and
debug binaries is available at
[https://download.grammatech.com/gtirb/files/](https://download.grammatech.com/gtirb/files/).
For information about how to use a symbol server with your debugger,
please see
[docs.microsoft.com#Specify_symbol_locations_and_loading_behavior](https://docs.microsoft.com/en-us/visualstudio/debugger/specify-symbol-dot-pdb-and-source-files-in-the-visual-studio-debugger?view=vs-2019#BKMK_Specify_symbol_locations_and_loading_behavior)
or your debugger's documentation.

## Ubuntu
Packages for Ubuntu 16 and 18 are available in the GTIRB apt
repository.  The GTIRB package has some dependencies which are only
available in other PPAs.  You will have to add these PPAs to your
system in order to install the GTIRB package.

Instructions for adding the appropriate PPAS and installing GTIRB on each
platform follow.

### Ubuntu16
```sh
sudo apt-get install software-properties-common
sudo add-apt-repository ppa:maarten-fonville/protobuf
sudo add-apt-repository ppa:mhier/libboost-latest
echo "deb https://grammatech.github.io/gtirb/pkgs/xenial ./" | sudo tee -a /etc/apt/sources.list.d/gtirb.list
sudo apt-get update
sudo apt-get install --allow-unauthenticated libgtirb gtirb-pprinter ddisasm
```

### Ubuntu18
```sh
sudo apt-get install software-properties-common
sudo add-apt-repository ppa:mhier/libboost-latest
echo "deb [trusted=yes] https://grammatech.github.io/gtirb/pkgs/bionic ./" | sudo tee -a /etc/apt/sources.list.d/gtirb.list
sudo apt-get update
sudo apt-get install libgtirb gtirb-pprinter ddisasm
```

## Arch Linux
Arch packages are available for download from
[https://grammatech.github.io/gtirb/pkgs/arch/](https://grammatech.github.io/gtirb/pkgs/arch/)
and may be directly installed with `pacman`.

Additionally, the Arch User Repository (AUR) https://aur.archlinux.org/ has packages
for GTIRB (`gtirb-git`) the GTIRB Pretty Printer
(`gtirb-pprinter-git`) and the datalog disassembler (`ddisasm-git`).
Note that installing `ddisasm-git` will cause the other two packages
to be installed as well given that they are both dependencies.

The following command will build and install GTIRB using the popular
[aur helper](https://wiki.archlinux.org/index.php/AUR_helpers)
[yay](https://github.com/Jguer/yay).
```sh
yay gtirb-git
```


# Building

GTIRB's C++ API should successfully build in 64-bits with GCC, Clang,
and Visual Studio compilers supporting at least C++17.  GTIRB uses
CMake which must be installed with at least version 3.10.

The common build process looks like this:
```sh
mkdir build
cd build
# Note: You may wish to add some -D arguments to the next command. See below.
cmake <path/to/gtirb>
cmake --build .
# Run the test suite.
bin/TestGTIRB
```

For customizing the GTIRB build, you can get a list of customization options by
navigating to your build directory and running:

```sh
cmake -LH
```

## Requirements

To build and install GTIRB, the following requirements should be installed:

- [CMake](https://cmake.org/), version 3.10.0 or higher.
   - Ubuntu 18 provides this version via the APT package `cmake`.
   - Ubuntu 16 and earlier provide out of date versions; build from
     source on those versions.
- [Protobuf](https://developers.google.com/protocol-buffers/), version
  3.0.0 or later.
  - Ubuntu 18 provides this version via the APT packages
    `libprotobuf-dev` and `protobuf-compiler`.
  - Ubuntu 16 and earlier provide out of date versions; build from
    source on those versions.

# Usage

GTIRB is designed to be serialized using [Google's protocol
buffers](https://developers.google.com/protocol-buffers/) (i.e.,
[protobuf](https://github.com/google/protobuf/wiki)), enabling
[easy and efficient use from any programming language](#using-serialized-gtirb-data).

GTIRB may also be used through a dedicated API implemented in multiple
languages. The APIs provide efficient data structures suitable for use
by binary analysis and rewriting applications; see
[below](#gtirb-api-implementations) for details.

## Using Serialized GTIRB Data

The serialized [protobuf](https://github.com/google/protobuf/wiki)
data produced by GTIRB allows for exploration and manipulation in the
language of your choice. The [Google protocol
buffers](https://developers.google.com/protocol-buffers/) homepage
lists the languages in which protocol buffers can be used directly;
users of other languages can convert the protobuf-formatted data to
JSON format and then use the JSON data in their applications.

The `proto` directory in this repository contains the protocol buffer
message type definitions for GTIRB. You can inspect these `.proto`
files to determine the structure of the various GTIRB message
types. The top-level message type is `IR`.

For more details, see [Using Serialized GTIRB Data](PROTOBUF.md).

## GTIRB API Implementations

The GTIRB API is currently available in C++, Python, and Common Lisp.
There is a *partial* Java API which is not ready for external use.
For language-independent API information, see [GTIRB
Components](doc/general/ComponentsIndex.md). For information about the
different API implementations, see:

  - [C++ API](doc/cpp/README.md)
  - [Python API](python/README.md)
  - [Common Lisp API](cl/README.md)
  - Java API **incomplete**
