* Overview

  The high level goal is to write and/or generate architecture-specific backends
  for /macaw/ based on the semantics discovered by /semmc/.  In particular, we
  are interested in making /macaw-ppc/ and /macaw-arm/.  We will hand-write some
  of the code, but we will generate as much as possible automatically.  We will
  read in the semantics files generated by /semmc/ and use Template
  Haskell to generate a function that transforms machine
  states according to the learned semantics.

  We will implement a base package (/macaw-semmc/) that provides shared
  infrastructure for all of our backends; this will include the Template Haskell
  function to create a state transformer function from learned semantics files.

** Repository Layout

- ~macaw-semmc~ contains the architecture-independent components of the translation from semmc semantics into macaw IR.
- ~macaw-ppc~ implements the PowerPC-specific backend of the translation.
- ~macaw-ppc-symbolic~ implements a translation of macaw IR (with PowerPC architecture-specific functions) into Crucible IR, which is suitable for symbolic execution.
- ~macaw-arm~ implements the ARM-specific backend of the translation.

** Building

The dependencies of this project that are not available on Hackage are tracked via git submodules.  To build with a reasonably modern version of ~cabal~ (i.e., one that supports ~new-build~):

#+BEGIN_SRC

 $ git submodule update --init
 $ ln -s cabal.project.dist cabal.project
 $ cabal new-configure
 $ cabal new-build macaw-ppc

#+END_SRC

To build with ~stack~:

#+BEGIN_SRC

 $ git submodule update --init
 # Choose one of the provided GHC version-specific
 # stack-ghc-<version>.yaml files, e.g. stack-ghc-8.2.yaml.
 $ ln -s stack-ghc-<version>.yaml stack.yaml
 $ stack build

#+END_SRC

** Code dependencies and related packages

  - macaw (binary code discovery)
  - macaw-x86 (x86_64 backend for macaw)
  - semmc (semantics learning and code synthesis)
  - semmc-ppc (PowerPC backend for synthesis)
  - dismantle-tablegen (disassembler infrastructure)
  - dismantle-ppc (PowerPC disassembler)
  - crucible (interface to SMT solvers)
  - parameterized-utils (utilities for working with parameterized types)

* Semantics background

   The /semmc/ library is designed to learn semantics for machine code
   instructions.  Its output, for each Instruction Set Architecture (ISA), is a
   directory of files where each file contains a formula corresponding to the
   semantics for an opcode in the ISA.  For example, the ~ADDI.sem~ file
   contains the semantics for the add immediate instruction in PowerPC.

   There are functions in /semmc/ for dealing with this representation.
   Formulas are loaded into a data type called ~ParameterizedFormula~, which
   contains formula fragments based on the ~ExprBuilder~ representation of
   /crucible/.  This can be thought of as a convenient representation of SMT
   formulas.

* Status

This codebase is a work in progress.  PowerPC support (both 32 and 64 bit) is reasonably robust.  Support for ARM is ongoing.

* License

This code is made available under the BSD3 license and without any support.