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71 lines
3.1 KiB
ReStructuredText
71 lines
3.1 KiB
ReStructuredText
Overview
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========
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This repository implements some shared code that can be re-used by multiple
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architecture-specific backends to bridge the semantics defined in the semmc
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repository [SemMC]_ to macaw [macaw]_. The semantics in SemMC are defined in
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terms of the SimpleBuilder [SB]_ IR from Crucible. The code in this library
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translates those SimpleBuilder-based formulas into a Haskell function that
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generates macaw IR expressions (see the ``genExecInstruction`` function in
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``Data.Macaw.SemMC.TH``). This repository contains code shared between all
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architectures; the intent is that each architecture will also define
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architecture-specific operations that are taken as an input to this library.
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Architecture-Specific Backends
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==============================
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See macaw-ppc as an example for what is required in an architecture-specific
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backend. At a high level, the required steps are:
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1. Define an architecture-specific register type
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2. Define architecture-specific functions and statements
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3. Define a transformation from architecture-specific locations into TH expressions
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4. Define a function to translate SimpleBuilder ``NonceApp``s into TH expressions
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5. Define a function translate SimpleBuilder ``App``s into TH expressions
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6. Define a function to translate *instructions* into TH expressions
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Architecture-Specific Register Type
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-----------------------------------
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Architecture-Specific Functions
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-------------------------------
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Translating Architecture-Specific Locations
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-------------------------------------------
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Translating ``NonceApp``
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------------------------
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This translator is for translating architecture-specific uninterpreted
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functions, which are represented using ``NonceApp`` in SimpleBuilder. These
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will be most often translated into architecture-specific functions, but may also
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require architecture-specific statements to represent side effects (including
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exceptions). This is also where all floating point operations are translated,
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as there are no floating point operations in macaw.
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Translating ``App``
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-------------------
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Very few ``App`` constructors in SimpleBuilder require custom translation. This
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is primarily intended to translate division-type operations into
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architecture-specific functions, as there are no division operations defined in
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macaw.
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Translating Instructions
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------------------------
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The final specialized matcher is for doing direct translations of instructions
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into architecture-specific statements. This is meant for instructions for which
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we cannot express semantics in the SimpleBuilder IR due to special side effects.
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Often, trap and system call-type instructions fall into this category.
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Note that this function is specified by TH ``Name`` instead of as a value-level
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function; this is required, as its type signature refers to an
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architecture-specific type, which we cannot mention in this shared library
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without incurring undesired dependencies.
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.. [SemMC] https://github.com/GaloisInc/semmc
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.. [macaw] https://github.com/GaloisInc/macaw
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.. [SB] https://github.com/GaloisInc/crucible/blob/master/crucible/src/Lang/Crucible/Solver/SimpleBuilder.hs
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