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\section{WebAssembly Micro Runtime}\label{sec:wamr}

\Acrfull{wamr}~\autocite{wamr} is a lightweight standalone \Gls{wasm} runtime by the \textquote{Bytecode Alliance}\iffalse{}\footnote{\url[2026-07-02]{https://bytecodealliance.org/}}\fi, designed for embedded devices.

\Gls{wamr} includes three main components: The runtime libraries required to load and execute \Gls{wasm} modules (the decode, validate, instantiate, invoke process mentioned in \autoref{sec:wasm}) are called \textquote{\Gls{vmcore}}.
\Gls{vmcore} can be embedded in C/C++ host applications.
A standalone version of \Gls{vmcore} is provided by the \textquote{\gls{iwasm}} program.
It acts as the host application and allows running \code{.wasm} files directly from the command-line.
The last component is \textquote{\gls{wamrc}}, a compiler transforming \code{.wasm} to \Gls{aot} compiled native code, necessary when not using one of \Gls{wamr}'s interpreter implementations.

\Gls{wasm} modules can be executed in five different running modes using \Gls{vmcore}\footnote{\url[2026-07-01]{https://bytecodealliance.github.io/wamr.dev/blog/introduction-to-wamr-running-modes/}}:
\begin{itemize}
  \item \sansbf{\Gls{aot}} mode sacrifices platform-independence for performance and runtime size efficiency. The \Gls{wasm} module is compiled to platform-native code with \Gls{wasm}-specific scaffolding to retain \Gls{wasm}'s security features.
  \item \sansbf{Classic Interpreter} is \Gls{wamr}'s slow reference implementation of a \Gls{wasm} interpreter, mainly targeted towards debugging purposes.
  \item \sansbf{Fast Interpreter} provides a speed boost over the classic interpreter by using a custom internal intermediate representation of \Gls{wasm} opcodes.
  \item \sansbf{LLVM \Gls{jit}} achieves the highest performance (excluding \Gls{aot} mode) by utilizing the LLVM framework for compilation.
  \item \sansbf{Fast \Gls{jit}} improves startup time over the LLVM \Gls{jit} by utilizing a lighweight compiler instead of LLVM, but trades some runtime performance.
\end{itemize}
In \Gls{aot} mode the \Gls{wasm} module is invoked by jumping into its native code, the interpreted modes follow a traditional opcode fetch, decode, execute loop.

Of those five modes, this thesis is concerned with \Gls{aot} mode and the classic interpreter for analyzability reasons: \Gls{aot} mode is most similar to native execution without the additional \Gls{wasm} layer. The classic interpreter allows a simpler understanding of fault effects than the fast interpreter or \Glspl{jit} as no different code representations are involved.

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