Program Modification is the process of systematically transforming a program's source code, intermediate representation, or executable form to alter its behavior, structure, or properties while preserving semantic correctness or achieving a specific design goal.

QA:

• How to use LD_PRELOAD to overwrite a called? Why is this called an sniffer?

Index

🧾 Formalization

Program modification can be viewed as an application of a computational transformation function $T: P \rightarrow P$', where:

• $P$ is the original program instance, represented in a formal language $L$,
• $P'$ is the modified program instance, also in $L$ or a related language,
• $T$ is a total or partial function defined by a set of transformation rules or operators.

Key technical aspects include:

• Correctness Preservation: $(T(p))\forall p \in P, \; \text{Semantics}(p) \equiv \text{Semantics}(T(p))$, or if semantics are intentionally changed, then $T$ satisfies a formal specification $S$.
• Levels of Abstraction: Modifications may occur at multiple levels—source code, abstract syntax trees (ASTs), control-flow graphs (CFGs), bytecode, or machine code.
• Transformation Mechanisms: Include but are not limited to refactoring, optimization, instrumentation, code generation, code injection, partial evaluation, and metaprogramming.
• Automation and Tool Support: Modifications are often automated via compiler passes, source-to-source translators, program synthesizers, or integrated development environments (IDEs) supporting live code editing.
• Applications: Bug fixing, performance optimization, feature addition, adaptation to new platforms, security hardening, dynamic program adaptation (e.g., runtime patching), and enabling introspection or reflection.

📌 Uses