mechanism the dynamic linker uses

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These hooks are strategically placed to give Zygisk fine-grained control over the process and its lifecycle, particularly during key phases like process initialization.

The Procedure Linkage Table (PLT) is a to resolve function addresses at runtime, enabling libraries to share code dynamically. By placing hooks in the PLT, Zygisk can intercept calls made to important functions within the Android runtime, allowing it to inject custom behavior at various points in the lifecycle of an app or system process. This enables precise control over each initialization phase, allowing developers to modify behaviors during critical stages of process execution.

For example, hooks in libandroid_runtime allow france mobile database to intervene in the Android runtime environment, while hooks in libart provide control over the Android Runtime (ART), which is responsible for running app code. Meanwhile, libnative_bridge handles native libraries, allowing Zygisk to manage interactions between the Android runtime and native code.

In the following diagram, you will see an illustration of the order of execution of these hooks and how they interact with the process lifecycle.



What is Specialization?
Once Zygote forks a new process for an app or service, it performs specialization. Specialization applies security sandboxing measures that restrict the behavior and privileges of the new app process. This ensures that each app runs in a controlled, isolated environment and cannot interfere with the system or other apps. During this process, the system enforces policies, such as setting user permissions, security contexts, and other app-level restrictions. Specialization is crucial to maintaining Android’s secure multi-user environment.

Additionally, Zygote forks a special process called system_server, which hosts a wide array of system services that are responsible for managing key Android operations. These services control how apps interact with the Android operating system and govern critical components like permissions, device policies, and app lifecycle management. With Zygisk, developers can hook into both system_server and app processes to alter their behavior or introduce custom functionality. This capability is particularly powerful because it allows developers to influence how apps and services operate in real-time, providing a high degree of control over system-level behavior. However, the custom code runs within the constraints of Android’s security sandbox, meaning it must adhere to the permissions and limitations that apply to the app or system process.