A number of DSU systems have been designed, but there is still little rigorous understanding of how to use DSU technology so that updates are safe.As a first step in this direction, we introduce a small update calculus with a precise mathematical semantics.In this paper, we present the details of the calculus, give some examples of its expressive power, and discuss how it might be used or extended to guarantee safety properties. Vaughan-Nichols of ZDNet alerted us that Linux 4.0 will provide support for “no-reboot patching.” The gist: When a security patch or other critical OS update comes out, you can apply it .But after the update, the new version of function handle will execute, which will dereference the global variable and crash. That is, when performing a system call, the kernel either executes old code or new code, but not a mix of both.
Our goal is to provide a simple yet expressive foundation for reasoning about dynamically updateable software.
Performance experiments show that for Flash Ed, the overhead due to updating is low: typically less than 1 percent.
Dynamic software updating (DSU) enables running programs to be updated with new code and data without interrupting their execution.
Proof-Carrying Code or Typed Assembly Language), which is native code accompanied by annotations that allow online verification of the code's safety.
We discuss how patches are generated mostly automatically, how they are applied using dynamic-linking technology, and how code is compiled to make it updateable.
We show how con-freeness can be enforced dynamically, and how it can be approximated via a novel static analysis.