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Prem Uppuluri

Hybrid System Call Interposition

Faculty Advisor
Prem Uppuluri
Research Supervisor
Prem Uppuluri
Description of Work
HSCI is a novel framework to operating system (OS) extensibility, which will support system call interposition based extensions as an alternative to modifying OS source code. The framework will generate easy to program, flexible, robust and non-circumventable extensions without requiring modifications to OS - instead, systemcalls are intercepted and redirected to the extensions. Previous research in this area can be categorized into: user-level systemcall interposition where secure mechanisms such as ptrace on Linux, are used to interpose systemcalls in the user memory, and kernel-interposition in which the systemcalls are interposed inside the kernel memory using dynamically loadable modules. The former, is easy to program, due to availability of good software-development tools such as debuggers at user level. However, they are inefficient as it involves data copying (context switch) between user and kernel memories. Kernel-interposition is efficient, but not robust, errors in kernel extensions can cause the kernel to crash. Our framework draws on the advantages of both these approaches. Here, an efficient filtering tool filters out network packets inside the kernel and dispatches the needed packets to the user level. The key contribution of this framework is the powerful yet efficient filtering language and enforcement mechanism which makes very few context switches and has low context switch overhead. The results from this framework will be used in developing a user-choice driven OS extensions. Examples of such an extension is a compressed file system, in which, the user has the flexibility to decide on the compression algorithm. This was not possible so far, since efficiency of the OS extension and flexibility were contradictory requirements.
Application Instructions
Project URL
Area(s) of Research
Information Assurance/Security, Operating Systems
Work for Credit or Volunteer