Mondrian memory protection

  • Authors:

  • Emmett Witchel;Josh Cates;Krste Asanović

  • Affiliations:

  • MIT Laboratory for Computer Science, Cambridge, MA;MIT Laboratory for Computer Science, Cambridge, MA;MIT Laboratory for Computer Science, Cambridge, MA

  • Venue:
  • Proceedings of the 10th international conference on Architectural support for programming languages and operating systems
  • Year:
  • 2002

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Abstract

Mondrian memory protection (MMP) is a fine-grained protection scheme that allows multiple protection domains to flexibly share memory and export protected services. In contrast to earlier page-based systems, MMP allows arbitrary permissions control at the granularity of individual words. We use a compressed permissions table to reduce space overheads and employ two levels of permissions caching to reduce run-time overheads. The protection tables in our implementation add less than 9% overhead to the memory space used by the application. Accessing the protection tables adds than 8% additional memory references to the accesses made by the application. Although it can be layered on top of demand-paged virtual memory, MMP is also well-suited to embedded systems with a single physical address space. We extend MMP to support segment translation which allows a memory segment to appear at another location in the address space. We use this translation to implement zero-copy networking underneath the standard read system call interface, where packet payload fragments are connected together by the translation system to avoid data copying. This saves 52% of the memory references used by a traditional copying network stack.