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School of Computer Science & Engineering
University of New South Wales
 Advanced Operating Systems 
 COMP9242 2002/S2 

Chorus

• Developed at INRIA, France, from 1980 on.
• Commercialised by Chorus Systèmes in 1988.
• Basic ideas similar to Mach
• Servers can be:
  • user-level,
  • dynamically loaded into kernel (to save system call costs).
• Support for group communication (multicast, any of a group).
• Like Mach, kernel threads, port groups.
• Uses password capabilities
  • but servers use ACL based protection.
• Uses copy-on-write, but receiver controls placement of data.

Chorus UNIX emulation

• System call redirection to server(s)
• All UNIX emulation in server (to avoid protection problems)
• Further information in[DA92,RAA$^+$90,RAA$^+$92,CDK94,Sin97].