代写Operating Systems代写C/C++程序

Operating Systems

1.  Suppose that a system has 5000 objects and 100 domains at sometime.

1% of the objects are accessible (some combination of r, w and x) in all domains, 10% are accessible in two domains, and the remaining 89% are accessible in only one domain. Suppose one unit of space is required to store an access right (some combination of r,w, x), object ID, or a domain ID. How much space is needed to store the full protection matrix, protection matrix as ACL, and protection matrix as capability list?

2.  Represent the ownerships and permissions shown in this UNIX directory listing as a protection matrix. (Note: aswis a member of two groups:

users and devel; gmw is a member only of users.) Treat each of the two users and two groups as a domain, so that the matrix has four rows (one per domain) and four columns (one per file).

- rw- r- - r- -  2  gmw users 908    May 26 16:45   PPP- Notes

- rwxr- xr- x  1  asw  devel 432     May 13 12:35  prog1

- rw- rw- - - - 1 asw  users 50094  May 30 17:51 project.t

- rw- r- - - - - 1 asw  devel 13124  May 31 14:30  splash.gif

3.  Some operating systems require that disk partitions must start at the beginning of a track. How does this make life easier for a boot-sector virus?

4.  Secret-key cryptography is more efficient than public-key cryptography, but requires the sender and receiver to agree on a key in advance. Suppose that the sender and receiver have never met, but there exists a trusted third party that shares a secret key with the sender and also shares a (different) secret key with the receiver. How can the sender and receiver establish a new shared secret key under these circumstances?

5.  Types of cryptosystems in detail.

6.  Can the Trojan-horse attack work in a system protected by capabilities?

7.   How can a parasitic virus (a) ensure that it will be executed before its host program, and (b) pass control back to its host after doing whatever it does?

8. List the two types of Hypervisor.

i.     Compare the types of hypervisors.

ii.     List the advantages of Virtualization.

iii.     Illustrate the key features of VMware server virtualization.

iv.     Explain guest operating system.

9. Solve the dining philosopher’s problem using semaphores.

10. Problems in omega switching network

11. Problems in scheduling

12.  Discuss about Space Sharing and Time sharing in the scheduling a multiprocessor.

13. Can the Trojan-horse attack work in a system protected by capabilities?

14. Name a C compiler feature that could eliminate a large number of security holes. Why is it not more widely implemented?

15.Some multicomputer allow running processes to be migrated from one node to another. Is it sufficient to stop a process, freeze its memory image, and just ship that off to a different node? Name two hard problems that must be solved to make this work.

16.  Explain the difference between preemptive and non-preemptive scheduling.

17. With respect to the RPC mechanism, consider the “exactly once” semantic. Does the algorithm for implementing this semantic execute correctly even if the ACK message back to the client is lost due to a network problem? Describe the  sequence of messages and discuss whether “exactly once” is still preserved.

18. Consider a system that supports 5,000 users. Suppose that you want to allow 4,990 of these users to be able to access one file.

a) How would you specify this protection scheme in UNIX?

b) Can you suggest another protection scheme that can be used more effectively for this purpose than the scheme provided by UNIX?