1. Windows Object Manager CS 470 -- Spring 2002

2. Overview The object paradigm NT Objects and the Object Manager Object Structure Object Naming Object Handles Object Retention and Resource Limits

3. Objects in Windows NT/2K/XP Provide a uniform access method Provide human readable names Centralize security Uniform charging method for use of resources Uniform object retention method Support resource inheritance by child processes

4. Examples of Objects Processes and Threads (Process Manager) Sections (Memory Manager) File (I/O Manager) Events, Semaphores, Mutants, Timers Access Tokens (Security system) Object Directories, Symbolic Links (Object Manager) Registry keys and many more…

5. Process Structure Process Access Token Thread a File c Section f Object Table Virtual Address Space Description Handle 1 Handle 2 Handle 3

6. Object Manager Creates and deletes objects Sole source of handles for accessing objects At each use of handle, verifies access is allowed by the particular user Deletes temporary objects when no longer needed Enforces quotas for various object types

7. Object Creation Allocation of memory for the object Attaches security descriptor (who can do what to the object) Insertion into object directory structure Create handle and return to caller

8. Opening Objects Caller specifies desired access rights Object manager calls security reference monitor; Security reference monitor checks against security descriptor to see what is permitted; Object manager stores granted access rights in object handle which is returned to caller. Handle needed for all object accesses. Object manager checks all accesses against granted access rights.

9. Object Structure Object Type Specific Object Body Object Header Type Object Object 1 Object 2 Object 3 Type name Access Types Name Directory Sec Desc Etc. Proc1 Handle Proc1 Count Etc. Handle Database Handle Count

10. Object Header Entries Object name Object directory Security Descriptor Quota Charges Open handle count Open handle database Reference Count Kernel/user mode Type Object Pointer

11. Type Object Attributes Object Type Name Access Types Synchronizable? Pool Type Default Quota Charges Generic Rights Map Methods: open, close, delete, parse, query name, query/set security Type Name, e.g. process Possible access methods Can threads wait on this Allowed to page out? How much to charge (paged, non-paged pool) What is GEN. READ, etc? Routines called by object manager during various generic services

12. Generic Object Services Close Duplicate Handle Query object Query security Set Security Wait for single object Wait for multiple objects Invalidates handle Shares an object Get info about attributes Get security descriptor Set security descriptor Synchronize with 1 object Synchronize with multiple objects

13. Object Names Used to distinguish objects, to find objects, and to share objects. Name lookup is expensive -- so done only during creation (to put in object tree) and open. Each computer (which may be a multiprocessor) has its own name space. Name space is a single tree

14. Object Directory Object Type Name List Body Services Create object dir Open object dir Query object dir Object Directory Type Name Parse Methods

15. Symbolic Link Object Type Symbolic Link Substitute String Creation Date Create Symbolic Link Open Symbolic Link Query Symbolic Link Body Services Type Name

16. Symbolic Link Example \ DeviceDosDevices Floppy0 mark1 Mark1.cMark1.ppt A: \Device\Floppy0

17. Object Handles Index into a process’s object table. So they are valid only in the process. Obtained by creating, opening, inheriting, or receiving a duplicated handle from another process. Attributes: Protect from Close, Audit on Close, Inheritable. Granted Access Rights Attributes Pointer to Object

18. Retention and Quotas Object Retention via open handle count and then by reference count Quotas for use of paged pool, non-paged pool, paging file, and security descriptor. Limits are soft until memory manager disallows extension. Typically single Quota Block for session, but Windows 2K/XP has jobs